Research On Nonlinear Governor Control And Primary Exploration Of Secondary Active Power Control

The active power control is of great importance for the safe and stable operation of power systems. As present various kinds of nonlinear governor controllers can not consider the speed-droop characteristic of practical governors, and should know system's post-disturbance operating point in the process of control, the nonlinear governor controller with speed-droop characteristic is focused in this paper. Meanwhile, there are some problems existing in the Automatic Generation Control (AGC) system, which is a popular secondary active power control system, for example, all controlled units should act when suffered a relative small load disturbance; the equal incremental method used in AGC to solve the economic load dispatch problem can't consider the valve point effect of practical units. So, this paper makes a primary exploration of secondary active power control problem, and attempts to give a scheme that can deal with the valve point effect of practical units. In detail, main contents of this paper are as follows:1. The governor controller with speed-droop characteristic is designed. Different from selecting single variable (such as rotor angle or rotor speed) as control output in normal nonlinear governor control methods, a combined output, or the linear combination of rotor speed and mechanical power, is chosen in the paper, and then the nonlinear governor controller is designed based on this combined output. Under the control of the proposed nonlinear governor controller, there will be a definite proportion relation between the differences of the rotor speed and the mechanical power with their initial values. Furthermore, this proportion is assigned as the speed-droop, and thus the proposed controller can reflect the speed-droop characteristic. Meanwhile, it does not need to know system's post-disturbance operating point in the process of control for the proposed controller.2. The paper attempts to give a secondary active power control scheme, which can deal with the valve point effect of practical units. Different from present AGC scheme, when the load disturbance is relative small, the unit that has best regulation performance (largest capacity, fast speed) will be selected and will act firstly, and thus the stable control mission will be completed. Then based on the status of the stable control mission and the residual capacity of the first acting unit, the scheme decides whether conduct economic load dispatch among other controlled units or not. In order to consider the valve point effect of practical units, the proposed control scheme can conduct economic load dispatch based on not only the traditional equal incremental method but also the improved particle swarm optimization algorithm. Based on PSASP, and selecting the EPRI-36 AC system as a sample system, the simulations of above controllers and algorithms are performed in the paper, and the results demonstrate their validities.The work of this paper is supported by the National Natural Science Foundation of China.