Search

With the increasing integration of renewable energy, the inertia of power systems evidently decreases and poses a critical challenge to planners. To guarantee the frequency stability of the system with high shares of renewable energy, this paper presents a novel multi-machine system frequency response (MSFR) model, which tends to additionally incorporate frequency responses from reheat generators and variable speed wind turbines (VSWTs) at the same time. After aggregating the multi-machine system into equivalent generators, the analytical trajectory of frequency nadir is deduced to construct linear frequency constraints through the fitting piecewise linear (FPWL) method. Then we propose a frequency-constrained stochastic generation planning model to satisfy the frequency nadir requirements. For the sake of online frequency support, the corresponding unit commitment is joined to flexibly adjust unit states. At last, the proposed model is applied to analyze the typical IEEE 24-bus test system. The derived simulation results have demonstrated the effectiveness of our model in terms of frequency deviations. Also, the benefits coming from different frequency control modes of VSWT-based wind farms are strongly revealed.

This paper proposes a novel energy bus-based automatic modeling method, which has the advantages of high extensibility and practicality. The proposed modeling method is applied to the energy station planning, which can optimize the capacity and inside topology simultaneously without any presupposition of the inside structure. Firstly, the traditional energy bus model is modified by introducing the distribution bus and defining the rules of energy flow. The concept of the digraph is utilized to model the energy station automatically, in which energy converters and connections are abstracted as nodes and edges. Then, the joint planning model considering the maintenance cost of the hardware-based real connections is constructed. Constraints mainly include energy conversion, power balance, inside topology, and the overall energy efficiency ratio (EER). The model is transformed into a mixed-integer linear program by the big M method and solved by Gurobi. Case studies based on a modified integrated energy system illustrate the validity of the proposed method. Results indicate the profound influences of the maintenance cost of real connections, energy price, and the overall EER limit on energy station planning.

The interconnection of sub-regions through tie lines can improve the overall economy of the system and provide a broad space for renewable energy consumption, such as wind power. However, at present, no detailed models exist for tie lines in the planning of multi-area power systems. In this paper, a novel multi-area and multi-objective model for the generation, transmission, and battery energy storage systems expansion planning is proposed in a central planning method that considers uncertainties of wind power and load. Tie lines among different subareas are used as support power sources, and detailed tie-line expansion planning models that consider the power flow direction, degree of power flow fluctuation, and number of power flow direction reversal in the tie line are presented to make the model more realistic. Besides, short-term operation problems (i.e., unit commitment) are incorporated in the long term planning issues to improve the adaptability of planning schemes. Linearized procedure for the different tie-line operation modes is implemented in order to improve the efficiency of the presented model. The proposed model is finally transformed into a mixedinteger linear programming formulation. The modified IEEE RTS-24 bus system is conducted to evaluate the practicality and effectiveness of the proposed method.