Modeling and Optimal Controller Design of Delta-connected Cascaded H-bridge STATCOM with Reduced Capacitance

doi:10.11985/2021.03.004

Abstract

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

CLC Number:

TM561

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.

Figures/Tables 9

References 20

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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