Research On Methodology Of Power System Preventive Control With Transient Stability Constraints

Both stability-constrained emergency control and transient stability preventive control are mainly important methods for the stability of power system .The former has been under intensive investigation and has made much progress in project applications. However, for the latter problem, no scheme has reached practical level up to now due to its inherent complexity. In this paper, preventive control models with transient stability constraints are constructed and systematic solution methods based on optimal algorithms for solving the nonlinear problems are studied in detail.Firstly several criterions of transient angle stability are discussed in this paper. Then one criterion suitable for industrial practices is put forward as transient stability constraints for preventive control. Based on optimal control theory, an effective approach, to calculate the gradients of transient stability constraints with respect to all control variables, is proposed by simultaneously computing generator dynamic equations and co-state equations. This approach could be called co-state equation methods. According to the proposed approach, the transient stability constraints are simplified which could improve the calculating efficiency, and a refined OPF-based transient stability preventive control model is established. Then an optimal algorithm named SQP is adopted to solve the preventive control problem. Since the high-dimensional transient stability constraints are simplified dramatically, the preventive control model is suitable for large scale power system meanwhile it could deal with multi-contingency effectively.Power system transient stability consists of transient angle stability and transient voltage stability. Only both of them are met, the power system will be guaranteed under stable operation. This paper proposes a criterion of transient voltage stability which is applicable to practical power system. According to the proposed criterion, transient voltage stability problem is described as a integral type constraints. Similarly to the transient angle stability constraints, the gradients of transient voltage stability constraints with respect to all control variables are also calculated by co-state equation methods. Then a simplified transient voltage stability constraint could be joined into the preventive control model.At last, by combined preventive control and optimal algorithm, the transient stability constrained preventive control is applied to solve optimal power flow problem and total transfer capability problem. Numerical test results demonstrate that approaches proposed in this paper can improve computational speed, decrease constraints dimension and the incorporation of multi-contingency don't aggravate calculate burden dramatically. That means the proposed models and approaches can handle transient-stability constrained preventive control effectively and efficiently.