Enhanced mathematical modelling of interior permanent magnet synchronous machines for loss minimization control

Energy management is a fundamental facility for humanity. At present, the awareness that renewable energy cannot satisfy the entire energy needs of the community and that traditional energy sources have a limited duration makes it imperative to address the problem of their careful and responsible use. Therefore, the need for an intelligent and functional use of energy has led the technical-scientific community to concentrate its efforts on the issues of sustainable development and energy savings. The electric drives industrial sector has suffered this influence in a visceral way. This sector plays a leading role in the industrial frame as it is one of the main consumers of electricity. Moreover, the topic of electrical drives design and optimization has become of considerable importance especially for the automotive sector and for hybrid and electric traction applications. In particular, in the last two decade, this sector has undergone a considerable technological development thanks to the exponential evolution of power electronics, the use of increasingly performing electric machines and new control techniques. In this scenario, the design and optimization of control algorithms for interior permanent magnet synchronous machines (IPMSM) has became of considerable interest in the scientific and technological community. In detail, the IPMSM is one of the most used electrical machine typologies in the electric traction applications due to the high efficiency and flux-weakening capability. The purpose of the research project “Realization of innovative algorithms for the minimization of the losses in synchronous brushless motors for automotive application” consists in the design and development of innovative Loss Model Algorithm (LMA) for interior permanent magnet synchronous machines (PMSM). The LMAs goal is the identification of the working points of the machine at minimum losses through the optimal determination of the control variables values. Therefore, the use of LMAs in electric drives can be of considerable utility in terms of energy savings especially for automotive application where energy autonomy is a crucial parameter. In detail, a LMA is a control algorithm based on the knowledge of the dynamic mathematical model of the IPMSM. Therefore, the performances of LMA are strictly dependent on the accuracy of the mathematical model and of its electrical and magnetic parameters. In this regard, the research carried out during the PhD course focused on the four macro topics, reported as chapters of the PhD thesis: 1. loss minimization control techniques for PMSM: state of art; 2. performances analysis of the power loss mathematical models; 3. efficiency measurement of electric drives equipped with interior permanent magnets synchronous machine (IPMSM); 4. enhanced mathematical modelling of IPMSM. The first chapter describes the state of art of main Loss Minimization control Algorithms (LMA) for electric drives equipped with PMSM. The LMAs can be classified into two general approaches named Search control and Loss Model Control, respectively. The main features of each approach are presented and discussed. Particular attention is devoted to the conventional IPMSM modelling approach employed in the LMC. Finally, the LMA chosen as a case of study is illustrated. The second chapter describes the performances analysis of the power loss mathematical models for LMC. In detail, the conventional IPMSM modelling approach and the IPMSM modelling approach that take into account the magnetic self-saturation effects and the variability the iron loss with the supply frequency are studied and discussed. In order to evaluate the performances of each modelling approach, several experimental investigations have been carried out on an electric drive equipped with an IPMSM. The third chapter is focused on the design and validation of accurate efficiency measurement approach for electrical drives equipped with IPMSMs. In particular, the efficiency measurement approaches for electrical drives described by the international standards and by the scientific literature are described and discussed. Particular attention was paid to the new standard IEC61800 and their prescriptions have been employed for the efficiency estimation of the electric drive under test. Finally, a new measurement approach for the comparison of the electrical drive efficiency, when it is controlled with several control algorithms, is presented and experimentally validate. The last chapter describes the enhanced mathematical modelling of IPMSM that take into account the magnetic saturation, cross-coupling, spatial harmonics and iron loss effects. This activity was carried out in collaboration with the Institute of Power Electronics System (ELSYS) of the ―Technische Hochschule Nürnberg Georg-Simon Ohm‖ during the PhD visiting period. In particular, the research activity was focused on the finite element modelization and analysis of IPMSMs and the Ansys Maxwell simulation environment (FE software) has been used for the simulation of the IPMSM under test. In detail, in order to define a high-fidelity IPMSM mathematical model, a large number of FEA investigations have been carried out. In this regard, the enhanced IPMSM mathematical model is described, implemented in Matlab®/Simulink environment and, for validation purpose, its performances have been compared with those of the IPMSM implemented in Ansys Maxwell environment.