Wastewater treatment plant residual pressure power generation system based on large and small units and its control method

Abstract

The invention discloses a wastewater treatment plant residual pressure power generation system based on large and small units, including a main pipeline and a bypass pipeline connected in parallel therewith; the main pipeline is provided with a pressure gauge, a main pipeline flow meter and a main pipeline electric valve in sequence along the water flow direction; the inlet of the bypass pipeline is located between the main pipeline flow meter and the main pipeline electric valve, and the outlet is connected to the main pipeline outlet; the bypass pipeline is provided with a bypass pipeline flow meter, an inlet electric valve, large and small unit power generation units and an outlet electric valve in sequence along the water flow direction. Also disclosed is a control method of the system, including a main pipeline control method and a large and small generator control method, by starting a large generator to generate electricity under a large flow and high pressure, and starting a small generator to generate electricity under a low flow and low pressure, the system does not require a converter, the control structure is simpler, the power generation reliability is strong, and it is suitable for wastewater treatment water residual pressure power generation with unstable water volume.

Description

Technical Field

[0001] The present invention belongs to the technical field of power generation, and in particular relates to a wastewater treatment plant surplus pressure power generation system based on large and small units. The present invention also relates to a wastewater treatment plant surplus pressure power generation system control method based on large and small units. Background Art

[0002] In the water purification and discharge process of the sewage treatment plant, due to a certain height difference, a large return water residual pressure is often generated in the drainage system. This part of the residual pressure can drive the turbine to generate electricity, and the generated electricity can also be incorporated into the power grid for use, thereby achieving the goal of energy conservation and emission reduction. However, the incoming water has unstable characteristics, and the water flow in the pipeline is difficult to control, which can easily cause large fluctuations in the power generation, affecting the actual use of power generation. In view of this, it is particularly necessary to develop a power generation system that can adapt to both large flow and small flow to achieve efficient energy recovery.

[0003] A Chinese invention patent application with a publication date of 2024-03-29 and publication number CN117780545A discloses a sewage treatment water residual pressure power generation system and a control method. The application scheme uses a relatively complex doubly fed speed-changing unit, and a back-to-back converter is required for control. The control method is relatively complex and its reliability is limited by the converter. Summary of the invention

[0004] The purpose of the present invention is to provide a wastewater treatment plant residual pressure power generation system based on large and small units. The system adopts large and small unit power generation units and has a simpler structure.

[0005] Another object of the present invention is to provide a control method for a wastewater treatment plant residual pressure power generation system based on large and small units.

[0006] The technical solution adopted by the present invention is a wastewater treatment plant residual pressure power generation system based on large and small units, including a main pipeline and a bypass pipeline connected in parallel therewith; The main pipeline is provided with a pressure gauge, a main pipeline flow meter and a main pipeline electric valve in sequence along the water flow direction, and the main pipeline electric valve is connected to a main pipeline control unit; The inlet of the bypass pipeline is located between the main pipeline flow meter and the main pipeline electric valve, and the outlet is connected to the main pipeline outlet; the bypass pipeline is sequentially provided with a bypass pipeline flow meter, an inlet electric valve, large and small unit power generation devices and an outlet electric valve along the water flow direction, and the large and small unit power generation devices are connected to the large and small unit power generation units.

[0007] The present invention is also characterized in that: The large and small units of power generation devices include a turbine, the turbine is coaxially connected to a large generator and a small generator, the large generator and the small generator are commonly connected to a motor converter, the motor converter is connected to the power grid through a cable, and a power sensor is provided at the connection point.

[0008] The main pipeline control unit includes a guide vane opening controller, and the guide vane opening controller is also connected to the pressure gauge, the main pipeline flow meter and the turbine through signal lines.

[0009] The turbine is a tubular turbine.

[0010] The power generation units of large and small units include a power value generator and an optimization controller. The power value generator is connected to the bypass pipe flow meter and the turbine through signal lines, the power value generator and the power sensor are connected to the optimization controller through signal lines, and the optimization controller is connected to the motor converter through signal lines.

[0011] Another technical solution of the present invention is a control method for a wastewater treatment plant residual pressure power generation system based on large and small units, including a main pipeline control method and a large and small generator control method.

[0012] Another technical solution of the present invention is also characterized in that: The main pipeline control method is specifically as follows: the guide vane opening controller calculates the power of the water flow in the main pipeline based on the main pipeline water flow pressure fed back by the pressure gauge and the main pipeline water flow rate fed back by the main pipeline flowmeter; when the water flow power is less than the maximum design power of the turbine, the guide vane opening controller controls the main pipeline electric valve to close, and opens the inlet electric valve and the outlet electric valve; when the water flow power is greater than or equal to the maximum design power of the turbine, the guide vane opening controller controls the main pipeline electric valve to open, and the inlet electric valve and the outlet electric valve remain open.

[0013] The large and small generator control method comprises the following steps: Step 1: The bypass pipe flow meter collects the water flow of the bypass pipe in real time and feeds it back to the power value generator, and the power value generator calculates the output power Pret according to the water flow of the bypass pipe and the speed of the turbine; Step 2: The power sensor collects the output power P of the motor converter and feeds it back to the optimization controller. The optimization controller compares P with Pret through a comparison element and outputs P* to feed back to the motor converter. Step 3: The motor converter controls the large generator or the small generator to start according to the value of P*.

[0014] The comparison method of P and Pret in step 2 is: If the deviation between P and Pret is less than or equal to 3%, the P* value tracks Pret; If the deviation between P and Pret is greater than 3%, after a delay of minutes, re-judge whether the deviation between P and Pret is still greater than 3%. If so, first perform PID calculation based on the deviation, and then normalize the calculated result as P*; if not, the P* value continues to track Pret.

[0015] Step 3 is as follows: Set the switching power value Ps of the large and small generators, and set the error bandwidth d of Ps; When P*≤Ps-d, the motor converter controls the small generator to operate and generate electricity; when P*>Ps+d, the motor converter controls the large generator to operate and generate electricity; If the small generator is running to generate electricity and P* gradually increases, when P*>Ps+d, the motor converter controls the small generator to switch to the large generator to generate electricity; if the large generator is running to generate electricity and P* gradually decreases, the motor converter controls the large generator to switch to the small generator to generate electricity.

[0016] The beneficial effects of the present invention are: 1. The present invention connects a bypass pipeline in parallel between the flow meter of the drainage main pipeline and the electric valve of the main pipeline, and sets the power generation devices of the large and small units in the bypass pipeline. The large and small generators are coaxially arranged to form an integrated variable speed operation. The system does not require a converter, which can not only improve the efficient operation of the hydraulic unit when the water flow changes greatly, but also improve the control reliability.

[0017] 2. By setting large and small generators, the present invention can enable the system to operate efficiently in the range of low pressure and low flow to high pressure and high flow, thereby improving the operating range of the system and increasing the power generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of the present invention; In the figure: 1. pressure gauge, 2. main pipeline flow meter, 3. bypass pipeline flow meter, 4. main pipeline electric valve, 5. inlet electric valve, 6. outlet electric valve, 7. turbine, 8. guide vane opening controller, 9. power value generator, 10. large generator, 11. small generator, 12. optimization controller, 13. power sensor, 14. motor converter. DETAILED DESCRIPTION

[0019] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Example 1 A wastewater treatment plant residual pressure power generation system based on large and small units, such as Figure 1As shown, it includes a main pipeline, and the main pipeline is provided with a pressure gauge 1, a main pipeline flow meter 2 and a main pipeline electric valve 4 in sequence along the drainage water flow direction, and the main pipeline electric valve 4 is connected to the main pipeline control unit through a signal line. It also includes a bypass pipeline, one end of the bypass pipeline is connected to the main pipeline between the main pipeline flow meter 2 and the main pipeline electric valve 4, and the other end is connected to the water outlet of the main pipeline. The bypass pipeline is provided with a bypass pipeline flow meter 3, an inlet electric valve 5, a large and small unit power generation device and an outlet electric valve 6 in sequence along the drainage water flow direction, and the large and small unit power generation device is connected to the large and small unit power generation unit through a signal line.

[0021] Example 2 A wastewater treatment plant residual pressure power generation system based on large and small units, such as Figure 1 As shown, it includes a main pipeline, and the main pipeline is provided with a pressure gauge 1, a main pipeline flow meter 2 and a main pipeline electric valve 4 in sequence along the drainage water flow direction, and the main pipeline electric valve 4 is connected to the main pipeline control unit through a signal line. It also includes a bypass pipeline, one end of the bypass pipeline is connected to the main pipeline between the main pipeline flow meter 2 and the main pipeline electric valve 4, and the other end is connected to the water outlet of the main pipeline. The bypass pipeline is provided with a bypass pipeline flow meter 3, an inlet electric valve 5, a large and small unit power generation device and an outlet electric valve 6 in sequence along the drainage water flow direction, and the large and small unit power generation device is connected to the large and small unit power generation unit through a signal line.

[0022] The large and small generator sets include a turbine 7, the water inlet of the turbine 7 is connected to the inlet electric valve 5, and the water outlet of the turbine 7 is connected to the outlet electric valve 6. The turbine 7 is coaxially connected with a large generator 10 and a small generator 11, and both the large generator 10 and the small generator 11 are connected to a motor converter 14 through a signal line. The motor converter 14 is used to control the switching of the large and small generators. At the same time, the large generator 10 and the small generator 11 are also connected to the motor converter 14 through a wire. The motor converter 14 is connected to the power grid through a cable to transmit the power of the large generator 10 or the small generator 11 to the power grid. The output end of the motor converter 14 is provided with a power sensor 13 for real-time acquisition of the output power of the generator.

[0023] Example 3 A wastewater treatment plant residual pressure power generation system based on large and small units, such as Figure 1As shown, it includes a main pipeline, and the main pipeline is provided with a pressure gauge 1, a main pipeline flow meter 2 and a main pipeline electric valve 4 in sequence along the drainage water flow direction, and the main pipeline electric valve 4 is connected to the main pipeline control unit through a signal line. It also includes a bypass pipeline, one end of the bypass pipeline is connected to the main pipeline between the main pipeline flow meter 2 and the main pipeline electric valve 4, and the other end is connected to the water outlet of the main pipeline. The bypass pipeline is provided with a bypass pipeline flow meter 3, an inlet electric valve 5, a large and small unit power generation device and an outlet electric valve 6 in sequence along the drainage water flow direction, and the large and small unit power generation device is connected to the large and small unit power generation unit through a signal line.

[0024] The large and small generator sets include a turbine 7, the water inlet of the turbine 7 is connected to the inlet electric valve 5, and the water outlet of the turbine 7 is connected to the outlet electric valve 6. The turbine 7 is coaxially connected with a large generator 10 and a small generator 11, and both the large generator 10 and the small generator 11 are connected to a motor converter 14 through a signal line. The motor converter 14 is used to control the switching of the large and small generators. At the same time, the large generator 10 and the small generator 11 are also connected to the motor converter 14 through a wire. The motor converter 14 is connected to the power grid through a cable to transmit the power of the large generator 10 or the small generator 11 to the power grid. The output end of the motor converter 14 is provided with a power sensor 13 for real-time acquisition of the output power of the generator.

[0025] The main pipeline control unit includes a guide vane opening controller 8, which is respectively connected to the pressure gauge 1, the main pipeline flow meter 2, the main pipeline electric valve 4 and the turbine 7 through signal lines. It can control the opening and closing of the main pipeline electric valve 4 according to the pressure measured by the pressure gauge 1 and the flow measured by the main pipeline flow meter 2. When the water flow rate of the main pipeline is too large and the water flow power exceeds the maximum design power of the turbine 7, the guide vane opening controller 8 controls the opening of the main pipeline electric valve 4 to maintain the safety of the turbine 7 and the large and small units of the power generation unit, otherwise the main pipeline electric valve 4 is closed.

[0026] Example 4 A wastewater treatment plant residual pressure power generation system based on large and small units, such as Figure 1 As shown, it includes a main pipeline, and the main pipeline is provided with a pressure gauge 1, a main pipeline flow meter 2 and a main pipeline electric valve 4 in sequence along the drainage water flow direction, and the main pipeline electric valve 4 is connected to the main pipeline control unit through a signal line. It also includes a bypass pipeline, one end of the bypass pipeline is connected to the main pipeline between the main pipeline flow meter 2 and the main pipeline electric valve 4, and the other end is connected to the water outlet of the main pipeline. The bypass pipeline is provided with a bypass pipeline flow meter 3, an inlet electric valve 5, a large and small unit power generation device and an outlet electric valve 6 in sequence along the drainage water flow direction, and the large and small unit power generation device is connected to the large and small unit power generation unit through a signal line.

[0027] The large and small generator power generation device includes a turbine 7, which is a tubular turbine. The water inlet of the turbine 7 is connected to the inlet electric valve 5, and the water outlet of the turbine 7 is connected to the outlet electric valve 6. The turbine 7 is coaxially connected with a large generator 10 and a small generator 11. The large generator 10 and the small generator 11 are both connected to a motor converter 14 through a signal line. The motor converter 14 is used to control the switching of the large and small generators. At the same time, the large generator 10 and the small generator 11 are also connected to the motor converter 14 through a wire. The motor converter 14 is connected to the power grid through a cable to transmit the power of the large generator 10 or the small generator 11 to the power grid. The output end of the motor converter 14 is provided with a power sensor 13 for real-time acquisition of the output power of the generator.

[0028] The main pipeline control unit includes a guide vane opening controller 8, which is respectively connected to the pressure gauge 1, the main pipeline flow meter 2, the main pipeline electric valve 4 and the turbine 7 through signal lines. It can control the opening and closing of the main pipeline electric valve 4 according to the pressure measured by the pressure gauge 1 and the flow measured by the main pipeline flow meter 2. When the water flow rate of the main pipeline is too large and the water flow power exceeds the maximum design power of the turbine 7, the guide vane opening controller 8 controls the opening of the main pipeline electric valve 4 to maintain the safety of the turbine 7 and the large and small units of the power generation unit, otherwise the main pipeline electric valve 4 is closed.

[0029] Example 5 A wastewater treatment plant residual pressure power generation system based on large and small units, such as Figure 1 As shown, it includes a main pipeline, and the main pipeline is provided with a pressure gauge 1, a main pipeline flow meter 2 and a main pipeline electric valve 4 in sequence along the drainage water flow direction, and the main pipeline electric valve 4 is connected to the main pipeline control unit through a signal line. It also includes a bypass pipeline, one end of the bypass pipeline is connected to the main pipeline between the main pipeline flow meter 2 and the main pipeline electric valve 4, and the other end is connected to the water outlet of the main pipeline. The bypass pipeline is provided with a bypass pipeline flow meter 3, an inlet electric valve 5, a large and small unit power generation device and an outlet electric valve 6 in sequence along the drainage water flow direction, and the large and small unit power generation device is connected to the large and small unit power generation unit through a signal line.

[0030] The large and small generator power generation device includes a turbine 7, which is a tubular turbine. The water inlet of the turbine 7 is connected to the inlet electric valve 5, and the water outlet of the turbine 7 is connected to the outlet electric valve 6. The turbine 7 is coaxially connected with a large generator 10 and a small generator 11. The large generator 10 and the small generator 11 are both connected to a motor converter 14 through a signal line. The motor converter 14 is used to control the switching of the large and small generators. At the same time, the large generator 10 and the small generator 11 are also connected to the motor converter 14 through a wire. The motor converter 14 is connected to the power grid through a cable to transmit the power of the large generator 10 or the small generator 11 to the power grid. The output end of the motor converter 14 is provided with a power sensor 13 for real-time acquisition of the output power of the generator.

[0031] The main pipeline control unit includes a guide vane opening controller 8, which is respectively connected to the pressure gauge 1, the main pipeline flow meter 2, the main pipeline electric valve 4 and the turbine 7 through signal lines. It can control the opening and closing of the main pipeline electric valve 4 according to the pressure measured by the pressure gauge 1 and the flow measured by the main pipeline flow meter 2. When the water flow rate of the main pipeline is too large and the water flow power exceeds the maximum design power of the turbine 7, the guide vane opening controller 8 controls the opening of the main pipeline electric valve 4 to maintain the safety of the turbine 7 and the large and small units of the power generation unit, otherwise the main pipeline electric valve 4 is closed.

[0032] The large and small units of the power generation unit include a power value generator 9 and an optimization controller 12. The bypass pipe flow meter 3 and the turbine 7 are connected to the power value generator 9 through a signal line. The power value generator 9 calculates the optimal shaft power of the turbine according to the bypass pipe flow meter 3 and the unit speed of the turbine 7. The power value generator 9 and the power sensor 13 are both connected to the optimization controller 12 through a signal line. The optimization controller 12 controls the switching of the motor converter 14 to the large generator 10 and the small generator 11 according to the optimal shaft power output by the power value generator 9 and the generator output power fed back by the power sensor 13.

[0033] Example 6 A control method for a wastewater treatment plant residual pressure power generation system based on large and small units: including a main pipeline control method and a large and small generator control method.

[0034] The main pipeline control method specifically includes the following steps: Step 1: The pressure gauge 1 measures the water pressure data of the main pipeline in real time and transmits it to the guide vane opening controller 8 through the signal line; the main pipeline flow meter 2 measures the flow data of the main pipeline in real time and transmits it to the guide vane opening controller 8 through the signal line; Step 2, the guide vane opening controller 8 calculates the power of the water flow in the main pipeline according to the water pressure and flow rate of the main pipeline. When the power is less than the maximum design power of the turbine 7, the guide vane opening controller 8 closes the main pipeline electric valve 4 by controlling the guide vane opening, and opens the inlet electric valve 5 and the outlet electric valve 6; When the power is greater than or equal to the maximum design value of the turbine 7 , the inlet electric valve 5 and the outlet electric valve 6 remain open, and the guide vane opening controller 8 controls the opening of the main pipeline electric valve 4 .

[0035] The control method of large and small generators specifically includes the following steps: Step 1: The bypass pipe flow meter 3 measures the flow data of the bypass pipe in real time and transmits it to the power value generator 1. The power value generator 9 calculates the output power Pret according to the flow data of the bypass pipe and the speed data of the turbine 7; Step 2, the power sensor 13 collects the output power P of the motor converter 14 and transmits it to the optimization controller 12, and the optimization controller 12 compares P with Pret through a comparison element to obtain P*; If the deviation between P and Pret is less than or equal to 3%, the P* value tracks Pret; If the deviation between P and Pret is greater than 3%, after a delay of 2 minutes, re-judge whether the deviation between P and Pret is still greater than 3%. If so, PID calculation is first performed based on the deviation, and then the calculated result is normalized and used as P*; if not, the P* value continues to track Pret, and P* is output after the comparison is completed.

[0036] Step 3, the motor converter 14 selects the corresponding large generator 10 or small generator 11 according to the P* value. Specifically, first set the large and small generator switching power value Ps, and set the error bandwidth d for the switching value; when the output power value P* is less than or equal to Ps-d, the motor converter 14 controls the small generator 11 to run and generate electricity, and the large generator 10 is turned off; when the output power value P* is greater than Ps+d, the motor converter 14 controls the large generator 10 to run and generate electricity, and the small generator 11 is turned off; when the output power value P* changes from small to large, and the small generator generates electricity, when P* increases to greater than Ps+d, the motor converter 14 controls the small generator 11 to switch to the large generator 10 for power generation; when the output power value P* changes from large to small, and the large generator generates electricity, when P* decreases to less than Ps-d, the motor converter 14 controls the large generator 10 to switch to the small generator 11 for power generation.

[0037] According to the fluctuation of water inflow in a sewage treatment plant, the efficiency of the motor will drop rapidly under low power conditions. The use of large and small units for power generation can increase the power generation by about 20%. The use of this system can expand the scope of application of hydraulic units and improve the efficiency of the system.

Claims

1. The wastewater treatment plant residual pressure power generation system based on large and small units is characterized by: It includes a main pipeline and a bypass pipeline connected in parallel therewith; The main pipeline is provided with a pressure gauge (1), a main pipeline flow meter (2) and a main pipeline electric valve (4) in sequence along the water flow direction, and the main pipeline electric valve (4) is connected to a main pipeline control unit; The inlet of the bypass pipeline is located between the main pipeline flow meter (2) and the main pipeline electric valve (4), and the outlet is connected to the main pipeline outlet; the bypass pipeline is provided with a bypass pipeline flow meter (3), an inlet electric valve (5), large and small unit power generation devices and an outlet electric valve (6) in sequence along the water flow direction, and the large and small unit power generation devices are connected to the large and small unit power generation units.

2. The wastewater treatment plant residual pressure power generation system based on large and small units according to claim 1 is characterized in that: The large and small generator sets power generation device comprises a water turbine (7), the water turbine (7) being coaxially connected to a large generator (10) and a small generator (11), the large generator (10) and the small generator (11) being commonly connected to a motor converter (14), the motor converter (14) being connected to a power grid via a cable, and a power sensor (13) being provided at the connection point.

3. The wastewater treatment plant residual pressure power generation system based on large and small units according to claim 2 is characterized in that: The main pipeline control unit comprises a guide vane opening controller (8), and the guide vane opening controller (8) is also respectively connected to the pressure gauge (1), the main pipeline flow meter (2) and the turbine (7) through signal lines.

4. The wastewater treatment plant residual pressure power generation system based on large and small units according to claim 2 or 3 is characterized in that: The water turbine (7) is a tubular water turbine.

5. The wastewater treatment plant residual pressure power generation system based on large and small units according to claim 4 is characterized in that: The large and small generator power generation units include a power value generator (9) and an optimization controller (12); the power value generator (9) is connected to a bypass pipeline flow meter (3) and a water turbine (7) via signal lines, respectively; the power value generator (9) and a power sensor (13) are connected to the optimization controller (12) via signal lines, respectively; and the optimization controller (12) is connected to a motor converter (14) via signal lines.

6. The control method of the wastewater treatment plant residual pressure power generation system based on large and small units according to any one of claims 1-5, characterized in that: It includes main pipeline control method and large and small generator control method.

7. The control method of the wastewater treatment plant residual pressure power generation system based on large and small units according to claim 6 is characterized in that: The main pipeline control method is specifically as follows: The guide vane opening controller (8) calculates the power of the water flow in the main pipeline according to the main pipeline water flow pressure fed back by the pressure gauge (1) and the main pipeline water flow rate fed back by the main pipeline flow meter (2). When the water flow power is less than the maximum design power of the turbine (7), the guide vane opening controller (8) controls the main pipeline electric valve (4) to close, and opens the inlet electric valve (5) and the outlet electric valve (6); when the water flow power is greater than or equal to the maximum design power of the turbine (7), the guide vane opening controller (8) controls the main pipeline electric valve (4) to open, and the inlet electric valve (5) and the outlet electric valve (6) remain open.

8. The control method of the wastewater treatment plant residual pressure power generation system based on large and small units according to claim 6 is characterized in that: The large and small generator control method comprises the following steps: Step 1, the bypass pipe flow meter (3) collects the water flow of the bypass pipe in real time and feeds it back to the power value generator (9), and the power value generator (9) calculates the output power Pret according to the water flow of the bypass pipe and the rotation speed of the turbine (7); Step 2, the power sensor (13) collects the output power P of the motor converter (14) and feeds it back to the optimization controller (12). The optimization controller (12) compares P with Pret through a comparison element, and then outputs P* and feeds it back to the motor converter (14). Step 3, the motor converter (14) controls the large generator (10) or the small generator (11) to start according to the value of P*.

9. The control method of the wastewater treatment plant residual pressure power generation system based on large and small units according to claim 8 is characterized in that: The method for comparing P and Pret in step 2 is: If the deviation between P and Pret is less than or equal to 3%, the P* value tracks Pret; If the deviation between P and Pret is greater than 3%, after a delay of 2 minutes, re-judge whether the deviation between P and Pret is still greater than 3%. If so, first perform PID calculation based on the deviation, and then normalize the calculated result as P*; if not, the P* value continues to track Pret.

10. The control method of the wastewater treatment plant residual pressure power generation system based on large and small units according to claim 8 is characterized in that: The step 3 is specifically as follows: Set the switching power value Ps of the large and small generators, and set the error bandwidth d of Ps; When P*≤Ps-d, the motor converter (14) controls the small generator (11) to operate and generate electricity, and when P*>Ps+d, the motor converter (14) controls the large generator (10) to operate and generate electricity; If the small generator (11) is running to generate electricity and P* gradually increases, when P*>Ps+d, the motor converter (14) controls the small generator (11) to switch to the large generator (10) to run to generate electricity; if the large generator (10) is running to generate electricity and P* gradually decreases, the motor converter (14) controls the large generator (10) to switch to the small generator (11) to run to generate electricity.

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