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Laser-induced graphene (LIG) is as a promising material for flexible microsupercapacitors (MSCs) due to its simple and cost-effective processing. However, LIG-MSC research and production has been centered on non-sustainable polymeric substrates, such as polyimide. In this work, it is presented a cost-effective, reproducible, and robust approach for the preparation of LIG structures via a one-step laser direct writing on chromatography paper. The developed strategy relies on soaking the paper in a 0.1 M sodium tetraborate solution (borax) prior to the laser processing. Borax acts as a fire-retardant agent, thus allowing the laser processing of sensitive substrates that other way would be easily destroyed under the high-energy beam. LIG on paper exhibiting low sheet resistance (30 Ω sq−1) and improved electrode/electrolyte interface was obtained by the proposed method. When used as microsupercapacitor electrodes, this laser-induced graphene resulted in specific capacitances of 4.6 mF cm−2 (0.015 mA cm−2). Furthermore, the devices exhibit excellent cycling stability (> 10,000 cycles at 0.5 mA cm−2) and good mechanical properties. By connecting the devices in series and parallel, it was also possible to control the voltage and energy delivered by the system. Thus, paper-based LIG-MSC can be used as energy storage devices for flexible, low-cost, and portable electronics. Additionally, due to their flexible design and architecture, they can be easily adapted to other circuits and applications with different power requirements. [ABSTRACT FROM AUTHOR]

The Buck converter is a commonly used voltage regulator (VR) structure that supplies power to the load devices and responds to load transients. In most of the applications, the VR is controlled by voltage or current mode control, and some nonlinear approaches are used to improve the transient response which brings more complexities to the closed loop design. To achieve a fast transient response without over-regulation under a load step transient, this paper proposes a digital single-cycle regulation (SCCR) controller, which comprised a fast path, a slow path, and a neutralization path. Unlike the conventional PID control, the neutralization path of the SCCR controller is used to offset the excessive energy change in the first cycle after a load step occurs, which makes the inductor current reach its new static condition in a shorter period of time. The mathematical model of the SCCR control is established in this paper and a scanning algorithm is proposed for the design of the compensator parameters. Experimental results are presented to verify the improvement of the transient response when compared to the conventional and nonlinear PID control, the recovery time is decreased by 64.3% and 43% for load step-up and step-down when compared with nonlinear PID control. [ABSTRACT FROM AUTHOR]

This paper aims to analyze the inrush load current and develop an inrush current suppressor circuit optimized for a low-voltage DC (LVDC) distribution network. The connection of a substantial input capacitor in the DC load can induce a surge current, leading to significant issues in the LVDC distribution network, such as DC bus voltage drop and potential system damage. To address this issue, this paper presents the design of a voltage control system for a triple-active-bridge (TAB) converter in the LVDC distribution network, evaluating the need for the inrush current suppressor circuit. Control stability during the occurrence of the inrush current is analyzed using the small-signal model of the TAB converter. In addition, this paper proposes an inrush current suppressor circuit, presenting a design methodology to achieve the desired current suppression performance. Experiments are conducted on a laboratory-scale LVDC distribution network utilizing a 4-kW prototype converter to validate the performance of the suggested inrush current suppressor. [ABSTRACT FROM AUTHOR]

The use of three-level converters with low switching frequency (SF) modulation is urgently needed for medium voltage high power applications. However, since it is not possible to frequently adjust the injected zero-sequence voltage and duty time of redundant vectors, the neutral point (NP) voltage problem of three-level converters becomes a tricky issue under low SFs. In this paper, an optimized low SF modulation with NP voltage control is proposed, which is based on half-wave symmetry selective harmonic elimination pulse width modulation. The proposed modulation specifically addresses the low-frequency NP voltage fluctuation of three-level converters, using the amplitude and phase of the 3n-order harmonics as degrees of freedoms (DOFs). In addition, it actively optimizes the control problem into constraint equations. By revealing the relationship between these new DOFs and low-frequency NP voltage fluctuation, and obtaining the optimum settings for the new DOFs, the newly established constraint equations can naturally suppress the low-frequency NP voltage fluctuation, without the need for real-time switching angle adjustments. It fits very well with the feature that switching angles can only be calculated offline and used via a table online. Experimental results show the validity and feasibility of the proposed modulation strategy. [ABSTRACT FROM AUTHOR]

A constant on-time variable frequency control (COTVFC) with feed-forward for a critical conduction mode (CRM) totem-pole power factor correction (PFC) converter is proposed in this paper. This control method only requires a single voltage loop, where the output is taken as the on-time of the main switches of the converter. The off-time of the main switches in different switching cycles is calculated by the voltage-second balance principle, which ensures that the converter always operates in the CRM. Feed-forward is introduced to improve the dynamic response of the converter. The control model is established and the transfer function from the on-time to the output is derived. On this basis, the control parameters of the voltage loop are designed. Then a simulation model is built in PSIM for simulation verification. Finally, a two-phase interleaved parallel GaN-based totem-pole PFC converter prototype is made for experimental verification. Simulation and experimental results verify the feasibility and effectiveness of the control method proposed in this paper. [ABSTRACT FROM AUTHOR]

The sub-synchronous resonance (SSR) characteristics and countermeasures of grid-forming permanent magnet synchronous generators (PMSGs) controlled by DC voltage synchronization control (DVSC) are investigated in this paper. First, small-signal models of two PMSGs connected to a series-compensated network are established, where a recently developed grid-forming control, i.e., DVSC is applied. Then, a modal-analysis method is conducted to evaluate the impacts of the control parameters, series compensation level (SCL), and electrical distances on stability. It is interesting to see that PMSGs with DVSC exhibit unstable SSR like traditional synchronous generators. Moreover, the dominant wind turbine (WT) is investigated using participate factor analysis. Then, a simple but effective SSR damping controller (SSRDC) is designed using feedforward control signals, which is only activated when SSR occurs. It is shown that the designed controller can provide strong damping support for SSR suppression. Electromagnetic transient simulations are performed in different scenarios to find the unstable SSR conditions, as well as to verify the correctness of the SSR analysis and the effectiveness of the proposed SSR damping scheme. [ABSTRACT FROM AUTHOR]

The stability and dynamic performance of the system are impacted by the uncertainties present in the converter model and controller parameters. This paper introduces a robust non-fragile control approach that addresses the influence of these uncertainties. The approach involves developing a control law that achieves quadratic stabilization of the closed-loop system while also satisfying the H∞ norm constraint for disturbance attenuation. Based on this concept, a robust non-fragile PI controller is designed explicitly for voltage mode control of a dc–dc buck converter. The effectiveness of the proposed control technique is evaluated from two perspectives: (i) its ability to withstand significant perturbations in plant parameters and load disturbances and (ii) its resilience in the presence of variations in controller parameters. The effectiveness of the proposed control scheme is validated using simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, taking into account the unidirectional conduction property of diodes, with an emphasis on the enhancement of system tolerance and robustness, a modified passivity-based control (PBC) method is introduced to three-phase cascaded unidirectional multilevel converters. This is the first time the PBC method has been utilized in cascaded unidirectional multilevel converters. This paper applies the PBC method to the current control loop and the overall DC bus voltage control loop. Meanwhile, considering that the classical PBC method regulates DC voltage with a steady-state error, the overall DC bus voltage is regulated via a combination of the PBC method and a PI controller to ensure zero-voltage tracking error. Moreover, the tolerance and robustness of the modified PBC method are verified by a theoretical analysis. Simulation results are furnished for assessing the correctness of the theoretical analysis, and the performance of the modified PBC method for three-phase cascaded unidirectional multilevel converters. [ABSTRACT FROM AUTHOR]

Predictive control systems can significantly reduce the cost of setting up and developing converters. Currently, existing methods for implementing control systems have shown their effectiveness. However, some problems, such as ease of design and configuration of the device, and resistance to changes in load parameters, still require searching for new approaches to implement predictive control systems. This paper presents a new method for modifying the predictive control system model for DC-DC boost converters. The developed control system, in addition to the function of maintaining the required level of output voltage, optimizes the operation of the device to achieve maximum efficiency. It is shown that the output voltage level is regulated by changing the duty cycle of the control signal; and the efficiency of the device, by changing the operating period. It is established that a modified system for calculating the objective function allows using a sufficiently large planning horizon due to the reduction in the required computing power. The presented simulation results demonstrate the advantages of the proposed control method, including a fast transient response and a high degree of robustness. [ABSTRACT FROM AUTHOR]

In this paper, an impulsive control algorithm with time-delay is proposed to alleviate the issue of interrelated state variables and the adverse effect of input voltage or load perturbations on output in the highly nonlinearity of the DC converter. The impulsive control is introduced concerning the state information of the control system, while the stability criterion is established by employing the average dwell time. The control principle similarity of the delayed impulsive effect and the spiking neural network are elucidated. Unlike the already existing control methods, such as proportional–integral (PI) control and sliding mode (SM) control, we leverage the state information of the switching state drive system in recent history at every sampling moment to conduct impulsive control with accurate and swift error feedback. Three typical controls are executed on the output load and source voltage operating point, characterizing the advantages superior to the PI and SM control algorithms. Hence, the proposed algorithm outperforms others in system performance indicators such as output voltage step-up, step-down, settling time and ripple. In terms of the variation of source voltage and irradiance in the photovoltaic system, the verification of voltage control stability is given in the case of the maximum power point module of the photovoltaic system, exhibiting minor output voltage ripple and shorter transient change time. [ABSTRACT FROM AUTHOR]

Multistage inverters containing DC-DC converters are more common in grid-tied photovoltaic (PV) systems, because of the low DC voltage value provided by the PV generator, which requires a two-stage topology. The challenge in the latter case is to control the DC-link voltage with an accurate estimation of the current injected into the grid by PV system. In this paper, a two-stage grid-tied PV design based on a high-gain DC-DC converter and a 7 level packed U cells (7L-PUC) inverter, controlled by Finite-Control-Set Model Predictive Control (FCS-MPC) is presented, with the proposal of a novel model for controlling the DC-link voltage by considering system losses. The simulation and experimental results demonstrate the high effectiveness of the proposed control strategy in terms of power quality as well as response time and accuracy under changes in weather conditions and demonstrate the feasibility of the proposed system. [ABSTRACT FROM AUTHOR]

The closed-loop control of coupled inductor-based high-step-up-gain boost converter in continuous conduction mode has non-minimum phase behavior due to right-half-plane (RHP) zero. The crossover frequency of the closed loop should be designed to be less than RHP zero for stable converter operation. Hence, the converter has lower bandwidth (BW) and a poor dynamic response. Combining the interleaving technique with coupled inductor boost converter (CIBC) can improve the dynamic response. As the number of interleaved phases at the input side of CIBC increases, RHP zero moves toward higher frequency. Thus, it improves the closed-loop BW. In addition, it is simple and easy to design closed loop of interleaved coupled inductor boost converter (ICIBC). Moreover, an interleaved operation reduces the size of inductance required for the same ripple in input current and reduces voltage dip during a step change in load. This paper presents a small-signal model of a multi-phase ICIBC to verify the claim. The laboratory prototype of CIBC and three-phase ICIBC is implemented to boost 24 V to 100 V at power level of 300 W. The experimental results of CIBC and three-phase ICIBC are obtained for a change in load from 150 to 300 W to validate results of small-signal model. A single-loop voltage mode control with Type II controller is implemented to regulate output voltage and to achieve desired dynamic performance of three-phase ICIBC for a load disturbance. [ABSTRACT FROM AUTHOR]

The concept of bipolar DC distribution has been shown to possess superior flexibility, efficiency, and quality when compared to the conventional unipolar approach. However, the control dynamics of the power conversion circuit for bipolar DC distribution are typically limited by the presence of DC-side capacitors. To enhance the stability and the reliability of DC power distribution systems, it is essential to ensure stable responses to both load dynamic characteristics and DC faults. This paper proposes a bipolar configuration and control strategy to improve the DC-link response characteristics of DC distribution systems. The proposed circuit utilizes a zig-zag transformer to enhance the DC voltage control dynamics of the converter. The zero-sequence impedance along the common mode path of the converter is effectively reduced by the zig-zag transformer, with an impedance range equivalent to the leakage components of the transformer. The converter of the bipolar structure can independently control the voltages of each DC pole, which enables faster dynamic responses of the voltage controls. Additionally, this structure facilitates the handling of asymmetric loads on each pole. The validity and the operation of the proposed configuration are verified through simulations and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, harmonic compensated individual-phase voltage control of four-leg inverters is proposed for microgrid applications. Individual-phase control, which is one of the promising voltage control methods of four-leg inverters, ensures robustness for high load unbalance rates. However, the odd harmonics generated by nonlinear loads and dead time deteriorate the quality of load voltages under single-phase control. The proposed method compensates for the odd harmonics included in the load voltages to improve the output power quality. In the proposed method, band-pass and all-pass filters are used to generate the virtual components for the individual-phase control. Additionally, the harmonics are compensated in the synchronous reference frame using a resonant controller, while the fundamental components are controlled by proportional-integral controllers. With the proposed method, the total harmonic distortion of the load voltages is maintained at a low level under unbalanced and nonlinear load conditions. The effectiveness of the proposed method is demonstrated through simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this paper, the application and design of a high-power factor isolated Ćuk converter-based LED driver are realized for up to 50 W power. For the power switch of the PFC isolated Ćuk converter, traditional Si and silicon carbide (SiC) MOSFETs, which are wide bandgap semiconductors, are used and compared. The application is conducted using a dsPIC30F4011 microcontroller including PI voltage control. A current sensor is added to limit maximum current. Moreover, PI control parameters are selected by genetic algorithm to avoid a complex mathematical procedure for controller design. The power LED model derived in this paper is used for the PI parameter selection process. In addition, the input side inductor of the converter is operated in discontinuous conduction mode, and the switching frequency of the power switch is 57 kHz. With the experimental setup, the total harmonic distortion (THD) of grid voltage and current, power LED voltage and current, switch voltage, and input side inductor current are shown for both the SiC and Si MOSFETs and compared. It is concluded from the application that the SiC-based driver gives better results than the Si-based driver on the basis of THD and efficiency. Further, both applications provide limits of IEC61000-3-2 C class standard. [ABSTRACT FROM AUTHOR]

A modified conceptual structure of MUPFC for controlling the voltage sags in interconnected power systems is presented in this paper. For this purpose, the conventional UPFC is distributed through several series and one shunt converters. By this way, the higher frequency components are removed which only the 3th-order is remained. Also, by using single-phase series converters, better dynamic performances with proper reliability are provided. So, there are more redundancy possibilities through different operating conditions. The proposed single-phase series converters are floated from the ground which there is not required high-voltage protections equipment through transmission lines resulted in lower initial and operational costs compared to conventional UPFCs. Real-time ability of the proposed scheme is investigated through a 3-phase transmission line stressed by fault events in which by distributing the series converters through the line, the ability of MUPFC through time domain simulations is evaluated. Results present proper performances of the proposed controller scheme for voltage sags fast restoration with high damping ratio. [ABSTRACT FROM AUTHOR]

In this paper, a novel active damping technique is proposed that can be applied in AC power converters with LCL filters. Active damping is performed in the discrete domain based on a single measurement of the output LCL filter current. The parameter tuning procedure, which is based on pole-placement, is applied in a new active damping structure. This simplifies the design of the cascaded control loop, which is superimposed onto the inner loop with the active damping, which results in improved controller dynamics and robustness. The proposed active damping method is applied with the cascaded-output current controller main loop of an AC power converter with a resonant LCL filter. The dynamic performance and robustness of the novel active damping method are analyzed through a series of simulation and experimental tests. Simulation and experimental results show that proposed active damping technique enables successful and effective decoupling of the local active damping and the main control loop design. [ABSTRACT FROM AUTHOR]

This paper proposes a modified structure and its control method for a hybrid modular multilevel converter (MMC)-based photovoltaic (PV)–battery energy storage system (BESS). The modified structure consists of PV arrays that are directly connected with sub-modules SMs, and batteries that are interfaced with the DC port of the SMs using a DC/DC converter. The control strategy implements an independent maximum power point tracking (MPPT) control for each of the PV arrays by individual SM voltage control for variable conditions. Embedded BESSs work as power and voltage compensators for the arms, and they are able to eliminate the weakness of the PV plant such as power mismatching and unsmooth power under variable illumination and partial shading. This is accomplished by average arm power control and moving average filter for the BESSs in each arm. Moreover, due to the contribution of the BESSs, it offers a lower total harmonic distortion (THD) under variable working conditions. The effectiveness and robustness of the method are verified by simulation results, which were obtained by conducting time-domain simulations in PSCAD/EMTDC under variable conditions. [ABSTRACT FROM AUTHOR]

As a vital component of power electronic transformers (PET), the reliability of a cascaded H-bridge rectifier (CHBR) is essential. Therefore, in this paper, a DC-port voltage balance strategy considering DC-port failure is researched to ensure the stable operation of a CHBR. However, if the DC-port voltage balance strategy is adopted to realize the single-phase balance of a CHBR, the three-phase currents become unbalanced. This paper uses a negative sequence control (NSC) strategy that is conducive to balancing DC-port voltage to achieve three-phase current balance. For the DC-port voltage balance, the matrix generation modulation (MGM) algorithm is proposed. In addition, the DC-port voltage balance boundary is analyzed to determine the range of the DC-port voltage balance in the CHBR. A 3-module cascading topology is adopted to demonstrate the MGM algorithm and the NSC strategy. Through experiments, results show the correctness and feasibility of the proposed strategy. [ABSTRACT FROM AUTHOR]

Hybrid ac/dc microgrid (HMG) comprises ac and dc microgrids (MGs) interconnected through an interlinking converter (IC). In islanded operation mode of HMG, a coordinated control structure must be implemented to realize voltage and frequency control in ac MG, voltage control in dc MG, active and reactive power sharing among ac sources, active power sharing among dc sources, global active power sharing among dc and ac sources, and reactive power sharing among ac sources and IC. To realize these objectives, a new coordinated control based on master–slave approach is proposed in this paper. In this method, the master source of each MG broadcasts its relative power loading as a common signal to the slave sources of the same MG and IC through a unidirectional low-bandwidth communication network. Based on this information, the slave sources and the IC adjust their operating point. The proposed method provides accurate power sharing as well as zero voltage and frequency deviation. It does not require a centralized control unit and features plug and play capability. The derivation of the proposed method is thoroughly discussed in this paper. Time domain simulation results based on CIGRE benchmark MG are presented to validate the proposed control strategy. [ABSTRACT FROM AUTHOR]

The three-phase cascaded H-bridge rectifier (CHBR) is widely used in high power and high voltage applications. This paper focuses on the load removed from the DC port of a three-phase CHBR, which can cause single-phase DC-port voltage unbalance issues and three-phases DC-port voltage unbalance issues. This paper proposes a voltage balance control strategy based on negative sequence current injection for three-phase CHBR to deal with the unbalance problem. An individual DC-port voltage control strategy is designed to balance the DC-port voltage in the faulty phase. In addition, a negative sequence current injection control strategy is responsible for balancing the DC-port voltages in the three phase CHBR. The effectiveness and feasibility of the proposed voltage control strategy based on negative sequence current injection is verified by the experimental results. [ABSTRACT FROM AUTHOR]

A high gain two-phase interleaved coupled inductor-based DC-DC converter step-up low input voltage sources like PV array and fuel cell in distribution generation system (DGS). The converter operates for a wide range of load changes when it is part of DGS. At light load, the converter operates in discontinuous conduction mode (DCM). A small-signal model (SSM) is required in both continuous conduction mode (CCM) and DCM to know the complete dynamic behavior of the converter. Steady-state and small-signal analysis of the two-phase interleaved coupled inductor boost converter (ICIBC) is quite complex when the converter operates in DCM. This paper presents the complete derivation of SSM of a two-phase ICIBC-based high step-up gain converter in DCM. The conditions of the converter operating in DCM are discussed. The small-signal model of two-phase ICIBC is derived using the state-space averaging method. The control-to-output voltage transfer function and steady-state voltage gain of the two-phase ICIBC are derived. When the converter operates in DCM, it eliminates the right half plane zero from the control-to-output voltage transfer function. Thus, it improves bandwidth and stability margin. Thus, single loop voltage control is sufficient to achieve regulated output voltage with faster response for all operating ranges of DCM. The laboratory prototype of two-phase ICIBC is implemented to step-up 24 V to 100 V at a power level of 300 W. The experimental results of two-phase ICIBC are obtained in DCM and CCM with step-change in load to validate the derived small-signal model. [ABSTRACT FROM AUTHOR]

The ancillary services are becoming more important due to the increasing integration of non-dispatchable and intermittent renewable energy sources. Such behavior under deregulation necessitates the procurement of these services suitably. This paper presents the multi-objective procurement of voltage control ancillary service in a dynamic pool deregulated system that is contingent to wind and solar power generation uncertainties. The shunt capacitors bid to supply this service and their switchings, although restricted due to life expectancy, depend on locational marginal prices. An improved multi-objective artificial electric field algorithm, which adopts the concept of Pareto-based non-dominated sorting, is presented to co-optimize total cost and voltage deviation. The particle's positions are updated through randomly picked Pareto solution to enhance exploitation capability. The sign and reorder mutation operations are employed to maintain diversity in the population, improve exploration, and evade local optima trap. The performance is investigated for different levels of wind and solar penetration on IEEE 30-bus and IEEE 118-bus test systems. The convergence of presented algorithm is analyzed and compared with other algorithms through statistical metrics and associated boxplots. [ABSTRACT FROM AUTHOR]

This paper proposes a high precision harmonic controller combined with repetitive and modulated model predictive controllers for standalone inverter applications. The proposed method is configured as a dual loop controller that includes an outer voltage controller with a plug-in repetitive controller (RC) and an inner current controller with a modulated model predictive controller (MMPC). The RC in the outer control loop effectively synthesizes the harmonic current reference when connecting a nonlinear load with a periodic harmonic current. Then, the MMPC-based current controller, with its ultra-wide bandwidth, regulates the harmonic current without additional harmonic current controllers. Thus, the abilities to precisely control the harmonic current and improve the output voltage quality are achieved. To combine the MMPC and the repetitive controller, an equivalent transfer function is derived from the ac sweep result of the MMPC. The stability of the RC is analyzed by applying the equivalent transfer function to the closed-loop voltage control model. To validate the performance of the proposed control method, a 3 kVA single phase 3-level T-type inverter prototype is built and tested. The harmonic compensation and dynamic performance of the proposed method are verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes the proportional integral (PI) backpropagation neural network (BPNN) algorithm to improve the transient voltage control performance in an LLC resonant converter whose voltage gain is highly nonlinear. In the proposed method, the PI linear controller roughly regulates the operating frequency of the LLC converter according to the voltage gain. Moreover, the BPNN nonlinear controller compensates for the frequency in the transient and steady states. It also improves the dynamics. Compared with traditional artificial neural network algorithms, the proposed BPNN can reduce the computational burden of the digital controller and improve the accuracy of the time-series prediction by reflecting previously predicted results in the learning process. Hence, the proposed method is suitable for real-time applications, such as power electronic converters. The structure and the learning procedure of the proposed PI-BPNN controller are explained in detail, together with the modeling and the control scheme of the LLC converter. A 5.5 kW LLC converter prototype is built and tested to verify the performance of the proposed method. The load step experimental results show that compared with the traditional PI control algorithm, the proposed PI-BPNN reduces the transient response time by up to 25%. [ABSTRACT FROM AUTHOR]

Flexible direct current (DC) grids face a serious challenge in terms of rapidly isolating DC faults. A DC circuit breaker is an effective solution for DC fault isolation. To improve the fault-isolation and reclosing capability of flexible DC systems, a new high voltage direct current (HVDC) circuit breaker topology with adaptive reclosing capability is proposed in this paper. The topology of the circuit breaker is a T-shaped structure, which has the ability to break the current in both directions and effectively reduce the cost of components. Meanwhile, after the fault is cleared, the circuit breaker is controlled to inject a voltage signal into the line. Based on this, to prevent the circuit breaker reclosing in the event of a permanent fault from having an impact on the system, a method for fault identification based on Euclidean distance that uses the voltage signal to identify the fault properties is proposed. Finally, the performance of the circuit breaker is simulated and verified by PSCAD/EMTDC simulation software, and compared with the typical existing circuit breakers to verify the effectiveness of the circuit breaker and reclosing scheme. [ABSTRACT FROM AUTHOR]

In order to meet global energy efficiency and environmental objectives, production costs of these key devices, and other similar, must be reduced. Back-to-back VSC systems are essential for wind power generation and industrial machine drivers. Sensor elimination is a viable path to achieve such goal, as long as the control is adequate and does not impair the main converter functions. This paper presents the results of an academic-industrial research work aiming at a new control technique capable of reducing the number of sensors from 13 to only 6, using a single PID feedback loop for each VSC based on the monitoring the DC-link power. This leads to an easy-to-implement control scheme which preserves all functions required by AC/DC/AC conversion systems, such as DC voltage control, active power flow, and reactive power generation in each AC port. The results obtained demonstrate the suitable performance and advantages of this timely proposed technique for medium-power Back-to-Back VSC systems. Finally, four cases of study are fully discussed and supported by simulation and experimentation through a laboratory prototype. [ABSTRACT FROM AUTHOR]

This paper presents the parameter design of a new topology of hybrid active power filter (HAPF), which makes the system capacity smaller. Based on the main topological circuit, the passive LC single-tuned circuit shunted into the HAPF effectively reduces the capacity of the system. By introducing the grid voltage feedforward method, the DC-side voltage control becomes relatively stable, and the fundamental reactive current flowing through the converter is effectively reduced. Meanwhile, to suppress the resonance of the HAPF, the state variable feedback method is adopted. According to theoretical analysis, a simulation model of the system is built in the MATLAB environment. Then a low-voltage experimental HAPF platform is built to validate the result of the simulations. [ABSTRACT FROM AUTHOR]

A predictive charge control method based on an LLC resonant converter is proposed in this paper. The input charge in each cycle is reflected in the change of the resonant capacitor voltage. The threshold is set to compare it with the resonant capacitor voltage to control the input charge. Based on an LLC discrete predictive model, the predictive charge control predicts the threshold of the resonant capacitor voltage to regulate the output voltage. When compared with existing control methods, the predictive charge control has the advantages of an intuitive concept, a strong robustness, a simple implementation, and a simple model. It has excellent dynamic performance under various working conditions. The resonant tank can enter the steady state within one cycle without affecting the steady-state performance of the system. Through a mode analysis, this paper analyzes the proposed predictive charge control in detail. A 500 W LLC resonant converter prototype is built to verify the proposed method. Results show that both the output voltage and the resonant tank return to the steady state without fluctuations in one cycle during the processes of input voltage change and load switching. [ABSTRACT FROM AUTHOR]

The capacity and equivalent switching frequency of parallel interleaved inverters can be increased, but there are problems with neutral point potential balance and parallel bridge circulating current. This paper regards the parallel three-level inverter as a five-level inverter and five-level space vector integrated modulation is applied. On this basis, a neutral-point potential control strategy based on the mid-point charge to calculate the adjustment factor k is proposed. By further meticulously partitioning specific sector regions, the selection method of redundant vectors in the switching sequence is optimized without increasing the switching times, and the midpoint voltage ripple is reduced. Then, the redundant state allocation in the process of splitting the five-level into three-level is used as a new degree of freedom to suppress the circulating current of the parallel bridge, therefore realizing the control of voltage and current sharing. Finally, simulation and experiments verify the correctness and effectiveness of the method. [ABSTRACT FROM AUTHOR]

According to the structure and characteristics of a three-phase cascaded H-bridge (CHB) of a high-power multilevel converter, the problem of DC side voltage imbalance in practical applications and the disadvantage where the complexity of the traditional centralized control voltage equalization scheme increases rapidly with an increase of the number of modules both need to be solved. In addition, with the characteristic that distributed control is conducive to the expansion of the system to high-power and multi-module cascade, a new quasi-distributed equalization control strategy is proposed in this paper. The new equalization control strategy combines the traditional closed-loop control with the modulation ratio correction method. On the basis of the traditional closed-loop control, an equalization control module is added to realize a balanced output of the DC side voltage. The control of the equalization control module is simple and flexible, and the complexity of the overall control algorithm is independent of the number of modules. Finally, the correctness and reliability of the control method are verified by experiments. [ABSTRACT FROM AUTHOR]

This paper proposes a new approach for evaluating distribution voltage regulators using quasi-static hardware-in-the-loop (HIL) simulation. Distribution voltage regulators are used to control the voltage using tap change transformers and are equipped with static control algorithms in order to accomplish different configurations of the distribution electric grid with typical load profiles. The growing penetration of renewable energy in electrical distribution systems is a great challenge for this equipment, and it becomes paramount that its measurement and control algorithms adapt to this new reality. Hardware-in-the-loop testing (HIL) techniques could be used for assessing the performance of the voltage regulator equipment. Most applications of HIL are concerned with accessing the dynamics of electrical system including not only grid modeling, but also the real equipment involved and should be used to test the efficiency of voltage regulation. However, a more simplified approach concerning the HIL tool could be applied to testing distribution voltage regulators in the laboratory prior to installation, evaluating the performance of algorithms and equipment by conducting quasi-static simulations. This paper presents this approach, joining NI LABVIEW laboratory controller software (National Instruments, LabVIEW. Available at https://www.ni.com/pt-br/support/downloads/software-products/download.labview.html#460283, 2023) and an open-source program OpenDSS (The Electric Power Institute, OpenDSS. Available at em https://opendds.org/, 2023). The effectiveness of quasi-static HIL platforms for assessing several aspects of static voltage tap regulators before installing them in the electric grid is demonstrated. The major advantage is the smaller computation complexity of a static simulations compared to dynamic simulators, allowing simpler hardware requirements. In this sense, a large number of medium to long term simulations could be easily performed providing a broader view of the behavior of the electric system including voltage regulators. [ABSTRACT FROM AUTHOR]

The uncertainty of solar generation is a challenging issue for the operation and control of distribution systems. Also, because of the large number of control and operation variables in advanced distribution networks, the centralized optimization technique requires high computational capabilities. In this paper, a distributed voltage regulation approach in a distribution system based on the predictor corrector proximal multiplier (PCPM) algorithm has been presented. This paper focuses on the voltage rise in distribution systems with high penetration of photovoltaics. The proposed method uses a clustering approach to divide the network into partitions based on the coupling degrees among different nodes. The optimal reactive power control strategy is conducted in each partition and integrated using PCPM. The proposed method is tested on 69 and 123 nodes IEEE distribution test systems. The results confirmed that the proposed method achieves the optimal solution with the same accuracy as the centralized method but in a much shorter computation time. [ABSTRACT FROM AUTHOR]

This paper presents a delay-locked loop (DLL) with multiple radiation-hardened techniques. A radiation-hardened charge pump (RH-CP) and a radiation-hardened voltage-controlled delay line (RH-VCDL) are proposed to mitigate effects on DLLs caused by single-event transient (SET). A lock detection module (LDM) is designed in the RH-CP to separate CP and VCDL when the DLL is locked. Thanks to LDM, the voltage transients caused by ion strikes on CP can be prevented from effecting the control voltage of VCDL and causing inverted lock error. A SET correction module (SCM) combined with sliced delay cells is used in the RH-VCDL to select the uncorrupted output and avoid missing pulses errors occurring at the output of DLL. The proposed DLL is designed in 22-nm CMOS process with an operation frequency of 5 GHz. Simulations at linear energy transfer (LET) between 40 and 100 MeV-cm2/mg show that RH-CP eliminates inverted lock error and RH-VCDL mitigates missing pulses generated by the DLL after ion strikes effectively. [ABSTRACT FROM AUTHOR]

Predictive type control systems are promising, as they can significantly reduce the cost of setting up converters. However, this still leaves the problem of controlling DC-DC converters unsolved. This paper presents a modified model of a predictive control system (MPCS) for DC-DC boost converters. For its implementation, a nonlinear model of the converter with discrete time switching, describing the continuous mode of operation, is proposed. The controller is synthesized by formulating the target function, which should be minimized taking into account the dynamic model of the converter. The proposed modified MPCS, used as a voltage control system, allows us to keep the output voltage at the reference level. The optimized method for calculating the target function makes it possible to significantly reduce the required computing power and expand the forecasting horizon. The presented simulation results show the advantages of the modified MPCS: a fast transient response and robustness. [ABSTRACT FROM AUTHOR]

This paper presents a fuzzy control system to automate the operation of capacitor banks installed in a transmission substation. This automation intends to standardize operation and control voltage at the substation output bus. The system was implemented and tested with real data from a 345/138 kV transmission substation. The results obtained through the simulations are compared with the manual commands executed by the technicians from an operation center in Brazil. The outcomes showed the effectiveness of the proposed system to maintain the bar voltage considering the current load regime. In addition, the capacitor banks' operations numbers were reduced and standardized. [ABSTRACT FROM AUTHOR]

In this paper, the dynamic stability of the power systems is improved through the rotor side convertor voltage control of a number of doubly fed induction generators (DFIGs). The multi-input backstepping method is used to design the control laws. Using the particle swarm optimization algorithm, the proposed control parameters are optimized to achieve a better performance. This optimal control law leads to a significantly improved performance in comparison with linear control methods such as state feedback control which implement optimized pole placement by linear matrix inequality design. The offered method results in a faster convergence rate and also robustness against changes in the operating points. The performance of the presented control scheme is validated in a standard 9-bus IEEE power system, with a DFIG located in bus number 9. [ABSTRACT FROM AUTHOR]

Renewable energy-based power systems, despite their numerous advantages, can lead to problems such as frequency fluctuations, voltage drops, and unstable power outputs. This paper suggests a control method for a doubly-fed induction generator (DFIG), equipped with battery energy storage system (BESS) to frequency, voltage control, and improve the fault-tolerant ability. In the proposed strategy, the main purpose is to provide a method for decoupled control of voltage and frequency of the rotor before injected into the network as well as to improve network stability in the presence of stabilizers and BESS. The proposed control strategy is applied to BESS and the rotor side of the converter of DFIG. In this strategy, each loop controller used a conventional PI controller with additional stabilizers to damp out the oscillations of frequency and voltage. In such a way, under various disturbances condition, system in the presence of a BESS has a fast response with fewer range of oscillation. Finally, parameters of the controllers and stabilizers are adjusted simultaneously by an intelligent algorithm. All the results are obtained by simulation in real-time condition with Simulink of MATLAB 2016b. [ABSTRACT FROM AUTHOR]

The unpredictable variations in the wind speed consistently require a significant endeavor to enhance the control performance of the wind power conversion system (WPCS). This paper aims to evaluate the performance of a permanent magnet generator-based WPCS making use of the vector control schemes where, the internal loop employs hysteresis current controller and the external loop employs proportional-integral (PI) controller. In order to devise a control system with most favorable closed-loop poles meant for desired control performance, the parameters of the PI controllers involved in the external speed and DC link voltage control loops have been designed incorporating explicit damping specification via pole-placement. The offline simulation results have been produced in MATLAB environment using Simulink to demonstrate the effectiveness of the proposed PI controller design. The offline simulation results are then validated through Typhoon HIL402 real-time hardware simulator. It has been verified that the vector control schemes incorporating the PI controller parameters as designed herein allows the WPCS to operate stably with desired control performance while extracting the peak power continually even under rapidly changing wind speeds. [ABSTRACT FROM AUTHOR]

A novel method for controlling the output DC link voltage of a single-phase power factor correction (PFC) converter without using a DC voltage sensor for electric vehicle (EV) charging is proposed in this paper. The conventional boost PFC converter normally uses three expensive sensors, i.e., at the input voltage, the input current, and the output voltage. These sensors are used to regulate the power quality and maintain system stability. To reduce the cost and hardware complexity in the power converter, a DC voltage sensorless control using an estimator is proposed. This method utilizes the available input voltage and current signals to predict the output DC link voltage. This predicted output voltage contains an average DC component superimposed with a small ripple content at double the line frequency (2f). The proposed control method tracks the reference sinewave signal to maintain a high-power factor. The converter also exhibits very stable behavior under transient load variations. Simulated and experimental validation results obtained with a 1 kW prototype PFC converter are included. [ABSTRACT FROM AUTHOR]

This paper proposed two PWM control scheme which is the Voltage Oriented Control (VOC) and Direct Power Control (DPC) on a heavy loaded LV-distribution network with photovoltaic (PV) integration in Malaysia. The surge in demand of power supply is overcome by deploying more PV to fulfil the load demand. However, this could give rise to power quality issues that can affect the stability of the grid. The focus in this work is to solve voltage dynamic concern which results in over and undervoltage problems within the distribution network and at the same time to evaluate on the performance of both control schemes under a heavy loaded condition. A 33 kV Malaysian LV-Distribution model integrated with PV is constructed to serve as a base model in this paper. From the base model, a load flow analysis is conducted in order to locate the weakest bus. The two proposed control schemes are introduced into the weakest bus in the grid system, and its performance of the controller will be evaluated based on three aspects such as compensation margin, voltage and current total harmonics distortion (vTHD and iTHD) and lastly the compensated voltage levels. It is shown that VOC control scheme has outperformed DPC due to a wider compensation margin and its ability to achieve the desired reference voltage with a faster settling time under heavy loaded condition. Therefore, the proposed PWM control scheme of both VOC and DPC under a heavy load scenario could be set as a benchmark to provide impactful insights and findings towards an actual implementation of the application within a distribution network or distributed generation. [ABSTRACT FROM AUTHOR]

To solve the problem of parameter mismatch in model predictive control (MPC), this paper presents a robust model predictive control method based on a fixed window optimization (FWO) algorithm for a three-level voltage source inverter that only needs to sample the current value. When compared with the traditional observer-based model predictive control (such as the Luenberger observer, sliding mode observer (SMO) and Kalman filter (KMF)), the proposed method does not require an observer with a complicated design, and its algorithm is simple and easy to understand. Meanwhile, high current sampling accuracy is not needed in the proposed method. However, it is necessary in some types of model-free predictive control. In addition, low switching frequency operation and delay compensation are also considered in this paper. In general, the proposed method is simple to implement and does not have high requirements in terms of the accuracy of its current sensor. Experimental results show that the proposed method can accurately estimate parameter values and improve the parameter robustness of MPC. [ABSTRACT FROM AUTHOR]

A novel pulse width modulation (PWM) overmodulation technique based on splitting variable modulating waveform is proposed in this paper. It aims to solve the disadvantages of complex and difficult application of the existing space vector pulse width modulation (SVPWM) overmodulation algorithm and offer a simpler implementation for overmodulation than classic SVPWM techniques. When the modulation index M is within the linear modulation range [0, 1], the modulating waveform is a sinusoidal wave. With the M is increasing within [1, 4/π], the modulating waveform area expands continuously until it becomes a square wave. The PWM output voltage of the vector control system is implemented by using triangle carrier-based sampling pulse width modulation. Furthermore, digital low-pass filters are used in the d-axis current and q-axis voltage of the system, in order to eliminate the negative influence of the PWM low-order harmonics on the proportion integration control in the overmodulation range. The control software is modified and improved to overcome the shortage of slow response speed. The basic logic of the software is to close the filtering process once the load or speed instructions changes and turn on the filtering process when the transient process ends. The contradiction between the filtering and dynamic responses is thus eliminated by using the basic logic. Compared with the SVPWM working in linear region, the constant torque speed regulating range of the AC motor has an improvement of 10% based on the proposed technique. Simulated and experimental results indicate the good effectiveness and feasibility of this technique. [ABSTRACT FROM AUTHOR]

A novel state estimation methodology is proposed in this paper for microgrids monitoring using synchronized and non-synchronized measurements. A Kalman filter model is proposed to track both system states and frequency along the time considering the measurements gathered from the grid by PMUs and smart meters allocated in the system. An augmented measurement Jacobian matrix is formed considering system states and frequency as variables to be estimated along the time. Distributed generation is connected to the grid by voltage source inverters (VSI) considering frequency and voltage droop control characteristics. A radial 18-bus test system is used for the computational simulations in order to prove the efficiency of the proposed methodology. The algorithm is tested considering microgrid in grid-connected and islanded operation modes providing satisfactory results with reduced estimation errors when compared to the RSCAD (Real-Time Simulation Software Package) software. The main contributions of this work include: (i) the explicit model of frequency and voltage droop control of VSI in a Kalman filter model; (ii) the capability of tracking microgrids frequency and system states along the time; (iii) the explicit model of derivatives of phasor measurement units and smart meters measurements with respect to the system states and frequency. [ABSTRACT FROM AUTHOR]

In this paper, a high efficiency implementation of constant voltage (CV) control of wireless charging system with LC/S compensation is proposed for stationary electrical vehicles. The LC/S compensation network is designed based on constant current (CC) design procedure with zero phase angle (ZPA). In the receiver side, semi-bridgeless rectifier (SBR) and pulse density modulation (PDM) control are both implemented to provide CV output without wireless communication devices. With the use of SBR topology and the implementation of the PDM control strategy for SBR switches, the soft-switching operation of SBR switches is also provided. Thus, the efficiency of the CV control mode is improved in a wide range of load. The experimental results of a 1.05 kW prototype are provided to demonstrate the effectiveness of the proposed system. The peak efficiency of the system is obtained 91.9% at full load condition. In experiment, the performance comparison of PDM control with phase-shift (PS) control method is also carried out for the proposed wireless charging system. The overall efficiency of the system with PDM control is significantly improved compared to PS control at light load conditions. [ABSTRACT FROM AUTHOR]

The min-projection strategy (MPS) is a switching rule with better convergence speed, which can improve the dynamic characteristics of three-phase grid-connected inverters. However, the grid-connected current harmonics of the system are large when the MPS is used directly in the digital control framework due to the limitations of the sampling frequency. To solve this problem, an improved min-projection strategy is proposed in this paper by introducing a zero voltage vector to the control. First, the non-zero voltage vector is selected through the switching law function of the MPS. Then the time occupied by the non-zero voltage vector and the zero voltage vector can be obtained through an error function, which is established by the principle of minimum current error. Finally, the switching signal can be obtained for control, based on the method of duty cycle modulation. This method can realize fast current tracking and current decoupling control, reduce the grid-connected current harmonics, and improve the steady state performance of the system without increasing costs. The effectiveness of the proposed method is verified by simulations and experimental results. [ABSTRACT FROM AUTHOR]

The bipolar DC bus configuration has been widely used in DC nano-grids due to its flexibility and stability. Input-parallel-output-series (IPOS) converters are utilized in bipolar DC bus and RES applications due to their simple structure. However, there is a big challenge with this structure. To ensure system safety and stability, the two output voltages of an IPOS converter need to be balanced. On this basis, an IPOS three-state boost converter with a balanced output voltage is proposed in this paper. At the same time, output voltage balance can be obtained by adjusting the duration of the three-state converter based on the volt-second balance method. In the proposed strategy, a switch series diode is added to the IPOS Boost converter topology, and the voltage across the main inductor can be changed through one degree of freedom, where the corresponding output voltage is regulated due to a change in inductor voltage. In addition, under different dead time conditions, adjusting the gate drive of the switch can be used to achieve voltage balance. Moreover, a comprehensive analysis and relative calculations are provided. Finally, a 20–200 V prototype is built to verify the analysis. [ABSTRACT FROM AUTHOR]

This paper describes how to use particle swarm optimization to implement a neural network-based admittance estimation strategy for controlling a dynamic voltage restorer (DVR) with optimized controller gains (PSO). To improve DVR efficiency, robustness, and tracking capability, a control strategy based on source admittance components is used to determine fundamental admittance components from distorted supply voltages. Because of the algorithm's simple formulas, estimating conductance and susceptibility from load currents is quick. To minimize the gains of proportional integral controllers, particle swarm optimization (PSO) is used. This improves dynamic response, tracking capability, as well as transient and steady-state stability. When consumer loads change on a regular or irregular basis, this algorithm is very effective. The admittance control strategy for DVR is modeled and simulated using MATLAB/Simulink and implemented using hardware setup d-SPACE made MicroLab box DS1202/DS1302 for mitigating harmonics and voltage sag/swell (2 GHz dual-core real-time processor and user-programmable FPGA). The suggested DVR's test results were satisfactory under both balanced and unbalanced load conditions. [ABSTRACT FROM AUTHOR]

The existing control strategies of DC solid-state transformer (DCSST) are based on DC distribution system, which is mainly concentrated on one side voltage stability control without considering the change of control objectives under different conditions. Thus, they are unsuitable for multiterminal and multisource DC microgrid. The coordinated control strategy of DCSST in multiterminal and multisource DC microgrid is studied in this paper. The DCSST circuit models based on the series–parallel structure of dual active full bridge converter are established, and the basic control modes are analyzed: control low voltage mode and control high voltage mode. Combined with the characteristics of DC bus voltage fluctuation and the operation conditions of DCSST, a unified coordinated control strategy is proposed. Experimental results show that the proposed control strategy can correctly identify the different power states of the two sides of the system, control the power exchange between the two sides of the system, and maintain the stable operation of the whole DC system. [ABSTRACT FROM AUTHOR]

The presence of ripple power in a converter system has a negative influence on both control performance and reliability. Active power decoupling (APD) is a practical technique to deal with such problems. However, the APD method requires extra sensors on the LC branch, which increases the complexity and cost of the control system. This paper puts forward a new APD method to handle undesirable ripple power for H-bridge PWM converters. When compared with previous APD methods, the proposed APD method eliminates the current and voltage sensors on the LC branch by utilizing a ripple voltage control loop. Then, both the cost and reliability of the converter system are improved. To improve the control performance, an APD method that only has a voltage sensor in the LC branch is also discussed. Simulation results show that the DC-link voltage ripples can be decreased due to the application of the proposed APD method. Finally, the effectiveness of the proposed method is verified by the experimental results. [ABSTRACT FROM AUTHOR]