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Background: Power distribution Internet of Things is a smart service system in which traditional distribution networks comprehensively apply modern computing technologies, such as cloud computing, mobile Internet of Things, and big data to realize the interconnection of all things in the power system and human-computer interaction. In the power distribution Internet of Things, there are many types of main power distribution equipment, and each type of power distribution equipment is connected with multiple sensor devices. These sensor devices play an important role in the smooth operation of the power distribution Internet of Things, so it is necessary to build a reliability evaluation system for these sensor devices. Objectives: The objective was to evaluate the reliability of the sensor device connected to the main equipment in the power distribution Internet of Things. Methods: Firstly, the G1-CV method (entropy weight method-coefficient of variation method) is used to construct the initial evaluation index system, and the comprehensive weight of each index is determined and ranked. Then the improved TriMap algorithm (ITriMap) is used to reduce the high-dimensional complex index system. Results: Simulation verification results show that the algorithm has a smaller reconstruction error than traditional dimensionality reduction algorithms such as t-SNE, Largr-Vias, UMAP, etc. The reduced index can scientifically and objectively measure the main equipment sensors of the power distribution network. Conclusion: An index reduction method based on the ITriMap algorithm is proposed to evaluate the reliability of sensors. Experimental results show that this algorithm greatly reduces the reconstruction error compared to other traditional methods. Discussion: In the future, on the basis of this article, we intend to construct a sensor reliability evaluation model for the main equipment of the power distribution Internet of Things using the 5- dimensional features after dimensionality reduction as input.

The detection algorithm of compensation current command signal is one of the key technologies of power quality regulator. The real time nature of the detection algorithm affects the effect of compensation. Conventional i p– i q detection algorithm is commonly filtered by Butterworth filters. However, its inherent delay characteristics make the detection real-time poor. In order to improve the real-time of the detection algorithm, this paper proposes an i p– i q detection algorithm based on Kalman filter. First, Establish equations of state and measurement for the Kalman filter based on i p– i q . Then, the Kalman filter algorithm is used to filter i p– i q to obtain DC component, inverting the DC component to obtain the three-phase fundamental current. Finally, the proposed algorithm is simulated by matlab and compared with the algorithm which using Butterworth filter. The results show that the proposed algorithm is better than the latter in real-time.

Harmonic is an important factor threatening the safe and stable operation of HVDC system. This paper firstly analyzes the mechanism of harmonics caused by converter transformer. Then., the whole process that harmonics transfer back and forth between the AC system and DC system through the converter is studied by switching function method., which shows the frequency of harmonics is changed systematic after commutation. The analysis method of Harmonic Multi-infeed Interaction Factor for harmonic transmission characteristics in multi HVDC(DC/DC) system is proposed in this paper. Research shows the induced harmonic magnitude from remote DC converters are relative to the electrical distance. PSCAD simulations verify the methods and conclusions.

The waveform data recorded by fault indicators imply rich fault information, and effective information mining of the data can help grasp the distribution of line faults and make targeted measures in distribution networks. In this paper, a fault type identification method based on fault indicator data is proposed. With the consideration of fault indicators' characteristics, such as big error, low reliability of voltage measurement and saturation condition of measured current in short-circuit fault, the characteristics of waveform data in three-phase short circuit, phase-to-phase short circuit, phase-to-phase grounding fault and grounding fault are analyzed respectively. Based on the characteristics analysis, a multi-level fault type identification method is proposed, successfully identifying disturbance and fault, grounding fault and short-circuit fault, symmetrical short-circuit and unsymmetrical short-circuit, phase-to-phase fault and phase-to-phase grounding fault. The effectiveness of the fault type identification method proposed is verified by the field recording data collected by fault indicator. The method proposed in this paper provides a feasible method for the identification of fault type of distribution lines, and it can help master distribution laws of distribution network faults.

To localize the fault in distribution networks effectively, a novel fault location method on wide area measurement systems is proposed. This method takes the advantage of the fastness and reliability of the measured data from the wide area measurement system. An leakage energy function is proposed on the basis of analyzing arc-suppression coil action and the waveform features of faulty phase. For the fault-free section, its energy function shows little difference with the normal working condition when the fault occurs in other sections. And for the faulty section, its energy function will increase and then decrease over time and the peak value is reached from the fault occurring to the arc-suppression coil outputs stable offset current. The proposed method localizes the faulty section according to the characteristic of energy function. And the experiments on PSCAD/EMTEC software manifest the effectiveness of our proposed method.

The wave-recording fault indicators widely used in distribution network provide a large amount of raw data which is used to judge the operation state of the distribution network. It is significant to improve the handling level of grounding fault. Firstly, This paper analyzes the invalid data of the existing transient wave-recording fault indicator. A preprocessing method of recording data, based on the characteristics of temporal and spatial distribution of recording start, was proposed. Then the tripping adaptability index is proposed which includes the probability of fault expansion, the loss of outage and the risk of personal injury. The fuzzy comprehensive evaluation method is adopted to evaluate the tripping adaptability of the current fault. Finally, based on the importance of load, an adaptive trip protection strategy for single-phase grounding fault in non-solidly grounding network is proposed.

Currently the issue of renewable energy related encourage policies, high penetration of renewable energy connect to the distribution network would lead to increased voltage levels, short circuit current increases, power supply reliability and power quality deterioration and other problems are particularly prominent. In the traditional distribution network, the uncertain factors that affect the voltage optimization result are the fluctuation of the load. The renewable energy integration represented by wind power and PV power not only changes the characteristics of the traditional distribution network power flow, but also because of its power electronic converter connection, making the distribution network voltage characteristics, whether steady or transient have brought significant changes, and then the distribution network voltage control has brought great challenges. To maintain the distribution network voltage level, how to set a reasonable control strategy for different renewable energy network connection situation makes the voltage in the distribution network be reasonably controlled and optimized to become an urgent problem to be solved. In order to achieve flexible control system supply voltage, improve the level of reactive power operation, and meet the demand of power users under the conditions of the initiative to network and renewable energy power generation operation optimization and control. In this paper, the voltage control problem of distribution network under the condition of large-scale renewable energy integration is studied. Firstly, the voltage characteristics of the distribution network under the uncertainty of renewable energy output are analyzed, and the voltage sensitivity analysis model of renewable energy connect network is established. On this basis, put forward renewable energy voltage control strategy, and finally a regional distribution network system as a case to verify the proposed method and strategy of correctness and effectiveness.