High-Frequency Injection-Based Stator Flux Linkage and Torque Estimation for DB-DTFC Implementation on IPMSMs Considering Cross-Saturation Effects

Abstract

Deadbeat-direct torque and flux control (DB-DTFC) is a direct torque control method that provides the fastest possible torque control, low ripple, easily integrated dynamic loss minimization control, and one control law that uses the inherent volt-second source properties of power electronics to enable operation over all operating conditions, including voltage limits. DB-DTFC is a model-based discrete time controller that relies on precise machine parameter, flux, and torque estimation to provide fast dynamic torque control. In this paper, a new method for high-frequency injection (HFI)-based self-and mutual incremental inductance estimation is proposed and evaluated in both simulations and experiments. In this new method, the estimated incremental inductances including cross-coupling inductance due to cross saturation are curve fitted offline and then used to calculate the apparent inductances. With the apparent inductances, the stator resistance and permanent-magnet flux linkage are estimated using recursive least squares method online. The stator flux linkage observer using the identified machine parameters yields improved stator flux linkage estimates that enable precise torque calculation. Experimental evaluation of the HFI-based flux estimates on torque estimation and control accuracy is performed at an interior permanent-magnet synchronous machine drive test bench with a torque transducer mounted.

Comparative Analysis of High Frequency Signal Injection Based Torque Estimation Methods for SPMSM, IPMSM and SynRM

“…Torque in Equation 6is a function of absolute (apparent) inductances. However, the inductances of the HF model (7) and (8) are incremental inductances [34], i.e., inductances estimated by means of HF signal injection will be incremental. It is needed therefore the establish the relationship between absolute and incremental inductances.…”

“…It can be seen from (32) and (33) that obtaining L dHF and L qHF is not straightforward due to cross-coupling between dq-axes. However, if the frequency of the injected HF signal is sufficiently higher than the rotor frequency, the rotor speed dependent terms can be safely neglected, the HF currents induced in the stator simplifying to (34) and (35). An orientative value for this assumption can be ω HF > ω r + 2 • π • 500 rad/s [12].…”

Current-Controller-Free Self-Commissioning Scheme for Deadbeat Predictive Control in Parametric Uncertain SPMSM

“…When considering the inductance variation under the saturated effect, the concept of incremental and apparent inductances must be concerned [12]. The values of incremental inductances can be much less than those of apparent inductances at heavily saturated conditions [13]. However, as for influence of inductance mismatch on DBPC, there is still lack of analysis in terms of incremental inductances and apparent inductances in the existing literature.…”

Discrete-Time Observer Design for Sensorless Synchronous Motor Drives

“…Motion-sensorless operation is commonly preferred [2]- [16]. Usually, a speed and position observer is first designed in the continuous-time domain and then discretized for the digital processor by means of the forward Euler, symplectic Euler, or Tustin approximations.…”

“…Higher fundamental frequencies and improved robustness at a given sampling frequency can be achieved by designing the control system directly in the discrete-time domain [16]- [22]. For the direct discrete-time control design, a holdequivalent discrete model-including the effects of the zeroorder hold (ZOH) and sampler-of the motor drive is needed.…”