Abstract
Voltage-source rectifiers (VSRs) have been widely used in modern power grids. The inductive grid impedance of the power grids poses a serious threat to the stability of the VSRs. In this article, a stability-margin-oriented design method for the controller parameters of the VSRs in weak power grids with inductive grid impedance is proposed. Firstly, the proportional gain of the dc-link voltage controller is designed based on the Routh Criterion to obtain the required gain margins. Then, regarding the lack of the phase margin, the grid-voltage feedforward gain is designed for improving the phase margin based on the singular value of the system. Furthermore, it is found that the lack of phase margin is very serious in the system with multiple VSRs in parallel. Therefore, the stability margin of the system when connecting multiple VSRs with the designed parameters is investigated and the effectiveness of the design method proposed in this article on guaranteeing the phase margin and the gain margin of the system is confirmed. Simulation and experimental results have been provided, which verifies the effectiveness of the design method proposed.
Highlights
Voltage-source rectifiers (VSRs) have been widely used as essential interfaces for power conversion systems which provide constant dc voltage supplies [1], such as highvoltage direct-current transmission systems [2], active frontend units for motor drivers [3], and battery energy storage systems [4]
As more and more VSRs are used in the power grids, the inductive grid impedance poses a serious threat to the stability of the control systems of the VSRs [5]-[9]
The large grid impedance can cause high-frequency oscillations to the current control loops of the VSRs when using LCL filters [5], [6], and it can interfere with the phase-locked-loops (PLLs) which can cause the harmonic oscillations to the grid-connected inverters in the renewable power generation systems [7]-[8]
Summary
Voltage-source rectifiers (VSRs) have been widely used as essential interfaces for power conversion systems which provide constant dc voltage supplies [1], such as highvoltage direct-current transmission systems [2], active frontend units for motor drivers [3], and battery energy storage systems [4]. In the weak grid where multiple VSRs are connected, the system cannot obtain a stable operation by merely adjusting the proportional gain of the dc-link voltage controller, which has not been shown in [14]-[23]. This article focuses on how to analytically and systematically design the parameters of the dc-link voltage controller to obtain sufficient GM and PM for the VSR in the weak grid and to guarantee the stable operation in case of multiple VSRs connected in parallel.
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