The advantages of higher voltage utilization in automotive traction drives are higher maximum power and lower losses due to less flux-weakening current. Applying carrier-based overmodulation (voltage utilisation > 91%), in some PWM sections pulse dropping occurs and the switching frequency decreases. Additionally, in the second overmodulation region (voltage utilisation > 95%) the degree-of-freedom of the voltage vector angle is constrained. This is a considerable challenge for Current Vector Control (CVC). This research proposes deadbeat flux trajectory control (DBFC) integrating synchronous optimal pulse pattern (OPP) to maximize the voltage utilization up to 99% but mitigating the disadvantages of six-step (100%): DC-bus and phase distortion. It is demonstrated that DBFC is one single control law enabling closed-loop control in SVPWM, synchronous OPP (q=3) and six-step without any switching or transitioning between various control laws.

To improve the control performance of an automotive traction drive, this work proposes a direct flux sensing concept: An array of six high-resolution flux sensors is integrated into a traction motor. One PCB with the flux sensors is placed between stator laminations and end windings of an electrically excited synchronous motor (EESM) for BEV traction applications. The Integrated Flux Sensor Array (ISA) offers several advantages: it provides more sensor information from 18 flux measurements (+ temperature), has no moving parts, requires less space, and reduces costs by more than 80% compared to a mechanical resolver. Flux is measured with low distortion through low order cancellation applying spatial multipath sampling. HV-testbench measurements demonstrate closed-loop control using the ISA concept replacing the resolver also at low speeds.

Optimized pulse patterns (OPPs) can be used to improve overall drive train performance. Recently, they have been applied to minimize the current harmonics of salient permanent magnetic synchronous motors. Applying OPPs to the electrical drive train, may improve the efficiency, but may have a negative effect on the DC link capacitor or air gap torque ripple. In electric vehicle applications it is crucial to consider their effect on various parameters. Certain limits may be exceeded which restrict the use of OPPs at these operating points. Therefore, this article presents analytical models derived from switching angles in the context of synchronous modulation to directly evaluate the beneficial or detrimental effects associated with OPPs on the overall electric drive system. Since the model equations are based on switching angles, they are particularly suitable for pulse pattern optimization. Switching angles can be identified that minimize either current harmonics, switching losses, DC-ink voltage ripple, DC-link current stress, or the air-gap torque of the machine with respect to low frequency modulation. Measurements on a machine test bench are performed to validate the correctness of the presented models.

With optimized pulse patterns (OPPs), it is inherently possible to maximize the voltage utilization of the electric drivetrain from linear modulation up to six-step operation. This not only increases the performance of the drive system, but also introduces additional degrees of freedom into the inverter design, which will be discussed in this paper. The implementation and specific characteristics of OPPs within the overmodulation region will be investigated. A novel method for controlling OPPs specifically for the overmodulation region is presented. Measurement results demonstrate the advantage of OPPs with overmodulation in automotive traction applications.

This paper introduces a direct flux sensing technique that can be used for stator flux linkage observation and state-of-the-art control techniques such as Deadbeat Flux Vector Control (DBFC), especially for the low-speed region. Two Integrated Sensor Arrays (ISA), consisting of six 3D high-resolution flux sensors each, are placed at the tip of the stator lamination teeth between the end windings of an Electrically Excited Synchronous Motor (EESM). With the 3D sensors, stray flux density is sampled simultaneously in the tangential, axial, and radial directions at each sensor location. The aim of the present work is to analyze the measurements in the different directions and to provide valuable insight into their properties. Moreover, a simple methodology to estimate the stator flux linkage based on flux density measurements is proposed. Experimental tests demonstrate that different axis selections and sensor arrangements influence the signal-tonoise ratio and magnitude of the measured flux density.

Knowing the magnetic flux inside an electric machine can provide valuable information, as it allows for monitoring the actual behavior of the motor during operation. This leads to more accurate torque delivery and enables prognostic and state-of-health analyses. By integrating Hall-effect sensors inside an e-motor, it is possible to measure the magnetic flux and gain all the benefits from this information, such as accurate torque, rotor position and speed, and magnets' temperature. This paper describes the design of an e-motor with an integrated flux sensing array (ISA), including all surrounding models and software solutions for efficient motor control, integrating health monitoring and failure prevention. The focus is on the analyses performed to estimate the magnetic flux linkage and determine the optimal sensor placement, the control architectures that can benefit from a more accurate flux estimation, and the design of the e-machine to integrate the flux sensors. The aim is to describe the demonstrator developed to compare the benefits of direct motor flux measurement in terms of controllability and to analyze motor behavior under various operating conditions, enabling the estimation of remaining useful life and anticipating failures.

Efficiency and power density of electric vehicle drive systems are important metrics for their performance evaluation. To address these aspects, Optimized Pulse Patterns (OPPs) can be integrated into the modulation strategy. This research investigates the effects of OPPs on the current distortion of salient permanent magnet synchronous motors (PMSMs) applying different symmetry conditions. It places a particular emphasis on three-pulse switching within the overmodulation region. A mathematical model of salient PMSMs is used to demonstrate that the voltage phase angle significantly influences current harmonics. It is revealed that even with a low number of pulses, satisfactory sinusoidal currents can be achieved at high voltage phase angles, thereby reducing the inverter's switching efforts while preserving current waveform quality. Different waveforms such as quarter- and half-wave symmetry (QWS), unrestricted half-wave symmetry (HWS) and restricted HWS are compared, with an innovative approach proposed for unrestricted HWS. The benefits and drawbacks of these waveforms in application to salient PMSMs are investigated, with emphasis on the overmodulation region. It is noted that HWS shows benefits over QWS at medium-load operating points and when zero-vectors are in the waveforms. In contrast, no significant advantages of HWS over QWS could be identified in the overmodulation region. The research proposes a practical OPP implementation strategy that balances effort and efficiency based on this knowledge. Unlike previous studies that used random initial angles to explore solutions, this study methodically examines the solution space for HWS and QWS, selecting initial angles that enhance the chances of finding the global optimum.

Optimized pulse patterns (OPP) can be applied to improve the overall efficiency of the powertrain in electric vehicles. However, controlling OPPs to obtain a fast step response and to reject errors and disturbances is challenging. Therefore, this paper presents the implementation of OPPs in the control structure for electric drives in vehicles. Different methods are presented such as open-loop and closed loop-control of OPPs. Measurements are carried out to identify the modulation strategy with the highest efficiency considering both, the inverter and the electrical machine. These measurements are discussed in order to derive an optimal control strategy.

The DC-link capacitor represents a critical component in electric vehicle traction inverters, given that it constitutes the largest single volume within a traction inverter. The DC-link capacitance must be selected carefully, to ensure that the voltage ripple remains within defined limits, as this has a direct impact on the design of other components connected to the high voltage bus. Typical approaches attempt to reduce the required DC-link capacitance by increasing the pulse width modulation (PWM) switching frequency. However, this leads to a compromise as higher switching frequencies can cause additional losses, potentially necessitating a larger area for costly silicon carbide (SiC) semiconductors. In this contribution, optimized pulse patterns (OPPs) are proposed as a solution to improve the DC-link voltage ripple, allowing a reduction in capacitor size and a significant decrease in switching frequency compared to the standard Space-Vector PWM. The paper outlines the mathematical methods for simulating and designing the DC-link regarding voltage ripple and current stress. It compares the simulations for Space-Vector PWM and OPPs, leading to the development of two distinct capacitor designs. The theoretical 20% reduction in the volume of the DC-link capacitor is confirmed through experimental validation on a 250 kW machine test bench setup.

Apply of Optimized Pulse Patterns (OPPs) with interior permanent magnet synchronous machines (IPMSM) is receiving significant attention from automotive industry as a mean to improve the efficiency of the traction drives. Traditionally, voltage harmonics or current harmonics have been considered for the optimization process. This paper discusses and compares three different cost functions to be used with IPMSM considering voltage, current, and power harmonic losses. The analysis will consider complexity, accuracy and parameter sensitivity. Current harmonics are first obtained from the voltage harmonics produced by the OPP. Analytical models obtained using the theory of asymmetric circuits will be used for this purpose. The variation of the machine parameters with the injection frequency will be shown to have a great impact on the behavior of the machine losses. A novel cost function considering this machine parameter variation to reduce the harmonic power losses is proposed in this paper. The proposed methodology will be implemented in Matlab. Simulink will be used for the preliminary validation of the analytical results. In addition, FEM is used to assess the accuracy of the analytical results.

Inverters of electric drivetrains have high requirements which need to be considered during development: Efficiency, power density and economic goals have to be met at output powers beyond 250kW. In order to achieve optimum design, simulations are required that represent the complex relationships of the semiconductors, the cooling, the power module technology and the modulation. In addition, the entire drive system, consisting of battery, inverter and electric machine, must be considered and simulated in order to achieve the maximum possible overall efficiency. The necessary methodology and simulations are presented in this paper.

Knowledge of machine flux is required for high-performance control of induction machines. Direct measurement of motor flux traditionally has not been considered practical due to several reasons, including robustness concerns, cost, low signal-to-noise ratios, etc. Consequently, flux estimators are used instead. However, the use of flux estimators raises additional concerns, including sensitivity to machine parameters and operating point. Moreover, they rely on fundamental quantities and cannot detect spatial harmonics and other phenomena, which could be relevant for control and/or monitoring purposes. This paper proposes the use of Hall-Effect sensors to measure the leakage flux near the end-ring. These sensors are inexpensive robust, and non-invasive. The measurement of end-ring leakage flux will allow estimating the machine flux, including fundamental and harmonic components, with little sensitivity to machine parameters. These measurements can be used both for control as well as monitoring purposes, including detection of broken bars, eccentricity and rotor temperature estimation.

The advantages of higher voltage utilization in automotive traction drives are higher maximum power and lower losses due to less flux weakening current. Applying overmodulation (voltage>91%), in some PWM sections pulse dropping occurs and the switching frequency decreases. Additionally, in the second overmodulation region (voltage >95%) the degree-of-freedom of the voltage vector angle is constrained. This is a considerable challenge for Current Vector Control (CVC).This research proposes deadbeat flux trajectory control (DBFC) integrating optimized synchronous pulse pattern (OPP) to maximize the voltage utilization up to 99% but mitigating the disadvantages of six-step (100%): DC-bus and phase distortion. It is demonstrated that DBFC is one single control law enabling closed-loop control in SVPWM, synchronous OPP (p=3) and six-step without any switching or transitioning between various control laws.

Optimized pulse patterns (OPPs) are used to minimize the current harmonics in the permanent magnet synchronous motors (PMSMs) supplied by voltage source inverters (VSI) in electric vehicles (EVs). These PMSMs are highly utilized machines and therefore they show a non-linear magnetic behaviour due to saturation effects. In this contribution, a new method based on current-dependent absolute and differential inductances of the machine is proposed to calculate the optimal switching angles regarding current harmonics considering these non-linearities. The improvement of the proposed method compared to the state-of-the art is evaluated by simulation and measurement results.

This article proposes an enhanced version of the deadbeat flux vector controller (DBFC) as a one single control law that can operate in the entire torque–speed plane. The operation at any feasible modulation index can be accomplished by adequate determination of the flux trajectories at the different operating regions (e.g., PWM, overmodulation (I and II), and six-step). Continuous and seamless transition between the four operating regions is guaranteed, where the modulation index changes linearly with speed between PWM and six-step (without abrupt change in torque or acoustic problems). With the proposed strategy, undesirable torque dynamics, stability problems, and increased computational efforts associated with using multiple control laws are avoided. The transient performance of DBFC at the maximum voltage limit is analyzed in detail in the flux plane. A time-optimal torque control algorithm is developed to achieve the fastest possible torque dynamics and to considerably reduce the settling time, without the use of a voltage margin. The torque can be controlled with high accuracy and high robustness to machine parameter variations. With DBFC, no tradeoff between good steady state six-step behavior and good transient performance is needed due to the decoupling of switching and calculation frequencies. The proposed DBFC controller offers valuable features, and it is simple to implement. Simulation and experimental results are provided to validate the proposed control algorithm, which is implemented on an automotive microcontroller with a high-power/high-performance automotive traction machine.

Through a combination of flux and current observers, deadbeat-direct torque and flux control for interior permanent magnet synchronous machines has preferred features comparing to the existing current vector control (CVC). These include simpler flux weakening control, less parameter sensitivity with increasing speed due to the Gopinath-style flux observer and evading of anti-windup strategies at the inverter voltage limit. The operation throughout the entire torque-speed range can be accomplished with a single control law. For the second flux weakening region, the algorithm inherently achieves the maximum torque per flux (MTPF) operation by applying the square-root-condition (SRC). In contrast to CVC, no look-up-table nor solving the parameter-dependent MTPF equation is required. In this article, the equivalence of the SRC method to the conventional MTPF strategy is demonstrated analytically, graphically, in simulation, and through experimental results without any stability problems. A sensitivity analysis regarding the machine parameters and iron losses compares and evaluates both methods. Superior performance of the SRC algorithm compared to the conventional method is proven.

Six-step operation of interior permanent magnet synchronous machines (IPMSMs) has many advantages such as the full utilization of the DC-link voltage and the minimization of the switching losses. Deadbeat Flux Control (DBFC) is a control strategy designed to achieve overmodulation and six-step operation with competent dynamic performance. This paper presents an upgraded implementation of the DBFC controller. One unique control law can operate in the entire torque-speed plane with a simple methodology for continuous and smooth transition between the four different operating regions (i.e., linear, overmodulation I, overmodulation II, and six-step), and under voltage and current limitations. Combining multiple controllers and switching between different control laws is completely avoided. This paper presents an approach for closed-loop torque regulation that has high dynamic performance, high accuracy, and is robust against parameter variations. The proposed controller is evaluated in simulation and experimentally. It is implemented on an automotive microcontroller for a 300 kW IPMSM traction drive.

Accurate flux linkage estimation is essential for Direct Torque and Flux Control (DTFC) of interior permanent magnet synchronous machines (IPMSMs). For this, a discrete-time Gopinath flux observer is used by combining the current and voltage models of the IPMSM. The factors affecting the flux estimation accuracy such as inverter nonlinearities, iron loss, discretization errors, and encoder offset-angle are analyzed in this paper with simulation and experimental results. Usually, the accuracy of the flux observer is evaluated by comparing the estimated and measured torques. However, this method is unreliable. Hence, this paper presents the Square-Root-Condition (SRC) as a more reliable and precise methodology to tune the flux observer and determine the flux estimation accuracy without measuring the flux or the voltage. SRC is an extension to Deadbeat-Direct Torque and Flux Control (DB-DTFC) that calculates the Maximum Torque per Flux (MTPF) solution based on the estimated flux. SRC does not rely on pre-calculated data or solving the parameter-dependent MTPF equation. Moreover, it has a minimum sensitivity to machine parameters.

Deadbeat-control is a well-established control technique that uses the inverse machine model to determine the voltage commands required to achieve the desired torque and flux commands. Its classic implementation requires solving a quadratic equation with an extensive number of terms. Moreover, it can be only solved in the dq-reference frame. In this paper, two novel implementations are presented. The first methodology, in the dq-reference frame, reduces the algorithm's complexity and computation time. Moreover, it is immune to estimation errors of the permanent magnet flux. A second methodology based on the flux vector orientation is also presented. As opposed to the classic implementation, the proposed method does not require solving a quadratic equation; this reduces its complexity and computation time. Furthermore, the proposed methodology can be solved both in the dq and αβ frames since it relies only on the stator flux's magnitude and angle. Up to date and to the best of the author's knowledge, DB-DTFC in the stationary frame has not been presented before for salient machines. DB-DTFC in the stationary frame reduces the reliance on the position observer and facilitates the implementation of overmodulation techniques and six-step operation. The proposed methodology can operate in the MTPF line without any adjustments and it shows an adequate dynamic performance. Simulation and experimental results validate the methodologies. Caveats regarding their implementation are also discussed.

For traction drives, the operation in the overmodulation and six-step regions is crucial to increase the torque-speed range and the drive's efficiency. Deadbeat flux-control (DBFC) shows superior dynamic performance as compared to current-vector-controllers in these regions. In this paper, an overmodulation strategy for DBFC is presented. This technique, named minimum flux-phase error (MFPE), permits a smooth transition from the linear to the six-step regions. Consequently, abrupt changes of the modulation index are prevented which results in smoother transients and a closer operation to the maximum-torque-per-ampere (MTPA) line. DBFC can be combined with DB-DTFC (deadbeat direct torque and flux control) to ensure controllability throughout the entire torque-speed range. The complete control strategy is shown in this paper. Results from a 300kW IPMSM hardware-in-the-loop (HiL) testbench are shown to validate the strategy. Challenging caveats of the method are also discussed.