Abstract:Load aggregators (LA) face the uncertainty of load and price when they participate in load curtailment bidding (LCB) in power market. A day ahead optimization model with the objective of minimizing the agency cost of LA is proposed. In this paper, the power purchase, LCB and the control of adjustable load are described as a mixed integer linear programming model. A bi-level programming model is used to deal with the uncertain load, so as to the historical scenario method to uncertain price combined with scenario reduction. Based on the data of Pennsylvania-New Jersey-Maryland (PJM) power market, the proposed strategy is analysed. The results show that the proposed strategy and scenario reduction method can reduce the aggregators' agency cost by more than 4% and risks by more than 10%, improve the performance rate by up to 17.8%, and provide bidding technical support for the LA under uncertain problems.

Abstract:The current electricity transaction process in the electricity market has problems such as high risk, time-consuming, and low efficiency. In order to solve such problems, an improved smart contract electricity transaction model based on blockchain is proposed. The blockchain is a decentralized database with advantages such as non-tampering and encryption security. The blockchain has the advantages of decentralization and high securing. The blockchain and smart contract are applied in the proposed model to improve the efficiency and security of the electricity transaction process. Firstly, the existing problems of the current electricity transaction model are analyzed. Risk assessment is carried out. A decentralized electricity transaction scenario is constructed. Secondly, the reliability coefficient is combined with smart contracts to establish an improved smart contract electricity transaction model based on blockchain. Finally, the feasibility of the model is verified by simulating electricity transaction. The results show that the improved smart contract electricity transaction model proposed is more efficient than the existing transaction model. The model effectively reduces the risk of being attacked and maintain the power market transaction order, thus providing a new idea for the electricity market transaction mode.

Abstract:With the increasing development of China's electricity spot market, electricity retailers attract power users to participate in power demand response by designing electricity plans so as to improve the interests of both parties. In this paper, the coefficient of peak avoiding response is introduced. The incentives of electricity plans are formulated on the basis of time-of-use electricity price to attract power users to actively transfer their load. Firstly, according to the designed electricity plans, the load transmission is calculated after the power users choose the electricity plans. Secondly, considering the influence of the change of electricity expenditure and the change of electricity consumption mode on the user utility, a decision model of electricity plans based on the utility function is established to calculate the selection of electricity plans. Thirdly, four kinds of electricity plans with the goal of maximizing the profit drive of electricity retailers are designed based on the load transmission of electricity retailers participating in spot market transactions. Finally, it is verified that the optimized electricity plans meet the interests of both parties by the analysis of an example.

Abstract:Due to the large installed capacity of new energy and the shortage of peak regulation resources on the generation side, there is a serious problem of abandonment of wind and light in the new power system. To solve this problem, a spot market joint clearing mode with both sides of generation and customer participating in peak regulation is proposed in this paper. Deep peak regulation on the generation side, peak regulation with flexible load, new energy consumption and the spot market are combines in this mode, which fully explores the peak regulation capabilities on both sides of generation and customer. Firstly, a model with two parts is established in this paper. The first part is for day-ahead market and real-time market, and the other one is for both sides of generation and customer participating in peak regulation. Energy storage and power customers are regarded as customer side peak regulation resources in the model. Power customers are divided into flexible adjustment customers and non-flexible adjustment customers according to the ability to track real-time scheduling instructions. Secondly, the settlement and allocation mechanism of peak regulation auxiliary service are designed, considering the contribution and benefit degree of each market subject. Finally, the effectiveness and reasonableness for new energy consumption of the proposed market mode are verified by a calculation example. The results show that the market mode proposed in this paper reduces the amount of wind and light abandonment by 17.3% compared with the mode that only the power generation side participates in peak regulation.

Abstract:Large scale bilateral transactions may lead to extreme power grid operation mode. The trading results adjustion by post security check may affect the generation plans and increase the production and operation risks of market members. It is of great significance for the orderly development of power market in the medium and long-term to provide the security analysis service before the transaction process and guide the market members to revise the medium and long-term physical transactions. A new mode of medium and long-term electricity security analysis based on market members' transaction willingness is proposed. In the mode, a two-step security check process including centralized electricity security analysis and electric energy limitation calculation is established, and an optimization analysis model based on security-constrained unit commitment (SCUC) is developed. Through coordinating the multi-period optimal dispatching of power balance and power grid security, it is available to acquire the executable conclusion of electricity contract as well as the subsequent power tradable space. The case analysis based on actual data of provincial power grid shows the effectiveness of the mechanism.

Abstract:After the AC system is short-circuited, voltage source converter-high voltage direct current (VSC-HVDC) can be equivalent to a current source with a certain amplitude and phase. In this paper, based on the equivalent model of VSC-HVDC when the receiving end grid fault occurs, the factors affecting the phase and amplitude of equivalent current source of VSC-HVDC are analyzed respectively. Studies show that the phase of the equivalent current source is mainly affected by the type of fault, and the amplitude is mainly affected by the control method, the amplitude limiter and the electrical distance. Because of the combination of different situations, the influence on the AC system short-circuit current is bceorning more complicated.The research results show that for AC side three-phase short-circuit fault, the influence of VSC-HVDC on short-circuit current can be divided into four situations, which contain zero feed in, limited amplitude of active control link, limited amplitude of reactive power control link and reference value of reactive power control link. The simulation results based on PSCAD software verify the relevant analysis.

Abstract:The valve-side bushing of converter transformer bears AC-DC compound voltage, which has strict requirements on the performance and quality of the bushing. Under DC voltage, the accumulation of space charge at the interface of different medium causes the distortion of local electric field, and the existence of metal particles greatly increases the local electric field strength, both of which reduce the insulation performance of the bushing. In this paper, according to the structure of valve-side bushing of converter transformer, the simulation model of valve-side bushing is established by using finite element analysis software. The electric field distribution of the bushing under different types of voltage after adding space charge and the influence of metal particles on the local electric field are analyzed. The results show that the space charge at the dielectric interface is easier to accumulate under DC voltage, and the space charge is able to cause the distortion of the local electric field inside the bushing under AC-DC compound voltage. The degree of local electric field distortion of metal particles under DC voltage is greater than that under AC voltage, and the influence of metal particles on the degree of electric field distortion has little to do with its location in SF₆.

Abstract:With the frequent occurrence of extreme natural disasters, in order to make the supporting effect of distributed generation (DG) work, such as gas turbine and fuel cell, a microgrid formation strategy considering dynamic reconstruction under extreme natural disasters is proposed, which increases the value of controllable DG to support critical loads. Firstly, Wasserstein distance is used to calculate the similarity of load probability distribution. And each load is divided into different time scenarios. Then, the current state information of the line is read. And the constraints satisfying the formation problem of radial microgrid are established. Taking maximizing the load recovery value as the objective function, the method of mixed integer linear programming is used to solve the static optimal solution for the formation of microgrid. At last, combined with the state change of loads, the dynamic optimal solution is solved without the limit of reconstruction times to find out the moment of structure change. After that, the limit of the number of reconstruction times is taken into account, and the optimal plan is determined to maximize value of the load in the dynamic process. The results show that the dynamic reconfiguration based on Wasserstein distance improves the electric quantity value of the loads supported by distribution network in extreme environment.

Abstract:A wind speed prediction method based on the combination of multi-channel long short-term memory network and convolution neural network is proposed to improve the prediction performance of wind speed. The prediction model is composed of multiple long short-term memory sub-networks and convolution networks. Future wind speed values are calculated by each sub-network with the different input data length, which can avoid difficultly selecting the input data length in the single prediction network. Convolution and max-pooling operations of the calculation results of sub-networks are performed by the convolution network, and the prediction values of the wind speed are output by the fully connected layer of the convolution network. In order to overcome the accumulation and drift of prediction errors, the dynamic error compensation method is used to correct the prediction values. The network can be used in the ultra-short-term prediction of wind speed. Simulation results show that the network can better fit the variation trend of the actual wind speed series than the existing prediction networks based on deep learning, and the network shows better prediction performance.

Abstract:With the increasing energy required by data center, a soft switch power factor correction (PFC) circuit based on totem pole structure is designed to meet the urgent need of high performance index of converter. A soft-switching PFC circuit based on the totem pole structure that can achieve high efficiency and high power density is proposed. The bridgeless PFC topology is combined with the third-generation wide bandgap GaN device, and it is realized through a fully digital control method. The circuit is switched to work in two states of critical current and quasi-square wave to ensure that the converter has the power factor correction function and realizes zero voltage switch (ZVS). The basic circuit structure of the totem pole bridgeless PFC is first introduced. The conditions for realizing the soft switching characteristics are obtained through the analysis of the circuit transient process. Then the system power factor correction function is realized according to the all-digital double closed-loop control method, combined with mathematical simulation to analyze different states totem pole PFC output characteristics. Finally, an AC/DC converter with 220 V input and 48 V/400 W output is built. The results show that while the PFC function is implemented, it can maintain ZVS characteristics in the full input voltage range, verifying the feasibility of the circuit design and control strategy.

Abstract:In order to improve the recognition accuracy of different voltage sag disturbance sources and effectively control the voltage sag, a method of voltage sag source identification based on beetle antennae search (BAS)-back propagation (BP) classifier model constructed by longicorn BAS and BP neural network is proposed. In this paper, the improved S-transform is used to extract 16 characteristic indicators to form a voltage sag source identification indicator system. In order to eliminate the influence of redundant information on the classification results, 9 indicators are selected as the input of the classifier using the combination weighting method. By optimizing the initial weights and thresholds of BP neural network by BAS, the BAS-BP classifier model is constructed to identify different types of voltage sag sources in distribution network. The simulation results show that the classifier model has certain anti-noise ability and applicability, and has a better classification than the conventional classifier model dose.

Abstract:Research on the development mechanism of cascading failure and identification the critical line of evolution path is of great significance for exposing weak links in the power system and reducing the risk of cascading failures. For this reason, an identification method for critical lines of power grid based on fault chain clustering algorithm is proposed. Firstly, an improved direct current power flow simulator of power system separation (DCSS) cascading failure simulation model, which combines with the random chemistry (RC) method to efficiently generate fault chain set with detailed timing information is established. Then, the hierarchical clustering of the failure chain set is realized by using edit distance as the similarity index, and the classified fault chain set can not only reduce the difficulty of subsequent data mining, but also more comprehensively identify the weak links in different cascading failure evolution modes. Finally, taking the Matpower 2 383 node system as an example, the importance of the lines identified by various algorithms is evaluated through the reduction of the system risk level after the expansion of critical lines. The results show that the proposed method can better reduce the risk level of cascading failure, which proves the effectiveness of the proposed model and algorithm.

Abstract:The intermittency, volatility, and anti-peak shaving characteristics of wind power cause a large amount of waste of wind power, which affects its economic and environmental benefits. In view of the different characteristics of wind power, pumped storage and thermal power output, the internal and external two-layer model is used to solve the problem. A dual-objective model with the largest internal wind-storage combined operation income and the smallest fluctuation of wind power is established firslyt to determine the pumping power or generate power of the pumped-storage unit. Then, an outer target model that takes into account the wind power forecast errors of different confidence levels is bulit to maximize the combined benefits of wind-storage. Secondly, the cooperative operation of pumped storage and wind power is used to deal with the uncertainty of wind power. Then the chance-constrained programming is used to deal with the random variables in the model. Finally, the particle swarm optimization-genetic algorithm (PSO-GA) hybrid optimization algorithm is used to solve the model. The IEEE 30-bus system verifies that the model increases the economic benefits of the system and reduces the volatility of wind power output.

Abstract:In the past, the structures of conventional direct current (DC) and flexible DC transmission projects were end-to-end or multi-terminal radiation. The corresponding stability control system uses the converter electric quantity and pole emergency switch off (ESOF) signal as the criterion of pole blocking. It is not suitable for the application of flexible DC power transmission engineering with ring structure, because the DC converter blocking failure cannot be identified reliably. According to the development experience of stability control system of Zhangbei voltage source converter based high voltage direct current(VSC-HVDC) transmission project, a new improved method of DC pole blocking detection is proposed in this paper for stability control. This criterion adopts the characteristic signal of DC control and protection as the main judgment object when DC light load is applied, and adopts the characteristic signal of DC control and protection combined with the converter electric quantity as the main judgment object when the DC power is above 10% of rated power. The improved detection is applicable to both HVDC transmission projects and ring structure flexible DC transmission projects. At the same time, the calculation method of stability control measures of Zhangbei VSC-HVDC transmission project is proposed, which provides a reference for the application of subsequent flexible DC transmission projects and HVDC transmission projects. Theoretical analysis and real-time digital simulation system (RTDS) experiment verifies the reliability of the criterion.

Abstract:The polar environment is complex and diverse, with low temperature all year round and accompanied by polar night conditions. In order to rationally configure the capacity of the polar environment microgrid system, and improve the reliability of it, so China's Antarctic Scientific Research Station-Zhongshan station is regarded as the research object. According to the characteristics of the polar environment, a wind-hydrogen-storage microgrid capacity optimization model is proposed, that uses surplus wind power to produce hydrogen and is equipped with battery energy storage devices. Considering the real-time impact of low temperature on wind turbine output, battery capacity and electrical load, taking the minimum annual cost of systems as the goal, the loss of power supply probability as the constraint, the capacity of the microgrid power supply system in the polar environment is optimized. The simulation results of the example are to be proved that the wind-hydrogen-storage system can not only improve the system economy and reliability, but also effectively reduce energy waste.

Abstract:With the rapid development and wide range application of AC/DC distribution network,its stability has also become the focus. The low-frequency oscillation at the DC side in the commissioning stage of an AC/DC distribution network project is analyzed. Based on the small signal modeling,the eigenvalue analysis method is used to analyze the influence laws of short circuit ratio (SCR),power level and control parameters on low-frequency oscillation. Next,the measures of changing controller parameters and adding additional controllers to suppress oscillation are proposed. The theoretical analysis and simulation test show that weak grid affects the stability of voltage source converter (VSC). Low frequency oscillation occurs when the 375 V DC side power increases to exceed the rated power. The integral coefficient of the Buck converter current inner loop proportional integral (PI) controller does not affect the stability of the system,but it affects the oscillation frequency after the oscillation occurs. If the proportional coefficient of the voltage outer loop PI controller is too small or the integral coefficient is too large,the system is unstable. Changing voltage outer loop PI controller parameters of Buck converter and adding additional controller can effectively suppress low-frequency oscillations. The theory and simulation analysis of the actual AC/DC distribution network oscillation influence factors are of reference significance for the commissioning and operation analysis of other AC/DC distribution network projects.

Abstract:Aiming at the special grid operation situation of the isolated power grid, the electric load balancing device is used to establish a frequency modulation model considering the coordinated output of the load side and the generator side. The ETAP simulation platform is used to simulate and analyze the power system of an industrial park in Sulawesi. It is found that when the system suddenly throws a large load, compared to the generator's independent frequency modulation model, the frequency modulation model of the load end and the generator end can make the system frequency fluctuation smaller and the stable frequency closer to the rated frequency. When the system is connected to a large load, putting in the electric load balancing device in advance can prevent the system frequency from falling off a cliff, and split the frequency falling process to relieve the pressure on the equipment in the system.

Abstract:The pollution flashover of composite insulators is mainly the flashover caused by alternate occurrence of arc development and dry band formation. At present, researchers have investigated the development of insulator arc along the surface. However, the formation mechanism and process of the dry band have not been fully analyzed due to its stochastic property. In this paper, the generalized finite difference time domain method is used to calculate composite insulators' surface electrothermal coupling field. The dry band formation and arc development are modeled to study the mechanism of the dry band influencing arc formation and the optimization strategy of insulator dimensions. Meanwhile, the flashover experiment of composite insulators under contaminated conditions is carried out. The experimental results are compared with the simulation results to verify the accuracy of the simulation model. The results show that the generalized finite-difference time-domain method is suitable for multi-field calculations near the insulator for its effectiveness in reducing computational complexity. Furthermore, dry band is more likely to generate where is close to the electrodes of insulators. Therefore, probability of flashover is decreased by insulator geometry optimization with no changing the insulator's creepage distance.

Abstract:Zero-value insulator infrared detection method is widely used with the characteristics of precision, efficiency and safety, but its measurement results are easily affected by the relative humidity and pollution degree of the environment. The coupling model of electric-thermal-flow field of polluted insulator string is established, and the influence of zero value insulator position, environmental relative humidity and pollution degree on the temperature distribution of insulator string is analyzed. Then, an infrared detection method of zero value insulator based on adjacent temperature rise difference is proposed and verified by experiments. The results show that the continuous saddle temperature distribution of insulator stringcanbe destroyed because of zero value. The farther the insulator is from the rotating center shaft, the lower the temperature rise is, and vice versa. The maximum temperature rise appears at the connection between the iron foot and the lower surface. With the increase of environmental relative humidity and pollution degree, the overall temperature rise of insulator string gradually increases, and the temperature rise difference between zero value insulator and normal insulator gradually increases. The experimental results show that it is feasible and effective for the zero-value insulator detection in field with this method.

Abstract:The extrinsic Fabry-Perot interferometer (EFPI) optical fiber ultrasonic sensor can be used for the detection and pattern recognition of the partial discharge ultrasonic signal inside the gas-insulated switchgear (GIS). Compared with the traditional piezoelectric sensor, it has many advantages such as high sensitivity and strong anti-interference ability. Based on this, four typical partial discharge models of tip, metal particles, suspension and quay are set in the GIS cavity filled with 0.4 MPa SF₆ gas. The EFPI sensor is used to detect the discharge ultrasonic signal. The waveform characteristics of a single ultrasonic pulse signal are extracted to form a characteristic parameter database, and the probabilistic neural network (PNN) algorithm and the support vector machine (SVM) algorithm are respectively used for pattern recognition. The recognition results of the two algorithms are compared and analyzed. The ultrasonic signals detected by the EFPI sensor have outstanding features. Based on the extraction of feature parameters, the two pattern recognition algorithms can achieve an average recognition rate of over 85%, and the recognition rate of SVM is higher than that of PNN.

Abstract:The oscillation wave partial discharge test has been used more and more in the detection of cable insulation defects, but the background noise interference and discharge pulse matching affect the accuracy of partial discharge location. A partial discharge localization method based on ensemble empirical mode decomposition and Hilbert marginal spectral energy is proposed to locate cable insulation defects accurately under oscillating wave voltage. Firstly, the partial discharge pulse signal is extracted by moving window threshold method. Then, the ensemble empirical mode decomposition algorithm is used to decompose the signal, and Hilbert transform is applied to each component to obtain its marginal spectral energy value. The proportion of different eigen modal function components in the original signal marginal spectral energy value is selected as the characteristic quantity, the signal similarity is calculated to match the incident pulse signal and the reflected pulse signal, and finally the partial discharge location is carried out by the time domain reflection method. The vibration wave withstand test is carried out on 35 kV cable, and the detected partial discharge signal is located and calculated. The results show that the pro-posed method can realize the location of cable insulation defect under the condition of strong Gaussian white noise, and the average location error can reach 1.15%.

Abstract:False data injection attack is one of the important factors that threaten the safe and stable operation of power systems. The research on the methods of the attack against power systems can provide decision-making basis for the improvement of power system defense measures. Considering the operation characteristics of high voltage direct current (HVDC) converter station and AC-DC coupling characteristics, a false data injection attack method for AC-DC hybrid system is proposed. Firstly, the basic principle of state estimation of AC-DC hybrid systems is analyzed. Secondly, the attack strategy in AC-DC hybrid systems is proposed, and the attack model is constructed. Finally, the improved IEEE 30-bus system is taken as an example for simulation verification. The results show that the false data injection attack against AC-DC hybrid system can bypass the bad data detection algorithm and endanger the safe and stable operation of the system, which verifies the effectiveness of the proposed model and method.

Abstract:Fuel cell electric vehicles are an important development direction of new energy vehicles. As the core energy unit of the vehicle, fuel cell performance directly affects the economy, power and reliability of the vehicle. The ejector is an important functional element in the hydrogen circulation system of the fuel cell. Firstly, the ejector is designed and modeled based on the Sokolov design method. Then the flow field analysis of the ejector fluid is carried out. Finally, based on the analysis results, the key influencing factors of ejection performance are explored. The results show that under different pressure conditions, the ejection coefficient and the working fluid inlet diameter show a parabolic trend, and the ejection coefficient is positively correlated with the ejection fluid inlet diameter. The ejection coefficient first increases and then decreases with the increase of the mixed fluid outlet diameter. Based on the above-mentioned influence rules, the ejection coefficient is optimized, and the hydrogen return performance of the ejector is increased by 13.55%, which further improves the hydrogen utilization rate of the fuel cell, and further improves the ejector structure optimization and ejection characteristics research.

Abstract:The access of distributed generations (DGs) leads to the loss allocation problems of distribution network (DN) becoming more complicated. When the marginal loss coefficients (MLC) method based on the proportional coefficients is applied in DN with DGs, the allocation gap between market members is too large, leading to lack of rationality. Firstly, the absolute value of the positive and negative network loss allocation calculated by the proportional method are summed. And then, based on this sum, the network loss allocation of each load bus are recalculated. Secondly, considering the equality constraints between the total loss allocation and the actual total loss, the reward and punishment coefficients are used to increase the positive network loss allocations and reduce the negative network loss allocations. The reward and punishment coefficients are obtained by solving the constructed equations and applied to correct the initial network loss allocations. The improved method can avoid the offset of positive and negative allocation, reduce the allocation gap of members, and reasonably allocate the loss in DN. The results which are obtained by IEEE 33-bus system show that the proposed method can be used as a reference for loss allocation of DN with DGs.

Abstract:Due to the large-scale construction of ultra high voltage direct current (UHVDC) transmission projects, the demand for reactive power regulation at the receiving end of UHVDC is increasing day by day, so the synchronous condensers is applied in the power system. In order to solve the vibration problem caused by unbalanced load distribution of the synchronous condensers, a fault diagnosis method based on variational mode decomposition and multiple-kernel support vector machine (VMD-MSVM) for load distribution of the synchronous condensers is proposed. Firstly, several measuring points are arranged outside the bearing seat of the synchronous condenser to collect vibration signals. Secondly, according to the characteristics of the signal nonlinear and complicated composition, the vibration signal is decomposed into multiple intrinsic mode function by using VMD modal function. Thirdly, intrinsic mode function is selectd to reflect the characteristics of failure mode, and calculate the energy entropy to constitute feature vector. Finally, the appropriate kernel function is selectd to build a multi-kernel support vector machine, and the feature vectors are input to multi-kernel support vector machine for fault diagnosis. The experimental results show that this method is suitable for the fault diagnosis of load distribution and has better fault identification effect.

Abstract:If commutation failure does not occur when single-phase high resistance grounded in single-circuit AC line of inverter,then single-phase circuit breaker tripping may lead to commutation failure. Firstly,the expression of converter bus voltage after single-phase circuit breaker trip is derived by using symmetrical component method. Based on the expression,the main factors affecting the converter bus voltage are analyzed,and it is found that it is related to the equivalent parameters of the system. Then,the influence mechanism of voltage deviation angle of commutator bus on extinction angle is studied. It is found that the zero-crossing forward angle of commutation bus voltage after the single-phase breaker trips is the main factor leading to the decrease of the extinction angle,and commutation failure will be induced in serious cases. Finally,the AC/DC simulation model was built on the PSCAD/EMTDC electromagnetic transient simulation software platform. The simulation verifies the effect of the tripping of single-phase breaker in single-circuit AC line on the commutation process of inverter. The simulation results are consistent with the theoretical analysis.

Abstract:Power electronic transformer (PET) is the key equipment to realize the power conversion and routing of AC/DC hybrid distribution network, which can greatly enhance the flexibility and controllability of power grid. At present, PET with cascaded H-bridge (CHB) and series resonant dual active bridge (SRDAB) is widely used because of its modular structure and high efficiency. In this paper, a 1.5 MW 10 kV AC-750 V DC PET uesd in practical engineering is analyzed. Firstly, the different switching transient characteristics under the forward and reverse power flow direction are described, and the reasons for the difference are analyzed. Secondly, the current on the rectifier side of SRDAB only flows through the diode. Therefore, the switching loss of SRDAB can be reduced by locking the power semiconductor device on the rectifier side, so as to improve the efficiency of PET. Finally, the experimental test on the PET project site proves the correctness of the loss analysis and the effectiveness of the efficiency optimization method. Using the proposed method, the PET operation efficiency can be improved by about 0.2%.

Abstract:With its good performance, the deep learning model is introduced into the transient stability assessment of power system. However, when applying online, the anti-noise ability and generalization ability of the models must be paid attention to. A deep learning model based on stacked sparse denoising auto-encoder (SSDAE) is proposed for real-time transient stability assessment. The corrupted data is generated by adding white Gaussian noise to the original input data. Then, the high-order features are extracted from the corrupted data. Finally, the original data is reconstructed by using the high-order features. The anti-noise ability is greatly improved after training. Besides, the weights and the degree of activation of the hidden layer neurons are suppressed to achieve the sparseness of the model, which can improve the generalization ability of the model. The simulation results show that the SSDAE based model has good anti-noise ability and generalization ability compared to other machine learning algorithms.

Abstract:The operation mode and heat storage time of concentrating solar power (CSP) have a profound impact on the benefits of CSP in power system. It has an important impact on the development of CSP by the reasonable evaluation on the benefits. An equivalent annual cost method for comprehensively evaluating the capacity benefit and electricity benefits of CSP is proposed in this paper. The start-up and shutdown of the unit and the cross-day adjustment of the energy storage power supply are considered by this method. The production simulation for the system with CSP is carried out in 8 760 h. By comparing the changes of thermal power installation demand and system coal consumption before and after the CSP is put into operation, the capacity benefits and electricity energy benefits of the CSP are evaluated, and then the national economy of the CSP is evaluated. Finally, the effectiveness of the proposed method is verified by the simulation of the actual power grid in northwest China. The results show that the national economic benefits of CSP are related to the investment of CSP, the way of peaking, the hour of heat storage and the scale of new energy power generation. The national economy of CSP participating in peak-shaving operation is better than it doesn't.

Abstract:The short-circuit current value of distribution network is small when high impedance grounding faults (HIGFs) occur,which cannot be detected tripped by the traditional over-current protection devices. If short-circuit cannot be tripped in time,it will lead to serious results. To solve the above problems,the fault components of microgrid in the operating conditions of HIGFs are analyzed. The phase differences characteristics between positive-sequence fault component of bus voltage and positive-sequence current fault components in the feeders are explained in detail. And based on the phase differences characteristics,the fault criterion for HIGFs in distribution network is proposed. Meanwhile,to overcome those problems caused by the imbalanced distribution network,the starting criterion is proposed. Based on the above fault criterion and the starting criterion,the new fault detection method is proposed. Finally,a medium distribution with the model of overhead lines is established in PSCAD/EMTDC,and simulation results verify the correctness of the fault detection method.