Kazuhiro Koiwa

Input current stabilization control of a matrix converter with boost-up functionality

This paper proposes a circuit topology of a matrix converter that adding a boost up function in the input side. The proposed circuit combines the matrix converter with a V-connection AC chopper. A conventional control method can be applied in this matrix converter, so called the virtual indirect method. In order to suppress the input filter resonance, this paper discusses about the input filter design with a damping resistor. In addition, this paper also proposed a stabilization control for the input current that is using a V-connection chopper. The basic operation and validity of the proposed method is confirmed by the simulation and experimental results. The total loss of the proposed circuit is 20 % less than that the loss of the conventional back to back system.

A Maximum Power Density Design Method for Nine Switches Matrix Converter Using SiC-MOSFET

This paper presents a matrix converter design for achieving maximum power density using a SiC device based on a front-loading design. To design the matrix converter to achieve maximum power density, the conduction loss and the switching loss of the matrix converter are theoretically derived and validated by simulation and experiment. Based on these formulas, the relationship between the efficiency and power density are revealed by using a Pareto-Front curve in order to solve the tradeoff problem between the power density and the efficiency. Moreover, in order to promote the widespread use of the matrix converter instead of a BTB system, it is quantitatively evaluated that the power density in the matrix converter is increased by 4.19 kW/dm3 in comparison to the BTB system. Moreover, the power density of the matrix converter that uses a SiC-MOSFET (ROHM) as the switching device with natural air cooling is 95.0% (2.1 kW/dm3) of the calculated maximum power density. Thus, the power density of the matrix converter is improved by 57.5% by the maximum power density design method. Based on the results, the design method for a high power density ac-ac direct converter is established according to the requisite specifications.

Experimental verification of single-phase inverter with power decoupling function using boost-up chopper

This paper discusses a circuit configuration for a single-phase voltage source inverter that features power decoupling function. Generally, the converter that is connected to a single-phase power grid is required to decouple the power ripple with a twice frequency of the power grid. The proposed circuit compensates the single-phase power ripple by using an active buffer with small capacitors 50μF at 200 W. In this paper, the fundamental operations of the proposed converter are confirmed by experimental results. Then, the proposed converter is evaluated with the maximum power point tracking (MPPT) under a simulated photovoltaic (PV) conditions. From the experimental results, the output current Total Harmonic Distortion (THD) is 3.51% and the output power factor is over 99%. In addition, the input current ripple is reduced 12.3%. Moreover, from the loss analysis, the maximum efficiency of the inverter including the active buffer circuit is 95.5%.

Improvement of waveform for high frequency AC-linked matrix converter with SVM based on virtual indirect control

This paper proposes a dead-time compensation for a secondary side matrix converter with space vector modulation in order to improve waveform of the high frequency AC-linked matrix converter. The proposed system is constructed by back-to-back configuration of two three-phase to single phase matrix converters and a high frequency transformer. In order to improve the waveform, the dead-time compensation for the primary side matrix converter has been proposed. However, the dead-time compensation for the secondary side matrix converter with space vector modulation based on virtual indirect control has not been discussed. In this paper, the dead-time compensation method for the secondary side matrix converter is revealed. As the result, it is confirmed that the average output voltage error between the command and measured voltage is reduced by 20% at low modulation index by adopting the dead-time compensation. Finally, a 2-kW prototype is demonstrated by experiment. The efficiency and the input power factor at the maximum point were obtained by 91.4% and 0.997. Moreover, the input current total harmonic distortion (THD) is 5.65% at 2-kW output power.

Space vector modulation based on virtual indirect control for high frequency AC-linked matrix converter

This paper proposes a space vector modulation of a high frequency AC-inked matrix converter which is applied to an electric transformer system. The one of problem of a commercial frequency transformer is bulky and heavy. In order to resolve this problem, we propose to use a high frequency transformer driven by three-phase to single phase matrix converter. In this paper, the virtual indirect control method with a space vector modulation is applied to the primary and secondary side matrix converter. Particularly, the control of the secondary side matrix converter should be considered because the input is rectangle which has multiple levels of voltage. The fundamental operation of the proposed system is demonstrated by experiment and simulation with 1-kW prototype. Besides, the volume and weight of the proposed system are compared with that of the commercial frequency transformer system at 50 kVA. As the result, it is confirmed that the volume and weight of the proposed system are reduced to 15% and 5%, respectively in comparison with that of the transformer system.

Evaluation of a maximum power density design method for matrix converter using SiC-MOSFET

This paper discusses a maximum power density design for a matrix converter using SiC device based on front loading design. In order to design the matrix converter at maximum power density, the conduction loss and the switching loss of the matrix converter are derived theoretically. Based on these equations, the relationship between the efficiency and power density are discussed by Pareto-front curve in order to solve the tread-off problem between the power density and the efficiency. From the experimental results, the maximum efficiency is 98.3% with two phase modulation at 3.9-kW output power and 25-kHz switching frequency (Devices: SiC-MOSFET BSM00003A ROHM). Moreover, the maximum power density of the matrix converter reaches 2.12 kW/dm3 (the design value is 2.22 kW/dm3) with a natural air cooling. Thus, the design method of a high power density AC-AC converter using a matrix converter is established according to the specifications.

Loss analysis and design method for high efficiency matrix converter

This paper discusses loss analysis formulas to achieve high efficiency and high power density for matrix converter. In this paper, the conduction loss and the switching loss of the matrix converter are derived theoretically based on virtual AC-DC-AC control method. Then, the validity of the equations is confirmed in simulation and experiment. From the experimental results, the maximum efficiency is 97.9% with 2-phase modulation at rated power (Devices: MOSFET R6046FNZ). In addition, it is confirmed that the total loss error between the calculation and experimental result is 8.65%. Finally, the relationship between the efficiency and power density is discussed by a pareto front curve. The power density is calculated from the volume of the switching device, heat-sink, input inductor and filter capacitor. As the result, the efficiency and maximum power density in the matrix converter are 97.0% and 9.7 kW/dm3 when the switching frequency is set to 85 kHz.

Miniaturization of the boost-up type active buffer circuit in a single-phase inverter

This paper discusses miniaturization of a single-phase grid connected inverter, which has power decoupling function for PV. The power ripple of twice grid frequency is compensated in the proposed circuit with the small capacitor (50 μF) at 200 W. However, the buffer inductor in the proposed circuit becomes large because the buffer inductor current is fluctuated at twice grid frequency by power ripple compensation, and the switching ripple is large at the peak current. In this paper, in order to reduce the size of the buffer inductor, the buffer inductance is optimized in terms of the volume and efficiency according to the switching frequency. As an experimental result, it is confirmed that the input current ripple is reduced by 90 % in the proposed circuit, and the output current THD is 3.5 %. On the other hand, the buffer inductance is reduced by 73 % at 64 kHz of the switching frequency. In addition, the volume of the proposed circuit can be reduced by 37% in compared to the conventional circuit. Finally, from the evaluation of the power density using the Pareto front curve, the proposed circuit can design the high power density in compared to the conventional circuit.

A damping control method for a matrix converter with a boost-up AC chopper

This paper proposes a circuit topology for a matrix converter with a boost-up AC chopper in the input stage. In order to suppress the input filter resonance, the authors have developed a stabilization control for the input current using a V-connection AC chopper. However, the input current is required as the signal for the damping control. In this paper, the damping control using the existing filter capacitor voltage is proposed. In order to verify effectiveness of the proposed damping control, the proposed circuit is demonstrated by a 1.8-kW prototype. As a result, it was confirmed that the input current THD can be suppressed approximately 72.5% improved by applying the input current-type or the filter capacitor voltage-type damping controls.

Verification of effectiveness of a matrix converter with boost-up AC chopper by using an IPM motor

This paper describes the matrix converter that features boost-up functionality. The proposed circuit topology connects a V-connection AC chopper at the input side of the matrix converter to achieve the boost-up function. The matrix converter and the V-connection AC chopper are controlled independently, where a virtual indirect control method is applied to the matrix converter, and an open-loop control is applied to the V-connection AC chopper. However, the efficiency of the proposed circuit is low due to the extra loss from the V-connection AC chopper. In this paper, the efficiency of the proposed circuit and the conventional matrix converter is evaluated by using a 3.7kW IPM motor in the simulation and the experiment. The simulation results confirm that by implementing field-weakening control in the conventional matrix converter, the losses are lower than that of the proposed circuit topology, where the proposed circuit improves the efficiency by 12%. According to the experimental results, it is obtained that the proposed circuit can improve the efficiency of 13% in compare with the conventional matrix converter.