基于非线性扰动观测的储能双向DC-DC变换器非奇异终端滑模控制策略

Nonsingular terminal sliding mode control strategy of bidirectional DC-DC converter in energy storage system based on the nonlinear disturbance observer

在光储直流微电网系统中,储能双向DC-DC变换器在储能设备与直流母线之间起着关键的接口作用,其在光伏输出功率及负载大信号扰动下的性能优劣至关重要,将直接影响着直流母线电压的稳定运行。为此,提出了一种基于非线性扰动观测器(nonlinear disturbance observer,NDO)的非奇异终端滑模控制策略。首先采用基于微分几何理论的精确反馈线性化方法,将双向DC-DC变换器系统的状态空间模型转化为布鲁诺夫斯基标准式,并利用非线性扰动观测器对系统扰动量进行估计和补偿。在此基础上设计非奇异终端滑模控制器,并根据李雅普诺夫稳定性理论,证明所提控制策略的稳定性;进而分析所提控制策略的收敛性。最后,通过仿真验证所提控制策略的有效性。仿真结果表明,与文献中典型非线性控制策略相比,本文所提控制策略在光伏输出功率和负载有较大扰动时响应时间较快,并具有电压过充小、稳态误差小的优点。

In DC microgrids based on photovoltaic and energy storage systems,the bidirectional DC-DC converter is a key interface between the energy storage equipment and DC bus,and its performance under the large signal disturbance of photovoltaic output power and load directly affects the stable operation of the DC bus.Therefore,a nonsingular terminal sliding mode control strategy based on a nonlinear disturbance observer is proposed in this study.First,the state-space model of the bidirectional DC-DC converter system is transformed into Brunovsky's standard form using the exact feedback linearization method based on differential geometry theory,and the disturbances are estimated using the nonlinear disturbance observer as the compensation channel.Moreover,we design a nonsingular terminal sliding mode controller and analyze the stability,as well as convergence,of the proposed control strategy based on Lyapunov stability theory.Finally,we perform simulations to prove the effectiveness of the proposed control strategy.The simulation results show that compared with typical nonlinear control methods in the literature,the proposed control strategy has a fast response time,small overshoot,and steady-state error under the large signal disturbance of photovoltaic output power and load.