Average Current Mode Control Research Articles

Improved resettable integrator control for a bridgeless interleaved AC/DC converter

Plug-in hybrid electric vehicles (PHEVs) consist of a front-end boost rectifier, which incorporates a power factor correction (PFC) circuit for battery charging. Bridgeless interleaved (BLIL) PFC boost converter topology is proved as a standard PFC converter as it has high efficiency, reduced input current ripple, and reduced electromagnetic interference (EMI). This paper proposes a digital nonlinear control technique that employs a resettable integrator to shape the input current of the converter in phase with the input voltage to achieve high input power factor. This control approach rejects power source and load perturbations better than linear feedback control methods. This is accomplished by summing up the sensed input current of a BLIL converter with a fictitious current synthesized with the input voltage. In this work, a BLIL converter is analyzed for its input power factor improvement, voltage stress across the devices, and dynamic response under variable supply and load conditions using simulation. The hardware is tested for a 300 W BLIL boost converter to validate the simulated results. The performance of the proposed controller is compared with that of conventional average current mode control. The experiment and simulation results prove that the resettable integrator controller shows a better performance than the conventional controller.

Design and Implementation of Single Phase AC-DC Buck-Boost Converter for Power Factor Correction and Harmonic Elimination

<p class="Abstract"><span>This paper discusses the Power Factor Correction (PFC) for single phase ACDC Buck-Boost Converter (BBC) operated in Continuous Conduction Mode (CCM) using inductor average current mode control. The proposed control technique employs Proportional-Integral (PI) controller in the outer voltage loop and the Inductor Average Current Mode Control (IACMC) in the inner current loop for PFC BBC. The IACMC has advantages such as robustness when there are large variations in line voltage and output load. The PI controller is developed by using state space average model of BBC. The simulation of the proposed system with its control circuit is implemented in MatLab/Simulink. The simulation results show a nearly unity power factor can be attained and there is almost no change in power factor when the line frequency is at various ranges. Experimental results are provided to show its validity and feasibility. <br />Keyword</span></p>

Cascaded Bidirectional Converter Topology for 700 W Transformerless High Frequency Inverter

Home inverter is an important system which provides uninterrupted power supply for domestic requirements. Most of the existing systems use line frequency transformers to generate the desired sinusoidal voltage and exhibit poor load regulation and efficiency. Under spurious conditions, reliable and stable operation of the inverter is a primary requirement. In this paper, 3-stage bidirectional (boost and buck) cascaded converter topology is proposed to boost an input battery voltage from 12 to 375 V and vice-versa. DC link is connected to H-bridge converter to obtain a desired sinusoidal output voltage. In the topology, first and third stages are non-isolated boost converters and second stage is a buck derived push–pull converter. Push–pull configuration of the 2nd stage provides electrical isolation to source from high voltage DC bus. Cascaded DC–DC converter outputs are regulated by designing an average current mode control and instantaneous voltage control is designed for H-bridge inverter. Hardware is designed and developed using digital signal controllers to supply 700 W domestic load. Experiments are conducted for different linear, nonlinear and dynamic load variations.

Zero voltage switching‐pulse width modulation technique‐based interleaved flyback converter for remote power solutions

The growing need to supplement the depletion of conventional energy resources has placed an impetus on the electrical power industry to provide new avenues for alternative energy resources. This study presents a soft switched [zero voltage switching (ZVS)-pulse width modulation (PWM)] interleaved flyback converter with an average current mode control designed for remote power solutions. The flyback DC–DC converter, a popular choice for low-power DC applications that requires an electrical isolation, is being considered in this study due to its simplicity, cost and lesser magnetic components. The lower energy efficiency which is a drawback in flyback converters is overcome using the soft-switching technique. The switching losses and conduction losses are minimised using the ZVS-PWM technique. Also, interleaving of the DC–DC converters is being used to reduce the size of the magnetic components and further improve the converter efficiency. The effectiveness of the converter is verified using the results obtained through MATLAB/Simulink. A prototype model is also developed to validate this system and is tested using dsPIC30F4011 processor. The experimental results prove the viability of the converter. Both simulation and experimental results show high efficiency and good output voltage regulation for a wide range of load and input variations.

Interleaved Digital Power Factor Correction Based on the Sliding-Mode Approach

This study describes a digitally controlled power factor correction (PFC) system based on two interleaved boost converters operating with pulsewidth modulation (PWM). Both converters are independently controlled by an inner control loop based on a discrete-time sliding-mode (SM) approach that imposes loss-free resistor (LFR) behavior on each cell. The switching surface implements an average current-mode controller so that the power factor (PF) is high. The SM-based digital controller is designed to operate at a constant switching frequency so that the interleaving technique, which is recommended for ac–dc power conversion systems higher than 1 kW, can be readily applied. An outer loop regulates the output voltage by means of a discrete-time proportional–integral (PI) compensator directly obtained from a discrete-time small-signal model of the ideal sliding dynamics. The control law proposed has been validated using numerical simulations and experimental results in a 2-kW prototype.

Analysis, Design, and Implementation of a High-Performance Rectifier

A high-performance rectifier is introduced in this study. The proposed rectifier combines the conventional pulse width modulation, soft commutation, and instantaneously average line current control techniques to promote circuit performance. The voltage stresses of the main switches in the rectifier are lower than those in conventional rectifier topologies. Moreover, conduction losses of switches in the rectifier are certainly lower than those in conventional rectifier topologies because the power current flow path when the main switches are turned on includes two main power semiconductors and the power current flow path when the main switches are turned off includes one main power semiconductor. The rectifier also adopts a ZCS-PWM auxiliary circuit to derive the ZCS function for power semiconductors. Thus, the problem of switching losses and EMI can be improved. In the control strategy, the controller uses the average current control mode to achieve fixed-frequency current control with stability and low distortion. A prototype has been implemented in the laboratory to verify circuit theory.

Small-Signal Modeling of <italic>I</italic><sup>2</sup> Average Current Mode Control

I 2 average current mode control is a promising control technique featuring fast dynamic response, cycle-by-cycle current limiting and accurate current control. It can be treated as peak current mode control with no peak-to-average error. By combining direct current feedback and average current feedback, I 2 average current mode control is a three-loop control system. Since it is a new control technique proposed in 2013, few papers exist which discuss the small-signal model for this control method. In this paper, a small-signal model for constant frequency I 2 average current mode control is proposed which successfully predicts the subharmonics oscillation when the duty cycle is close to or greater than 0.5. The characteristics of I 2 average current mode control are also compared with average current mode control and peak current mode control to show its advantages.

A Scalable <italic>N</italic>-Color LED Driver Using Single Inductor Multiple Current Output Topology

Constant current sources are required to drive multiple color LED strings and the LED drivers that drive these LED lighting systems should provide multiple constant currents from a single dc source. In this paper, a single inductor multiple current output (SIMCO) converter that can provide N - independently controllable constant current outputs is reported. The average current in each color LED string is controlled independently by using hybrid average current mode control (HACMC). The HACMC combines the advantage of both average current mode control and charge control method. Traditional dimming approaches such as pulse width modulation and analog dimming can be incorporated in the proposed topology for color tunability and correlated color temperature control. The proposed approach uses a simple control logic, which is modular and can be scalable to N color LED lighting systems. The operation of the SIMCO converter with the HACMC is explained in detail. Simulation and experimental results with 48 V input and 12 W for $N = 3$ (RGB) color systems are presented.

A Novel Photovoltaic Power Harvesting System Using a Transformerless H6 Single-Phase Inverter with Improved Grid Current Quality

The pumping of electric power from photovoltaic (PV) farms is normally carried out using transformers, which require heavy mounting structures and are thus costly, less efficient, and bulky. Therefore, transformerless schemes are developed for the injection of power into the grid. Compared with the H4 inverter topology, the H6 topology is a better choice for pumping PV power into the grid because of the reduced common mode current. This paper presents how the perturb and observe (P&O) algorithm for maximum power point tracking (MPPT) can be implemented in the H6 inverter topology along with the improved sinusoidal current injected to the grid at unity power factor with the average current mode control technique. On the basis of the P&O MPPT algorithm, a power reference for the present insolation level is first calculated. Maintaining this power reference and referring to the AC sine wave of bus bars, a sinusoidal current at unity power factor is injected to the grid. The proportional integral (PI) controller and fuzzy logic controller (FLC) are designed and implemented. The FLC outperforms the PI controller in terms of conversion efficiency and injected power quality. A simulation in the MATLAB/SIMULINK environment is carried out. An experimental prototype is built to validate the proposed idea. The dynamic and steady-state performances of the FLC controller are found to be better than those of the PI controller. The results are presented in this paper.

Modeling and Control of the Distributed Power Converters in a Standalone DC Microgrid

A standalone DC microgrid integrated with distributed renewable energy sources, energy storage devices and loads is analyzed. To mitigate the interaction among distributed power modules, this paper describes a modeling and control design procedure for the distributed converters. The system configuration and steady-state analysis of the standalone DC microgrid under study are discussed first. The dynamic models of the distributed converters are then developed from two aspects corresponding to their two operating modes, device-regulating mode and bus-regulating mode. Average current mode control and linear compensators are designed accordingly for each operating mode. The stability of the designed system is analyzed at last. The operation and control design of the system are verified by simulation results.

Line Current Distortion Compensation for DCM/CRM Boost PFC Converters

This paper proposes a line current distortion compensation method, which is a fusion of the conventional variable on-time (VOT) control and the average current mode (ACM) control, for DCM/CRM boost PFC converter with zero current switching (ZCS)/zero voltage switching (ZVS)/valley switching (VS)/switching frequency limitation (SFL) functions. In this paper, the mathematical analyses of the line current distortion for the DCM/CRM boost PFC converter with ZCS/ZVS/VS/SFL functions are also derived to explain the causes of the line current distortion. In order to increase efficiency, the ZVS/VS/SFL functions are needed but the line current will be further distorted. To compensate the distorted line current, the ACM-based VOT (ABVOT) control for the DCM/CRM boost PFC converter is proposed. In addition, the constant-on-time-based noise-immunity S/H method is proposed to replace the multiplier, which is always needed for the conventional ACM-based control. The performance of the proposed ABVOT control with S/H method will be demonstrated by simulation and experiment results.

ZCS Bridgeless Boost PFC Rectifier Using Only Two Active Switches

Existing bridgeless boost (BLB) converter with soft switching utilize more than two active switches and extra resonant networks. In this paper, a new zero-current-switching BLB rectifier with high power factor (PF) using only two active switches is proposed. The proposed BLB converter is based on a totem-pole BLB (TPBLB) configuration, which allows the current to flow from high side to low side and vice versa during resonance. Hence, no auxiliary active switch is needed to provide soft switching for all semiconductor devices. The soft switching also reduces the body diode reverse recovery problem, hence allowing the TPBLB to operate in continuous conduction mode. Standard components are used to prove that the proposed converter is working with an acceptable performance compared with other BLB converters with soft switching. In order to achieve smooth input current waveform, high PF, and wide soft-switching operations, a pulsewidth modulation controller is proposed and developed, which combines a conventional PF correction average current mode controller with several logic gates and a phase detector. A detailed analysis of the converter operation and control is presented. Design considerations and parameter values calculations are given. An experimental prototype is developed and tested to verify the converter performance.

English

Dc power supplies are extensively used inside most of electrical and electronic appliances such as in computers, televisions, audio sets and others.And the electrical energy available in the utility grid is not suitable for direct use .So in particular, applications requiring DC source must involve an interface device between the AC power line and the load requiring the DC voltage. Conventional AC/DC conversion involves diode rectifiers with large capacitor to reduce DC voltage ripple. The filter capacitor reduces the ripple present in the output voltage but draws non sinusoidal line current which reduces the power factor. So power factor correction (PFC) techniques are gaining increasing attention. The most popular topology for active PFC is boost converter as it draws continuous input current. This input current can be manipulated by average current mode control technique. But there are ripple in the input current due to inductor of boost converter which can be minimized by using two phase interleaved boost converter. So here average current mode controlled interleaved boost converter in continuous conduction mode using PI controller, is represented which provides high power factor and low THD

Dual-Purpose Offline LED Driver for Illumination and Visible Light Communication

This paper presents a dual-purpose offline LED driver with illumination control and visible light communications (VLC). LEDs, due to their nonlinear I-V characteristics, are driven by constant current sources. The proposed dual-purpose offline LED driver realizes a constant current source by a buck converter without a capacitor using average current mode control. VLC is implemented through variable pulse position modulation scheme using a shunt switch in parallel to LED string. Conventional LED drivers are typically designed to perform illumination control with pulsewidth modulation (PWM) dimming at low frequencies (<; 20 kHz), which results in audible noise due to the mechanical vibrations of inductors and piezoelectric properties of ceramic capacitors. The proposed converter presents an illumination control with PWM dimming frequencies above the audible range. The detailed control and modeling of the proposed dual-purpose LED driver using high-frequency model of LED string is discussed. The effects of the phosphor on phosphor-based white LEDs for VLC are reported. The proposed driver is experimentally evaluated on 110/120 ac mains with 450-lm output. The linear characteristics of PWM dimming for data transfer of 2 Mb/s are demonstrated. Detailed simulation and experimental results to validate the operation of the proposed converter are presented.

Nonlinear Dynamics and Bifurcation Analysis of a Boost Converter for Battery Charging in Photovoltaic Applications

Photovoltaic (PV) systems with a battery back-up form an integral part of distributed generation systems and therefore have recently attracted a lot of interest. In this paper, we consider a system of charging a battery from a PV panel through a current mode controlled boost dc-dc converter. We analyze its complete nonlinear/nonsmooth dynamics, using a piecewise model of the converter and realistic nonlinear v–i characteristics of the PV panel. Through this study, it is revealed that system design without taking into account the nonsmooth dynamics of the converter combined with the nonlinear v–i characteristics of the PV panel can lead to unpredictable responses of the overall system with high current ripple and other undesirable phenomena. This analysis can lead to better designed converters that can operate under a wide variation of the solar irradiation and the battery's state of charge. We show that the v–i characteristics of the PV panel combined with the battery's output voltage variation can increase or decrease the converter's robustness, both under peak current mode control and average current mode control. We justify the observation in terms of the change in the discrete-time map caused by the nonlinear v–i characteristics of the PV panel. The theoretical results are validated experimentally.

An Fpga-based Single-phase Interleaved Boost-type Pfc Rectifier Employing Gan Hemt Devices

The recent development of higher blocking voltage gallium nitride (GaN) power FETs has the potential to enhance the power density of future power electronic converters. However, the new generation power semiconductors create new challenges to Power Electronics design that include: circuit layout to reduce parasitics, very high frequency digital control implementation, electromagnetic compatibility, passive components design, among others. In this work, GaN devices are used to assemble a 100 W single-phase two-channel interleaved boost-type power factor correction converter in order to evaluate some of the GaN devices challenges. The constructed hardware is able to operate with a switching frequency up to 1 MHz per channel, and hence a 2 MHz effective ripple frequency at the input and output terminals of the interleaved system. Furthermore, in order to cope with the high frequency requirements an average current mode control strategy is implemented in an FPGA device. Finally, experimental results verify the feasibility of the developed digital feedback control scheme and laboratory prototype.

English

A bridgeless PFC rectifier allows the current to flow through a minimum number of switching devices compared to the conventional PFC rectifier. Accordingly, the converter conduction losses can be significantly reduced and higher efficiency can be obtained, as well as cost savings. In bridgeless cuk converter, only two semiconductor devices are working during one switching cycle and hence the conduction losses are minimised. CUK PFC rectifier is designed to operate in Discontinous Conduction Mode (DCM) to achieve almost a unity power factor and low total harmonic distortion of the input current. The simulation of both the closed loop based on average current mode control and open loop bridgeless cuk converter is carried out using MATLAB simulink. The closed loop model of the bridgeless cuk converter gives a higher power factor of 0.99 and better voltage regulation.

Steady-State and Dynamic Input Current Low-Frequency Ripple Evaluation and Reduction in Two-Stage Single-Phase Inverters With Back Current Gain Model

Due to nonlinear time-varying characteristic of a single-phase dc/ac inverter, its front-end dc/dc converter tends to draw an alternate current ripple current at twice the output frequency, which may cause interaction issues, e.g., stability problem and input ripple current limit in distributed generation systems. A novel method is proposed to evaluate the behavior of low-frequency input current ripple. This approach is based on back current gain Ai (s) (input current to output current) model of the dc/dc converter. The theoretic model with different control schemes is verified in Saber environment. It is indicated and proved that the average current mode control strategy is more effective as compared with linear voltage mode control and open-loop control schemes. Design principles are presented based on Ai (s) as guidelines. Dynamic response with bandwidth limitation is also discussed and improved with proposed proportional-resonant (PR) filter placed based on Ai (s) model. Detail simulation and experiment results for different linear control and nonlinear control strategies, 50 and 400 Hz, buck-type stand-alone two-stage single-phase systems are provided to verify the proposed back current gain model and PR-filter solutions.

Dynamic modeling of a dual active bridge DC to DC converter with average current control and load‐current feed‐forward

SummaryBidirectional power flow is needed in many power conversion systems like energy storage systems, regeneration systems, power converters for improvement of the power quality and some DC‐DC applications where bidirectional high power conversion and galvanic isolation are required. The dual active bridge (DAB) is an isolated, high voltage ratio DC‐DC converter suitable for high power density and high power applications, being a key interface between renewable energy sources and energy storage devices. This paper is focused on the modeling and control design of a DC‐DC system with battery storage based on a DAB converter with average current mode control of the output current and output voltage control. The dynamic response of the output voltage to load steps is improved by means of an additional load‐current feed‐forward control loop. An analytical study of the load‐current feed‐forward is presented and validated by means of both simulations and experimental results. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Comparative Performance Analysis of High Density and Efficiency PFC Topologies

In this paper, the efficiency and power factor performance of improved power factor correction (PFC) topologies suitable for a high density and efficient design are compared. Several topologies, including a conventional average current mode control boost PFC, an interleaved boost PFC, a back-to-back bridgeless boost PFC, and a semi-bridgeless boost PFC, are assessed through loss analysis and simulation using whole height 1 U and 2 kW class prototypes. Based on this, an optimal topology is selected for which an additional comparative analysis involving input line measure improvement control is conducted. The results of these experiments can be adapted for use in the circuit selection of high-performance converters with power factor improvement circuits.