This paper presents the theoretical derivation and implementation of a novel direct power control for open-winding brushless doubly-fed reluctance generator (OW-BDFRG). As one of the promising brushless candidates, the OW-BDFRG is characterized with two stator windings fed by a dual controllable two-level three-phase converters through a common DC bus with common mode voltage elimination. The parameter-free control strategy is designed to obtain maximum power point tracking with variable speed constant frequency (VSCF) for wind energy conversion systems (WECSs). Compared to the traditional three-level converter systems, the DC bus voltage, ACside voltage and capacity ratings of the proposed converter system are notably high while the reliability, redundancy and fault tolerance are significantly improved. Effectiveness, correctness and robustness of the proposed control strategy and the common mode voltage elimination scheme are evaluated and confirmed through simulation and experimental tests on a 42 kW generator prototype typical for VSCF-WECS. Index Terms-Brushless doubly-fed machines, power control, common mode voltage, open-winding, variable speed constant frequency, maximum power point tracking. NOMENCLATURE u p , u c Power, control winding phase voltages [V] i p , i c Power, control winding phase currents [A] R p , R c Power, control winding resistances [Ω] p p , p c , p r Power, control and rotor pole pairs L p , L c Power, control winding self-inductan. [H] ψ p , ψ c Power, control winding flux linkages [Wb] ψ pc , L pc Mutual flux [Wb] and inductance [H] f p , f c , ω p , ω c Power, control winding frequencies [Hz] and their angular frequencies [rad/s]
This paper presents the simulation and experimental evaluation of a novel power error comparison direct power control (PEC-DPC) strategy of the open-winding brushless doubly-fed reluctance generator (OW-BDFRG) for wind energy conversion systems (WECSs). As one of the promising candidates for limited speed range application of pump-alike and wind turbine with partially-rated converter. The emerging OW-BDFRG employed for the proposed PEC-DPC is fed via dual low-cost two-level converters, while the DPC concept is derived from the fundamental dynamic analyses of the calculated and controllable electrical power and flux of the BDFRG with two stators measurable voltage and current. Compared to the traditional two-level and three-level converter systems, the OW-BDFRG requires lower rated capacity of power devices and switching frequency converter, though have more flexible switching mode, higher reliability, redundancy and fault tolerance capability. The performance correctness and effectiveness of the proposed DPC strategy with the selected and optimised switching vector scheme are evaluated and confirmed on a 25 kW generator test rig. Index Terms-Brushless doubly-fed wind power generators, open-winding, direct power control, dual two-level converters. I. INTRODUCTION T HE brushless doubly-fed (reluctance) generators (BD-FGs) ,  have some essential features in dealing with issues related to reliability and maintenance operation in long-running variable speed constant frequency (VSCF). Such advantages are due to their robust structure since carbon brushes and slip-rings are eradicated. Moreover they adopt a similar doubly-excited feature similar to doubly-fed induction generators (DFIGs). The BDFGs have evolved from DFIGs but moved the rotor winding to the stator, thus characterised by two standard distributed three-phase stators with different Manuscript
--In this paper, a new open-winding control strategy is proposed for a brushless doubly-fed reluctance generator (BDFRG) used for standalone wind turbine or ship generators. The BDFRG is characterized with two windings on the stator: a power winding and a control winding. The control winding is fed with dual two-level three-phase converters, and a vector control scheme based on space vector pulse width modulation (SVPWM) is designed. Compared to traditional three-level inverter systems, the dc-link voltage and the voltage rating of power devices in the proposed system are reduced by 50% while still greatly improving the reliability, redundancy and fault tolerance of the proposed system by increasing the switching modes. Its performance is evaluated by simulation in MATLAB/SIMULINK, and an experimental study on a 42-kW prototype machine.Index Terms--Brushless doubly-fed reluctance generator (BDFRG), dual two-level converters, open-winding, space vector pulse width modulation (SVPWM).
This paper presents a novel control strategy to force a vertical take-off and landing (VTOL) aircraft to accomplish the pinpoint landing task. The control development is based on the image-based visual servoing method and the back-stepping technique; its design differs from the existing methods because the controller maps the image errors onto the actuator space via a visual model which does not contain the depth information of the feature point. The novelty of the proposed method is to extend the image-based visual servoing technique to the VTOL aircraft control. In addition, the Lyapunov theory is used to prove the asymptotic stability of the VTOL aircraft visual servoing system, while the image error can converge to zero. Furthermore, simulations have been also conducted to demonstrate the performances of the proposed method.
The development and testing of an integrated power module (IPM) for a waste heat recovery system is described. The IPM is part of a waste heat recovery system based on the organic Rankine cycle. The waste heat system can recover energy from a wide variety of heat sources including landfill gas, reciprocating engine exhaust, solar, geothermal, boilers, and other industrial processes. The IPM incorporates a high performance, high speed permanent magnet generator with an integrated expansion turbine and low loss magnetic bearings. The IPM operates between 20,000 rpm and 26,500 rpm depending on the energy available from the heat source. The varying frequency voltage supplied by the generator is connected to the grid using an active/active power electronics package that can deliver power at 400–480 Vac (50 Hz or 60 Hz). Active magnetic bearings (AMBs) were chosen for the application because they can operate directly in the working fluid, have low losses, and provide high reliability and remote monitoring capabilities. This system has a flow-through design and an inboard impeller layout that produces desirable rotordynamics for a simple magnetic bearing control. An extensive shop testing procedure is described, and measurements and predictions are presented, showing good correlation. Shop testing of the IPM in the waste heat system has been completed for 15 systems. The magnetic bearings and backup bearings have performed as designed. The thrust balancing system has limited the thrust load that must be reacted by the axial magnetic bearings to 25% of the design load capacity in the worst case. The first field unit was installed in April 2009 at a biogas site.
A new direct power control (DPC) strategy for openwinding brushless doubly-fed reluctance generators (BDFRGs) with variable speed constant frequency is proposed. The control winding is open-circuited and fed by dual traditional two-level three phase converters using a common DC bus, and the DPC strategy aiming at maximum power point tracking and common mode voltage elimination is designed. Compared to the traditional three-level converter systems, the DC bus voltage, the voltage rating of power devices and capacity of the single two-level converter are all reduced by 50% while the reliability, redundancy and fault tolerance of the proposed system still greatly improved. Consequently its effectiveness is evaluated by simulation tests on a 42 kW prototype generator in MATLAB/SIMULINK.
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