光伏接入直流受端电网下直流换相失败影响机理初探

A Preliminary Study on the Influence Mechanism of DC Commutation Failure Considering Photovoltaic Access in Terminal Power Grid

随着“双碳”目标推进,大量新能源发电系统将接入高压直流输电系统受端电网,但鲜有文献涉及该研究场景,新能源接入是否会对直流运行带来不利影响存疑。为此,该文分析了电网发生交流故障后光伏、直流的输出特性及交互影响规律,发现直流发生换相失败后将向光伏输送50、100、150Hz正负序电流分量,导致光伏输出功率及并网点电压的波动,并通过受端电网反馈传递导致直流系统直流电流及超前触发角指令的波动,进而带来直流后续换相失败风险,最后结合PSCAD/EMTDC仿真软件搭建了受端电网含光伏接入的高压直流输电系统模型,并通过仿真验证了上述结论的合理性及有效性。

With the promotion of the"carbon peaking and carbon neutrality"goals,many renewable energy power generation systems will be connected to the receiving grid of the high voltage direct current(HVDC)transmission system.However,few studies have covered this research scenario,and whether renewable energy will adversely affect DC operations is doubtful.For this reason,this paper analyzes the output characteristics and interactive influence rules of photovoltaic and HVDC under AC power grid faults.It is found that positive and negative sequence current components of 50,100,and 150Hz will be transmitted to the photovoltaic system after HVDC commutation failure,resulting in fluctuations of photovoltaic output power and voltage of connecting points.The feedback transmission of the receiving grid leads to the fluctuation of the HVDC current and the advance trigger angle order of the HVDC system,thus bringing the risk of HVDC subsequent commutation failure.Finally,combined with the PSCAD/EMTDC simulation software,the high-voltage DC transmission system model of the receiving grid with photovoltaic access is built,and the rationality and validity of the above conclusions are verified by simulation.