A regenerative braking energy recuperation from elevator operation in building by active rectifier

Elevators- means of vertical transportation to carry people and goods are an indispensable part in offices, high-rise buildings, hospitals, commercial areas, hotels, car-parks when blooming urbanization develops worldwide. However, the level of energy consumption in elevator operation is significant, so energy saving solutions have been outlined and applied in practice. With frequent braking phases, regenerative braking energy is wasted on braking resistors. Therefore, this paper proposes regenerative braking energy recuperation method for elevator operation in building by active rectifiers enabling the braking energy to be fed back into utility grid. Simulation results conducted by MATLAB with data collected from OCT5B building-RESCO new urban area, Ha noi, Vietnam have verified saving energy of using active rectifiers replacing diode rectifiers up to 33%.

Methods of improving power indices of electric drive active rectifiers for mine hoists

The research deals with analyzing peculiarities of using active rectifiers in frequency controlled electric drives of underground mine hoists. There are developed MATLAB models aimed at comparing two types of control systems – hysteresis-based and the one with pulse-width modulation. The research aims to analyze power modes and parameters of active rectifiers, quality of voltage control, current and power of active rectifiers and to determine ways of improving power indices of electric equipment of hoists as well as provide power compatibility of electric equipment and underground mines’ grids. Main attention is paid to analyzing circuitry of control systems of active rectifiers, parameters of power transformers and reactor equipment at underground mines’ substations, frequency converters and synchronous slow-speed motors. There are also analyzed statistic data on power consumption at underground mines equipped with automated systems of commercial and technical power meters and specific consumption of power. The research results reveal advantages of the pulse-width modulation control system as compared with the hysteresis one by using such indices as speed-performance, quality of control, potential of controlling reactive power and the power factor. Application of the research results will enable determining structures and methods of adjusting control over the active rectifier in the frequency-controlled drive of underground mine hoists.

Development and research of improved PWM algorithm of an active rectifier with variable switching angle tables

Modern electric drives of rolling mills are based on frequency converters with active rectifiers (AR). During operation, active rectifiers consume non-sinusoidal current, having a negative effect on the supply network. In order to improve the performance index of voltage quality, AR special algorithms of pulse-width modulation are used. Selective harmonic elimination (SHE) PWM algorithm has become widespread. However, application of SHE PWM algorithm does not always allow to optimize the operation of the AR under the conditions of changing parameters of the electro-technical complex under various operating modes. Therefore, a solution is needed to improve the electrical power quality index of plant networks with powerful frequency converter with AR. To carry out the research, a mathematical model of the frequency converter with active rectifiers was implemented with an improved PWM algorithm in the Matlab-Simulink environment based on the parameters of the main electric drive of the 2000 cold rolling mill “LPC-11” of PJSC “ММК”. The main assumption of the simulation model is that the inverter is represented as a current source. An improved algorithm with the ability to select tables of switching angles based on SHE PWM has been developed. The operation of the FC with AR with the proposed improved PWM algorithm with variable tables of switching angles has been investigated. A comparative analysis of the instantaneous values of AR voltages and currents when transferring to the tables with similar switching angles and significantly different ones has been made. It has been found that changing the tables of switching angles does not have a significant negative effect on the operation of the FC with AR. The proposed improved PWM algorithm can be used to improve the performance index of power quality in electrotechnical complexes with FC and AR by using optimal tables of switching angles in conditions of various modes of the power supply system. The adequacy of the simulation model has previously been confirmed by experimental data and previous studies.