It is urgent demand for the evaluation and control of power grid operation to establish a set of scientific, systematic and reasonable index system. This paper discussed how to establish the index system according to the operation demand of transmission network, which could effectively evaluate the grid status and provide assistant decision-making information； made clear the purpose of constructing the index system for grid operation； expounded the main architecture and implementation ideas of the index system. The index system evaluated the transmission network operation from two levels: the results and the reasons, which not only reflected whether the current operating status of transmission network were satisfied, but also explored the reasons of unsatisfied states of transmission network. The result evaluation analyzed the demands of main stakeholders of transmission network, including the satisfaction degree of both external demand and internal demand. Based on the methods of decomposition and transformation, the reason evaluation provided the decomposition index for each result evaluation index, constructed the strategy chain corresponding to the result evaluation index, and proposed the method of strategy evaluation, in order to find the weaknesses in grid operation. Then, the principles and methods of index selection were proposed for the index system. The index system designed based on the proposed architecture, has the advantages of obvious hierarchy, clear index relationship, close contact with the main business of dispatch center, which can provide guidance for the dispatchers and the system to make the control decisions.
The status of transmission network operaion is satified when the demand from the diverse transmission system stakeholders is satified. Therefore, the evaluation index system for transmission network operation is actually evaluating the demand satisfaction from the stakeholders in transmission system. Especially, the external demand is the demand for transmission network operation from the external stakeholders of the transmission system, including the generation enterprise, the distribution enterprise, the interconnected transmission enterprise. The external demand was analyzed and concluded as follow: the local transmission system should accomodate power energy with specified quality and quantity from or provide it to the specified node in the specified time. Different types of external nodes had different demands, so this paper studied different quality and quantity demands of the power energy from different external nodes in detail, and expounded the evaluation methods for the satisfaction degree of the external demand. According to the specific external demand, the scientific and reasonable index was selected to evaluate the instantaneous demand satisfaction degree or in statistics cycle time, thus the external demand index set was proposed for the evaluation index system of transmission network operation.
Compared with the AC power distribution network, the DC distribution network has characteristics of lower line losses, better power quality, higher reliability, etc., and it is suitable for the accessing of all kinds of distributed generation and DC loads. Firstly, this paper studied the accessing of distributed generation, electric vehicle charging and discharging station into DC distribution network. And then a double-ring topology structure was put forward for DC distribution network, which was suitable for the accessing of distributed generation and electric vehicle charging and discharging station. Finally, various distributed generation and the proposed topology structure were simulated with using simulation software PSCAD/EMTDC. The simulation results show that the DC voltage and DC loads in the DC distribution network will not fluctuate sharply, when the capacity of distributed generation changes along with the change of external environment. At the same time the DC distribution network can transfer energy with AC system, and also can regulate the power flow of AC system. The simulation results can verify the feasibility and effectiveness of the proposed topology structure for DC distribution network.
The reactive power control of smart substation needs to achieve real-time in situ balance. Capacitor banks were usually configured in traditional substation as reactive power compensation. Along with the development of flexible AC transmission technology, dynamic reactive power compensation device was gradually used in the reactive power compensation of smart substation, but there were few coordination configurations between these two reactive power compensation methods. In view of the above situation, the configuration scheme of reactive power optimization was suggested for smart substation, in which capacitor banks were coordinated with static var compensator （SVC）. On the basis of the original optimal cover that only the considered equal capacity grouping configuration of capacitors, this paper improved the optimal cover method with considering the influence of SVC. Through the analysis of equal capacity grouping and several typical unequal capacity grouping, this paper constructed the multi-objective optimization mathematical model with the minimum reactive power mismatch area and the optimal investment cost as objectives, and then converted it into a single-objective function of the minimum annual loss as an evaluation function for the reactive power configuration of substation. Based on the genetic algorithm optimization, the configuration optimization schemes of SVC with equal or unequal grouping capacitor banks were obtained respectively and compared to get the optimal scheme. Finally, the reactive load data of a smart substation was used to verify the effectiveness and practicality of this configuration method.
To comprehensively analyze the influence of new energy grid on the energy structure and power structure in China, taking the minimum power generation costs and pollutant emissions as the planning objective functions, this paper constructed an optimization model for new energy and power structure. This model selected the amount of primary energy consumption and new annual generating capacity as the decision variables, and constructed the constraint conditions from many aspects, such as the balance of energy supply and demand, the energy consumption, the balance of power supply and demand, the power consumption and demand, installed capacity and growth rate, etc. Through measuring the optimal energy structure and the scale of new energy development, installed capacity and construction sequence in reference scenario, energy security scenario or low carbon development scenario in China, this paper comparatively analyzed and compared the cost-effectiveness in three scenarios. Finally, a sensitivity analysis was carried out for the total primary energy consumption and the proportion of non-fossil energy consumption. The results show that, the greater the development and utilization of new energy scale are, the greater the resources and environmental benefits are, and the less the operation cost and the degree of dependence on foreign energy are. In addition, reducing the fossil energy consumption can be beneficial to reduce the operation cost of energy system
Photovoltaic （PV） power forecast is significant to reduce the impact of PV generation on the power system since the output of PV system has a strong randomness. This paper presented a method based on least square support vector machine （LSSVM） and gray relational analysis （GRA） to predict the PV output power, which was a combination of traditional forecasting methods including direct and indirect forecasting. First, it analyzed the effects of irradiance and weather types on PV output, and selected training samples through GRA, so that the training samples could reflect the weather attributes at forecast days more exactly. Then the predictive model could forecast output power 24 hours ahead with using LSSVM, and it had been tested and evaluated by the measured data of solar-PV building demonstration project in Tianjin. The results show that the prediction method of GRA-LSSVM has better prediction accuracy.
In the present study of optimal location of distributed generation （DG）, the simplified approach of annual wind-solar resource and load data is suggested, and the results cannot meet the real application requirements, due to the small scale of distribution network in numerical example. This paper proposed an optimal location method of DG for large-scale distribution network which had multiple feeders, considering not only the annual load data, but also the annual wind and solar resource data. Firstly, a model of DG location for large-scale distribution network with multiple feeders was given, which had accurately considered the annual data of load, wind and solar resource. Secondly, the solving strategy of the proposed model was given based on genetic algorithm. Finally, the model was verified by an actual case, which was a large-scale distribution network with multiple feeders. It is shown that the network loss of the distribution network considering impact of annual data of load, wind and solar resource on wind turbines' location is better after the optimization of fan location, and the network loss with using the integral optimization of the whole distribution network with multiple feeders is also better than that of optimization in single feeder.
The inherent requirement of low carbon electricity and the comprehensive construction of smart grid can promote the large scale development of distributed generation （DG）. However, there will be many uncertainty factors in the marketization progress of DG. To identify the investment risk of DG, and contribute to DG guarantee mechanism-making, the investment risk was analyzed in detail from five aspects, including policies and regulations, market environment, related stakeholders, technical equipment, operation management. Then the risk evaluation index system and coping strategies were proposed. Finally, the relevant suggestions of DG investment guarantee mechanism was also proposed from external supervision, marketing and stakeholders.
CO2 mineralization and sequestration provides an effective way to reduce greenhouse gas emissions, which is suitable for the lack of geological conditions of reservoir area. According to the problems of traditional mineralization technology, such as complicated processes, extreme reaction conditions and the raw materials with high prices in China, this paper proposed the CO2 mineralization and sequestration technology, which used cheap fly ash as raw materials and recyclable ammonium salts NH4HSO4 as dissolution agent. This technology can greatly reduce the reaction temperature of mineralization dissolution, and can not only effective dissolve metallic elements such as Ca, Mg for CO2 mineralization and sequestration, but also produce high value-added products containing Al, Fe elements. This paper also studied the influence of the composition of fly ash, solvent concentration, solid-liquid ratio and other conditions on metal dissolution rate, and obtained the dissolution laws of metallic elements from fly ash in mild condition. The results show that 37% of Ca and 72% of Mg can be extracted from fly ash in 2 h with 3.5 mol/L NH4HSO4 and 25 g/L solid-liquid ratio, respectively. The fly ash of Wuhai Thermal Power Plant is more suitable for CO2 mineralization than the others, because of the highest calcium content.
For the long-distance UHV transmission system, its transmission capacity is mainly restricted by small disturbance stability. UHV transmission system with large-scale power supply has characteristics of long transfer distance and huge transfer power, whose transmission capacity has always been a concern. Based on the characteristics of sending system, the receiving system was equivalent to single machine system of load, and the equivalent damping coefficient of the system was deduced in detail. The influence of parameters of generator, network on the system’s equivalent damping coefficient was discussed, from two aspects of generator and system network. The simulation results of UHV large power transmission system in PSASP indicate that: the parameters of generator or network can influence damping coefficient and thus affect the UHV system transmission capacity. The results also verify the correctness of the theoretical derivation； can provide theoretical basis and policy for the improvement of UHV transmission capacity, which is valuable to engineering application.
Accurately assessing the lighting performance of back striking and shielding failure of HV transmission lines has a great reference value for the design and construction of lines. Based on the multi-wave impedance model of towers, taking the intersection method as the judgment of insulation flashover and the improved electric geometry method （EGM） as the calculated method for the trip-out rate of shielding failure, the lightning performances of back striking and shielding failure of ±800 kV, ±500 kV double-circuit DC transmission lines were analyzed for three different kinds of towers, as well as the related influencing factors. The results show that: along with the reduction of both tower height and surge grounding resistance, the lighting performance of back striking is enhanced； along with the decrease of slope angle of ground, protecting angle as well as the lowering of the height of tower, the lighting performance of shielding failure is enhanced. The optimum arrangement scheme was obtained through comparing the type of tower and the array style of conductors which could influence the lighting performance, and the corresponding suggestions were proposed.
With the gradually increase of electricity load density and the accessing of a large number of distributed generation, the current distribution network is faced with the problem of insufficient power supply capability. The DC distribution network is different from the AC distribution network in many aspects, such as power supply capacity, line losses, the adaptability for all kinds of power and load accessing, etc. Through the analysis on the power supply capability of AC line, this paper derived the power supply capability calculation model of DC line under different constraints, and compared the load moment and supply distance of commonly used wires under the assumed different voltage levels and typical load distribution patterns. It is concluded that, when calculating the power supply capability, the voltage constraints and line losses constraints play a different role in AC and DC systems. Finally, the selection basis was proposed for the calculation of the power supply capability of power line in AC and DC distribution network, which could provide a reference for the far-reaching research in future.
Capacitor commutated converter （CCC） can compensate reactive power absorbed by converter through the transformation of the main circuit structure in traditional DC transmission system with appropriate capacitor, which can make the amplitude and phase of actual commutation voltage change, reduce the reactive power absorption by converter and the probability of commutation failure of the inverter-side, so as to improve the stability of DC system. However, with the above advantages, CCC DC system also has inherent defects. This paper firstly studied the mechanism and steady-state characteristics of HVDC transmission system whose rectifier side and inverter side were based CCC. The model was built with using PSCAD, and verified by simulation, whose results were compared with traditional DC transmission system. Secondly, this paper specially analyzed the characteristics of avoiding commutation failure, the recovery characteristics after a short single-phase fault, and the follow-up fault mechanism, for CCC DC transmission system, as well as studied the impact of series capacitor size on recovery process. The research results can play a great role for improving the dynamic characteristics of CCC HVDC transmission system and its further development.
In the galloping process of iced bundle conductor, the coupling relationship of conductor’s torsional vibration and transverse vibration may cause unsteady motion. Based on the coupling movement of section model of transmission line, the expression of aerodynamic parameters of transmission line on unsteady state was derived, which was numerically simulated. The simulated results of aerodynamic parameters were verified by using the existing wind tunnel data. The simulation of unsteady state aerodynamic parameters can provide beneficial theory supplement for some difficult wind tunnel tests.
This paper presented the rendering method of galloping distribution map for transmission line based on the meteorological-geographical method following the frequency method and the galloping coefficient method. Based on the statistics and analysis on the icing galloping conditions of transmission line over the years, the meteorological model and geographical model were built for icing galloping, through the summary of meteorological and topographic features, laws. In combination with operation experience, galloping area partition and classification standard were put forward. The standard technical system of rendering method for galloping distribution map was established. Finally, this paper used the meteorological-geographical method to draw the galloping distribution map for some province, and inspected its matching with the actual situation, which could conclude that the method was reasonable and correct.
Along with the development of power grid construction, the wider application and deeper research of FRP （fiber reinforced polymer） materials on transmission lines are necessary. Based on previous researches of insulator cross arm, this paper completed the design and manufacture work of 110 kV composite cross arm without insulator, and achieve its safe operation in network. The test results prove that this cross arm can change the characteristics of traditional cross arm that needs insulator, and reduce the risk of windage yaw flashover； it can improve the disadvantages that human can not touch the insulator cross arm at silicone rubber umbrella skirt and it easy be attacked by birds and insects； meanwhile, it is not as brittle as porcelain insulator cross arm. Therefore, this new cross arm has more research prospect.
Along with the development of power grid, the high-low voltage electromagnetic loop network was formed in order to obtain the maximum transmission power and meet user demands for electricity, under the condition that the higher voltage network could not meet the request of power supply reliability. Through the analysis on the specific structure and electromagnetic loop network running problems in Jibei power grid, the districting power supply scheme in TangChengQin region was proposed. There are many 500/220 kV electromagnetic loop structures, coupled with heavy local load in TangChengQin region, so it is necessary to implement districting power supply in TangChengQin region, with considering the safety of power supply. Combined with the constructions of 500 kV, 220 kV power transmission and transformation projects in Jibei, the districting power supply scheme that Tangshan power grid was divided into five 220 kV power supply areas was proposed. By means of the calculation and analysis on power gird balance, short circuit current and reliability, as well as stability verification, it proves that the districting power supply scheme is feasible, which can provide a reference for the research work of districting power supply for Jibei power grid and other areas.
The potential distribution near the Yulongling electrode site within 10 km when a grounding line in converter stations sharing a DC common grounding electrode is being maintaining while the other one is under monopolar ground-return mode, has a directly relationship to the maintenance work of Chusui ±800 kV DC transmission engineering and Xingan ±500 kV DC transmission engineering. The potential distribution near the grounding electrode site was researched by using software CDEGS and the research results were compared with the actual measurements during the system debugging. The results show that in the above operating case, the peak distribution occurs above the electrode sites inner ring and outer ring, and the ground potential above the inner ring is higher than that above the outer ring, which decays rapidly. The step voltage peak is also at the rings but less than the design value, and the contact voltage can meet the limit requirement according to the standard measures. The actual measurements and calculated results are basically consistent except that the step voltage value in some area is high due to the low soil resistivity, so the maintenance operation in this area should take appropriate protective measures.
The starting current of large-capacity synchronous motor during direct starting is very large, which will cause the voltage of power grid dropping sharply. Therefore, the step-down starting mode of autotransformer was used for the starting of large synchronous motor. The system power flow calculation model with considering large-capacity motor was built, and the influences of the starting mode of large-capacity motor on the 110 kV power grid and the voltage of power supply system in user substation were analyzed. According to different capacities of system and the different starting modes of motor, bus voltage drop and starting process were simulated with using dynamic simulation software. The theoretical calculation and simulation results show that the large-capacity synchronous motor should avoid small mode of system operation during starting, which verifies the feasibility of reducing system voltage drop with using step-down starting mode of autotransformer. In addition, the simulation model can be used to determine the operation mode of the system during motor starting and the autotransformer taps during its step-down starting. In order to ensure the voltage quality of power grid, the step-down starting mode of autotransformer with appropriate taps should be used for the starting of large-capacity motor, compared with the direct starting mode.
The traditional dynamic model of wind farm based on single turbine dynamic model was a high order model, which was difficult to process the data of power transmission and calculate the capacity of reactive power compensation, so this paper proposed a new kind of equivalent modeling scheme of offshore wind farm for reactive power compensation. Based on the requirements of the national standard “technical rule for connecting wind farm to power system” （GB/T 19963-2011）, combined with the operational features of offshore wind farm systems, the wind turbines could be equivalent to current controlled voltage sources, the power transformer in multi generator system with reactive power loss of transformer was considered as a linear system, and the collection system was equivalent to a single branch according to the principle that the power transfer characteristics of the equivalent wind farms were the same as the real wind farms. Then, this paper established the model of offshore wind farm systems for reactive power compensation, and analyzed a specific offshore wind farm with simulation software PSCAD. The results verify the feasibility of equivalent model of offshore wind farm, which is simpler and more practical than the traditional dynamic model of offshore wind farm, and suitable for the design scheme of reactive power compensation for offshore wind farm.
Meteorological data of Yongxing weather station in Xisha from 1973 to 2011 were collected and analyzed. The annual mean wind speed, wind power density, utilization hour of specific wind turbine and annual energy output were calculated using Weibull statistical distribution and wind power curve of specific wind turbine. Combined with daily extreme wind speed data from 1973 to 2011, the extreme wind of 50-year recurrence interval was calculated using Peak over Threshold （POT） approach and Generalized Pareto distribution model. The analysis results show that the wind power density of Yongxing Island is less than expected, which is below 100W/m2 in a typical year, and it concentrates in the latter half of the year with more tropical cyclones, although the Yongxing Island is located in the deep sea. Moreover, the extreme wind of 50-year recurrence interval is 42.2 m/s, which is significantly higher than reference wind speed （27 m/s） on the land. Therefore, the wind turbine of higher class should be adopted in wind power development in Xisha.
Using a new type of flat heat pipe as efficient heat transfer components, which used paraffin wax as a heat transfer and storage medium, a new heat-pipe-type phase-change thermal storage heat exchanger was designed and manufactured, which added vertical fins on both sides of the flat heat pipe. A series of experiments for the heat storage-release properties of the phase-change thermal storage heat exchanger were performed: the temperature distribution variation of paraffin with time was measured； the effects of different fluid flow and heat storage temperature on the heat storage-release process were analyzed, with changing the fluid working conditions of heat storage-release. The analysis results show that the new flat micro heat pipe array plays a good role as enhanced heat transfer components of the phase-change thermal storage system in the heat storage-release process； in the heat storage process, the higher temperature of the heat transfer fluid, the greater melting rate of phase-change materials； in the heat release process, the heat release rate of thermal storage system gradually increases with the increase of fluid flow under the same fluid temperature. The experiment results show that the thermal storage system with new flat heat pipe has good heat storage-release property.
The combination of wind power and reverse osmosis is new ideas for the development of seawater desalination. The seawater desalination based on traditional desalination design is limited by fixed load operation with power supply stability, and can’t be adapt to the variety of energy supply. So a new modeling method for reverse osmosis seawater desalination was proposed based on wind power, which built the osmosis model of reverse osmosis seawater desalination, and could calculate the operation parameters of desalination system based on energy supply. Under the same operating conditions, the calculation accuracy of this method is as good as traditional desalination design method through the comparison of calculation results, so it can be applied in the design of seawater desalination system based on wind power.
For conventional cooling tower, one index thickening parameter was used respectively in the area above or below tower throat, which could determine the tower wall thickness. However, for large-scale cooling tower and indirect dry cooling tower, the wall thickness of tower down ring beam was much larger than that of conventional cooling tower. The index thickening method could not meet the need of the positioning design for the wall thicknesses of these towers. Therefore, this paper proposed the improved method for the positioning calculation of tower thickness, in which sectional treatment was used for the area below tower throat with increasing an index thickening parameter. Under the condition of tower stability, the improved method can effectively reduce the concrete consumption of cooling tower.
The corrosion environment of chimney in coal-fired power plant with wet FGD （flue gas desulfurization） belongs to strong corrosion grade. In recent years, there are some problems of short life and poor corrosion resistance performance in coating type or block type anticorrosion. In order to solve the above problems, and achieve the goals of reliability and economy, this paper researched and developed the anticorrosion system of hybrid polymer structural layer in integral lining of the steel chimney internal cylinder. Based on the application of the new materials of hybrid polymer structural layer, the material properties were determined through adhesive strength test, DSC thermal analysis test, etc. The overall spray casting in steel tube combined with the miscellaneous spray process of ‘three lines-four holes’ formed a thermostable, anticorrosion and firm layer completely coating the cylinder wall, which could improve the anticorrosion performance. The industrial application and the science & technology identification results show that: the quality of the anticorrosion system is reliable； the technology has reached the domestic advanced level as a whole. The hybrid polymer structural layer is suitable for the internal steel tube anticorrosion in a new chimney internal steel tube corrosion or the anticorrosion transformation of old chimney internal steel tube, and it can be equipped with the corrosion online monitoring system, which can realize the life cycle management.
