小电容应用下的三角形联结级联H桥STATCOM建模和最优控制器设计*

doi:10.11985/2021.03.004

摘要/Abstract

摘要：

三角形联结级联H桥静止同步补偿器(Static synchronous compensator, STATCOM)能够提高电网的传输效率和电能质量。H桥直流侧小电容的使用可以减少STATCOM的建造成本和占地面积。然而直流侧电容的减小造成电容电压的波动增大,导致小电容STATCOM数学模型和传统STATCOM有所不同。文章考虑了H桥直流侧小电容应用下的电容电压波动对系统模型的影响,建立了针对三角形联结级联H桥STATCOM的基于多变量系统的状态空间模型,进而提出了一种基于多变量最优控制的有限时域线性二次调节器(Linear quadratic regulator,LQR),旨在将系统内部的多个变量在所定义的性能指标函数下进行最优调节,该方法相较传统的级联PI(D)控制器系统,具有通用性好、便于处理内部变量耦合问题等特点。最后,通过仿真对所建模的三角形联结级联H桥STATCOM系统和有限时域LQR控制器进行了验证。

关键词: 三角形联结级联H桥STATCOM, 小电容, 变换器建模, 有限时域线性二次调节器

Abstract:

Delta-connected cascaded H-bridge (CHB) multilevel converter-based STATCOM (Static synchronous compensator) is able to enhance transmission efficiency and power quality of power systems. The application of small capacitors at the dc side of H-bridges can effectively reduce the cost and the volume of STATCOM. However, the application of small capacitors is accompanied by higher capacitor voltage ripple, leading to that STATCOM model is different from that of the conventional STATCOM. With consideration of the impact of capacitor voltage ripple on system model, a multivariable state-space model integrating branch currents and branch capacitor voltages is built, based on which a finite-horizon LQR (Linear quadratic regulator) controller for delta-connected cascaded H-bridge STATCOM with reduced capacitance has been proposed. Compared with the widely utilized cascaded PI(D) controller, the proposed LQR controller is more applicable to handle systems containing variable coupling. Simulations verify the efficiency of the finite-horizon LQR controller.

Key words: Delta-connected cascaded H-bridge STATCOM, small capacitor, converter modeling, finite-horizon linear quadratic regulator

中图分类号:

TM561

王恒宜, 汪飞. 小电容应用下的三角形联结级联H桥STATCOM建模和最优控制器设计^*[J]. 电气工程学报, 2021, 16(3): 25-32.

WANG Hengyi, WANG Fei. Modeling and Optimal Controller Design of Delta-connected Cascaded H-bridge STATCOM with Reduced Capacitance[J]. Journal of Electrical Engineering, 2021, 16(3): 25-32.

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参数	数值
电网频率f/Hz	50
载波频率f_c/Hz	5 000
子模块电容值C/μF	50
支路电感L/mH	9.2
支路电阻r/Ω	0.056 6
支路子模块数N	8
误差权矩阵Q	diag(10⁴,10⁴,10⁴, 2, 2, 2)×10^-7
控制权矩阵R	diag(1,1,1,1,1,1)×10^-7