Abstract
This paper represents control strategy of anisotropic permanent magnet synchronous motor (IPMSM) in the field-weakening region. Field weakening controller allows to increase maximum achievable speed with output torque reduction. Proposed control system consists of four general modes: MTPA (maximum torque per ampere), MC (maximum current), FW (field weakening), and MTPV (maximum torque per voltage) which must be chosen accordingly to motor speed, current and torque references. Operation point is found as an intersection of torque hyperbola and voltage ellipse curves in d-q motor’s current reference frame involving motor parameters’ limits. However, due to nonlinear dependence between torque and voltage equations, it is quite complicated to obtain both right control mode selection and reference output calculation. In order to solve this problem, a unified control algorithm adopted for wide speed and torque reference with online constraints calculation is proposed. Matlab/Simulink control model of PMSM motor and control system were designed in order to show developed strategy performance. Simulation results shows increasing of speed limit by more than 2.5 times related to nominal speed with high controller’s response. However, speed limit increasing leads to a decrease in motor’s output torque. Due to this fact, presented control strategy is not suitable for applications where nominal torque level is essential for all speed operation points.
Highlights
Permanent magnet synchronous motors are widely popular in different industrial applications, such as machinery [1], power generation [2,3,4], as a source for high current consumers [5,6] with current limiting [7, 8] devices, autonomous research units [9], hybrid [10,11,12], electric [13] vehicle motion, aircraft [14], etc
According to [16,17] for wide speed applications anisotropic permanent magnet synchronous motors are more suitable than isotropic ones because of smaller airgap between rotor and stator surfaces, which leads to additional reluctance torque in field weakening operation region [18]
There are four general operation modes, which must be chosen due to a reference speed, torque values, motor parameters and current, voltage constraints: Maximum torque per ampere strategy (MTPA), Maximum current strategy (MC), FW and Maximum torque per voltage strategy (MTPV), which is detailly presented on figure 1
Summary
Permanent magnet synchronous motors are widely popular in different industrial applications, such as machinery [1], power generation [2,3,4], as a source for high current consumers [5,6] with current limiting [7, 8] devices, autonomous research units [9], hybrid [10,11,12], electric [13] vehicle motion, aircraft [14], etc. There are four general operation modes, which must be chosen due to a reference speed, torque values, motor parameters and current, voltage constraints: MTPA (maximum torque per ampere), MC (maximum current), FW (field weakening) and MTPV (maximum torque per voltage), which is detailly presented on figure 1. MC strategy must be chosen when motor’s reference speed and torque are higher than stan standard value (arc which starts from MTPA curve endpoint (point A) and ends in point B which is an intersection of MPTV curve and maximum current circle). In finite speed motors point “C” known as characteristic current [24] locates beyond the maximum current circle. This mode involves to use voltage reference limit as constraint instead of maximum current limit used in MC strategy. FW – area inside of the shape, limited by three mentioned above strategies (0-A-B-C points)
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