Abstract:In a multi-energy collaborative system, cooling, heating, electricity and other energy sources are coupled to complement each other. Through multi-energy coordination and solidarity, their operating efficiency and economic benefits can be significantly improved. Demand response as a multi-energy supply-demand balance method can further improve system flexibility and economy, and electricity demand response as a viable method has been implemented in multiple provinces. In order to clarify the impact of electricity demand response on the optimal operation mode of multi-energy cooperative system, a multi-energy cooperative system optimized operation model that considers market-based elastic price-type demand response is proposed. Firstly, the main components of the multi-energy collaborative system is analyzed, based on the energy hub model, the multi-energy coupling characteristics are studied, and a price-based demand response model based on market elasticity is constructed. Based on this, an optimal operation model is established to minimize the daily operation cost of multi energy collaborative system. Finally, combined with actual case calculation analysis, it is verified that the adoption of price-based demand response measures can be significant to improve the economy of multi-energy collaboration systems.

Abstract:The development of electricity to gas technology alleviates the phenomenon of abandoning wind and light, and strengthens the coupling between power grid and natural gas network. On the premise of safety, the produced hydrogen is mixed into the natural gas pipeline network for long-distance transportation, which makes the natural gas network become a porter of renewable energy, fully alleviates the contradiction between energy supply and demand in time and space, and improves the energy utilization rate and system economy. In this paper, the economic analysis model of hydrogen doped electricity gas integrated energy system is established. Taking a certain electricity gas integrated energy system in Central China for an example, the economy performance of the system under different hydrogen blending ratio is analyzed compared with the local hydrogen storage system with different hydrogen storage capacity. The results show that both hydrogen blending and local hydrogen storage can improve the economy performance of the system, and the benefit of hydrogen blending is better than that of local hydrogen storage, but hydrogen blending leads to the increase of the cost of power grid side and the benefit of gas network side at the same time. In actual operation, it is necessary to comprehensively consider the gas price pricing strategy and the gas network structure of the system in order to select the best maximum hydrogen blending ratio, so as to achieve the optimal economy of the system.

Abstract:Considering the continuous electricity and heat load growth of integrated energy, as well as the rapid development of power sources such as combined heat and power(CHP) and wind turbine, an optimization model that considers the integrated demand response of electricity and heat is proposed. Firstly, the dispatchable value of electric load and thermal load are analyzed on the load side and a real-time electricity price model is established for electric load. The model is adjusted by price-based demand response. The transmission delay characteristics of thermal load are taken into account and auto regression moving average(ARMA) model is used to describe. The fuzzy comfort characteristics of heat load are taken into account so that the thermal load is flexible. It is the thermal demand response. Based on the two response modes, the electric and thermal loads are adjusted to increase the space for wind power to connect to the grid. Secondly, electric boilers and heat storage devices are added on the source side. They increase the flexibility of the system and decouple the rigid demand of CHP "power determined by heat". Finally, minimizing the daily operating costs and wind abandon costs of the system is the target. CPLEX in Matlab is used to solve the model. The calculation example shows that the method can significantly improve the absorption capacity of wind power, which can reduce the operating cost of the system and improve the efficiency of energy utilization.

Abstract:Distributed integrated energy microgrid has the typical characteristics of cold/heat/electricity/gas multi energy coupling. How to optimize the operation of the combined cooling, heat and power supply and a variety of energy storage equipment has been one of the key and difficult research work at this stage. In this paper, the model of energy storage equipment and combined cooling heating and power(CCHP) system are established, which are based on the constraints of balance equation of electricity/cooling/heating and flue gas waste heat utilization, charge and discharge of energy storage equipment, upper and lower limits of each equipment in the system, the comprehensive operation optimization objective is operation economy and total CO₂ emission in one operation cycle by configuring weight coefficient. A typical scenario of a university town is constructed, taking the cold storage equipment as an example, the capacity of energy storage equipment are 0 MW, 2 MW, 4 MW, and the influence of energy storage capacity on the operation optimization of distributed energy microgrid is analyzed. With the appropriate capacity of energy storage equipment, the lower the comprehensive operation optimization goal in a cycle, the better the requirements of economy and environmental protection can be considered.

Abstract:Under the increasingly severe global energy situation, the traditional single power system energy structure has been unable to meet the needs of development. With the rapid development of power-to-gas(P2G) and gas turbine technology, the connection between the power system and natural gas system becomes closer. As the basis and key of coupling analysis of the power-gas system, the study of energy flow calculation is ofgreat importance. Firstly, the mathematical models of power system and natural gas system are analyzed. Aiming at the problem of choosing initial pressure value in natural gas system which is difficult to be solved in Newton method, the particle swarm optimization(PSO) is proposed to optimize the initial pressure value, and then Newton method is used to solve the energy flow of the power-gas integrated energy system(IES). Finally, the feasibility and accuracy of the proposed method are verified in the power-gas coupling system composed of IEEE 14-bus power distribution system and 14-node natural gas system.

Abstract:In view of the problem that the energy storage device equipped with photovoltaic(PV) in the community has limited capacity and single operation mode, the energy storage device and virtual energy storage generated by linepack reserves and controllable load of air conditioning are combined into an energy storage system. The technology to coordinate the control of the energy storage system under three modes are proposed, including smoothing PV fluctuation, smoothing grid active power fluctuation and peak and valley electricity price arbitrage. In the mode of smoothing PV fluctuation and smoothing grid active power fluctuation, the wavelet packet decomposition is used to obtain the reference instruction of virtual energy storage output power. The instruction of virtual energy storage output power is determined according to the state information of air conditioner, gas pipeline and so on. The energy storage device is selectively used as the backup of virtual energy storage according to the state of S. In peak-valley electricity price arbitrage mode, the energy storage device is used to charge and discharge during idle period combined with time-of-use electricity price information. Three modes are coordinated to realize source-storage-losd energy management. The output power of the energy storage system under different mode combination is obtained by Matlab simulation, which verifies the correctness and effectiveness of the control technology.

Abstract:With the development of integrated energy system and the deepening of power market reform, the production and marketing of power and heat are getting closer. Building a healthy and efficient market has attracted more and more attention. Firstly, a combined power and heat market is constructed based on Stackelberg game theory. The independent energy trading center is responsible for organizing transactions between energy suppliers and users and clearing the market. Then, based on the proportional sharing principle, a nodal heat price calculation method is proposed considering production cost and pump operation cost. The thermal loss occurred in the transmission is considered by modifying the thermal demand function of users. An interactive iteration algorithm is proposed to solve the optimal equipment output, nodal power price, nodal heat price and integrated demand response. Finally, the detailed solution process is shown in the case study, which reflects the validity and practicability of the proposed model.

Abstract:In order to solve the problems of low standardization of power grid security and stability control device (SSC) and nonstandard operation management of power grid security and stability control system (SSCS) and lack of standard basis for the application of new technology of SSCS, it is necessary to make a comprehensive analysis of the current SSCS standard system and study the adaptability of the SSCS standard. Fristly, the standard system architecture of SSCS is described, including design and development, network access management, maintenance inspection and operation management. Then, the current situation of SSCS standard system is classified and interpreted, the typical standards for each aspect are introduced, and the development status of standards in each link and the problems in practical application is discussed. Finally, combined with the new requirements of power grid development for SSCS and the new problems in actual operation and management of SSCS, it puts forward suggestions for improving the standard system of SSCS, which has guiding significance for the future revision of relevant standards of SSCS.

Abstract:In order to solve the problem of boundary data fluctuation influence on the security check result caused by new energy and load forecast, security check method based on extreme scenario analysis is proposed for the long and medium-term power market. The volatility boundary data is divided into two categories, namely positive data and negative data, according to their forecast deviation influence on the security check result. On this basis, the extreme scenario of long and medium-term power market is defined, compared to the traditional deterministic security check method. Based on the multi-period unit commitment model, long and medium-term security check method for extreme scenario is constructed, which can quantify the expected execution of the transaction quantity of different power generation enterprises. Finally, case study based on the actual data of a provincial power grid in China shows that extreme scenario analysis can effectively identify operation problems which are difficult to detect under the basic scenario. The results show that the proposed method can identify the execution deviation of long and medium-term power transaction under extreme scenarios more accurately and is suitable for provincial power grids with high proportion of new energy access to improve the feasibility of transaction verification results.

Abstract:The protection relays such as transformer relay, busbar relay and so on are installed outdoors which adopt the distributed architecture. And the ring network communication mode is adopted among the distributed slaves. Testing ring network messages is difficult. A new test device is designed and developed, which can fulfill function test of ring network. The device adopts dual central processing unit(CPU) architecture. The master CPU is responsible for testing process management. The slave CPU is responsible for testing the data exchange of ring network. The device can build the ring network messages by configuration file. The devide can finish the following test function, including delay characteristics, data consistency, forwarding characteristics and abnormal message simulation. The reliability and real-time in the actual transmission process of ring network messages can be checked and it can be taken as supplement for the ring network performance test. One device can fulfill function test and performance test of all distributed slaves. The device has been used on-site widely and provides good test method for the protection relays installed outdoors.

Abstract:Concentrated solar power plant(CSP) with thermal storage system has good flexibility and schedulability, which can effectively improve regulation level and renewable energy accommodation of power system. Firstly, based on the operation mechanism of CSP with thermal storage system, the operation model of CSP with heat storage and electric heater is developed to describe the energy conversion characteristics and operation constraints of CSP. Furthermore, with the aim of minimizing the comprehensive cost of the system, considering the operation constraints of the system, the optimal dispatching model of power system with large-scale wind power and CSP is proposed and solved by optimization software CPLEX. The model comprehensively considers reserve capacity provided by CSP, operation stability and economy of the system, for which the optimal day-ahead scheduling strategy is obtained. The feasibility and effectiveness of proposed method are verified by example results of IEEE 39-bus system.

Abstract:Spatial load forecasting is of great significance to the planning and construction of distribution network. In order to improve the accuracy of spatial load forecasting of distribution network, based on extreme learning machine, a spatial load forecasting algorithm is put forward in this paper. The parameters of the particle swarm optimization mode are adopted. Firstly, the load is classified according to the property of land use. Then, the FCM algorithm is used to carry out cluster analysis for each type of load and a refined load density index system is established. Next, the training samples are carried out with the extreme learning machine to improve the accuracy of prediction, which selected according to the characteristic indexes of the plots to be predicted. The example is simulated by the search data. By comparing with the relative error without the introduction of FCM algorithm, the relative error without the introduction of PSO optimization algorithm and the relative error with the adoption of PSO-ELM algorithm, it can be obtained that the PSO-ELM algorithm proposed in this paper has a high accuracy and meets the requirements of practical engineering.

Abstract:Sectionalizing strategy for the blackout power system could restore the isolated sections of the system in parallel and accelerate the whole restoration process. But the effect of the partition result having on the subsystem restoration is not taken into account in current researches. Due to that it is difficult to establish the partition optimization model considering the subsystem restoration time directly, the optimization strategy based on the rough set theory is proposed, adjusting the partition result achieved by using spectral clustering algorithm. The restoration time duration is the objective function of optimization model and also the index to evaluate the island restorations. The decision table with uncertainty based on rough set theory is used to filter and adjusts the units to achieve the optimal partition result. IEEE 39-bus system and IEEE 118-bus system are used to test the effectiveness of the proposed methodology.

Abstract:Both parallel transformer and series transformer are core AC devices of unified power flow controller(UPFC), and special operating conditions of UPFC can easily affect transformer differential protection, which is the main protection for these two types of transformers. The differential protection could have various manifestations under different operation conditions and varied faults. In order to evaluate the affection for differential protection from different kinds of faults, the factors that may impact the sensitivity and reliability of differential protection are discussed when faults happen based on the control system of actual UPFC project. According to the simulation results of typical internal and external faults, the behavioral characteristics of differential protection are analyzed, and the adaptability analysis of differential protection is formed as well. The relationship between valve control protection and AC relay protection in aspect of protecting equipment are also discussed. A technical reference is provided for the implementation of AC relay protection of the UPFC project in terms of anti-misoperation and anti-rejection.

Abstract:In distributed generation systems, constant power (PQ) control is often used in order to transmit energy from wind energy and photovoltaics to the micro-grid unit as efficiently as possible. When the micro-grid system is operating with a non-linear load, in order to ensure the quality of the incoming network current, the harmonic suppression function is added to the traditional PQ control strategy, that is, the PQ control and the active power filter (APF) function are combined into one. A multi-function grid-connected inverter with APF function is formed, which not only transmits active power to the grid, but also achieves the purpose of compensating for harmonics. This paper starts with the grid-connected inverter and analyzes its working principle and PQ control strategy. Based on this, the harmonic suppression function is added and explained in detail, mainly including harmonic detection based on instantaneous reactive power theory, and multi-resonant controller section. Finally, simulation and experiment verify the correctness and feasibility of this control strategy.

Abstract:Accurately determining the relative position of the voltage sag disturbance source is significant for defining the responsibilities of both the power supplier and the consumer and the subsequent formulation of governance measures to improve power quality. Method for demarcating voltage sag disturbance source of distribution network based on phase comparison principle of positive sequence current fault component is proposed. Positive sequence fault component equivalent networks are established when different types of fault occur in different locations. Then the correlation between phase distribution of positive sequence current fault components and fault locations of all incoming and outgoing lines in substation are analyzed. Finally, the demarcation criterion and action boundary of the method for demarcating voltage sag disturbance source based on phase comparison principle of positive sequence current fault component are constructed. The method divides the disturbance source of the voltage sag, and only uses the current measurement information of the incoming and outgoing lines at the station. The measurement information is easy to obtain and has good engineering application prospect. The effect of voltage sag disturbance source demarcation is verified by modeling and simulating based on PSCAD when short circuit faults, phase jump and load disturbance occur.

Abstract:Supplied by medium-voltage-DC power source, the AC-DC hybrid microgrid derives a stable AC-DC system voltage which ensures the parallel-operation stability of the multiple converters. The distribution network is configured with energy router to build low-voltage AC-DC system voltage and provide power to the AC-DC loads. Under the premise of ensuring fault isolation of the AC and DC systems, energy router can achieve two-way power transmission of AC and DC power supply, which enhance the consumption of multi-source and improves the reliability of microgrids. A system topology of the low voltage AC-DC hybrid microgrid based on the universal energy router technology is proposed, and the port configuration and control mode of the energy router are optimized. The multi-source parallel control strategy is studied, which effectively improves the stability of multi-source parallel operation. Also the control strategies including primary regulation, secondary regulation and fast conversion of converter control modes, can effectively enrich the operation modes of the distribution network and optimize the consumption path of new energy sources such as photovoltaics and wind power.

Abstract:With high penetration of distributed generation and electric vehicle loads integrated into distribution systems, the safe and economic operation of power system has met an enormous challenge. Based on this background, traditional planning model of distribution system is modified which makes it applicable to the coordinated optimization of distributed generation and electric vehicle charging stations. With the uncertainties of renewable resources represented by time-sequence multi-state models, coordinated allocation model aiming at minimizing total network losses of distribution systems is constructed which subsequently implements an equivalent process on the proposed model through second-order cone relaxation. To verify the effectiveness of proposed model, IEEE 33-bus distribution system is used as the test system. The results demonstrate that the presented method can effectively involve the uncertain characteristic of renewable resources in the coordinated planning problem and thereby meets the practical application requirements.

Abstract:Silicone rubber composite insulator has the advantages of high mechanical strength, excellent antipollution flashover performance, light weight, convenient operation and maintenance. It has been widely used in power grid construction. As silicone rubber material has excellent hydrophobicity and hydrophobicity mobility, its surface can still maintain good antifouling flashover ability after contamination. In some industrial areas, there is special industrial dust pollution, and the special industrial dust pollution in such areas has obvious impact on the performance of composite insulators, which makes the composite insulator surface in operation more prone to fouling. After fouling the hydrophobicity of the insulator surface is significantly reduced and the insulation performance is weakened. In order to study the natural pollution characteristics of composite insulators in special industrial dust areas, the composite insulators operated in a special industrial park in Jiangsu are sampled to study the pollution characteristics. The results show that the surface contamination of composite insulators operating in this area is generally heavy, the density of pollution equivalent salt is high, and the soluble salt components of pollution are mainly CaSO₄ and Na₂SO₄. The main components of insoluble ash are C, O, Si, containing carbon powder, SiO₂, CaO and other substances, which affect the surface conductivity and absorption of insulators.

Abstract:Oil-paper insulation structure equipment often has yellow waxy deposits when it disintegrates. It is called X-wax because it does not have a fixed chemical formula. X-wax will generate a large amount of gas during the formation process. After formation, X-wax will adhere to the insulation paper and enter the pores to increase the dielectric loss, resulting in an increase in overall loss and a rise in local temperature. However, there is no detailed report on the mechanism of X-wax production. Based on molecular dynamics, the first step of the X-wax production process is simulated:the generation of free radicals, and a mineral insulating oil simulation model containing 30 molecules is established. The free radical generation in the oil model is simulated based on the ReaxFF force field at 473 K, 393 K and 373 K and the first free radical generation at each temperature with the generated trajectory file is captured. During the simulation process, it is found that the carbon-hydrogen bonds on the naphthenes are easily split into two free radicals, and the recombination between the macromolecular radicals could form X-wax, and the hydrogen radicals interacted to generate hydrogen. Through the analysis of the temperature curve, it is found that within the simulated temperature range, the free radical generation rate and temperature are positively correlated.

Abstract:Existing detection techniques for partial discharge based on transformer bushings have low sensitivity and cannot detect timely, while ultra-high frequency(UHF) technology has high anti-interference ability and can achieve contactless detection. UHF detection technology for bushing partial discharge detection method is proposed. A 35 kV bushing partial discharge simulation model is established and a partial discharge test is performed for different types of defects. The conclusions include that both oil-impregnated paper amid the capacitances and the oil channel are effective paths for UHF electromagnetic wave propagation. Transverse magnetic wave(TM) is greatly attenuated during the propagation process(from -16 dB to -5 dB). The initial component of the transverse electric wave(TE) is less than 1% and the main component is the transverse electromagnetic wave(TEM). The main energy in the UHF band concentrates in the lower frequency domain, and the partial discharge of different defect types of the bushing corresponds to different characteristic spectra. The contactless UHF sensor of the bushing can realize the live detection of the bushing, thereby ensuring the safety and reliability of the power transformer operation.

Abstract:Dissolved gas analysis (DGA) in transformer oil is an important way to monitor the state of transformer equipment. CO, CH₄ and C₂H₂ are the representative dissolved gases in transformer oil. Based on the density functional theory, the optimal adsorption site of the transition metal atom Pt on the surface of WSe₂, one of the typical layered transition metal disulfides (LTMDs), is determined in the beginning. The adsorption behavior of these three gases on the surface of Pt-WSe₂is attained. The optimal structure of gas adsorption, charge transfer, adsorption energy, electronic density of states (DOS), deformation charge density (DCD), and frontier orbital are analyzed. As an electron acceptor, Pt-WSe₂ attracts electrons from all three gas molecules. The adsorption type of CO and C₂H₂ molecules is chemisorption, which means that the adsorption effect is strong. CH₄ adsorption is physical adsorption and the adsorption effect is weak. The adsorption of all the three gas molecules leads to an increase in the band gap of the Pt-WSe₂, resulting in the increase in the resistivity. The potential of applying Pt doped WSe₂ modified material to the detection of typical dissolved gas in transformer oil is explored and a theoretical basis is provided.

Abstract:Due to the shortage of transmission corridors, the construction of overhead transmission lines in China is often parallel or cross-erected with oil and gas pipelines. Electromagnetic interference and the pipeline's safety and protection of "two lines and one place" have become research hotspot. However, few studies are on the induced overvoltage of neighboring pipelines when lightning strikes transmission lines. The electromagnetic analysis software CDEGS is used to simulate the influence factors and protective effect of overvoltage induced by lightning of the pipeline anticorrosive coating when the transmission line tower is close to the oil and gas pipeline. A simplified model of the tower and pipeline is established. The distance between the line and pipeline, geological conditions and the structure of the grounding grid of the tower are simulated and analyzed. Corresponding construction suggestions for pipeline overvoltage protection are given. The research results provide reference for the construction and reconstruction of "two lines and one place".

Abstract:With the development of the electric vehicle dynamic wireless charging technology, aiming at the current incomplete theoretical work of dynamic wireless charging modeling, dynamic charging load model is established according to road conditions, and different power is assigned to different vehicles through clustering of EV models and states, so as to complete the establishment of dynamic charging load. Wavelet neural network is used to process and predict the timing sequence information, and then combined with back propagation neural network to predict the traffic flow on the charging road, and the short-term traffic flow forecasting accuracy is 85%. Fuzzy C-means algorithm is used to divide the charging type of EV and the charging power corresponding to the type, and the EV entering the charging road is divided into 7 types. The corresponding charging power is allocated according to various charging types to complete the daily load modeling.

Abstract:In order to ensure the safety and stability of the power grid and the efficient operation of the power market, grid dispatchers and power market participants have put forward higher requirements for the accuracy of power load forecasting. However, the distributed power and intermittent loads increase the difficulty of predicting loads accurately. In order to solve the problem that the current load forecasting method cannot simultaneously model the change law of the load itself and its influencing factors, load forecasting method based on long short-term memory(LSTM) is proposed. LSTM is used to construct recurrent neural network(RNN), and comprehensively historical load and various load influence factors are considered to establish load forecasting model. The method utilizes the feature extraction ability of the neural network and the memory ability of the LSTM to identify the internal variation law of the load and the nonlinear influence of various influencing factors on the load in a longer historical time range. The actual load datas are used to verify the prediction performance of different historical time windows and different network architectures. Meanwhile, compare with other load prediction algorithms. Experimental results show that the model can improve the accuracy of load forecasting.

Abstract:Coordinated charging of electric vehicles (EVs) is becoming an important topic for the smart demand management. Traditional model-driven methods are highly dependent on the accuracy of models for charging behavioral characteristics. However, affected by the strong stochastics of related parameters, etc., the selection of relevant models cannot fully reflect their uncertainties. Considering that the data-driven model-free reinforcement learning algorithms has the advantages of not relying on pre-modeling, and adapting to data samples with strong nonlinear relationships, it is proposed to be applied to optimize the charging loads of the EV charging stations. In the Markov decision process customized for the satisfaction of EV charging need, both a charging completion degree index and a penalty term for user's charging satisfaction are introduced to improve the policy evaluating function. Specifically, in order to guarantee the computational speed underneath the volume of charging data, the temporal difference learning algorithm is used for the training with incremental updates. The simulation is carried out with the real-world data from one charging station. Results show that the proposed algorithm can accurately and quickly calculate the coordinated charging schedules without the pre-modeling for the EV charging behavior parameters.

Abstract:The stator of doubly-fed induction generator-based wind turbine (DFIG-WT) is directly connected to the power grid, and the rotor of DFIG-WT system exchanges power with main grid via a back-to-back converter. The power electronic switches of back-to-back converter are prone to open-switch fault, which affects the stable operation of the system. A deep belief network (DBN) based fault diagnosis method for the open-switch faults of converters of DFIG-WT system is present in this paper. Firstly, the output response of DFIG-WT system with single and double switch faults of rotor-side converter (RSC) and grid-side converter (GSC) is analyzed. Based on the open-switch fault data of DFIG-WT, multilayer restricted Boltzmann machines (RBMs) are constructed to extract the deep information of rotor currents and grid currents under various fault and operation conditions, which fully takes advantage of excellent pattern recognition ability of DBN to improve the fault diagnosis accuracy. The simulation results indicate that the proposed DBN based fault diagnosis method is able to precisely detect the single and double open-switch faults of DFIG-WT system.

Abstract:Thermal runaway and fire extinguishing are both urgent problems in large-scale applications of lithium iron phosphate battery (LFP) modules. In this paper, the thermal runaway characteristic of a single LFP module and a cluster of LFP modules are studied under constant current overcharge mode. Water mist is used as a fire extinguishing agent to study its fire extinguishing effect on single and cluster LFP modules. The experimental results show that the temperatures of the modules in the cluster rise sharply after combustion, with a temperature rise rate of 42.74℃/s in the first 18 s. The peak temperature is nearly 1 000℃, which is significantly higher than that of the peak temperature of the single module (600℃). After 100 seconds of continuous spraying of water mist, the temperatures of all the modules drop rapidly, and the fires are completely extinguished without reignition, thus proving that the fire extinguishing effects by using water mist are satisfactory. Above results provide an effective theoretical and experimental support for the safety and fire extinguishing of the LFP-based energy storage power station.

Abstract:High-voltage gas insulate switchgear(GIS) shell circulation is the main cause of operating losses in substations. Circulation can cause the device to heat up. If the substation is operated for a long time, the transmission capacity of the power system and the insulation performance of the equipment will be seriously affected. The purpose of this article is to simplify the loss calculation procedure and improve the calculation accuracy of GIS shell circulation and the efficiency of engineering designers and on-site operation and maintenance. The basic theory of high current bus and engineering electromagnetic field is applied. Based on the principle of hollow current transformers, an equivalent model of GIS shell circulation is established. For steady-state operation of 550 kV GIS and short-circuit fault conditions, circulating currents of shells, short wiring, and grounding wires at different locations are calculated. The circulation and loss distribution rules are given. The calculation results show that when the 550 kV GIS is in steady-state operation, the short-circuit circulating current value at the inlet and outlet ends is greater than other locations; the current value at the fault point near the ground wire is the largest in the fault state; the calculated current of the ground wire and the short wire is greater than the measured value, mainly it is caused by the distribution of grounding resistance. The total loss of GIS system is given through calculation, which gives theoretical guidance for the actual operation of GIS.

Abstract:UHVDC is more and more widely used in power grid, and multi-HVDC is adopted to connect the sending and receiving power grids. When one HVDC fault occurs, emergency power support is realized by runup other HVDC. In the case of weak receiving power grid, when one HVDC needs runup greatly, commutation failure will occur if the traditional extinguishing angle control strategy is adopted on the inverting side. Therefore, the causes of commutation failure and the influence of AC system strength and runup amount are analyzed. Then, an improved extinguishing angle control strategy on the inverter side is proposed, which introduce extinction angle measure value into the controller and realize closed-loop control, so as to ensure commutation margin and avoid commutation failure. Then experimental verification is carried out on RTDS simulation system, and test results show that the proposed strategy can solve the commutation failure problem when runup HVDC with weak receiving end greatly.

Abstract:Bonus incentive is an important means to stimulate the value creation ability of talent team and realize the high-quality innovation development of science and technology enterprises. Regarding the specific implementation measures of bonus incentives for state-owned technology enterprises. Firstly, the implementation policies of bonus incentives for technology enter-prises in China are sorted out, and then the implementation points of bonus incentives for posts and project income, principles and constraints of bonus incentives, total project incentives are analyzed. In-depth analysis and research on individual incentive calculation models and other aspects are given, and incentive distribution calculation models and specific implementation suggestions are given. Only by strictly fulfilling the democratic decision-making procedures, achieving compliance, fairness and transparency, insisting on creating more dividends, and avoiding egalitarianism, the target effect of dividend incentives for technology-based enterprises can be achieved. The suggestions in the article can provide reference and reference for the specific implementation of medium and long-term bonus incentives for Chinese technology enterprises.