Analysis of series-parallel resonant converter

A frequency-domain steady-state analysis is given for a series-parallel resonant converter (SPRC) operating in the continuous conduction mode (CCM) using Fourier series techniques. Equations for performance parameters are derived under steady-state conditions to provide simple design tools. The topology of the SPRC combines the advantageous properties of both the series resonant converter (SRC) and the parallel resonant converter (PRC). The key results of the work are: a novel half-wave rectifier SPRC, conditions for obtaining high part-load efficiency; and several boundary frequencies and limiting conditions such as the capacitive/inductive load boundary and open-circuit and short-circuit cases. Experimental results measured for an 80-W converter above the resonance at different load resistances and input voltages show excellent agreement with the theoretical performance predicted by the equations     

Steady-state analysis of the constant-frequency clamped seriesresonant converter

A constant-frequency diode-clamped series resonant converter (CFCSRC) is proposed as a solution to problems associated with frequency-controlled resonant converters. This converter has two resonant frequencies, and control is achieved by varying the relative time spent at each switching frequency. Two zero-current-switching (ZCS) modes are examined and plotted in the output plane. An equation is given for the boundary between the two ZCS modes, as well as an expression for the boundary between ZCS and non-ZCS operation; both are plotted in the output plane. The output equation for the main mode is shown to be hyperbolic. Converter peak voltages limited to the input voltages, and peak currents are less than those of the frequency-controlled clamped series resonant converter over a large operating range. Data from a prototype converter are compared with theoretical data and are shown to be in good agreement with the theoretical model     

A Normalized Model for the Half-Bridge Series Resonant Converter

Closed-form steady-state equations are derived for the halfbridge series resonant converter with a rectified (dc) load. Normalized curves for various currents and voltages are then plotted as a function of the circuit parameters. Experimental results based on a 10-kHz converter are presented for comparison with the calculations.     

Analysis and Design of Series Resonant Converter by State-Plane Diagram

Analysis based on the state-plane diagram is given for series resonant converters operating in the frequency range 0.5 ? fs/fo ? 1.0. When the voltages and currents in the converter are normalized, design parameters take on special geometric meanings in the normalized state diagram. Examples of converter design using graphical methods are given for the cases of ? and ? control. Control characteristics of the converter operating in the continuous conduction mode are derived. The concept of the energy reflection coefficient is introduced as a measure of power transfer efficiency in the converter design.     

AC/DC converter topologies for the Space Station

A new class of AC/DC converter topologies (Type-1 converters) is described, suitable for use in an advanced single-phase sine-wave voltage, high-frequency power distribution system, of the type that was proposed for a 20 kHz Space Station primary electrical power distribution system. The converter comprises a transformer, a resonant network, a current controller, a diode rectifier, and an output filter. The input AC voltage source is converted into a sinusoidal current source using the resonant network. The output of this current source is rectified by the diode rectifier and is controlled by the current controller. The controlled rectified current is then filtered by the output filter to obtain a constant voltage across the load. Three distinct converter topologies, Type-1A, Type-1B, and Type 1-C, are described, and their performance characteristics are presented. All three types have a close-to-unity rated power factor (greater than 0.98), low total harmonic distortion in input current (less than 5%), and high conversion efficiency (greater than 96%)     

A Large-Signal Dynamic Simulation for the Series Resonant Converter

A simple nonlinear discrete-time dynamic model for the series resonant dc-dc converter is derived using approximations appropriate to most power converters. This model is useful for the dynamic simulation of a series resonant converter using only a desktop calculator. The model is compared with a laboratory converter for a large transient event.     

Single-phase power-factor-correction AC/DC converters with threePWM control schemes

Three pulse-width modulation (PWM) control schemes for a single-phase power-factor-correction (PFC) AC/DC converter are presented to improve the power quality. A diode bridge with two power switches is employed as a PFC circuit to achieve a high power factor and low line current harmonic distortion. The control schemes are based on look-up tables with hysteresis current controller (HCC) to generate two-level or three-level PWM on the DC side of diode rectifier. Based on the proposed three control schemes, the line current is driven to follow the sinusoidal current command which is in phase with the supply voltage, and two capacitor voltages on the DC bus are controlled to be balanced. The simulation and experimental results of a 1 kW converter with load as well as line voltage variation and shown to verify the proposed control schemes. It is shown that unity PFC is achieved using a simple control circuit and the measured line current harmonics satisfy the IEC 1000-3-2 requirements     

Modeling the Full-Bridge Series-Resonant Power Converter

A steady state model is derived for the full-bridge series-resonant power converter. Normalized parametric curves for various currents and voltages are then plotted versus the triggering angle of the switching devices. The calculations are compared with experimental measurements made on a 50 kHz converter and a discussion of certain operating problems is presented.     

Generalized approach to the small signal modelling of DC-to-DCresonant converters

A generalized small-signal analysis approach that is based on both the Taylor's series expansion and the state-plane diagram is presented. A generalized discrete small-signal model for a double-ended DC-to-DC resonant converter operating in the continuous conduction mode is also given. Based on the model derived, the frequency responses for two transfer functions, namely, the line-to-output and the control-to-output transfer functions, are obtained. The technique is verified by applying it to the conventional series resonant converter whose small-signal analysis is known     

Effects of output filter on cross regulation in SRC

Cross regulation performance of multioutput series resonant converter (SRC) topologies using capacitive or inductive filters is analyzed. The steady state cross regulation characteristics are derived using the state-plane techniques and are illustrated by the examples of two-output SRCs with capacitive and inductive filters. The characteristic curves show that over some range of output currents, the cross regulation performance of an SRC with an inductive filter is much improved over the SRC with capacitance filter and less dependent on the tolerances in leakage inductances and the loading on unregulated outputs. It is shown that the converter control characteristics of an SRC with an inductive filter are relatively unaffected by the addition of the second output. The theoretical results are verified by simulation     

Design of the Series Resonant Converter for Minimum Component Stress

For a given output voltage and power, the peak resonant capacitor voltage and peak inductor and switch currents of the series resonant converter depend strongly on the choice of transformer turns ratio and of tank inductance and capacitance. In this paper the particular component values which result in the smallest component stresses are determined, and a simple design strategy is developed. The procedure is illustrated for an off-line 200 W, 5 V application, and it is shown that an incorrect choice of component values can result in significantly higher component stresses than are necessary.     

不平衡电网三相四开关变换器预测功率控制

为了提高三相四开关变换器并网电能质量,提出一种适用于不平衡电网条件的有限控制集模型预测直接功率控制策略。分析三相四开关变换器的工作机制和电压矢量变化关系,并建立其功率预测模型。使用αβ静止坐标系下的电网电压以及其90°延迟信号计算功率补偿值,设计价值函数,选择最优电压矢量对应的开关状态。该控制策略无需传统的正负序分离控制及锁相环技术,易于实现。仿真和试验结果表明,在不平衡电网条件下,所提出的控制策略能够有效降低并网电流畸变,消除功率波动,提高并网电能质量。     

Analysis and design of (LC)(LC)-type series-parallel resonantconverter

A series-parallel resonant converter employing (LC)(LC)-type tank circuit operating in lagging power factor (PF) mode is presented and analyzed using complex ac circuit analysis. Design curves are obtained and the converter is optimized under certain constraints. Detailed Space Integrated Control Experiment (SPICE) simulation results are presented to evaluate the performance of the designed converter under varying load conditions. Results obtained from an experimental converter are also presented. The results obtained from the theory, SPICE simulation, and the experimental converter are compared. The proposed converter has high efficiency from full load to very light load (<10%). Switching frequency variation required for a wide change in the load (near load open circuit to full load) is narrow compared with the series resonant converter (SRC)     

Low-harmonic thyristor rectifiers applying current injection

Application of the third harmonic current injection in three-phase full-bridge thyristor rectifiers is analyzed. Spectra of the rectifier output terminal voltages are derived. Results of the optimal current injection for diode bridge rectifiers are generalized for the thyristor rectifiers, and the waveform of the optimal injected current is derived. It is shown that for the optimal third harmonic current injection, the current injection network takes 8.571% of the rectifier input power from the thyristor bridge output terminals, regardless the thyristor firing angle. A current injection network with a passive resistance emulator that provides recovery of the power taken from the thyristor bridge output terminals is proposed. Volt-ampere ratings of the magnetic components are derived. An algorithm to control the switches in the resistance emulator is presented. Analytically obtained results are experimentally verified.     

High power factor AC/DC/AC converter with random PWM

A three-phase AC/DC/AC converter is presented with a power factor preregulator to improve the power quality in the input side and a pseudorandom noise generator to reduce the emitted acoustic noise and the mechanical vibration for an induction motor drive. The space vector modulation with hysteresis current control for a voltage source rectifier is adopted to simplify the hardware circuit. A control scheme is presented to drive the supply current following the reference current. The amplitude of reference current for the pulsewidth modulation (PWM) rectifier is derived from the DC bus voltage regulator and the estimated output power. Random switching frequency technique for a three-phase PWM inverter system to reduce the annoying tonal noise and resonant vibration from an induction motor is described. By randomly varying the instantaneous PWM switching frequency from one cycle to the next, the frequency distribution of harmonics is spread in a wide frequency range. The major advantage for using such a strategy is the nonrepetitive output spectral characteristic that results in reduction of torque pulsations in motor drive systems. The nearly unity power factor at the three-phase rectifier and the absence of acoustic noise concentrated at the specific tones which is usually present with conventional sinusoidal modulation are verified by the experimental tests     

Effect of FET output capacitance on ZVS of resonant converters

The analysis of resonant converters including the capacitance of the switches is presented. New dc characteristics are obtained for the series, parallel, and series-parallel resonant converters (SPRC). The operating regions where the converters operate with zero-voltage switching (ZVS) are determined as a function of the switch capacitance. The more pronounced effect can be seen in the series resonant converter (SRC), while the parallel resonant converter (PRC) is the most insensitive. The results of the analysis have been verified on an experimental prototype     

Small signal analysis of the LCC-type parallel resonant converter

In this paper, the small signal analysis of the LCC-type parallel resonant converter (LCC-PRC) operating in the continuous conduction mode is given. This analysis is based on both the state-plane diagram, which has been successfully used to obtain the steady state response for resonant converters, and the Taylor series expansion. Applying perturbation directly to the steady state trajectory, a discrete small signal model for the converter can be derived in terns of the input voltage, switching frequency, and the converter state variables. Based on this analysis, closed-loop form solutions for the input-to-output and control-to-output transfer functions are derived. It is shown that the theoretical and computer simulation results are in full agreement     

Control technique for high power factor multilevel rectifier

Three control techniques for a high power factor multilevel pulsewidth modulation (PWM) rectifier are proposed. The proposed rectifier is based on series connection of full-bridge cell to achieve a high power factor, low current distortion, low voltage stress of power semiconductors and two balanced output voltages. The look-up table is used in the proposed control schemes to reduce the hardware circuit. A capacitor voltage compensator is used to balance two dc capacitor voltages in order to obtain high quality PWM voltage pattern. Based on the proposed control schemes, two-level or three-level PWM pattern can be generated on the ac side of the adopted rectifier. The proposed techniques for a high power factor multilevel rectifier illustrate its validity and effectiveness through the respective simulations and experiments. According to the measured results, the current harmonics drawn from the mains meet the International Electrotechnical Commission (IEC) 1000-3-2 limits     

Three-phase single-stage ac/dc boost integrated series resonant converter

A new ac/dc 3-/spl phi/ single-stage converter is proposed integrating a 3-/spl phi/ discontinuous current mode (DCM) boost with a dc/dc fixed frequency series resonant converter (SRC). This converter has the following features: natural power factor correction, soft switching, high-frequency (HF) transformer isolation with the series resonant tank operating in above resonance mode, etc. A new complementary gating control scheme is used for simultaneous control of boost converter and the SRC. Modes of operation are presented and analyzed. Based on the analysis, design curves are obtained. An optimum design is given and a design example is presented. Results obtained from SPICE simulation for the designed converter are given to verify the performance of the proposed converter for varying load as well as line voltage. Experimental results obtained from a laboratory prototype converter are presented to verify the theory.     

串联输出DC／DC谐振变换器的稳态分析

分析了高于谐振频率工作的串联输出谐振变换器的工作模式,采用状态变量法计算获得了若干描述稳态工作的特性曲线,为分析和设计这种变换器提供了基础