General Steady-State Modeling and Linearization of Power Electronic Devices in AC-DC hybrid Grid
Abstract : Power electronic devices are important in the modern power system. Control functions and operational characteristics of power electronic devices bring higher nonlinearity and heavier calculation burden for power system analysis, especially in optimization problems. In this paper, a general steady-state model of power electronic devices in the AC-DC hybrid grid is proposed, which considers the high voltage direct current (HVDC) connections and the flexible AC transmission systems (FACTS). Power electronic devices are equivalently represented by impedance, transformers, and controlled sources. The linearized steady-state model is derived and then the specific formulation with minimized error is presented. The effectiveness of the proposed method is verified by optimal power flow (OPF) calculation in the IEEE and Polish test systems.
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? Other penalty functions such as the log-barrier method utilized in solving the interior point method also exist.
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? Decentralized control is less susceptible to network security problems; however, it does not allow for collaboration among resources which can result in a sub-optimal operating point.
? The genetic algorithm is inherently a method for unconstrained optimization. However, as discussed in , modifications may be made to this method in order for it to be applied to the constrained problem.
? The genetic algorithm (GA) consists of 3 major processes: reproduction (selection), crossover, and mutation.
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• The proposed method is found to quickly and accurately calculate the optimal power flow and reject solutions that violate the inequality constraints beyond some specified tolerance.
• While optimizations were not addressed directly in this dissertation, the proposed modeling approach offers tools optimization of system operation.
• The HSSPFC method proposed in this chapter for VSR control is more versatile in that in the event of a loss of communication with the grid, it can continue operate without any loss of performance.
• In order to achieve this, a modified P&O method is proposed where the voltage is adjusted until the power moves back into the feasible region.
? Therefore, by simplifying control loops and converters, this paper proposes a simplified model for the microgrid system power flow and the dynamic response under exposure to a fault.
? The mathematical model equivalent simplification method is used in this paper. This method is concise and efficient and does not rely on the performance of a computer or change the program algorithm of the software.
? The simplified model was built based on PSCAD (Power System Computer Aided Design) simulation software and was carried out under short circuit fault conditions to verify its validity.
? Through the mathematical model equivalent simplification method, there is no need to apply a new program or algorithm. The reduction of the amount of simulation data can reduce the dependence on the performance of the computer
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