Power Control for Grid-Tied Single Phase Three Level Inverter Without AC Voltage Sensor

Single phase three level T-Type inverter (3LT²I) has revealed great performance in many fields especially in renewable energy generation system. In order to participate in grid regulation, it's necessary to control the power exchange between renewable energy and the grid. This paper proposes an improved power control strategy of single phase three level T-type grid-tied inverter with constant switching frequency based on instantaneous power theory, carrier based PWM and virtual-flux concept. Firstly, the instantaneous power theory of single phase power system is introduced. Then, a virtual flux observer through the modulation signal directly is introduced which simplify the calculation process and avoid extra error. In addition, fast and accurate power tracking is achieved due to dual loop control strategy. Simulation and experiment have been conducted to verify the proposed modulation strategy.