94 research outputs found

    Totem-pole bridgeless boost PFC rectifier using series-parallel resonant network

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    A new series-parallel resonant bridgeless boost (SPBBR) power factor correction (PFC) rectifier is proposed in this paper. It is based on a totem-pole bridgeless boost (TPBLB) configuration which allows bi-directional current to flow during resonance to provide soft-switching for all semiconductor devices. Therefore, no additional active switch is needed. The resonant is produced by a resonant network which is placed before the output capacitor. A detailed analysis of the converter operation and control is presented. Design considerations and parameter values determination are also given. Simulation results is used to verify the theoretical analysis of the SPBBR

    Bridgeless Step/Up Unity Power Factor Rectifier for High Voltage Applications

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    Power electronic devices with front- end rectifier are widely used in computer, communication and electric vehicle industries. These rectifiers are nonlinear in nature and generate current harmonics which pollute utility power. International harmonic standards (e.g., IEC 61000-3-2 and EN 61000-3-2) have been put in place to confine power pollution. These standards limit the current harmonics generated by loads to a specified threshold depending on load power and application. In other words, a high power factor is required. Power supplies with active power factor correction (PFC) techniques are becoming necessary for many types of electronic equipment to meet the harmonic regulations and standards. However, classical PFC schemes have lower efficiency due to significant losses in the diode bridge. Several bridgeless topologies have been introduced to decrease diode bridge conduction losses. Most of the step-up PFC rectifiers utilize boost converter at their front end due to its natural PFC capability. In this thesis, a new bridgeless PFC topology based on Cuk converter is presented. Similar to Cuk converter, the proposed topology offers several advantages in PFC applications, such as easy implementation of transformer isolation, inherent inrush current limitation during start-up and overload conditions, and lower electromagnetic interference (EMI). These advantages make the proposed topology a viable solution for high voltage DC loads such as electric vehicle battery charger. Chapter III presents steady state analysis for the proposed rectifier. The rectifier is analyzed only during the positive half of the line frequency due to symmetry. Design procedure, simulation and measurements to verify the capability of the rectifier are presented in Chapter IV. Harmonics content and efficiency of the proposed rectifier versus conventional Cuk full bridge PFC rectifier are also presented

    High Efficiency PFC Frontend for Class-D Amplifiers

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    Soft-Switched Step-Up Medium Voltage Power Converters

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    With a ten-year average annual growth rate of 19 percent, wind energy has been the largest source of new electricity generation for the past decade. Typically, an offshore wind farm has a medium voltage ac (MVac) grid that collects power from individual wind turbines. Since the output voltage of a wind turbine is too low (i.e., typically 400 690 V) to be connected to the MVac grid (i.e., 20 40 kV), a heavy line-frequency transformer is used to step up the individual turbines output voltage to the MV level. To eliminate the need for bulky MVac transformers, researchers are gravitating towards the idea of replacing the MVac grid with a medium voltage dc (MVdc) grid, so that MV step-up transformers are replaced by MV step-up power electronic converters that operate at the medium frequency range with much lower size and weight. This dissertation proposes a class of modular step-up transformerless MV SiC-based power converters with soft-switching capability for wind energy conversion systems with MVdc grid. This dissertation consists of two parts: the first part focuses on the development of two novel groups of step-up isolated dc-dc MV converters that utilize various step-up resonant circuits and soft-switched high voltage gain rectifier modules. An integrated magnetic design approach is also presented to combine several magnetic components together in the modular high voltage gain rectifiers. The second part of this dissertation focuses on the development of several three-phase ac-dc step-up converters with integrated active power factor correction. In particular, a bridgeless input ac-dc rectifier is also proposed to combine with the devised step-up transformerless dc-dc converters (presented in the first part) to form the three-phase soft-switched ac-dc step-up voltage conversion unit. In each of the presented modular step-up converter configurations, variable frequency control is used to regulate the output dc voltage of each converter module. The operating principles and characteristics of each presented converter are provided in detail. The feasibility and performance of all the power converter concepts presented in this dissertation are verified through simulation results on megawatts (MW) design examples, as well as experimental results on SiC-based laboratory-scale proof-of-concept prototypes

    Single-Sensor DCM PFC Based Onboard Chargers for Low Voltage Electric Vehicles

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    Grid-connected plug-in electric vehicles (PEVs) are considered as one of the most sustainable solutions to substantially reduce both the oil consumption and greenhouse gas emissions. Electric vehicles (EVs) are broadly categorized into low power EVs (48/72 V battery) and high power EVs (450/650 V battery). Low power EVs comprise two-wheelers, three-wheelers (rickshaws), golf carts, intra-logistics equipment and short-range EVs whereas high power EVs consist of passenger cars, trucks and electric buses. Charger, which is a power electronic converter, is an important component of EV infrastructures. These chargers consist of power converters to convert AC voltage (grid) to constant DC voltage (battery). The existing chargers are bulky, have high components’ count, complex control system and poor input power quality. Henceforth, to overcome these drawbacks, this thesis focuses on the onboard charging solutions (two-stage isolated and single-stage non-isolated) for the low voltage battery EVs. Power factor correction (PFC) is the fundamental component in the EV charger. Considering the specific boundaries of the continuous conduction mode (CCM) operation for AC-DC power conversion and their complexity, the proposed chargers are designed to operate in discontinuous conduction mode (DCM) and benefiting from the characteristics like built-in PFC, single sensor, simple control, easy implementation, inherent zero-current turn-on of the switches, and inherent zero diode reverse recovery losses. Proposed converters can operate for the wide input voltage range and the output voltage is controlled by a single sensor-based single voltage control loop making the control simple and easy to implement, and improves the system reliability and robustness. This thesis studies and designs both single-stage non-isolated and two-stage isolated onboard battery chargers to charge a 48 V lead-acid battery pack. At first, a non-isolated single-stage single-cell buck-boost PFC AC-DC converter is studied and analyzed that offers reduced components’ count and is cost-effective, compact in size and illustrates high efficiency. While the DCM operation ensures unity power factor (UPF) operation at AC mains without the use of input voltage and current sensors. However, they employ high current rated semiconductor devices and the use of diode bridge rectifier suffers from higher conduction losses. To overcome these issues, a new front-end bridgeless AC-DC PFC topology is proposed and analyzed. With this new bridgeless front-end topology, the conduction losses are significantly reduced resulting in improved efficiency. The low voltage stress on the semiconductor devices are observed because of the voltage doubler configuration. Later, an isolated two-stage topology is proposed. The previously proposed bridgeless buck-boost derived PFC converter is employed followed by an isolated half-bridge LLC resonant converter. Loss analysis is done to determine optimal DC-link voltage for the efficient operation of the proposed conversion. The converters' steady-state operation, DCM condition, and design equations are reported in detail. The small-signal models for all the proposed topologies using the average current injected equivalent circuit approach are developed, and detailed closed-loop controller design is illustrated. The simulation results from PSIM 11.1 software and the experimental results from proof-of-concept laboratory hardware prototypes are provided in order to validate the reported analysis, design, and performance

    Soft-Switched Step-Up Medium Voltage Power Converters

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    With a ten-year average annual growth rate of 19 percent, wind energy has been the largest source of new electricity generation for the past decade. Typically, an offshore wind farm has a medium voltage ac (MVac) grid that collects power from individual wind turbines. Since the output voltage of a wind turbine is too low (i.e., typically 400 690 V) to be connected to the MVac grid (i.e., 20 40 kV), a heavy line-frequency transformer is used to step up the individual turbines output voltage to the MV level. To eliminate the need for bulky MVac transformers, researchers are gravitating towards the idea of replacing the MVac grid with a medium voltage dc (MVdc) grid, so that MV step-up transformers are replaced by MV step-up power electronic converters that operate at the medium frequency range with much lower size and weight. This dissertation proposes a class of modular step-up transformerless MV SiC-based power converters with soft-switching capability for wind energy conversion systems with MVdc grid. This dissertation consists of two parts: the first part focuses on the development of two novel groups of step-up isolated dc-dc MV converters that utilize various step-up resonant circuits and soft-switched high voltage gain rectifier modules. An integrated magnetic design approach is also presented to combine several magnetic components together in the modular high voltage gain rectifiers. The second part of this dissertation focuses on the development of several three-phase ac-dc step-up converters with integrated active power factor correction. In particular, a bridgeless input ac-dc rectifier is also proposed to combine with the devised step-up transformerless dc-dc converters (presented in the first part) to form the three-phase soft-switched ac-dc step-up voltage conversion unit. In each of the presented modular step-up converter configurations, variable frequency control is used to regulate the output dc voltage of each converter module. The operating principles and characteristics of each presented converter are provided in detail. The feasibility and performance of all the power converter concepts presented in this dissertation are verified through simulation results on megawatts (MW) design examples, as well as experimental results on SiC-based laboratory-scale proof-of-concept prototypes

    Soft-Switched Step-Up Medium Voltage Power Converters

    Get PDF
    With a ten-year average annual growth rate of 19 percent, wind energy has been the largest source of new electricity generation for the past decade. Typically, an offshore wind farm has a medium voltage ac (MVac) grid that collects power from individual wind turbines. Since the output voltage of a wind turbine is too low (i.e., typically 400 690 V) to be connected to the MVac grid (i.e., 20 40 kV), a heavy line-frequency transformer is used to step up the individual turbines output voltage to the MV level. To eliminate the need for bulky MVac transformers, researchers are gravitating towards the idea of replacing the MVac grid with a medium voltage dc (MVdc) grid, so that MV step-up transformers are replaced by MV step-up power electronic converters that operate at the medium frequency range with much lower size and weight. This dissertation proposes a class of modular step-up transformerless MV SiC-based power converters with soft-switching capability for wind energy conversion systems with MVdc grid. This dissertation consists of two parts: the first part focuses on the development of two novel groups of step-up isolated dc-dc MV converters that utilize various step-up resonant circuits and soft-switched high voltage gain rectifier modules. An integrated magnetic design approach is also presented to combine several magnetic components together in the modular high voltage gain rectifiers. The second part of this dissertation focuses on the development of several three-phase ac-dc step-up converters with integrated active power factor correction. In particular, a bridgeless input ac-dc rectifier is also proposed to combine with the devised step-up transformerless dc-dc converters (presented in the first part) to form the three-phase soft-switched ac-dc step-up voltage conversion unit. In each of the presented modular step-up converter configurations, variable frequency control is used to regulate the output dc voltage of each converter module. The operating principles and characteristics of each presented converter are provided in detail. The feasibility and performance of all the power converter concepts presented in this dissertation are verified through simulation results on megawatts (MW) design examples, as well as experimental results on SiC-based laboratory-scale proof-of-concept prototypes

    A High Frequency, High Efficiency, High Power Factor Isolated On-board Battery Charger for Electric Vehicles

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    In this paper, a high frequency, high efficiency and high power factor isolated on-board battery charger is proposed. The proposed topology includes two parts, AC/DC power factor correction (PFC) circuit unit and DC/DC converter unit. For the PFC circuit, SiC based totem-pole interleaved bridgeless PFC is selected, the diode bridge rectifier is eliminated. In addition, it can operate in continuous conduction mode (CCM) thanks to the low reverse recovery losses of the SiC MOSFETs. Besides, the interleaved technology minimizes the input current ripple. The DC/DC converter unit is composed of two LLC resonant converters sharing the same full-bridge inverter with constant switching frequency. The outputs of two LLC resonant converters are connected in series. One of the LLC resonant converter is operating at the resonant frequency, which is the highest efficiency operation point; while magnetic control is adopted for the second LLC resonant converter to fulfill the duty of providing closed-loop control for constant voltage (CV) and constant current (CC) charge modes. The proposed topology can achieve zero voltage switching (ZVS) for all primary switches and zero current switching (ZCS) for all secondary diodes during both CC and CV modes. Furthermore, the constant switching frequency is simplified the electromagnetic interference (EMI) filter design. Simulation studies for 3.3kW power level and 100kHz switching frequency are performed, the simulation results are presented to verify the feasibility and validity of the proposed topology

    Totem-Pole Bridgeless Boost PFC Rectifier Using Series-Parallel Resonant Network

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    A new series-parallel resonant bridgeless boost (SPBBR) power factor correction (PFC) rectifier is proposed in this paper. It is based on a totem-pole bridgeless boost (TPBLB) configuration which allows bi-directional current to flow during resonance to provide soft-switching for all semiconductor devices. Therefore, no additional active switch is needed. The resonant is produced by a resonant network which is placed before the output capacitor. A detailed analysis of the converter operation and control is presented. Design considerations and parameter values determination are also given. Simulation results is used to verify the theoretical analysis of the SPBBR

    Wide Band Gap Power Semiconductor Devices and their Applications

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    DC power supplies are being widely used in almost every modern day appliance. Basic DC power supply should only consist of AC/DC rectification unit with bulk capacitor. But irregular current drawn by rectifier pollutes the power system. Standards related to power quality puts a limit on harmonics that are being injected by a device into power system. To comply with standards Power factor correction (PFC) circuits are employed with rectification unit. Addition of an extra unit, puts a limit on overall efficiency of power supply. Advent of Wide Band Gap (WBG) power semiconductor devices have provided us with the opportunity to improve the efficiency of existing electronic circuits with relatively simple control schemes. According to recent research, it has been forecasted that GaN based devices are ideal choice for medium voltage and high speed applications. However, SiC based devices are estimated to take over high voltage applications. Conventional PFC circuit based on bridged CCM average current controlled Boost converter was chosen for this study. Simulation was made to compare the performance of GaN, SiC and Si based switches. Results from simulation revealed that 38% reduction in switching losses can be achieved by using GaN HEMT instead of Si MOSFET. Practical evaluation was performed on Transphom Totem Pole PFC and All in One Power supply. Both of these devices are based on GaN HEMTs. Totem pole PFC is the major breakthrough achieved by GaN HEMT in the field of PFC circuit. Very low reverse recovery of switches made it possible to implement this circuit with very high efficiency for high power applications. 94% efficiency was observed during evaluation of DC power supply, which validates the claim of superior performance of WBG devices
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