Abstract
Parallel operation of inverter modules is the solution to increase the reliability, efficiency, and redundancy of inverters in microgrids. Load sharing among inverters in distributed generators (DGs) is a key issue. This study investigates the feasibility of power-sharing among parallel DGs using a dual control strategy in islanded mode of a microgrid. PQ control and droop control techniques are established to control the microgrid operation. P-f and Q-E droop control is used to attain real and reactive power sharing. The frequency variation caused by load change is an issue in droop control strategy whereas the tracking error of inverter power in PQ control is also a challenge. To address these issues, two DGs are interfaced with two parallel inverters in an islanded AC microgrid. PQ control is investigated for controlling the output real and reactive power of the DGs by assigning their references. The inverter under enhanced droop control implements power reallocation to restore the frequency among the distributed generators with predefined droop characteristics. A dual control strategy is proposed for the AC microgrid under islanded operation without communication link. Simulation studies are carried out using MATLAB/SIMULINK and the results show the validity and effective power-sharing performance of the system while maintaining a stable operation when the microgrid is in islanding mode.
Highlights
The key issues related to microgrids is the parallel operation of different generations in islanded mode [1]
The real and reactive power are reallocated through droop controller and DG1 power increases to supply the demand power according to the supervisory droop control
Throughout the load variations, the frequency is at a stable level
Summary
The key issues related to microgrids is the parallel operation of different generations in islanded mode [1]. Distributed generators (DGs) during islanding operation of the microgrid are commonly coupled via inverters to an AC distributed system. Various techniques have been introduced for controlling the inverter parallel operation or power-sharing [2]. A microgrid system requires the operation, control structure, power and voltage regulation and energy management [3]. The basic structure of a microgrid contains one or several renewable energy sources (RES), different types of load and energy backup systems integrated together [4]. The actual performance observed when the microgrid operates in islanded mode was presented in [5]. As well as switching among the different operation
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