Coordinated dynamic voltage stabilization based on model predictive control

Abstract

Keeping voltages of all buses within acceptable bounds is very important for power system operations. This paper presents an approach for optimal coordination of static var compensators (SVCs), transformer under load tap changers (ULTCs) and load shedding to improve voltage performance following large disturbances. The approach is based on model predictive control (MPC) with a decreasing control horizon. The MPC formulation leads to a mixed integer quadratic programming (MIQP) problem, since both continuous and discrete controls are considered. Trajectory sensitivities are used to evaluate the effect of controllers on voltage performance. The iterative optimization process of MPC helps ensure that errors introduced due to any model inaccuracies and approximations are minimized. The MPC based coordination of these controllers is applied to a modified WECC system to enhance the voltage performance and to a modified 39-bus New England system to prevent voltage collapse.

Coordinated Voltage Control With Online Energy Margin Constraints

“…Based on the definition of the Lie derivative on the energy manifold, the impact factors can be calculated. Based on (19), the change of the energy margin due to changes in bus voltages is given by (22) In (22), is the Lie derivative. Based on (18), it is (23) When control variable is changed, the change in the energy margin is obtained by (24) Similarly, the impact factor of the tap ratio is computed by (25) The change in energy margin due to a change in control variable is given by (26) The impact factor of is computed by (27) The change in the energy margin caused by a change in is obtained by (28) Hence, the impact factor of is (29) The values of impact factors are the sensitivity of the energy margin with respect to the variables along the system trajectory.…”

“…and online adaptive control [18].The model predictive control (MPC) method is applied to CVC [19]- [22]. The coordination of actions in secondary voltage control is solved by the optimal coordinated voltage controller based on MPC [19].…”

“…With the state space model, a MPC strategy is adopted for coordinated secondary voltage control [21]. Based on agent coordination, a distributed non-cooperative MPC formulation with neighbor-to-neighbor communication is proposed for long-term voltage control in multi-area power systems [22]. Other methods include genetic algorithm [23], Lagrangian decomposition algorithm [24], and graph theory for neighborhood compensation [25].…”