This paper discusses two overmodulation controls, namely, square wave and trapezoidal, in the indirect matrix converter (IMC) for motor drive application. The differences between these two modulations are analyzed based on the output-input voltage transfer ratio (VTR), the efficiency, and the current total harmonic distortions under two load conditions. Moreover, the performance is then improved by implementing four-step commutation methods in the primary side of the IMC. The validity of the proposed methods will be demonstrated through simulation and experimentally. The experimental results show that the VTR can be improved from 0.866 to 0.97 in the square wave modulation and 0.92 for the trapezoidal wave modulation in an induction motor drive system. Index Terms-AC/AC converter, indirect matrix converter (IMC), overmodulation, pulsewidth modulation (PWM), square wave, trapezoidal wave.

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This paper proposes a parallel operation system of permanent magnet synchronous motors (PMSMs) and verifies the suppression effect of the proposed damping control for the torque vibration caused by resonance between synchronous reactance and inertia moment. The proposed system is composed by two types of power converters, a main inverter with a V/f control and an auxiliary inverter with the field-oriented control and the damping control. In general, PMSM cannot be driven by the V/f control such as an induction motor because the speed vibration is caused by the resonance between the synchronous reactance and the inertia moment. In the proposed system, the multiple PMSMs are driven in parallel by the main inverter with the V/f control. When the motor speed vibration occurs, the damping control for the auxiliary inverter suppresses this vibration in PMSM. From the frequency characteristics, it is clear that the power capacity of the auxiliary inverter is 10% lower than that of the main inverter when the frequency components included in the speed command are lower than 12 rad/s. As a result, the experimental results demonstrated that the proposed system can reduce the speed vibration from 400 r/min to nearly 0 r/min with the damping control in our prototype of 1500-W PMSM drive system. The experimental results well agree with the theoretical analysis results.