Research On Three-Phase Parallel Inverter System Based On Input Or Output Power Control

The three-phase AC power for ventilation unit, lighting and electric hearters in metro is provided by auxiliary inverter power supply, which is consist of three-phase inverter in wireless parallel. This paper mainly studies the wireless parallel of three-phase inverter.The control of three-phase inverter is the base of the research on the three-phase parallel inverter system. The AC parameters in three-phase system can be transformed into DC form by Park transformation. On the basis of brief introduction and analysis of the hardware, the voltage singleloop dynamic model of three-phase inverter in dqO coordinate system is derived and the control parameters are designed. And the experimental result verify the control method in dqO coordinate.The three-phase inverter parallel system should be analyzed and designed properly. This paper describes the basic priciples of output power droop method, analyzed the effect of output impendance and wire impendence. And a new input power droop method is proposed. At the end of chapter3, power calculation and phase testing is discussed.Experimental waveforms and current data of the wireless parallel system verify the principle of input power droop method and output power droop method. In steady-state, system performance well in each droop method. In dynamic state, the difference of control of inverter lead different performance. The current control loop can prevent big difference of output current at the moment of load changing, but it also hinder the recover of existing difference of output current.