Transmission system operators have an increased interest in the active participation of wind power plants (WPP) in the power balance control of power systems with large wind power penetration. The emphasis in this study is on the integration of WPPs into the automatic generation control (AGC) of the power system. The present paper proposes a coordinated control strategy for the AGC between combined heat and power plants (CHPs) and WPPs to enhance the security and the reliability of a power system operation in the case of a large wind power penetration. The proposed strategy, described and exemplified for the future Danish power system, takes the hour-ahead regulating power plan for generation and power exchange with neighbouring power systems into account. The performance of the proposed strategy for coordinated secondary control is assessed and discussed by means of simulations for different possible future scenarios, when wind power production in the power system is high and conventional production from CHPs is at a minimum level. The investigation results of the proposed control strategy have shown that the WPPs can actively help the AGC, and reduce the real-time power imbalance in the power system, by down regulating their production when CHPs are unable to provide the required response.

A novel scheme for optical millimetre-wave (mm-wave) generation based on tandem sub-carrier multiplexing in hybrid communication systems is suggested. The method is analysed mathematically for optimum settings. The tandem single side-band (TSSB) method is tolerant to fibre chromatic dispersion. However, the TSSB technique is prone to critical interference of unwanted harmonics which may result in poor data transmission bit error rate (BER). Based on the proposed mathematical derivation for TSSB modulation, a framework is provided to enhance the mm-wave generation system performance. Up to 2 Gb/s data transmission over multiple 60 GHz sub-bands is considered. The model includes a single-mode fibre with chromatic dispersion factor of 16 ps/(nm km). Two cascaded dual electrode Mach–Zehnder modulators are used to generate TSSB 60 GHz sub-bands. Three oscillators are required to generate two tandem mm-wave signals. A proper selection of these three frequencies is vital to guarantee a successful data transmission. Mathematical analysis is carried out to verify the proposed scheme and a summary of appropriate frequency sets is presented and discussed. The BER curves are obtained. The results verify that the TSSB-based mm-wave generation framework proposed in this study guarantees data transmission with an acceptable BER.

The authors analysed the cross-correlation of photovoltaic (PV) output fluctuation for the actual PV output time series data in both the Tokyo area and the whole of Japan using the principal component analysis with the random matrix theory. Based on the obtained cross-correlation coefficients, the forecast error for PV output was estimated with/without considering the cross-correlations. Then the operation schedule of thermal plants is calculated to integrate PV output using the proposed unit commitment model with the estimated forecast error. The system-balancing cost of PV system was also estimated with or without demand response. Finally, validity of the concept of ‘local production for local consumption of renewable energy’ and alternative policy implications were discussed.

A theorem is presented which has applications in the numerical computation of fixed points of recursive functions. If a sequence of functions {f_n } is convergent on a metric space I ⊆ ℝ, then it is possible to observe this behaviour on the set 𝔻 ⊂ ℚ of all numbers represented in a computer. However, as 𝔻 is not complete, the representation of f_n on 𝔻 is subject to an error. Then f_n and f_m are considered equal when its differences computed on 𝔻 are equal or lower than the sum of error of each f_n and f_m . An example is given to illustrate the use of the theorem.

This paper discusses the methodology used in the development of advanced traveller information system (ATIS). This system is designed as a part of web geographical information system (GIS) based advanced public transport systems. Web GIS-based ATIS system includes spatial data for the designed functionalities and provides GIS capabilities to the users through the internet. In addition to these functionalities, a route planning algorithm to plan the shortest route between the selected bus transit points is also designed using ant system algorithm and is integrated with web GIS. This study presents the ant system algorithm adopted for the shortest route finding with the methodology developed for the web GIS-based ATIS system for the study area of the city Chandigarh in India using open source software MapServer as web map server. This study also discusses the three-tier logical architecture used in the methodology for providing GIS capabilities to the user over the internet.

This study analyses an interconnection system based on differentially sinusoidal pulse width modulation, used for the interconnection to the grid of a variable speed wind turbine. The modulation technique used provides specific advantages in comparison with the commonly used sinusoidal pulse width modulation (SPWM) technique, such as lower DC bus voltage requirements, smaller switching losses for the same switching frequency as well as less higher harmonic content in the voltage waveforms produced. The respective control system is also described in detail. Thus this study provides a guide enabling the design of any interconnection system based on this modulation technique.

Closed-form analytical formulas are provided to calculate the dc bus harmonics of a three-phase sinusoidal pulse width modulation (SPWM) inverter. The harmonic analysis is performed by using a double Fourier series approach to determine the dc bus current frequency spectrum. For an arbitrary modulation index and load power factor, the full harmonic components of the inverter dc side current are calculated. Based on the developed analytical model, an equivalent circuit is proposed for the inverter harmonic analysis towards the dc bus. Moreover, the impacts of line harmonics and zero sequence injection in controller towards the dc bus are presented. The results show that the 5th and 7th ac line harmonics on the dc side current is appearance of the 6th harmonic in the dc side. The impact of zero sequence injection to the controller on the dc side is negligible. In addition to analytical formulation, different simulations and extensive measurements performed which the results verified the presented analytical framework.

The P -matrix is commonly used to analyse surface acoustic waves (SAW) elements such as the interdigital transducer (IDT) but, when some IDTs are connected through their acoustic ports, their frequency response could be calculated easily in terms of their admittances. Instead of the P -matrix, Y -matrix also allows coupling of the system to another electric or electronic device. Here, the authors present a general method to obtain the Y -matrix (with size N × N) of a SAW device with N electrical terminals connected to N different voltage sources. This method considers the reflections from the edges or any other non-electrical elements that can cause reflections beyond P -matrices. In addition, it has been shown that when there are no reflections and there are two P -matrices, this method converges to well-known previous results. Furthermore, the authors present two cases that could be used to analyse a SAW device: the input admittance and the equivalent P -matrix for a SAW device when a Y -matrix is connected to the electrical port of the SAW device. Also, the authors have calculated the acoustic relations for two SAW devices connected through their electric ports. Furthermore, these methods are exemplified through their application to a SAW system composed of three different IDTs and to an IDT and an inductor connected to its electrical port.

The authors developed a high-efficiency gallium-nitride (GaN) Class-E converter for a 6.78 MHz magnetic resonant wireless power transfer system. A negative-bias gate driver circuit made it possible to use a depletion mode GaN high-electron-mobility transistor (HEMT), and simplified the converter circuit. As the depletion mode GaN HEMT with very small gate–source capacitance provided almost ideal zero-voltage switching, the authors attained a drain efficiency of 98.8% and a total efficiency of 97.7%, including power consumption of a gate driver circuit, at a power output of 33 W. In addition, the authors demonstrated a 6.78 MHz magnetic resonant wireless power transfer system that consisted of the GaN Class-E converter, a pair of magnetic resonant coils 150 mm in diameter with an air-gap distance of 40 mm, and a full-bridge rectifier using Si Schottky barrier diodes. The system achieved a dc–dc efficiency of 82.8% at a power output of 25 W. The efficiencies of coil coupling and the rectifier were estimated to be ∼ 94 and 90%, respectively.

To monitor water level at long distance, a fibre-based time-domain reflectometry network is proposed. A collimator at each fibre end of a tree-type network retrieves 1.55 μm wavelength pulses that are reflected back from remote surfaces. Since this enables a power-supply-free sensor network with non-metal media, this system is expected to be less susceptible to lightning strikes and power cuts than conventional systems that use electrically powered sensors and metal cables. In the present Letter, a successful simultaneous monitoring experiment of two water levels in the laboratory, as well as a trial for detecting a disturbed surface by beam-expanding is reported.