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.

Non-isolated integrated chargers take advantage of the electric vehicle’s on-board power electronic for charging purposes: the traction drive inverter is a good candidate to be used in the battery charging process, while the stator windings of the electrical traction motor can be utilized as static inductors. In a typical non-isolated three-phase grid-connected system, there exist a leakage current flowing through the common mode (CM) parasitic path between the vehicle’s chassis and the DC ground. Large leakage current lead to potential electric shocks to the end-users, as well as on-board electronics failures. In this paper, a 3-level Active Neutral Point Clamped (ANPC) inverter is used together with the stator windings of a permanent magnet synchronous machines (PMSM) for charging purposes. The issue of CM leakage current through the parasitic path is analysed for different earthing systems. Different modulation techniques are critically compared in terms of effectiveness in reducing the leakage current, grid currents distortion and capability in reducing the DC current ripple during battery charging. Simulation results are provided in support of the analysis.

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.

Wide-bandgap (WBG) power semiconductor devices have acquired more and more interest in power circuits, since they allow to operate at higher switching frequencies and temperatures compared to the conventional silicon-based devices, while also improving efficiency and power density. In electric drive applications they can produce significant electrical stress at the machine terminals due to their inherently elevated voltage gradients (dv/dt), hence resulting in a reduced lifetime of the entire system. Voltage overshoot at the electrical machine terminals depends on many factors, such as voltage dv/dt, cables type and length, electrical machines input impedance etc. In this paper, a novel control based on a recent multilevel drive architecture is presented. This control is able to minimize the voltage overshoot at the terminals of an electrical machine independently form the system layout, increasing the overall reliability and lifetime of the winding’s insulation system.

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.

High reliability motor drives for more electric transportation has been the topic of research both for the academia and the industry. Multi-phase electric drives have been long investigated for fault tolerant applications due to their inherent redundant construction. They represent an ideal component for safety critical applications in transportation, e.g. in ground vehicle and aerospace applications. This paper reviews the drive topologies and control strategies, focusing on the multi-three-phase architecture with modular inverter topologies. The impact of the PWM switching pattern on DC link capacitor current ripple has been analytically investigated and an approach will be proposed in order to minimize DC current ripple RMS value, when using more than one three-phase converter. Numerical simulations results agree with the analytical ones.

Wireless power transfer systems are characterized by a loosely coupled magnetic circuit and a power electronics interface. For the optimization of the system power factor, a compensation circuit composed of capacitors is adopted to form a resonant tank with the power coil. The behavior of the overall circuit in terms of power transfer and current/voltage waveform depends on several parameters, which can make the analysis and optimization of the system complex. This paper proposes an analytical derivation of an equivalent RLC system that greatly simplify the design in terms of Zero Voltage Switching (ZVS) regions. In addition to this, the RLC equivalent circuit allows an easy analytic calculation of the output power depending on all WPT system parameters. The analytical model will be validated by simulation results.

This paper presents a storage system integration on the photovoltaic module side of a traditional grid-connected PV plant. The proposed retrofit application is based on a wide voltage range Dual Active Bridge topology, used as bidirectional DC/DC converter. Wide voltage operation capability at PV side is required to allow the integration of the retrofit storage system on a broader range of existing PV plants, characterized by different PV string operating voltage and commercial grid-connected inverters. Dual Active Bridge topology was chosen as a galvanically-insulated bidirectional single stage conversion stage to interface storage batteries to the PV side of the existing photovoltaic plant. The storage battery is charged during the overproduction of the PV plant and the storage system sustains the end-user domestic loads when solar irradiation is insufficient. The proper operation of the commercial inverter, the design and control strategy of the whole system showed the effectiveness of the proposed solution. A full-size 3.2kW converter prototype was manufactured and experimental validation was carried out.

This paper assesses the use of a modified three phase VSI topology with additional switches (H8) together with suitable modulation techniques as a mean for common-mode voltage reduction in electric drives with the aim of mitigating the onset of harmful bearing currents. Bearing currents in inverter-fed motors are related to the high dv/dt variation, induced at the motor terminals by the converters. The problem, already known in industry for Si-Based converters, is now aggravated by the use of wide-bandgap devices in More Electric Aircraft applications. This paper evaluates the use H8 topology for mitigating the phenomenon, comparing its performance against the one of a conventional three-phase full-bridge converter, by means simulation and experimental results.

Current source inverter (CSI) is a family of power converters which has been recently investigated for photovoltaic power conversion in grid-tied operation, due to the inherent boost capability and ease of control. This paper assess Photovoltaic three-phase Current Source Inverters by two different CSI topologies and space vector modulation commutation strategies. Different CSI solutions are therefore analyzed by means of numerical simulations and the results are compared in terms of ground leakage current and THD of the injected grid currents. Extensive simulation results show that the CSI7 topology can improve the common mode performance while at the same time increasing the efficiency of the conventional CSI, at the price of a negligible added complexity.

This paper presents a grid-tied single phase photovoltaic microinverter based on Current Source Inverter (CSI) topology. The main topic of this work is related to the identification of a topology and a PWM strategy able to minimize the obvious issues of the basic CSI solution: efficiency and ground leakage current. The strong reduction of this last issue allows the use of the proposed solution in conjunction with Photovoltaic module in building integrated installations. Simulation results and a low voltage experimental validation present the effectiveness of the proposed solution in mitigating ground leakage currents.

This paper presents design strategies for the optimized design of the rotor poles in synchronous permanent magnet machines. The strategies are aimed at the reduction of torque ripple and cogging torque. Sinusoidally rounded magnet and rotor step-skewing are investigated, then a new proposal to reduce the cost of magnetic pole made in rare earth is presented. The goal is to introduce into a rotor pole, a fraction of low cost ferrite magnets on either side of the main rare earth NdFeB permanent magnet. The design procedure begins with some analytical consideration that allows to optimize the geometrical design of the magnets. Using Finite Element (FE) simulations, the effectiveness of the analytical model is verified and the results of the various methods are compared.

This paper presents the design of an axial flux permanent magnet machine for in-wheel application. The machine design and optimization are developed using two-dimensional (2-D) multi-layer finite element analysis approach. The three-dimensional model of the machine has been approximated with a set of simulations in which the two-dimensional geometrical parameters were varied appropriately in order to reproduce the actual three-dimensional magnetic behavior. During design optimization, special attention was paid to the reduction of flux linkage harmonic content and to the reduction of cogging torque through the change of the permanent magnet profile and dimensions. Finally, a prototype machine was built to validate the effectiveness of the proposed method.

This paper analyzes the power losses of photovoltaic micro-inverters based on flyback topology. A double secondary winding flyback converter topology was considered to inject alternating current into the grid. The purpose of this work is the identification and quantification of the different power losses present in a simple flyback topology and in the interleaved version with two different control strategies. The power losses comparison was carried out after designing a 250 W power converter using commercial, low cost components. Simulations in Matlab/Simulink environment highlighted the effectiveness of the interleaved architecture.

This paper analyzes the performance of a grid-tied photovoltaic module integrated, transformerless, three-phase Current Source Inverter (CSI). The design exploits CSI inherent step-up capability to obtain a single stage power interfacing between the low voltage PV input and the high AC voltage output, to be fed into the distribution grid. A modified CSI converter topology is proposed along with a suitable PWM strategy and a simple closed loop control. The theoretical analysis and simple analytic expressions highlighted the performance and limitations of the topology when employed in single-stage PV microinverter supplied by a single low voltage PV panel. The principle of operation and control is described, and the traditional CSI topology has been simulated numerically in Matlab/Simulink environment. Results obtained with the proposed topology are presented and evaluated in order to validate the theoretical assumptions.

Many transformerless topologies for photovoltaic systems were proposed in order to minimize power losses and avoid high levels of ground leakage current (that can arise in such systems). The most efficient PWM strategies achieve this goal by decoupling the grid from the DC Link during the freewheeling phases of the output current. These strategies usually operate only with a unity power factor. However, as solar inverters have penetrated into power distribution networks, new issues have arisen and modifications of regulations governing grid connection of distributed systems were introduced in some countries. One of the new requirements for the inverters connected to the low-voltage grids is the possibility to provide reactive power. This paper proposes a transformerless inverter topology with a wide-range power factor operation. Simulation results and extensive experimental results, focused mainly on ground leakage current analysis, showed the effectiveness of the proposed solution.

This paper is aimed at the modeling and simulation of wind power system, with particular emphasis on small wind turbines employing surface permanent magnet synchronous generators (SPMSGs). Generator and inverter front-end interaction is analytically and numerically modeled, in order to evaluate the generator's efficiency depending on its electric parameters, both during normal and power limited operation. Passive and active rectifier front-end are taken into account to assess the influence of power electronics front-end over system performances. The final target of this work is to determine design guidelines for small wind turbine system optimization. The analysis is carried out through simulations which take into account the interactions of the SPMSG's electrical parameters and through the evaluation of the generator's efficiency at different operating conditions and inverter front-end architectures. The data obtained was further validated with experimental characterization of two different system architectures.

In the recent years the research on photovoltaic converters has been focused on topologies that do not feature a line frequency transformer, in order to reduce costs and successfully increase the overall efficiency. The main problem in removing the galvanic isolation is that the parasitic capacitance present between the cell and the metal frame enclosing the panel (usually earth-connected) enables a common-mode current to be injected into the grid by the converter. This paper proposes an active common-mode filter able to compensate the high-frequency common-mode voltage variations at the output of the power converters, that represent the principal cause of ground leakage current. The advantage of this solution concerns the capability to operate with an arbitrary power factor. In this work it is applied in cascade to a converter with standard full-bridge topology driven by a three-level PWM strategy. Simulation and experimental results shows the feasibility of the proposed approach.

The design of a photovoltaic (PV) grid-connected converter usually comprehends a galvanic isolation between the grid and the photovoltaic panels. Recently, in low power systems, the galvanic isolation has been removed with the aim to increase efficiency and reduce the cost of the converter. Due to the presence of a parasitic capacitance between the photovoltaic cells and the metal frame of the PV panel, usually connected to earth, a high value of common mode current (i.e., ground leakage current) can arise. In order to limit the ground leakage current (which deteriorates the power quality and generates EMI), new converter topologies have been proposed. Their effectiveness is based on the symmetrical (ideal) commutations of the power switches and some of them adopt a further voltage level derived from a capacitive divider of the DC bus voltage. Unfortunately, in actual implementations, asymmetrical power switches transients and variations of this added voltage lead to higher ground leakage current with respect to the ideal case. After a review of the state of the art this paper investigates these two issues and presents a particular solution (based on digital control and PWM strategy) that, in conjunction with a compensation strategy of power switches actual commutations, guarantees low ground leakage current regardless the parameters tolerance of the power circuit. Simulation and experimental results confirm the effectiveness of the proposed solution.