Motor characterization has a fundamental role in dynamics, torque accuracy, and efficiency of vector controlled Synchronous Reluctance Machine (SynRM) drives. Control performances and robustness in the whole speed/torque range, including the flux-weakening region, and in sensorless operation strongly rely on the knowledge of machine flux versus current characteristics. A convenient flux saturation approximating function is proposed in this paper, together with an efficient parameters self-identification procedure. The adopted strategy is very simple and can be performed at stand-still by injecting a proper voltage stimulus (current control is not involved), and does not require any additional hardware (motor can be either connected or disconnected from mechanical load). Nevertheless, an excellent fitting for the flux curves on both axes is obtained, using reasonable memory and computational resources. These features make the technique very suitable to motor self-identification in industrial drives. Experimental results based on a commercial drive and two SynRMs are reported to demonstrate the effectiveness of the proposal. Extensions of the method to the evaluation of the whole flux map (including cross-saturation effects) or to interior permanent-magnet machines is also investigated and verified.

Maximum Torque Per Ampere (MTPA) based on motor parameters is a common approach to achieve high efficiency and torque density in Interior Permanent Magnet Synchronous Machine Drives (IPMSMs). However, uncertainty (e.g., due to identification errors, magnetic saturation, or temperature variation) results in undesired deviation from the optimal operating trajectory. To solve this problem, MTPA tracking methods have been proposed, which exploit signal injection to search the minimum current point for a certain load torque in a closed-loop fashion. Closed-form design of the MTPA tracking loop dynamics has never been addressed in past literature and represents the main topic of this paper. A recent and efficient tracking method has been considered for the analysis and case study, i.e., [14]. Nonlinear small-signal gain of the loop can be calculated in closed form, leading to two valuable results. Dynamics can be programmed by optimal design of the tracking regulator, and online adaptation can be applied, making the designed MTPA tracking dynamics invariant with the operating point. A straightforward and effective solution is proposed for the regulator design, which allows us to obtain the desired bandwidth and first-order tracking response in the whole range of operation, being also suitable for auto-tuning and online adaptation. The method has been studied analytically and in simulation, also considering the influence of noise and parametric uncertainties. Finally the technique has been implemented on the hardware of a commercial industrial drive, proving the effectiveness of the proposal. The concepts described in this paper, design approach and adaptation strategy, analyzed here for the first time, are general and can be applied to any control scheme implementing closed-loop MTPA tracking.

Flux-Weakening (F-W) based on feedback voltage regulation is commonly adopted in Interior Permanent Magnet Synchronous Motor (IPMSM) drives. Voltage space vector magnitude is controlled in closed-loop, modifying the current reference, following a value related to the inverter limitations. Stable and fast voltage control allows to operate with lower voltage margin, leading to higher torque vs. speed capability. Theoretical analysis and gain adaptation of the flux-weakening regulation loop was reported in [1][2], partially overcoming the difficulties due to the strong non-linearity of the plant. An approximated closed-form design method was proposed in [3]. This allowed application of the algorithm to drives where auto-tuning is needed, ensuring stability and dynamical performances. The method was further refined in [4]. A fundamental enhancement is introduced in this paper, namely the use of a speed regulator with explicit torque reference output. An advantage of this technique is that the speed loop becomes linear in the whole operating range and accurate control of machine torque is possible. Thanks to a novel gain adaptation for the voltage regulator, the flux-weakening behavior is decoupled from the speed control response at speed steady state (at constant or slowly-changing torque), improving performance of the overall drive control. Adoption of this novel method allows smooth operation with invariant dynamical behavior of both the speed and F-W control loops. Extensive simulations and experimental tests are reported to prove the validity of the proposal. Sensorless operation of the drive system has also been considered in the tests to further validate the proposed solution.

Flux-Weakening (F-W) methods based on feedback voltage regulation are widely adopted in Interior Permanent Magnet Synchronous Motor (IPMSM) drives. Generally, the setpoint must be lower than maximum available voltage, to prevent saturation of current regulators during transients. However, the margin should be small, to exploit torque capability of the machine and avoid additional current magnitude during F-W operation. The trade-off between F-W control bandwidth and the necessity of voltage margin has not been analyzed in-depth in previous literature. In fact, F-W regulator design aiming at a certain bandwidth has been addressed by means of gain adaptation, but the choice of the target bandwidth remained as an open issue. In this paper, the crucial transient conditions which can cause the saturation of current regulators, specifically the reduction of input voltage, the fast acceleration of the drive and the transient torque demand, are considered. The input voltage reduction affects the available voltage, while fast acceleration and increase of torque demand push towards higher voltage, requiring disturbance rejection action by the F-W controller. All these conditions are analyzed in terms of worst-case requirement and the proposed analytical modeling is verified by means of simulations and experiments. The findings can be applied in the design of automatic tuning procedures and design for high-reliability or safety-critical applications.

This paper presents a vibration control unit formed by an electromagnetic proof-mass transducer connected to a sweeping resistive–inductive (RL)-shunt, which can be used to control broadband flexural vibrations of thin structures. The shunt is composed of a resistor and an inductor in series, whose values vary harmonically in time. The design and practical implementation of an electromagnetic transducer and harmonically varying shunt is first discussed. The unit is then tested on a thin-walled cylinder exposed to a broadband disturbance, considering two operation modes: fixed and sweeping RL-shunts. The former mode sets the unit to control the resonant response of a target flexural mode of the cylinder. The latter mode sets the unit to control the resonant responses of multiple modes of the cylinder with natural frequencies confined in a target frequency band. The study demonstrates the practical feasibility of a unit, which sweeps the natural frequency and the damping ratio of the transducer between 36 Hz and 187 Hz and between 4% and 60%. Also, it shows the unit generates broadband control of the flexural vibration of a cylinder, with reductions of the peak responses of the natural modes resonating in frequency band of the sweep comprised between 2 and 13 dB.

Multiport power conversion topologies provide the functionality of more single (and independent) converters but with just one transformer having multiple windings (i.e., ports). In automotive on-board chargers, the multiport approach combined with symmetrical series resonant circuits, the so-called multiport series resonant converter (MSRC), enable the required galvanic isolated connection from the grid-side converter (i.e., usually an AC-DC power factor correction (PFC) stage) to the vehicle’s batteries, i.e., the main high-voltage (HV) traction and the auxiliary low-voltage (LV), theoretically allowing to achieve increased power densities and enabling a flexible (and bidirectional) power routing among the different ports. High efficiency figures are normally specified in the considered application field for a very wide voltage ratios among the different ports, due to the variability of battery voltages, thus requiring proper and optimized control strategies of the underlying converter. The variation of the battery voltage is in fact highly affecting the MSRC operation, especially for light loads at a low state-of-charge, and high losses can be experienced since zero voltage switching conditions are lost. Beside the conventional control approach of the MSRC, where the power flow is set with a phase-shift between the individual full bridges or by changing the switching frequency, this paper proposes a novel and coordinated approach, including the manipulation of both and the additional modulation of the duty-cycle as a function of the grid-side DC-link voltage (i.e., the output of the PFC stage), aiming at introducing a zero-voltage interval on the full bridge output voltages. A full mathematical description of the adopted converter topology is reported, also including accurate simulation models for losses estimation allowing a fair comparison between the proposed duty-cycle mode control and the conventional control strategy. Detailed operation guideline for achieving zero-voltage switching within the connected full bridges is also reported. Experimental results validate the proposal and highlight a significant peak and average efficiency improvements with respect to standard control approaches.