Modelling for Composite Load Model Including Participation of Static and Dynamic Load

Abstract

It is well recognized that voltage problems in power system is much affected through the connected loads. Different types of load can be modeled on their characteristics basis for computation of power system problems effectively. For different power system studies especially in the area of power system optimization problems that includes voltage control with reactive power compensation, transfer function \(\Delta Q{/}\Delta V\) of composite load is required. This chapter gives a detailed mathematical modelling to compute the reactive power response with small voltage perturbation for composite load. Composite load is defined as a combination of static and dynamic load model. To develop this composite load model, the exponential load is used as a static load model and induction motors are used as a dynamic load model in this chapter. To analyze the dynamics of induction motor load, fifth, third and first order model of induction motor are formulated and compared using differential equations solver in MATLAB coding. Since the decentralized areas have many small consumers which may consist large numbers of induction motors of small rating, it is not realistic to model either a single large rating unit or all small rating induction motors together that are placed in the system. In place of using single large rating induction motor a group of motors are being considered and then aggregate model of induction motor is developed using law of energy conservation and this aggregate model is used as a dynamic load model. Transfer function of composite load is derived in this chapter by successive derivation for exponential model of static load and for fifth and third order induction motor dynamic load model using state space model.