Next Generation Inverters Equipped with Virtual Synchronous Compensators for Grid Services and Grid Support

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Dead Time Management in GaN Based Three-Phase Motor Drives

This paper deals with the dead time selection in Gallium Nitride (GaN) FET based three-phase brushless DC motor drives. The GaN wide-bandgap (WBG) technology enables the increase of the switching frequency compared with silicon MOSFET. In inverter applications, it is necessary to insert a dead time in the switching signals, to avoid cross conduction in the inverter leg. The dead time selection is a compromise between the switching time and the quality of the inverter output waveforms. GaN FETs can operate with dead times in the range of tens of ns. In this paper the advantages of the GaN technology in the reduction of dead time in terms of output waveforms distortion and speed ripple compared with silicon MOSFET are carried out. Furthermore, an evaluation on the dead time compensation technique compared with the hardware technology reduction is investigated demonstrating the effectiveness and the saving of software and hardware resources obtained by GaN FET devices

Optimal Design of Grid-Side LCL Filters for Electric Vehicle Ultra-Fast Battery Chargers

This paper proposes a complete design procedure for LCL filters intended for electric vehicle (EV) ultra-fast battery chargers. The basic modeling of LCL filters is reported and the optimal ratio between grid-side and converter-side inductance is discussed. The design methodology is based on the identification of all parameter constraints, which allow to graphically determine the filter design space. Once the available space is identified, the feasible design which minimizes the total required inductance is selected, since inductors dominate the overall LCL filter volume, loss and cost. The proposed design procedure is directly applied to a 50 kW, 20 kHz 3-level unidirectional rectifier for a modular EV ultra-fast charger. The performances of the selected design, in terms of harmonic filtering and current control dynamics, are verified by means of simulation in PLECS environment, proving the validity of the proposed design methodology

Optimal Design of Grid-Side LCL Filters for Electric Vehicle Ultra-Fast Battery Chargers

This paper proposes a complete design procedure for LCL filters intended for electric vehicle (EV) ultra-fast battery chargers. The basic modeling of LCL filters is reported and the optimal ratio between grid-side and converter-side inductance is discussed. The design methodology is based on the identification of all parameter constraints, which allow to graphically determine the filter design space. Once the available space is identified, the feasible design which minimizes the total required inductance is selected, since inductors dominate the overall LCL filter volume, loss and cost. The proposed design procedure is directly applied to a 50 kW, 20 kHz 3-level unidirectional rectifier for a modular EV ultra-fast charger. The performances of the selected design, in terms of harmonic filtering and current control dynamics, are verified by means of simulation in PLECS environment, proving the validity of the proposed design methodology

Battery Sources and Power Converters Interface in Waterborne Transport Applications

In recent years the electrification in the waterborne transport application is in noticeable development. To face the high battery cost, a proper design of the energy storage system is required. For battery sources, the solution worthy of investigation is the use of a hybrid energy storage system (HESS). HESS is composed of a power-dense battery and an energy-dense battery. The use of a HESS allows better optimization of the energy and power levels of the energy storage system. In the paper, the battery source requirements in the waterborne transport application are evaluated to achieve the best trade-off among energy, maximum power, and life cycle. Furthermore, the power converters selection, to balance the power flow among the batteries and the vessel electrical network is described

Simple Tuning Method of Virtual Synchronous Generators Reactive Control

The integration of renewable energy sources requires new control strategies to make static converters able to provide ancillary grid services, such as virtual inertia and grid support during faults. To address this issue, the idea of making inverters behave as synchronous machines is well known in the literature as the concept of Virtual Synchronous Generator. Thanks to this solution, inverters can provide both inertia and reactive grid support as traditional synchronous machines. However, the tuning of the excitation control of Virtual Synchronous Generator for proper reactive power management has not been properly analyzed in the literature. Therefore, the goal of this paper is to provide a simple tuning criterion for the VSM excitation control with improved dynamic behavior using a feed-forward term. This way, the VSM is able to provide the desired reactive support during faults and quickly track the desired reactive power setpoints. Both a theoretical analysis and experimental tests are provided for a 15 kVA system

A Lead-Lag Filter for Virtual Synchronous Machines with Improved Electromechanical Damping

Traditional power systems based on synchronous generators often feature low frequency electromechanical oscillations. However, the integration of renewable energy sources through power converters can help tackling this issue. In fact, thanks to the concept of Virtual Synchronous Machine (VSM), it is possible to make the inverters behave as real synchronous machines (SMs). This way, the inverters can be integrated into the grid as traditional SMs and can even outperform them when it comes to damping low frequency oscillations in the power system. In order to do that, proper damping algorithms must be adopted in the VSM model. Therefore, this paper presents a simple and straighforward damping method for VSMs based on a single lead-lag filter acting on the VSM active power feedback. The proposed method and its integration in the VSM model are described. Then, the proposed solution has been experimentally compared to conventional methods, along with comparison metrics, to highlight its benefits