光伏直流升压系统中级联DC/DC变流器的均流/均压控制策略

CURRENT-SHARING/VOLTAGE-SHARING CONTROL STRATEGYOF CASCADEDDC/DC CONVERTER FOR PHOTOVOLTAIC DC BOOST SYSTEM

输入并联输出串联级联DC/DC变流器可减小开关器件承受的电流/电压应力,适用于低电压输入高电压输出的光伏直流升压系统。为了保证级联变流器的稳定工作,必须确保各模块的输出电压均衡。分析统一占空比控制策略的缺点,提出采用均流型MPPT控制策略实现输出均压和光伏模块的最大功率跟踪,针对均流型MPPT控制策略在光照强度发生变化时的暂态特性的不足提出在均流环的基础上叠加输出电压环的均流均压型MPPT控制策略,以改善系统的动态均压能力。并提出光伏直流升压系统中输入并联输出串联级联DC/DC变流器的模块化设计结构。仿真结果验证了该方法的有效性。

The input parallel output series cascaded DC/DC converter can reduce the current/voltage stress on the switching device,and is suitable for the photovoltaic DC boost system with low voltage input and high voltage output.In order to ensure the stable operation of the cascaded converters,it is necessary to ensure that the output voltages of each module are balanced.The shortcomings of the unified duty cycle control strategy are analyzed,and a current-sharing MPPT control strategy is proposed to achieve output voltage equalization and the maximum power tracking of photovoltaic modules.In view of the shortcoming of the transient characteristics of the current-sharing MPPT control strategy when the light intensity changes.A current sharing and voltage sharing MPPT control strategy is proposed,which superimposes the output voltage loop on the basis of the current sharing loop,so as to improve the dynamic voltage sharing capability of the system.And a modular design structure of the input-parallel output-series cascaded DC/DC converter in the photovoltaic DC boost system is proposed.The simulation results verify the effectiveness of the method.