Due to the growing demand for diversified business, the information interaction mode which is compatible with the business requirements and system characteristics is the implementation foundation of smart distribution grid and utilization. Firstly, two typical information interaction modes and corresponding deployment patterns were proposed, which were called the interface adapter way and the integrated way, based on the analysis on the business requirements and architecture of smart distribution grid and utilization. Then, the combination scheme of communication mode of smart distribution grid and utilization was proposed, according to its physical demand. The information security protection system of the secondary system was analyzed combined with the requirements of power system information security. Finally, through the analysis on the business requirements, system architecture, information interaction mode and deployment patterns, physical communication solution and security protection system, this paper established the typical mode of information interaction in smart distribution grid and utilization. The proposed mode has been applied in practical engineering such as the optimal operation of smart distribution grid and utilization.
In recent years, distributed generation obtains rapid development for its energy-saving and environment protection. However, the network access of distributed energy will cause certain impact on the interests of the distribution network operators （DNO）, which may hinder harmonious development of them. This pape reconciled the both interests of DNO and distributed generation owners （DGO）, and studied the combined optimization problem of distributed generation investment and distribution network construction planning. The profit distribution coefficient was introduced during the construction of objective function so as to achieve the win-win purpose. Besides, the model needed to satisfy both the security and stability operation of distribution network and the emission reduction targets constraints. And the two-point estimate model was used to determine the uncertainty factors in the model. This paper used improved cuckoo search algorithm （ICSA） to solve the constructed model. At last, a IEEE33 nodes distribution system was used to verify the feasibility and effectiveness of the provided model by cases comparison.
For the antifreezing industrial demand of direct air-cooling condenser in winter, the model on finned tube scale was coupled with that on air-cooling unit scale, both the whole heat transfer characteristics in finned tube bundle and the impingement heat transfer characteristic of condensate water in air-cooling finned tube were studied, which could provide the third thermal boundary condition for the calculation of the in-tube condensation heat transfer and freezing in direct air-cooling condenser under the condition of low temperature operation in winter. The air-cooling condenser cell model and finned tube model were constructed. Then, the simulation results of finned tube under 3D inlet wind velocity boundary condition was simplified as input-output type agent model. The velocity distribution at the windward surface and symmetric boundary was obtained from air-cooling condenser cell numerical simulation. Then the finned tube agent model was applied in the symmetric boundary to obtain the spatial distribution of the impingement heat transfer characteristics and average convective heat transfer characteristics of finned tube at symmetric boundary. The numerical calculation results show that, the impinging heat transfer coefficient has a larger magnitude than the average convective heat transfer coefficient； at the windward surface, the distributions of those two coefficients are both up-down asymmetrical and left-right asymmetrical； and the impinging heat transfer coefficient decreases with the decrease of the rotational speed.
Based on the operating experience of UHV transmission lines built in China, this paper studied the features of UHV transformer, the identification scheme for inrush current, the disposition and setting of relay protection for main transformer and voltage regulation compensation. Specific disposition schemes for both main protection and backup protection of each set of UHV transformer protection were proposed, also the function and range of each differential protection were defined to make sure that this protection scheme could reliably act on various types of failures happened in transformer. And then, the coordinate setting proposals were given and the feasibility of this proposed protection scheme had been proved by experiments on typical faults. The scheme has been successfully applied in 1 000 kV transformer protection in East China, which provides important references for the design of transformer relay protection in other UHVAC projects.
The dynamic equivalent model of power system inevitably exists some errors. The trajectory sensitivities of the tie lines power to the equivalent parameters reveal the quantitative relation between the equivalent error and model parameter, which can be used to optimize the equivalent model parameters. Thus, a trajectory sensitivity-based optimization method was proposed for dynamic equivalent model parameters. Firstly, the definition and calculation of trajectory sensitivity were introduced. Then, the structure of the dynamic equivalent system with consideration of synthesis loads was discussed. The dominant parameters were classed into static or dynamic dominant parameters and optimized separately according to different characteristics of the trajectory sensitivities. Finally, the algorithm was applied in the optimization of the equivalent model of the IEEE 10-machine 39-bus system. The fictitious impedances, inertia time constant, stator impedance and rotor resistance of the equivalent motor were optimized. The simulation results show that the proposed method can improve the precision of the equivalent model effectively. It has a fast convergence speed and needs very little computation tasks, and so has a good application prospect.
To make better use of energy storage batterys role in reducing network loss and alleviating peak-valley difference, a Pareto multi-objective optimization model was proposed for energy storage battery in distribution network with considering network loss reduction and peak-valley difference alleviation, which took the minimum network power loss in distribution system and the minimum variance between load of every period and the average value as objective functions, the charge/discharge power of storage battery as control variables, and transformed the constraints on battery capacity and static security into penalty function. According to daily load curve, the optimal charge and discharge periods of energy storage battery were obtained. Combined with forward-backward sweep calculation method, fast non-dominated sorting genetic algorithm II （NSGA-II） with elitist strategy was adopted to solve the multi-objective model. Based on satisfaction-maximizing method, this paper analyzed three optimization schemes in Pareto solution set: the minimum network loss, the best load shifting effect and the compromise solution between two objectives, in order to obtain different optimization schemes of energy storage battery. Finally, taking IEEE33 distribution system as example, this paper proved the validity and feasibility of the proposed method, and analyzed the advantages and disadvantages of operation schemes under different decision strategies, which could provide decision-making reference for the economic operation decision of distribution networks.
Comprehensive and optimal utilization of electricity, thermal energy and gas is a significant way to enhance the utilization efficiency of energy and achieve energy sustainable development. However, the research of integrated energy system just has been started. There are many works needed to accomplish for the establishment of a mature integrated energy system. At the beginning of the study, one of key and necessary basic works is to clarify the research ideas and content. This paper expounded the constitutions of integrated energy system, analyzed its advantages, proposed a framework of optimal planning and operation for integrated energy system, and discussed the key technologies needed to be solved for establishing integrated energy system, which could provide references for the study and implementation of integrated energy system.
According to the distribution of wind energy resource and the present situation of wind power integration in Beijing, the forecast of wind power generation development in Beijing power grid was provided, which focused on the output characteristics of the planned wind power projects and the development of wind power generation in Beijing during the 13th national five-year plan. A calculation method of the maximum proliferation ratio of wind power in Beijing power grid was proposed, whose boundary condition included the load characteristics of grid, the peak shift capability of local power generation plants, the new energy processing features and the power flow exchange limit with the outside grid. The method was used to calculate the maximum penetration ratio of wind power in Beijing power grid during the end of the 12th, 13th national five-year plan. Finally, this paper suggested some related technical measures to promote the development of wind power in Beijing power grid.
With the promotion of the new urbanization and beautiful countryside macro policy in China, the process of the urban-rural integration accelerates, which drives the fast increase in the demand of the rural power network. In the background of the new urbanization and beautiful countryside, the analysis of the demand of the rural power network has the important practical significance to the establishment and improvement of the development model and construction standard of rural power network. Combining the power demand characteristics of rural power network in the background of the new urbanization and beautiful countryside, the power demand evaluation indexes for town are established and the analogy forecasting method is proposed based on full sample space, which could extend the load forecasting from a single dimension to hyperspace. It is applicable to the big data environment where the power data intersected the economic and social development in the process of urbanization. On this basis, this paper synthesizes the three classic forecasting methods, including the regression analysis method, the grey model and the per capita consumption method, and proposes a combination forecasting method based on the goodness of fit empowerment, which could realize the automatic optimization adjustment of weight. The numerical example results show that the combination forecasting method can improve the accuracy and reliability of the forecasting results.
In recent years, international situation changes and domestic economic restructuring lead to the fluctuation of energy industry development trend during the 12th five year, especially electric power industry. The relative policy and plan have been adjusted. Under these influences, the non-fossil energy 15% objective which would be realized in 2020 during the 13th five year is uncertain. To ensure the realization of this objective, a new energy and electric power planning was provided according to the changes under the new situation. Based on the planning scheme, the sensitivity analysis and the maximum deviation analysis methods were proposed to quantify the influence of the implementation deviation of non-fossil energy planning on the target percentage. And the according suggestions were also provided. The research shows that the main influence factors of the target percentage are the development progresses of hydropower and nuclear power, as well as their output channel construction. Whether the target percentage can reach 15% largely depends on whether the development of hydropower and nuclear power can be completed according to the planning. If the development and utilization of two types of power supplies are not enough to reach the planning objectives, wind power and solar power generation can be increased to remedy the vacancy. But if the vacancy of hydropower exceeds 0.58 billion kw, or that of nuclear power exceeds 0.27 billion kw, the ‘15% objective’ of non-fossil energy cant be achieved. Accelerating the construction of the Sichuan-Tibet hydropower output channel can help to solve the problem of waste water, which is a strong guarantee for the ‘15% objective’ realization of non-fossil energy.
The rapid development of new urbanization and the deep implementation of beautiful countryside construction put forward a series of new requirements for the distribution network construction in Zhejiang province. Korea and Zhejiang have high similarity in natural and socio-economic characteristics and the size of power grid. So the gradual development characteristics and development course of the distribution network in Korea have great reference and guiding significance for the future development of that in Zhejiang. This paper demonstrated the comparability of Korea and Zhejiang in detail from three aspects, carried out detailed analysis on the characteristics of distribution network development in Korea, compared their distribution network technologies and found the direction of the distribution network construction in Zhejiang province, which could targeted and efficiently improve the overall level of Zhejiang distribution network, in order to better adapt to the requirements of new urbanization and beautiful countryside construction on the distribution network construction in Zhejiang province.
Firstly, the development and present situation of theoretical study and engineering application of the unified power flow controller （UPFC） at home and abroad were introduced. Then, the constraints in developing Nanjing Western grid were described in detail, such as limited transfer capacities of power imported channels, unbalanced power flow distributions and so on. Through the comparison with other convention solutions, the feasibility, necessity and inevitability of UPFC applied in Nanjing Western grid to improve the systems reliability and transfer capacity were investigated. Through the analysis and calculation, it is found that the application of UPFC not only can effectively control power flow, enhance the transfer capacity of the existing power grid, which can avoid constructing city-crossed cable channel with huge investment and difficult construction； but also can be well adapted to the changes of power grid frame in the future. Therefore, the application of UPFC in Nanjing Western grid or even Jiangsu grid in the future can prominently improve the transfer capacity, utilization efficiency and running security of power grid, which can achieve good economic and social benefits.
With using the PSD-BPA software developed by China Electric Power Research Institute, this paper studied the influence of UHV grid on Tianjin 500 kV Grid in detail. The operation of UHV substation in Tianjin South has little influence on the current, voltage and transient stability level of Tianjin 500 kV Grid, but has large influence on the short-circuit current, which enhances the short-circuit level of Tianjin 500 kV substation, so as to the short-circuit current of Tianjin South and Jinghai substation exceeding the standard. According to the over-limitation problem of short-circuit current, this paper proposed three measures to limit the short-circuit current, analyzed three restrictive measures with using PSD-BPA software and verified those limiting effect. Finally, this paper compared these three measures from two aspects of the limiting effect for short-circuit current and the impact on the security and stability operation of power grid, and discussed the advantages and disadvantages of these three restrictive measures.
In allusion to such defects as sensitive to initial clustering center and not convenient to determine clustering number during utilizing traditional fuzzy C-Means （FCM） algorithm to extract power load patterns, this paper constructed objective function to reflect clustering effect, and used a quantum particle swarm algorithm for global optimization to determine the optimal clustering center and classification aiming at the defects of traditional intelligent optimization algorithm, such as easy convergence, falling into local optimum, etc. After determining the optimal clustering center and clustering number, the characteristics vector was constructed to fully reflect each kind of load. At last, by compared with the calculated results of traditional FCM algorithm, the effectiveness and correctness of the proposed algorithm in electricity recognition were verified.
To assess the impact of node-fault on the static performance of power grid, this paper proposed the vulnerability comprehensive index for power grid based on the complex network theory. This paper constructed the structural vulnerability index consisting of the largest connected subset and the average efficiency of the network, as well as the functional vulnerability index consisting of the proportion of the loss load and the grid power transmission efficiency. On this basis, this paper proposed a vulnerability comprehensive index based on the entropy value fuzzy comprehensive assessment method, which could overcome the strong subjectivity and the inconsistency with the real data when its vulnerability indexes were empowered. Finally, the numerical simulations and analyses for the attacks: random, node degree, node electrical betweenness, traditional line betweenness and line electrical betweenness, were investigated based on the IEEE-118 bus system respectively. The impacts of these five types of attacks on the grid comprehensive vulnerability index and every single index were analyzed, meanwhile, the rationality of the comprehensive index was verified.
To determine the load transfer between medium voltage feeders in distribution network, combining with the maximum load current and allowable peer ampacity of the lines and some constraints, a practical method is proposed to calculate and analyze the load transfer based on N-1 security criterion. On the basis of understanding the basic connection relation between the feeders, the possibility of the load transfer is determined, which might be supported by a single feeder or multiple feeders. The transfer capacity and the transfer solution schemes to meet the constraints could be calculated, analyzed and obtained when a feeder starting terminal was in failure. The load loss rate under different fault conditions of one single substation could be obtained by summarizing all the transfer information of the lines from the substation. The practicability and the effectiveness of the method have been verified through the practical engineering application in a real distribution network.
To test the capability of 10 kV lightning protection device with series gaps to cut off the power frequency continuous current after the device breakdown by lightning, this paper designed a test loop in combination with impulse test and power frequency continuous current test. In order to generate power frequency continuous current with high amplitude under higher voltage, a LC series and parallel resonant circuit was used in which the parameters of each element were calculated and selected and their reasonable values were given. Finally, a synchronization control circuit was chosen to extract the impulse signal to conduct the power frequency continuous current circuit, which could realize the synchronization in impulse test and power frequency continuous current test. The calculation results show that the combined test circuit can generate 1.2/50 μs impulse waveform, and 50 Hz sinusoidal current wave with 100 ms oscillation, which can meet the requirement of testing the capability of lightning protection device with series gaps to cut off electric arc under power frequency continuous current after the device breakdown by lightning.
According to the existing problems in the capacity configuration of current micro-grid, a new multi-objective optimization method was proposed for the capacity configuration of micro-grid, by which the combined solution and configuration optimization of distributed generation capacity and energy storage capacity in micro-grid planning could be carried out at the same time. Taking a auxiliary power system in 1 000 kV substation as example, this paper applied micro-grid planning software DGPO to design three different supplementary power schemes for UHV auxiliary power system, including photovoltaic storage micro-grid system, wind storage micro-grid system and wind-photovoltaic storage micro-grid system. Finally, a grid-connected/off-grid photovoltaic storage micro-grid system was recommended as supplementary power for substation.
Due to different disturbance conditions, the transient control strategy of photovoltaic power generation system is different, even for the same fault disturbance, because there are many types of inverters in photovoltaic power station and there control parameters are also different. In order to study the transient characteristics of large-scale photovoltaic power station, and avoid constructing detailed model for every kind of inverter, the equivalent model of photovoltaic power station needed to be established under disturbance. The equivalent models of photovoltaic phalanx group and photovoltaic inverter group were set up by using multiplier method. Through using the test data of photovoltaic power station simulation in Qinghai Haixi, the simulation validation and error analysis show that the proposed equivalent modeling method and mathematical model for photovoltaic inverter group are valid.
In recent years, large-scale wind turbine tripping accidents occur frequently, causing a serious threat to the security and stability of power grid. Its necessary to study the mechanism of these accidents and propose strategy to prevent more accidents. This paper firstly analyzed the high voltage problem of wind machines with dynamic reactive power compensation devices during grid fault, and put forward simulation to study the impact of SVC （static var compensator） response time on the transient voltage characteristics of wind farms. The results point out that the adjustment lag of SVC transient reactive power is the main factor leading to wind turbine tripping accidents caused by high voltage under fault. Then the reactive power coordination control strategy was proposed for wind farms during grid fault, which through coordinating SVC and wind turbines reactive power output, could peremptorily lock SVC when the fault occurred and put crowbar into operation to protect circuit, and then make SVC back into operation with a certain time delay after the fault clearance, so as to improve the fault crossing ability of wind turbines. The simulation results show that the proposed control strategy can effectively suppress wind turbine high-voltage tripping accidents caused under fault.
In load rejection test-based parameters identification of synchronous machine, the excitation voltage was conventionally assumed to keep constant during the test. But considering the regulation effects of the excitation control systems, it was hard to be satisfied. Therefore, an improved load rejection test-based parameters identification method for synchronous machine was proposed with considering the variation of excitation voltage. The measured excitation voltage was taken as input excitation to the field winding. The differential algebraic equations of the field and damper windings were solved. The field winding current was obtained and compared with the measured curve. Taking the minimum error as optimization objective and the classical parameters of synchronous generators as initial values, ant colony optimization was utilized to identify the parameters of d axis. Then the stator voltage in q axis was calculated through the stator flux in d axis. According to the measured stator voltage, the stator voltage in d axis was derived and used to identify the parameters of q axis. The parameters identification results of a generator in a hydraulic power plant in Yunnan power grid validated the effectiveness of the improved method. Compared with the existed method, the improved method has better accuracy and fewer restrictions about test conditions, which has a good prospect of engineering application.
