High-power Synchronous Machines Research Articles

Method for Stabilizing the Operation of Synchronous Machines Using a Virtual Load Sensor

The article considers the methods of increasing the stability of high-power synchronous machines when stabilizing the torque angle in the structure of the automatic excitation control system. A mathematical model of an electric machine in open and closed automatic control systems is obtained, studies of electromagnetic processes and analysis of existing and proposed optimal control systems are carried out. A contactless sensor of torque angle of the synchronous motor based on measuring the available parameters of the synchronous machine and allowing us to calculate the torque angle in static and dynamic modes of operation of synchronous generator and compatible with the new control system was developed. The presented excitation control system of synchronous machine with a measuring sensor of torque angle that provides higher performance in dynamic modes, as well as allowing to stabilize the reactive power, the power factor and the voltage on the stator of the synchronous machine.

Simulation and testing of single-supply back-to-back high-power synchronous machines

Of a special concern is the steady state and dynamic single-supply back-to-back operation of synchronous machines. This issue is of theoretical and practical interest in the field of electrical machines, especially high power, and there are no detailed references in the literature. The recoverable character of operation is fundamental. The dynamical process produced by coupling together of the two machines to network is analyzed. Important information regarding electromechanical stresses is obtained by simulation. The proposed test method at rated load is experimentally validated. It is quite appropriate for high-power machines, comparing with other methods. This study considerably increases the test capacity of limited power test bench.

A novel approach to reliable determination of surge armature current of a synchronous machine

Calculation of a short circuit current of a symmetrical fault in a high-power synchronous machine in accordance with national standards is time-consuming and imprecise. The process involves multiple graphic operations and a triple transition from an analog transient process to its discrete form and back. As a result, optimizing procedures cannot be applied to transient identification techniques that meet national standards and it is impossible to compensate for random factors in the identification process. Therefore, a surge current derived from experimental data is not adequate for transients in high-power synchronous machines. Modern equipment for recording of short-term transients solves many processing problems. Express determination of a surge current is obtained using a digital waveform recorder, which allows precise calculation of 50-Hz peaks and discrete representation of the 100-Hz component of the transients. This method of information extraction and processing replaces all the time-consuming graphic operations of the national standards. Results of a study of a 110-MW synchronous machine based on laboratory tests for various stator voltages are presented. The study has confirmed the viability of the proposed approach for express determination of a surge current without the need to determine the parameters of transients.

Probabilistic and statistical methods for studying transient high-power synchronous machines

The theoretical foundations of the probabilistic-statistical method based on the effective point samplings for the identification of transients in synchronous machines are given. For the first time, during the stand tests of a 110-MW turbogenerator in the experiment with sudden short-circuits, the processing has been performed based on hardware and digital primary information.

Modernization of probability and statistics methods of study of transient processes of high-power synchronous machines

The modernization of the theoretical basis of the probabilistic-statistical method, which is based on effective point sampling for the identification of transient processes of synchronous machines using the example of experience in symmetric sudden short circuits, is presented.

Experimental determination of synchronous machine reactances from DC decay at standstill

Measurement of parameters of high-power synchronous machines from steady-state or transient AC operational tests requires a great deal of electrical power. This paper presents a new application of a floating-point analog-to-digital converter which is employed in a microcomputer-embedded system that implements a standstill time response method to measure synchronous machine parameters. Floating-point quantization of the stator current response of a locked-rotor synchronous machine to a step signal is used to find the direct-axis and quadrature-axis reactances. Compared to previous solutions, this testing technique is characterized by higher precision, while still reducing the required power and minimizing the testing time. Simulated and experimental results are finally presented to compare the precision of this system with current state-of-the-art solutions.