Control Strategy Research Of The Inverter Parallel System

With the rapid development of science technology and society, various industries are stricter to the requirement of power supply system. Relative to the power supply system of single inverter module, the parallel power supply system of multiple inverter modules not only has a huge advantage on redundancy, capability, but also has greater flexibility, reliability, and lower costs of designing and operating.Compared to other control strategies of the inverter parallel system, and classified their advantages and disadvantages respectively, and this paper focus on the inverter parallel system, which controlled without interconnection, as the investigated subject. The performance of single inverter module has a great influence on the operation of the inverter parallel system, so single inverter module with excellent performance is the precondition of the inverter parallel system to operate stably. According to actual requirements, analyzed and constructed the emulational model of the single inverter module, and designed three kinds of closed loop controller, which verified and compared the simulation results of three controllers,and the results show that the single inverter module under the double closed loop controller has desirable merits such as high steady state accuracy, fast dynamic response, high quality output voltage.Through theoretical analysis of the inverter parallel system model, it is concluded that the inverter module output voltage amplitude and phase is correlative with both output active power and reactive power, which can control output voltage phase and amplitude to achieve power share, and average the load current. The system circulating current and several factors affecting circulating current were analyzed, which verified the impact of these factors on the system circulating current by the simulation experiment. Aiming at the problem that system has low dynamic response under the traditional droop control algorithm without interconnection, and the paper presents that differential items of power were added to the traditional algorithm to enhance the dynamic performance of the inverter parallel system. The simulation results show that new droop control algorithm without interconnection can improve the dynamic performance of inverter parallel system, and restrain the system circulating current, average the load current, and system can operate stably.