Search results for "Verters"

A Design Methodology for Low-Power MCML Ring Oscillators

2007

In this paper, a low-power design method for MCML based ring oscillators is presented. The proposed method takes into account the parasitic capacitances of the MOS transistors. To validate it, some ring oscillators with different oscillation frequencies were designed in a 0.18 mum CMOS technology. SPICE simulations demonstrate the effectiveness of the design method.

Extension and Tuning of Virtual Synchronous Machine to Avoid Oscillatory Instability in Isolated Power Networks

2020

The risk of oscillatory instability introduced by virtual synchronous machines (VSM) control in isolated power networks is investigated. The considered control is a common scheme widely studied in literature, in several configurations and for different case studies. The impact of the VSM control on the system stability is examined for the existing power network of a Mediterranean island. The VSM control is implemented within the power converters interfacing the energy storage systems (ESS) installed in the network. Simulations and analysis show the occurrence of oscillatory instability in the system, with the ESS-VSM and the synchronous machines of the network progressively swinging against…

Dynamic Control of Static Converters for the Transition from Grid-on to Grid-off Operation of AC/DC Microgrids

2022

In this paper, specific control logics defined for generators, controllable loads and electric energy storage systems are illustrated in order to improve the reliability of AC/DC hybrid microgrids in their grid-off operation following failure events such as short-circuits, line breaks, sudden disconnections of generating units or loads, etc. After defining specific control schemes, these were modelled in a digital environment and finally tested with dynamic simulations. Finally, the paper highlights the role of virtual synchronous machine control for the self-healing capacity of islanded hybrid microgrids.

INVERTER-BASED DISTRIBUTED GENERATORS, MODELING AND CONTROL

In the last few years, electrical power generation is moving from a centralized generation towards distributed generation including on-site Renewable Energy Sources (RESs). In order to overcome RES related issues, as intermittent and fluctuating power, storage elements are included in the on-site generation system. The interaction between distributed generator (DG) units including RES, storage and front-end power converters should be carefully modeled in order to analyze the power system stability. An accurate modeling of DGs is required. In this thesis, a new modeling approach has been proposed for the inverter-based DGs based on the concept of electrostatic synchronous machines. Detailed …

Grid-forming converters. A critical review of pilot projects and demonstrators

2022

Grid-forming control can be a useful solution for all dynamic issues in weak grids and for providing ancillary services. It represents the new frontier in modern power electronics, responding to the needs of power systems more and more rich in renewables and, for this reason, with lower inertia. Today, the research on grid-forming is mainly oriented to propose new and more effective control schemes and to evaluate their performances with simulation tools, but few works in the literature focus on the results of on-field experimentation. Therefore, this paper aims to provide a comprehensive review of grid-forming pilot projects and demonstrators developed worldwide. The work describes the mai…

Fundamental Analysis of Grid-Forming Converters Enhanced with Feedforward Controls

2022

The grid-forming control for power converters can be enhanced by proper feedforward terms included in the active power control loop. Two basic structures are identified, the feedforward angle and the feedforward frequency. The formal analysis of the transfer functions reveals a structural similarity. The two schemes exhibit however a fundamental difference in their transient capabilities. The grid-forming controls are characterized with the introduction of two specific factors, for the direct assessment of the inertia and the damping which can be provided by the grid-forming converter. The sensitivity analysis of the two feedforward schemes indicates that the enhancement of the transient pe…

Non linear digital control improving transient response:design and test on a multiphase VRM

2010

Investigation on Cascode Devices for High Frequency Electrical Drives Applications

2019

In the last years a widespread development in the market of electrical drives employing high-speed electrical machines has occurred in various industrial fields, due to the extremely high power density that can be reached. Nevertheless, to maintain output power quality without using bulky filtering networks, DC-AC converters should be controlled by means of higher PWM switching frequencies. New switching device technologies, such as Field Effect Transistors based on SiC and GaN, are therefore gathering momentum in order to comply with the higher working frequencies. To operate under high frequencies and at the same time at high voltage levels, alternative circuital configurations for switch…

A novel digital control for DC/DC converters to improve steady-state performances

2006

This paper describes an innovative digital PWM control implementation for low voltage, high current DC-DC converters. The proposed technique, based on the use of a low resolution DAC, improves steady-state performances, minimizing limit cycle effects. The novel technique is tested on a FPGA-based single phase buck converter operating at 250 kHz. A detailed description of the proposed architecture is given and test results, simulation and experimental ones, are shown

Hybrid Modelling and Control of a Class of Power Converters With Triangular-Carrier PWM Inputs

2021

In this paper, a new control design procedure for a class of power converters based on hybrid dynamical systems theory is presented. The continuous-time dynamics, as voltage and current signals, and discretetime dynamics, as the on-off state of the switches, are captured with a hybrid model. This model avoids the use of averaged and approximated models and includes the PWM as well as the sample-and-hold mechanism, commonly used in the industry. Then, another simplified hybrid system, whose trajectories match with the original one, is selected to design the controller and to analyse stability properties. Finally, an estimation of the chattering in steady state of the voltage and current sign…