Search

The rapid development of renewable energy makes the power grid gradually change from traditional power system to high proportion renewable energy power system. The rapid development of electric vehicles, energy storage and controllable load increases the uncertainty of load. The flexible adjustable load is less, which can not meet the consumption demand of large wind and solar power generation, and can not support the power valley filling demand when the wind power output is insufficient. Energy storage system is very important for the safe and stable operation of renewable energy internet. How to consider the reliability and economy, this paper proposes a distribution network planning scheme considering energy storage system.

Based on historical power transmission and transformation project data, this paper constructs a support vector regression forecasting model by screening the key influencing factors of power transmission and transformation projects, and then predicts the cost of power transmission and transformation projects above 110kV in a certain province. The results show that the support vector regression forecasting model can quickly predict the project cost of power transmission and transformation projects by inputting key factors of the project. The establishment of this prediction model provides a more scientific basis for rationally controlling the cost of power transmission and transformation projects.

According to the characteristics and development trend of microgrid, instead of being the pure load, demand-side is treated as a kind of possible power supply (equivalent effect of reduction of the load) which can actively participate in the planning and operation in microgrid. An integrated resources planning model considering direct load control (one of demand responses) in microgrid was proposed. The validity of the proposed model was proved. It can be achieved to minimize the total cost of system planning by using demand response to actively participate in the planning. Depth discussions for the case were done to give comparative analysis of different control strategies, parameters and costs and more planning proposals were given.

The integration of renewable energy resources and storage systems makes power delivery route reconstruction after the N-1 fault taking place more complicated. To solve the calculation problem of smart grid power transfer capability, the time-varying characteristics of renewable energy resources and storage systems were analyzed. Based on this, an N-1 recovery model was proposed on the base of the transfer capability index. Through making the calculation formula of the transfer capability index linear and adopting the artificial intelligence (AI) optimal algorithm based on topology simplification, the operation modes of the power grid, new energy generations and new energy storage systems can be optimized and the maximum power transfer capability of the grid can be achieved.

High penetration of distributed renewable energy is the trend of future power and energy systems. Under the background of retail electricity market reform, retail price mechanism is of great significance to facilitate large-scale integration and consumption of user-side renewable energies. Considering the adoption of renewable energy is essentially the diffusion process of technological innovation, we presented an evaluation method for measuring the diffusion capability of distributed photovoltaic with the retail price mechanism. Firstly, based on the residential double-step tariff structure, the decision models were proposed for energy transactions between retailers and customers using Ramsey pricing theory. Secondly, by introducing the methodology of system dynamics, the market feedback mechanism between the electricity price design and the integration capacity of distributed photovoltaic was analyzed, thus the evolutionary model of distributed photovoltaic dynamic diffusion under the price policy was established. Finally, the criterion of stable diffusion of distributed photovoltaic based on Lyapunov function was developed in this paper.

Because of the situations that the interconnection among multi distributed energy system (DES) and interaction among electric, heating and cooling system are not given full consideration, optimal planning of energy internet near user side based on bi-level programming is studied in this paper. First, schematic structure along with mathematic models of each unit is proposed and load characteristic is analyzed. Considering the interconnection of multiple energy as well as multiple distributed system and the combined dispatch of multi energy flow, a bi-level programming model is then presented. The minimum of total annual cost is the objective of upper model whose decision variables are the capacity of each energy unit and minimum annual operating cost is the lower model’s objective whose decision variables are the output of all energy units. Then, the elitist strategy genetic algorithm is employed to solve the upper model, and branch and bound algorithm is applied to optimizing lower model. The simulation results indicate that the proposed planning method of energy internet is effective, multiple energy flow interaction and multiple energy router interconnection are more economic than traditional combined cooling heating and electricity (CCHP) and can alleviate the mismatch of heat-to-electricity ratio between gas turbine and loads, and the multiple energy networks by which DES are interconnected contributes to higher economic benefits than single electric or heating network.

In order to promote all types of energy utilization, interaction between supply and demand as well as efficient operation, a new generation of energy systems which treats the electricity grid as the core came into being. Unlike traditional power system, the electricity network and gas network in the new generation of energy systems are closely linked through gas-fired units, and influence each other. Therefore, to ensure the safe operation of the future electricity network and natural gas network, the integrated framework for generation, electricity network and gas network expansion planning need to be carried out. Under the premise of meeting the electricity network and gas network safe operation constraints, we propose a multi-stage planning model for the combined generation, electricity network and gas network, in which investment cost and operating cost of the combined system are minimized. Combined generation, electricity network and gas network expansion planning is a large-scale, high-dimensional, non-convex and nonlinear optimization problem, which is difficult to solve. To solve this problem, we propose an incremental piecewise linear method to convert the original model into a large-scale mixed-integer linear optimization problem, allowing the use of sophisticated mathematical optimization method to quickly obtain the optimal solution.

This paper takes the AC / DC interconnected system based on DAB energy router as the research object, analyzes the fault characteristics of AC side and DC side in detail, compares and analyzes the influence of DAB energy router on fault characteristics in the system with different grounding methods of DC capacitor midpoint in converter station, and explores the mechanism of interaction between AC and DC sides. The effect of dab on the interaction of AC and DC side faults under different fault types and capacitor neutral grounding modes is analyzed. Finally, the method of post fault system partition and fault analysis is proposed, which lays a theoretical foundation for fault detection and rapid location of AC / DC hybrid distribution system, and provides theoretical support for system equipment selection.

The scenario generation method suitable for solar and wind power obeying any probability distribution and the concept of cluster was brought up to improve the consumption ability of distribution network of medium and high voltage for renewable energy. The planning model of renewable energy access was established based on cluster partition considering the investments and power generation interests of power producers as well as the power match degree within clusters. The Benders decomposition method was employed to solve the planning problem, and the complicated planning problem of renewable energy generation is decomposed into the decomposed investment operation model. Therefore, the access planning of renewable energy taking account of the solar and wind power was realized.

In order to achieve accurate verification of the implementation of power grid infrastructure investment plan, support the dynamic monitoring and risk assessment of annual investment plan implementation. Based on the “three rates in one” Investment completion collection value of 110 kV and above grid infrastructure projects, this paper constructs a risk assessment model for the implementation of the investment plan of grid infrastructure projects. Evaluate the rationality of the current reported investment progress, predict the risk of the implementation of the investment plan and quantify the risk amount of the implementation of the plan, timely discover the risk of the implementation of the investment plan, promote the timely resolution of problems, and improve the investment lean management level of power grid enterprises.

In the integrated energy service system, distribution network shall manage to settle its own power balance issue. The market competition that grid corporations open the sale services of electricity to the society and interruptible load is encouraged to participate in ancillary services becomes a development tendency. At this time, a corresponding control strategy was required to instruct interruptible loads scheduling. In this paper, a control strategy using discrete Fourier transform is proposed in combination with the requirements of the electricity market. Under the constraint of the new evaluation criteria, different types of resident interruptible loads were on-demand dispatched in different periods. The root mean square error (RMSE) of the feeder daily forecast could improves the power load control capability of distribution network as well as the quality of power supply.

The development of HVDC technology makes it possible to build a multistage HVDC distribution power system. Firstly, the basic principles and main constraints of voltage level sequence for DC distribution are analyzed in detail. Based on the analysis of the DC distribution capacity of each voltage level, a series of voltage levels of DC distribution network with high voltage, medium voltage, low voltage and ultra-low voltage are proposed, taking the load demand as the basic foundation, considering the manufacturing level of relevant equipment and the need of power grid structure optimization. Finally, the specific voltage level sequence of DC distribution network is proposed.

The DC distribution transformer for electric vehicle charging facility is the key equipment in future active distribution power system, whose reliability relates to robust and reliable operation of distribution power system. With redundancy modules, reliability of the DC distribution transformer is increased as well as the cost. The reliability with different control methods for general DC distribution transformer is analyzed and compared, and an objective function is presented for optimized design. Solutions for minimum value of the function under different circumstances are discussed, and the best scheme for balance between reliability and economy is obtained. Finally, an engineering application is analyzed. Suggested model and number of sub-modules is given, and validity and feasibility of the proposed method is verified.

With the development of DC power transmission technology, it is possible to develop a multilevel urban DC distribution system in integrated energy system. With the basic principle and main constraints of designing for DC distribution voltage level sequence, a sequence of voltage levels of DC distribution power system in different voltage levels is proposed, and the power supply capability, economy evaluation and reliability on voltage level sequence of multilevel DC distribution is discussed in detail through a specific example.

Considering the negative impact of large-scale application of Electric Vehicles (EVs) on power network planning and operation, this paper proposes a coordinated charging strategy for EVs based on valley load tracking, aiming at reducing load fluctuation. By optimizing the charging sequence of EVs, the valley period of the daily load curve tends to be smooth, which plays a better role in filling the valley and reduces the peak-valley difference. Finally, an example is analyzed by Monte Carlo simulation, which proves that the proposed coordinated charging strategy is efficient and practical.

The analysis on fault characteristic of Distribution Electronic Power Transformer (D-EPT) can help design its operation and protection scheme, hence improve the reliability of the D-EPT as well as the distribution power grid. The DC pole-to-pole short-circuit fault at DC-Link is analyzed with R-L-C resonant mode and free-wheeling mode, and the theoretical analysis on the short-circuit voltage and current is based on several influence factors and relevant system parameters, which indicates that the fault characteristics are related to the configuration, operation and system parameters of D-EPT.

One- and two-step breakdown phenomena were observed on the zirconium-doped hafnium oxide (ZrHfO) high-k dielectric films with equivalent oxide thicknesses 1.8 and 2.5 nm, respectively. The difference in the breakdown sequence was attributed to the bulk high-k layer thickness and interface layer structure. The trap generation and charge trapping in the high-k stack was investigated using a new stress–relax method through analyzing the relaxation current change. The results showed that new traps were only created under the high bias condition and the density could be comparable to or even larger than that of the preexisted traps.

Memory devices containing the nanocrystalline Si embedded Zr-doped HfO2 high-k dielectric film, which have many advantages over the conventional non-doped high-k films, have been prepared and characterized. The memory effect was manifested by the large counterclockwise capacitance–voltage hysteresis, e.g., 2.98 V, and negative differential resistance region in the positive bias current–voltage characteristics. A large memory operation window, e.g., 0.72 V, with a long charge retention time, e.g., >10,000 s, was achieved under the proper gate stress voltages. It is a viable dielectric for future nano-size metal oxide semiconductor field effect transistors and capacitors.