System and method for in-pipe hydraulic turbines

Abstract

Systems and methods relating to power generation systems are disclosed. As an example, the power generation system includes a controller that adjusts the speed of a turbine located along a bypass conduit in accordance with downstream pressure via a regenerative drive. The power generation system further includes a bypass valve located along the bypass conduit for controlling the system pressure when the turbine is not adjusted in accordance with downstream pressure.

Description

Technical Field

[0001] References to related applications This application claims the benefit of priority to U.S. Non-Provisional Patent Application No. 18 / 190,672, filed Mar. 27, 2023, entitled “Systems and Methods for In-Duct Hydro Turbines”. The entire content of the above application is hereby incorporated by reference for all purposes.

[0002] This disclosure relates to the operation of an in-duct hydro turbine that controls the pressure of a fluid, disposed in parallel with a pressure control valve having a similar function.

Background Art

[0003] A fluid distribution system may receive fluid at a pressure higher than the pressure desired by the fluid consumer. For example, a water distribution system may receive water from a pump or a reservoir located geographically higher than the water consumer and supply it at a pressure higher than the desired pressure. The desired pressure for the fluid consumer (e.g., the desired downstream pressure) may fall within an allowable pressure range (APR). The APR may be determined based on the maximum pressure limits of connected equipment (e.g., piping and / or valves), the pressure required to suppress leaks, and the energy cost of pumping. The minimum APR pressure may be determined based on the minimum operating pressure of connected equipment (e.g., washing machines, boilers, showers, etc.) and the minimum pressure of fire extinguishing equipment in the fire extinguishing flow rate. A fluid distribution system may include multiple pressure control zones to ensure that the fluid consumer receives fluid within the APR. The pressure control zone pressure of a fluid refers to an area within a specified geographical region and elevation. A pressure control zone may include a pressure reduction station, which includes a pressure reducing valve that reduces the inlet pressure of the pressure reducing valve to a regulated low pressure regardless of upstream pressure or flow rate changes. While pressure reducing valves effectively reduce fluid pressure, they can cause energy loss and lead to energy waste. Although it is possible to place a fixed-speed turbine in place of, or in parallel with, a pressure reducing valve, such a configuration may lack operational redundancy and / or may require additional pressure control to ensure the desired pressure is supplied downstream of the fluid distribution system.

[0004] Recognizing the above problems, the inventors have developed a power generation system having a controller that includes a bypass conduit containing a bypass control valve and a turbine, a main conduit containing a main control valve, and an executable instruction stored in a non-temporary memory, wherein the executable instruction causes the controller to adjust the turbine speed according to the downstream pressure.

[0005] By adjusting the speed of the hydraulic turbine in response to the downstream pressure within the power generation system, it is possible to improve the operational efficiency of a fluid-powered power generation system. In particular, increasing the speed of the hydraulic turbine increases the pressure drop in the hydraulic turbine, thereby minimizing the pressure drop in the bypass valve and maximizing the electrical output and performance of the system.

[0006] This disclosure may offer several advantages. In particular, this approach may improve the efficiency of power generation systems. Furthermore, this approach may provide an approach arranged to start a hydraulic turbine in a way that reduces losses and improves system efficiency. In addition, this approach may simplify the control of a system that operates two devices to control the downstream pressure in a fluid distribution system.

[0007] The advantages described above and other advantages, as well as the features of this disclosure, will be readily apparent from the following detailed description, either on its own or in conjunction with the accompanying drawings.

[0008] The above summary should be understood as being provided for the purpose of introducing a simplified excerpt of concepts that will be further explained in the detailed description. It does not identify any important or essential features of the subject matter of the claims, and the scope of the claims is defined solely by the claims that follow the detailed description. Furthermore, the subject matter of the claims is not limited to implementations that resolve any of the defects described above or in any part of this disclosure. [Brief explanation of the drawing]

[0009] The advantages described herein can be better understood by reading, either alone or with reference to, an example of an embodiment of the embodiment referred to herein as “Detailed Description”. [Figure 1] Figure 1 is a schematic diagram of an exemplary power generation system. [Figure 2] Figure 2 is a flowchart illustrating an exemplary method of operating the power generation system. [Figure 3]Figure 3 is a flowchart illustrating an exemplary method of operation for a power generation system. [Figure 4] Figure 4 is a flowchart illustrating an exemplary method of operation for a power generation system. [Figure 5] Figure 5 is a plot showing the pressure within the system in Figure 1. [Figure 6] Figure 6 shows a plot illustrating the causes of pressure drop that may be beneficial when adjusting the speed of a hydraulic turbine. [Figure 7] Figure 7 is a plot showing the full operating range of a fixed-speed hydraulic turbine and a variable-speed hydraulic turbine. [Figure 8] Figure 8 shows a graphical representation of the operation sequence of a hydraulic turbine according to the method in Figure 2-4.

[0010] Detailed explanation This description concerns the operation of a power generation system. As an example, the power generation system may be configured as shown in Figure 1. The power generation system may operate according to the method shown in Figures 2-4. In particular, the power generation system may adjust the speed of the bypass valve or the hydraulic turbine (e.g., turbine speed) in response to the downstream pressure within the power generation system. Figure 5 shows a plot of an example of pressure drop within the power generation system. Figure 6 shows operating conditions under which adjusting the hydraulic turbine speed may be beneficial. The full operating ranges for fixed-speed and variable-speed turbines are shown in Figure 7. Finally, a graphic representation of the power generation system of Figure 1 operating according to the method shown in Figures 2-4 is shown in Figure 8.

[0011] Referring to Figure 1, a power generation system 100 is shown. The power generation system 100 generates electricity from the energy of a fluid 158 (e.g., water) flowing through a pipe or main conduit 151. The generated electricity may be supplied to a fixed power grid 114. The fixed power grid 114 may supply electricity to electricity consumers.

[0012] The pipe or main conduit 151 includes a main control valve 150, which controls the pressure of a fluid 158 located in the pipe or main conduit 151 downstream of the main control valve 150. The fluid 158 flows through the pipe or main conduit 151 in the directions indicated by arrows 160 and 166. The fluid 158 may also flow into the bypass conduit 170 as indicated by arrow 162. The fluid 158 may flow out of the bypass conduit 170 as indicated by arrow 164. The upstream pressure of the fluid 158 can be measured and determined via an upstream pressure sensor 148. The downstream pressure of the fluid 158 can be measured and determined via a downstream pressure sensor 152. Thus, the downstream pressure is the pressure in the main conduit 151 downstream of the main control valve 150.

[0013] The bypass conduit 170 is arranged in parallel with the pipe or main conduit 151 and includes an upstream shut-off valve 144 and a downstream shut-off valve 132. The flow meter 142 may output a signal indicating the flow rate of the fluid 158 through the bypass conduit 170. The position of the bypass control valve 138 can be monitored via a position sensor 140. A midstream pressure sensor 141 provides an indication of the fluid pressure in the bypass conduit 170 between the bypass control valve 138 and the hydraulic turbine 130. The hydraulic turbine 130 converts energy from the fluid 158 into rotational energy. The fluid may be discharged from the hydraulic turbine 130 and pass through the downstream shut-off valve 132, as shown by arrow 164.

[0014] The hydraulic turbine 130 generates electricity by rotating the generator 120 (e.g., an electromechanical device), and the rotational speed of the hydraulic turbine 130 can be measured via a tachometer 122. The electricity output from the generator 120 is supplied to a regenerative drive 118. The regenerative drive 118 converts the electricity generated by the generator 120 into alternating current (AC) electricity, which can be supplied to the grid connection panel 116 and the fixed power grid 114. The regenerative drive 118 may include a rectifier 115 and an inverter 117. The rectifier 115 converts the AC electricity into direct current (DC) electricity, and the inverter converts the DC electricity into AC electricity at the grid frequency.

[0015] The power generation system 100 may include a controller 12 that detects the system operating state and adjusts the system actuators to adjust the operating state of the power generation system 100. For example, the controller 12 may include a central processing unit 104, random access memory 106, read-only memory 102, and input / output hardware 108 (e.g., buffer circuits, timers / counters). The controller 12 manages the operation of the power generation system 100 to maintain a desired pressure downstream of the main control valve 150 while maximizing the flow rate through the bypass conduit 170. Furthermore, the fluid flow preferentially flows along the path with the least resistance between the main pipe 151 and the bypass conduit 170. The combination of pressure drops in the various devices arranged along the bypass conduit 170 is mainly determined by the position of the bypass control valve 138 and the rotational speed of the hydraulic turbine 130. The controller 12 may include a user interface 110 for receiving input from a user (e.g., a person) and providing feedback data to the user. The user interface may be a touchscreen display, a keypad, or other known device. In some examples, controller 12 may receive inputs and / or commands from an external controller via I / O 108.

[0016] The pressures at various locations in the bypass conduit 170 are indicated by the letter "P" followed by a location number. For example, "P1" is the fluid pressure at location P1, which is the inlet of the bypass conduit 170. P2 is the pressure at the outlet of the upstream shut-off valve 144. P3 is the pressure between the flow meter 142 and the bypass control valve 138. P4 is the pressure between the bypass control valve 138 and the hydraulic turbine 130. P5 is the pressure at the outlet of the hydraulic turbine. P6 is the pressure at the inlet of the downstream shut-off valve 132. P7 is the pressure at the outlet of the downstream shut-off valve 132.

[0017] The system in Figure 1 provides a power generation system comprising: a bypass conduit including a bypass control valve and a turbine; a main conduit including a main control valve; and a controller including executable instructions stored in a non-temporary memory, the executable instructions causing the controller to adjust the turbine speed in accordance with the downstream pressure. In the first example, the power generation system includes adjusting the turbine speed to reduce the turbine speed when the downstream pressure is less than or equal to a value obtained by subtracting a first offset pressure from a desired downstream pressure. In the second example (which may include the first example), the power generation system includes adjusting the turbine speed to increase the turbine speed when the downstream pressure exceeds a value obtained by adding a second offset pressure to the desired downstream pressure. In the third example (which may include either or both of the first and second examples), the power generation system includes adjusting the turbine speed to maintain the turbine speed when the downstream pressure is greater than a value obtained by subtracting a first offset pressure from a desired downstream pressure and less than or equal to a value obtained by adding a second offset pressure to the desired downstream pressure. In the fourth example (which may include one or more of the first to third examples), the power generation system is such that the desired downstream pressure is the pressure in the main pipe located downstream of the main control valve. In the fifth example (which may include one or more of the first to fourth examples), the power generation system is such that the controller adjusts the turbine speed by commanding the regenerative drive. In the sixth example (which may include one or more of the first to fifth examples), the power generation system is such that the regenerative drive includes a rectifier and an inverter. In the seventh example (which may include one or more of the first to sixth examples), the power generation system further includes additional executable commands that cause the controller to adjust the bypass control valve according to the desired downstream pressure.

[0018] The system in Figure 1 also provides a power generation system comprising: a bypass conduit including a bypass control valve and a turbine; a main conduit including a main control valve; and a controller including executable instructions stored in a non-temporary memory, the executable instructions causing the controller to operate the power generation system in a plurality of operating states (including a fourth operating state in which the turbine speed is adjusted according to the downstream pressure). In the first example, the power generation system includes a plurality of operating states, including a first operating state in which the turbine speed is zero and the bypass control valve is fully closed. In the second example (which may include the first example), the power generation system includes a plurality of operating states, including a second operating state in which the turbine speed is zero and the bypass control valve is partially open. In the third example (which may include one or both of the first and second examples), the power generation system includes a plurality of operating states, including a third operating state in which the turbine speed is at the minimum non-zero speed and the bypass control valve is partially open. In the fourth example (which may include one or more of the first to third examples), the power generation system includes a plurality of operating states, including a fifth operating state in which the turbine speed is maintained and the bypass control valve is fully open.

[0019] Referring to Figure 2, a flowchart of the operation method of the power generation system in Figure 1 is shown. The method in Figure 2 can be applied to the system in Figure 1 in combination with the methods in Figures 3 and 4. The method in Figure 2 can be performed via a controller. The controller can receive input from sensors and adjust actuators to change the operating state of the device in the physical world. The method in Figure 2 can maximize the output power of the power generation system by increasing the pressure drop in the hydraulic turbine.

[0020] At 202, method 200 determines the operating conditions and parameters of the power generation system. As an example, method 200 may receive input values from various sensors described herein and determine the position of the bypass valve, the speed of the hydraulic turbine, the upstream pressure, the downstream pressure, the flow rate in the bypass conduit, and the midstream pressure. Method 200 may obtain the values of the control parameters from the memory of the controller. The control parameters are stored in a table, function, or other memory location. Method 200 proceeds to 204. At 204, method 200 determines whether an operation command has been received or input to the power controller. If so, the answer is "yes" and method 200 proceeds to 206. If not, the answer is "no" and method 200 proceeds to 205.

[0021] At 205, method 200 assumes an off state. The off state includes fully closing the bypass control valve and commanding the speed of the hydraulic turbine to zero. Thereby, the fluid flow rate through the hydraulic turbine and the bypass conduit decreases to zero or nearly zero. Method 200 returns to 202.

[0022] At 206, method 200 determines whether the fluid flow rate through pipe or main conduit 151 exceeds a start threshold flow rate. As an example, the start threshold flow rate may be based on the size of the pipe or past water demand. If so, the answer is "yes" and method 200 proceeds to 208. If not, the answer is "no" and method 200 proceeds to 207.

[0023] At 207, method 200 assumes state A. State A includes operating the bypass control valve in a pressure control mode according to the method of FIG. 3. State A also includes commanding the speed of the hydraulic turbine to zero. Thereby, state A controls the downstream pressure when the flow rate through the fluid distribution system is insufficient to maintain the minimum non-zero speed of the hydraulic turbine (e.g., the speed at which the hydraulic turbine can be operated to generate electricity). Method 200 returns to 202.

[0024] In 208, method 200 determines whether the fluid flow rate through the pipe or main pipe 151 exceeds the minimum threshold flow rate. For example, the minimum threshold flow rate may be based on the size of the pipe or past water demand. If so, the answer is "yes" and method 200 proceeds to 210. Otherwise, the answer is "no" and method 200 proceeds to 209.

[0025] In 209, method 200 assumes state B, which involves operating the bypass control valve in pressure control mode according to the method in Figure 3. State B also includes commanding the speed of the hydraulic turbine to a minimum non-zero rotational speed. Thus, state B controls the downstream pressure by adjusting the position of the bypass valve while the speed of the hydraulic turbine increases to the minimum operating speed of the hydraulic turbine. Method 200 returns to 202.

[0026] In 210, method 200 determines whether the fluid flow rate through the pipe or main pipe 151 exceeds the maximum threshold flow rate. For example, the maximum threshold flow rate is determined based on the size of the pipe, past water demand, or the minimum operating speed of the hydraulic turbine. If so, the answer is "yes," and method 200 proceeds to 213. Otherwise, the answer is "no," and method 200 proceeds to 211.

[0027] In 211, Method 200 assumes state C, which involves fully opening the bypass control valve and operating the hydraulic turbine in pressure-controlled mode according to the method in Figure 4. This maximizes the pressure drop in the hydraulic turbine and minimizes the pressure drop in the bypass valve, thereby improving system efficiency. Method 200 returns to 202.

[0028] In 213, method 200 assumes state D, which involves operating the bypass control valve in pressure control mode according to the method in Figure 3. State D also includes maintaining the current speed of the hydraulic turbine. Thus, state D maximizes the output of the generator when the fluid flow rate in the system is high. Method 200 returns to 202.

[0029] In this way, method 200 can adjust the operating state of the power generation system and improve the efficiency of electric power generation. In particular, the method in Figure 2 performs start control and operation control. For example, when an operation command is issued, the set pressure or desired pressure of the bypass control valve is adjusted to a value 1-10 pounds / square inch (PSI), or preferably 2-5 PSI, higher than the set downstream pressure of the main control valve. If there is fluid flow in the main pipe and the bypass valve is open, the fluid begins to flow through the bypass conduit. When the fluid flow rate in the bypass conduit exceeds the start threshold flow rate, it is a sufficient flow rate for the generator to generate electricity. Nevertheless, the hydraulic turbine must be started. Therefore, the bypass control valve operates in pressure control mode, and the regenerative drive adjusts the speed of the hydraulic turbine to a minimum speed value. The regenerative drive adjusts the amount of torque applied to the hydraulic turbine via the generator to achieve the desired minimum hydraulic turbine speed. The desired minimum hydraulic turbine speed can be in the range of 400-1,200 revolutions per minute (RPM). The bypass valve is adjusted to the fully open position, and the hydraulic turbine is operated in pressure control mode. In this mode, the regenerative drive controls the torque applied by the generator to the hydraulic turbine, thereby adjusting the turbine's speed. This reduces and / or minimizes the pressure difference across the bypass valve, maximizes the pressure difference across the hydraulic turbine, and increases power output. If system demand increases and the flow rate in the main pipe exceeds a threshold, power can be generated while maintaining the desired downstream pressure by commanding the bypass valve to pressure control mode while maintaining the hydraulic turbine's rotational speed.

[0030] Next, referring to Figure 3, a flowchart of how the bypass control valve operates in pressure control mode is shown. The method in Figure 3 can be applied to the system in Figure 1 in combination with the methods in Figures 2 and 4. The method in Figure 3 can be performed via a controller. The controller can receive input from sensors and adjust actuators to change the operating state of the device in the physical world. The method in Figure 3 can control the pressure drop in the bypass control valve in the bypass conduit.

[0031] In 302, method 300 determines the operating conditions and parameters of the power generation system. For example, method 300 may receive input values ​​from various sensors described herein and determine the downstream pressure. Method 300 may obtain the values ​​of control parameters from the controller's memory. The control parameters are stored in a table, function, or other memory location. Method 300 proceeds to 304.

[0032] In 304, method 300 determines whether the downstream pressure Pds (e.g., the pressure at the downstream sensor 152) exceeds the desired downstream pressure or set pressure (Psp) minus the offset pressure (e.g., a pressure value of 0.1–2 PSI). If so, the answer is "yes" and method 300 proceeds to 306. Otherwise, the answer is "no" and method 300 proceeds to 305.

[0033] In 305, method 300 gradually opens the bypass control valve. As an example, the bypass control valve may be opened a small amount (e.g., 0.5% of the total valve stroke) further from its current position by activating a solenoid valve to allow water to flow out of the closed chamber that controls the position of the bypass control valve. Method 300 returns to 302.

[0034] In 306, method 300 determines whether the downstream pressure Pds (e.g., the pressure at the downstream sensor 152) exceeds the desired downstream pressure or set pressure (Psp) plus an offset pressure (e.g., a pressure value of 0.1–2 PSI). If so, the answer is "yes," and method 300 proceeds to 309. Otherwise, the answer is "no," and method 300 proceeds to 307.

[0035] In 307, method 300 holds or maintains the current opening amount of the bypass control valve. Method 300 returns to 302.

[0036] In 309, method 300 gradually closes the bypass control valve. For example, the bypass control valve may be closed a small amount (e.g., 0.5% of the total valve stroke) further from its current position by activating a solenoid valve to allow water to flow into a closed chamber that controls the position of the bypass control valve. Method 300 returns to 302.

[0037] In this way, if the speed of the hydraulic turbine is not adjusted according to the downstream pressure, the position of the bypass control valve is adjusted according to the downstream pressure of the main pipe, thereby providing the desired downstream pressure downstream of the main control valve as water flows through the bypass conduit and the main pipe.

[0038] Moving on to Figure 4, a flowchart of a method for controlling the pressure drop in a hydraulic turbine is shown. The method in Figure 4 can be applied to the system in Figure 1 in combination with the methods in Figures 2 and 3. The method in Figure 4 is performed via a controller. The controller receives input from sensors and can adjust actuators to change the operating state of the device in the physical world.

[0039] In 402, method 400 determines the operating conditions and parameters of the power generation system. As an example, method 400 may receive input values ​​from various sensors described herein and determine the downstream pressure. Method 400 may obtain the values ​​of control parameters from the controller's memory. The control parameters are stored in a table, function, or other memory location. Method 400 proceeds to 404.

[0040] In 404, method 400 determines whether the downstream pressure Pds (e.g., the pressure at the downstream sensor 152) exceeds the desired downstream pressure or set pressure (Psp) minus the offset pressure (e.g., a pressure value of 0.1–2 PSI). If so, the answer is "yes" and method 400 proceeds to 406. Otherwise, the answer is "no" and method 400 proceeds to 405.

[0041] In 405, method 400 gradually reduces the speed of the hydraulic turbine. For example, the speed of the hydraulic turbine can be reduced by commanding the regenerative drive to output a greater amount of electrical energy. Demanding a greater amount of electrical energy output from the regenerative drive increases the torque output of the generator, which can slow down the hydraulic turbine. In this way, the torque output of the generator (e.g., the torque resisting the movement of the hydraulic turbine) can be adjusted to control the speed of the hydraulic turbine. Method 400 returns to 402.

[0042] In 406, method 400 determines whether the downstream pressure Pds (e.g., the pressure at the downstream sensor 152) exceeds the desired downstream pressure or set pressure (Psp) plus an offset pressure (e.g., a pressure value of 0.1–2 PSI). If so, the answer is "yes," and method 400 proceeds to 409. Otherwise, the answer is "no," and method 400 proceeds to 407.

[0043] In step 407, method 400 maintains or keeps the current speed of the hydraulic turbine. Method 400 returns to step 402.

[0044] In 409, method 400 gradually increases the speed of the hydraulic turbine. As an example, the speed of the hydraulic turbine can be increased by commanding the regenerative drive to reduce the amount of power output. Requesting the regenerative drive to reduce the amount of power reduces the torque output of the generator, which can increase the speed of the hydraulic turbine. Thus, the speed of the hydraulic turbine can be increased by adjusting the torque output of the generator (e.g., the torque resisting the motion of the hydraulic turbine). Method 400 returns to 402. In this way, the speed of the hydraulic turbine can be adjusted according to the fluid pressure in the main pipe downstream of the main valve. By adjusting the speed of the hydraulic turbine, the pressure drop in the hydraulic turbine is controlled to a desired downstream pressure drop.

[0045] The method in Figure 2-4 provides a method for a power generation system, which includes adjusting the turbine speed in response to the downstream pressure of a fluid distribution system via a controller. In the first example, the method includes adjusting the turbine speed in response to the flow rate in the fluid distribution system exceeding a first threshold flow rate. In the second example (which may include the first example), the method further includes adjusting the position of a bypass control valve in response to the flow rate in the fluid distribution system being less than a first threshold flow rate. In the third example (which may include one or both of the first and second examples), the method includes adjusting the bypass control valve in response to the downstream pressure in the fluid distribution system. In the fourth example (which may include one or more of the first to third examples), the method includes gradually opening the bypass control valve in response to the downstream pressure of the fluid distribution system being less than or equal to a desired downstream pressure minus a first offset pressure. In the fifth example (which may include one or more of the first to fourth examples), the method includes gradually closing the bypass control valve in response to the downstream pressure of the fluid distribution system exceeding a desired downstream pressure plus a second offset pressure. In the sixth example (which may include one or more of the first through fifth examples), the method includes the controller instructing the regenerative drive to adjust the turbine speed.

[0046] Referring to Figure 5, a typical pressure drop plot 500 in a power generation system is shown. The solid line 502 represents the pressure drop in a power generation system with a fixed-speed hydraulic turbine. The dashed line 506 represents the pressure drop when the variable-speed power generation system shown in Figure 1 is operated according to the method in Figure 2-4. If the dashed line 506 is not visible but the solid line 502 is visible, the dashed line 506 is the same as the solid line 502. The points (e.g., 520) represent the pressure in the power generation system observed at a location (e.g., P1) within the power generation system.

[0047] The horizontal line 510 represents the level or value of the upstream pressure. The horizontal line 512 represents the level or value of the downstream pressure. The horizontal axis represents the location where the pressure is measured, and these locations correspond to the locations shown in Figure 1. For example, P1 in Figure 1 is the location in the bypass conduit at the inlet of the upstream shut-off valve 144. P7 in Figure 1 is the location in the bypass conduit at the outlet of the downstream shut-off valve 132. The vertical axis represents the fluid pressure in the power generation system, and the pressure increases in the direction of the arrows on the vertical axis.

[0048] It can be observed that the pressure drop at position P1 relative to the upstream pressure is zero. The pressure drop across the upstream shut-off valve that generates the pressure at position P2 is minimal. Furthermore, the pressure drop across the flow meter is minimal, as indicated by the pressure difference between P2 and P3. The pressure drop across the bypass control valve for a fixed-speed hydraulic turbine (e.g., the difference between the solid pressure at P3 and the solid pressure at P4) is more pronounced. The pressure drop across the bypass control valve in a system with a variable-speed hydraulic turbine (e.g., the difference between the dashed pressure at P3 and the dashed pressure at P4) is significantly smaller than in a fixed-speed hydraulic turbine system. This allows for a larger pressure drop across the hydraulic turbine, improving output and system efficiency. The pressure drop in the hydraulic turbine of a fixed-speed hydraulic turbine (e.g., the difference between the pressure at P4 and the pressure at P5) is greater than the pressure drop in the bypass control valve of a fixed-speed hydraulic turbine, but smaller than the pressure drop in the hydraulic turbine of a variable-speed hydraulic turbine (the difference between the pressure at P4 and the pressure at P5). Therefore, a variable-speed hydraulic turbine operating according to the method shown in Figure 2-4 can provide additional power output. The pressure drop between the outlet of the hydraulic turbine and the inlet of the downstream shut-off valve (e.g., the difference between the pressure at P5 and the pressure at P6) is negligible. The pressure drop at the downstream shut-off valve (e.g., the difference between the pressure at P6 and the pressure at P7) is relatively small.

[0049] Therefore, when the hydraulic turbine and bypass control valve operate according to the method shown in Figure 2-4, the pressure drop in the bypass control valve can be minimized and the pressure drop in the hydraulic turbine can be maximized. A high pressure drop in the bypass valve in a fixed-speed hydraulic turbine causes a direct loss of power generation performance in the fixed-speed hydraulic turbine.

[0050] Referring to Figure 6, plot 600 is shown illustrating the causes of pressure drop for which adjusting the speed of the hydraulic turbine may be beneficial. The vertical axis represents the pressure in the water distribution system, and the horizontal axis represents the fluid flow rate through the water distribution system. Line 616 represents the inlet pressure of the power generation system detected via the upstream pressure sensor 148. Line 614 represents the pressure obtained by subtracting the pressure loss due to the inlet and outlet shut-off valves, system piping, and bypass valves (e.g., lines with limited pressure and flow) from the inlet pressure in the system. The dashed line 602 represents the pressure drop that can be supplied by a variable-speed hydraulic turbine for a given fluid flow rate through the water distribution system. The solid line 604 represents the pressure drop in a fixed-speed hydraulic turbine for different fluid flow rates through the water distribution system.

[0051] Leaders 606, 608, and 610 represent the fluid pressure drop in the water distribution system at flow rate f1. Points 650 and 652 correspond to the pressure in the system at flow rate f1. Leader 610 represents the minimum pressure loss in the piping, bypass control valve, and shut-off valve. Leader 608 represents the additional pressure drop in the variable-speed hydraulic turbine available when the power generation system is operated according to the method in Figure 2-4. Leader 606 represents the pressure loss in the hydraulic turbine of the fixed-speed hydraulic turbine. Note that the pressure drop in the fixed-speed and variable-speed hydraulic turbines occurs up to line 614 where the pressure and flow rate are limited as the system fluid flow rate increases.

[0052] It is understood that the pressure drop in a fixed-speed hydraulic turbine changes depending on the fluid flow rate through the system. Therefore, by adjusting the pressure drop in the bypass control valve, a pressure difference can be generated between lines 604 and 614, thereby producing the required downstream pressure or desired downstream pressure via the power generation system and the main control valve 150. However, the pressure drop in the bypass control valve causes a loss of system energy.

[0053] To increase the pressure drop in a hydraulic turbine, the speed of a variable-speed hydraulic turbine can be increased, thereby improving the output and efficiency of the hydraulic turbine. As a result, the pressure drop provided through the bypass control valve can be reduced to meet the desired downstream pressure in the water distribution system.

[0054] Next, referring to Figure 7, plot 700 is shown, which illustrates the full operating range of a fixed-speed hydraulic turbine compared to a variable-speed hydraulic turbine. The vertical axis represents the pressure within the water distribution system, and the horizontal axis represents the fluid flow rate through the water distribution system.

[0055] Line 702 represents the inlet pressure to the power generation system detected via the upstream pressure sensor 148. Line 704 represents the pressure obtained by subtracting the pressure losses of the inlet and outlet shut-off valves, system piping, and minimum bypass valve from the inlet pressure in the system (e.g., lines with limited pressure and flow rate). A dashed line (e.g., 706) represents the pressure drop that can be provided through a variable-speed hydraulic turbine for a given fluid flow rate through the water distribution system. A solid line 708 represents the pressure drop in a fixed-speed hydraulic turbine for different fluid flow rates through the water distribution system.

[0056] Figure 7 shows how the operating points or conditions of a fixed-speed and variable-speed hydraulic turbine are adjusted with respect to the fluid flow rate through the power generation system. In particular, the operation of the fixed-speed hydraulic turbine (e.g., solid line 708) moves from the left side of the plot to the right side, reaching the maximum flow rate when the pressure drop from the hydraulic turbine can no longer increase at point 750.

[0057] Ideally, a power generation system can be designed to frequently operate under pressure and flow limiting conditions (e.g., line 704). However, a fixed-speed hydraulic turbine operates under such conditions only under specific operating conditions (e.g., point 750). Because the demand for fluid flow can fluctuate significantly over time, a fixed-speed hydraulic turbine can leave a lot of potential energy that can be extracted from the fluid. In a fixed-speed hydraulic turbine operating to the left of the flow and pressure limiting point (e.g., 750), additional pressure drops in the system are provided via a bypass control valve. Under operating conditions to the right of the flow and pressure limiting point (e.g., point 750), the fluid flow through the fixed-speed hydraulic turbine is blocked, and additional system flow is supplied via a main control valve.

[0058] Current variable-speed hydraulic turbines can improve system efficiency by operating along line 704, where pressure and flow rates are limited, according to the method shown in Figure 2-4. Furthermore, since the variable-speed hydraulic turbine does not reach the pressure limiting condition, the maximum flow rate through the bypass conduit can be increased compared to the flow rate through the bypass conduit of a fixed-speed hydraulic turbine. The variable-speed hydraulic turbine can provide an expanded flow rate range, indicated by line 752, by operating with increasing flow rates between flow rates f2 and f3. Larger flow rates can be achieved by reducing the speed of the hydraulic turbine at a given inlet pressure.

[0059] Referring to Figure 8, the startup sequence of the power generation system is shown. The power generation system shown in Figure 1 is started and operated according to the method in Figure 2-4. The vertical axis represents the pressure in the water distribution system, and the horizontal axis represents the fluid flow rate through the water distribution system. Line 802 represents the inlet pressure of the power generation system detected via the upstream pressure sensor 148. Line 804 represents the pressure obtained by subtracting the pressure loss due to the inlet shut-off valve, outlet shut-off valve, system piping, and minimum bypass valve from the inlet pressure in the system (e.g., lines with limited pressure and flow rate). A dashed line (e.g., 806) represents the pressure drop provided through the variable-speed hydraulic turbine for a given fluid flow rate through the water distribution system. A solid line 808 represents the pressure drop in the fixed-speed hydraulic turbine for different fluid flow rates through the water distribution system.

[0060] The power generation system can initially be in an off state, as indicated by point F1. The off state can exist when there is no operation command for the power generation system. When the power generation system is off, the bypass control valve is completely closed, and the rotational speed of the hydraulic turbine is commanded to zero. Therefore, the regenerative drive operates to maintain the rotational speed of the hydraulic turbine at zero. When the power generation system receives a start command or operation command, the shut-off valve and bypass control valve are opened, fluid flows into the bypass conduit, and the system transitions to operating state A. As the fluid flow rate increases and the flow rate through the bypass conduit reaches the level indicated by F2, the power generation system reaches state B. When the power generation system reaches the flow rate indicated by F2, the hydraulic turbine is released from its stopped state and can rotate.

[0061] The fluid flow rate through the bypass conduit continues to increase as the flow rate through the system increases, and the downstream pressure is controlled by controlling the position of the bypass valve. As the overall system flow rate increases, the bypass valve reaches the fully open position. Point F3 indicates the fully open state of the bypass valve. If the fluid flow rate increases further due to increased demand, the speed of the hydraulic turbine is adjusted via the regenerative drive, and in a variable-speed hydraulic turbine, the pressure drop in the hydraulic turbine reaches the level indicated by point F4. However, in the case of a fixed-speed hydraulic turbine, the pressure drop at flow rate f5 indicated by point F4' is smaller than the pressure drop in a variable-speed hydraulic turbine indicated by point F4. If the system flow rate demand increases further, the variable-speed hydraulic turbine follows the trajectory of line 804 from point F4 to F5. The variable-speed hydraulic turbine can operate in pressure-controlled mode, adjusting the speed of the hydraulic turbine to control the downstream pressure in operating state C. If the system flow rate demand increases further, the fixed-speed hydraulic turbine system moves along the minimum velocity curve indicated by solid line 808 from point F4' to F5. If the flow demand exceeds the flow rate of F5 and increases further, the bypass valve is held fully open, the hydraulic turbine speed is maintained, and the power generation system operates in state D.

[0062] Therefore, the pressure in the power generation system can be controlled by adjusting the bypass control valve and the speed of the hydraulic turbine. The pressure can be adjusted to minimize the pressure drop at the bypass control valve and maximize the pressure drop at the hydraulic turbine. As a result, the efficiency and performance of the system can be improved.

[0063] The exemplary control and estimation routines included herein can be used in combination with various variable-speed hydraulic turbine system configurations. The control methods and routines disclosed herein are stored as executable instructions in non-temporary memory and can be executed by a control system, including a controller, in combination with various sensors, actuators, valves, regenerative drives, and other hydraulic turbine hardware. Certain routines disclosed herein may represent one or more of a number of processing strategies, such as event-driven, interrupt-driven, multitasking, and multithreading. Therefore, the various movements, operations, and / or functions illustrated may be executed in the illustrated order, in parallel, or, in some cases, omitted. Similarly, the order of processing is not necessarily required to realize the features and benefits of the exemplary examples described herein and is provided for ease of illustration and description. Depending on the specific strategy used, one or more of the illustrated movements, operations, and / or functions may be repeatedly executed. Furthermore, at least some of the described operations, operations, and / or functions can be graphically represented by code programmed into non-temporary memory of a computer-readable storage medium within the control system. Control operations can transform the operating state of one or more sensors or actuators in the physical world when performing the described operations by executing commands within a system that combines variable-speed hydraulic turbine hardware elements with one or more controllers.

[0064] This concludes the disclosure. Experts in the field will likely be able to conceive of many changes and modifications without deviating from the spirit and scope of the disclosure. For example, a fluid (e.g., water) distribution system using hydraulic turbines of different sizes to support different fluid flow rates may be able to utilize this disclosure to its advantage.

Claims

1. Bypass conduit including bypass control valve and turbine, Main control valve and lead pipe, A controller including executable instructions stored in a non-temporary memory, wherein the executable instructions cause the controller to adjust the speed of the turbine in accordance with the downstream pressure. A power generation system including a power generation system.

2. The power generation system according to claim 1, wherein adjusting the speed of the turbine includes reducing the speed of the turbine when the downstream pressure is less than or equal to a value obtained by subtracting a first offset pressure from a desired downstream pressure.

3. The power generation system according to claim 2, wherein adjusting the speed of the turbine includes increasing the speed of the turbine when the downstream pressure exceeds the desired downstream pressure plus a second offset pressure.

4. The power generation system according to claim 3, wherein adjusting the speed of the turbine includes maintaining the speed of the turbine when the downstream pressure is greater than the value obtained by subtracting the first offset pressure from the desired downstream pressure, and less than or equal to the value obtained by adding the second offset pressure to the desired downstream pressure.

5. The power generation system according to claim 1, wherein the desired downstream pressure is the pressure in the main pipe located downstream of the main control valve.

6. The power generation system according to claim 1, wherein the controller adjusts the speed of the turbine by issuing a command to the regenerative drive.

7. The power generation system according to claim 6, wherein the regenerative drive includes a rectifier and an inverter.

8. The power generation system according to claim 1, further comprising additional executable instructions, the additional executable instructions causing the controller to adjust the bypass control valve in accordance with a desired downstream pressure.

9. A method for a power generation system, comprising the step of adjusting the turbine speed in accordance with the downstream pressure in a fluid distribution system via a controller.

10. The method according to claim 9, wherein the speed of the turbine is adjusted when the flow rate in the fluid distribution system exceeds a first threshold flow rate.

11. The method of claim 10, further comprising the step of adjusting the position of a bypass control valve when the flow rate in the fluid distribution system is less than the first threshold flow rate.

12. The method of claim 11, wherein the bypass control valve is adjusted according to the downstream pressure in the fluid distribution system.

13. The method of claim 12, wherein the bypass control valve is gradually opened in response to the downstream pressure being less than or equal to the value obtained by subtracting a first offset pressure from a desired downstream pressure.

14. The method of claim 13, wherein the bypass control valve is gradually closed in response to the downstream pressure exceeding the value obtained by adding a second offset pressure to the desired downstream pressure.

15. The method according to claim 14, wherein the controller commands the regenerative drive to adjust the speed of the turbine.

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