Search

This article proposes a novel application method, inverse application of artificial intelligence (IAAI) for the control of power electronic converter systems. The proposed method can give the desired control coefficients/references in a simple way because, compared to conventional methods, IAAI only relies on a data-driven process with no need for an optimization process or substantial derivations. Noting that the IAAI approach uses artificial intelligence to provide feasible coefficients/references for the power converter control, rather than building a new controller. After illustrating the IAAI concept, a conventional application method of artificial neural network is discussed, an optimization-based design. Then, a two-source-converter microgrid case is studied to choose the best droop coefficients via the optimization-based approach. After that, the proposed IAAI method is employed for the same microgrid case to quickly find good droop coefficients. Furthermore, the IAAI method is applied to a modular multilevel converter (MMC) case, extending the MMC operation region under unbalanced grid faults. In the MMC case, both simulation and experimental online tests validate the operation, feasibility, and practicality of IAAI. [ABSTRACT FROM AUTHOR]

A control approach for aircraft Starter/Generator (S/G) with Permanent Magnet Machine (PMM) operating in Flux Weakening (FW) mode is presented. The proposed strategy helps the previous approaches which are adopted for the Variable Voltage Bus (VVB) or Voltage Wild Bus (VWB) concept for an aircraft Electric Power System (EPS), to cover a wide speed range in motoring and generation modes. Compared to prior works, the proposed control approach adjusts the q-axis reference voltage with a single current regulator, and the maximum available voltage provided by the converter is used to evaluate the d-axis voltage. By adopting the proposed approach, the DC bus voltage can be fully utilized, increasing aircraft efficiency by allowing the S/G system to operate at a wide range of speeds. The results of the analytical design and the performance of the system were verified by time-domain simulations using MATLAB/Simulink and experiments and compared to the conventional method. [ABSTRACT FROM AUTHOR]

The main challenges of the input current control in synchronous DC-DC buck converters are the nonlinear model of the system, changes of the operating point in a wide range, and the need to use an input LC filter for current smoothing, which may result in the instability of the closed-loop system. In this paper, a step-by-step approach is developed for the design and improvement of a PI-feedforward closed-loop controller. It is shown that a linear PI controller cannot stabilize the closed-loop system properly during wide changes in model parameters, e.g., an equivalent series resistance of the input filter. To cope with the stability issues, a fixed-frequency sliding mode controller (SMC) has been developed in this paper for the implementation of an electro-mechanical actuator (EMA) emulator. Moreover, a systematic approach is proposed for controller tuning and the selection of the SMC's gains. To achieve high power efficiency, high-frequency GaN switches are used for the practical implementation of the DC-DC converter. Despite large changes in the load current, the designed nonlinear controller can track the input current reference satisfactorily. Steady-state and dynamic responses of the proposed SMC are compared with conventional linear controllers. Considering the Lyapunov stability theorem, it is proved that the designed SMC can stabilize the closed-loop system in the entire utilizable domain. The proposed nonlinear SMC controller enjoys a very simple control law. Hence, despite having very high switching and sampling frequencies, it can be easily implemented. The experimental response of the designed synchronous DC-DC buck converter is evaluated experimentally by implementing the control strategy in a TMS320F28335PGFA DSP from Texas Instrument. Moreover, the comprehensive comparison of the proposed SMC controller and a PI-feedforward controller proved the superior performance of the developed closed-loop system, in terms of the transient time response, robustness, and stability of the EMA emulator. [ABSTRACT FROM AUTHOR]

Harmonics generated from power electronic converters will impose significant power quality challenges to the electric grid onboard future aircraft. In this article, we propose an innovative modulation scheme that enables using a buck–boost dc–dc converter as a harmonic absorber. To demonstrate the effectiveness of the proposed method, a hybrid power generation system involving a high-speed electrical generator and a high voltage battery is introduced. The electrical generator is connected to a dc bus through an ac–dc converter and the battery to the dc bus with a dc–dc converter. For the studied hybrid power generation system, it is identified that the first carrier frequency side-band harmonic (fc-3f0) from the ac–dc converter is most relevant and is targeted for cancellation. For the control of the dc–dc converter, a new modulation technique, called equal-gate-width modulation is proposed. It allows active control of the magnitude and phase angle of some specific harmonic components from a dc–dc converter. By properly tuning the phase angle and amplitude, the controlled harmonics can thus be used to cancel harmonics from other converters on a common dc bus. Without losing generality, this article focuses on the development of this specific harmonic cancellation scheme and the effectiveness of our proposed methods has been demonstrated using experimental results. [ABSTRACT FROM AUTHOR]

This paper considers the formal design for the grid frequency control in an offshore wind farm connected with line-commutated converter high voltage dc (HVDC) link. The control paradigm is based on using the grid frequency control to regulate the HVDC rectifier firing angle or dc-link current and hence control the power flow in the system. The dynamic behaviors of the system are verified by comparing the response from derived transfer functions and PSCAD simulations; hence the grid frequency controllers are designed. The control system performance has been validated by simulations of normal operation and fault regimes. The work provides a good basis for wider research investigation into wind farm operation. Index Terms--DC power transmission, induction generators, power conversion, power transmission control, wind power generation.

The paper considers a solution for integration of large offshore doubly fed induction generator-based wind farms with a common collection bus controlled by a STATCOM into the main onshore grid using line-commutated high-voltage dc connection. A design procedure is described and the controlled system is validated using PSCAD/EMTDC simulations confirming high performance of the proposed control strategy in both normal operation conditions and faults. Engineering issues related to STATCOM capacitor sizing and reduction of STATCOM rating are considered and their effectiveness is confirmed. Index Terms--Controller design, doubly fed induction generator (DFIG), frequency, high-voltage dc (HVdc) transmission, stability, STATCOM, voltage, wind energy.

The paper considers a control solution for integration of large offshore doubly fed induction generator based wind farms with a common collection bus, controlled by a static compensator, into the main onshore grid, using line-commutated high-voltage direct current connection. The paper's main focus is a mathematically grounded study of the power system interactions. That study produced an appropriate plant model for formal control design. A design procedure is described and the controlled system is validated using power systems computer-aided design/electromagnetic transient program simulations, which confirm the high performance of the proposed control strategy in both normal operation and fault conditions. Index Terms--Controller design, doubly fed induction generator (DFIG), frequency, high-voltage direct current (HVDC) transmission, stability, static compensator (STATCOM), voltage, wind energy.

This article proposed a harmonic suppression scheme that used a dc-dc converter as an active harmonic injector to cancel voltage harmonics on the HVdc bus within a hybrid power generation centre (HPGC). A permanent magnet synchronous generator and a battery are considered to supply power to a common HVdc bus through their dedicated ac-dc and dc-dc converters respectively within the HPGC. We proposed simplified mathematical models of harmonics from the ac-dc and dc-dc converters. Thereafter, an active power sharing scheme between the PMSG and the battery is developed to control the magnitudes of targeted harmonics to be the same. The targeted harmonics on the HVdc bus can thus be cancelled by properly tuning the carrier signal phase angles within ac-dc and dc-dc converters. A closed-loop control scheme has been developed and this scheme is with no extra hardware cost. To demonstrate the effectiveness of the proposed scheme, we selected the first-band harmonic (fc − 3f0) as the targeted harmonic component. The harmonic cancellation scheme for this component has been developed and validated using experimental results. It has been demonstrated that the proposed method can achieve over 90% reduction of this specific harmonic component on the HVdc bus within this HPGC using one dc-dc converter. [ABSTRACT FROM AUTHOR]

The accurate magnetic model is mandatory for high-performance control of high anisotropy synchronous machines. This paper presents a time-efficient and accurate magnetic model identification based on triangle current injection while the machine under the test is driven at a constant speed by a prime mover. The current injection pattern allows scanning the whole range of current, reducing the identification time compared to the standard constant-speed method (CSM) with the same level of accuracy. The ohmic voltage drop and inverter nonlinearities are compensated by using the average voltage of motor and generator modes. The synchronous reluctance machine is used as a case study for validation through the comparison between the experimental results obtained by the proposed method and the CSM against finite element simulation. Moreover, the temperature variation of the machine winding is measured showing no considerable changes during the identification test. [ABSTRACT FROM AUTHOR]

In this article, the equivalent relationship between the nearest-three-virtual space vector and carrier-based pulsewidth-modulation scheme is established based on space vector coordinate for a three-level neutral-point-clamped (3L-NPC) converter. Moreover, to solve the neutral-point voltage imbalance problem of the studied 3L-NPC converter-fed high-speed drives, an active modulation strategy with the generalized bias-offset injection technique is proposed. Meanwhile, the excessive computational burden is significantly overcome by the fast calculation approach. The effectiveness of the proposed modulation algorithm is validated through both simulation and experimental results obtained from a 45 kW, 32 kr/min aircraft electric starter/generator prototype system. [ABSTRACT FROM AUTHOR]

In this article, a virtual space vector based overmodulation algorithm is presented for three-level neutral-point (NP) clamped converters in high-speed aerospace motor drives. With the proposed inscribed polygonal-boundary compression technique, the output voltage capability is enhanced under a lower crossover angle and compression coefficient. As a result, it brings an opportunity for the operation of the studied aircraft electric starter/generator (ESG) systems easily extending from the linear modulation range into the overmodulation region. Furthermore, an active capacitor voltage balancing control method is investigated to recover NP potential imbalance in the case of high modulation index and low power factor operating conditions. To simplify the digital implementation of the algorithm, a fast calculation approach is adopted in this work. The modulation performance of the proposed strategy is verified by both simulation and experimental results with a 45 kW, 32 k r/min ESG prototype system. [ABSTRACT FROM AUTHOR]

This article proposes a new duty-ratio regulation-based strategy to improve the torque performance for the direct torque control (DTC) of three-phase permanent magnet synchronous motors (PMSMs). The conventional DTC schemes utilize two hysteresis regulators that are hard to be tuned to satisfy proper torque performance for wide speed ranges because of the contrary change in the positive and the negative torque deviations of the converter's voltage vectors with the rotational speed variations. In contrast, the proposed method uses a duty-ratio regulator that considers the operating speed impact on the torque deviation of the active voltage vectors and avoids triggering those of them that produce high torque deviations, therefore reducing the torque ripple of the DTC system. Moreover, it proposes a virtual reference generator to mitigate the steady-state torque error. The proposed method provides enhanced torque control performance, meanwhile maintaining the main advantages of the conventional DTC techniques, including simple structure, fast transient response, and good robustness. The feasibility and effectiveness of the proposed strategy are verified through a detailed comparative assessment with the conventional DTC scheme and two existing duty regulation-based methods using experimental results obtained from a 0.75-kW PMSM drive system. [ABSTRACT FROM AUTHOR]

Permanent magnet machines have been used in the high‐speed drive applications due to their high‐efficiency, high‐power‐density, and wide‐speed range characteristics. However, control of such high‐speed permanent magnet machines machine is always challenging and proper flux‐weakening controller design is essential to achieve high performance of these machines. In this paper, an improved feedforward flux‐weakening control scheme for interior permanent magnet synchronous machine (IPMSM) drives are proposed. The proposed method identifies optimal d‐axis and q‐axis currents under different operation regions using maximum‐torque‐per‐ampere curve, voltage limit, and current limit curves with a fast Newton–Raphson algorithm. To ensure the optimal performance of the control mechanism, effects of inductance variations due to the magnetic saturation are considered and an innovative high‐frequency staircase voltage injection method is used to identify the q‐axis inductance. The experimental results show that compared with other existing flux‐weakening methods, the proposed technique can improve the DC‐link voltage utilisation without the need to tune any controller gains and can fully utilise maximum available torque with desirable transient performance. [ABSTRACT FROM AUTHOR]

In future electrified aircraft, multispool more electric engines (MEEs) are expected to be equipped with electric generators connected to each shaft for power offtake and supplying onboard electrical loads. These can be interfaced to a common high-voltage DC bus architecture via power electronic converters. Such system architecture enables the establishment of an "electrical bridge" to circulate the desired amount of power between the engine shafts, and decouple their speeds. This paper introduces the possible benefits from the electric power transfer (EPT) for engine performance and scrutinizes a novel EPT-adopted design (EPTAD) for future MEEs. For this purpose, a zero-dimensional (0D) engine model has been developed by using the intercomponent-volume (ICV) method. By using the engine model, the CFM56-3 engine is redesigned to realize the EPTAD. Comparing the simulation results for the EPTAD and baseline CFM56-3 engines shows significant improvement for engine performance in terms of specific fuel consumption (SFC) and surge margin (SM), mainly at cruise (CR) condition. Results show that almost 3.2% and 2.2% of fuel burn reduction is achieved for the short- and medium-haul flights, respectively, with a 1150 kW EPT system. It is also shown that variable bleed valves (VBVs) can be eliminated in the EPTAD engine with a 1150 kW EPT system. [ABSTRACT FROM AUTHOR]

The more-electric aircraft concept has made the extraction of electrical power from both high-pressure shaft and low-pressure shaft of the aircraft engine essential for future aircraft. With each shaft driving one electrical generation channel, an advanced dual-channel enhanced power generation system can be formed. This article aims to address the power quality issues of this dual-channel power generation system, specifically focusing on the reduction of harmonics on a common dc bus. A simplified model to estimate second carrier harmonic of dc current in two-level converters is developed and reveals the fact that while this second carrier harmonic component magnitude can be determined by modulation index and dc-link current, its phase angle is solely dependent on the angle of carrier signals. Based on the developed model and these key findings, a new harmonic cancellation method is proposed through active power sharing and phase angle shifting of the carrier signals within different power sources. The method has demonstrated high robustness and is effective under different fundamental frequencies and power sharing ratio. Both simulation and experimental results are presented in this article to validate the proposed harmonic model and the enhanced cancellation method. [ABSTRACT FROM AUTHOR]

The idea of electric propulsion for transportation is not new; indeed, the first cars, nearly 200 years ago, were electric. However, our dependence on fossil fuels over the last 100 years is now being questioned, and as a global society, we are moving toward more-electric transportation solutions. Electric propulsion of aircraft is part of this trend, either all-electric or through a large variety of the proposed hybrid propulsion systems. This article considers some of these systems, their technological requirements, and the ongoing research and development in motors and drives necessary to make this technological change a feasible option for the future of passenger flight. [ABSTRACT FROM AUTHOR]

For the direct-current (dc) electrical power distribution system onboard more electric aircraft, the voltage quality of dc bus is of a great concern since there could be significant harmonics distortions when feeding different power electronics loads. This problem can be potentially addressed by introducing a dc filter to the point-of-load converters regulated by the finite control set model predictive control (FCS-MPC). To optimize this filter, genetic algorithm (GA) is utilized for searching the optimal design, which guarantees a low mass and low power losses. Different from the conventional filter design methods, the proposed method treats $LC$ as design variables, which need to be optimized while ensuring the output power quality. First, relations among variables, operation conditions, and constraints are built based on commercial data and circuit simulations. Then, the design and optimization are developed with these relations and a Pareto front is finally given by GA. After that, the best design is obtained by an index integrating two objectives. Lastly, the design approach is verified by an experiment where an FCS-MPC regulated converter was used as a particular example fed by three different LC filters. [ABSTRACT FROM AUTHOR]

The perturbation and observation method (P&O method) is commonly used for maximum power point tracking in wind energy conversion systems. However, the selection of a suitable step size for this method is the key challenge when employing this technique. To address this, the paper presents a new method, called the FLC‐P&O method, in which a combination of fuzzy logic control (FLC) and the conventional P&O method is used. Both simulation and experimental results are presented in order to demonstrate the performance of the proposed MPPT method. Experimental testing is performed on both a laboratory wind simulator and a practical wind turbine. The results confirm that the FLC‐P&O method can provide better maximum power point tracking performance compared to the conventional P&O method. Moreover, the implementation and testing of the proposed technique on a practical wind turbine can extract more energy compared to conventional P&O. All findings are verified experimentally. © 2020 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This article proposes an improved power generation architecture (PGA) for future more electric aircraft applications. In the proposed architecture, a starter/generator is connected to the high-pressure (HP) shaft, and a generator is connected to the low-pressure (LP) shaft. Their outputs supply a common dc bus via active power converters. A back-to-back (B2B) converter is deployed to link the ac terminals of the two generators. The proposed topology embraces three main advantages. First, with the B2B converter, the HP generator can operate at a high speed without flux weakening; thus, the magnitude of stator current will be decreased when output same active power. This will lead to the reduction of power losses on the generators and the active rectifiers. Second, the proposed PGA allows power transfer from the LP and to the HP shafts. This can potentially reduce the fuel consumption and increase aircraft engine compressor surge margins when the engine is at low-speed setting. Third, the B2B converter provides an additional power flow path to the generators under converter fault scenarios, hence improving the postfault operation ability. For the proposed PGA, engine benefits, modeling, control design, and efficiency improvements are illustrated in detail. The control performances of the proposed PGA, engine performance improvement by transferring power from the LP to HP shaft, and power loss reduction are verified via simulations and experimental results collected from a twin-shaft aircraft power generation test rig. [ABSTRACT FROM AUTHOR]

A design procedure for the dual active bridge (DAB) converter is presented, which aims to optimised power density and computational effort. When designing a DAB, the selection of circuit design parameters such as switching frequency, leakage inductance and semiconductor technologies is a complex question when targeting losses and weight minimisation of the final design. In this study, analytical models of the operating waveforms, the losses and the weight of all DAB components are developed. The proposed design algorithm is used for designing a 3 kW high-frequency DAB for an aircraft DC power system. [ABSTRACT FROM AUTHOR]

This paper introduces a modulation technique for the single-phase dual active bridge (DAB) in which the switching frequency and transformer flux linkage are modulated to achieve improved power transfer characteristics and reduced converter losses. By analysing the DAB, it is noticed that in the traditional single phase shift (SPS) modulation, the transformer flux linkage decreases with increasing power. The proposed flux control modulation (FCM) counteracts this decrease and aims to keep the transformer utilisation constant on the whole load range by a reduction in switching frequency. This has two effects: first, the reduced frequency substantially lowers switching losses and second, the power transfer characteristic of the DAB is linearised, facilitating the control of this converter. The new modulation technique is validated by simulation. [ABSTRACT FROM AUTHOR]

This paper presents an overview of technology related to on-board microgrids for the more electric aircraft. All aircraft use an isolated system, where security of supply and power density represents the main requirements. Different distribution systems (ac and dc) and voltage levels coexist, and power converters have the central role in connecting them with high reliability and high power density. Ensuring the safety of supply with a limited redundancy is one of the targets of the system design since it allows increasing the power density. This main challenge is often tackled with proper load management and advanced control strategies, as highlighted in this paper. [ABSTRACT FROM AUTHOR]

This paper deals with the innovative “variable-voltage” bus concept for future more-electric aircraft platforms. Using new functionalities and opportunities offered by innovative sources actively controlled by power electronics, there is an opportunity for a significant increase of their output power (within powertrain capabilities, machine thermal limits, and power converter maximum current) to supply increased load demands under certain conditions. This paper investigates applications of this concept to satisfy power demands for the wing ice-protection system for business jet. The study includes a detailed study into the control challenges of the proposed approach and suggests corresponding theoretical solutions. Furthermore, the controller design aspects are explored with considerations to achieve stable operation. The concept is tested in simulation environment and validated through experimental studies. This paper might be of interest for the researchers and engineers focused on innovative solutions for future aircraft platforms. [ABSTRACT FROM AUTHOR]

This paper describes a high-performance neutral point voltage balancing technique for a neutral point clamped (NPC) converter. Conventional neutral point voltage balancing methods do not function well under low power factor, low pulse ratio, and near-unity modulation index operation conditions. These conditions are essentially dominant operation conditions for aircraft starter/generator systems. This paper introduces an alternative space vector modulation technique for three-level NPC converters in an aircraft starter generator system. The selection of voltage space vectors is optimized for high modulation index and low power factor operation. Disturbances caused by a low pulse ratio are also compensated. The proposed method maintains neutral point voltage balance and ripple minimization over the full range of operating conditions. This paper also provides a detailed analysis of the sources of neutral point voltage imbalances and ripples in high-speed drives with deep flux weakening. Simulation results obtained from a Simulink/PLECS model and experimental results obtained from a 45 kVA, 32 krpm aircraft starter generator test rig prove that the proposed method eliminates the neutral point voltage imbalance and significantly reduces the neutral point voltage ripple. [ABSTRACT FROM AUTHOR]

It is known that, when tightly regulated, actively controlled power converters behave as constant power loads (CPLs). These loads can significantly degrade the stability of their feeder system. The loop-cancelation technique has been established as an appropriate methodology to mitigate this issue within dc–dc converters that feed CPLs. However, this has not yet been applied to uncontrolled rectifier based ac–dc converters. This paper therefore details a new methodology that allows the loop-cancelation technique to be applied to uncontrolled rectifier based ac–dc converters in order to mitigate instability when supplying CPLs. This technique could be used in both new applications and easily retrofitted into existing applications. Furthermore, the key contribution of this paper is a novel adaptive stabilization technique, which eliminates the destabilizing effect of CPLs for the studied ac–dc power system. An equation, derived from the average system model, is introduced and utilized to calculate the adaptable gain required by the loop-cancelation technique. As a result, the uncontrolled rectifier based ac–dc feeder system is always stable for any level of CPL. The effectiveness of the proposed adaptive mitigation has been verified by small-signal and large-signal stability analysis, simulation, and experimental results. [ABSTRACT FROM AUTHOR]

Stability studies are a crucial part of the design of power electronic systems, especially for safety critical applications. Standard methods can guarantee stability under nominal conditions but do not take into account the multiple uncertainties that are inherent in the physical system or in the system model. These uncertainties, if unaccounted for, may lead to highly optimistic or even erroneous stability margins. The structured singular value-based $\mu$ method justifiably takes into account all possible uncertainties in the system. However, the application of the $\mu$ method to power electronic systems with multiple uncertainties is not widely discussed in the literature. This paper presents practical approaches to applying the $\mu$ method in the robust stability analysis of such uncertain systems. Further, it reveals the significant impact of various types of parametric uncertainties on the reliability of stability assessments of power electronic systems. This is achieved by examining the robust stability margin of the dc/dc buck converter system, when it is subject to variations in system load, line resistance, operating temperature, and uncertainties in the system model. The $\mu$ predictions are supported by time-domain simulation and experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes an active switching harmonic current reduction method within the dc-link capacitor of two-level, three-phase, back-to-back converters. This method is based on the derived analytical solution for switching harmonic currents in the dc-link. It is shown that by controlling the pulse width modulation carrier waveform's phase angles, the harmonics in the second carrier band of the rectifier and the inverter can be synchronized such that cancellation occurs in the dc-link capacitor. This synchronization is provided by harmonic phase feedback control. The feasibility of the proposed approach has been verified experimentally and results are presented in this paper. [ABSTRACT FROM PUBLISHER]

Power electronic systems are prone to instability. The problem, generally attributed to the constant power load (CPL) behavior of their power electronic controlled loads, can become more acute when the systems are subject to parametric uncertainties. The structured singular value (SSV) based $\mu$ method has proven to be a reliable approach for assessing the stability robustness of such uncertain systems. Despite its numerous benefits, the $\mu$ method is not often applied to electrical power systems (EPS) with multiple uncertainties. This may be due to the mathematical complexity underlying the $\mu$ theory. This paper aims to make the $\mu$ approach more application-friendly by providing clearer insights into the meaning and usefulness of the robust stability measure $\mu$ for EPS with multiple parametric uncertainties. This is achieved by presenting a methodology for translating $\mu$ analysis results from the frequency domain to the more perceivable uncertain parameters domain. The method directly demonstrates dependences of system stability on uncertain system parameters. Further, it clearly identifies robust stability domains as subsets of the much wider stability domains. The work is based on a representative EPS connected to an ideal CPL. $\mu$ analysis predictions are evaluated and validated against analytical results, for example, CPL system. [ABSTRACT FROM PUBLISHER]

This paper focuses on the analysis of a single dc bus multigenerator electrical power system (EPS) for future more electric aircraft. Within such a single bus paradigm, the paper proposes a detailed control design procedure and provides a stability analysis based on the derivation of the output impedance of the source subsystem and input impedance of the load subsystem, including control dynamics. The single bus characteristic is analyzed and the stability properties of the EPS are investigated when supplying constant power loads. In addition, the paper highlights the impact on stability of the number of parallel sources and of the power sharing ratio. The theoretical analysis is instrumental in designing an optimally stable single dc bus EPS. The key findings are validated by experimental results. [ABSTRACT FROM AUTHOR]

Droop control has been widely applied in dc microgrids (MGs) due to its inherent modularity and ease of implementation. Among the different droop control methods that can be adopted in dc MGs, two options have been considered in this paper: I–V and V–I droop. I–V droop controls the dc current depending on the dc voltage while V–I droop regulates the dc voltage based on the output current. The paper proposes a comparative study of V–I/I–V droop control approaches in dc MGs focusing on steady-state power-sharing performance and stability. The paper presents the control scheme for current-mode (I–V droop) and voltage-mode ( V–I droop) systems, derives the corresponding output impedance of the source subsystem, including converters dynamics, and analyzes the stability of the power system when supplying constant power loads. The paper first investigates the impact on stability of the key parameters including droop gains, local control loop dynamics, and number of sources and then performs a comparison between current-mode and voltage-mode systems in terms of stability. In addition, a generalized analytical impedance model of a multisource, multiload power system is presented to investigate stability in a more realistic scenario. For this purpose, the paper proposes the concept of “global droop gain” as an important factor to determine the stability behaviour of a parallel sources based dc system. The theoretical analysis has been validated with experimental results from a laboratory-scale dc MG. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of two soft magnetic materials on a high-speed machine design, namely, 6.5% silicon steel and cobalt–iron alloy. The effect of design parameters on the machine performance as an aircraft starter-generator is analyzed. The material properties which include B-H characteristics and the losses are obtained at different frequencies under an experiment and used to predict the machine performance accurately. In the investigation presented in this paper, it is shown that machines designed with 6.5% silicon steel at a high core flux density has lower weight and lower losses than the cobalt–iron alloy designs. This is mainly due to the extra weight contributed by the copper content especially in the end-windings. Due to the high operating frequencies, the core losses in the cobalt–iron machine designs are found to outweigh the copper losses incurred in the silicon steel machines. It is also shown that change in stack length/number of turns has a considerable effect on the copper losses at starting, however has no significant advantage on rated efficiency which happens to be in a field-weakening operating point. It is also shown that the performance of the machine designs depends significantly on material selection and the operating point of the core. The implications of the variation of design parameters on the machine performance is discussed and provide insight into the influence of parameters that effect overall power density. [ABSTRACT FROM PUBLISHER]

A novel maximum torque per Ampere (MTPA) controller for the induction motor (IM) drives is presented. It is shown to be highly suited to applications that do not demand an extremely fast dynamic response, for example, electric vehicle drives. The proposed MTPA field oriented controller guarantees asymptotic torque (speed) tracking of smooth reference trajectories and maximizes the torque per Ampere ratio when the developed torque is constant or slow varying. An output-feedback linearizing concept is employed for the design of torque and flux subsystems to compensate for the torque-dependent flux variations required to satisfy the MTPA condition. As a first step, a linear approximation of the IM magnetic system is considered. Then, based on a standard saturated IM model, the nonlinear MTPA relationship for the rotor flux are derived as a function of the desired torque, and a modified torque–flux controller for the saturated machine is developed. The static and dynamic flux reference calculation methods to achieve simultaneously an asymptotic field orientation, a torque–flux decoupling, and an MTPA optimization in a steady state, is proposed. The method guarantees a singularity free operation and can be used as means to improve stator current transients. Experimental tests prove the accuracy of the control over a full torque range and show successful compensation of the magnetizing inductance variations caused by saturation. The proposed MTPA control algorithm also demonstrates a decoupling of the torque (speed) and flux dynamics to ensure asymptotic torque tracking. In addition, a higher torque per Ampere ratio is achieved together with an improved efficiency of electromechanical energy conversion. [ABSTRACT FROM AUTHOR]

The paper proposes a method of active switching harmonics current reduction in the dc-link capacitor of a two-level, three-phase, back-to-back converter. Based on the derived analytical solution for switching harmonic currents in the dc-link, it is shown that by specific control over the pulsewidth-modulated (PWM) carriers’ phase angles, the targeted harmonics of the rectifier and the inverter can be synchronized in phase such that their cancellation occurs in the dc-link capacitor. This synchronization is provided by harmonic phase feedback control. A three-step procedure to implement the method is detailed in the paper. The effectiveness of the proposed approach is verified experimentally. [ABSTRACT FROM AUTHOR]

This paper proposes an improved voltage regulation method in a multisource-based dc electrical power system in the more electric aircraft. The proposed approach, which can be used in terrestrial dc microgrids as well, effectively improves the load sharing accuracy under high droop gain circumstance with consideration of cable impedance. Since no extra communication line and controllers are required, it is easily implemented and also increases the system modularity and reliability. By using the proposed approach, the dc transmission losses can be reduced and the system stability is not deteriorated for normal and fault scenarios. In this paper, optimal droop gain settings are investigated and the selection of individual droop gains as well as the proportional power sharing ratio has been described. Simulation and experimental results validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper develops a modeling method for robust stability analysis of nonlinear electrical power systems over a range of operating points and under parameter uncertainties. Standard methods can guarantee stability under nominal conditions, but do not take into account any uncertainties of the model. In this study, stability is assessed by using structured singular value (SSV) analysis, also known as $\mu$ analysis. This method provides a measure of stability robustness of linear systems against all considered sources of structured uncertainties. The aim of this study is to apply the SSV method for robust small-signal analysis of nonlinear systems over a range of operating points and parameter variations. To that end, a modeling methodology is developed to represent any such system with an equivalent linear model that contains all system variability, in addition to being suitable for $\mu$ analysis. The method employs symbolic linearization around an arbitrary operating point. Furthermore, in order to reduce conservativeness in the stability assessment of the nonlinear system, the approach takes into account dependences of operating points on parameter variations. The methodology is verified through $\mu$ analysis of the equivalent linear model of a 4-kW permanent magnet machine drive, which successfully predicts the destabilizing torque over a range of different operating points and under parameter variations. Further, the predictions from $\mu$ analysis are validated against experimental results. [ABSTRACT FROM PUBLISHER]

The dynamic phasor (DP) concept has been widely used in modeling electrical power systems. So far, the DP concept has been restricted to modeling systems with one single electrical source at a fixed fundamental frequency, either one generator or an ideal three-phase AC source. This paper aims to extend the DP modeling methodology to a wider application area. Two major achievements have been introduced: 1) application of DPs for multi-source, multi-frequency systems; 2) modeling of systems with time-varying frequencies. These two techniques enable the use of DPs to study nearly all types of electrical power systems (EPS). The developed theory is validated using a twin-generator system from the More Open Electrical Technologies (MOET) project. The accuracy and effectiveness of the developed models is confirmed by comparing the simulation results of detailed switching models and DP models under both balanced and unbalanced conditions. [ABSTRACT FROM AUTHOR]

The more‐electric aircraft (MEA) has become a dominant trend for next‐generation aircraft. The electrical power system (EPS) on‐board may take many forms: AC, DC, hybrid, frequency‐wild, variable voltage, together with the possibility of novel connectivity topologies. To address the stability, availability and capability issues as well as to assess the performance of the power quality and transient behaviour, extensive simulation work is required to develop the EPS architectures. The study develops a fast‐simulation model of active front‐end rectifiers based on the dynamic phasor concept. The model is suitable for accelerated simulation studies of EPS under normal, unbalanced and line fault conditions. The performance and effectiveness of the developed model have been demonstrated by comparison against time‐domain models in three‐phase and synchronous space‐vector representations. The experimental verification of the dynamic phasor model is also reported. The prime purpose of the model is for the simulation studies of MEA power architectures at system level; however it can be directly applied for simulation study of any other EPS interfacing with active front‐end rectifiers. [ABSTRACT FROM AUTHOR]

In this study, a functional model for diode-bridge (DB) rectifiers is developed based on the dynamic phasor concept. The developed model is suitable for accelerated simulation studies of the electric power systems under normal, unbalanced and line faulty conditions. The high accuracy and efficiency of the developed model have been demonstrated by comparison against three-phase time-domain model and against the model employing synchronous space-vector representations. The experimental verification of the developed model is also reported. In addition, an error analysis shows that the error of the developed model is <10% at the most severe unbalanced conditions. The prime purpose of the model is for the simulation studies of more-electric aircraft power architectures at a system level; however, it can be directly applied for simulation study of any other electrical power system interfacing with uncontrolled DB rectifiers. [ABSTRACT FROM AUTHOR]

This article introduces the more electric aircraft concept and investigate the potential benefits of the technology for manned aircraft. Typical aircraft electrical power systems and loads are described as well as the exciting, future challenges for the aerospace industry. The importance of power electronics as an enabling technology for this step change in aircraft design are considered and examples of typical system designs are discussed. [ABSTRACT FROM PUBLISHER]

Distributed generation with a combustion engine prime mover is still widely used to supply electric power in a variety of applications. These applications range from backup power supply systems and combined wind-diesel generation to providing power in places where grid connection is either technically impractical or financially uneconomic. Modelling of such systems as a whole is extremely difficult due to the long-time load profiles needed and the computational difficulty of including small time-constant electrical dynamics with large time-constant mechanical dynamics. This paper presents the development of accelerated, reduced-order models of a distributed internal combustions engine generator unit. Overall these models are shown to achieve a massive improvement in the computational time required for long-time simulations while also achieving an extremely high level of dynamic accuracy. It is demonstrated how these models are derived, used and verified against benchmark models created using established techniques. Throughout the paper the modelling set as a whole, including multi level detail, is presented, detailed and finally summarised into a crucial tool for general system investigation and multiple target optimisation. [ABSTRACT FROM AUTHOR]

Safety issues related to the electrification of more electric aircraft (MEA) need to be addressed because of the increasing complexity of aircraft electrical power systems and the growing number of safety-critical sub-systems that need to be powered. Managing the energy storage systems and the flexibility in the load-side plays an important role in preserving the system's safety when facing an energy shortage. This paper presents a system-level centralized operation management strategy based on model predictive control (MPC) for MEA to schedule battery systems and exploit flexibility in the demand-side while satisfying time-varying operational requirements. The proposed online control strategy aims to maintain energy storage (ES) and prolong the battery life cycle, while minimizing load shedding, with fewer switching activities to improve devices lifetime and to avoid unnecessary transients. Using a mixed-integer linear programming (MILP) formulation, different objective functions are proposed to realize the control targets, with soft constraints improving the feasibility of the model. In addition, an evaluation framework is proposed to analyze the effects of various objective functions and the prediction horizon on system performance, which provides the designers and users of MEA and other complex systems with new insights into operation management problem formulation. [ABSTRACT FROM AUTHOR]

This paper presents the development of a supercapacitor energy storage system (ESS) aimed to minimize weight, which is very important for aerospace applications, whilst integrating smart functionalities like voltage monitoring, equalization, and overvoltage protection for the cells. The methodology for selecting the supercapacitor cells type/size is detailed to achieve the safest and most energy-dense ESS. Additionally, the development of the interface electronics for cells' voltage monitoring and overvoltage protection is presented. The proposed design implements a modular distributed architecture coordinated using communication buses to minimize the wirings and associated complexity and to enable system reconfiguration and expansions, as well as fault diagnoses. Validating the proposed ESS functionalities has been done via experimental testing and the results are presented and discussed. [ABSTRACT FROM AUTHOR]

To improve the design of electric drives and to better predict the system performance, numerical simulation has been widely employed. Whereas in the majority of the approaches, the machines and the power electronics are designed and simulated separately, to improve the fidelity, a co-simulation should be performed. This paper presents a complete coupled co-simulation model of synchronous reluctance machine (SynRel) drive, which includes the finite element model of the SynRel, the power electronics inverter, the control system, and application examples. The model of SynRel is based on a finite element model (FEM) using Simcenter MagNet. The power electronics inverter is built using PLECS Blockset, and the drive control model is built in Simulink environment, which allows for coupling between MagNet and PLECS. The proposed simulation model provides high accuracy thanks to the complete FEA-based model fed by actual inverter voltage. The comparison of the simulation results with experimental measurements shows good correspondence. [ABSTRACT FROM AUTHOR]

A centralised smart supervisor (CSS) controller with enhanced electrical energy management (E2-EM) capability has been developed for an Iron Bird Electrical Power Generation and Distribution System (EPGDS) within the Clean Sky 2 ENhanced electrical energy MAnagement (ENIGMA) project. The E2-EM strategy considers the potential for eliminating the 5 min overload capability of the generators to achieve a substantial reduction in the mass of the EPGDS. It ensures optimal power and energy sharing within the EPGDS by interfacing the CSS with the smart grid network (SGN), the energy storage and regeneration system (ESRS), and the programmable load bank 1 secondary distribution board (PLB1 SDU) during power overloads and failure conditions. The CSS has been developed by formalizing E2-EM logic as an algorithm operating in real time and by following safety and reliability rules. The CSS undergoes initial verification using model-in-the-loop (MIL) testing. This paper describes the EPGDS simulated for the MIL testing and details the E2-EM strategy, the algorithms, and logic developed for the ENIGMA CSS design. The CSS was subjected to two test cases using MIL demonstration, and based on the test results, the performance of the ENIGMA CSS is verified and validated. [ABSTRACT FROM AUTHOR]

In this paper, a flexible switching table (FST) for direct torque control (DTC) of permanent magnet synchronous motors (PMSMs) was proposed to enhance the steady-state and dynamic performances of the drive system. First, the influence of each converter output voltage vectors on the torque and stator flux deviation rates was analyzed to assess the voltage selection strategies of the conventional STs and their impact on the DTC system's performance. Then, a new flexible ST was proposed which uses a simple algorithm to adaptively select the appropriate voltage vector for two of its states according to the system operating condition. The effectiveness and feasibility of the proposed FST were verified through a comparative evaluation with the conventional STs using experimental results obtained from a 0.75 kW PMSM drive system. [ABSTRACT FROM AUTHOR]