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Regional energy Internet is an energy local area network with wide integration and cross-penetration of multi-energy resources in a region. Electric energy acts as an important medium for energy conversion and utilization in the whole system. Therefore, AC/DC distribution network, which can realize different types of energy conversion, transmission and efficient utilization, is an important component of the physical foundation of regional energy Internet in the future. In this paper, the main elements of regional energy internet are introduced firstly, and then the requirements for the development of distribution network are presented. In the meanwhile, the necessities of the development of AC and DC distribution network technology for the construction of regional energy internet are proposed, and the current development at home and abroad is introduced briefly. Secondly, this paper illustrated the advantages of AC/DC distribution network technology based on flexible substation in realizing multi-energy complementarity, and also the flexibility of power flow control and high efficiency of energy utilization. Based on these factors, and combined with the development of power electronics technology and the technology of information and communication, the new form of future distribution network development is figured out. Finally, taking Zhangbei flexible substation and AC/DC distribution network demonstration project as an example, the practical application of this technology is introduced.

Hybrid AC/DC microgrid (MG) is a promising electrical power system architecture that enables to harmonize AC and DC energy conversions. Due to the complicated configuration, comprehensive stability analyses for a complete hybrid MG still stand as an unsurmountable challenge. To address this issue, this paper decomposes the MG system into several electrical modules, i.e., an AC source, a DC source, multi-paralleled interlinking converters (ICs) and line impedances. These modules are first individually modeled in the small signal sense. They are then combined to establish a full autonomous mathematical expression for characterizing dynamics of the hybrid MG. To investigate MG system stability, the influences of diversified operating points, line impedances and the selected key control parameters are examined by evaluating eigenvalue loci of the derived mathematical model. Time-domain simulations reveal the perfect matching between the results given by Matlab/Simulink and eigenvalue loci plots.

High penetration of non-synchronous generation from increased competition by renewable energy generators alters the dynamic behavior, namely, the frequency performance of a power system. Given this, it is important to identify a minimum level of synchronous generation where system frequency performance is satisfactory. To address this issue, in this paper we develop, calibrate and simulate a load frequency control model of a power system, using the Australian National Electricity Market (NEM) as a case study. The minimum inertia requirements to satisfy frequency operating standards, i.e., rate of change of frequency limits and frequency nadir were determined for a variety of single and multiple contingency scenarios. The study determines that a certain inertia level must always be sustained to meet the system security criteria. Simulation results show that the NEM system should always maintain at least 28.3% of the network’s current inertia capacity to ensure optimal frequency regulation and power system security.

Under the pressure of energy crisis and environmental pollution, the construction of community integrated energy systems (CIES) has caused widespread concern worldwide. To realize the optimal configuration of central energy station in a CIES, this paper presents an optimal configuration method for CIES considering electrical and heat storage devices. The system considers four energy conversion equipment, two energy storage devices and two types of distributed generator, which can simultaneously meet the load requirements of cooling, heat and electricity in the system and ensure economic efficiency. First, the model of energy station in CIES is established based on the type of optional devices and the form of input energy. Then, taking minimum annual total cost as the objective function, the mixinteger linear programming (MILP) method is adopted to optimize the type and capacity of the equipment. Finally, case studies are conducted under different scenarios to verify the effectiveness of the proposed method.

The energy-economy-environment are mutually influential and mutually restrictive, so studying the relationship between the three is of great significance. This paper firstly analyzes the interaction mechanism between energy, economy and environment, including positive impact and negative impact. Then the index system of the new situation such as high-quality economic development, energy transformation, and ecological civilization are designed. Finally, the pressure-state-response model is used to build an evaluation index system for coordinated development of energy, economy and environment under the new situation. The research results can lay the foundation for the coordinated assessment of energy, economy and environment in the new situation and support the energy system optimization model.