用于提升弱电网下LCL并网逆变器鲁棒性的模型预测控制

Model predictive control for improving LCL grid-connected inverters robustness under weak grids

  • 摘要: LCL并网逆变器传统线性控制策略中的数字延时会降低系统带宽,在电网电感较大的弱电网条件下易出现谐振失稳问题。为此,研究了一种比例谐振-有限控制集模型预测级联控制策略(PR-MPC)。首先,外环采用比例谐振控制器调节并网电流。其次,为降低控制延迟,内环设计了一种低复杂度多目标有限控制集模型预测控制(FCS-MPC),通过定义电容电压和电感电流双目标价值函数,实现了谐振的固有阻尼。进一步,利用极小化原理求出最优逆变器电压参考,并设计了一种逆变器电压参考跟踪价值函数,降低了计算复杂度。与传统有源阻尼PR控制相比,所提PR-MPC省去了调制环节,提升了系统带宽和弱电网下的鲁棒性。实验结果验证了所提PR-MPC策略的有效性。

     

    Abstract: The digital delay in the conventional linear control strategy of LCL grid-connected inverters reduces the system bandwidth and is prone to resonance instability problems under weak grid conditions with large grid inductance. For this reason, a proportional resonant-finite control set model predictive cascade control strategy(PR-MPC) is investigated in this paper. Firstly, the outer loop is kept as a proportional resonant controller to regulate the grid-connected current. Second, to reduce the control delay, a low-complexity multi-objective finite control set model predictive control(FCS-MPC) is designed for the inner loop. The intrinsic damping of the resonance is achieved by defining a bi-objective value function of capacitor voltage and inductor current. Further, the optimal inverter voltage reference is derived using the principle of minimization and an inverter voltage reference tracking value function is designed to reduce the computational complexity. Compared with the conventional active damped PR control, the proposed PR-MPC eliminates the modulation link and improves the system bandwidth and robustness under weak grid. Experimental results verify the effectiveness of the proposed PR-MPC strategy.

     

/

返回文章
返回