Andrew Forsyth

• The University of Manchester

A hierarchical control architecture is proposed for the optimal day-ahead commitment of multiple grid support services within a virtual power plant (VPP). The day-ahead optimisation considers pricing and cost data to determine the commitment schedule, and a robust Model Predictive Control (MPC) approach is included to minimise the unbalance fees du...

A control technique for multi-MHz multi-level converters to overcome the conversion ratio non-linearity introduced by the minimum/maximum pulse width constraints of gate-drivers and PWM signal generators is presented. The control capitalizes on the converter architecture to significantly reduce the conversion ratio non-linearity without the need of...

We present a new strategy to optimise the energy density of supercapacitor cells, by systematically varying the amount of graphene-related additive, while mass balancing the positive and negative electrodes. The capacitance and the electrochemically stable potential window of the electrodes have been determined for several electrodes with different...

To capitalize fully on modern component technologies such as nanocrystalline cores and wide-bandgap devices, multi-objective converter design optimization is essential, requiring simple, accurate component models. In this work, a lumped parameter thermal model is presented for nanocrystalline inductors with ceramic heat spreaders. The key challenge...

An investigation is described into the optimization of multi-phase, high power, bi-directional DC-DC interleaved converters suitable for Electric Vehicle (EV) applications. Two dual-interleaved topologies were considered initially for the optimization, the main difference being the magnetic devices: either discrete inductors (DI) or an Interphase T...

A two-phase buck–boost converter utilizing dual interleaving is presented in this paper. The dual interleaving consists of an interphase transformer that doubles the ripple frequency together with two conventional buck-boost switching arms, mitigating the inductor ripple current and aiding to increase the power density of the converter. A descripti...

The current state-of-the-art positive electrode material for chloroaluminate ion batteries (AIBs) or dual-ion batteries (DIBs) is highly crystalline graphite; however, the rate capability of this material at high discharge currents is significantly reduced by the modest conductivity of graphite. This limitation is addressed through the use of graph...

A new criterion and potentiostatic method is demonstrated to determine the electrochemically stable potential window (ESPW) of supercapacitors, enabling the calculation of the optimal electrode mass ratio for two different electrode-electrolyte pairings. The criterion uses the decay of electrode current in a three-electrode test cell during potenti...

A comparison of the performance of graphene‐based supercapacitors is difficult, owing to the variety of production methods used to prepare the materials. To the best of our knowledge, there has been no systematic investigation into the effect of the graphene production method on the supercapacitor performance. In this work, we compare graphene prod...

This paper presents a method for the forecasting of the voltage and the frequency at the point of connection between a battery energy storage system installed at The University of Manchester and the local low-voltage distribution grid. The techniques are to be used in a real-time controller for optimal management of the storage system. The forecast...

A split core technique is proposed to mitigate the gap losses in high frequency nanocrystalline cores, which enables significant size reductions in thermally limited designs. Finite element analysis is used to examine the gap loss dependency on core width, D, revealing a non-linear relationship of the form loss $\propto D^{\alpha}$ is approximatel...

The averaged small-signal model of the dual-interleaved buck converter is extended to include the phase interaction effects that arise from the interleaved sampling of the phase currents. Sampler decomposition techniques are used to extend the averaged model, revealing a slow-scale instability that can place significant restrictions on the choice o...

Three pulse-width-modulation (PWM) digital control approaches are evaluated to provide the current sharing between phases in high-power dual-interleaved DC-DC converters. The implementation of a digital peak current, multi-sample averaged current and an enhanced single-sample averaged current control in a TMS320F28377D is described. A summary of st...

A scale-up process of high-rate-capability supercapacitors based on electrochemically exfoliated graphene (EEG) and hybrid activated carbon (AC)/EEG are studied in this work. A comparison of the rate capabilities of large-scale EEG and AC/EEG-based pouch cell and commercial high-power supercapacitors are also presented in this paper. The oxygen con...

Circuit level analytical models for hard-switching, soft-switching and dv/dt-induced false turn on of SiC MOSFETs and their experimental validation are described. The models include the high frequency parasitic components in the circuit and enable fast, accurate simulation of the switching behaviour using only datasheet parameters. To increase the...

To extend the operating range of the snubber assisted zero-voltage and zero-current transition dual-interleaved boost converter beyond its inherent soft-switching limit of D = 0.5, a resonant pulse transformer is proposed instead of the resonant inductor. The 1: 2 turns ratio of the transformer ensures full discharge of the snubber capacitor at all...

The emergence of wide-bandgap devices, e.g. silicon carbide (SiC), has the potential to enable very high-density power converter design with high-switching frequency operation capability. A comprehensive design tool with a holistic design approach is critical to maximise the overall system power density, e.g by identifying the optimal switching fre...

All-GaN integrated cascode heterojunction field effect transistors were designed and fabricated for power switching applications. A threshold voltage of +2 V was achieved using a fluorine treatment and a metal-insulator-semiconductor gate structure on the enhancement mode part. The cascode device exhibited an output current of 300 mA/mm by matching...

All-GaN integrated cascode heterojunction field effect transistors were designed and fabricated for power switching applications. A threshold voltage of +2 V was achieved using a fluorine treatment and a metal-insulator-semiconductor gate structure on the enhancement mode part. The cascode device exhibited an output current of 300 mA/mm by matching...

This work investigates design optimisation and design trade-offs for multi-kW DC-DC Interleaved Boost Converters (IBC). A general optimisation procedure for weight minimisation is presented, and the trade-offs between the key design variables (e.g. switching frequency, topology) and performance metrics (e.g. power density, efficiency) are explored....

Finite element analysis is used to examine the gap losses that occur in finely laminated nanocrystalline inductor cores under high frequency operation. The losses are seen to be concentrated in the region of the air gap and the dependence of the losses on key design parameters and operating conditions is explored. The results show that gap losses c...

DC bus power quality and rate-of-change in electrical generator power are compared for different energy storage system (ESS) rate-limit controller designs. The rate-limit feature enables the electrical generator(s) on a MEA to be protected from sudden load transients, which is anticipated to reduce their maintenance requirements and extend lifetime...

This paper evaluates three PWM digital control approaches to achieve the current sharing between phases in high power dual interleaved DC-DC converters. The implementation of a digital peak current, multi-sample averaged current and an enhanced single-sample averaged current control in a TMS320F28377D is described. Experimental results from a 60 kW...

Within the field of power converter design, the use of optimisation techniques is a popular method to ensure that the best possible design is achieved for a given objective, e.g. weight or volume reduction. However, there is currently a lack of efficient unified frameworks for optimising the system level design of converters in terms of the device,...

To provide a basis for controller design in interleaved dc-dc converters, an improved small-signal averaged model is presented. Sampler decomposition techniques are used to represent the interleaved operation of the individual control loops within the converter. The resultant model reveals interaction effects and instability phenomena that are not...

Grid-connected battery energy storage systems with fast acting control are a key technology for improving power network stability and increasing the penetration of renewable generation. This paper describes two battery energy storage research facilities connected to the UK electricity grid. Their performance is detailed, along with hardware results...

The use of soft-switching techniques, interleaved topologies and silicon carbide (SiC) MOSFETs can improve the efficiency and power-density of high-power, high-voltage DC-DC converters for electric vehicle and aircraft applications. In this paper, to extend the operating range of the Snubber Assisted Zero Voltage and Zero Current Transition (SAZZ)...

This paper analyzes some operational issues of three-phase surface-mounted permanent magnet synchronous generators (PMSGs) connected to a diode rectifier. This simple configuration coupled to a single-switch dc–dc converter is used in small-scale wind energy conversion systems, as well as in energy harvesting systems, to reduce costs. The diode rec...

IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. Abstract— Analytical models for hard-sw...

A comprehensive and unified analysis is presented for the discontinuous conduction/current mode operation of dual interleaved buck and boost converters with an interphase transformer or coupled inductors. By exploiting the symmetry in the current waveforms between the buck and boost modes of operation, detailed operating maps are derived showing th...

This paper presents a steady-state analysis for the bidirectional dual active bridge (DAB) dc-dc converter operating in extended-phase-shift (EPS) control by proposing a new model that produces equations for RMS and average device currents, and RMS and peak inductor/transformer currents. The DAB converter performance is evaluated based on the mathe...

This paper presents an analysis of the energy loss distribution in a cascode array and a study of the behavior of two GaN cascode devices in an inverter leg configuration. A simple model of the cascode connection is developed to get estimations of energy losses and its accuracy is validated through experimental measurements using a Double Pulse Tes...

A DC-DC converter topology is presented combining the soft switching effects of the Snubber Assisted Zero Voltage and Zero Current Transition (SAZZ) topology and the increased inductor frequency of the dual interleaved boost converter with interphase transformer. The snubber capacitors and output capacitances of the main devices are discharged prio...

This work makes a novel contribution to the analysis of quasi-square-wave operation of dual-active bridge (DAB) converter by deriving equations for root mean square (RMS) and average device currents and RMS and peak inductor/transformer currents - these equations are useful in predicting device and passive component losses. Quasi-square-wave operat...

A system-level behavioural modelling technique is described for a switched reluctance motor drive (SRMD). The model enables simple and efficient analysis or simulation of multiple drive systems such as pumps, actuators and engine starters within a more-electric network for example on-board an aircraft. The behavioural model is based on a power bala...

This paper presents the simulation of a three-level and a seven-level active rectifiers controlled with Internal Model Control in order to demonstrate that both can be controlled with this technique and showing the advantages of the seven-level active rectifier over the conventional topologies. The paper also presents the results of a real time emu...

An apparatus 2 comprising a cryogenic chamber 4 and a galvanic input interface 6 to the cryogenic chamber 4 configured to receive a lower amplitude electric current 8. A converter 10 is located within the cryogenic chamber 4 and configured to convert the lower amplitude electric current 8, provided by the galvanic input interface 6, to a higher amp...

A system-level modeling technique for a switched reluctance generator (SRG) is described for aerospace applications. Unlike existing techniques, this model is very simple and only reproduces the average behavior of the input-output variables that are required for system-level analysis of the aircraft power distribution system. The model is paramete...

The design of a 200-A, all-SiC power-module-based on bipolar junction transistor devices is described, and the impact of the module is assessed on the performance of a 50-kW dc–dc converter for electric vehicle applications, particularly the overall weight and efficiency. Using a hard-switching dual-interleaved topology, which has proven high effic...

There is a growing need for highly efficient, power dense DC-AC converters to support a number of future more electric aircraft technologies. SiC has been identified as a potential technology to improve the efficiency of these converters. To analyse the semiconductor losses, this paper presents the semiconductor loss equations for the two-level con...

An energy management controller based on multiple charge/discharge profiles is proposed and analysed for an energy storage system. Each profile is designed to use the available energy more aggressively in different power regions, including the low or the high power regions, or both regions to minimise the rate-of-change of power source output. The...

An adaptive energy management control with an integrated variable rate-limit function is described for an energy storage system (ESS). The proposed control protects the primary power source(s) in the system as effectively as possible from sudden load transients within the constraints of the available stored energy. The control can be designed to us...

This paper shows the performance evaluation and practical demonstration of a high-power bi-directional DC-DC converter with a power density of 20 kW/l, using 1200V/100A SiC MOSFET modules from CREE. The converter is based on a dual-interleaved topology with hard-switching operating at 75 kHz. To increase the power density, water-cooled magnetic com...

Physically derived mathematical models of motors are frequently used to simulate system performance. These can be constructed at various levels of fidelity depending on the application requirements. To accurately capture the dynamics of brushless permanent magnet motors, the effects of electrical commutation should be included. Short time-step simu...

This paper details the design, construction, and testing of a MOSFET based solid-state power controller rated at 270V, 200A, equivalent to 54kW, with an overload capability of 400A. The power switch is a parallel array of 21 fractionally rated Si MOSFET devices which current share to achieve the overall rating while minimising on-state losses. A tr...

This paper describes the development of an active load for a 100 kVA, ±270 V dc electrical systems evaluation platform for uninhabited autonomous vehicles, typically airborne. The 30 kW, 3 kHz bandwidth active loads emulate in real time the dynamic behaviour at the dc-bus side of typical aerospace equipment, providing a flexible and cost-effective...

This paper presents simulation advances on the research of a single DC source Multilevel Active Power Filter (MAPF), which emerge as a possible solution to improve the power quality of the utility supply of on-land Power Substation of the Metro Line B of Mexico City. Multilevel voltage waveforms may be produced with the proposed filter to generate...

Multilevel Inverters are increasingly being used in high-power and medium voltage applications; there are many modulation techniques available to control their operation. In this paper, the Space Vector PWM Technique (SVPWM) to control a hybrid multilevel inverter is described. The inverter produces thirteen-level, SVPWM, three-phase waveforms usin...

A dc-dc converter has been developed for retrofitting inside the vacuum space of the HTS rotor of a synchronous generator. The heavy copper sections of the current leads used for energising the HTS field winding were replaced by cryogenic power electronics; consisting of the converter and a rotor control unit. The converter board was designed using...

Design of air-core inductors is not widely known. The major advantage of an air-core inductor is that it is free from iron loss and hence offers better performance than ferrite cores. This paper discusses design details of high frequency air-core inductor used in a dual active bridge (DAB) DC-DC converter for aerospace applications. The paper will...

This paper contributes to the steady-state analysis of the bidirectional dual active bridge (DAB) dc–dc converter by proposing a new model that produces equations for rms and average device currents, and rms and peak inductor/transformer currents. These equations are useful in predicting losses that occur in the devices and passive components and a...

This study presents a novel controller for bidirectional control of a dual active bridge (DAB) DC-DC converter. The proposed controller uses the high-frequency AC-link current of the DAB DC-DC converter as a control parameter so that the dynamic power and regeneration demands of advanced aircraft electric loads can be met using ultracapacitors. A m...

A two-stage conversion system is described for regulating the DC current in a superconducting coil, for example, the field winding of a superconducting synchronous machine. An ambient temperature converter provides a low, controlled current to a cryogenic converter, co-located with the superconductor, which steps up the current by over a hundred ti...

By exploiting the half-cycle symmetry in the waveforms of the dual-interleaved boost converter, a small-signal, sampled-data model is developed, which includes the differential inductance of the interphase transformer and a peak current-mode controller. The model is validated by Saber simulation and experimental results from a 10-kW prototype. Sign...

A power dense DC-DC converter is required to interface a supercapacitor energy buffer with a higher voltage traction drive in a small electric vehicle application. A converter design and component selection process is described for a bidirectional, 18 kW, dual interleaved boost converter with interphase transformer. The physical construction of the...

The paper discusses the development and validation of motor simulation models to aid in the design of actuators for use with automotive variable geometry turbochargers. The specific focus is on the benefit of increasing the fidelity of the motor model, against the tradeoff of increased complexity. Several separate models of the same brushless perma...

An intelligent agents based platform is presented which offers an instantaneous, automatic decision-making capability, enabling the execution of complex system level power management and mission planning/re-planning tasks on board a UAV. The agents platform is integrated with a 100 kW, aircraft power systems experimental test facility to demonstrat...

A control and communication system is described, which forms part of the power electronic excitation system for a superconducting synchronous machine. The communication channel uses a single slip-ring connection and provides feedback of the superconductor current, transmits status and control signals in either direction, and provides power rails fo...

Generalised analytical expressions are derived to calculate the current levels and soft switching boundaries for the triple active bridge DC-DC converter for all operating modes including the option of duty-ratio control as well as phase shift control.

Higher-voltage, 540 V, aircraft DC-bus power quality is examined experimentally and by computer simulation during a short-circuit fault across the phase terminals of a 70 kW, five-phase, permanent magnet fault-tolerant generator. The DC-bus transients caused by the short-circuiting of the generator phases are seen to exceed the limits in MIL-STD-70...

The impact of the onboard electrical power system on the operation of the mechanical prime mover, for example an aircraft gas-engine, is examined through experimental testing on a 100kW aircraft power system facility. Hardware- in-the-loop techniques are used to control two motor drives such that they emulate the dynamic characteristics of the shaf...

There is an increase in the use of multi-pulse, rectifier-fed motor-drive equipment on board more-electric aircraft. Motor drives with feedback control appear as constant power loads to the rectifiers, which can cause instability of the DC filter capacitor voltage at the output of the rectifier. This problem can be exacerbated by interactions betwe...

Two techniques are presented to balance the filter capacitor voltages of a multipulse rectifier with the active injection operating on a variable-frequency supply. The active injector consists of a low-rated bidirectional switch that modifies the behavior of a 12-pulse rectifier at either low or high frequency, resulting in 24-pulse or multilevel p...

A second-harmonic direct current (DC) ripple compensation technique is presented for a multi-phase, fault-tolerant, permanent magnet machine. The analysis has been undertaken in a general manner for any pair of phases in operation with the remaining phases inactive. The compensation technique determines the required alternating currents in the mach...

More Electric Aircraft are currently being developed so that in the future all non-propulsive power on an aircraft can be provided by the electrical system. In this electrical system, it is expected that several motor loads will run in parallel from a single DC bus. The paper will investigate the interactions between five motor loads connected to a...

This paper investigates the effect of snubber capacitor on the zero voltage switching (ZVS) boundary of the dual active bridge (DAB) DC-DC converter. The analysis is performed to determine the minimum current required during transistor turn- off to achieve successful ZVS and the ZVS boundary operating conditions of the converter are obtained. The o...

A 20kW bidirectional dual active bridge DC-DC converter prototype is designed and built for aerospace energy storage applications. The converter employs high power IGBT modules on the high voltage and low voltage sides. This paper presents the theoretical analysis and experimental results of turn-off performance of those high power IGBTs with capac...

Simulation results are used to illustrate the features and capabilities of a l00kW, 540V DC laboratory system that is under development at the University of Manchester. The laboratory system comprises a twin-spool gas engine emulator with fault-tolerant generators, four active load emulators, an energy storage system and a reconfigurable distributi...

A control strategy to operate a hybrid multilevel inverter is described in this paper. The inverter produces seven-level PWM voltage waveforms using twelve transistors and a three-phase transformer for harmonic elimination offering the following advantages: flying capacitors with neutral clamped circuits are not required, a small number of switchin...

Reliability of IGBT power modules is crucial to their use in failure critical systems and with the advent of all electric and hybrid vehicles the need for good reliability data for IGBT modules is essential. IGBT power modules are constructed of layers and power dies, all of which are interconnected with solder or bond wires. These materials have d...

High-voltage DC-bus power quality is examined experimentally and by computer simulation during a short-circuit fault across the phase terminals of a five-phase, permanent magnet fault-tolerant generator. The DC-bus transients are seen to exceed the limits in MIL-STD-704F [1] and a control algorithm is proposed for a supercapacitor-based energy stor...

To meet the peak power demands of aircraft electric loads such as actuators and avionic systems, and to absorb regenerated power, an ultracapacitor-based energy storage system is examined in which a bidirectional dual active bridge DC-DC converter is used. Analysis is performed for the DAB converter producing equations for the device RMS and averag...

A power-based control method is proposed and analysed for a supercapacitor energy storage device. The performance of the energy storage device is examined by simulation and experimentally when operating on a high voltage DC bus with a multi-phase, fault-tolerant generator and a high power, pulsed load such as an actuation or avionic system. In the...

The use of IGBT power modules in the automotive industry is becoming more and more common due to the increase in hybrid and all electric vehicles. But, unlike industrial applications the duty cycle or usage of such devices due to the environment or operating requirement is very random and not well defined. This makes predicting when the device will...

High-voltage DC-bus power quality is examined experimentally and by computer simulation during a short-circuit fault across the phase terminals of a five-phase, permanent magnet fault-tolerant generator. The DC-bus transients are seen to exceed the limits in MIL-STD-704F [1] and a control algorithm is proposed for a supercapacitor-based energy stor...

Hardware-in-the-loop (HIL) techniques are used to examine the start-up sequence for an all-electric UAV system powered by a two-spool gas engine with embedded electrical generators on both spools. Start-up begins with the auxiliary power unit charging the high voltage DC bus to enable the high pressure spool switched reluctance starter/generator (S...

This paper presents a simple practical implementation of direct-frequency control for current injection series resonant converter (CISRC) to regulate the output voltage. Based on the control-to-output frequency response obtained from the small-signal model of the converter, a PI controller is proposed which provides robustness in relation to extern...

To carry out stability and voltage regulation studies on more electric aircraft systems in which there is a preponderance of multi-pulse, rectifier-fed motor-drive equipment, average dynamic models of the rectifier converters are required. Existing methods are difficult to apply to anything other than single converters with a low pulse number. Ther...

A dual-interleaved boost converter is presented with zero-voltage switching for applications in electric vehicle power trains. The topology has one input inductor and an interphase transformer (IPT) between the two channels. By using an appropriate differential inductance value for the IPT, the converter achieves transitions with zero-voltage switc...

Two techniques are presented to balance the filter capacitor voltages of a multi-pulse rectifier with active injection operating on a variable frequency supply. The active injector consists of a low-rated, bidirectional switch that modifies the behaviour of a 12-pulse rectifier at either low or high-frequency, resulting in 24-pulse or multi-level P...

A direct-frequency control for Current Injection Series Resonant Converter (CISRC) is developed to regulate the output voltage. The PI controller is used and the design is based on the open-loop control-to-output frequency responses. Controller design also involves a trade-off between reducing the output voltage ripple and maintaining the high qual...