Reactive Power Control Strategy of Low-Voltage Microgrid Applying Dynamic Droop Coefficient

doi:10.12204/j.issn.1000-7229.2022.01.009

Abstract

Abstract:

In the low-voltage microgrid, due to the influence of the impedance of the line and the impedance mismatch, the conventional droop control often has the problems of power coupling and uneven distribution of steady-state reactive power. Aiming at the above problems, an improved droop control method with adaptive coefficients is proposed. This strategy adjusts the equivalent line impedance to inductive by introducing the reference virtual reactance, weakening the coupling problem caused by the line resistive component, so that inductive droop control can be applied; secondly, low-bandwidth communication is introduced, and the droop is adaptively adjusted according to the power sharing requirements. Coefficient is adjusted to eliminate the problem of line impedance mismatch, so as to achieve accurate and even distribution of reactive power. Compared with traditional droop control, this method is suitable for microgrid control under any line impedance condition, and has good dynamic and steady-state performance. The simulation results in Matlab/Simulink prove the correctness and effectiveness of the method.

Key words: microgrid, improved droop control, virtual reactance, low bandwidth communication, power sharing

CLC Number:

TM761

LUO Zhaoxu, LIU Yang, LUO Qin, QIN Jianheng. Reactive Power Control Strategy of Low-Voltage Microgrid Applying Dynamic Droop Coefficient[J]. ELECTRIC POWER CONSTRUCTION, 2022, 43(1): 78-86.

Figures/Tables 14

Fig.1 Simplified equivalent model of two inverters in parallel

Fig.2 Equal distribution of reactive power between two inverters with the same capacity

Fig.3 Equivalent circuit diagram after introducing virtual reactance

Fig.4 Schematic diagram of the introduction process of the virtual reactance

Fig.5 Block diagram of voltage and current double closed-loop control

Fig.6 Bode diagram of inverter output impedance before and after virtual reactance introduction

Fig.7 Frame of dynamic droop coefficient control

Fig.8 Block diagram of microgrid structure with network communication unit

Fig.9 Process of dynamic coefficient adjusting reactive power

Table 1 Simulation parameters

Fig.10 Power output under working condition 1

Fig.11 Power output under working condition 2

Fig.12 Power output under working condition 3

Fig.13 Power output under working condition 4

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