Series-parallel Resonant Converter Research Articles

Design of 10 kW, 400 kHz AC Power Supply for Ferrite Inductively Coupled Plasma

This article describes the design and implementation of a 10 kW, 400 kHz ac power supply for a ferrite inductively coupled plasma (ICP) reactor. The developed power supply is composed of an ac inverter and a front-end converter not only to offer stable dc input voltage for the inverter but also to respond to the dynamic load characteristic of the plasma reactor. A brief introduction of a series-parallel resonant converter (SPRC) with a trapezoidal approximation and determining a design point considering a wide load range are described. In the case of the inverter, a low-loaded quality factor design method based on the analysis of a series-parallel resonant inverter (SPRI) to obtain high efficiency is proposed. With respect to the plasma ignition, a control logic without an additional plasma ignition circuit is proposed. Finally, the performance of the developed power supply is demonstrated under various experimental conditions including an experiment with a ferrite ICP load.

Accurate Steady-State Modeling and Design Based on State Trajectory Analysis for LCC Resonant Converter With Voltage Doubler Rectifier

The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> series–parallel resonant converter with a voltage doubler rectifier, widely used in X-ray machines, is required to meet an extremely wide output range. However, state-of-the-art models are based on fundamental harmonic approximation and cannot maintain good accuracy over the entire output range. The state trajectory method has the potential to achieve a full range of high accuracy without high complexity, but it only applies to simple topologies, like <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> with a full-bridge rectifier. For <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> with a voltage multiplier, the capacitors in the multiplier are involved in the resonance, which can be modeled as a five-element resonant circuit. Moreover, the conduction sequence of components in the minor mode is different from that in the major mode, which is usually ignored in the steady-state model. The influence of the output capacitance of power transistors on the state trajectory is so unclear that the model accuracy decreases considerably at high frequencies. In this article, the equivalent parallel resonant capacitance is derived through the current distribution. The steady-state model of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> converter with a voltage doubler rectifier is developed for both major mode and minor mode. The deviation of the state trajectory and modeling accuracy induced by the output capacitor is investigated. Based on the proposed model and device stress analysis, the design procedure for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> under a wide operation range is presented. The simulations and experiments verify the accuracy of the model and the validity of the design method. The simulation mismatches are less than 2.3% over the entire output range. The maximum experimental mismatch is 15%.

Optimal trajectory based start-up control of LCC resonant converter for X-ray generator applications

LCC series–parallel resonant converter (LCC-SPRC) is the preferred high voltage DC power supply (HVPS) topology for medical X-ray imaging generator applications, due to its advantage in wide operating ranges, and full-range soft switching capability. In this paper, an Input-Single-Output-Series (ISOS) type LCC-SPRC which utilizes the cascaded twelve-level rectifier as the interface with a 140 kV X-ray tube, is presented. However, the existing control strategies cannot meet the requirements of high-voltage generator output voltage response time for real industrial practice. By modeling LCC-SPRC with state plane trajectory analysis (SPTA), the start-up trajectory curve is precisely predicted. By adjusting the current limit band further, the operating mode can be improved to stabilize the initial state, regulating the state variables onto the optimized trajectory locus within the shortest time cycle. Experiment results based on a 140kV/42kW setup are presented to indicate the correctness and feasibility of the proposed method.

Designing of Higher-Order Series-Parallel resonant converter with improved ZVS under variable source condition for constant DC-bus System

Every Renewable based energy source requires an additional buffer unit to deliver power to either a standalone system or a grid system. Most of the time unit buffer either provides constant voltage DC-power or AC-power. Higher efficiency in the conversion process can only be achieved if ongoing losses of the buffer system are low. Square sine control approach for Higher-Order Series-Parallel resonant DC-DC Converter is presented in the paper which provides excellent results in both highly and lightly loaded conditions. This control also provides stable bandwidth for input voltage source acceptance which is mostly to be considered as a PV-based source. The strategy also enhances the reliability of the converter by providing a stable and most delightful way of soft switching triggering so as to maintain the output voltage by un-affecting the switching cycle of the Solid-State Semi-conducting Device (SSSD). Selection for the components used in converter design was also studied with a susceptive case study. Further to this control for the entire converter unit is maintained to single variable control so as to reduce the complexity of the system and enhance efficiency. The simulated results of the programmable single variable square sine-wave control is presented for the higher-order resonant converter operating under variable input condition.

Multimode Constant Power Control Strategy for LCC Resonant Capacitor Charging Power Supply Based on State Plane Analysis

A novel constant power charging strategy is proposed for LCC resonant capacitor charging power supply (CCPS) in this article, which combines the advantages of discontinuous current mode (DCM) and continuous current mode (CCM) to increase the charging speed of capacitor and the utilization of input grid capacity. In order to implement the multimode constant power control (CPC) strategy, a steady-state model of LCC series-parallel resonant converter is built by state plane analysis, and the analytical expressions for output voltage, average output current, and switching frequency are derived. By the analytical expressions, this control strategy directly determines the relationship of the output voltage and the switch frequency, so the frequency control curve of the pulse frequency modulation could be realized easily. Accordingly, the converter operating along the control curve can take advantage of high average and low peak current of CCM, small switching loss of DCM. Finally, the accuracy of LCC state plane model and the effectiveness of multimode CPC are verified by the simulation and a 2-kW CCPS experiment.

Design Optimisation for Modified Series-Parallel Resonant Converter

Optimum design with systematic design procedure for a resonant converter is presented in this paper. For the converter design with high efficiency constraint of minimum power losses loss and cost are considered. For reducing the size of the converter, an integrated structure of high frequency transformer-inductor is proposed. A step-by-step systematic procedure for designing the converter is presented that results in high input line power factor and reduction of the stresses on the components of resonant tank circuit of the converter is given. Simulation and experimental results on a prototype of modified series-parallel resonant converter (MSPRC) are presented to validate the optimum design procedure.

A Simple Technique for Fundamental Harmonic Approximation Analysis in Parallel and Series–Parallel Resonant Converters

Due to its voltage-fed nature and a capacitive output filter, the rear-end rectifier of parallel and series–parallel resonant converters with capacitive filters draw discontinuous currents. Not only simple and elegant techniques such as fundamental harmonic approximation (FHA) analysis, but also time-domain, state-space, and state-plane approaches fail to model such converters with reduced labor. This letter presents a technique to restore the simplicity of FHA analysis about such converters. Authenticity and accuracy of the proposed technique is demonstrated through PSIM 11.0 simulation platform. Furthermore, a detailed comparison with the existing modeling techniques is also provided.

A Switched-Capacitor DC–DC Converter With Variable Number of Voltage Gains and Fault-Tolerant Operation

This paper presents research results of voltage gain number control methods of a power electronic resonant zero-current switching dc–dc switched-capacitor (SC) voltage multiplier (SCVM) in a topology with fault tolerance capability (FSCVM). The converters operated under the basic switching patterns are constant-voltage-gain dc–dc series-parallel resonant SC converters. However, this paper presents a method for the output voltage regulation by a special switching strategy. A variable voltage gain is made possible by selecting the number of active switching cells, using an appropriate control method. This creates a set of voltage ratio ranges. In addition, the proposed topology and method of control enable a fault-tolerant operation of the FSCVM under various failures of the device. The paper presents an analysis of the concept, simulation results and an experimental verification in a three-cell FSCVM dc–dc resonant boost converter operating at a 200-watt charge. Issues regarding the selection of components related to the problem of inrush currents that can occur during the voltage ratio increase are also analyzed in this paper, and the design for low inrush currents is demonstrated.

An Accelerated Model of Modular Isolated DC/DC Converter Used in Offshore DC Wind Farm

Modular isolated dc/dc converter (MIDC) is the most important equipment in the offshore dc wind farm. However, the simulation of the accurate MIDC model consumes too much time, which makes it difficult to carry out further studies about this topology. In this paper, an accelerated model that can dramatically decrease the consuming time of the MIDC simulation is proposed. Through an in-depth analysis about the MIDC submodule (SM), the LLC series–parallel resonant converter, four equivalent mathematical models that can completely describe the operation modes of the SM are deduced. Thereafter, based on the fourth-order Runge–Kutta method, a detailed design procedure of the MIDC accelerated simulation model is given. Moreover, the influences of different discretization methods on the simulation accuracy and computational speed of the accelerated model are also studied. Finally, the initial simulation model, the nested parent–child simulation method-based simulation model, and the accelerated simulation model of the MIDC with different numbers of SMs are built in the PSCAD/EMTDC. The simulation results prove the effectiveness of the proposed accelerated model.

Nonlinear interconnected high gain observer for series-parallel resonant DC/DC converter

We are considering the problem of state observation in series-parallel resonant converters (LCC). This is a crucial issue in (LCC) output voltage control as the control model is nonlinear and involves non-physical state variables, namely real and imaginary parts of complex electrical variables. An interconnected high gain observer is designed to get online estimates of these states. The observer is shown to be globally asymptotically stable. The global stability of the observer is analytically treated using the Lyapunov theory; finally we present numerical simulation to illustrate the performance of the suggested approach.

Analytical Modeling and Controller Design of a Modular Series Parallel Resonant Converter System for a Solid State 2.88-MW/115-kV Long Pulse Modulator

In this paper, two control strategies for voltage balancing in a modular serial parallel resonant converter modulator system, which is used in a high-voltage-pulsed power application, are presented and verified by simulations and measurements. The system is based on two series parallel resonant converter modules, forming an input series output parallel stack. To obtain the given output voltage pulse of 115 kV, nine of these input series output parallel stacks are connected in parallel at the input and in series at the output, forming an input parallel output series system. A robust input voltage balancing by an auxiliary circuit and an output voltage balancing by control is introduced and proven by measurements. In addition, an alternative approach, where the input and output voltage balancing is achieved purely by control, is given and verified by simulations. For designing the control of this system, a large and a small signal model is derived and the influence of component tolerances is investigated.

A Digitally Controlled Power Converter for an Electrostatic Precipitator

Electrostatic precipitators (ESPs) are devices used in industry to eliminate polluting particles in gases. In order to supply them, an interface must be included between the three-phase main line and the required high DC voltage of tens of kilovolts. This paper describes an 80-kW power supply for such an application. Its structure is based on the series parallel resonant converter with a capacitor as output filter (PRC-LCC), which can adequately cope with the parasitic elements of the step-up transformer involved. The physical implementation of the prototype includes the use of silicon carbide—SiC—semiconductors, which provide better switching capabilities than their traditional silicon—Si—counterparts. As a result, a new control strategy results as a better alternative in which the resonant current is maintained in phase with the first harmonic of the inverter voltage. Although this operation mode imposes hard switching in one of the inverter legs, it minimizes the reactive energy that circulates through the resonant tank, the resonant current amplitude itself and the switching losses. Overall efficiency of the converter benefits from this. These ideas are supported mathematically using the steady state and dynamic models of the topology. They are confirmed with experimental measurements that include waveforms, Bode plots and thermal behavior. The experimental setup delivers 80 kW with an estimated efficiency of 98%.

Hardware Implementation of Solar Photovoltaic System based Half Bridge Series Parallel Resonant Converter for Battery Charger

The long established battery chargers are having many drawbacks such as prominent ripple charging current, less efficiency and bulky in size. To overcome these drawbacks of conventional battery charger, several charging circuits have been proposed and inevitability force to design a high-performance battery charger with small in size and improved efficiency. In this paper solar photovoltaic system based half-bridge series–parallel resonant converter (HBSPRC) charger is proposed for battery interface. The converter is designed to abolish low and high-frequency ripple currents and thus take full advantage of the life of secondary battery circuit. This is achieved by designing converter switches turn on at zero current and zero voltage with switching frequency greater than that of resonance frequency which leads to freewheeling diodes need not have very fast reverse-recovery characteristics. The performance of the power converters depends upon the control method adopted; in this work fuzzy logic controller is used for controlling the output voltage of HBSPRC. The fuzzy control scheme for the HBSPR converter has been designed and validated in hardware implementation of HBSPRC switching technique. From the results, it is found that the proposed battery charging system which reduces the switching loss and voltage stress across the power switches which increases the efficiency of the converter.

Lyapunov‐based high‐performance controller for modular resonant DC/DC converters for medium‐voltage DC grids

This study presents a high-performance controller based on the Lyapunov stability criterion that enhances the dynamic performance and disturbance rejection capability of resonant DC/DC converters when compared with classical PI control. The series–parallel resonant converter (SPRC) is used as the candidate converter to which this controller design is applied but the design can be generalised to other types of resonant DC/DC converters. By using a multiple module approach, low-power modules of this resonant converter are stacked to enable operation at medium-voltage DC (MVDC). The proposed controller design is applied to modular structure of the SPRC to verify its high-performance output in conjunction with active sharing control loops that ensure uniform current/voltage distribution across the multiple interconnected modules. Detailed controller design, closed-loop stability criteria, robustness and parameter sensitivity are investigated and controller performance is compared and verified against the classical PI control in simulation and low-scaled experimental prototype. Operations in single-module and two-module input-series output-parallel modes are both studied. The study affirms the selection of the modular DC/DC converter architecture and its associated proposed controls for high-performance MVDC applications.

Development of a 1.5 kV, 1.2 kA Pulsed-Power Supply for Light Sintering

This paper presents the design and experimental results of the 36-kW pulsed-power supply for the xenon flash lamp. The continuous conduction mode series-parallel resonant converter is modified. This means that not only the few hundred kilohertz of high switching frequency is introduced to replace the resonant inductor with the leakage inductor of transformer but also the high output current is accomplished by using three-phase delta-connected transformers. In addition, the snubber capacitor of the inverter switches and the power factor correction module is both omitted in the compact structure. Although these main components have changed, the efficiency and power factor of the rated dummy load reach 96% and 0.96%, respectively. Within 36-kW average power, the proposed pulsed-power supply can generate as versatile combination of output pulse. For example, it can generate 20-ms pulse with 1-Hz repetition rate or generate 1-ms pulse with 20-Hz repetition rate. The used insulated gate bipolar transistor is protected from the turn-OFF peak voltage by the snubber circuit, and the effect of the snubber circuit is shown at the actual load condition.

Development of 50-kV 100-kW Three-Phase Resonant Converter for 95-GHz Gyrotron

This paper describes the development of a 50-kV 100-kW cathode power supply (CPS) for the operation of a 30-kW 95-GHz gyrotron. For stable operation of the gyrotron, the requirements of CPS include low output voltage ripple and low arc energy less than 1% and 10 J, respectively. Depending on required specifications, a three-phase series-parallel resonant converter (SPRC) is proposed for designing CPS. In addition to high-efficiency performance of SPRC, three-phase operation provides the reduction of the output voltage ripple through a minimized output filter component that is closely related to the arc energy. For allowing symmetrical resonant current from three-phase resonant inverter, the high-voltage transformers are configured as star connection with floated neutral node. This facilitates balanced voltage on each secondary winding. In addition, distinctive design of the high-voltage rectifier is introduced, taking into consideration the effective series stacking of diodes by means of the parallel resonant capacitor. In particular, the implementation of the high-voltage part including transformer and rectifier is presented in detail. For providing high power density and high reliability, effective methods for winding the high-voltage transformer and stacking rectifier diodes are discussed. Finally, the developed CPS achieves 95.5% of maximum efficiency, 0.92 of maximum power factor, 500 W/liter of power density, 0.6% of output voltage ripple, with 8.3-J arc energy.

Performance analysis of LCLC resonant converter with PI and fuzzy gain scheduled PI controllers

Purpose The purpose of this paper is to analyze the performance of LCLC resonant converter (RC) with proportional integral controller and fuzzy gain scheduled proportional integral controller. Design/methodology/approach The drawbacks of series RC and parallel resonant converter (PRC) are explained using relevant references in Section 1 of this paper. The necessity of RCs and the merits of zero voltage and zero current switching are given in the Section 2. In Section 3, the modeling of LCLC RC using state space technique is done. In Section 4, the open loop analysis and performance evaluation of proportional integral controller, fuzzy gain scheduled proportional controller using MATLAB Simulink is obtained. The hardware specification is given and experimental results are taken for LCLC RC. In Section 5, conclusion of study is given. Findings The LCLC RC overcomes the drawbacks of series and PRC. The fuzzy gain scheduled proportional integral controller is suitable for load variations in RC. Originality/value The output of the converter is not affected with the load variations since the controller suggested in the paper works for load changes and can be a solution for load parameter deviation applications. Also performance of the RC is improved by the fast response of the proposed controller.

Performance Analysis of PI and Fuzzy Control for Modified LCC Resonant Converter Incorporating Boost Converter

In this paper, the modified LCC type of series-parallel Resonant Converter (RC) was designed and state-space modeling analysis was implemented. In this proposed converter, one leg of full bridge diode rectifier is replaced with Synchronous Rectifier (SR) switches. The proposed LCC converter is controlled using frequency modulation in the nominal state. During hold-up time, the SRswitches control is changed from in-phase to phase-shifted gate signal to obtain high DC voltage conversion ratio. Furthermore, the closed loop PI and fuzzy provide control on the output side without decreasing the switching frequency. The parameter such as conduction loss on primary and secondary side, switching loss, core and copper also reduced. Simultaneously, the efficiency is increased about 94.79 is realized by this scheme. The proposed converter with an input of 40 V is built to produce an output of 235 V with the help of ZVS boost converter [1] even under line and load disturbances. As a comparison, the closed loop fuzzy controller performance is feasible and less sensitive than PI controller.

Experimental Validation of a Series Parallel Resonant Converter Model for a Solid State 115-kV Long Pulse Modulator

Medium and high beta cavities used in linear colliders or spallation sources are supplied by klystrons or inductive output tubes amplifiers. The cathode voltage for these amplifiers can be generated by long-pulse modulators generating highly accurate high voltage pulses in the length of milliseconds. With existing modulator topologies, all the demanding requirements like fast pulse rise time, high accuracy, and low voltage ripple hardly can be satisfied at the same time. Common designs like bouncer modulator topologies using pulse transformers become huge for long pulses. The series–parallel resonant converter (SPRC) avoids this drawback as the transformer is operated at high frequencies. In this paper, the comprehensive multidomain model of an SPRC including an electrical model of the inverter, a magnetic model, and an isolation design procedure of the transformer is verified with a prototype of a single module operated under full-load conditions. In addition, a comparison between the predicted parasitics like leakage inductance and stray capacitance of the transformer and the measured values are given. An evaluation of the isolation of the transformer, which is especially crucial for a series connection of the modules, is also performed. In addition, different possibilities to realize the desired series inductance are discussed.

Wide-Air-Gap Transformer Model for the Design-Oriented Analysis of Contactless Power Converters

A wireless power converter topology with a small size and a high conversion efficiency has an increasing demand on small-power applications. Some design techniques to transmit power by customized cores have been already developed. However, when transferring energy by wide-gap transformers employing small-sized commercialized cores, the power losses on the winding greatly increase as the frequency increases. Then, the efficiency of the contactless power system decreases significantly due to the conduction loss and reactive components in the resonant circuit. Even though series-parallel resonant converters are largely employed, which can provide an infinite shunt impedance regardless of the coupling coefficient, when a commercialized core is employed for loosely coupled contactless power transfer applications, the large leakage inductance of the transformer significantly influences the additional power dissipation on the transformer windings. In this paper, an operating principle on how the contactless transformer with commercialized core contributes to the low efficiency is discussed. Also, a new frequency-dependent R- L ladder circuit model is introduced for the design-oriented analysis of wide-air-gap contactless power converters including the frequency-dependent losses of the transformer. A new design procedure with the proposed model is suitable for the contactless transformers employing commercialized cores. The proposed design approach is validated by 98.8-W hardware experiments. Finally, the simulation waveforms and the hardware results are compared to verify the accuracy of the frequency-dependent transformer model.