On line tuning of the stator inductance in a MRAS observer for sensorless DFIM drives

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 which are already exploited by the observer, so that only a marginally additional computational effort is required in the implementation. Some guidelines to design the tuning loop are given. Finally the performances of the proposed scheme are experimentally tested and discussed

Design guidelines for wound Inter-Phase Reactors in high-power rectifier systems

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 affecting the column peak flux density

Effects of Manufacturing Dissymmetry in Axial Flux PM Machines

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

Comprehensive steady-state analytical model of a three-phase diode rectifier connected to a constant DC voltage source

This study deals with the analytical modelling of the steady-state operation of a three-phase diode rectifier whose dc bus is connected to a constant voltage source. Such a system exhibits several operation modes that are fully investigated. Analytical expressions of the boundaries of each mode as well as the average dc and the rms ac currents are deduced as a function of the ac and dc parameters, including voltage drops across diodes. They allow us to evaluate the power delivered to the dc bus as well as the efficiency of the conversion in each mode of operation. These results can also be extended to practical rectifiers with bulk dc capacitors and allow for performing parametric analyses and optimization in the design of drives or permanent magnet synchronous generators directly connected to a diode rectifier. The theoretical results are validated by experimental tests

Stator inductance self-tuning in an air-gap-power-vector-based observer for the sensorless control of doubly fed induction machines

This paper focuses on the improvement of an air-gap-power-vector-based observer for sensorless doubly fed induction generators. After showing how a mismatch in the machine inductances can worsen the performance of the basic observer scheme, an adaptive tuning of the stator inductance is proposed. The adaptation is achieved by minimizing the error between the squared modulus of two suitable air-gap complex power space vectors. A criterion to settle the dynamics of the adaptation mechanism is provided, and a sensitivity analysis in the steady-state operation is performed. Some experimental results are reported and discussed in order to validate the soundness of the proposed adaptive tuning algorithm

Numerical Integration of ODEs in Real Time Systems like State Observers: Stability Aspects

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 some peculiarities of the numerical integration in hybrid systems are touched by introducing a simple hybrid model for testing the performances of some numerical integration schemes. Finally some experimental tests are shown, dealing with a control of a sensorless drive whose model is characterised by stiffness