Lagging Power Factor Mode Research Articles

Comparison of Phase-Shift and Modified Gating Schemes on Working of DC-DC LCL-T Resonant Power Converter

This brief discusses the operation and performance comparison of LCL-T DC-DC resonant power converter when controlled with fixed-frequency phase-shifted gating (PSG) and modified-gating signals (MGS) schemes. The converter is designed to operate in lagging power factor mode to accomplish zero-voltage switching (ZVS) of the inverter switches. The operating principle of the converter with the two proposed gating schemes is explained. A brief steady-state analysis of the converter using Fourier series approach is presented. The choice between PSG and MGS schemes is made by comparing the performance of the converter. It is found that both the gating schemes are effective in regulating the output voltage for variable input voltage and loading conditions. However, the efficiency of the converter is found to be higher with MGS due to the fact that only one switch loses ZVS as compared to two with the PSG when operated with maximum input voltage. Also, the variation in pulse-width angle (δ) required to regulate the output voltage is small in MGS as compared to that with PSG. A 300 W experimental prototype of the converter has been built and tested to verify the theoretical results. It is experimentally confirmed that the MGS control gives the better performance than the PSG control for different input voltage and loading conditions.

DSP microcontroller‐based fuzzy control of a DC/DC parallel resonant converter using phase‐shift PWM technique

Purpose – To analyze the operating performance of an ac‐dc‐ac‐dc PWM parallel resonant converter operating at lagging power factor mode controlled based on fuzzy logic control method.Design/methodology/approach – A range of published works relevant to dc‐ac‐dc converters and their control methods based on PWM technique are evaluated and their limitations in converter output voltage control are indicated in the first section of this paper. The Simulink model and different stages of the converter are described in the second section. In Section 3, the general mathematical model of the system is derived and the phase‐shift PWM switching technique is explained. The equivalent circuit of the high‐voltage high‐frequency transformer used in the converter and the effects of the transformer parameters on the converter operation are presented in Section 4. In Section 5, fuzzy logic control and the basic concepts of this method are described and its application to the proposed converter output voltage control is expl...

Steady‐state modeling of a phase‐shift PWM parallel resonant converter

PurposeTo derive an analytical model for a dc‐ac‐dc parallel resonant converter operating in lagging power factor mode based on the steady‐state operation conditions and considering the effects of a high‐frequency transformer.Design/methodology/approachA range of published works relevant to dc‐ac‐dc converters and their control methods based on pulse‐width‐modulation technique are evaluated and their limitations in output measurement of higher output voltage converters are indicated. The circuit diagram of the converter is described and the general mathematical model of the system is obtained by deriving and combining the mathematical models of the different converter blocks existing in the system. The derived mathematical model is used to study the steady‐state and transient performance of the converter. The deriving procedure of the analytical model for a parallel resonant converter is extensively given and the analytical model obtained is verified by simulation results achieved using MATLAB/SIMULINK and the program written by the authors.FindingsThe paper suggests an analytical model for dc‐ac‐dc parallel resonant converters. The model can be used in the output voltage estimation of a converter in terms of its phase‐shift angle and the dc‐link voltage.Research limitations/implicationsThe resources in the library of the authors' university and also the English resources relative to dc‐ac‐dc converters reachable through the internet were researched.Practical implicationsThe analytical model suggested can be used in estimating the output voltage of the converters used in high‐voltage applications or where there are difficulties in employing sensors in measurement of the output voltage due to high price or implementation problems.Originality/valueThe originality of the paper is to present an analytical model for dc‐ac‐dc parallel resonant converters. Using this model makes it possible to estimate the output voltage of the converter using the dc‐link voltage and the phase‐shift angle. The proposed model provides researchers to regulate the output voltage of the converters using feed‐forward control technique.

Performance, design and control of a series-parallel (CL2-type) resonant DC∕DC converter

The three-element resonant network has various topological alternatives, one of which, a prospective compound topology, is investigated in detail. The converter uses one capacitor (C) and two inductors (L2), to form a compound type CL2 network. Various advantages and limitations of the converter are detailed, and a new design procedure for such converters is also introduced. The converter may be controlled by varying the switching frequency or by pulse-width modulation. An experimental prototype has been produced and an excellent performance in the lagging power-factor mode has been confirmed.

Low-harmonic resonant CLL-type AC/DC converter

A new resonant AC/DC converter is presented. It has been shown that the series parallel CLL topology is particularly useful in resonant rectifier applications. The transformer may be designed to replace one or both the inductances used in the resonant network. The converter is operated only in the lagging power factor mode. Dispensing with the need of an external device snubber. Such a converter is analysed and simulation results are obtained by using MATLAB. Two new control strategies are proposed. Both control schemes are implemented and compared. Scheme 1 requires reduced hardware and no current sensor, but scheme 2 uses a current sensor and an additional PI controller. Scheme 2 performs better than scheme 1 in terms of total harmonic distortion (THD) of the converter input current. A laboratory prototype has been fabricated and excellent performances have been confirmed.

A Low Harmonic High Power Factor Half Bridge Resonant AC/DC Converter

A new resonant rectifier is introduced in this paper. Due to the suitability of operation in the lagging power factor mode, the series parallel CLL topology is utilized. The converter has been analyzed and simulation results have been obtained by using MATLAB. Control requirements have been identified and two new control schemes have been developed. The first scheme does not require any current sensor to improve the current drawn from the supply. The technique is to use a PI controller to maintain the output voltage constant, with an additional gain proportional to the rectified AC input voltage to create a fixed frequency modulation to improve the input current waveform. The second scheme uses a current sensor and forces both the output voltage and the input current to follow the corresponding desired references using two PI controllers. A laboratory prototype has been fabricated to realize the proposed converter topology along with the control schemes and satisfactory results have been found.

Operation of high-frequency resonant converters on the utility line with improved characteristics

Operation and characteristics of Class-D-type resonant converters on the utility line are presented. Two types of resonant converters (LCC- and LCL-type) operating with variable frequency control as well as variable pulse width (fixed frequency) are considered. Analysis and simple design procedures (with design examples) are given. SPICE simulation and experimental results obtained for the designed converters (rated at 250 W) are presented to verify the theory. It is shown that high-line power factor (PF) (>0.95) and line-current total harmonic distortion (THD) of <25% are obtained for the LCC-type converter (with a capacitor ratio of one) for a wide-load range (from full load to 10% rated load) without any active control, and the switch-peak current decreases with the load current. Although the LCL-type converter gives about 20% THD at full load, it increases to about 29% at lighter loads. However, the LCL-type resonant converter can operate in lagging PF mode for the entire line cycle and for a wide-load variation.

Analysis and design of a fixed-frequency LCL-type series-resonant converter with capacitive output filter

A fixed-frequency modified (LCL-type) series-resonant converter which uses a capacitive output filter is analysed using the Fourier series approach. Based on the analysis a simple design procedure is given. Detailed SPICE simulation results are presented for the designed converter to evaluate its performance for varying input supply voltage and for load variation. Experimental results obtained from a MOSFET based 500 W, 115 V output converter are presented to verify the analysis. The converter operates in lagging power factor mode for a very wide variation in the load and the supply voltage and is suitable for high voltage output applications.

A fixed-frequency modified series-resonant converter: analysis, design, and experimental results

It is shown that a fixed-frequency modified (LCL-type) series-resonant converter operates in five different modes with variations in the load current and the supply voltage. The converter is analyzed using the state-space approach for these operating modes. Both the general solutions and the steady-state solutions are obtained. Based on the analysis, design curves are obtained and a simple design procedure is illustrated using a design example. Detailed experimental results obtained from a MOSFET-based 500 W converter are presented to verify the analysis. It is shown that using a proper design, the converter operates only in modes 2 and 3, ensuring a lagging power factor mode of operation for very wide variations in the load and supply voltage. >

A fixed frequency LCL-Type series resonant converter

A fixed frequency LCL-type series resonant converter (SRC) which uses an inductive output filter is proposed. Steady-state analysis of the converter is presented using complex ac circuit analysis. Based on the analysis, a simple design procedure is given. Detailed space integrated control experiment (SPICE) simulation results are presented to evaluate the performance of the designed converter under varying load and supply voltage conditions. Also, detailed experimental results obtained from a metal-oxide-semiconductor field-effect transistor (MOSFET) based 500 W converter are presented to verify the analysis and SPICE simulation results. The results obtained from the analysis, SPICE simulation and the experimental converter are compared. The proposed converter requires a narrow variation in pulsewidth while maintaining lagging power factor mode of operation for a very wide variation in the load as well as supply voltage.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A comparison of parallel resonant converters operating in lagging power factor mode

Three different parallel resonant converter (PRC) configurations are compared for their performance. The discontinuous capacitor voltage mode is emphasized in the comparison and is shown not to exist in the case of PRC with the resonating capacitor on the primary side of the high-frequency (HF) transformer. It is further shown that the condition for discontinuous capacitor voltage (DCV) mode in the case of a PRC with the assumption of an ideal HF transformer and a PRC with secondary-side resonance differ only in the ratio M/(M+L+L/sub p/), which is equal to 1.0 for PRCs with the assumption of an ideal HF transformer. The comparison study shows that the PRC with the resonating capacitor on the primary side of a nonideal HF transformer is more appropriate for low-voltage high-current applications, while the PRC with resonating capacitor on the secondary side of a nonideal HF transformer is better suited to supply large-voltage medium- and low-current loads. Experimental results obtained from prototype units designed and built are presented to support the theory. >

Analysis, design, and optimization of a secondary-side resonant converter operating in the discontinuous capacitor voltage mode

A high-frequency link parallel resonant DC/DC power converter (PRC) operating in the lagging power factor mode with the resonating capacitor on the secondary side of the high-frequency (HF) transformer is analyzed for operation in the discontinuous capacitor voltage mode (DCVM) using a state-space approach. Converter equations are solved for operation under steady-state condition. Based on the analysis, design curves are obtained for DCVM operation. A method of obtaining the optimum operating point under certain constraints for DCVM operation is developed and is used to develop a simple design procedure. Experimental results obtained with a MOSFET-based 1 kW PRC are presented to support the theory. >

Analysis of a parallel resonant converter with secondary-side resonance

A high-frequency (HF) link parallel resonant DC/DC converter operating in the lagging power factor mode with the resonating capacitor on the secondary side of the HF transformer is analyzed using a state-space approach. Closed-form solutions (except for the duration of diode conduction) are obtained for steady-state conditions, and design curves are obtained. A method of obtaining optimum operating point under certain constraints is developed and is used as the basis of a simple design procedure. A theoretical study comparing the performance of three MOSFET-based 1-kW converters with different transformer turn ratios under load changes from rated-load to 10% load is carried out. Experimental results obtained with these converters with different transformer turn ratios are also presented. >