Abstract
Abstract: The nonlinearity and uncertain variation of machine parameters are always caused by cross coupling and magnetic saturation effects, which are easily neglected in the conventional control strategy. In this paper, a current trajectory control strategy (CTCS) is proposed to take the cross coupling and magnetic saturation effects into account under voltage and current constraints. It can be considered as a calculating method considering parameter variation and separating among each iteration step which treats the calculated result of the former step as the initial value of the next step. At first, the torque command is translated into the current reference. Then, the increments between the target value and real value of the torque and the voltage are respectively calculated, which are subsequently converted into the current modification vector in did, diq framework for further analysis. In order to take the influence caused by cross coupling and magnetic saturation effects on the CTCS into consideration, self and mutual inductances are analyzed by finite element analysis (FEA). The results of the simulation and experiment show that the rapid response and robustness on reference speed variation could be achieved by employing the proposed CTCS, and the seamless switching between the constant torque and flux-weakening operation can also be realized.
Highlights
The interior permanent magnet synchronous machine (IPMSM) has become an ideal choice for electric vehicles (EVs) nowadays because of its higher torque density, wider speed range, and higher reliability compared with other types of machines [1,2]
This paper proposes a novel current trajectory control strategy which uses the voltage and torque incremental value to derive the dq-axis current reference under predefined electrical constraints
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Summary
The interior permanent magnet synchronous machine (IPMSM) has become an ideal choice for electric vehicles (EVs) nowadays because of its higher torque density, wider speed range, and higher reliability compared with other types of machines [1,2]. Dating back to the 1990s, in [8,9], the operation region of a motor has already been divided by precalculating the current reference for each region and pre-settling the speed reference for operation interval switching Based on this principle, numerous methods have been studied to compute the current control target from analytical equations which substantially control the terminal voltage of a motor. Due to the nonlinear parameters of IPMSM caused by magnetic saturation, cross-coupling effects, and temperature, is the definite switching point of two algorithms difficult to derive, but it imposes impediments in conventional optimal control which assume that the motor parameters are fixed [14]. The demagnetization of a permanent magnet caused by temperature is neglected, as well as the influence of error aroused by inaccurate observations Both a simulation and A 10 kW IPMSM prototype are studied to validate the sensitivity of the proposed method about reference speed variations
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