High‐frequency modelling of permanent magnet synchronous motor with star connection

Abstract

Permanent magnet synchronous motor (PMSM) has been widely applied in a pulse width modulation inverter-fed adjustable speed drive (ASD) system. However, electromagnetic interference (EMI) has become a critical issue in such a system. Plenty of high-frequency harmonic components, generated by high dv/dt or di/dt of the modern transistors, can be observed on the line-to-line voltage across motor terminals. To study the conducted EMI issues existed in the ASD system, an improved model of PMSM is developed to represent the high-frequency behaviour, and the equivalent circuit parameters for common mode (CM) and differential mode (DM) are extracted based on the measurements. The model calculated CM and DM impedances are in good agreement with the measured ones from the impedance analyser, which verifies the effectiveness of the proposed high-frequency model.

High‐frequency modelling of permanent magnet synchronous motor for conducted EMI studies

“…The proposed high‐frequency model of PMSM is based on the model developed by Wu et al [12] using behavioural modelling method, but here the model is improved with physics‐based modelling of eddy current effects in the iron core. As shown in Fig.…”

“…With these circuits, 13 equations are developed for 13 unknown parameters of the circuit. Wu et al [12] obtained these equations. Table 1 shows the summary of equations extracted for calculating C g 1 , C g 2 , L 1 , R 1 , L T , R T , C T , L s1 , R s1 , C s1 , L start , C start and R start .…”

“… CM equivalent circuits for different frequency ranges [12] (a) 10–100 kHz, (b) 0.1–1 MHz, (c) 1–5 MHz, (d) 5–30 MHz…”

“…An additional method should be used for estimating the number of unknown parameters. Wu et al [12], used vector‐fitting method, which often gives non‐physical results (e.g. negative resistances) and trial and error to complete the circuit model, which is not a very convenient way and makes it difficult to repeat the modelling procedure for a different motor.…”

“…Most high‐frequency models of the motors are not accurate in mid‐frequencies, because of difficulties in modelling the skin effect, proximity effect and also distributed behaviour of motor parasitic capacitances and leakage inductances [5, 11, 12, 20]. In physics‐based modelling, skin effect, proximity effect and permeability dependence of magnetic materials on frequency can be included in the calculations, and the leakage inductances can be calculated using exact stator and rotor slot shapes and winding configuration.…”