Abstract
Taking the Steady-state Security Region (SSR) of AC/DC hybrid power system as a link, the mathematical model of coordinated control optimization problem is established by using the complementarity between preventive control and corrective control. Firstly, taking into account the probability and severity of anticipated accidents, a two-layer optimization model of coordinated control with dynamic constraints is established with the lowest total cost of coordinated control as the objective function. Secondly, invalid anticipated accidents are eliminated based on the theory of dominant event, which reduces the scale of the model and the complexity of optimization space. Finally, based on the constraint relaxation outer-layer optimization method, the anticipated accident with the minimum Steady-state Security Distance(SSD) is eliminated from the preventive control subset and incorporated into the corrective control subset, providing fixed anticipated accident subsets for the inner-layer optimization. In the inner-layer optimization, the SSDs are used to replace the power flow equations as the constraint condition, then the nonlinear constraints are transformed into linear constraints, which can reduce the difficulty of solving the mathematical model. The transformed IEEE 39 node AC/DC hybrid system is analyzed and calculated, and the calculation results verify that the proposed method can effectively improve the efficiency of solving optimal control scheme, and provide the possibility for online application.
Highlights
Nowadays, the power system is developing towards the direction of large power grid and AC/DC hybrid connection, and its operating environment is more and more complex, which makes the issue of static security of the power grid more challenging than ever, and the study of power system security control is becoming more and more important [1]–[4]
Based on the above analysis, this paper proposed a coordinated control optimization model based on state Security Region (SSR)
The coordinated control process of AC/DC hybrid power system based on SSR is divided into three steps: Step 1: Divide the anticipated accident set into preventive control subset p and corrective control subset c
Summary
The power system is developing towards the direction of large power grid and AC/DC hybrid connection, and its operating environment is more and more complex, which makes the issue of static security of the power grid more challenging than ever, and the study of power system security control is becoming more and more important [1]–[4]. The safety margin and optimal control information of the system can be obtained by observing the Steady-state Security Distance (SSD) between the operating point and the boundary surfaces of SSR [15]–[17]. The advantages of the coordinated control method and the main contributions of this paper can be listed as follows: 1) Based on the theory of SSR of AC/DC hybrid power system, the boundary surfaces of SSR are represented by hyperplanes, and the calculation methods of expressions of hyperplanes and SSD are provided. (xαi ,j) i=1 n where (xαi ,j) denotes the distance from the critical point i=1 xα,j to the origin
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