Publication: Design of robust control strategy for interior permanent magnet motor based hybrid and electric vehicle
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Date
2022-12-01
Authors
Hassam Muazzam
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Abstract
Electric traction motors are the most integral part of Electrified Powertrain of
Electric Vehicles (EV). Among all traction motors, based on high efficiency over a
large speed range, high-power density, reliability, high torque to inertia ratio, control
maturity and high fidelity Interior Permanent Magnet Synchronous Motor (IPMSM)
in EV is preferred choice for today’s automotive industry. In this dissertation, a
state-of-the-art control strategy based on Linear Parameter Varying (LPV) is designed
for EVs to address the crucial challenge of torque derating. An IPMSM based EV is
modelled by taking into account the variations in operating and ambient temperature.
IPMSM control requires accurate knowledge of an immeasurable critical Permanent
Magnet (PM) flux linkage parameter which effects the torque directly. It results in
reduced efficiency due to torque derating and hence power loss, unable to meet road
loads and reduced life span of electrified powertrain. A novel virtual sensing scheme
for estimating PM flux linkage through measured stator currents is designed for an
IPMSM centric electrified powertrain. The proposed design is based on a Uniform
Robust Exact Differentiator (URED) centric Super Twisting Algorithm (STA). A
closed loop torque compensation control architecture with LPV based Field Oriented
Control (FOC) has been designed to manage the thermal effects. In order to curtail
deteriorating of FOC due to parameter variation, a robust LPV observer has been
proposed to estimate the degraded PM flux linkage and instantaneous torque
production caused by uncertainties in stator resistance arises due to thermal effects. The LPV observer along with the current controller is designed and their gains are
computed by solving Linear Matrix Inequalities (LMIs) using convex optimization
and singular value decomposition. The testing has been performed for EV operation
against the Worldwide Harmonized Light Vehicles Test Procedure (WLTP) class 3,
New European Driving Cycle (NEDC) and Federal Test Procedure (FTP) driving
cycles considering thermal effects in Matlab/Simulink. URED based STA ensures
robustness and finite-time convergence of the time derivative of the quadrature axis
stator current of IPMSM. The efficacy of LPV observer controller architecture for
compensating the derating torque of IPMSM based EV is demonstrated through the
validity of results and detailed data analysis using Mean Square Error (MSE) which
was in range between 0.021 to 0.035 for the driving cycles respectively. Moreover,
LPV based FOC is compared with conventional FOC control counterpart. The
comparative results show that the MSE value is reduced up to 6 times for FTP which
establish superiority of the proposed control scheme.