Variable phase-pole machines possess the capability to expand their operational range by employing magnetic pole change while adhering to the same electrical voltage and current limits. This article proposes a strategy to achieve a pole change with constant torque while simultaneously optimizing current distributions for stator copper loss minimization. The overall outcome is the ability to facilitate smooth $dq0$ current transitions while reducing the energy consumption of variable phase-pole machine drives. Experimental results affirm the efficacy of this approach during the pole change process.

The active short-circuit is a standard safety measure for permanent-magnet synchronous machine drives in electric vehicles, but it can lead to harmful torque and current transients. This paper introduces a mathematical and graphical method to determine the safe operating area of pre-fault current conditions, complying with user-defined torque bounds and preventing magnet demagnetization during short-circuit transients. The method incorporates an inductance-based motor model considering magnetic saturation, which is used to outline a strategy for transitioning to safe initial conditions in the minimum time for the available voltage. Experiments on a 35 kW permanent-magnet synchronous machine support the efficacy of the proposed strategy, offering promise for its use in automotive propulsion where compliance to safety standards such as the ISO 26262 is paramount.

Magnet-free variable phase-pole machines are competitive alternatives in electric vehicles where torque-speed operating region, reliability, cost, and energy efficiency are key metrics. However, their modeling and control have so far relied on existing fixed-phase and pole-symmetrical models, limiting their drive capabilities especially when switching the number of poles on the fly. This paper establishes the harmonic plane decomposition theory as a space-discrete Fourier transformation interpretation of the Clarke transformation, decomposing all pole-pair fields into a fixed number of orthogonal subspaces with invariant parameters. The model remains unaltered for all phase-pole configurations, guaranteeing continuity even under phase-pole transitions. Relations of the state and input space vectors, and model parameters to those of the vector space decomposition theory used for multiphase machines are established via the use of the complex winding factor. Experiments confirm the modeling theory and demonstrate its practical usefulness by performing a field-oriented-controlled phase-pole transition. Non-trivial configurations with more than one slot/pole/phase and a fractional phase number are also demonstrated.

Active short-circuit is a standard emergency procedure applied to three-phase permanent-magnet synchronous machine drives in battery-electric and hybrid electric drivetrains to comply with stringent automotive safety standards, such as the ISO 26262. Unfortunately, the ensuing torque and current transients can harm the passengers and the driveline itself. This paper develops and validates a mathematical and graphical method to determine the safe operating area of pre-fault current conditions to guarantee that the torque remains within user-defined acceptable bounds and that the permanent magnets do not demagnetize during the short-circuit transient. The new method utilizes an inductance-based dynamic model of the motor, including magnetic saturation. The proposed methodology promises to be useful in the design, initial testing, and commissioning of permanent-magnet synchronous machines used for the propulsion of automobiles.

This thesis examines the modeling and parameter estimation of multiphase electrical machine (MPEM) and fault-tolerant permanent-magnet synchronous machine (PMSM) drives for traction applications. These drive systems typically require a wide constant power-speed range, substantial overload capability, and high efficiencies along with operational reliability.

A class of MPEMs known as variable phase-pole machines (VPPMs) has been identified as possible magnet-free candidates to fulfill these requirements. However, research on their modeling and subsequent parameter estimation is scarce. State-of-the-art models such as the vector-space decomposition (VSD)assume a fixed number of phases and half-wave symmetry of the stator current distribution. Therefore, the first part of this thesis proposes an alternative modeling through the harmonic plane decomposition (HPD). Using the HPD, we showcase reference generations for rotor field-oriented control to accomplish different non-trivial phase-pole configurations and a strategy for switching between them. A constrained loss-minimization also demonstrates that VPPMs can improve the overload capability and reduce losses compared to an identical machine operated with a fixed phase-pole number.

The second part of the thesis identifies the HPD parameters of a VPPM using standard tests performed on a reduced set of harmonic planes using solely a three-phase sinusoidal supply. This part shows that an optimally weighted least-squares estimation of the machine parameters can accurately determine the full suite of rotor resistances and unsaturated magnetizing inductances while segregating rotor and stator leakages. A key to doing so is to include a regularization term.

The third part of the thesis investigates inter-plane cross saturation. This phenomenon occurs between harmonic planes because the excited harmonics of the magnetic field share the same flux paths through the machine’s steel. In response, we propose an advanced Γ-model with saturable rotor bridge and stator inductances taking, respectively, the bridge and air-gap magneticflux densities as inputs. The result is saturation models with a single input implicitly accounting for the phase displacement and different amplitudes ofthe space-harmonic magnetic fields.

The fourth part of the thesis investigates a fault case of PMSMs termed active short-circuit (ASC) in which the machine terminals are deliberately clamped to a DC-rail. The resulting transient may cause irreversible demagnetization of the rotor permanent magnets and impose a sudden and appreciable braking torque on the machine shaft. From the non-linear flux maps of the PMSM, we deduce the set of initial conditions that do not demagnetize the permanent magnets and obey a user-defined torque limit. The model is used to elaborate a direct flux-vector-control based strategy to control the state variables into the safe operating area of initial conditions before applying the ASC. The strategy optimally uses the assigned voltage resources to decrease the stator-flux magnitude to an acceptable level within a predictable time. It is displayed and experimentally demonstrated how the strategy consequently protects the machine from a detrimental transient.

This work shows that appropriate modeling of VPPMs enables efficient use of the available input power and may extend the torque-speed operating region. It is also a prerequisite for accurate control in dynamic operation. While experimental parameter estimation of the HPD model can be made simpler and more robust using regularized estimators, dealing with magnetic cross-saturation poses a challenge when demanding constant and accurate torque output during pole-changing and harmonic injection. Currently, PMSMs remain commonplace in traction applications. Steps to improve their fault tolerance to ASCs are taken in this thesis, relieving a common concern in automotive applications that need to comply with functional safety standards such as ISO 26262.

Denna avhandling undersöker modelleringen och parameterestimeringenav elektriska flerfasiga maskiner (MPM:er) samt feltoleranta drivsystem för permanentmagnetiserade maskiner (PMSM:er) i framdrivningstillämpingar. Dessa drivsystem kräver vanligtvis ett brett hastighetsomfång med konstanteffekt, betydande överbelastningskapacitet och hög verkningsgrad samtidigt som de ska uppvisa hög driftsäkerhet.

En klass av MPM:er kända som variabla fas-pol-maskiner (VPPM:er) har identifierats som magnetfria kandidater för att uppfylla dessa krav. Dock är forskningen kring deras modellering och efterföljande parameterestimering knapphändig. Vanliga modeller såsom vektorrumsdekompositionen (VSD) antar ett fixerat antal faser och halvvågssymmetri hos statorströmfördelningen. Därför föreslår första delen av denna avhandling en alternativ modellering medelst övertonsplandekomposition (HPD). Genom att använda HPD:n åstadkoms olika icke-triviala fas-pol-konfigurationer med lämpliga val av strömreferenser för rotorfältorienterad strömreglering. Vi ger också exempel på en strategi för att växla mellan dem. Genom en förlustminimering med bivillkor visas det också att VPPM:er fördelaktigt kan tillämpas för att förbättra överbelastningsförmågan och minska förlusterna jämfört med en identisk maskinsom tillämpar ett fixerat fas-pol-tal. Avhandlingens andra del identifierar HPD-parametrarna hos en VPPM genom standardtester utförda på en reducerad uppsättning övertonsplan med enbart en trefas sinusoidal spänningskälla. Denna del visar att en optimaltviktad minsta-kvadrat-estimering av maskinparametrarna noggrant kan bestämma hela omfånget av rotorresistanser och omättade magnetiseringsinduktanser samtidigt som den separerar rotor- och statorläckage. En nyckel till detta är att inkludera en regulariseringsterm.

Avhandlingens tredje del fortsätter med att studera korsmättnad mellan övertonsplan. Fenomenet uppstår eftersom de exciterade rumsövertonerna av det magnetiska fältet delar samma magnetiska flödesbanor genom maskinens stål. Som lösning föreslår vi en avancerad Γ-modell med mättnadsbara rotorbryggor och statorinduktanser som använder bryggornas och luftgapets magnetiska flödestätheter som indata för respektive mättnadsfunktion. Resultatet är mättnadsmodeller med en enda inmatningsvariabel som implicit tar hänsyn till fasförskjutningen och de olika amplituderna av de magnetiska rumsövertonsfälten.

Avhandlingens fjärde del undersöker ett felfall hos PMSM:er, benämndaktiv kortslutning, där maskinterminalerna aktivt ansluts till antingen positiv eller negativ DC-bus. Den resulterande transienten kan orsaka irreversibel demagnetisering av permanentmagneterna installerade i rotorn och åsamkar ett plötsligt och avesvärt bromsmoment på maskinaxeln. Från de icke-linjära flödeskartorna av en PMSM härleder vi intitalvilkoren som undgår att demagnetisera permanentmagneterna och respekterar en användardefinierad vridmomentbegränsning. Modellen används för att utarbeta en strategi baserad på direkt flödesvektorreglering för att styra tillståndsvariablerna till det säkra operationsområdet innan den aktiva kortslutningen tillämpas. Strategin använder de tilldelade spänningsresurserna optimalt för att minska statorflödet till en acceptabel nivå inom en förutsägbar tid. Experiment demonstrerar hur strategin följaktligen skyddar maskinen från en skadlig transient.

Denna avhandling visar att en lämplig VPPM-modell möjliggör effektivanvändning av tillgänglig effekt och kan utvidga arbetsområdet för kontinuerlig drift. Modellen är också en förutsättning för verkningsfull styrning avstatorströmmen. Ehuru experimentell parameterestimering av HPD-modellen kan förenklas och göras mer robust genom att använda regulariserade estimatorer, utgör hanteringen av magnetisk korsmättnad en utmaning när konstantoch noggrant vridmoment krävs under polbyten och övertonsinjektion. För närvarande är PMSM:er vanliga inom traktionstillämpningar. Åtgärder för att förbättra motståndskraften mot fel till följd av aktiva kortslutningar hos dessa maskiner föreslås i denna avhandling, vilket bemöter ett problem inom fordonsapplikationer som behöver efterleva funktionella säkerhetsstandarder såsom ISO 26262.

The Clarke transformation is mathematically a Vandermonde matrix of a discrete Fourier transformation. Its purpose is to transform space-vector quantities in the space domain. One necessary condition is that the base function forms an n-th root of unity. This condition translates into requiring all sampling points to be equally spaced. However, manufacturing constraints and imperfections in electric machines may result in non-equally spaced magnetic axes, especially in the case of multiphase electrical machines, making the conventional inverse Clarke transformation used in classic vector control inaccurate. The mathematical inverse Clarke transformation solves this issue, and the existence of this matrix is always ensured. This avoids additional control action and for model predictive controllers, an accurate model is crucial. Analytical results and a simple experimental validation on a multiphase induction machine show the improvements introduced by changing the transformation matrix.

The Clarke transformation is mathematically a Vandermonde matrix of a discrete Fourier transformation. Its purpose is to transform space-vector quantities in the space domain. One necessary condition is that the base function forms an n-th root of unity. This condition translates into requiring all sampling points to be equally spaced. However, manufacturing constraints and imperfections in electric machines may result in non-equally spaced magnetic axes, especially in the case of multiphase electrical machines, making the conventional inverse Clarke transformation used in classic vector control inaccurate. The mathematical inverse Clarke transformation solves this issue, and the existence of this matrix is always ensured. This avoids additional control action and for model predictive controllers, an accurate model is crucial. Analytical results and a simple experimental validation on a multiphase induction machine show the improvements introduced by changing the transformation matrix.

Multiphase induction machines are investigated as competitive magnet-free candidates for high torque-density, overload-capable, and wide torque-speed range applications. These benefits are enabled by torque-enhancing harmonic injection and phase-pole changes. However, such operational modes may subject the different harmonic planes to cross-saturation. Consequently, a well-performing drive requires an accurate model. This paper models the inter-plane cross saturation between the excited harmonic planes in the main flux path and the rotor slot-bridges. It is valid even for unsynchronized harmonic magnetic fields manifesting themselves during current control as low-frequency beats in the voltage amplitude. An advanced Gamma-model also including the skin effect of the rotor is proposed and validated against experiments. The results indicate that the proposed model represents the behavior of a 15-kW variable phase-pole machine more accurately than a constant parameter Gamma-model. This warrants better field orientation and torque output predictions in future drives.

Multiphase electrical machines are inherently fault tolerant due to the higher number of phases. An important step in achieving a fault tolerant control is the ability to detect and identify the fault. In variable phase-pole drives, which are a class of multiphase machines that change the number of pole pairs during real-time operation, there are further unexplored possibilities. Based on the harmonic plane decomposition theory for variable phase-pole machines, a fault detection and identification algorithm is proposed, which analyzes the spatial harmonics of the current distribution. The fault detection is fast, operation independent, non-invasive, parameter-insensitive, and computationally simple. Experimental tests validate the proposed method.

To exploit the benefits of field-oriented controlled variable phase-pole machines, optimal current references need to be generated.This article proposes a steady-state Joule-loss minimization obeying inverter constraints and air-gap flux-density limitations.Different from previous attempts, the phase-pole configuration is not limited to exciting a single pole order. Instead, multiplepole-order fields are superimposed to accomplish the optimal current injection at all evaluated torque-frequency operating points.Two main conclusions are drawn from the solution to the optimization problem using experimentally identified parameters of avariable phase-pole machine. To begin with, adequate current injection extends the operating range. Secondly, the RMS currentis reduced, particularly in the high-torque region.