Inverter Nonlinearity Effects Research Articles

High-Fidelity Model Identification for Synchronous Reluctance Motor Drives

This paper presents an accurate model identification method for the synchronous reluctance machine (SynRel), considering the nonlinear magnetic behavior and spatial harmonics. The availability of the high-fidelity magnetic model is essential for high-performance control and modeling the vibro-acoustic behavior of the electric drive, allowing to predict not only the average torque but also the torque ripple behavior versus rotor position. The magnetic coenergy variation is calculated based on the flux linkages in order to yield the torque ripple. During the identification, the current disturbances introduced by the spatial effects and the inverter nonlinearities are properly suppressed by the merged proportional-integral (PI) controller with a repetitive technique. Besides, the inverter nonlinearity and digital control effects are carefully addressed to improve identification accuracy. The effectiveness of the proposed identification method is demonstrated by the comparison of the finite element (FE) simulation results and experiments for two SynRel prototypes.

Novel Machine Parameter Estimation Scheme Toward Accurate Maximum Torque Production for Dual Three-Phase PMSMs

This article proposes a hybrid signal injection-based maximum torque per ampere (MTPA) control for dual three-phase permanent magnet synchronous machines (PMSMs). The proposed method consists of a real dc current injection in the harmonic subspace and a virtual ac current injection in the fundamental subspace. The real dc current injection in the harmonic subspace does not impact the average torque production, and induced losses are small enough to be neglected. In the meantime, to guarantee the accuracy of the proposed MTPA method, a novel machine parameter estimation scheme considering voltage source inverter nonlinearity effects is proposed in this article, which can track the variation of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$q_{1}$ </tex-math></inline-formula> -axis inductance and resistance accurately. Therefore, the proposed method only requires command voltages and currents in the torque model, and the variations of machine parameters are compensated by the proposed parameter estimation scheme. As the command voltages have correspondence with the variations of machine parameters, the magnetic saturation and temperature effects have been taken into account. The proposed method is validated by simulations and experimental results under various torque, speed, and temperature conditions. Additionally, the accuracy of the proposed method is validated, and its performance is proven to be superior through comparison of the derived results with those obtained from various existing methods.

A Robust and Practical Approach to Estimate the Number of Shorted Turns in PMSM With ITSC Faults

This article puts forward a novel method to estimate the fault severity index and consequently the number of shorted turns in permanent magnet synchronous motors (PMSMs) with interturn short circuit (ITSC) fault. In this method, the machine is excited with dc current at standstill conditions to obtain the winding resistance seen by the d-axis of the machine. The estimated d-axis resistance contains useful information pertaining to the fault severity index and is used to extract the fault severity index and the number of shorted turns in the faulty motor. The proposed method enables the estimation of fault severity index without complex machine modeling and extensive experiments with different machine prototypes, or finite-element analysis (FEA) models to analyze the relationship between the machine currents and short-circuit current. To enhance the accuracy of the estimation algorithm, this article addresses practical issues associated with inverter nonlinearity effects such as distortion voltage due to deadtime effects and voltage drops across the switching devices and proposes method to estimate the fault severity index that is immune to the aforementioned issues. Determining the fault index is critical in order to design appropriate mitigation techniques, as well as defining a safe operating area for the machine to avoid further damage to the winding. To verify the efficacy of this algorithm, experiments are conducted on a three-phase PMSM with artificial taps that imitate the behavior of ITSC fault, and the results which demonstrate the practicability of this algorithm are presented.

Analysis of inverter non‐linearity influence on modulation technique selection in a dual three‐phase induction machine drives

This study aims to investigate the correlation between inverter non-linearity and modulation technique selection in a dual three-phase induction machine (D3IM) drives. Even though vector space decomposition (VSD) technique is in the literature perceived as the most suited and well-adapted control strategy for D3IM, herein conducted analysis has established that VSD vector selection principle together with inverter non-linearity effects can lead to a significant decrease in the performance of a driven machine. It is demonstrated that by changing vector selection principle, the influence of the mentioned inverter limitations could be reduced without any major negative influence on other important aspects that determine technique suitability for the use in D3IM drives. The experimental results gathered from two separate test stations undoubtedly show the mutual impact of the inverter non-linearity and vector selection strategy on the drive overall performance.

Suppression of Injection Voltage Disturbance for High-Frequency Square-Wave Injection Sensorless Drive With Regulation of Induced High-Frequency Current Ripple

In the square-wave voltage signal injection sensorless drive of the interior permanent-magnet synchronous machine, the injection voltage can be distorted by the inverter nonlinearity effects especially when the injection voltage is low. If that happens, a high-frequency (HF) current signal which contains the rotor position information could be also distorted, which directly leads to an error in the position estimation. This paper analyzes the effects of the inverter nonlinearity on injection voltage, on induced current ripple, and on the position estimation performance in sequence and proposes a voltage injection method to minimize the impact of the inverter nonlinearity by the regulation of the HF current ripple. By simulations and experiments, the performance of the proposed method has been verified. The experimental results show 19.7% reduction of position estimation error under 15% of rated voltage signal injection without increasing the current ripple at a certain operating condition. Moreover, the performance of position estimation is kept uniform regardless of the loading condition.

Harmonic Analysis of the Effects of Inverter Nonlinearity on the Offline Inductance Identification of PMSMs Using High Frequency Signal Injection

Offline inductance identification of a permanent magnet synchronous motor (PMSM) is essential for the design of the closed-loop controller and position observer in sensorless vector controlled drives. On the base of the offline inductance identification method combining direct current (DC) offset and high frequency (HF) voltage injection which is fulfilled at standstill, this paper investigates the inverter nonlinearity effects on the inductance identification while considering harmonics in the induced HF current. The negative effects on d-q axis inductance identifications using HF signal injection are analyzed after self-learning of the inverter nonlinearity characteristics. Then, both the voltage error and the harmonic current can be described. In addition, different cases of voltage error distribution with different injection conditions are classified. The effects of inverter nonlinearities on the offline inductance identification using HF injection are validated on a 2.2 kW interior PMSM drive.

Sensorless IPMSM position estimation based on multi SVPWM with elimination of inverter nonlinear effects

AbstractThis paper presents a position‐sensorless interior permanent magnet synchronous motor (IPMSM) control system at low and zero speed based on a multi‐space‐vector pulse‐width modulation (MSVPWM) pattern with the elimination of nonlinear inverter effects. In conventional sensorless methods based on the MSVPWM pattern, the high‐frequency (HF) components of voltage and current are used to estimate the rotor position information. However, the inverter nonlinear effects, such as forward voltage drops and deadtime, distort the HF components of the voltage and current so that an error occurs in the position estimation. Therefore, an improved position estimation scheme is developed in this paper. The compensated HF components of the voltage taking account of the inverter nonlinear effects can be used to decrease the estimation error. The proposed method can be implemented without increasing any hardware cost. Experimental results confirm the effectiveness of the proposed method. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

A Novel Method for Compensating Inverter Nonlinearity Effects in Carrier Signal Injection-Based Sensorless Control From Positive-Sequence Carrier Current Distortion

In conventional rotating carrier signal injection-based sensorless method, a positive-sequence carrier current has no use, and only the negative-sequence carrier current is used to estimate the rotor position information. The inverter nonlinearity effects, however, distort the negative-sequence carrier current and result in inaccurate position estimation. With the aid of theoretical analysis and experimental measurement, it is proven in this paper that the positive-sequence carrier current distortion resulting from inverter nonlinearity effects can be used to compensate the influence of inverter nonlinearity on negative-sequence carrier current. Hence, a new online postcompensation scheme is developed in this paper by utilizing the distortion of positive-sequence carrier current due to inverter nonlinearity effects. The proposed method can be easily implemented on standard voltage source inverter without any offline commissioning process or hardware modification. Experimental results confirm the effectiveness of the proposed method in suppressing the influence of inverter nonlinearity on the rotor position estimation.

Analysis and Compensation of Inverter Nonlinearity Effect on a Sensorless PMSM Drive at Very Low and Zero Speed Operation

It has been well established in the literature that inverter nonlinearity effects afflict saliency-based sensorless drives. The inverter nonlinearity leads to the generation of signals that corrupt the useful position information. The resulting effect differs depending on the injection approach utilized in the drive. Various compensation techniques to overcome this effect have been published in the literature. This paper is concerned with the zero-vector current-derivative technique. The effect of the varying ON-state resistance of the inverter power devices on the position signal is investigated in detail. Knowledge of the source of the corrupting signals facilitates compensation and determines its applicability. Two approaches for inverter nonlinearity compensation are compared. The first approach utilizes a lookup table from offline-processed data, while the second one is a simpler approach based on the current-dependent resistance characteristic of the inverter switching devices. Experimental performance under sensorless condition is shown for both approaches.

Pure-Integration-Based Flux Acquisition With Drift and Residual Error Compensation at a Low Stator Frequency

We have developed a pure-integration-based flux acquisition method for ac adjustable-speed drives. Based on the current-measurement-error analysis, a simple resonant-type observer is utilized to eliminate the drift or dc offset that originated in the current acquisition process. All the processes in correcting the problem do not rely on motor parameters and do not interfere with other higher frequency contents such as inverter nonlinearity and motor cogging effects. The proposed technique further contains a residual error compensator to completely correct the initial value error and to eliminate miscellaneous dc offset errors of the integrator. The acquisition accuracy of the flux is significantly improved through pure integration by restraining the error of the flux magnitude and phase angle at a low stator frequency. Since the proposed scheme is based on a two-phase current measurement system, it is suitable for retrofitting ac drives, where two current sensors are commonly used.