This article presents the innovative integrated control strategies of the battery energy storage system (BESS) to support the system operation of an offshore island microgrid with high penetration of renewable energy. An intelligent energy management system (iEMS) was implemented to perform the supervisory control and data acquisition of diesel generators, distribution feeders, photovoltaic (PV) systems, and the BESS. An expert system was designed and embedded in the iEMS to derive the decision making for fast power discharging of BESS to improve the system transient stability for the severe contingency of large disturbances caused by the tripping of generators and PV farm. To mitigate the impact of PV generation fluctuation and to maintain the stable operation of diesel generators, the adaptive control of power charging and discharging of the BESS is applied to reduce the ramping rate of PV generation. To achieve the economic dispatch of the microgrid, the strategy of peak shaving and valley filling of the system net load curve by the BESS was derived considering the forecasting daily profiles of system loading and PV power generation. The computer simulation of actual diesel generator tripping and the field test of intentional PV system shutdown have been executed to demonstrate the effectiveness of the proposed control strategies of the BESS system to improve the system operation and transient stability of the study microgrid with high penetration of renewable energy.

To enhance the outage quality of a distribution system with a high penetration of PV renewable energy, this paper proposes a coordinating control strategy for an on-load tap changer (OLTC) of the main transformer in a distribution substation and PV smart inverters. The voltages at the end-points of all distribution feeders that are served by the main transformer and the power generation of each PV system are collected using a SCADA system. The hourly tap position of the OLTC is then derived from the daily profiles of feeder voltage and the injected power that is generated by all PV systems along the feeder. Thereafter, the PV smart inverters perform autonomous control of reactive power compensation so that the voltage at the point of common coupling (PCC) can be fixed at the specified voltage level. To demonstrate the effectiveness of the proposed voltage control strategy, a main transformer, which serves six feeders of the Taiwan Power Company (Taipower) with high PV penetration, was considered in a case study. The proposed coordinating control of the OLTC and PV smart inverters dramatically improved the voltage quality of the distribution feeder and enabled the effective mitigation of the impact of large PV integration in the distribution system.

This paper presents the innovative control scheme of renewable ancillary services to support the system operation of a bulk power system with high penetration of renewable energy. The smart inverters of PV systems can be controlled to adjust the renewable generation of real and reactive power according to the variation of system voltage and frequency. The dispatch control of renewable ancillary services is integrated with the energy management system (EMS) to achieve the coordination control of renewable energy and synchronous generators. The sensitivity factors of renewable system was applied to determine the generation curtailment for the mitigation of line overloading. The ancillary service of reactive power compensation by renewable energy was considered to improve the system voltage quality. The emergency generation control of renewable systems with fast ramping up capability was applied to illustrate the effectiveness of renewable ancillary service to improve the system frequency response after sudden generator tripping. Based on the computer simulation of an actual power system with large renewable energy to be integrated, the functions of virtual synchronous generators by the photovoltaic (PV) systems and wind farms have to be applied to ensure the successful steady state operation and to improve the system transient stability for severe disturbance contingency.

This article proposes a fault identification method that is embedded in an asset management system (AMS) to identify the faulted location based on the fault flags reported from the fault indicators (FIs). The fault identification model based on the Petri-net technology is developed using the distribution network topology generated by a geographic information system. The proposed method uses the data set of fault flags generated by FIs, the statuses of circuit breakers, the available precurrent and postcurrent measurements of FIs, and the loadings of distribution feeders and laterals. The hybrid communication system is applied to provide two-way communication between the control center and FIs. The AMS with the embedded fault identification method can dispatch the repair crews to the fault location faster to accelerate the customer service restoration. A distribution feeder of Taiwan Power Company was selected for the computer simulation to demonstrate the effectiveness of the proposed method by using the communication-capable FIs to identify the exact fault location of distribution lines after a short circuit fault occurs in a distribution system.

To support transformer load management, a narrow-band power line carrier (PLC)-based identifier has been designed and developed for the determination of customers served by each distribution transformer. The transmission characteristics of a PLC signal over low-voltage distribution lines is simulated by using the mathematical model of distribution transformers, line conductors, and customer loading at high frequencies of the carrier signal. After completing the development of PLC-based identifier, a field test has been executed to verify the performance of the identifier to determine the connectivity of the distribution transformer and the customers served without requiring power service interruption. With the customer account numbers updated by the PLC identifier, the monthly energy consumption and the service type of customers served by each distribution transformer are retrieved from the customer information system. The daily power profile and peak loading of the distribution transformers are then derived according to the energy consumption and the typical load patterns of the customers served.

This paper proposes an innovative transformer management system (TMS) for energy control of customer loads and photovoltaic (PV) systems to solve the problems of transformer overloading and over voltage due to power injection by PV renewable energy. The operation status of distribution transformers is monitored by transformer terminal unit (TTU) and reported to the control master station via the hybrid communication system. The demand response of customer load control is activated to reduce the loading level of transformers for mitigation of overloading problem. For the residential customers with installation of roof top PV system, the TTU is applied to perform the power factor control of smart inverter to prevent the over voltage problem. The hybrid communication system consisting of power line carrier, radio frequency and optical fiber is used to provide two-way communication for data collection and controls of customer loads and PV system. According to the field testing of the proposed TMS in Taipower, the adaptive energy control of customer loads according to the over loading level of distribution transformer is executed to support the demand response for peak load shaving effectively. The over voltage problem due to PV power injection has also been solved by TTU for control of PV smart inverters to perform the proper reactive power compensation.