Multi Quasi PR Parallel Controller for Unbalanced Load of Three phase Four bridge Arm Inverter

Simulation of Multi Quasi PR Parallel Controller for Unbalanced Load of Three phase Four bridge Arm Inverter
1. The three-phase four bridge arm inverter adds a bridge arm to the traditional three-phase bridge inverter, which directly controls the neutral point voltage and generates neutral point current flowing into the load by adding a bridge arm. This increases one degree of freedom, allowing the three-phase four bridge arm to generate three independent voltages for the inverter power supply, thereby enabling it to maintain symmetrical output of three-phase voltage under unbalanced loads
2. Topology advantage:
a. Has a high DC utilization rate and a small DC input capacitance;
b. Reduce the asymmetry of three-phase output when unbalanced load is reduced;
c. Adding inductance to the neutral line can improve the filtering effect of the system output terminal, suppress the switching ripple in the circuit, and reduce the harmonics of the three-phase voltage
3. Modulation strategy: Carrier based PWM modulation (harmonic injection PWM (HIPWM)) can achieve the equivalence of harmonic injection and traditional 3D-SVPWM control, and solve the problem of three-phase four bridge arm phase coupling
4. Control: The outer loop adopts PR controller, and the inner loop adopts PI control. And for the 5th and 7th harmonic currents generated by nonlinear loads, proportional multi resonance control is adopted, that is, the 5th and 7th harmonic controllers are connected in parallel
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