Abstract
An asymmetric, cross-coupling effect, as well as digital control delays, in a permanent-magnet synchronous motor (PMSM) will deteriorate its current-control performance in the high-speed range, especially for electric motors used in electric vehicles (EVs) with features such as high-power density and a low carrier/modulation frequency ratio. In this paper, an angle-compensating, complex-coefficient, proportional-integrator (ACCC-PI) controller is proposed, which aims to provide an excellent decoupling performance even with considerable digital control delay. Firstly, the current open and closed loop complex-coefficient transfer functions were established in the synchronous rotation coordinate system. The proposed method, along with existing ones, were then evaluated and theoretically compared. On this basis, the parameter-tuning method of the ACCC-PI controller was presented. Finally, simulation and experimental results proved the correctness of the theoretical analysis and the proposed method.
Highlights
A permanent-magnet synchronous motor (PMSM) has the advantages of a compact structure, good performance, high efficiency and power density and a wide speed range
In a typical double-loop, control-structure based, field-oriented control (FOC) strategy of a PMSM used as drive motor, the outer loop determines the speed response and the inner loop decides the steady and dynamic performance of the whole drive system
In the high-speed operation, the asymmetric coupling effect between the d-axis and q-axis current dynamics becomes so significant that, without proper compensation, the current-control performance leads to instability as the fundamental frequency of the PMSM increases
Summary
A permanent-magnet synchronous motor (PMSM) has the advantages of a compact structure, good performance, high efficiency and power density and a wide speed range. Based on the experimental results, the advantages and disadvantages of the two PI regulators were compared in terms of decoupling of the control structure, the dynamic response speed of the current loop and parameter robustness [17]. An alternative decoupling method based on a complex-coefficient, proportional-integrator (CC-PI) controller was proposed, which could prevent the current loop from being unstable in the case of low carrier ratio. On this basis, the parameter tuning method of an ACCC-PI controller was presented. Considering the digital control angle delay, the actual d q axes’ components U d and U q of the voltage vector Us are illustrated in Equation (7). AccoDrdiginitgaltCooEnqtruoal tDioenlay(7s) and Fieg ufrMe 1obde, lthoef PcMurSrMent-loop control block dia the digital control delays of the PMSM is shown in Figure 3, id* and iq* repre andFigqu-raex3i. sCucroremnt-mlooapncdontcroulrbrloecnktd,iargerasmpewcitthivdiegliyta.l cTonhtreoladnelgaylseodf tehleaPyMShMa.d a similar coup
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