Konstantin Borisov

Experimental investigation of a naval propulsion drive model with the PWM-based attenuation of the acoustic and electromagnetic noise

An extensive experimental investigation of a 40-hp ac drive was conducted with the focus on mitigation of the acoustic and electromagnetic noise, and vibration, by means of random pulsewidth modulation (RPWM) employed in the drives inverter. The drive was a laboratory model of an electric propulsion system for naval vessels, particularly electric submarines, in which the noise mitigation is crucial for survivability. Three PWM methods were compared: 1) the classic deterministic PWM, characterized by a constant switching period equal to the sampling period of the digital modulator; 2) the known RPWM technique, referred to as RPWM I, in which the switching and sampling periods are varied simultaneously in a random manner; and 3) a novel RPWM method, referred to as RPWM II, with a constant sampling period and the switching periods randomly varied around an average value equal to the sampling period. The experimental results have confirmed the mitigating properties of RPWM with respect to the acoustic and electromagnetic noise, and vibration. Because of the fixed sampling frequency, the RPWM II technique is technically more convenient than the classic RPWM I method and only marginally less effective in flattening the peaks of noise spectra. Importantly, conclusions drawn from the described study are valid for ac drives in general.

Attenuation of Electromagnetic Interference in a Shunt Active Power Filter

Shunt active power filters (APF) are commonly used for the reduction of current harmonics and improvement of the power factor in power systems with nonlinear loads, such as diode rectifiers. A pulsewidth modulation (PWM) power converter constitutes the main component of the APF. The low-order harmonics of the line current are attenuated, but the switch-mode operation of the converter results in electromagnetic interference (EMI) spreading to the grid. Specifically, clusters of harmonics appear in the frequency spectra of voltages and currents of the converter at multiples of the switching frequency. In this paper, transferring the discrete spectral power of those harmonics to the continuous spectral power density is proposed as means for mitigation of the EMI. It is accomplished by randomization of the switching periods using a novel random PWM method (RPWM II). In contrast to the existing random PWM methods, in RPWM II the sampling frequency of the digital modulator is constant and equal to the average switching frequency. Computer simulations and experimental investigation of an APF designed for shipboard power systems are described, and the results are presented. They demonstrate significant reduction of the EMI, a feat achieved at practically no expense.

A novel random PWM technique with minimum computational overhead and constant sampling frequency for high-volume, low-cost applications

A novel random PWM technique for three-phase voltage-source inverters, characterized by a minimum computational overhead, a variable switching frequency, and a constant sampling frequency, is presented. The technique is based on two strategies: (1) the so-called arithmetic PWM (APWM), which yields the same switching patterns as the classic space-vector modulation, but with minimized computational effort, and (2) randomization of switching periods by variations of the delay of switching cycles with respect to corresponding sampling cycles. Simplicity of the technique, named a variable-delay random PWM (VDRPWM) method, allows its implementation in cheap, low-end processors. It makes the VDRPWM the best choke for high-volume low-cost applications, such as domestic and automotive AC drives and AC UPSs. The random aspect of the technique has a mitigating effect on the acoustic and electromagnetic noise emitted by the drive. This feature has been confirmed by experimental investigation of a 40-hp induction motor drive employing the VDRPWM.

Multifunctional VSC Based on a Novel Fortescue Reference Signal Generator

This paper presents a novel reference signal generator (RSG) for voltage-source converters (VSCs) that enables the maximization of its functionality. The proposed RSG is based on a combination of the Fortescue decomposition with recursive discrete Fourier transform. The method is characterized by computational efficiency, excellent detection accuracy, and fast dynamic response. An experimental prototype of a multifunctional VSC with the proposed RSG has been built, and experimental results are presented. The functionality of the VSC can be extended to such modes of operation as harmonic compensator, active power filter, pulsewidth modulator (PWM) rectifier, PWM inverter, balancing compensator, and STATCOM, with the update of only six coefficients in the RSG.

A Computationally Efficient RDFT-Based Reference Signal Generator for Active Compensators

Several methods for generation of the control reference signals for active compensators have been proposed. Many of those reference signal generation techniques use Alters to extract the desired components of the current. Frequency domain methods are generally not used due to high computational complexity as well as susceptibility to frequency variation and numerical errors. In this paper a computationally efficient and robust Recursive Discrete Fourier Transform based reference signal generator is proposed for use in active compensator applications. In addition to mathematical analysis, discussions and simulations, an experimental prototype of an active compensator with the proposed reference signal generator has been built and experimental results have been obtained.

PEBB-based shunt active power filter for shipboard power systems

The future vision of naval electric distribution systems describes a system capable of supplying an electric propulsion system as well as other demanding loads such as high power pulsed loads. The system must also be flexible and reconfigurable. Such a system, containing numerous power electronic devices, will require appropriate compensation systems to maintain some minimum acceptable level of power quality. In this paper, we propose and implement a power electronics building block (PEBB) based shunt active power filter with digital control for future naval electric distribution systems. Various configurations of the software phase locked loop (SPLL), as well as various harmonic extraction strategies are analyzed by comparing them with respect to their steady state and transient performance.

A novel reference signal generator for active power filters based on Recursive DFT

A novel reference signal generator is proposed for active power filters. The method takes advantage of a computationally efficient Recursive DFT and it is based on extraction of the positive sequence component from the measured current with the Fortescue decomposition. The extraction of the positive sequence component ensures the correct evaluation of the active and reactive current components under both balanced and unbalanced line current conditions. Computer simulations and experimental results are presented in the paper. They demonstrate excellent dynamic performance and excellent detection accuracy of the method as compared to the commonly used d-q synchronous reference signal generators.

Mitigation of electromagnetic interference and acoustic noise in vehicular drives by random pulse width modulation

Results of two interrelated studies devoted to assessment of mitigating effects of random pulse width modulation on the electromagnetic and acoustic noise generated in vehicular AC drives are presented. Computer simulations and experimental investigation have demonstrated that the random modulation, especially its technically convenient RPWM II version, significantly reduces both types of the noise. Therefore, it can be used as an effective and inexpensive tool for meeting the respective engineering standards.

A Computationally Efficient RDFT Based Reference Signal Generator for Active Compensators

Several methods for the generation of the control reference signals for active compensators have been proposed. Many of those reference signal generation techniques use filters to extract the desired components of the current. Frequency-domain methods are generally not used due to high computational complexity as well as susceptibility to frequency variation and numerical errors. In this paper, a computationally efficient and robust recursive discrete Fourier transform-based reference signal generator is proposed for use in active compensator applications. In addition to mathematical analysis, discussions, and simulations, an experimental prototype of an active compensator with the proposed reference signal generator has been built, and experimental results have been obtained.

Mitigation of Electromagnetic Noise in a Shunt Active Power Filter Using Random PWM

Shunt active power filters (APF) are commonly used for the reduction of current harmonics and improvement of the power factor in power systems with nonlinear loads, such as diode rectifiers. A PWM power converter constitutes the main component of the APF. The low-order harmonics of the line current are attenuated, but the switch-mode operation of the converter results in electromagnetic interference (EMI) spreading to the grid. Specifically, clusters of harmonics appear in the frequency spectra of voltages and currents of the converter at multiples of the switching frequency. In this paper, transferring the discrete spectral power of those harmonics to the continuous spectral power density is proposed as means for mitigation of the EMI. It is accomplished by randomization of the switching periods using a novel random PWM method, RPWM II. In contrast to the existing random PWM methods, in RPWM II the sampling frequency of the digital modulator is constant and equal to the average switching frequency. Computer simulations and experimental investigation of an APF designed for shipboard power systems are described, and the results are presented. They demonstrate significant reduction of the EMI, a feat achieved at practically no expense.