基于LCC-MMC混合双极直流输电系统的新能源并网控制策略研究

Control strategy on LCC-MMC hybrid bipolar HVDC system applying to renewable energy integrating

研究了基于电网换相变流器(LCC)和模块化多电平变流器(MMC)的混合双极直流输电系统应用于新能源并网场景的控制策略,该混合双极直流输电系统包括两个LCC和两个MMC,分别呈对角排布。LCC控制直流电压,MMC调节有功功率和无功功率(或系统频率和交流电压),此外,MMC还兼具有源滤波功能,用于平抑交直流侧的谐波电流。该并网系统的优势在于不需要交直流滤波器和大容量直流平波电抗器,节省了占地面积和成本,能够实现有功功率和无功功率的解耦控制,同时具备兼容新能源功率间歇性波动的能力。因此,该系统兼具传统直流和柔性直流的优点,有良好的经济性和应用前景。最后基于PSCAD/EMTDC软件平台的仿真,验证了该并网系统的可行性和对应控制策略的有效性。

Hybrid bipolar HVDC transmission system based on was to renewable energy integrating and its corresponding control strategies were studied. This system was composed of two diagonally located LCCs and two MMCs. In a pole, DC voltage was regulated by the LCC, and the active and reactive power （or system frequency and AC voltage） was controlled by the MMC. And the MMC also functioned as AC and DC active harmonic filters to suppress the AC and DC harmonic currents. Many merits such as no AC and DC filters, saving footprint and cost, independent control ability of active and reactive power, capable of tolerating intermittent power of renewable energy etc, existed in this system. Therefore, the proposed system had promising application prospect, as it combined benefits of LCC-HVDC and MMC-HVDC and overcame their disadvantages. Simulation results based on PSCAD/EMTDC platform validated the effectiveness of the control strategies.