With reference to the newly released microgrid standards, design and real-time implementation of a centralized microgrid control system is presented in this article. In the grid-connected mode, the utility grid will provide the voltage and frequency reference at the point of connection. The assets within the microgrid will follow power command references provided by the control system. In the islanded mode, the energy storage system (ESS) can provide the voltage and frequency reference to all other generators. Based on the state-of-charge of the ESS, a rule-based dispatch is proposed, with priority given to diesel generator and then the storage in the middle state of charge range. To alleviate power fluctuations, meet smooth planned islanding requirement, and compensate for the feeder losses ignored in dispatch algorithm, a supplementary slackbus power control based on closed-loop feedback and first-order filter is proposed. The potential of the storage system in firming short-time power fluctuation and providing long-term load shifting capabilities is exploited. An emergency dispatch function for unplanned islanding considering the speed of response limitation of a diesel generator is also proposed. The proposed control strategy is implemented and tested on a controller hardware-in-the-loop test bench. It demonstrates the capability of the control system to reduce load shedding and renewable curtailment, and to implement power management at the point of interconnection. Index Terms-Controller hardware-in-the-loop (C-HIL) test, microgrid control system (MGCS), rule-based dispatch, slackbus power control, smooth transition, state of charge (SoC) management.

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Abstract. The future of the power grid lies in large scale integration of distributed generation devices with the utility system, at either a medium or low voltage level. These new distributed generation technologies can offer benefits and opportunities to manufacturers and utilities in need of supplementary energy sources. However, a large increase in the number of distributed generation interconnections may potentially cause a number of technical concerns relating to the operation of the system in question. Because existing distribution networks were not originally designed to include complex distributed power-electronic systems, detailed testing of existing and future protection and control devices is necessary. The growing use of photovoltaic devices, wind turbines and other complex power electronic systems is changing the nature of distribution systems. The performance and stresses on wind farm components will therefore depend on control and protection system reaction. In fact, this new generation of intelligent grids is becoming as complex as sophisticated high-voltage AC/DC transmission systems. This paper describes how the Monte Carlo simulation technique and parallel simulators can be used to evaluate worst-case stresses for different fault and operating conditions.