Research Of Static Var Generator And Compensation System Based On Cascaded H-bridge

With the rapid development of the power electronics and control theory, pulse width modulation static var generator(PSVG) based on full-controlled devices emerges as the times require.This kind of static var generator with bipolar compensation function and high performance will be applicated in power system.The paper chooses H-bridge cascaded pulse-width modulation static var generator(HPSVG)as research objection and makes a serial of study and probe into topology structure、work principal、control method and digital realization.Firstly, The article takes single-phase pulse width modulation static var generator as example and deeply narrates the principle of producing capacitive and inductive reactive power by PSVG.Giving the topology structure based on H-bridge cascaded multilevel pulse width modulation static var generator, narrating the work process of the circuit of PWM and gaining theoretical multilevel waveform,the result is verified by Matlab simulation.Secondly, As to three-phase pulse width modulation static var generator,it gives the voltage balance equation in the rotating coordinate system by analyzing. Providing the vector control system structure of three-phase static var generator without auxiliary DC power source on the basis of that and analyzing its work principle.Especially, the paper makes detail analysis that how the system maintains the constancy of Ud in DC side.The system simulation shows the control structure of system is correct and feasible.Thirdly, the paper provides reactive power dynamic compensating control structure diagram based on H-bridge cascaded high voltage pulse width modulation static var generator according to the reactive power dynamic compensating requirement of power supply system client.The compensating system has the function of power factor closed-loop control and sets up the LC serial resonance passive filter,so it effectively decreases harmonic current in user side.Meanwhile LC filter also supports fixed capacitive reactive current so that it reduces the capacity of static var generator.Similarly by system simulation, checking the given reactive dynamic compensating system performance in the strike of active and reactive current.The result indicates the system can maintain the power factor stability of user side.Finally, setting up a three-phase two H-bridge cascaded SVG based on the control chip of TMS320F2812 and giving the experimental waveform under the condition of capacitive reactive power compensation.