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Recent research on wind-farm control methods has focused until now on maximising the efficiency and durability of farm operations, as verified for a normalised electrical layout. However, with the increase of turbine size and capacity, it is necessary to develop modifications of the farm management plan that can support the increasing demands of the wind-turbine industry. Here the authors propose a modification that focuses on a proportional reactive power-dispatch method that is applied to radial offshore farm networks. They improve a previously developed method of proportionally distributing reactive power commands by considering the actual configuration of an offshore platform. To confirm the applicability of this method in transient state, they examine case studies using a time-varying signal for a reactive power reference under fluctuating wind. Electromagnetic transients using DC software tools are used to estimate the electrical loss and verify the efficiency of this strategy.

The expansion of renewable energy in recent electric power systems has affected the associated networks, and their speed is gradually increasing. Renewable generators that do not have their own reserve capacity produce variable amounts of power that often generate balancing issues in grid operation. Therefore, a high penetration of the renewable generator is expected to impact on the stability of the power system greatly. As a countermeasure against these issues, a proposal has been derived to use the energy storage system (ESS) to contribute to the stability of the power system. An ESS, which is planned to be composed at the point of connection of renewable generators, must be evaluated in advance to meet its own objectives. In this paper, based on structural analysis, progress has been made in the development of a user-defined model dedicated to power system analysis tools for use in stability analysis. Based on IEEE 1547, the active response capability for ESS is configured and verified through the simulation based on PSS/e software tool.

In recent years, the expansion of renewable energy in electric power systems has been increasing at such a rapid pace that it has started affecting frequency stability. Renewable generators connected to the grid produce variable amounts of power, and in most cases have no inherent inertia response (IR) to the system frequency. Therefore, the high penetration of renewable generators in the system results in low inertia and frequency distortion. If renewable generators account for a high proportion of the supply in a power system, the use of energy storage systems (ESSs) with frequency-support algorithms (in the place of synchronous generators) can stabilize the network. The participation of ESSs in frequency support must be organized precisely, so that they are fully devoted to their own purpose. In this paper, the frequency-support parameters of ESSs are calculated for achieving stable frequency response from a network. An estimation and calibration process is conducted during the active power-order change of the ESSs in the substation, and is verified through electromagnetic-transients-including-DC (EMTDC)-based simulations.

The recent development of a number of advanced wind farm (WF) operation strategies, using designed verification studies, has resulted in various operational and economic improvements. These applications focused on stabilised conditions to confirm the improved effect derived from a maximum power extraction condition. In the case of large-scale WFs, however, a physical area with realistic environmental variations should be considered in order to conduct applicable case studies. In this study, the authors propose a modified reactive power allocation strategy, based on proportional techniques, with the system components of a WF structure for utilisation under a variety of practical situations. The proposed method introduces a modified loss prediction model, which takes the resistive components of the wind turbine into consideration. Each analysis is conducted to confirm the feasibility of active reference assignment in terms of loss reduction and flexibility. The simulations are based on electromagnetic transients using DC software tools to perform electrical loss estimation, in order to verify the effectiveness of this strategy.

This paper proposes a modification process for a proportional dispatch method for a strict radial wind farm structure based on a machine learning application. The general approaches of proportional dispatch require greater consideration of the constraints, because of grid expansion. This paper presents a new theoretical approach for a modified proportional dispatch method that is more advanced than the general algorithm and takes the voltage restriction for each wind farm unit into account. A linearization method for calculating the ohmic loss caused by reactive power flow under the voltage constraint is proposed as a major modification. To ensure that the proposed method can be applied to the controller in a stable manner, we design a machine learning-based look-up table operation. Along with the general proportional and even-dispatch methods, the proposed algorithm is simulated in order to verify it under reality-based wind farm conditions, by focusing on both electrical loss and voltage violation. The proposed modified method shows delivery improvements in compliance with the required voltage condition when simulated with PSCAD/EMTDC.

In regard to electric devices, currently designed large-scale distributed generation systems require a precise prediction strategy based on the composition of internal component owing to an environmental fluctuating condition and forecasted power variation. A number of renewable resources, such as solar or marine based energies, are made up of a low voltage direct current (DC) network. In addition to actively considering a power compensation plan, these generation systems have negative effects, which can be induced to a connected power system. When a storage is connected to a DC-based generation system on an inner network along with other generators, a precise state analysis plan should back the utilization process. This paper presents a cooperative operating condition, consisting of the shared DC section, which includes photovoltaic (PVs) and energy storage devices. An active storage management plan with voltage-expectation is introduced and compared via a commercialized electro-magnetic transient simulation tool with designed environmental conditions. Owing to their complexity, the case studies were sequentially advanced by dividing state analysis verification and storage device operation.

In the future, Distribution network will face many challenges due to increased acceptance of renewable resources such as photovoltaic (PV)and wind power. Typical problems that arise from increased penetration of renewable resources include overvoltage issues, load imbalances on each feeder, and fluctuations in power output. In this paper, we consider installing Soft-Open Points (SOPs) to solve these problems. SOP is a power electronic device installed at the normally-open point (NOP) of the distribution network. Typically, SOPs are comprised of voltage source converters (VSCs), which can control the power flow between the feeders. In this paper, we discuss the method of calculating the optimal operating point of a SOP using the Particle-Swarm Optimization (PSO) algorithm using the characteristics of the SOP that can independently control the active and reactive power flows. The IEEE-33 bus test system was modified to verify the proposed method and the objective function for the bus voltage deviation and the index for the total line losses can be minimized simultaneously by using the PSO algorithm to optimize the multiple objective function Algorithm.

Renewable generation in power systems has proved to be challenging for system operators owing to the increasing levels of penetration. The operation of power systems currently requires additional flexibility and reserves due to the intermittency and unpredictability of renewable generators. However, it is difficult to precisely predict and control the stochastic nature of renewable sources, nevertheless, its capacity continues to increase. To monitor and control renewable generators efficiently, the entire system needs to be established in a hierarchical order. This study proposed the concept of a substation that is uniquely designed for renewable interconnection. The purpose of this substation is simple: to make the renewable generators dispatchable to operators such that each group of renewable generators is sufficiently stable to be considered as conventional generators. For this purpose, methods for sizing and controlling energy storage system are proposed based on forecasts and error distributions.

Power System with high penetration of inverter based renewable generators have several problems such as voltage instability and frequency deviation. The most severe problems for such network is lack of inertia due to fewer number of synchronous generators connected to the grid. As portion of synchronous generators in network decrease, low inertia of system can be a major problem which hinder the additional renewable generator deployment. Energy Storage System (ESS) is adequate solution for this problems by providing inertia response and governor response to low inertia network. In this paper, actual network system study was conducted to integrate large wind farms in small network with low inertia. ESS and is installed at each point of interconnection of windfarms. Inertia response operation strategy of ESS is suggested to protect system from low frequency load shedding and also provide emergency reactive power compensation to prevent cascading failure of network due to voltage under fault ride through standard of wind turbines.

Climate change and global warming are becoming important problems around the globe. To prevent these environmental problems, many countries try to reduce their emissions of greenhouse gases (GHGs) and manage the consumption of energy. The Korea Electric Power Corporation (KEPCO) introduced smart grid (SG) technologies to its branch office in 2014. This was the first demonstration of a smart grid on a building, called the Smart Grid Station (SGS). However, the smart grid industry is stagnant despite of the efforts of KEPCO. The authors analyzed the achievements to date, and proved the effects of the SGS by comparing its early targets to its performance. To evaluate the performance, we analyzed the data of 2015 with the data of 2014 in three aspects: peak reduction, power consumption reduction, and electricity fee savings. Furthermore, we studied the economic analysis including photovoltaic (PV) and energy storage system (ESS) electricity fee savings, as well as running cost savings by electric vehicles. Through the evaluation, the authors proved that the performance surpassed the early targets and that the system is economical. With the advantages of the SGS, we suggested directions to expand the system.

Owing to the variability of large-scaled wind power system, the development of wind farm management technologies and related compensation methods have been receiving attention. To provide an accurate and reliable output power, certain wind farm adopts a specified management system including a wind prediction model and grid expectation solutions for considering grid condition. Those technologies are focused on improving the reliability and stability issues of wind farms, which can affect not only nearby system devices but also a voltage condition of utility grid. Therefore, to adapt the develop management system, an expectation process about voltage condition of Point of Common Coupling should be integrated in operating system for responding system requirements in real-time basis. This paper introduce a grid imposing method for a real-time based wind farm management system. The expected power can be transferred to the power flow section and the required quantity about reactive power can be calculated through the proposed system. For the verification process, the gauss-seidel method is introduced in the Matlab/Simulink for analysing power flow condition. The entire simulation process was designed to interwork with PSCAD for verifying real power system condition.

Various control methods and applications have been introduced to power systems in order to alleviate the uncertainties of relying on renewable sources. This paper, focusing on a reactive power allocation process, discusses the development of a self-modification algorithm and its introduction to an online reference management system. The algorithm is designed to predict unexpected situations occurring in real-time operations, when, due to technical issues, the control system becomes unavailable. A test system has been formed to check the feasibility of the composed method. As the main purpose of the feasibility study is checking availability with a complex solution, case studies are designed to adapt a reactive power allocation method based on loss minimization. When unexpected systemic errors were induced, the proposed modification plan changed order automatically with maintaining previous objective function. The improved effects, caused by realistic responses, are classified according to EMTDC (Electro-Magnetic Transient Design and Control) analysis.

Metallic return cable in modern LCC HVDC system had been considered a necessary choice for newly installed projects, due to environmental concern near earth electrode. Like most of neutral cable that has been installed so far, it is unnecessary for those cables to require same specification to pole cable in the system. Usually, their voltage and current insulation limit is much lower than those of pole cables’ requirement. To ensure reliable operation of HVDC system and to optimize neutral cable’s insulating capability, further study on phenomena occurred on the neutral cable after fault on the system has to be measured and mitigated. In this paper, short circuit faults has been applied to LCC HVDC system, monitoring the effect on the neutral cable, and the counter measures to protect them are being considered.