Yung-Ruei Chang

Bio: Yung-Ruei Chang is an academic researcher from Atomic Energy Council. The author has contributed to research in topics: Microgrid & Electric power system. The author has an hindex of 2, co-authored 3 publications receiving 14 citations.

Ancillary voltage control for a distribution feeder by using energy storage system in microgrid

Abstract: This paper presents ancillary voltage control for a distribution feeder by using energy storage system (ESS) in microgrid. The microgrid consists of photovoltaic, wind power, and distribution generator. The active and reactive power control, voltage and frequency droop control for the power converter of ESS are proposed to reduce microgrid impact on the distribution feeder. The voltage variation along the feeder due to change of renewable power generation is derived by executing power flow analysis. The actual voltage fluctuation on the microgrid is measured, which is used to control active and reactive power output of the power converter via energy management system in the microgrid SCADA platform. Three operation scenarios of the microgrid with ESS are tested to verify the effectiveness of the proposed control method. It is found that the power output of ESS can be well regulated to reduce voltage fluctuation on the microgid, which is complied with grid connect code to achieve better voltage control performance for the distribution feeder.

Over frequency control of photovoltaic inverters in an island microgrid

Abstract: This paper discusses the power variation of photovoltaic power plant (PVPP) impact on the frequency response of an isolated island microgrid. An island microgrid with PVPPs and diesel generators is selected for study. The power system network, diesel generation units, load and PVPP data are collected in detail. And the one-line diagram of the study system with regarding peak and off-peak loading is set up in the simulation software for the steady state load flow analysis. After that, the transient stability analysis is executed with considering the tripping and power variation of various PVPP ramp rates with and without considering the over frequency compensation of photovoltaic (PV) inverters. The dynamic response of diesel generators and system frequency are examined carefully. It is found that the over frequency phenomenon can be controlled effectively by the regulation of PV inverters to achieve better reliability of the microgrid.

Operation of a Micro Off-Shore Island Considering PV Power Generation Ramp-Rates

Abstract: This paper investigates the impact of photovoltaic generation system (PVGS) power variation on the transient response for a small off-shore island. The Chimei Island in Taiwan is elected for study. First, the power system network, diesel generation units, load and PVGS data are collected in detail. And the one-line diagram and the associated generator control model are set up in the Cyme Psaf program. After that, the transient stability analysis is executed with considering the tripping and power variation with various ramp rates of PVGS. The dynamic response of diesel generators and system frequency are examined carefully. It is therefore to obtain the maximum installation capacity of a single and total PVGS without violating the lowest operation frequency limitation.

Reactive Power Management in Renewable Rich Power Grids: A Review of Grid-Codes, Renewable Generators, Support Devices, Control Strategies and Optimization Algorithms

Abstract: Power electronic converter (PEC)-interfaced renewable energy generators (REGs) are increasingly being integrated to the power grid. With the high renewable power penetration levels, one of the key power system parameters, namely reactive power, is affected, provoking steady-state voltage and dynamic/transient stability issues. Therefore, it is imperative to maintain and manage adequate reactive power reserve to ensure a stable and reliable power grid. This paper presents a comprehensive literature review on the reactive power management in renewable rich power grids. Reactive power requirements stipulated in different grid codes for REGs are summarized to assess their adequacy for future network requirements. The PEC-interfaced REGs are discussed with a special emphasis on their reactive power compensation capability and control schemes. Along with REGs, conventional reactive power support devices (e.g., capacitor banks) and PEC-interfaced reactive power support devices (e.g., static synchronous compensators) play an indispensable role in the reactive power management of renewable rich power grids, and thus their reactive power control capabilities and limitations are thoroughly reviewed in this paper. Then, various reactive power control strategies are reviewed with a special emphasis on their advantages/disadvantages. Reactive power coordination between support devices and their optimal capacity are vital for an efficient and stable management of the power grid. Accordingly, the prominent reactive power coordination and optimization algorithms are critically examined and discussed in this paper. Finally, the key issues pertinent to the reactive power management in renewable rich power grids are enlisted with some important technical recommendations for the power industry, policymakers, and academic researchers.

Optimal microgrid planning for enhancing ancillary service provision

Abstract: Microgrids have presented themselves as an effective concept to guarantee a reliable, efficient and sustainable electricity delivery during the current transition era from passive to active distribution networks. Moreover, microgrids could offer effective ancillary services (AS) to the power utility, although this will not be possible before the traditional planning and operation methodologies are updated. Hence, a probabilistic multi-objective microgrid planning (POMMP) methodology is proposed in this paper to contemplate the large number of variables, multiple objectives, and different constraints and uncertainties involved in the microgrid planning. The planning methodology is based on the optimal size and location of energy distributed resources with the goal of minimizing the mismatch power in islanded mode, while the residual power for AS provision and the investment and operation costs of the microgrid in grid-connected mode are maximized and minimized, respectively. For that purpose, probabilistic models and a true multi-objective optimization problem are implemented in the methodology. The methodology is tested in an adapted PG&E 69-bus distribution system and the non-dominated sorting genetic algorithm II (NSGA-II) optimization method and an analytic hierarchy process for decision-making are used to solve the optimization problem.

Risk assessment of renewable energy-based island microgrid using the HFLTS-cloud model method

Abstract: Difficulty in power supply has always been the main factor hindering the sustainable development of islands. It is an effective way to address the energy supply issue of off-grid islands by building island microgrid system with abundant renewable energy, such as wind energy and solar energy. However, island microgrids offer a mix of the high penetration rate of renewable energy and the complex island environment, being confronted with many challenges in the whole life cycle. To implement the project smoothly and make full use of the advantages of renewable energy-based island microgrids, a risk assessment must be incorporated. In this study, based on a three-dimensional model, we take a holistic view of identifying risks that includes four categories (technical, economic, environmental and social aspects). Later, a reasonable and applicable risk assessment framework is constructed, in which the fuzziness and randomness of information are taken into consideration. The hesitant fuzzy linguistic term set is used to endow the index evaluation information, and the cloud model is used to transform the evaluation information. The final results show that the overall risk level of China’s island microgrids is “Slightly High”, particularly in the technical aspect. Furthermore, corresponding mitigation strategies are put forward. This study conducts a comprehensive study on the risk assessment and risk response measures of island microgrids, which is conducive to deal with potential risks, thereby to minimize the loss and promote the island microgrid development.

Multi-Objective Probabilistic Power Resources Planning for Microgrids with Ancillary Services Capacity

Abstract: Microgrids have become an attractive strategy to guaranty a reliable, efficient and sustainable electricity delivery to the distribution network, as well as to offer effectively ancillary services to the power utility. Therefore, special features have to be introduced to the planning methodology, while the optimization problem has also to be re-evaluated to contemplate the large number of variables, multiple objectives, and different constraints and uncertainties. Hence, a probabilistic multi-objective microgrid planning methodology based on the optimal size and location of distributed generation is proposed. In this methodology, the mismatch power in islanded mode and the annual energy losses in grid-connected mode are minimized, while the residual power for reserve provision is maximized. For that purpose, probabilistic models, distributed storage units, and constructive constraints are contemplated in the methodology. The methodology is tested in an adapted PG&E 69-bus distribution system and the NSGAII optimization method is used to solve the optimization problem.