Coordinated Control for High-Power Back-to-Back Inverter Testing with Wide Power Factor and Frequency Range

Back-to-back inverter testing is commonly used to test high-power inverters in laboratory settings. This test involves a second AC/DC converter to feed the AC power back to the DC bus, thereby reducing the demand on the DC power supply to only compensate for system losses. However, this circulating power path presents challenges in zero-sequence current (ZSC) control, particularly when employing space vector pulse width modulation (SVPWM). This necessitates the implementation of an additional control loop. This paper addresses the aforementioned challenge by proposing a coordinated control strategy between the two converters. A detailed system model is developed, and the proposed method is elaborated upon. Furthermore, the paper analyzes the relationship between power factor, modulation index, and fundamental frequency. In comparison with existing methods, the proposed control strategy enables a wide range of power factor and modulation index, while maintaining the modulation strategy of the inverter under test unchanged, thereby improving testing accuracy. The effectiveness of the proposed method is validated using Matlab/Simulink.