结合随机空间矢量脉宽调制的静止无功发生器双序控制策略

A Double-Sequence Control Strategy of Static Var Generators Combined with Random Space Vector Pulse Width Modulation

针对采用传统空间矢量脉宽调制(SVPWM)技术的静止无功发生器(SVG)输出电流及电压中含有幅值较高的高次谐波分量问题,提出一种将双随机SVPWM与SVG双序同步相结合的控制策略。首先,在三相三线制系统中将不平衡负载电流与SVG补偿电流分别进行正负序变换,采用基于前馈解耦的电压、电流双闭环控制对正序无功及负序分量进行同步补偿,其中电压外环采用模糊PI控制器以稳定直流侧电压。然后,采用随机开关频率与随机脉冲位置相结合的双随机SVPWM技术,以获得更宽的谐波频谱,优化并网电流波形。不同工况下的仿真及实验表明:所提控制策略可大幅削减SVG输出电流及电压的谐波幅值,驱散集中于开关频率及其整数倍处的谐波能量,获得连续的功率谱密度;实验中采用此控制策略的并网电流谐波畸变率降低至3.88%,功率因数提高到0.972,验证了此控制策略的有效性。

A control strategy combining double random space vector pulse width modulation(SVPWM)with static var generator(SVG)double sequence synchronization is proposed to solve the problem that the output current and voltage of SVG based on traditional SVPWM technology contains higher-order harmonic components with high amplitude.First,positive and negative order transformations between the unbalanced load current and the SVG compensation current are respectively carried out in the three-phase three-line system.The feed forward decoupling based voltage and current double closed-loop control is used to synchronously compensate the positive sequence reactive power and negative order components.A fuzzy PI controller is used in the voltage outer loop to stabilize the DC side voltage.Then,a double random SVPWM technique based on combination of random switching frequency and random pulse position is used to obtain a wider harmonic spectrum and to optimize the grid current waveform.Finally,simulation and experimental results under different working conditions are compared.The results show that the proposed control strategy greatly reduces the harmonic amplitude of the SVG output current and voltage,disperses the harmonic energy concentrating at the switching frequency and its integer multiples,and obtains continuous power spectrum density.The current harmonic distortion rate is reduced to 3.88%by using this control strategy in experiments and the power factor is increased to 0.972.These results verify the effectiveness of the proposed control strategy.