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The 18 papers in this special section focus on contactless energy transfer (CET) systems. These papers can be grouped into the following categories: 1) a review paper on acoustic CET systems; 2) capacitive coupled CET systems; 3) novel control methods applied for CET systems: adaptive sliding mode, phase-locked loop based, etc.; and 4) modern inductive coupled CET systems with uni- and bidirectional energy flow directions, multiple and individual users, etc.

The operation of more electric aircraft is dependent on the embedded power grid. Therefore, the onboard power-distribution system must be reliable, having a high level of survivability, and promptly respond to any change in aircraft’s operation. Recent studies have presented a number of frequency-response-based tools with which to analyze both single- and multi-converter systems. The methods can be efficiently applied for on-board system analysis, stability assessment and adaptive control design. Most often, wideband measurement techniques have been applied to obtain the frequency response from a specific converter or a subsystem required for the analysis. In the methods, a broadband excitation such as a pseudo-random binary sequence (PRBS) is used as an external injection, and Fourier techniques are applied to extract the spectral information. This paper presents implementation techniques of the wideband methods using power-hardware-in-the-loop measurements based on OPAL-RT real-time simulator. The presented methods make it possible to modify the system characteristics, such as impedance behavior, in real time, thereby providing means for various stability and control design tools for on-board power distribution systems. Experimental measurements are shown from a high-power energy distribution system recently developed at DNV GL, Arnhem, Netherlands. acceptedVersion

In this paper, a modular three-phase multilevel inverter specially suited for electrical drive applications is proposed. Unlike the cascaded H-bridge inverter, this topology is based on power cells connected in cascade using two inverter legs in series. A detailed analysis of the structure and the development of design equations for the load voltage with $n$ levels are carried out using pulsewidth-modulation phase-shifted multicarrier modulation. Simulations and experimental results for a 15-kW three-phase system, with nine voltage levels, validate the study presented.

In this paper, a new control-oriented modeling methodology for the thermal dynamics of water-cooled Proton Exchange Membrane Fuel Cells (PEMFCs) is presented and validated. This methodology is not only useful for control applications, but also can be used for predicting the temperature variation across the stack, allowing to monitor its operation. The methodology has been validated in a real 600-W, 20-cells, water cooled PEMFC, with encouraging results for both the stationary and the transient states. Results show that the proposed methodology is accurate and suitable for control purposes.

In this paper, the problem of fault diagnosis of a wind farm is addressed using interval nonlinear parameter-varying (NLPV) parity equations. Fault detection is based on the use of parity equations assuming unknown but bounded description of the noise and modeling errors. The fault detection test is based on checking the consistency between the measurements and the model, by finding if the formers are inside the interval prediction bounds. The fault isolation algorithm is based on analyzing the observed fault signatures online and matching them with the theoretical ones obtained using structural analysis. Finally, the proposed approach is tested using the wind farm benchmark proposed in the context of the wind farm faultdetection-and-isolation/fault-tolerant-control competition., This work has been funded by the Spanish MINECO through the project CYCYT SHERECS (ref. DPI2011-26243), by the European Commission through contract i-Sense (ref. FP7-ICT-2009-6-270428), by AGAUR through the contracts FI-DGR 2013 (ref. 2013FIB00218) and FI-DGR 2014 (ref. 2014FI B1 00172) and by the DGR of Generalitat de Catalunya (SAC group Ref. 2014/SGR/374).

Recent technological advances have enabled distributed control systems to be implemented via networks. This allows feedback control loops to be closed over communication channels. This paper develops a control system with high-speed and real-time communication links. Two-degrees-of-freedom control is utilized in this servo control system, and sigma-delta modulation is employed to compress data and to transmit the signal over the transmission channels between the controller and the controlled plant. Simulation results show that the controller can compensate the possible existing noise in the transmission channels. In addition, the developed system is implemented in field-programmable gate arrays. We developed a real-time closed-loop control system that has a communication channel whose control-sampling period is 600 ns and can reduce the sampling period of the controller module to hundreds of nanoseconds.

This paper proposes position and force control of a screw motor with power-saving axial-gap displacement adjustment. The motor has a helical-shape mover, which moves in a helical-shape stator without contact. Due to the fabrication process, the actual helical shapes of the mover and the stator are not completely uniform, and the air-gap length between the mover and the stator slightly changes, depending on the mover rotation angle. The d-axis current remains a finite value, and copper loss arises even when the mover is located at the center between the stator cores. A power-saving axial-gap displacement adjustment method is proposed to solve this problem. The proposed control is experimentally verified.

A robust servo-system, based on a combination of linear robust control and sliding mode control have been proposed. This new control system can be said to be a non-linear system (sliding mode control system) which has a inner loop of linear control (two-degree-of-freedom control). Due to this inner loop of linear control, a disturbance is strongly suppressed but not completely. Then, the outer loop of sliding mode control eliminates this disturbance suppression error. First in this paper, a linear robust-servo design of two-degree-of-freedom control system is shown. Next, a sliding mode control is applied to this system and the disturbance suppression characteristics are discussed. Then, through the simulations and experiments, it is proved that the introduction of non-linear control (sliding mode) drastically improves the disturbance suppression characteristics of a linear system (two-degree-of-freedom control).

Fuzzy controllers are used in many applications because of their rapid design by translating heuristic knowledge, robustness against perturbations, and smoothness in the control action. However, they require parallel processing and special operators (such as fuzzification or defuzzification) which are not available in standard digital signal processors (DSPs), thus complicating their direct implementation. This paper describes an efficient design methodology that allows starting with any kind of fuzzy controller and subsequently transforming it until a system suitable for easy DSP implementation is obtained. Such methodology is greatly aided by the design environment Xfuzzy 3. The parking problem of an autonomous robot is described to illustrate the steps of this methodology. Real experiments with the autonomous robot ROMEO 4R demonstrate efficiency of the designed fuzzy controller embedded into a stand-alone card based on a fixed-point DSP from Texas Instruments., his work was supported in part by the Spanish CICYT Projects DPI2005-02293 and TEC2005-04359, and by the Projects TIC2006-635 and TEP2006-375 from the Andalusian regional Government.

The authors argue that one should keep things simple when controlling bidirectional pulsewidth modulation rectifiers by considering the utility grid as a virtual electric machine. The advantage is that the air-gap flux of this big machine can be directly measured in a straightforward way. Therefore, as shown in this paper, principles of field orientation can be applied to control the power flow, yielding high-dynamic performance.