An electrically driven vapor-compressor balancing valve control system and method

Abstract

The present application relates to the technical fields, specifically relates to a kind of electric drive steam compressor balance valve control system and method, electric drive steam compressor balance valve control system, including compressor, gas pipeline, gas pipeline, bypass pipeline, balance valve, import pressure sensor, export pressure sensor, drive motor, frequency converter and control cabinet;Import pressure sensor detects compressor gas inlet pressure, export pressure sensor detects compressor gas outlet pressure, drive motor is adjusted frequency by frequency converter, and frequency converter sends drive motor actual operation current signal, actual operation frequency signal, actual operation power signal to control cabinet, and control cabinet acquires compressor gas inlet pressure and gas outlet pressure, while control cabinet receives balance valve opening degree feedback, and control cabinet controls the opening degree of balance valve according to drive motor actual operation frequency, so that the opening degree of balance valve can be dynamically adjusted according to needs, and energy consumption is saved.

Description

Technical Field

[0001] This invention relates to the field of compressor technology, and in particular to a control system and method for a balance valve of an electrically driven steam compressor. Background Technology

[0002] The steam compressor is the core equipment in the MVR system, and its stable operation is one of the important conditions for the operation of the entire MVR system.

[0003] MVR systems operate under complex and variable conditions. Under extreme conditions, steam compressor surge can occur, leading to mechanical damage and insufficient aerodynamic performance. Existing remedial measures for steam compressor surge involve connecting the inlet and outlet of the steam compressor with pipes and installing a balancing valve (regulating valve) on the connected pipes. Under normal circumstances, the balancing valve is fully closed. Once the steam compressor surges, the balancing valve opens until the surge disappears. However, because the balancing valve is in a constantly open state, the steam flowing from the steam compressor outlet through the balancing valve into the steam compressor inlet increases power consumption. This increased power consumption is ineffective for the entire MVR system and is considered wasted power. Therefore, it is necessary to improve the control method of the balancing valve to save energy. Summary of the Invention

[0004] The purpose of this invention is to provide a control system and method for a balancing valve of an electric steam compressor, which can dynamically adjust the opening of the balancing valve as needed to save energy.

[0005] To achieve the above objectives, in a first aspect, the present invention provides an electric-driven steam compressor balance valve control system, comprising a compressor, an outlet pipe, an inlet pipe, a bypass pipe, a balance valve, an inlet pressure sensor, an outlet pressure sensor, a drive motor, a frequency converter, and a control cabinet.

[0006] The outlet pipe is connected to the compressor outlet, the inlet pipe is connected to the compressor inlet, the bypass pipe is connected to the outlet pipe and the inlet pipe at both ends, the balance valve is installed on the bypass pipe, the inlet pressure sensor is installed on the inlet pipe, the outlet pressure sensor is installed on the outlet pipe, the drive motor is installed on one side of the compressor, the frequency converter is connected to the drive motor, and the control cabinet is connected to the balance valve, the inlet pressure sensor, the outlet pressure sensor, and the frequency converter.

[0007] Secondly, the present invention also provides a method for controlling the balance valve of an electrically driven steam compressor, comprising:

[0008] The compressor inlet pressure is detected by an imported pressure sensor, and the compressor outlet pressure is detected by an outlet pressure sensor.

[0009] The actual operating current, actual operating frequency, and actual operating power of the drive motor are sent to the control cabinet via the frequency converter.

[0010] The control cabinet controls the opening degree of the balancing valve according to the actual operating frequency.

[0011] The control cabinet controls the opening degree of the balancing valve according to the actual operating frequency, including:

[0012] When the actual operating frequency is less than the preset frequency threshold, the control cabinet adjusts the opening of the balance valve according to the actual operating current.

[0013] When the actual operating frequency is greater than or equal to the preset frequency threshold, the control cabinet adjusts the opening of the balance valve according to the actual operating power.

[0014] Wherein, when the actual operating frequency is greater than or equal to a preset frequency threshold, the control cabinet adjusts the opening of the balancing valve according to the actual operating power, including:

[0015] When the actual operating frequency is greater than or equal to the preset frequency threshold, the control cabinet will use the actual operating power of the drive motor as the actual operating power of the compressor, and calculate the theoretical boundary power of the compressor based on the compressor inlet pressure and outlet pressure.

[0016] If the actual operating power of the compressor minus the theoretical boundary power is less than the margin, the balance valve is adjusted to increase in advance, and when the actual operating power is greater than the sum of the theoretical boundary power and the margin, the balance valve is kept at its current opening.

[0017] If the actual operating power of the compressor minus the theoretical boundary power is greater than or equal to the margin, and the actual operating power is greater than the recorded power, then the opening of the balance valve will decrease by 1% every preset interval until the opening of the balance valve is 0.

[0018] This invention discloses a control system and method for a balancing valve of an electrically driven steam compressor. The outlet pipe and the inlet pipe are connected to the relevant steam interface of an MVR system for supplying steam to and from the compressor. An inlet pressure sensor detects the compressor inlet pressure, and an outlet pressure sensor detects the compressor outlet pressure. The drive motor's frequency is adjusted by a frequency converter. The frequency converter sends the actual operating current signal, actual operating frequency signal, and actual operating power signal of the drive motor to a control cabinet. The control cabinet collects the compressor inlet and outlet pressures and receives feedback on the balancing valve opening. The control cabinet controls the opening of the balancing valve according to the actual operating frequency of the drive motor, thereby dynamically adjusting the balancing valve opening as needed and saving energy. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of a balance valve control system for an electrically driven steam compressor according to the present invention.

[0021] Figure 2 This is a flowchart of a method for controlling the balance valve of an electrically driven steam compressor according to the present invention.

[0022] Figure 3 This is a flowchart illustrating how the control cabinet of the present invention controls the opening degree of the balancing valve according to the actual operating frequency.

[0023] Figure 4 This is a flowchart of the present invention showing how the control cabinet adjusts the opening of the balance valve according to the actual operating power when the actual operating frequency is greater than or equal to a preset frequency threshold.

[0024] Figure 5 This is a flowchart of the low-frequency balancing valve control of the present invention.

[0025] Figure 6 This is a flowchart of the high-frequency balancing valve control of the present invention.

[0026] 1-Compressor, 2-Outlet pipe, 3-Inlet pipe, 4-Bypass pipe, 5-Balance valve, 6-Inlet pressure sensor, 7-Outlet pressure sensor, 8-Drive motor, 9-Inverter, 10-Control cabinet. Detailed Implementation

[0027] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0028] Please see Figures 1-6 In a first aspect, the present invention provides an electric steam compressor balance valve control system, comprising a compressor 1, an outlet pipe 2, an inlet pipe 3, a bypass pipe 4, a balance valve 5, an inlet pressure sensor 6, an outlet pressure sensor 7, a drive motor 8, a frequency converter 9, and a control cabinet 10.

[0029] The outlet pipe 2 is connected to the outlet of the compressor 1, the inlet pipe 3 is connected to the inlet of the compressor 1, the two ends of the bypass pipe 4 are connected to the outlet pipe 2 and the inlet pipe 3 respectively, the balance valve 5 is installed on the bypass pipe 4, the inlet pressure sensor 6 is installed on the inlet pipe 3, the outlet pressure sensor 7 is installed on the outlet pipe 2, the drive motor 8 is installed on one side of the compressor 1, the frequency converter 9 is connected to the drive motor 8, and the control cabinet 10 is connected to the balance valve 5, the inlet pressure sensor 6, the outlet pressure sensor 7, and the frequency converter 9 respectively.

[0030] In this embodiment, the outlet pipe 2 and the inlet pipe 3 are connected to the relevant steam interface of the MVR system for supplying steam to the compressor 1. The inlet pressure sensor 6 detects the inlet pressure of the compressor 1, and the outlet pressure sensor 7 detects the outlet pressure of the compressor 1. The frequency of the drive motor 8 is adjusted by the frequency converter 9. The frequency converter 9 sends the actual operating current signal, actual operating frequency signal, and actual operating power signal of the drive motor 8 to the control cabinet 10. The control cabinet 10 collects the inlet pressure and outlet pressure of the compressor 1. At the same time, the control cabinet 10 receives feedback on the opening degree of the balance valve 5. The control cabinet 10 controls the opening degree of the balance valve 5 according to the actual operating frequency of the drive motor 8, thereby dynamically adjusting the opening degree of the balance valve 5 as needed and saving energy.

[0031] Secondly, the present invention also provides a method for controlling the balance valve of an electrically driven steam compressor, comprising:

[0032] S1 detects the inlet pressure of compressor 1 through inlet pressure sensor 6 and the outlet pressure of compressor 1 through outlet pressure sensor 7;

[0033] The outlet pipe 2 and the inlet pipe 3 are connected to the relevant steam interface of the MVR system for supplying steam to the compressor 1. The inlet pressure sensor 6 detects the inlet pressure of the compressor 1 and sends the data to the control cabinet 10. The outlet pressure sensor 7 detects the outlet pressure of the compressor 1 and sends the data to the control cabinet 10.

[0034] S2 sends the actual operating current, actual operating frequency, and actual operating power of the drive motor 8 to the control cabinet 10 via the frequency converter 9.

[0035] The frequency of the drive motor 8 is adjusted by the frequency converter 9, and the frequency converter 9 sends the actual operating current, actual operating frequency and actual operating power of the drive motor 8 to the control cabinet 10.

[0036] S3 control cabinet 10 controls the opening degree of balance valve 5 according to the actual operating frequency;

[0037] The specific steps are as follows:

[0038] S31 When the actual operating frequency is less than the preset frequency threshold, the control cabinet 10 adjusts the opening of the balance valve 5 according to the actual operating current.

[0039] The compressor 1 converts the energy of the drive motor 8 into steam kinetic energy through a high-speed rotating impeller. The steam kinetic energy is then converted into steam pressure energy. The steam kinetic energy is proportional to the square of the rotational speed. Therefore, when the compressor 1 operates at low speed, it has very little pressure energy, which is insufficient to meet the requirements of the MVR system. The compressor 1 will only function in the MVR system when the rotational speed exceeds a certain value. The compressor 1 adjusts the actual operating frequency of the drive motor 8 through the frequency converter 9. The actual operating frequency of the drive motor 8 determines the rotational speed of the steam compressor 1. The compressor 1 will inevitably operate at low frequency throughout its entire operating cycle. Therefore, the compressor 1 is divided into two operating stages: low frequency (actual operating frequency of drive motor 8 < f, where f represents a preset frequency threshold) and high frequency (actual operating frequency of drive motor 8 ≥ f). Different control strategies for the balance valve 5 are formulated for the two operating stages of the compressor 1. The value of f can be adjusted according to whether the compressor 1 meets the compression ratio required for MVR. The set value is generally around 75% of the rated frequency. When the actual operating frequency of the drive motor 8 is less than f, the balance valve 5 is adjusted in real time according to the operating current of the steam compressor 1. Since the entire MVR system is a closed loop system, when the actual operating frequency of the compressor 1 is less than f, the outlet pressure of the compressor 1 is too low to drive the steam to flow in the entire MVR system. In order to ensure the flow of steam at the outlet of the compressor 1, the balance valve 5 needs to be opened to allow the compressor 1 to self-circulate (the steam at the outlet of the compressor 1 enters the inlet loop of the compressor 1 through the balance valve 5). The larger the opening of the balance valve 5, the better the flow of steam at the outlet of the compressor 1. The opening of the balance valve 5 gradually increases as the frequency of the compressor 1 increases and gradually decreases as the frequency of the compressor 1 decreases. The basis for increasing and decreasing the opening of the balance valve 5 is the operating current of the compressor 1 (derived from the actual operating current of the frequency converter 9). The purpose is to ensure that the operating current of the compressor 1 does not exceed the rated current.

[0040] S32 When the actual operating frequency is greater than or equal to the preset frequency threshold, the control cabinet 10 adjusts the opening of the balance valve 5 according to the actual operating power;

[0041] The specific steps are as follows:

[0042] S321 When the actual operating frequency is greater than or equal to the preset frequency threshold, the control cabinet 10 uses the actual operating power of the drive motor 8 as the actual operating power of the compressor 1, and calculates the theoretical boundary power of the compressor 1 based on the inlet pressure and outlet pressure of the compressor 1.

[0043] When the actual operating frequency of compressor 1 is ≥ f (where f represents a preset frequency threshold), the actual operating power of drive motor 8 is collected as the actual operating power of compressor 1. The inlet and outlet pressures of compressor 1 are collected to calculate the theoretical boundary power of compressor 1.

[0044] S322 If the actual operating power of compressor 1 minus the theoretical boundary power is less than the margin, the balance valve 5 will be adjusted to increase in advance, and when the actual operating power is greater than the sum of the theoretical boundary power and the margin, the balance valve 5 will be kept at its current opening.

[0045] The theoretical boundary power calculation parameters are the factory parameters of compressor 1. Under normal circumstances, the actual power is greater than the theoretical boundary power. Once the actual power drops below the theoretical boundary power, compressor 1 will experience surge. The actual power and theoretical boundary power are acquired in real time by controllers such as PLC or DCS, and are continuous data that changes over time. The comparison between the actual power and the theoretical boundary power is used as the basis for increasing or decreasing the opening of the balance valve 5. Based on this basis, appropriate technical processing is performed to derive the control method for the balance valve 5. Figure 6 As shown, the actual power Wtx and Wty are the actual power at times x and y, respectively, and the theoretical boundary power Wtx and Wty are the theoretical boundary power at times x and y, respectively. The theoretical boundary power is the data obtained from real-time signal acquisition, and the margin Mg and the recorded power W are values ​​that do not change with time.

[0046] To prevent actual surge damage to compressor 1, proactive control is implemented. When the actual power minus the theoretical boundary power is less than the margin Mg (Mg is set as a percentage of the actual power; the higher the power of compressor 1, the larger Mg becomes), the balance valve 5 is adjusted and increased in advance. The increase is related to the current opening value of the balance valve 5 and the flow characteristics of the balance valve 5 itself. Generally, the opening of a regulating valve and the flow rate are not linearly related. The same increase in amount does not necessarily increase the flow rate at different openings. Therefore, the opening of the balance valve 5 is segmented, with each segment corresponding to a specific increase. For example, the 0-100% opening of the balance valve 5 is divided into three segments: 0-A1%, A1%-A2%, and A2%-100%, corresponding to increases of B1%, B2%, and B3%, respectively. When the current opening of the balance valve 5 is at 0-A1%, and the actual power minus the theoretical boundary power is less than the margin Mg, the opening of the balance valve 5 is increased by B1%, and so on. Values ​​A1 and A2 are in the range of 0-100, and A1 < A2. Values ​​B1 to B3 are in the corresponding range, and B1 > B2 > B3. As the opening of the balance valve 5 increases, both the actual power and the theoretical boundary power change. Once the actual power exceeds the theoretical boundary power + margin Mg, the balance valve 5 maintains its current opening, and the actual power is assigned to the recorded power W.

[0047] S323 If the actual operating power of compressor 1 minus the theoretical boundary power is greater than or equal to the margin, and the actual operating power is greater than the recorded power, then the opening of balance valve 5 will decrease by 1% every preset interval until the opening of balance valve 5 is 0.

[0048] Under the premise that actual power - theoretical boundary power ≥ margin Mg and actual power > recorded power W, the opening of balancing valve 5 decreases by 1% every fixed time interval T until the opening of balancing valve 5 is 0. The time interval T is generally taken as less than 1 minute. As the actual power and theoretical boundary power continuously change, balancing valve 5 will automatically increase or decrease its opening. When the load of the MVR system decreases, compressor 1 needs to operate at a reduced frequency. The actual power will decrease and will no longer exceed the recorded power W. Therefore, after the frequency is reduced, the recorded power W will be reset to zero, and balancing valve 5 will close. During the closing process, a new moment occurs where actual power - theoretical boundary power < Mg. The recorded power W will be assigned a new value, and balancing valve 5 can then adjust at the new frequency. The PLC or DCS controller executes program statements in a loop, and the program controls balancing valve 5 to achieve dynamic adjustment.

[0049] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for controlling the balancing valve of an electrically driven steam compressor, characterized in that, The control system for a balancing valve of an electric steam compressor includes a compressor, an outlet pipe, an inlet pipe, a bypass pipe, a balancing valve, an inlet pressure sensor, an outlet pressure sensor, a drive motor, a frequency converter, and a control cabinet. The outlet pipe is connected to the outlet of the compressor, the inlet pipe is connected to the inlet of the compressor, the two ends of the bypass pipe are connected to the outlet pipe and the inlet pipe respectively, the balance valve is installed on the bypass pipe, the inlet pressure sensor is installed on the inlet pipe, the outlet pressure sensor is installed on the outlet pipe, the drive motor is installed on one side of the compressor, the frequency converter is connected to the drive motor, and the control cabinet is connected to the balance valve, the inlet pressure sensor, the outlet pressure sensor, and the frequency converter respectively. The method for controlling the balance valve of the electric-driven steam compressor includes: The compressor inlet pressure is detected by an imported pressure sensor, and the compressor outlet pressure is detected by an outlet pressure sensor. The actual operating current, actual operating frequency, and actual operating power of the drive motor are sent to the control cabinet via the frequency converter. The control cabinet controls the opening degree of the balancing valve according to the actual operating frequency, specifically including: When the actual operating frequency is less than the preset frequency threshold, the control cabinet adjusts the opening of the balance valve according to the actual operating current. When the actual operating frequency is greater than or equal to a preset frequency threshold, the control cabinet adjusts the opening of the balancing valve according to the actual operating power, specifically including: When the actual operating frequency is greater than or equal to the preset frequency threshold, the control cabinet will use the actual operating power of the drive motor as the actual operating power of the compressor, and calculate the theoretical boundary power of the compressor based on the compressor inlet pressure and outlet pressure. If the actual operating power of the compressor minus the theoretical boundary power is less than the margin, the balance valve is adjusted to increase in advance. When the actual operating power is greater than the sum of the theoretical boundary power and the margin, the balance valve is kept at its current opening, and the actual operating power is assigned to the recorded power. If the actual operating power of the compressor minus the theoretical boundary power is greater than or equal to the margin, and the actual operating power is greater than the recorded power, then the opening of the balance valve will decrease by 1% every preset interval until the opening of the balance valve is 0.

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