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A phase-locked loop (PLL) is commonly used in grid-connected power converter for synchronization. A single input single output (SISO) linear model of PLL with the phase angle of the point of common coupling (PCC) voltage as input and the estimated phase angle as the output is generally used in the PLL analysis and design. However, an undesirable coupling between the magnitude and phase of the input voltage is present when a filtering stage is incorporated before the control loop, which a SISO model cannot capture, and could result in a significant disturbance in the PLL estimated phase during grid faults. This paper proposes a generalized multi-input multi-output (MIMO) linear model that captures the complete PLL dynamics during symmetrical faults for a PLL equipped with any prefilter. Furthermore, a compensation method that decouples the magnitude dynamics of the input voltage from the phase dynamics is proposed in this paper. The proposed compensation improves the PLL's phase tracking performance by ensuring that the prefiltered PLL acts only on the PCC voltage phase changes. A vital application of the proposed compensation method for PLL is during a grid fault case, wherein the converters are expected to contribute to the fault current, which requires an accurate measurement of the PCC voltage phase. The compensation method's effectiveness is demonstrated using power hardware in the loop simulation of a hardware voltage source converter interfaced to a distribution system simulated in real-time. [ABSTRACT FROM AUTHOR]

Three-port converters with high voltage gain are desirable solutions for integrating renewable energy and energy storage devices into high voltage dc bus. A high gain three-port converter with soft switching is proposed in this paper, which can realize zero voltage switching for all switches and zero current switching for all diodes in various operating modes. Single coupled inductor is used to achieve high voltage gain and to reduce the voltage stress of switches so that switches with low on-resistance can be selected to reduce the conduction loss. In addition, the advantages of fewer components, higher voltage gain, and very low switch voltage stresses make the proposed converter more suitable for application in renewable energy systems than similar solutions. Various operating modes, performance analysis, design considerations, efficiency analysis, and control method of the proposed converter are discussed. A laboratory prototype with 30 V renewable energy source, 48 V energy storage device and 400 V output is designed to verify the performance of the proposed three-port converter. [ABSTRACT FROM AUTHOR]

Parasitic capacitance has a considerable impact on conductive electromagnetic interference (EMI), especially on the common mode (CM) noise. In vehicular applications, such as more electric aircraft and electrical vehicles, the value of CM stray capacitance can vary during the drive cycle, due to some change in environmental, and operating conditions, resulting in fluctuations in EMI level. Designing EMI filters according to potentially overestimated CM capacitance results in additional weight, volume, and cost which should be avoided. In this paper, for the first time, the parasitic capacitance relevant to CM noise is estimated in real-time using unscented Kalman filter (UKF). The UKF is employed due to its ability in dealing with nonlinearity and stochastic nature of the EMI as well as the measurement noises. The proposed method is tested on a typical dc–dc buck converter in different operating conditions. The effectiveness of the proposed method is tested using some hardware-in-the-loop experiments using dSPACE1104 development platform. [ABSTRACT FROM AUTHOR]

This article proposes a novel control for the multiple-input, single-inductor, multiple-output dc–dc converters. It is digitally and discretely implemented, which can have an outstanding performance in low-power applications so that at the power of 10 mW, it has an efficiency of 92.5%. Conventionally, in this power range, an attempt is made to take advantage of an analog design that is flexible. Thus, a fully programmable (software designed) converter with digital design using a microcontroller is in great demand. This converter design basis is to deploy the microcontroller's central processing unit (CPU) as little as possible. Also, it only turns on the CPU when necessary to be employed in low-power, portable systems, e.g., energy-harvesting technologies. Therefore, construction costs are significantly reduced. Depending on the energy level of the inputs, they can simultaneously be utilized to charge the outputs. This article uses stability analysis, time-multiplexing control method, and variable-frequency pulsewidth modulation in the proposed control design. Each output can be charged with different frequencies according to its load, and the maximum switching frequency is equal to 10 kHz. Also, the proposed technique for zero-current switching has been digitally implemented; it can be utilized to determine the optimal value of the inductor discharge duty cycle based on the inductor's left-side voltage. Comparative simulations and experimental results reveal the superiority and practicality of the proposed approach. [ABSTRACT FROM AUTHOR]

The cascaded dc–dc converter is a popular topology for large-scale medium-voltage photovoltaic (PV) system with the advantages of high voltage conversion ratio, high efficiency, great flexibility, and independent control capability. However, the absence of optimal string maximum power point tracking (MPPT) operation under power mismatch is a big issue in common centralized control. Furthermore, the cost and time delay are unacceptable resulting from the distance among PV strings in the large-scale PV station and the cascaded dc–dc converter needs to adopt the distributed control method without real-time communication. To this end, by introducing other necessary constraints including voltage constraints, power constraints, and gain constraints on the basis of the distributed MPPT control strategy, a distributed multimode control scheme is proposed in this article. Each submodule (SM) can be switched flexibly between multiple operation modes to maximize the extracted solar energy. Individual string MPPT and autonomous distribution of output voltage are achieved without communication under the proposed distributed control strategy. In this way, optimal operation range is wider, mode switching is simpler, and applicability and robustness are improved. A downscaled prototype and a 35-kV/6-MW simulation system are constructed to verify the effectiveness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

A dc–dc converter used for fuel cell vehicles should be characterized by a wide voltage-gain range and low input current ripple. In order to meet the above requirements, a new nonisolated dc–dc converter consisting of an active switched-inductor cell, a zero current ripple cell, and a switched-capacitor (SC) cell was proposed in this article. The proposed converter integrates with the advantages of a wide voltage-gain range, zero input current ripple, low voltage stresses across power semiconductors, and common ground structure. Thanks to the use of a zero current ripple cell, not only the input current ripple is reduced but also the energy transfer path of the SC cell is changed, thereby reducing the instantaneous peak current of the SC structure. The operating principles, the characteristics analysis, and the parameter design of the proposed converter are given. In addition, to show the merits of the proposed converter, a comparison study is demonstrated. Finally, a prototype of 400 V, 1000 W/50 kHz is developed to validate the effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]

This article proposes a unidirectional high step-up dc–dc converter. The study approaches principle of operation, analysis, guide design, and experimental validation. The high-voltage gain is reached using coupled inductors and voltage multiplier cells (VMC). An interleaved structure of two phases is employed to provide a low-current ripple in the input side. The current balance between the phases occurs due to the insertion of a built-in transformer, which also contributes to increasing the voltage gain. The energy from the leakage inductances is reused, reducing voltage spikes across the semiconductors. Additionally, the proposed converter provides an input–output common ground, which is a requirement for many applications. To verify the proposed converter, a 1-kW prototype, 48–800 V, and 16.67 of voltage gain, was designed and tested. The maximum peak efficiency reached was 94.89% and the rated power efficiency was 93.86%. [ABSTRACT FROM AUTHOR]

This article presents a novel low-cost, single-switch, high-step-upresonant dc–dc converter with high reliability. The proposed converter topology comprises a low count of components and a simple structure and achieves the low ripple input current characteristic. The inductors in the resonant network participate in the resonant process rather than creating voltage spikes across the switch and likely reverse recovery problems. The circuit operates in the soft-switching condition (ZVS–ZCS conditions in the turn-off and turn-on transitions), leading to a significant reduction of the switching losses. Moreover, employing film capacitors instead of electrolytic capacitors reduces the size of the circuit and improves reliability. The operational principle and comprehensive steady-state analysis in the continuous conduction mode are discussed in detail, alongside the design considerations of the proposed converter. The validity of the theoretical equations is investigated via experiments, achieving maximum efficiency of 97.69% for a converter designed at the input of 24.5 V, the negative output of 200 V, and the maximum powerof 200 W. [ABSTRACT FROM AUTHOR]

This article introduces a new nonisolated soft-switching coupled-inductor (CI) step-up dc/dc converter. The presented topology utilizes a three-winding CI (TWCI) along with a voltage multiplier circuit to increase the voltage conversion ratio without needing a high duty cycle. Using this circuit, a high voltage gain can be achieved without requiring a large number of turns ratio in the CI. The input current ripple of the introduced converter is very low, which is very desirable for renewable energy sources applications. The TWCI also creates an additional design freedom to increase the voltage gain, which indicates more circuit flexibility. Additionally, the voltage stress across the single power switch is limited with the help of a regenerative clamp capacitor. The leakage inductor of the CI is used to create a resonant tank to reduce power losses further. The leakage inductances help provide the zero-current switching conditions for the single power switch and decrease the reverse-recovery issues for all diodes, leading to an efficiency improvement. The operation principle, steady-state analysis, and design considerations are discussed thoroughly. Finally, the theoretical analysis is validated through experimental results obtained from a 200 W prototype with 250 V output voltage. [ABSTRACT FROM AUTHOR]

Slow load transient performance, potential cross-regulation, and low efficiency are the major drawbacks for pseudocontinuous conduction mode single-inductor dual-output (SIDO) dc–dc converters. To overcome these drawbacks, this article proposes a voltage-ripple (VR)-based dynamic freewheeling (DF) control technique for hybrid conduction mode (HCM) SIDO buck converter. With the employment of VR controller, the proposed control technique improves the load transient performance significantly. As the fast recovery during load transition, the cross-regulation is minimized. Additionally, due to the DF controller, the freewheel current value automatically updates in each switching period, which can improve the efficiency of the HCM SIDO buck converter, especially under the light load conditions. Finally, the proposed converter has been verified through experimental results. The transient response time on 0.5 A load change takes only 1–2 switching periods. No observable cross- regulation is found and maximum efficiency of 92.03% is achieved. Finally, the experimental waveforms are presented to verify the theoretical research. [ABSTRACT FROM AUTHOR]

In this article, a novel single-phase single-stage ac–dc converter based on semi dual-active-bridge dc–dc converter is proposed for unidirectional power flow applications. Dual-phase-shift (DPS) and single-phase-shift (SPS) modes are adopted individually according to their operation. Only two control variables, which are primary side phase shift and the phase shift between the two bridges, are used. The optimal voltage and current waveforms in different operation modes are analyzed. The detailed transition process between the DPS mode and SPS mode is given, and the mode transition is seamless. The proposed converter can achieve high power factor correction without an inner current tracking loop. In addition, the switches can achieve zero-voltage switching on within a wide operating range and the rectifier diode can obtain zero-current switching off. The power transfer capability, mode transition mechanism, soft-switching range, mode operation range, and parameter design are analyzed. Besides, a 1 kW experimental prototype is built to verify the effectiveness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

In this article, we propose a monitoring procedure based on a multilayer neural network with multivalued neurons (MLMVN) capable of preventing catastrophic failures of dc–dc converters. The neural classifier allows both the detection of any malfunction and its localization. Thanks to the low computational complexity, the proposed method operates online, estimating the deviations of the passive components from their nominal values: this allows control strategies to be promptly adopted and operation of the dc–dc converter to be kept in high efficiency and reliability conditions. Since measuring the voltage and current on each component increases the complexity of the system, a testability analysis is proposed with the aim of identifying the minimum number of measurements needed to distinguish the classes of failure. To make the testability phase easier and more intuitive, a graphical representation is proposed. As a case study, prognostic analysis has been applied to prevent catastrophic failures in a synchronous Zeta converter. Several fault conditions have been analyzed through simulations and experimental tests. The obtained results confirm the ability of the proposed method to prevent failures and, also, show that the application of MLMVN results in a better performance than classic solutions available in the literature, such as support vector machine. [ABSTRACT FROM AUTHOR]

The switched-quasi-Z-source bidirectional dc–dc converter (SQBC) has the characteristics of wide voltage gain and low voltage stress, and is suitable for the power interface between the supercapacitors and the dc bus in the multisource system of electric vehicles. On the basis of the SQBC, an optimal design method for inductance parameters and variable switching frequency control strategy are proposed in this article. While remaining the wide voltage gain and low voltage stress characteristics of the topology, the soft-switching operation within the full voltage gain range is achieved without adding additional auxiliary devices. The variable switching frequency control strategy keeps the converter operating at the critical soft-switching point with the lowest switching losses per switching cycle, further improving the operation efficiency of the converter. Finally, an experimental prototype with a rated power of P = 300 W, input voltage of Ulow = 50–150 V and output voltage of Uhigh = 300 V was built, and its maximum efficiency is 98.28%, which verified the correctness and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The introduction of the switched affine system opens new perspectives for the control design of dc–dc converters. In order to overcome the drawbacks of the continuous-time switching control methods, several sampled-data-based switching control approaches have been proposed in the literature. However, in these works, the solution of control parameters involves a nonlinear optimization problem. In addition, the designed switching laws are nonlinear functions about the system state, which require higher computational resources. In this article, a periodic time-triggered hybrid control is proposed based on a new design framework. All the design conditions are in linear matrix inequality formulations, which can be conveniently solved by common semidefinite programming software. Moreover, the proposed switching law is a linear function about the state, reducing the online computing burden. Finally, a unified view of the classical continuous-time switching scheme and the proposed method is established. Simulation and experiment tests on a buck–boost converter demonstrate the good performance of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This article proposes a new single switch trans-inverse high step-up converter applicable in sustainable sources of energies such as photovoltaic (PV) and fuel cell (FC). Through developing a single-ended primary-inductor converter by a three-winding built-in transformer (BIT) mixed with a switched-capacitor voltage multiplier cell, high voltage gains as well as low voltage stress across the mosfet can be achieved to reduce the required duty cycle and the conduction losses. The third winding of the BIT acts in a trans-inverse manner whose turns ratio should be lower than unity. Hence, with a lower number of windings the voltage gain can also be improved. Furthermore, the quasi-resonance operation of the proposed converter, reduces the associated switching losses of the mosfet and also guarantees zero current switching of diodes through the whole switching cycle. Meanwhile, low input current of the proposed converter serves as an interesting feature to maintain PV and FC lifetime. The detailed steady-state analysis of the proposed high-efficiency converter is presented with an extensive performance comparison to explore its advantages. Finally, a 200-W prototype with 20–250-V voltage conversion is developed in the laboratory to examine the carried steady-state analysis. [ABSTRACT FROM AUTHOR]

In a conventional current-mode dc–dc buck converter, two sensed inductor current signals are processed in three separate comparators to regulate the converter under various load conditions. These independent sensing currents and comparators not only consume large quiescent current and silicon areas but also cannot guarantee the accuracy of the current limit threshold. This article proposes a current-mode dc–dc buck converter with an accurate current limit using a multiplex pulsewidth modulation (PWM) comparator. Through a multiplex PWM comparator, only one sensing current and one comparator are required to process the inductor current information and complete the regulation of the converter under various load conditions. The response speed of overcurrent protection is also increased without consuming more power and silicon area. Moreover, by generating the zero temperature coefficient (ZTC) sensing current and adding ZTC reference current with slope compensation information, the accuracy of the current limit threshold is greatly improved under various temperatures in a wide input voltage range. The proposed buck converter with a multiplex PWM comparator was fabricated using a standard 1P3M 0.18 μm BCD (BiCMOS/DMOS) process and the experimental results show that the proposed scheme functions properly in the 5-A load range, and the current limit threshold also varies only 8.1% in the temperature range from −40 to 125 °C with the input voltage up to 60 V. [ABSTRACT FROM AUTHOR]

This article introduces a nonisolated, high step-up voltage multiplier cell (VMC)-based dc–dc converter for applications such as module-integrated converter and power optimizers. The VMC combines switched capacitor with autotransformer techniques and active clamp circuit. The autotransformer tertiary winding is employed to increase voltage gain without operating the main switch under extreme duty cycle condition, to reduce the current through the main switch before it turns offand to ensure its zero-voltage switching (ZVS) operation on a wide operation range. The auxiliary switch in the clamp circuit provides ZVS for the main switch and vice-versa. Thus, both switches are turned on with zero voltage and there is no switching loss. Hence, high switching frequency is used to reduce the passive components’ volume and weight. Besides, the low dc-bias and bidirectional magnetizing current allows a smaller magnetizing inductance in the autotransformer to further minimizing the dimensions of the magnetic core. The leakage inductances are used to provide zero-current switching condition for the diodes, eliminating their reverse-recovery losses. The operation principle, steady-state analysis, and design guidelines are depicted and validated through experimental results obtained from a 350-W prototype of the proposed converter. Efficiency of 96.5% at full load is also reported. [ABSTRACT FROM AUTHOR]

Four-switch buck-boost (FSBB) converter features positive output voltage and low voltage stress of power switches. In this article, a pulsewidth modulation plus phase-shift control scheme is proposed to achieve zero-voltage-switching for all the power switches in full input voltage and load range and minimize the inductor current ripple and root mean square (RMS) value. The implementation of the proposed control scheme is given. A prototype of a 500-W FSBB converter is built and tested in the lab, and the experimental results verify the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

In this article, a family of nonisolated zero voltage switching (ZVS) bidirectional dc–dc converters (BDCs) with simple auxiliary circuit and continuous current at low voltage side source ($V_L$) is proposed. The auxiliary circuit is only composed of a single switch, a capacitor, and a small inductor which is applied to all proposed nonisolated BDCs to provide soft switching condition for all semiconductor elements. Thus, in terms of components count, the presented converters are superior to other counterpart BDCs. In addition, the continuous current at $V_L$ is maintained, while the main and auxiliary switches in both operating modes are turned on and off at ZVS. Moreover, all diodes turn off at zero current switching which mitigate the reverse recovery problem. Hence, a suitable overall efficiency is achieved in all proposed BDCs. The proposed bidirectional buck/boost converter is analyzed for both step-up and step-down operating modes in details and a 100 W converter prototype is implemented to verify the main converter features and the theoretical analysis. [ABSTRACT FROM AUTHOR]

Zero-voltage zero-current switching (ZVZCS) phase-shift full-bridge (PSFB) dc–dc converters are candidate converters for high-power switching mode power supply because of their low cost and high efficiency. However, these converters still have some definite weaknesses, e.g., resetting obstacles of high-value currents, extra electrical stress on the power devices. Hence, customers seldom adopt these topologies in high-power applications. This article proposes a new ZVZCS PSFB dc–dc converter to solve the above problems. A clamping circuit with two mosfets, two diodes, and a resetting transformer ensures ZCS of the lagging-leg switches over a wide load range, and no extra electrical stress arises on the primary or secondary components. The clamping circuit has a high current reset ability and can break through the power limitation of conventional ZVZCS PSFB dc–dc converters. The volume of the resetting transformer is small because of the low voltage-second product, and the added mosfets cause low power loss because of the wide soft-switching load range and low on-resistance. The experimental results from a 12-kW prototype prove the rightness and advantages of the proposed converter. [ABSTRACT FROM AUTHOR]

Coupled inductor single-input–dual-output (CI-SIDO) converters are promising converters used in the applications that demand multiple voltage supplies due to their high efficiency and small volume. However, this class of converters suffers from poor cross-coupling and cross-regulation issues, which affects the dynamic performance and stability. These issues can be suppressed with peak current mode control because of its faster dynamic response. To design the controller and study dynamic performance, a small-signal model of the system is essential, which consists of a converter model and current modulator model. However, developing the current modulator model for PCM controlled CI-SIDO converters is challenging because it consists of two reference current for two inductor currents each consisting of three slopes. No literature is available that derives a unified model of PCM controlled CI-SIDO converters. Therefore, this article proposes a unified small-signal model for PCM controlled CI-SIDO converters. The proposed model is applicable to three topologies of CI-SIDO converters, i.e., CI-SIDO buck, CI-SIDO boost, CI-SIDO boost and buck converter. The proposed unified model is a useful tool to study the dynamic performances, stability, and design outer controllers. Finally, the accuracy of the proposed unified model is verified by performing simulation and experiment of PCM controlled CI-SIDO converters considering inner-loops closed. [ABSTRACT FROM AUTHOR]

Nonisolated high-voltage gain soft-switching dc–dc converter is an ideal candidate for distributed generation system converters. This article proposes a high-voltage gain soft switching quasi-Z-source dc–dc converter. The converter integrates a coupled inductor and switched capacitor into a quasi-Z-source network. Soft switching is achieved for all active devices in the converter by controlling the auxiliary switch Sa. By inheriting the advantages of the quasi-Z-source network and coupled-inductor/switched-capacitor, the converter has high voltage gain, high efficiency, low input current ripple, low voltage spike of main switch, and common ground. In addition, the efficiency of the converter is improved by recycling the energy of leakage inductance, resulting from an inherent active clamp of the main switch. The steady-state operation, voltage relationship, current/voltage stress, and power dissipation of each component of the converter have been analyzed and derived in detail. The properties of the proposed converter are verified by designing a 200 W prototype in the laboratory. When the input voltage is 48 V and the output voltage is 380 V, the converter efficiency reaches 96.92%, while the efficiency is 93% in a hard switching. The key waveforms of the converter obtained from the experiment agree well with the theoretical analysis results. [ABSTRACT FROM AUTHOR]

This article introduces a new coupled inductor based dual-input ultra-high step-up dc–dc converter with a high voltage conversion ratio, low voltage stress across semiconductor components, and high efficiency features. The coupled inductor and voltage multiplier circuit (VMC) techniques have been utilized to enhance the voltage gain. The blocking voltages of power switches are clamped by VMC at low values and can be controlled via the turn ratio of the coupled inductors that decreases the voltage rate of power switches and converter's cost. The presented dual-input structure can transfer power to the load from two independent voltage sources. Besides, the inputs and output ports are common ground, which can reduce the electromagnetic interference influences. Operation modes delineation, steady-state analysis, and comparison section are provided for describing the proposed structure performance. Finally, to confirm the effectiveness of the presented topology, experimental waveforms with a 200 W output power at 50 kHz switching frequency are presented. [ABSTRACT FROM AUTHOR]

In this article, we propose a high step-up interleaved dc–dc converter with zero-voltage switching, which is based on the coupled-inductor technique and voltage multiplier cell. A capacitor is placed in series with the secondary windings of the coupled inductors to increase voltage gain so low-voltage-rated and on-resistance mosfets can be employed to reduce conduction losses. By using auxiliary switches, soft switching is provided for a wide range of load variations. Due to the presence of the leakage inductor, all diodes are turned off with zero-current switching condition, so the reverse recovery problem is alleviated. Besides, the thermal stress of the phases and the input current ripple are low due to the interleaved structure applied. The operation principle and steady-state analysis of the presented converter are discussed. Finally, in order to verify the operation of the proposed converter, a 28 V input voltage to 460 V output voltage prototype with a rated power of 250 W is implemented and tested in the laboratory. [ABSTRACT FROM AUTHOR]

The circuit parameters mismatch of input-parallel output-parallel (IPOP) dual active bridge (DAB) converter modules will cause power imbalances of the system. To solve this problem, in this article, we present a simple sensorless current sharing control based on dual-phase-shift (DPS) modulation method. First, the full process operation mode of IPOP DAB is analyzed. Then, the power balance mechanism of the IPOP DAB converter is discussed, and a sensorless current sharing control method is proposed. The core principle of the proposed method is based on the perturbation algorithm to estimate the parameter mismatches of each DAB cell. Once the parameter mismatches are known, the phase shifts that achieve current sharing are calculated. The implementation scheme based on CAN Bus is given, and sensitivity and stability analysis of the proposed method is conducted. Finally, the simulation and experimental results verify the effectiveness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

A generalized output branch with coupled inductor is proposed in this article, with which a diversity of single-input dual-output (SIDO) configurations can be synthesized through substituting it for the original inductor in the conventional single-input single-output (SISO) converters. Furthermore, for each configuration, multiple SIDO converters will be generated after realizing the auxiliary voltage source in the generalized output branch with two different nodes. Because the number of magnetic components remains unchanged in comparison with the SISO converter, high power density can be achieved in the derived SIDO converters with coupled inductor. Moreover, the cross-regulation problem is effectively alleviated, and soft-switching operation is realized for switches. Hence, both optimized steady-state and dynamic performance can be obtained. In this article, three example SIDO configurations based on buck, boost, and buck−boost converters are derived, and an example family of 12 SIDO converters from buck converter is demonstrated in detail. Afterwards, a unified operation principle and performance analysis suitable for all these 12 converters are also introduced, which is helpful for the topology comparison. Finally, experimental verification of the theoretical analysis is also conducted. [ABSTRACT FROM AUTHOR]

High step-up dc–dc converters are widely used in new energy applications such as photovoltaic cell, fuel cell, dc microgrid, etc. Active switched-inductor (ASL) converter has simple operation and low stress on switches. To further increase the voltage gain, some SC (switched-capacitor)/ASL step-up converters have been proposed recently. However, these SC/ASL step-up converters have voltage oscillation on switches, which leads to the voltage stress on switches is higher than the theoretical value. In this article, a novel high step-up SC/ASL converter is proposed. Compared with other SC/ASL step-up converters, the proposed converter has lower voltage stress on the switches, output diodes, and output filter capacitors, and the efficiency is higher. In addition, the proposed converter can achieve self-voltage balancing on switches. This article analyzes the proposed converter from operation principle, continuous conduction mode (CCM) analysis, CCM operation with unbalanced inductors, input current ripple analysis, discontinuous conduction mode and boundary conduction mode analysis, switches self-voltage balancing characteristic, voltage stress, current stress, comparison analysis, and design considerations. Finally, a 200 W, 25–45 V/380 V, 50 kHz experimental prototype has been established in the laboratory to evaluate the proposed converter, which reached a peak efficiency of 97.3%. [ABSTRACT FROM AUTHOR]

In this article, a new high step-up transformerless dc–dc converter based on a voltage multiplier and a coupled inductor topology is presented. The proposed converter has two stages. In the first stage, a modified boost converter is designed by the coupled inductor, and in the second stage, a new voltage multiplier by using a coupled inductor is illustrated. In this converter, high voltage gain can be achieved by adjusting the turn ratio of two coupled inductors and the duty cycle, which result in three degrees of design freedom. Using a single power switch with low on-resistance in the converter structure leads to simple control and low conduction loss. In addition, total voltage stresses of active elements are decreased, which increases efficiency. Steady-state performance and theoretical achievements are confirmed by experimental test results on a test setup with one 200-W dc–dc prototype. [ABSTRACT FROM AUTHOR]

This article presents a ground breaking traction drive for fuel cell-powered light rail vehicles based on a multilevel cascade converter with H-bridge cells. The converter provides dc–ac power conversion with unique buck–boost capability to compensate for the variation of fuel cell terminal voltage with the load power. In comparison to a conventional boost inverter, based on the cascade connection of a boost dc–dc converter and a voltage source inverter, the proposed converter has the significant benefits of much smaller inductor size, lower dc side current ripple, and multilevel voltage waveforms at the ac output. This article presents the converter modeling and design of the boost inductor and submodule capacitors, taking into account the full speed range of the motor. The concept has been fully validated on a bespoke experimental prototype driving an induction motor, showing the suitability of the proposed converter as a traction drive for hydrogen-powered rail vehicles. [ABSTRACT FROM AUTHOR]

In this article, a new triple-switch triple-mode (TS-TM) high step-up dc–dc converter is proposed. The proposed converter consists of three switches, four diodes, two magnetically coupled inductors, and three capacitors. This converter can provide a high voltage conversion ratio with high power efficiency and low voltage stress across the power semiconductor components. Due to the low voltage stresses of the power semiconductors and implementing the coupled inductors technique, the proposed converter is a low-cost and high-efficient structure in comparison to the other similar TS-TM structures. In order to clarify the advantages of the proposed converter, the required mathematical calculations and comparison results with similar converters are presented. Also, a novel TS-TM with transformer is proposed to overcome the electromagnetic interface problems. Furthermore, a 500 W experimental prototype is built and its performance with different values of duty cycles is tested to prove the claimed features of the proposed converter. A total of 94.5% maximum power efficiency of the assembled prototype has been obtained at 260 W output power. [ABSTRACT FROM AUTHOR]

Harmonics generated from power electronic converters will impose significant power quality challenges to the electric grid onboard future aircraft. In this article, we propose an innovative modulation scheme that enables using a buck–boost dc–dc converter as a harmonic absorber. To demonstrate the effectiveness of the proposed method, a hybrid power generation system involving a high-speed electrical generator and a high voltage battery is introduced. The electrical generator is connected to a dc bus through an ac–dc converter and the battery to the dc bus with a dc–dc converter. For the studied hybrid power generation system, it is identified that the first carrier frequency side-band harmonic (fc-3f0) from the ac–dc converter is most relevant and is targeted for cancellation. For the control of the dc–dc converter, a new modulation technique, called equal-gate-width modulation is proposed. It allows active control of the magnitude and phase angle of some specific harmonic components from a dc–dc converter. By properly tuning the phase angle and amplitude, the controlled harmonics can thus be used to cancel harmonics from other converters on a common dc bus. Without losing generality, this article focuses on the development of this specific harmonic cancellation scheme and the effectiveness of our proposed methods has been demonstrated using experimental results. [ABSTRACT FROM AUTHOR]

Non-isolated high-gain dc–dc converters are essential for applications with low input voltage, such as solar PV modules and fuel-cells. Due to the high step-up conversion ratio, the input current increases significantly with increase in power rating. This leads to considerable conduction loss in the non-ideal elements of the converter, degrading the efficiency. Moreover, peak-to-peak ripple of the input current also increases with an increase in power rating. This increases the size of the passive elements, thereby limiting the power density. An n-phase Interleaved Complementary Current-fed Topology (n-phase ICCFT) is proposed in this article to address the aforementioned limitations. Two pulse width modulated (PWM) schemes are proposed to implement the interleaving of the n-phases. Detailed steady-state analysis with various operating modes and the gain characteristics of the proposed converter are analyzed in the article. A comparative analysis of the two PWM schemes in terms of ripple characteristics, capacitor current stress, and power loss is reported. Operation of a two-phase ICCFT with the proposed PWM schemes is verified using PLECS simulation and experiments using a proof-of-concept hardware. [ABSTRACT FROM AUTHOR]

This letter proposes a coupled-inductor-based soft-switching noninverting buck–boost converter (NIBBC) with reduced auxiliary component count. Instead of using multiple auxiliary passive components to achieve soft switching, the proposed coupled-inductor-based NIBBC uses the coupled inductor as the main inductor, and the auxiliary current generated by the magnetic coupling effect is used to obtain the soft switching for all switches. With simple pulsewidth modulation under fixed frequency, full-load range zero-voltage switching can be obtained under a wide voltage range. Unlike the conventional method utilizing the coupled inductor only to generate nonactive power, the coupled inductor of the proposed converter also takes participant in the power transmission. Besides, the added diode can achieve zero current turn-off that avoids the diode recovery issue. The operating principle, the soft switching, and the parameter designs are analyzed in this letter. Finally, experimental results have verified the effectiveness of the proposed solution. [ABSTRACT FROM AUTHOR]

An analytical method to synthesize a nonisolated multi-inductor (uncoupled) dc–dc converter having an arbitrary voltage conversion ratio is presented in this article. The proposed method provides a direct approach to synthesize the converter unlike the traditional topology synthesis methods, which involve circuit manipulations or selecting a connection matrix from a pool of possible matrices. As a result, the proposed method simplifies the topology synthesis of a converter having known properties to a four-step process. To this end, the voltage conversion ratio is decomposed, allowing to synthesize it using single inductor switching cells. The resultant single inductor switching cells can be either cascaded or differentially connected as pairs or embedded within a switching cell to realize a multi-inductor-converter. Several existing converter topologies have been synthesized to demonstrate the applicability and usefulness of this straightforward method. The operation of the synthesized converters having arbitrary conversion ratios is verified using simulation results. The voltage gain and the operation of such a converter is further validated using experimental results. [ABSTRACT FROM AUTHOR]

In this article, an interleaved coupled-inductor (CI) based bidirectional dc–dc converter (BDC) is proposed with a higher voltage conversion ratio (VCR). In this proposed interleave CI-based BDC (ICI-BDC), the CIs can operate as both a filter inductor and a transformer simultaneously, so that the power density is improved. Moreover, as a transformer, the turns ratio of CIs is used to improve the VCR with a voltage stress reduction purpose. Furthermore, the interleaved technique can well achieve the low current ripple and reduced current stress in this topology. To control ICI-BDC, the pulsewidth modulation plus phase-shift (PPS) control is employed, where the duty cycle is used to match the two side voltages, and the phase-shift angle is used to control the amount and direction of power flow. Uniquely, a difference value is set between the two side duty cycles, and the duty cycle of the high voltage side is smaller than that of the low voltage side by a fixed value. In this proposed control method, all the switches can achieve soft-switching even at light load condition, which can improve transmission efficiency. Experimental results obtained from a 1-kW prototype show a nearly high efficiency under all loading conditions, validating the viability of the proposed ICI-BDC topology and control method. [ABSTRACT FROM AUTHOR]

Hybrid energy storage microgrid represents the future direction of distributed energy development. However, under the influence of interference, the dynamic performance of the output side interface will be severely deteriorated. In this article, a linear active disturbance rejection controller with reference differential feedforward and cascade linear extended state observer (ADRC-RDCO) is proposed to deal with unknown modeling error and the unknown dynamics of the interface converter. In this strategy, a cascaded linear extended state observer is introduced to cope with the steady-state offset in the disturbance estimation error, so as to implement the accurate reconstruction of the disturbance state. Furthermore, a control law with RDF is applied to offset a portion of the tracking error of the given signal to achieve the purpose of optimizing the tracking accuracy of the given signal. Then, the tracking performance and stability of ADRC-RDCO are analyzed theoretically. On the basis of discussing the relationship between dynamic characteristics and control parameters, a parameter configuration method is proposed. Finally, the proposed ADRC-RDCO technology was verified on the 40 kW microgrid platform. [ABSTRACT FROM AUTHOR]

Different from the typical topology derivation of power electronics converters (PECs) depending on manual effort, this article aims to explore a programmable method based on graph theory for multiport dc–dc converters with reduced switches. By mathematically modeling converters with graph theory and transforming their working criteria into the corresponding graph constraints, the topology derivation can be automatically and conveniently solved with the aid of computer program. In this article, first, the principle of the proposed graph theory-based programmable method is introduced in detail. Then, it is employed to derive multiport dc–dc converters with reduced switches, and a diversity of new topologies are simultaneously excavated, among which a favorable one is selected to be theoretically introduced and experimentally verified. The proposed method remains relatively simple with the increasing number of ports, as the graph constraints of working criteria are almost the same for different number of ports. More importantly, because PECs can be essentially regarded as graphs with different components and their connecting relationships, the proposed method is applicable for many various converters. [ABSTRACT FROM AUTHOR]

A bidirectional discontinuous-conduction-mode constant on-time variable-frequency control strategy for a three-phase interleaved dc–dc converter suitable for traction applications is proposed in this article. The strategy enhances the converter efficiency at low-power conditions, providing fairly constant efficiency over the entire power range, by synchronously controlling both the bottom and top switches of the three boost phases. Simulation and experimental results demonstrate the validity and effectiveness of the proposed approach on a 10-kW bidirectional interleaved boost converter. [ABSTRACT FROM AUTHOR]

In order to solve the problems of existing three-port isolated dc-dc converter such as power decoupling and the nonzero instantaneous power of the standby port, a three-port isolated bidirectional current-fed series-resonant dc-dc converter is proposed in this article. The operational principle and general transfer power expressions of various ports are analyzed with the duty-cycle plus phase-shift control. Then, the power decoupling at the topology level is realized by setting the switching frequency equal to the resonant frequency of the resonant tank on the high-voltage side; thus, the transfer power of the two ports on the low-voltage sides can be controlled independently. Moreover, it is proved that the proposed converter realizes the zero instantaneous power of the standby port. On this basis, an optimized modulation strategy by taking the minimum root mean square value of the resonant current as the objective function is presented. The exact relationship between the desired transfer power and various phase shifts is accordingly obtained. The detailed experimental results verify the correctness of the proposed converter and corresponding modulation strategy. [ABSTRACT FROM AUTHOR]

Most dc power distribution architectures are organized as a typical cascaded converter system that is composed of source and load converters, and may experience a system oscillation due to the negative impedance effect of constant power loads. The load-side virtual impedance method is a possible solution to such stability problem, which however makes the dynamic response of the load converter slow, and thus increases the requirement of the filter capacitance. In this article, an auxiliary circuit that is connected to the output port of the load converter is proposed to enhance the transient performance of the power converter system, while the system can be stabilized by the virtual impedance method. The control and parameter design of the proposed auxiliary circuit is introduced. The capacitance requirement of the system for an expected transient deviation of the output voltage is significantly reduced by using the proposed auxiliary circuit. An example design is given to verify the feasibility of the proposed method with simulation analysis and experimental results. [ABSTRACT FROM AUTHOR]

In this article, an optimal structure for a high step-up nonisolated dc–dc converter is proposed. In this topology, the required high voltage gain can be obtained with a low number of elements. Furthermore, by implementing an auxiliary circuit, zero-voltage switching condition for the switches is provided, input current ripple has been reduced to almost zero, and all of the power diodes turn off and on under zero-current conditions. In the proposed structure, to regulate voltage gain, the extendable number of diode–capacitor voltage multiplier (DCVM) stages are combined with a coupled inductor. The voltage stresses across the semiconductors can be regulated by the number of the DCVM stages and the turns ratio of the coupled inductor. Thus, it provides two degrees of freedom for the designer to use low-rated semiconductors, which increases the converter efficiency. In this article, the performance of the proposed converter, in terms of voltage stress, voltage gain, and efficiency, has been analyzed, and a comprehensive comparison between the presented topology and other similar topologies presented. Finally, to verify the performance of the proposed topology, a 500 W (40 V/400 V) laboratory prototype has been developed and tested. The experimental results confirm its superiority and suitability. [ABSTRACT FROM AUTHOR]

This article proposes a multi-input multi-output digital control strategy for a bidirectional interleaved boost converter with coupled inductors, designed to operate as an interface between an ultracapacitor and a high-voltage dc-bus in a hybrid nanogrid. The control strategy keeps the high-voltage side dc-bus of the nanogrid stable when the voltage at the low-voltage side, connected to the ultracapacitor, changes in a wide range. Bidirectional energy flow control with current protection is allowed too. The high-voltage regulation loop is closed around an inner, low-voltage side current control loop. In parallel to these, a third, clamp voltage regulator is set to keep tight control over switch voltage stress. This article discusses the controller organization, the design criteria, and shows the subsequent implementation on a general purpose digital control platform. The achievable performance is experimentally verified on a 1.5-kW converter prototype. [ABSTRACT FROM AUTHOR]

The grid inverters play an important role in renewable energy systems, transferring the dc power to the ac grid. Galvanic isolation is usually needed between the dc source and the grid due to safety reasons and grounding leakage current mitigation. In this article, a soft-switching isolated grid inverter is proposed based on the current-fed matrix-type configuration. The topology of this converter is composed of a current-fed H-bridge on the side of dc source and a direct matrix converter on the grid side, which are linked by a high-frequency transformer. The current-fed H-bridge on the primary-side can smooth the dc-source current and control the dc-source current directly. The avoidance of dc-link energy-storage element in the single-stage matrix converter can prolong the system's life. A space-vector-modulation-based soft-switching scheme is proposed for the matrix converter on the grid side and a model-based commutation method is adopted in the current-fed H-bridge on the dc side. With the proposed modulation methods, the soft switching can be realized for all devices in the converter. Finally, a laboratory prototype of the proposed converter has been built to verify the effectiveness of the proposed method experimentally. [ABSTRACT FROM AUTHOR]

This article proposes a new active power flow controller for dc–dc multiactive bridge (MAB) converters with minimum current point tracking (MCPT) to minimize conductive losses. Unlike recent efforts in this area, the proposed controller does not require look-up table for implementation nor complex nonlinear converter modeling and is not circuit parameter dependent. The proposed control scheme is also generalized for MAB converters with any number of ports and is derived in per unit form to enable standard implementation for buck/boost/unity-gain operating modes. The proposed MCPT algorithm is based on an innovative adaptive perturb and observe tracking of the minimum current point (MCP) on the MAB converter current characteristic plane. This MCP is tracked while active power regulation is simultaneously achieved based on a new phase shift decoupler to enable direct regulation of individual port active power. Detailed design procedure of the proposed controller is presented and extensive simulation is carried out to validate the effectiveness of the proposed MCPT closed loop controller. Experimental implementation is also provided to substantiate the simulation results. [ABSTRACT FROM AUTHOR]

In this article, we propose steady-state modeling of dc–dc converters driven by multiple pulsewidth modulation (PWM) signals. The proposed dc–dc converter modeling uses a switched state-space framework, and the switching signal discontinuities are represented by a Fourier series to obtain the average model. The advantage of the proposed modeling is that it is not dependent on the dc–dc converter topology, and the dimension of the state-space model does not increase with the number of storage devices. Additionally, the duty cycle and phase displacements among the driving PWM signals can be arbitrary and systematically modeled. The effectiveness of the proposed modeling is supported by simulation and experimental results. [ABSTRACT FROM AUTHOR]

This article proposes a bidirectional battery charger for grid to vehicle and vehicle to grid operations of electric vehicles (EV). The dc stage of the proposed converter offers a quadratic buck–boost voltage gain ratio, which makes it suitable for interconnecting the battery pack unit of EVs with both dc and ac grids as a home EV charger. A high-voltage gain ratio, low voltage, and current stress of switches, high values of utilization factors (UF) for both directions are achieved. Continuous input current and common electrical ground are preserved at the dc–dc stage and also, the continuous output current of the proposed converter makes the realization of the pseudo dc-link method possible for connecting to an ac grid. Consequently, the switching power loss in the dc–ac stage of the EV charger is reduced, and as a result, it allows the proposed charger to run more efficiently and cooler. The operating principle, steady-state characteristics including the current, voltage stress, and UF of the switches, and comparison with other state-of-the-art dc–dc bidirectional converters are carried out in detail. Finally, to verify the theoretical achievements, a 500-W laboratory prototype of the proposed EV charger is implemented. The EV charger exhibits the capability for ac and dc regulation and demonstrates peak efficiency of 97.8% in the forward and 97.5% in the backward direction modes of operation. [ABSTRACT FROM AUTHOR]

This article aims to accomplish the output voltage tracking task for buck converters without current feedback, diminishing the performance degradation from model-plant mismatches and load variations. The following contributions overcome these difficulties: a) the combination of Luenberger and disturbance observer (DOB) techniques for a parameter-independent voltage-derivative observer; b) the pole-zero cancellation control incorporating the DOB and active-damping injection techniques; and c) the exponential convergence guarantee to the target tracking system subject to the variable convergence rate mechanism. Convincing experimental evidence confirms the effectiveness of proposed tracking control using a prototype 3 kW buck converter control system. [ABSTRACT FROM AUTHOR]

For grid-connected voltage-source converters (VSCs), it is commonly required that its power outputs can track the power references given by operators under various grid conditions. To achieve this objective, this article presents a Lyapunov-based nonlinear power control algorithm. The system dynamics is developed in the stationary frame, which facilitates the design of the control algorithm in the absence of phase-locked loops that may cause instability issues in ultraweak grids. A virtual resistance is then introduced to allow fast power tracking performance and relax the requirement on accurate system parameters. Furthermore, to simplify the control design, the quasi-stationary line impedance model is applied, based on which a nonlinear control algorithm that only utilizes the output voltage and current information is developed. Afterward, the stability of the closed-loop system is analyzed via the Lyapunov theory. The theoretical results illustrate that the power regulation goal can be achieved and the VSC can maintain synchronization with the power grid. Finally, experimental results demonstrate the effectiveness of the proposed control algorithm under temporary grid faults and various short-circuit ratios. [ABSTRACT FROM AUTHOR]

This article contains a new passivity-based control design approach for dc microgrids. The design is purely based on experimental data—bypassing the requirement of the network modeling. This approach permits the control of dc microgrids and preserve stability, despite of further interconnection of new passive loads and new passivity-based-controlled converters. This model-free approach generates control laws in a pure numerical way; bypassing the requirement of dealing with a high number of variables and equations that naturally appear in an increasingly complex dc microgrid. Experimental results are presented to corroborate the advantages of our approach. [ABSTRACT FROM AUTHOR]

The buck converter is frequently introduced in the industry to maintain the stability of the voltage output when having the interference suddenly. In order to promote the robustness of the buck converter, a novel hybrid H2 model following control (HHMFC) is developed based on digital redesign sliding mode control in this article. First, we design H2 model following SMC in the continue-time domain. Then, by using the digital redesign approach, the continuous SMC is redesigned to a corresponding discrete-time SMC and the proposed HHMFC is achieved. Finally, we apply the developed HHMFC to realize a robust buck converter. With both the simulation and experiment results, we can conclude that the proposed HHMFC can easily and successfully apply to the practical realization for the buck converter with better robustness performance. [ABSTRACT FROM AUTHOR]