Research On Coordinated Control Strategy And Performace Of Dual PWM Converter

Dual PWM converter has been widely applied in power industry, especially inthe field of speed regulation system for permanent magnet synchronous motor(PMSM), due to advantages of sinusoidal net side current, adjustable power factorand bidirectional flow energy. The main contents and innovatations are as following:1) The mathematical model of three-phase PWM rectifier is established anddiscretized according to instantaneous reactive power theory in two phase static frame.And on this basis, predictive current control based on instantaneous reactive power(IP-PCC) strategy for grid-side rectifier of dual PWM converter is proposed toimprove the problems about steady state error and sensitivity of variation of rectifierstructural parameters of PCC method. Instantaneous reactive power is set to zero inorder to satisfy unit power factor operation for rectifier system. The cost function isconstructed according to sum of squares of instantaneous power tracking errors in asingle sampling period. And ac current components are predicted by minimizing costfunction in fixed time period. Meanwhile, virtual flux variable is introduced intoIP-PCC method, and an improved low pass filter (FOLP) is adopted for estimatingvirtual flux which added compensation term because of the integral initial values andDC bias problems for pure integrator, to realize IP-PCC strategy without ac sourcevoltage sensor of PWM rectifier.2) According to relationships among of variables in static and rotating coordinatesystems which based on the stator and rotor flux, mathematical model ofinstantaneous power for motor-side inverter of dual PWM converter that consisted ofstator current decoupled components and stator flux is built with the help of vectorcontrol approach. And on this basis, predictive instantaneous power control (PIPC)system for inverter is came forward to improve the power factor. The instruction valueof instantaneous active power is calculated around the premises that keep stator fluxamplitude constant. Then expected switch voltage of PWM inverter is forecastedaccording to instantaneous power tracking error. Observability condition of PMSMspeed control system is analyzed. The structure of discrete sliding mode observer(D-SMO) and high frequency rotating voltage signal injection are raised to realizePIPC policy without location sensor in the whole speed range.3) Power flow situation of dual PWM converter is analyzed. According to thestructure of PIPC method, a load power feed-forward control strategy is proposed torealize the coordination of IP-PCC strategy of PWM rectifier and PIPC method of PWM inverter through making predictive instantaneous active power component inPIPC method as load power. Finally, coordinated control for dual PWM converter willbe realized without observation for load power.Dual PWM converter experiment platform in velocity modulation domain ofPMSM is developed. The experiment about predictive current control strategy ofgrid-side PWM rectifier and predictive instantaneous power control method ofmotor-side PWM inverter and load power feed-forward coordinate control strategy ofdual PWM converter are debugged online by means of hardware and software basedon theory analysis and simulation to verify the effective and feasible of relatedtheories.