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This paper proposes a novel transient stability assessment (TSA) method for hybrid AC/DC systems with VSC-HVDC via port energy. The port energy of VSC-HVDC is described as the function of port state variables and control variables. The representation of port energy greatly enhances the accuracy of the transient stability study and can be extended to arbitrarily power electronics devices. At the same time, this approach can avoid formulating energy function with the complex internal controls of VSC-HVDC. Furthermore, iterative potential energy boundary surface (IPEBS) is employed to TSA. The maximum potential energy is searched on the instability of rotor angle’s swing curves as the critical energy through the dot product criterion. Then, the influence of the VSC-HVDC for transient stability is studied, including the VSC-HVDC transmission capacity of active and reactive power. The accuracy of the proposed energy function calculation is discussed via the different fault location. The feasibility and validity of the proposed method are demonstrated via the modified IEEE 39-bus hybrid AC/DC system.

This paper presents a spectrum analysis-based method to calculate the optimal sizing and operation strategy for a hybrid energy storage system (HESS) combining batteries (BT) and supercapacitors (SC) to integrate high penetrations of wind power into the power grid. BTs and SCs have different response times and energy densities, which can be used to complementarily compensate the generation-demand imbalance. In this paper, the unbalanced power is first converted from time domain to frequency domain by discrete Fourier transform (DFT). Then upper and lower cut-off frequencies are determined to calculate the optimal sizing for each energy storage source. Moreover, a chance-constrained programming model is established to explore the optimal operation strategy for HESS. The model is solved by Monte Carlo simulation and a genetic algorithm. Simulation results on a practical system demonstrate that the proposed method can effectively reduce the ESS investment cost and maximize the economic profits.

This paper proposes a multi-objective approach for low-carbon economic dispatch with carbon capture power plants (CCPPs) and demand response (DR). First, brief dispatching model of CCPPs is presented. The operation mechanism of CCPPs and DR for different objectives is analyzed. Then, the multi-objective low-carbon economic dispatch model with CCPPs and DR is proposed. The objectives include minimizing the bidding cost of conventional power units and wind power, minimizing carbon emissions, maximizing utilized wind power and minimizing DR cost. The weighting coefficients of the objectives are calculated by analytic hierarchy process (AHP). The optimization model is recast as a mixed integer linear programming (MILP) formulation and solved by CPLEX. Finally, numerical results performed on the modified PJM 5-bus system verify the feasibility and effectiveness of the developed model by comparing to single objective cases.