Starting control method for converter of full-power variable-speed pumped storage unit

Abstract

The invention relates to the technical field of pumped storage units, in particular to a full-power variable-speed pumped storage unit converter start control method, which comprises the following steps of: when a unit starts to start, keeping a grid-side circuit breaker and a machine-side circuit breaker in a disconnected state; controlling the excitation device to generate initial excitation current; controlling the opening degree of a guide vane through a speed regulator to control the speed increase of the rotating speed of a motor, judging the current required operation state, and if the current required operation state is a power generation state, enabling a machine-side converter to enter a power control mode to finish starting; and if the state is a water pumping state, closing the guide vane, enabling the machine-side converter to enter a brake deceleration state, reversely driving the pump turbine to accelerate after the rotating speed of the motor is reduced to 0, entering a water pumping working condition mode, and finishing starting. Through the control method, an extra direct-current capacitor charging loop of a traditional full-power converter can be omitted, and the unit cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of pumped storage unit control, and in particular to a full-power variable-speed pumped storage unit converter start-up control method. Background Art

[0002] Renewable energy power generation has strong volatility, intermittency, and randomness, and its ability to support the safety and stability of the power grid is weak. With the development of a high proportion of new energy power systems, power balance, power grid dispatching and operation, and safety control face many challenges and adverse effects. The development of energy storage provides a new idea for solving problems such as suppressing power fluctuations of new energy. Pumped storage is currently the most mature, economical, and cleanest energy storage method. It has functions such as peak load regulation, frequency regulation, and emergency standby, and plays an important role in the construction of new power systems. Variable speed pumped storage units have attracted widespread attention due to their high efficiency, flexible operation, and rapid response.

[0003] Among them, the research on doubly-fed variable-speed pumped-storage units is relatively in-depth, while the research on full-power variable-speed pumped-storage units is still in its infancy. In addition, the research is mainly on the operation process of full-power variable-speed pumped-storage units, and there is less research on the starting control of full-power variable-speed pumped-storage units. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a full-power variable-speed pumped storage unit converter startup control method, which can save the additional DC capacitor charging circuit of the traditional full-power converter, reduce the unit cost, and improve the reliability of the unit startup operation due to the reduction of unit components. And when the future pumped storage unit can work in off-grid mode (grid-building type), it can complete the DC side voltage building without relying on the power grid and only rely on the machine-side converter.

[0005] The present invention is achieved by adopting the following technical solutions: A full-power variable-speed pumped storage unit converter startup control method comprises the following steps: Step S1. When the unit starts to start, keep the grid-side circuit breaker and the machine-side circuit breaker in the disconnected state; Step S2. Controlling the excitation device to generate an initial excitation current; Step S3. The motor speed is controlled and increased by controlling the guide vane opening through the speed regulator, specifically comprising the following steps: Step S 31 . The current motor speed is less than the rated speed p % is adopted, the open-loop control mode is adopted, the speed governor is used to control the guide vane opening to slowly open at a slope related to the speed, and the excitation current is controlled to follow the motor speed to reach the rated excitation current; Step S 32. The current motor speed is greater than the rated speed p %, the hysteresis control switching logic is adopted to switch the guide vane control mode to closed-loop control, and the given speed increase curve is used as the command value of the closed-loop control to control the motor to increase speed steadily and quickly; Step S 33 . The current motor speed rises to the point where the DC side voltage reaches the rated voltage. w %, close the circuit breaker on the machine side, and use the short-time strong excitation function of the excitation device to make the terminal voltage of the motor reach the rated value, so that the DC voltage reaches the rated value; Step S 34 . After the DC voltage reaches the rated value, the grid-side circuit breaker is closed, the grid-side converter is put into operation, and the DC voltage is closed-loop controlled to a stable state; Step S4. Determine the current operating state. If it is in the power generation state, the machine-side converter enters the power control mode and completes the startup. If it is in the pumping state, close the guide vanes, and the machine-side converter enters the braking and deceleration state. After the motor speed drops to 0, it drives the pump turbine to increase speed in the reverse direction, enters the pumping mode, and completes the startup.

[0006] The hysteresis control switching logic specifically refers to: When , the guide vane control mode switches from open-loop control to closed-loop control; When the guide vane control mode is switched from closed-loop control to open-loop control.

[0007] The calculation method of the initial excitation current is: , In the formula, is the initial excitation current, is the rated excitation current, A coefficient ranging from 0 to 1.

[0008] The step S 31 It also includes calculating the guide vane opening at the current moment. The calculation method of the guide vane opening at the current moment is: , In the formula, is the guide vane opening at the current moment, is the guide vane opening at the previous moment, is the current motor speed, is a positive number, is the rated speed, is the guide vane step coefficient, is the maximum guide vane opening.

[0009] The step S 31 It also includes calculating the current excitation current, and the calculation method of the current excitation current is: , In the formula, is the current excitation current, is the rated excitation current, is a coefficient between 0 and 1, is the current motor speed, is the rated speed.

[0010] The command value of closed-loop control specifically refers to: , In the formula, is the command value of closed-loop control, is the current time, is the time to switch to closed-loop control, The time it takes for the motor speed to stabilize.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The startup control method of the present invention can save the extra DC capacitor charging circuit of the traditional full-power converter, reduce the cost of the unit, and improve the reliability of the unit startup operation due to the reduction of unit components. In addition, when the pumped storage unit can work in the off-grid mode (grid-connected type) in the future, it can complete the DC side voltage building without relying on the grid and only relying on the machine-side converter.

[0012] 2. In the present invention, the hysteresis control switching logic can avoid the current motor speed being The problem of frequent switching of control methods caused by nearby fluctuations.

[0013] 3. The present invention can control the motor to increase speed stably and quickly by using the speed increase curve as the command value of the closed-loop control.

[0014] 4. In the present invention, by calculating the initial excitation current, it is possible to avoid giving a relatively large excitation current initially, and the excitation current can be gradually increased.

[0015] 5. The present invention can ensure that the guide vane can increase at a certain positive value through the calculation method of the guide vane opening at the current moment, and the slope of the guide vane opening increase gradually decreases as the motor speed increases, thereby avoiding the motor speed increasing too fast and losing control.

[0016] 6. Through the calculation method of the current excitation current, the excitation current can be controlled to follow the motor speed to reach the rated excitation current.

[0017] 7. The present invention can control the motor to increase speed stably and rapidly by calculating the command value of closed-loop control. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, wherein: Figure 1 It is a structural schematic diagram of a full-power pumped storage unit and a full-power converter in the present invention; Figure 2 It is a schematic diagram of the switching logic of the hysteresis control in the present invention; Figure 3 It is a schematic diagram of the closed-loop control motor speed curve in the present invention; Figure 4 It is a schematic diagram of a DC voltage rising curve in the present invention; Markings in the figure: 1. Top-level controller, 2. Speed ​​governor, 3. Pump-turbine, 4. Excitation device, 5. Motor, 6. Grid-side circuit breaker, 7. Generator-side circuit breaker, 8. Grid-side converter, 9. Generator-side converter, 10. Transformer, 11. Power grid. DETAILED DESCRIPTION

[0019] Example 1 As a basic implementation mode of the present invention, the present invention includes a full-power variable-speed pumped storage unit converter startup control method, which includes the following steps: Step S1. When the unit starts to start, keep the grid-side circuit breaker and the unit-side circuit breaker in the disconnected state.

[0020] Step S2: Control the excitation device to generate an initial excitation current.

[0021] Step S3. The motor speed is controlled and increased by controlling the guide vane opening through the speed regulator, specifically comprising the following steps: Step S 31 . The current motor speed is less than the rated speed p %, an open-loop control method is adopted, in which the guide vane opening is controlled by the speed regulator to slowly open at a slope related to the speed, and the excitation current is controlled to follow the motor speed to reach the rated excitation current.

[0022] Step S 32 . The current motor speed is greater than the rated speed p %, the hysteresis control switching logic is adopted to switch the guide vane control mode to closed-loop control, and the given speed increase curve is used as the command value of the closed-loop control to control the motor to increase speed steadily and quickly.

[0023] Step S 33 . The current motor speed rises to the point where the DC side voltage reaches the rated voltage. w %, close the machine-side circuit breaker, and use the short-time strong excitation function of the excitation device to make the terminal voltage of the motor reach the rated value, so that the DC voltage reaches the rated value.

[0024] Step S 34. After the DC voltage reaches the rated value, the grid-side circuit breaker is closed, the grid-side converter is put into operation, and the DC voltage is closed-loop controlled to a stable state.

[0025] Step S4. Determine the current operating state. If it is in the power generation state, the machine-side converter enters the power control mode and completes the startup. If it is in the pumping state, close the guide vanes, and the machine-side converter enters the braking and deceleration state. After the motor speed drops to 0, it drives the pump turbine to increase speed in the reverse direction, enters the pumping mode, and completes the startup.

[0026] Example 2 As a preferred embodiment of the present invention, the present invention includes a full-power variable-speed pumped storage unit converter startup control method, which includes the following steps: Step S1. When the unit starts to start, keep the grid-side circuit breaker and the unit-side circuit breaker in the disconnected state.

[0027] Step S2: Control the excitation device to generate an initial excitation current.

[0028] Step S3. The motor speed is controlled and increased by controlling the guide vane opening through the speed regulator, specifically comprising the following steps: Step S 31 . The current motor speed is less than the rated speed p %, an open-loop control method is adopted, in which the guide vane opening is controlled by the speed regulator to slowly open at a slope related to the speed, and the excitation current is controlled to follow the motor speed to reach the rated excitation current.

[0029] Step S 32 . The current motor speed is greater than the rated speed p %, the hysteresis control switching logic is used to switch the guide vane control mode to closed-loop control, and the given speed increase curve is used as the command value of the closed-loop control to control the motor to increase speed steadily and quickly. Among them, the hysteresis control switching logic specifically refers to: When , the guide vane control mode switches from open-loop control to closed-loop control; When the guide vane control mode is switched from closed-loop control to open-loop control.

[0030] Step S 33 . The current motor speed rises to the point where the DC side voltage reaches the rated voltage. w %, close the machine-side circuit breaker, and use the short-time strong excitation function of the excitation device to make the terminal voltage of the motor reach the rated value, so that the DC voltage reaches the rated value.

[0031] Step S 34 . After the DC voltage reaches the rated value, the grid-side circuit breaker is closed, the grid-side converter is put into operation, and the DC voltage is closed-loop controlled to a stable state.

[0032] Step S4. Determine the current operating state. If it is in the power generation state, the machine-side converter enters the power control mode and completes the startup. If it is in the pumping state, close the guide vanes, and the machine-side converter enters the braking and deceleration state. After the motor speed drops to 0, it drives the pump turbine to increase speed in the reverse direction, enters the pumping mode, and completes the startup.

[0033] Example 3 As another preferred embodiment of the present invention, the present invention includes a full-power variable-speed pumped storage unit converter startup control method, which includes the following steps: Step S1. When the unit starts to start, keep the grid-side circuit breaker and the unit-side circuit breaker in the disconnected state.

[0034] Step S2. Control the excitation device to generate an initial excitation current. The calculation method of the initial excitation current is: , In the formula, is the initial excitation current, is the rated excitation current, A coefficient ranging from 0 to 1.

[0035] Step S3. The motor speed is controlled and increased by controlling the guide vane opening through the speed regulator, specifically comprising the following steps: Step S 31 . The current motor speed is less than the rated speed p %, an open-loop control method is adopted, in which the guide vane opening is controlled by the speed regulator to slowly open at a slope related to the speed, and the excitation current is controlled to follow the motor speed to reach the rated excitation current.

[0036] Step S 32 . The current motor speed is greater than the rated speed p %, the hysteresis control switching logic is adopted to switch the guide vane control mode to closed-loop control, and the given speed increase curve is used as the command value of the closed-loop control to control the motor to increase speed steadily and quickly.

[0037] Among them, the command value of closed-loop control specifically refers to: , In the formula, is the command value of closed-loop control, is the current time, is the time to switch to closed-loop control, The time it takes for the motor speed to stabilize.

[0038] Step S 33 . The current motor speed rises to the point where the DC side voltage reaches the rated voltage. w%, close the machine-side circuit breaker, and use the short-time strong excitation function of the excitation device to make the terminal voltage of the motor reach the rated value, so that the DC voltage reaches the rated value.

[0039] Step S 34 . After the DC voltage reaches the rated value, the grid-side circuit breaker is closed, the grid-side converter is put into operation, and the DC voltage is closed-loop controlled to a stable state.

[0040] Step S4. Determine the current operating state. If it is in the power generation state, the machine-side converter enters the power control mode and completes the startup. If it is in the pumping state, close the guide vanes, and the machine-side converter enters the braking and deceleration state. After the motor speed drops to 0, it drives the pump turbine to increase speed in the reverse direction, enters the pumping mode, and completes the startup.

[0041] Example 4 As the best embodiment of the present invention, the present invention includes a full-power variable-speed pumped storage unit converter startup control method. The structure of the full-power pumped storage unit and the full-power converter can be as shown in the attached manual. Figure 1 As shown, the full-power pumped storage unit includes a top-level controller 1, a speed regulator 2, a pump turbine 3, a motor 5, an excitation device 4, a machine-side circuit breaker 7, a full-power converter, a grid-side circuit breaker 6, a transformer 10, and a power grid 11. The full-power converter includes a machine-side converter 9 and a grid-side converter 8. The top-level controller 1 controls the full-power converter, the excitation device 4, and the speed regulator 2 according to the dispatch instruction requirements. The top-level controller 1 sends active power and reactive power instructions to the full-power converter, sends excitation current instructions to the excitation device 4, and sends opening or speed instructions to the speed regulator 2. The speed regulator 2 performs closed-loop control on the speed of the unit by controlling the guide vane opening. The full-power converter adopts a vector control method to perform closed-loop control on the grid-connected power. The excitation device 4 performs closed-loop control on the excitation current. Among them, the motor 5 specifically refers to a generator or an electric motor. The top-level controller 1 is called a main controller / master control in a wind turbine generator set. The top-level controller 1 may also be a coordination controller, which is a conventional PLC or industrial computer or the like.

[0042] The startup control method comprises the following steps: Step S1. When the unit starts to start, the top-level controller keeps the grid-side circuit breaker and the machine-side circuit breaker in the disconnected state.

[0043] Step S2. In order to prevent the motor speed of the electric excitation motor from rising rapidly when the guide vanes are opened, the top-level controller controls the excitation device to generate an initial excitation current, so that the motor speed can be prevented from rising rapidly by relying on the magnetic resistance torque of the motor. The motor specifically refers to a generator or an electric motor. The calculation method of the initial excitation current is: , In the formula, is the initial excitation current, is the rated excitation current, A coefficient ranging from 0 to 1.

[0044] Step S3. The top-level controller controls the guide vane opening through the speed regulator to increase the motor speed, which specifically includes the following steps: Step S 31 . The current motor speed is less than the rated speed p %, for example p The value 10 can be taken, and an open-loop control method is adopted. The top-level controller sends an opening instruction to the speed governor. The speed governor controls the guide vane opening to slowly open at a slope related to the speed, for example, slowly opening at a rate of 1° / second, and controls the excitation current to follow the motor speed to reach the rated excitation current.

[0045] In this process, it is necessary to calculate the guide vane opening at the current moment. The calculation method of the guide vane opening at the current moment is: , In the formula, is the guide vane opening at the current moment, is the guide vane opening at the previous moment, is the current motor speed, is a small positive number such as 0.01, is the rated speed, is the guide vane step coefficient, is the maximum guide vane opening.

[0046] In this process, the current excitation current needs to be calculated. The calculation method of the current excitation current is: , In the formula, is the current excitation current, is the rated excitation current, is a coefficient between 0 and 1, is the current motor speed, is the rated speed.

[0047] Step S 32 . Current motor speed SPD Greater than rated speed of p %, the hysteresis control switching logic is used to switch the guide vane control mode to closed-loop control. Figure 2 , When , the guide vane control mode switches from open-loop control to closed-loop control; When the motor speed is , the guide vane control mode switches from closed-loop control to open-loop control. The problem of frequent switching of control methods caused by nearby fluctuations.

[0048] Then, the top-level controller gives a speed increase curve as the command value of the closed-loop control to control the motor to increase speed steadily and quickly, as shown in the attached manual. Figure 3 shown.

[0049] Among them, the command value of closed-loop control specifically refers to: , In the formula, is the command value of closed-loop control, is the current time, Attached to the instruction manual Figure 3 The time to switch to closed-loop control is shown in Attached to the instruction manual Figure 3 The time it takes for the motor speed to stabilize is shown.

[0050] Step S 33 . In the closed-loop control mode, the motor speed continues to increase. The current motor speed increases to a point where the DC side voltage reaches the rated voltage. w %hour, w The value can be 50, and the circuit breaker on the machine side can be closed. The short-term double excitation function of the excitation device (generally the maximum excitation multiple is 2 times, lasting 10s) can be used to increase the terminal voltage of the motor and reach the rated value, thereby increasing the DC side voltage according to the set curve until the DC voltage reaches the rated value.

[0051] Step S 34 . Refer to the instruction manual Figure 4 In t At time 3, after the DC voltage reaches the rated voltage, the grid-side circuit breaker is closed, the grid-side converter is put into operation, and the DC voltage is closed-loop controlled to a stable state.

[0052] Step S4. Determine the current operating state. If it is in the power generation state, the machine-side converter enters the power control mode and completes the startup. If it is in the pumping state, close the guide vanes, and the machine-side converter enters the braking and deceleration state. After the motor speed drops to 0, it drives the pump turbine to increase speed in the reverse direction, enters the pumping mode, and completes the startup.

[0053] Example 5 As another preferred embodiment of the present invention, the present invention includes a full-power pumped storage unit converter starting device, including a memory and a processor. The processor is used to execute instructions stored in the memory to implement the full-power pumped storage unit converter starting control method as described in any one of the above embodiments 1-4.

[0054] In summary, after reading the present invention document, ordinary technicians in this field can make various other corresponding transformation schemes based on the technical scheme and technical concept of the present invention without creative mental labor, which all fall within the scope of protection of the present invention.

Claims

1. A full-power variable-speed pumped storage unit converter startup control method, characterized in that: The following steps are involved: Step S1. When the unit starts to start, keep the grid-side circuit breaker and the machine-side circuit breaker in the disconnected state; Step S2. Controlling the excitation device to generate an initial excitation current; Step S3. The motor speed is controlled and increased by controlling the guide vane opening through the speed regulator, specifically comprising the following steps: Step S 31 . The current motor speed is less than the rated speed p % is adopted, the open-loop control mode is adopted, the speed governor is used to control the guide vane opening to slowly open at a slope related to the speed, and the excitation current is controlled to follow the motor speed to reach the rated excitation current; Step S 32 . The current motor speed is greater than the rated speed p %, the hysteresis control switching logic is adopted to switch the guide vane control mode to closed-loop control, and the given speed increase curve is used as the command value of the closed-loop control to control the motor to increase speed steadily and quickly; Step S 33 . The current motor speed rises to the point where the DC side voltage reaches the rated voltage. w %, close the circuit breaker on the machine side, and use the short-time strong excitation function of the excitation device to make the terminal voltage of the motor reach the rated value, so that the DC voltage reaches the rated value; Step S 34 . After the DC voltage reaches the rated value, the grid-side circuit breaker is closed, the grid-side converter is put into operation, and the DC voltage is closed-loop controlled to a stable state; Step S4. Determine the current operating state. If it is in the power generation state, the machine-side converter enters the power control mode and completes the startup. If it is in the pumping state, close the guide vanes, and the machine-side converter enters the braking and deceleration state. After the motor speed drops to 0, it drives the pump turbine to increase speed in the reverse direction, enters the pumping mode, and completes the startup.

2. A full-power variable-speed pumped storage unit converter startup control method according to claim 1, characterized in that: The hysteresis control switching logic specifically refers to: When , the guide vane control mode switches from open-loop control to closed-loop control; When the guide vane control mode is switched from closed-loop control to open-loop control.

3. A full-power variable-speed pumped storage unit converter startup control method according to claim 1 or 2, characterized in that: The calculation method of the initial excitation current is: ， In the formula, is the initial excitation current, is the rated excitation current, A coefficient ranging from 0 to 1.

4. A full-power variable-speed pumped storage unit converter startup control method according to claim 1, characterized in that: The step S 31 It also includes calculating the guide vane opening at the current moment. The calculation method of the guide vane opening at the current moment is: ， In the formula, is the guide vane opening at the current moment, is the guide vane opening at the previous moment, is the current motor speed, is a positive number, is the rated speed, is the guide vane step coefficient, is the maximum guide vane opening.

5. A full-power variable-speed pumped storage unit converter startup control method according to claim 1, characterized in that: The step S 31 It also includes calculating the current excitation current, and the calculation method of the current excitation current is: ， In the formula, is the current excitation current, is the rated excitation current, is a coefficient between 0 and 1, is the current motor speed, is the rated speed.

6. A full-power variable-speed pumped storage unit converter startup control method according to claim 1, characterized in that: The command value of closed-loop control specifically refers to: ， In the formula, is the command value of closed-loop control, t is the current time, t 1 is the time to switch to closed-loop control, t 2 is the time it takes for the motor speed to reach a stable state.

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