Abstract
Injection-based encoderless control methods are the state-of-the-art solution for estimating the rotor position around zero speed. It is known that stability is a major issue in this category of algorithms. Most of these methods become incapable of tracking the rotor position when the machine is driven into deep magnetic saturation. In recent literature, this behavior is often assumed to be a property of the electrical machine. Thus, recent research in this field has focused on the optimization of the electrical machine. The purpose of the following work is to investigate the impact of injection-based encoderless algorithms on the stability issue in deep magnetic saturation. By investigating various algorithms for a reluctance synchronous machine (RSM), it is shown for the first time that the issue results primarily from the algorithm used. One of the investigated algorithms is capable of working without load limitation, confirming the statement that the algorithm is the source of the problem. The reason for this behavior is analyzed using a novel convergence criterion for the RSM, which is derived and verified. A Finite-Element-Method (FEM)-based simulation procedure is proposed to predict the convergence region with high accuracy. This opens new practical relevant possibilities at the design stage of the system. The investigation demonstrates that a deviation between the real and estimated operating point causes the problem. This deviation results in incorrect parameters and thus leads to the instability of the injection-based model.
Highlights
S YNCHRONOUS machines are a focus of current research due to their high efficiency and robustness
Following on from the above, the novelty of this paper is the investigation of the impact of the injection-based algorithms on the issue of stability in deep magnetic saturation
This is a result of magnetic saturation and leads to the problem that the actual rotor angle cannot be determined directly using such a conventional model
Summary
S YNCHRONOUS machines are a focus of current research due to their high efficiency and robustness. The authors of [11] investigated the observability of the induction machine and the synchronous machine for encoderless control, by applying the conventional theory of observability Their criterion guarantees observability when an EMF-based method is used and without taking parameter deviations into account. The authors of [16] stated that observability is not sufficient for a stable operation of injection-based encoderless algorithms. There is no comparison between different existing injection-based methods regarding the overload capability problem. Following on from the above, the novelty of this paper is the investigation of the impact of the injection-based algorithms on the issue of stability in deep magnetic saturation. The deviations in the estimated parameters are caused by the deviation between the real and the assumed operating point of the machine This behavior is assessed by the new stability criterion.
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