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The current research on health index for power grid in integrated energy system is mainly focused on single equipment components, which includes the high voltage equipment with high monomer value and a large number of low voltage power distribution equipment, rather than the power system network. Furthermore, those research includes qualitative evaluation and simple calculation model. This paper has carried out the research of distribution network health index theory and its application. The concept and research status of the health index of equipment were summarized. The definition, classification method and model of distribution network health index were proposed.

With the opening of electricity market and the popularization of residential intelligent home, the design and implementation of demand response (DR) projects for large-scale residents to participate in grid interaction will be one of the key points for the operation optimization of electricity retailers. In view of decision-making of the electricity retailer considering residential DR, the characteristics of residential load were analyzed in detail, and then a decision model of the electricity retailer in day-ahead market was established based on potential game, aiming at maximizing its profits with the premise no increasing of the residential electricity cost after DR. Therefore, in order to solve the strategies iterative problems with the large-scale residential players, a distributed parallel iterative algorithm was put forward, which could coordinate strategies updating of residential players via their community agents, and it can protect the residential users’ interests as well as effectively reduce the cost of purchasing electricity and the peak load of the residents.

The short-circuit fault of electric vehicle charging facility based on the DC distribution network and energy router will lead a R-L-C resonant under-damped response. The theoretical deduction on R-L-C resonant under-damped response about fault voltage and current is made to analyze the effects of key influence factors and relevant system parameters. The simulation verified the validity of fault characteristics on resonant under-damped short-circuit current and capacitor voltage, which also indicated the relationship between fault characteristics and basic parameters of energy router employed in electric vehicle charging facility.

As a result of large-scale electric vehicles starting charging at a station, power quality problems, such as voltage sags, will occur in the power grid. Based on this, a custom power device called Dynamic Voltage Restorer (DVR) is proposed to be connected to the electric vehicle charging station to deal with power quality problems. Considering that the filter capacitor can be set at different locations of DVR, i.e. parallel connection at converter side, line side and load side, this paper compares and analyses the mathematical models of three different topologies of DVR, and points out that the disturbance suppression ability of the topology of filter capacitor parallel on load side is relatively strongest, which is more suitable for the application of electric vehicle charging station.

With the progress of automation control technology, residential buildings become more and more intelligent. Home energy management in active distribution power grid connecting renewable energy and electric vehicle has received increasing interest. In this paper, typical structures about the smart home energy management system (SHEMS) is revealed. To reduce the customer electricity bill, an optimal strategy of SHEMS is proposed. The results from simulation show to us that the proposed strategy gives people who live in smart home a more economical and comfortable life.

The multi-level cascade converter is composed of H-bridge module in series. An improved 15-level hybrid cascade converter based on DC energy storage of electric vehicle can be obtained by changing the ratio of DC energy storage to supply voltage from 1:1:1 to 4:2:1 of the traditional cascaded 7-level converter cascaded by three H-bridge modules. In this paper, the modulation strategy of the 15 level hybrid cascade converter is studied, and a new algorithm for the switching angle of the multilevel converter powered by DC energy storage device for electric vehicle is proposed. Based on Saber simulation software, three different modulation strategies, stepped-wave modulation, PWM and partial PWM, are applied to verify and compare. Finally, the simulation results of total harmonic distortion, low-order harmonic component and switching loss of the converter based on the output voltage without any filter are compared, and the related modulation strategies are discussed.

Dynamic voltage restorers have been examined to compensate voltage sags in distribution networks to avoid production losses, especially in the Premium Power Park(PPP). If the compensation strategy can be optimized to extend the compensation time as long as possible, then the application of DVR in power system can be more popular, and the intelligent level of the power grid can also be effectively improved. As a result, this paper proposed a time-maximized compensation strategy to achieve a maximum compensation time based on the energy-minimized compensation strategy. According to the formula of dc-link discharge, the calculating formula of optimum phase angle jump of load voltage is deduced, and the principle and characteristic of the compensation strategy are analyzed respectively for single-phase and three-phase system. Simulation and experimental results are presented to confirm the effectiveness of the proposed compensation strategy.

As a prospective electric component in the power grid, the reliability of electronic power transformer (EPT) affects the security of the power grid. The fault tolerant strategy about the redundancy control can improve the reliability of EPT, hence secure the power grid. This paper presents the design of fault tolerant strategy on a cascaded multi-level converter (CMLC) based EPT. The operational principle and control scheme for the redundancy control are introduced and analyzed. The proposed fault tolerant strategies are implemented on a single phase nine-level CMLC based EPT in Saber simulation platform. Simulation is illustrated to verify the performance of the proposed fault tolerant design with redundancy control.

Dynamic Voltage Restorer (DVR), as a device of voltage sag compensation, demands fast transient response, and the disturbance of source voltage is a main impact on control performance. The DVR control strategy based on discrete state space will enhance control bandwidth and stability. However, for the discrete space control system, the number of parameters is relatively more which will lead to a complicated design process. To solve this problem, this paper proposed a control parameter design method based on the idea of virtual resistor. Firstly, by means of state feedback control, an adjustable virtual resistor can be series in filter inductor. According to the requirements of steady-state error, phase margin and Routh's criterion in w domain, the variation regions of PI parameters and virtual resistance can be solved by a step-by-step method, and then the appropriate control parameters can be selected. Experimental results from a digital signal processor-based system are included to support theoretical analysis.