三相SPWM混合调制Boost集成式光伏逆变器

Boost-integrated Photovoltaic Inverter With Three-phase SPWM Hybrid Modulation

相比于传统两级式光伏发电系统,三相Boost集成式光伏逆变器具有结构简单、成本低、集成度高、可实现单级能量变换等优点。现有的三相电压源型逆变器SPWM调制策略均可直接应用于Boost集成式升压逆变器。然而,其直流母线电压随着调制比M而大范围变化,导致开关管承受较大的电压应力;更重要的是,由于占空比呈正弦规律变化,升压电感电流含有很大的低频纹波分量,导致电流应力和通态损耗严重增加。为此,基于叠加原理,提出了三相SPWM混合调制策略。其可实现集成式逆变器直流母线电压与逆变输出电压/电流的解耦控制,降低器件电压应力;升压电感在每个开关周期内的充电时间恒定为DTs,从而从理论上彻底消除了其电流的低频脉动。通过一台1.4k W/10k Hz的原理样机,对三相SPWM混合调制Boost集成式逆变器的可行性进行了实验验证。

Compared to the traditional two-stage photovoltaic(PV)power generation system,the three-phase boost-integrated PV inverter has advantages of its simpler structure,lower cost,higher integration,and its capability of single-stage power conversion.The existing SPWM strategies for three-phase voltage source inverter can be directly applied to the boost-integrated inverter.However,its DC-link voltage varies widely with the modulation ratio M,leading to a high voltage stress across the power switches.Besides,since the boosting inductor is charged with variable duty cycle,the inductor current presents some undesirable low-frequency harmonics,resulting in a significant increment of current stress and conduction loss.For addressing these issues,a novel three-phase SPWM hybrid modulation strategy is proposed in this paper.It can realize decoupling control between DC-link voltage and output voltage/current of integrated inverter,hence reduce the voltage stress.In addition,the inductor charging time in each switching period keeps constant as DTs,which completely eliminates the low-frequency ripple in theory.A 1.4kW/10kHz prototype was used to validate the feasibility of boost integrated inverter with three-phase SPWM hybrid modulation.