Abstract

This paper presents a vector fitting (VF)algorithm-based gray-box structure and parameters identification method for voltage source converter(VSC). Terminal impedance frequency responses of VSC is first measured by frequency scanning method. Then, these impedance frequency responses are fitted by a polynomial transfer function using VF algorithm. Finally, the theoretical terminal impedance formulas of possible control structures are compared with the fitted transfer function. The actual control structure can be selected, and the actual internal parameters can be identified. Simulation results are given to validate effectiveness of the proposed method. The proposed gray-box method can identify both the circuit and controller information even if no internal information of the VSC is provided by vendors due to industrial confidence. In addition, the effect of measurement noise on parameters identification accuracy can be mitigated by increasing the order of the fitted transfer function.

Highlights

  • Renewable energy sources, such as wind power and solar power, have been increasingly penetrating into traditional power systems [1]

  • In step 3, match degree of converter current control (CCC) and grid current control (GCC) with the measured frequency responses is checked by comparing non-passivity regions (NPRs) (NPR is the frequency range where phase angle of output impedance is larger than 90o or lower than −90o) [18]

  • This paper presents a vector fitting (VF)-based parameter identification method which is able to identify control structure, parameters of controller and circuit of Voltage source converters (VSCs)

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Summary

INTRODUCTION

Renewable energy sources, such as wind power and solar power, have been increasingly penetrating into traditional power systems [1]. In [7], [10], the parameters of L filter and LCL filter can be identified, where pseudorandom binary sequence (PRBS) is injected into current control loop of VSC, and the impedance information is obtained by performing FFT on perturbed voltage and current. In [6], parameters of dc voltage controller, current controller and phase-locked loop (PLL) are identified by equalizing theoretical and measured terminal impedance frequency responses with assumption that the control structure is known. This paper presents a gray-box parameters identification method to identify circuit and controller parameters of VSC based on measured output impedance, where parameters of LCL filter, proportional coefficient of current controller and sampling time can be identified.

SYSTEM DESCRIPTION
Principle of the Proposed Parameters Identification Method
Implementation Procedure of the Proposed Method
Implementation of the Proposed Method
CONCLUSION

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