Characteristic Analysis and Indexing of Multimachine Transient Stabilization Using Virtual Synchronous Generator Control

Yuko Hirase,Hiroshi Kikusato,Dai Orihara,Kazusa Uezaki,Jun Hashimoto

doi:10.3390/en14020366

Abstract

As distributed power sources via grid-connected inverters equipped with functions to support system stabilization are being rapidly introduced, individual systems are becoming more complex, making the quantification and evaluation of the stabilizing functions difficult. Therefore, to introduce distributed power sources and achieve stable system operation, a system should be reduced to a necessary but sufficient size in order to enable the quantification of its behavior supported by transient theory. In this study, a system in which multiple distributed power supplies equipped with virtual synchronous generator control are connected is contracted to a two-machine system: a main power supply and all other power supplies. The mechanical torque of each power supply is mathematically decomposed into inertia, damping, synchronization torques, and the governor effect. The system frequency deviations determined by these elements are quantitatively indexed using MATLAB/Simulink. The quantification index displayed in three-dimensioned graphs illustrates the relationships between the various equipment constants of the main power supply, the control variables of the grid-connected inverter control, and the transient time series. Moreover, a stability analysis is performed in both the time and frequency domains.

Highlights

Conventional power systems use synchronous generators as their main power source, the swing characteristics of which suppress the power system swing owing to the load power and generated power fluctuations [1]
The governor time constant of the virtual synchronous generator (VSG) (Tvsg ) was fixed at 0 s according to the Kawasaki topology, and the droop coefficient of the synchronous generator (SG) (Rsg ) was fixed at 2.5%
VSG2 and VSG3 were set to different values: 2.50 s and 5.00 s, respectively

Summary

Introduction

Conventional power systems use synchronous generators as their main power source, the swing characteristics of which suppress the power system swing owing to the load power and generated power fluctuations [1]. Due to recent advancements in distributed power sources, such as renewable energy, a large number of grid-connected inverters are being connected to power systems. The inertial power of the entire system, which generally suppresses the fluctuations of the power system, is insufficient when the capacity of the grid-connected inverters exceeds the capacity of the main power supply, making it challenging to maintain stability [2,3]. There is a need for the grid-connected inverters of distributed power sources to have power generation functionality and to suppress the fluctuations of the power system [4]. The problem of the capacity of grid-connected inverters exceeding that of the main power supply was previously regarded as being characteristic of microgrids (MGs), a similar problem has recently been identified in large-scale smart grids. To leverage open-source system validation platforms (SVPs) for interoperable test procedures, research using power/controller hardware-in-the-loop (PHIL/CHIL) is being actively promoted [15,16,17,18]; Ref. [19]

Results

Discussion

Conclusion