Discontinuous PWM Techniques of Three-Leg Two-Phase Voltage Source Inverter for Sonar System

Abstract

Pulse width modulation (PWM) methods are important for the detection performance of a sound navigation and ranging (sonar) system because they determine the output noise of the system. However, only few studies have been conducted on PWM methods for reducing harmonics of a sonar system. In this study, we propose a discontinuous pulse width modulation (DPWM) method for three-leg two-phase (3L2P) inverters. Further, we derive a complete harmonic solution for a double-variable-controlled waveform for the proposed DPWM and conventional continuous pulse width modulation (CPWM) methods. Using these harmonic solutions, we analyze the normalized weighted total harmonic distortion (NWTHD) characteristics according to the modulation index (MI) of the inverter and phase difference of the output voltage for each method. Further, based on the results, we present a superiority map between the conventional CPWM and proposed DPWM methods in terms of the NWTHD. An NWTHD measurement experiment was performed to verify the proposed method. The experiment included additional evaluations of switch losses, phase difference variability, and voltage utilization, which are important factors for sonar systems. This is because improving only NWTHD performance while other factors degrade is not very useful. The results of the experiment confirm that the NWTHD for the proposed DPWM method was 92.5% of that for the conventional CPWM method. We confirm that the mean error of the NWTHD between the analytical and experimental values under similar conditions was less than ~2.2%. In addition, it was verified that the important factors, except NWTHD, were the same throughout additional experiments. Therefore, if the CPWM or DPWM method is selected based on the proposed selection criteria, realizing advantageous operation in terms of the NWTHD is possible.

Investigated Analysis and New Zero-Sequence Harmonic Injection Pulsewidth Scheme for Overmodulation Region

“…Another approach is to adopt discontinuous pulsewidth modulation (DPWM) schemes. Several DPWM schemes were developed [9], [15], [16]. They effectively reduce switching losses since these schemes clamp at least one segment to the DC bus positive or negative rail.…”

An Estimation Method of an Electrical Equivalent Circuit Considering Acoustic Radiation Efficiency for a Multiple Resonant Transducer

“…Existing acoustic transducers used in active sonar systems have been developed for broadband, high power, and high efficiency [1][2][3][4][5]. For driving transducers in broadband, multiple resonant modes should be adjacently located in the operating frequency [4,5].…”

Optimized Design of a Sonar Transmitter for the High-Power Control of Multichannel Acoustic Transducers

“…Since an acoustic transducer is a complex impedance load, a matching/filter circuit between a transmitter and an acoustic transducer is required for minimizing reactance and reducing THD (total harmonic distortion) [4,[10][11][12][13][14][15]. To utilize their load characteristics, various control methods have been studied for the transmitters driving transducers with variable impedance [2,[16][17][18].…”

“…This paper presents the design and control of a sonar transmitter for the widely distributed impedance load to which the study field is generally inaccessible. The underwater acoustic transducer was developed to be driven both in multiple channels and in high-power conditions for achieving the detection ability of active sonar systems [3,17,[24][25][26]. To control phases of transmission signal among transducers, the transducers are required to be independently driven [17].…”

“…The underwater acoustic transducer was developed to be driven both in multiple channels and in high-power conditions for achieving the detection ability of active sonar systems [3,17,[24][25][26]. To control phases of transmission signal among transducers, the transducers are required to be independently driven [17]. To individually drive each transducer, it is necessary to consider impedance characteristics varied by the transmission signal types and mutual radiation effect.…”