突发散热故障时的光伏MPPT变换器控制方法研究

A control method for a photovoltaic MPPT converter with a sudden heat dissipation fault

作为光伏发电系统的重要组成,MPPT变换器能够实现光伏电池最大功率点跟踪(maximumpowerpoint tracing, MPPT)控制。但在环境通风不畅和冷却装置失效等突发性散热故障情况下,变换器极易发生过热停机保护,导致光伏电池无法输出功率,严重影响光伏发电的可靠性与经济性。为此,以一个300 W级MPPT变换器为对象,对其功率器件温升特性进行了试验分析。随后,结合传统MPPT算法和主动热管理策略,提出了一种突发散热故障时的光伏MPPT变换器控制方法。通过对器件驱动信号占空比的动态限制和开关频率的分级调节,所提方法能够主动调整器件工作损耗,进而充分挖掘变换器输出功率。相关实验表明,所提方法可最大程度保留变换器散热故障时的光伏出力,并减少散热故障修复前的光伏发电经济损失。根据实验结果,构建了所提方法性能评价指标,并分析了方法性能的影响因素。

As an important component of a photovoltaic power generation system,an MPPT converter is responsible for the maximum power point tracking control of photovoltaic cells.However,the converter is prone to overheating and shutdown when there are sudden heat dissipation faults,such as poor environmental ventilation and cooling device failure.The shutdown of the converter causes the output of the photovoltaic cell to be cut off,which seriously affects the reliability and economy of photovoltaic power generation.To address this,the temperature rise characteristics of power devices are analyzed in this paper by taking a 300 W MPPT converter as the object.Then,a control method for a photovoltaic MPPT converter when there is a sudden heat dissipation fault is proposed by combining the traditional MPPT algorithm with an active thermal management strategy.Through the dynamic limitation of the device duty cycle and the hierarchical adjustment of the device switching frequency,the proposed method is able to actively adjust the device loss,so as to fully exploit the output power of the converter.Related experiments show that the proposed method can retain the photovoltaic output of the converter during the heat dissipation fault to the greatest extent and reduce the economic loss of photovoltaic power generation before the repair of the heat dissipation fault.From the experimental results,this paper constructs a performance evaluation index of the proposed method and analyzes the influencing factors on the performance of the method.