Research On Waveform Control Technology Of Metro Auxiliary Inverter Under Complex Load Situation

In recent years, with the continuous development of urban rail transit in China, the low voltage400V load of metro has become increasingly diversified and complicated. In order to make the auxiliary inverter system achieve both high quality output and reliability under various situations, such as pump load, unbalanced load and nonlinear load, the paper studies a slipt-capacitor inverter with neutral inductor topology and its control strategy.First, the paper contrasts some main circuit topology of auxiliary inverter. The former DC/DC part adopts high frequency isolation method, and makes two full-bridge converter circuit in series, so as to reduce the voltage rating of each power tube and improve the switch frequency. Adopting the topology of slipt-capacitor inverter with neutral inductor, the DC/AC part can not only improve the capability of the system with unbalanced load, but also keep the stability of the system as a whole.Secondly, the paper analyses the causes of the auxiliary inverter voltage waveform distortion and points out that the equivalent output impedance of the inverter is the root cause of the output waveform distortion. It lays a foundation for the subsequent chapters to select the appropriate control strategy.Again, the control strategy for the DC/DC isolation converter is studied. It uses the phase shifting control strategy to realize the zero-voltage-switch of the switching tubes. At the same time, the input equalizing control strategy and the equalizing resistance are used to keep the voltages of the two DC/DC module in balance.Next, the paper studies the control strategy of the DC/AC inverter on focus. The double closed loop system with voltage outer ring and current internal ring is designed to make the system have high stability and quick response ability at the same time. The voltage loop adopts a modified PR controller and the current loop uses a simple proportion controller. The parameters of the two controllers are discussed in detail. Based on the actual situation of the system, the TUS transformation method is selected.Finally, the paper carries on the simulation, experiment and actual subway test that prove the practicability and validity of the topology and control strategy.