Research On Direct Power Control For PWM Rectifiers Without Line Voltage Sensors

For converter,"green" means no power grid harmonic pollution, unit power factor.This article studies PWM rectifier with unity power factor, bidirectional flow of the powerand sinusoid current, etc. It is truly "green electricity", has become a hot area of powerelectronics technology.The typical topologies PWM rectifier is analyzed in this paper, its principal andfour quadrant run was studied, and the mathematic model of three-phase voltage sourcePWM rectifier in three-phase stationary, two-phase stationary and two-phase synchronousrotating coordinate system are established. Provide theoretical basis for the instantaneouspower calculation.According to instantaneous power theory, the mathematical power model isestablished, and direct power control strategy is proposed, the instantaneous active andreactive power output of the rectifier are chose as the controlled object of closed loopcontrol. Without grid voltage sensor, the control principal and procedure of voltage directpower control (V-DPC) and virtual flux direct power control (VF-DPC) are analyzed.The switch frequency of direct power control system using hysteresis comparator isnot fixed， it is inconvenience to the output filter design. For that, based on PI regulator,the fixed frequency of VF–DPC is proposed, use PI regulator as the power controllerinstead of hysteresis comparator, so that a fixed switch frequency modulation algorithm ofspace vector PWM can be used for generating switch control signals.The experiment platform of PWM rectifier has been designed in this paper. Thecontrol board is based on TMS320F28335of Texas Instruments (TI), the intelligent powermodule (IPM) PS22A76of Mitsubishi is the core of power drive. Also the methods fordesigning fuse, AC side inductance, dc side capacitance, sampling circuit, soft start circuit,DSP control circuit are given. To realize digital control of PWM rectifier, the main program and interrupt program are designed.Based on Matlab/Simulink, the simulation model of voltage PWM rectifier isestablished. The simulation and experimental waveforms verify the proposed controlstrategies and algorithms.