Search

A new high step-up dc-dc converter is proposed in this study. This new high step-up converter utilises the input voltage, clamped-capacitor, and the secondary side of the coupled-inductor to charge the switched-capacitor and the secondary side of the coupled inductor also charges two multiplier capacitors in parallel during the turn-on interval of the switch. The input voltage, coupled-inductor, and multiplier capacitors are in series connection to the output to accomplish the purpose of high voltage gain during the turn-off interval of the switch. By adjusting the turns ratio of the coupled inductors, the proposed circuit does not need to be operated at high duty cycle to achieve the high voltage gain. The voltage stress of the switch and diodes can be decreased to cut down the cost. Moreover, the energy of the leakage inductance can be recovered to reduce the voltage spike of the switch. Therefore, the switch with lower conduction resistance can be applied to reduce the conduction loss and increase the efficiency. Finally, simulation and experiments are conducted. A prototype circuit with input voltage of 24 V, output voltage of 400 V, and output power of 200W is implemented to validate the property of the proposed converter. [ABSTRACT FROM AUTHOR]

In this study, a novel high step-up dc-dc converter with high voltage gain and reduced switch stress is proposed. Utilising the coupled inductor to replace the boost inductor for high step-up converter is widely used in the application of high voltage gain converter. It can not only achieve a high voltage gain but also use the core effectively by using the coupled inductor. The techniques of voltage lift, voltage multiplier and clamp mode are also used in the proposed topology. Furthermore, the proposed converter can avoid the extreme duty cycle that will cause a lot of conduction losses. The leakage inductance energy of the coupled inductor will cause a huge voltage on the components of circuit, so that it needs to choose the components with high voltage and current ratings; then the efficiency is reduced and the cost is increased. The converter proposed in this paper can not only recycle the leakage inductance energy to the output but also increase the efficiency. A 300 W prototype converter which is implemented with an input voltage of 26 V and an output voltage of 400 V will demonstrate the effectiveness of this proposed converter. [ABSTRACT FROM AUTHOR]

A novel interleaved boost converter with zero-voltage switching (ZVS) and zero-current switching (ZCS) characteristics is proposed in this paper. By using the interleaved approach, this topology not only decreases the current stress of the main circuit device but also reduces the ripple of the input current and output voltage. Moreover, by establishing the common soft-switching module, the soft-switching interleaved converter can greatly reduce the size and cost. The main switches can achieve the characteristics of ZVS and ZCS simultaneously to reduce the switching loss and improve the efficiency with a wide range of load. This topology has two operational conditions depending on the situation of the duty cycle. A driving circuit is designed for the proposed topology to determine the two conditions automatically. The operational principle, theoretical analysis, and design method of the proposed converter are presented. Finally, simulations and experimental results are used to verify the feasibility and exactness of the proposed converter. [ABSTRACT FROM AUTHOR]

One of the methods to improve efficiency and torque performance of the single-phase brushless dc (BLDC) motor is to find out the optimum commutation angle at each different speed. We used the finite-element method (FEM) to simulate the back-EMF voltage and the coil current for the single-phase BLDC motor, and then adjust the conduction time of switches by detecting the waveform of coil current. The motor can improve its efficiency, noise, and vibration when it obtains the optimal shift angle of each speed. We used PSPICE to verify the exactness of FEM simulation results of the single-phase BLDC motor. We adopted Microchip's dsPIC30F4011 digital signal processor (DSP) to process the Hall signal and the driving signals of switches of the driving system prototype of the single-phase BLDC fan motor. Finally, we used the related experimental results to confirm the feasibility and effectiveness of the proposed driver. [ABSTRACT FROM AUTHOR]

The coevolutionary algorithm (CEA) based on the Lagrangian method is proposed for hydrothermal generation scheduling. The main purpose of hydrothermal generation scheduling is to minimize the overall operation cost and the constraints satisfied by scheduling the power outputs of all hydro and thermal units under study periods, given electrical load and limited water re- source. In the proposed method, a genetic algorithm is successfully incorporated into the Lagrangian method. The genetic algorithm searches out the optimum using multiple-path techniques and possesses the ability to deal with continuous and discrete variables. Regardless of the objective function characteristic the genetic algorithm does not have to modify the design rules and possesses the ability to go over local solutions toward the global optimal solution. The genetic algorithm can improve the disadvantages of the traditional Lagrangian method, which updates Lagrange multipliers according to the degree of system constraint violation by the gradient algorithm, and further searches out the global optimal solution. The developed algorithm is illustrated and tested on a practical Taiwan power system. Numerical results show that the proposed CEA based on the Lagrangian method is a very effective method for searching out the global optimal solution. [ABSTRACT FROM AUTHOR]

For improved efficiency and torque performance, brushless DC (BLDC) motors require a phase advance circuit. In a conventional phase advance circuit, the induced voltage of the Hall sensor is assumed to be a sinusoidal wave. But the actual induced voltage of the Hall sensor includes other harmonic components which influence the real phase advance angle. Performance curves of phase advance angle versus frequency for a conventional circuit do not work well when the harmonic components are considered. We therefore propose an improved circuit in which the phase advance angle is more accurate than that of a conventional circuit when the harmonic components are considered. Furthermore, the proposed circuit provides better performance. We present experimental results to verify the related theoretical analysis. [ABSTRACT FROM AUTHOR]

A single-phase brushless dc motor requires an asymmetric air gap to eliminate the dead point where the excitation net torque is zero. In this paper, we use the finite-element method (FEM) to analyze the properties of cogging torque, starting torque, and electrical circuits. Others have discussed the influences of various asymmetric air gaps on these properties. However, the optimum asymmetric air-gap condition is very difficult to find. Here, we describe an optimum asymmetric air-gap structure that not only produces an optimum starting torque but also reduces the cogging torque to a tolerable range. We compare simulation results with the measurement results to illustrate the accuracy of the FEM model. [ABSTRACT FROM AUTHOR]

This paper presents the parallel application of the magnetic amplifier (magamp) postregulators with a sliding-mode control. The system can be robust and with fast dynamic response based on the sliding-mode control. The controller can be designed in the time domain directly, which makes the design strategy easier and realizable. When the load increases, the parallel operation is adequate to be adopted. With the sliding-mode control and proper current distribution, the output currents of the parallel modules can be same when the capacity of the individual module is equal. Even if the capacities of the modules are different, the module with more capacity can also provide more output current and work well. Therefore, the purposes of controlling the output current distribution and achieving the stability of output voltage based on this kind of control strategy are achieved. Simulations and experimental results show that the parallel modules of magamp postregulators with the sliding-mode control can obtain the well dynamic behavior and proper current distribution. [ABSTRACT FROM AUTHOR]

This paper presents the related principle and analysis of the dimmable electronic ballast controlled by the switch- controlled capacitor (SCC). A Fourier-series expansion is used to derive the operational principle of the zero-voltage-switching Class-D series-parallel-load-resonant dimmable electronic ballast regulated by the SCC. By the adaptation of the SCC, the lightness of the system can be adjusted, while the operation frequency of the Class-D converter can be kept constant. The dimmable effect controlled by the variable SCC is examined. The analytical results are verified by simulations and experiments. Furthermore, the design considerations for the dimmable electronic ballast with SCC control are also presented in this paper. [ABSTRACT FROM AUTHOR]

Presents continuous and discontinuous mode small-signal dynamic models of magnetic amplifier (magamp) post regulators with current-mode control using the external-reset and the self-reset methods with current-mode control. Dynamic performance of the magamp post regulator expressed in terms of circuit parameters; Designing feedback compensation and experiments.

Develops a small-signal model of the synchronous-switch post regulator with coupled inductors. Explanation of the performance variations in the switch due to coupling coefficients; Comparison results of the multiple-output converter using the technique of post regulation; Experiments conducted to verify the validity of the proposed small-signal model.

Presents the results of a study in which a small-signal model of multiple-output flyback converters is developed. How regulation for multiple outputs is achieved; Regulation of main output with conventional pulsewidth modulator (PWM); Analysis of converter closed-loop performance.