Ryuji Iijima

Loss analysis of Z-source inverter using SiC-MOSFET from the perspective of current path in the short-through mode

This paper discusses suitable short-through mode for a Z-source inverter using SiC-MOSFET to achieve high switching frequency operation. The Z-source inverter has short-through mode for boost operation and several control techniques about short-through mode have been discussed from points of device stress and boost ratio; however, loss analysis from perspective of short-through mode implementation has not been studied well, especially in the case of using SiC-MOSFET. Losses with two types of short-through mode and three switching frequencies are investigated experimentally. As a result, it was confirmed that the conduction loss and switching loss of the Z-source inverter can be reduce by employing a 3-leg short through mode.

Z-source with rectangular wave modulation inverter for Hybrid/Electric vehicles

An improved circuit topology of Z-source inverter is presented that will meet the requirements and features of the Hybrid/Electric vehicle power control system. It is able to perform rectangular wave modulation for motor drive control depending on the drive condition of a motor which cannot be achieved from the conventional Z-source inverter.

Experimental verification of capacitance reduction in MMC-based STATCOM

This paper proposes capacitance reduction in modular multilevel converter (MMC) based static synchronous compensator (STATCOM). The MMC-based STATCOM consists of several series connected single-phase STATCOM; therefore, the required capacitance to achieve a constant dc voltage is comparatively high. The basic concept of the capacitance reduction and control principle have been proposed in single-stage STATCOM. This paper extents them to MMC configuration. A control method including capacitor peak voltage based control and voltage balancing control is proposed. The control was demonstrated in a fabricated small-scale setup of 3-cascaded single-phase STATCOM, and waveforms in stead-state and transient are shown. By applying the proposed control technique, the peak voltage was confirmed to be almost constant while the current set-point is changed in step, and a good voltage balancing in dc-side capacitors of each cell was also confirmed.

Improved impedance source inverter for hybrid/electric vehicle application with continuous conduction operation

This paper proposes an improved impedance (Z) source inverter topology. Compared to the traditional impedance-source inverter, it can reduce Z-source inverter device voltage stress significantly to perform the same voltage boost, and provides the controllable and stable output power in all load condition. The control strategy of the proposed Z-source inverter is exactly the same as the traditional one. An input filter is also proposed to suppress the power source stress due to pulse input current. The operation principle of the improved topology is analyzed in detail. Experimental results are given to demonstrate the new features of improved topology. Compared to conventional topology 32% reduction of dc-link voltage stress and 75% of input current ripple reduction is achieved.

Loss comparison of Z-source inverter from the perspective of short-through mode implementation and type of switching device

This paper reports power losses of Z-source inverter due to switching device and short-through mode. The Z-source inverter has number of possibilities of short-through mode. This paper compares losses with 1-leg short-through, and 3-leg short-through modes. When SiC-MOSFETs are used as a switching devices, employing the 3-leg short-through mode is confirmed to be an advantage due to comparatively low switching losses. On the other hand, 1-leg short-through mode for Si-IGBTs is advantage due to comparatively low conduction losses. It is understood that optimization of switching pattern of short-through mode is required to archive high efficiency for Z-source inverter.

Investigation of eliminating free-wheeling diode conduction of Z-source inverter using SiC-MOSFET

In this paper, the current paths in the circuit of Z-source inverter using SiC-MOSFET are studied. The Z-source inverter can boost the input voltage using short-through operation, and also invert the DC voltage to AC voltage. Short-through operation is able to eliminate the free-wheeling diodes. This leads to reduce the number of semiconductor devices used in motor drive system with boost function. In the free-wheeling operation, the current flows through the reverse conducting SiC-MOSFET, and never flows the body-diode of SiC-MOSFET. Therefore, the degradation of SiC-MOSFET due to body-diode bipolar action is not needed to take account. These phenomena are examined experimentally. And it is concluded that SiC-MOSFET is suitable for high-performance high-reliable and low-cost Z-source inverter.