Improved Non-Isolated Bidirectional DC-DC Converter Assisted with an Active Resonant Network

OP VVV Electrical Engineering Technologies with High-Level of Embedded Intelligence CZ.02.1.01/0.0/0.0/18_069/0009855 and project No. SGS-2021-021This paper proposes a new non-isolated bidirectional dc-dc converter (NI-BDC) with an auxiliary resonant network (ARN) that is typically operated in both boost and buck modes. Regardless the direction of power flow, soft-switching capabilities such as zero voltage switching (ZVS) and zero current switching (ZCS) conditions has been obtained under light and heavy loads. This converter avoids the need of coupled inductors as against conventional converters thus reducing the size of the converter and minimizes the device count. The auxiliary resonant network mainly consisting of resonant inductor, capacitor, auxiliary switch and a diode. Furthermore, the zero voltage switching and zero current switching conditions have been achieved in both boost and buck modes that reduces reverse recovery conduction period of the body diodes of all the power switches. The proposed converter operates with soft-switching at constant switching frequency giving continuous inductor current. The detailed operating principles for boost and buck modes are described. The theoretical analysis and simulation results are presented

A novel fuzzy logic control for a zero current switching-based buck converter to mitigate conducted electromagnetic interference

This research provides a new control technique for mitigating conducted electromagnetic interference (EMI) in a buck converter designed for solar applications. Indeed, hard-switching direct current to direct current (DC-DC) converters, commonly used in industrial applications, pose a significant risk to the surrounding environment regarding electromagnetic compatibility (EMC). Usually, the fast-switching phase induces abrupt changes in current and voltage, which adds to substantial electromagnetic interference in both conducted and radiated modes and excessive auditory noise. An architecture based on the duality of soft-switching topology and fuzzy logic control technology is developed to address these issues. On the one hand, resonant circuit topologies are used to induce switches to achieve soft switching conditions, which subsequently lessen the effects of EMI. On the other hand, the adoption of fuzzy logic control technology is interesting since it can reduce electrical stresses during switching. Furthermore, the simulation results show that zero current switching (ZCS) soft-switching closed-loop fuzzy logic converters outperform typical open-loop converters and soft-switching closed-loop converters with proportional integral (PI) control in terms of EMC requirements

A unified analysis of PWM converters in discontinuous modes

Three discontinuous operating modes of PWM (pulsewidth modulated) converters are considered: the discontinuous inductor current mode (DICM), the discontinuous capacitor voltage mode (DCVM), and a previously unidentified mode called the discontinuous quasi-resonant mode (DQRM). DC and small-signal AC analyses are applicable to all basic PWM converter topologies. Any particular topology is taken into account via its DC conversion ratio in the continuous conduction mode. The small-signal model is of the same order as the state-space averaged model for the continuous mode, and it offers improved predictions of the low-frequency dynamics of PWM converters in the discontinuous modes. It is shown that converters in discontinuous modes exhibit lossless damping similar to the effect of the current-mode programming

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

Bidirectional High Current DC/DC Converters for Capacitive Deionisation Water Treatment

This thesis proposes three new DC/DC topologies and related technologies to control salt removal from water sources using the capacitive deionisation (CDI) technique. These technologies are critical in improving energy utilization, higher product yield and water recovery, and simpler design. A lossless bidirectional current sensing circuit is proposed. The proposed circuit avoids the use of conventional current shunt and extracts the current information from the winding resistance of the inductor (DCR) without introducing excessive conduction loss. Moreover, this improved DCR current sensing circuit has a high bandwidth and a low error over the entire range, even near the zero-crossing. A successful application of the proposed circuit is demonstrated in a 5-phase interleaved Buck/Boost bidirectional converter. The same converter has been used for CDI cell characterization. A time-domain analysis of the three-phase interleaved LLC topology is presented. The proposed analysis method reveals various facts that cannot be explained with the conventional Fundamental Harmonic Analysis (FHA) methods, including the number of resonant frequencies. The theory also gives a more accurate prediction of the gain-frequency-power relationship and the soft-switching conditions. Extensive simulations and experiments validate the correctness of the theory. Two new switch-capacitor two-phase interleaved flyback converters are proposed, which can invert the polarity of the input voltage and efficiently supply a high current while inheriting all the advantages of the Buck and Boost counterparts, such as the intrinsic current sharing, high conversion ratio, lower current ripple, and reduced switching loss. The operating principle, key waveform, simulation, and experimental results are presented. Finally, a new two-phase interleaved bipolar four-quadrant converter is proposed. Without sacrificing efficiency, it enables high-current discharge at extremely low cell voltage and features seamless transition. The proposed converter combines the switch-capacitor flyback converter with the switched-capacitor Buck converter in a creative manner so that the input and the output share a common ground reference while featuring a bipolar output, which can simplify the wiring when connecting more units in parallel. A switching pattern is proposed to enable a seamless transition between different operation modes. An auxiliary switching network is introduced to correct the loss of natural inductor current balancing in the transition mode

DC-DC power converter research for Orbiter/Station power exchange

This project was to produce innovative DC-DC power converter concepts which are appropriate for the power exchange between the Orbiter and the Space Station Freedom (SSF). The new converters must interface three regulated power buses on SSF, which are at different voltages, with three fuel cell power buses on the Orbiter which can be at different voltages and should be tracked independently. Power exchange is to be bi-directional between the SSF and the Orbiter. The new converters must satisfy the above operational requirements with better weight, volume, efficiency, and reliability than is available from the present conventional technology. Two families of zero current DC-DC converters were developed and successfully adapted to this application. Most of the converters developed are new and are presented

A comparative study of electric power distribution systems for spacecraft

The electric power distribution systems for spacecraft are compared concentrating on two interrelated issues: the choice between dc and high frequency ac, and the converter/inverter topology to be used at the power source. The relative merits of dc and ac distribution are discussed. Specific converter and inverter topologies are identified and analyzed in detail for the purpose of detailed comparison. Finally, specific topologies are recommended for use in dc and ac systems

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

One-cycle control of switching converters

A new large-signal nonlinear control technique is proposed to control the duty-ratio d of a switch such that in each cycle the average value of a switched variable of the switching converter is exactly equal to or proportional to the control reference in the steady-state or in a transient. One-cycle control rejects power source perturbations in one switching cycle; the average value of the switched variable follows the dynamic reference in one switching cycle; and the controller corrects switching errors in one switching cycle. There is no steady-state error nor dynamic error between the control reference and the average value of the switched variable. Experiments with a constant frequency buck converter have demonstrated the robustness of the control method and verified the theoretical predictions. This new control method is very general and applicable to all types of pulse-width-modulated, resonant-based, or soft-switched switching converters for either voltage or current control in continuous or discontinuous conduction mode. Furthermore, it can be used to control any physical variable or abstract signal that is in the form of a switched variable or can be converted to the form of a switched variable

Realization of a 10 kW MES power to methane plant based on unified AC/DC converter

This paper presents a galvanic isolated multi output AC/DC topology that is suitable for Microbial electrosynthesis (MES) based Power to Methane energy storage systems. The presented scheme utilizes a three phase back to back converters, a single-input and multiple-output three phase transformer, single diode rectifiers and buck converters that employ a proper interconnection between MES cells and the mains. The proposed topology merges all the required single phase AC/DC converters as a unified converter which reduces the overall system size and provides system integrity and overall controllability. The proposed control scheme allows to achieve the following desired goals:1) Simultaneous control of all cells; 2) Absorbing power from the grid and covert to methane when the electricity price goes down; 3) the power factor and the quality of grid current is under control; 4) Supplying MES cells at the optimal operating point. For verification of system performance, Real time simulation results that are obtained from a 10-kW MES energy storage are presented.Postprint (author's final draft