Contact loss measurement based on arc light detection makes it possible to estimate the current-collecting performance from catenary lines in electric railways before commercial operation, or after the installation, of new overhead contact systems and new pantographs. This measurement system consists mainly of a photo acceptor, a photo detector and a plastic optical fiber for connecting them. However, the system performance is affected by sunlight because the system detects only visible rays. Therefore, the authors develop a conversion system that can change a broad range of wavelengths—from ultraviolet to visible rays—emitted by the arc light to a voltage signal. The developed measurement system equipped with the wavelength converter can detect ultraviolet rays indirectly. This paper describes the operating principles of the wavelength converter and presents experimental results obtained with the measurement system.
Object movement detection by high order correlation analysis of optical sensor array signals is introduced. The optical sensors observe the moving object surface which is assumed to be a non-uniform speckle-like texture. The measurement system is applicable to general robotic movement detection because: it employs a noncontact measurement method, the system can be made very compact, and it enables approximation of the movement trace with a sequence of arcs instead of the conventional connection of simple line segments. The authors looked into estimation of the running trace of an autonomous vehicle by observing the ground pattern.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
This paper proposes a transformerless shunt hybrid filter for harmonic compensation of a three-phase six-pulse diode rectifier, where the ac line-to-line voltage is 3.3kV or 6.6kV. The hybrid filter consists of a single tuned LC filter per phase and an active filter with a dc capacitor voltage as low as 300V or 600V. The two filters are directly connected in series with each other without any transformer. The passive filter absorbs harmonic currents produced by the rectifier, whereas the active filter improves the filtering characteristics of the passive filter. The required rating of the active filter is much smaller than that of a conventional shunt active filter used alone. In addition, no additional switching-ripple filter is required for the active filter, because the LC filter acts not only as a tuned LC filter around the 7th-harmonic frequency but also as a switching-ripple filter around 10kHz. A feedforward control scheme is also proposed to improve the active filter performance. Experimental results obtained from a 200-V, 5-kW laboratory system and simulation results of a 3.3-kV, 300-kW system confirm the validity and effectiveness of the system. The hybrid filter gives satisfactory compensation performance, thus allowing us to put it into practical use.
This paper focuses on a shunt active filter based on the detection of harmonic voltages at the point of installation. The objective of the active filter is to attenuate harmonic propagation resulting from series/parallel resonance between capacitors for power factor correction and line inductors in a power distribution line. The active filter acts as a low resistor to the external circuit for harmonic frequencies, and it is installed on the end bus of the power distribution line, just like a 50 /spl Omega/ terminator installed on the end terminal of a signal transmission line. Therefore, the function of the active filter is referred to as "harmonic termination" in this paper. Experimental results obtained from a laboratory system rated at 200 V and 20 kW verify that the active filter for the purpose of harmonic termination has the capability of harmonic damping throughout the power distribution line.
This paper proposes a hybrid active filter for the damping of harmonic resonance in industrial power systems. The hybrid filter consists of a small-rated active filter and a 5th-tuned passive filter. The active filter is characterized by detecting the 5th-harmonic current flowing into the passive filter. It is controlled in such a way as to behave as a negative or positive resistor by adjusting a feedback gain from a negative to positive value, and vice versa. The negative resistor presented by the active filter cancels a positive resistor inherent in the passive filter, so that the hybrid filter acts as an ideal passive filter with infinite quality factor. This significantly improves damping the harmonic resonance, compared with the passive filter used alone. Moreover, the active filter acts as a positive resistor to prevent an excessive harmonic current from flowing into the passive filter. Experimental results obtained from a 20-kW laboratory model verify the viability and effectiveness of the hybrid active filter proposed in this paper.
This paper proposes a new rectifing system consisting of a series active filter and a double-series three-phase twelve-pulse diode rectifier. The supply current in the proposed system has a sinusoidal wave shape because the series active filter suppresses the current harmonics produced by the diode rectifier. Since almost no 5th- and 7th-harmonics are produced by the double-series twelve-pulse diode rectifier, the required peak rating of the series active filter is only 7% of the diode rectifier.In this paper, the control scheme and operating characteristics of the series active filter are theoretically and experimentally discussed. A novel conception that connection of a parallel capacitor to each diode of the rectifier makes a great contribution to reducing the required rating of the series active filter is also presented and verified by some experimental results.
In recent years, static VAr generators (SVGs) have been developed for improving power factor and stabilizing transmission systems. The active/reactive power control based on the p-q theory or the d-axis/q-axis current control based on d-q transformation is applied to an SVG. This paper deals with a comparative study of the two control schemes under single-line-to-ground faults. With the focus on three-phase supply currents and the DC capacitor voltage of the SVG, the two schemes are compared by computer simulation under an unbalanced condition that a supply voltage sag is caused by a single-line-to-ground fault.
This paper presents an intensive discussion on conducted electromagnetic interference (EMI) emissions from an inverter-driven air conditioner. Common-mode voltages produced by the pulsewidth-modulated (PWM) inverter may cause a high-frequency leakage current. The use of a spectrum analyzer and a line-impedance stabilization network (LISN) makes it possible to refer the leakage current in the time domain to the conducted-EMI emission levels in the frequency domain, which are prescribed by the EMI regulations. Simulation-based estimation of the conducted-EMI emission levels in advance allows engineers to efficiently design a cost-effective EMI filter intended for meeting the regulations. This paper achieves modeling of the inverter-driven air conditioner with focus on common-mode voltages and leakage-current propagation paths. The simulation circuit developed can be used to predict conducted-EMI emission levels and to design the cost-effective EMI filter. Simulated results agree fairly with experimental ones in both cases of the EMI filter being connected and disconnected.
The secondary coil installed on an EV is required to be small in size, light in weight, and efficient in power transfer, as well as tolerant in lateral misalignment with a large air gap. Also, a wireless power transfer (WPT) system needs high power transfer. Both downsizing and high power transfer bring a thermal problem the secondary coil. This paper proposes a WPT system combining the so-called "series and series" connected resonant capacitors with a double-current rectifier to achieve a secondary coil current reduction that is an essential matter of the problem. The proposed WPT system employs solenoid coils that are superior to circular coils in terms of misalignment and flux-distribution performance. The secondary WPT coil rated at 18 A is designed, constructed, and tested to verify the principles of operation. The system efficiency is 90.0% at nominal air gap 135 mm without misalignment in output power 7 kW.
This paper focuses on a battery energy storage system that can be installed in a 6.6-kV power distribution system. This system comprises a combination of a modular multilevel cascade converter based on single-star bridge-cells (MMCC-SSBC) and multiple battery modules. Each battery module is connected to the dc side of each bridge-cell, where the battery modules are galvanically isolated from each other. Three-phase multilevel line-to-line voltages with extremely low voltage steps on the ac side of the converter help in solving problems related to line harmonic currents and electromagnetic interference (EMI) issues. This paper proposes a control method that allows each bridge-cell to independently adjust the battery power flowing into or out of each battery module. A three-phase energy storage system using nine nickel-metal-hydride (NiMH) battery modules, each rated at 72V and 5.5Ah, is designed, constructed, and tested to verify the viability and effectiveness of the proposed control method.
This paper presents a DSP-controlled shunt active filter for harmonic termination of a power distribution line. The purpose of the active filter based on voltage detection is to damp out harmonic propagation caused by line inductors and shunt capacitor for power factor correction. However, time and phase delays inherent in the control circuit of the active filter might lead to poor harmonic damping performance. The hardware and software designs are important for achieving stable operation and satisfactory damping performance. This paper provides the details of design and implementation of a fully-digital controller for the active filter. Experimental results verify the viability and effectiveness of the DSP-controlled shunt active filter.
This paper presents an application of a modular multilevel cascade converter based on single-delta bridge-cells (MMCC-SDBC) to a STATic synchronous COMpensator (STATCOM), particularly for negative-sequence reactive-power control. The SDBC is characterized by cascade connection of multiple single-phase H-bridge (or full-bridge) converter cells per leg, thus leading to flexible circuit design, low voltage steps, and low EMI emissions. However, no paper has been published on such a STATCOM with experimental verification. This paper designs, constructs, and tests a 100-V 5-kVA PWM STATCOM based on the SDBC with focus on operating principle and performance. Experimental results verify that it can control not only positive-sequence reactive power but also negative-sequence reactive power and low-frequency active power intended for flicker compensation of arc furnaces.
This paper presents a magnetic saliency-based position estimation approach for a permanent magnet (PM) motor fed by a voltage-source pulse width modulation (PWM) inverter. The proposed real-time estimation algorithm detects motor current harmonics and calculates the inductance matrix, including rotor position information. Position estimation can be performed every period of PWM or carrier cycle. An experimental system using an interior permanent magnet (IPM) synchronous motor has been constructed. Experimental results verify that position estimation within 10/spl deg/ in electrical angle is obtained at standstill and at speeds as low as 1 r/min by the proposed approach.
This paper proposes a control method for eliminating dc magnetic flux from the series transformer of a dynamic voltage restorer. The method is characterized by intentionally injecting no compensating voltage during a one-sixth line cycle (=3.3 ms at 50 Hz). The control method is independent of an initial phase angle of a voltage sag, thus requiring no flux detection. The period, during which no compensating voltage is injected, is one-third as short as that of an existing method. This paper confirms the effectiveness and viability of the proposed method. A 200-V 5-kW laboratory system verifies experimentally that the proposed method brings no dc magnetic flux to the series transformer. Moreover, the proposed method brings a smaller dc voltage drop to the dc load of a three-phase diode rectifier than the existing method does in the same conditions.
