Abstract
Coupled with the power system through power-electronic interfaces, renewable energies including wind power and photovoltaic can control the power quickly and flexibly. In the steady-state stability analysis, by neglecting the fast dynamics of power-electronic interfaces, the renewable energy power is simplified to a static power injection model and can be described as an algebraic equation in the dynamic process. Based on this simplified model, the steady-state stability of sending-end system with mixed synchronous generator and power-electronic-interfaced renewable energy is studied. By proposing a triangular transformation model based on the classical model of power system, the steady-state stability analysis becomes feasible. The mechanism of steady-state stability is revealed, and the influence of renewable energy on the steady-state stability limit is quantitatively investigated. When the renewable energy power increases, the steady-state stability limit of the sending-end system first increases and then decreases. Reducing the power output of synchronous generator can change for a higher integration limit of renewable energy. Simulation results validate the conclusion.
Highlights
Coupled with the power system through power-electronic interfaces, renewable energies including wind power and photovoltaic change the stability of power system. e dynamic equations of power system due to the introduction of power-electronic interfaces become more complex, and it is difficult to analyze the influence of renewable energy on the power system stability
With the increasing maturity of detailed models of wind power, photovoltaic, and other renewable energies, the research on the stability of power system with large-scale renewable energy mainly relies on numerical simulation methods [1,2,3,4,5,6,7,8], namely, establishing a detailed mathematical model for simulating the dynamic process of renewable energy, and carrying out the numerical simulation through such stability analysis software as BPA, PSASP, and PSS/E. e numerical simulation method has the advantages of good model detail and high precision and can simulate the response characteristics and dynamic process of renewable energy in detail
In equation (1), the electromechanical transient process of the thermal generator with slow speed is described by differential equations, and the regulating process of the renewable energy with fast speed is simplified to algebraic equations. is model is reasonable for the analysis of the steady-state stability of power system. e main advantage of this model is that the model is simple and beneficial to the analysis of stability mechanism, while the disadvantage is that the detailed dynamic process of renewable energy is simplified
Summary
Coupled with the power system through power-electronic interfaces, renewable energies including wind power and photovoltaic change the stability of power system. e dynamic equations of power system due to the introduction of power-electronic interfaces become more complex, and it is difficult to analyze the influence of renewable energy on the power system stability. Since the response time constant of renewable energy is much less than the inertia constant of thermal generator, the renewable energy can be approximately equivalent to a constant power load in the steady-state stability analysis. E simulation result of a certain sending-end system with renewable energy in China is shown, and it can be seen that in the dynamic process after fault, both wind power and photovoltaic power fast converge to the steady state, and there is no such phenomenon as the electromechanical oscillation of the thermal generator. E power system of a thermal generator and a renewable energy generator transmitting power to an infinite bus (see Figure 2(a)) is defined as “renewable-thermal infinite bus sending-end system,” where a classical model is used for the thermal generator, and the transient resistance is incorporated into the network, and after the star-delta transformation, the equivalent circuit (see Figure 2(b)) can be achieved For this system, the following algebraic differential equations based on the classical model can be formulated:. In equation (1), the electromechanical transient process of the thermal generator with slow speed is described by differential equations, and the regulating process of the renewable energy with fast speed is simplified to algebraic equations. is model is reasonable for the analysis of the steady-state stability of power system. e main advantage of this model is that the model is simple and beneficial to the analysis of stability mechanism, while the disadvantage is that the detailed dynamic process of renewable energy is simplified
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