Quantitative and qualitative indicators of the modernization of the electric drive of a pumping unit of a network with throttle control of the coolant supply of a centralized heat supply system are determined. The possibility of modernizing the electric drive by replacing outdated electric motors of energy efficiency class IE1, which are still used in electric drives of pumping units, with electric motors of energy efficiency classes IE2 and IE3 from different manufacturers, has been substantiated. The energy consumption was calculated based on the technical data of the pump and electric motors provided by the manufacturers and includes the calculation of the energy consumption of pumping units in a typical operating cycle typical for district heating networks, which involves operation at reduced load for a long time. Comparative calculated data on the daily and annual energy consumption of the considered electric motors in a typical operating cycle of a pumping unit, with respect to the least energy-efficient electric motor among those considered, were obtained. The practical significance of the results obtained is to understand that the selection of an electric motor by efficiency at variable load, i.e., actually on the basis of the IE energy efficiency class assigned in accordance with the IEC 60034-30-1 standard, is incorrect, It is substantiated that the choice should be made using the efficiency interpolated by the method of polynomial interpolation of the motor loss curve, while taking into account the economic feasibility of choosing an electric motor between energy efficiency classes, in this case IE2 and IE3, and different manufacturers.

The quantitative and qualitative parameters of the frequency regulation of the electric drive of the pumping units of the centralized heat supply network were determined. The necessity and possibility of using the frequency-regulated electric drive of pumping units in the networks of centralized heat supply, in the mode of their operation of quantitative and qualitative regulation of the coolant supply, is well-founded. The frequency control parameters were calculated on the basis of technical data related to the operating mode, where the flow rate of the coolant changes according to the hydraulic load typical for HVAC applications defined by the European Union Regulation, as well as the technical data of the pump, frequency converter and electric motors provided by the manufacturers. The definition of parameters concerns the operation of pumping units in a typical operating cycle characteristic of district heating networks, which involves operation with a reduced load for a long time. The results were obtained that correspond to the range of the speed of rotation of the electric drive, its power, torque, coolant supply and hydraulic pressure of the pump in a real typical network of centralized heat supply. The practical significance of the obtained results is that they can be used for the modernization of the electric drive of pumping units of the centralized heat supply network, which until now are operated with non-regulated electric drives based on an asynchronous motor with a short-circuited rotor and throttle regulation of the coolant supply.

Approaches to determining the structure of the reactive power consumed by the electric drive of pumping units of the centralized heat supply network are substantiated, and recommendations are given for their application when conducting their energy audit for the development of measures to increase their power factor. A method for calculating the reactive energy consumed by both the frequency converter and the drive asynchronous electric motor is defined. The dependence of the reactive power consumed by the electric motor on its torque and the dependence of the reactive power consumed by the frequency converter on the power of the electric motor and its torque have been established. These dependencies are set for the proportional control mode u/f=const. The results prove that the main part of the consumed reactive power falls on the electric motor and depends on its operating modes, mainly on the amount of its load. The reactive power consumed by the frequency converter depends on the power and torque of the drive electric motor in accordance with its operating mode and is a small part of the total reactive power consumed by the electric drive. The proposed approach allows the energy auditor, when conducting an energy audit of frequency-regulated electric drives of pump units of the centralized heat supply network, to preliminarily, using a simplified procedure, estimate the amount of reactive energy consumed by the electric drive and the modes of operation and the compliance of the modes of operation of the centralized heat supply network with technological requirements.

The relationship between thermodynamic and hydraulic parameters of the heat supply network has been established. The dependence of the electric power consumed by the electric drive of the pump unit on the pressure and supply of the coolant was determined. It is proved that the regulated electric drive system has advantages over the non-regulated electric drive system in the context of energy efficiency of the pumping unit and the district heating network in general. Approaches and criteria for the synthesis of a regulated electric drive system, including its automatic control system, were determined, regulation methods were analyzed, and the most acceptable version of the electric drive was chosen: a controlled frequency converter - an asynchronous motor with a short-circuited rotor, taking into account the above, an energy-saving mechanical system of a centralized heat supply network was synthesized. The peculiarity of this system is that the protection of parameters of hydraulic and temperature regimes in the network of centralized heat supply is ensured with the help of extreme automatic control systems. At the same time, the assignment of mode parameters is provided by the temperature controller of the heat exchange point of the network. Regulation of the pressure and productivity of the pumping unit is carried out by changing, according to a certain law, the frequency and power supply of the asynchronous motor. Встановлено взаємозвязок термодинамічних та гідравлічних параметрів мережі централізованого теплопостачання. Визначено залежність споживаної електричної потужності електроприводом насосного агрегату від гідравлічного напору та кількості подачі теплоносія. Доведено, що система регульованого електроприводу має переваги над системою нерегульованого електроприводу в контексті енепгоефективності насосного агрегату та мережі централізованого теплопостачання загалом. Визначено підходи та критерії до синтезу системи регулюваного електроприводу, в тому числі системи його автоматичного керування. Проаналізованого методи регулювання та обрано найбільш прийнятний варіант електроприводу: керований перетворювач частоти – асинхронний двигун з короткозамкненим ротором. З урахуванням вище наведеного, синтезовано енергозберігаючу електромеханічну систему мережі централізаваного теплопостачання. Особливістю цієї системи є те, що дотримання параметрів гідравлічного та температурного режимів в мережі централізованого теплопостачання забезпечується за допомогою екстремальних систем автоматичного керування. При цьому завдання режимних параметрів здійснюється температурним регулятором теплообмінного пункту мережі. Регулювання напору та продуктивності насосного агрегату здійснюється за рахунок зміни, за певним законом, частоти та напруги живлення асинхронного двигуна.

The transition to energy independence requires the application of flexible approaches and the diversification of distributed energy generation technologies. This article substantiates the feasibility of using a hybrid power supply system incorporating renewable generation sources and a cogeneration plant to enhance the reliability of power supply to centralised heat supply boiler houses. Criteria and approaches to structuring and balancing the hybrid system are proposed, based on an analysis of the nature of electricity consumption and the nature of generation by its structural elements, using the example of Ukraine’s district heating enterprises. The structure of the hybrid system has been determined, taking into account seasonal variations in operation and the stochastic nature of load and generation, whilst applying economic and environmental approaches in accordance with the institutional requirements of the European Union and Ukraine. A discrete mathematical model of the energy balance with a system of technical constraints is proposed to justify the parameters of the hybrid system’s components. It is proposed that the parameters of the structural elements of the photovoltaic power station, wind power station, storage battery and cogeneration plant be determined on the basis of actual electricity consumption data from a district heating boiler house. Operating modes of the hybrid power supply system have been established depending on technological requirements and conditions for integration with the centralised electricity grid. The results obtained can be used in the design of hybrid power supply systems for district heating enterprises.