基于脉冲密度调制PDM(pulse density modulation)的双边协同控制使得无线电能传输WPT(wireless power transfer)系统在耦合系数和负载阻抗变化的情况下能够保持最大效率传输,但是在系统启动及电池恒流恒压充电切换时会产生远高于额定值的电流/电压超调。为了解决超调问题,保证电池充电稳定性,提出了一种抗饱和控制策略。首先,基于WPT系统的等效电路模型分析最大效率点跟踪的工作原理;然后,结合WPT系统两侧控制量的协同工作过程,解析系统启动及电池恒流恒压充电切换时的超调现象,给出恒流恒压控制器设计方法,将反计算抗饱和算法与控制器设计相结合,提出抗饱和控制策略;最后,搭建了仿真模型,验证所提出的抗饱和策略能够有效抑制控制器饱和导致的超调,减少系统到达稳态的时间,降低电流/电压的超调带来的元器件应力。
In this paper,the problem of guaranteed cost control and anti-windup design is studied for a class of switched systems with actuator saturation.The switching strategy and anti-windup compensator are designed to ensure the asymptotic stability of the closed-loop system and to obtain the minimum upper bound of the cost function.Some sufficient conditions for the existence of an anti-windup compensator of guaranteed cost are given by using the multiple Lyapunov functions method.On this basis,the minimum upper bound of the cost function is determined by solving the optimisation problem under the constraint of linear matrix inequality(LMI).Finally,a numerical example is given to verify the effectiveness of the proposed method.
Loss of synchronization is one of the main issues for a grid-feeding converter in a weak grid after being subjected to a large disturbance.The synchronous transient is highly nonlinear due to phase movement and frequency limiters.However,none of the previous research has considered the anti-windup PI in the phase-locked loop,which is commonly implemented in reality and introduced as an additional nonlinear transient.This work provides a taxonomy to evaluate and compare the effect of different anti-windup PI limiters on synchronization stability,including clamping,back-calculation and combined method.Different anti-windup PI limiters allocate zeros and poles differently and have different impacts on damping and stability enhancement.A case study implemented in Matlab/Simulink serves to compare the trajectory of the converter phase and frequency using different anti-windup PI in the scenario of both with and without equilibrium points during the fault.Simulation results show that anti-windup PI limiters increase damping during the fault and thus improve the synchronization stability margin.
Junru ChenChenchen GeDi QiangHua GengTerence O'DonnellFederico Milano
