Hybrid Three-Phase/Single-Phase Microgrid Architecture With Power Management Capabilities

Abstract

With the fast proliferation of single-phase distributed generation (DG) units and loads integrated into residential microgrids, independent power sharing per phase and full use of the energy generated by DGs have become crucial. To address these issues, this paper proposes a hybrid microgrid architecture and its power management strategy. In this microgrid structure, a power sharing unit (PSU), composed of three single-phase back-to-back (SPBTB) converters, is proposed to be installed at the point of common coupling (PCC). The aim of the PSU is mainly to realize the power exchange and coordinated control of load power sharing among phases, as well as to allow fully utilization of the energy generated by DGs. Meanwhile, the method combining the modified adaptive backstepping-sliding mode control approach and droop control is also proposed to design the SPBTB system controllers. With the application of the proposed PSU and its power management strategy, the loads among different phases can be properly supplied and the energy can be fully utilized as well as obtaining better load sharing. Simulation and experimental results are provided to demonstrate the validity of the proposed hybrid microgrid structure and control. I. INTRODUCTIONWith the high penetration of DGs, the concept of microgrids that can operate in either grid-connected or islanded modes is becoming more attractive [1]- [5]. A microgrid is a local controllable low-voltage distribution network consisting of a number of DGs, energy storage systems, and dispersed loads. DGs are often connected to the microgrid through power electronic interface converters, which are aimed at controlling the power injection while improving the power quality at the same time. Both the customers and power utilities can benefit from the microgrid concept, which can offer diversified energy options and high power quality and reliability [6]-[10]. Additionally, the use of low or zero emission generators in microgrids can increase the overall efficiency of energy utilization, dealing with environmental concerns, such as CO 2 emissions and reduction of dependence on conventional power generation [11], [12]. Accurate power management control among DGs is an important issue for the autonomous operation of microgrids. Typically, frequency and voltage droop control schemes are adopted to achieve power sharing among DGs without relying on communication [9], [10], [13]. Nevertheless, droop controlled microgrids are prone to have some stability and power sharing accuracy problems due to complex feeder impedances and high control gains [14]-[16]. To address these problems, stability-constrained and adaptive decentralized droop controllers have been proposed in [17]-[19]. In [20], the reactive power sharing accuracy was improved with the consideration of impedance voltage drop, the DG local load effects and the use of a virtual inductor loop. Methods based on virtual complex impedance loop and reactive power control error estimation were also proposed in [21] and [22], respectively. In or...

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