Predictive Control of Power Converters and Electrical Drives

4.3 Cost Function

The objective of the current control scheme is to minimize the error between the measured currents and the reference values. This requirement can be written in the form of a cost function. The cost function is expressed in orthogonal coordinates and measures the error between the references and the predicted currents:

4.1

where and are the real and imaginary parts of the predicted load current vector i^p(k + 1), for a given voltage vector. This prediction is obtained using the load model, which will be explained in detail in the sections below. The reference currents and are the real and imaginary parts of the reference current vector i^*(k + 1). For simplicity, we will assume that this reference current does not change sufficiently in one sampling interval, so we will consider i^*(k + 1) = i^*(k). This assumption may introduce a one sample delay in the reference tracking, which is not a problem if a high sampling frequency is considered. In other cases it is possible ...