Machine Parameters Estimation Using Closed-Loop Control Signal Curve Fitting

Apart from the current limits, the voltage limits will also affect the achievable performance of a motor drive. The voltage limits for a fault-tolerant drive will decide the maximum operating speed of the machine before flux weakening, hence the maximum attainable output power. Unlike current limits, the voltage limits of the fault-tolerant drive depend on the machine parameters. Hence, an accurate machine parameter needs to be obtained to estimate the voltage variations under different fault scenarios. By using the measured currents and plugging it into the machine voltage equations, the theoretical voltages for the machine can be calculated using some initial values for the machine parameters. Accurate machine parameters can be obtained by optimizing the machine parameters to minimize the theoretical voltage and the actual control voltages. It is shown that the estimated machine parameters are accurate enough to predict the control voltage references under varying operating conditions.