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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。
DCT-HVDC projects on the same tower have not seen any experience in design and operation in the world. However, the conventional AC harmonic calculation and filter design algorithms are only applicable to the conventional single-circuit DC-DC project and can not meet the requirements of double Back to the station DC project design requirements. In this paper, the technical difficulties in the design of DC double station project are analyzed, and the improved algorithms and solutions are put forward. First of all, according to the characteristics of the HVDC transmission system, assuming that the harmonic voltage at the entrance of the HVDC transmission line is 0, the harmonic current calculations at the rectifier side and the inverter side are decoupled from each other, which avoids modeling the DC line in the calculation process, In this way, the DCT-HVDC project can be equivalently considered for two conventional single-circuit HVDC projects respectively; then, two single-circuit HVDC project operating conditions are synthesized into a new double-circuit operation condition. In this operation mode , Taking the largest incompatible current of various power combinations as the harmonic current source for checking the performance of the filter, thereby eliminating the influence of the different power combination modes on the harmonic current and greatly reducing the calculation amount. Next, Finally, taking Xiluodu power transmission Guangdong ± 500k VDCT-HVDC project as an example, the preliminary design and calculation of the project have verified that the proposed improved model is reasonable Sexual and engineering value.