A three-switch high-voltage converter

A novel single active switch two-diodes high-voltage converter is presented. This converter can operate into a capacitor-diode voltage multiplier, which offers simpler structure and control, higher efficiency, reduced electromagnetic interference (EMI), and size and weight savings compared with traditional switched-mode regulated voltage multipliers. Two significant advantages are the continuous input current and easy isolation extension. The new converter is experimentally verified. Both the steady-state and dynamic theoretical models are correlated well with the experimental dat

A Mode-Based Averaged Power Converter Model for Large Transients

Power converters employ high-frequency switching between multiple switch states, each of which causes the system to exhibit a different dynamic behavior. Averaged models are a common simplification used for describing the behavior in one or two specific cycles of switch states, also called operating modes. In this context, we propose extending the method of Sun et al. (2001), which allows averaging in two operating modes, to a converter model with four operating modes. We show in simulations that our model results in a reasonable approximation of the true moving average of the original switching converter model during large transients that pass through multiple operating modes

A general approach to synthesis and analysis of quasi-resonant converters

A method for systematic synthesis of quasi-resonant (QR) topologies by addition of resonant elements to a parent pulse-width modulation (PWM) converter network is proposed. It is found that there are six QR classes with two resonant elements, including two novel classes. More complex QR converters can be generated by a recursive application of the synthesis method. Topological definitions of all known and novel QR classes follow directly from the synthesis method and topological properties of PWM parents. The synthesis of QR converters is augmented by a study of possible switch realizations and operating modes. In particular, it is demonstrated that a controllable rectifier can be used to accomplish the constant-frequency control in all QR classes. Links between the QR converters and the underlying PWM networks are extended to general DC and small-signal AC models in which the model of the PWM parent is explicitly exposed. Results of steady-state analyses of selected QR classes and operating modes include boundaries of operating regions, DC characteristics, a comparison of switching transitions and switch stresses, and a discussion of relevant design trade-offs

Topological issues in single-phase power factor correction

The equipment connected to an electricity distribution network usually needs some kind of power conditioning, typically rectification, which produces a nonsinusoidal line current due to the nonlinear input characteristic. With the steadily increasing use of such equipment, line current harmonics have become a significant problem. Their adverse effects on the power system are well recognized. They include increased magnitudes of neutral currents in three-phase systems, overheating in transformers and induction motors, as well as the degradation of system voltage waveforms. Several international standards now exist, which limit the harmonic content due to line currents of equipment connected to electricity distribution networks. As a result, there is the need for a reduction in line current harmonics, or Power Factor Correction - PFC. In this dissertation, we address several issues concerning the application to single-phase PFC of various high-frequency switching converter topologies. The inherent PFC properties of second-order switching converters operating in Discontinuous Inductor Current Mode - DICM are well known, and Boost converters are widely used. However, their output voltage is always higher than the amplitude of the rectified-sinusoid input voltage. In addition, it is expected that the level of the differential-mode EMI is much higher in DICM, as compared to the Continuous Inductor Current Mode - CICM. Therefore, we first investigated the requirements for the EMI filter for a PFC stage based on a Boost converter operating in DICM. The high-level of differential-mode EMI that is associated with DICM operation prompted our interest to investigate the application of two-switch fourth-order converters for PFC. The switching cell of these converters contains two inductors, which can operate in DICM or in CICM, and one capacitor, which can operate in Discontinuous Capacitor Voltage Mode - DCVM or in Continuous Capacitor Voltage Mode - CCVM. As a consequence, in these topologies several combinations of operating modes can be obtained, which have characteristics that otherwise cannot be obtained in second-order switching converters. We analyze three fourth-order topologies operating in DCVM and CICM, which have both an input current with reduced high-frequency content and an inherent PFC property. One of the converters, i.e. the Buck converter with an LC input filter, is then selected for a more detailed analysis. In addition, a fourth-order topology with galvanic isolation and operating in DCVM and CICM is presented and analyzed, as well. We also consider the operation in CCVM and CICM, which is analyzed for a fourth-order topology with step-down conversion ratio. The 'zero-ripple' technique is applied to obtain an input current having a very low high-frequency content, and average current mode control is used to shape the input current. Methods for improving the efficiency of the PFC stage are addressed, too. We compare several Boost-type topologies that have lower conduction losses than the combined diode bridge and Boost converter, as well as one fourth-order topology that is able to operate with bipolar input voltage, in other words it can perform direct AC/DC conversion. Finally, we propose a novel Zero Voltage Transition - ZVT topology, which reduces the switching losses by creating zero voltage switching conditions at the turn-on of the active switch. This topology can be used in a variety of converters, for DC/DC or PFC applications.reviewe

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

Development of a three-phase interleaved converter based on SEPIC DC-DC converter operating in discontinuous conduction mode for ultra-fast electric vehicle charging stations

One of the main challenges that impact transportation systems electrification is their batteries' charging process. This work presents the development of a three-phase ultra-fast Electric Vehicle (EV) charger based on the SEPIC converter. Since SEPIC operating in Discontinuous Conduction Mode (DCM) is usually recommended for low-power applications, this work proposes a scheme for its employment in high-power EV chargers. This is achieved through three single-phase modules of interleaved SEPIC converters. The presented scheme ensures reducing the stresses on the semiconductor devices since the power is divided over the interleaved modules. The design addresses DCM operation in terms of both capacitor voltage and inductor current (DCVM and DICM, respectively). This paper examines the analysis of the proposed converter and the small-signal modelling. Also, the converter efficiency is assessed. A Constant Current (CC) charging approach is deployed for charging the EV battery. The validation of the designs is explored through simulation results using MATLAB/Simulink platform. A 4 kW experimental prototype for the interleaved SEPIC DC-DC converter is built to verify the claimed contributions with 92% efficiency.Qatar Foundation; Qatar National Research FundScopu

A review on mitigation technologies of low frequency current ripple injected into fuel cell and a case study

© 2020 Hydrogen Energy Publications LLC This paper reviews the state-of-the-art of mitigation technologies of low frequency current ripple (LFCR) injected into fuel cell (FC). Although there are their own merits and demerits, the optimized LFCR control techniques and topology structures are characterized in many aspects like performance, durability, reliability and lifetime of FC. Three mains topologies and mitigation methods of LFCR have been investigated based on the literature review, which are the passive compensation methods, active compensation methods, and passive and active hybrid compensation methods. Some rules based tables are set to evaluate the LFCR against the topologies, control strategies, current ripple, application and advantages/limitations. Moreover, the mitigation control strategies are compared side by side with their specific applications in FC system. To select and implement them, this review can provide a reference and basis for the researchers in related fields. Finally, a case study in an uninterruptible power supply application is conducted

Design of robust controllers for telecom power supplies

A Telecom power supply is studied and analyzed from control system viewpoint. It consists of three stages: AC/DC rectifier, a backup battery, and a Telecom load. The AC/DC rectifier stage can be composed of paralleled DC/DC converters preceded by paralleled AC/DC converters. However, paralleled DC/DC converters are only considered in this thesis because they constitute the main dynamics in practice. A system of paralleled DC/DC converters operating in continuous inductor current mode with either voltage mode control or peak current mode control are modeled and analyzed using state-space representation. The H∞ control design is used in order to guarantee the robust stability and robust performance of the system in spite of different uncertainties. Also the H∞ loop-shaping design is used to design robust controllers in the presence of uncertainties. μ-analysis is used to evaluate the robustness of the system. Simulation results are presented to demonstrate the control design procedure and to compare between the two approaches presented. A Telecom power system can be composed of voltage-loop and current-loop subsystems. The multi-input-multi-output proportional-integral-derivative (PID) controller is first designed achieving robust stability and robust performance of the voltage-loop. Then, the multi-input-multi-output proportional-integral (PI) controller for current-loop is designed to achieve robust stability and robust performance of the overall system. μ-analysis is used to evaluate the robustness of PID and PI controllers. Simulation results are also presented to demonstrate and validate the control design. The required output characteristic of a Telecom power system contains three modes of operation: constant-voltage, modified constant-power, and constant-current modes. This nonlinear operation can be achieved by using the fuzzy-logic approach. A fuzzy PID-like controller is implemented to achieve the robust output voltage in spite of load disturbances. A fuzzy PI-like controller is implemented to ensure the overload protection reaching the optimal output characteristic of a Telecom power system. Also the internal-model control (IMC) method is applied to basic DC/DC converters: buck, boost, and buck-boost converters. IMC scheme is used to improve the dynamic performance of basic converters by achieving a robust output voltage against line and load disturbances. Simulations show good dynamic performance of the IMC controller.reviewe

Stability challenges and solutions in current-mode controlled power electronic converters

This dissertation focuses on stability issues in single-staged and multi-staged current controlled power electronic converters. Most current-mode control (CMC) approaches suffer from sub-harmonic oscillations. An external ramp is usually added to solve this problem. However, to guarantee stability this ramp has to be designed for the worst possible case which consequently over damps the response. Adaptive slope compensation (ASC) methods are the solution for this problem. In paper 1 of this dissertation, first three ASC methods will be investigated and analyzed through their small signal models. Then, through simulation analyses and experimental test of a variable-input voltage converter the results will be validated. Two of the methods studies in the first paper are peak CMC methods and the last one is called the projected cross point control (PCPC) approach. This method is relatively new. Therefore, a detailed discussion of the principles of operation of PCPC will be presented in paper 2. In addition, the small signal model of PCPC is developed and discussed through simulation and experimental analyses in the second paper of this dissertation. Peak, average, and hysteresis CMC schemes are used for comparison. In paper 3, the stability issues which arise in multistage converters will be addressed. A solid state transformer (SST) as an example of a multistage converter will be studied. A comprehensive small signal modeling will be conducted which helps for stability analysis of SST. Time domain simulations in Computer Aided Design software (PSCAD) are presented which validates the frequency domain analysis --Abstract, page iv

Power Factor Improvement of Single Phase AC-DC System using Parallel Boost Converter

Power factor in an AC electrical power system is described as the ratio of the actual power passing though the load to the virtual power flowing through the circuit or the cosine angle of the potential and charge of an AC circuit. A phase difference Ø exists between the potential and charge of an AC circuit and cosine which is called the circuit’s power factor. Suppose we get an inductive circuit we generally get the lagging by the voltage and that will be called a lagging power factor. And suppose we get the capacitive circuit then the current will be leading by the voltage and that will be referred as a leading power factor. The usage of power electronic system has reached to a new application stage that include residential, commercial, and aerospace and many others. Power electronic interfaces e.g. Switch Mode Power Supplies (SMPS) have proved to be superior over traditional linear power supplies. However their nonlinear behavior puts a question mark on their efficiency. The current drawn by the SMPS from the line is distorted resulting in a high Total Harmonic Distortion (THD) and low Power Factor (PF). Other adverse effects on the power system includes increased magnitudes of neutral current in three phase systems, overheating of transformers and induction motors etc. Therefore there is a continuous need of power factor improvement and reduction of line current harmonics. A large range of PFC circuits have been proposed with diverse operating modes to solve the situation. These PFC circuits adjust the waveforms of the current in the input side so that the maximum power can be tapped from the supplies. For every equipment the load should try to match a resistive one as closely as possible, only then the PF will be near to unity as there will be reduction of reactive power in the circuit. The current in this situation is free from all the lower as well as higher order harmonics thus copies the input voltage waveform. So this causes the current in the circuit to be at the lowest possible value to do the same work. As a result, the losses associated with circuit are reduced. Hence the consumption in power is reduced greatly. Boost converter accomplishes this active power-factor correction (ACMC) in discontinuous as well as in continuous modes. Simulation of a single phase bridge converter without using any converter is performed first. Then a current control circuit and a voltage control circuit were added to the boost converter which improved the input THD. This project aims to develop a circuit for power factor improvement using two Boost converters connected in parallel. It is based on the power sharing method to improve the current quality and to reduce the switching losses. In this method current in one circuit has to keep up with the one in parallel to it