Current Mode Control Technique Research Articles

Linear–Assisted DC/DC Converters with Modified Current-Mode Control Applied to Photovoltaic Solar Systems

This article shows the proposal of a current-mode one-cycle control for linear-assisted DC/DC converters. Linear assisted DC/DC converters are structures that allow to take advantages of the two classic alternatives in the design of power supply systems: voltage linear regulators (classic NPN topology or LDO –low dropout–) and switching DC/DC converters. The current-mode one-cycle control technique is proposed in order to obtain the duty cycle of the linear-assisted converter switch. The proposed structure can provide an output with suitable load and line regulations. Thus, the paper shows the design and simulation results of the proposed current-mode one-cycle linear-assisted converter.

A New Double-Switch SEPIC-Buck Topology for Renewable Energy Applications

In addition to their conventional use in electric motor drives, DC-DC converters have a variety of other uses, such as energy storage, energy conversion, cyber security systems, uninterruptible power supplies, and renewable energy systems. An innovative DC-DC converter is suggested in this article. Designing a new, high-gain DC-DC converter scheme known as a double-switch SEPIC-buck converter (DSSB) is possible after making some adjustments to the SEPIC converter that is currently known in accordance with accepted techniques. The output voltage magnitude of the proposed converter is either larger than or less than the input voltage magnitude and is the same sign as the input voltage. According to the theoretical and analytical study that has been supported by the real-world application, high voltage gain, low switching stress, and low inductor current ripple are the main characteristics of the proposed DSSB converter. The related small-signal model was also used to build the closed-loop system. The frequency response and output voltage behavior were investigated when the input source voltage abruptly changed as a step function. Based on the comparison study with other DC-DC converters, the DSSB converter outperforms currently known DC-DC converters such as Buck, SEPIC, Boost, Buck-Boost, and other SEPIC converter topologies in terms of voltage gain, harmonic content, normalized current ripple, dynamic performance, and efficiency. Additionally, the frequency response and control of the proposed converter using an alternate current (AC), small-signal, analysis-based, current-mode control technique are both provided. Thus, the DSSB is regarded as safe in overcurrent situations because of the small-signal analysis with the current control strategy. As a result of the verification of the proposed control technique, the resistance to changes in the DSSB parameters, improved dynamic performance, and higher control accuracy are further advantages of current-mode control based on small-signal analysis over other control approaches (PI controllers). Finally, the experimental and simulation results from Simplorer 7 and MATLAB/Simulink are used to validate the findings of the analytical and comparative investigation.

Microcontroller-Based Trapezoidal Slope Compensation Technique for Peak Current Mode Control at MHz Frequencies

Slope compensation is necessary for the peak cur-rent mode control technique to ensure the stability of the power converter. Micro-controllers (μCs) existing in the market implement the slope compensation using built-in digital to analog converters (DACs). DACs exhibit finite transient times, which can be negligible when the μCs are used to control the power converters at switching frequencies in the order of a few hundreds of kHz. However, for high device switching frequency (HDSF) operation ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\geq 1\, \rm{MHz}$</tex-math></inline-formula> ), the DAC transient time becomes significant and can make it difficult, if not impossible, to achieve the conventional ramp slope compensation. Hence, in this paper, a novel concept of ‘trapezoidal’ slope compensation is proposed by considering the transient time of the μC. A detailed analysis is performed to understand the effect of the transient period on the converter stability. The proposed technique is validated with an experimental prototype of 400 W at 1 MHz switching frequency and it is shown to ensure stability of the converter at all operating points within the specification.

Current mode control of single phase grid tie inverter with anti-islanding

The aim of this paper is to explore the use of various current mode control (CMC) techniques to design a single phase grid tie inverter integrated with anti-islanding protection. Three types of CMC techniques have been discussed, namely current hysteresis control (CHC), constant frequency control (CFC) and average current mode control (ACMC). The performance of the grid tie inverter in the event of grid voltage failure is also studied to help install an anti-islanding mechanism. The proposed control techniques shall eliminate the use of Phase locked loop (PLL) control as the current reference is generated from the grid voltage itself. All three current mode control techniques of an inverter have been simulated in MATLAB/Simulink to evaluate the performance of the designed inverter. The simulated results show a current THD of less than 5% in all three methods and a good anti-islanding response.

Study of Power Quality Phenomenon Based on Design and Simulation of Boost Type PFC Converters

This paper present design and simulation of boost type Power Factor Correction (PFC) converter which improved the power quality. With the enormous development in the usage of power converters circuits like rectifiers which is non linear loads, the current drawn by these non- linear loads will not follow the supply voltage (i.e. non simulation). This results in high Total Harmonic Distortion (THD) and poor Power Factor (PF). Hence there is a need of converter topology to improve the PF and reduce line current harmonic. Boost type PFC converters is most popular topology for improving the PF in supply AC side. Average Current Mode (ACM) control technique is employed to control the boost converter in Continuous Conduction Mode (CCM). Simulation of proposed system is carried out using MATLAB/ Simulink platform.

Asymmetric slope compensation for digital hybrid current mode control of a three-level flying capacitor buck converter

The three-level flying capacitor (3LFC) buck converter has the potential to provide better efficiency and higher power density as compared to the traditional buck converter. However, due to the flying capacitor?s instability issues, control is challenging. In this paper, the digital hybrid current mode (DHCM) control method, which combines the average and peak current mode control techniques, is modified and implemented to a 3LFC buck converter. For flying capacitor (FC) voltage balancing, a novel asymmetric slope compensation (ASC) technique is presented. The proposed ASC technique achieves FC voltage balancing by adjusting the slope compensation of the two switching pairs asymmetrically, and therefore is applicable to any type of digital peak current mode control (PCM) method. The ASC technique for DHCM control of the 3LFC buck converter is verified in simulations and experimentally with an ARMbased mixed-signal microcontroller on a 250-kHz, 24-V input, and 35-W/4-A output prototype. The overall control method enables the implementation of the 3LFC buck converter for accurate and fast current regulation, and therefore is especially advantageous for LED and laser diode driver applications.

Modified LQR Technique for Fuel-Cell-Integrated Boost Converter

Fuel cells (FCs) are an alternative source of energy whose by-products are heat, vapor, and water. For medium-power and standalone operation, an FC is integrated with a boost converter, as the required voltage level is higher than the supply. Control of such a converter with a slow dynamic source requires a fast-acting controller, since the demand executed by the controller affects the action taken by the hydrogen valve in FCs. In this article, a linear-quadratic regulator (LQR) is developed to control the power converter. In practical applications, the conventional LQR produces offset in output voltage due to effective series resistance (ESR) of the output capacitor. To make the LQR dynamic with load perturbation, information of inductor reference current is required, which changes with variation in load current. To solve these two problems, two modifications in the classical LQR have been proposed to minimize the impact of ESR (m-LQR) and incorporate control action based on the reference inductor current (M-LQR). The proposed methods are compared with the conventional average current-mode control technique. The M-LQR-based scheme is found to outperform the classical m-LQR technique in terms of improved transient dynamics and reduced offset at the steady state. In addition to numerical simulations, the proposed control techniques have been validated experimentally.

Constant off-Time Digital Current-Mode Controlled Boost Converters With Enhanced Stability Boundary

The right-half-plane (RHP) zero in a continuous conduction mode boost converter results in a significantly restricted closed-loop bandwidth (BW) for higher voltage gain and/or load current conditions. A compensating ramp is used for current-mode control (CMC), and a higher ramp slope degrades the BW. Variable-frequency digital CMC offers inherent current-loop stability and real-time tuning scope for higher closed-loop BW. However, the challenges are to select the sampling frequency and sampling instant of the output voltage with discontinuous ripple due to the effective series resistance of the output capacitor, and its impact on stability. This paper shows that an event-based current-mode constant off -time digital modulator achieves superior stability and performance in a boost converter along with the reduced RHP zero effect over other digital CMC techniques. Using a discrete-time framework, the fast-scale stability conditions and small-signal models are analytically derived for various digital CMC techniques, which are validated using SIMPLIS simulation. A boost converter prototype is tested, and the analytical predictions are verified experimentally. Further, the analysis is extended to a non-inverting buck–boost converter.

Improved design of a DC-DC converter in residential solar photovoltaic system

&lt;span&gt;With growing demand in renewable energy, solar photovoltaic (PV) technology is becoming more popular. A number of research has been carried out to increase the efficiency of the PV system. One of them is improving the Switch Mode Power Supplies (SMPS) performance to ensure maximum solar energy extraction. This paper looks at buck type SMPS suitability for use in solar PV installed in residential houses. The main issues that affect the response from the output are identified. The work will utilise the LT SPICE software to carry out the simulation. The primary objective of the study is to design an improved converter controller which is more robust and is able to maintain constant output. The emphasis is on good efficiency, stability and low output voltage ripple. This could be achieved by using the current mode control (CMC) techniques – an alternative design to the voltage mode control technique (VMC). Results obtained via simulations reveal strong evidence of CMC superiority over the VMC.&lt;/span&gt;

Digital hybrid current mode control for DC–DC converters

A digital hybrid current mode (HCM) control technique which combines peak current and average current mode (ACM) control methods is studied. The proposed controller consists of three control loops, an analogue fast current loop, a digital slow current loop and an outer voltage loop. For the control method, both continuous and discrete-time models are built. Similarly, a continuous-time model for ACM control is provided for comparison. For both control techniques, a compensator design method is proposed. The control methods are implemented on a 6 W synchronous buck converter with a mixed-signal ARM-based microcontroller. Controller models are verified with the frequency response measurements of the inner and outer loops. In digital HCM control, higher DC gain and phase margin is achieved with the same gain margin compared to digital ACM control. Furthermore, the transient responses of the systems are analysed. When the outer voltage loop is open, 30% faster dynamic response is measured by the digital HCM method. With voltage compensation, comparable dynamic response on the output voltage is achieved without inductor current overshooting by the digital HCM control.

Linear Peak Current Mode Control of Semi Bridgeless AC-DC Converter

Objectives: The main objective of this work is to obtain input power factor closer to unity and regulation of output voltage of semi bridgeless AC-DC converter using linear peak current mode control. Methods/Statistical Analysis: Linear Peak Current Mode control technique is applied to Semi-Bridgeless AC-DC Converter in this paper. This technique helps in achieving power factor closer to unity. The output voltage of the converter is regulated at 200V. The prototype is designed for 200W. Simulation results are obtained for 200W using PSIM software(Simulation Software Package) the converter is analyzed under variable load and supply conditions. Findings: At variable load conditions, power factor is maintained closer to unity and output voltage is regulated to 200V. The efficiency for the converter is found to 96% at full load conditions. Application: Battery charging applications.

Decoupled control strategy for the operation of capacitor‐excited induction generator for DC power applications

In this study, voltage oriented decoupled current mode control technique has been proposed for the operation of the capacitor-excited induction generator with pulse-width modulation (PWM) rectifier systems for supplying isolated DC loads. The proposed controller maintains constant voltage at the DC load terminals and also maintains unity power factor with very less harmonics at the PWM rectifier input terminals. The configuration and implementation of the control scheme employing dSPACE 1103 real-time controller have been fully described. A method for predetermining the steady-state performance of the proposed system has been developed and described with relevant analytical expressions. The effective load at the generator terminals becomes only resistance, since unity power factor is maintained at the PWM rectifier input terminals by the closed-loop controller. To verify the successful working of the proposed control strategy during transient conditions, the proposed system has been modelled in the MATLAB/Simulink toolbox and results are presented. A prototype system consisting of CEIG, PWM rectifier and the associated control circuits has been built in the laboratory for experimental verification. A close agreement between the experimental results and predicted values confirms the validity of the analysis and successful working of the proposed control strategy.

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.

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

Smart DC Grid for Autonomous Zero Net Electric Energy of Cluster of Buildings

—- The main objective of this paper is to create a smart dc micro-grid capable of 100% autonomous zero net electric energy in the cluster of buildings to facilitate a low-carbon sustainable electricity supply system under considerations of urban and rural scenarios. The propose model comprises of house clusters with an autonomous communication developed for the residential area, taking the consideration of stochastic behavior of wind and solar irradiation. Voltage droop and Slope compensation peak current mode control technique for the synchronous bidirectional boost converters is employed for the energy storage systems (ESSs). The bidirectional converter stage for house clusters plays a pivotal role in standalone operation. In case a battery pack is laid off from any house cluster, the dc bus voltage still be stabilized due to the proximity bidirectional converter stages of other house clusters or community bank. The houses in the cluster comprise of permanent magnet synchronous generator (PMSG), solar photo voltaic (PV), battery bank and variable load. The proposed model is simulated on MATLAB/Simulink environment and suffices the real time environment.

Current-Mode Synthetic Control Technique for High-Efficiency DC–DC Boost Converters Over a Wide Load Range

This paper proposes a current-mode synthetic control (CSC) technique for the design of boost converters to overcome the difficulty in designing a current-ripple hysteresis boost converter and to maintain high conversion efficiency over a wide load range. The CSC technique has a high accuracy because of the additional voltage path through the error amplifier. A smooth load transient response is maintained when the operation transits from continuous conduction mode with a nearly constant switching frequency to discontinuous conduction mode with a load-dependent switching frequency. Generally, ripple performance, light-load efficiency, and switching frequency are traded off in the design of hysteresis control regulator. In this paper, a balance among the load-dependent switching frequencies at light loads results in high power conversion efficiency compared with conventional pulsewidth modulation converter and attains compact ripple performance. The experimental results show that the output voltage ripple can be kept ${<;}{\rm 50}~{\rm mV}$ over a wide load current range from 10 to 400 mA, where as power conversion efficiency is maintained at 78% at a load current of 10 mA when the switching frequency is decreased from 5 to 2 MHz.

A Novel UVLO Circuit with Current-Mode Control Technique for DC-DC Converters

A novel Under Voltage Lockout (UVLO) circuit featuring with fast response speed and low temperature coefficient threshold voltages is proposed in this paper. Compared with the conventional structure, the proposed circuit achieves the fast response ability thanks to the current-mode control technique is utilized. Meanwhile, this UVLO realizes hysteretic threshold by a feedback control path to improve the interference rejection capability. In addition, the threshold voltage varies slightly with the variation of the supply voltage and temperature by using a bandgap core. The proposed circuit implemented with 0.5μm BCD technology has an input high threshold voltage of 8.5V and a hysteresis of 1.5V, and start or shut off the power quickly. Test results verified that the proposed UVLO has the qualification to be applied to DC-DC converters.

Modeling and Analysis of Projected Cross Point Control—A New Current-Mode-Control Approach

This paper features the projected cross point control (PCPC) approach which is a recent current-mode control (CMC) technique. PCPC benefits from several advantages including fixed switching frequency, wide stability range, high current loop gain, improved audio susceptibility, and simpler design procedure. An introduction of its principles of operation is followed by detailed discussions about its stability and dynamic response. This paper then describes the development of the small-signal model of PCPC and derives transfer functions, such as current loop gain, audio susceptibility, and output impedance. Finally, simulations and experimental results are presented. Peak, average, and hysteresis CMC schemes are used for comparison.

Predictive Digital Current Control of Single-Inductor Multiple-Output Converters in CCM With Low Cross Regulation

This paper presents a new digital current-mode control technique for single-inductor multiple-output converters in continuous-conduction mode. This predictive control method can calculate all the required duty cycles corresponding to the outputs for the next switching cycle. Since the calculation is based on every current reference representing the load current, all current control loops corresponding to different outputs are theoretically independent, which can greatly reduce the cross regulation. To avoid subharmonic oscillation, proper predictive digital current control is adopted. Inductor current estimation is used to remove the current sensing circuit, and corresponding calibration techniques are presented. Simulation and experimental results are given to verify the effectiveness of this control technique.

Nonlinear control of fuel cell hybrid power sources: Part II – Current control

In this paper is proposed a nonlinear current-mode control for the fuel cell/battery/ultracapacitor hybrid power sources (HPS) that improves the ripple factor of the fuel cell current. The nonlinear current control is analyzed and designed using a systematic approach. The design goal is to generate an anti-ripple via buck current controlled source in order to mitigate the inverter current ripple. All the results have been validated in several simulations. The simulation results successfully show that nonlinear current-mode control determines in the low frequency-domain better performances than other current-mode control techniques, such as the hysteretic current-mode controller or the peak current-mode controller. The current ripple factor is one of the used performance indicators.