Input Current Distortion Research Articles

A Novel Current Injection Circuit For Adjustable Speed Drives

An adjustable speed drive creates the harmonics. The novel current injection circuit does not need any additional active devices. With the significant reduction in current harmonics, the AC input line current is sinusoidal. The ZVS technique is used for all the switches operation. The rectifier diodes are by soft switching. The output voltage regulated by fixed duty ratio with varying switching frequency. The advantages of proposed AC-DC-AC systems are low price, compact, high efficiency, and simplicity. Nine level diode clamped inverter produces the voltage harmonics of 8.75%. The Total Harmonic Distortion (THD) of input current is as low as 7.72 % and power factor as high as 0.99. Theoretical results are verified initially through PSIM simulation and validated with an experimental prototype of 2.5Kw.

Modulation Method and Control Strategy for Full-Bridge-Based Swiss Rectifier to Achieve ZVS Operation and Suppress Low-Order Harmonics of Injected Current

The Swiss-type rectifier (SR) uses a three-phase unfolder circuit to convert the ac voltage into two time-varying positive voltages. The power factor correction of ac sides and the stable dc voltage output can be realized by using two dc-dc topologies without any bulky decoupling capacitors. By applying the phase-shifted full-bridge topology into the dc structure, both the soft-switching and the high-frequency electrical isolation can be achieved. However, the power coupling between two full bridges using the traditional modulation method will affect the zero-voltage switching (ZVS) condition of lagging legs. Then, the duty cycle loss caused by the transformer leakage inductance will affect the input and output performance. Therefore, a new method using the up-counting mode modulation is proposed to implement the ZVS for both the lagging switches. Then, the relationship between the duty cycle loss and the extra 6N ± 1 harmonics added into the input current is theoretically analyzed. Hence, to suppress the low-order harmonics, a novel compensation strategy is proposed. The proposed modulation method and control strategy have been successfully verified by the experiments. 95% efficiency under half-rated power and 3% input current total harmonic distortion (THD) under rated power have been achieved under a 10-kW 380 Vac input/400 Vdc output prototype with 90-kHz switching frequency.

A Two-Switch, Isolated, Three-Phase AC–DC Converter

A new, three-phase, single-stage, isolated ac–dc converter (rectifier) that employs only two switches and achieves less than 5% total harmonic distortion of the three-phase input currents and provides a tightly regulated, isolated, output voltage is introduced. The rectifier features zero-voltage-switching of both switches over the entire input and load range without any additional soft-switching circuitry. The rectifier is derived by combining the three-phase, power-factor-correction, discontinuous-current-mode boost rectifier that is also known as Taipei rectifier with the conventional LLC resonant half-bridge converter. The introduced rectifier requires single feedback loop with frequency control to regulate the output voltage. The evaluation was performed on a 1-kW prototype operating with a three-phase line-voltage range from 180 to 264 $V_{\text{L}-\text{L}}$ and delivering a tightly-regulated, isolated, output voltage of 54 V. The measured efficiency of the prototype at nominal line voltage V IN = 208 VL-L is above 95% from 90% of full load down to 50% of full load. The maximum voltage stress is approximately 430 V.

A Low THD Three-Level Rectifier For Gen-Set Applications

A low input current total harmonic distortion (THD) rectifier is presented, tailored around an open-end winding permanent magnet synchronous generator. Specifically, a six-level converter topology is obtained by connecting the generator stator winding to a three level T-type unidirectional rectifier on one side, and to an auxiliary two-level inverter on the other side. The T-type rectifier manages the entire active power stream and operates at the line frequency in order to minimize the switching power losses. The auxiliary inverter is instead driven by a standard PWM technique, being tasked to sinusoidally shape the input current and to actively balance the voltage across the dc-bus capacitors of the T-type rectifier. Such an inverter, being rated at a lower power and at a lower voltage than the T-type rectifier, can exploit low-cost power mosfet s. The proposed topology, featuring a very low input current THD, could well supplement in aircraft, portable or distributed generation applications, modern high-speed permanent magnet synchronous generators featuring a quite small stator impedance. Simulation and experimental results confirm the effectiveness of the proposed configuration.

Experimental verification of a linear AC LED driver with a light flicker compensating circuit and high power factor operation by modulating the current regulator

AbstractThis article proposes a linear PFC regulator with a light flicker compensating circuit for LED lighting applications. The proposed circuit is small in size because it includes no reactors or electrolytic capacitors. The light flicker compensating circuit, which is connected in parallel to the LED string, consists of four ceramic capacitors and diodes. These capacitors are operated in series in the charge state and in parallel in the discharge state by using a diode network circuit. Therefore, an external controller and large capacitors are not required. The proposed circuit is experimentally validated using a 9 W prototype. From the experimental results, it is found that the power fluctuation of the LED string is less than the JIS and JLMA limitations, and the power factor is 0.95. In addition, the power loss is analyzed at an efficiency of 89.4% for the prototype circuit. Also, by modulating the current regulator, sinusoidal input current can be achieved. The second proposed circuit is experimentally validated using a 7.5 W prototype, and the power factor and input current distortion are found to be 0.999 and 2.1%, respectively.

Control for Three-Phase LCL-Filter PWM Rectifier with BESS-Oriented Application

This paper deals with a battery energy storage system (BESS) in only one of its multiple operating modes, that is when the BESS is charging the battery bank and with the focus on the control scheme design for the BESS input stage, which is a three-phase LCL-filter PWM rectifier. The rectifier's main requirements comprise output voltage regulation, power factor control, and low input current harmonic distortion, even in the presence of input voltage variations. Typically, these objectives are modeled by using a dq model with its corresponding two-loop controller architecture, including an outer voltage loop and a current internal loop. This paper outlines an alternative approach to tackle the problem by using not only an input–output map linearization controller, with the aim of a single-loop current control, but also by avoiding the dq modeling. In this case, the voltage is indirectly controlled by computing the current references based on the converter power balance. The mathematical model of the three-phase LCL-filter PWM rectifier is defined based on the delta connection of the filter, which accomplishes the requirements of a 100 kW BESS module. Extensive simulation results are included to confirm the performance of the proposed closed-loop control in practical applications.

Improvement of ZVS Range and Current Quality of the Nine-Switch Single-Stage AC–DC Converter

The nine-switch single-stage three-phase ac-dc isolated converter integrates a three-phase active front-end ac-dc converter and a three-phase high-frequency galvanically isolated dc-dc converter in one stage, leading to a device count reduction of 25% compared to an equivalent two-stage configuration. The advantage of the nine-switch converter can be truly realized if it can achieve similar efficiency and input current quality as a two-stage converter. In this article, a design methodology is proposed, which ensures zero-voltage switching of the bottom and the middle switches of the nine-switch converter for the entire line cycle and also reduces its input current total harmonic distortion below 5%. By implementing space vector pulsewidth modulation, the dc-link voltage of the nine-switch converter is reduced to the level of an equivalent two-stage converter. The analytical claims are verified with a 3-kW laboratory prototype operating at 400-V ac input, 800-V dc-link voltage, and 380-V isolated dc output voltage.

An Improved Deadbeat Control Method for Single-Phase PWM Rectifiers in Charging System for EVs

In single-phase AC charging system for electric vehicles (EVs), the single-phase pulse width modulation (PWM) rectifier with deadbeat predictive current control (DPCC) is characterized by fast current dynamic response and simple algorithm. However, in steady state, the performance of the DPCC is affected by the circuit parameters mismatch and control delay, which will result in the AC side power-factor degradation and the input current distortion. Moreover, the performance of dynamic response to load mutation can be improved, as the traditional DPCC adopted PI controllers in the voltage loop. In this paper, an improved deadbeat control method is proposed. In the current loop, the AC side voltage compensation parameter is proposed to improve the power factor and reduce the total harmonic distortion (THD). The voltage loop uses an active disturbance rejection controller (ADRC), which improves the dynamic performance of the system. The feasibility and effectiveness of the proposed deadbeat control method is verified by simulation and experimental results.

Two-Layer Pulsewidth Modulation Strategy for Common-Mode Voltage and Current Harmonic Distortion Reduction in Vienna Rectifier

Vienna rectifier, which is a nongenerative-boost-type rectifier, is widely used in industrial applications, such as wind turbine systems. However, the Vienna rectifier will face the challenge of reducing common-mode voltage (CMV), maintaining the sinusoidal input currents, and balancing neutral-point (NP) voltage in practice. As these issues are mutually coupled, the conventional space vector modulation (SVM) and various types of enhanced schemes cannot solve these problems properly, especially under nonunity power factor operation. To overcome these limitations, a two-layer pulsewidth modulation scheme through vector selection is developed. In the first layer of the proposed strategy, the NP voltage oscillations are mitigated by adjusting the switching sequence and dwell time of large, medium, small, and zero vectors with reduced CMV as the same in large, medium, and zero vector modulation. In the second layer of the proposed strategy, the switching states are reselected, and the dwell times are real time adjusted to eliminate the distortions in input currents. Through the aforementioned two-layer control method, CMV reduction, input current distortion elimination, and NP voltage balancing in Vienna rectifier can be realized simultaneously. The correctness and effectiveness of the proposed SVM method are verified by the experiment.

Accurate Operation Analysis Based Variable On-time Control for 360–800 Hz CRM Boost PFC Converters

The critical conduction mode (CRM) boost power factor correction (PFC) converter is widely used in low-to-medium power applications due to its low switching loss and simple control. In order to compensate the negative inductor current, variable on-time control provides a longer on-time near the zero-crossing input voltage, where the input voltage vin varies sharply especially in 360-800 Hz applications. Therefore, it is imprecise to assume that vin is constant during the switching period. Considering that vin is variable during the switching period, an accurate operation analysis is studied in this article. Moreover, a comparative analysis between the proposed accurate operation analysis and imprecise assumption-based operation analysis is conducted. Based on the operation analysis, an input filter capacitor (IFC) current compensation method is proposed to minimize the phase-leading caused by IFC current in the input current. The effectiveness of the proposed methods is verified with a 160 W gallium nitride-based CRM boost PFC converter. With the proposed methods, the input current total harmonic distortion is only 1.7% at 360 Hz input with full load and 2.42% at 800 Hz input with full load.

A Modified One-Cycle Control for Vienna Rectifiers with Functionality of Input Power Factor Regulation and Input Current Distortion Mitigation

In this paper, aiming at incorporating reactive power compensation functionality into the Vienna rectifiers, a modified one-cycle-control (MOCC) strategy is proposed by which the three-phase Vienna rectifier can be regulated in leading, lagging or unity power factors with near-sinusoidal input current waveform. First, a brief review of the working principle of the conventional OCC (COCC) strategy is conducted. Then, the MOCC strategy with the functionality of input current phase-shift control is discussed in detail. To mitigate input current distortion caused by the current phase-shift, a method whereby the signal of one phase current which is flowing in an uncontrollable region is injected into the other two phases’ current command signals is further presented. The constraints to the implementation of the MOCC scheme and the reactive power compensation capacity of the rectifier under MOCC control are analyzed as well. The proposed MOCC strategy is as easy to implement as the COCC strategy. Moreover, the MOCC strategy also preserves all other advantages of the COCC strategy, such as no phase-locked loop, no frame transformation and constant switching frequency. Finally, the theoretical analysis of the proposed MOCC strategy is fully verified by simulation and experimental results from a 1 kV·A three-phase Vienna rectifier prototype.

A Remotely Central Dimming System for a Large-Scale LED Lighting Network Providing High Quality Voltage and Current

Standard TRIAC-based dimmers introduce power quality issues especially for a large-scale lighting network. Other existing dimming protocols involve additional wiring systems and/or additional controllers to light emitting diode (LED) drivers. This paper proposes a central dimming system for a large penetration of LED lamps. The dimming system is remotely controlled through a webpage or a desktop application. Dimming is achieved while maintaining high voltage and current quality waveforms, which results in a high power factor and a low input current harmonic distortion. The system does not require additional wiring or specific adjustments to commercial dimmable LED drivers. The system allows scheduling a dimming profile to endorse energy saving. In the proposed dimming system, dimming function is achieved by connecting a voltage source converter (VSC) between the grid and the LED lamps. An advanced feature is added to the VSC dimmer to remotely send/receive messages between the system and the user through a graphical user interface. Thus, the user can communicate with the VSC dimmer by sending commands and receiving feedback information. The influence of communication delay on system stability is analyzed by using small signal models. A VSC dimmer prototype (500 VA/120 V) has been built with a communication module to provide remote control. Experimental results and comparisons between utilizing the TRIAC-based dimmer and the VSC dimmer for dimming function are discussed in the paper.

Simple Analog-Based Accurate Variable On-Time Control for Critical Conduction Mode Boost Power Factor Correction Converters

In order to suppress the input current distortion of critical conduction mode (CRM) boost power factor correction (PFC) converters, variable on-time (VOT) control has been adopted in many analog commercial integrated chips (ICs). However, the quantitative VOT expression applicable to analog control has not been studied until now. According to the fitting functional form of VOT, this paper proposes a uniform and simple VOT expression, which can be directly implemented by analog circuits and provide accurate VOT control just as digital control. Only an inverse signal of the rectified input voltage is additionally introduced to achieve accurate VOT control, and the inherent voltage feedback loop of PFC is utilized to eliminate the effect of the input rms voltage and output power. With the proposed quantitative design consideration, the optimum input current total harmonics distortion (THD) is naturally obtained without trial-and-error design. The experimental results of a 160-W prototype are built to verify the effectiveness and advantages of the proposed VOT control.

Three-Phase Buck–Boost Derived PFC Converter for More Electric Aircraft

In more electric aircraft (MEA), three-phase power factor correction (PFC) rectifiers of several kilowatts are required. In this paper, a three-phase buck–boost derived PFC converter with three switches and with input inductors connected in delta configuration for use in MEA is presented. The proposed converter is operated in a discontinuous conduction mode to achieve PFC at ac input. This avoids the inner current control loop which further eliminates the current sensors. It requires only one output voltage sensor unlike five sensors in conventional PFC converter for its control implementation. This makes the system cost effective, more reliable, and robust. A simple voltage control loop is used to generate the gate signals. The steady state operation of the converter and detailed design calculations are presented. For each power component, the analytical expressions for calculating the average and rms current ratings are derived to facilitate the converter design. The small-signal model of the converter is presented to aid the controller design. The experimental results from a 2 kW laboratory prototype are presented to confirm the operation of the proposed converter. An input power factor of 0.999, an input current total harmonic distortion of as low as 2.76%, and a high conversion efficiency of 96% are achieved from the prototype.

Power factor adjustment and input current distortion mitigation for three‐phase unidirectional rectifier

In order to improve the power quality, many researchers in the worldwide are committed to investigating the feasibility of integrating reactive power compensation (RPC) and harmonic current compensation (HCC) functionalities for unidirectional rectifier, while the capability of RPC for unidirectional rectifier is very limited. Hence, with the aim of enlarging the capability of RPC for unidirectional rectifier, this article introduces a versatile control strategy for three-phase star-connected unidirectional rectifier. The operating principle and the reasons that limit the capability of RPC for unidirectional rectifier are analysed in detail. On this basis, a novel criterion for judging input current distortion zone is proposed. Furthermore, the additional focus of this article is to quantify the constraint relationship between the degree of input current distortion compensation and input power factor regulating range. Simulations and experimental results are conducted to verify the feasibility and effectiveness of the proposed control strategy, as well as the correctness of the theoretical analysis on the proposed constraints of the input power factor regulation.

Flyback PFC With a Series-Pass Module in Cascode Structure for Input Current Shaping

A flyback power factor corrector (PFC) using a series-pass module (SPM) to shape its input current is presented. The input current is profiled by the SPM with its waveform controlled to be in the same wave shape and phase with the supply voltage and its magnitude controlled to regulate the output voltage. The SPM is constructed by two series-connected power semiconductor devices in a cascode structure. One of them is a high-voltage device of low on -state resistance for sharing major voltage stress, while the other one is a low-voltage device with high-output impedance for profiling the current through the SPM. The SPM has a local control for clamping the voltage across the low-voltage device. Such arrangement allows the PFC to exhibit lower total input current harmonic distortion than that using a single high-voltage series-pass device. To minimize power loss, the operating point of the low-voltage device is regulated around the boundary between its high-gain and fully turn- on operating region by adjusting the duty cycle of the main switch in the flyback converter. A 100-W 85–265-Vac/36-Vdc prototype has been built and evaluated. The conducted electromagnetic interference under different supply voltages will also be given.

Boundary Conduction Mode Modified Buck Converter with Low Input Current Total Harmonic Distortion

Buck Power Factor Correction (PFC) converter is widely used for a broad range of AC/DC applications because of its many advantages like protection against short circuit, high efficiency at universal input voltage, low output voltage, less voltage stress on the switch, low inrush current and low component cast. However the inherent dead zone introduces a large harmonic distortion in the average input current, resulting in a low Power Factor (PF) and high Total Harmonic Distortion (THD). A constant on-time controlled Boundary Conduction Mode (BCM) buck-flyback converter is introduced in this paper. It can achieve low input current THD and high PF. The operating principle of the traditional and proposed converter is discussed and the effectiveness of proposed topology is evaluated by simulation results. Keywords: Boundary Conduction Mode (BCM), Buck Converter, Power Factor (PF), Total Harmonic Distortion (THD)

Simple digital algorithm for improved performance in a boost PFC converter operating in CCM

In power factor correction (PFC) converters, achieving both good steady-state input current waveform and fast output dynamic response is a challenge. This is due to the effect of the double-line frequency ripple present in the sensed output voltage signal which tends to distort the reference current applied to the current controller, thus leading to a distorted input current waveform. Low bandwidth (BW) voltage loop designs to reduce this input current distortion make the output dynamic response very sluggish. A digital control algorithm for the estimation of the average value of the sensed output voltage is proposed in this study to achieve low total harmonic distortion input current and fast dynamic response with a higher BW voltage loop. The proposed algorithm is computationally less intensive and requires no additional sensors or circuitry. The effectiveness of the proposed control algorithm is validated through simulation and experimental tests on a 300 W boost PFC converter prototype operating in continuous conduction mode.

Two methods for controlling three‐time fundamental frequency neutral‐point voltage oscillation in a hybrid VIENNA rectifier

This study presents two methods of controlling neutral-point voltage oscillation in a hybrid VIENNA rectifier, which is composed of the parallel association of a three-phase single-switch Boost rectifier with a VIENNA-type rectifier. The neutral-point oscillation reason has been analysed with a mathematical model. Meanwhile, the two neutral-point control methods of a simplified method based on a zero-sequence component injection and a dual-carrier pulse-width modulation (PWM) method are proposed to control the voltage deviation of the split DC-link and three-time fundamental frequency neutral-point voltage fluctuation with a decrease from ±1.6 to ±1 V, respectively. Moreover, the significant oscillation in the neutral-point voltage caused by unbalanced loads or asymmetric capacitor parameters can also be effectively suppressed by using the dual-carrier PWM method. Furthermore, the performance comparison between these two methods is provided. The experimental results show that the system after being introduced the proposed two methods still exhibits a low-order input current harmonic such as second, third, and fourth harmonics as well as the input current total harmonic distortion is lower than the standard 5%.

A Digital Pulse Train Controlled High Power Factor DCM Boost PFC Converter Over a Universal Input Voltage Range

In this paper, a digital-based pulse train (PT) control technique for a boost power factor correction (PFC) converter operating in a discontinuous conduction mode (DCM) is presented, which can achieve nearly unity power factor (PF) over a universal input voltage range. Different from traditional digital control techniques, which usually require complex arithmetic operations, the digital-based PT control technique only needs a simple operation. Besides, a DCM boost PFC converter with digital PT control can operate at a high switching frequency, which is less dependent on the processing speed of a digital controller. Thus, the proposed control strategy can be implemented with general purpose digital controllers, such as low-speed and low-cost microcontroller unit, for the DCM boost PFC converter where the cost is a focus. The operation principle of the digital PT controlled DCM boost PFC converter is analyzed. Experimental results are provided, which show that high PF and low input current total harmonic distortion can be maintained over a universal input voltage range of 90–264 V ac.