Power Flow Control of Renewable Energy Based Distributed Generators Using Advanced Power Converter Technologies

Abstract

Abstract-This paper describes a design concept in which a digital controlled power interface embedded with a battery energy storage system (BESS) named battery interfaced static synchronous generator (BISSG) is constructed to improve the power quality of micro-grid (MG) systems. Some distributed generation (DG) systems, e.g., the wind turbine generator (WTG) and the Photovoltaic (PV) systems conventionally generate real power based on natural conditions thus their output power are fluctuating from time to time. To eliminate this shortcoming, the proposed BISSG attempts to smooth the output power of DG with fast charging and discharging its BESS. To achieve a cost-effective design, the proposed BISSG is designed to maximize its control capability in terms of bilateral real power regulation and reactive power compensation for MG voltage support or power factor correction. It is important to note that the proposed BISSG is able to fulfill various real power dispatching functionalities required by the system operator. In this paper, the mathematical model of BISSG and its related controllers are firstly addressed. Then, simulation studies and hardware tests on a simplified MG network are carried out. Typical results are presented with brief discussions to demonstrate the feasibility and effectiveness of the proposed control scheme.Index Terms-Renewable energy, wind turbine generator, battery interfaced static synchronous generator, distributed generation, micro-grid. I. INTRODUCTIONWith the rapid development of new energy technologies, more and more renewable energy sources are being integrated into power distribution systems in the form of distributed generations (DG). In recent years, power converter interfaced DG systems, renewable energy sources (RES) based micro-grids (MG) and state-of-the-art communication and control technologies have been recognized to play important roles in the development of future energy policies. Short-term goals of these energy policies include reduction in high-polluting power generations and global greenhouse gas emissions, improved diversity and security of energy supply, and exploitation of possible incentives for creating local value added opportunities for the related industrial sectors. Based on the related technical reports in the open literature, potential Manuscript received September 25, 2013; revised January 16, 2014 [7]. Based on the standards such as IEEE1547, IEEE 929 and UL1741, DG inverter systems should operate at unity power factor [8]; however, this regulation has some limitations in practical applications, especially when some system-level control functions are to be performed. On the other hand, considering the installation quantity of PV and WTG has been continuously increased in recent years and the WTG and the PV systems generate real power based on nature conditions thus their output powers are not stable; this leads to a problem that fast output power fluctuation of the DG with high capacity can cause network frequency and voltage variations, especially in i...