Ronggang Ni

Maximum Efficiency Per Ampere Control of Permanent-Magnet Synchronous Machines

High-efficiency electric drive systems claim not only optimally designed electric machines but also efficiency-oriented control strategies. Taking machines and drives into synergetic consideration, this paper proposes a novel vector control algorithm named maximum efficiency per ampere (MEPA) control, aiming to maximize the efficiency of permanent-magnet synchronous machines (PMSMs) during operation. Different from conventional id = 0 or maximum torque per ampere control, MEPA fully considers the cross effect and iron loss from which the full-order loss model of PMSMs is built. Due to the proposed concise and accurate analytical approach to iron loss calculation, the optimal current phasor angle for MEPA can be quickly found, and the estimation of efficiency is consistent with measurement. Comparison among different control algorithms is drawn from both analytical and experimental results, from which the effectiveness of MEPA is verified.

Investigation of

Flux-weakening capability of permanent-magnet synchronous machines (PMSMs) is fundamentally determined by d- and q -axis inductances. Based on axial flux permanent-magnet machines (AFPMs), this paper extracts the intrinsic factors that influence the d- and q-axis inductances of PMSMs, meanwhile revealing the fact that the d- and q-axis inductances of fractional slot concentrated winding machines are not inevitably larger than that of distributed ones. The proportion of each of the d- and q-axis component inductances for multigap AFPMs is first studied. By analyzing armature inductance in conjunction with differential leakage inductance, this paper introduces a novel parameter to decouple the influence of slot-pole combinations and physical dimensions so that the “inductance ability” of different slot-pole combinations can be quantified. An improved method of calculating the slot leakage inductance of semiclosed slots is then put forward, which proves to be more accurate than the conventional method. The investigations and conclusion in this paper are not restricted to AFPMs but applicable to radial flux permanent-magnet machines as well. Validations of various slot-pole combinations are carried out with finite-element analysis and experiments.

d

Alternating-current motor drive systems consume the majority of global electricity, but most of them are still not efficient enough. This paper proposes a complete solution to the efficiency enhancement of general induction motor (IM) drive systems with the least cost and a high reliability. On the motor side, the squirrel-cage rotors of IMs are replaced with optimally designed interior permanent-magnet (PM) rotors without damping windings; meanwhile, other assemblies remained unchanged. Stators with both wye- and delta-connected windings are investigated, and super premium efficiency (IE4) is achieved on all the remanufactured motors in this paper. On the drive side, the maximum efficiency per ampere algorithm is realized based on the position-sensorless control to better exert the motor efficiency and reduce the system cost. For applications where an original IM is used under a grid drive, this paper safely switches the remanufactured interior PM synchronous motors from an inverter to the grid drive. A total of seven prototypes with different rated powers and velocities are remanufactured, and various experiments are provided as the verifications of the effectiveness and practicability of the proposed solution.

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For the purpose of improving the performance of sensorless interior permanent magnet synchronous motor (IPMSM) drives, an enhanced electromotive-force (EMF)-based position observer adopting second-order generalized integrator (SOGI) to eliminate the harmonic error is proposed. The inverter nonlinearities and flux spatial harmonics that give rise to the harmonic error of position estimation are analyzed. A harmonic decoupling network consisting of multiple SOGIs based adaptive filters is adopted to achieve the multiple selective EMF harmonic elimination (MSEHE). The application of the frequency-locked loop ensures the SOGI resonance frequency adaptive, which is critical for the variable-speed operation in IPMSM drive applications. Using the SOGI-MSEHE in the position tracking estimator, the low-order harmonics in the estimated EMF can be effectively eliminated, contributing to cancelling the position estimation harmonic error. The effectiveness of the proposed enhanced position observer is verified by the experimental results at a 2.2-kW IPMSM sensorless drive.

q

To diminish the position estimation error with harmonic fluctuations for position sensorless interior permanent-magnet synchronous motor (IPMSM) drives, a multiple adaptive vector filter (AVF) cross-feedback network (CFN) is proposed for a model-based position observer. A full-order Luenberger observer is utilized to obtain back electromotive force (EMF) information. The harmonic fluctuations in the position estimation error caused by inverter nonlinearities and flux spatial harmonics are analyzed. Accordingly, a newly proposed multiple-AVF CFN with an easy-to-implement structure is adopted to detect and compensate the back-EMF harmonic distortions and, hence, to eliminate the position error harmonic fluctuations. Consequently, the position estimation accuracy can be enhanced, which improves the position sensorless control performance. The proposed scheme was verified on a 2.2-kW sensorless IPMSM drive. Experimental results confirm the effectiveness of the method in eliminating the harmonic fluctuations in the position estimation error.

-Axis Inductances Influenced by Slot-Pole Combinations Based on Axial Flux Permanent-Magnet Machines

Rotor position estimated with high-frequency (HF) voltage injection methods can be distorted by voltage errors due to inverter nonlinearities, motor resistance, and rotational voltage drops, etc. This paper proposes an improved HF square-wave voltage injection algorithm, which is robust to voltage errors without any compensations meanwhile has less fluctuation in the position estimation error. The average position estimation error is investigated based on the analysis of phase harmonic inductances, and deduced in the form of the phase shift of the second-order harmonic inductances to derive its relationship with the magnetic field distortion. Position estimation errors caused by higher order harmonic inductances and voltage harmonics generated by the SVPWM are also discussed. Both simulations and experiments are carried out based on a commercial PMSM to verify the superiority of the proposed method and the investigations in this paper.

Efficiency Enhancement of General AC Drive System by Remanufacturing Induction Motor With Interior Permanent-Magnet Rotor

Non-line-start permanent magnet synchronous machines (NLSPMSMs) are normally considered not able to operate stably under grid drive. However, this paper proposes an effective control strategy to achieve soft start and synchronous switching of NLSPMSMs from inverter to grid drives so that to extend the application field. The system electromechanical model during switching is deduced and analyzed numerically to verify the stability under grid drive. For the control strategy, model-based sliding-mode observer is adopted during soft start for low-cost position sensorless drive, and two digital phase lock loops are used to obtain the phases of grid and inverter voltages for phase tracking. Experiments are carried out on five NLSPMSMs with different rated powers and velocities, and test results show that all these prototypes can be safely switched to grid drive and robust to load variation. Tested waveforms are coincident with numerical analysis, and the system efficiencies of NLSPMSMs under inverter and grid drives are compared.

Enhanced Position Observer Using Second-Order Generalized Integrator for Sensorless Interior Permanent Magnet Synchronous Motor Drives

High Frequency (HF) voltage injection methods have been widely used in the low speed drive applications of Permanent Magnet Synchronous Machines (PMSMs). This paper compares two of the HF voltage injection methods, which are HF sinusoidal voltage injection method in the d-q reference frame and INdirect Flux detection by On-line Reactance Measurement (INFORM) method in the α-β reference frame. Implementation methods are deliberated in detail and the position estimation error caused by magnetic field distortion is also discussed. Experiments using a commercial PMSM are carried out for verifications.

Multiple-AVF Cross-Feedback-Network-Based Position Error Harmonic Fluctuation Elimination for Sensorless IPMSM Drives

This paper presents results obtained in the designing of a heating device, which utilized eddy current, hysteresis and induction current induced by rotating permanent magnets. The structure will be mentioned in the paper firstly. Then, the finite element method is used for the thermal power analyses, regard less of the temperature variety in every components. In order to solve temperature problems, which is coupled with electromagnetic and fluid field, we have to Establish a coupled calculation method of temperature and thermal power. The experiment is also carried out after calculating. The results show that the device is very useful to heat liquid.

Square-Wave Voltage Injection Algorithm for PMSM Position Sensorless Control With High Robustness to Voltage Errors

The information of the initial rotor position is essential for smooth startup and robust control of permanent magnet synchronous machines (PMSMs). RoTating Voltage Injection (RTVI) methods in the stationary reference frame have been commonly adopted to detect the initial rotor position at standstill without any position sensors. However, although the Pulsating sqUare-wave Voltage-Injection (PUVI) method performs better in estimation time and accuracy, it is rarely used because the estimation result may converge to the q-axis. In this paper, this fault convergence is avoided by modifying the initial states of the position observer, and the PUVI method can finally be used for the robust initial rotor position detection. Modified signal processing techniques are proposed for both RTVI and PUVI methods for better implementations in fixed-point processors and easier observer gain designs. Detailed comparisons between these two methods are provided. Furthermore, two position estimation observers, i.e., the proportional–integral observer and the extended state observer are compared, and their parameter tuning methods are studied as well. Both simulation and experimental results are provided for verifications.