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Relevance. When operating submersible equipment for oil production in aggressive environments and transferring wells to the cyclic operation mode, a decrease in the service life of the submersible installation for oil production is observed. In the first case, this is due to the formation of salt deposits and clogging of the working parts of the electric pump with mechanical impurities. In the second case – an increase in the number of starts of the submersible electric motor. To solve the existing problems, it is possible to implement closed control systems for submersible electric motors based on state variable observers, which determines the relevance of the study. Aim. To develop an observer with operational monitoring of the angular velocity of the rotor and the moment of resistance on the shaft of a submersible asynchronous motor at inconsistency of the initial conditions in various operating modes and its testing using modeling tools. Methods. The observer is built on the basis of known engine models in a fixed coordinate system α, β, the theory of IIR-filters to obtain a forecast of estimates of the angular velocity of the rotor and the torque on the shaft and their correction in real time. Results. The authors have proposed the original structure of an observer with operational monitoring of the angular velocity of the rotor and the moment of resistance on the shaft of a submersible asynchronous motor. Conclusions. The paper demonstrates the observer performance with inconsistency of initial conditions and electric motor model data in various operating modes. In all modes, stable estimates of the speed and torque of resistance on the electric motor shaft are obtained. At the same time, the error in estimating the angular velocity under the condition of changing the load on the shaft and starting in the loaded state is no more than 1.2%, which is acceptable in submersible electric motor control systems. It is revealed that the developed observer, under the condition of changing the active resistance of the stator and rotor in the ranges from –25 to +25% of the nominal value, obtains estimates of the angular velocity with an integral error of no more than 5%, except for starting the motor with a decrease in the active resistance of the rotor by 25% of the nominal value –5.53%, which is acceptable in engineering practice.

Relevance. The stock of oil wells in the Russian Federation, where production is carried out with the help of electric centrifugal pumps or electric-driven vane pumps, is expanding every year. This trend will continue for at least a couple of decades. In its turn, the number of wells with readily available oil products in the commissioned stock is decreasing. This leads to the need to improve production quality and reduce energy consumption to maintain profitability and production volumes. This can be achieved by implementing vector energy-efficient control systems for submersible motors based on observers of induction motor state variables. In this case one should take into account transients in the supply cable of considerable length, which transmits energy from a frequency converter to a motor. The observers are based on adjustable mathematical models that describe electrical, electromechanical and mechanical processes in electric drive and related process automation systems as reliably as possible. Using complex and cumbersome adjustable mathematical models in digital signal processors due to limited performance and memory causes objective difficulties in obtaining solutions of increased accuracy in real time. On this basis, the development of an analytical model of the dynamic system "long cable – submersible induction motor with fixed rotor" in the polar coordinate system is an urgent task. Aim. Development of analytical description of the mathematical model of the induction motor with a fixed rotor in the polar coordinate system taking into account the influence of a long cable. Methods. Electric drive theory, electric machine theory, mathematical models of submersible induction motors and reduced long cable model, Vandermonde's determinant, analytical methods for solving differential equations. Result and conclusions. The authors have developed an analytical model of the regulated induction motor with a fixed rotor in the polar coordinate system taking into account the supply cable of considerable length. The developed analytical model is recommended for use in vector energy-efficient electric drive with application of phase discrimination principles taking into account the influence of processes in the supply cable line. Such electric drive has a potential for increasing the profitability of oil production from low- and medium-debt wells.

Relevance. Today, one of the important trends in the Russian oil and gas industry is the increase in the fund of low-yield wells, in this regard, the improvement of technologies for mechanized production of low-yield wells is relevant. Installations of electric centrifugal pumps have become widespread in mechanized oil production, however, the operation of low-flow wells by electric centrifugal installations is accompanied by a number of complications, in particular, insufficient heat removal from the submersible engine by the flow in the well. A promising method of increasing the efficiency of electric-centric installations in low-flow wells is the implementation of a periodic short-term pumping mode. Object: thermal processes in the «submersible engine – borehole fluid» system of an electric centrifugal pump installation operating in a periodic short-term mode. The purpose of the research is to study the formation of a temperature field in a submersible electric motor and the fluid flowing around it during operation of an electric centrifugal pump in a periodic short-term mode. Methods: modeling of thermal processes in a well based on the numerical solution of the system of heat transfer equations in the «submersible engine – borehole fluid» system. Results. Based on the simulation results, it is shown that the temperature of the submersible electric motor and the liquid reaches maximum values at the initial stage during the well commissioning, during further operation of the well in a periodic short-term mode, the temperature of the submersible motor and the borehole fluid decreases significantly (the heating of the submersible motor and the liquid relative to the initial temperature decreases by more than 2 times). The influence of the power of the submersible engine (after the output of the well to the mode) on the thermal field in the well was investigated and it was found that with an increase in power, the heating of the submersible engine and the liquid increases in proportion to the degree of growth in power. The influence of the duration of pumping and accumulation periods on the temperature of the submersible engine and liquid (after the well is put into operation) has been studied. It is established that with an increase in the duration of the pumping period, the temperature of the submersible engine and the liquid grows, as a result, from the point of view of reducing the amplitude temperature of the electric centrifugal pump installation nodes in the periodic short-term mode, it is necessary to set the shortest possible periods of pumping and accumulation cycles. The results of numerical calculations are compared with experimental data and it is shown that the proposed model can be used to calculate the thermal regime of a submersible engine during operation of an electric center installation in a periodic short-term mode.

The article investigates the functioning of the electrotechnical complex of the electric centrifugal pump installation in case of variations in external temperature influences. A mathematical model of the analyzed complex is created taking the thermal nonstationary processes into account. It is also proposed to build an electromechanical system with an adjustable submersible electric motor with a subblock of parameter identification and a block for the estimation of state variables. This will allow considering external temperature influences during the control.

Relevance. Nowadays in the oil-producing fields of the Russian Federation the control stations of electric centrifugal pumps are widely used. They have the ability to change the engine speed. Such control stations can be used to increase or decrease the rotational speed of the installation to optimize the operation of the «centrifugal pump installation – formation» system. Accounting for thermal condition of the electric centrifugal pump installation is important for optimizing its operation. The use of asynchronous electric motors, which allows regulating the rotational speed of the drive without overheating the immersion part, improves the operational performance of immersion units. To date, there are no comprehensive theoretical studies on application of the control station with an adjustable frequency converter voltage. The aim of the research is to study thermal regime of a submersible installation depending on content of gas accumulated at the centrifugal pump intake. Object: installation of electric centrifugal submersible pumps (namely, their thermal regime). Results. The authors have studied the experimental results of operation of an electric centrifugal pump of the type ODI RA7-110-1500 with gas separator at frequencies of more than 50 Hz. Such field studies were carried out to assess the production capabilities of the well. The experiments were conducted at frequencies of 50, 52, 55 Hz, taking into account the content of gas accumulated in the reservoir oil at the intake of the centrifugal pump and its temperature. The analysis of the results of the experiments showed that the pressure of the centrifugal unit does not depend on the existing gas separator. Temperature mode of the submersible installation was studied taking into account water content of the reservoir oil, saturation pressure, gas factor containing gases such as nitrogen and methane, and pressure at the pump intake. It was established by analytical calculations that high content of free gas in the annular space of an oil well leads to increase in temperature mode of a submersible installation.