This paper proposes a high-performance speed measurement method for electric drives using incremental encoders. The proposed solution improves the period-based speed estimation method. Such methods suffer from low resolution of time measurement at high speeds. The proposed method solves this problem by processing every speed estimation between the consecutive execution of the speed controller predicting the speed signal in order to achieve maximum performance of the speed loop. The processing algorithm was suggested for the speed estimation. The new method was studied and compared with conventional methods with the modelling experiment. It shows a good step response transient with lower oscillation in comparison to conventional methods for the same tuning of the speed controller.

Optimized method for speed estimation using incremental encoder

This paper studies braking of reciprocating compressor and its impact on the noise. It proposes the solution for decreasing of the reciprocating compressor noise and vibrations, which happens at stoppage. These vibrations and resulting noise are caused by the gas pressure in the cylinder, which impacts the compressor's piston and can reverse the motor at stoppage. The authors analyze conventional solutions and reports results of the experiments, which prove that conventional solutions are not applicable. Therefore, several new ideas of compressor motor braking are proposed and checked experimentally. With their help the method with better performance is selected for further study and improvements. This paper demonstrates that the proposed method totally eliminates noise and vibration peak at the stoppage of reciprocating compressor, therefore, it is recommended for use in the mass production.

Stoppage noise reduction of reciprocating compressors

This paper discusses open phase faults, which can happen in a system grid-converter-motor drive, and measures to properly handle this type of fault. The authors of this paper provide classification of algorithms used for the detection of the loss of phase and explain the distinctive features of each group of methods. They review existing algorithms, which are based on the analysis of the current signals, discuss their pros and cons and suggest possible areas of usage for each group of methods. The authors also propose one novel method for detection of open phase, which was developed for low-cost systems with low resolution analog-to digital converters (ADC). This paper mainly considers methods for three-phase motors as the most popular machines, however some algorithms can be used in multiphase drives. The authors of the paper also share their more than 20 years’ experience combined, in this area, which was obtained by developing industrial and commercial drives, and focus on the requirements of the IEC/UL 60730 safety standard, where the phase-loss detection algorithm is one of the essential parts of control system.

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Phase Loss Detection Using Current Signals: A Review

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

Nowadays, a quiet working and living environment is very important to people, therefore makers of home appliances, who tightly compete with each other, wage war on every decibel. As a result, methods of decreasing noise pollution have become a popular topic, attracting the attention of researchers. This article studies the braking of reciprocating compressors and its impact on the additional noise and vibrations at the stoppage. The manuscript explains the nature of these undesirable phenomena and proposes solutions to decrease them. The author analyzed conventional solutions and experimentally checked them. The results of these experiments proved that considered noise decreasing techniques are not applicable to the developing device, thus a new method has to be proposed. The author proposed several new techniques of compressor braking and checked them experimentally. Based on the analysis of these experiments, the method with better performance was selected for further study and improvements. The main innovation of the proposed method is the usage of exact mechanical position of the rotor to start braking and exclude reverse rotation of the piston, which produces noise. This article demonstrates that the proposed method eliminates additional noise and vibrations at the stoppage of reciprocating compressors, therefore, it is recommended for use in new motor drives. Taking into account the significant improvement of the acoustic profile of the proposed braking algorithm, it was included in the control algorithm of reciprocating compressors in mass production.

Stoppage Noise Reduction of Reciprocating Compressors

This paper proposes speed estimation method for the incremental position encoders. This method uses variable angular path to keep the bandwidth and accuracy in the specified range regardless of the current speed. This paper also describes existing speed estimation methods, their strong and weak points. Moreover, non-idealities of the incremental encoders are discussed and compensation algorithm is proposed. Proposed speed estimation algorithm uses period-based calculation method with the variable angular path. The experimental results obtained in the flux-vector control system of a Permanent Magnet Synchronous Motor (PMSM) prove feasibility and show perfect performance of the algorithm even in the low speed range at startup.

Speed estimation algorithm with specified bandwidth for incremental position encoder

The protection of the adjustable speed induction motor drives is usually implemented using single-mass thermal model. For more precise estimation of the thermal condition of electrical machine it is advisable to use more complex several-mass models. In this study it was investigated that for frequency regulated machines their rotor can be represented as a single thermal mass. That research allows to simplify the thermal model and to recommend three-mass model for implementation to protect the machine from overheat by means of control system. The recommended masses are rotor, stator windings, and stator iron. The experiments were conducted using 5.5 kW squirrel cage induction machine and proved that its rotor has a single time constant purely visible in the temperature transient.

Rotor Thermal Model for Real-time Protection in Adjustable Induction Motor Drives

The electrical equipment needs testing after manufacturing. This can be done in the operational environment or using specialized test benches. The special test bench can help to examine all possible operation modes including fault conditions. This paper considers the design of an IGBT driver test bench. Each operating condition can be separately tested to ensure the manufacturing quality of the IGBT driver sample. The simulation results are provided for the fault condition tests.

Development of an IGBT Driver Test Bench

The unmanned aerial vehicles and aircraft electric propulsion systems use propellers to create a lifting force or thrust. Over last years their penetration in our life is growing with the quadcopters for photography and filming, delivery services, and other applications. This rases a problem of safety when starting the propellers, and many solutions use sound generation by the propulsion motors to attract attention of human and warn him from being harmed by the blades. This sound is replacing the command "Clear Prop!"—a phrase said before a propeller is starting up by the pilot to ensure there is no one in the area of the propeller. The sound is generated by feeding the motor windings with some current having frequency in the audible range prior to start of the motors. This paper considers two implementations of the sound generation using melody and recorded sound. The melody is defined by notes or tones and their durations, and the sound is recorded as 8-bit mono pulse-code modulation data. The algorithms for implementation are presented as well as samples of the sound playback.

Implementation of a "Clear Prop!" Function in Propulsion Inverter of Electric Aircraft

Moscow Metro has signal systems that ensure the safety of train traffic, such as automatic speed control system and centralization and interlocking systems. The traction electric drive of a metro train should not interfere with the operation of rail devices during standstill or movement. The main harmonics of the traction current are harmonics multiple of 300 Hz, appearing during rectification of the alternating voltage, and harmonics multiple of 50 Hz, in case of partial faults in traction substation. To reduce the influence of the harmonic composition of the traction electric drive, the frequencies encoding the information signals are chosen in intermediate ranges. However, during the movement of the train, the frequency of the motor and, consequently, of the currents change. Being superimposed on the main harmonic of 300 Hz, the amplitude of these frequencies can be amplified and create interference in the signals of automatic speed control and collision prevention control systems. This paper proposes an algorithmic way to reduce the harmonic composition of traction current, based on the repetitive control method. The algorithm was tested on the traction electric drive of a subway train couch and showed a 10-fold decrease in the harmonic amplitude of 300 Hz.

Ksenia Fedorova

Papers

Speed estimation algorithm with specified bandwidth for incremental position encoder

Rotor Thermal Model for Real-time Protection in Adjustable Induction Motor Drives

Development of an IGBT Driver Test Bench

Implementation of a "Clear Prop!" Function in Propulsion Inverter of Electric Aircraft

Repetitive Control Method for Suppression of Higher Harmonics in Supply Current of Subway Couches