RU2591984C1 - Method for control of compressor shop - Google Patents

Abstract

FIELD: measurement technology.

SUBSTANCE: invention relates to operation of shop controls in compressor workshops compressor stations. In control method of compressor shop, which involves control of fuel gas consumption, load is changed in turn groups GCU, operating in line, for which two GCU group simultaneously change of rotation frequency of low-pressure turbine rotors in opposite directions at equal value. For neutralising effect of noise on measurement efficiency software filters are applied with large time constants. Measurement of changed efficiency is performed after time delay, exceeding at least 3…5 times of maximum time constant of filters. Direction of each rotor rpm change pitch of low pressure turbines is determined by the sign of increment efficiency obtained at previous step, the end of optimisation of the group is considered small increment efficiency or approximation of working point GCU to process limitation.

EFFECT: reduced consumption of fuel gas, higher efficiency of compressor shop.

1 cl, 1 dwg

Description

The invention relates to the field of operation of workshop controllers in the compressor shops of compressor stations in the main gas pipeline system and can be used to reduce fuel gas consumption consumed by the compressor shops of compressor stations in the main gas pipelines.

A known method of controlling the operation of a complex of assemblies of a compressor workshop, in which the pressure of the transported gas at the inlet and outlet of the superchargers is measured, the rotor speed of the superchargers, the value of the main gas parameter (output pressure or flow) of the compressor shop, which is compared with the set value of the main parameter, and then formed the control action on the fuel supply systems of the GPU drives included in the compressor shop (Patent No. RU 2181854 C1. Method for controlling a complex of units compressor shop / Applicant: Closed Joint-Stock Company Research and Production Company Sistema-Service, Open Joint-Stock Company Gazprom. - Publish. 04/27/2002). The required values of the rotor speeds of the supercharger rotors are determined using static functions, including the function of the dependence of the mechanical power on the supercharger shaft on the gas flow rate of the GPU drive. The frequency determination algorithm is as follows. For a given value of the workshop parameter (pressure or flow), the polytropic capacity of the workshop corresponding to this value is calculated. Further, using the above static functions, a series of complexes of values of the GPU rotation frequencies of the workshop that provide this polytropic power of the workshop, as well as the total fuel gas consumption corresponding to these complexes of the workshop as a whole, are found by calculation. Then, using the interpolation methods, the frequency set is found at which the required capacity of the workshop is ensured by the minimum fuel gas consumption in the workshop as a whole. After that, the corresponding values of the rotational speeds of the rotors of the superchargers are set for the GPU workshop as tasks.

The main disadvantage of this method is the key role in determining the optimal rotational speeds of the superchargers of theoretical static functions, which, despite the adjustment in the patent according to the measured real parameters of the gas compressor, are too coarse to take into account the individual characteristics and dependencies of the individual gas compressor.

There is also another way of regulating the workshop, in which, with a stable operating mode of the workshop, the workshop controller cyclically redistributes the load between individual gas compressor units in order to determine the sensitivity coefficient of each gas compressor unit, which characterizes the increment of the total fuel gas consumption of the compressor workshop with respect to the increment of power supplied by the compressor workshop to the gas pipeline when changing the power of the i-th GPU. Based on the coefficients determined in this way, such a distribution of power loads between gas compressor units is carried out that minimizes the fuel gas consumption of the workshop (Patent No. RU 2210006 C2. Workshop regulation method / Applicant: DK Ukrtransgaz (UA). - Publish. 08/10/2003) .

The sensitivity coefficient of each gas compressor unit is determined by modulating the rotation speed of this gas compressor unit with an infralow frequency F with modulation amplitude ΔN, at the same time incrementing the total fuel gas flow through the compressor workshop and incrementing a parameter characterizing the increment of power given by the compressor workshop to the gas pipeline when the power of this gas compressor unit changes after transient process and dividing the increment of the fuel gas flow rate by the increment of the parameter characterizing the power increment, given to the gas pipeline by GPA data, while the value of the infralow frequency F is chosen in the range from 0.005 to 0.02 Hz, the amplitude ΔN is in the range from 0.005 to 0.01 Nnom, and the modulation is carried out for 4-11 periods of infralow frequency.

The main disadvantage of this method is the extreme difficulty of its practical implementation (if at all possible), since in order to ensure that the adjustable workshop parameter (pressure, flow, compression ratio) meets the specified setpoint, change the rotational speed of the low-pressure turbine rotor by more than ± 20 ... 30 rpm is unacceptable (a trial change of mode is carried out at one gas compressor unit, and this leads to a deviation of the workshop parameter from the setpoint), which, in turn, makes it very difficult to identify the positive effect of changes in fuel gas consumption and workshops due to the strong noise of the fuel gas flow signal. The latter is compounded by the fact that the deviation of the fuel gas flow rate of the entire workshop is measured in order to highlight its change associated with this test change in the regime of one gas compressor unit.

This method is the closest to the claimed. It is selected as a prototype.

The basis of the invention is the task of improving the method (algorithm) for detecting changes in the fuel gas flow of the workshop during load redistribution between the gas compressor units of the compressor shop (CC) of the compressor station of the main gas pipeline while maintaining the specified workshop mode for the selected parameter (output pressure, flow rate, compression ratio).

The technical result of the proposed method is to reduce fuel gas consumption (increasing the efficiency of the CC).

The technical result is achieved by the fact that in the method of regulating the compressor shop, including controlling the fuel gas consumption of the compressor shop in relation to the power supplied by the shop to the gas pipeline (workshop efficiency), the loads of the gas compressor units working on the highway are changed in turn, for which two gas compressor stations are simultaneously changed the rotational speed of the rotors of low pressure turbines (HPH) in opposite directions by the same amount. To neutralize the effect of noise on the measurement of efficiency, software filters with large time constants are used. Measurement of the changed efficiency is carried out after a time delay exceeding at least 3 ... 5 times the maximum filter time constant. The direction of each step of changing the rotational speed of the TND rotors is determined by the sign of the efficiency increment obtained in the previous step, while the end of the optimization (maximizing the efficiency) of the group is considered to be a small (less than the dead band) increment of the efficiency or approximation of the GPU operating point to the technological limit. After the optimization of one group is completed, they proceed to the optimization of the following groups. The procedure is carried out cyclically.

The drawing shows the dependence of efficiency on the reduced flow rate Q _pref . The proposed method is designed to maximize the efficiency (minimize fuel gas consumption) of a full-pressure CC working in a two-stage mode in groups of two gas compressor units in a group connected in series.

,For two gas compressor units of the same group, the mass flow rate is the same, and the volumetric flow rate differs by the compression ratio of the first (along the gas) GPA (since the compression ratio is 1.15 ... 1.2, then the flow rates differ by 15 ... 20%). In the normal mode, the rotational speeds of both GPUs are almost the same (differ by 50 ... 150 rpm, which corresponds to the same distance from the limitations of both GPUs), their modes are indicated on the figure by dots A1, A2. For the gas compressor unit group (with similar characteristics), the most economical mode corresponds to the maximum speed of the first gas compressor unit along the gas flow and the minimum speed of the second (A.N. Kozachenko, V.I. Nikishin, B.P. Porshakov. Pipeline transport energy. M., 2001 city, ch. 3). This can be explained as follows: the drawing shows the dependence of the efficiency on the reduced flow

,

where Nnom = 4800 / min - nominal revolutions, N - current revolutions of the supercharger, Q - volumetric flow. Therefore, with an increase in the speed of the first gas unit, the flow rate is divided by a larger number, and the operating point of the first gas unit is shifted to position B1, a decrease in the speed of the second gas unit is offset by a shift in the operating point to position B2, and thus the efficiency reaches its maximum. At the same time, a change in the RPA of the GPA group in different directions has a number of additional positive properties. First, with such a change in speed, the flow rate of the group changes insignificantly, which mitigates the threat of introducing this group or the neighboring one into the surge. The second, general change in the group capacity is also insignificant, which contributes to maintaining the given workshop mode. The resulting slight deficit or excess of the total capacity of the workshop can be eliminated by a general (unidirectional) background change in the frequencies of the GPU of the workshop in the right direction. Finally, the simultaneous dilution of the frequencies of the superchargers allows you to make the effect of the change in efficiency more tangible in comparison with the prototype, since the total simultaneous trial change in the frequencies will be twice as much as that of the prototype.

In view of the above, the solution to the above problem is based on the principle of sequential optimization (maximizing efficiency) of gas compressor units operating on the highway. The efficiency of the group is calculated as the ratio of the total polytropic power of two gas compressor units to the total fuel gas consumption of two gas compressor units. Since some of the basic measured parameters (pressure drops on the constriction devices) fluctuate greatly, this makes it practically impossible to directly measure small changes in efficiency. (It is known that the theoretically achievable effect does not exceed 1 ... 1.5%, therefore, measurement of small increments of a highly noisy parameter is required (A.N. Kozachenko, V.I. Nikishin, B.P. Porshakov. Pipeline transport energy. M., 2001, Ch. 3).). In order to neutralize the influence of noise, the measured and calculated parameters are filtered by software filters with large time constants - of the order of 50 ... 90 s.

The proposed method works as follows. In the group to be optimized, the current efficiency value is stored and a test step is performed: a significant change in the speed of two gas compressor units in the group in different directions. For example, the first in the direction of the gas GPU increases the frequency by 50 rpm, and the second in the direction of the gas of the gas compressor decreases by 50 rpm (the total frequency change in two gas units is 100 rpm). As you know, a reliable value at the filter output is set after a time exceeding the filter time constant by at least 3 ... 5 times. Therefore, the measurement of the changed efficiency is made 5 minutes after the change of frequencies. The efficiency increment obtained as a result of the test step is calculated, and depending on the result obtained, the further direction of the optimization algorithm is selected. The result may be:

1. Positive. The test step turned out to be successful, and the algorithm repeatedly produces a similar change in rotational speeds;

2. Negative. The next step of the algorithm is to change the rotation frequencies of the GPA group in the directions opposite to the previous step;

3. Inessential. The efficiency increment lies within the dead band. The next step is the transition to the optimization of the next group. This can happen in the following cases:

- working points of the GPA group are close to points B1, B2 in the drawing - the optimization of this group is completed;

- operating points of both gas compressor units lie on one side of the curve maximum in the drawing - optimization in this mode is impossible;

- the technical condition of one or both of the GPA group does not allow to obtain a positive effect.

At each step, the remoteness of the operating point from technological limitations is controlled, and when the margin is reduced to less than 3 ... 5%, the optimization of the efficiency of this group ceases. In this case, the algorithm also proceeds to optimize the next group in turn.

Claims (1)

A method for regulating a compressor workshop, including controlling the fuel gas flow rate of the compressor workshop with respect to the power supplied by the workshop to a gas pipeline, characterized in that, to control the fuel gas flow rate, the workshops alternately change the loads of groups of gas pumping units (GPU) operating in the route, for which two gas compressor units the groups simultaneously change the rotational speeds of the rotors of low pressure turbines in opposite directions by the same amount, to neutralize the effect of noise on the measurement of efficiency, software filters with large time constants, the measurement of the changed efficiency is carried out after a time delay exceeding at least 3 ... 5 times the maximum filter time constant, the direction of each step of changing the rotational speed of the low pressure turbine rotors is determined by the sign of the efficiency increment obtained in the previous step, at This end of the optimization of the group is considered a small increase in efficiency or the approach of the GPU operating point to the technological limitation, after the optimization of one group is completed, the following groups procedure performed cyclically.

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