This paper deals with digital control of a series active filter integrated with a diode rectifier where the series active filter is controlled to function as a current source. A predictive current regulator is considered for the series active filter to achieve good ripple characteristics and predictable switching losses. The operating conditions, and the effect there of on the current regulator are considered and oversampling and prediction of the load voltage is suggested to improve the active filtering performance without increasing the switching frequency.
This paper describes voltage balancing of all the four split dc capacitors for a five-level diode-clamped PWM inverter intended for a transformerless mediumvoltage motor drive with a three-phase diode rectifier used as the front end. A dc-voltage-balancing circuit is installed on the dc link, and introduces a new midpoint-voltage-balancing method based on phase-shift control. As a result, the dc mean voltages of the four split dc capacitors can be balanced, independent of the inverter control. Experimental results obtained from the 200-V 5.5-kW downscale model verify that the dc mean voltage of the four split capacitors are balanced well under all the operating conditions.
Active power line conditioners, which are classified into shunt and series ones, have been studied with the focus on their practical installation in industrial power systems. In 1986, a combined system of a shunt active conditioner of rating 900 kVA and a shunt passive filter of rating 6600 kVA was practically installed to suppress the harmonics produced by a large capacity cycloconverter for steel mill drives. More than one hundred shunt active conditioners have been operating properly in Japan. The largest one is 20 MVA, which was developed for flicker compensation for an arc furnace with the help of a shunt passive filter of 20 MVA. In this paper, the term of "active power line conditioners" is used instead of that of "active power filters" because active power line conditioners would cover a wider sense than active power filters. The primary intent of this paper is to present trends in active power line conditioners using PWM inverters, paying attention to practical applications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Solving a short mileage and a long charging time is indispensable to putting electrical vehicles (EVs) on the full-scale market. A moving wireless power transfer (WPT) system is one of the effective solutions, because it can feed electric power to moving EVs. This paper proposes a moving WPT system consisting of several stationary ground-side (primary) coils and a moving vehicle-side (secondary) coil. This system is characterized by the use of the common vehicle-side coil to both moving and stationary WPT situations. Theoretical analysis concludes that the moving WPT system resulting from a stationary WPT system is the same in equivalent circuit as the stationary system. The moving WPT system employs solenoid coils that are superior to circular coils in terms of misalignment and flux-distribution performance. A downscaled moving WPT system rated at 3 kW is designed, constructed, and tested to verify the principles of operation, and the capability of continuous power transfer.
For the treatment of nasopharyngeal carcinomas, radiotherapy with or without adjunctive chemotherapy has been generally accepted as the first choice. However, recent advances in skull base surgery and imaging diagnosis have extended the indications for surgical intervention in the treatment of recurrent or residual carcinomas.Although there are several approaches to nasopharyngeal surgery, such as the transpalatal, transmaxillary, transpterygoid, transmandibular-transcervical and infratemporal fossa approaches, Mann et al recently developed the anterolateral transfacial approach.We operated on a 57-year-old male with recurrent nasopharyngeal carcinoma using this approach. This approach is characterized by temporary removal of the malar complex and resection of the coronoid process and pterygoid plates to achieve an excellent view of the nasopharynx and retromaxillary f ossa. This approach has the cosmetic advantage of preserving facial contouring by using the malar complex as a free bone graft, as well as the functional advantage of maintaining mouth opening by rehabilitation of mandibular movement. This approach is thought to be a valuable procedure for resection of nasopharyngeal carcinomas.
This paper provides a theoretical and experimental discussion on a modular multilevel triple-star bridge-cell converter with focus on mitigating the capacitor-voltage fluctuation contained in each bridge cell. A new control method proposed in this paper is characterized by properly superimposing both common-mode voltage and circulating currents in the whole speed range. Moreover, this paper optimizes the amplitude and frequency of the superimposed common-mode voltage on the basis of theoretical analysis, thus resulting in minimizing the voltage fluctuation. The optimized control method makes both voltage fluctuation and cluster-current amplitude smaller than do the existing methods. Experimental waveforms obtained from a three-phase downscaled system using a 370-V, 15-kW, 75-Hz, six-pole, permanent-magnet synchronous motor verify good start-up performance from a standstill to the rated speed, keeping both capacitor-voltage and cluster current within acceptable levels.
No abstract is provided for this article.
This paper proposes a new dc-voltage-balancing circuit for a five-level diode-clamped inverter intended for a medium-voltage motor drive with a three-phase diode rectifier used as the front end. This circuit consists of two unidirectional choppers and a single coupled inductor with two galvanically isolated windings. The inductor produces no net dc magnetic flux because the individual dc magnetic fluxes generated by the two windings are canceled out with each other. This makes the inductor compact by a factor of six, compared with the balancing circuit including two noncoupled inductors. Moreover, introducing phase-shift control to the new balancing circuit makes it possible to adjust the midpoint voltage. As a result, the dc mean voltages of all the four split dc capacitors can be balanced, independent of inverter control. Experimental results obtained from a 200-V 5.5-kW downscaled model verify the effectiveness of the new balancing circuit.
This paper presents a simple method for reduction of switching and snubbing losses in a large-capacity static VAr compensator (SVC) consisting of multiple three-phase voltage-source square-wave inverters. The proposed method is characterized by a "commutation capacitor" connected in parallel with each switching device. The commutation capacitor allows the SVC to perform zero-voltage switching, and to reduce switching losses. The electric charge stored in the commutation capacitor is not dissipated, but regenerated to the DC-link capacitor. Moreover, a soft-starting method for the SVC is also presented to avoid forming a short circuit across the commutation capacitor during startup. Experimental results obtained from a 10 kVAr laboratory setup are shown to verify the viability of the operating principle of the commutation capacitor.
Shunt passive filters, which are connected in parallel to harmonic‐producing loads, have been used widely for harmonics suppression in power systems because of low cost and high efficiency. However, they have such inherent problems as series and parallel resonance. On the other hand, shunt active filters, which are also placed in parallel, have such an inherent problem as initial and running costs are high compared with those of shunt passive filters. To solve these inherent problems in shunt passive and shunt active filters, the authors have proposed a combined system of a shunt passive filter and a small rated series‐active filter. The purpose of this paper is to reduce the required rating of the series‐active filter, considering a practical application of the combined power filter to harmonic compensation for large‐capacity thyristor converters. The points are summarized as follows: The required rating of the series‐active filter can be reduced less than one‐tenth by connecting a series‐resonant circuit in parallel to the secondary of current transformer. It is clarified theoretically and verified experimentally that compensation characteristics of the new combined system are equivalent to those of the already‐proposed system with no series‐resonant circuit.
This paper is focused on a voltage-detection-based shunt active filter for installation on a power distribution system. A main objective of the active filter is to achieve damping of harmonic propagation coming from series/parallel resonance between capacitors for power factor correction and line inductors in the distribution system. The active filter installed at the end terminal of a distribution feeder is controlled in such a way as to present infinite impedance to the external circuit for the fundamental frequency, and as to exhibit low resistance for harmonic frequencies. As a result, the active filter acts as a damping resistor for the harmonic propagation, just like a 50-Ω terminator installed at the end of a signal transmission line. It is verified by experiment that the active filter intended for harmonic termination has the capability of harmonic damping throughout the distribution feeder.
No abstract is provided for this article.
This paper deals with a new control method for an atmospheric-pressure discharge plasma generator. The plasma generator consists of a voltage-source inverter, a step-up transformer, a resonant inductor and two parallel electrode plates. The high-frequency high voltage induced by series resonance between the equivalent capacitance of the plates and the resonant inductor generates glow plasma between the plates. However, a continuously-applied voltage may cause streamer or arc discharges instead of glow plasma, when the plates are under atmospheric pressure. This paper discusses an application of pulse density modulation (PDM) to the plasma generator, and proposes a new PDM method suitable for atmospheric-pressure plasma. A conventional PDM method repeats alternate run and stop to adjust the output power. The switching pattern is designed to minimize power variations. In contrast, the switching pattern of the proposed PDM method is designed to achieve a quick decrease in discharge current and electrode voltage during the inverter is stopped. As a result, the proposed method makes it possible to eliminate the streamer or arc discharges, leading to stable glow plasma. Experimental results are shown to verify the viability of the proposed PDM method.
This paper proposes cooperative control of multiple active filters based on voltage detection for harmonic damping throughout a power distribution system. The arrangement of a real distribution system would be changed according to system operation, and/or fault conditions. In addition, shunt capacitors and loads are individually connected to, or disconnected from, the distribution system. Independent control might make multiple active filters produce unbalanced compensating currents. This paper presents hardware and software implementations of cooperative control for two active filters. Experiment results verify the effectiveness of the cooperative control with the help of a communication system.
This paper addresses a specific filter for integration into a motor drive system with an active front end. Three circuit configurations are investigated with focus on the high-frequency leakage current flowing out of a common grounded heat sink for two insulated-gate bipolar transistor modules. The motor drive system used in this experiment consists of a voltage-source pulsewidth modulation rectifier and inverter with the same carrier frequency as 14 kHz, together with an interior permanent magnet synchronous motor (IPM-SM) rated at 190 V and 5.5 kW. Experimental waveforms, along with putting an interpretation on their filtering performance, lead to the best filter configuration among the three.
