State feedback linearized model for phase-controlled series-parallel resonant converters

This paper proposes a linearized large-signal state space model for phase-controlled series-parallel resonant converter. The model combines multiple-frequency and average state-space modeling techniques to generate a universal model with DC state variables that are easier to control compared to the fast resonant tank dynamics. In order to perform linearization, the proposed model utilizes a state feedback scheme from output filter inductor current. The model also serves as a tool for large signal prediction/estimation of converter state variables. The model accuracy was verified by comparing with a detailed switching model of the converter built in MATLAB simulation environment

Higher Order Series Resonant Dc-Dc Converter For High Voltage Applications

The conventional series resonant High Voltage (HV) DC-DC converter power supply is able to absorb the leakage inductance of the HV transformer, provides lower component stress and prevents the HV transformer from being saturated but poses poor controllability at light load and lower efficiency. To overcome these problems, this research work proposes higher order resonant topologies of series resonant HV DC-DC converter with two different output voltage control strategies. A fourth order LCCL series resonant HV DC-DC converter was designed consisting of four storage elements; a capacitor connected in parallel with a linear variable inductor (LVI) and the leakage inductance of the HV transformer in series. Two control strategies are proposed to regulate the output voltage of the LCCL series resonant HV DC-DC converter. First control strategy, is based on varying the switching frequency while keeping the resonant frequency constant. In the second control strategy, the switching frequency is kept constant while the output voltage control is achieved by varying the resonant inductance. This is accomplished by using a LVI in the tank circuit. Operation of the converter is carried out in continuous conduction mode. Both control schemes which are implemented to the LCCL series resonant based HV DC-DC converter show the capability to produce high output voltage at 75% efficiency for input power of 18 W. The result is verified for both simulation and experimental setup

DESIGN OPTIMIZATION OF RESONANT DC-DC CONVERTERS

Resonant DC/DC converters are the class of converters, which have L-C resonant tank serving as a major part of the power conversion process. The fundamental concept of the resonant converter is that the circulating energy in an L-C resonant circuit is manageable by changing the operating frequency, and therefore the converter can condition the input power to the desired output voltage. The development in power conversion technology is steady demand for high power efficiency and high power density. A high efficiency is achieved by using series resonant converter (SRC) topology. It may operate in either continuous or discontinuous conduction modes. After exploring the advantages of using a resonant converter, the series resonant converter is implemented. Increasing the frequency is desirable for power converters operation. However, the switching losses will increase by increasing the frequency of operation. Hence, the efficiency of the system reduces drastically. In order to reduce switching losses and increasing high frequency operation, a series resonant converter has been developed. The resonant tank of SRC consists of a resonant capacitor and a resonant inductor connected in series. The output load resistance is in series with the resonant tank and the impedance of the resonant tank is a function of the switching frequency, and hence the voltage across the output impedance can be modulated by the switching frequency

A 10kW series resonant converter design, transistor characterization, and base-drive optimization

Transistors are characterized for use as switches in resonant circuit applications. A base drive circuit to provide the optimal base drive to these transistors under resonant circuit conditions is developed and then used in the design, fabrication and testing of a breadboard, spaceborne type 10 kW series resonant converter

Improved Topologies Of Series Resonant And Llc Resonant Dc-Dc Converters For Medium Output Voltage Applications

Resonant converters are currently the preferable choice of power conversion for many low and medium voltage applications. Double series resonant dc-dc converter has lesser component count, good efficiency and better voltage gain compared to other series resonant dc-dc converters operating in discontinuous conduction mode. However, it has the issue of non-uniform voltage stress on transformers. Similarly, LLC resonant dc-dc converters have been extensively explored for low output voltage applications; however, their benefits in the medium voltage power supply application are not well explored. This thesis proposes four improved topologies of resonant medium voltage dc-dc converters to address the aforementioned issues. First of all, a double series resonant dc-dc converter having uniform voltage stress on transformers is proposed. The secondary windings of the both transformers are connected in series and fed to a voltage multiplier circuit, therefore, the proposed converter solves the problem of non-uniform voltage stress on transformers without any compromise in the performance. Next, a double series resonant dc-dc converter with single transformer is proposed. In this converter, transformer has two primary windings and one secondary winding. Due to the use of single transformer, the converter has smaller size, lower core losses and consequently better efficiency. The third and fourth proposed topologies are full-bridge LLC resonant inverter fed voltage multiplier based medium voltage dc-dc converters. In order to make the realization of LLC operation easier, the turn ratio of transformers is reduced by using voltage multiplier circuits at the secondary sides in both converters. Using a voltage multiplier circuit, the turn ratio of transformer is reduced and LLC operation of converter can be easily achieved. The third proposed converter has only one resonant tank. While, the fourth proposed converter has two resonant tanks. Due to the use of two resonant tanks, the load current is equally divided between two resonant tanks, so that it has lower current stress on the components of the resonant tanks. The main features of these LLC resonant dc-dc converters are good control with narrow variation in switching frequency and lower switching and conduction losses. The performance and effectiveness of all the proposed converters is verified by both the simulation and experiment. In all the proposed converters, power switches and output diodes operate under soft-switching conditions; therefore, the proposed converters have lower switching loss and higher efficiency. Among all the proposed converters, interleaved LLC resonant inverter fed voltage multiplier based medium voltage dc-dc converter is the best choice, because it has the highest efficiency about 95 % at 300 W output power compared to other three proposed converter topologies

Linearized large signal modeling, analysis, and control design of phase-controlled series-parallel resonant converters using state feedback

This paper proposes a linearized large signal state-space model for the fixed-frequency phase-controlled series-parallel resonant converter. The proposed model utilizes state feedback of the output filter inductor current to perform linearization. The model combines multiple-frequency and average state-space modeling techniques to generate an aggregate model with dc state variables that are relatively easier to control and slower than the fast resonant tank dynamics. The main objective of the linearized model is to provide a linear representation of the converter behavior under large signal variation which is suitable for faster simulation and large signal estimation/calculation of the converter state variables. The model also provides insight into converter dynamics as well as a simplified reduced order transfer function for PI closed-loop design. Experimental and simulation results from a detailed switched converter model are compared with the proposed state-space model output to verify its accuracy and robustness

A Review of Resonant Converter Control Techniques and The Performances

paper first discusses each control technique and then gives experimental results and/or performance to highlights their merits. The resonant converter used as a case study is not specified to just single topology instead it used few topologies such as series-parallel resonant converter (SPRC), LCC resonant converter and parallel resonant converter (PRC). On the other hand, the control techniques presented in this paper are self-sustained phase shift modulation (SSPSM) control, self-oscillating power factor control, magnetic control and the H-∞ robust control technique

Resonant DC/DC Converters: Modeling, Control Strategies, Simulation, and Experimental Studies

Resonant power converters are switched RLC circuits where the switching action creates oscillatory current and voltage waveforms at the resonant frequency of the circuit . There are two basic types of resonant converters: the series type and the parallel type. In the series resonant converter the output i s connected in series with the resonating elements which are comprised of the resonant inductor and capacitor. In the parallel resonant converter, the voltage across the capacitor is sensed and coupled to the output port. The output parameter (voltage in the series resonant converters or current in the parallel resonant converters) and the switching frequency characterize the operation of resonant converters. An accurate analysis of series and parallel resonant converters i s given i n terms of these parameters. In this thesis, resonant converters with lumped losses are analyzed. State-plane portraits are generated from the solutions of circuit equations of these second order system, whereby the steady state, system dynamics, and the peak stresses are determined. Equation for the switching boundary i s given under the lossless assumption. Control strategies for the resonant converters are discussed and a novel method of control, optimal control, is proposed in controlling the parallel resonant converters. Typical circuits are simulated by using SPICE2 and Interactive Circuit Design Program (ICD). A parallel resonant converter was built. The simulation and the experimental results verify the analytical results

A Review of Resonant Converter Control Techniques and The Performances

paper first discusses each control technique and then gives experimental results and/or performance to highlights their merits. The resonant converter used as a case study is not specified to just single topology instead it used few topologies such as series-parallel resonant converter (SPRC), LCC resonant converter and parallel resonant converter (PRC). On the other hand, the control techniques presented in this paper are self-sustained phase shift modulation (SSPSM) control, self-oscillating power factor control, magnetic control and the H-∞ robust control technique