A Multi-loop Transient Stability Control via Power Modulation from Energy Storage Device
Abstract : This paper presents an optimal transient-stability control strategy that modulates the real power injected and absorbed by distributed energy-storage devices. These devices are located at the high-voltage bus of several generators in a synchronous power system. The system is broken into areas based upon groupings of generators. The control strategy consists of two parallel feedback loops. One loop focuses on preserving the synchronism of the generator to its own area. The second loop focuses on preserving the synchronism of a given area to the other areas. Each control loop strategy is based upon local and center-of-inertia frequency measurements. The strategy is derived from two perspectives. With the first, the goal is to remove as much kinetic energy gained during a disturbance as quickly as possible before it is converted to potential energy. With the second perspective, an optimal transient control costfunction is minimized. Both perspectives result in the same strategy. The performance of the control strategy is evaluated on a four-machine power system model and on a 34-generator reduced-order model of the western North-American grid. The results show that this control approach significantly improves the transient stability of power systems.
? It is worth pointing out that the active and reactive power adjustment methods presented in existing literature usually consider case studies with test systems having a share of renewable power generation up to 50%.
? Therefore, this paper focuses on modifying the outer control scheme of the WGs.
? Other methods of existing literature attempted to modify the form of performing current limitations on the grid side converter, whereas other methods have proposed to modify the form of active and reactive power injection (e.g., based on signals measured at the connection point of the WGs).
? This is a classical constrained-input, minimum-time optimal control problem and the application of Pontryagin’s minimum principle yields the well-known bang-bang solution.
? An optimal control problem can be formulated to determine the best trajectory for Pc(t).
? The first constraint limits the maximum power absorption and delivery of the storage device and the second guarantees that the kinetic energy is gone at the end of the active control period.
? The state equations are derived from with d and ?d as the states.
• In a static synchronous compensator (STATCOM) based method has been proposed to enhance LVRT capability of four parallel-operated fully decoupled WGs fed to a power system by a proportional–integral–derivative (PID) damping controller designed based on the modal control theory.
• This paper bridges the research gap on how to mitigate the amplitude of the first swing while enhancing the damping of rotor angle oscillations triggered by major electrical disturbances.
• To this aim, a power-angle modulation (PAM) controller is proposed to adjust the post-fault active power response of the WG system
? The performance of the control strategy is evaluated on a four-machine power system model and on a 34-generator reduced-order model of the western North-American grid. The result shows that this control approach significantly improves the transient stability of power systems.
? To compare the performance of the multi-loop control strategy with that of the single-loop control, the simulation is repeated; however, in this case, the single-loop control strategy is implemented rather than the proposed multi-loop control strategy.
? The performance of the control strategy is demonstrated on this contingency. Using the latched control, the speed of all the generators in the system grouped by their respective areas.
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