The Current Source Inverter (CSI) is a power electronics topology that allows for the realization of variable speed drives (VSD). Compared to the most common Voltage Source Inverter (VSI), which can be directly connected to a voltage source, the CSI needs a pre-stage to generate a constant current bus. This paper therefore seeks to challenge this 'accepted' consideration that a CSI always needs this pre-circuit and seeks to remove this circuit by proposing an innovative $i_{dc}$ Current Control scheme. The proposed scheme is applied to a single stage motor drive driven by a CSI converter. It is shown how implementing this control scheme removes the need for the front-end stage, thus removing an unnecessary converter and optimizing the efficiency at the same time. The CSI state-space equations are presented and the developed models are verified using simulations. Stability analysis of small - signal model is considered through Nyquist criterion with the robustness in presence of variations of the most important system parameters.\\ Experimental results driving a Permanent Magnet Synchronous Machine (PMSM) are shown confirming the validity of the proposed control, potentially paving the way to a larger adoption of the CSI topologies for motor drive applications.

When compared to the much more common voltage-source inverter (VSI), the current-source inverter (CSI) is rarely used for variable speed drive applications, due to its disadvantages: the need of a constant DC-link current, typically realized with a front-end converter, and the need for reverse-voltage blocking (RVB) devices, typically implemented with in-series diodes. This limits the overall efficiency of the architecture. This paper investigates latest progress of the CSI research, with the aim of demonstrating why CSI could come back in the near future. Different architectures based on modern wide-bandgap (WBG) switches are analyzed, with an emphasis on why CSI can be advantageous compared to VSI.

Hybrid stepper motors are widespread in industrial automation due to their robustness and high torque performance in low speed range, e.g. 3D printers, pick and place, and generally in many low power positioning applications. In order to increase the efficiency and dynamic performance, current/speed/position closed loop controls are implemented for high performance sensored stepper drives. The main challenge comes from the high number of magnetic poles which these motors feature, increasing the ratio between the fundamental and switching frequency. This paper critically evaluates four current control structures based field oriented control: classic PI regulators, sliding mode control, deadbeat predictive current control and model predictive current control. Simulations and experimental results aim to evaluate the dynamic performance, phase current amplitude and distortion in order to support the critical comparison.

In motor drive applications, single-stage current source inverters (CSIs) can manage only a limited speed range when the output voltage is greater than input voltage, due to the intrinsic boost capability. The classical solution adopted in low-speed region to control the input dc current, consists in the insertion of a prestage power converter. This article proposes a single-stage CSI that replaces the input inductance $L_{\text{dc}}$ with coupled inductor. In this way, it is possible to add the needed time interval for the discharge of the magnetic energy of primary inductance $L_{m}$ when the converter works in low-speed region or at standstill, extending the operating region of the converter. This solution allows to increase the efficiency of traditional CSIs for applications when the motor works most of the time in the high-speed region, thanks to the single-stage power conversion. Experimental and simulation results driving a permanent magnet synchronous machine are shown, confirming the validity of the proposed architecture.

With their cost-effective manufacturing process, hybrid stepper motors (HSMs) are a popular choice for position control in low-power industrial applications. These versatile motors offer a compelling solution for reducing system costs and size since at standstill/low speeds, HSMs typically have higher torque density with respect to low-power permanent magnet (PM) motors. This higher torque density determines a reduced use of rare-earth PMs and, therefore, a lower environmental footprint. In practical applications, the commonly used microstepping control faces low efficiency, low dynamic performance, vibrations, and a variable maximum continuous torque depending on the working point. In this paper, the operating region of an HSM is extended in the field-weakening (FW) region, showing how field-oriented control (FOC) with FW allows one to strongly increase the drive performance with a slight cost increase thanks to the availability of low-cost magnetic encoders. Due to the fact that FOC provides only the requested current, the HSM faces lower temperatures, lower insulation degradation, and lower permanent magnet demagnetization issues. An experimental evaluation comparing the commonly used microstepping and the proposed FOC with FW is performed on four commercial HSMs with different DC voltage power supplies using an industrial test bench. In particular, the experimental campaign has a focus on steady-state conditions in the case of the maximum continuous torque, showing the advantages of FOC with FW because the advantages in transient conditions are well known.