F. Carastro

University of Nottingham, Nottigham, England, United Kingdom

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Publications (19)5.75 Total impact

  • C. Ji, P. Zanchetta, F. Carastro, J. Clare
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    ABSTRACT: 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.
    IEEE Transactions on Industry Applications 01/2014; 50(4):2660-2670. · 1.67 Impact Factor
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    ABSTRACT: This paper considers monitoring of semiconductor thermal cycling in high-power resonant converters. For the experiments, a dedicated single-phase resonant converter rated at 1 kV, 250 A (250-kW peak power, duty ratio 10%, 25-kW average power, AND pulse length 1 ms) was been developed. This converter represents one phase of a multiphase resonant power supply designed for long-pulse modulation (typically 1–2 ms) when equipped with a suitable output transformer. Pulsed operation is obtained by direct modulation of the high-frequency power supply. The main aim of the study reported here is to develop a methodology to assess performance and reliability issues related to the use of standard commercially available power switch technology, relying on a physics-based multichip insulated gate bipolar transistor (IGBT) structure model, and to experimentally monitor the chip temperature using high-speed thermal imaging, during the pulse, to identify any limitations of the proposed modulator technology. First, an overview of the converter, including its nominal electrical design, is provided. Optimization of the turn-OFF snubber capacitance is performed through a series of experiments, employing calorimetrically measured losses, to determine a value, which minimizes the overall power losses. Accurate calorimetric measurements of the switching losses and infrared measurements of the IGBT surface temperatures during transient operation are presented. Simulations including multichip structures, experimental results, and high-quality chip thermal images are provided to validate the effectiveness of the proposed approaches.
    IEEE Transactions on Power Electronics 01/2012; 27(1):37-45. · 4.08 Impact Factor
  • Chao Ji, P. Zanchetta, J. Clare, F. Carastro
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    ABSTRACT: 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.
    Energy Conversion Congress and Exposition (ECCE), 2011 IEEE; 01/2011
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    ABSTRACT: 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.
    Energy Conversion Congress and Exposition (ECCE), 2010 IEEE; 10/2010
  • Chao Ji, P. Zanchetta, F. Carastro, J. Clare
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    ABSTRACT: 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.
    Industrial Electronics (ISIE), 2010 IEEE International Symposium on; 08/2010
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    ABSTRACT: 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.
    Power Modulator and High Voltage Conference (IPMHVC), 2010 IEEE International; 06/2010
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    ABSTRACT: 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 a 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.
    01/2010;
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    ABSTRACT: This work proposes the development of a control technique to ensure soft-switching of the active devices in a high-voltage high-frequency power supply, during all operational conditions. The study is carried out with relevance to an industrial electrostatic precipitator system, based on a series-resonant converter topology. The main operational features of the circuit are presented, detailing the requirements for high efficiency and high reliability. Based on theoretical analysis, the development of specific control solutions is thoroughly discussed. Experimental results are presented to demonstrate the validity of the considered approach for maximizing circuit performance and reducing the risk of degradation of the power switches.
    Microelectronics Reliability. 01/2010; 50:1738-1743.
  • Todor Filchev, Fabio Carastro, Pat Wheeler, Jon Clare
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    ABSTRACT: 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.
    01/2010;
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    ABSTRACT: Compact thermal impedance models allow fast, fully coupled electro-thermal simulation of multi-chip power modules. Usually, these models are generated through a time and labour intensive process of curve fitting to data points obtained experimentally or from finite-element simulations. This paper demonstrates a new, much faster, technique which mathematically derives such models and validates it against experimental measurements for an example multi-chip module. The ease of use and coupling capabilities of the models when used with an accurate device model is then demonstrated.
    Power Semiconductor Devices & IC's (ISPSD), 2010 22nd International Symposium on; 01/2010
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    ABSTRACT: This paper investigates the electro-thermal stress levels and related degradation risk affecting standard technology multichip IGBT modules when used in pulsed power resonant converters. Indeed, these feature fairly unique operational characteristics, which differentiate them substantially from more common power electronics applications (e.g., inverters, dc-dc converters). First, an overview of the converter functioning is provided; then, an a priori minimisation of the electro-thermal stress levels affecting the active switches (IGBTs) is searched for: this is based on an experimental parametric study of the turn-off snubber and of the DC-link capacitance value for which the overall switching power losses can be minimised. Accurate calorimetric measurements of the switching losses and infrared measurements of the IGBTs surface temperature during transient operation are presented. Simulation is used to complement the gained information in the frequency range not covered by the experimental method.
    Pulsed Power Conference, 2009 IET European; 10/2009
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    ABSTRACT: This paper considers the semiconductor thermal cycling monitoring of high power resonant converters. For the tests a single phase resonant converter rated at 1 kV, 250 A (250 kW peak power, duty ratio 10%, 25 kW average power, pulse length 1 ms) has been developed. This represents one phase of a multi-phase resonant power supply designed for long-pulse modulation (typically 1 ms-2 ms) when equipped with a suitable output transformer. Pulsed operation is obtained by direct modulation of the high frequency power supply. The main aim of the work reported here is developed a physic-based multi-chip IGBT structures and experimentally monitoring the chip temperature using high speed thermal imaging, during the pulse, to identify the limitations and reliability of the modulator technology proposed. The paper provides a brief overview of the prototype test rig. Simulations including multi-chip structures, experimental results and high quality chip thermal images are provided to validate the effectiveness of the proposed approaches.
    Energy Conversion Congress and Exposition, 2009. ECCE 2009. IEEE; 10/2009
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    ABSTRACT: This paper considers the calorimetric measurements of losses and the semiconductor thermal cycling monitoring of high power resonant converters. For the tests a single phase resonant converter rated at 1 kV, 250 A (250 kW peak power, duty ratio 10%, 25 kW average power, pulse length 1 ms) has been developed. This represents one phase of a multi-phase resonant power supply designed for long-pulse modulation (typically 1 ms-2 ms) of RF tubes when equipped with a suitable output transformer. Pulsed operation is obtained by direct modulation of the high frequency power supply. The main aim of the work reported here is to monitor semiconductor losses of the IGBT modules through calorimetry and the device temperature using high speed thermal imaging, during the pulse, to identify the limitations and reliability of the modulator technology proposed. The paper provides an overview of the technology and design of the prototype test rig studied. Experimental results, showing semiconductor losses obtained through calorimetry and high quality chip thermal images are provided to validate the effectiveness of the proposed approaches.
    High Power RF Technologies, 2009. IET. Conference on; 03/2009
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    ABSTRACT: This paper considers the calorimetric measurements of losses and the optimisation of high power resonant converters. For the tests a single phase resonant converter rated at 1 kV, 250 A (250 kW peak power, duty ratio 10 %, 25 kW average power, pulse length 1 ms) has been developed. This represents one phase of a multi-phase resonant power supply designed for long-pulse modulation (typically 1 ms to 2 ms) of RF tubes when equipped with a suitable output transformer. Pulsed operation is obtained by direct modulation of the high frequency power supply. The main aim of the work reported here is to calorimetrically monitor semiconductor losses and to experimentally optimise the value of turn-off snubber capacitors across the devices. The paper provides an overview of the technology and design used on the test rig prototype under study. Experimental results and semiconductor losses obtained through calorimetry will be provided to validate the effectiveness of the proposed techniques.
    01/2009;
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    ABSTRACT: This work is about the analysis of reliability issues in pulsed power resonant converters, which feature fairly unique operational characteristics, differentiating them substantially from more common power electronics applications (e.g., inverters, dc–dc converters). First, an overview of the converter functioning is provided; then, an a priori minimisation of the electro-thermal stress levels affecting the active switches (IGBTs) is searched for: this is based on an experimental parametric study of the turn-off snubber and of the DC-link capacitance value for which the overall switching power losses can be minimised. Accurate measurements of the switching losses in the IGBT modules are performed by means of a calorimetric technique. Finally, infra-red measurements of the IGBTs surface temperature during transient operation are presented, showing that the introduction of soft-switching strongly reduces the amplitude of lower frequency thermal cycles.
    Microelectronics Reliability. 01/2009;
  • F. Carastro, M. Sumner, P. Zanchetta
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    ABSTRACT: This paper investigates the use of energy storage added to a shunt active filter configuration in order to enhance its operation in maintaining power quality conditioning at a particular part of a grid system. The specific application considered is for a microgrid. In the proposed configuration the shunt active filter with energy storage (SAFES) can supply both reactive and real power for a short duration, to "fill in" the power required in the presence of load changes within the microgrid until the main generation can respond. In this way voltage quality is maintained and no power is drawn from the main grid. To perform both voltage and harmonic compensation in the presence of a non-linear load a novel control strategy based on the state space pole placement design has been developed for the SAFES installed in a microgrid. Simulation studies and experimental results show that the proposed controller is able to regulate the grid voltage at its nominal value and also control the power sharing between the SAFES and the local supply. It also provides high bandwidth control of current harmonics.
    Industry Applications Society Annual Meeting, 2008. IAS '08. IEEE; 11/2008
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    ABSTRACT: 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.
    IEEE International Power Modulators and High Voltage Conference, Proceedings of the 2008; 07/2008
  • F. Carastro, M. Sumner, P. Zanchetta
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    ABSTRACT: 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
    IEEE Industrial Electronics, IECON 2006 - 32nd Annual Conference on; 12/2006
  • F. Carastro, M. Sumner, P. Zanchetta
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    ABSTRACT: 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
    Power Electronics and Motion Control Conference, 2006. EPE-PEMC 2006. 12th International; 10/2006