Abstract
The motor integration of singe-phase-supplied Variable-Speed Drives (VSDs) is prevented by the significant volume, short lifetime, and operating temperature limit of the electrolytic capacitors required to buffer the pulsating power grid. The DC-link energy storage requirement is eliminated by using the kinetic energy of the motor as a buffer. The proposed concept is called the Motor-Integrated Power Pulsation Buffer (MPPB), and a control technique and structure are detailed that meet the requirements for nominal and faulted operation with a simple reconfiguration of existing controller blocks. A 7.5 KW, motor-integrated hardware demonstrator validated the proposed MPPB concept and loss models for a scroll compressor drive used in auxiliary railway applications. The MPPB drive with a front-end CISPR 11/Class A EMI filter, PFC rectifier stage, and output-side inverter stage achieved a power density of 0.91 KW L−1 (15 W in−3). The grid-to-motor-shaft efficiency exceeded 90% for all loads over 5 kW or 66% of nominal load, with a worst-case loss penalty over a conventional system of only 17%.
Highlights
Mobility, transportation, and industrial systems are increasingly electric, from the drivetrain to the auxiliaries, driven by improvements in battery performance and lifetime, government and private mandates to reduce greenhouse gas emissions, and an improved user experience
In this work, the focus was on the single-phase to three-phase Variable-Speed Drives (VSDs) power conversion system for this particular application, the requirements for single-phase to three-phase variablespeed conversion are quite general (e.g., a 10 kW, 230 Vrms, single-phase VSD in [4], or a single-phase to three-phase VSD with Power Factor Correction (PFC) operation in [5])
The corresponding waveforms at a mechanical output power of 7.5 kW and 3700 rpm are shown in Figure 5, where the grid current iG is in phase with the grid voltage vG for unity power factor operation and the product of the grid current and grid voltage resulting in pulsating input power, translated to a torque pulsation
Summary
Transportation, and industrial systems are increasingly electric, from the drivetrain to the auxiliaries, driven by improvements in battery performance and lifetime, government and private mandates to reduce greenhouse gas emissions, and an improved user experience. Grid Voltage Range (VG) Grid Frequency ( fG) Battery Voltage Range (VB) EMI Standard (Input) These power conversion systems are realized with a two-stage system [10] comprising a front-end PFC rectifier, an electrolytic DC-link capacitor to buffer the power pulsation from the single-phase grid supply, and a VSD inverter to drive the motor and compressor [11]. The MPPB concept was previously proposed with the PFC rectifier omitted and the inverter stage directly supplied from a single-phase-grid diode bridge rectifier [29] This concept results in a rectifier sine wave voltage at the DC-link, so the input current is only sinusoidal if the motor voltage stays below the rectified input voltage [30].
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