DC-DC Single Ended Primary Inductance Converter Research Articles

Investigation of a power factor correction converter utilizing SEPIC topology with input current switching

The single-ended primary-inductor converter (SEPIC) is a popular converter topology that can be employed in diverse application fields where the needed output voltage is greater or lesser than the input voltage. The non-inverted output voltage of a SEPIC converter provides additional advantages when compared to a buck-boost or Ćuk converter. Furthermore, the position of the capacitor in the SEPIC converter provides inherent isolation and circuit safety. One drawback in the conventional bridge-diode SEPIC AC-DC converter is the lack of controllability which can be overcome by adding extra active switch(es) or by replacing the passive diode(s) with active switch(es). However, introducing more active switches increases the control complexity and may increase the requirement for additional driver circuits. To address this trade-off, this article proposes a single-phase AC to DC modified SEPIC converter with input current-switching capability without adding any extra active switch(es). The existing active switch of the DC-DC SEPIC converter was shifted towards the input side and thus no additional switch has been introduced. This allows the option of input-current switching without any additional complexity in the control or driver circuit. The circuit topology, principles of operation, and ideal voltage gain equations for the suggested circuit have been derived and included in this research work. The proposed circuit has been simulated in both open-loop conditions and closed-loop control with varying duty cycles and output load. Results from the simulation show that the proposed converter provides better efficiency (∼90 %) and lower total harmonic distortion (THD) (10 %) for varying duty cycles when compared to a conventional converter. The converter also shows good dynamic response. A low-power 15V hardware prototype has been built to experimentally validate the performance of the proposed converter. Experimental results illustrate that the suggested converter can improve the power factor by up to 0.968 while operating at an efficiency above 75 %. This converter topology can be suitable for applications where high output voltage gain, high power factor, and lower THD are needed without isolation requirements.

Comprehensive Analysis of Voltage Step-Up Techniques for Isolated SEPIC

High step-up converters are often used in photovoltaic applications due to low voltage of photovoltaic modules. In this paper, a study of several voltage step-up cells added on primary and secondary sides of an isolated dc-dc SEPIC (single ended primary inductor converter) is made, in order to increase its static gain and synthesize a family of converters. To perform this study and select the most appropriate resulting converter, theoretical and comparative analyzes are accomplished. They include a brief description of each converter, tables and curves with relevant information, such as voltage gain, voltage stresses and component count, and the identification of the use of coupled inductor or transformer based on the analysis of dc magnetizing current. Moreover, theoretical analysis and experimental results on a 50 kHz and 200 W prototype of selected isolated SEPIC with voltage doubler cell are presented to validate the proposed topology and concept.

A Moth-Flame Optimized Robust PID controller for a SEPIC in Photovoltaic Applications

The paper presents a robust proportional integral derivative (PID) controller improved by the metaheuristic moth-flame optimization (MFO) technique for a DC-DC single-ended primary inductor converter (SEPIC) to achieve aimed user output performance in photovoltaic systems. Having non-linear dynamics, SEPIC with the conventional linear PID controllers possessing constant tuning gains cannot exhibit robust performance under the input and load variations. To confront the problem, a process-adaptive PID controller, whose tuning gains are adjusted by the MFO algorithm to ensure the continuity and stability of output voltage and the power, is designed and simulated. Comparative performance analysis of MFO tuned PID controller compared with the classic PID controller is conducted. The simulation results reveal a substantial performance improvement of the MFO-PID controller over the traditional PID controller in terms of maintaining constant regulated output voltage and having excellent setpoint tracking capability with minimal settling times and overshoot under considerable input and load disturbances.

Maximum power point tracking technique based on sweeping the characteristic curve of the photovoltaic module

Maximum power point tracking (MPPT) techniques play a very important role in photovoltaic (PV) systems considering that it is necessary to ensure the operation at the maximum power point (MPP) under random irradiance and/or temperature conditions. In this context, this work presents an MPPT technique based on sweeping the current versus voltage (I-V) characteristic of the PV device. A dc-dc single-ended primary inductance converter (SEPIC) topology connected to a fixed resistive load is responsible for obtaining the points that compose the aforementioned curve. Thus, it is possible to impose a proper duty ratio to the active switch and achieve the operation at the MPP. Prominent advantages of the algorithm include low implementation complexity and high efficiency, as well as the fact that it is not susceptible to fast changes in the atmospheric and partial shading conditions. An in-depth discussion of the concepts involving the proposed solution is presented. A thorough comparison with the well-known perturb and observe (P&O) and incremental conductance (INC) techniques is also performed.

Steady State Behavior of a Single-Switch Non-isolated DC-DC SEPIC Converter Topology with Improved Static Voltage Gain

This paper presents the analysis of steady state behavior of a single switch non-isolated Single Ended Primary Inductance Converter (SEPIC) topology for achieving high DC voltage gain using diode-capacitor voltage multiplier. A voltage boosting module consisting of inductor and capacitor in addition with two diodes is introduced in the conventional SEPIC configuration in order to derive the DC-DC conversion technology proposed in this work. The voltage gain of the converter is extended using a diode-capacitor voltage multiplier cell. The converter suggested in this work has a single controlled switch. Hence, the conduction losses and the control complexity of the switch are very much reduced. The open loop configuration of the proposed non-isolated converter is described under continuous inductor current mode. The voltage boosting capability of the presented converter is compared with that of the existing modified SEPIC structure. The presented positive output converter topology has low switch voltage-current stress compared to the existing modified SEPIC topology given in the literature. The inductor and capacitor components of the suggested converter are so chosen that the DC output voltage and current waveforms show very low percentage of ripples. A DC voltage level of 24 V is given as input to the proposed converter. The DC voltage obtained across the load terminals is around 370 V which is achievable with low duty ratio (= 0.7) of the active switch. The voltage conversion ratio is very much influenced by the variation of the duty cycle of the power switch. In this work, the converter topology is presented and its various modes of operation are explained with equivalent circuits. The PSIM software platform is effectively and efficiently utilized to validate the performance of the converter. The obtained results convey that the proposed DC-DC conversion technology with extended voltage gain has the capability to maintain the steady-state output voltage and current profiles with almost negligible amount of ripples owing to the use of suitably designed non-dissipative elements in LC filter.

Plotting Characteristic Curves of Photovoltaic Modules: A Simple and Portable Approach

This work presents a simple and low-cost curve tracer for the analysis of photovoltaic (PV) modules. The proposed system allows the plotting of current versus voltage (I-V) and power versus voltage (P-V) characteristics in a fast and straightforward approach employing a dc-dc single-ended primary inductance converter (SEPIC) topology. Thus, it is possible to obtain variable impedance seen from the PV source by properly adjusting the duty cycle imposed to the active switch and consequently, by plotting several points that accurately define the aforementioned curves. The curve tracer is analyzed through simulation and experimental tests while its performance is evaluated considering uncontrolled environmental conditions and also the eventual occurrence of partial shading.

Experimental evaluation of global maximum power point techniques under partial shading conditions

Shading plays an important role in the operation of photovoltaic (PV) systems, especially when one of the cells or modules in the string is submitted to lower irradiance levels due to partial shading (PS). As a result of this condition, the cells or modules absorb the power generated by the unshaded parts, thus causing hot spots that can irreversibly damage the device. In order to mitigate this problem, bypass diodes (BDs) are often connected in parallel with the cells or modules to limit the reverse voltage and the power loss as a consequence. However, the occurrence of multiple peaks in the power versus voltage (P-V) curve is observed. Although conventional maximum power point tracking (MPPT) algorithms are successfully used when PV arrays operate under uniform irradiance conditions, they may fail to determine the global maximum power point (GMPP) if PS comes to occur. Considering that several MPPT algorithms for the operation under PS have been proposed during the last few years, this work presents a detailed analysis of some techniques dedicated to global maximum power tracking (GMPPT), aiming at defining which one presents the best performance. A dc-dc single-ended primary inductance converter (SEPIC) associated with microprocessor ATmega328P is employed to track the GMPP and assess the operation of each technique experimentally. The performance of the well-known perturb and observe (P&O) algorithm is also evaluated under PS condition for comparison purposes.

Analysis and design of IMC-PI Controller with faster set point tracking and disturbance rejection for Interleaved DC-DC SEPIC converter based Power Factor Correction

This paper deals with the internal model controller (IMC) - proportional integral (PI) controller for interleaved DC-DC single ended primary inductance converter (SEPIC)-based power factor correction (PFC). The transfer function of the proposed converter exhibits seventh order dynamics with complex right hand plane (RHP) poles and zeros. IMC-based PI controller is used to achieve perfect control since it contains the internal model of the process implicitly or explicitly. The cascade control strategy is implemented for the proposed converter with IMC-based PI controller as inner current and outer voltage controller. The dynamic and steady state performance parameters of the proposed scheme are evaluated using MATLAB/Simulink software. The simulation results reveal that the proposed scheme offers excellent stability characteristics, robustness, faster set point tracking and disturbance rejection for various uncertainties in the process as compared to conventional PI controller.

A Hankel matrix reduced order SEPIC model for simplified voltage control optimization and MPPT

This study focuses on the realization of efficient solar power fed DC-DC Single Ended Primary Inductor Converter (SEPIC) using second order ACO (Ant Colony Optimisation) tuned PI (Proportional Integral) controller. Second order model of the DC-DC SEPIC converter is derived using Hankel Matrix method from the original fourth model to reduce the number of sensors used and to ease the controller design. PI controller parameters are derived from the second order model by using GA (Genetic Algorithm) based optimisation and ACO techniques. Statistical analysis shows that ACO yields better results when compared to GA. To harvest the maximum power from the Photo Voltaic (PV) panel, Incremental Conductance (IC) based Maximum Power Point Tracking (MPPT) method is chosen due to its high tracking accuracy. Extensive simulation studies have been carried out by using MATLAB/SIMULINK software tool. Simulation results for varying irradiation, temperature and load conditions have been presented in this paper. To substantiate the simulation results, an experimental prototype model of 120 Watts controlled by C2000 Piccolo TMS320F28035MCU digital controller is set up. Results reveal that the proposed cascade control technique can provide regulated output voltage and 80–99% of MPPT simultaneously using a single stage non-isolated DC-DC SEPIC Converter.

Analysis and Design of Single Phase Power Factor Correction using DC-DC SEPIC Converter with Bang-Bang and PSO based Fixed PWM Techniques

This paper presents the design and analysis of single phase Power factor correction (PFC) using DC-DC Single Ended Primary Inductance converter (SEPIC).The proposed system applies cascade approach where outer loop is implemented with Particle Swarm Optimization (PSO) tuned PI controller to synchronize the output voltage with reference voltage and inner current loop is controlled by Bang-Bang/PSO based Fixed PWM control techniques. The performance characteristics of these two approaches are analyzed by simulation results. The PSO based Control strategy yields an advantages of unity power factor (UPF), low percent THD(%THD), well synchronized output voltage for the variations in the line and load. It also provides efficient tracking of reference voltage compared to Bang-Bang control.

Performance of solar photovoltaic array fed water pumping system utilizing switched reluctance motor

This paper discusses the design and performance analysis of a solar photovoltaic (SPV) array fed water pumping system utilizing a special class of highly rugged machine with simple drive system called switched reluctance motor (SRM) drive. The proposed method of water pumping system also provides the cost effective and highly reliable solution for solar water pumping system. A unique approach of variable DC link voltage operation of SRM drive with electronic commutation for switches of mid-point converter is used with the elimination of voltage and current sensor in the motor side results in reduction in cost and losses of the system. A DC-DC single-ended primary-inductor converter (SEPIC) is used to achieve maximum power from SPV array. The characteristic of providing output voltage with no polarity reversal and having features like minimal active components and low noise operation makes SEPIC suitable for solar water pumping. The water pump with a SRM motor is used in the proposed system because of its similar operational characteristics compared to SPV generator.Keywords: SPV Array, MPPT, SEPIC converter, Soft starting, SRM, Centrifugal water pump

Isolated Three-Phase High Power Factor Rectifier Based on the SEPIC Converter Operating in Discontinuous Conduction Mode

This paper presents the analysis and design of a three-phase high power factor rectifier, based on the dc-dc single-ended primary-inductance converter (SEPIC) operating in discontinuous conduction mode, with output voltage regulation and high frequency isolation. The input high power factor is naturally attained through the operational mode without the use of current sensors and a current control loop. To validate the theoretical analysis, a design example and experimental results for a 4-kW, 380-V line-to-line input voltage, 400-V output voltage, 0.998 power factor, 40-kHz switching frequency, and 4% input current total harmonic distortion laboratory prototype are presented, considering two distinct modulators. In addition, experimental results for the output voltage closed-loop control are presented.

Parasitic Effects on the Performance of DC-DC SEPIC in Photovoltaic Maximum Power Point Tracking Applications

This paper presents an analysis of the effect of parasitic resistances on the performance of DC-DC Single Ended Pri- mary Inductor Converter (SEPIC) in photovoltaic maximum power point tracking (MPPT) applications. The energy storage elements incorporated in the SEPIC converter possess parasitic resistances. Although ideal components significantly simplifies model development, but neglecting the parasitic effects in models may sometimes lead to failure in predicting first scale stability and actual performance. Therefore, the effects of parasitics have been taken into consideration for improving the model accuracy, stability, robustness and dynamic performance analysis of the converter. Detail mathematical model of SEPIC converter including inductive parasitic has been developed. The performance of the converter in tracking MPP at different irradiance levels has been analyzed for variation in parasitic resistance. The converter efficiency has been found above 83% for insolation level of 600 W/m2 when the parasitic resistance in the energy storage element has been ignored. However, as the parasitic resistance of both of the inductor has increased to 1 ohm, a fraction of the power managed by the converter has dissipated; as a result the efficiency of the converter has reduced to 78% for the same insolation profile. Although the increasing value of the parasitic has assisted the converter to converge quickly to reach the maximum power point. Furthermore it has also been observed that the peak to peak load current ripple is reduced. The obtained simulation results have validated the competent of the MPPT converter model.

A New Approach of Minimizing Commutation Torque Ripple for Brushless DC Motor Based on DC–DC Converter

Brushless dc motor still suffers from commutation torque ripple, which mainly depends on speed and transient line current in the commutation interval. This paper presents a novel circuit topology and a dc link voltage control strategy to keep incoming and outgoing phase currents changing at the same rate during commutation. A dc-dc single-ended primary inductor converter (SEPIC) and a switch selection circuit are employed in front of the inverter. The desired commutation voltage is accomplished by the SEPIC converter. The dc link voltage control strategy is carried out by the switch selection circuit to separate two procedures, adjusting the SEPIC converter and regulating speed. The cause of commutation ripple is analyzed, and the way to obtain the desired dc link voltage is introduced in detail. Finally, simulation and experimental results show that, compared with the dc-dc converter, the proposed method can obtain the desired voltage much faster and minimize commutation torque ripple more efficiently at both high and low speeds.