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This paper investigates the influence of power semiconductor parasitic components on the ground leakage current in the three-phase Current Source Inverter topology, in the literature called H7 or CSI7. This topology allows reducing converter conduction losses with respect to the classic CSI, but at the same time makes the topology more susceptible to the parasitic capacitances of the semiconductors devices. In the present work, a grid-connected converter for photovoltaic power systems is considered as a case study, to investigate the equivalent circuit for ground leakage current. The same analysis can be extended to applications regarding electric drives, since the HF model of electric machines is characterized by stray capacitance between windings and the stator slots/motor frame. Simulation results proved the correctness of the proposed simplified common-mode circuit and highlighted the need of an additional common-mode inductor filter in case of resonance frequencies of the common-mode circuit close to harmonics of the power converter switching frequency. Experimental results are in agreement with the theoretical analysis.

Higher magnitudes of the stator currents, low efficiency, and degradation of the output torque in high speed machine are caused by iron losses, which are not sufficiently small to be neglected. A Finite Control Set Model Predictive Control (FCS-MPC) which takes iron losses into account in the prediction model on a high speed motor is proposed in this paper and compared to classical FCS-MPC that neglects iron losses influence. Performances of both models are analysed and compared under steady-state and transient conditions including acceleration condition using a 3-Level Hybrid Active Neutral Point Clamped (HANPC) inverter topology. Accurate simulations of a 3-Level HANPC inverter driving a high speed PMSM are presented comparing the proposed control respect to classical FCS-MPC and the classical Field Oriented Control (FOC) together with neutral point (NP) balance and loss minimization control (LMC).

Multi-phase electric drives can be employed in a great variety of applications. Their advantage in terms of fault-tolerance capability is becoming the focus of the work of many research activities, especially in the field of transportation electrification. The main topic is to create redundant and modular multi-three-phase drives to increase the overall system reliability and fault-tolerance. To this aim, distributed control architectures have been assessed. In this paper, a centralized master-slave control is compared against a distributed droop control architecture, in order to identify advantages and drawbacks. Both of the control strategies are applied to a double three-phase drive. The aim of the work is to assess whether the droop control architecture can be a valid alternative to a centralized master-slave control in terms of performances, but with the additional benefit of having a proper full redundant fault-tolerant 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.

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 prestage to generate a constant current bus. This article therefore seeks to challenge this “accepted” consideration that a CSI always needs this precircuit 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.

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.

This paper analyzes the relation between the ground leakage current and the power semiconductor parasitic components of a three-phase Current Source Inverter (CSI) topology named in literature H7 or CSI7. This topology is characterized by the presence of an additional switch which allows to reduce conduction power losses and decouple the DC side from the AC side during the application of the Zero current Vector to reduce ground leakage current. This work deals with the significant variation of this current depending on power converter parasitic capacitors. In this work the analysis is applied to grid-connected converters for a string photovoltaic applications, even if the behavior is the same also in case of electrical drives. The analysis is assessed by numerical simulations and experimental results with different parasitic capacitances that confirm also the validity of the proposed equivalent common-mode circuit.

New sensorless observers (i.e., from stator currents/voltages measurements only), to be included into a simple observer-based sensorless control for the tracking of non-definitely zero speed references in nonsalient-pole surface permanent magnet synchronous machines (PMSMs), are proposed. They are obtained through a “minimum distance” modification from recently presented position-sensorless observers (i.e., from rotor speed and stator currents/voltages measurements only). The rotor speed estimate is here directly provided by the phase locked loop (PLL)-based third-order steady-state linear kalman filter (SSLKF) that has been previously used to mitigate the distortions on the estimated position. Experimental results illustrate the effectiveness of the proposed approach in a speed sensor fault-tolerant scenario.

High-Frequency signal injection is widely adopted for zero and low-speed operating conditions in sensorless control of Interior Permanent Magnet Synchronous Motors (IPMSM) drives. However, the audible noise emissions caused by induced HF current has restricted in some cases its practical application. Low-frequency signal injection solve the noise problem, but it introduces new issues. In particular, the filtering for signal separation is not trivial and affects negatively the current control loop and the dynamic performance of the angle tracking estimator. To overcome these limitations, some new strategies and modifications respect to the traditonal sensorless control are proposed in this paper, using the esteem of specific signal components estimated from known information of the drive. The simulations were carried out considering a discrete-time controller and quantiziers on measured currents and pulsed voltages. The results demonstrated the feasibility of the proposed method.