A recently proposed single-stage CSI with discharge path exhibits the ability to control the drive from zero speed without the insertion of an additional pre-stage converter to control the input DC current. In this paper the characteristics of this power converter are analyzed deriving expressions for the voltage gain of the CSI connected to PMSM, in both low speed and high speed regions. Furthermore, the limitations of the topology in terms of critical speed (i.e. the maximum allowed speed) and maximum torque in the whole range are underlined. To solve the issue, a proper design of the coupled inductor is necessary to guarantee the nominal torque in the whole speed range. Simulations are reported to evaluate the proposed approach.

Single-stage Current Source Inverters (CSIs), supplied by a DC voltage source, are an alternative to Voltage Source Inverters (VSIs) for applications that operate always above a base speed due to their intrinsic boost capability that allows to achieve higher speeds with limited DC voltage. The resonance problem given by the interaction between the output capacitor Cfand the motor inductor L0has been extensively studied for CSIs. Furthermore, it is found that the inductor Ldcon the DC side also affects the resonance. This leads to an additional LCL resonance on the output currents. This paper investigates the resonances of single-stage CSI using the average small-signal converter model. An analytical expression for the additional LCL resonance is computed and a control strategy is proposed to attenuate the peaks of the resonances. Simulations are reported to evaluate the correspondence between the average small-signal model and the full model developed in PLECS.

For applications that operate always above a base speed (e.g. compressors, fans) the single-stage Current Source Inverters (CSIs), supplied by a DC voltage source, are an alternative to Voltage Source Inverters (VSIs) due to their intrinsic boost capability that allows to achieve higher speeds with limited DC voltage, as it regularly happens in more electric aircraft (MEA) and hybrid electric vehicles (HEVs) applications. The resonance problem in high speed region is taken into account for single-stage CSIs. Using additional voltage measures in the commonly used DC-link current control it is possible to damp the resonance of the CL filter adding a voltage loop only on the d-axis without reduce the bandwidth of the current loop. It is also shown that the DC-link current control is able to damp the resonance on the q-axis without the insertion of other control loops. Simulations are reported to evaluate the proposed method.

The Current Source Inverters (CSIs) are an alternative to Voltage Source Inverters (VSIs) for electric motor applications. Despite the advantageous characteristics of intrinsic voltage boost capability, absence of electrolytic capacitors and reduced machine voltage stress, the increased component count and the need of a pre-stage for the inductor current control have limited the adoption. For some applications which have to operate always above a base speed (e.g. pumps, actuators, fans), single-stage CSI converter with improved efficiencies have been proposed. Owing to the advantage of the direct measurement of the terminal voltage, a simple and robust sensorless control is proposed for a single-stage CSI converter. Simulations on a SiC-based CSI7 converter driving a Permanent Magnet Synchronous Machine (PMSM) confirm the validity of the proposed control, potentially paving the way to a larger adoption of the CSI7 topology for motor drive application.

Voltage Source Inverters (VSIs) are usually adopted for high-speed motor drive applications due to the topology simplicity and the wide availability of control strategies for this topology. An alternative is the Current Source Inverter (CSI) which allows to achieve high speed range with limited DC voltage due to its intrinsic boost capability, and this is of interest in aerospace applications or electrical vehicles (EV), but a pre-stage is necessary to control the DC input current. In this work an hybrid solution is proposed to extend the speed range of a single stage CSI (i.e. CSI without pre-stage) driving a Permanent Magnet Synchronous Machine (PMSM). In fact using a single stage CSI with DC current control, the machine cannot work properly in low speed region, so the control is composed by two different strategies: one is proposed in this work for low speed operations and the other one is already known for high speed.

Extended Kalman Filters (EKFs), Phase Locked Loops (PLLs), and Stator Flux Observers (SFOs) are widely used for sensorless control of Permanent Magnet Synchronous Motors (PMSMs) drives. Their use (in their most advanced version) is here extended, on the basis of model analogies and suitably-guaranteed closed loop stability properties, to the sensorless speed regulation control of Hybrid Stepper Motors (HSMs), in which position and speed sensors are not employed to reduce costs and increase robustness with respect to high temperature and high-vibration environments. Both realistic simulations and experimental results demonstrate the feasibility of the proposed methods in terms of closed-loop performance and robustness to parameters mismatch.