大功率并网变流器离散域电流控制策略  

Discrete-Time Domain Current Control Strategy for High Power Grid-Connected Converters

作　　者：王旭[1] 杨淑英[1] 李典 张兴[1] Wang Xu;Yang Shuying;Li Dian;Zhang Xing(National and Local Joint Engineering Laboratory for Renewable Energy Access to Grid Technology Hefei University of Technology,Hefei 230009 China)

机构地区：[1]合肥工业大学可再生能源接入电网技术国家地方联合工程实验室,合肥230009

出　　处：《电工技术学报》2024年第8期2523-2540,共18页Transactions of China Electrotechnical Society

基　　金：安徽省科技重大专项资助项目(202003a05020029)。

摘　　要：兆瓦级大功率并网变流器的开关频率较低,延迟和离散化误差对控制性能影响较大,导致动态响应慢、电网背景谐波影响大等问题。因此,直接离散域控制系统设计成为必要。该文针对LCL滤波并网变流器建立离散域数学模型,并基于此提出桥臂侧电流和网侧电流融合的离散域电流控制器。同时,为了在不额外增加电流传感器和检测电路的情况下获取并网电流信息,设计电容电压微分器,实现网侧电流的估算,降低硬件复杂性和控制成本。研究表明,该文设计的离散域电流控制器,具有较好的动态性能和电网背景谐波抑制能力。最后,通过硬件在环半实物仿真系统对所提设计进行了实验验证。For high-power grid-connected converters,the switching frequency usually is low.Consequently,the adverse effects enforced by the control delay and discretizing errors are heavy.However,traditional current control strategies generally ignore these effects,reducing the performance of the designed controller.Recently,some strategies were presented to compensate for the control delay and the discretizing errors.However,most suffer from low dynamic response and high sensitivity to the power grid harmonics.Therefore,a current control strategy combining the bridge arm-side and the grid-side currents is designed directly in the discrete-time domain,and pole-zero placement is used in synchronous coordinates.Meanwhile,a differentiator to the capacitor voltage is introduced to estimate the grid-side currents.Consequently,hardware complexity and the corresponding control cost are reduced.The discrete-time model of the converter with LCL is built in synchronous coordinates as the output filter,including the computational delay,firstly.The corresponding structure of the combined state-space control scheme is as follows:the harmonic control loop of the grid-side currents is constructed and combined with the fundamental current control loop on the bridge arm-side using the full state-feedback control.And then,the integral controller is introduced for improved disturbance rejection,and the reference-feedforward controller is designed to increase the reference-tracking dynamic performance.Consequently,the closed-loop transfer function of the system is obtained based on the discrete-time model and the control scheme.Then the state feedback function matrix and the feedforward module are optimized based on the pole-zero placement.Finally,a differentiator is introduced to estimate the grid-side currents,reducing the hardware cost.Experiment results based on a hardware-in-loop simulator show that the response time of the bridge arm-side currents to a 1000 A step-up change is about 4.5 ms;the recovery time of the bridge arm-side current

关 键 词：LCL型并网变流器 低开关频率 离散域控制 背景谐波 

分 类 号：TM464[电气工程—电器]