低直流电压下混合型MMC器件损耗分布优化控制

Loss Distribution Optimal Control of Hybrid MMC Devices at Low DC Voltage

低直流电压运行工况下,混合型模块化多电平变换器(MMC)器件损耗分布不均匀,逆变工况下,半桥子模块(HBSM)下部绝缘栅双极型晶体管(IGBT)损耗尤为突出,降低了换流器运行可靠性。为此,提出一种全、半桥模组输出电压差异化控制与HBSM降压相结合的损耗分布优化方法。首先计算低直流电压下混合型MMC的器件损耗。然后利用全、半桥模组输出电压差异化控制降低目标器件的通态损耗。分析发现,差异化控制降低通态损耗的同时会增加器件开关损耗,因此结合HBSM电容降压减小其开关损耗,使器件损耗优化效果达到最佳。最后,通过小功率实验平台验证所提方法的有效性。

Under the low DC voltage operating condition,the loss distribution of the hybrid modular multilevel converter(MMC)device is uneven,and the insulate-gate bipolar transistor(IGBT)loss of the lower part of half-bridge sub-module(HBSM)is particularly prominent under the inverter operating condition which reduces the reliable operation of the converter.Therefore,a loss distribution optimization method is proposed combining the differentiated control of output voltage of full-bridge and half-bridge modules with voltage reduction of HBSM.Firstly,the device loss of hybrid MMC at low DC voltage is calculated.Then,the output voltage differential control of the full-bridge and halfbridge modules is used to reduce the conduction loss of the target device.The analysis show that differential control reduces conduction losses while increasing device switching loss,so the switching loss is reduced by combining the capacitor voltage reduction of HBSM,so that the optimization effect of device loss is optimal.Finally,the effectiveness of the proposed method is verified through a low-power experimental platform.