Showing papers on "Boost converter published in 2019"

A Novel Composite Nonlinear Controller for Stabilization of Constant Power Load in DC Microgrid

Abstract: Transportation electrification involves the wide utilization of power electronics based dc distribution networks and the integration of a large amount of power electronic loads. These power electronic loads, when tightly controlled, behave as constant power loads (CPLs) and may cause system instability when interacting with their source converters. In this paper, a composite nonlinear controller is proposed for stabilizing dc/dc boost converter feeding CPLs by integrating a nonlinear disturbance observer (NDO)-based feedforward compensation with backstepping design algorithm. First, the model is transformed into the Brunovsky’s canonical form using the exact feedback linearization technique, to handle the nonlinearity introduced by the CPL. Second, the NDO technique is adopted to estimate the load power variation within a fast dynamic response, serving as a feedforward compensation to increase the accuracy of output voltage regulation. Then a nonlinear controller is developed by following the step-by-step backstepping algorithm with strictly guaranteed large signal stability. The proposed controller not only ensures global stability under large variation of the CPL but also features fast dynamic response with accurate tracking over wide operating range. Both simulations and experiments are conducted to verify the proposed strategy.

DC–DC Boost Converter With a Wide Input Range and High Voltage Gain for Fuel Cell Vehicles

Abstract: In fuel cell vehicles, the output voltage of the fuel cell source is typically much lower than the voltage required by the dc bus, and also this output voltage drops significantly as the output current increases. In order to match the output voltage of the fuel cell source to the dc bus voltage, a new dc–dc boost converter with a wide input range and high voltage gain is proposed to act as the required power interface, which reduces voltage stress across the power devices and operates with an acceptable conversion efficiency. A prototype rated at 300 W/400 V has been developed and the maximum efficiency of the proposed converter was measured as 95.01% at 300 W. Experimental results are presented to validate the effectiveness of the proposed converter.

Analysis and Design of High-Efficiency Hybrid High Step-Up DC–DC Converter for Distributed PV Generation Systems

Abstract: High step-up converters are required for distributed photovoltaic generation systems, due to the low voltage of the photovoltaic source. In this paper, a new hybrid high voltage gain dc–dc converter is created by merging the standard boost converter with a coupled inductor and different switched-capacitor techniques. With a single switch and no requirement of higher duty cycle values, the proposed converter achieves a high voltage gain and high efficiency, in addition to lowered voltage and current stresses of the components. A 200-W prototype was implemented experimentally to evaluate the converter, which reached a maximum efficiency of 97.6%.

An Integrated Step-Up Inverter Without Transformer and Leakage Current for Grid-Connected Photovoltaic System

Abstract: In this paper, an integrated step-up inverter without transformer is investigated for photovoltaic (PV) power generation. The proposed topology can be derived by combining a traditional boost converter with a single-phase full bridge dc–ac converter. The main features of the integrated inverter are: First, the leakage current caused by the solar cell array-to-ground parasitic capacitance can be theoretically reduced to zero due to the characteristics of the converter configuration, which can improve the efficiency and the reliability of the PV generation system; second, the output ac voltage of the proposed inverter can be higher than the input dc voltage, which is capable of connecting low voltage PV panels to the grid; third, only five active switches are used in the presented inverter, and those switching devices can be synchronously driven by various sinusoidal pulsewidth modulation methods based on the carrier; therefore, the proposed inverter is compact and with curtailed cost. The working principle and analysis of the proposed integrated inverter are elaborated. Finally, simulation and experimental results are obtained in a lab prototype, which agree well with the theoretical analysis.

Adaptive Backstepping Sliding Mode Control for Boost Converter With Constant Power Load

Abstract: The negative impedance characteristics of a constant power load (CPL) can easily lead to the instability of the DC bus voltage. To improve the stability of the DC bus voltage, an adaptive backstepping sliding mode control strategy for a boost converter with the CPL in DC microgrid is proposed. First, to carry out the backstepping control, the zero dynamic stability of the system under different output functions is studied by using input-output exact feedback linearization theory. The model is transformed into a linear system in Brunovsky canonical form, which solves the nonlinear problem caused by the CPL and the non-minimum phase problem of the boost converter. Then, under the premise of ensuring large signal stability, an adaptive mechanism is introduced into the design of the backstepping sliding mode control. The adaptive backstepping sliding mode controller is designed by adaptively updating the switching gain in real time. Furthermore, the Lyapunov theory is used to prove the global asymptotic stability of the overall closed-loop system. Finally, the numerical simulation and experimental results show that the proposed control strategy has better dynamic regulation performance and stronger robustness compared with the conventional double closed-loop PI control method.

Input–Output Linearization of a Boost Converter With Mixed Load (Constant Voltage Load and Constant Power Load)

Abstract: Power converters and electric motor drives when tightly regulated behave as constant power loads. These loads are different from resistive loads and have destabilizing negative impedance characteristics, which impact a system's stability. A boost converter is intrinsically nonlinear and is a nonminimum phase system at the output voltage with respect to the control input. The linear approximation of this boost converter loaded with a constant power load has a zero and poles in the right half of the $s$ -plane, making the system unstable and very difficult to control. Control techniques that employ some form of system inversion cannot be implemented for a nonminimum phase system. This paper describes a technique to modify the nonminimum phase boost converter to a minimum phase for a constant power load, further implementing the input–output linearization technique to stabilize the system. This paper also provides a methodological analysis of the problem followed by the proposed solution. Furthermore, it verifies the analysis of the proposed solution through simulation and experimental results.

High-Speed Maximum Power Point Tracking Module for PV Systems

Abstract: Maximum power point tracking (MPPT) is a basic and indispensable requirement for photovoltaic (PV) systems under normal irradiance and under partial shading conditions (PSCs). Although the simple perturb and observe algorithm is quite effective under normal conditions, it fails to recognize the global maximum operating point (GMOP) under the PSC. This paper explores the fast determination of GMOP under PSCs using a proposed high-speed MPPT module, which operates in conjunction with a boost converter. With this high-speed MPPT module, the tracking time of the MPPT controller is considerably reduced. The tracking accuracy and efficiency are significantly better than other techniques in the literature. The concept is first implemented on a PV system simulation model and the results are further validated with a prototype implementation of a 300 W PV-fed boost converter operated under various PSCs. The enthusiastic results were finally verified in an installation of a 2.5 kW PV system. The results demonstrate that the proposed high-speed MPPT controller outperforms both duty sweep and particle swarm optimization based MPPTs.

High-Voltage-Gain DC–DC Step-Up Converter With Bifold Dickson Voltage Multiplier Cells

Abstract: This paper presents an interleaved boost converter with a bifold Dickson voltage multiplier suitable for interfacing low-voltage renewable energy sources to high-voltage distribution buses and other applications that require a high-voltage-gain conversion ratio. The proposed converter was constructed from two stages: an interleaved boost stage, which contains two inductors operated by two low-side active switches, and a voltage multiplier cell (VMC) stage, which mainly consists of diodes and capacitors to increase the overall voltage gain. The proposed converter offers a high-voltage-gain ratio with low voltage stress on the semiconductor switches as well as the passive components. This allows the selection of efficient and compact components. Moreover, the required inductance that ensures operation in the continuous conduction mode (CCM) is lower than the one in the conventional interleaved boost converter. The distinction of the proposed converter is that the inductors’ currents are equal, regardless of the number of VMCs. Equal sharing of interleaved boost-stage currents reduces the conduction loss in the active switches as well as the inductors and thus improves the overall efficiency, as the conduction power loss is a quadratic function. In this paper, the theory of operation and steady-state analysis of the proposed converter are illustrated and verified by simulation results. A $\text{200-W}$ hardware prototype was implemented to convert a $\text{20-V}$ input source to a $\text{400-V}$ dc load and validate both the theory and the simulation.

Practical Design Considerations for a Si IGBT + SiC MOSFET Hybrid Switch: Parasitic Interconnect Influences, Cost, and Current Ratio Optimization

Abstract: In this paper, a hybrid switch (HyS) consisting of a large current rated Si insulated-gate bipolar transistor (IGBT) device connected in parallel with a small current rated SiC MOSFET device (low SiC/Si current ratio below unity) is proposed for high-current high-power converters. A systematic analysis involving a parametric sweep to understand the influence and to derive a boundary line of the parasitic interconnection inductance unbalance between Si and SiC within the HyS is presented. The boundary line prescribes the selection of an appropriate gate sequence control. A comprehensive cost analysis was performed using commercial 1.2 kV devices to demonstrate the cost viability of a 1:4 or 1:6 SiC/Si current ratio HyS compared to a SiC MOSFET. An algorithm using a dynamic junction temperature prediction is presented to select an optimum SiC/Si current ratio, which ensures a reliable HyS operation. Using a design example, the possibility of reliability using a 1:6 SiC/Si HyS is studied. A 650 V Si-IGBT- and SiC-MOSFET-based HyS (1:5 SiC/Si current ratio) was successfully demonstrated in a dc–dc boost converter. Also, electromagnetic interference analysis is presented for the HyS-based converter operation.

Practical Stabilization of Switched Affine Systems With Dwell-Time Guarantees

Abstract: Using a hybrid systems approach, we address the practical stabilization of operating points for switched affine systems, ensuring a minimum dwell time and an admissible chattering around the operating point. Two different solutions are shown to induce uniform dwell time, based on time or space regularization. The proposed solutions provide useful tuning knobs to separately adjust the switching frequency during transients and at the steady state. The strengths of the method are illustrated by simulating a boost converter.

A Family of Scalable Non-Isolated Interleaved DC-DC Boost Converters with Voltage Multiplier Cells

Abstract: In this paper, a family of non-isolated interleaved high-voltage-gain DC-DC converters is presented. This family can be used in a wide variety of applications, such as in a photovoltaic systems interface to a high voltage DC distribution bus in a microgrid and an X-ray system power supply. The general structure of this family is illustrated and consists of two stages: an interleaved boost stage and a voltage multiplier stage. The interleaved boost stage is a two-phase boost converter, and it converts the input DC voltage to an AC square waveform. Moreover, using the interleaved boost stage increases the frequency of the AC components so that it can be easily filtered with smaller capacitors and, therefore, makes the input current smoother than the one from the conventional boost converter. The voltage multiplier cell (VMC) can be a Dickson cell, Cockcroft-Walton (CW), or a combination of the two. The VMC stage rectifies the square-shaped voltage waveform coming from the interleaved boost stage and converts it to a high DC voltage. Several combinations of VMCs and how they can be extended are illustrated, and the difference between them is summarized so that designers can be able to select the appropriate topology for their applications. An example of this converter family is illustrated with detailed modes of operation, a steady-state analysis, and an efficiency analysis. The example converter was simulated to convert 20 V DC to 400 DC , and a 200 W hardware prototype was implemented to verify the analysis and simulation. The results show that the example has a peak efficiency of 97% of this family of converters and can be very suitable for interfacing renewable energy sources to a 400 V DC DC distribution system.

Interconnection and Damping Assignment Passivity-Based Control Applied to On-Board DC–DC Power Converter System Supplying Constant Power Load

Abstract: In the more electric aircraft context, dc distribution systems have a time-varying structure due to the flexible distributed loads and complex operation conditions. This feature poses challenges for system stability and increases the difficulty of the stability analysis. Besides, the risk of instability may be increased under constant power load condition due to the negative incremental impedance characteristic. To this end, this article proposes an improved interconnection and damping assignment passivity-based control scheme. Particularly, an adaptive interconnection matrix is developed to establish the internal links in port-controlled Hamiltonian models and to generate the unique control law. The damping assignment technique is addressed to tune the dynamic characteristic. In order to meet the load requirements of different voltage levels, the design procedures were given for determining the control law in both boost converter and buck converter cases. The simulation and experimental results are performed to demonstrate the validity of the proposed control approach.

Power Quality Improvement and PV Power Injection by DSTATCOM With Variable DC Link Voltage Control from RSC-MLC

Abstract: The study proposes a method to optimize dc-link voltage of distribution static compensator based on load compensation requirement using reduced switch count multilevel converter (RSC-MLC) integrated with photovoltaic (PV) system. The proposed method is capable of compensating reactive power, unbalance, and harmonics demanded by three-phase unbalanced and nonlinear loads connected to the distribution side, leading to improvement of power quality. It is also capable of providing real power support to the load and thus prevents source from getting over loaded whenever required. During off-peak loads, the dc-link voltage can be brought down to a lower value, which will reduce the voltage-stress across switches of inverter and minimizes the switching losses. The variation of dc-link voltage is provided using RSC-MLC, which requires dc voltage supply. This method utilizes renewable resources of energy such as solar cells as the dc voltage source. The output voltage of PV panel is boosted to a higher value using high gain boost converter and given to RSC-MLC. The maximum power point tracking of PV panels is achieved by using Perturb and Observe algorithm. The results have been verified through simulation and experimental studies.

A High-Power-Density Power Factor Correction Front End Based on Seven-Level Flying Capacitor Multilevel Converter

Abstract: This paper presents a power factor correction (PFC) front end based on a seven-level flying capacitor multilevel (FCML) boost converter. Compared to the conventional two-level boost converter, the proposed seven-level FCML converter features the use of low-voltage-rated transistors, reduced voltage stress, and high effective switching frequency on the filter inductor. These characteristics of the FCML converter lead to drastic reduction in the filter inductor size while maintaining high efficiency and, therefore, significantly improve the power density of the PFC front end compared to conventional solutions. On the other hand, the small inductance imposes challenges on the PFC control. The dynamics of the seven-level FCML converter has been analyzed, and a feedforward control has been implemented to overcome these challenges. A hardware prototype is designed for universal ac input (90 to 265 Vac), 400-V dc output, and 1.5-kW power rating. Compared to existing solutions, the hardware prototype demonstrates improved efficiency and power density while maintaining high power factor and low THD. A power density of 219 W/in3 (490 W/in3 for the power stage) has been achieved, and a peak efficiency of 99.07% has been experimentally verified.

High-Efficiency and High-Density Single-Phase Dual-Mode Cascaded Buck–Boost Multilevel Transformerless PV Inverter With GaN AC Switches

Abstract: This paper introduces a high-efficiency and high-density single-phase dual-mode cascaded buck–boost multilevel transformerless photovoltaic (PV) inverter for residential application. This inverter topology combines a regulated cascaded H-bridge multilevel inverter stage with an unregulated GaN-based ac boost converter. The cascaded H-bridge inverter and the ac boost share a common inductor. Compared with the traditional cascaded H-bridge PV inverter, this topology significantly enlarges the input voltage range due to the additional ac boost. And, a flexible number of PV panels can be used. To control the multiple dc-link PV voltages and to reduce the switching loss of the ac boost, this paper further introduces a dual-mode operation. The two modes are buck mode and buck–boost mode. To maximize the utilizations of the dc-link voltages, this paper presents a minimized ac boost duty-cycle generation strategy with feedforward. Then, a dual-mode modulation based on the boost feedforward duty-cycle generation is introduced. This paper also uses an indirect current control for this inverter, since the ac boost is an unregulated stage. The ac boost stage is implemented with two interleaved phases and the ac switches based on the 650-V E-mode GaN FETs. Finally, an 8-port 2-kW prototype based on this topology is developed and demonstrated. Compared with the state-of-the-art microinverter-based 2-kW PV inverter system, the developed inverter prototype achieves 40% reduction of the total power loss, 25% improvement of the power density, 37.5% reduction of the power connectors, 50% reduction of the device count, and 87.5% reduction of the main magnetic count. Operating with natural convection cooling, this PV inverter achieves 98.0% efficiency at 60% of load and 97.8% efficiency at full load. The power density of the packaged PV inverter is 5.8 W/in3.

Gate Control Optimization of Si/SiC Hybrid Switch for Junction Temperature Balance and Power Loss Reduction

Abstract: The hybrid switch concept of paralleling a higher-current main Si IGBT and a lower-current auxiliary SiC mosfet offers an improved cost/performance tradeoff in power converters. Currently, the gate control strategy of these two internal devices emphasizes on minimizing the total power loss, and is referred to as the efficiency control mode in this paper. However, there is a serious risk of overheating and reliability degradation of the SiC mosfet if solely relying on this control strategy. In this paper, we propose a new method of gate control optimization, referred to as the thermal balance control mode, to keep the junction temperature of both devices within the specified temperature range, and to minimize the total power loss simultaneously. We first investigate the dependency of the hybrid switch switching losses on the gate control pattern both theoretically and experimentally. We then extensively study control optimization in these two distinct control modes in a dc–dc boost converter. It is found that the thermal balance control mode can achieve almost the same total power loss as the efficiency control mode, but much lower and more balanced junction temperatures of the two internal devices. Experimental results demonstrate that the Si/SiC hybrid switch in an optimal thermal balance control mode can achieve a 163% higher power handling capability in the 20-kHz boost converter or four times higher switching frequency in the 4-kW boost converter than a single IGBT solution with hard switching condition, and yet a considerably lower component cost than a single SiC mosfet solution in the boost converter.

Control and Optimization of Residential Photovoltaic Power Generation System With High Efficiency Isolated Bidirectional DC–DC Converter

Abstract: Currently, residential photovoltaic power generation system is increasingly used worldwide. In this paper, an optimized structure of residential photovoltaic (PV) power generation system with 1500V DC bus is proposed. It includes PV panels, a three-level boost converter, a high efficiency isolated bidirectional DC-DC converter, battery and three-phase five-level DC-AC converter that can work under islanding mode or grid-connected mode. The higher DC bus voltage greatly reduces line loss and improves efficiency of the system. An energy management scheme used for the system is proposed in this paper to guarantee the stability of the system and to increase its economic benefits. Besides, the optimized method for the structure of the bidirectional dc-dc converter is proposed. This structure can achieve higher DC voltage gain and higher efficiency. Furthermore, for low voltage battery application in the residential system, LLC and CLLC under DC transformer (DCX) mode are evaluated and the LLC is selected as the isolated bidirectional DC-DC converter. The optimized designed method of bidirectional LLC is proposed. Finally, experiments are carried out to verify the performance of the optimized converters and the system.

Digital Implementation of Fractional Order PID-Type Controller for Boost DC–DC Converter

Abstract: In this paper, the problem of designing a fractional order PID-type controller is considered for a boost converter. By using the output capacitance and input inductance values this paper characterizes integer order PID-type control gains which will make the closed-loop system transfer function approximately equal to a first order system with a unit DC gain and prescribed time constant τ. Next, a procedure to compute the design parameters of a fractional order PID-type controller is given together with a descritized control algorithm for DSP implementation. By using a floating-point DSP, the proposed control algorithm is implemented in real time. Finally, experimental results are given to show the practical feasibility and effectiveness of the proposed fractional order PID-type control system under several operating conditions. The results illuminate that the proposed controller can be better than a conventional integer order PID-type controller.

Cascade Control With Adaptive Voltage Controller Applied to Photovoltaic Boost Converters

Abstract: DC–DC boost converters have been widely employed at the dc input of grid-tied photovoltaic (PV) inverters. In order to comply with grid standards, their control systems must usually work in two operation modes: Maximum power point tracking (MPPT) mode and limited power tracking (LPT) mode. MPPT algorithms reach high dynamic and static efficiencies when they operate with high-speed PV voltage control, because PV voltage is not significantly dependent on solar irradiance variations. On another hand, high-speed LPT mode can be obtained by controlling inductor current, which is proportional to the power injected into the dc bus. Both modes can be integrated in a cascade control scheme with an inner and fast current loop and an outer voltage loop. The main challenge is that both voltage and current small-signal models are highly dependent on the operation point of the PV array, temperature, and solar irradiance. This may cause control interactions between both loops and instability, especially when small film capacitors are used in parallel with the PV array. A common approach is to increase the input capacitance and design a low-speed PV voltage controller, which is not the best solution when high MPPT dynamic efficiency is necessary. To overcome these challenges, this paper proposes a cascade control structure based on an inner non-linear current controller and an outer adaptive voltage controller with fast detection of the PV array's model without requiring extra current sensor. A control design methodology and a MATLAB stability analysis tool are presented to support application engineers. The proposed control system has been experimentally validated using a PV array and a boost converter switched at 40 kHz. PV voltage settling time lower than 8 ms has been achieved for low and high solar irradiance, demonstrating the efficacy of the proposed technique.

Design Optimization and Model Predictive Control of a Standalone Hybrid Renewable Energy System: A Case Study on a Small Residential Load in Pakistan

Abstract: Renewable energy sources (RESs) offer a promising prospect for covering the fundamental needs of electricity for remote and isolated regions. To serve the customers with high power quality and reliability, design optimization methodology and a possible power management strategy (PMS) for wind-diesel-battery-converter hybrid renewable energy system (HRES) is proposed in this paper. The analysis is applied to a real case study of a standalone residential load located in a remote rural area in Pakistan. Firstly, optimal component sizing is investigated according to actual meteorological and load profile data. Different hybrid configurations are modeled, analyzed, and compared in terms of their technical, economic and environmental metrics with the aid of HOMER® software. The main objective is to determine the most feasible and cost-effective solution with least life-cycle cost, keeping in view the impact of carbon emissions. Secondly, a suitable PMS based on the state of charge (SOC) of the battery is proposed and implemented in MATLAB/Simulink® software for the designed HRES. The PMS is targeted to maintain load balance and extract maximum wind power while keeping the battery SOC within the safe range. Model predictive control (MPC) approach is applied to improve the output voltage profile and reduce the total harmonic distortion (THD). The boost converter is used for maximum power extraction from the wind. The DC-DC buck-boost battery controller is utilized to stabilize the DC bus voltage. The design optimization results show that the hybridization of wind, battery, and converter presents optimal configuration plan with minimum values of total net present cost (14,846 $) and cost of energy (0.309 $/kWh), which means 76.7% reduction in both total system cost and energy cost and 100% saving in harmful emissions when compared to the base case using diesel generator. The proposed system is able to support hundred percent of the load demand with excess energy of 30.1%. Performance analysis of PMS under variable load and fluctuating wind power generation is tested, and promising results with efficient load voltage profile is observed. Further, THD is reduced significantly to 0.26% as compared to 2.62% when the conventional PI controller is used. The output of this work is expected to open a new horizon for researchers, system planners for efficient design and utilization of HRES to curb drastic increase in load demand for urban as well as rural areas.

Fuzzy-Controller-Designed-PV-Based Custom Power Device for Power Quality Enhancement

Abstract: In this paper, a three-phase series hybrid active filter (SEHAF) interconnected with photovoltaic (PV) system and dc–dc boost converter is proposed to minimize sag, swell, and harmonics caused due to nonlinear power electronic loads. The SEHAF consists of a voltage source inverter (VSI) with a capacitor connected across it to provide consistency in managing and compensating the reactive power. This minimizes the sag, swell, and harmonics present in the source and load voltages. With the integration of PV, the voltage across the dc-link capacitor of VSI is controlled effectively, which helps in better compensation. Reference current generation is done using the proposed robust extended complex Kalman filter (RECKF) technique. The performance of the PV-integrated-HAF is analyzed using a synchronous reference frame with proportional-integral (PI) as well as fuzzy logic controller (FLC) and is compared with the proposed RECKF technique. The PV-integrated hybrid power system is developed using MATLAB/SIMULINK. Further, real-time digital simulation using OPAL-RT OP5142 is also carried out to support the simulation results. It is observed that the proposed control scheme provides better harmonic compensation compared to conventional PI and FLC.

Analysis and Design of a High Power Density Flying-Capacitor Multilevel Boost Converter for High Step-Up Conversion

Abstract: This paper explores the use of the flying-capacitor multilevel (FCML) topology in high step-up conversion. Compared to the conventional two-level boost converter, the FCML topology utilizes high energy density capacitors to facilitate inductors with storing and transferring energy during the conversion process, which brings features, such as lower voltage stress on the switches, reduced voltage stress on the inductor, and high effective switching frequency at the switching node. As a result, the total volume of the passive components in the converter is greatly reduced while maintaining high efficiency at high voltage gain. To demonstrate the potential high power density and high efficiency, a hardware prototype that converts 100 V to 1 kV with 820-W maximum output power is built. Such specifications require careful optimizations in many aspects of the converter to ensure a high power density and efficiency design. The implemented solutions and associate design process are presented in detail, with comparison with other state-of-the-art solutions. The hardware prototype has successfully demonstrated a peak efficiency of 94.1%, and 329 W/in $^3$ (20 W/cm $^3$ ) overall power density.

Open-Switch Fault-Tolerant Operation of a Two-Stage Buck/Buck–Boost Converter With Redundant Synchronous Switch for PV Systems

Abstract: In photovoltaic systems, dc–dc converters have been identified as one of the most critical and challenging subsystem in terms of failure rate. Thus, this paper proposes fault-tolerant operation of a two-stage buck/buck–boost converter under open-circuit switch failure. Remedial actions are efficient in any failure of one of the two switches of the converter. Here, a new unified approach is considered, for the overall fault-tolerant operation of the two stages of the converter. The fault-tolerant circuit we propose lies on performing redundancy by implementing the equivalent synchronous switch for the two main switches of the two stages, in offline mode. The fault-tolerant circuit results from the basic two-stage buck/buck-boost converter and its equivalent circuit with a synchronous switch, merged together to form the new dc–dc fault-tolerant circuit. Therefore, postfault operation at full power can also be performed. By using a switch fault management unit with reduced complexity, inserted between the control block and the switches, we have designed an unified, efficient, and optimized fault-tolerant control, suitable in both healthy and postfault operations. Some selected experimental tests, which all confirm the good performances of the proposed fault-tolerant approach, are presented and discussed.

Sliding-mode control of a boost converter under constant power loading conditions

Abstract: The cascade connection of two dc-dc switching converters for constant power supply is studied. The source converter is of boost type while the load converter is of buck type. The natural unstable behaviour of the cascade connection for both on and off states of the boost converter is counteracted by a sliding-mode control strategy that combines unstable trajectories to generate a stable one for the regulated boost converter dynamics. Experimental results using an electronic load to emulate a buck converter-based constant power load are in good agreement with the theoretical predictions. A similar agreement is later obtained when a buck converter with a dynamic behaviour close to an instantaneous constant power load is employed instead of the electronic load.

A Composite Sliding Mode Controller for Wind Power Extraction in Remotely Located Solar PV–Wind Hybrid System

Abstract: Ensuring electrification of remote locations continues to be a major challenge for power engineers To deal with the effect of intermittent nature of wind, this paper presents the design and implementation of a composite sliding mode controller (CSMC) for a battery energy storage (BES) supported solar photovoltaic (PV)–wind hybrid system in a remote location This control technique comprises of a soft-switching sliding-mode observer (SS-SMO) and a nonsingular terminal sliding mode controller (NTSMC) The SS-SMO is used to observe the disturbances, whereas the NTSMC is used as a speed controller The chattering problem caused by the conventional sliding mode controller is alleviated by replacing the conventional signum switching function with the smooth hyperbolic tangent function in disturbance observer loop The fast and finite time convergence NTSMC based speed controller along with the SS-SMO based disturbance rejection unit, serves the benefits of CSMC This technique exhibits robustness against model uncertainties and external disturbances Moreover, the complexity of the system is reduced by replacing the mechanical speed and position sensors with parameter estimation A double-stage configuration using a dc/dc boost converter is adopted for a PV system A comparative analysis is presented between the proposed and conventional techniques A prototype of the hybrid system is developed in the laboratory with permanent magnet synchronous generator The CSMC-based controller with disturbance rejection ability is implemented to harvest peak wind power A perturb and observe maximum power point tracking technique is adopted to harvest peak solar power A voltage control technique is adopted to maintain the voltage at the point of common coupling

Luenberger Observer Based Current Estimated Boost Converter for PV Maximum Power Extraction-A Current Sensorless Approach

Abstract: A continuous change in the solar irradiance level and local atmospheric conditions, such as temperature and humidity, necessitate the use of maximum power point tracking (MPPT) technique of a photovoltaic (PV) system. MPPT ensures to harvest maximum power. Generally, voltage and current sensors are required to track the power of a PV system. The proposed method tracks the power of a PV system without the use of any current sensor. It not only reduces the cost of the system, but also reduces the communication burden, internal disturbances, and complexity. The proposed scheme estimates the current internally by using Luenberger observer technique. Thus, the estimated current is given to perturb and observe based MPPT technique, to generate the required duty for a dc–dc boost converter. The proposed scheme is experimentally investigated, and thus, obtained results are compared with well-established MPPT techniques. A comparison shows that the proposed system results are in a good agreement with the current sensor based MPPT technique.