Demand-side adjustable resources and demand response markets have multi-time scale characteristics, and with the reduction of decision-making time scales, the accuracy of load forecasting increases and the uncertainty of response decreases. In order to fully combine the advantages that long-time-scale decision-making can fully call various adjustable resources and short-time-scale decision-making with less uncertainty, this paper proposes a demand-side adjustable resource aggregation response strategy based on multi-stage decision-making. Specifically, a multi-stage demand response decision-making framework is constructed, a demand-side adjustable resource aggregation response model is established, and a multi-stage demand-side adjustable resource aggregation response model is formed. Based on this, the objective function considering aggregated response income and response deviation is set for each stage decision, and the solution strategy is designed based on the branch and bound method, forming a demand-side aggregated response strategy is proposed based on the branch and bound method. Finally, an example is used to compare the response effect of the demand response strategy applying single-stage decision-making and the strategy proposed in this paper, and it is verified that the strategy proposed in this paper can effectively improve the aggregate response capacity and response accuracy of demand-side adjustable resources.

The coordinated optimal operation of transmission and distribution networks is a promising solution for optimally allocating the generating resources in multi-level power grids and accommodating large-scale distributed renewable energy. However, for the coordinative operation models of transmission and distribution networks, the traditional iteration-based solving approaches have great limitations in computational performance and institutional mechanisms. Thus, a coordinative optimal operation method of transmission and distribution networks based on multi-parametric programming is proposed, in which the operational information of distribution networks is completely characterized. The proposed method has great numerical calculation stability and it is compatible with the current dispatching management mechanism. Case studies are presented to verify the effectiveness of the proposed method and discuss the influence of various factors. The results indicate that the synergistic effect of transmission and distribution networks is realized, and the optimalized dispatch results is satisfied. Meanwhile, the increase in wind power penetration level and installed capacity in distribution networks can both help to reduce total operation cost.

Aiming at the problems of unreasonable micro-service splitting, poor reliability and bottleneck of large-scale data processing in the traditional scheduling cloud data integration architecture, a general distributed architecture solution based on the scheduling cloud platform is proposed. Firstly, the typical architecture of cloud platform is constructed, and the cloud platform components are effectively integrated with the actual business system based on the cloud computing concept.Secondly, the key distributed technologies are explored and studied, including metadata based file distributed storage, multi-executor distributed task processing center, data agent based distributed database storage, business module distributed deployment and other architectures. A comprehensive load scheduling algorithm based on exception task recovery mechanism is proposed. Finally, the efficiency of massive data processing, processing and access, and the performance of the system under high concurrency scenarios are improved under the proposed distributed architecture through real scenarios verification.

Aiming at the problems of small unit power, heterogeneity of battery capacity and different travel behavior of electric vehicle (electric vehicle, EV) users, a charging load modeling method of EV cluster considering users’ travel chain is proposed, which can make EV cluster better participate in power grid dispatching and operation. Firstly, the Markov property of EV users’ behavior is analyzed, and on the basis of dividing the multi-state charge state interval of EV, the one-step transition probability in the interval of charging and travel state is derived, and the charging load model of EV cluster considering travel characteristics is established based on Markov chain theory. Then, the evaluation process of dispatchable capability for EV cluster is designed, and the evaluation method of dispatchable capability is constructed. Finally, the aggregation model and dispatchable capability evaluation method for EV cluster are simulated and verified, and the results show that the aggregation model and evaluation method are more accurate and effective compared with various algorithm.

To meet the wide access of distributed photovoltaic （PV） in distribution network, this paper presents a generating method for spatiotemporal probability distribution of distributed PV output based on Latin hypercube sampling. In this paper, after the factors that affect PV output are analysed, FFT filtering combined with second-order difference screening is used to decompose PV output into basic values and fluctuation values considering the similarity of the external environment in a small range, which improves the traditional method. The correlation is considered to exist only between the fluctuation values in a small range instead of the whole output values of the traditional method. Further the relationship between the correlation coefficient and the distance is further established by the correlation coefficient matrix fitting method. The Lilliefors test process is added before the sampling space transformation in the Nataf transform to determine whether the distribution of the fluctuation value satisfies the normal distribution. Complex calculation caused by the spatial transformation can be avoided and the multivariate joint distribution can be constructed quickly if the distribution of fluctuation value satisfies the normal distribution. Finally, by using the PV output simulation generating model, the simulated probability distribution of PV output can satisfy the probability distribution of single PV output in time series and fit the probability distribution PVs output simulation of the correlation coefficient matrix in space.

Reducing carbon emissions on the power generation side is the key to building a new power system and achieving the“carbon peak and carbon neutrality”goal in China. The essence of the impact of electricity spot market operation on carbon emissions in the power generation industry is achieved through its impact on the power generation structure. A theoretical priority curve for power generation is constructed based on the marginal cost of generating units. By comparing the power generation cost and carbon emissions between economic dispatch and real dispatch, the impact of spot market on power generation cost efficiency and carbon emissions is analyzed using multiple linear regression method. The research results indicate that during the trial operation of the Guangdong spot electricity market, the total cost of power generation significantly decreases, but the total carbon emissions of electricity will also change. Therefore, it is recommended to accelerate the entry of the spot market into formal operation on the one hand, and further integrate the electricity market with the carbon market on the other hand.

With the gradual integration of large-scale new energy, hybrid multiple sending terminals HVDC (H-MSTDC) system gradually develops from single terminal structure to multiple sending and receiving terminals. The operation mode of multiple converter stations and capacity allocation among converter stations increase the complexity of reliability evaluation. The typical connection structure and operation mode of H-MSTDC system are analyzed by considering the capacity distribution coefficient among converter stations in multiple sending terminals and receiving terminals, and the comprehensive reliability index of each receiver and system of H-MSTDC system is constructed. The reliability evaluation model is proposed based on subsystem division and uniform design method. Finally, based on the alternative connection structure of a two-sending and two-receiving project in southeast Tibet and considering the capacity allocation coefficient, the reliability evaluation of H-MSTDC system is carried out, and the variation trend of system reliability under the influence of extreme geographical environment is analyzed, which can provide reference for practical projects.

The pole-to-ground fault is the most common fault of DC lines in modular multilevel converter based high voltage direct current (MMC-HVDC) system, It is of great engineering significance to analyze the fault characteristics and master the fault current level for the design of relay protection and the optimization of related parameters. As the basis of analysis, the fault current expression of MMC on its DC side is firstly analyzed in this paper, then in view of the MMC-HVDC system with the unilateral grounding metal loop, the coupling effect of the system on the ground resistance on both sides of the fault point is analyzed. According to the causes and essence of coupling, the equivalent decoupling method is proposed, and a practical calculation method for pole-to-ground fault current is obtained. The correctness of the calculation method is verified by comparing with the electromagnetic transient simulation results under PSCAD/EMTDC.

A fixed-time output voltage regulation algorithm based on variable gain second-order sliding mode control is proposed for DC-DC buck converters. Firstly, taking into account external interference and unknown modeling dynamics, a state space mathematical model of buck circuit with uncertainty is obtained using the average state space method. Secondly, a sliding mode variable with a relative order of 2 is constructed based on the obtained mathematical model, and a novel sliding mode control algorithm with variable gain is proposed to achieve a fixed-time output voltage modulation control with convergence time independent of the initial system value. In addition, it is concluded through Lyapunov analysis that the closed-loop system can achieve global fixed-time stability. Finally, the effectiveness of the proposed algorithm is verified by comparing it with existing algorithms through simulation.

Charging modules are the most critical component of electric vehicle DC charging piles. Considering the open circuits fault characteristics of core devices such as power switches and electrolytic capacitors, a fault diagnosis method based on wavelet packet transform（WPT） and sparrow search algorithm-back propagation（SSA-BP）neural networks is proposed. The method takes the output voltage of the charging module as the original signal. Firstly its DC component is rejected through pre-processing, and the processed signal is decomposed into wavelet packet. Then the energy of each sub-band signal is calculated, and the initial feature vector is obtained through normalization. Finally the DC component and the normalized feature vector as the final fault feature quantity are put into the SSA-BP neural network, and then the classification results are output to achieve fault diagnosis. In order to verify the feasibility and superiority of this method, a two-stage simulation model with an output of 15 kW is built under different operating conditions. Experiment results show that this method could effectively improve fault diagnosis accuracy with diagnosis rate of 93.85%. And it has practical guiding significance for fault diagnosis of electric vehicle DC charging piles.

An effective and economical DC fault current limiting method is a key technology in the construction and development of flexible DC transmission grid. Based on this, an economical flux-coupling DC fault current limiter (FCL) is proposed, which greatly reduces the number of power electronic devices used. Firstly, its working principle and mathematical model are analyzed, and the mathematical expression of branch current of FCL is analyzed. Secondly, the joint operation steps with the direct current circuit breaker (DCCB) are given, and the mathematical expression of DC current is analyzed in four stages. Finally, the correctness of the theoretical derivation results, the excellent performance of the proposed FCL in reducing electrical and thermal stress and its economical efficiency are verified in the MATLAB/ Simulink platform.

To evaluate the potential interference of grounding electrode in monopolar operation on buried oil and gas pipeline, a circuit simulation model considering cathodic protection system and polarization effect of the pipeline is established by using Beasy software. Through simulation calculation, the influence of different monopolar polarity, operating current of grounding electrode and distance away from the pipeline on the distribution of polarization potential of pipeline is studied. The results shows that the higher the operating current is, the greater the polarization potential shifts. The linear relationship between the operating current and polarization potential is found out that the closer the grounding electrode is to the pipeline, the shorter the pipeline span under severe interference is at the near end of the grounding electrode, and meantime, the greater the polarization potential shifts. The cathodic protection system of the pipeline can suppress certain stray current generated by HVDC. For real conditions, the suppressing effect of the cathodic protection system should be considered to evaluate HVDC interference on the pipeline.

Gas relay is an important protection device for oil-immersed transformers, which triggers alarm signals and generates protective actions by collecting decomposing gas in oil, but it is difficult to dynamically grasp the gas accumulation capacity and requires manual participation in subsequent processing. In this paper, a dynamic identification and automatic detection method of gas volume based on image analysis is proposed, which automatically introduces gas into the gas sensor system for characteristic gas composition analysis, so as to monitor the operating status of transformers in real time, check potential safety hazards and improve reliability. Firstly, an endoscopic camera is installed in the gas relay observation window to obtain oil level images, and the oil level position is detected by image analysis algorithm. Secondly, the nonlinear mapping relationship between oil level and gas capacity is established through BP neural network, so as to calculate the gas capacity. The experimental results show that the detection error rate of this method is only 3.61%, and the prediction error of most test samples is within 2%, which has high accuracy and can reliably realize the automatic protection of oil-immersed transformers.

Aiming at the problem that the traditional voltage regulation strategy is difficult to deal with the two-way over-limit and violent fluctuation of the voltage after the high-permeability PV is connected to the medium voltage bus, and the importance of the load is not considered to affect the voltage regulation strategy. This paper proposes a distribution network voltage regulation strategy considering the importance of load and high permeability photovoltaic. Firstly, the importance index system of user load is constructed from three aspects: new energy efficiency, voltage quality and power load efficiency. Then, based on the combined variable weight method of improved AHP and improved CRITIC, the comprehensive weight of the index is determined, and then the importance coefficient of the load is determined. Secondly, according to the improvement level of voltage positive and negative deviation and voltage fluctuation after regulation, and combined with the important coefficient of load, the voltage regulation benefit function is constructed to measure the advantages and disadvantages of the regulation strategy. With the maximum regulation benefit as the optimization objective, the improved genetic algorithm is used to solve the voltage regulation strategy of distribution network in multi-time and multi-scenario. Finally, taking the improved IEEE 33-bus system as an example, the results show that the proposed strategy can effectively meet the voltage regulation requirements of high penetration photovoltaic access distribution network, and also take into account the guidance of user demand on voltage regulation strategy.

Aiming at carbon peaking and carbon neutrality goals, based on the existing research on the national energy consumption forecast, a forecasting technology for energy and electricity consumption demand in the southern region that takes into account the constraints of multi-level development goals is proposed. Three energy and electricity consumption scenarios in the southern region are constructed: the baseline scenario, dual-control of energy consumption scenario, and dual-control of carbon emission scenario. A forecasting method for multi-timescale load characteristics based on industrial decomposition is established, and the future power load characteristics of the southern region are deduced. The result shows that under the dual-control of carbon emission scenario, the terminal energy consumption in the southern region will reach a peak plateau before 2045, with a peak of 1 billion tons of standard coal. Terminal sector electricity consumption maintains a reasonable growth trend, entering a plateau with an average annual growth rate of about 3% after 2025, and further decreasing to 1% after 2050. Affected by the transformation of industrial structure, the fluctuation characteristics of load in the southern region will gradually increase. The pressure on the power sector to reduce emissions has gradually become prominent, and it is necessary to speed up the construction of new power systems in the southern region for promoting the low-carbon energy transformation and supporting the achievement of the carbon peaking and carbon neutrality goals.

Accurate calculation of wire length is the key to ensure the construction quality of continuous span fabricated stringing. Aiming at the problem of inaccurate calculation of wire length caused by the existing method ignoring the stress difference of each span of continuous span, the traditional idea of calculating the wire length of continuous span by changing a single wire stress, and the stress of each span of continuous span is accurately solved. Accurately calculation method for the construction wire length of continuous span fabricated stringing is proposed. Firstly, the influence of plastic creep elongation on the wire is considered, and the state equation is used to calculate the wire stress in the construction condition. Then the stress calculation method based on the condition of the wire suspended by the pulley is used to realize the accurate solution of the wire stress of each span. Finally, considering the influence of factors such as tension insulator hardware string, tower deflection and other factors on the wire length of the tension section of the continuous span and the adjustment of the wire length to obtain the wire length of the continuous span. The proposed method has been successfully applied in a 220 kV power transmission and transformation project in Jiangmen, Guangdong.