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Within future homes and electrical power networks, emphasis is being placed on intelligent, distributed measurement devices. In particular, the recognition of individual or aggregated loads through harmonic signature has been proposed as a useful way to enhance the value of home energy monitoring/control. Clearly, the cost of implementing such measurement devices is a major barrier to acceptance. In a recent project, a challenge was set to implement real-time software on an ARM® Cortex™ LPC1768 microcontroller platform (chip cost c. £4). The software must be capable of measuring a single-phase AC frequency, real and reactive power flows and provide a full breakdown of the voltage and current (and power) behaviour via harmonic analysis from DC to the 40th, in real-time with a new output every 20 ms. In addition, the algorithm must be capable of adapting the measurement when the frequency is not nominal (50 Hz) so that spectral leakage is minimised. It is found that the LPC1768 processor is capable of supporting such an algorithm when it is coded appropriately. This knowledge de-risks the proposed use of such cheap microcontrollers for these relatively complex tasks.

To avoid stray current and maintain the benefit of no phase-split in the DC traction power supply system, an AC traction power supply system was proposed for the urban public transport such as metro and light rail transit. The proposed system consists of a main substation (MSS) and cable traction network (CTN). The MSS includes a single-phase main traction transformer and a negative-sequence compensation device, while the CTN includes double-core cables, traction transformers, overhead catenary system, rails, etc. Several key techniques for the proposed system were put forward and discussed, which can be summarized as (1) the power supply principle, equivalent circuit and transmission ability of the CTN, the cable-catenary matching technique, and the selection of catenary voltage level; (2) the segmentation technology and status identification method for traction power supply network, distributed and centralized protection schemes, etc.; (3) a power supply scheme for single-line MSS and a power supply scheme of MSS shared by two or more lines. The proposed industrial frequency single-phase AC traction power supply system shows an excellent technical performance, good economy, and high reliability, hence provides a new alternative for metro and urban rail transit power supply systems.

A novel pulse-width modulation-less three-phase multilevel DC–AC inverter using only one DC source is presented in this study. The proposed approach enables multilevel output to be realised by a few cascaded H-bridges and a three-leg inverter using minimum number of power switches. As an illustration, a 19-level three-phase inverter has been implemented based on cascading four H-bridges and a three-leg inverter. Switching strategy has been derived for the proposed inverter such that a three-phase power system with 19 output levels can be realised with proper capacitor voltage regulation and a single energy source. Only 22 power switches instead of 108 are required to achieve the objective. Experimental results are included to demonstrate the outstanding performance of the proposed inverter. Although only 50 Hz results are presented, the proposed inverter could be applied in aircraft systems by only changing the switching frequency.

The objective of this paper is to propose an active ripple filter (ARF) using the patented DC-side direct current control for eliminating the double-line-frequency current ripple in a single-phase DC/AC conversion system. The proposed ARF and its control strategies can not only prolong the usage life of the DC energy source but also improve the DC/AC system performance. At first, the phenomena of double-line-frequency current ripple and the operation principle of the ARF are illustrated. Then, steady-state analysis, small-signal model, and control loop design of the ARF architecture are derived. The proposed control system includes: (1) a DC current control loop to provide the excellent ripple eliminating performance on the output of the DC energy source; (2) a voltage control loop for the high-side DC-bus voltage of the ARF to achieve good steady-state and transient-state responses; (3) a voltage feedforward loop for the low-side voltage of the ARF to cancel the voltage fluctuation caused by the instability of the DC energy source. Finally, the feasibility of the proposed concept can be verified by the system simulation, and the experimental results show that the nearly zero double-line-frequency current ripple on the DC-side in a single-phase DC/AC conversion system can be achieved.

This study presents a unified time-domain formulation of switching frequency for hysteresis current controlled AC/DC and DC/AC grid connected converters. It is shown that the generalised expression of switching frequency obtained can be used for any mode of operation of the converter based on phase relation between the reference AC current and grid voltage. The presented analysis provides information of maximum, minimum and average switching frequencies for all modes of the converter operation. The analytical results derived under different configurations are verified through the experimental results obtained using FPGA-based implementation of the controller for the converter. The applications of the results are shown on the three different single-phase systems operating in current control mode: (i) static synchronous compensator, (ii) boost rectifier and (iii) grid interface of wind-turbine system. The results of switching operations in these applications are verified using simulation studies performed in power systems CAD/electromagnetic transients including DC (PSCAD/EMTDC) software.

Modular multilevel converter (MMC) is troubled by the inherent second harmonic of single-phase ac power. By adding feedforward to the modulation signal, low-frequency harmonic voltages are significantly reduced thus overcoming an important weakness of MMC. Capacitors of sub-modules do not have to be over-sized. If desired for protection, transformers can be wye-connected with grounded neutral. The reduction method is based on harmonic function analysis. In addition to deriving algebraic formulae of harmonic voltage components of ‘open loop’ control, this study makes original contributions by deriving formulae which include feedforward control. Analytical insights from the formulae have shown the way to design feedforward methods to reduce low-frequency harmonics. Validation is by simulations using SIMULINK/MATLAB.

A power filter is necessary to connect the output of a power converter to the grid so as to reduce the harmonic distortion introduced in the line current and voltage by the power converter. Many a times, a transformer is also present before the point of common coupling. Magnetic components often constitute a significant part of the overall weight, size and cost of the grid interface scheme. So, a compact inexpensive design is desirable. A higher-order LCL-filter and a transformer are increasingly being considered for grid interconnection of the power converter. This study proposes a design method based on a three-winding transformer, that generates an integrated structure that behaves as an LCL-filter, with both the filter inductances and the transformer that are merged into a single electromagnetic component. The parameters of the transformer are derived analytically. It is shown that along with a filter capacitor, the transformer parameters provide the filtering action of an LCL-filter. A single-phase full-bridge power converter is operated as a static compensator for performance evaluation of the integrated filter transformer. A resonant integrator-based single-phase phase locked loop and stationary frame AC current controller are employed for grid frequency synchronisation and line current control, respectively.

This paper proposes a single-phase, soft-switching, high step-up ac–dc converter based on a diode-capacitor voltage multiplier (DCVM) with a power factor correction (PFC). By applying the PFC technology, the proposed converter promises a near-unity power factor and a low distortion line current, while providing an adjustable, high step-up dc voltage that the conventional DCVM circuits cannot achieve. To reduce the switching losses, an auxiliary circuit for implementing a soft commutation is added to the power stage of the proposed converter. For operating at a fixed switching frequency, both the main and the auxiliary switches in the power stage are turned off with the zero-current transmission (ZCT). The operating principle, the design considerations and the control strategy of the proposed converter all are detailed and investigated in this paper. A 1.2 kV/500 W laboratory prototype, which employs a commercial PFC IC UC3854 as a controller, is built for test, measurement and evaluation. Under the full-load conditions, the measured power factor, the total harmonic distortion of the line current and the system efficiency are 99.6, 4.86 and 94%, respectively. The experimental results demonstrate the validity of the proposed converter.

Nikola Tesla was a major contributor to the electrical revolution that transformed daily life at the turn of the twentieth century. His inventions, patents, and theoretical work formed the basis of modern AC electricity, and contributed to the development of radio and television. Like his competitor Thomas Edison, Tesla was one of America's first celebrity scientists, enjoying the company of New York high society and dazzling the likes of Mark Twain with his electrical demonstrations. An astute self-promoter and gifted showman, he cultivated a public image of the eccentric genius. Even at the end of his life when he was living in poverty, Tesla still attracted reporters to his annual birthday interview, regaling them with claims that he had invented a particle-beam weapon capable of bringing down enemy aircraft. Plenty of biographies glamorize Tesla and his eccentricities, but until now none has carefully examined what, how, and why he invented. In this groundbreaking book, W. Bernard Carlson demystifies the legendary inventor, placing him within the cultural and technological context of his time, and focusing on his inventions themselves as well as the creation and maintenance of his celebrity. Drawing on original documents from Tesla's private and public life, Carlson shows how he was an \"idealist\" inventor who sought the perfect experimental realization of a great idea or principle, and who skillfully sold his inventions to the public through mythmaking and illusion. This major biography sheds new light on Tesla's visionary approach to invention and the business strategies behind his most important technological breakthroughs.