Voltage quality and load sharing improvement in islanded microgrids using distributed hierarchical control

Abstract

In this study, to compensate voltage unbalance and harmonics and improve load sharing, a distributed hierarchical control scheme is proposed for islanded microgrids. In the proposed scheme, a method is proposed, which can improve the voltage quality of sensitive load bus by determining the amount of effort made by each distributed generation (DG) and taking their rated power constraints into account for compensation. Moreover, this method is capable of improving the load sharing among DG units adaptively using circulating currents rule. Compared to the previous proposed methods, the method proposed in this study does not need a central controller, and communication is only needed between adjacent DG units. Furthermore, in this scheme, the contribution of each DG unit in compensation will be in proportion to its rated power, and none of them will be overloaded. Also, to compensate the error of load current sharing components, there is no need to have any information about impedance of DGs feeders and load type. To show the efficiency of the proposed scheme, simulation studies are performed on a typical islanded microgrid in MATLAB/Simulink environment.

Multi‐objective control scheme for operation of parallel inverter‐based microgrids during asymmetrical grid faults

“…In [27], an autonomous control scheme was presented to achieve LVRT and grid voltage support with multiple DG units. In [28], a distributed hierarchical control scheme was discussed for islanded MGs.…”

Secondary‐control‐based harmonics compensation scheme for voltage‐ and current‐controlled inverters in islanded microgrids

“…The harmonics compensation in MGs by using the VCM units is proposed in [9]- [22]. These methods can be classified to local-data- [9][10][11][12][13][14][15] or communication-based compensation [16][17][18][19][20][21].…”

“…In islanded MGs, the VCM units which are known as grid forming units are responsible of voltage and frequency regulation. The harmonics compensation in MGs by using the VCM units is proposed in [9][10][11][12][13][14][15][16][17][18][19][20][21][22]. These methods can be classified to local-data-based compensation [9][10][11][12][13][14][15] or communication-based compensation [16][17][18][19][20][21].…”

“…In [22,23], a coordinated control of VCM DG units and active power filters is proposed while a supervisory control scheme of VCM DG units and active power filter is proposed in [24], for power quality improvement of multi-area MG. In [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24], only the VCM units are considered while in an MG, CCM inverters are also present; furthermore, the limited capacity of VCM units should be considered.…”

“…In the present paper, in comparison to the methods presented in [10][11][12][13][14][15][16][17][18][19][20][21][22][23], CCM units are also considered and a coordinated control of VCM and CCM interfacing inverters are presented. The CCM units are fed by PV units.…”