Single-Phase High-Frequency Resonant Direct AC–AC Converter With Constant Off-Time Pulse Coding Modulation for Fluid Water Induction Heating

As a new driving system of the tunable color electroluminescence (TCEL) devices, a series of technical trials on the pulse code modulation has been investigated. It has been shown from the results that the control of number of pulse ratio driving system with a constant pulse height and a constant pulse width is the best system for the continuous color mixing and variations with constant luminance. A series of technical data on the dual coloring TCEL devices are presented and discussed. This TCEL devices open a wide varieties of applications in the field of information display systems.

This paper proposed a single-stage resonant buck-boost ac voltage regulator. The proposed regulator can output a voltage which is larger or lower than the input ac one and is dependence on depending on the instantaneous duty-ratio. This property is not found in the conventional single-stage ac voltage regulator that the ac output instantaneous voltage is always lower than the input ac voltage. The proposed ac voltage regulator uses a series-resonant circuit to configure adaptively the resonant voltage pulse trains. The proposed ac voltage synthesized the resonant voltage pulse trains following the input voltage amplitude to the synthesized sinusoidal waveform (SSW) before output filter. Because the SSW very closes sinusoidal waveform, the proposed ac voltage regulator can use a simple LC filter to filter the undesired harmonics and to get the sinusoidal voltage waveform with low total harmonic distortion (THD). The proposed ac voltage regulator is controlled by constant frequency pulse width modulation technique. Its control circuit is simple. A design example of a 600W proposed ac voltage regulator is examined to assess the system performance. Under rated output power, the power efficiency is over 91% and the total harmonic distortion (THD) is within 6%.

Information processing systems require the data in coded form. Some generation procedures are described for pulse code, pulse width, and pulse density modulation. In case of sampling the idea of error diffusion is introduced. This concept has been developed to generate the pulse density modulation, but can also be used to advantage in other modulation techniques, e.g. pulse code modulation, to increase flexibility.

Comparison of modulation format for analog data transmission over laser space communication links

The active clamp flyback (ACF) converter is gradually becoming popular in the application field of low or medium output power range due to its advantage of soft switching and high conversion efficiency. An asymmetric half-bridge (AHB) flyback converter has been proposed in previous studies. The main advantages of the AHB flyback are the same number of components as the ACF converter and the soft switching technique. In this paper, an AHB flyback converter with constant off-time (COT) plus pulse frequency modulation (PFM) is proposed, so that the resonant time is not affected by the input voltage and load, and can achieve a wide range of zero voltage switching (ZVS) operating range. Compared to pulse width modulation (PWM), the PFM control with COT can make the system more stable. Finally, a prototype circuit with a specification input of 48 V to an output of 2.5 V/8 A is made for verification.

This paper proposes a novel single-stage ac-ac converter for realizing a high-efficiency high power-density 7.2kV medium voltage (MV) solid state transformer (SST) based on half bridge LLC resonant converter and 15kV SiC AC switch. The new topology is proposed to address major challenges in MV SSTs such as achieving soft switching for the MV switches across wide voltage and load ranges. The topology is analyzed through both time domain analysis and first harmonic approximation to provide useful equations for circuit design. The LLC based SST (LLC-SST) always operates at unity voltage gain mode, soft switching behavior over wide voltage range is investigated and proper fully zero voltage switching (ZVS) design methodology are discussed. A novel 15kV SiC AC switch based on 1700V SiC MOSFETs in series connection is developed and tested at a DC voltage of 10kV/15A. Critical parameters, such as Eon, E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">of</inf> f, Eos <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</inf> , Rds, on and leakage current, of the fabricated AC switch are characterized for system design. A full-scale 100kVA and compact LLC-SST module that converts 480Vac to 7.2kVac is developed to verify the theoretical analysis. The LLC-SST modular power density is around 25W/inch <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Peak efficiency is expected to be higher than 98.5%. A 300Vac to 4.2kVac preliminary power test with 1kΩ resistive load bank (18kW) has been demonstrated to verify the feasibility of the proposed single-stage ac-ac converter and validity of the fabricated 15kV AC switch operation. The proposed LLC-SST module can be used as a building block in three-phase architectures (6.9kVac three-wire and 12.47kVac/13.8kVac four-wire) for replacing line frequency transformer (LFT) in the medium voltage power system.

This paper presents a double half bridge resonant inverter for induction heating (IH) system composed of two partly coupled coils. Induction coils are electrically characterized by their electrical equivalents, usually a series RL circuit, where the inductance is determined by the magnetic energy stored in the system and the resistance is associated with the power dissipated in the load. Pulse width modulation based control strategy for double half bridge resonant inverter based power supply circuit is presented. The aim of this work is to simulate and obtain the electrical equivalent of the inductor system for accurate power study with two concentric coils by considering the frequency dependent eddy current losses associated with both the pan and the coil. This paper gives an idea about the in new control modes taking advantage of the coupling between coils in order to provide the target output power. The performed analysis includes the description of the operation and principle of the control strategy. The power converter system is designed and the simulation results are presented to prove the performance of the double half bridge inverter for partly coupled induction heating coil.KeywordsDouble half bridge resonant inverterInduction heating coilHigh frequency AC (HFAC) power supply

The Solar Energy Research Institute's (SERI) Wind Research Program is using pulse code modulation (PCM) telemetry systems to study horizontal-axis wind turbines. SERI has developed a low-cost PC-based PCM data acquisition system to facilitate quick PCM data analysis in the field. The SERI PC-PCM system consists of AT-compatible hardware boards for decoding and combining PCM data streams and DOS software for control and management of data acquisition. Up to four boards can be installed in a single PC, providing the capability to combine data from four PCM streams direct to disk or memory. This paper describes the SERI PC-PCM system hardware, focusing on the practicality of PC-based PCM data reduction. A related paper highlights our comprehensive PCM data management software program which can be used in conjunction with this hardware to provide full quick-look'' data processing and display. The PC-PCM hardware boards support a subset of the Inter-Range Instrumentation Group (IRIG) PCM standard, designed to synchronize and decommutate NRZ or Bi-Phase L PCM streams in the range of 1 to 800 Kbits/sec at 8 to 12 bits per word and 2 to 64 words per frame. Multiple PCM streams (at various rates) can be combined and interleaved into a contiguousmore » digital time series. Maximum data throughput depends on characteristics of the PC hardware, such as CPU rate and disk access speed. 7 refs., 6 figs., 4 tabs.« less

This paper presents a novel soft-switching PWM utility frequency AC to high frequency (HF) AC power conversion circuit incorporating boost-active clamp single stage inverter topology. This power converter is more suitable and acceptable for cost effective HF consumer induction heating (IH) applications. Its operating principle and the operation modes are presented using the switching mode equivalent circuits in addition to the operating voltage and current waveforms. The operating performances of this high frequency inverter using the latest IGBTs are illustrated, which includes HFAC power regulation ranges and actual efficiency characteristics based on zero voltage soft switching (ZVS) operation ranges and the power dissipation analysis as compared with those of the previously developed high frequency inverter. In addition, a dual mode selected control scheme of this high frequency inverter based on a constant frequency asymmetrical pulse width modulation (PWM) and pulse density modulation (PDM) control scheme is discussed in this paper in order to extend the soft switching operation ranges and to improve the power conversion efficiency at the low power settings. This power frequency converter practical effectiveness is substantially proved on the basis of experimental results from practical design example.

A model representative of any time-sampled, real-valued input and output digital system without feedback from system input to output (there may be internal feedback loops) is presented, and properties that are necessary for an optimum (nonlinear) digital system are developed. The model itself consists of a cascade of three mapping operations that successively transform the real-valued input sequence into an M-ary valued digital sequence, thence into an N -ary valued digital sequence, and finally into a real-valued output sequence. The operating routine and optimality criterion function chosen permit us to consider the problems of prediction, interpolation or synchronous operation as well as a wide variety of loss functions. The derived properties are discussed with particular regard to the quadratic loss function and synchronous or interpolatory operation and then applied to the determination of several optimum systems. Optimum nonlinear amplitude quantizers, pulse code and delta modulation systems, and stepped controllers are described. In particular, conditions are given under which delta modulation is superior to pulse code modulation and some remarks are made concerning suboptimal delta modulation systems and their relation to previous work.

In power communication systems, the pulse code modulation (PCM) equipment plays an important role. Its security has been a focus of attention, when the concept of cyber physical system is proposed. In order to solve the security problem of PCM equipments, a Bayesian Network (BN) model is used in this paper. By analyzing the vulnerabilities of PCM equipments, the BN model can be established to evaluate the security of PCM equipments rationally. For illustration, four PCM equipments are selected from some substations. They are utilized to show the feasibility of the BN model in evaluating the security of PCM equipments. Empirical results show that some effective counter measures can be found to help decision maker improve the security of PCM equipments. The BN model can effectively evaluate the security of PCM equipments, the most reasonable and effective countermeasures are advanced.

Technological advances are continually increasing the economic viability of efficient codecs in telephone networks. A subjective evaluation is described here of the μ255 Pulse Code Modulation (PCM) algorithm and three more efficient techniques, Nearly Instantaneous Companding PCM (NIC PCM), Cummiskey-Jayant-Flanagan Adaptive Differential PCM (ADPCM), and Subscriber Loop Carrier Adaptive Delta Modulation (SLC∗ ADM). These codecs are compared under the conditions of: (i) single encodings as a function of line bit rate, input level, received volume, and error rate, (ii) tandem encodings with intermediate baseband conversion, and (iii) local, exchange, and toll network reference connections where mixed tandem encodings might be found along with typical analog impairments such as loss and random noise. The simulation of the codec algorithms on a minicomputer facility enabled the production of subjective test tapes containing speech processed under these conditions. These tapes were then evaluated in listening-type subjective tests. It is shown that (i) NIC PCM, ADPCM, and SLC ADM have approximately a 12- to 16-kb/s advantage over μ255 PCM for equivalent subjective ratings, (ii) NIC PCM, ADPCM, and SLC ADM perform comparably over the range of conditions tested; and (iii) 64-kb/s μ255 PCM can be deployed in a multiple encoding environment with very few restrictions, whereas the use of lower bit rate NIC PCM, ADPCM, and SLC ADM codecs would necessitate more stringent application rules to avoid excessive degradation in tandem encoding situations.

Up to now, the design of space communications systems has been dominated by the low received power which characterizes these systems. Two changing conditions will alter this emphasis. The first is the increase in available transmitter power caused by increased booster capability. The second is the reduction in available bandwidth due to a great increase in traffic requirements. Present systems use modulation systems which require minimum power at the expense of lavish use of bandwidth. Future systems must find a better compromise of characteristics. Multilevel pulse code modulation (PCM) is a modulation system offering such a compromise. Multilevel PCM is an extension of binary PCM to multilevel signals. In multilevel PCM the signal is sampled, quantized, and the value of the quantized sample is represented by a stream of symbols which may have any number of levels. Multilevel PCM was described and the approximate performance was computed in 1948 by Oliver, Pierce, and Shannon. Since then it has largely been ignored. This is the first exact computation of performance. The performance of multilevel PCM is compared with other systems on an equal bandwidth basis. It is found that multilevel PCM requires less input power than any commonly used modulation system of equal bandwidth. For example, to obtain 60-db signalto-noise ratio out and using only twice the information bandwidth, multilevel PCM requires 20 db less input power than any commonly used modulation system.

Modulation is a process through which a message has to pass in order to be effectively transmitted. However, there are some limitations to Pulse Code Modulation and Delta Modulation that can cause data redundancy, quantization error, slope overload distortion and granular noise which result in a bad communication process. Throughout the past few years, Pulse Code Modulation (PCM), Delta Modulation (DM) and Differential Pulse Code Modulation (DPCM), in digital communication systems, have proven to have unparalleled advantages over analog communication systems; this is in terms of error minimization and distances of transmission enhancements. Delta Modulation, a simplified version of Pulse Coded Modulation also pauses major problems in noise and quantization error. Consequently, and to combat the arising problems, communication engineers have developed newly adaptive compression and modulations techniques for better digital transmission. One of these innovative systems is the Differential Pulse Coded Modulation (DPCM) that can solve the aforementioned problems. Thus the focal point of this article is to explore the simulation of these systems using Simulink (The Math Works, Inc., USA). Eventually, the systems are tested on both image and audio inputs to prove the superiority of DPCM over DM and PCM systems in reducing noise and increasing the signal to quantization noise ratio, thus insuring a smooth and successful transfer of data.

This paper presents a novel soft-switching PWM utility frequency AC to high frequency (HF) AC power conversion circuit incorporating boost-active clamp single stage inverter topology. This power converter is more suitable and acceptable for cost effective HF consumer induction heating (IH) applications. Its operating principle and the operation modes are presented using the switching mode equivalent circuits in addition to the operating voltage and current waveforms. The operating performances of this high frequency inverter using the latest IGBTs are illustrated, which includes HFAC power regulation ranges and actual efficiency characteristics based on zero voltage soft switching (ZVS) operation ranges and the power dissipation analysis as compared with those of the previously developed high frequency inverter. In addition, a dual mode selected control scheme of this high frequency inverter based on a constant frequency asymmetrical pulse width modulation (PWM) and pulse density modulation (PDM) control scheme is discussed in this paper in order to extend the soft switching operation ranges and to improve the power conversion efficiency at the low power settings. This power frequency converter practical effectiveness is substantially proved on the basis of experimental results from practical design example.