A Novel Transmission Planning Method for Integrating Large-Scale Wind Power

It is of great significance for the safe and stable operation of power system to master the fluctuation characteristics of wind power output. On the basis of analyzing a large number of field measured data, a weighted mixed Gaussian probability model is proposed to simulate short-time wind power fluctuation characteristics of wind farm cluster, that evaluation indices to reflect the short-time maximum fluctuation of wind power output and maximum likelihood estimation algorithm based on Expectation Maximization (EM) to estimate model parameters are put forward. This model is compared with various other kinds of probability distribution model and the simulation results show that the weighted mixed Gaussian probability model possesses the highest precision, so as the effectiveness of the weighted mixed Gaussian probability model is verified.

In view of the frequency fluctuation of the micro-grid system containing wind power, hybrid energy storage system composed of batteries and supercapacitors is adopted to coordinate the output, so as to maintain the frequency stability of the micro-grid and provide the possibility for the micro-grid to further absorb wind power and other clean energy. Firstly, by analyzing the characteristics of wind power output, the power deviation signal of the system is decomposed into low-frequency and high-frequency parts through wavelet packet decomposition, so as to maximize the consumption of wind power output power on the premise of meeting the stability of the system. Then, the high frequency part of the power gap is further divided to determine the initial FM power distribution scheme of the energy storage system. Finally, the energy storage output is modified by the Logistic regression function to take into account both the energy storage adaptive frequency modulation and the energy storage charged state self-recovery. Example analysis shows that the proposed control strategy can realize the optimal distribution of wind power, ensure the full utilization of wind farm output, improve wind power grid connection capacity, and increase efficiency and economy.

With the development of concentrated wind power areas, new energy’s dispatching problems are more prominent with its fast expansion. However, we can maximize the utilization of wind power under power curtailment conditions by optimal wind power dispatching. The paper studies on the basic theories of wind power turbines, and analyses the power’s control and output characteristics of wind turbine, which analyses the double-fed inductor generator’s excellent decoupling control of power and its excellent reactive power output capability. By studying the characteristics of wind power output, this paper provides a strategy for optimal dispatch in wind power generation. The calculation results show that the total active and reactive power output of the wind farm match the request of dispatch center. And the total active loss and total reactive loss is the least in the meantime.

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.

The principle of power determined by heat and the anti-peak-regulation characteristics of wind power output cause the difficulty of peak regulation in the power grid along with the production of the abandon wind. By analyzing the topological differences between power system and thermal system, establishing positive and negative spinning reserve constraints of the district heating network, and considering both the hot and the cold start-up cost of the units as well as the thermoelectric coupling of the CHP units, a unit commitment model of wind power accommodation in combined heat and power system— whose objective function is to minimize the total coal consumption and environmental cost of the units—is presented in this paper. In this model, unit commitment and optimized dispatch are combined, the electric load is shared by all the units, and the heat load is balanced by the local CHP plants respectively. Finally, the optimization results show that while meeting power and heat load demand, the model of this paper can timely start up or shut down units according to load change and spinning reserve demand, reduce total minimum technical output of operating units, and further improve wind power accommodation rate.

With the construction of northern and western wind power base, large-scale regional wind power grid connection begins to affect power system and several power grid accidents in Fuxin grid resulted in partial off-grid in recent years, causing certain damages on the security and stability of power system.The author takes Fuxin power grid as example to analyze on two problems existing in large-scale wind power centralized grid connection: frequent fluctuations and reactive voltage control, study on the effect of large-scale wind power centralized grid connection on the security and stability of power system and proposes countermeasures and suggestions. Basic Situation of Fuxin Wind Power BaseFuxin wind farm are mainly based in the northwest area of Fuxin and eastern Zhangwu.By the end of 2014, there has been a wind power capacity of 1,693,300 kilowatts in operation, among which there are 6 220 kV substation, 5 66 kV substation that delivers power to load centers like Jinzhou and Shenyang by 220 kV tie line.According to Fuxin City Plan, there will be an installed capacity of 16,167,000 kilowatts by 2015, among which 8.117 million kW are thermal power (increasing 6.3 million kilowatts) and 8.05 million kilowatts are new energy (increasing 6.25 million kilowatts); power generation will be as much as 58.1 billion kwh.

The second phase of Jiuquan wind power base in China has been built with 3GW of first batch. This paper deliberately researches its power output characteristics based on the observation data in 2012, which provide technical reference for further work of power grid planning. Moreover, on the basis of northwest China grid data package in Power System Analysis Software Package (PSASP), this paper compares the voltage control effect under different reactive power compensation schemes after the second phase wind farms integrated. Analysis results indicate that wind power output characteristics in Jiuquan are obviously random and low. The power output change rate is low as well. As for reactive power compensation strategies, centralized compensation at low voltage side is better than dispersed compensation to control system voltage. Finally, choosing reactive power compensation devices and reactive power allocation schemes rationally can maintain the system voltage both effectively and economically.

Different from conventional generators, wind power is an intermittent energy source, power system dispatch and control is confronted with new challenges. This paper establish the mathematical model of wind power and energy storage system for simulation and analysis, and study the wind power prediction using statistical methods and physical methods, and study the key technologies of automatic generation control and automatic voltage control which were in the large-scale wind power and energy storage system. The results show that the wind power prediction is reasonable for grid, and the power quality and stability of wind farm connected to power grid can be well improved by battery energy storage.

When large-scale wind power island is connected to VSC-HVDC power grid, the interdependence between wind turbine and VSC-HVDC power grid will be closer. Especially in the fault process, the interaction between wind turbine and VSC-HVDC power grid is more prominent, which makes the fault crossing of large wind power isolated islands connected to VSC-HVDC power grid face many new problems. Therefore, it is necessary to study the fault response characteristics of wind power connect to VSC-HVDC power grid and the fault ride through scheme of VSC-HVDC power grid and wind power joint system. When large-scale wind power is connected to the VSC-HVDC power grid and the VSC-HVDC mode is used for long-distance transmission, the operation characteristics of wind power and VSC-HVDC power grid will affect each other. The adaptability of wind power connected to the VSC-HVDC power grid will become an important problem affecting the operation of the power grid. Especially when the VSC-HVDC power grid fails, the response characteristics of the wind turbine, the interaction between VSC-HVDC power grid and wind power in the event of power grid failure, and how to realize fault ride through together. The focus of study should be to clarify the fault characteristics and interaction between wind power and VSC-HVDC power grid, realizing the joint fault ride through, and deepen the understanding of the interaction between wind power and power electronic controller in case of fault of VSC-HVDC power grid. Finally, to ensure the safe and stable operation of wind power sent through VSC-HVDC power grid, it is important to give full play to the flexible control of VSC-HVDC power grid, so as to work without synchronous power support.

In recent years, wind power and photovoltaic power generation have developed rapidly, and the installed proportion of wind power and photovoltaic power will further increase in the future. Aiming at the strong uncertainty of wind power and photovoltaic power, a scene generation method of wind and solar active power output based on k-medoids clustering and generative adversarial networks is proposed to avoid problems of model convergence and gradient disappearance, meanwhile preserving the diversity of generated results. Using the active power output data of two wind power plants and six photovoltaic power plants in Western China for 365 days a year, the data samples are clustered into ten scenarios by k-mediods method, which are used as training sets under different typical scenarios. The distribution characteristics of active power output data are effectively fitted by the generative adversarial networks, and its generation effect is analyzed. The results show that the scene generation method of wind and solar active power output based on k-medoids clustering and generative adversarial networks has the advantages of fast convergence and high precision.

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

With the development of power system with high proportion of renewable energy, large-scale wind power consumption has been in a tough situation in China. Recently, the transformation of "coal-to-electricity" has been promoted constantly in northern regions, and market trading mechanism of wind power for heating has been established and completed gradually, which has provided amount of absorption space for wind power. In order to make quantitative description of corresponding relationship between incremental wind power and incremental heating load, a calculation model for wind power consumed by electric heating load based on multi-state probability distribution is proposed in this paper. According to wind power output depicted by multiple probability distributions, we figure out both theoretical and practical wind power generating capacity with or without peak regulation constraints. On this basis, the contribution of heating load to reduce wind curtailment rate is obtained by comparing with consumption capacity before and after the load access to grid. Finally through a series of case study, it is proved that incremental electric heating load can indeed cut down wind curtailment of power system to some extent.

Wind curtailment, caused by wind power uncertainty, has become a prominent issue with the large-scale grid connection of wind power. To fully account for the uncertainty of wind power output, a short-term hydro-wind-thermal operation method based on a wind power confidence interval is proposed. By utilizing the flexible start-stop and efficient ramp-up of cascade hydropower plants to smooth fluctuations in wind power output, a multi-objective optimal scheduling model that minimizes the cost of power generation and maximizes the consumption of clean energy is constructed. To reduce the solution’s complexity, we chunk the model according to the energy type using a hierarchical solution. The overall solution framework, which integrates a nonparametric method, a heuristic algorithm, and an improved particle swarm algorithm, is constructed to solve the model rapidly. The simulation results of a regional power grid show that the proposed method can attain an efficient solution in 83.5 seconds. Furthermore, the proposed method achieves an additional 455,600 kWh of hydropower and a reduction of ¥233,300 in the cost of coal consumption. These findings suggest that the proposed method is a good reference for the short-term operation of a hydro-wind-thermal combination in large-scale wind power access areas.

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 rapid increase of wind power centralized grid-connection scale, the security and stability of power grid are greatly affected. In order to simulate the dynamic characteristics of wind farm accurately, a large-scale wind power online equivalent method based on multi-source data fusion is proposed. The operating state of the state estimation modeling network is identified by the fusion of multi-source real-time data such as SCADA, PMU and security and stability control system. When the error of branch power flow or node voltage at the boundary is large, the active power regulation range of wind power generators is determined by comprehensively considering the actual measurement collected by the wind farm centralized control system and the prediction information of the wind power prediction system. The active power of each wind farm is determined by quadratic programming model. The wind power generators are grouped according to the topology in the wind farm, then each group is subdivided according to static characteristic and operating state in turn. The dynamic models and static parameters of equivalent wind power generators and equivalent transformers are calculated. The proposed method is proved to be fast and effective through the analysis of a practical power grid example.