Additional Transmission Lines Research Articles

Impedance matching bandpass filter with a controllable spurious frequency based on λ /2 stepped impedance resonator

An impedance matching bandpass filter (BPF) with arbitrary image impedance ( Z 2 ) of parallel/antiparallel coupled lines SIR is presented in this study. The proposed structures consist of conventional SIRs and additional transmission lines with an electrical length of π /2– θ 2 at the input and output ports. Moreover, the coupling coefficients of the coupled line can be controlled by the image impedance and it does not affect the bandpass responses. Since the first spurious frequency of the conventional SIR BPF can be suppressed with a transmission zero by using antiparallel coupled lines, the proposed BPF can provide wide stopband and high attenuation characteristics. For the experimental validation of the proposed filter, three types of BPFs with 20–50 and 50–100 Ω termination impedances were designed and fabricated at the operating centre frequency ( f 0 ) of 2.6 GHz. By using the antiparallel coupled line instead of the parallel coupled line, the first spurious frequency is occurred at 3.71 f 0 and the stopband rejection considerably improved.

Using locally produced photovoltaic energy to charge electric vehicles

Mobility in Switzerland currently consumes about 35% of the total energy demand. While internal combustion engines still generate most of it, the increasing number of electric vehicles changes the landscape by decoupling energy production from consumption. This allows using more sustainable energy sources, such as photovoltaics (PV), hydroelectric power plants or wind turbines. In the past years, the number of PV installations has grown rapidly in Switzerland. It is expected that PV has the highest growth potential of all renewable energy sources. Solar panels are especially interesting, as they can be installed on most buildings, which distributes the electricity production. However, due to frequent fluctuations in production, PV poses a challenge for the existing power grid. It is unclear to what extent PV production can be increased without the need for extensions of the power grid, such as additional transmission lines or storage capabilities. Electric vehicles could be used to consume fluctuating electricity production. In this paper, we study the effects of using locally produced photovoltaic power to recharge electric vehicles of commuters in individual Swiss municipalities. Such an analysis not only gives us indications of the potentials and limits of using photovoltaics to satisfy mobility energy demands, but can also be used to better direct subsidies and plan the electrical grid.

Fibonacci series-based local search in spider monkey optimisation for transmission expansion planning

The power system is a complex interconnected network which consists of four components: generation, distribution, transmission, and load. The loads may be varying in nature. For supplying these loads, with an aim of minimum losses in transmission and distribution, the additional transmission lines are required to be added for expansion. To find out the optimum locations of these additional lines are a complex and challenging task. Swarm intelligence motivated algorithms have been proved to be efficient to deal this type of optimisation problem. Therefore, this work applies a recent swarm intelligence motivated algorithm namely, spider monkey optimisation (SMO) to identify the optimum locations for the additional lines in the system. Further, to augment the solution search capacity of SMO algorithm, a Fibonacci series-based local search (FLS) is proposed and incorporated with SMO. The modified SMO is named as Fibonacci inspired spider monkey optimisation algorithm (FSMO). The authenticity of the suggested FSMO is analysed through statistical analysis over 20 benchmark functions. Further, both the algorithms, FSMO and SMO are applied to solve the transmission expansion planning (TEP) problem for IEEE-24 bus system. The reported results are judged against other state-of-art algorithms for solving TEP issues.

A Broadband High-Efficiency Doherty Power Amplifier With Integrated Compensating Reactance

This paper presents a high-efficiency gallium nitride Doherty power amplifier (DPA) using an integrated compensating reactance (CR) for broadband operation. With an additional quarter-wavelength transmission line integrated in the peaking amplifier output, a CR is generated to compensate the load impedance of the carrier amplifier in the low-power region and thus enhance the back-off efficiency over a wide frequency range without affecting the Doherty load modulation at saturation. For this purpose, a peaking output matching network (OMN) is employed to convert the output impedance of the peaking device into quasi-short circuit when it is off and achieve proper impedance matching when it is on. A two-point matching technique using the transmission (ABCD) matrix is employed to design such desired OMN. Measurement results show that the DPA has a 6-dB back-off efficiency of 50%-55% and a saturated efficiency of 57%-71% over the frequency band of 1.7-2.8 GHz (49% fractional bandwidth). When driven by a 20-MHz long term evolution modulated signal at 6.5-dB back-off power, the DPA can achieve an average efficiency of more than 50% with high linearity after linearization over the design frequency band.

Transmission Lines Overload Alleviation by Generation Rescheduling and Load Shedding

AbstractIn this paper, transmission lines overload alleviation for the Sudan National Grid has been performed. Resizing the transmission system components is not suitable during the operation. On the contrary, in that case, alleviation of the overloads by generation rescheduling is suitable and effective. Decreasing the generation station output relieves transmission line overload, but to maintain the power equilibrium, the output of other generation stations must be increased, making sure no additional transmission lines are being overloaded. A simple, efficient, fast, and accurate technique for the alleviation of line overloads by corrective generation rescheduling and load shedding is applied to alleviate the overloads. The method ensures that alleviation of the existing violations does not create any new violations. The load shedding is used as a last choice in cases when generation rescheduling has not completely alleviated the overloads. An overload that cannot be relieved by only rescheduling the g...

An Impedance-Transforming Coupled-Line Wilkinson Power Divider with Port Isolations and Extensions

An impedance-transforming coupled-line Wilkinson power divider with port isolations and extensions is proposed in this article. It is composed of a coupled line section, an isolation resistor, and three extended transmission lines at each port for physical isolation and convenient installation. By substituting additional transmission lines for the three port extensions and introducing coupled lines, the power divider achieves suppressed insertion loss with enhanced physical output isolation. Closed-form design equations are successfully derived and verified. The excellent agreement between simulated and measured results shows that the proposed power divider can realize required functions with good matching, low insertion loss, fine isolation, and wide bandwidth.

Negative Group Delay Circuit with Improved Signal Attenuation and Multiple Pole Characteristics

This paper presents a design of a transmission line negative group delay (NGD) circuit with multiple pole characteristics. By inserting an additional transmission line into a conventional NGD circuit, the proposed circuit provides further design parameters to obtain wideband group delay (GD) and to help reduce signal attenuation. As a result, the number of gain compensating amplifiers can be reduced, which can contribute to stable operation when integrated into RF systems. The multiple pole characteristics can provide wider NGD bandwidth and can be obtained by connecting resonators with slightly different center frequencies separated by quarter-wavelength transmission lines. For experimental validation, an NGD circuit with two poles GD characteristic is designed, simulated, and measured.

Flexible and miniaturized power divider

A new flexible and miniaturized power divider (PD), based on the Wilkinson PD topology, is carried out in this paper. Flexibility and size reduction are achieved simultaneously thanks to both an open-stub loading the input port and additional transmission lines (TLines) connecting the output ports to the isolation resistance. Design equations and rules are given. As a proof-of-concept, two PDs working at 2.45 GHz were fabricated and measured. Then, on the basis of the previous developments, a 1:4 power-dividing feeding network was realized. It highlights the high performance and flexibility of the proposed PD. Agreement between simulation and measurement results is very good, for PDs as well as for the feeding network, thus validating the proposed approach. This concept is straightforward to be applied at higher frequencies, in particular in the millimeter-wave range on CMOS technologies, where flexibility in the choice of the TLines characteristic impedances and size reduction are mandatory.

Estimating life-cycle energy payback ratio of overhead transmission line toward low carbon development

The energy conservation plays an important role for low carbon development. In order to evaluate the energy conservation in the full life-cycle, a scheme to estimate the energy consumption, or alternatively the energy pay, in constructing an overhead transmission line is proposed in this paper. The analysis of a typical projection is given for demonstration. With new additional overhead transmission lines, the energy consumption, known as the power loss in power network, is expected to be decline, which is defined in this paper as the energy payback. In order to estimate this kind of contribution, the scheme that consisted of load forecast, production simulation for generating systems, load flow simulation and power loss calculation has been proposed. Case studies, based on the IEEE 24-bus test system, are given to demonstrate the efficacy of the schemes. Moreover, several presumptive scenarios are deployed and analysed with the presented schemes for comparison.

Electromagnetic noise in electric circuits: Ringing and resonance phenomena in the common mode

It is generally believed that electromagnetic noise originates from the coupling of electric signals in a circuit with electric signals in surrounding materials in the environment. However, the noise phenomenon had not been quantified until now. In order to study the phenomenon of noise, we considered a standard circuit (two transmission lines), to which an additional transmission line was introduced in order to explicitly take into account the effect of conductors in the environment. We performed calculations using a newly developed multiconductor transmission-line theory for the resulting three-line circuit in order to determine the magnitude of the coupling between the circuit and the conductors in the environment under various conditions. We observed ringing and resonance phenomena in the common mode, which influenced the performance of the normal mode as electromagnetic noise. Our findings were confirmed by recent experiments in which conductor lines were arranged in various ways using a printed circuit board (PCB). The ordinary usage of electricity in the standard electric circuit was found to be worst in exciting the common mode noise.

Long-range response to transmission line disturbances in DC electricity grids

We consider a DC electricity grid composed of transmission lines connecting power generators and consumers at its nodes. The DC grid is described by nonlinear equations derived from Kirchhoff's law. For an initial distribution of consumed and generated power, and given transmission line conductances, we determine the geographical distribution of voltages at the nodes. Adjusting the generated power for the Joule heating losses, we then calculate the electrical power flow through the transmission lines. Next, we study the response of the grid to an additional transmission line between two sites of the grid and calculate the resulting change in the power flow distribution. This change is found to decay slowly in space, with a power of the distance from the additional line. We find the geographical distribution of the power transmission, when a link is added. With a finite probability the maximal load in the grid becomes larger when a transmission line is added, a phenomenon that is known as Braess' paradox. We find that this phenomenon is more pronounced in a DC grid described by the nonlinear equations derived from Kirchhoff's law than in a linearised flow model studied previously in Ref. \cite{witthaut2013}. We observe furthermore that the increase in the load of the transmission lines due to an added line is of the same order of magnitude as Joule heating. Interestingly, for a fixed system size the load of the lines increases with the degree of disorder in the geographical distribution of consumers and producers.

Trantanella Wilkinson power divider with additional transmission lines for simple layout

By adding extra transmission lines between 90° transmission lines at an arbitrary phase angle from the input terminal, a modified Trantanella Wilkinson power divider with a simple layout is presented. Design equations for characteristic impedances and complex isolation components are derived from even- and odd-mode analysis. Parallel and series RC circuits are chosen to realise the complex isolation components, and bandwidths are also discussed. For both parallel and series RC circuits, two experimental circuits were fabricated under the same conditions. The experimental results showed good agreement with the results of simulation.

Grid infrastructure for renewable power in Europe: The environmental cost

Climate mitigation policies in Europe call for an extensive build-up of renewable power, which will increase from 320 GW in 2012 to 536 GW by 2020. The renewable expansion will mainly consist of the installation of new wind and solar power plants, which require additional transmission lines. The European Network of Transmission System Operators for Electricity estimates that 45,300 km of new or upgraded lines are necessary in the region over the next decade to accommodate the renewable power sources. Building a grid for renewables will help Europe achieve its climate goals, but other resulting environmental impacts have not yet been quantified. In this article a LCA (Life Cycle Assessment) for the transmission grid expansion is performed. The results show that the grid extension projects correspond to a total impact of 10.7 Mton CO2 eq. and 11.2 Mton Fe eq. Electricity transmission in Europe in 2020 will be more material intensive, requiring about 10% more metal inputs per kWh than today. Manufacturing processes for the production of transmission equipment are important for some impacts categories, particularly water depletion. Finally, a sensitivity analysis regarding recycling rates indicates that the results in some impact categories present great variation depending on the rates assumed.

Realization of Multi-Band 3-dB Branch-Line Couplers Using Fourier-Based Transmission Line Profiles

A new procedure for the design of multi-band branch-line couplers utilizing microstrip non-uniform transmission lines with Fourier-based profiles is presented in this article. The general method is accomplished by replacing the quarter-wave uniform transmission lines of a conventional coupler with multi-band non-uniform transmission lines of the same lengths, without including additional transmission lines or matching networks. The design of non-uniform transmission line couplers is performed using even- and odd-mode analysis. The proposed structure is relatively simple and is fabricated on a single-layered microstrip board. Two design examples of dual- and triple-band branch-line couplers suitable for global system mobile (GSM), wireless local area networks, and WiFi communications are designed, fabricated, and experimentally evaluated to validate the proposed methodology.

Novel Dual-Band Matching Network for Effective Design of Concurrent Dual-Band Power Amplifiers

In this paper, a systematic approach to the synthesis of a novel dual-band matching network is proposed and applied to design a dual-band power amplifier (PA) capable of maintaining high power efficiency at two arbitrary, widely spaced frequencies. The proposed network incorporates two different stages. The first one transforms the targeted complex impedances, at the two operating frequencies, to a real one. The second stage is a dual band filter that ensures the matching of the former real impedance to the termination impedance. An additional transmission line is incorporated between the two stages to adjust the impedances at the second and third harmonics without altering the impedances seen at the fundamental frequencies. The harmonic termination control is very effective in enhancing the efficiency of radio frequency transistors, especially when exploiting the Class J design space. The proposed dual-band matching network synthesis methodology was applied to design a dual band PA using a packaged 45 W Gallium Nitride (GaN) transistor. The PA prototype maintained a peak power efficiency of about 68% at operating frequencies of 800 MHz and 1.9 GHz. In addition, a Volterra based digital pre-distortion technique was successfully applied to linearize the PA response around the two operating frequencies.

Distributed Transmission Line Negative Group Delay Circuit With Improved Signal Attenuation

In this letter, a novel design and implementation of a distributed negative group delay circuit (NGDC) with reduced signal attenuation is demonstrated. By inserting an additional transmission line Z2 into the conventional NGDC, the proposed NGDC provides further design parameters in order to obtain the required differential-phase group delay (GD) time and help to reduce the signal attenuation. As a result, the number of gain compensating amplifiers can be reduced, which can contribute to the efficiency enhancement as well as the stable operation when integrated into the RF system. Both theory and experiment are provided to validate the proposed structure. From the experiment, for the same GD time of -7.9 ns, the signal attenuation of the proposed circuit is 16.5 dB, an improvement signal attenuation of the conventional circuit of 19.2 dB.

Application of Differential Evolution Algorithm in Transmission Expansion Planning

Transmission expansion planning has become a complicated procedure more than it was. The rapid growth of the transmission networks and the deregulation has introduced more objectives and uncertainties to the transmission network planners. As a result of that, new approach and criteria that can replace the old ones are needed for TEP problem. The main goal of this process is to locate the additional transmission lines that must be added to meet the forecasted load in the system adequately with minimum cost. There have been several methods applied for this purpose; mathematical optimization methods, heuristic and Meta heuristic methods. This paper reviews the use of Meta heuristic method by the means of differential evolution algorithm (DEA) to solve this multi objective optimization problem. In addition, some suggestions have been made by the author that can make the DEA more efficient and applicable in the real world networks.

Real and Reactive Power Control in a Three Phase Unbalanced Load Supported by Solar PV Plant at Consumer End

In-order to improve the performance of electrical network with three phase industrial loads the real power and reactive power control is essential in today’s power crisis scenario. The reactive support is obtained by conventional devices like synchronous condenser, static capacitors, and Flexible AC Transmission System (FACTS) devices. These devices support only reactive power with additional initial cost and maintenance cost. The proposed Voltage Source Inverter (VSI) based solar power plant gives real power support at day time and it is utilized as a STAticvar COMpensator (STATCOM) at night time and gives reactive power support to the loads. The installation of solar power plant at consumer side eliminates the need for additional transmission lines and related losses and also leaves the existing lines free for other utilities and loads. The proposed Individual Phase Current Sensing (IPCS) control technique for VSI based solar power plant gives better support on reactive power at both balanced and unbalanced load conditions compared with conventional Sinusoidal Pulse Width Modulation (SPWM) technique. A proto type is fabricated and tested for various loads. The power factor cos∅ of the system is improved from 0.954 to 0.991 for balance load and 0.987 for unbalanced loads.

Installation, integration and power tests of the new fast ECRH launcher of FTU

A new ECRH launcher mainly aimed at experiments on MHD stabilization has been recently installed in FTU and integrated with a Real Time controller. The new plug-in antenna is capable of injecting two beams over wide angular ranges, ±40° in toroidal and ±15°<θ<∓44° in poloidal direction with fast mirror speed. The power is delivered to the launcher with two additional transmission lines (TL) connected to the existing ECRH system with remotely controlled switches. After the optical alignment of the TLs, a campaign of tests on the steering antenna was made with the launcher ex- and in-vessel. A procedure to calibrate the absolute mirror angular position was developed and successfully used. First high power pulses were carried out on plasma target delivering 2×0.3MW EC power for 200ms.

Can Hybrid Solar-Fossil Power Plants Mitigate CO2 at Lower Cost than PV or CSP?

Fifteen of the United States and several nations require a portion of their electricity come from solar energy. We perform an engineering-economic analysis of hybridizing concentrating solar thermal power with fossil fuel in an Integrated Solar Combined Cycle (ISCC) generator. We construct a thermodynamic model of an ISCC plant in order to examine how much solar and fossil electricity is produced and how such a power plant would operate, given hourly solar resource data and hourly electricity prices. We find that the solar portion of an ISCC power plant has a lower levelized cost of electricity than stand-alone solar power plants given strong solar resource in the US southwest and market conditions that allow the capacity factor of the solar portion of the power plant to be above 21%. From a local government perspective, current federal subsidies distort the levelized cost of electricity such that photovoltaic electricity is slightly less expensive than the solar electricity produced by the ISCC. However, if the cost of variability and additional transmission lines needed for stand-alone solar power plants are taken into account, the solar portion of an ISCC power plant may be more cost-effective.