Nonlinear Coordinated Control Of Statcom And Generator Excitation Differential Algebraic System

In recent years, with a large number of non-linear power equipments such as high power wind turbine and electrified railway have being in operation, maintain the system reactive power balance and ensure the electricity system safety and stable operation become the primary task of the power grid. Flexible AC Transmission system (FACTS) is a kind of new power system network technology based on modern power electronic technology. Based on our countrie’s power grid instability and reactive power distribution unbalanced situation, more and more FACTS equipments have been put into operation. As an important member of FACTS family, Static Synchronous Compensator (STATCOM) which has been known as the most ideal static reactive compensation device can rapidly provide enough reactive power to support system voltage through dynamic process. Generator excitation control has been considered by overwhelming majority of scholars as an important mean to ensure the power output of generator stability and damp the low frequency oscillation of power grid, is also be used as one of main carriers in electric power system’s nonlinear control study. Therefore, how to coordinate STATCOM and generator excitation control is a work with highly theory value and practical engineering significance.Based on differential algebraic system control theory as the cornerstone, mainly completed the following work:(1) Select the most practical value of salient pole type generator as research object, the three-order nonlinear mathematical model is established for the generator excitation. Meanwhile, starting with the internal structure of STATCOM, this paper uses the STATCOM’s pulse control angleθ and the angle a which is between the voltage vector of output of the STATCOM and the voltage vector of an infinite system as control variables. Based on the d-q-0coordinate axis, a new type mathematical model of STATCOM is put forward. The new model has overcomed the previous mathematical model’s strong constraints conditions. The simulation results show that both of the two models which are established in the paper are correct and reasonable.(2) Combining the two models mentioned above, the six-order nonlinear coordinated control system is established basing on differential algebraic system theory. Selecting reasonable combination output function, the design of nonlinear coordination control strategy is completed. Then, the nonlinear control law u is obtained under the method of multi-index nonlinear control (MNC). The simulation results compared with the method of Linear Optimal Control (LOC) indicate that the MIMO system model and the nonlinear control law u presented in this paper are reliable and effective.(3) In order to cut the control strategy’s reliance on the system constraint condition, and to reduce the difficulty of configuration c、k parameters which are included in the nonlinear control law u, nonlinear control method with objective holographic feedbacks (NECOHF) is introduced into the coordinated control system by this paper. According to object holographic feedback control principle, six tracking targets which are concerned by engineering practice are selected. In order to get the nonlinear control law u containing all target control feedback information, multi objective control problem is switched from the nonlinear space into linear space by the dynamic constraint method. Then, the design of coordination controller for MIMO system is completed. The simulation results show that the design process of NECOHF controller is not only simple to complete, but also effective to avoid complicated calculation. The controller shows excellent reliability and controlling when the power system encounter with common disturbance. It has a certain application value.