Input current shaped ac-to-dc converters

Input current shaping techniques for ac-to-dc converters were investigated. Input frequencies much higher than normal, up to 20 kHz were emphasized. Several methods of shaping the input current waveform in ac-to-dc converters were reviewed. The simplest method is the LC filter following the rectifier. The next simplest method is the resistor emulation approach in which the inductor size is determined by the converter switching frequency and not by the line input frequency. Other methods require complicated switch drive algorithms to construct the input current waveshape. For a high-frequency line input, on the order of 20 kHz, the simple LC cannot be discarded so peremptorily, since the inductor size can be compared with that for the resistor emulation method. In fact, since a dc regulator will normally be required after the filter anyway, the total component count is almost the same as for the resistor emulation method, in which the filter is effectively incorporated into the regulator

Minimum component high frequency current mode rectifier

In this paper a current mode full wave rectifier circuit is proposed. The current mode rectifiercircuit is implemented utilizing a floating current source (FCS) as an active element. Theminimum component full wave rectifier utilizes only a single floating current source, twodiodes and two grounded resistors. The extremely simple implementation enjoys highfrequency operation and provides both inverting and non-inverting rectified outputssimultaneously. The rectifier system can work up to a frequency of 500MHz with acceptabledistortion. The circuit exhibits low power consumption at ±0.75V supply voltage. Thenon-ideal and temperature analysis was also performed to study their impact on itsperformance. It was also shown that FCS can work as half wave rectifier as well. Theperformance of the circuit is evaluated using 0.18μm TSMC CMOS parameters using Hspice.Keywords: current-mode circuits; floating current source; high frequency; rectifier

An Integral Battery Charger with Power Factor Correction for Electric Scooter

This paper presents an integral battery charger for an electric scooter with high voltage batteries and interior-permanent-magnet motor traction drive. The battery charger is derived from the power hardware of the scooter, with the ac motor drive that operates as three-phase boost rectifier with power factor correction capability. The control of the charger is also integrated into the scooter control firmware that is implemented on a fixed-point DSP controller. Current-controlled or voltage-controlled charge modes are actuated according to the requirements of the battery management system, that is embedded into the battery pack. With respect to previous integrated chargers, the ac current is absorbed at unitary power factor with no harmonic distortion. Moreover, no additional filtering is needed since the pulsewidth modulation ripple is minimized by means of phase interleaving. The feasibility of the integral charger with different ac motors (induction motor, surface-mounted phase modulation motor) is also discussed, by means of a general model purposely developed for three-phase ac machines. The effectiveness of the proposed battery charger is experimentally demonstrated on a prototype electric scooter, equipped with two Li-ion battery packs rated 260 V, 20 A

PFC Topologies for AC to DC Converters in DC Micro-Grid

With increasing dominance of renewable energy resources and DC household appliances, the novelty of DC micro grid is attracting significant attention. The key interface between the main supply grid and DC micro grid is AC to DC converter. The conventional AC to DC converter with large output capacitor introduces undesirable power quality problems in the main supply current. It reduces system efficiency due to low power factor and high harmonic distortion. Power Factor Correction (PFC) circuits are used to make supply currents sinusoidal and in-phase with supply voltages. This paper presents different PFC topologies for single phase AC to DC converters which are analyzed for power factor (PF), total harmonic distortion (THD) and system efficiency by varying output power. Two-quadrant shunt active filter topology attains a power factor of 0.999, 3.03% THD and 98% system efficiency. Output voltage regulation of the presented active PFC topologies is simulated by applying a step load. Two-quadrant shunt active filter achieves better output voltage regulation compared to other topologies and can be used as grid interface

The Proposal for Implementation of Controlled Power Rectifier (3000/4000KW) in MTA New York City Transit (MTA-NYCT)

The MTA New York City Transit (MTA-NYCT) will require a robust and reconfigurable power system capable of supplying high power in order to be able to provide services based on for cased future forecast growth of the city population. A critical component in such a system is the Phase Controlled Rectifier. As such, the issues associated with the inclusion of a power electronics rectifier need to be addressed. These issues include input Alternating Current (AC) interface requirements, the output Direct Current (DC) load profile, and overall stability in the output voltage for Train car loads. Understanding these issues, providing possible solutions and determining the means of assuring smooth compatibility with MTA New York City Transit (MTA-NYCT) Traction Power systems is the focus of this thesis. By using a Simulink® model of an actual MTA-NYCT Traction Power System, actual train car load, 12 -Pulse count, high power rectifiers were exercised. The Simulink® results are compared between the Traction Power Systems of Uncontrolled Rectifier and Controlled Rectifier analysis results. In subway normal operation hour, with uncontrolled rectifier systems, subway cars load current level are 2800 Amps to 3600 Amps, and Voltage level 450 VDC to 600 VDC in running condition. In this Simulation, with controlled rectifier system, subway cars load current level are 3200 Amps to 4000 Amps, and Voltage level 550 VDC to 625 VDC established. These experiments led to the conclusion that increasing the continuous current and the overall stability in the output voltage, reducing the harmonics, there are tradeoffs in terms of complexity and size of the passive components, and optimization based on source and load specifications is also required.

Power factor-corrected transformerless three-phase PWM converter for UPS applications

This thesis describes the research of a new transformerless three phase PWM converter for uninterruptible power supplies (UPS) applications. The removal of the bulky three phase transformer in larger power UPS can provide a significant saving in weight and cost of the overall system. The converter consists of a new four-wire rectifier coupled with a four-wire inverter via a dc bus. The supply and load neutral may be connected together without any neutral current flowing into the utility regardless of the load on the inverter. This allows the load to be at the same potential as the utility. The rectifier, inverter and complete UPS and control system are described in detail and simulation results are used extensively to back up the theory. An experimental prototype of the four-wire rectifier provides further confirmation of the principles. A further proposal to digitize the system is given. This would reduce the size of the required control circuit and simplify the hardware requirements

Modeling and Analysis of Power Processing Systems

The feasibility of formulating a methodology for the modeling and analysis of aerospace electrical power processing systems is investigated. It is shown that a digital computer may be used in an interactive mode for the design, modeling, analysis, and comparison of power processing systems

A comparative study of electric power distribution systems for spacecraft

The electric power distribution systems for spacecraft are compared concentrating on two interrelated issues: the choice between dc and high frequency ac, and the converter/inverter topology to be used at the power source. The relative merits of dc and ac distribution are discussed. Specific converter and inverter topologies are identified and analyzed in detail for the purpose of detailed comparison. Finally, specific topologies are recommended for use in dc and ac systems