This paper presents an analysis of the natural voltage balancing dynamics of a three-phase flying capacitor converter when supplying an induction motor. The approach substitutes double Fourier harmonic series for the pulsewidth modulation switching waveforms and the frequency response of the motor, to create a linear state-space model of this type of load. The model requires the mid-frequency response (500 Hz-20 kHz) of the induction motor impedance to be identified, and takes skin and proximity effects into account by adding parallel R-L networks to a standard motor model. Model parameters were measured by applying FFT analysis to variable frequency square waves injected into the motor terminals, and fitting parameter values to these measurements using a least squares minimization method. From the analysis, it was found that the converter voltage balancing behavior degrades substantially at low motor speeds, and that a balance booster filter, as previously proposed, considerably improves the dynamic response. Experimental verification results using a scaled-down flying capacitor converter drive are included in the paper.

Natural Capacitor Voltage Balancing for a Flying Capacitor Converter Induction Motor Drive

Double pulse test (DPT) is a widely accepted method to evaluate the switching characteristics of semiconductor switches, including SiC devices However, the observed switching performance of SiC devices in a PWM inverter for induction motor drives is almost always worse than the DPT characterization, with slower switching speed, more switching losses, and more serious parasitic ringing This paper systematically investigates the factors that limit the SiC switching performance from both the motor side and inverter side, including the load characteristics of induction motor and power cable, two more phase legs for the three-phase PWM inverter in comparison with the DPT, and the parasitic capacitive coupling effect between power devices and heat sink Based on a three-phase PWM inverter with 1200 V SiC MOSFETs, test results show that the induction motor, especially with a relatively long power cable, will significantly impact the switching performance, leading to a switching time increase by a factor of 2, switching loss increase up to 30% in comparison with that yielded from DPT, and serious parasitic ringing with 15 μs duration, which is more than 50 times of the corresponding switching time In addition, the interactions among the three phase legs cannot be ignored unless the decoupling capacitors are mounted close to each phase leg to support the dc bus voltage during switching transients Also, the coupling capacitance due to the heat sink equivalently increases the junction capacitance of power devices; however, its influence on the switching behavior in the motor drives is small considering the relatively large capacitance of the motor load

Evaluation of Switching Performance of SiC Devices in PWM Inverter-Fed Induction Motor Drives

Induction motor drive systems fed with cables are widely used in many industrial applications. Accurate prediction of motor terminal overvoltage, caused by impedance mismatch between the long cable and the motor, plays an important role for motor dielectric insulation and optimal design of dv/dt filters. In this paper, a novel modeling methodology for the investigation of long-cable-fed induction motor drive overvoltage is proposed. An improved high-frequency motor equivalent circuit model is developed to represent the motor high-frequency behavior for the time- and frequency-domain analyses. The motor equivalent circuit parameters for the differential mode (DM) and common mode (CM) are extracted based on the measurements. A high-frequency cable model based on improved high-order multiple-π sections is proposed. The cable model parameters are identified from the DM impedances in open circuit (OC) and short circuit (SC). To obtain a computationally efficient solution that could potentially be integrated with the motor drive controller, the system equations are discretized and solved using transmission-line modeling (TLM) approach. The proposed methodology is verified on an experimental 2.2-kW ABB motor drive benchmark system. The motor overvoltage transients predicted by the proposed model is in excellent agreement with the experimental results and represents a significant improvement compared with the conventional models.

https://carlho88.webs.com/Paper/Trans/2010/PE10_TLM.pdf

High-Frequency Modeling of the Long-Cable-Fed Induction Motor Drive System Using TLM Approach for Predicting Overvoltage Transients

This paper overviews the silicon carbide (SiC) technology. The focus is on the benefits of SiC based power electronics for converters and systems, as well as their ability in enabling new applications. The challenges and research trends on the design and application of SiC power electronics are also discussed

/pdf/overview-of-silicon-carbide-technology-device-converter-2b1ygipox2.pdf

Overview of Silicon Carbide Technology: Device, Converter, System, and Application

This paper presents some of the key advances in power electronics pertaining to shipboard electric power system applications. The focus is on the emerging wide bandgap semiconductor devices, i.e., silicon carbide (SiC) and gallium nitride (GaN) devices, and their potential impact on future shipboard power conversion and drives. Their benefits on power converter efficiency and power density are explained through a case study of a medium-voltage (MV) class motor drive system. SiC and GaN also enable new applications, including solid-state transformers, while posing new design and application challenges such as gate drive, protection, and interaction with loads. In addition to device related topics, this paper also overviews other important advances in power electronics, including topology, control, passive components, thermal management, filters, and packaging. The significance of power electronics building blocks (PEBBs) concept for shipboard power system development is discussed. Recognizing the growing complexity of shipboard power systems, some system-level technologies related to future MV direct current (dc) system architecture are highlighted.

Advances in Power Conversion and Drives for Shipboard Systems

A three-phase induction motor model which represents the motor behavior over a wide range of frequencies from 10 Hz ? 10 MHz is presented in this paper. The model is universal in the sense that common mode, differential mode and bearing circuit models are combined into one three-phase equivalent circuit model. The proposed model is basically an extension of the low frequency IEEE Standard 112 circuit model. The proposed model was simulated and verified experimentally with results presented.

Ranga Tallam

Papers

Universal Induction Motor Model with Low-to-High Frequency Response Characteristics