考虑转换效率提升的两阶段光伏逆变器设计

Design of Two-stage Photovoltaic Inverter Considering the Improvement of Conversion Efficiency

为提高光伏逆变器效率,提出了一种新型两阶段多功能光伏逆变器(QMFI),其借助于两阶段结构,使得部分有功功率可以在一个功率转换器内从光伏阵列直接传输到电网或负载,从而提高转换效率。除了有功功率传输外,还考虑了QMFI最大功率点跟踪(MPPT)的实现和非有功电流(即无功、谐波或不平衡电流)的补偿,提出了QMFI的数学模型,用于指导控制参数的设计。同时,提出一种基于旋转坐标系的分析模型,推导了QMFI的空间矢量脉冲宽度调制策略,直观揭示了非有功电流补偿对两阶段有功潮流的影响。与传统方案相比,QMFI既能实现更高效率的有功功率输送,又具有实现MPPT和提高电能质量的功能。最后,通过3 kV·A样机验证了方案的可行性和有效性。

In order to improve the efficiency of photovoltaic inverter,a new two-stage multifunctional photovoltaic inverter(QMFI)was proposed.With the help of the two-stage structure,part of the active power could be directly transmitted from the photovoltaic array to the grid or load in a power conversion stage,thus the conversion efficiency was significantly improved.In addition,the realization of maximum power point tracking(MPPT)of QMFI and the compensation of non-active current(i.e.reactive,harmonic or unbalanced current)were also considered.A mathematical model of QMFI was proposed to guide the design of control parameters.At the same time,an analysis model based on the rotating frame was proposed,and the space vector pulse width modulation strategy of QMFI was derived,which directly reveale the influence of non-active current compensation on the two-stage active power flow.Compared with the traditional scheme,QMFI can not only achieve more efficient active power transmission,but also realize MPPT and improve power quality.The feasibility and effectiveness of the scheme were verified by a 3 kV·A prototype.