Study On Neutral Point Clamped Seven-level Reactive Compensation Controller

With the development of new energy sources and universal application of power electronic equipment,it is inevitable to burden the power supply system.These electrical equipment and power generation devices are integrated into the power grid,which directly results in grid voltage fluctuations,current distortions that are no longer standard sine waves and the grid voltage and current are out of phase.How to choose a suitable topology and strategy of control to achieve efficient and accurate reactive harmonic current compensation that has become a research hotspot.For this reason,according to‘compare'and‘analyze'several existing basic topologies,this dissertation proposes a neutral-point clamped seven-level reactive power compensation controller,which uses fewer switching devices and DC capacitors to achieve multi-level voltage output and reactive harmonic current compensation.This article first introduces the research background of this topic and the current research status in domestic and abroad,analyzes the existing topology,multilevel modulation strategy and automatic control strategy,and proposes a new seven-level topology static var generator(SVG).By analyzing the compensation principle of the reactive harmonic current and the working principle of the neutral-point clamped seven-level topology,a mathematical model is constructed,and the carrier stack modulation method suitable for the topology is selected,and finally the methods i_p-i_qcurrent detection method is selected by comparing several current detection,the detection method is given when the load is unbalanced.A bi-second-order generalized integral phase-locked loop(DSOGI-PLL)is proposed to achieve real-time phase-locking of the grid voltage.Secondly,a new seven-level SVG voltage and current control strategy.This article is designed.The quasi-PR+repetitive control method is selected to achieve the current closed-loop control;the hardware voltage equalization method is choosed for the neutral point voltage control,it is choosed the voltage equalization method based on carrier stack modulation for the low-voltage capacitor balance control.According to the proposed topology to design the system capacity,the inductance and capacitance parameters are calculated,and Matlab/Simulink software to build an overall simulation model is used,the feasibility of the system topology and control strategy is verified,and the simulation results is analyzed.Finally,the hardware circuit and software program of the neutral point clamped seven-level reactive power compensation controller are designed,the overall control block diagram and software flowchart of the system are given,the system hardware experimental platform is built,the experimental waveforms are observed,the compensation effect is analyzed,and Seven-level SVG compensate is verify for harmonics and reactive current.