Improvement Of Transmission Capacity Research Articles

Look-Up-Table-Based Direct-Detection-Faster-Than-Nyquist-Algorithm-Enabled IM/DD Transmission with Severe Bandwidth Limitation

The emergence of new applications is driving a dramatic growth in the capacity of data center interconnects. Intensity modulation and direct detection (IM/DD) has the characteristics of low cost, low power consumption and a small footprint. Industry and academia have conducted much research on IM/DD systems as a cost-effective solution. However, optical/electronic bandwidth and fiber dispersion are the restricting factors for the improvement of transmission capacity. Pattern-dependent distortion is an important aspect that affects system performance. In this paper, we propose a look-up table (LUT)-based direct-detection-faster-than-Nyquist (DDFTN) algorithm to compensate for pattern-dependent distortion. The performances of feedforward-equalization (FFE) only, the original DDFTN, least-squares (LS)-based DDFTN, and LUT-based DDFTN algorithms in IM/DD-based 112/140 Gbit/s four-level pulse-amplitude modulation (PAM-4) signal transmission were evaluated. The experimental results indicate that LUT-based DDFTN performs better with low computational complexity.

Optimal Control Measures For Dynamic Stability Level Of Northeast Power Grid

Due to the rapid development of new energy such as nuclear power at the transmission end of Northeast power grid, the improvement of transmission capacity of Lugu UHVDC and the large-scale development of power base, the problem of dynamic stability of Northeast Power Grid has surfaced. Based on the reality of Northeast power grid, this paper deeply and carefully carries out the dynamic stability level analysis of Northeast power grid from three aspects of source, network and load, studies the effective methods and measures to improve the damping ratio and robustness of main vibration modes between power grid regions, takes into account the scientificity, systematicness and scientificity of the measures, and provides reference for domestic and foreign related grid operation.

Analysis of SSO in DFIG grid with series compensation

Doubly fed induction generator (DFIG) has become the most widely used type of wind power generation due to its superior technical performance. Series compensation technology is widely used in large-scale and long-distance wind power transmission system because of its high cost performance and significant improvement of transmission capacity. However, it may cause subsynchronous oscillation (SSO). This paper first introduces the definition and harm of subsynchronous oscillation, and then analyzes the advantages and disadvantages of series compensation technology, as well as the mechanism and suppression measures of subsynchronous oscillation of DFIG connected system through series compensation. Through modeling and simulation analysis, the suppression effect of additional subsynchronous damping controller (SSDC) on subsynchronous oscillation of DFIG control system is verified.

Transmission Capacity Improvement Using Unified Power Flow Controller with New Control Strategy

This paper presents Unified Power Flow Controller (UPFC) with a new control strategy to improve the transmission capacity in power system network. With the growing demand of electricity, it is not possible to erect new lines to face the situation. Therefore UPFC is optimally utilizes to enhance the existing transmission network. A detail explanation of the controllers for both shunt and series converters of UPFC and DC link capacitor rating are presented in this study. To justify the performance of the UPFC model, 230kV transmission system in Upper Myanmar National Grid is considered as case study. The proposed control system performance is checked by applying different faults across a transmission line to which UPFC is connected. This is necessary because of the chance for occurance of fault is larger for this case study network. And, loading condition is changed to study the control system response. The simulation results show the effectiveness and suitable performance of the control strategy at improving transmission capacity. Transmission network model and all simulations have been done using MATLAB/Simulink software.

SPM-Improved Transmission Performance of Software-Reconfigurable IMDD PONs Based on Digital Orthogonal Filtering

Extensive explorations are undertaken of the feasibility of utilizing self-phase modulation (SPM) to mitigate the channel fading effect associated with digital-orthogonal-filtering-enabled software-reconfigurable intensity-modulation direct-detection passive optical networks (PONs). A comprehensive theoretical model is developed and subsequently verified, based on which numerical simulations are undertaken to investigate the effectiveness of the effects of both SPM and adaptive channel power loading in maximizing the signal transmission capacity of each individual channel in the aforementioned PON systems. It is shown that, for the channel experiencing the worst channel fading effect, the SPM effect can enhance its transmission capacity by a factor as large as 2, and a further 45% transmission capacity improvement is also obtainable when adaptive channel power loading is applied. The signal transmission capacity improvement enabled by the coexistence of these two effects increases almost linearly with transmission distance. The research work not only provides a new means for dynamically manipulating the signal transmission capacity of each individual channel, but also allows the utilization of low-cost optical components without comprising the overall PON system performance.

Subcarrier Index-Power Modulated Optical OFDM and Its Performance in IMDD PON Systems

A novel transmission technique known as subcarrier index-power modulated optical orthogonal frequency division multiplexing (SIPM-OOFDM) is proposed, for the first time, by introducing an extra subcarrier index-power information-bearing dimension into conventional OOFDM. Detailed numerical simulations are undertaken of SIPM-OOFDM performance characteristics to identify optimum SIPM-OOFDM transceiver parameters and also to explore corresponding maximum achievable transmission performances over passive optical network systems based on intensity-modulation and direct-detection. It is shown that, compared to conventional OOFDM, SIPM-OOFDM offers considerable signal transmission capacity improvement without increasing minimum required optical signal-to-noise ratios and degrading chromatic dispersion/nonlinearity tolerances.

Improvement of Transmission Capacity by FACTS devices in Central East Europe power system

Abstract: The increased demand for power transfer in combination with environmental and economic issues which set constraints to building new lines, force the implementation of new technologies into the existing system in order to improve its power capability. This paper investigates the use of specific FACTS devices and WAMS systems to maximize total transfer capability generally defined as the maximum power transfer transaction in Central-East-Europe power system. Optimal allocation and control of these devices will be very important for TSO or other power market regulators. Effectiveness, optimal allocation and utilization of phasor measurement units (PMUs) for different types of FACTS devices designed for power flow control and increasing transfer capacity were investigated. Paper also compares the economic aspects of these devices.

Cost-Effective Direct-Detection All-Optical OOK-OFDM System With Analysis of Modulator Bandwidth and Driving Power

Optical orthogonal frequency-division multiplexing (OFDM) with advanced modulation format [e.g., quadrature amplitude modulation (QAM) and quadrature phase-shift keying (QPSK)] provides many transmission advantages. As the OFDM data rate is limited by the electronic digital-to-analog (DAC) and analog-to-digital (ADC) integrated circuits, an all-optical technique (i.e., all-optical OFDM) is used to construct an OFDM symbol; hence, it can provide a significant improvement in transmission capacity. In this work, we propose and demonstrate a cost-effective 275-Gb/s direct-detection all-optical OFDM system for access or data center networks. As all wavelength channels (11 wavelengths in the experiment) are produced by one laser source, only the temperature control of one master laser is enough. In addition, each wavelength channel in the all-optical OFDM signal is encoded using on-off keying (OOK) modulation format; the traditional generation and detection circuits used in the transmitter (Tx) and receiver (Rx) of the present passive optical network can still be used. We also numerically analyze the requirements of the opt-comb-MOD (modulator used to generate the optical comb source) and the data-MOD (modulator used to generate the OOK data) in the system.

Improvement of transmission capacity in optical orthogonal frequency division multiplexed access link using an adaptive sampling and L1-minimization based on compressive sensing

A new technique, which can increase the data rate in optical orthogonal frequency division multiplexed access link, is proposed in this paper. An adaptive sampling based on a compressive sensing (CS) technique is implemented in order to save channel bandwidth. The CS tells us that all signals with high sparsity, which is sampled below the Nyquist/Shannon limit, can be reconstructed successively using sufficient measurement. In this paper, it is reported that the compression ratio of 40 % is observed within the error free optical transmission (FEC limit: BER of 10−3) in case of QPSK symbols. It means that its data rate can be increased by 1.7 times (from 1.56 to 2.3 Gbps) using the proposed technique without the use of optical and electrical devices with higher physical bandwidth.

Research on Energy Transmission Capacity Improvement of the Aircraft Electric Power System

A minimum transmission power loss calculation method is proposed, and the specific load configuration is obtained to improve energy transmission capability of the aircraft electric power system. Themethod is divided into three steps. First, a node table-style format of the aircraft electric power system is proposed according to its characteristics. Second, the transmission power loss equation is modeled by introducing the power flow calculation method. Third, the system transmission power losses with different load types are studied. Using particle swarm optimization algorithm, the minimum transmission power losses with different system load types are obtained.With the optimum load configuration, the transmission power loss is reduced and energy transmission capacity of the aircraft electric power system will be improved effectively.

Improvement of Transmission Capacity by Thyristor Controlled Reactive Power

This paper shows that thyristor controlled reactive power can be used as an efficient tool to improve damping of large power systems. If thyristor switched capacitors are used there will also be positive contribution to transient stability. Examples of power systems where damping is the critical factor have been investigated. The use of supplementary control of generators and control of reactive power has been studied. Basic configurations of thyristor switched capacitors and thyristor controlled reactors are presented.

Improvement of Transmission Capacity by Thyristor Controlled Reactive Power

Improvement of Transmission Capacity by Thyristor Controlled Reactive Power