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To utilize the full potential of the direct matrix converter (DMC) and improve the output waveform quality, a three-level output strategy for conventional 3 × N ( N ≥3) DMCs is presented, where three-level output voltages are achieved without any changes in the topology. In this developed strategy, the DMC is treated as a two-stage converter that consists of a fictitious rectifier and a neutral-point clamped (NPC) three-level inverter. By applying a phase-shifted carrier modulation strategy to the rectifier and a modified carrier-based double-signal pulsewidth modulation strategy to the NPC inverter, sinusoidal input and output, reduced switching losses, and controllable input power factors are achieved in conventional 3 × N DMCs. The developed three-level output strategy improves output waveform quality while sacrificing input performance to some extent. Finally, the effectiveness of the developed strategy is verified by both simulations and experimental results.

In single-phase voltage source inverters (VSI) under a weak grid, the frequency coupling, caused by the asymmetrical system structure, poses a challenge to system modeling and controller design. In this article, a frequency coupling suppression control strategy is presented, where all the frequency coupling components in the current reference are eliminated. As a result, the single-phase grid-tied inverter is directly modeled as a simple single-input single-output (SISO) admittance rather than a complicated multiple-input multiple-output (MIMO) admittance matrix. The SISO admittance model is simple, compact, and accurate, which facilitates design-oriented analysis. The admittance characteristic analysis shows that the Sym-PLL has a critical impact on the system stability under weak grid conditions. To improve the system stability, a prefilter-based impedance-shaping control strategy is proposed by mitigating the negative resistor behavior of the Sym-PLL. Finally, simulations and experimental results validate the effectiveness of the frequency-coupling suppression control strategy.

Resistance emulating control is attractive due to the advantages of ease to use and less voltage sensor. However, it is only suitable for rectification mode. This letter presents a simple stabilized negative resistance emulating control for inverter mode, which overcomes the limitation of the conventional resistance emulating control. To stabilize the converter, a stabilizer based on negative inductance emulating is designed. Moreover, the unity power factor is realized by the steady-state inductance emulating technique. Since only the input current information is required, this control scheme is cost-effective and robust. Experimental results verify the effectiveness of the proposed method.

This paper proposes a coupled-inductor-based soft switching non-inverting 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 PWM modulation under fixed frequency, full load range ZVS can be obtained under wide voltage range. Unlike the conventional method utilizing the coupled inductor only to generate non-active 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 which avoids the diode recovery issue. The operating principle, the soft switching and parameter designs are analyzed in this paper. Finally, experimental results have verified the effectiveness of the proposed solution.

A decoupled extended phase shift (EPS) control is proposed to decrease the control complexity and achieve full load range zero-voltage-switching (ZVS) for dual active bridge (DAB) dc-dc converters. In the proposed solution, full load range ZVS is achieved by adding an extra small fixed duty cycle and utilizing the magnetizing current. In addition, the two control variables are decoupled, since the control of the duty cycle is only determined by the voltage conversion ratio and is independent of the phase shift angle, which avoids the detection of operation mode and switching of control laws. The ZVS model considering junction capacitors and magnetizing inductance, ZVS region under full load range, and derivation of control law are analyzed in detail. Finally, the effectiveness of the proposed solution is experimentally verified on a 500W, 250kHz GaN-Based prototype.

Reliable fault diagnosis and identification are essential for permanent magnet synchronous motor (PMSM) drive system with high reliability requirements. Since open-switch fault and output current sensor fault both affect the residual of output phase current, it is difficult to identify them apart from each other. Thus, this paper proposes an open-switch fault and output current sensor fault diagnosis and identification method for matrix converter (MC) based PMSM drive system. The finite control set model predictive control (FCS-MPC) method is applied in MC based PMSM drive system. The fault identification method is proposed based on the extracted different faulty features of open-switch fault and output current sensor fault. After the open-switch fault is separated from the current sensor fault, an error-voltage based open-switch fault diagnosis strategy is applied to locate the faulty switch. Hardware-in-the-loop tests are carried out to verify the effectiveness of the proposed method.

An LLC-DAB bidirectional converter with reduced switch count as a DC-DC transformer (DCX) is proposed in this paper. It can achieve voltage regulation, full load range zero voltage switching (ZVS) for eight main switches and wide load range ZVS for four auxiliary switches, with consideration of the switch junction capacitors under different power direction. A part portion of total power is transferred through an auxiliary DAB circuit to achieve voltage regulation and bidirectional power conversion. The main power is transferred through LLC circuit with an easy PWM scheme achieving high conversion efficiency. Different from the existing LLC-DAB DCX structure, the two secondary side transformer outputs are in parallel, and connected to the same full-bridge circuit. In this way, the auxiliary DAB circuit can not only adjust the output voltage, but also can inject current into the secondary side to help achieving ZVS of switches without synchronous rectifier (SR) circuit. The converter operation principle is analyzed under different power directions, and ZVS is analyzed with the consideration of all the switch junction capacitors. Based on the analysis, the design consideration is introduced. Finally, a 2-kW prototype with 750V input and 400V output is built up to verify the effectiveness of the proposed solution.

It is a challenge for dual active bridge (DAB) converters to take good balance between full load range zero-voltage-switching (ZVS) and control complexity with wide voltage range. Dual phase shift (DPS) control can extend ZVS range greatly compared with single phase shift (SPS) control, and it has less control variables with reduced operation modes compared with triple phase shift (TPS) control. However, with conventional DPS control, at least a pair of switches will be operated under hard switching within a large power range, which severely reduces the efficiency especially at high switching frequency. To solve this problem, based on Lagrange multiplier method (LMM), an optimized DPS control utilizing magnetizing current is proposed. In this paper, the magnetizing inductance is designed to create possibility of full load range ZVS achievement for all power switches. Based on ZVS analysis considering switch junction capacitors and power characteristics analysis, a power control law premised on full load range ZVS achievement is proposed to achieve low current stress. Finally, the effectiveness of the proposed solution is verified by experimental results obtained with a 500W, 250kHz GaN-Based prototype.

This article proposes an adaptive power decoupling control strategy for a single-phase rectifier with an unbalanced split-capacitor decoupling circuit. Since a capacitance mismatch estimator is integrated into the control strategy, the impact of capacitance mismatch is eliminated. Meanwhile, the capacitance mismatch estimator can provide an auxiliary online monitor for the health of split capacitors. Moreover, the mechanism of capacitor voltages self-balance is explained. Finally, experiments are conducted to verify the effectiveness of the proposed method.

To ensure the safety and reliability, the aging test of on-board charger (OBC) and dc/dc auxiliary power module (dc/dc-APM) in electric vehicles are indispensable. However, a wide range of battery voltage levels and fast response to power conversion between forward and backward operations are still challenging aspects of the aging test power system. In this article, an improved ac/dc converter is proposed for the aging test application in electric vehicles. The converter consists of two identical topologies, which is made up of three cascaded converters. The first stage is a single-phase ac/dc rectifier, which realizes unity input power factor and power transmission between the ac grid and dc bus. The second stage is the LLC-dc/dc transformer (LLC-DCX) which provides electrical isolation and fixed voltage transfer ratio. Besides, the natural bidirectional power flow can be achieved by the proposed solution. The third stage is a synchronous buck converter (SBC) which guarantees the high dynamic performance and wide range voltage regulation. Experiments based on an 8-kW prototype are conducted to verify the feasibility and effectiveness of the proposed converter and the related control strategies.

Working as a dc–dc transformer (DCX), which operates at the resonant frequency, is a suitable solution to achieve the maximum conversion efficiency of the LLC converter. However, because the fixed-frequency modulation is applied, the voltage regulation performance is limited. To achieve tight voltage regulation and fully utilize the advantages of LLC -DCX operation under bidirectional isolated power application, in this article, a single-stage dual active bridge (DAB) LLC hybrid bidirectional converter based on the sigma converter structure is proposed. In the proposed converter, the main power flows through the LLC converter, and DAB is used for the power flow direction control and output voltage regulation. In addition, a mathematical model of the proposed converter is derived for the controller design, which is verified by circuit simulation. Based on the model, the design of the controller and the circuit parameters are discussed with the goal of fast dynamics. Finally, the experimental results of a 1200-W prototype verify the effectiveness and advantages of the proposed topology and controller design.

For the high-power Li-ion battery (LIB) formation and grading system, using a multistage conversion structure, an isolated bidirectional dc–dc converter with a high input voltage, and a large output current is needed to achieve isolation and a relatively fixed voltage conversion gain. This article proposes a modulation strategy and modifies the topology to achieve natural bidirectional power transfer, automatic power sharing, and power limitation for an input-series–output-parallel (ISOP) LLC-DC transformer (DCX) converter. First, an active pulsewidth modulation (PWM) strategy is proposed to avoid synchronous rectifier (SR) sensing and to achieve the natural bidirectional power flow for each submodule. The resonant current always keeps discontinuous, and the conversion gain can keep constant if ignoring the conductive resistance. Second, clamping diodes are added in the conventional LLC converter to limit the inrush current during startup, and to achieve a constant power limitation under an overload condition. Third, with the proposed modulation, the power sharing of the two-module ISOP LLC converter is analyzed and compared with the conventional ISOP LLC converter. Finally, experiments based on an 8-kW (output: 15 V/533 A) prototype composed of the two-module ISOP LLC converter are conducted to verify the effectiveness of the proposed solution.

Two modulation strategies based on carrier-based modulation (CBM) scheme (named RCMV-CBM1 and RCMV-CBM2) are proposed to reduce the common-mode voltage (CMV) of a five-phase voltage source inverter. The basic characteristic of them is that two kinds of carriers with opposite phase are adopted. By applying the opposite carrier to some specific phases, the switching states with higher CMV absolute value can be avoided. In RCMV-CBM1, the output phase with the third largest modulated signal uses the opposite carrier, and the peak-to-peak value of CMV is reduced by 40%. In RCMV-CBM2, the output phases with the second largest and fourth largest modulated signals use the opposite carrier, and the peak-to-peak value of CMV is decreased by 80%. However, the ripple analysis reveals that RCMV-CBM1 has an advantage over RCMV-CBM2 in current quality. In addition, the optimized RCMV-CBM1 and RCMV-CBM2 are presented for reducing the output current ripple. Finally, a scaled-down prototype is built to verify the correctness and effectiveness of the proposed modulation strategies.

A family of modulation schemes based on mathematical construction for the multimodular matrix converter (MC) with ordinary multiwindings transformer is proposed in this paper. The key to the schemes are the calculation of offset signals. A geometric method is introduced to determine the range of the offset signals. The modulation schemes could be divided in two categories based on the geometric positions of the offset signals: continuous modulation (Method I) and discontinuous modulation (Method II). The former has the advantages of ease of use and good power quality. While the later has the advantage in power losses. Additionally, both methods can achieve the maximum linear voltage transfer ratio. To obtain better output current quality, a switching pattern with specific sequence is provided. Finally, a scaled-down prototype is built to verify the correctness and effectiveness of the proposed modulation strategies.

Based on the equivalency between the full-bridge indirect matrix converters (MCs) and the 3 $\times$ 1-modular MCs, the carrier-based modulation strategy is first tailored for the 3 $3\!\times\! 1$ -modular MC. It can be directly expanded to $3\!\times\! N$ -modular MC, but in order to improve the power quality, the phase-shifted (PS) method and phase disposition (PD) method are proposed. The former is suitable for the $3\!\times\! N$ -modular MC with any multiwinding transformers (including phase-shifting transformers). Moreover, the latter is only applicable to the $3\!\times\! N$ -modular MC with ordinary multiwinding transformers. The PD method has advantages over the PS method in the output current quality and efficiency. However, the PS method is superior to the PD method in the input current quality. Experimental results verify the correctness and effectiveness of the proposed modulation schemes.

A new topology based on indirect matrix converter (IMC) is proposed to enhance the input reactive power capability. This topology consists of a conventional IMC and an auxiliary switching network (ASN), which is connected to the dc-link of the IMC in parallel. With the aid of ASN, an implicit current source converter-based static synchronous compensator can be embedded into an IMC, which lays a foundation for the input reactive power control. Based on the proposed topology, two modulation schemes are presented, and the formations of the output voltage and input reactive current are decoupled in both of them. To minimize power loss and improve input current quality, a double closed-loop control algorithm is introduced, in which the current through the dc inductor in ASN is controlled to be minimum. Different from the conventional IMC, the input reactive power of the topology is independent of its load condition without considering the practical constraints. The effectiveness of the proposed topology and modulation scheme is confirmed by experimental results.

To expand the matrix converter application in high power area, a new three-level diode-clamped matrix converter topology as well as a related multicarrier-based modulation scheme is proposed. The topology inherits the features from the conventional multilevel inverter and the indirect matrix converter, which is composed of a cascaded-rectifier and a three-level diode-clamped inverter. The proposed topology can overcome the voltage rating limits of the power semiconductors for high-voltage applications to some extent. Meanwhile, except the general advantages, such as bidirectional power flow, sinusoidal input and output currents, simple switch commutation, and a compact structure, it also avoids the voltage balance issue that exists in most conventional multilevel inverters. Finally, the functionality and effectiveness of the proposed topology and modulation scheme are verified by simulation and experimental results.

In this paper, a modulation strategy based on mathematical construction is proposed to extend the input reactive power range for the three-phase matrix converter, which offers clear physical meanings and less computational efforts. This strategy is developed based on the construction of the modulation matrix composed by the sum of several matrices, one of which is used to generate the required output voltage. The others are intended to provide more degrees of freedom for control such that the matrix converter can produce the input reactive power as much as possible. In the framework of mathematical construction method, an optimization problem for the maximum input reactive power is formulated, whose analytical solution is difficult to obtain. Usually, optimization problem can be solved by using some numerical methods, but lots of time will be consumed. Therefore, a suboptimal method is presented to mitigate the computational burden. Besides, the proposed strategy is compared with the optimum-amplitude and indirect SVM methods, in terms of the maximum input reactive power for different operating conditions. It is shown that the proposed method can obtain the maximum input reactive power over most situations. Finally, the correctness of the proposed method is confirmed by simulation and experimental results.

To adapt the battery voltage and increase charging efficiency in vehicle to grid (V2G) systems, an ac/dc matrix converter topology is presented. Aim to solve the problem of relatively large charging current ripple in the classical current space vector modulation strategy, a sectional optimized modulation strategy, is proposed, which can reduce the charging current ripple within the whole output range. And the comparative analysis is carried out between them. A simple controller with active damping is briefly introduced; it can work at two charging modes: constant voltage charging and constant current charging. The simulation and experimental results demonstrate the validity and effectiveness of the proposed method.

Active power decoupling methods are developed to deal with the inherent ripple power at twice the grid frequency in single-phase systems generally by adding active switches and energy storage units. They have obtained a wide range of applications, such as photovoltaic (PV) systems, light-emitting diodes (LEDs) drivers, fuel cell (FC) power systems, and electric vehicle (EV) battery chargers, etc. This paper provides a comprehensive review of active power decoupling circuit topologies. They are categorized into two groups in terms of the structure characteristics: independent and dependent decoupling circuit topologies. The former operates independently with the original converter, and the latter, however, shares the power semiconductor devices with the original converter partially and even completely. The development laws for the active power decoupling topologies are revealed from the view of “duality principle,” “switches sharing,” and “differential connection.” In addition, the exceptions and special cases are also briefly introduced. This paper is targeted to help researchers, engineers, and designers to construct some new decoupling circuit topologies and properly select existing ones according to the specific application.