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This paper reviews the design procedure of wound-type Inter-Phase Reactors used in high power rectifier systems, and gives some guidelines for an optimized sizing aimed at minimizing costs and active mass. In particular, the paper proposes a design algorithm to identify the optimal number of coils and turns and clarifies the role of the air-gap in minimizing the magneto-motive force unbalance and...
This paper analyses the operation of a variable-speed wound-field synchronous generator (WFSG) connected to a constant-voltage dc-system. The challenges for the operation under variable speed and constant voltage and the need for a dc-dc converter to adjust the stator side voltage are pointed out. The boost converter introduces a degree of freedom which can be used to optimize the WFSG efficiency...
This paper proposes a control scheme for a stand-alone DFIG-DC system where the stator and the rotor are connected to a dc load by an uncontrolled diode bridge and a VSI respectively. The stator frequency and the dc voltage regulation are achieved by a field oriented control, however, with respect to the classical ac stand alone DFIG, the role of the rotor currents is swapped, namely: the d-axis and...
The operation of a synchronous generator connected to a dc load by a six-pulse diode bridge is analyzed in this paper. The dc load has in parallel a high electrolytic capacitor to reduce the ripple in the dc voltage: the dc voltage is regulated acting on the field current of the generator. Such a layout is currently used to create a stable and reliable dc-bus for stand-alone dc systems as in electro-diesel...
This paper considers the control of a doubly fed induction machine (DFIG) connected to a dc-bus or dc-grid by using a diode rectifier placed on the stator-side and a single PWM converter on the rotor. In this system, the torque and the frequency have to be regulated simultaneously, in order to make the prime mover operating at the maximum power point and to guarantee at the same time a flux level...
This paper presents a new self-sensing method for the direct estimation of the slip position angle in the DFIG connected to a dc network. This connection is made by the stator through a diode bridge and by the rotor through a single voltage source inverter. Considerable savings are obtained when this system is used in networks where several systems should work together, because only a dc-link is needed...
The application of an energy transmission system to a rotating shaft by using a counter-weighted-free-wheeled-rotor permanent magnet synchronous machine is analyzed in this paper. This solution avoids slip rings and can generate a power amount which can be significantly higher if compared to other contact-less solutions. The guidelines for the design of such a machine are discussed by considering...
The paper discusses the effects that various kinds of manufacturing dissymmetry can cause in axial flux PM machines. A case study is considered, and, in particular, two effects are investigated: the circulation current in parallel paths at no load and the mechanical stresses together with the resulting axial force and bending torques on the machine shaft.
The paper presents a method to evaluate the e.m.f.s and torques waveforms in a surface PM Synchronous Machine. The key feature is the mix of FEM2D and analytical procedures, in order to exploit the positive features of FEM methods (easy applicability even in case of complex geometry), but maintaining some flexibility of the analytical approach. The method is based on the FEM identification of suited...
The paper presents an analytical model of the air gap field in a surface mounted PM Synchronous Machine. The method is FEM2D based, because it starts from the FEM identification of suited “field functions”: each field function describes the air gap flux density behavior, related to one field perturbation cause, acting alone (stator slotting, rotor anisotropy, field excitation source, armature reaction...
The paper presents simulated and experimental results concerning some rectifying solutions used as AC/DC stage in grid connected Wind Energy Conversion Systems (WECSs), employing direct drive, axial flux, modular Permanent Magnet Synchronous Generators (PMSGs). The solutions are based on three-phase diode bridge rectifiers, configured to give 6-pulse and 12-pulse rectifiers.
This paper proposes a scheme for the self tuning of the stator inductance in a Rotor Current MRAS Observer for the sensorless control of Doubly Fed Induction Machines. The effect of mismatched parameters in this observer is briefly discussed and the strong dependence of the estimated rotor position on the stator inductance is highlighted. A self tuning scheme is formulated by using only quantities...
This paper deals with some design criteria of axial flux permanent magnet synchronous machines, wound with concentrated coils: in particular, the application to direct drive wind power generation is considered. The structure and the features of these machines are illustrated, the main sizing equations are deduced, and some guidelines for the design are presented, also by means of a sensitivity analysis,...
This paper deals with the performance of some numerical integration methods for Ordinary Differential Equations in real time applications involving stiffness. After summarising the main results about accuracy and stability of some well known schemes, the point of view of the control is emphasized, by showing the impact of the numerical integration on the dynamics of the discretized model. Moreover...
The paper analyses and compares some solutions of AC/DC converter stages in grid connected Wind Energy Conversion Systems (WECSs), using modular Permanent Magnet Synchronous Generators (PMSGs). The converter dispositions here analyzed are based on 3-phase diode bridge rectifiers, and consider also the possibility of a commutation in winding connections.
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