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This paper presents a dual active bridge (DAB) converter with reactive power control capability (Q-capability) for a battery energy storage system (BESS) or an electric vehicle (EV) to deliver vehicle-to-home (V2H) and vehicle-to-grid (V2G) services. The DAB topology is preferable for EV charging systems due to its galvanic isolation and bidirectional power flow capabilities. However, this topology increases reactive current peak and loses zero voltage switching (ZVS) operation at light loads if it is not controlled with improved modulation strategies and proper Q control. This paper proposes a mixed modulation method and a reactive power optimization (RPO) algorithm based on power system load flow concepts. Due to the complexities associated with the analytical solution using time domain analysis, this paper develops detailed universal expressions of a DAB converter using the harmonic analysis method. Analytical identification of ZVS boundaries and DSP implementation of the RPO algorithm become easier with these universal expressions. Multiple modes analysis for different operational states is no longer required. Simulation results have been shown for different modulation strategies of the DAB converters. The theoretical analysis of modulation strategies, RPO algorithm and ZVS operation are validated by experimental results on a DAB prototype. Results show that the proposed control strategy reduces the reactive power and provide ZVS operation over a wide ranges of voltages. [ABSTRACT FROM AUTHOR]

This article presents an energy management strategy for a microgrid having solar PV arrays and a battery energy storage system (BESS). Most of the energy management strategy used for commercial photovoltaic (PV) inverters and battery inverters do not consider the future load behavior and cannot ensure the energy resiliency for a PV and battery storage based microgrid. This article proposes the use of a model predictive control strategy that considers future load behavior and energy cost profile to determine an optimum power flow trajectory to achieve energy resiliency, minimize the operating cost and maximize the profit of the microgrid. The proposed control strategy of the energy management system (EMS) is validated using both simulations in MATLAB/Simulink environment and by carrying out laboratory experiments on a developed laboratory test platform. For the converters of the test platform, this article develops a magnetically linked seven-level multilevel converter (acting as the solar PV inverter) and a full-bridge inverter with an advanced pulsewidth modulation technique (acting as the BESS inverter). Commercial inverters usually require large and bulky power frequency transformers for the grid integration of renewable energy sources. The high-frequency magnetic link-based power electronic converter can produce multiple balanced dc power sources with reduced size, ensures lower power losses during the energy conversion process and can also ensure galvanic isolation. The results from the simulation and experimental studies of the EMS demonstrate that the developed energy management strategy ensures both the minimization of the operating cost of the system and the increased resiliency of the whole system. [ABSTRACT FROM AUTHOR]

This article presents low-frequency ripple power steering control strategies for a power conversion topology that comprises a high frequency linked three-port converter (HFL-TPC) and a voltage source inverter (VSI) for PV-BESS/EV applications. The proposed topology has three interfaces, which can be connected with a photovoltaic (PV) port, battery energy storage systems (BESS) and/or electric vehicles (EVs) port, and a four-quadrant ac port. The proposed topology inherently exhibits double line frequency (DLF) power fluctuation that needs to be decoupled and steered away from the PV port. In this article, we have developed and demonstrated two control strategies to deal with the DLF ripple. The first control strategy utilizes loop gain of the closed loop control system to decouple the DLF power, however, a residual DLF power still exists at the ac port. To completely decouple the DLF fluctuations, an improved sequence-based control strategy is proposed where the DLF voltage components are converted into positive and negative sequence components and controlled separately on their respective synchronous reference frames. To verify the practical feasibility of the proposed low-frequency ripple power steering control strategies, a 40 V, 400 W HFL-TPC is built and tested. Experimental results show that the proposed methods decouple the DLF power fluctuation and selectively steer it to the BESS/EV port. Comparative results reveal that the sequence-based control strategy shows a higher degree of DLF ripple suppression. [ABSTRACT FROM AUTHOR]

This work studies a multilevel inverter topology composed of two MPUC7s cascaded connected fed by only one dc power source by using a high-frequency link (HFL). This topology can provide up to 49 voltage levels by using four asymmetrical dc links, 12 power switches, and an HFL system. The dc link with higher voltage is fed by a dc source. The other dc links, with lower voltage, are supplied from the main one via high-frequency transformer with unidirectional power flow that processes up to 33% of the load power. A nearest-level control, analysis of power distribution among each dc link, and the HFL system design are presented in detail. Besides, comparisons with other multilevel topologies using HFL are carried out. Experimental results are presented to validate the theoretical studies. [ABSTRACT FROM AUTHOR]

All-SiC power modules have lately received great attention for multiphase motor propulsion systems due to their low radiator temperature and high efficiency. However, the application of all-SiC power modules for dual 12-phase 12-slot winding permanent-magnet propulsion systems remains an ongoing challenge, owing to synchronous operation. In an effort to overcome this challenge, this article quantified and compared the all-SiC power module with Si-insulated gate bipolar transistor (IGBT) to underpin the all-SiC power module as the preferred choice for propulsion inverter application. The motor mathematical model and control strategy were illustrated in detail. Moreover, the crucial features of the propulsion inverter and synchronous control were elucidated by the theoretical and experimental analysis. The synchronous switching of the dual all-SiC power modules allowed the same slot windings to achieve excellent operation. The experimental results were given for the operation of propulsion systems based on all-SiC power modules. The motor operations under different speeds were investigated as well. Finally, the fault tolerance of the dual 12-phase 12-slot permanent magnet synchronous motor (PMSM) was validated under an open circuit. [ABSTRACT FROM AUTHOR]

Nowadays, the three-level T-type inverters (3LT2Is) are widely employed in applications with high-performance requirements. The 3LT2Is commonly suffer from neutral point voltage (NPV) unbalance and common-mode voltage (CMV) variation. The medium vector pulse width modulation (MVPWM), which generates the reference voltage using medium and V0[OOO] zero voltage vectors, eliminates the CMV variation in 3LT2Is. However, it cannot keep the NPV balance, negatively affecting power quality. This article proposes a hybrid method to simultaneously eliminate CMV variation and guarantee the NPV balance without topological change or extra hardware. The proposed method uses MVPWM when NPV is balanced, eliminating CMV variation. If NPV goes unbalanced, it utilizes novel high/low triangle PWM (H/LPWM) and MVPWM in a hybrid manner to balance the NPV. The H/LPWM, similar to MVPWM, synthesizes voltage using medium and V0[OOO] voltage vectors to maintain the CMV elimination advantage during the NPV balancing process. However, the difference between H/LPWMs and MVPWM switching patterns adjusts the average neutral point current to balance the NPV. Noteworthy that the proposed method provides NPV balancing ability for the entire power factor range. As a result, it is usable for various applications of 3LT2I, such as photovoltaic inverters and motor drives. The proposed method is carrier-based, which reduces the execution time and simplifies the practical implementation. The simulation study and experimental evaluation have been accomplished, and their results demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The power flow from a grid-connected photovoltaic (PV) system is highly variable and creates complexities in the power scheduling for the utility. In this article, a grid-connected PV–fuel cell–electrolyzer hybrid system with a fixed power dispatch to the grid using a modified least mean square (LMS) algorithm is proposed. The modified LMS algorithm has been used to control the power flow to the grid besides controlling the power quality at the point of common coupling. Any variation in the PV power is balanced by power from the fuel cell by introducing a power management scheme. Furthermore, self-sufficiency in hydrogen supply for the fuel cell is achieved by using the excess PV production to power an electrolyzer to produce hydrogen from water. The sizing of sources and electrolyzer for a 38-kW commercial load and scheduled power dispatch to the grid has been done using a deterministic balance approach to achieve a carbon-neutral energy generation. The performances of the system during steady-state and transient conditions are verified by extensive simulation analysis with MATLAB Simpower system block set. Finally, experimental analysis using a hardware prototype is used to corroborate the simulation results. [ABSTRACT FROM AUTHOR]

Nonlinear droop control has been introduced to establish an effective power-sharing between distributed generators without the need for communication links in microgrids (MGs). However, one of the missing studies in the literature is the effects of nonlinear droop relations on the stability of the MGs. In this article, the stability of an inverter-based MG operating with the nonlinear frequency droop-control has been analyzed. A complete small-signal state-space linearized model of the MG system, with optimized nonlinear droop relations, has been developed considering the dynamics of the overall system and is updated periodically. The stability of the system is then checked online at different operating points. Small-signal stability analysis of an islanded MG was performed using MATLAB/Simulink and the results were experimentally verified on an MG setup. [ABSTRACT FROM AUTHOR]

Among the multiphase solutions, multi-three-phase drives are becoming more and more widespread in practice as they can be modularly supplied by conventional three-phase inverters. The literature reports several control approaches to perform the torque regulation of multi-three-phase machines. Most of such solutions use the vector space decomposition (VSD) approach since it allows the control of a multi-three-phase machine using the conventional control schemes of three-phase drives, thus reducing the complexity of the control algorithm. However, this advantage is practically lost in the case of open-three-phase faults. Indeed, the postfault operation of the VSD-based drive schemes requires the implementation of additional control modules, often specifically designed for the machine under consideration. Therefore, this article aims to propose a novel control approach that allows using any control scheme developed for three-phase motors to perform the torque regulation of a multi-three-phase machine both in healthy and faulty operation. In this way, the previously mentioned drawbacks of the VSD-based control schemes in dealing with the faulty operation of the machine are avoided. Moreover, the simplicity of the control algorithm is always preserved, regardless of the machine's operating condition. The proposed solution has been experimentally validated through a 12-phase induction motor, rated 10 kW at 6000 r/min, using a quadruple-three-phase configuration of the stator winding. [ABSTRACT FROM AUTHOR]

An overmodulation method is proposed for an in-wheel system where two motors are coupled to a sum gear. In the dual-motor dual-inverter single shaft systems, the output voltage magnitudes of two inverters are not the same in the overmodulation range due to the angle offset between two motors. In this article, to maintain torque balance in the overmodulation region, holding vectors are defined between adjacent vertices of two voltage hexagons. Around these vectors, the holding region is also defined by the holding angle. If a reference voltage vector is in the holding region, it is modulated to the holding vector; otherwise, it is modulated to the vector on the arc of inscribed circle. For a given the modulation index (MI), the holding angle is obtained based on the Fourier series expansion. The proposed method keeps the output voltages of two inverters the same even if two motors have the angle offset. Further, it has the characteristic of maintaining the linearity between the reference and output MI to the maximum MI. The proposed overmodulation method is demonstrated by simulation and experimental results. [ABSTRACT FROM AUTHOR]

This article presents a discrete convolution-based method for reliability evaluation of a grid-connected photovoltaic (PV) system, where special consideration is given to the variable availability of PV array components. Along with the negative impacts of variable solar irradiance and ambient temperature on the PV power generation, they affect the reliability of PV system power electronic components. A variable availability model based on the power loss in the semiconductors of PV system components is needed to account for this effect in the reliability analysis. The article proposes a 3-D capacity outage model of a PV farm that accounts for the variable availability and the redundancies associated with the topologically complex multistring PV arrays. The outage model is used to construct a PV capacity outage probability and frequency table (COPAFT), which along with conventional generation COPAFT, is convolved with the distribution of load to determine system reliability. An integration limit assessment tool is also developed within the proposed framework, ensuring that the PV power integration does not violate the system frequency stability. Simulations on the modified IEEE RTS-79 system demonstrate the efficacy of the proposed method. [ABSTRACT FROM AUTHOR]

Unlike VSIs, the single-stage inverters (SSIs) from the family of Z-converters are capable of boosting input dc to a desired ac voltage. The Z-network of these converters consists of a symmetric X-shaped network or a combination of inductors and capacitors. The basic Z-source converter (ZSC), connected in X-shaped fashion is modeled as a fourth-order system. This can be further modeled as a second-order system to reduce the sensor count but this may lead to an unstable system if there is an asymmetry in network parameters. Also, the source current of SSIs contains second-order ripple current (SRC) component, which oscillates at twice the supply frequency and has detrimental effects on sources. To alleviate the above problems, a parametric uncertainty compensation and ripple mitigation (PUCRM) control methodology is proposed. PUCRM control can be used to maintain stability and achieve desired performance during parametric uncertainties in the dc–dc stage and to reduce SRC propagating to the sources while feeding ac loads. PUCRM consists of a nominal dual-loop PI controller, which regulates the SSIs to achieve desired performance and a nonlinear integral sliding mode component that mitigates the uncertainties and ripple component. The proposed method is verified using simulation and experimentation. [ABSTRACT FROM AUTHOR]

In this article, a multioutput-based transformerless hybrid solar inverter (TLHSI) with no right half-plane zero (RHPZ) and reduced common-mode leakage/ground current is presented for photovoltaic (PV) based microgrid applications. In the proposed multioutput TLHSI, two magnetically coupled inductor coils are placed between the input and dc output sides along with a dc-link capacitor to continuously provide the stored energy to the dc load so that the RHPZ is eliminated and, thus, makes it a minimum phase system. Furthermore, a hybrid unipolar sinusoidal pulsewidth modulation technique is established to nullify the high-frequency components of common-mode voltage across the PV to ground stray capacitor. Also, it normalizes both dc and ac loads at the same instant from a single dc input during each operating state of the proposed TLHSI. The shoot-through issue is resolved in the proposed TLHSI, which increases the system reliability. Furthermore, as the deadtime is not required in between the switching pulses, the quality of the inverter output voltage improves. The performance analysis of the proposed TLHSI is compared with the existing topologies. To validate the performance of TLHSI, a scaled down 340 W laboratory prototype is developed. [ABSTRACT FROM AUTHOR]

This article evaluates the performance of a relatively new pulsewidth modulation (PWM) method i.e., 240 $^\circ$ -clamped space vector PWM (240CPWM), in three-phase grid-connected photovoltaic (PV) converters under various grid voltage conditions. 240CPWM is a minimum switching loss PWM method that reduces the switching loss by 85% at unity power factor and has better total harmonic distortion (THD) as compared to conventional space vector PWM. A unique six-pulse dynamically varying dc-link voltage is required for 240CPWM. Typically, a three-phase grid-connected PV system consists of a dc–dc stage followed by a dc–ac stage. In this article, the dc–dc stage is operated in closed-loop control to shape the dynamic dc-link voltage required for 240CPWM. The dc–ac stage is operated in the current control mode using a proportional–integral controller along with a harmonic compensator to ensure sinusoidal grid currents along with maximum power point tracking. The modulation index of the dc–ac stage is uncontrolled and fixed at the maximum value, and the primary control mechanism changes the magnitude, phase, and wave shape of the dc-link voltage. The coordinated control of dc–dc and dc–ac stages is ensured for better dynamic performance and grid support functions. Finally, the performance of the grid-connected PV converter with 240CPWM is validated using a three-phase 3-kW 208-V hardware prototype under nonunity power factors, voltage unbalance, and voltage sag/swell conditions for the first time. The implemented control with 240CPWM achieves smooth operation under nonunity power factor and grid voltage disturbance conditions with THD as low as 3.5% and peak combined efficiency of dc–dc and dc–ac stages as 96.4%. [ABSTRACT FROM AUTHOR]

Model predictive control (MPC) has become one of the most attractive control techniques due to its outstanding dynamic performance for permanent magnet synchronous motor (PMSM) drives. However, the tuning of weighting factors for the cost function of MPC is a time-consuming procedure and weighting factors can significantly affect torque ripples of PMSM drives. For the purpose of optimizing the weighting factors in cost functions of MPC, this article proposes an artificial neural network (ANN) based method, which applies genetic algorithm as the back propagation algorithm. Since this method is trained offline, it does not increase any computation complexity of MPC. Consequently, any optimization targets that combine the performance metrics of MPC are defined and the optimal weighting factors for the given targets can be fast and precisely found through the proposed method. Besides, this method is robust to the variations of motor parameters like stator resistance and permanent magnet flux. The superiority of the proposed method over conventional ANN is evaluated by comparative simulations, in terms of current total harmonic distortion, tracking performance, and neutral-point potential balance. Finally, the feasibility and robustness of the proposed method are verified on the platform of PMSM drives fed by three-level T-type inverter. [ABSTRACT FROM AUTHOR]

Common mode voltage (CMV) reduction in a traditional H6 (six switch) 3-φ inverter usually demands additional power semiconductors to avoid poor harmonic performance. However, apart from tending to the CMV related issues, these extra switches do not add any other capability to the inverter. To address this limitation, in this article, a novel H8 inverter configuration is proposed which not only reduces the CMV by 66.6%, the phase current total harmonic distortion (THD) is also improved. The proposed H8 inverter employs two additional power semiconductor devices along with the conventional H6 inverter in a manner that it can generate 15 space vectors (SV). By considering the CMV attribute of each SV, a unique sector configuration is proposed where the SV diagram is divided into 18 asymmetrical sectors and three distinct SV sequences are identified. A special pulsewidth modulation scheme is devised to operate the proposed topology to achieve reduced CMV and improved harmonic performance. A comparison study reveals that the proposed topology offers better phase current THD, low CMV, low losses, and low semiconductor requirement. Simulation and experimental results are included to justify the various claims. [ABSTRACT FROM AUTHOR]

This article proposes a novel approach for mitigating grid frequency deviation during disturbances, utilizing the inverter angles for inverter-based resources connected with multiple dc microgrids. The proposed approach generates dynamic multiple-input–multiple-output system models of dc microgrids interfaced with inverters based on the alternating direction method of multipliers. These frequency-domain-based models generate input–output transfer functions relating to dispatchable distributed energy resource (DER) set points. These are then used as control inputs and grid frequency/individual point of common coupling (PCC) angles ($\delta$) for ac–dc multi-microgrid structures depending on their locations in the distribution network. A sensitivity relationship of powers with respect to change in global distribution frequency or individual angle $\delta$ for each section of ac–dc multi-microgrid is then used to optimally control the DER dynamics such as the frequency deviations are minimal. This approach is tested on commonly seen fault/dynamics and it was observed that the proposed architecture outperforms the state-of-the-art by more than 20% in mitigating frequency deviations. [ABSTRACT FROM AUTHOR]

In conventional discontinuous pulsewidth modulation (DPWM) methods, the drastic change of the modulation index during the clamping transient results in grid current oscillation, which deteriorates the power quality. This article presents a semi-DPWM method for a three-level T-type grid-connected PV inverter. The semi DPWM is achieved by injecting a continuous sinusoidal signal during the clamping transient, which reduces the grid current oscillation and reduces the total harmonic distortion of the current. First, a detailed analysis of the grid current oscillation is presented, then a semi-DPWM method is proposed to suppress the oscillation current. The experiment is carried out on a 48-kW grid-tied PV inverter to validate the effectiveness of the method. Compared with the space vector PWM, results show that more than 42.5% switching loss has been reduced with the semi DPWM and the efficiency is increased from 97.03 to 97.22% at the rated load. Besides, the semi DPWM method significantly suppresses the current oscillation and maintains good power quality under various operation conditions. [ABSTRACT FROM AUTHOR]

The electronic commutation and the low inductance nature of the brushless dc motor (BLDC) deteriorate the expected performance. The ripples in the current waveshape are primarily due to the commutation of the phases, which is carried to produce a synchronously rotating magnetic field. This commutation ripples lead to mechanical pulsation and noise on the rotor side. This article presents a novel strategy for reducing the commutation torque ripple. The proposed topology uses a hybrid Ćuk voltage gain dc–dc converter at the front end, which has high voltage gain and which reduces voltage ratings of the dc supply. An auxiliary switch is connected across the dc link of the inverter to control the rate of rising incoming phase current during the phase change of the inverter with the help of the dc–dc converter. A prototype of a 1HP BLDC motor is used to validate the proposed topology both analytically and experimentally. [ABSTRACT FROM AUTHOR]

An isolated multilevel bidirectional dc–dc converter is presented in this article to interface the low-voltage (LV) battery and the high-voltage (HV) propulsion inverter in electric vehicles. The proposed topology achieves a HV step-up ratio in the motoring mode by reconfiguring two split capacitor half-bridge circuits in series/parallel through the symmetrical modulation of a voltage bidirectional, two quadrant switch. This reconfiguration generates a high-frequency multilevel voltage output at the dc-bus side of the inverter, which reduces the output filter volume. The dc-bus voltage is regulated by the duty cycle modulation of the intermediary switch in the motoring mode, simplifying the sensing and control. During regenerative braking, the converter is operated with phase shift modulation between the HV half bridges and the LV full bridge to regulate the battery voltage. The presented modulation strategies achieve zero voltage switching for the full-bridge devices over a wide load range. A comprehensive analysis of the proposed multilevel converter in motoring and braking modes along with the design constraints and soft switching boundary conditions is presented in this article. Detailed experimental results on a 1.5-kW laboratory prototype are presented to verify the design approach and illustrate the converter performance. [ABSTRACT FROM AUTHOR]

The output current of PWM inverters may contain low-frequency harmonics due to nonidealities, such as fluctuating dc voltage and dead-time. Low-frequency harmonics are detrimental to the inverter's current controller performance as well as its operation. They increase losses, cause synchronization problems in a grid-connected inverter, and cause torque pulsations in motors. Reducing low-frequency harmonics through conventional means require a big and expensive filter. In this article, a method to reduce low-frequency current harmonics is proposed. This method uses a virtual impedance, which is a controller block that mimics the behavior of a real impedance. Because it is virtual, it does not have physical drawbacks to the system, such as volume, weight, and losses. It can be designed only to affect the disturbance signals and to assume characteristics unlike a real impedance. It can also be added as a plug-in block to an already existing controller, saving a significant amount of design effort. Simulation and experimental results show a decrease of current THD to almost 1/3 of the original THD when no virtual impedance is used, demonstrating the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This article develops a two-stage volt-VAr control strategy coordinating the discrete controls of legacy grid devices and the operation of smart inverters (SIs) in power distribution grids with high penetration of photovoltaic generation. The first stage dispatch problem optimally coordinates the tap settings of on-load tap changers, on/off status of shunt capacitor banks, and SIs’ active power output. The second stage incorporates the SI volt-VAr mode, i.e., $\mathbf{Q(V)}$ as per IEEE-1547, and an adaptive volt-VAr droop function, $\mathbf{Q(\Delta V)}$ , to dispatch the SI reactive power generation. Both dispatch problems are formulated as mixed-integer linear programming problems to maintain tractable formulations and reduce the complexity and computational burden that usually arise when solving large-scale optimal power flow problems. The proposed two-stage strategy is tested on a modified IEEE 123-bus system considering different droop settings. The dispatch strategy augmented with $\mathbf{Q(\Delta V)}$ droop outperforms the model with only $\mathbf{Q(V)}$ droop in stabilizing the PCC voltage while maintaining less active power curtailment. [ABSTRACT FROM AUTHOR]

1500-V photovoltaic (PV) configuration is the standard design in the solar PV industry. Extending the maximum dc voltage from 1000 to 1500 V can reduce the installation cost of the entire power plant. However, it may affect the reliability of the corresponding 1500-V PV inverters, due to the increased loading stresses, i.e., voltage stress and thermal loading of power devices. In this context, this article proposes a solution to the reliability enhancement of silicon carbide-mosfet-based 1500-V PV inverters with variable gate resistance. This solution offers a possibility to adaptively adjust the switching speed to make a compromise between the switching power loss and voltage overshoot during commutation, thus enhancing the reliability. The evaluation results based on the mission profile of a 125-kW 1500-V PV system installed in Denmark indicate that the PV inverter with the proposed design, i.e., variable gate resistance, can improve reliability performance compared to the fixed gate resistance solution while ensuring a safer operating voltage margin. [ABSTRACT FROM AUTHOR]

High penetration of photovoltaic (PV) generators in active distribution networks (ADNs) cause overvoltage due to reverse power flow. Smart inverter (SI) functionalities can be configured to provide efficient voltage regulation and reactive power support in ADNs. Moreover, the mismatch between peak PV generation and peak demand make battery energy storage systems (BESSs) increasingly important assets in power grids, capable of enabling higher penetration of renewable energy resources by mitigating the system-wide effects of PV intermittency. In this work, we propose the inclusion of local piecewise Volt-VAr and Volt-Watt droop functions of PV (as per the IEEE-1547) as constraints in a multiperiod distribution grid optimal power flow (DOPF) formulation. This approach is an efficient voltage control method for unbalanced multiphase networks, making the inverter dispatch solutions abide by the IEEE-1547 standard and therefore suitable at the local inverter controller level. We adopt a well-known LinDist3Flow version of DOPF, and the resulting multiperiod DOPF becomes a mixed-integer linear programming problem. Simulations on the IEEE 123-node feeder with 15 utility-scale PV and BESS inverters validate the efficacy of the proposed formulation in performing effective voltage regulation and control that abide by the IEEE-1547 standard. The case studies show that SI droop-integrated DOPF can ensure reduced variation in bus voltages, reducing the risk of voltage violations, and net load smoothing can be achieved with BESS, reducing the disparity between inexpensive midday and expensive evening energy price. [ABSTRACT FROM AUTHOR]

The service of grid voltage regulation is required nowadays from inverter-based resources (IBRs) particularly at the lower voltage level. In the transmission network, this is easily managed by leveraging solely the reactive power (Q) capability of the IBR, but in distribution networks that are mix of $L$ and $r$ the voltage magnitude is coupled with both active (P) and reactive power injection. There are methods in the literature designed for these cases that utilize both P and Q in voltage regulation, but they usually require network and load data, which may not be readily available. Furthermore, they often disregard an apparent nonmonotonic relation between the inverter terminal voltage and the P/Q ratio risking instability. To fill this gap, this article introduces a network-agnostic P–Q adjustment technique for photovoltaic (PV) systems or other IBRs. The proposed technique tracks in a step-like manner the reference voltage set point if it is feasible, or the maximum grid voltage otherwise. This allows identification of the critical P/Q ratio without any prior information at the cost of limited voltage ripple due to a variable step-size strategy implemented. The superior performance of the proposed scheme is validated through simulations in MATLAB-Simulink in a reduced UKGDS 95-bus system and through lab experiments on a scaled down laboratory grade prototype. [ABSTRACT FROM AUTHOR]

This article investigates the total PWM-induced power losses in interior permanent magnet (IPM) machines excited by wide bandgap (WBG)-based voltage-source inverters with different pulsewidth modulation (PWM) schemes and a wide range of switching frequencies. The PWM current ripple characteristics are predicted and compared using an accurate analytical model. Three enhanced power loss estimation models are utilized to estimate the PWM-induced power losses in each of three major machine materials: the stator form-wound windings, the stator and rotor iron cores, and the permanent magnets in the rotor cavities. The variation trend of each loss component versus PWM frequency and modulation scheme is provided. Experiments have validated the model accuracy in two IPM machines designed for traction applications. Both measured and predicted results suggest that increasing the PWM frequency is beneficial for suppressing the PWM-induced power losses in IPM machines. In conjunction with the reduction in machine-related power losses, it has also been demonstrated that a higher PWM frequency in IPM drives with WBG-based inverter exhibits the appealing potential for improving the system-level efficiency in traction applications. [ABSTRACT FROM AUTHOR]

The five-level active neutral-point-clamped (5L-ANPC) inverter has been applied to increase the power capacity of photovoltaic (PV) systems. However, this type of configuration requires to balance neutral point (NP) voltage and flying capacitor (FC) voltage properly. For the operation of the transformerless five-level inverter, another requirement is to suppress the leakage current associated with the common-mode voltage (CMV) vectors. Due to the mutually coupled issues, the conventional model predictive control (MPC) methods reported so far cannot deal with them properly at the same time. To address these problems, a novel double-vector MPC (DV-MPC) strategy with zero CMV vector is proposed in this article. First, 19 voltage vectors with zero CMV are implemented as candidate vectors. Then, for the purpose to reduce output current ripples, two voltage vectors are penalized by the cost function without weighting factors to track the reference voltage. In addition, the dwell times are optimized to further mitigate current ripples. Finally, to avoid the sharply increasing computational burden of the online iteration caused by the introduction of the second vector and its corresponding redundant switching states, a voltage-balance strategy is presented for the DV-MPC method, which can determine the suitable switching combinations directly and adapt them to the selected vectors to balance the voltages of the NP and FCs together. The effectiveness of the proposed method is verified by the simulation and experiment at the end of this article. [ABSTRACT FROM AUTHOR]

In this article, multiple parallel photovoltaic (PV) inverters based microgrid is developed to enhance the reliability and accessibility of electricity in remote areas. A self-adaptive control strategy is presented for a microgrid to ensure a seamless transition between the islanded mode (IAM) and grid-connected mode (GCM) of operation with a proportional power sharing. This microgrid consists of two solar PV inverters based on local distributed generation (DG) units. Each PV-inverter unit feeds an active power to support local loads and the power demand of each local load is shared between respective DG units and microgrid. The PV-battery-interfaced main unit with a self-adaptive control strategy in parallel with a PV array supported unit-2 is considered to operate in the IAM and GCM of operation. The control strategy achieves transient free operation during load disturbances, power variation at the PV array side, and off-grid operation. Moreover, the microgrid ensures high-quality performance at the point of common coupling and provides the seamless transition between GCM and IAM to guarantee a continuous power to critical loads. The microgrid simulation and experimental results are presented under various operating conditions, such as load variation, intermittent power generation, and automated mode transition between GCM and IAM. [ABSTRACT FROM AUTHOR]

The integration of single-phase microgrids (MG) and unbalanced loads to three-phase MGs results in power quality issues at the point of common coupling (PCC). These issues include unbalanced voltage, unequal power flow, and inaccurate reactive power sharing. In this article, an energy storage system (ESS) has been proposed with novel control methods to help mitigate unbalance issues in these islanded multimicrogrids (MMGs). It presents two novel control methods: modified reverse droop control and multifunction control to compensate the reactive power of the MMG and generate the needed active and reactive power references of the ESS. The developed control methods mitigate PCC voltage and power unbalance of the MMG and also achieve the load power sharing proportionally among different rated photovoltaics (PV) inverters. In addition, the system stability with the proposed control is also presented under different scenarios. The proposed multifunction controller operation is validated using Opal-RT real-time simulator and experimentally using control hardware-in-the-loop. The results demonstrate that the PCC unbalanced voltage and power are reduced significantly by 97.8%, and the proper reactive power sharing is achieved among the different PV inverters in the proposed system. [ABSTRACT FROM AUTHOR]

In this article, Harris hawks’ optimization (HHO) for selective harmonic elimination method (SHEM) of a voltage source inverter has been applied to a traction motor drive for light rail transportation. The main objective of SHEM's pulsewidth modulation (PWM) strategy is to remove the low-order harmonics by solving nonlinear equations while satisfying the required fundamental component's magnitude. The HHO applied in this article to a two-level, three-phase inverter aims at solving the associated nonlinear equations with a high accuracy and convergence probability as a strong metaheuristic algorithm. SHEM simulations are carried out via MATLAB/Simulink on a 125 kW traction motor drive platform for various SHEM angles to verify its performance in comparison with the SHEM with sinusoidal PWM (and space vector modulation (SVM) techniques. Experimental results obtained on a physical simulator of the light rail transportation system in the laboratory have shown remarkable findings in view of the dc-link voltage magnitude on the performance of the associated traction motor drive. In the light of different fundamental frequency operations, number of SHEM angles, and operating dc-link voltages, a general evaluation of the SHEM has been made in considering its application to a light rail traction motor drive. It has also been shown that the application of online SHEM on a GPU framework is possible in real-time. [ABSTRACT FROM AUTHOR]

Commutation failure (CF) in the line-commutated converter based high-voltage direct-current system will result in a large amount of reactive power surplus on the rectifier ac system. It will cause the transient overvoltage and lead to the massive disconnection of the renewable sources. In this article, the mechanism of the transient overvoltage caused by CF is analyzed and the suppression strategy based on improved voltage-dependent current order limiter (VDCOL) control is proposed. First, during the process of CF, the dynamic behavior of reactive power consumption of the rectifier is analyzed. It is proposed that when the inverter returns to normal commutation, the sudden increase of the inverter dc voltage will cause the decreasing of the dc current, which will result in the large decreasing of reactive power consumption of the rectifier. Then, the dynamic change process of the rectifier ac voltage is deduced. Second, the peak value of transient overvoltage as affected by the occurrence and removal time of the short-circuit fault is deduced and analyzed. Then, by improving the operating characteristic of the VDCOL control, the control strategy of overvoltage suppression is proposed. Based on the PSCAD platform's CIGRE-HVDC benchmark model, the effectiveness of the proposed strategy is verified by the simulation results. [ABSTRACT FROM AUTHOR]

This article presents a new topology for a single-stage nine-level (9L) switched-capacitor inverter. The structure of the proposed topology is not only simple but also compact. The proposed topology is developed with self-voltage balancing and a low number of power components. The output voltage (vo) gain is four times higher than the input voltage (vin). Each mode of operation is discussed with a detailed current path. The conventional sinusoidal pulsewidth modulation technique is used to generate the gate pulses. Next, the experimental results are obtained from a 1 kW prototype setup. The proposed topology is tested under different scenarios such as load change, input voltage changes, and modulation variations. Both simulation and experimental results have good agreement in terms of efficiency. Finally, a detailed comparative study is performed with other recent 9L inverters to prove the merits of the proposed topology. [ABSTRACT FROM AUTHOR]

DC-link-based variable speed constant frequency (VSCF) ac power generating system is being considered as one of the popular power architectures in the new generation aircraft to provide backup power to the 115 V, 400 Hz aircraft loads. These systems directly convert the variable frequency output of the generator to the fixed frequency of 400 Hz using a voltage source inverter. These inverters use dc-link capacitors that are heavy and space consuming. In aircraft, the weight requirement is very critical; hence, minimizing the dc-link capacitance is one of the major research challenges to achieve high power density in the VSCF power converter. In this article, novel control strategies to minimize the dc-link capacitance of the ac–dc–ac VSCF power converter are presented. The proposed control strategies enable to achieve 95% reduction in dc-link capacitance value when compared with the conventional control strategy, while the control is robust enough to meet MIL-STD-704F transient specification at the inverter output. The proposed strategies are validated through controller hardware-in-loop testing of the VSCF system based on an 80 kVA brushless synchronous generator and a four-leg inverter. The transient and steady-state operation of the VSCF system with a 95% reduction in dc-link capacitance has been verified for rated power operation. [ABSTRACT FROM AUTHOR]

This article proposes a fault-tolerant solution for the three-phase dc–ac converter using a modified impedance source boost inverter. Besides the additional modified impedance source, the solution is based on the reconfiguration of the topology to maintain the desired operation in case of an open-circuit failure mode of a power device. The proposed topology presents important features such as a boost capability to operate under fault condition and avoid extra active power devices in normal operation (without failures). Besides that, the circuit does not require dead times between the switches of each leg, which increases the reliability of the topology. Regarding the control solution for this converter, it is adopted a closed-loop current controller combined with a vectorial voltage modulator. Since this modulator is also function of the shoot-through, it will be possible to recover the amplitude voltage space vectors due to failures in power devices. The combination of these elements allows to obtain three-phase balanced ac currents with reduced total harmonic distortion even in fault-tolerant operation mode. The fault-tolerant performance of this solution is confirmed through several simulations and experimental results. [ABSTRACT FROM AUTHOR]

Three phase inverters with switching frequencies above 100 kHz have recently become feasible thanks to the significant progress made in wide band gap (WBG) semiconductor technology. The main drivers behind the intense research and development of these ultrahigh switching frequency pulsewidth modulation (PWM) inverters are the extraordinary gravimetric and volumetric power densities that can be achieved. On the other hand, not as much attention has been devoted to the loads that these inverters supply, quite frequently consisting in ac motors. The impact of sub-MHz PWM and of the associated tens of nanoseconds range switching transients on motor terminal overvoltage, common mode currents, and losses are still to be discussed exhaustively. The authors have thus decided to investigate what happens to induction motors (IM) supplied by inverters having switching frequencies up to 350 kHz. After an introduction on WBG semiconductor devices, the article presents some interesting experimental observations conducted on a 1.1 kW four-pole IM fed by a silicon carbide (SiC) inverter. Further insight is provided by tests on a laminated steel toroid, supplied by a single-phase full bridge SiC inverter. Discussions on the experimental results highlight the previously unreported impact of common mode losses, which become a predominant part of the PWM harmonic losses. [ABSTRACT FROM AUTHOR]

Current-fed dual active bridge converter offers multiport structure and can be used in applications, such as renewable energy systems, hybrid electric vehicles, etc. Dual pulsewidth modulation plus phase shift control provides three degrees of freedom for power control, which include duty ratios of primary and secondary side bridges (d1 and d2) and the phase difference between them (δ). Converter operation at the optimum point ($d_1^{\text{opt}}$ , $d_2^{\text{opt}},\ $ δopt) can help achieve multiple objectives, such as achieving zero voltage switching (ZVS) and minimizing current stress along with controlling the power flow. When a CF-DAB is operated as a multiport converter, the optimal control point ($d_1^{\text{opt}}$ , $d_2^{\text{opt}},\ $ δopt) depends on the voltages and currents at different ports, and determining it online is a challenge. In this article, ZVS behavior and current stress of CF-DAB converter are analyzed under various operating conditions pertaining to different source voltages/currents and load power. Based on the analysis, an algorithm has been proposed for determining ($d_1^{\text{opt}}$ , $d_2^{\text{opt}},\ $ δopt) for the given operating condition. Experimental results on a laboratory prototype have been presented, which validate the theoretical analysis and the proposed algorithm. [ABSTRACT FROM AUTHOR]

In this article, a new topology for a grid-connected solar photovoltaic inverter for the direct connection to the medium-voltage grid is proposed. This topology employs an LLC resonant converter with a high-frequency (HF) isolation transformer in the dc–dc stage. The output of the dc–dc stage is a rectified sine wave voltage and current at the line frequency. An unfolder inverter interfaces between this dc stage and the grid. A combined phase-shift and frequency control method is used to control the LLC resonant converter. The phase-shift angle and switching frequency values of the LLC resonant converter are regulated to track the reference current signal for the whole operation range. The Lagrange multiplier method is applied to find the optimal trajectory to calculate the optimal phase-shift angle and switching frequency pairs for any operation condition by considering power converter and HF transformer losses to achieve the highest efficiency at a varying current. The transformer leakage and magnetization inductances are properly designed to provide a zero-voltage switching (ZVS) for a wide operation area, and additional resonant inductor requirement is removed. The LLC converter operates in a ZVS region except in a narrow band around the zero-current crossings of the inverter output. Using an HF transformer in the LLC resonant converter, a bulky line frequency transformer requirement is eliminated, and thus, a more compact and efficient design is obtained. The proposed topology is validated by the simulation and experimental results. [ABSTRACT FROM AUTHOR]

Conservation voltage reduction (CVR) is a utility practice that reduces load demand by strategically lowering voltage magnitudes across voltage-dependent loads. This work presents a topology-assisted integrated voltage control scheme for effective CVR implementation in three-phase active electric distribution networks (EDNs) with increased spatio-temporal load variations. The proposed formulation finds suitable network configuration and voltage control devices’ settings corresponding to reduced energy demand, loss, and unbalances. The EDNs have state-of-the-art voltage regulating devices, such as, capacitor banks, onload tap changer, and voltage regulators (VRs), along with smart inverters. The inverters facilitate bidirectional power flow by interfacing battery energy storage systems and solar PV installations to the grid. The proposed formulation is solved using multiobjective particle swarm optimization on the modified IEEE 34-bus system. The results for various cases show that the proposed load-variation-driven instantaneous topology adaptations with localized voltage management significantly improve the system performance under practical operating conditions. A comparison with a previous method, based on the results for a 13-bus real-life distribution system, proves the efficacy of the proposed method. [ABSTRACT FROM AUTHOR]

This article discussesthe control method for an ac/dc rectifier system consisting of a three-phase diode rectifier, a buck converter, and an instantaneous reactive power compensator (IRPC). The IRPC makes the grid current sinusoidal by controlling only the instantaneous reactive power. Thus, it is possible to reduce the size of the dc capacitors and ac inductors. This article analyzes the overlap in the rectifier, derives the suitable gain in the damping control, and proposes a modified control method for the IRPC to reduce the current ripple. A 4.5-kW laboratory setup was assembled and examined to verify the theory developed in this article. As a result, the modified control method effectively suppresses the spike current around the overlap duration and damps the overshoot/ringing caused by the resonance. The proposed ac/dc rectifier exhibits an improved power conversion efficiency of 98.2%. [ABSTRACT FROM AUTHOR]

Impedance-source inverters (ZSIs) are getting more attention in renewable energy generation over conventional inverters due to their inherent boosting ability and shoot-through immunity. However, most of the ZSI expansion abilities are somehow limited by the component stresses and poor performance, particularly at a low modulation index. In this article, a new coupled inductor-based switched quasi-ZSI is proposed to accomplish enhanced boost inversion at a high modulation index. It offers a robust boosting feature even with a very low turns ratio, which significantly reduces the passive circuit element's size. The working principle, steady-state analysis, and the design guidelines for selecting circuit parameters are addressed. The proposed inverter significantly improves the input current ripple with enhanced boosting with appropriate control of the impedance-network active switch. A comprehensive comparative analysis with allied topologies is presented to show the proposed inverter's effectiveness. The superior features offered are more suitable for renewable energy generation from low- and variable-voltage renewable sources, such as solar PV and fuel cells. A laboratory prototype is made for experimental verification. Analytical, MATLAB simulation and experimental results are presented to validate the proposed theory. [ABSTRACT FROM AUTHOR]

Ground fault diagnosis is difficult to carry out in dc–ac systems due to the presence of power electronics. Additionally, it is common that neither relays could protect efficiently these systems as ac devices are not prepared to actuate under dc currents and vice versa. Previous studies were able to detect if the fault was in ac or dc but the faulty point still being incognita. This article presents a ground fault location method for the ac side of dc–ac systems that complements previous detection methods. It is based on a grounding resistor connected between the midpoint of the dc bus and ground. Then, an instantaneous voltage window record is analyzed into a histogram, obtaining two representative voltage peaks that are correlated. These values are the one with most repetitions and the one with most amplitude. Attending to a coefficient defined by these two parameters, the fault location can be estimated. The effectiveness of this method has been corroborated with simulations and experimental tests in a 140 kW dc–ac converter, achieving promising results. [ABSTRACT FROM AUTHOR]

This article presents an artificial loading method for induction machines using industrial static frequency converters variable frequency converters (VFCs), low-cost programmable logic controllers for command and control, and standardized communication protocols. Different approaches of artificial loading method are presented in this article. Induction machine full load testing is difficult, especially at high power and almost impossible for vertical axis machines. Mechanized IM start/stop procedure and closed-loop loading method, here presented, reduce overall testing time. The overall manpower cost is reduced thanks to the lack of IMs mechanical coupling. Moreover, thermal test at rated IM current and power losses equivalation are presented in this article. Bi-directional VFC utilization for a single motor cannot always be a solution for artificial loading because of high variations of grid power (voltage). Two identical IMs without mechanical coupling driven by two identical dc bus interconnected VFCs artificial loading method is presented in this article. The power circulation between the machines is performed via the common dc link. This opens the possibility to test machines with rated power larger than the lab power source rating. The rated current artificial loading conditions are achieved without mechanical coupling, without VFC oversizing, and using standard equipment. [ABSTRACT FROM AUTHOR]

The development of more electric aircraft (MEA) has accelerated in recent years. Power converter systems for MEA require higher reliability compared with the conventional power converter systems as well as higher energy efficiency. A power device at high altitude might break down at a certain rate because of cosmic rays. Thus, it is necessary to carefully consider the reliability of single event burnout together with the converter design. This study examines a failure in time (FIT) rate comparison among three different inverter configurations using 3.3-kV and 6.5-kV full SiC power modules (FSPMs) under several operating conditions. It presents module and inverter configuration selection criteria in consideration of the FIT rate. In addition, the transitions of FIT rates during the flight are calculated using actual flight data to help the power converter system designers understand how the FIT rate should be considered. Furthermore, this study verifies a high-frequency switching operation at various bus voltages for a 6.5-kV FSPM and the power loss calculation for MEA applications. [ABSTRACT FROM AUTHOR]

Although it is commonly assumed that power swing is symmetrical and will have identical effects on all three-phase voltages and currents, there is another type of power swing, which is asymmetrical and mainly occurs during single-pole tripping (SPT), the impact of which on power systems integrated with the inverter-based resources (IBRs) has not been investigated so far. Since the likelihood of the occurrence of asymmetrical power swing is increasing in today's heavily loaded transmission lines, this article investigates the impact of IBR integration on the performance of distance protection during single-pole tripping. Furthermore, a new scheme is proposed to detect earth faults that occur during asymmetrical power swings to enhance the performance of power swing blocking functions. To do so, the superimposed component of the zero-sequence current during SPT is extracted. Then, the moving average window is used to calculate the average of both zero-sequence current and its superimposed component. Furthermore, to enhance the security of the proposed scheme, a new technique based on the phase angle shift between the three-phase currents is devised to detect the asymmetrical power swing conditions. This article shows that as the penetration level of IBRs increases, the standard reclosing dead-time needs to be revisited otherwise it can create an unstable power swing condition, even during SPT. Moreover, this article shows that the proposed earth fault detection scheme can efficiently detect all single-line-to-ground faults occurring during SPT. [ABSTRACT FROM AUTHOR]

This article presents two single-phase to single-phase three-wire converters based on two-level and three-level neutral-point-clamped legs. The converters present a shared-leg between the grid and load. A space-vector pulsewidth modulation technique considering the harmonic distortion and the semiconductor losses is presented, besides the dc-link voltage-balance technique to balance the neutral-point voltage. The converters can supply the loads with constant amplitude and frequency under grid voltage disturbances. These characteristics make the proposed converters suitable for applications as uninterrupted power supply. The proposed converters are compared to a conventional two-level converter from simulated results for evaluating the semiconductor losses and harmonic distortion. The experimental results are provided to illustrate and validate the operation of the proposed systems. [ABSTRACT FROM AUTHOR]

When a fault occurs on the tie line of ac/dc hybrid system, the change rule of electrical quantity on the inverter side is different from that of infinite ac power source. Sensitivity and reliability of the traditional relay protection methods will be affected. A longitudinal protection method for ac/dc hybrid system based on voltage wave similarity comparison is proposed. The protection compares the similarity of the measuring voltage wave and the calculated reference voltage wave, and determines the fault location roughly. By comparing the judgment results of voltage similarity between both ends of line, a reliable judgment can be made to distinguish between internal and external faults. In order to improve the reliability of voltage wave similarity comparison, dynamic time warping method is used to overcome the influence caused by phase error, and Pearson correlation coefficient method is used to judge the similarity of voltage wave. The simulation results of real time digital simulation system (RTDS) show that the proposed method can identify the fault which occurs on the tie line of ac/dc hybrid system accurately which has high reliability and good applicability. [ABSTRACT FROM AUTHOR]

Some induction motors present saliencies that periodically modify the air-gap flux following a sinusoidal shape. Consequently, these modulations are reflected in the transient leakage inductance. Therefore, transient leakage inductance can be expressed as a constant term or offset, which comes from the symmetrical machine, plus all motor saliency sinusoids, modulated by the mentioned saliencies. Since saliencies are linked to the rotor position or flux, calculation of transient leakage inductance enables encoderless vector control. A way to calculate transient leakage inductance is to excite the machine with voltage steps and estimate the resulting phase current slopes since they are inversely proportional to phase transient inductance. For creating a vector, only the three current slopes resulting from a single active state are sufficient. The vector sum of the three current slopes leads to the so-called saliency-offset vector, which is a vector composed of an offset, which is created due to the contribution of the transient inductance offset, plus several saliency phasors, superposed to the offset. To access saliencies, it is critical to accurately identify the offset of the saliency-offset vector, especially in induction motors since offset is much bigger than saliencies. This article presents an advanced signal processing scheme that identifies the offset in the saliency-offset vector, assuming offset amplitude differsdepending on the voltage step applied. Using a feedforward scheme, the offset is eliminated, leading to a saliency vector where rotor slotting can be extracted from. A novel excitation is proposed to reduce additional current distortions coming from the one-active excitation. [ABSTRACT FROM AUTHOR]

Multiphase drives are the subject of great interest for the transportation electrification. Multi-three-phase machines are used with modular three-phase converters to obtain a redundant structure and their great advantage is the fault-tolerance capability. Starting from a symmetrical multi-three-phase machine, a reconfigurable architecture drive can be obtained. The main characteristic of a reconfigurable architecture is the ability to change the winding configuration to better match the operating point, specifically the machine speed. The main advantage of this architecture is the capability of reducing the number of active converters when the machine operates at low speed, thus reducing total converter power losses. However, system complexity increases, since reconfiguration cells are needed to interconnect the winding sets. The proposed reconfigurable multi-three-phase drive architecture exhibits two main benefits at low speed operation: increased efficiency and reduced phase current ripple for a given switching frequency. The reconfigurable architecture was assessed by means of analytical as well as numerical simulations, and the benefits obtainable at low speed operation were also demonstrated experimentally on a reduced scale prototype, capable of “on the fly” reconfiguration without stopping the machine. [ABSTRACT FROM AUTHOR]

In this article, two novel sinusoidal pulsewidth modulation (SPWM) strategies with simple implementation are proposed for an open-winding machine fed by isolated dc-bus dual two-level three-phase inverters to reduce switching frequency and current harmonics. The proposed strategies utilize zero sequence voltage injection and unbalanced reference voltage distribution to generate discontinuous PWM with low current harmonics and less switching action. Two different zero sequence voltages are introduced in this article corresponding to two proposed PWM strategies with different switching actions in a PWM cycle. The novelty of this article is low current harmonics and less switching actions in a PWM cycle compared with the conventional SPWM strategy. Moreover, compared with the subhexagonal center PWM strategy, the proposed SPWM strategies have advantages of easy implementation and half switching commutations with the same current harmonic characteristics. The superiority of the proposed SPWM strategies is validated by simulation and experiment results. [ABSTRACT FROM AUTHOR]

This articleproposes a new control scheme for extension of speed range of dual inverter fed induction motor drives with open-end stator windings. One of the inverters connected to one end of the stator windings is fed by a dc power source whereas the inverter connected to the other end of the windings is fed by a capacitor. The control scheme ensures that only active power required by the drive is supplied by the inverter fed by dc power source and the reactive power alone is provided by the capacitor fed inverter. The modulation index of the capacitor fed inverter is varied to provide higher voltage to the motor at higher speeds keeping the capacitor voltage constant, thereby facilitating operation above base speed without field weakening. An alternative scheme in which the capacitor voltage is allowed to vary while keeping the modulation index of the capacitor fed inverter at its maximum value is also presented in this article. The proposed schemes, based on constant v/f ratio control, are simple compared to the existing schemes. Validation of the proposed schemes is carried out under transient and steady state operating conditions by extensive simulation using PLECS software. Experimental verification is also carried out on a laboratory prototype using a digital signal controller for implementation of the control scheme. [ABSTRACT FROM AUTHOR]