同塔双回高压直流工程交流滤波器设计

Design of Alternating Current Filter for Double Circuit High Voltage Direct Current Transmission Project

同塔双回高压直流(DCT-HVDC)工程在世界上尚未见到设计和实际运行的经验,而以往的交流谐波计算和滤波器设计算法,只适用于传统单回直流工程,无法满足双回共站直流工程的设计要求。文中对双回共站直流工程设计存在的技术难点进行了分析,提出了改进算法和解决方案。首先,根据直流输电系统的特点,假设直流输电线路入口处的谐波电压为0,使整流侧和逆变侧的谐波电流计算相互解耦,避免了计算过程中对直流线路的建模,这样,DCT-HVDC工程可以等效为2个常规的单回直流工程分别加以考虑;然后,将2个单回直流工程运行工况合成为一个新的双回运行工况,在该运行方式下,取各种功率组合的各次最大不相容电流作为滤波器性能定值校核的谐波电流源,从而消除了不同功率组合方式对谐波电流的影响且大大减少了计算量;接着,研究了DCT-HVDC工程滤波器投切策略的确定方法和基本原则;最后,以溪洛渡送电广东±500k VDCT-HVDC工程为例,通过工程初步设计和计算,验证了所提出的改进模型的合理性和工程应用价值。

About double circuit transmission high voltage direct current （DCT-HVDC） project, there is no actual operation and design experience in the world. The previous alternating current side harmonic calculation and filter design methods are only suitable for the traditional single circuit HVDC project, and can not be used for the harmonic calculation and filter design of the DCT-HVDC project.In this paper, the technical difficulties of DCT-HVDC are analyzed, and some solutions are proposed. First, based on the characteristics of the HVDC system, the harmonic voltages on the entrance of the DC line are assumed to be zero. It decouples the harmonic current calculation process of the rectifier side and inverter side, and avoids the modeling of the DC line in the harmonic current calculation. The DCT-HVDC project can thus be reduced as two traditional single circuit HVDC projects. Second, two operation modes of the single circuit HVDC projects are synthesized as a new DCT-HVDC operation mode. In this mode, the maximal harmonic combination is picked up among different power combinations as the harmonic current sources for the performance and rating calculation, which eliminates the adverse effect of different power combinations on harmonic calculation and greatly reduces the computation burden. Third, the algorithm and basic principle of filter switching strategy are studied. At last, the validity of the proposed method is demonstrated by the engineering calculation and preliminary design of the Xiluodu-Guangdong ±500 kV DCT-HVDC project.