基于电流纹波预测的交错并联三相逆变器任意功率因数全范围软开关策略

Current Ripple Prediction Based Full Range Soft Switching Method for Two Parallel Interleaved Three-phase Inverters Under Any Power Factor

随着分布式能源的大力发展,新的并网标准要求并网逆变器具有更宽的功率因数运行范围,实现对电网的无功补偿;同时,为实现高频化及高转换效率,软开关技术是一种重要的途径。因此,文中提出一种基于交错并联三相逆变器拓扑的任意功率因数全范围软开关控制策略。采用断续脉宽调制通过变开关频率来控制电感电流脉动的大小,使开关管开通前开关管的输出电容放电至0,以实现零电压开通(zero voltage switching,ZVS)。首先,分析采用电流脉动预测理论实现ZVS的工作原理;其次,给出不同功率因数下全范围ZVS所需的开关频率自适应运行原则等,基于电流纹波预测理论及负载环境计算和选取开关频率,因此在全范围及全功率因数均可实现ZVS;最后,通过搭建一台3.5 kVA全SiC MOSFET实验样机,验证所提出控制策略的有效性。

In this paper,a zero-voltage-switching(ZVS)control strategy for two parallel interleaved three-phase inverters under any power factor situation is presented.The variable switching frequency can be simply calculated based on inductor current ripple prediction(CRP)to minimize the unnecessary conduction loss.Discontinuous pulse width modulation(DPWM)method is used to simplify the ZVS realization because only two phases are high frequency switching.The switching frequency variation range in a line cycle is narrow under any load,power factor,or modulation index.No additional high frequency current sensor or zero-crossing detection circuit is required.Due to the high switching frequency and low filter inductance,the size and cost of the inverter can be significantly reduced.The proposed control strategy has good ZVS performance and dynamic response under various load conditions.A 3.5 kVA experimental prototype using SiC MOSFETs verifies the effectiveness of the proposed control strategy.