多路单级式直流侧串联光伏逆变系统的研究与分析

Research and Analysis of the Dc-link Cascaded Inverter for Single-stage Solar Power System

多路单级式直流侧串联光伏逆变系统拓扑结构由光伏阵列、直流侧串联电容、级联的单相全桥逆变器和隔离变压器构成。由于减少了直流升压环节,拓扑结构更简单,而将直流侧电容相串联则能够减少主电路电流,使用MOSFET作为开关器件在该拓扑结构中更具优势,MOSFET能够使开关损耗减少,同时在并网逆变环节采用载波移相SPWM调制方式降低开关频率,使得系统效率更加提高。通过对拓扑结构中两路级联的建模和分析,并对其进行控制策略的分析,使用变步长的导纳增量MPPT法、双闭环和载波移相调制方式,最终通过仿真验证了拓扑结构的有效性,研究结果表明单级式多路直流侧串联光伏逆变系统具有较优越的谐波抑制能力和直流电压控制简单化。

The dc-link cascaded inverter for solar power system consists of PV array , dc-link capacitors , cascaded full bridge converters and isolated transformers. This topology decreases the boost converter which makes the structure simpler. The connected capacitors decrease the current of the main circuit and the use of MOSFETs have more superiority in decreasing the switching loss. The switching frequency can be further decreased by using the phase-shift modulation SPWM which directly influences the losses of the switching devices. By analyzing this new topology for two cascaded full bridges, it uses variable step MPPT , double control loop and phaseshift SPWM and finally the simulation confirms the effectiveness of the new topology. The result shows that the dc-link cascaded inverter has superior harmonic suppression and the simplification of the dc link control.