A Robust Method for Induction Motor Magnetizing Curve Identification at Standstill

Abstract

Modern electric drives use a self-commissioning procedure to precisely identify motor parameters for achieving high-performance control. Typically, the induction motor magnetizing curve is identified using no-load rotational test. However, some applications necessitate the electric drive to identify the magnetizing curve at standstill conditions. As one of the well-known standstill approaches, the traditional flux integration exhibits several practical problems. Any imperfection in measured current, estimated stator resistance, and dead-time compensation directly affects the accuracy of the estimated magnetizing curve because of error accumulation in open-loop integration. This paper proposes a robust yet simple solution against those practical concerns. It can identify the magnetizing curve without using any dead-time compensation and stator resistance. Only industry-standard dc-link voltage and phase current measurements are used. Its superior features are experimentally verified on a number of motors and the results are confirmed by no-load rotational test results. Its robustness against current offset and extra longer integration duration is also proved.

Standstill Self-Commissioning of an Induction Motor Drive

“…We apply the robust flux-integration method [6] to measure the stator flux linkage as a function of the magnetizing current. In this method, DC-current steps are supplied to the stator using a current controller.…”

“…The excitation signal for identifying the rotor-side parameters has to include adequately high frequencies, since frequencies lower than the inverse rotor time constant access mainly the main-flux path. To avoid distortions due to the deep-bar effect, we first identify the three parameters of the rotor-cage impedance model (6). A DC-biased sinusoidal voltage is used to maintain the current sign unchanged, which decreases the effect of inverter nonlinearities.…”

“…However, these methods are sensitive to the estimation errors of the stator resistance and inverter output voltage, since they are based on integrating the induced stator voltage. In [6], a robust method to identify the stator inductance is proposed. This method requires neither the stator resistance estimate nor the compensation for the inverter nonlinearities.…”

“…The Γ model with the nonlinear stator inductance is considered. First, the stator inductance is measured using the robust flux-integration method [6]. Then, the rotor-side parameters are identified using the DC-biased single-phase sinusoidal excitation and solving the parameters from the motor model linearized to the actual operating point.…”

Low-Switching-Loss Finite Control Set Model Predictive Current Control for IMs Considering Rotor-Related Inductance Mismatch

“…Aiming at this problem, three up-to-date categories of remedy measures can be employed. Firstly, online parameter identification strategies can be incorporated into the machine control process to avoid the parameter mismatch phenomenon [23][24][25]. By observing the real-time machine parameters and then substituting them into the DPPM, the predictive control algorithms will be endowed with strong robustness.…”