Ting-Yen Hsieh

Economic dispatch in an offshore island system with high wind power penetration

Generation cost of an island power systems typically exceed that of a large grid system. Therefore, most countries initiate their plans to develop renewable energy on remote offshore islands. However, the integration of a significant amount of renewable power in isolated systems requires careful consideration in order to ensure high reliability and security for the power system operation. To consider system economics and stability simultaneously, an optimal algorithm to determine the real-time economic dispatch (ED) is the first step. In several island power systems, the incremental fuel cost is non monotonicity so that several conventional economic dispatch methods could not be applied to those systems. This study discussed various ED methods and implemented mixed integer linear programming (MILP) to an actual island power system.

Adaptive Setting and Simulation of Distance Protection Relay in a Long Transmission System Connected to an Offshore Wind Farm

Offshore wind power has become the focus of the worlds renewable energy development. In Taiwan, several demonstration offshore wind turbines will be scheduled to be established by 2015, and more than 300MW capacity of offshore wind farm to be installed by 2020. As the penetration level of wind energy increases, more reliable protection systems for offshore wind farms are required. The wind farm protection system is usually divided into different protection zones including the wind farm area, wind farm collection system, wind farm interconnection system and the utility area. Different protective zones have different protection schemes and relay settings. This project has proposed an adaptive distance relay that protects submarine cables between an offshore wind farm and an AC grid. The double-circuit submarine cables that connect offshore wind farm in Penghu and Taiwan grid will be utilized as an example. First, the apparent impedance of the relay is mathematically derived using a detailed equivalent circuit model, and the characteristic trip boundaries of the relay in various scenarios are obtained. The nonlinear characteristics of the trip boundaries that are used in a typical distance relay with four protection zones will be discussed. Furthermore, the effects of the uncontrollable factors on the performance of a distance relay have been considered into the simulations. These system disturbances include wind speed variation, system short circuit faults, or system component failures. These case studies have been presented using the simulation package to evaluate the feasibility of the distance relay setting that is developed in this project.

Capacity determination of a dynamic energy storage system in an island power system with high renewable energy penetration

With the development of renewable energy, many countries developed their projects in offshore islands, resulting in high penetration of renewable energy in those island systems. However, large renewable energy integration affects the original unit scheduling and system transient stability. When a contingency event occurs, such as a generator trip, the frequency stability would be reduced, even leading to additional tripping of renewable energy resources, causing a cascade faults on the grid. Although load shedding scheme is one of the methods to solve this problem, it reduces system reliability and affects the interests of customers. With the development of modern battery technologies, dynamic energy storage system provides instant power support during a very short time to decrease the impact of disturbance when an accident occurs. In this work, the optimal capacity of a dynamic energy storage system is determined by using the proposed training tool, which combines power system analyses and neural-network training. With the dynamic energy storage system, when a generator tripping occurs, the power supplied by the dynamic energy storage system avoids low-frequency load shedding.

A review of flexibility requirement of electric generators in high wind power penetration systems

With blossoming of wind power generation in the grid, many system operators recognize the requirement for additional flexibility to accommodate the variability and uncertainty from wind generation. Because of the high penetration of wind power, power systems are facing great operational challenges in maintaining generation balance. This study reviews the system flexibility requirement in a high wind power penetration system, and summarizes the indices to identify capabilities of new generators to satisfy the flexibility requirements. According to the review results, it presents that a system with more flexible units would accommodate much higher penetration of renewable energy and reduce the operational cost.

Identification of transmission bottlenecks before and after large scale renewable energy integration in Taiwan

Renewable power has been growing fast in Taiwan over the recent years. Owing to the inherent variability from renewable energy, integration of such generation into the grid brings a huge challenge to short-term system operation and long-term grid planning. Compared with traditional thermal power plants, renewable power output has random and fluctuant characteristics. Additionally, the existing power grids would have insufficient capacity to transfer those additional renewable energies, which increases the risk of the overload of the transmission lines. Transmission congestion would increase system operation cost and waste nature resources. Therefore, it is significant to identify transmission bottlenecks after large scale renewable energy integration in advance. This study examines the current transmission bottlenecks and investigates future potential congested transmission lines after large scale renewable energy integration in Taiwan, which presents a significant reference on the network reinforcement, FACTS control, or unit rescheduling.

Multipoint fuzzy prediction for load forecasting in green buildings

A novel load forecasting mechanism that uses fuzzy logic and big data, termed multipoint fuzzy prediction (MPFP), is proposed. The prediction mechanism is based on historical data and, therefore, is adaptive to dynamic changes over time when the database is updated properly. The MPFP can be combined with green buildings and renewable energy sources to reduce peak loads and energy consumption. An energy management system (EMS) can be integrated into the framework to achieve an improved level of performance. On the basis of a prediction of load curves, the EMS can discharge energy storage devices when electricity prices are high and charge them when electricity prices are low, reducing costs. Real power demand data were employed to illustrate the validity of the proposed MPFP scheme.

Evaluation of maximum installed capacity of electric scooter charging station for microgrid in Yuan Ze University campus

In this study, a methodology for determining the proper installed capacity of electric scooter charging station in Yuan Ze University (YZU) is developed. The system structures and parameters of distribution systems, and the measures of charging station are analyzed and organized. The continuous three phase power flow is used to evaluate the whole system voltage variations, and voltage unbalances. Then, the proper installed capacity of charging station can be determined to ensure the service stability and power quality. The outcomes of this research would contribute to the suitable planning and design for power distribution systems in campus.

Intelligent control scheme for output efficiency improvement of parallel inverters

Parallel inverters are often used for the interconnection of Renewable Energy Generation Systems (REGSs); however, the output efficiency using the conventional current-sharing control scheme is low at light loads. Therefore, an intelligent control scheme for output efficiency enhancement of parallel inverters is proposed in this paper. The proposed control scheme is based on the output efficiency curve of a single inverter and then an artificial-intelligence-based algorithm is used to find the optimal output efficiency of parallel inverters. The integration of the proposed control scheme into a Photovoltaic Generation System (PVGS) with a rated output power of 20kW interconnected by 10 inverters with rated output power of 2kW is simulated in this paper. Simulation results demonstrate the performance of the proposed intelligent control scheme in output efficiency improvement of parallel inverters at light loads.