Input AC Supply Research Articles

A Sensorless DTC Scheme for 60-Pulse AC-DC Converter Fed 5-Level Six-Leg NPC Inverter Based Medium Voltage Induction Motor Drive

A new approach to improve the power quality of medium voltage induction motor drive (MVIMD) at both utility and drive end is presented. Here, 3-multi-winding transformers (MWT) (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) are utilized and each MWT converts 3-phase input AC-supply into two isolated 5-phase AC-supplies with unique (18°) phase-shift among them. Moreover, due to unique (±6° and 0°) angle in the primary sides of these MWTs, the line current drawn from the grid has 60-pulses. By applying this technology, the input current harmonics are decreased to well below the requirement of the IEEE 519 standard. This 60-pulse AC-DC converter gives 6-isolated DC-supplies, which are input of a 5-level six-leg neutral point clamped (NPC) inverter feeding an induction motor. A modified direct torque control (DTC) strategy is used in this study for 5-level six-leg NPC inverter fed induction motor drive (IMD). Because of it, this IMD has better performance than the existing IMD. The system performance is evaluated using MATLAB-Simulink software and is then experimentally verified on a prototype developed in the laboratory under all required operation of IMD to validate the performance of the system.

LED STREET LIGHTS BASED ON DC-DC CONVERTERS OF MODULAR DRIVES

This paper proposes a led street lights based on dc-dc converters of modular drives to save energy and if one of the coverters get damaged other converter doesn’t get comporise so the LED does’nt stop working and by using this method the LED doen’t get damage and increase life-period.In this paper, Light Emitting Diode (LED) electric light unit for street lights based on DC-DC converters were proposed. The driver consists of two modules which are basically converters that are DC-DC type. The foremost in position is a Buck-Boost converter which is obligated to decrease total harmonic distortion (THD) and the second module which is obligated for decreasing the voltage which leads to the control of power. These two converters operate in Discontinuous Conduction Mode(DCM), to construct the system in opposition to failure. Each circuitry contributes their individual LEDS if any of the converters is malfunctioned the system cannot be completely failed. In this paper the input ac supply of 127V is rectified and the rated power of 50 W are performed

Differential Flatness Controller for BLIL PFC Boost Rectifier

Electric Vehicle uses AC/DC boost converters for charging high energy battery pack from the input AC supply. They incorporate a PFC controller to improve the input side power factor and also regulate the output voltage with reduced ripple. PFC converter is followed by DC /DC converter which provide high-frequency isolation from the battery bank. This paper presents a technique based on differential flatness principle to improve the power factor of the converter based on the input power. In this case, input power is taken as the reference instead of intermediate dc bus voltage, unlike the conventional ACM (ACM) control. This flatness approach improves the dynamic behavior of the converter with good load adaptive regulation. The converter is initially analyzed with ACM controller and compared with the flatness theory based controller. The front-end converter topology considered in this work is BLIL AC/DC converter and for the second stage, an isolated resonant DC/DC converter is preferred as it is best suited for charging applications. The results reveal that the differential flatness controller improves the dynamic response of the converter under varying load conditions and soft switching is achieved in the second stage converter which results in improving the overall converter efficiency.

Implementation of a low cost ac-dc converter for high and low power applications

This paper proposes an ac-dc converter that gives multiple outputs capable of feeding both high and low power applications. The input ac supply is converted to dc by a diode bridge rectifier, filtered and fed to a modified multiport converter (MPC). This paper focuses on the design of the modified multiport converter that has a cascaded combination of zeta and a buck converter. This is designed as a single input and multiple output converter (SIMO) structure which can operate two loads, one with a high power and other with a low power application, depending on the time instant. The need for opting a multiport converter, reduces the number of switches utilized, thereby reducing the switching losses in the circuit. The zeta in the MPC boosts the input voltage and the buck converter reduces the input voltage and is accordingly fed to the need of the load. The design of the components have been analysed through steady state. MATLAB Simulink has been used to simulate the converter circuit and the varied outputs of the zeta and buck modes are compared. A hardware prototype of the ac-dc converter has been implemented and their results have been shown.

A Polynomial Current Controller for a Third-Harmonic Modulated Power Factor Correction Rectifier Feeding a Vector Controlled Induction Motor Drive

This paper presents the analysis, design, and hardware implementation of a digital polynomial Regulation, Steady-State Error and Tracking (RST) current controller-based third-harmonic modulated boost-type power factor correction (PFC) rectifier. The proposed rectifier is used at the front end of a vector controlled induction motor drive (VCIMD) to eliminate harmonics at the input AC supply. The proposed PFC rectifier modifies the input current to a sinusoid with unity power factor apart from offering DC bus voltage regulation. In this paper, a digital proportional-integral (PI) and RST current controllers are compared in terms of total harmonic distortion (THD) and power factor (PF) at the point of common coupling for different loading conditions. The RST current controller tracks the set-point accurately with zero steady-state error and offers good disturbance rejection that enables further reduction of supply current THD as compared to a conventional PI current controller. The control algorithm for the PFC front end rectifier along with vector control technique is implemented using a digital signal processor, and the dynamic performance is analyzed for step changes in reference speed and load torques, demonstrating significant improvement in the performance indices.

Repetitive control‐based single‐phase bidirectional rectifier with enhanced performance

In this study, a single-phase pulse-width modulation rectifier with regenerative capability has been presented. Here, the main purpose is to achieve unity power factor with least harmonics on AC-side source current while having regulated DC voltage at output. It is very difficult to achieve aforementioned goals with commonly used proportional-integral (PI) regulators due to their limited control bandwidth, especially under rapidly varying input AC and dynamic load conditions. The disturbances on DC side are mainly due to double frequency ripple components, which are periodic in nature and are very much prominent in single-phase rectification. The problem may be further exaggerated due to the presence of periodic noise/disturbances in input AC supply. Hence, a repetitive controller (RC) is designed, which is well known for its capabilities in tracking periodic disturbances. The systematic design and modelling of stable RC controller based on internal model principle theory has been presented. The proposed control technique has been developed and simulated in MATLAB/SimPower System. The experimental results have been presented and analysed in detail to validate the performance of the proposed RC control technique in comparison with its PI counterpart.

A current sensorless power factor correction control for LED lamp driver

This paper proposes a new control technique to achieve a unity power factor at the input AC supply for light-emitting diode (LED) lamps controlled by AC–DC converter, without using a current sensor. Only two analog to digital converters (ADCs) for measuring the input and output voltages are used. This technique achieves isolation between power circuit and controller; it can be implemented by using a zero-crossing processing, which has a greater accuracy than other techniques. Simulation and experimental results illustrate the effectiveness and feasibility of the proposed control technique, which achieves low harmonic contents in the supply current, a near unity power factor (PF), a sinusoidal current waveform, and a fast dynamic response under transient operation.

Modeling of Three-Phase Uniform Symmetrical Sampling Digital PWM for Power Converter

A mathematical approach of modeling and analyzing three-phase pulsewidth modulation (PWM) is presented. The three-phase flyback converter required a unique pattern of PWM to optimize the power transfer in the magnetic circuit used in the converter. The three-phase PWM is generated digitally based on uniform symmetrical sampling technique using Xilinx chip. The generated PWM pattern is able to reduce the magnitude of the low order of harmonic components present in the input ac supply. Although software simulation could simulate the PWM pattern, it does not represent the exact pattern as being generated digitally. The mathematical approach used is to model the PWM pattern exactly as being created digitally. The proposed mathematical technique could also be used to analyze any digital PWM. The result of the mathematical analysis on the PWM pattern could be used to study the characteristics of the pattern such as maximum and minimum value of duty cycle, pulsewidth, turn-on time, turn-off time, and modulation index. To verify the validity of the proposed technique, the results obtained from the mathematical model, experimental, and simulation using PSpice were compared