基于SAADR-PI的NPC三电平容错光伏并网逆变器FCS-MPC策略

FCS-MPC Strategy for NPC Three-level Fault-tolerant PV Grid-connected Inverters Based on SAADR-PI Control

为使并网逆变器在故障重构后仍向电网输送高质量电能,针对中性点钳位三电平逆变器容错拓扑,提出了基于自适应自抗扰比例积分控制器的有限控制集模型预测控制策略。首先,在直流侧电压控制环节引入自适应自抗扰比例积分控制器,以提高系统动态响应速度,增强系统鲁棒性能;然后,利用基于参考电压构造代价函数的并网模型预测电流控制策略,实现对参考电流的准确跟踪,并在代价函数中引入直流侧电容电压和开关频率约束项,以抑制中点电压不平衡问题,降低开关损耗;最后,在Matlab/Simulink中建立光伏并网系统模型并进行时域仿真。仿真结果表明,所提策略在稳态及光照阶跃变化时,直流侧电压调节具有更快的动态响应和更平滑的瞬态性能,且并网电流谐波含量低、波形质量好,可保证故障后依然能向电网输送高质量电能。

For purpose of transferring high-quality power to the grid after fault reconstruction,a finite-control-set model predictive control(FCS-MPC)strategy based on self-adaptive auto disturbance rejection proportional integral(SAADR-PI)control is proposed for neutral point clamped(NPC)three-level inverter fault-tolerant topology.Firstly,the SAADR-PI controller is adopted to quicken the response speed and enhance the robust performance of the control system at DC side of the inverter.Then,the predictive current control strategy by grid-connected model based on the reference voltage cost function method is utilized to accurately track the reference current.The voltage difference between the upper and lower capacitors of the DC bus and the switching frequency constraints are introduced into the cost function to suppress the voltage imbalance and reduce the switching loss.Finally,the model of photovoltaic grid-connected system is established in Matlab/Simulink and the time-domain simulation is implemented.The simulation results show that the proposed strategy in this paper has a faster dynamic response and smoother transient performance in both the steady state and illumination step change.And the grid-connected current has low harmonic content and good waveform quality,which ensure that high-quality power can still be transmitted to the grid after fault.