Operational reliability evaluation of restructured power systems with wind power penetration utilizing reliability network equivalent and time-sequential simulation approaches

Nowadays, solar and wind power generation is an important part of the power sources in many countries all over the world. However, due to the variability and uncertainty of these sources, stable operation of the power system with large solar and wind power penetration is a big challenge for system operators. In order to enhance the contribution efficiency of solar and wind power in the power market, a strong ancillary service system is essential and must be reasonable priced. The ancillary services considered in this paper are spinning reserve, non-spinning reserve. In addition, a model for calculating and comparing generation costs for energy and ancillary services, with and without penetration of solar and wind power in the power market have been proposed. Consequently, this model has been developed and validated with a case study. The results show that in a power system with large proportion integration of solar and wind power, the energy and ancillary services generation costs for the power system are high. Besides, the feed-in tariffs of solar and wind power are more expensive than the traditional electricity generation, which leads to high locational marginal prices of the electricity market.

Under the “double carbon” goal, high wind power penetration will become an important feature of new power systems dominated by new energy in the future. Since wind power often has anti-peak shaving characteristics, the peak shaving problem of wind power high-penetration power systems is particularly prominent. Quantitative calculation of the system peak shaving cost of a high proportion of wind power grids is of great significance to the establishment and improvement of the peak shaving market in the northern part of our country, the promotion of rational system development and planning flexibility, and the improvement of system flexibility. Based on the analysis of existing wind power system peak shaving cost estimation methods, this paper proposes a comprehensive cost estimation method for system peak shaving under high wind power penetration rate, considering flexible resource investment and peak shaving market, and studies different wind power systems. The changing law of system peak shaving cost under the penetration rate; and the actual power system in a certain area of my country is used to simulate the peak shaving cost under different wind power penetration, which shows the effectiveness and rationality of the method.

Frequency response is a key concern for power system security. Usually, it is estimated in a deterministic approach. But in most cases, power systems behave stochastically. Moreover, presence of wind power imposes further variability on generation profile of a power system. Hence, it appears more pragmatic to address these uncertainties during an evaluation of frequency response. This paper develops an index to assess frequency response of a power system with high wind power penetration. A probabilistic method is used for this purpose. K-means algorithm, a well-known data mining technique is employed. The developed index is called a ‘probabilistic frequency response index’. A realistic interconnected power system is investigated for a case study. Impact of increased wind power penetration on probabilistic frequency response index is analysed.

An integrated development environment based situational awareness for operational reliability evaluation in wind energy systems incorporating uncertainties

Minimum energy storage (ES) and spinning reserve (SR) for day-ahead power system scheduling with high wind power penetration is significant for system operations. A chance-constrained energy storage optimization model based on unit commitment and considering the stochastic nature of both the wind power and load demand is proposed. To solve this proposed chance-constrained model, it is first converted into a deterministic-constrained model using p-efficient point theory. A single stochastic net load variable is developed to represent the stochastic characteristics of both the wind power and load demand for convenient use with the p-efficient point theory. A probability distribution function for netload forecast error is obtained via the Kernel estimation method. The proposed model is applied to a wind-thermal-storage combined power system. A set of extreme scenarios is chosen to validate the effectiveness of the proposed model and method. The results indicate that the scheduled energy storage can effectively compensate for the net load forecast error, and the increasing wind power penetration does not necessarily require a linear increase in energy storage.

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

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.

With increasing heating demand and installed capacity of wind farms, combined heat and power (CHP) systems with inflexible generation are confronted with a major challenge for the efficient utilization of the wind power. Distributed heat sources (DHSs), such as electric boilers and heat storage, offer an effective way to enhance wind power penetration in a combined heat and power system by reducing the electric-heat coupling of the CHP unit. In this paper, an assessment approach for the wind power penetration of a CHP system with DHSs is proposed, and a two-stage multiple types of DHSs optimal configuration strategy to realize the minimum construction cost at a certain permissible wind power curtailment rate is established. After that, the proposed strategy is applied to a case study of a practical CHP system with in-depth analysis and detailed discussion, which reveals the effectiveness of the proposed strategy and indicates its promising applications for DHS configuration.

Guest Editorial: Situational awareness of integrated energy systems

Controlling the frequency of power systems with high wind power penetration is more difficult due to the high variability of the wind power. One possible mainstream energy carrier in the future, particularly for the transportation sector, is Hydrogen, and water electrolysis is one of the most attractive ways to produce it. In this study, a detailed model of a steam turbine generator has been produced in MATLAB Simulink and used to investigate a scenario in which there is a 25% penetration of wind power. To improve the frequency stability of the power system, large scale alkaline electrolysers used in future Hydrogen filling stations could adjust their load with respect to the frequency deviation from nominal and can significantly reduce fluctuations in system frequency. For the case examined, five times less spinning reserve is required in order to maintain the power system frequency within operational limits when electrolysers are utilised as a form of demand side management (DSM), compared to the base case where no electrolyser DSM plant is available. Actual operational data from a pressurised alkaline electrolyser is used to evidence the fast load changing capability of such electrolysers.

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

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.

Operational reliability evaluation integrating prediction models for enhanced situational awareness in wind-integrated system

Geographic aggregation and wind power output variance in Denmark

In this paper, a probabilistic analytical approach for reliability evaluation of power systems with high penetration of wind and solar photovoltaic (PV) renewable power generation is presented. Due to intermittent nature of wind and solar power, the traditional deterministic method cannot properly address such uncertainties, probabilistic methods need to be utilized. In this paper, the loss of load method, one of the most effective probabilistic analytical methods, is adopted. The generation model is represented by the capacity outage probability table (COPT). The load model is presented by the load duration curve (LDC). Both generation and load models are used to obtain the system reliability considering wind and PV sources with certain forced outage rate (FOR). Simulation results are obtained using MATLAB. It is found that renewable energy sources can significantly improve the system reliability, but not as good as conventional power generators with the same rated capacity due to the actual reduced capacity value of renewable energy sources caused by intermittency. This analytical analysis is useful for the power system planner to quantify reliability improvements by installing grid-connected hybrid renewable power generation.