模块化多电平换流器自适应故障限流控制策略

直流断路器(DCCB)的造价和体积与其开断电流大小密切相关.文中从降低DCCB的开断电流层面出发,设计了适用于半桥模块化多电平换流器(MMC)故障限流的自适应限流控制器.通过在直流故障工况下调整MMC直流电压和子模块电容电压参考值,可自动快速限制故障电流发展速度.采用数学解析的方法对自适应控制器的限流原理进行了分析.在PSCAD/EMTDC仿真环境下搭建四端柔性直流电网进行仿真验证.仿真结果表明:相比于无任何限流措施的控制方案,自适应限流控制可有效降低断路器的开断电流,明显减少避雷器吸收的能量,同时可加快故障后的系统恢复.

Adaptive Fault Current Limiting Control Strategy for Modular Multilevel Converter

The cost and bulk of DC circuit breaker (DCCB) are closely related to its breaking current. From the aspect of reducing the breaking current of DCCB, an adaptive controller is designed for fault current limiting of half-bridge modular multilevel converter (MMC). By adjusting the reference value of the DC voltage and the capacitor voltage of the sub-modules in MMC under DC fault condition, the development speed of fault current can be limited automatically and quickly. The current limiting principle of the adaptive controller is analyzed by mathematical analysis. A four-terminal DC grid is simulated in the PSCAD/EMTDC environment to verify the effectiveness of the adaptive controller. The simulation results show that, compared with the control scheme without current limiting control, the proposed adaptive controller can not only reduce the breaking current of the DCCBs and energy absorbed by the arresters, but also speed up the recovery of the system after fault.