Novel Three-Phase AC–AC Sparse Matrix Converters

A novel three-phase ac-ac sparse matrix converter having no energy storage elements and employing only 15 IGBTs, as opposed to 18 IGBTs of a functionally equivalent conventional ac-ac matrix converter, is proposed. It is shown that the realization effort could be further reduced to only nine IGBTs in an ultra sparse matrix converter (USMC) in the case where only unidirectional power flow is required and the fundamental phase displacement at the input and at the output is limited to plusmnpi/6. The dependency of the voltage and current transfer ratios of the sparse matrix converters on the operating parameters is analyzed and a space vector modulation scheme is described in combination with a zero current commutation method. Finally, the sparse matrix concept is verified by simulation and experimentally using a 6.8-kW/400-V very sparse matrix converter, which is implemented with 12 IGBT switches, and USMC prototypes.     

Hybrid Full-Bridge Three-Level LLC Resonant Converter—A Novel DC–DC Converter Suitable for Fuel-Cell Power System

This paper proposes a novel hybrid full-bridge (H-FB) three-level (TL) LLC resonant converter. It integrates the advantages of the H-FB TL converter and the LLC resonant converter. It can operate under both three-level mode and two-level mode, so it is very suitable for wide-input-voltage-range applications, such as fuel-cell power systems. Compared with the traditional full-bridge converter, the input current ripple and output filter can be reduced. In addition, all the switches can realize zero-voltage switching from nearly zero to full load, and the switches of the TL leg sustain only half of the input voltage. Moreover, the rectifier diodes can achieve zero-current switching, and the voltage stress across them can be minimized to the output voltage. A prototype of 200-400-V input and 360-V/4-A output is built in our laboratory to verify the operation principle of the proposed converter     

三相AC/DC电压源变换器控制技术研究

为了改进AC/DC变换器的性能,本文提出一种基于汉密尔顿消散模型的AC/DC控制算法。介绍了一种基于汉密尔顿消散模型的AC/DC控制器设计方法,并对这种控制算法进行了分析。     

Explicit Space–Time Codes Achieving the Diversity–Multiplexing Gain Tradeoff

A recent result of Zheng and Tse states that over a quasi-static channel, there exists a fundamental tradeoff, referred to as the diversity-multiplexing gain (D-MG) tradeoff, between the spatial multiplexing gain and the diversity gain that can be simultaneously achieved by a space-time (ST) code. This tradeoff is precisely known in the case of independent and identically distributed (i.i.d.) Rayleigh fading, for Tgesn_t+n_r-1 where T is the number of time slots over which coding takes place and n_t,n_r are the number of transmit and receive antennas, respectively. For Tt+n_r-1, only upper and lower bounds on the D-MG tradeoff are available. In this paper, we present a complete solution to the problem of explicitly constructing D-MG optimal ST codes, i.e., codes that achieve the D-MG tradeoff for any number of receive antennas. We do this by showing that for the square minimum-delay case when T=n_t=n, cyclic-division-algebra (CDA)-based ST codes having the nonvanishing determinant property are D-MG optimal. While constructions of such codes were previously known for restricted values of n, we provide here a construction for such codes that is valid for all n. For the rectangular, T>n_t case, we present two general techniques for building D-MG-optimal rectangular ST codes from their square counterparts. A byproduct of our results establishes that the D-MG tradeoff for all Tgesn_t is the same as that previously known to hold for Tgesn_t+n _r-1     

The MIMO ARQ Channel: Diversity–Multiplexing–Delay Tradeoff

In this paper, the fundamental performance tradeoff of the delay-limited multiple-input multiple-output (MIMO) automatic retransmission request (ARQ) channel is explored. In particular, we extend the diversity-multiplexing tradeoff investigated by Zheng and Tse in standard delay-limited MIMO channels with coherent detection to the ARQ scenario. We establish the three-dimensional tradeoff between reliability (i.e., diversity), throughput (i.e., multiplexing gain), and delay (i.e., maximum number of retransmissions). This tradeoff quantifies the ARQ diversity gain obtained by leveraging the retransmission delay to enhance the reliability for a given multiplexing gain. Interestingly, ARQ diversity appears even in long-term static channels where all the retransmissions take place in the same channel state. Furthermore, by relaxing the input power constraint allowing variable power levels in different retransmissions, we show that power control can be used to dramatically increase the diversity advantage. Our analysis reveals some important insights on the benefits of ARQ in slow-fading MIMO channels. In particular, we show that 1) allowing for a sufficiently large retransmission delay results in an almost flat diversity-multiplexing tradeoff, and hence, renders operating at high multiplexing gain more advantageous; 2) MIMO ARQ channels quickly approach the ergodic limit when power control is employed. Finally, we complement our information-theoretic analysis with an incremental redundancy lattice space-time (IR-LAST) coding scheme which is shown, through a random coding argument, to achieve the optimal tradeoff(s). An integral component of the optimal IR-LAST coding scheme is a list decoder, based on the minimum mean-square error (MMSE) lattice decoding principle, for joint error detection and correction. Throughout the paper, our theoretical claims are validated by numerical results     

Coding for the Feedback Gel'fand–Pinsker Channel and the Feedforward Wyner–Ziv Source

We consider both channel coding and source coding, with perfect past feedback/feedforward, in the presence of side information. It is first observed that feedback does not increase the capacity of the Gel'fand-Pinsker channel, nor does feedforward improve the achievable rate-distortion performance in the Wyner-Ziv problem. We then focus on the Gaussian case showing that, as in the absence of side information, feedback/feedforward allows to efficiently attain the respective performance limits. In particular, we derive schemes via variations on that of Schalkwijk and Kailath. These variants, which are as simple as their origin and require no binning, are shown to achieve, respectively, the capacity of Costa's channel, and the Wyner-Ziv rate distortion function. Finally, we consider the finite-alphabet setting and derive schemes for both the channel and the source coding problems that attain the fundamental limits, using variations on schemes of Ahlswede and Ooi and Wornell, and of Martinian and Wornell, respectively     

Control of Three-Phase, Four-Wire PWM Rectifier

This paper presents the analysis, design, and control of a four-wire rectifier system using split-capacitor topology. The proposed controller does not require any complex transformation or input voltage sensing. A detailed analysis of the distortions in the line and the neutral currents is presented. It is shown that the single-carrier-based, conventional sine-triangle PWM (CSPWM) scheme results in a peak-to-peak neutral current ripple, which is greater than the peak-to-peak ripple of any of the line currents. Also, for the same operating condition, the distortions in the line and the neutral currents increase considerably, when a three-limb boost inductor is used instead of three single-phase inductors. A three-carrier-based SPWM scheme is proposed in this paper. Compared to CSPWM, the proposed scheme significantly reduces the neutral current ripple when three single-phase inductors are used, and reduces both line and neutral current ripples when a three-limb inductor is used. The control scheme is verified through Matlab simulation. It is implemented on an field-programmable gate-array (FPGA)-based digital controller and tested on a prototype. Simulation and experimental results are presented.     

A Model-Based Controller for A Three-Phase Four-Wire Shunt Active Filter With Compensation of the Neutral Line Current

This paper presents a model-based controller for a three-phase four-wire shunt active filter, which uses a three-leg split-capacitor topology to implement the voltage source inverter. The controller is aimed to compensate reactive power and harmonic distortion in the general case of distorted and unbalanced source voltages and load currents, including distorted loads connected between a phase and the neutral line. In addition, the controller is able to compensate for the homopolar component of the load current, that is, the current flowing to the source via the neutral line can be considerably reduced without modifying the actual topology. The complete model in (fixed frame) alphabetagamma-coordinates is presented. Special attention is given to the homopolar component (referred here as the gamma-component) of the line current, source voltage and control input, which are instrumental for the control design purpose. Experimental results in a 2 kVA prototype are provided to illustrate the benefits of the proposed solution.     

Novel Current-Mode AC/AC Converters With High-Frequency AC Link

A novel circuit-topology family of the current-mode AC/AC converter with high-frequency AC link, based on a Flyback converter, is proposed. These circuit topologies, which can transfer one unregulated sinusoidal voltage with high total harmonic distortion (THD) into another regulated constant-frequency sinusoidal voltage with low THD, are composed of input cycloconverter, high-frequency storage transformer, and output cycloconverter. The circuit-topology family includes single four-quadrant power switch mode, push-pull mode, half-bridge mode, and full-bridge mode circuits. The single four-quadrant power switch mode and push-pull mode converters are suitable for low input voltage fields, but the half-bridge mode and full-bridge mode converters are suitable for high input voltage fields. The operational mode, steady principle, and transient voltage feedback control strategy of the kind of converter are investigated. The output characteristic curve, its relation to internal resistance, and the design criteria for the key circuit parameters are given. The theoretical analysis and the test result of the 500 VA 220 V 15% 50 HzAC/220 V 50 HzAC prototype have shown that the converters have advantages such as high-frequency galvanic isolation, simple topology, two-stage power conversion [low frequency alternating current (LFAC)/high frequency alternating current (HFAC)/LFAC], bidirectional power flow, high efficiency, high power density, low THD of the output voltage, strong adaptability to various loads, higher line power factor, low audio noise, etc.     

Time-Interleaved Multirate Sigma–Delta Modulators

A time-interleaved (TI) implementation of multirate sigma-delta modulators (SDMs) is proposed. In multirate SDMs, the first integrator is clocked at a rate that is lower than that of the rest of the integrators. In the proposed architecture, each integrator clocked at a high rate is replaced by two parallel integrators operating in interleaved mode and clocked at the same low rate as the first one. The new architecture has several nice features. First, every integrator operates at the same low rate, which simplifies the clock circuitry when compared to the original multirate modulator. Second, there are no delayed cross paths, which is typical of TI-SDMs. Third, no high-rate sample-and-hold at the input of a TI-SDM is required. Finally, as time interleaving is not applied to the first integrator, the proposed modulator is robust against circuit mismatches, unlike other TI architectures. The same strategy can be applied to continuous time (CT) modulators. To the authors' knowledge, this is the first TI-CT-SDM ever reported     

On the Stopping Redundancy of Reed–Muller Codes

The stopping redundancy of the code is an important parameter which arises from analyzing the performance of a linear code under iterative decoding on a binary erasure channel. In this paper, we will consider the stopping redundancy of Reed-Muller codes and related codes. Let R(lscr,m) be the Reed-Muller code of length 2^m and order lscr. Schwartz and Vardy gave a recursive construction of parity-check matrices for the Reed-Muller codes, and asked whether the number of rows in those parity-check matrices is the stopping redundancy of the codes. We prove that the stopping redundancy of R(m-2,m), which is also the extended Hamming code of length 2^m, is 2m-1 and thus show that the recursive bound is tight in this case. We prove that the stopping redundancy of the simplex code equals its redundancy. Several constructions of codes for which the stopping redundancy equals the redundancy are discussed. We prove an upper bound on the stopping redundancy of R(1,m). This bound is better than the known recursive bound and thus gives a negative answer to the question of Schwartz and Vardy     

三相四线制有源电力滤波器的设计与仿真

三相四线制有源电力滤波器能够很好地提高滤波器的滤波性能,实现在大功率场合下的谐波抑制和无功补偿。通过研究主电路拓扑结构,给出了主电路设计方法,包括触发电路的设计,IPM驱动电路的设计和同步信号电路的设计。综合运用瞬时无功理论中的p-q法和ip—iq法,提出了一种新的基于瞬时无功理论的有效的三相四线制谐波检测新方法,此方法能将三相电流中的零序电流剔除。最后文章利用Matlab／Simulink构建了仿真模型,设定了仿真模型中各部分的参数,仿真结果验证了该方法的准确性和有效性。     

A New Planar InGaAs–InAlAs Avalanche Photodiode

We discuss a new simple InGaAs–InAlAs avalanche photodiode (APD) with a planar buried multiplication region. Some of the advantages compared to standard APDs are as follows: 1) The thickness of the avalanche and the charge control regions are accurately controlled by molecular beam epitaxy growth in contrast to the standard diffusion process; 2) InAlAs is the multiplication material (avalanching faster electrons) instead of InP (avalanching slower holes); 3) InAlAs avalanche gain has a lower noise figure than that for InP; 4) a guard ring is not required; 5) fabrication is as simple as that for a p-i-n detector; 6)the APD has high wafer uniformity, and high reproducibility; 7)the InAlAs breakdown voltage is lower than InP, and its variation with temperature is three times lower than that for InP; 8) excellent aging and reliability including Telcordia GR-468 qualification for die and modules; 9) high gain-bandwidth product as high as 150 GHz; and 10) high long-range (LR-2) bit-error-rate$10^-12$receiver sensitivity of$-$29.0 dBm at 10 Gb/s,$-$28.1 at 10.7Gb/s, and$-$27.1 dBm at 12.5 Gb/s.     

Zero-Error Source–Channel Coding With Side Information

This correspondence presents a novel application of the theta function defined by Lovasz. The problem of coding for transmission of a source through a channel without error when the receiver has side information about the source is analyzed. Using properties of the Lovasz theta function, it is shown that separate source and channel coding is asymptotically suboptimal in general. By contrast, in the case of vanishingly small probability of error, separate source and channel coding is known to be asymptotically optimal. For the zero-error case, it is further shown that the joint coding gain can in fact be unbounded. Since separate coding simplifies code design and use, conditions on sources and channels for the optimality of separate coding are also derived     

Microprocessor Control of DC/AC Static Converters

Microprocessor control of power electronic systems offers the possibility of improvements in reliability, maintenance and servicing, and increased control flexibility. This paper describes several pulsewidth modulation (PWM) waveforms where a predetermined number of unwanted harmonics can be canceled. The advantages and disadvantages of the different methods of delaying the signals in small microprocessor controlled PWM inverter drive systems are considered. Several examples of single-phase and three-phase PWM inverters, with the laws which govern the commutation angles, output waveforms, and their respective frequency spectra are presented.     

A Novel Three-Phase Three-Leg AC/AC Converter Using Nine IGBTs

This paper proposes a novel three-phase nine-switch ac/ac converter topology. This converter features sinusoidal inputs and outputs, unity input power factor, and more importantly, low manufacturing cost due to its reduced number of active switches. The operating principle of the converter is elaborated; its modulation schemes are discussed. Simulated semiconductor loss analysis and comparison with the back-to-back two-level voltage source converter are presented. Finally, experimental results from a 5-kVA prototype system are provided to verify the validity of the proposed topology.     

Control of Single-Phase-to-Three-Phase AC/DC/AC PWM Converters for Induction Motor Drives

This paper proposes a novel control scheme of single-phase-to-three-phase pulsewidth-modulation (PWM) converters for low-power three-phase induction motor drives, where a single-phase half-bridge PWM rectifier and a two-leg inverter are used. With this converter topology, the number of switching devices is reduced to six from ten in the case of full-bridge rectifier and three-leg inverter systems. In addition, the source voltage sensor is eliminated with a state observer, which controls the deviation between the model current and the system current to be zero. A simple scalar voltage modulation method is used for a two-leg inverter, and a new technique to eliminate the effect of the dc-link voltage ripple on the inverter output current is proposed. Although the converter topology itself is of lower cost than the conventional one, it retains the same functions such as sinusoidal input current, unity power factor, dc-link voltage control, bidirectional power flow, and variable-voltage and variable-frequency output voltage. The experimental results for the V/f control of 3-hp induction motor drives controlled by a digital signal processor TMS320C31 chip have verified the effectiveness of the proposed scheme     

Vector Control of Front-End Converters for Variable-Speed Wind–Diesel Systems

This paper presents a novel power-balance control method for a wind–diesel generation feeding an isolated grid. The system is based on a variable-speed wind energy conversion system (WECS) connected to an ac load using a power converter. An energy storage system (ESS), connected to the ac load using an additional converter, is used to balance the power generated by the WECS with the load. In this paper, the vector control systems for both interfacing power converters are discussed; the control uses the WECS converter to regulate the ac load voltage and the ESS converter to regulate the power flow to achieve a power balance. A small signal model is used to design the control systems. Finally, the proposed control is implemented in a 2-kW experimental prototype and the experimental results are fully analyzed and discussed in the paper.     

5-W Reliable Operation Over 2000 h of 5-mm-Wide 650-nm AlGaInP–GaInP–AlGaAs Laser Bars With Asymmetric Cladding Layers

Reliable operation of 650-nm laser bars with GaInP quantum wells embedded in AlGaInP waveguide layers and n-AlInP and p-AlGaAs cladding layers is reported. The 5-mm-wide bars consisting of ten emitters with 100-$muhbox m$-wide stripe width showed reliable operation over 2000 h at 5 W.