Geographic aggregation and wind power output variance in Denmark

Difference between grid connections of large-scale wind power and conventional synchronous generation

Output power fluctuation of high penetration of wind power causes demand and supply imbalance in electric power systems and results in frequency deviation if the fluctuation is not fully compensated by other regulable power plants. In Japan, some electric utilities have started to accept only the wind farms which disconnect and give up generating power during light‐load periods with less adjustable reserve. Otherwise, wind farms are required to employ battery energy storage systems (BESSs) to charge the generated power during the light‐load periods. Instead of these uneconomical solutions, this paper proposes autonomous frequency regulation by controllable loads such as electric water heaters (EWHs). In the paper, the acceptable increase of wind power generation by the proposed load control has been evaluated quantitatively in the power system of the Hokkaido Island in Japan. The result indicates that the acceptable increase of wind power generation goes from 250 to 675 MW by applying the proposed autonomous frequency regulation on all EWHs, and the total cost to implement the autonomous frequency regulation on the EWHs is around 1/26 compared with a solution using BESSs. Copyright © 2009 John Wiley & Sons, Ltd.

As wind power costs have declined, capacity has grown quickly, often times in adjacent areas. Price and volatility risk from wind power’s intermittency can be mitigated through geographic diversification and transmission. But wind power generation has a fat-tailed and right-skewed distribution. In this article we investigate how geographic diversification of wind power and the effect of wind power on market prices varies across the distribution of production. In a case study from Denmark and Sweden, we show that during tail-end production periods, correlations between areas increase substantially as does congestion in the transmission network. This leads to highly non-linear price effects. The marginal effect of wind power on the local prices is shown to be substantially higher at the 10th decile of wind power production. This has implications for valuation models of wind power projects and for operations of electricity markets with high penetrations of wind power.

In the last two decades, the wind power generation has been rapidly and widely developed in many regions and countries for tackling the problems of environmental pollution and sustainability of energy supply. However, the high share of intermittent and fluctuating wind power production has also increased the burden of system operator for securing power system reliability during the operational phase. Moreover, the power system restructuring and deregulation have not only introduced the competition for reducing cost but also changed the strategy of reliability evaluation and management of power systems. The conventional long-term reliability evaluation techniques have been well developed, which have been more focused on planning and expansion rather than operation of power systems. This paper proposes a new technique for evaluating operational reliabilities of restructured power systems with high wind power penetration. The proposed technique is based on the combination of the reliability network equivalent and time-sequential simulation approaches. The operational reliability network equivalents are developed to represent reliability models of wind farms, conventional generation and reserve provides, fast reserve providers and transmission network in restructured power systems. A contingency management schema for real time operation considering its coupling with the day-ahead market is proposed. The time-sequential Monte Carlo simulation is used to model the chronological characteristics of corresponding reliability network equivalents. A simplified method is also developed in the simulation procedures for improving the computational efficiency. The proposed technique can be used to evaluate customers’ reliabilities considering high penetration of wind power during the power system operation in the deregulated environment.

The variable and uncertain nature of the leading renewable energy resources, such as wind power generation, imposes the development of a sophisticated balance mechanism between supply and demand to maintain the consistency of a power system. In this study, a two stage stochastic programming model is proposed to procure the required load-following reserves from both generation and demand side resources under high wind power penetration. Besides, a novel load model is introduced to procure flexible reserves from industrial clients. Load following reserves from Load Serving Entities (LSE) are also taken into account as well as network constraints, load shedding and wind spillage. The proposed methodology is applied to an illustrative test system, as well as to a 24-node system.

Aiming at the large-scale wind power transmission end grid wind and thermal power shared transmission channel decoupling out, the wind power output power is blocked, the transmission channel utilization rate is not high and so on. Based on a comparative analysis of wind and fire electrolytic coupling / coupling transmission operation characteristics, this paper The goal is to maximize the output power of wind power, maximize the utilization of transmission channels, and minimize the operating costs of thermal power units. Aiming at the dispatching output of wind power and thermal power units as optimization variables, a multi-objective optimization model of coupled wind power and thermal power transmission is proposed. The target differential evolution algorithm solves the model, and finally obtains a set of optimized scheduling output plans for wind and thermal power, which provides a scientific basis for operators to make scheduling decisions. Finally, a regional power grid is taken as an example to prove the rationality of the model and the effectiveness of the proposed algorithm.

According to the characteristics of double fed asynchronous generator rotor energy flow, research and design based on the DSP control with two-way flow of energy function of Dual PWM converter and discusses the grid side converter control method of Dual PWM converter in particular. The wind turbine simulation model is established by using the electromagnetic transient PSCAD/EMTDC software. The simulation system is used to simulate the P, Q decoupling control and maximum wind energy tracking control of the generator. Wind is a natural phenomenon generated by the solar radiation heat, the earth's surface caused by uneven heating of the atmosphere. It is estimated that only 1% of the wind on the ground will be able to meet the needs of the world's energy. With the continuous improvement of the level of wind power generation technology, the cost of wind power gradually reduced, considering environmental benefits, the cost will be close to the cost of coal-fired power generation. Therefore, great efforts to develop wind energy as the representative of the renewable energy and new energy, to achieve sustainable development, has become the consensus of the whole society, strategic choice to solve the energy crisis and environmental problems. 2.Overview of control technology of doubly fed wind power gener ation Wind power is the kinetic energy contained in the natural wind into electrical energy in the process, the wind turbine wind energy capture and convert it into mechanical energy, driven by rotary generator, and the generator for converting mechanical energy conversion into electrical energy. As countries around the world pay more attention to wind power, wind power has become the world's fastest, most widely studied and applied new energy technology. With the development of wind power technology, wind turbine, wind turbine generator, converter and its control system and the way of the wind turbine, there are different types of. Among them, the doubly fed wind power generation system due to the converter control capacity is small, the speed of operation range wide characteristics become currently the world's most widely used VSCF wind power generation system. Variable speed constant frequency generator in asynchronous generator rotor side applied three-phase low frequency current to realize AC excitation, the output power is constant frequency and constant voltage amplitude, frequency, phase of the exciting current control. At the same time, the active power and reactive power decoupling control of the generator is realized by using the vector control technology. Control active power capable of adjusting the rotation speed of the wind turbine, to capture the maximum wind power tracking control; regulation of reactive power adjustable power factor and improve the dynamic and static stability of the wind turbine and power system operation. In addition, the VSCF wind power generation technology, so to achieve good flexible connection between the generator and power grid system, compared with the traditional constant speed constant frequency generation system easier to achieve grid connected operation and operation

Power prediction of a wind farm cluster based on spatiotemporal correlations

Penghu Island is a small isolated power system with 70MW peak load and 30MW off-peak load. According to the operation records of the installed wind farms, Penghu has bettter wind conditions than any other site in Taiwan. The total capacity of wind farms in Penghu reaches up to 10.2MW, which means 35% penetration on wind power is possible during minimum load. The high level of wind power generation in the Penghu power system makes the decision of diesel unit commitment and control of the power system more difficult due to the high variability of wind power output in a time frame ranging from seconds to hours. This work investigates the significant factors that affect the system transient stability as high penetration of wind power is integrated. Additionally, the possible impact and coping strategies for the high wind power penetration are studied, and several specific suggestions are proposed to Taiwan Power Company. These strategies include revising the load shedding methods, unit commitment scheduling, wind turbine operation, the suitable energy storage system planning, and wind turbine protection.

As the fast development of China’s economy, the power generation has increased rapidly to support the economic growth. In China, thermal power, as a traditional power generation, consumes more fossil energy and brings great damage on environment. As for wind power, a clean and renewable power generation, uses wind energy and is beneficial to environment. In order to describe the differences between these two generations in detail, this paper compared the thermal power with the wind power from the generating total cost to the environmental impact in a quantitative way. And the scenario analysis was adopted for predicting the energy conservation and the emission reduction by wind power. The results show that: (1) Coal is still the dominant input for energy consumption in China and the installed capacity of thermal power takes 65% to total installed capacity. As for the wind power, wind energy only has a share of 5.89% to the total energy consumption and the installed capacity of wind power contributes 8% on total installed capacity. (2) The total cost of thermal power is higher than that of wind power, with 0.47 yuan/KWh. (3) Comparing with the thermal power, the wind power save 238.87 million tons of coal equivalent in total. In addition, the wind power reduces 668.54 million tons of CO2 emissions, 1.73 million tons of SO2 emissions, 1.8 million tons of NOx emissions and 0.3 million tons of smoke emissions during 2008 to 2015. (4) The coal conservation and the emission reduction by wind power are much greater in high economic growth rate scenario.

Sampled-data based discrete and fast load frequency control for power systems with wind power

Integrating large-scale wind plants with the electricity grids has many challenges for grid operators. Besides the variability and uncertainty of wind power, coordinating between different technologies of generation in the same grid can be considered the main problem, specifically for short-term frequency stability. Therefore, a large penetration of wind power generation in modern power grids has a risky influence on the power-system frequency. Wind-generation plants have contradictory behaviour compared to classic thermal plants, especially in active generated power-shortage events due to the variable nature of wind power. Existing experience in wind plants keeps part of the available wind power unloaded, using what are known as deloading techniques. Different deloading techniques are usually applied to emulate the thermal-plant-governor function and confirm a proper spinning reserve for any active-power shortages. These techniques decrease the generated power from wind plants continuously from maximum point tracking ones. Consequently, the practical capacity, annual generated energy and economical income of wind plants are reduced. In addition, grid-protection and control sub-schemes are set and designed according to the well-known conventional responses of thermal plants, which increase the need for thermal-plant-behaviour emulation. In this paper, instead of the usual deloading methods, a supercapacitors scheme is proposed with wind turbines to emulate the response of conventional power plants. The study discusses the technical and economic benefits of the proposed addition of supercapacitors in the wind-plant-planning phase. Restricted frequency grid-code indices are selected to evaluate studied behaviours. Simulation results of the IEEE four-generation two-area system determines the effectiveness of suggested schemes technically. The System Advisor Model (SAM) program estimates the economic benefits of a typical US study case compared with the existing wind-deloading technique.

Optimization of wind power generation to minimize operation costs in the daily scheduling of hydrothermal systems

The PV and wind power generation have a disadvantage of unstable power output, resulting negative impact on utility and micro grid operation. The battery energy storage system is the effective means of smoothing wind or solar power generation fluctuations. For effective regulation of power output levels and state of charge (SOC) of battery require a suitable control strategy. This paper presents the results of wind/photovoltaic (WPPV) hybrid power system simulation analysis using PSCAD to improve the smoothing problem of wind/PV/BESS hybrid power generation fluctuations.

Wind power generation has the characteristics of intermittency and uncertainty. It is significant to predict intervals of short-term wind power precisely for optimizing the grid power system operation scheduling and reserve capacity. The paper proposed a simple short-term wind power intervals prediction model based on artificial bee colony-neural network (ABC-NN). A new criterion was developed in this method to get better prediction results. Then generalized morphological filter was applied in the de-noising of wind power time sequence by analyzing of wind power constitute components. The simulation results demonstrate that the new method has a better performance in wind power intervals prediction.