Showing papers on "Boost converter published in 2002"

Z-source inverter

Abstract: This paper presents an impedance-source (or impedance-fed) power converter (abbreviated as Z-source converter) and its control method for implementing DC-to-AC, AC-to-DC, AC-to-AC, and DC-to-DC power conversion. The Z-source converter employs a unique impedance network (or circuit) to couple the converter main circuit to the power source, thus providing unique features that cannot be obtained in the traditional voltage-source (or voltage-fed) and current-source (or current-fed) converters where a capacitor and inductor are used, respectively. The Z-source converter overcomes the conceptual and theoretical barriers and limitations of the traditional voltage-source converter (abbreviated as V-source converter) and current-source converter (abbreviated as I-source converter) and provides a novel power conversion concept. The Z-source concept can be applied to all DC-to-AC, AC-to-DC, AC-to-AC, and DC-to-DC power conversion. To describe the operating principle and control, this paper focuses on an example: a Z-source inverter for DC-AC power conversion needed in fuel cell applications. Simulation and experimental results are presented to demonstrate the new features.

Adaptive piezoelectric energy harvesting circuit for wireless remote power supply

Abstract: This paper describes an approach to harvesting electrical energy from a mechanically excited piezoelectric element. A vibrating piezoelectric device differs from a typical electrical power source in that it has a capacitive rather than inductive source impedance, and may be driven by mechanical vibrations of varying amplitude. An analytical expression for the optimal power flow from a rectified piezoelectric device is derived, and an "energy harvesting" circuit is proposed which can achieve this optimal power flow. The harvesting circuit consists of an AC-DC rectifier with an output capacitor, an electrochemical battery, and a switch-mode DC-DC converter that controls the energy flow into the battery. An adaptive control technique for the DC-DC converter is used to continuously implement the optimal power transfer theory and maximize the power stored by the battery. Experimental results reveal that use of the adaptive DC-DC converter increases power transfer by over 400% as compared to when the DC-DC converter is not used.

LLC resonant converter for front end DC/DC conversion

Abstract: A new LLC resonant converter is proposed for front end DC/DC conversion in a distributed power system. Three advantages are achieved with this resonant converter. First, ZVS turn on and low turn off current of MOSFETs are achieved. The switching loss is reduced so we can operate the converter at higher switching frequency. The second advantage is that with this topology, we can optimize the converter at high input voltage. Finally, with this topology, we can eliminate the secondary filter inductor, so the voltage stress on the secondary rectifier will be limited to two times the output voltage, better rectifier diodes can be used and secondary conduction loss can be reduced. The converter utilizes leakage and magnetizing inductance of a transformer. With magnetic integration concept, all the magnetic components can be built in one magnetic core. The operation and characteristic of this converter is introduced and efficiency comparison between this converter and a conventional PWM converter is given which shows a great improvement by using this topology.

Multi-stage switched capacitor DC-DC converter

Abstract: A three-stage switched capacitor DC-DC converter capable of generating an output boosted voltage in increments of less than power supply voltage. A first stage of the DC-DC converter comprises two capacitors and three switches, which alternate a connection of the two capacitors. The two capacitors are connected in series when charging by turning one of the switches ON, and are connected in parallel when discharging by turning the other two of the switches ON.

Optimized piezoelectric energy harvesting circuit using step-down converter in discontinuous conduction mode

Abstract: An optimized method of harvesting vibrational energy with a piezoelectric element using a step-down DC-DC converter is presented. In this configuration, the converter regulates the power flow from the piezoelectric element to the desired electronic load. Analysis of the converter in discontinuous current conduction mode results in an expression for the duty cycle-power relationship. Using parameters of the mechanical system, the piezoelectric element, and the converter an optimal duty cycle can be determined where the harvested power is maximized for a given frequency of mechanical excitation. It is shown that, as the magnitude of the excitation increases, the optimal duty cycle becomes essentially constant, greatly simplifying the control of the step-down converter. The expression is validated with experimental data showing that the optimal duty cycle can be accurately determined and maximum energy harvesting attained. A circuit is proposed which implements this relationship, and experimental results show that the converter increases the harvested power by approximately 325%.

A pseudo-CCM/DCM SIMO switching converter with freewheel switching

Abstract: This paper presents a single-inductor multiple-output (SIMO) converter operating in pseudo-continuous conduction mode (PCCM) and/or discontinuous conduction mode (DCM). With the proposed freewheel switching control, this converter can handle large load currents with a much smaller current ripple, while retaining low cross regulation. It can also work in DCM for high efficiency at light loads. A prototype of a single-inductor dual-output (SIDO) boost converter was fabricated with a standard 0.5-/spl mu/m CMOS n-well process. The two outputs are regulated at 2.5 and 3.0 V, respectively. At an oscillator frequency of 1 MHz, the efficiency reaches 89.4% at a total output power of 320 mW. Compared with prior designs, both current and voltage ripples are reduced. This design can be extended to have multiple outputs and for different types of dc-dc conversions, or be applied to single-output converters for fast transient response.

Multi-input DC/DC converter based on the multiwinding transformer for renewable energy applications

Abstract: A multi-input DC/DC power converter based on the flux additivity is proposed in this paper. Instead of combining input DC sources in the electric form, the proposed converter combines input DC sources in magnetic form by adding up the produced magnetic flux together in the magnetic core of the coupled transformer. With the phase-shifted pulsewidth-modulation (PWM) control, the proposed converter can draw power from two different DC sources and deliver it to the load individually and simultaneously. The operation principle of the proposed converter has been analyzed in detail. The output voltage regulation and power flow control can be achieved by the phase-shifted PWM control. A prototype converter with two different DC voltage sources has been successfully implemented. Computer simulations and hardware experimental results are presented to verify the performance of the proposed multi-input DC/DC power converter.

Cascaded DC-DC converter connection of photovoltaic modules

Abstract: New residential scale photovoltaic (PV) arrays are commonly connected to the grid by a single DC-AC inverter connected to a series string of PV modules, or many small DC-AC inverters which connect one or two modules directly to the AC grid. This paper shows that a "converter-per-module" approach offers many advantages including individual module maximum power point tracking, which gives great flexibility in module layout, replacement, and insensitivity to shading; better protection of PV sources, and redundancy in the case of source or converter failure; easier and safer installation and maintenance; and better data gathering. Simple nonisolated per-module DC-DC converters can be series connected to create a high voltage string connected to a simplified DC-AC inverter. These advantages are available without the cost or efficiency penalties of individual DC-AC grid connected inverters. Buck, boost, buck-boost and Cuk converters are possible cascadable converters. The boost converter is best if a significant step up is required, such as with a short string of 12 PV modules. A string of buck converters requires many more modules, but can always deliver any combination of module power. The buck converter is the most efficient topology for a given cost. While flexible in voltage ranges, buck-boost and Cuk converters are always at an efficiency or alternatively cost disadvantage.

A comparison of high-power converter topologies for the implementation of FACTS controllers

Abstract: This paper compares four power converter topologies for the implementation of flexible AC transmission system (FACTS) controllers: three multilevel topologies (multipoint clamped (MPC), chain, and nested cell) and the well-established multipulse topology. In keeping with the need to implement very-high-power inverters, switching frequency is restricted to line frequency. The study addresses device count, DC filter ratings, restrictions on voltage control, active power transfer through the DC link, and balancing of DC-link voltages. Emphasis is placed on capacitor sizing because of its impact on the cost and size of the FACTS controller. A method for the dimensioning the DC capacitor filter is presented. It is found that the chain converter is attractive for the implementation of a static compensator or a static synchronous series compensator. The MPC converter is attractive for the implementation of a unified power flow controller or an interline power flow controller, but a special arrangement is required to overcome the limitations on voltage control.

A zero-voltage and zero-current switching three-level DC/DC converter

Abstract: This paper presents a novel zero-voltage and zero-current switching (ZVZCS) three-level DC/DC converter. This converter overcomes the drawbacks presented by the conventional zero-voltage switching (ZVS) three-level converter, such as high circulating energy, severe parasitic ringing on the rectifier diodes, and limited ZVS load range for the inner switches. The converter presented in this paper uses a phase-shift control with a flying capacitor in the primary side to achieve ZVS for the outer switches. Additionally, the converter uses an auxiliary circuit to reset the primary current during the freewheeling stage to achieve zero-current switching (ZCS) for the inner switches. The principle of operation and the DC characteristics of the new converter are analyzed and verified on a 6 kW, 100 kHz experimental prototype.

Analysis and design considerations of a load and line independent zero voltage switching full bridge DC/DC converter topology

Abstract: The analysis and design of a zero voltage switching (ZVS) full bridge DC/DC power converter topology is presented in this paper. The converter topology presented here employs an asymmetrical auxiliary circuit consisting of a few passive components. With this auxiliary circuit, the full bridge converter can achieve ZVS independent of line and load conditions. The operating principle of the circuit is demonstrated, and the steady state analysis is performed. Based on the analysis, a criterion for optimal design is given. Experiment and simulation on a 350-400 V to 55 V, 500 W prototype converter operated at 100 kHz verify the design and show an overall efficiency of greater than 97% at full load.

A novel multicell DC-AC converter for applications in renewable energy systems

Abstract: This paper presents a novel DC-AC converter for applications in the area of distributed energy generation systems, e.g., solar power systems, fuel-cell power systems in combination with supercapacitor or battery energy storage. The proposed converter is realized using an isolated multicell topology where the total AC output of the system is formed by series connection of several full-bridge converter stages. The DC links of the full bridges are supplied by individual DC-DC isolation stages which are arranged in parallel concerning the dc input of the. total system. Therefore, all switching cells of the proposed converter can be equipped with modern low-voltage high-current power MOSFETs, which results in an improved efficiency as compared to conventional isolated DC-AC converters. Furthermore, the cells are operated in an interleaved pulsewidth-modulation mode which, in connection with the low voltage level of each cell, significantly reduces the filtering effort on the AC output of the overall system. The paper describes the operating principle, analyzes the fundamental relationships which are relevant for component selection, and presents a specific circuit design. Finally, measurements taken from a 2-kW laboratory model are presented.

Voltage-based maximum power point tracking control of PV system

Abstract: Photovoltaic (PV) generators exhibit nonlinear v-i characteristics and maximum power (MP) points that vary with solar insulation. An intermediate converter can therefore increase efficiency by matching the PV system to the load and by operating the solar cell arrays (SCAs) at their maximum power point. An MP point tracking algorithm is developed using only SCA voltage information thus leading to current sensorless tracking control. The inadequacy of a boost converter for array voltage based MP point control is experimentally verified and an improved converter system is proposed. The proposed converter system results in low ripple content, which improves the array performance and hence a lower value of capacitance is sufficient on the solar array side. Simplified mathematical expressions for a PV source are derived. A signal flow graph is employed for modeling the converter system. Current sensorless peak power tracking effectiveness is demonstrated through simulation results. Experimental results are presented to validate the proposed method.

A new matrix converter motor (MCM) for industry applications

Abstract: The trend in electrical drives is to integrate the frequency converter, the electrical motor, and even the gear or the pump into a single unit, in order to reduce the costs, to increase the overall efficiency and the equipment reliability. This paper presents the first integrated regenerative frequency converter motor for industry applications, based on a matrix converter topology. The low volume, the sinusoidal input current, the bidirectional power flow, and the lack of the bulky and limited-lifetime electrolytic capacitors recommend this topology for this application. This paper shows how the matrix converter disadvantages-the lack of bidirectional power devices, the lower voltage transfer ratio, and the overvoltages caused by the input filter during power-up-that have delayed the industrial implementation have been overcome. In order to demonstrate the validity of the solution, a 4-kW matrix converter motor prototype is built using a standard frequency converter motor enclosure for testing the requirements for an industrial drive. The tests demonstrate the good performance of the drive.

A magnetic-less DC-DC converter for dual voltage automotive systems

Abstract: The automotive industry is moving toward 42 volt to meet the more electric needs. Several dual voltage (42 and 14 volt) architectures have been proposed for the transition and accommodation of 14-volt loads. A DC-DC converter that connects the 42 and 14 volt architectures is one key device in any dual voltage architecture. This paper presents a compact, efficient, magnetic-less bi-directional DC-DC converter for dual voltage (42/14 Volt) automotive systems. The DC-DC converter is based on the generalized multilevel converter topology having the ability to balance battery voltages, emit zero or low electromagnetic interference (EMI), and have low cost by using low-voltage metal oxide field effect transistors (MOSFETs). The main circuit of the DC-DC converter is analyzed and its control scheme is presented in the paper. A self-powered gate drive circuit is developed for the DC-DC converter to reduce costs, signal connections, and circuit complexity. A prototype has been built and experimental results are presented.

A DC link capacitor minimization method through direct capacitor current control

Abstract: If we make the converter side DC link current the same as the inverter side DC link current in a PWM converter-inverter system, no current will flow through the DC link capacitor and as a result, no DC link voltage variation occurs. This leads to the possibility of significantly reducing the size of DC link capacitors which are expensive, bulky and have a lifetime limit, if we can manage to match inverter and converter currents at the DC link. However, a converter inherently involves a delay in supplying the required current. Therefore, matching the converter current to the inverter current necessitates the use of a differentiator to meet the requirements of a fast dynamic response. But in practice, differentiating the measured value is almost impossible. In this paper, the authors propose a new differentiation method that utilizes a one-step predictor developed from converter and inverter dynamics. In the model, the DC link voltage is regarded a variable. Since the inverter current compensation term is applied in terms of voltage, the response is fast. Simulation and experiments are performed with only 40 /spl mu/F DC link capacitance for a 9 kW motor, and the results support the validity of the proposed scheme.

A new ZVT-PWM DC-DC converter

Abstract: In this paper, a new active snubber cell that overcomes most of the drawbacks of the normal "zero voltage transition-pulse width modulation" (ZVT-PWM) converter is proposed to contrive a new family of ZVT-PWM converters. A converter with the proposed snubber cell can also operate at light load conditions. All of the semiconductor devices in this converter are turned on and off under exact or near zero voltage switching (ZVS) and/or zero current switching (ZCS). No additional voltage and current stresses on the main switch and main diode occur. Also, the auxiliary switch and auxiliary diodes are subjected to voltage and current values at allowable levels. Moreover, the converter has a simple structure, low cost, and ease of control. A ZVT-PWM boost converter equipped with the proposed snubber cell is analyzed in detail. The predicted operation principles and theoretical analysis of the presented converter are verified with a prototype of a 2 kW and 50 kHz PWM boost converter with insulated gate bipolar transistor (IGBT). In this study, a design procedure of the proposed active snubber cell is also presented. Additionally, at full output power in the proposed soft switching converter, the main switch loss is about 27% and the total circuit loss is about 36% of that in its counterpart hard switching converter, and so the overall efficiency, which is about 91% in the hard switching case, increases to about 97%.

Integrated magnetic for LLC resonant converter

Abstract: A new LLC resonant converter is proposed for front end DC/DC conversion in a distributed power system. This converter shows some potential benefits in this application. This paper proposes several integrated magnetic designs for LLC resonant converter. This converter has three magnetic components. With magnetic integration, first, a number of components can be reduced; secondly, flux ripple cancellation is achieved so that core loss is reduced. From these benefits, higher power density can be achieved. In design of the integrated magnetic structure for LLC resonant converter, a general model of four winding integrated magnetic structure is derived which can be used to derive integrated magnetic structure for different topologies. Finally, the test result is shown.

Multiple-input DC-DC power converter for power-flow management in hybrid vehicles

Abstract: The search for a compact, lightweight, and efficient energy storage system (battery and/or combination of other emerging technologies, including ultracapacitors, flywheel energy storage system, advanced batteries, and fuel cells) that is both affordable and has acceptable cycle life remains the major roadblock to large-scale production of EVs and HEVs. In this paper a multiple input DC-DC power converter (MI-PEC) devoted to combine the power flowing from combined on-board energy sources is presented; the proposed arrangement for the propulsion system includes electric generator (EG), ultracapacitor tank (UC) and battery systems.

Multiple input DC-DC power converter for fuel-cell powered hybrid vehicles

Abstract: Customer demands for greater acceleration, performance, and vehicle range in pure EVs plus mandated requirements to further reduce emissions in HEVs increase the appeal for combined on-board energy storage systems and generators. This paper deals with a multiple input DC-DC power converter devoted to combine the power flow of multi-source on-board energy systems. The proposed energy storage arrangement includes fuel cell generator, ultracapacitor tank, and battery system. Possibility of optimization of the output capacitors bank in relation to the RMS value of the current ripple is investigated.

Novel zero-voltage and zero-current-switching (ZVZCS) full-bridge PWM converter using coupled output inductor

Abstract: A novel zero-voltage and zero-current-switching (ZVZCS) full-bridge pulse-width-modulated (PWM) converter is proposed to improve the previously proposed ZVZCS full-bridge PWM converters. By employing a simple auxiliary circuit with neither lossy components nor active switches, soft-switching of the primary switches is achieved. The proposed converter has many advantages such as simple auxiliary circuit, high efficiency, low voltage stress of the rectifier diode and self-adjustment of the circulating current, which make the proposed converter attractive for the high voltage and high power applications. The principles of operation and design considerations are presented and verified on the 4 kW experimental converter operating at 80 kHz.

Segmented arc generator

Abstract: A segmented arc generator is adapted to convert mechanical power such as wind or water power into electrical power at a wide range of wind or shaft speeds. A rotor has a plurality of salient poles disposed about a periphery of a rotor ring. A stator has a stator ring disposed radially about and in close proximity to the rotor ring. The stator ring includes a plurality of stator coils wound on a ferromagnetic structure and having permanent magnets imbedded within the structure. Relative motion between a rotor pole and a corresponding stator coil induces a coil voltage across that coil. A phase controlled converter in electrical communication with the stator coils rectifies the output voltage. A pulse width modulated inverter is in electrical communication with the phase controlled converter for converting the D.C. voltage output by the phase controlled converter to an A.C. voltage of controlled amplitude and phase relationship determined with respect to a voltage waveform present on a connected utility grid. A switching matrix selectively places the coils in series or parallel or a combination of series and parallel connections with respect to one another in response to control signals that are based on present operating conditions of the generator. A boost converter circuit provides and maintains a minimum D.C. voltage to the pulse width modulated inverter when the voltage induced in the coils falls below a threshold value.

Feedforward maximum power point tracking of PV systems using fuzzy controller

Abstract: A feedforward maximum power (MP) point tracking scheme is developed for the interleaved dual boost (IDB) converter fed photovoltaic (PV) system using fuzzy controller. The tracking algorithm changes the duty ratio of the converter such that the solar cell array (SCA) voltage equals the voltage corresponding to the MP point at that solar insolation. This is done by the feedforward loop, which generates an error signal by comparing the instantaneous array voltage and reference voltage. The reference voltage for the feedforward loop, corresponding to the MP point, is obtained by an off-line trained neural network. Experimental data is used for off-line training of the neural network, which employs back-propagation algorithm. The proposed fuzzy feedforward peak power tracking effectiveness is demonstrated through the simulation and experimental results, and compared with the conventional proportional plus integral (PI) controller based system. Finally, a comparative study of interleaved boost and conventional boost converter for the PV applications is given and their suitability is discussed.

Control method and circuit to provide voltage and current regulation for multiphase DC/DC converters

Abstract: A multiphase DC/DC converter with voltage-mode hysteretic control and instantaneous current sharing functionality method and circuit. The disclosed method and circuit provides independent output voltage regulation and phases current regulation for the converter in two separate loops; one of which is concerned with voltage regulation preferably hysteretic regulation and the other which is concerned with phase current regulation. In one embodiment, each phase in the DC/DC converter is driven by a frequency divided signal derived directly from the output voltage ripple so that each phase has a switching frequency equal to the output voltage ripple frequency divided by the number of paralleled phase. In another embodiment, only the phase that carries the smallest current among a set of phases will be turned ON in each switching cycle to supply power to the output, avoiding multiple switching. Current sharing and regulation is achieved without shortening the ON time and with no multiple switching in any cycle.

A new green power inverter for fuel cells

Abstract: This paper presents a new grid connected inverter for fuel cells. It consists of a two stage power conversion topology. Since the fuel cell operates with a low voltage in a wide voltage range (25 V-45 V) this voltage must be transformed to around 350-400 V in order to invert this DC power into AC power to the grid. The proposed converter consists of an isolated DC-DC converter cascaded with a single phase H-bridge inverter. The DC-DC converter is a current-fed push-pull converter. A new dedicated voltage mode startup procedure has been developed in order to limit the inrush current during startup. The inverter is controlled as a power factor controller with resistor emulation. Experimental results of converter efficiency, grid performance and fuel cell response are shown for a 1 kW prototype. The proposed converter exhibits a high efficiency in a wide power range (higher than 92%) and the inverter operates with a near unity power factor and a low current THD.

The forward converter: from the classic to the contemporary

Abstract: The evolution of the forward power converter is first reviewed, in a tutorial fashion, from the classic to the contemporary. Salient features are then discussed and results are compiled to form practical design guidelines. Performance parameters are discussed, including operating principle, voltage conversion ratio, efficiency, device stresses, small-signal dynamics, noise and EMI and parts count. The extension of each converter to a synchronous rectifier and/or to a current doubler is also discussed.

Multiple energy-source power converter system

Abstract: A flexible integrated power converter system that connects various types of electrical power sources together and supplies a defined type of electrical energy to a load, such as a standard household mains voltage supply, is provided. Each of the electrical power sources is electrically isolated from the load, as well as each other. A respective input converter is coupled to each power source. Each input converter may include a small high-frequency transformer driven by an efficient soft-switched dc-dc converter. The voltages produced by each of the input converters are combined in parallel and delivered to a single output inverter. The output inverter converts the combined voltages to an ac voltage that may be delivered to a load.

Synergetic control for DC-DC boost converter: implementation options

Abstract: The theory of synergetic control was introduced in a power electronics context in a previous paper. In this paper we review the theory, then focus on some practical aspects with reference to both simulations and actual hardware. In particular we address management of the current limit condition and solve it with several different approaches. Adaptive and other control laws are introduced to improve the control performance. Various other control laws are introduced to improve the control performance, and then they are evaluated by applying the classical voltage reference step test.

Voltage and current stress reduction in single-stage power factor correction AC/DC converters with bulk capacitor voltage feedback

Abstract: Single-stage power factor correction (PFC) AC/DC converters integrate a boost-derived input current shaper (ICS) with a flyback or forward DC/DC converter in one single stage. The ICS can be operated in either discontinuous current mode (DCM) or continuous current mode (CCM), while the flyback or forward DC/DC converter is operated in CCM. Almost all single-stage PFC AC/DC converters suffer from high bulk capacitor voltage stress and extra switch current stress. The bulk capacitor voltage feedback with a coupled winding structure is widely used to reduce both the voltage and current stresses in practical single-stage PFC AC/DC converters. This paper presents a detailed analysis of the bulk capacitor voltage feedback, including the relationship between bulk capacitor voltage, input current harmonics, voltage feedback ratio, and load condition. The maximum bulk capacitor voltage appears when the DC/DC converter operates at the boundary between CCM and DCM. This paper also reveals that only the voltage feedback ratio determines the input current harmonics under DCM ICS and CCM DC/DC operation. The theoretical prediction of the bulk capacitor voltage as well as the predicted input harmonic contents is verified experimentally on a 60 W AC/DC converter with universal-line input.

A novel tri-state boost converter with fast dynamics

Abstract: A challenging problem in the design of boost converters operating in continuous-conduction mode is posed by the dynamically shifting right-half-plane (RHP) zero in the converter's small-signal control-to-output transfer function. The paper proposes a novel tri-state boost converter without such a zero in the transfer function. The additional degree of freedom introduced in the converter in the form of a freewheeling interval has been exploited through an easy control technique to achieve this elimination. The absence of the RHP zero allows the control scheme to achieve larger bandwidth under closed-loop conditions, resulting in fast response. Analytical, simulation and experimental results of the tri-state boost converter have been presented and compared with those of the classical boost converter both under open-loop and under closed-loop operating conditions. The results clearly demonstrate the superior dynamic performance of the proposed converter. The proposed converter can be used in applications wherever fast-response boost action is needed.