Firstly, starting from the definition and classification of insider threats, this paper combs and analyzes the security protection methods of insider threats developed on the basis of general information systems, Then combining with the specific business analysis of the power information physical system (CPPS), it points out the insider threat challenges faced, and summarizes the research status of CPPs insider threat protection from the aspects of safety regulation guidance, error prevention technology research, domain knowledge application, authority allocation research and data leakage protection; Finally, comparing the differences between CPPs and general information systems, this paper puts forward the characteristics of using CPPs to carry specific business, designs targeted protection measures against insider threats, and finally looks forward to the application prospect of blockchain technology and zero trust in related fields.

The distributed integration of large-scale and high-density renewables energy complicates the distribution system structure. Besides, the fluctuation and randomness features of renewable energy bring great adverse effect on network power flow and voltage stability. To solve these problems, taking the active power loss and system voltage deviation as the control objectives, the reactive voltage optimization is studied in this paper based on the equipped static var compensator. An improved algorithm combining beetle colony antennae search algorithm with attractive repulsion and bidirectional learning is proposed. On the basis of the above research, together with the enhanced IEEE 33-node distribution system model, both the reactive voltage control effect of the proposed distribution system and the particle swarm optimization algorithm are verified. The results show that the proposed optimization algorithm can optimize the system power loss on the premise of ensuring the system voltage stability. Besides, compared with the conventional particle swarm optimization algorithm, the proposed optimization algorithm has great improvement in calculation time, convergence speed, and optimal search solution.

In view of the similarities and differences in data composition, data accuracy and refresh frequency of different measurement data in distribution network state estimation, a new estimation fusion system is proposed on the premise of ensuring the structure of the traditional state estimator. At the same time, the improved generalized maximum likelihood (GM) estimation and estimation fusion system are combined to estimate the system node voltage amplitude and phase angle. Firstly, GM estimation is used to enhance the robustness of the estimation model. By using adaptive project statistics and analyzing the weight function of the objective function in GM estimation, the improved GM estimation method is applied to the state estimation. Secondly, considering that the traditional measurement system is different from the phasor measurement system in terms of measurement channel and instrument sampling rate, based on the traditional state estimator, the phasor measurement data is fully utilized to estimate the state of different estimation modules. At the same time, the multi-sensor data fusion theory (MDF) is used to fuse the estimated results to obtain the optimal estimation value. Finally, the simulative analysis on the improved IEEE 14 and IEEE 33-bus distribution network examples verifies the validity and reliability of the improved GM estimation and estimation fusion system.

High impedance Grounding fault (HIF) often occurs in distribution network, it usually accompanies with arc, and tend to cause security risks. But due to its weak fault characteristics, it is difficult to be detected. This paper improves the DenseNet and proposes a lightweight one-dimensional multi-scale DenseNet to realize HIF detection. Specifically, multi-scale features of sequence signals are extracted by multi-scale convolution layer, features are transferred by dual channel fully connected module, and the performance of the model is improved by using the ELU activation function. At the same time, the simulation model is improved to simulate the phenomenon of random fluctuation and zero rest offset of fault waveform in the actual situation. The measured data and simulation data verify that the algorithm can identify the high resistance grounding faults in different network structures and different grounding media, and verify the anti-noise ability of the model.

In order to solve the problem of weak sensing and location failure of existing distribution automation terminals in the steady-state characteristics of high resistance grounding fault in distribution network, a fault detection and section location method of injecting non power frequency signal into neutral flexible grounding equipment is proposed. According to the disposal strategy of permanent grounding fault in distribution network, the non power frequency characteristic current signal is injected into the neutral point through the flexible grounding device injection transformer, the steady-state quantity of characteristic frequency current amplitude is obtained by each feeder distribution automation terminal of distribution network, and the characteristic frequency current amplitude section positioning criterion based on fault section and non fault section is constructed to realize fault section location. In order to enhance the anti-transition resistance and anti-interference ability of fault detection and location, the selection of injection frequency domain affecting fault detection and location is analyzed in detail, and the optimal non power frequency signal injection frequency band of neutral point is formulated. The simulation model of grounding fault section location based on non power frequency signal injection in distribution network is built in PSCAD simulation environment. The simulation results show that this method has strong anti-transition resistance ability and can accurately locate the fault section in a wide range.

Due to the increasing of cable-wire hybrid lines, the zero-sequence current waveform similarity between faulty lines and sound lines increases greatly, which makes fault line selection more difficult for nowadays power distribution networks. To solve these problems, a fault line selection method of complete ensemble empirical mode decomposition based on adaptive noise (CEEMDAN) and independent component analysis (ICA) is proposed. The zero-sequence current at the head end of each line is decomposed to obtain intrinsic mode functions (IMF) component, and then multi-dimensional source signal is constructed by ICA method. The fault signal is identified by kurtosis threshold criterion, then the zero-sequence current signals are reconstructed after setting the fault signal to zero, and the line with zero-variance of reconstructed zero-sequence signal is identified as fault line. Simulation results show that the proposed method is less affected by different fault conditions, of high reliability and strong anti-interference, and can be used for line selection for high resistance grounding multiple faults. Meanwhile, the “sort push-pull” strategy based on kurtosis value is proposed.

To effectively perceive the comprehensive situation of regional distribution network with massive renewable resources, an evaluation approach based on trapezoidal fuzzy number and measurement of alternatives and ranking according to compromise solution (MARCOS) is proposed. First, the comprehensive situation evaluation index system of regional distribution network is constructed, which involves four aspects of security situation, economic situation, low-carbon situation, and regulation situation. Then, the trapezoidal fuzzy number is used to express and analyze the semantic evaluation information of experts on qualitative indicators, and the evaluation information is fused based on fuzzy theory to reduce the impact of uncertainties on the comprehensive situation evaluation results of distribution network. Further, the trapezoidal fuzzy MARCOS method is used to process the decision-making information, thereby the final evaluation results are obtained. Finally, taking Taiyuan as an example, the proposed method is used to evaluate and analyze the comprehensive situation of the regional distribution networks within the jurisdiction of the city, and the feasibility and effectiveness of the proposed method are verified by combining with the realities.

Aiming at the scare historical data of newly-built wind farms and difficulty in accurately predicting the power, a wind power forecasting method is put forward with few data considering the spatial coupling relationship based on the historical data of neighboring wind farms. First, spatial attention is proposed to quantify the influence degree of adjacent wind farms on the target wind farms, and the corresponding wind farms are weighted. Then, the hidden temporal correlation information in wind power sequence is obtained by the gated recurrent unit networks. Finally, the weight and offset of output layers are optimized by the crisscross optimization algorithm. The experiment results from the actual data of four neighboring wind farms in Inner Mongolia show that the proposed method can effectively quantify the impact of wind farms and improve the prediction accuracy of wind farms with fewer data.

Aiming at the multiple uncertainties brought by the randomness and correlation of distributed generation, fluctuating load and line parameters to flexible interconnected distribution network, a probabilistic loss allocation method for flexible distribution network considering the time series characteristics and uncertainty of source network load is constructed. Firstly, the time series model with multiple uncertain parameters is established, and the three-point estimation method based on nataf inverse transform is transformed into AC/DC probabilistic power flow in multi-time scenario; Then, the network loss impact index system of random equipment is proposed. Based on the time scenario, the improved analytic hierarchy process entropy weighting method is used to determine the network loss change contribution rate of DG and EV charging piles. The network loss change is allocated to DG and EV charging piles based on the contribution rate, and the probability density function of allocated electricity is fitted by Cornish Fisher level, The annual network loss allocation probability density function is obtained by integrating the time scenario; Finally, the effectiveness of the proposed algorithm is verified based on the improved 33-node flexible distribution network and the improved Dongguan Songshan Lake topology.

Conventional automatic voltage control is real-time feedback control, which lacks foresight. With the increasing penetration of renewable power, slow discrete voltage regulation devices may be adjusted frequently due to the fluctuations of renewable power, which impairs their lifetime. To better utilize slow devices, this paper proposes a day-ahead and intro-day two-stage reactive power rolling dispatch method for power systems with high renewable power penetration. In day-ahead scale, the adjustable times for each hour is scheduled beforehand based on a two-stage robust optimization. While in intra-day scale, the optimal rolling dispatch determines the specific action time. And the extra adjustable number correction is introduced to further enhance the flexibility. The grid test results show the proposed method outperforms conventional methods. The coordination of fast and slow reactive power devices is achieved and the voltage control performance is enhanced by utilizing the forecasting information.

The spatial and temporal variability of the redundant capacity of special transformers for adjacent buildings in the city brings the feasibility of joint regulation of orderly charging to charging stations built on the basis of the special transformers of buildings. Based on this, a special transformer mutual assistance mode (referred to as mutual assistance mode) and its orderly charging optimization control model are proposed, in which charging station operators combine special transformers across buildings to supply power to clusters of charging stations. First, the interests of operators, special transformer owners and electric vehicle (EV) users are analyzed. And a three-party game regulation mechanism for orderly charging is established. Secondly, in order to quantify the effect and implementation difficulty of the mutual assistance mode, a system of indicators for evaluating the effectiveness of regulation, a evaluation model of the complementarity of joint special transformers and a quantitative model of the difficulty of joint regulation are proposed. And a limit distance evaluation model of joint charging stations is established. Then, comprehensively considering the charging cost of EV users, the rental income of special transformers and the gross profit of operators, an optimization model for the control of orderly charging in the mutual assistance mode is put forward. Finally, the effectiveness of the proposed model is verified.

Electricity spot market clearing results are affected by market participants’ bids and various coupling constraints. A rational explanation offers insight into the causes of market clearing results, as consequence, improves market operators’ ability to organize spot market transactions and mitigate risks. The paper proposes a comprehensive analysis method for day-ahesd spot market clearing results. On one hand, based on the existing operating experiences and optimization principles for market clearing, the method screens key states of unit dispatch plans and grid safety, and analyze the causes. On the other hand, based on the Pearson correlation theory and isolated forest algorithm, untypical clearing prices can be located speedily and analyzed combining with physical laws of power grid operations. At last, based on a provincial spot market case, the paper locates untypical states for unit opertaion, grid operation and clearing prices and gives explanations for them, which verifies that the proposed method can provide foundations of the disclosed spot market information, and improves the explainability of the spot market clearing results.

Virtual power plants (VPP), as an advanced technology that aggregates and optimizes the utilization of renewable energy, controllable load and energy storage system, can effectively promote the green and low-carbon transformation of power system. It is of great significance for the investment and operation of VPP to comprehensively evaluate the benefits of virtual power plants. This paper constructs a set of evaluation index system to comprehensively evaluate the economic, social and environmental benefits of VPP. The proposed approach can reasonably evaluate the value of VPP in terms of construction, power grid operation, energy conservation, emission reduction, and social effects. The benefit evaluation index system has been applied to a VPP application pilot, and the calculation process of its benefit evaluation index are elaborated in detail.

With the promotion of “carbon peaking and carbon neutrality” goals and wide access of renewable energy, the corresponding management and operation complexity of electric power market transaction subject have increased greatly with the dramatically increased number of participants. Power market transaction platform based on blockchain technology is an effective way to solve the safety, efficiency and fairness problems in transaction process. And the consensus mechanism is the key of the blockchain technology in power trading. RAFT is suitable for blockchain with dynamic changes, asynchronous network and node mobility. But it has disadvantages such as easy election disputes and inability to adapt to malicious nodes. Therefore, this paper proposes an improved RAFT consensus mechanism for power transaction blockchain based on credit scoring. The RAFT consensus mechanism is combined with the operation characteristics of power market. And the election disputes and the speed of RAFT master selection are improved by replacing node voting with credit scoring. The adaptability of RAFT to malicious nodes is improved by setting audit nodes for auditing log copy and election results. The above improvements can meet the requirements of effective consistency of cluster nodes and improve the speed and throughput of RAFT consensus mechanism. Finally, the effectiveness and rapidity of the improved RAFT consensus mechanism proposed in this paper are verified by a practical case simulation.

The oil paper/oil interfaces in transformer oil paper materials with different aging degrees have different space charge accumulation characteristics under DC electric field, which can characterize the aging state and insulation per-formance of oil paper insulation system to a certain extent. In this paper, one type of insulating paper and two types of insulating oil materials are used to make oil paper/oil double-layer samples respectively. The space charge distribution and the change of polarization/depolarization current of the combined samples of different oil paper materials are tested respectively. The characteristics of interface charge are analyzed according to the space charge, the interface barrier parameters are extracted, and the change law of collapse current is studied by polarization/depolarization current, and the correlation between the trap parameters and the trap parameters in the sample is found.

When the very fast transient overvoltage (VFTO) propagates through capacitive voltage transformers (CVT), it can create significant interference on their secondary sides, and affect the normal operation and functioning of secondary equipment. In this paper, the CVT equivalent calculation circuit model is established, and the disturbance voltage of the secondary cable is deduced and calculated. Based on the electromagnetic transient simulation software, the overall simulation model of the secondary cable disturbance caused by the VFTO in a 500 kV GIS substation is established, the interference voltage at the end of the secondary cable is simulated and analyzed, and the effects of the length of the secondary cable and the grounding mode of the shield on the disturbance are studied. It also puts forward the combined anti-interference measures of using spiral tube damping busbar, grounding at both ends of the shield, using multi-strand conductors and installing filter capacitors, which greatly reduce the amplitude and harmonic components of the disturbance voltage of the secondary cable.