一种提高虚拟同步机电流质量的电压-电流级联闭环控制方案  

A Cascaded Harmonic Voltage and Current Closed-Loop Control Method to Improve the Current Quality of Virtual Synchronous Generators

作　　者：徐菘 杨博 刘浩 陆帅 Xu Song;Yang Bo;Liu Hao;Lu Shuai(State Key Laboratory of Power Transmission Equipment&System Security and New Technology Chongqing University,Chongqing 400044 China)

机构地区：[1]输配电装备及系统安全与新技术国家重点实验室(重庆大学),重庆400044

出　　处：《电工技术学报》2024年第6期1871-1885,共15页Transactions of China Electrotechnical Society

基　　金：重庆市研究生科研创新资助项目(CYB21018)。

摘　　要：当虚拟同步机(VSG)接入畸变电网时,其输出电流质量恶化。现有基于公共耦合点(PCC)电压采样的各种谐波治理方案受限于线路阻抗的大小而抑制效果不佳。为此,该文提出一种电压-电流级联闭环控制策略实现了VSG基波电压和线路谐波电流的协调闭环控制。在基波频率下,VSG跟随功率控制回路的基波电压指令实现功率传输;在谐波频率下,通过单个一阶复矢量滤波器对谐波电流总和进行整体提取,并采用闭环输出谐波电压补偿的参考量,从而等效增强了谐波电压补偿量的参考信号,大幅提升了VSG输出电流的谐波抑制效果。相比于现有方案,该方法克服了由于线路阻抗过低而抑制效果不佳的问题,能在不增加额外电感器件的条件下提高VSG在畸变电网下的输出电流质量。最后,该文搭建15 kW的样机进行实验,并与现有的三类方法进行对比,较为全面地验证了该方法的有效性且增强了谐波的抑制效果。With the increasing amount of renewable energy sources and energy storage devices in the power grid,more power electronic inverters get tied to the grid as current sources.As a result,the overall grid rotary inertia and frequency stability will decrease.So Virtual Synchronous Generators(VSG)schemes are being implemented in grid-tied inverters.VSGs are inverters in voltage source control mode.Particularly,its output voltage vector instantaneous angle is obtained by the rotor dynamics equation of the virtual synchronous generator to provide inertia and frequency support to the grid,just as the rotary synchronous generators.However,when VSG is connected to the grid,even a slight amount of grid voltage distortion would induce significant harmonics currents.Therefore,various VSG harmonic current suppression schemes are introduced.Existing VSG harmonic current suppression methods are mainly based on PCC voltage feedback, whose voltage harmonics get extracted and added to the VSG output voltage commands. Therefore, the line connecting VSG and PCC would have no net harmonic voltage across, and no harmonic current would be induced. However, the existing methods based on PCC voltage feedback have practical limitations. As the line impedances are usually small, it only takes a tiny amount of harmonic voltage difference to induce a significant amount of harmonic currents. Slight noises and nonlinearity in the feedback path will introduce harmonic voltage difference and large harmonic current. Therefore, some paper proposes adding extra inductors in series with the PCC connecting line, but extra volume and cost are incurred. This paper introduces a VSG output harmonic current closed loop to receive the voltage harmonic signal feedback. Therefore, the noises and the nonlinearity in the previous open-loop PCC harmonic voltage feedbacks can be eliminated, and the VSG output voltage can accurately track the voltage harmonics at the PCC point. As a result, the output current harmonics suppression is more effective. This paper firs

关 键 词：虚拟同步机 谐波抑制 阻抗重塑 电能质量 

分 类 号：TM464[电气工程—电器] TM341TM762