Fabio Carastro

High voltage high frequency power transformer for pulsed power application

This paper presents a new topology for a high voltage 50kV, high frequency (HF) 20kHz, multi-cored transformer. The transformer is suitable for use in pulsed power application systems. The main requirements are: high voltage capability, small size and weight. The HV, HF transformer is the main critical block of a high frequency power converter system. The transformer must have high electrical efficiency and in the proposed approach has to be optimized by the number of the cores. The transformer concept has been investigated analytically and through software simulations and experiments. This paper introduces the transformer topology and discusses the design procedure. Experimental measurements to predict core losses are also presented. The losses of epoxy coated nanocrystalline are compared to the losses in new bare (uncoated) core.

Mitigation of Voltage Dips and Voltage Harmonics within a Micro-grid, using a Single Shunt Active Filter with Energy Storage

This paper presents the application of a controller based on state space design for a shunt active filter with energy storage (SAFES) within a local power supply network in the presence of distributed generation. The aim is to guarantee voltage regulation and harmonic cancellation at the load site caused by a load step change or harmonic distortion. To achieve this objective, the SAFES is controlled to inject the appropriate current to the line. The reference fundamental current for the SAFES is calculated such that in the presence of voltage sags, it works in conjunction with local distributed generation, (which usually has slow dynamic response) to control the voltage at the point of common connection (PCC). The multivariable controller employs a full state observer to provide the SAFES reference voltage. This paper provides a theoretical analysis of the controller behaviour in presence of plant variations. Simulation results show that the proposed method makes it possible to regulate the grid voltage at its nominal value and can also provide harmonic injection if required

Repetitive Control for High-Performance Resonant Pulsed Power Supply in Radio Frequency Applications

This paper presents a novel three-phase series resonant parallel loaded resonant converter topology for radio frequency applications. The proposed converter is capable of producing a series of “long pulses” as output voltage, each one lasting 1 ms in time. Three individual single-phase resonant stages are able to independently operate in conjunction with three separate single-phase output rectification stages. Due to this important feature, the converter has a strong ability of rejecting the influence of unbalance in the resonant tanks. A proportional-integral + repetitive control strategy has been used for the output pulsed voltage regulation, resulting in a fast rise time, a reduced overshoot, and a constant amplitude. The soft switching of semiconductor devices is ensured at full power by a combined frequency and phase shift modulation, even in the presence of large tank unbalances.

High performance SiC MOSFET module for industrial applications

A novel 1.7kV, 500A low inductance half-bridge module has been developed for fast-switching SiC devices. The module has a maximum temperature rating of 175°C. There are 12 GE SiC MOSFET chips per switch and the MOSFETs body diode is utilized as the freewheeling diode. The modules typical on-resistance is 3.8mOhms at 25°C and 5.8mOhms at 175°C. Internal loop inductance measured from DC input terminals is 4.5nH, approximately 75% lower than that of a standard IGBT module. When connected to a low inductance busbars, the module can be switched in 50ns without excessive voltage and current overshoots. Double pulse inductive switching losses at VDS=1000V, Id=450A and TJ=150°C are: EON=21.5mJ, EOFF=16.5mJ and EREC=6mJ. The losses are at least ten times lower when compared to a similarly rated IGBT module, highlighting the SiC advantage for higher switching frequency applications. Short circuit testing was performed, demonstrating good ruggedness albeit the need for a fast protection circuit.

Control and implementation of a high voltage series resonant power supply for industrial electrostatic precipitators

This paper considers the design of a high voltage high frequency power supply for industrial electrostatic precipitator applications. The supply is based on a series resonant series-loaded converter. The main aim of this, university-industry partnership, work is to design and experimentally validate the capability of the proposed configuration in achieving higher efficiency and more flexible transient response when compared with a traditional line frequency based power supply. Closed-loop behaviour of the power supply, during sparking events, is also investigated with a non-linear precipitator model.

High Speed Thermal Imaging applied to a Long Pulse Resonant Converter Modulator for Power device Reliability Assessment

This paper considers the design of a modulator supply for RF tube applications. The supply is based on direct modulation of a series resonant parallel loaded power supply. The main aim of this work is to monitor semiconductor losses of the IGBT modules through calorimetry and the device temperature using high speed thermal imaging, during the pulse. The paper provides an overview of the technology and design used on the test rig prototype under study. The final experimental rig layout designed for internal device temperature and loss measurement will be presented. The overall goal of the work is to identify the limitations and reliability of the modulator technology proposed.

Shunt Active Filter for Voltage and Power Improvements within a Micro-grid

This paper discusses the application of a shunt active power filter with energy storage, for voltage and power improvements within a local power supply network (micro-grid) in presence of distributed generation. Theoretical analysis investigates the control the shunt active power filter in response to voltage sag. The shunt active filter operates over a short period of time, and is coordinated with the response of a distributed generator with a slower dynamic response. Simulation results show that the proposed method makes it possible to regulate the grid voltage at its nominal value and also allows the power sharing between the active filter and the local synchronous generator

Readiness of SiC MOSFETs for Aerospace and Industrial Applications

This paper highlights ongoing efforts to validate performance, reliability and robustness of GE SiC MOSFETs for Aerospace and Industrial applications. After summarizing ruggedness and reliability testing performed on 1.2kV MOSFETs, two application examples are highlighted. The first demonstrates the 1.2kV device performance in a prototype high frequency 75kW Aviation motor drive. The second highlights the experimental demonstration of a 99% efficient 1.0MW solar inverter using 1.7kV MOSFET modules in a two-level topology switching at 8kHz. Both applications illustrate that SiC advantage is not only in improved performance, but also in significant system cost savings through simplifications in topology, controls, cooling and filtering.

High performance pulsed power resonant converter for radio frequency applications

This paper presents a high performance three-single phase pulsed power resonant converter for radio frequency applications. The proposed converter is capable to produce as output voltage a series of “long pulses”, each one lasting from 1 ms and duty cycle of 10%. A Repetitive control approach has been used for the converter output voltage regulation, resulting in short rising time, low ripple and smooth transient. Three individual single phase resonant stages are able to be operated independently. Due to this important feature, the converter has a strong ability of rejecting the influence of resonant tank unbalances. The soft-switching of power devices is maintained at full power even in the case of large tank unbalances. Experimental results confirm and validate the feasibility of the converter.

An improved resonant converter for long-pulse generation in high-energy physics applications

This paper presents a novel three-single phase resonant converter topology for long pulse modulators in high-energy physics applications. The proposed converter generates a flat top pulse voltage that lasts one millisecond. Each single phase can be operated with independent frequency and phase shift. Based on that, the whole converter has a strong ability of rejecting resonant tank unbalances. A Repetitive type control stragegy has been used resulting in pulse high dynamics performance and reduced overshoot, which satisfy the system specifications. The soft-switching, zero current switching (ZCS), is ensured by combined frequency and phase control at full power in all IGBTs.