The Optimization Algorithm of Torque Compensation for PMSM Systems with Periodic-Nonlinear Load - Intelligent Computing for Sustainable Energy and Environment - page 333

The Optimization Algorithm of Torque
Compensation for PMSM Systems
with Periodic-Nonlinear Load
Ning Chen, Yong Fan, Weihua Gui, Hao Zhang, and Shouyi Yu
School of Information Science and Engineering,
Central South University, Changsha, 410083, China
[e-mail]
Abstract. Non-linear variations of load torque cycles in the low fre-
quency operation of interior permanent magnet synchronous motor lead
to rotor imbalance. To deal with this issue, we apply a low-frequency
torque compensation algorithm based on control parameterization
method. Given the load torque, the control variable is approximated
by a piecewise constant function whose magnitudes are taken as decision
vectors. The control problem is thus transferred into a mathematical pro-
gramming problem , which can be solved by the Sequential Quadratic
Programming (SQP) algorithm. The simulation results show that, the
state variables are close to their target values. Thus, the method avoids
chattering and ensures system stability.
Keywords: IPMSM, control parameterization, sequential quadratic pro-
gramming algorithm.
1 Introduction
Permanent magnet synchronous motor (PMSM) is becoming more and more
popular in the field of Robot, NC Machine Tool, Electric Vehicle, Compressor,
because of its high power density, high eciency, low loss and easy to control.
Due to system nonlinearity and instability of control parameters in practice
especially in low frequency operations, the reciprocating compressor performs
three procedures including suction, compression and exhaust. The speed of rotor
is affected by load torque and electromagnetic torque, i.e., when load torque is
large but electromagnetic torque is small, the rotor speed is low. Variations in
load torque and electromagnetic torque lead to fluctuations of the rotor speed
and cause chattering. The cyclical fluctuations of rotor speed within a cycle will
lead to system speed imbalances and significantly reduce system performance.
It may also cause pipeline rupture when Inverter Air-Conditioner operates in
low frequency state for a long time. During the low frequency process, periodic-
nonlinear variations of the compressor load torque have fatal consequences to the
stable operation of the system. The traditional FOC control strategy is effective
for real-time speed control, but the speed loop is slower and the reference torque