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Motivated by concerns about the environment and energy shortages, considerable progress has recently been made in the development of photovoltaic (PV) and other forms of distributed generation. These developments have contributed greatly to awareness of the importance of renewable energy and governmental policies to revise energy priorities to ensure the adoption and significant growth of renewable energy. Safely and reliably interconnecting various photovoltaic generators is a major challenge in the development of modern power systems and the interconnection of PVs may have effects that require close attention. Standards or guidelines for grid-connected photovoltaic generation systems considerably affect PV development. This investigation reviews and compares standards and guidelines for distributed generation, and especially for PV integration. Pertinent standards and guidelines that ensure the successful operation of PV systems are presented. This investigation serves as a reference for improving standards for grid-connected photovoltaic generation systems.

The current unit scheduling criteria on Penghu Island entail applying net load demand to determine the numbers of online diesel units. The net load may underestimate the number of required online units in a system with high wind power penetration, especially under off-peak load and high wind conditions, both of which engender insufficient operating reserves. Therefore, this study proposes new unit scheduling criteria that integrate the system equivalent speed droop with the M factor by considering different loads and wind conditions. This study also identified the maximum allowable power loss and the required size of the operating reserve by considering system reliability. Finally, this study determined the allocation modes for units and the required generation distributions for various loads. In accordance with the requirements of system loads at specific times, the proposed unit scheduling criteria could provide system operators with corresponding unit operating modes, as well as generation distributions, thereby sustaining power reliability and quality levels.

This article develops an intelligent underfrequency security control mechanism for offshore island power systems, for which frequency stability is a major concern. The security control mechanism is divided into two main categories: preventive control and corrective control. The developed preventive?corrective control system involves modules for forecasting the frequency nadir, the rate of change of frequency, intelligent load shedding, and protection strategies. The forecasts assist in the rescheduling of diesel generators, wind power curtailment, or intelligent underfrequency load shedding (UFLS). An actual island power system is considered to elucidate the feasibility of the proposed control system. The results of this study provide system operators with a valuable reference for preventive dispatch and the planning of load shedding.

The major drawback of the battery charging in traditional electric vehicles is the use of plug-in charging devices. The aim of this paper is to propose a wireless battery charging method, in addition to power transfer, data related to battery status, vehicle ID code, or emergency messages can be simultaneously transferred between the grid and vehicle. This work applies inductive power transfer to complete the charging system. The proposed control system can monitor the operating status on the secondary (vehicle) side in real time and adjust charging current depending on the battery status. Furthermore, the proposed mechanism is able to make an immediate stop, if there is any contingency, such as overcharging voltage or current. This will be beneficial to efficient and safety concern during the charging process.

This paper presents a new hybrid approach that combines Modified Priority List (MPL) with Charged System Search (CSS), termed MPL-CSS, to solve one of the most crucial power system’s operational optimization problems, known as unit commitment (UC) scheduling. The UC scheduling problem is a mixed-integer nonlinear problem, highly-dimensional and extremely constrained. Existing meta-heuristic UC solution methods have the problems of stopping at a local optimum and slow convergence when applied to large-scale, heavily-constrained UC applications. In the first step of the proposed method, initial hourly optimum solutions of UC are obtained by Modified Priority List (MPL); however, the obtained UC solution may still be possible to be further improved. Therefore, in the second step, the CSS is utilized to achieve higher quality solutions. The UC is formulated as mixed integer linear programming to ensure the tractability of the results. The proposed method is successfully applied to a popular test system up to 100 units generators for both 24-hr and 168-hr system. Computational results show that both solution cost and execution time are superior to those of published methods.

The penetration of renewable energy is gradually increased. Therefore, power system flexibility, which is required to maintain system security and to cope with renewable generation uncertainty, becomes more important. Various technologies, such as flexible generators, demand management, energy storages, network reconfiguration, and even efficient system operations, are capable to improve power system flexibility. Nevertheless, among them, flexible generation resources can provide a direct way to enhance the power system flexibility. This work first applies fuzzy analytic hierarchy process (FAHP) to calculate the flexibility index of generation resources. Then, the process of unit scheduling is implemented under various operation scenarios to investigate the relationship between the generation flexibility and the cost of unit scheduling. Finally, the required flexibility and the corresponding capacity of flexible generators under a specified penetration of renewable power generation are investigated under different operation scenarios.

The operational security of power systems for wind farm integration becomes more important as the penetration of wind generation increases. A wind farm may contain hundreds of wind turbines (WT) and thus the power system simulations based on the complex model of a WT consumes much time. This paper proposes an equivalent wind farm model with the frequency-regulation function. The main research works include the establishment of the generic model of a WT, the development of single-and multi-machine equivalent models for a large wind farm, the clustering of WTs based on the developed nonlinear wake model and the Fuzzy C-means(FCM) clustering algorithm, the integration of the frequency-regulation function into the equivalent wind farm (WF) model, and the validation of the developed equivalent WF model by various operating scenarios. The results demonstrate that the proposed multi-machine equivalent method based on the FCM clustering provides a more accurate model than a single-WT equivalent model. Consequently, the research results provides a solution for simulating a large-scale wind power integration, providing efficient, accurate, and fast steady-state and dynamic analyses.

This research is mainly to design a large radial-type permanent magnet synchronous generator (PMSG) based wind generator. First, the design process for the PMSG is introduced. The basic parameters of the generator's construction were calculated according the electromagnetic theory. Then, the coupled transient electromagnetic process using magnetic circuit analysis and finite element method (FEM) was applied to design the wind-generator model. Next, this work compared the simulation results by commercial software with the calculation results based on the electromagnetic theory. In this study, the structure and characteristics of the tooth are analyzed under two assumptions. The first one is that the radius of the rotor of inner-rotor PMSG is same as the radius of the stator of the out-rotor PMSG, and vice versa. The second one is that the thickness and angle of the permanent magnet are fixed. The simulation results demonstrate that inner-rotor PMSG has higher output power. Moreover, the cost of the permanent magnet for the out-rotor PMSG is less.

In recent years, the integration of wind power generation, especially for offshore wind power, has increased rapidly. Therefore, the requirements of grid codes on wind power integration becomes a major factor in the power system reliability. This paper compares and summarizes the grid codes and the corresponding works about wind power integration around the world. The grid codes issued by Denmark, Ireland, UK, Germany, Spain, China, US, Canada, and other representative countries have been studied. The main requirements of the grid codes include reactive power, frequency regulation, fault ride through, and power quality. Additionally, several grid codes also address the requirements on communication, ramp rate, and offshore wind power plants (WPP). Finally, this paper provides the information about the future trend of grid code requirements on offshore wind power integration, which helps the grid operators ensure a safe operation for high wind-power penetration.

The study concerns the ramp rate problem that is associated with the large-scale integration of wind power. As planned 3GW wind farms are built in Taiwan, the potential variability of the net load must be estimated to determine the flexibility requirement. This work will use numerical weather predictions in Taiwan to estimate total power output from 3 GW wind farms, and analyze the ramping characteristics of the net load using statistical approaches. Its results can provide the operators of Taiwan's power generation system an important reference for determining the required ramping capability in the future.

With the significant increase of the wind power generation technology, there are many studies about the wind turbine control and the impact on the power system after integration. However, the mechanical and aerodynamic behaviors of the wind turbine were usually simplified when studying control and influence on the power system. Namely, the dynamic performance was studied with a fairly simple model of the power system because many research works did not consider the modelling of the whole wind turbine system. Since the mechanical and electrical systems are coupled, the complete model should consist of mechanical and electrical parts. Thus, this study highlights that a complete wind turbine modelling should consider the characteristics of the blades, mechanical system, yaw and pitch, and generator. In this study, the mechanical dynamics of a wind turbine is simulated by ADAMS; aerodynamic of blades is simulated by FAST; the model of the generator, yaw control system and pitch control system is constructed by MATLAB/Simulink.

Islands incur more difficult and expensive energy supplies; many offshore islands, therefore, develop renewable energy to supply energy and reduce CO2 emissions. However, most of renewable energy sources, such as wind and solar, are intermittent and variable sources of power. To overcome the integration problems, numerous islands have utilized several useful methods. For instance, the island of Gran Canaria applied the pumped storage systems to reutilize energy, and the island of Lolland developed renewable hydrogen community. The operation experience of these islands is extremely worthy to appreciate. This article introduces eight offshore islands and discusses about their present situations, policies, successful experience and challenges about renewable energy development. Those islands include Samso, Reunion, Cyprus, Crete, King Island, Agios Efstratios, Utsira and El Hierro. The successful experience on those islands can provide useful information for other islands for developing renewable energy.

Some essential differences exist between a wind power generation system and a conventional generator. The impact on the transient stability of a power system must be explored if wind power, particularly large-scale wind power, is to be integrated into existing power systems. In a wind power system, one of the main issues in power system safety and operation is rotor angle stability. Rotor angle stability is determined by its critical clearing time (CCT). This study examines the grid connection of 1833 MW of wind power capacity into the existing Taipower system and explores the impact of integrating large-scale wind power on a power system’s CCT. It was observed via simulation that the penetration of wind power in the system peaks at 12%. The simulation uses PSS/E power system analytical software to establish a 1626-bus power system for Taiwan and contains details of power grid component parameters and wind turbine models. We assume that a balanced three-phase short-circuit ground fault occurs on each 345 kV bus. The CCT for each case is then acquired. Finally, this study compares and investigates the causes of differences in system CCT before and after integrating 1833 MW of wind power into the Taipower system.

The Penghu islands have abundant wind resources; the capacity factor of local wind farms exceeds 47% and these wind farms are slated for expansion. However, wind turbine power output is unstable and excessive turbine installation may negatively affect system stability. This paper seeks to determine an upper limit of the wind power penetration in the Penghu region power system to minimize waste and optimize system safety.

The layout scheme of wind farms is a challenging job having many design objectives and constraints due to the multiple wake phenomenon. Wake effect calculation is one of the significant problems in the wind farms and needs to be modeled to decrease the power loss due to near and far wake effect. This paper reviews the wake models in general and far wake models in particular. The comparison of different far wake models shows that the Jensen׳s far wake model is a good choice to solve the wind farm layout problem due to its simplicity and relatively high degree of accuracy. This research also focuses on the studies carried out on wind farm layout optimization problem and the current state of the art of fitness functions used for the optimization of wind farms using Jensen׳s wake model. It is found that there is a need of more optimization techniques to be applied to solve the layout problem. In addition, future advancements have been identified for better positioning of wind turbines in larger wind farms.

This paper proposes a novel stratification-based wind power forecasting method and develops a hybrid forecasting model at different stratifications using charged system search algorithm. The proposed model applies the concept of segmentation from the theory of optimal stratification to forecast short-term wind power outputs. Additionally, the proposed method elucidates different weighting values of each individual model at different segmentation blocks. Based on the forecasting results, the proposed stratification-based hybrid model outperforms traditional stand-alone models and unstratified hybrid models in terms of forecasting accuracy, which verifies the proposed forecasting model for accurate wind power forecasting.

Offshore wind power has become the focus of the world's 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.

The combination of wind and pumped storage is a useful method to compensate the fluctuation of wind power generation, which would exploit the abundant wind potential and increase wind power penetration. Taiwan Power Company (TPC) develops renewable energy actively in recent years. Moreover, TPC has started planning a high penetration wind power system and building offshore wind farms around the coast of Zhangbin, Yunlin and Penghu. The target of the offshore wind power installed capacity is up to 3 GW by 2025. However, the integration of the large scale of wind power would give huge challenges to the system operator because wind is randomly characterized. In this study, after high penetration wind power is integrated, the impacts of system frequency and the dispatch of conventional units will be discussed. Additionally, the hybrid system combing wind power with pumped-storage will be planning to reduce the effect of system frequency.

The Vietnamese government have plan to develop the wind farms with the expected capacity of 6 GW by 2030. With the high penetration of wind power into power system, wind power forecasting is essentially needed for a power generation balancing in power system operation and electricity market. However, such a tool is currently not available in Vietnamese wind farms as well as electricity market. Therefore, a short-term wind power forecasting tool for 24 hours has been created to fill in this gap, using artificial neural network technique. The neural network has been trained with past data recorded from 2015 to 2017 at Tuy Phong wind farm in Binh Thuan province of Viet Nam. It has been tested for wind power prediction with the input data from hourly weather forecast for the same wind farm. The tool can be used for short-term wind power forecasting in Vietnamese power system in a foreseeable future.

In this paper, nine, seven, five and three level diode clamped multilevel inverters (9L-7L-5L-3L DCMI) have been designed and used in wind generation system. The DCMI is designed to operate at low switching frequency with low THD by increasing the number of output voltage levels. The proposed designed DCMI is then connected to permanent magnetic synchronous generator (PMSG) wind turbine to generate an AC output voltage. A low switching frequency sinusoidal pulse width modulation (SPWM) triggering circuit is adopted as the controlling signals. Several cases were studied with varying number of levels and/or modulation indices used. The overall system is modeled in MATLAB/Simulink and a satisfied result be obtained.

With additional control loops, the wind turbines (WTs) have the frequency control capability to improve frequency nadir (FN) when a large disturbance occurs. To prevent the rotor speed of WT from reaching the minimum limit during the low wind speeds, a novel kinetic energy (KE) based droop control loop is proposed. In several traditional control loops, the droop gain is presented by a quadratic function of the WT rotor speeds. However, implementing a quadratic function in the generic model of WT is difficult. Therefore, in this study, a new linear-gain droop control loop is proposed for the doubly-fed induction generator (DFIG) based wind farm (WF). In the proposed control loop, the droop gain is a linear function of the WT rotor speeds. By selecting the proper coefficients of the linear function, the proposed linear droop gain can achieve a good approximation to the quadratic droop gain. The performance of the proposed droop control loop is demonstrated based on three wind-speed conditions. To verify the responses of system frequency and WT power output, four indices are developed. The simulation results demonstrate that the frequency control capability of the proposed linear-gain droop control loop is close to that of KE-based droop control loop.

As renewable power generation becomes more prevalent, the problem of frequency stability has become a particular concern of transmission system operators (TSOs), especially those of small power transmission systems. Traditional wind generation systems do not provide frequency regulation because they are decoupled from the power grid. Therefore, as conventional thermal generators are replaced by wind generators, the issue of frequency regulation for wind generation systems has become increasingly important. To release the kinetic energy stored in the rotating mass, inertia and droop control loops can be added into the controller of a wind turbine (WT). This work proposes an advanced control strategy with the time-varying gains of two control loops. In the proposed strategy, the gains are determined based on the desired frequency-response time. Moreover, the initial gain of the control loop is determined based on the wind speed, considering the operating condition of each WT in a wind farm (WF). The effectiveness of the proposed method is verified using an actual power system, revealing that it can be used to improve frequency regulation in a power grid.

One of the most important tasks for day-ahead electricity markets is to do the Security-Constrained Unit Commitment (SCUC). SCUC generally combines the needs of unit commitment, network limits, and regulation in a constrained optimization problem for different time frames. Different electricity markets utilize different SCUC methods. The main goal of this work is to introduce SCUC operation experience in several electricity markets and summarize significant issues in the current SCUC problem. For instance, in addition to traditional constraints in the SCUC process, this work also investigates the effect of frequency stability, transmission switching, or optimal generation scheduling on the SCUC methods. Additionally, the integration of renewable energy also bring the impact to the traditional SCUC methods. The above mentioned issues concerning the SCUC topic will be studied herein.

As the penetration of renewable power increases, the associated challenges in power systems also increase. It is expected that a power system faces increasing flexibility on conventional thermal generators, energy storages, demand side management, or increased interconnection cooperated with up-growing contributions from variable renewable energy sources. Therefore, energy from less flexible baseload generators needs to be replaced by a combination of renewable energy sources and more flexible conventional resources. This work will introduce the characteristics of flexibility in power systems, investigate the tools and metrics for evaluating flexibility, and concluding main sources of operational flexibility in power systems.

This paper is focused on the model development of doubly fed induction generator (DFIG)-based wind turbines. The model integrates mechanical and electrical systems. In the mechanical system, the aerodynamic properties are calculated in every section and every angle of attack by using a finite element analysis software, and the dynamic structure analysis is performed by using the Fatigue, Aerodynamics, Structures, and Turbulence (FAST) code. On the other hand, the electrical system includes DFIG modeling, the grid side converter (GSC) with DC bus voltage control, and the rotor side inverter (RSI) with direct power control (DPC). By using the direct power control strategy, the active power, reactive power, and power factor from the DFIG can be controlled to meet the requirements of the grid code. Moreover, the actual measured wind speed data are used in this work to simulate the outputs from the DFIG in order to confirm the feasibility of the wind turbine modeling. According to the simulation results, the proposed model is useful and can provide a reference for further studies about wind turbine technology. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Modern wind turbine technology has been a great improvement over the past couple decades, leading to large scale wind power penetration. The increasing penetration of wind power resulted in emphasizing the importance of reliable and secure operation of power systems, especially in a weak power system. In this paper, the main wind turbine control schemes, the wind penetration levels and wind farm dynamic behavior for grid code compliance were investigated in the Penghu wind power system, a weak isolated power system.

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.

Over the last decade, wind power penetration has increased substantially because of environmental considerations. With the integration of so much wind power generating capacity, system operators are facing the challenge of maintaining the stability of the power system. Use of the complex wind turbine (WT) model to analyze the steady-state operation and dynamic stability of the power system with high wind power penetration requires a long computation time. Accordingly, generic models of various WTs have been developed. This work develops both generic and complex models of the WT that is based on the doubly fed induction generator (DFIG), which is the so-called type-3 WT. Both generic and complex models include inertia of the WT and pitch control with the anti-windup mechanism to ensure that they can represent the electrical and mechanical parts of a real WT. This work compares the characteristics of the developed complex and generic models. The simulation results demonstrate that the developed generic model of the type-3 WT reasonably approximates the complex model.

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.

In response to the global renewable energy development, the associate transmission line upgrade is significant. The wind resource in Taiwan is abundant, especially in offshore areas. The target for the installed capacity of the offshore winds in Taiwan is up to 3GW by 2025. However, it is necessary to evaluate the potential transmission congestion owing to the offshore wind power integration and identify the maximum allowed capacity of offshore wind power in Taiwan. There are many constraints for wind power integration. One of the main impacts is congestion of the transmission line due to the limitation of transmission capacity. Therefore, this study implemented system simulations under various scenarios and achieved the maximum allowed capacity of the offshore wind power integration in Taiwan. This analysis was based on the constraints of transmission line limits, and the actual system parameters were utilized. The simulation results provide a significant reference to develop Taiwan's offshore wind energy.

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.

The paper focuses mainly on the maximum control method of boost chopper circuit based PMSG wind turbine. It includes a full bridge rectifier, boost chopper circuit, and a two-level voltage converter. Therefore, this PMSG system can directly connect with the gird; and the active power and reactive power can directly control by the grid voltage oriented vector control. The maximum power control method of the boost chopper based PMSG was studied to charge a constant resistance. In this study, the maximum power control is improved to apply in gird connection system.

Taiwan is developing the renewable energy actively, in which the wind energy is seen as one of important resources. However, the suitable locations for wind farm constructions are less and less on the shore, and the trend of wind farm development in the future will toward to offshore where the installation capacity of the wind farm could reach hundreds of megawatts. As the installation capacity of the wind farm increases, the effects on the interconnected AC grid are also more notable. In this paper, the off-peak system in Taiwan is used as a studied system in which the Penghu area and Taiwan grid is connected by submarine cables. This study explores the wind farm transmission system including HVAC, HVDC, and hybrid HVAC-HVDC systems and compares the differences of their impact on the system.

The energy costs of island systems are usually higher than those of large grid systems. Therefore, majority of the countries worldwide usually initiate their plans for developing renewable energy on remote islands. The electricity cost of Matsu Islands accounted for roughly 5% of total annual deficit of Taiwan Power Company. Hence, power generation is a critical energy economics issue for the Matsu Islands. This study will examine the possibility of wind power integration into Matsu Islands and investigate the transient frequency response in this system when a fault or disturbance occurs. According to the simulation results, the main target of this study is to improve the system stability on the remote island systems, and achieve the maximum renewable energy penetration.

Renewable portfolio targets have been established in many regions around the world. Regional targets such as 20% renewable energy by year 2020 are not uncommon. As the levels of wind power penetration increase, there are many power system impacts. This work investigated possible challenges and technical requirements for high penetration of wind power systems. The main issues to discuss covers reserve determination, wind power forecasting, unit commitment with appropriate generation portfolio, wind turbine and storage system technical development, demand response management, electricity market design, and frequency stability.

Renewable energy resource on islands is rich, which is of unique potential dominance in electricity development. In Taiwan, Green Island power system is a small, isolated system with a load level of 4.39 MW at peak and 0.81 MW at the minimum. It has been mainly fed from diesel generators. This paper is to study the effect of generator outage events on the system transient stability in the Green Island under a high penetration of renewable energy integration. Simulation results reveal that the system stability would not be affected and even improved as long as the renewable energy generators do not trip offline when system contingence occurs. Moreover, addition of one extra generator unit could significantly reduce the drop of the system's transient frequency. The work can provide several important operational experience to isolated micro grids with high penetration of renewable energy.

In the plentiful wind resource on Penghu Island, the capacity factor of the wind park is up to 47%. It is expected that, in a near future, more wind generating units will soon be integrated into this power system. However, many blackouts occurred at the Penghu Island in the past, and the present power protection scheme has not taken the influence of the wind generating units into consideration; therefore, it is necessary to revise the defense plan for Penghu's power system. In this paper, different generation/load patterns in different seasons are considered, and then, system steady-state and transient responses in some specific buses and important feeders are analyzed. The accurate modeling on wind turbines and relay settings are performed by using the power system simulation program PSS/E. The original power defense scheme using only under-frequency load shedding is examined, and a new protection scheme is proposed based on numerous contingency simulations, including islanding operation protection for some specific cases. It is expected that the reliability improvement of the Penghu system can be achieved by using the new defense scheme.

A five-year, NT$8.09 billion project to turn Penghu, Taiwan, into a world-class low-carbon island was formally launched in 2011. The project is a major milestone in Taiwan’s development of renewable energy. The initiative, which will install large onshore wind power generators, is predicted to reduce carbon dioxide emissions by more than 50% in 2015 from 2005 levels. The study examines the plan for large onshore wind farms and the corresponding connected network, and performs simulation analysis for the integrated wind power system. Simulation results of the system impact analysis will be a valuable reference for the government and power utility. Additionally, this study examines several successful renewable development projects on other islands worldwide, the environmental conditions for the Penghu wind energy project, and the preplanning process for the Houliao Energy Park on Penghu.

The paper uses PSS/E software to study connecting an offshore wind farm with 864 MW into the 2015 Taiwan power system. Major simulation works include: steady-state power flow, fault current computation, transient stability analysis and the impact analysis on critical fault clearing time. Three connection methods, i.e., single-point, separatepoint and multi-point connection, are proposed, in which the single-point connection is divided into two voltage levels (161kV and 345kV). During the steady-state operation, simulation results indicate that the 345 kV single-point connection method demonstrates the best performance. In addition, the fault current from a wind farm is partially determined by its connection location. In terms of transient stability, when grid faults take place, the 161kV singlepoint connection method appears to report the smallest voltage drop as compared to other connection scenarios. Its amplitude of frequency disturbance, however, is the greatest of all connection scenarios. As for the analysis on critical fault clearing time, simulation results indicate that the critical fault clearing time in all connection cases is approximately two times greater than that required by the Taipower standard. Simulation results in this study can be expected to provide valuable guidelines for connecting offshore wind farms into the power systems in the future.

Modern wind plants in offshore wind farms have grown in capacity into facilities that can no longer be ignored in transmission planning studies. Additionally, a large penetration of wind generation in an offshore wind farm into the power system will bring a number of challenges on system planning, operation, and impact analyses. This paper will provide an overview of the important state-of-the-art technologies in offshore wind energy systems, including the designs on internal electric system of an offshore wind farm, transmission system to shore, generator type, system frequency, transmission cable, communications medium and SCADA system, offshore substation and transformer. Additionally, the development on reactive power compensation, collection grid topologies, redundancy design for improving system reliability, power quality standard and measurement, and protection scheme on switching transient will also illustrated in this paper.

The continuation power flow method combined with the Jacobi-Davidson method is presented to trace the critical eigenvalues for power system small signal stability analysis. The continuation power flow based on a predictor- corrector technique is applied to evaluate a continuum of steady state power flow solutions as system parameters change; meanwhile, the critical eigenvalues are found by the Jacobi-Davidson method, and thereby the trajectories of the critical eigenvalues, Hopf bifurcation and saddle node bifurcation points can also be found by the proposed method. The numerical simulations are studied in the IEEE 30-bus test system.

A large-scale PV installation has a profound effect on the power quality and operation of the grid. Therefore, as installations of PV systems increase, changes to both technologies and interconnection standards are needed to address these high PV penetration systems. This paper investigates the main technical impacts of large-scale PV generations on power grids and associated interconnection standards. A case study by using the PSS/E software in the Kinmen power system was implemented to study the steady-state and transient characteristics for the high penetration PV systems.

Kinmen Island lacks fossil-fuel energy, However, it has rich potential for solar and wind energy resources because of its excellent climate and geographical location. Therefore, a large scale utilization of the renewable energy sources is favoured. In June 2004, the Kinmen County government published the Strategic Plan for the Sustainable Development of Kinmen, which focuses on maintaining the ecology of the islands. In the near future, a high penetration of renewable power can be predicted to be installed in this island. However, a large renewable energy penetration into a diesel power system would face technical and economic problems. Therefore, this study intends to discuss the system operation of the Kinmen system and investigates the original unit commitment scheduling. Based on the simulation results, a new unit commitment scheduling will be proposed in this work.

Over the past one to two decades, probabilistic forecasts have become more popular. Probabilistic forecasts take uncertainty into account and predict a probability distribution function (pdf). This study provides an overview of state-of-the-art technologies on wind-power probabilistic forecasts, and describes the fundamental concepts on those forecasting methods. Additionally, this study also summarizes various methods to evaluate the performance of a probabilistic forecast model. Finally, this study presents a case study using the ensemble prediction model, in which the wind-speed data were provided by the numerical weather prediction system (NWP) of the Central Weather Bureau (CWB) of Taiwan.

With the increasing penetration of the wind power generation, the impact of the wind power integration on power systems becomes more significant. For power system operators, maintaining power system security is the first priority. If a complete wind turbine model is used to analyze the steady-state operation and dynamic stability for a large-scale power system with wind power integration, it would take much computation burden and time. Thus, the generic models of various wind turbines have been developed to reduce the simulation time for wind power systems. The characteristics of a generic model should be similar to that of a complete model, but its structure is simpler than a complete model. This study developed both generic model and complete models for a doubly-fed induction generator (DFIG) based wind turbine, which is also called type-3 wind turbine. Additionally, this study compared the characteristics of the developed complex and generic models. According to the simulation results, this study demonstrates that the developed generic model of a DFIG-based wind turbine has the good approximation of a complete wind turbine model.

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.