中点箝位式三电平光伏并网逆变器的三单相Quasi-PR控制策略

Three-Phase Independent Quasi-PR Control Strategy for Neutral Point Clamped Tri-Level Grid-Connection Photovoltaic Inverter

准比例谐振(quasi-proportion resonant,Quasi-PR)控制器可克服传统比例谐振(proportion resonant,PR)控制器带宽窄、抗频率偏移能力差的缺点,基于此提出了基于三单相Quasi-PR控制的中点箝位式(neutral point clamped,NPC)三电平光伏并网逆变器控制策略。Quasi-PR控制器继承了传统PR控制器的优点,避免了矢量控制策略中复杂的坐标变换、解耦控制和前馈补偿等,简化了控制算法。同时当电网频率发生偏移时,Quasi-PR控制器仍能实现对交流电流的无静差跟踪。此外,为减少电网不平衡时产生的较大谐波电流含量,设计了基于Quasi-PR控制的分次谐波补偿器。仿真结果表明了所提控制策略的有效性。

In view of the fact that the defects of narrow bandwidth and weak ability against frequency deviation in traditional proportion resonant （PR） controller can be remedied by quasi-proportion resonant （Quasi-PR） controller, based on three-phase independent Quasi-PR controller a control strategy for neutral point clamped （NPC） tri-level photovoltaic （PV） grid-connection inverter is proposed. The Quasi-PR controller inherits the advantages of traditional PR controller, so the complex coordinate transformation, decoupling control and feed-forward compensation in vector control strategy can be avoided and the control algorithm is simplified. Meanwhile, when grid frequency deviation occurs, the astatic tracking to AC current can still be performed by Quasi-PR controller. Besides, to decrease the content of higher harmonic current caused by unbalance in power grid, a Quasi-PR control based selective harmonic compensator is designed. The validity of the proposed control strategy is verified by simulation results.