Power System Preventive Control Based On Fast Numerical Integration

With the expansion of the electric power system, power system security and stability issues have become increasingly prominent. The emergency control and preventive control are important means to ensure the operation of power system safe and stable. The research of emergency control is relatively mature, various emergency stability control devices have been widely used. The requirements of the computation speed of preventive control algorithms are very demanding. There is still some distance between research result and practical engineering application.In this paper, the preventive control will be regarded as such a problem, which is optimal parameter selection problem of the objection function with constraint functions contain the differential-algebraic equations.At first, this paper first outlined the specific steps of the transient stability calculation. In order to increase the computation speed, a fast time-domain simulation methods is proposed, in which explicit numerical integration is applied based on the second-order generator model. Using the second-order equations of the generator rotor motion, the traditional differential calculation process based on alternating iterative method is changed, thus the speed of transient stability computation is improved.Then, according to the reference, a transient angle stability criterion suitable for practical engineering application is introduced. The mentioned criterion is added to the preventive control model, thus the OTS model with transient stability constraints is established. By the optimal control theory, the generator’s state equation and co-state equation are deduced. Through the simultaneous solution of the two sets of equations, we can calculate the gradient for the transient stability constraints to the control variables. This OTS model approach is different from the general paper in which the transient stability constraints are discreted. The dimension of the transient stability constraints significantly reduced, and thus a larger increase in computing speed.So, the preventive control problem considering transient stability constraints becomes an optimization problem. When using interior point method to solve optimization problems, it has the following characteristic:rapid convergence, strong robustness and not sensitive to initial value. In the end, interior point method is used to solve this model.