基于级联Ｈ桥变流器的风电网宽频带谐波阻抗测量装置

在风力发电中，风电场电力汇集系统与大电网耦合会引发高频谐振问题并影响电网电能质量，深入研究电网阻抗频率特性具有重要意义。基于主动干预法，向公共连接点注入一定扰动电流，提出了一种风电网宽频带谐波阻抗测量装置解决方案。此方案采用三相级联Ｈ桥变流器作为谐波发生单元，控制部分采用分层控制策略。在100~5000 Hz时，向风电场35 kV公共母线注入不同频率的谐波电流，通过测量注入点处的电压、电流数据，进而获得风电场35 kV端口输入阻抗。提出的测量装置无需整流环节，能够发出幅值和频率均可控的正负序谐波电流，可以获得准确的正/负序谐波阻抗，具有体积小、结构简单、控制可靠的优点。最后详细的Matlab仿真全面验证了系统拓扑及控制策略的有效性。

Wide-Band Harmonic Impedance Measurement Device for Wind Grid Based on Cascaded H-Bridge Converter

In wind power generation, the coupling of the wind farm power pooling system with the grid may cause high frequency resonance problems and affect the power quality of the grid. It is therefore important to study the grid impedance frequency characteristics in depth. A wide-band harmonic impedance measurement device is proposed for wind grid based on the active intervention method, which injects a certain disturbance current into the common connection point. This solution uses a three-phase cascaded H-bridge converter as the harmonic generation and a stratified control strategy for the control part. The harmonic currents of different frequencies are injected into the 35 kV bus of the wind farm in the range of 100~5000 Hz, and the input impedance of the 35 kV port of the wind farm is obtained by measuring the voltage and current at the injection point. The proposed measurement device does not require rectification and is able to emit positive and negative sequence harmonic currents with controllable amplitude and frequency. The device can obtain accurate positive sequence and negative sequence harmonic impedance with the advantages of small size, simple structure and reliable control strategy. Finally, detailed Matlab simulations have verified the effectiveness of the system topology and control strategy.