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

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.

High-temperature superconducting (HTS) generators for large-scale wind power generation systems attract much research attention. Excitation systems in HTS generators, particularly brushless HTS exciters, are a new challenge. To verify the possibility of a brushless HTS exciter in a large-scale wind power generator, we designed and fabricated HTS coils for a laboratory-scale wind power generator employing a brushless exciter. In order to supply dc current into the HTS coils, a brushless exciter was considered in the generator. All of the field coils were wound with an HTS coated conductor made of 2G GdBCO wire. The conduction cooling test was executed in a cryogenic test chamber to check the performances at 30 K. The detailed results of the operating performance of the HTS coils were discussed in detail.

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

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

Large-scale offshore wind power generation has become one of the research hotspots in the development of new energy in the world. However, the planning of far-reaching offshore wind power is faced with many technical difficulties, such as the need to consider the optimization of line transmission capacity caused by the truncation effect in combination with the wind power output probability, and solve the problem that traditional algorithms cannot solve the dynamic programming problem, and the greedy algorithm for solving the dynamic programming problem cannot solve the global optimal solution. Therefore, in order to solve the above problems, based on the full life cycle (FLC) investment calculation of the collecting and transmission system, the topology optimization model of the offshore wind power system is established. In addition, in order to solve the grid-connection problem of offshore wind farms, an improved topology optimization algorithm based on greedy idea is proposed. The optimization results show that the critical values of economic transmission distance of HVAC, FFTS and HVDC are usually 50 km and 170 km respectively. Finally, the collection scheme of the wind farm cluster including three far-reaching offshore wind farms are analyzed, and the results show that the total cost of the optimized point-to-point scheme is reduced by 5.6% and 10.2% respectively compared with the star topology and the circular collection topology, with significant economic benefits.

Wind power prediction is an effective way to decrease the effects for the large-scale grid-connected wind power generation. Improving accuracy of short-term wind prediction is the key to wind power prediction. There is often a lot of redundant information in the observed values of wind speed to result in large computation and affect the predictive validity. In this paper, a support vector machine (SVM) method was proposed based on information granulating. Firstly, original data was dealt with fuzzy information granulation to form information granulation. Secondly, adopting SVM is widely used in regression prediction to predict the changes of short-term average wind speed in trends and in space. At last, the actual data was compared with the predicted data to verify results. The verification experiments show that granulated data can not only reflect the characteristics of wind but also reduce redundant information. The predicted result was changing in the space of average wind speed. So, this method can predict the short-term wind speed space.

The development of wind power generation can promote the transformation of energy structure and the green development of the economy. The land is the spatial carrier of wind power generation projects, which has a basic supporting role for wind power generation. This paper analyzes the situation of land utilization for wind power generation, sorts out relevant national policy documents, and summarizes the problems existing in the implementation of wind power projects, which is of great significance for promoting the development of the wind power industry. The results showed that the installed capacity of wind power and electricity generation increased rapidly in the past decade. The land supplied area for wind power generation reached its peak in 2016 and then fluctuated, with the land supplied area decreasing but the power generation efficiency improving. In the process of wind power land utilization in China, there are some problems, such as the insufficient connection between industry planning and territorial spatial planning, lack of coordination mechanism between government departments for examination and approval, lack of land standards, prominent problems in the use of stock land and the renewal and renovation of old wind farms, and complicated land requisition compensation. Based on this, the paper puts forward corresponding countermeasures and suggestions from the aspects of territorial space planning, land use examination and approval, land use standard, utilization of stock land, popularization and application of land saving technology and land saving mode.

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.

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

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.

Geographic aggregation and wind power output variance in Denmark

The power area of Asia-Africa-European power transmission is rich in new energy resources such as wind resources and solar resources. West Asia and Africa have the potential to build large-scale renewable energy power generation bases. Based on the basic idea of Levelized Energy Cost Analysis (LCOE), this paper proposes an improved feasibility analysis model of new energy power generation technology, comprehensively considering the impact of policies, technology, politics and other factors on the cost of power generation. Feasibility of power transmission from large renewable energy bases in West Asia and Africa to Europe are measured under interregional grid interconnection. The results show that: the wind and solar power generation bases in West Asia and Africa are feasible of transferring electricity to Europe, and solar intercontinental interconnected transmission is more feasible than wind power.

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.

This paper deals with a flux-controllable NI HTS flux-switching machine (FSM) for electric vehicle (EV) applications. In a variable-speed rotating machine for EVs, such as electric buses, electric aircraft and electric ships, an electric motor capable of regulating the flux offers the advantage of constant output operation. In general, conventional HTS rotating machines have excellent flux-regulation performance, because they excite an HTS field coil. However, it is difficult to ensure any flux-regulation capabilities in HTS rotating machines using HTS field coils that apply the no-insulation (NI) winding technique, due to the inherent charge and discharge delays in these machines. Nevertheless, the NI winding technique is being actively researched as a key technology for the successful development of HTS rotating machines, because it can dramatically improve the operational stability of HTS field coils. Therefore, research to implement an HTS rotating machine with flux-regulation capabilities, while improving the operating stability of the HTS field coil using the NI winding technique, is required for EV applications. In this paper, we propose an HTS rotating machine with a flux switching structure, a type of topology of a rotating machine that is being actively studied for application to the electric motors used in EVs. The proposed HTS flux-switching machine (FSM) uses NI field coils, but additional field windings are applied for flux regulation, which enables flux control. In this study, an NI HTS field coil was also fabricated and tested because the characteristic resistance value should be used for the design and characteristic analyses of machines which utilize an NI coil. The simulation model used to analyze the flux-regulation performance capabilities of the NI HTS FSM were devised based on the characteristic resistance values obtained from a charging test of the fabricated NI HTS field coil. This study can provide a good reference for further research, including work on the manufacturing of a prototype NI HTS FSM for EV applications, and it can be used as a reference for the development of other HTS rotating machines, such as those used in large-scale wind power generation, where flux-regulation capabilities are required.

Dispatch modeling of a regional power generation system – Integrating wind power