Two-sample PLL with improved frequency response applied to single-phase current sensorless bridgeless PFCs

A new implementation of the recently proposed fixed-frequency two-sample (2S) quadrature generation subsystem (QSG) digital Phase Locked Loop PLL, applicable to single-phase Power Factor Correction (PFC), is proposed. Its characteristics are high accuracy and low computational burden. The proposed PLL includes a frequency feedback loop to improve the synchronization under line frequency variations. Its performance within a digital controller of a current sensorless bridgeless PFC is evaluated by simulations and experimentally. The obtained results are compared with previously published PLLs in the literature.This work has been supported by the Spanish Ministry of Economy and Competitiveness under grant TEC2014-52316-R ECOTREND Estimation and Optimal Control for Energy Conversion with Digital Devices

Review on State-of-the-Art Unidirectional Non-Isolated Power Factor Correction Converters for Short-/Long-Distance Electric Vehicles

Electrification of the transportation sector has originated a worldwide demand towards green-based refueling infrastructure modernization. Global researches and efforts have been pondered to promote optimal Electric Vehicle (EV) charging stations. The EV power electronic systems can be classified into three main divisions: power charging station configuration (e.g., Level 1 (i.e., slow-speed charger), Level 2 (i.e., fast-speed charger), and Level 3 (i.e., ultra-fast speed charger)), the electric drive system, and the auxiliary EV loads. This paper emphasizes the recent development in Power Factor Correction (PFC) converters in the on-board charger system for short-distance EVs (e.g., e-bikes, e-trikes, e-rickshaw, and golf carts) and long-distance EVs (passenger e-cars, e-trucks, and e-buses). The EV battery voltage mainly ranges between 36 V and 900 V based on the EV application. The on-board battery charger consists of either a single-stage converter (a PFC converter that meets the demands of both the supply-side and the battery-side) or a two-stage converter (a PFC converter that meets the supply-side requirements and a DC-DC converter that meets the battery-side requirements). This paper focuses on the single-phase unidirectional non-isolated PFC converters for on-board battery chargers (i.e., Level 1 and Level 2 charging infrastructure). A comprehensive classification is provided for the PFC converters with two main categories: (1) the fundamental PFC topologies (i.e., Buck, Boost, Buck-Boost, SEPIC, C k, and Zeta converters) and (2) the modified PFC topologies (i.e., improved power quality PFC converters derived from the fundamental topologies). This paper provides a review of up-to-date publications for PFC converters in short-/long-distance EV applications.Qatar National Research FundScopu

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

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

An Integrated Single-phase On-board Charger

With the growing demand for transportation electrification, plug-in electric vehicles (PEVs), and plug-in hybrid electric vehicles (PHEVs), cumulatively called electric vehicles (EVs) are drawing more and more attention. The on-board charger (OBC), which is the power electronics interface between the power grid and the high voltage traction battery, is an important part for charging EVs. Besides the OBC, every EV is equipped with another separate power unit called the auxiliary power module (APM) to charge the low voltage (LV) auxiliary battery, which supplies all the electronics on car including audio, air conditioner, lights and controllers. The main target of this work is a novel way to integrate both units together to achieve a charger design that is not only capable of bi-directional operation with high efficiency, but also higher gravimetric and volumetric power density, as compared with those of the existing OBCs and APMs combined. To achieve this target, following contributions are made: (i) a three-port integrated DC/DC converter, which combines OBC and APM together through an innovative integration method; (ii) an innovative zero-crossing current spike compensation for interleaved totem pole power factor correction (PFC) and (iii) a new phase-shift based control strategy to achieve a regulated power flow management with minimum circulating losses

Analysis and Design of High Efficiency Grid-to-Vehicle (G2V) Plug-in Chargers for Local e-Transportation

Electric transportation worldwide has witnessed a tremendous increase in the use of electric vehicles (EV's) due to increased awareness of environmental issues. Road EV's compromise a broad spectrum of vehicles right from two-wheelers three-wheelers (rickshaws/Auto/Trio), cars and electric buses. E-Rickshaw has gained popularity in the Asian market post-2010 because of their symbolic resemblance with traditional auto-rickshaw. The fast growth of the market is principally pushed by the low ownership cost of electric three-wheelers, falling battery prices, and favorable government policies and support. These EVs run on low-cost 48 V, 120 Ah lead acid battery packs having low depth-of-discharge (DOD). Hence, frequent battery charging becomes essential for such EVs. Conventional battery chargers available in the market utilize flyback converter based topologies in order to charge such battery packs. On one hand such battery chargers are easy to implement, these topologies fail to achieve unity power factor (UPF) operation leading to high total harmonic distortion (THD) and poor input power quality at the input. Thus active power factor correction (PFC) becomes a vital constituent in AC-DC converters. By understanding the constraints posed by continuous current mode (CCM) based battery chargers, the proposed converters are designed to operate in discontinuous current mode (DCM) because of its evident benefits such as inherent PFC, zero current turn-on and zero diode reverse recovery losses. By omitting sensors at the input and utilizing only the output sensors, regulated voltage or current can be obtained which makes the system cost-effective and improves its reliability and robustness to high frequency noise. This thesis presents both isolated and non-isolated battery charger for local e-transportation EVs utilizing 48 V lead acid battery pack. At first, a non-isolated single-stage interleaved buck-boost float charger is proposed by considering the advantages such as reduced current stresses, minimum number of semiconductor devices and absence of bulky high frequency transformer. DCM operation of the proposed converter ensure UPF operation for variable input voltage and utilizing just a single sensor makes this charger configuration economical and easy to implement. However, such a configuration had high current stress on the semiconductor devices leading to increased thermal requirement and reduced efficiency at light loads. Thus addressing these problems, a high efficiency two-stage battery charger is proposed. The battery charger uses an interleaved DCM buck-boost converter in order to achieve PFC at variable input voltage, whereas the second stage is an unregulated half-bridge LLC resonant converter which provides isolation as well as soft-switching for the primary switches. Synchronous rectification (SR) along with only capacitive filter is used on center tapped transformer secondary to improve converter efficiency. Due to DCM of the front-end AC-DC converter achieves zero current turn-on of the switches and DC-DC converter switches achieve zero voltage turn-on because of the LLC resonant. The proposed battery charger implements constant current (CC) and constant voltage (CV) method of charging using simple PI controllers, thus making it suitable for commercial use. Small signal models for both the battery charger configurations are developed using the current injected equivalent circuit approach and a detailed controller design is illustrated. Simulation results using PSIM11.1 software and experimental results from proof-of-concept laboratory hardware prototypes are provided in order to validate the reported analysis and design which demonstrates their performance

Soft-Switching Techniques of Power Conversion System in Automotive Chargers

abstract: This thesis investigates different unidirectional topologies for the on-board charger in an electric vehicle and proposes soft-switching solutions in both the AC/DC and DC/DC stage of the converter with a power rating of 3.3 kW. With an overview on different charger topologies and their applicability with respect to the target specification a soft-switching technique to reduce the switching losses of a single phase boost-type PFC is proposed. This work is followed by a modification to the popular soft-switching topology, the dual active bridge (DAB) converter for application requiring unidirectional power flow. The topology named as the semi-dual active bridge (S-DAB) is obtained by replacing the fully active (four switches) bridge on the load side of a DAB by a semi-active (two switches and two diodes) bridge. The operating principles, waveforms in different intervals and expression for power transfer, which differ significantly from the basic DAB topology, are presented in detail. The zero-voltage switching (ZVS) characteristics and requirements are analyzed in detail and compared to those of DAB. A small-signal model of the new configuration is also derived. The analysis and performance of S-DAB are validated through extensive simulation and experimental results from a hardware prototype. Secondly, a low-loss auxiliary circuit for a power factor correction (PFC) circuit to achieve zero voltage transition is also proposed to improve the efficiency and operating frequency of the converter. The high dynamic energy generated in the switching node during turn-on is diverted by providing a parallel path through an auxiliary inductor and a transistor placed across the main inductor. The paper discusses the operating principles, design, and merits of the proposed scheme with hardware validation on a 3.3 kW/ 500 kHz PFC prototype. Modifications to the proposed zero voltage transition (ZVT) circuit is also investigated by implementing two topological variations. Firstly, an integrated magnetic structure is built combining the main inductor and auxiliary inductor in a single core reducing the total footprint of the circuit board. This improvement also reduces the size of the auxiliary capacitor required in the ZVT operation. The second modification redirects the ZVT energy from the input end to the DC link through additional half-bridge circuit and inductor. The half-bridge operating at constant 50% duty cycle simulates a switching leg of the following DC/DC stage of the converter. A hardware prototype of the above-mentioned PFC and DC/DC stage was developed and the operating principles were verified using the same.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Soft-Switched Step-Up Medium Voltage Power Converters

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

Implementation of Sliding Mode Control in a Semi Bridgeless Boost Converter with Power Factor Correction

ABSTRACT: This paper proposes a new sliding surface for controlling a Semi-Bridgeless Boost Converter (SBBC) which simultaneously includes Power Factor Correction (PFC) and DC bus regulation. The proposed sliding surface is composed of three terms: First, a normalized DC voltage error term for controlling DC bus and rejecting DC voltage disturbances, normalization was performed for increasing system robustness during start-up and large disturbances. Second, an AC current error term for implementing a PFC scheme and guarantying fast current stabilization during disturbances. Third, an integral of AC current error term for increasing the stability of the overall system. Also, an Adaptive Hysteresis Band (AHB) is implemented for keeping constant the switching frequency and reducing the THDi. The proposed sliding surface was validated by means of sliding mode conditions and Lyapunov stability criteria. Simulations for comparing performance were performed between: a cascade PI control, a hybrid PI-Sliding Mode Control (PI-SMC), and Sliding Mode Control (SMC) with the proposed surface; additionally, it is presented an stability analysis for the proposed surface in start-up and under large perturbations. It is also presented experimental results for PI-SMC and SMC implemented in a SBBC prototype. The proposed surface implemented in the SMC presents the best dynamic behavior removing DC over voltages and responding faster under DC voltage changes or DC load current perturbations

Soft-Switched Step-Up Medium Voltage Power Converters

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

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