Search

At high speed, electric vehicles (EVs) have limited torque when powered by an induction machine (IM). In IM, the high-speed region is called field weakening, and the region is known for torque limitation. This article proposes a control method that increases the torque without applying discontinuous-modulation techniques, which is commonly used. A bespoke model-based voltage control method has been developed, which enables reaching the hexagonal voltage reference trajectory for the field weakening region. So far, all model-based control methods are constrained by the inscribed voltage circle, which lies within the hexagonal voltage boundary. This restriction limits the available inverter output voltage across the motor windings, which, in turn, restricts the output torque of the drive. To achieve the hexagonal voltage trajectory, this article introduces a new calculation of the $d$ -axis current for the entire speed range in the field weakening region. This calculation is based on the hexagonal voltage boundary equations and the stator voltage vector position. This generates a new reference $d$ -axis current that minimizes the difference between the hexagonal voltage boundary and its inscribed voltage circle. As a result, the proposed $d$ -axis current maximizes the output torque and output power in the field weakening region. The proposed method is presented analytically. Simulation and experimentally validated results are presented to confirm its feasibility and effectiveness.

Switched reluctance motor (SRM) is been considered for electric drive applications because of its low cost and robustness. Nevertheless, the power electronics needed to operate the drive increases its cost and volume, and also reduces its running reliability. Hence, the number of switches, diodes, and sensors involved are needed to be reduced by improving the power converter topology. Therefore, sensorless torque control of SRM using a single current sensor Resistor-Dump (R-Dump) converter is proposed in this study. An R-Dump converter is proposed in this study because it has minimal power components compared with mostly use converters like an asymmetric half-bridge converter (AHBC). The sensorless control is developed based on a new sliding mode observer (SMO) that is defined to only use a single current measurement and an inductance model to estimate the rotor position of the SRM. Furthermore, the proposed drive is simulated in MATLAB/SIMULINK and compared with a conventional SMO based senseless SRM drive. Results from the simulation show that the proposed converter topology, torque control, and position estimation methods can significantly reduce the size and cost of the SRM drive with a negligible increase in torque ripple compared to the conventional methods.

Rising power demands in more electrical aircraft (MEA) put power converters for commercial airplanes under increasing pressure to fulfill current harmonic distortion regulations as specified, for example, in DO-160G. Today, the implementation of filters is seen as an effective tool for dealing with harmonics; however, their increased weight and volume are not welcomed in the aerospace industry. This paper proposes a circuit, named forced commutation controlled series capacitor (FCSC-rectifier), which is able to maintain low individual harmonic current levels without the need for filter components. The FCSC-rectifier includes a variable capacitive line reactance that interacts in a controlled manner with the inductive line impedance. The result is that the converter input current is nearly purely sinusoidal with a power factor of almost unity. The FCSC-rectifier is to be used for stand-alone variable-voltage, variable-frequency generation systems and can, therefore, power the full authority digital electronic control system (FADEC) in an MEA. This paper shows that the FCSC-rectifier can maintain a high power factor and acceptable current harmonic levels without the use of filters, despite large voltage and frequency variations. A full description of the circuit modes of operation is presented in this paper together with simulation results showing circuit performance characteristics over a range of voltages and frequencies. Results are experimentally verified using a 1-kW test circuit.

This paper presents a new method to measure the voltage across the submodule (SM) capacitors in a modular multilevel converter (MMC). The proposed technique requires only one voltage sensor per arm. This reduces the number of sensors required compared with conventional sensor-based methods. Therefore, the cost and complexity of the system are reduced, which in turn improves the converter’s overall reliability. The proposed method employs an exponentially weighted recursive least square algorithm to estimate the SM capacitor voltages through the measured total arm voltage and the switching patterns of each SM. There is thus no need for extra sensors to measure these control signals as they are directly provided from the controller. The robustness of the proposed method is confirmed via introducing deviations for the capacitance values, dynamic load changes, dc voltage change, and startup transient condition. Simulation and experimentally validated results based on a single-phase MMC show the effectiveness of the proposed method in both, steady-state and dynamic operations.

This paper presents a new voltage estimation method for the submodule (SM) capacitor in a modular multilevel converter (MMC). The proposed method employs a Kalman filter algorithm to estimate the SM voltages of the converter. Compared with sensor-based methods, this scheme requires only one voltage sensor to achieve the voltage-balancing of the converter. This sensor is connected to the total arm voltage; the proposed algorithm also requires the switching patterns of each upper SM switch, which are provided by the controller used without the need for extra sensors. The substantial reduction in the number of voltage sensors improves the system reliability and decreases its cost and complexity. Extensive simulation and experimental analyses carried out to validate the proposed estimation scheme under different conditions include steady-state analyses, the effect of variations in capacitance and inductance, the impact of low carrier and effective switching frequency on the accuracy of the estimation, step changes to the load, and range changes in dc voltage. The results obtained are experimentally verified using a single-phase MMC.

Saving fuel and reducing emissions are major drivers in the marine industry, with a large number of potential modifications and machinery options available to enable the greening of shipping. Assessing which technology and what combination of solutions gives favourable economic results needs careful consideration of the vessel’s operational profile. Electrification of shipboard systems introduces operational flexibility, offering the potential for fuel savings and emission reductions. Auxiliary drives, energy storage and onshore power supply are three approaches which address the issues of ship fuel consumption/emissions, specifically during in-harbour operation of vessels. In this paper, the impact of these three technologies on ship environmental performance and energy consumption is assessed by considering a real case RoRo vessel sailing a real operational profile. Models of the resultant system are built such that the machinery configurations can be analysed separately or in conjunction with each other. The results stress the importance of the operational profile of the vessel, showing significant fuel and emissions reductions during in-harbour operations but relatively small savings when considering operation through a complete return voyage. The sensitivity of the results to fuel and utility costs are also considered and shown to have a large impact on the economic feasibility (or otherwise) of different solutions.

International audience; For the Ice Giants, atmospheric entry probes provide critical measurements not attainable via remote observations. Including the 2013-2022 NASA Planetary Decadal Survey , there have been at least five comprehensive atmospheric probe engineering design studies performed in recent years by NASA and ESA. International science definition teams have assessed the science requirements, and each recommended similar measurements and payloads to meet science goals with current instrument technology. The probe system concept has matured and converged on general design parameters that indicate the probe would include a 1-meter class aeroshell and have a mass around 350 to 400-kg. Probe battery sizes vary, depending on the duration of a post-release coast phase, and assumptions about heaters and instrument power needs. The various mission concepts demonstrate the need for advanced power and thermal protection system development. 17 Page 2 of 13 A.A. Simon et al. show an Ice Giant mission with an in situ probe is feasible and would be welcomed by the international science community.

DC microgrids have been widely used in distributed generation networks due to intermittent nature of renewables, low conversion losses, common interface with dc renewable sources and high reliability. In order to regulate the dc bus voltage and achieve proportional power sharing, the conventional V-dP/dV droop control strategy is performed by calculating the slope of tangent of P-V characteristic. However, the main challenges of this control scheme are poor dynamic behaviour and low quality of PV power. This paper presents a decentralized coordinated PV droop control method, which applies dP/dI for accurate energy distribution and faster response speed. Moreover, the inner control parameter $\text{d}^{2}\text{P}/\text{dI}^{2}$ is used to further minimize the PV power fluctuation in a steady state which allows to track the error with a corrective action. The proposed control strategy seamlessly transfers the MPPT algorithm to voltage regulation mode in a fully decentralized approach. Simulation study is conducted to demonstrate how the transient and dynamic responses have been significantly improved.

Several studies have proved that sensorless control methods can improve the overall robustness and costs of a drive while maintaining the desired performance. However, the general approach of these sensorless strategies involves flux estimation which is significantly affected by the uncertainties associated with the machine's terminal measurement errors and noise. In this paper, a simple robust sensorless control of Switched Reluctance Machine (SRM) is described. The inherent robustness to parameter variations and measurement noise coupled with the high stability and simple computation of a Sliding Mode Observer (SMO) is utilized to eliminate the errors often involved in a flux-linkage based position estimation for the SRM. The proposed method is tested under different operating conditions. Results obtained show that it is reliable and less susceptible to errors and noise commonly found in sensorless control of SRM. The method was also found to handle the model uncertainties associated with the approximated model used for the estimation but with reduced performance at low speed.

The efficient utilization of energy is of high importance for shipboard applications, for environmental and economic reasons as well as maximized vessel operation. The electrification of marine systems facilitates the storage and generation of energy from multiple sources, offering the potential for energy savings, due to the flexibility associated with electric systems. In this paper, an energy management system (EMS) based on bond graph system models used in conjunction with a stochastic search algorithm is proposed and developed. The EMS optimizes the configuration of the vessel’s onboard machinery system based on the current operating condition. The approach is universal, with the system model and optimization routine being separate and distinct. The effectiveness of the proposed EMS is demonstrated using a real operating profile of a roll-on/roll-off vessel fitted with a hybrid machinery configuration including energy storage, onshore power supply, and photovoltaic generation. The results show fuel savings of around 23% compared with current fuel consumption levels.

This paper presents a novel predictive model reference adaptive system (MRAS) speed estimator for sensorless induction motor (IM) drives applications. The proposed estimator is based on the finite control set-model predictive control (FCS-MPC) principle. The rotor position is calculated using a search-based optimization algorithm which ensures a minimum speed tuning error signal at each sampling period. This eliminates the need for a proportional–integral (PI) controller which is conventionally employed in the adaption mechanism of MRAS estimators. Extensive experimental tests have been carried out to evaluate the performance of the proposed estimator using a 2.2-kW IM with a field-oriented control (FOC) scheme employed as the motor control strategy. Experimental results show improved performance of the MRAS scheme in both open- and closed-loop sensorless modes of operation at low speeds and with different loading conditions including regeneration. The proposed scheme also improves the system robustness against motor parameter variations and increases the maximum bandwidth of the speed loop controller.

This paper proposes an on-time estimation of induction machine parameters based on the extended Kalman-filter. So far, the real-time performance of Extended Kalman-filter algorithms has not been validated in the variation of motor parameters. Furthermore, the conventional parameter estimations in extended Kalman-filter has not been developed accurately based on the correct non-linear state space model. This paper proposes a new state space model of induction machine included motor parameters with less dependency to other model variables. This leads to achieve more accurate estimation results even in a situation where a sudden variation of motor parameters happens. This paper describes the proposed method analytically. Simulation results for an induction machine are presented and discussed.

This paper presents a new Direct Instantaneous Torque Control (DITC) developed to minimize the inherent torque ripple of an aerospace switched reluctance motor (SRM). In addition to good performance, the reliability and robustness of the overall system are of great concern in aerospace and other safety-critical applications. By taking that into consideration, a DITC, that is less prone to the common erroneous operating conditions associated with SRM control such as measurement errors and noise, integration errors and parameter variation errors, is developed and compared with the traditional current chopping control (CCC). The proposed control scheme involves simple torque estimation, distribution, and regulation strategies. The results obtained show that both the proposed DITC and the traditional CCC methods ensure accurate reference tracking. However, the proposed control exhibits better torque ripple reduction capability without compromising the system’s reliability and robustness

This paper presents a detailed experimental study of wind turbine DFIG response to non-zero grid faults that may occur at a considerable distance from the generator. An analytical solution of the generalized DFIG machine equations operating under non-zero fault conditions is developed in which the fault response is separated into three components: a natural response that describes zero voltage behavior, a component describing the retained voltage behavior and the forced response corresponding to the applied rotor voltage via the rotor-side power converter. The DFIG system fault response is examined experimentally using a 7.5kW test facility detailing example of a 500ms, 15% fault.

Over the last decade various high-capacitance devices have become available in the market such as supercapacitors, ultracapacitors, and recently, Li-ion capacitors. The cell voltage limit of each of these technologies is a small percentage of the system-level voltage so they must, therefore, be connected in series to attain a high voltage. During charging and discharging, manufacturing tolerances between the cells result in voltage mismatch across the stack. Mismatched voltages are an inefficient use of the energy storage medium and can lead to dangerous failures in the cells if voltages exceed safety limits. Transformer-based voltage equalization techniques are the preferred circuit topologies in applications with low system voltage due to simplicity of control and low number of switches. The drawback of these circuits is the number of isolated windings that are required on a single core. This paper describes for the first time a solution to that problem by using a classical two windings transformer that in principal can be applied to any number of capacitors. This paper describes the operation of the circuit, shows simulation results and practical results based on a prototype with five cells.

One of the most commonly utilised maximum power point tracking (MPPT) algorithms for photovoltaic (PV) generators is the incremental conductance (INC) algorithm. Yet, the operating characteristics of this algorithm at high perturbation frequencies, when the system response to MPPT perturbations is never allowed to settle, have not been addressed in the literature. This study characterises system behaviour in this operating mode experimentally for a standalone PV system with a dc motor–pump load. Results show that the INC algorithm operating at a high perturbation rate offers higher energy utilisation efficiency and better system performance despite the resulting non-periodic waveforms of the system.

The reduction of emissions in harbours is of particular importance due to the proximity to human habitation. Vessels normally run onboard generators, typically using diesel fuel, to provide the service loads while berthed. New and upcoming regulations aim to decrease emissions from shipping, and coupled with increased environmental consciousness of ship owners and harbour operators, shore supply is becoming a more popular and feasible option. Cold ironing provides an alternative locally emission-free solution by having berthed ships plug in to the shore electrical network, such that the onboard electrical energy demand is supplied from land. Electrically, a number of different shore network topologies are possible, providing different infrastructural options of supplying power to multiple berths. This paper examines the electrical characteristics of one such installation and the impact on the shoreside electrical network for an existing port using actual visiting ship power profiles. The paper examines how the cold ironing system influences important electrical network characteristics such as bus voltages and power quality, as well as the potential impact on the rest of the utility distribution system.

This paper presents a new current sharing control strategy for parallel-connected, synchronised three-phase DC-AC converters employing space vector pulse width modulation (SVPWM) without current sharing reactors. Unlike conventional control methods, the proposed method breaks the paths of the circulating current by dividing the switching cycle evenly between parallel connected equally rated converters. Accordingly, any inter-module reactors or circulating current control will be redundant, leading to reductions in system costs, size, and control algorithm complexity. Each converter in the new scheme employs a synchronous dq current regulator that uses only local information to attain a desired converter current. A stability analysis of the current controller is included together with a simulation of the converter and load current waveforms. Experimental results from a 2.5kVA test rig are included to verify the proposed control method.

This paper presents a novel speed estimation scheme for induction motors (IMs) based on back electromotive-force model reference adaptive system (back-EMF MRAS). The scheme is employed for the purpose of sensorless fault-Tolerant torque-controlled drives used in a limp-home mode operation in electric vehicle (EV) applications. The proposed scheme was experimentally tested on a laboratory dynamometer using a 19-kW IM and a 29-kW controller, which are both currently used in the automotive industry for EV applications. The scheme was also implemented on an electric golf buggy which was equipped with a 5-kW IM. A performance comparison was carried out between the proposed and conventional back-EMF MRAS schemes for starting from standstill, sensitivity to parameter variations and constant speed operation with load variations. Utilizing the golf buggy, the behaviors of the new scheme was separately investigated for vehicle starting from standstill, wide speed range including field weakening region, and hill-starting operations. The proposed scheme is computationally easy to implement, robust against sensitivity to parameters variations, inverter nonlinearity and errors due to digitization in the field weakening region. This scheme is not only consistent for vehicle starting from standstill, it also provides a reliable vehicle-drive in the field weakening region and during vehicle hill-starting. The dynamometer and vehicle test-drive results show the suitability of the proposed scheme for the purpose of EV fault-Tolerant limp-home mode operation.

This paper presents a robust sensorless control technique for an Induction Motor (IM) used for Electric Vehicle (EV) applications. In order to estimate the rotor speed, a new back-electromotive-force (back-EMF) based-model reference adaptive system (MRAS) estimator is proposed. The new back-EMF MRAS is independent from the stator resistance and stator inductance parameters. Hence the proposed scheme is immune to these parameters variations. It also is robust against inverter nonlinearity and shows consistency at starting from standstill. The proposed scheme has been experimentally implemented and tested on a 19-kW induction motor (IM), of a type used for the automotive industry for EV applications. A comparison is carried out between the performance of the conventional and the proposed back-EMF MRAS. Tests include sensitivity to stator resistance variation and capability to start from standstill. Experimental results show the improved performance achieved using the proposed sensorless control scheme and its suitability for EV applications.

A near-state three-dimensional space-vector modulation (NS 3-D SVM) switching scheme, which aims to reduce the common-mode noise in a three-phase four-leg voltage source inverter, is proposed. The impact of common-mode noise, which is related to electromagnetic interference issues for a high-voltage level four-leg system, is investigated first. Identification of the section in a 3-D space, selection of the near-state switching vectors, and sequence of the selected switching vectors are then introduced in steps to describe the proposed switching scheme. The proposed switching scheme is based on classical 3-D SVM, producing higher dc-link utilization, less harmonic content, and reduced switching loss compared to sinusoidal PWM. Theory, simulation, and experimental results show that the near-state 3-D SVM can work under both balanced and unbalanced load conditions.

Cold ironing (or onshore power supply) addresses airborne emissions while ships are berthed in port. By providing the electrical power demands from shoreside electricity, the onboard auxiliary generators can be switched off for a locally emission-free solution. The net emissions will of course be dependent on the actual shoreside electricity mix, but reductions can be realised in most cases. This study looks at the various electrical configurations available for cold ironing of berthed vessels. Shoreside generation using liquefied natural gas as an alternative fuel is also considered as a complement to cold ironing. This provides the possibility of hybridised solutions combining power supply from the grid or from clean, onsite generators. Using real data from an operational European port, the various cold ironing configurations are modelled and optimal trade-off solutions were identified. This is achieved by considering the reduction in emissions and minimisation of component costs as a multi-objective non-linear optimisation problem. The results show that CO2 emissions can be reduced by up to 40% by using cold ironing, while the use of liquefied natural gas shore generation can reduce the sulphur and particulate emissions in port to extremely low levels.

The performance of the doubly fed induction generator (DFIG) during grid faults is attracting much interest due to the proliferation of wind turbines that employ this technology. International grid codes specify that the generator must exhibit a fault-ride-through (FRT) capability by remaining connected and contributing to network stability during a fault. Many DFIG systems employ a rotor circuit crowbar to protect the rotor converter during a fault. Although this works well to protect the generator, it does not provide favorable grid support behavior. This paper describes an experimental investigation of an alternative FRT approach using a brake chopper circuit across the converter dc link to ensure that the dc-link voltage remains under control during a fault. Two different approaches to chopper control are examined and the resulting FRT performance is compared with that of a conventional crowbar approach. The new chopper-based control methods are experimentally evaluated using a 7.5-kW DFIG test rig facility.