The present work is a survey on aircraft hybrid electric propulsion (HEP) that aims to present state-of-the-art technologies and future tendencies in the following areas: air transport market, hybrid demonstrators, HEP topologies applications, aircraft design, electrical systems for aircraft, energy storage, aircraft internal combustion engines, and management and control strategies. Several changes on aircraft propulsion will occur in the next 30 years, following the aircraft market demand and environmental regulations. Two commercial areas are in evolution, electrical urban air mobility (UAM) and hybrid-electric regional aircraft. The first one is expected to come into service in the next 10 years with small devices. The last one will gradually come into service, starting with small aircraft according to developments in energy storage, fuel cells, aircraft design and hybrid architectures integration. All-electric architecture seems to be more adapted to UAM. Turbo-electric hybrid architecture combined with distributed propulsion and boundary layer ingestion seems to have more success for regional aircraft, attaining environmental goals for 2030 and 2050. Computational models supported by powerful simulation tools will be a key to support research and aircraft HEP design in the coming years. Brazilian research in these challenging areas is in the beginning, and a multidisciplinary collaboration will be critical for success in the next few years.

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Aircraft Hybrid-Electric Propulsion: Development Trends, Challenges and Opportunities

Square root calculation is a widely used task in real-time control systems especially in those, which control power electronics: motors drives, power converters, power factor correctors, etc. At the same time calculation of square roots is a bottle-neck in the optimization of code execution time. Taking into account that for many applications approximate calculation of a square root is enough, calculation time can be decreased with the price of precision of calculation. This paper analyses existing methods for fast square root calculation, which can be implemented for fixed point microcontrollers. It discusses algorithms’ pros and cons, analyses calculation errors and gives some recommendations on their use. The paper also proposes an original method for fast square root calculation, which does not use hardware acceleration and therefore, is suitable for implementation at a variety of modern Digital Signal Processors, which have high-speed hardware multipliers, but do not have effective dividers. The maximum relative error of the proposed method is 3.36% for calculation without division, and can be decreased to 0.055% using one division operation. Finally, the most promising methods are compared and results of their performance comparisons are depicted in tables.

https://ijpeds.iaescore.com/index.php/IJPEDS/article/download/20435/13233

Review of fast square root calculation methods for fixed point microcontroller-based control systems of power electronics

Square root calculation is a widely used task in real-time control systems especially in those, which control power electronics: motors drives, power converters, power factor correctors, etc. Meanwhile, calculation of square roots is a bottle-neck in optimization of the code execution time, therefore solution of this problem can help to accelerate a number of routines used for the control of power electronics. Taking into account that for many applications approximate calculation of a square root is enough, calculation time can be seamlessly decreased with the pay of decreased precision. This paper proposes novel method for fast square root calculation, which is based on the approximation of parabola with hyperbola. The comparison of the proposed method and Newton-Raphson, which is one of the best existing methods, is also given. It shows that proposed method is faster and provides precision of 0.25%, which is higher than two iterations of Newton-Raphson method.

Fast Square Root Calculation for Control Systems of Power Electronics

While drilling, the drilling tool can reach the target layer more quickly and efficiently with the accurate borehole trajectory information. It can reduce the drilling cost. However, in the process of traditional well inclination measurement with drilling, due to the interference form the rotary vibration of drill string, the inclinometer needs to stop drilling to complete the measurement of drill tool attitude. And the sensor is installed far away from the drill, so the measurement error and the risk of well control are increased. In order to solve the problem that the interference of near the bit inclinometer which caused by complex shock vibration and drill string rotation, this paper proposes a method of dynamic measuring inclination angle that based on unscented kalman filter and cross-correlation extraction algorithm (UKF+CC). It is a composite filtering method that combine UKF, cross-correlation extraction algorithm, low pass filtering with sliding slide filtering. In this method, firstly, a limiter filter is used to filter the step excitation signal caused by impact noise. Then UKF filter is used to filter out the most colored noise caused by vibration acceleration, at the same time, low-pass filtering is used to deal with the magnetic interference noise in the output signal of tri-axis fluxgate, and using sliding filter to smooth the radial acceleration signal in the tri-axis acceleration sensor. Finally, the radial or tangential direction magnetic signal of the tri-axis fluxgate is used as the reference signal, and use reference signal to extract accurately the gravity acceleration component of the near bit position by cross-correlation detection method, then can finish the accurate calculation of dynamic well inclination angle. The results are verified by the simulation test and the simulation experiment of the rotating vibration test platform. When the drilling tool rotation speed within 60-300r/min, the maximum measurement error is +0.09°, the overall measurement accuracy of inclination angle under different drilling tool rotation speed is better than ±0.1°and the measured results are not affected by the rotation speed and vibration of drilling tool, it realizes the dynamic and accurate measurement of the inclination angle in the process of drilling.

Dynamic Measurement of Well Inclination Based on UKF and Correlation Extraction

The paper describes a synchronous generator model developed based on the multiple reference frame theory. The main physical phenomena included in the model are the machine armature non-sinusoidal voltage waveform and the influence of armature current in load conditions on the armature voltage waveform higher harmonic components. The modified multiple reference frame theory model is proposed. In this modified theory model the field and armature currents are the cause of the non-sinusoidal airgap spatial field distribution. The influence of this airgap spatial field distribution is also investigated. The resulting nonuniform saturation of the pole shoe affects the machine voltage waveform in load conditions. Simulation and measurements of the machine performance in steady and transient states are conducted in order to validate the model.

Multiple Reference Frame Theory in the Synchronous Generator Model Considering Harmonic Distortions Caused by Nonuniform Pole Shoe Saturation

This paper presents the results of simulation and practical tests of the inverter-based power converter with a sine output filter designed for implementation in an aircraft power system. In order to reduce the output voltage harmonic distortion, the converter utilises active software harmonics filtering. This work provides an analysis of the converter performance under two control algorithms applied for the active filtering operation. The first control algorithm is based on discrete Fourier transform (DFT) where the control system injects measured higher harmonics with inverse polarity into the inverter command voltage and DFT provides the measurement of the converter output voltage. The second control method is based on repetitive controller (RC) algorithms which adjusts the inverter command voltage using a self-learning approach. The second method significantly reduces the demand for CPU computational resources. The software filtering in both systems shows a good performance and ensures the converter output voltage with less than 5% THD under all load conditions. This paper discusses the structures for both proposed control systems as well as the implementation in MATLAB models and microcontroller software. Both algorithms are modelled in software and implemented in a practical microcontroller. The advantages of the RC-based control method are demonstrated through the software analysis and performance of the system.

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Simulation and Testing of a Power Converter for Aircraft AC Electric Power Generation System using Software Elimination of Higher Harmonics

This paper consider the utilization of the division operation in real-time motion control microcontroller systems. It is shown that the most typical case is calculation of the inverse DC-link voltage for the correction of the inverter control signals due to DC-link voltage deviations. The benchmark of the division operation shows that it takes approximately 30 or more CPU cycles to perform division on fixed- or floating-point microcontrollers. Also programmer should use right math libraries to achieve good results. At last it is suggested to use Newton-Raphson equation for inverse DC-link voltage calculation. The accuracy of this method and its benchmark are given.

http://ieeexplore.ieee.org/iel7/7133660/7146959/07146982.pdf

Optimization of the division operation for real-time control systems

This paper deals with the design and tests of an aircraft ac power-supply converter control system. Possible topologies of power converters are shown, and an appropriate topology with three independent half-bridge inverters is justified. A control scheme with inverter nonidealities and nonlinear load compensation for the selected topology is presented. Practical aspects of the designing software for the control system, are shown and a low-level code optimization to decrease the computing time of the control algorithm is presented. Test results with and without compensation for selected harmonics are shown. The form of the voltage and its spectrum are given for full and nonlinear load.

Design and tests of a new promising ac electric-power generation system for aircraft

This paper deals with the method of elimination of the DC offset impact on the speed estimation system which uses sine/cosine incremental position encoder. The impact of the DC offset in the input signals to the PLL-based speed estimation is shown. The problem can be solved by means of the highpass filter which should be implemented in the angle domain instead of time domain. The simulation and experimental results are presented. The operation of the filter is correct in the wide range of operation speeds of the drive including zero speed.

Method of digital filtering of sine/cosine incremental position encoder signals for elimination of DC offset impact

This article deals with the simulation of the power converter with voltage-source inverter and sine-filter. The repetitive control system was designed. The existing power converter has a control system which makes Fourier transform of the output voltage to inject these harmonics with opposite phase. The new proposed system based on repetitive controller which is much simpler and with smaller CPU load. The higher harmonics elimination works perfect and the power converter produces output voltage with less than 5% THD under linear or non-linear load. This paper describes the improved control system structure and its implementation in MATLAB Simulink environment. The advantages of the repetitive algorithm facing Fourier transform harmonic compensation are shown. The performance of the new control method is shown in simulation results. The algorithm is carried out in C language using MATLAB S-Function block so it is suitable for implementation in the real-time control systems.

Vasiliy Kulmanov

Papers

Simulation and Testing of a Power Converter for Aircraft AC Electric Power Generation System using Software Elimination of Higher Harmonics

Optimization of the division operation for real-time control systems

Design and tests of a new promising ac electric-power generation system for aircraft

Method of digital filtering of sine/cosine incremental position encoder signals for elimination of DC offset impact

Simulation of power converter with repetitive control system for higher harmonics elimination