Inverter-fed Interior Permanent Magnet Research Articles

Unidirectional Finite Control Set-Predictive Torque Control of IPMSM Fed by Three-Level NPC Inverter with Simplified Voltage-Vector Lookup Table

This paper proposes a unidirectional finite control set-predictive toque control (UFCS-PTC) method for a three-level neutral-point-clamped (3L-NPC) inverter fed interior permanent magnet synchronous motor (IPMSM). The proposed algorithm can lower the complexity of PTC fed by 3L-NPC by reducing the number of admissible voltage vectors (VVs) effectively. The candidate VVs are restricted within 60° of the voltage space voltage diagram (VSVD), which is the nearest to the flux trajectory for each 60° flux sector. After the segmentation of the VSVD and flux trajectory, the proposed method can keep VVs in one direction during the prediction process, which can result in significant torque/flux reduction. Therefore, the UFCS-PTC can reduce the number of admissible VVs from twenty-seven to six while achieving excellent steady-state performance in terms of reduced flux and torque ripples. Additionally, the proposed method eliminates the need for weighting factor calculation for neutral point voltage associated with a 3L-NPC inverter. The UFCS-PTC of IPMSM also has other features, such as improved balancing capability of the DC-link capacitors’ voltage, small computation time due to the reduced number of admissible voltage vectors considered in the cost function, and easy implementation. The effectiveness of the proposed method is verified through experimental results.

Model-Free Predictive Current Control for Three-Level Inverter-Fed IPMSM With an Improved Current Difference Updating Technique

Parameter mismatches in conventional model predictive current control (MPCC) would worsen torque and THD performance. To eliminate the parameter dependence of MPCC, this letter proposes a model-free predictive current control (MFPCC) for a three-level inverter-fed interior permanent magnet synchronous motor (IPMSM). Firstly, to increase the current difference updating frequency in the diode neutral-point-clamped (NPC) three-level inverter, a synchronous updating method is proposed in a manner where the number of updated current differences during one sampling period is increased up to 6. Secondly, for the sake of computational burden alleviation, a candidate vector selection algorithm is introduced in such a way that the number of candidate vectors is reduced to only 7–9. Then, the problem of neutral-point voltage fluctuation which is inherent to the three-level NPC inverter is investigated, and a reasonable replacement method incorporating the redundancy characteristic of small vectors is developed. Finally, experimental results verify that the system robustness against mismatched parameters can be greatly enhanced by use of the proposed control scheme; meanwhile, steady-state performance and dynamic-state response of the system can be improved to some extent as well.

Modified LUT-based DTC of NPC 3-Level Inverter fed Sensorless IPMSM Drive with DC Link Voltage Balance

In the proposed work, a modified look-up table-based direct torque control (DTC) scheme is reported for a neutral point-clamped three-level inverter-fed interior permanent magnet synchronous motor drive. In the classical DTC scheme, there are significant torque and flux ripples in the drive due to low number of available switching states. To reduce the oscillations in torque and flux, a three-level inverter-operated IPMSM drive is discussed. In a three-level inverter, the increased count of active voltage vectors is results in more sinusoidal output waveforms. Moreover, stator flux plane has 12 sectors in the proposed work unlike classical DTC. Besides, the higher level of flux and torque hysteresis comparators is implemented. DC link capacitor voltage balancing scheme is also instigated to minimize voltage stress on semiconductor devices, improve stator current THD and increased capacitor life. Based on the sector information, flux and torque hysteresis output and capacitor voltage balance logic, an improved LUT is established and explained for a three-level DTC scheme. Consequently, improved stator current (THD) and decrement in torque and flux ripples are observed. To make the system robust, model reference adaptive control (MRAC) based sensorless speed estimation algorithm is realized. The proposed DTC scheme is compared with a two-level inverter-fed and a three-level-inverter-fed DTC scheme without DC link voltage balance strategy. To carry out the analysis, MATLAB/Simulink environment is utilized. Moreover, to validate the simulation results, experimental analysis of the proposed technique is carried out using dSPACE1104.

A Computer-Aided Design Process for Optimizing the Size of Inverter-Fed Permanent Magnet Motors

A process for designing an inverter-fed motor while taking into account the performance of the inverter is proposed. To draw a comparison, the classical approach to machine sizing is discussed and its shortcomings in achieving a more optimal solution to the motor-drive system design problem are pointed out. The results prove that designing the motor as an independent system may give less optimal solutions compared to the case where an integrated system is considered. Therefore, the machines and the inverters should be designed simultaneously. An inverter-fed interior permanent magnet motor is investigated, and the corresponding design guidelines are presented. These guidelines are based on the knowledge extracted from an inclusively modeled, sampled, and simulated design space. The reliability of the design, the inverter efficiency, and the priorities of the transient, rated and flux weakening operations are assigned as the selection criteria. Moreover, various user-package interfaces are proposed to show how the designer should be guided towards a more realistic design choice. Finally, four different design cases are presented and compared to the output of the classical machine sizing process. The proposed approach serves as a proposal for the next generation of processes implemented with the aid of a high-performance cloud-computing service.

A Simple Duty Cycle Control Strategy to Reduce Torque Ripples and Improve Low-Speed Performance of a Three-Level Inverter Fed DTC IPMSM Drive

This paper presents a novel duty cycle-based direct torque control (DDTC) strategy for a three-level neutral point clamped inverter fed interior permanent magnet synchronous motor. DDTC methods proposed in the literature for three-level inverter fed DTC (3L-DTC) are complicated, parameter dependent, and pay little attention to inverter inherent switching constraints. In this paper, a simple yet robust duty ratio calculation method, which respects the inverter switching constraints, is proposed. Additionally, a novel switching strategy is adopted to minimize the effects of flux drooping phenomena seen in 3L-DTC drives during low-speed operations. The proposed 3L-DTC method is efficient in reducing both torque and flux ripples while operating at low switching frequencies. Therefore, it is suitable for medium-high power ac drives. Experimental results on a scaled down test rig and comparative analysis are provided to validate the effectiveness of the proposed strategy.

Three-Level Inverter-Fed Direct Torque Control of IPMSM With Torque and Capacitor Voltage Ripple Reduction

This paper proposes a new direct torque control (DTC) method for a three-level neutral point clamped (3L-NPC) inverter-fed interior permanent magnet synchronous motor (IPMSM) drive. Theoretically, in comparison to a two-level inverter, a 3L-NPC inverter is advantageous for reducing the torque and flux ripples in DTC drives. Nonetheless, the ripples can still be excessive and detrimental if low switching frequencies are desired. To reduce the torque and flux ripples while maintaining a low average switching frequency, a switching table-based DTC scheme employing two voltage vectors in each sampling period is proposed in this paper. A duty ratio calculation method with minimal parameter dependence is developed, taking into account the dynamic torque and flux characteristics of an IPMSM. In addition, the problems of neutral point voltage fluctuations and smooth voltage vector switching, which are inherited from the 3L-NPC inverter, are addressed. Simulation and experimental results are presented to prove the effectiveness of the proposed method.

Modeling and Simulation Technique of Two Quadrant Chopper and PWM Inverter-Fed IPMSM Drive System and Its Application to Hybrid Vehicles

This paper presents a state space model of a two quadrant chopper and PWM inverter-fed Interior Permanent Magnet Synchronous Motor (IPMSM) drive system and its application to hybrid vehicles. The drive system has two different state equations for motoring and regenerating action. This paper presents a common state equation by using State Space Averaging method. Using this model of the IPMSM drive system, detailed simulation and controller design of the drive system, including PWM inverter switching, are given. The validity of this model and usefulness, according to a comparison among Maximum Torque/Ampere control, Maximum Torque/Flux control, and Maximum Efficiency optimization, are confirmed from simulation results.

An Overmodulation Method for PWM-Inverter-Fed IPMSM Drive With Single Current Sensor

In order to lower the cost and expand the working range of pulsewidth modulation (PWM)-inverter-fed interior permanent magnet synchronous motor drives, the control methods under the overmodulation mode with only a dc-link current sensor are investigated. The space vector modulation of the PWM inverter is analyzed in detail, and an adjustment scheme for the reference voltage vectors is developed to fulfill the requirements by phase current reconstruction under overmodulation. Furthermore, in order to simplify the control process and reduce the control errors, a specified overmodulation method based on the superposition principle is proposed for the PWM inverter with phase current reconstruction, which overcomes the shortcoming of the PWM adjustment scheme. Experimental results demonstrate the feasibility and the effectiveness of the proposed control method, which realizes the single current sensor overmodulation control with maximum voltage transfer ratio.

Development and Testing of a New Controlled Wavelet-Modulated Inverter for IPM Motor Drives

This paper presents the development, implementation, and performance testing of a novel resolution-level vector controller (RLVC) for a wavelet-modulated (WM) inverter-fed interior permanent-magnet (IPM) motor drive system. The RLVC is designed to adjust the output voltage of the WM inverter in response to changes in the load torque and command speed. The adjustments in the WM inverter output voltage is accomplished through changing the maximum value of the scale j that is required to generate the WM inverter switching signals. The complete IPM motor drive system incorporating the RLVC is successfully implemented in real time using a digital signal processor board ds1104 for a laboratory 1-hp IPM motor. The performances of the proposed RLVC IPM motor drive system are investigated at different dynamic operating conditions, including sudden changes in the command speed and load torque. The simulated and experimental performance results show stable, fast, and accurate adjustments of the inverter output voltage in response to load and speed changes in the tested IPM motor drive system.

Development and Implementation of a Novel Fault Diagnostic and Protection Technique for IPM Motor Drives

This paper presents the practical implementation of a novel fault diagnostic and protection scheme for the interior permanent-magnet (IPM) synchronous motors using wavelet packet transform (WPT) and artificial neural network. In the proposed technique, the line currents of different faulted and normal conditions of the IPM motor are preprocessed by the WPT. The second level WPT coefficients of line currents are used as inputs of a three-layer feedforward neural network. The proposed protection technique is successfully simulated and experimentally tested on the line-fed and inverter-fed IPM motors. The Texas Instrument 32-bit floating-point digital signal processor TMS320C31 is used for the real-time implementation of the proposed protection algorithm. The offline and online test results of both line-fed and inverter-fed IPM motors are given. These test results showed satisfactory performances of the proposed diagnostic and protection technique in terms of speed, accuracy, and reliability.

A microcomputer-based control and simulation of an advanced IPM synchronous machine drive system for electric vehicle propulsion

Describes a high-performance microcomputer-based control and digital simulation of an inverter-fed interior permanent magnet (IPM) synchronous machine that uses a neodymium-iron-boron magnet. The fully operational four-quadrant drive system includes a constant-torque region with zero speed operation and a high-speed field-weakening constant-power region. The control uses the vector or field-oriented technique in constant-torque region with the direct axis aligned to the stator flux, whereas the constant-power region control is based on torque angle orientation of the impressed square-wave voltage. All the key feedback signals for the control are estimated with precision. The drive system is basically designed with an outer torque control loop for electric vehicle application, but speed and position control loops can be added for other industrial applications. The distributed microcomputer-based control system is based on Intel-8096 microcontroller and Texas Instruments TMS32010 type digital signal processor.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>