Optimal generation scheduling of interconnected wind‐coal intensive power systems

Assessment of large scale wind power generation with new generation locations without measurement data

The variability of large scale wind power generation at high penetration levels has a significant impact on the secure and economic operation of onshore power systems. Grid bottlenecks, high gradients and wasting of wind energy can be avoided using local Energy Storage Systems (ESS) with dedicated power and capacity. The storage type considered in this study is an adiabatic compressed air energy storage (ACAES). This paper presents a comparison of different ESS applications aiming both to increase the profit of the power plant operator in selling the electricity into the electricity market and to support the intermittent electricity production of the wind park. This contribution presents the investigation methodology and discusses computation results for a region in Germany.

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

Policy analysis for grid parity of wind power generation in China

Numerous problems have emerged with the rapid development of wind power in Xinjiang. The predominant problem is the inhibition of the healthy development of the wind power industry by wind power curtailment in Xinjiang. In this study, wind power heating and high energy-consuming industries were coupled to increase wind power consumption in Xinjiang on the load side. The feasibility analysis of wind power heating in Dabancheng showed that the heating load characteristics coincide with the wind characteristics and the electric heating technology can fulfill the requirements for wind power heating. A business model innovation achieved a win–win situation. Furthermore, a wind power heating system was designed in Dabancheng, the boiler capacity and the heat storage capacity were calculated, and a heating system model with heat storage technology was established. Wind power heating with heat storage can improve the consumption of wind power and increase the local electric load and system adjustability. Furthermore, heating with curtailed wind power can save 2942 tons of standard coal as well as reduce 5172 tons of CO2, 2.9 tons of SO2, 22 tons of NOX, and 2 tons of soot emissions. Non-grid-connected distributed wind power was applied to the high energy-consuming coal chemical industry to reduce wind power curtailment, expand the consumption market, and reduce pollution. A multifunctional wind-photovoltaic complementary system with hydrogen energy storage coupled with traditional high energy-consuming coal chemical industry was established. The implementation plan using wind and solar energy to produce, store, and apply hydrogen energy was proven beneficial. Wind power consumption was improved on the load side. The wind power curtailment problem was reduced by increasing local load using the curtailed wind power to provide clean heat in Dabancheng and constructing the multifunctional wind–photovoltaic complementary system. This study will contribute to the healthy and sustainable development of the wind power industry in Xinjiang.

Two-stage stochastic optimal operation of integrated electricity and heat system considering reserve of flexible devices and spatial-temporal correlation of wind power

The electricity supply chain system consists of power plants, transmission and distribution. Differences in power plant characteristics cause differences in fuel costs and emissions. Inaccuracies in scheduling the plant have an impact on the surge in fuel use. This becomes the basis for the optimization of power plant scheduling. Optimization on the generator side is usually using the economic dispatch model. However, the Economic Dispatch Model does not consider optimization on the transmission network. Optimization on the transmission network is needed because there are losses in the transmission network. Losses will be even greater when the distance between the power plant and the customer is getting further away. So if distance can be minimized, fuel costs can be reduced. Minimizing the distance for shipping goods can use the transportation model, but the transportation model cannot be used for electricity distribution. This is because there are differences between goods and electricity. Therefore, this study proposes the Single Echelon Economic Dispatch (SEED) model. This model is a combination of the economic dispatch model and the transportation model. This model is able to do simultaneous optimization between the generator side and the transmission side. The model is applied to the Mahakam system in East Kalimantan, using all PLN’s power plants. Load consists of two types, namely low load and peak load. As a result, in peak load and low load conditions, the P11 power plant produces the biggest losses and emissions. This is because electricity production in P11 has to go through a longer path compared to other plants. The P11 is also a power plant that requires the highest fuel costs

The rapidly increasing penetration of wind power into sending-side systems makes the wind power curtailment problem more severe. Enhancing the total transfer capability (TTC) of the transmission channel allows more wind power to be delivered to the load center; therefore, the curtailed wind power can be reduced. In this paper, a new method is proposed to enhance TTC, which works by optimizing the day-ahead thermal generation schedules. First, the impact of thermal generation plant/unit commitment on TTC is analyzed. Based on this, the day-ahead thermal generation scheduling rules to enhance TTC are proposed herein, and the corresponding optimization models are established and solved. Then, the optimal day-ahead thermal generation scheduling method to enhance TTC is formed. The proposed method was validated on the large-scale wind power base sending-side system in Gansu Province in China; the results indicate that the proposed method can significantly enhance TTC, and therefore, reduce the curtailed wind power.

With the integration of large scale wind power, the characteristics of power system operation has been changing, and, some problems come forth. On-line security assessment and control decision support system provides the stability and security state message for dispatcher in time, and, some suggestions to improve the level of power system stability and security. To suit the requirements of large amount wind power integrated power system, the technology of on-line security assessment and control decision support must be modified. This paper focuses on the technology of on-line security assessment and control decision for operation of power system with large scale wind power and designing the support system. In the paper, the study and application of on-line security assessment and control decision support technology in China are introduced. Considering the wind power in China having some distinct characteristics such as large scale, centralized development, long-distance and high voltage transportation, the new requirements to on-line security assessment and control decision support are analyzed. They includes need for new information, on-line modelling with large scale wind farm, transfer limitation calculation under the constraint condition of wind power integration requirement, auxiliary preventive control decision based on the forecasting and adjustment properties of wind power output, coordinated emergency control wind power with hydraulic and thermal power. On the basis of technical rule for connecting wind farm into power grid and the interaction between wind power and power grid, the advices on engineering application of on-line security assessment and control decision support technology for large amount wind power integrated power system, are proposed, for example, with respect to the standard of security assessment and selection of pre-contingency sets. (7 pages)

Among northern China, CHP is the main electric and heating source to provide electricity and heat. While, with the increasing integration of wind power, the peak regulation capacity is lacking. Wind power curtailment occurs frequently because of the contradiction between heating and electric load. District heating system plays the majority role in heating supply because of its efficiency and cleanness. There are enormous heat storage capacity contained in district heating system, if the stored heat energy could be utilized efficiently the contradiction between heating and electric load could be relieved and the wind power curtailment ld be avoided considerably. This study presents an approach that takes advantage of the heat in the primary heating circuit to absorb surplus wind power. The expressions of the components in heating system are given to establish the mathematical model. Followed, the thermodynamic properties of heating pipelines are analyzed, the heat storage capacity and heat transmit delay characters are studied. Then, the consumption capacity of surplus wind power is discussed, and the temperature changes are also be considered. Finally, a case study are undertook to prove the effectiveness. The results show that by utilizing the heat in heating network, the wind power curtailment rate could be reduce by 20.6% which means about 219.4MWh surplus wind energy could be consumed during a valley electric load period.

The demand on energy supply increases continuously as economies develop and world population grows. Most of the energy in the world comes from the fossil fuels and the increase in energy demand accelerates the rate of depleting the fossil fuel resources. As fossil fuel is finite and also due to the environmental considerations, renewable energy (RE) resources have been actively developed as the alternative sources for electricity generation. Renewable sources used for large-scale electricity production can include wind, photovoltaic (PV), waves and so on. Among all the RE resources, wind power generation is witnessing rapid developments in recent years. Unfortunately, wind tends to be unsteady. The fluctuating and uncertain output powers from wind farms can be problematic, especially if there is a high penetration level of the renewable source in a grid system. The fluctuations may lead to excessive voltage variations and unacceptable degree of frequency deviations. Moreover, the unsteady and uncertain input wind power can cause firm power dispatch commitment from wind farms a difficult task. Expensive generation reserves have to be provided for grid system to ensure adequate level of system security and reliability is guaranteed. In fact, power generation from wind farms has often been excluded in the dispatch planning of the grids. Unless other viable techniques can be found, the above issues can constitute major impediment to the successful large-scale integration of wind power generation into grid systems. In this connection, the use of energy storage system (ESS) is one possible solution to mitigate the negative impacts of the unsteady wind power on electricity supply systems and to improve on the dispatchability of the wind power. In this investigation, in order to smoothen the fluctuations in the wind and to realize the dispatch planning of the wind power in a way similar to that of conventional generators, it is proposed that a three-level ESS is incorporated in a large-scale wind power generation scheme. In essence, at cluster-level of wind turbine generators (WTG), the solution involves having the high- and mid-frequency components of the aggregated wind power routed to supercapacitors (SC) and battery banks respectively of a battery-supercapacitor hybrid energy storage system (BSHESS) by a high-pass filter (HPF) and a band-pass filter (BPF). It then results in the smoothening of the wind power harnessed by the cluster. In this thesis, the BSHESS control scheme to reduce the wind power perturbations has been shown. A statistical method is also developed to determine the capacities of the minimum-cost BSHESS to meet the power smoothing objective at pre-specified probability level. Application of the proposed design approach is demonstrated using data obtained from an existing wind farm. As for dispatch planning, attention is to use a low-pass filter (LPF) to extract the low-frequency intrinsic mode and residue functions of wind power. The relatively slow-changing characteristics of the low-frequency wind power components, which contain most of the energy in the wind power, allow accurate forecasts of the power components to be obtained using artificial neural network (ANN). Dispatch planning of the wind power is then realized through buffering the low-frequency power fluctuations by a proposed power flows control strategy applied to a pumped hydroelectric storage (PHS) system. Focusing on low-frequency wind power for dispatch planning is a distinct advantage over the dispatch planning methods proposed by other researchers. Furthermore, a statistical method to determine the power and energy capacities of the PHS is included. The efficacy of the developed approach to dispatch planning is again illustrated based on data obtained from an existing wind farm. In all the above works, suitable cut-off frequencies for the HPF, BPF and LPF are derived based on the developed concept of minimum overlap energy and the outcome of empirical mode decomposition (EMD) analysis. EMD method is used to gain insights into the frequency-time characteristics of wind power. In this manner, the wind power can then be grouped into high-, mid- and low-frequency bands.

A new flexibility based probabilistic economic load dispatch solution incorporating wind power

Wind power curtailment in winter of Northern China is mainly caused by the limited flexibility of combined heat and power (CHP) plants. Improving the profitability of CHP by heat storage is a promising alternative to increase the integration of wind power. Dispatching method of CHP and heat storage is proposed in this paper based on two linear models. The first model is used for the pre-judging of time intervals of heat charging and discharging while the second is for the determination of power output of the CHP units and heat storage. Wind power curtailment and operation cost are both considered in the objective function of the second model. Operation results with different amounts of wind power generation and heat storage capacity are analyzed. Case studies are presented to demonstrate the benefits of heat storage on improving the integration of wind power economically with proposed methods.

Correlational broad learning for optimal scheduling of integrated energy systems considering distributed ground source heat pump heat storage systems

Hundreds of cascading trip faults have occurred in recent years in Chinese wind farms, leading to challenges in the secure operation of the power system. To prevent cascading trip faults, the concept of a voltage security region (VSR) has been discussed in previous studies. However, the VSR proposed in previous work cannot provide decoupled voltage control ranges for each wind farm, which would be a more promising and applicable solution for wind farms in China. In addition, with increasing wind farm active power penetration, the VSR of a wind power integration area may not exist. In this situation, the control centre must curtail some wind power to guarantee security. Thus, this study proposes an iterative VSR model to guarantee secure operation and obtain a larger VSR in wind farms considering wind power curtailment. In each wind farm, the VSR is designed to guarantee normal operation of each wind turbine generator, while in the control centre, the region is designed to guarantee normal operation both under normal conditions and N–1 contingencies considering wind power curtailment. The proposed VSR demonstrated good performance in a simple test case and in a real system in Northern China using a Monte Carlo method.