Research On Parallel Connection Technology Of Auxiliary Inverter For Low Floor Vehicle

In this paper, author has made study on the auxiliary inverter of DC-AC part of low-floor light rail vehicle auxiliary converter, and focused on the control program of single inverter and the flow control technology of multiple inverters parallel system.Based on the circuit topology of three phase two-level auxiliary inverter, this paper derives three-phase static coordinate model, two-phase static coordinate model and two-phase stationary coordinate model of the inverter. And uses the double-loop of voltage and current control strategy based on dq rotating coordinate to decouple inverter system; makes quantitative analysis of the system output filter parameters and determines L, C values of the filter based on the ripple wave requirement of output voltage and current; selects PI controller, selects the type â…¡ control system for voltage outer loop which has high precision, and the type â…  system for current inner loop which has fast dynamic response; establishes appropriate simulation models, makes analysis and comparison of results which shows that the control strategy has good steady-state and dynamic performance, also with a strong load capacity.Making analysis of the circulation characteristics of two auxiliary inverter parallel system, gets the conclusion that cause lies in the difference of the inverter output voltage frequency and amplitude of inverter each side, a formula has been established to derive relationships between circulation and distribution of active power, reactive power; in power systems theory, there is a relationship which the voltage is linear with the frequency of power generation equipment, so it can be considered that the frequency, amplitude have a linear relationship with active and reactive power respectively; in order to obtain a flow equalize system, uses conventional droop control method to make sure the inverter output voltage frequency, amplitude are able to follow the unified set point values; through simulation analysis that droop control strategy compares with no current control strategy, can draw a conclusion that the droop control can be a good method to suppress parallel system circulation.Sets up the experimental platform of digital control for auxiliary inverter system, including hardware device and software device design; uses DSP+FPGA architecture for the core controller, DSP exchanges information with FPGA between the Dual-port RAM, DSP implement the core control algorithm, FPGA samples output voltage and current and protects system from fault; paper achieves the function of sampling conditioning circuit, also the software functions of Quartus â…¡ based for FPGA an CCS based for DSP. Finally, dual closed-loop control experiment for single auxiliary inverter has been done on the35kW experiment platform of auxiliary inverter, obtained waves under resistive load condition, and analyzed its experiment data, obtained experimental result that inverter output stable three-phase industrial frequency AC220V under resistive load condition; done validation experiment of load mutation for single auxiliary inverter, obtained experimental result that inverter can keep output voltage unchanged before or after load mutation; Through above experiments, the correctness and validity of the dual closed-loop control has been verified.