A Novel Modified DTC-SVM Method with Better Overload-capability for Permanent Magnet Synchronous Motor Servo Drives

Abstract

Direct torque control with space vector modulation (DTC-SVM IntroductionDirect torque control with space vector modulation is a modification of the original direct torque control (DTC) method [1][2][3]. The excellent dynamic torque-control capabilities of traditional DTC are well known in the literature for permanent magnet synchronous motors and for other motor types as well [4][5][6][7][8][9]. However, there are serious disadvantages and among them the most important are: varying switching frequency and the excessive amount of torque-ripple generated [10][11][12]. DTC-SVM solves these problems, as it uses fixed switching frequency and the torque-ripple is significantly reduced compared to DTC, while the dynamics of the torque-control is essentially identical to that of traditional DTC [13][14][15]. Therefore, DTC-SVM is currently considered as one of the most promising alternatives of the nowadays widely used field-oriented control [16,17].DTC-SVM was introduced in [1][2][3]. These publications highlighted the main advantages of DTC-SVM. Since then many investigations have been carried out for this method. Special applications requiring high dynamic performance, excellent efficiency and high precision have been examined such as artillery speed servo systems [18], electric vehicles [19], electric pitch servo systems for wind generators [20]. Also, asymmetric permanent magnet synchronous machines have been investigated and special solutions have been invented for these machines [21]. In order to improve the performance of DTC-SVM several modifications have been developed. Most of the modifications aim at reducing the torque-ripple, increasing the dynamic performance and the efficiency of the method [22][23][24][25][26][27][28]. Sensorless methods using extended Kalman-filter have also been invented [29].However, the overload-capabilities of DTC-SVM and its stability during overloading have not been investigated yet. This article deals with these issues and suggests a modified DTC-SVM (MDTC-SVM) method which has significantly improved overload-capabilities and it is stable during overloading.

Improved Modified DTC-SVM Methods for Increasing the Overload-capability of Permanent Magnet Synchronous Motor Servo- and Robot Drives – Part 2

“…The basic equations of permanent magnet synchronous motor drives are well-detailed in [11,30]. The terminology, the abbreviations and the notations will be the same as in [30] and in Part 1 for detailed information see [30] and Part 1. Also, like [30] and Part 1, this article assumes a surface-mounted permanent magnet synchronous motor.…”

“…The IPC-SF computes the voltage vector reference that is synthesized by the two-level voltage source inverter (VSI) using space vector modulation (SVM). (A detailed description of space vector modulation can be read in [11,[30][31][32].) ψ c1 and ψ c2 are the real-and the imaginary axis components of the stator flux vector, respectively.…”

“…4 Simulation results for torque-ripple and torquecontrol dynamics Simulation was carried out for a synchronous servo motor in Matlab-Simulink environment, using the same parameters as in [30] and Part 1. The parameters can be found in Table 1 of [30]. Investigations were carried out for the normal operation region only.…”

“…This article focuses on this issue and proposes two simplified forms of the Improved Modified DTC-SVM (IMDTC-SVM) method that has been introduced in Part 1. The two simplified forms have a significantly higher overload-capability than that of either the MDTC-SVM introduced in [30] or the classical DTC-SVM. Although the simplified forms have a slightly lower overload-capability than that of the standard IMDTC-SVM, they are remarkably simpler in structure, they require significantly less computation and the tuning of the complete control system is in one of the two cases much simpler.…”

“…Although the simplified forms have a slightly lower overload-capability than that of the standard IMDTC-SVM, they are remarkably simpler in structure, they require significantly less computation and the tuning of the complete control system is in one of the two cases much simpler. This article is intended to continue the thread of [30] and Part 1.…”