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The object of the study is a frequency converter based on IPC technology. The purpose of the study is to determine the device's performance characteristics by means of a mathematical apparatus describing the area of existence of operating modes for active and reactive power. On the basis of combinatorial laws, variants of non-repeating states of thyristor keys were obtained. The initial phases of active and reactive power components are determined by varying in accordance with the cosine law with two non-repeating combinations of key switching on each pair of conjugate reactive elements. The input of two constants made it possible to simplify the arguments influencing the magnitude and direction of the transmitted power by the device. A comparative analysis of the regime parameters and the characteristics obtained with the help of the simulation model and calculated by the proposed method confirms the identity of the results. The error of the method fluctuates between 0.5% and 1.5%. The developed method made it possible to determine a number of unique variants of the transmitted power level when adjusting the angle \(\delta_{sr}\) in the range from 0º \(\div\)360º . This allows to adjust the magnitude and direction of the transmitted power when "sliding" or slow and arbitrary frequency changes. Thus, the proposed method made it possible to determine with a high degree of accuracy the domain of existence of the regime parameters with the construction of switching diagrams of keys to maintain an ordered unidirectional power flow with frequency matching by the device under study.

Purpose of this work is in the development and modification of control scheme and of basic algorithms of discontinuous space-vector modulation for synchronous and balanced regulation of multi-inverter topology of six-phase open-end winding installation with four insulated dc sources. This purpose has been achieved due to including in the control and modulation scheme of specialized control correlations connecting coefficients of modulation of inverters, required power ratio between dclinks, and voltages of the corresponding dc sources. So, basic novelty of this research is in the fact, that the elaborated and investigated control and modulation algorithms for installation on the base of inverters with discontinuous space-vector modulation (with both 300 -non-switching intervals and 600 - non-switching intervals) insure both required power sharing capability between dc links and advanced harmonic composition (without even harmonics and subharmonics) of spectra of the phase and line voltages of six-phase installation. Mutual comparison of behavior of system with two basic schemes of modified discontinuous pulsewidth modulation (PWM) has been executed. Investigation of harmonic composition of the phase voltage of multi-inverter system illustrates an important fact, that for the all analyzed control modes, connected with balanced adjustment of drive under different conditions, phase voltage of installation has symmetry for any control regimes, including control modes with fractional frequency ratios between switching frequency of converters and fundamental frequency of installation, with absence in its spectra of undesirable subharmonics. Factor of minimization of subharmonics in spectra of voltage and current of ac drives of different topologies is especially important for the medium-voltage medium-power installations on the basis of PWM converters.

The paper presents deal with the heat pump designed mainly for heat supply systems using the qualitative law of regulation of the heat supply mode (constant flow rate of the heat carrier). For this purpose, an air-to-water heat pump with carbon dioxide as a refrigerant and compressor driven be gas piston unit is used. The aim of the work is to develop a scheme in which the position of the operating point of the heat pump compressor does not depend on fluctuations in the refrigerant flow rate, as well as using the heat produced by the gas engine - driven by the heat pump compressor. This goal achieves by elaboration of internal heat exchangers with an adjustable heat exchange surface area. The heat exchange surface area regulates by installing of an intermediate heat-conducting cylindrical element between the refrigerant and thermal agent circuits. The intermediate cylindrical element moved by using, for example, an electric stepper drive. The conditions, under which the sleeve can be considered as a thermally thin body. To increase the COP of the heat pump (HP), the additional heat exchanger, installed at the outlet of the ejector used in the pump has been used. It is. In the heat exchanger, the working fluid has been heated by using the waste heat of the gas piston unit (GPU. It had been shown that in the temperature control loop the PI controller may be used, and to compensate for the flow rate pulsations, it is necessary to use a combined control system.

The work deals with the development of a control system for heat exchangers with variable surface area of heat transfer, used, in particular, for heat pumps intended primarily for heat supply systems using the high-quality law of regulation of the heat supply mode (with a constant flow rate of the heat carrier). The aim of the work is to develop a scheme for the control of a heat exchanger with a variable surface area of heat exchange in which main disturbances will be compensated: i.e. the temperature of the heat carrier, heat carrier’s flowrates, and changes in the thermophysical parameters of the heat carriers. This goal has been achieved using a custom PID controller in the contour of control of the drive of the moving heat-insulating insert. To solve this problem, we obtained the equations of the statics of the heat exchanger with regard to the adjustable insert, the dynamic model of the heat exchanger taking into account this insert. The novelty of the work is control laws of an adjustable heat-conducting insert between the primary and secondary coolants of the heat exchanger, which allow compensating the main disturbances, which influence the heat exchanger. A method has been developed for solving differential-integral equations of heat exchanger statics with an insert (HEI), which allowed analytically expressing the ratio of average integral heat carrier temperatures in a heat exchanger depending on the heat exchanger length, which allows building a control system for a heat exchanger with a variable heat exchange surface area.

The scope of the work is to study the steady-state symmetrical load modes of operation of a new promising phase-regulating transformer circuit. This allows obtaining the value of the designed capacity of device. The device is based on a three-phase transformer windings connection into hexagon circuit, equipped with additional three phase regulating autotransformer, connected to hexagon circuit in a special manner. Besides, it should be equipped with semi-conductor switching keys, which give the possibility to control fast transition processes. The proposed circuit gives the possibility to round regulation of phase angle in the range of 0-360°, so the device could be used as frequency converter for flexible tie between energy systems with different frequencies and belongs to the group of FACTs controllers. The autotransformer provides the possibility of fine adjustment of the phase angle of the output three-phase voltage, so maintaining the flow of active power in the interconnection line. One of the most important features of such devices is the value of calculated designed capacity, which determines demand of the active materials for such devices. The scope of the work was achieved by conducted analytical study, based on electrical and transformer circuit’s theory. The currents in the windings of the device in symmetrical load modes were calculated for several variants of the phase-regulating unit circuit’s diagrams. On their basis, the maximum values of the devices currents and designed capacity for a number of the considered variants of circuits were determined, allowing a comparative analysis of different circuit modifications.

The paper aims to provide argumentation of centralized district heating system use from the consideration of harmlessness for both public health and environment, in comparison with the use of individual heating units, installed in residential areas of the Chisinau municipality. Proposed goal have been reached performing the comparison on quantitative harmful emissions resulting from the operation of these two types of heating, using emissions factors, deducted from the specific consumption of thermal energy. The issue's relevance is proved by the existence of considerable number of disconnected users from the centralized heating, though last years, this trend is decreasing. As regard to new buildings, they continue to give priority to the individual heating. Statistical data provided by specialized institutions of the municipality underlines the increased share of incidents of intoxication with combustion products, namely carbon oxide, followed by poisoning from gas leaks, shingles caused by explosions in violation of the operating rules of such equipment, also registering lethal cases. New results are the determination of the difference in emission values for both cases. The importance of the obtained results is that for the generation of thermal energy in a centralized heating system using cogeneration technology, harmful emissions into the environment are 28% less than when using individual heat supply systems. This received ascertainment could serve as an important argumentation for the obvious priority of the centralized heating system in the municipality versus the use of individual units.

The purpose of this research is to determine the effective way of implementation of the control algorithm, as an important functional part of information and control computer systems. The search criterion is the minimum of internal hardware FPGA resources required for the control unit implementation. This criterion allows miniaturization of dimensions, improves reliability by reducing the number of interconnections inside the chip, and ensures the possibility of a compact arrangement of various system components, which is especially important when using the “system-on-chip” design technology. The control unit holds a prominent place in the digital information and control systems. A comparative analysis of two control unit models represented as a finite state machine with either hard or programmable logic was proposed. Advantages and disadvantages of both models were determined according to the peculiarities of the information and control system algorithms, and, it was proved that the FSM model with a programmable logic matched these peculiarities in a greater degree. The purpose of this study was achieved due to the application of the proposed method for the implementation of the FSM with the programmable logic using the embedded memory of the FPGA and ProASIC chips. The main result was a substantial decrease in the LUT number used. The experimental results were obtained applying the chips of the world's top manufacturers - Xilinx, Altera/Intel, Microsemi. The studies were carried out based on the onboard computing complex control algorithm.

The aim of the work is to develop technical measures to improve the quality of the power transmission process through electrical link, which contains a frequency converter based on a PST (phase-shifting transformer) with circular rotation of the output voltage phase in relation to the input, made according to the triangle scheme and controlled by means of power electronics. To achieve this goal, the use of longitudinal inductive elements (chokes) has been proposed as one of the measures that significantly improves the controlled mode parameters in the process of frequency conversion. The problem has been solved by performing computational experiments on simulation models of electrical links, combining two power systems with a frequency of 60 and 50 Hz, respectively. The structure of electrical links at various stages of the study has included several circuit variants of a frequency converter (single-channel circuit, dual-channel with reversing control winding sections, dual-channel circuit without reversing control winding sections) and has developed by authors earlier. In the process of research, the value of inductance of chokes has been changed, as well as their place of connection. The controlled transmission's characteristics have been analyzed as well. The novelty of the work lies in the use of longitudinally included inductive elements as a possible solution to the problem of improving the quality of power transmission when combining power systems with different operating frequencies using static frequency converters. The optimal values of the parameters of inductive elements, comprised between 0.03-0.035Hn for all circuit versions of the converter, have been identified.