Current Shaping Method Research Articles

A Closed-Loop High-Frequency Current Shaping Method to Achieve Trapezoidal Transformer Current in a Current-Fed Dual Active Half-Bridge Converter for Minimum RMS Current and Wide-Range ZVS

This article proposes the use of primary and secondary side duty ratio control along with the phase shift control in a current-fed dual active half-bridge (DAHB) converter to achieve trapezoidal transformer current, which results in zero voltage switching (ZVS) of all the switches and minimum rms current even at light loads, for a wide range of input voltage. The high-frequency transformer current is directly sensed at specific transition instants by a delay-adjusted sampling strategy to be used as control variables in a current control structure. This is better because the voltage control of capacitor voltages would have required more expensive sensors. A simple and accurate small-signal model of the converter is developed, and the relevant transfer functions are derived. The controller design details are provided. Finally, experimental results on a 1-kW laboratory prototype demonstrate the effectiveness of the closed-loop duty ratio control in achieving trapezoidal transformer current resulting in improved efficiency and ZVS of the switches, compared to a simple phase shift control.

PMSM Current Shaping for Minimum Joule Losses While Reducing Torque Ripple and Vibrations

This paper presents a current shaping method for torque ripple and mean air-gap radial force-shape harmonics reduction, under minimum Joule losses, used for air-born and structure-born vibration reduction in 3-phase PMSM electric drives. The main source for structure-born noise in electric powertrains is the torque ripple, while the main source for air-born noise are the radial air-gap forces. The proposed method uses a Fourier-decomposed LUT model obtained from updating the 2D electromagnetic FE model using test-bench results. Modal testing is used to update the structural model, and the vibration response on the machine full RPM range is determined using the vibration-synthesis method. The proposed current shaping algorithm is deterministic and can be used on any topology of 3-phase PMSMs. The torque and mean air-gap force harmonics that are intended for reduction can be arbitrary selected and their minimization can be fully completed if the maximum current and voltage constraint are respected. On the machine under test, vibration reduction is accomplished, especially for the mechanical orders that interact with the second mode-shape.

Comparative Performance Analysis of Reference Voltage-Controlled Pulse Width Modulation for High-Speed Single-Phase Brushless DC Motor Drive

The recent advancements in power switching device material and manufacturing technology have enabled the design of highly efficient and compact high-speed motor direct drives. The use of high-switching frequency pulse width modulation in these drives provides speed and torque control capabilities and it can also serve as an effective phase current shaping method for torque ripple minimization. This paper builds upon the previous paper introducing a torque ripple minimization technique for gallium nitride high-electron mobility transistor-based high-speed single-phase brushless dc motor drive. It presents an in-depth performance analysis in comparison with the conventional high-speed control techniques. Four different high-speed control techniques are implemented and tested to quantify the maximum speed, efficiency, torque ripple, and vibration. The vibration of the motor drive is measured using a microelectromechanical systems accelerometer with a ferroelectric random access memory for high-speed data acquisition with the maximum bandwidth of 1 kHz.

Pseudo-impulse tail current shaping for phase noise reduction in CMOS LC oscillators

In this paper, a low phase noise oscillator using tail current shaping method is presented. The current shaping is achieved using two paths for current disconnection and current injection, as a result of which, the total tail current is shaped to a sharp and sawtooth waveform, close to an impulse. Each switching transistor is ON only in 22% of an oscillation period, and tail current is mostly supplied to these transistors near the outputs peak points. In those moments, the oscillator sensitivity to noise sources is minimum. The proposed oscillator is designed and simulated in 0.18 μm RF CMOS technology with 1.8 V supply, and using the inductor model offered by the process, with quality factor of 11. Post layout simulations predict an oscillation frequency of 1.65 GHz, and phase noise of −127.7 dBc/Hz at 1 MHz offset, which is 6.3 dB better than that of simple cross coupled oscillator with the same core oscillator power consumption of 2.2 mW. The proposed circuit, however, consumes an extra power of about 1.9 mW for the added current shaping circuits. Compared to conventional tail current shaping technique, the proposed oscillator offers better tail current shaping, and a much higher start-up current and gain, which is desirable.

Grid Current Shaping Method with DC-Link Shunt Compensator for Three-Phase Diode Rectifier-Fed Motor Drive System

This paper proposes grid current shaping method using dc-link shunt compensator for three-phase diode rectifier system without electrolytic dc-link capacitor. In the proposed method, the diode rectifier system can satisfy the grid regulation IEC61000-3-12 without any power factor correction circuit or heavy grid filter inductor. The proposed grid current shaping method can be realized by applying DSC with reduced-rating components and without electrolytic capacitor, which is connected parallel to the dc link. Since DSC has no electrolytic capacitor, the system with DSC has high circuit reliability. Furthermore, DSC can enhance the system efficiency, especially in flux-weakening area, since the motor drive inverter recovers the reduced modulation index, which has been spent in the additional control for small passive components. This paper presents the control method for DSC and analyzes the effect of proposed method. The feasibility of proposed method is verified by simulation and experimental results.

Accuracy Enhancement of Parameter Estimation and Sensorless Algorithms Based on Current Shaping

Dead time is typically incorporated in voltage source inverter systems to prevent short circuit cases. However, dead time causes an error between the output voltage and reference voltage. Hence, voltage equation-based algorithms, such as motor parameter estimation and back electromotive force (EMF)-based sensorless algorithms, are prone to estimation errors. Several dead-time compensation methods have been developed to reduce output voltage errors. However, voltage errors are still common in zero current crossing areas, and an effect of the error is much worse in a low speed region. Therefore, employing voltage equation-based algorithms in low speed regions is difficult. This study analyzes the conventional dead-time compensation method and output voltage errors in low speed operation areas. A current shaping method that can reduce output voltage errors is also proposed. Experimental results prove that the proposed method reduces voltage errors and improves the accuracy of the parameter estimation method and the performance of the back EMF-based sensorless algorithm.