Abstract:Renewable energy generations, especially wind power and solar PV generations, are, at this stage, among the most effective technologies in generating electricity from renewable energy resources. There are already large number of wind farms and solar PV farms connected to the high voltage transmission grid worldwide. Distributed generation based on renewable energy resources provides another feasible solution in promoting emission reductions at distribution level. Given all these increasing penetrations of renewable energy based generation sources, however, the renewable sources are intermittent in nature and have introduced various challenges to power system operations and planning. As such many of the large scale renewable energy farms are running at low capacity factors. This special issue provides a timely overview of methodologies of handling the renewable generation grid connection issues aiming at enabling more renewable energy utilization as well as Greenhouse Gas (GHG) emission reductions. This special issue accepted 11 papers covering the recent research findings in renewable energy grid connection related areas. These papers covered a comprehensive range from primary energy to policy studies.

Abstract:This paper presents a macroscopic view on the prevailing policy and potential issues in respect of the sustainable wind power development in China. It starts byanalyzing the characteristics of wind power resources andpin-pointing the relationship between the regulatory policiesand various economic, taxation, legal and grid integration attributes relating to the wind power development. Then itfollows by analyzing the status quo and capabilities of thewind power manufacturing industry in China including itsoperational efficiency and grid integration standards. The economic and environmental benefits are estimated by relating to the associated costing analysis in respect of themajor contributing factors such as manufacturing, operationaland financial factors. Results of the associated benefit sanalysis indicate that the use of the wind power generation

Abstract:The installation of wind energy has experienced rapid development during recent years. As a result,the operation of power system can be greatly affected.Therefore, the operators of different countries have formulatedthe grid codes which reinforce technical requirements for wind power plants. In this paper, recent gridcodes published in different countries have been carefully reviewed. The basic requirements of active power controland reactive power compensation, both of which have particular influence on wind power plants operation, are focused on. Based on this review, it is understood that withthe increasing integration of wind energy, there is a worldwide trend to regulate the performance of windpower plants so that they can contribute to the stability and reliability of power system.

Abstract:Rapid growth in electricity network peakdemand is increasing pressure for new investment which may be used for only a few hours a year. Residential air conditioningis widely believed to be the prime cause of therise in peak demand but, in the absence of detailed residential demand research, there is no bottom-up empirical evidenceto support this supposition or to estimate its impact. This paper first examines the developments in network peakdemand, at a national, network distribution, and local distribution feeder level to show recent trends in peak demand.Secondly, this paper applies analytics to the half-hourlyconsumption data of a sample of Ausgrid’s interval meteredcustomers, combined with local weather data, to develop analgorithm which can recognize air-conditioner use and canidentify consumption patterns and peak load. This estimate isthen compared to system peaks to determine residential airconditioning’simpact on overall demand. Finally, this paper considers the future impacts of air-conditioning load on peakdemand as penetration rates reaches saturation levels andnew minimum energy performance standards take effectreducing new units peak impacts.

Abstract:In this paper, a computation framework for addressing combined economic and emission dispatch(CEED) problem with valve-point effects as well as stochastic wind power considering unit commitment (UC)using a hybrid approach connecting sequential quadratic programming (SQP) and particle swarm optimization(PSO) is proposed. The CEED problem aims to minimizethe scheduling cost and greenhouse gases (GHGs) emission cost. Here the GHGs include carbon dioxide (CO2), nitrogendioxide (NO2), and sulphur oxides (SOx). A dispatchmodel including both thermal generators and wind farms is developed. The probability of stochastic wind power basedon the Weibull distribution is included in the CEED model.The model is tested on a standard system involving sixthermal units and two wind farms. A set of numerical casestudies are reported. The performance of the hybrid computation almethod is validated by comparing with othersolvers on the test system.

Abstract:The integration of large amount of wind power into a power system imposes a new challenge for the secureand economic operation of the system. It is necessary to investigate the impacts of wind power generation on the dynamic behavior of the power system concerned. This paper investigates the impacts of large amount of wind power on small signal stability and the corresponding control strategies to mitigate the negative effects. The concepts of different types of wind turbine generators(WTGs) and the principles of the grid-connected structuresof wind power generation systems are first briefly introduced.Then, the state-of-the-art of the studies on the impacts of WTGs on small signal stability as well aspotential problems to be studied are clarified. Finally, the control strategies on WTGs to enhance power system damping characteristics are presented.

Abstract:The power grid in a typical micro distribution system is non-ideal, presenting itself as a voltage source with significant impedance. Thus, grid-connected convertersinteract with each other via the non-ideal grid. In this study, we consider the practical scenario of voltage-source converters connected to a three-phase voltage source with significant impedance. We show that stability can becompromised in the interacting converters. Specifically, the stable operating regions in selected parameter space maybe reduced when grid-connected converters interact undercertain conditions. In this paper, we develop bifurcationboundaries in the parameter space with respect to Hopftypeinstability. A small-signal model in the dq-frame isadopted to analyze the system using an impedance-based approach. Moreover, results are presented in design-orientedforms so as to facilitate the identification of variation trends of the parameter ranges that guarantee stable operation.

Abstract:The design of electrical layout is a key elementin the offshore wind farm planning. We present a novel electrical layout design optimization method for off shore wind farms in this paper. The proposed method can be used to generate the network model based on fuzzy c-means(FCM) and binary integer programming (BIP) methods. It can automatically allocate wind turbines to the near estsubstations and obtain the topology structure of cablesutilized to connect wind turbines or turbine and substation.The objective of this optimization is to minimize the investment costs of cable connection and the transmission power losses. The results of case study clearly demonstrated the feasibility of the proposed method and showed that it can be used as a reliable tool for electrical layout design of off shore wind farms.

Abstract:This paper presents the concept of control ling distributed electric loads with thermal energy storage as apassive electric energy storage system (PEESS). Examples of such loads include different types of thermostatically controlled appliances (TCAs) such as hot water heaters, air conditioners, and refrigerators. Each TCA can be viewed asa thermal cell that stores electricity as thermal energy. Acentralized control mechanism can be used to control thetiming of each thermal cell to consume electric energy so that the aggregated electricity consumption of the thermalcells will vary against a baseline consumption. Thus, when the aggregated consumption is higher than the baseline, the PEESS is charging; otherwise, the PEESS is discharging.The overall performance of a PEESS will be equivalent tothat of a battery energy storage device. This paper presentsthe configuration and formulates the control of a PEESS.The modeling results demonstrate the feasibility ofimplementing the PEESS.

Abstract:This paper presents a series of operating schedules for Battery Energy Storage Companies (BESC)to provide peak shaving and spinning reserve services inthe electricity markets under increasing wind penetration.As individual market participants, BESC can bid in ancillary services markets in an Independent System Operator(ISO) and contribute towards frequency and voltage supportin the grid. Recent development in batteries technologiesand availability of the day-ahead spot market prices would make BESC economically feasible. Profit maximization of BESC is achieved by determining the optimumcapacity of Energy Storage Systems (ESS) required formeeting spinning reserve requirements as well as peak shaving. Historic spot market prices and frequency deviationsfrom Australia Energy Market Operator (AEMO) areused for numerical simulations and the economic benefitsof BESC is considered reflecting various aspects in Australia's National Electricity Markets (NEM).

Abstract:This paper presents an improved thermal design methodology for wind power converters. It combines analysisand experimental thermal design tools, including heat transfer correlations, flow network modeling (FNM), computational fluid dynamics (CFD), and experimental measurement techniques.Moreover, a systemic product development process isintroduced and an effective combination between the product development process and the thermal design methodology isachieved. The draft CFD modeling at the initial design stage isdone. Furthermore, it uses the detailed CFD modeling and experimental measurement techniques to provide a higher degree of accuracy at latter design stages. The key advantage of the improved methodology is its emphasis on the use of varied design tools, each of which is actively applied at its optimal point in the proposed product development process.Thus, during the earlier stages of the product development process, the thermal risk is systematically reduced, and longterm reliability of products is maintained in a higher degree.