Optimal secondary voltage-VAR control using pilot point information structure

French researchers have recently introduced the concept of "secondary" voltage-VAR control based on "pilot points". Operator control of the input reference values on primary AVR's is termed secondary, voltage-VAR control. The French have proposed that such secondary control can be automated by monitoring certain key buses and making adjustments based on these "pilot point" voltages. The pilot points and the control strategy proposed are based on engineering intuition. We pose the problem of determining the optimal pilot point or points as an optimization problem using a Chebyshev norm. That is, we seek a pilot point and a control strategy that will minimize the maximum voltage deviation under a class of disturbances. If all voltage magnitudes are monitored we show that optimal secondary control is achieved through the solution of an overdefined set of equations in the Chebyshev sense. Various control strategies based on less information (a number of pilot points) are investigated including the original French strategy. As an example of optimal pilot point for the IEEE 30 bus test system is determined.