Improvement of Conventional Droop Methods Performance During the Fault Occurrence in an Islanded Micro-Grid Using the Concept of Virtual Impedance

Subject Areas : Power Engineering

Sobhan Tahanzadeh ¹ , Farshad Zandi ² , Bahador Fani ³ , Matin Dashtipour ⁴ , Ehsan Adib ⁵ , Esmaeel Rokrok ⁶

1 - Department of Electrical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
2 - Department of Electrical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
3 - Smart Microgrid Research Center- Najafabad Branch, Islamic Azad University, Najafabad, Iran.
4 - Department of Electrical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
5 - Department of Electrical and Computer Engineering, Isfahan University of Technology, Isfahan, Iran
6 - Engineering Department, Lorestan University, Lorestan, Iran.

Received: 2022-03-18 Accepted : 2022-06-08 Published : 2022-05-22

Keywords: Conventional droop method, Islanded micro-grid, Voltage Regulation, Reactive power sharing, Short Circuit Fault,

Abstract :

Most Micro-Sources (MSs) are interfaced to a Micro-Grid (MG) using power electronics converters. Therefore, a MG can be envisioned as a group of parallel converters. A well-known method to control a group of parallel converters in the decentralized control structure in a MG is to use frequency and voltage droop characteristics. A problem associated with conventional droop characteristics is that reactive power is not always properly shared among MSs which may lead to converter overloading. The nature of conventional droop characteristics is linear. Therefore, these characteristics do not have a sufficient degree of freedom to function properly in nonlinear conditions, such as the occurrence of short circuit faults. Most of proposed methods in the literature are limited to specific MG structures or need extensive information of grid. For this purpose, in this paper, a new power control strategy based on a decentralized method for autonomous micro-grid consisting of voltage source inverters is presented. The control strategy based on voltage and frequency droop control methods. In the proposed method, conventional droop characteristics are corrected by using virtual impedance loop to adjusting the y-intercept of conventional curves. The proposed approach also improves voltage regulation both under normal micro-grid conditions and when faults occur.

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