Research On Control And Parallel Technology For High Power Three-Phase Inverter

As an important part of AC power supply, three phase inverter is widely used in areas like electric vehicles, power instruments, industrial instruments and transportation systems. Parallel technology has got intensive studies for its great potential application. The requirement for inverters got higher and higher, and high efficiency and high reliability are the development trends. There are two main ways to increase the capacity of inverter, including designing high power inverter and applying parallel technology to achieve power modularization.Analyze the structures which are suitable for application of high power combined type inverters and propose the power circuit design of 400kVA combined type three phase inverters, and then modeling combined type three phase inverter in ABC,αβand dq coordinate system.Adopting unified control scheme and three-phase voltage closed-loop control scheme for synchronous rotating dq coordinate system for high power combined three phase inverter. Adopt control method combined with digital PID voltage feedback control and repetitive control. Analyze the principle of PID control and repetitive control and give the design method of relevant PID digital controller repetitive controller for 400kVA three phase inverter. The matlab simulation is performed to verify the theoretical research.Propose two methods which could increase system dynamic performance: load current feed-forward and change the modulation ratio. Introduce short circuit current protection technology of high power three phase inverter, propose control scheme combined with transient current limiting method and software current limiting which will guarantee automatic short circuit current limiting protection of high power three phase inverter.Analyze structure, circulating current characteristic and output power of parallel system composed with two high power three phase. Analyze differences of inverter circulating current and output power distribution when the output impedance characteristic is not the same, and get the general rule of influence for circulating current and power distribution of output impedance.Adopt distributed logic control scheme based on power error of high power three phase inverter parallel system. Analyze scattered logic control principle based on scattered logic control, inverter output power detection and PWM pattern of bus signal synthesis. Based on the output impedance characteristic of 400kVA three phase inverter parallel system, the dissertation applies parallel control scheme which uses reactive power to regulate voltage magnitude and synchronous phase lock to realize phase synchronization.Hence, aiming at two 400kVA combined type three phase inverters, the dissertation researches the waveform control and parallel control technologies of high power three phase inverters with full digitalized control method. Centering on high power combined type three phase inverters, the dissertation analyses and studies the topology of power circuit, mathematical model of control system, waveform control technology and parallel system model in detail.The experimental verification is realized in two 400kVA combined three phase inverters. The experiment result verifies the feasibility of voltage waveform control and parallel control scheme of high power three phase inverter.