This paper presents node voltage control in a loop distribution system using the series and shunt converters of a UPFC (Unified Power Flow Controller). The purpose of voltage control is to control and regulate all node voltages within the appropriate range. The currents in the loop distribution system can be divided into loop and mesh currents, which can be controlled by the series and shunt converters, respectively. The node voltage control methods by the series and shunt converters are derived. The authors propose cooperative control using the series and shunt converters to minimize the converter capacity. The effectiveness of the proposed cooperative control is verified by experiments in steady and transient states using a laboratory prototype of the loop distribution system.
This paper proposes a high efficiency drive method for an open-winding induction machine with a single constant voltage source and a single capacitor. By focusing on the phase voltage of the open-winding machine is determined by the phase difference and the DC voltage of each power converter, it is possible to control the peak value of the phase voltage by controlling the voltage of the capacitor. Thus, a reduction in the iron loss due to harmonic voltages of the open-winding machine is expected. In the proposed method, the voltage of the capacitor is controlled by the difference between the two reference voltages of the power converter which depends on the machine power factor and phase difference of the power converter connected to both ends of the winding. From the experimental results, the converter loss and the machine loss can be reduced by controlling the voltage of the capacitor in accordance with the machine speed using the proposed method.
This paper presents the characteristics of pulse width modulation (PWM) patterns of a matrix converter (MC) under a high input power factor. The various PWM patterns of nine bidirectional switches for the MC can be established. All of the combinations of duty cycles with four commutations in three phases during one control period only using input voltage values under a high input power factor are derived. The PWM patterns of the derived duty cycles for low output voltage harmonics are evaluated. The characteristics and evaluations of the output voltage harmonics and switching losses for the PWM patterns have been verified by theories and experiments.
A five element multiplex resonant (LLCLC) full-bridge DC-DC converter controlled by pulse-frequency-modulation (PFM) is proposed in this paper. The high frequency (HF)-link resonant DC-DC converter proposed herein can perform wide-range output power and voltage regulations with a narrow frequency range owing to an anti-resonant tank which works effectively as a wide-range variable inductor. The advantageous characteristics of the anti-resonant tank provide overcurrent protection in the case of the short-circuited load condition as well as the start-up interval, thus the technical challenges of the conventional LLC DC-DC converter can be overcome, and the reliability of the relevant switch-mode power supplies can be improved. The operating principle of the LLCLC DC-DC converter is described, after which its performance is evaluated in an experimental setup based on the 2.5kW prototype. Finally, the feasibility of the proposed DC-DC converter is discussed from the practical point of view.
A practical evaluation of a novel utility-frequency AC (UFAC) to high-frequency AC (HFAC) power converter, called a frequency converter, for induction heating (IH) applications is presented in this paper. The proposed frequency converter can process the UFAC to HFAC power conversion without any diode full-bridge rectifier (bridgeless), thereby reducing the number of semiconductor power devices and eliminating the associated conduction power losses. In addition, power factor correction (PFC) can be naturally achieved while boosting the UFAC source voltage to the non-smoothed DC-link voltage. The operating principle of the proposed frequency converter together with its IH load power regulation scheme is described, and the circuit performance is demonstrated in an experiment based on its 3.0kW-30kHz laboratory prototype. Finally, the feasibility of the proposed frequency converter is evaluated from a practical point of view.
A contactless outlet for dc distribution systems was proposed. It uses an inductive contactless power transfer circuit with a Series/Parallel (S/P) compensation circuit to prevent voltage fluctuation. However, the output voltage of the circuit rises in light load conditions. In this paper, the main circuit and control method for reducing the rise in output voltage and a method to estimate the output voltage are presented. The proposed circuit and methods were verified and evaluated experimentally using feedback control.
This paper discusses pulse density modulation (PDM) control methods for a single-phase to three-phase matrix converter (MC) in high-frequency applications. The proposed circuit is used as an interface converter for a wireless power transfer system. This converter can input a frequency of several hundred kilohertz and output a low frequency, i.e. 50Hz or 60Hz, for commercial power grids. The proposed circuit achieves zero voltage switching operation by using the PDM control method and obtains high efficiency. In this paper, two PDM control strategies are compared: PDM control based on space vector modulation (SVM) (the conventional method) and the proposed PDM method, which combines SVM and delta-sigma modulation. Also, the experimental results of the proposed system will be demonstrated and discussed. As a result, the total harmonic distortion (THD) of the output voltage with the conventional method and the proposed method are 9.05% and 1.87%, respectively, when the modulation ratio is 0.5. Thus, the validity of the proposed method has been confirmed for improvement of the output waveforms.
Various sensorless control methods in a low-speed region characterized by containing zero speed have been reported. In particular, a position sensorless control method using rotor saliency is difficult to apply to a PMSM that does not have rotor saliency. In addition, the method based on rotor saliency suffers from problems such as too much electromagnetic noise and increase in harmonic loss. A new position sensorless method has been developed for permanent magnet synchronous motor (PMSM) drives. This method utilizes the induced voltage caused by magnetic saturation (IVMS) of the PMSM. The sensitivity of the rotor position in IVMS depends on the magnetic saturation characteristic of the rotor. Moreover, we have developed mathematical models of the magnetic flux characteristics considering the magnetic saturation and cross-coupling effects for PMSMs. That is the motor models can express nonlinear characteristics. IVMS can be evaluated in the proposed simulations using the mathematical models. In this paper, a study of IVMS in the proposed simulations is discussed. The experimental results and simulated results using the proposed model and the behavior model are presented. The mode change threshold values required for sensorless control are identical to the values obtained in the proposed simulations.
This paper presents a direct-type single-phase to three-phase matrix converter with a pulse density modulation (PDM) control method for high-frequency applications. The input frequency of the proposed converter is several hundred kilohertz, and the output frequency is a commercial frequency. The proposed converter reduces the switching loss by zero voltage switching from the PDM control. In this study, the PDM based on space vector modulation (SVM) is applied to a direct-type matrix converter. From the experimental results, the total harmonic distortion in the output voltage is 2.09%, and the maximum efficiency is 95.0%.