Method and equipment for selecting the minimum speed of self-starting of variable speed pumped storage unit pump

Abstract

The present invention discloses a method and device for selecting the minimum speed for self-starting of a variable-speed pumped-storage unit pump. An adaptive module is added to the variable-speed pumped-storage unit pump self-starting strategy, and the adaptive module is located in the rotor side vector control; the input of the adaptive module is the reference input and the real-time head, and the optimal opening corresponding to the reference input and the real-time head is obtained by using the optimal opening generator, so as to calculate the flow head characteristic curve at different speeds under the optimal opening, find the minimum speed when the flow is greater than zero in the flow head characteristic curve, and obtain the minimum speed after considering a certain safety margin, and use this minimum speed as the reference speed when the unit is started from a stationary condition to a pumping phase adjustment condition or a pumping phase adjustment condition; the present invention can avoid the phenomenon that the variable-speed unit does not pump water, or the reverse flow phenomenon occurs during the self-starting process, and ensure the safe and stable operation of the unit.

Description

Technical Field

[0001] The invention belongs to the technical field of pumped storage, and in particular relates to a method for selecting a minimum speed for self-starting of a variable speed pumped storage unit pump, and also relates to a device for selecting a minimum speed for self-starting of a variable speed pumped storage unit pump. Background Art

[0002] Variable speed pumped storage units have good regulation performance, can promote the consumption of new energy such as solar energy and wind power, and are important flexible regulating power sources for new power systems. The variable speed unit pump condition can achieve self-starting without the need for additional static frequency converter (SFC) equipment, which not only greatly reduces the relevant investment in the power station, but also effectively improves the regulation performance of the unit.

[0003] During the self-starting process of the variable-speed pumped storage unit pump, if the speed is too low, during the conversion from the phase adjustment condition to the pumping condition, the volute pressure will be greater than the tailwater pipe pressure, and the water cannot be pumped normally, or the pumping flow rate will be negative (reverse flow) during the unit startup process, affecting the safe and stable operation of the unit. Therefore, in order to improve the stability of the unit during the condition conversion process, it is urgent to propose a method to clarify the minimum speed of the variable-speed unit under different reference inputs and different real-time heads. Summary of the invention

[0004] The purpose of the present invention is to provide a method for selecting the minimum speed for self-starting of a variable-speed pumped storage unit pump operating condition, which solves the problem that the volute pressure is greater than the tailwater pipe pressure during the conversion of the unit from a pumping phase adjustment condition to a pumping condition, resulting in failure to pump water normally; or the pumping flow rate is negative (backflow) during the unit startup process.

[0005] The present invention also aims to provide a device for selecting the minimum speed for self-starting of a variable speed pumped storage unit pump.

[0006] The first technical solution adopted by the present invention is: adding an adaptive module to the self-starting strategy of the variable speed pumped storage unit pump working condition, the adaptive module is located in the rotor side vector control, and the adaptive module can make the initial speed from the pumping phase adjustment working condition to the pumping working condition reach the minimum speed; the adaptive module can play a role in the stationary working condition to the pumping phase adjustment working condition, and can also play a role in the pumping phase adjustment working condition, but the purpose is to make the initial speed from the pumping phase adjustment working condition to the pumping working condition of the unit reach the minimum speed, and the adaptive module can be obtained according to the minimum speed determination method;

[0007] The input of the adaptive module is the reference input and real-time head, and the output is the minimum speed. The optimal opening generator is used to obtain the optimal opening corresponding to the reference input and real-time head, and the flow head characteristic curve at different speeds under the optimal opening is calculated, so as to calculate the flow head characteristic curve at different speeds under the optimal opening. The minimum speed when the flow is greater than zero is found in the flow head characteristic curve as the minimum speed, and this minimum speed is used as the reference speed when the unit is started from a static condition to a pumping phase adjustment condition, or in a pumping phase adjustment condition, so as to avoid the phenomenon that the unit does not pump water, or the situation that the pumping flow is negative (reverse flow) during the start-up of the unit.

[0008] The method for selecting the minimum speed of the variable speed pumped storage unit pump working condition self-starting adopted by the present invention, for a specific reference input and real-time head, firstly, uses the optimal opening generator to obtain the optimal opening corresponding to the reference input and the real-time head; then, uses the pump similarity and the pump working condition flow head characteristic curve to determine the working condition point where the flow rate is zero at different speeds of the optimal opening and its corresponding head, finds the speed corresponding to the real-time head and considers a certain safety margin to obtain the corresponding minimum speed;

[0009] The specific steps include:

[0010] Step 1: Determine the maximum head of the unit during normal operation according to the hydrological conditions of the unit H max and minimum head H min ;

[0011] Step 2, determining the reference input change range corresponding to each head of the unit according to the operating range of the maximum head and the minimum head of the unit;

[0012] Step 3: Change the lift and the corresponding reference input range respectively. m , n Divide equally and create m OK n The matrix of columns makes the lift and reference input correspond one to one;

[0013] Step 4: Input the reference force after equal division in step 3 P ij and lift H ij , i =1… m , j =1… n ; The optimal opening of the unit under different reference input and head is obtained through the optimal opening generator ;

[0014] Step 5: Optimal opening obtained from step 4 , the optimal opening is obtained through the analysis and calculation of the water pump similarity law. The flow head characteristic curve of the unit at different reference speeds is shown below;

[0015] Step 6: According to the flow head characteristic curve obtained in step 5, select the minimum speed at which the flow rate is greater than zero when the reference head is taken as the minimum speed. ;

[0016] Step 7, based on step 6 Feedback to the reference speed required for the unit to start from the stationary condition to the pumping phase adjustment condition .

[0017] The present invention is also characterized in that:

[0018] In step 3, lift H and reference input P The matrices are:

[0019] (1)

[0020] (2).

[0021] In step 4, the optimal opening generator is based on the pump coordinated opening ω r - Q - α opt Curved surface, pump joint working condition ω r - Q - H Surface and ω r - Q - P The surface obtains the data of the optimal efficiency point, and the optimal efficiency point is obtained according to the data of the optimal efficiency point. P ref - H - ω ropt Surfaces;

[0022] According to the pump joint opening ω r - Q - α opt Surface and P t - H - Q Surface P ref - H - α opt Surfaces;

[0023] in, P t For actual input, Q For flow; P ref - H - ω ropt The surface represents the result of the optimal speed. P ref - H - α opt The surface represents the result of the optimization of the opening, and the optimal opening is obtained .

[0024] In step 5, the water pump similarity law formula is:

[0025] (3)

[0026] In formula (3), , Different speeds for water pump working conditions; Q 1. Q 2 indicates the speed is , flow rate at that time; H 1. H 2 indicates the speed is , In step 6, first select the coordinates of the point when the flow rate is zero and the head is the reference head in the flow-head characteristic curve ( Q j0 , H jref ), and then according to the point coordinates, the speed corresponding to the flow rate of zero is obtained. Then the minimum speed required for the unit to switch from pumping phase adjustment to pumping condition is obtained. , finally according to draw P ij -H ij- A surface graph is generated and an adaptive module is generated based on the surface graph.

[0027] The minimum speed required for the unit to switch from pumping phase adjustment mode to pumping mode The formula is:

[0028] (4)

[0029] Formula (4) indicates that the selected minimum speed is slightly larger than the speed when the flow rate is zero. R It is a safety margin, generally taken as 1.01~1.05.

[0030] In step 7, the adaptive module obtained in step 6 generates the corresponding Feedback to the reference speed required for the unit to start from the stationary condition to the pumping phase adjustment condition .

[0031] The reference speed fed back to the unit when it starts from the stationary condition to the pumping phase adjustment condition is:

[0032] (5)

[0033] The unit is started from a stationary condition to a pumping phase adjustment condition through the excitation preparation stage, the excitation stage, the constant torque speed increase stage, the constant power speed increase stage, the power reduction speed increase stage and the demagnetization flux stage.

[0034] The second technical solution adopted by the present invention is a device for selecting the minimum speed for self-starting of a variable speed pumped storage unit pump operating condition, comprising a storage medium and a processor, wherein the storage medium is used to store a program, and when the program is executed by the processor, the processor implements a method for selecting the minimum speed for self-starting of a variable speed pumped storage unit pump operating condition.

[0035] The beneficial effects of the present invention are as follows: the present invention clearly proposes a method and device for selecting the minimum speed for self-starting of a variable-speed pumped-storage unit pump. When the reference input and head of the unit are determined, the optimal opening of the unit at this time can be obtained through the optimal opening generator; the flow-head diagram of the unit at different speeds under this opening is obtained by analysis and calculation, and the minimum speed at which the flow is greater than zero under the corresponding reference head at this time is found in the diagram as the minimum speed, and this minimum speed is used as the reference speed when the unit is started from a static condition to a pumping phase adjustment condition. The present invention effectively solves the problem that when the initial speed of the unit is selected to be relatively low, the volute pressure of the unit is greater than the tailwater pipe pressure and water cannot be pumped normally, or the pumping flow is negative (backflow) during the start-up of the unit, further improving the stability of the unit's transition process, ensuring the stable operation of the power system, and having important significance for improving the operation theory and technology of variable-speed pumped-storage units. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flow chart of a method for selecting the minimum speed for self-starting of a variable speed pumped storage unit pump operating condition according to the present invention;

[0037] Figure 2 It is a system control block diagram after adding an adaptive module to the method for selecting the minimum speed for self-starting of the variable speed pumped storage unit pump working condition of the present invention;

[0038] Figure 3 It is a schematic diagram of the optimal opening generator under the pump working condition of the variable speed pumped storage unit of the present invention;

[0039] Figure 4 It is the flow-head characteristic curve of the variable speed pumped storage unit of the present invention at different speeds under the optimal opening;

[0040] Figure 5 It is a flow rate time domain variation diagram of the variable speed pumped storage unit of the present invention when the initial speed is 0.9pu at the optimal opening;

[0041] Figure 6 It is a flow rate time domain variation diagram of the variable speed pumped storage unit of the present invention when the initial speed is 0.91pu at the optimal opening;

[0042] Figure 7 It is a flow rate time domain variation diagram of the variable speed pumped storage unit of the present invention when the initial speed is 0.92pu at the optimal opening. DETAILED DESCRIPTION

[0043] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments so that the advantages and features of the present invention can be more easily understood by those skilled in the art.

[0044] Example 1

[0045] The control system block diagram of the method for selecting the minimum speed of the variable speed pumped storage unit pump self-starting in the present invention is as follows: Figure 2 As shown, the control system includes a pump turbine, a servo system, a water diversion pipeline, a doubly fed generator, an optimal speed generator, an optimal opening generator and an adaptive module. The adaptive module is located in the rotor side vector control. The input of the adaptive module is the reference input and the real-time head, and the output is the minimum speed.

[0046] In the control system, the machine side vector controls the stator flux and motor speed ω r Output the machine side switch signal S rabc Thus controlling the PWM output rotor voltage on the machine side v rabc , grid-side vector control is based on the bus voltage reference value v DCref , grid-side reactive power reference value Q gref and v DC , Q g The difference output grid-side switch signal S gabc ; Among them, the grid-side converter mainly controls the DC bus voltage of the unit v DC and reactive power ( v Dcrefis the reference DC bus voltage, Q gref is the reference reactive power); the machine-side converter mainly controls the stator flux of the unit and motor speed ( The servo system adjusts the output according to the speed signal. y , thereby adjusting the mechanical torque of the pump turbine T m When the unit starts from the stationary condition to the pumping phase adjustment condition, the unit inputs the reference input through the adaptive module. and lift H The minimum speed required for starting can be obtained, so this speed can be used as the reference speed for starting .

[0047] When the unit is switched from pumping phase adjustment to pumping operation, the reference speed is changed. and lift H The reference speed at this time is obtained through the optimal speed generator .

[0048] Setting of adaptive module and optimal opening of unit α opt , Reference head H and reference input When the unit reference input and head are determined, the optimal opening can be obtained, and the flow head characteristic curve at different speeds under the optimal opening can be calculated and analyzed. The minimum speed when the flow is greater than zero is found in the curve, and a certain safety margin is considered as the minimum speed obtained by the unit after passing through the adaptive module.

[0049] Example 2

[0050] The method for selecting the minimum speed of the variable speed pumped storage unit pump self-starting in the working condition of the present invention is as follows: Figure 1 The specific steps are as follows:

[0051] Step 1, determine the maximum head and minimum head during normal operation of the unit;

[0052] Step 2, determining the reference input change range corresponding to each head of the unit according to the operating range of the maximum head and the minimum head of the unit;

[0053] Step 3: Change the lift and the corresponding reference input range respectively. m , n Divide equally and create m OK n The matrix of columns makes the lift and reference input correspond one to one;

[0054] Step 4: Input the reference force after equal division in step 3 P ij and lift H ij , i =1… m , j =1… n ; The optimal opening of the unit under different reference input and head is obtained through the optimal opening generator ;

[0055] Lift H and reference input P The matrices are:

[0056] (1)

[0057] (2).

[0058] The optimal opening generator is based on the pump coordinated opening ω r - Q - α opt Curved surface, pump joint working condition ω r - Q - H Surface and ω r - Q - P The surface obtains the data of the optimal efficiency point, and the optimal efficiency point is obtained according to the data of the optimal efficiency point. P ref - H - ω ropt Surfaces;

[0059] According to the pump joint opening ω r - Q - α opt Surface and P t - H - Q Surface P ref - H - α opt Surfaces;

[0060] in, P t For actual input, Q For flow, ω r is the motor speed;P ref - H - ω ropt The surface represents the result of the optimal speed. P ref - H - α opt The surface represents the result of the optimization of the opening, and the optimal opening is obtained .

[0061] Step 5: Optimal opening obtained from step 4 , the optimal opening is obtained through the analysis and calculation of the water pump similarity law. The flow head characteristic curve of the unit at different reference speeds is shown below;

[0062] The similarity law formula of water pump is:

[0063] (3)

[0064] In formula (3), , Different speeds for water pump working conditions; Q 1. Q 2 indicates the speed is , flow rate at that time; H 1. H 2 indicates the speed is , Step 6: According to the flow-head characteristic curve obtained in step 5, select the minimum speed at which the flow rate is greater than zero when the reference head is 0 as the minimum speed. ;

[0065] First, in the flow-head characteristic curve, select the coordinates of the point where the flow is zero and the head is the reference head ( Q j0 , H jref ), and then according to the point coordinates, the speed corresponding to the flow rate of zero is obtained. Then the minimum speed required for the unit to switch from pumping phase adjustment to pumping condition is obtained. , finally according to draw P ij -H ij- Surface plot, where P ij Represents reference input, H ij Represents the lift; and generates an adaptive module based on the surface graph.

[0066] In step 6, the minimum speed required for the unit to switch from pumping phase adjustment mode to pumping mode The formula is:

[0067] (4)

[0068] In formula (4), R For safety margin, take 1.01~1.05.

[0069] Step 7: Generate the corresponding adaptive module according to step 6 Feedback to the reference speed required for the unit to start from the stationary condition to the pumping phase adjustment condition .

[0070] In step 7, the reference speed fed back to the unit when it starts from the stationary condition to the pumping phase adjustment condition is:

[0071] (5)

[0072] The unit is started from a stationary condition to a pumping phase adjustment condition through the excitation preparation stage, the excitation stage, the constant torque speed increase stage, the constant power speed increase stage, the power reduction speed increase stage and the demagnetization flux stage.

[0073] Example 3

[0074] Taking an actual pumped-storage power station as an example, the head range of the unit in normal operation is 430m-480m. After adding an adaptive module to the unit, the reference input of the unit is set to 245MW and the reference head is set to 430m.

[0075] When the unit reference input and reference head are determined, the unit passes through the optimal opening generator, such as Figure 3 As shown, it can be concluded that the optimal opening of the unit at this time is 18°. Through the analysis and calculation of the water pump similarity law, the flow head characteristic curve of the unit at different initial speeds at the optimal opening of 18° can be obtained, as shown in Figure 4 As shown, the two horizontal dotted lines represent the minimum head of the unit during normal operation. H min and maximum lift H max ; It can be seen from the figure that when the reference head is 430m and the flow rate is greater than zero, the minimum speed is 0.92pu. When the initial speed is less than 0.92pu and the flow rate is less than zero, the volute pressure of the unit will be greater than the tailwater pipe pressure, and water cannot be pumped normally, resulting in hydraulic instability of the unit.

[0076] Figure 5 , Figure 6 and Figure 7The flow rate time domain variation diagrams are respectively when the initial speed of the unit is 0.9pu, 0.91pu and 0.92pu. By comparison, it can be seen that when the initial speed is 0.9pu, the reference head is 430m and the input is 245MW, the corresponding steady-state flow rate of the unit is -12.7m³ / s. Figure 5 It can also be seen from the figure that the pump cannot supply water at this time. When the initial speed is 0.91pu, the reference head is 430m and the input is 245MW, the corresponding steady-state flow rate of the unit is -8.6 m³ / s. Figure 6 It can also be seen that the pump fails to supply water at this time; when the initial speed is 0.92pu, the reference head is 430m and the input is 245MW, the corresponding steady-state flow rate of the unit is 1.25m³ / s. Figure 7 It can also be seen that the pump does not fail to pump water at this time. Therefore, it can be seen that the present invention can select the minimum speed according to the reference input and head of the unit by adding an adaptive module, thereby avoiding the phenomenon that the volute pressure is greater than the tailwater pipe pressure and the water cannot be pumped normally, reducing the hydraulic instability during the unit startup and working condition conversion process, and reducing the impact on the stability of the power grid.

Claims

1. A method for selecting the minimum speed for self-starting of a variable speed pumped storage unit pump, characterized in that: An adaptive module is added to the variable speed pumped storage unit pump operating condition self-starting strategy, and the adaptive module is located in the rotor side vector control; the input of the adaptive module is the reference input and the real-time head, and the optimal opening corresponding to the reference input and the real-time head is obtained by using the optimal opening generator, so as to calculate the flow head characteristic curve at different speeds under the optimal opening, find the minimum speed when the flow is greater than zero in the flow head characteristic curve, and obtain the minimum speed after considering the safety margin; and use this minimum speed as the reference speed when the unit is started from the static working condition to the pumping phase adjustment working condition or the pumping phase adjustment working condition; the specific operation is as follows: Step 1, determine the maximum head and minimum head during normal operation of the unit; Step 2, determining the reference input change range corresponding to each head of the unit according to the operating range of the maximum head and the minimum head of the unit; Step 3: Change the lift and the corresponding reference input range respectively. m , n Divide equally and create m OK n The matrix of columns makes the lift and reference input correspond one to one; Step 4: Input the reference force after equal division in step 3 P ij and lift H ij , i =1… m , j =1… n ; The optimal opening of the unit under different reference input and head is obtained through the optimal opening generator ; Step 5: Optimal opening obtained from step 4 , the optimal opening is obtained through the water pump similarity law analysis and calculation. The flow head characteristic curve of the unit at different reference speeds is shown below; Step 6: According to the flow head characteristic curve obtained in step 5, select the minimum speed at which the flow rate is greater than zero when the reference head is reached, and add the safety margin to obtain the minimum speed. ; Step 7, based on step 6 Feedback to the reference speed required for the unit to start from the stationary condition to the pumping phase adjustment condition .

2. The method for selecting the minimum speed for self-starting of a variable speed pumped storage unit pump according to claim 1, characterized in that: In step 3, lift H and reference input P The matrices are: （1） （2）。 3. The method for selecting the minimum speed for self-starting of a variable speed pumped storage unit pump according to claim 2, characterized in that: In step 4, the optimal opening generator is based on the pump coordinated opening ω r - Q - α opt Curved surface, pump joint working condition ω r - Q - H Surface and ω r - Q - P The surface obtains the data of the optimal efficiency point, and the optimal efficiency point is obtained according to the data of the optimal efficiency point. P ref - H - ω ropt Surfaces; According to the pump joint opening ω r - Q - α opt Surface and P t - H - Q Surface P ref - H - α opt Surfaces; in, P t For actual input, Q For flow; P ref - H - ω ropt The surface represents the result of the optimal speed. P ref - H - α opt The surface represents the result of the optimization of the opening, and the optimal opening is obtained .

4. The method for selecting the minimum speed for self-starting of a variable speed pumped storage unit pump according to claim 1, characterized in that: In step 5, the water pump similarity law formula is: （3） In formula (3), , Different speeds for water pump working conditions; Q 1. Q 2 indicates the speed is , flow rate at that time; H 1. H 2 indicates the speed is , The lift at that time.

5. The method for selecting the minimum speed for self-starting of a variable speed pumped storage unit pump according to claim 1, characterized in that: In step 6, first select the coordinates of the point where the flow rate is zero and the head is the reference head in the flow head characteristic curve ( Q j0 , H jref ), and then according to the point coordinates, the speed corresponding to the flow rate of zero is obtained. Then the minimum speed required for the unit to switch from pumping phase adjustment to pumping condition is obtained. , finally according to draw P ij -H ij- A surface graph, and generating an adaptive module according to the surface graph; in, P ij Represents reference input, H ij represents the lift; The minimum speed required for the unit to switch from pumping phase adjustment mode to pumping mode The formula is: （4） In formula (4), R For safety margin, take 1.01~1.

05.

6. The method for selecting the minimum speed for self-starting of a variable speed pumped storage unit pump according to claim 1, characterized in that: In step 7, the adaptive module obtained in step 6 generates the corresponding Feedback to the reference speed required for the unit to start from the stationary condition to the pumping phase adjustment condition ; The reference speed fed back to the unit when it starts from the stationary condition to the pumping phase adjustment condition is: （5） The unit is started from a stationary condition to a pumping phase adjustment condition through the excitation preparation stage, the excitation stage, the constant torque speed increase stage, the constant power speed increase stage, the power reduction speed increase stage and the demagnetization flux stage.

7. The equipment for selecting the minimum speed of the variable speed pumped storage unit pump self-starting, characterized by: It includes a storage medium and a processor, the storage medium is used to store a program, and when the program is executed by the processor, the processor implements the method for selecting the minimum speed for self-starting of the variable-speed pumped storage unit pump operating condition as described in any one of claims 1-6.

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