A Starting Control Method for the Converter of a Full-Power Variable-Speed Pumped-Storage Unit

Abstract

The present invention relates to the technical field of pumped-storage units, and particularly to a starting control method for a full-power variable-speed pumped-storage unit converter, including: when the unit starts, keeping the grid-side circuit breaker and the machine-side circuit breaker in the off state; controlling the excitation device to generate an initial excitation current; controlling the guide vane opening through the governor to control the speed increase of the motor, and judging the currently required operating state. If it is the power generation state, the machine-side converter enters the power control mode to complete the start; if it is the pumping state, closing the guide vane, the machine-side converter enters the braking and decelerating state. After the motor speed drops to 0, it drives the pump-turbine to increase speed in the reverse direction and enters the pumping working condition mode to complete the start. Through this control method, the additional DC capacitor charging circuit of the traditional full-power converter can be omitted, reducing the unit cost.

Description

Technical Field

[0001] The present invention relates to the technical field of pumped - storage unit control, and particularly to a starting control method for a full - power variable - speed pumped - storage unit converter. Background Art

[0002] New - energy power generation has strong volatility, intermittency, and randomness, and has weak support for the safe and stable operation of the power grid. With the development of a high - proportion new - energy power system, power balance, power - grid dispatching 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 new - energy power fluctuations. Pumped - storage is currently the most mature, economical, and clean energy - storage method, with functions such as peak shaving, frequency modulation, and accident standby, and plays an important role in the construction of a new - type power system. Variable - speed pumped - storage units have been widely concerned 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, and the research on full - power variable - speed pumped - storage units is still in its infancy. Moreover, the research mainly focuses 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] To solve the above - mentioned technical problems, the present invention proposes a starting control method for a full - power variable - speed pumped - storage unit converter, which can eliminate the additional DC - capacitor charging circuit of the traditional full - power converter, reduce the unit cost, and improve the reliability of the unit starting operation due to the reduction of unit components. And when future pumped - storage units can operate in an off - grid mode (grid - forming type), they can build the DC voltage only by the machine - side converter without relying on the power grid.

[0005] The present invention is realized by adopting the following technical solutions:

[0006] A starting control method for a full - power variable - speed pumped - storage unit converter includes the following steps:

[0007] Step S1. When the unit starts, keep the grid - side circuit breaker and the machine - side circuit breaker in the open state;

[0008] Step S2. Control the excitation device to generate an initial excitation current;

[0009] Step S3. Control the guide - vane opening through the governor to control the motor speed to increase, which specifically includes the following steps:

[0010] Step S 31 . When the current motor speed is less than pWhen it is

[0011] Step S 32 . When the current motor speed is greater than p % of the rated speed, the hysteresis control switching logic is adopted to switch the guide vane control mode to closed-loop control. Using the given speed-up curve as the command value for closed-loop control, the motor is controlled to increase speed stably and rapidly;

[0012] Step S 33 . When the current motor speed rises to make the DC side voltage reach w % of the rated voltage, close the machine-side circuit breaker. Through the short-time strong excitation function of the excitation device, make the terminal voltage of the motor reach the rated value and make the DC voltage reach the rated value;

[0013] Step S 34 . After the DC voltage reaches the rated value, close the grid-side circuit breaker, and the grid-side converter is put into operation to control the DC voltage to a stable state in closed-loop;

[0014] Step S4. Judge the current required operating state. If it is the power generation state, the machine-side converter enters the power control mode to complete the start; if it is the pumping state, close the guide vane, the machine-side converter enters the braking deceleration state. After the motor speed drops to 0, it drives the pump-turbine to increase speed in reverse and enters the pumping working condition mode to complete the start.

[0015] The so-called hysteresis control switching logic specifically refers to: When , the guide vane control mode is switched from the open-loop control mode to the closed-loop control; When , the guide vane control mode is switched from the closed-loop control to the open-loop control mode.

[0016] The calculation method of the initial excitation current is:

[0017] ,

[0018] In the formula, is the initial excitation current, is the rated excitation current, is a coefficient from 0 to 1.

[0019] The said step S 31 also includes calculating the guide vane opening at the current moment. The calculation method of the guide vane opening at the current moment is:

[0020] ,

[0021] 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.

[0022] The step S 31 also includes calculating the current excitation current, and the calculation method of the current excitation current is:

[0023] ,

[0024] In the formula, is the current excitation current, is the rated excitation current, is a coefficient from 0 to 1, is the current motor speed, is the rated speed.

[0025] The command value of the closed-loop control specifically refers to:

[0026] ,

[0027] In the formula, is the command value of the closed-loop control, is the current time, is the time when switching to the closed-loop control, is the time when the motor speed reaches stability.

[0028] Compared with the prior art, the beneficial effects of the present invention are shown in:

[0029] 1. The starting control method of the present invention can omit the additional DC capacitor charging circuit of the traditional full-power converter, reduce the cost of the unit, and improve the reliability of the unit starting and operating due to the reduction of unit components. And when future pumped-storage units can operate in the off-grid mode (grid-forming type), they can build the DC voltage only by the machine-side converter without relying on the power grid.

[0030] 2. In the present invention, through the hysteresis control switching logic, it is possible to avoid the problem of frequent switching of the control mode when the current motor speed fluctuates near .

[0031] 3. By using the speed-up curve as the command value of the closed-loop control, the present invention can control the motor to accelerate stably and quickly.

[0032] 4. In the present invention, by calculating the initial excitation current, it is possible to avoid initially giving a large excitation current and enable the excitation current to increase gradually.

[0033] 5. Through the calculation method of the guide vane opening at the current moment, it can ensure that the guide vane increases by a certain positive value, and the slope of the increase in the guide vane opening gradually decreases as the motor speed increases, avoiding the out-of-control situation caused by too rapid increase in the motor speed.

[0034] 6. Through the calculation method of the current excitation current, it can control the excitation current to reach the rated excitation current following the motor speed.

[0035] 7. Through the calculation of the command value in the closed-loop control, it can control the motor to increase speed stably and rapidly. Brief Description of the Drawings

[0036] The present invention will be further described in detail below in conjunction with the specification drawings and specific embodiments, where:

[0037] Figure 1 is a schematic structural diagram of the full-power pumped-storage unit and the full-power converter in the present invention;

[0038] Figure 2 is a schematic diagram of the hysteresis control switching logic in the present invention;

[0039] Figure 3 is a schematic diagram of the closed-loop control motor speed curve in the present invention;

[0040] Figure 4 is a schematic diagram of the DC voltage rising curve in the present invention;

[0041] Markings in the figure:

[0042] 1. Top-level controller, 2. Governor, 3. Pump-turbine, 4. Excitation device, 5. Motor, 6. Grid-side circuit breaker, 7. Machine-side circuit breaker, 8. Grid-side converter, 9. Machine-side converter, 10. Transformer, 11. Power grid. Specific Embodiments

[0043] Example 1

[0044] As a basic 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:

[0045] Step S1. When the unit starts, keep the grid-side circuit breaker and the machine-side circuit breaker in the off state.

[0046] Step S2. Control the excitation device to generate an initial excitation current.

[0047] Step S3. Control the guide vane opening through the governor to control the motor speed to increase, specifically including the following steps:

[0048] Step S 31 . When the current motor speed is less thanp When it is % , an open-loop control method is adopted. The guide vane opening is controlled by the governor to slowly open at a speed-related slope, and the excitation current is controlled to follow the motor speed to reach the rated excitation current.

[0049] Step S 32 . When the current motor speed is greater than % of the rated speed, a hysteresis control switching logic is adopted to switch the guide vane control method to closed-loop control. Using the given speed-up curve as the command value for closed-loop control, the motor is controlled to increase speed stably and quickly. p When it is % , a hysteresis control switching logic is adopted to switch the guide vane control method to closed-loop control. Using the given speed-up curve as the command value for closed-loop control, the motor is controlled to increase speed stably and quickly.

[0050] Step S 33 . When the current motor speed rises to make the DC side voltage reach % of the rated voltage, the machine-side circuit breaker is closed. Through the short-time strong excitation function of the excitation device, the terminal voltage of the motor reaches the rated value, and the DC voltage reaches the rated value. w When the current motor speed rises to make the DC side voltage reach % of the rated voltage, the machine-side circuit breaker is closed. Through the short-time strong excitation function of the excitation device, the terminal voltage of the motor reaches the rated value, and the DC voltage reaches the rated value.

[0051] Step S 34 . After the DC voltage reaches the rated value, the grid-side circuit breaker is closed, and the grid-side converter is put into operation to control the DC voltage to a stable state in closed-loop control.

[0052] Step S4. Judge the currently required operating state. If it is the power generation state, the machine-side converter enters the power control mode to complete the start-up; if it is the pumping state, the guide vane is closed, the machine-side converter enters the braking deceleration state. After the motor speed drops to 0, it drives the pump-turbine to increase speed in the reverse direction and enters the pumping working condition mode to complete the start-up.

[0053] Embodiment 2

[0054] As a preferred embodiment of the present invention, the present invention includes a full-power variable-speed pumped-storage unit converter start-up control method, which includes the following steps:

[0055] Step S1. When the unit starts, keep the grid-side circuit breaker and the machine-side circuit breaker in the open state.

[0056] Step S2. Control the excitation device to generate an initial excitation current.

[0057] Step S3. Control the motor speed to increase by controlling the guide vane opening through the governor, which specifically includes the following steps:

[0058] Step S 31 . When the current motor speed is less than % of the rated speed, an open-loop control method is adopted. The guide vane opening is controlled by the governor to slowly open at a speed-related slope, and the excitation current is controlled to follow the motor speed to reach the rated excitation current. p When the current motor speed is less than % of the rated speed, an open-loop control method is adopted. The guide vane opening is controlled by the governor to slowly open at a speed-related slope, and the excitation current is controlled to follow the motor speed to reach the rated excitation current.

[0059] Step S 32. When the current motor speed is greater than p % of the rated speed, the hysteresis control switching logic is adopted to switch the guide vane control mode to closed-loop control, and the given speed-up curve is used as the command value of the closed-loop control to control the motor to increase speed stably and quickly. Among them, the hysteresis control switching logic specifically refers to: When, the guide vane control mode is switched from the open-loop control mode to the closed-loop control; When, the guide vane control mode is switched from the closed-loop control to the open-loop control mode.

[0060] Step S 33 . When the current motor speed rises to make the DC side voltage reach w % of the rated voltage, close the machine side circuit breaker, and make the terminal voltage of the motor reach the rated value through the short-time strong excitation function of the excitation device, so that the DC voltage reaches the rated value.

[0061] Step S 34 . After the DC voltage reaches the rated value, close the grid side circuit breaker, and the grid side converter is put into operation to control the DC voltage to a stable state in closed loop.

[0062] Step S4. Judge the currently required operating state. If it is the power generation state, the machine side converter enters the power control mode to complete the start; if it is the pumping state, close the guide vane, the machine side converter enters the braking and decelerating state, and after the motor speed drops to 0, it drives the pump-turbine to increase speed in reverse and enters the pumping working condition mode to complete the start.

[0063] Embodiment 3

[0064] As another preferred embodiment of the present invention, the present invention includes a full-power variable-speed pumped storage unit converter start control method, which includes the following steps:

[0065] Step S1. When the unit starts, keep the grid side circuit breaker and the machine side circuit breaker in the open state.

[0066] Step S2. Control the excitation device to generate an initial excitation current. The calculation method of the initial excitation current is:

[0067] ,

[0068] In the formula, is the initial excitation current, is the rated excitation current, is a coefficient from 0 to 1.

[0069] Step S3. Control the opening of the guide vane through the governor to control the motor speed to increase, specifically including the following steps:

[0070] Step S 31. When the current motor speed is less than p % of the rated speed, an open-loop control method is adopted. The guide vane opening is slowly opened with a speed-related slope through a speed governor, and the excitation current is controlled to follow the motor speed to reach the rated excitation current.

[0071] Step S 32 . When the current motor speed is greater than p % of the rated speed, a hysteresis control switching logic is adopted to switch the guide vane control method to closed-loop control. Using the given speed-up curve as the command value of the closed-loop control, the motor is controlled to increase speed stably and quickly.

[0072] Among them, the command value of the closed-loop control specifically refers to:

[0073] ,

[0074] In the formula, is the command value of the closed-loop control, is the current time, is the time when switching to closed-loop control, is the time when the motor speed reaches stability.

[0075] Step S 33 . When the current motor speed rises to make the DC side voltage reach w % of the rated voltage, the machine-side circuit breaker is closed. Through the short-time strong excitation function of the excitation device, the terminal voltage of the motor reaches the rated value, and the DC voltage reaches the rated value.

[0076] Step S 34 . After the DC voltage reaches the rated value, the grid-side circuit breaker is closed, and the grid-side converter is put into operation to control the DC voltage to a stable state in closed-loop.

[0077] Step S4. Judge the current operating state to be run. If it is the power generation state, the machine-side converter enters the power control mode to complete the start; if it is the pumping state, the guide vane is closed, the machine-side converter enters the braking deceleration state. After the motor speed drops to 0, it drives the pump-turbine to increase speed in reverse and enters the pumping working condition mode to complete the start.

[0078] Embodiment 4

[0079] As the best implementation mode of the present invention, the present invention includes a converter start control method for a full-power variable-speed pumped storage unit. Among them, the structures of the full-power pumped storage unit and the full-power converter can be as shown in the accompanying Figure 1As shown in the figure, the full-power pumped storage unit includes a top-level controller 1, a governor 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 governor 2 according to the requirements of the dispatching instruction. The top-level controller 1 sends active power and reactive power commands to the full-power converter, sends an excitation current command to the excitation device 4, and sends an opening or speed command to the governor 2. The governor 2 performs a closed-loop control on the unit speed by controlling the guide vane opening. The full-power converter adopts a vector control method to perform a closed-loop control on the grid-connected power. The excitation device 4 performs a closed-loop control on the excitation current. Among them, the motor 5 specifically refers to a generator or a motor. The top-level controller 1 is called the main controller / master controller in a wind turbine generator set. The top-level controller 1 can also be a coordination controller, which is a conventional controller such as a PLC or an industrial control computer.

[0080] The start control method includes the following steps:

[0081] Step S1. When the unit starts, the top-level controller keeps the grid-side circuit breaker and the machine-side circuit breaker in the open state.

[0082] Step S2. In order to prevent the motor speed from rising rapidly when the guide vane of the electro-excited motor is opened, the top-level controller controls the excitation device to generate an initial excitation current, so that the reluctance torque of the motor can be relied on to prevent the motor speed from flying up. Among them, the motor specifically refers to a generator or a motor. Among them, the calculation method of the initial excitation current is:

[0083] ,

[0084] In the formula, is the initial excitation current, is the rated excitation current, is a coefficient from 0 to 1.

[0085] Step S3. The top-level controller controls the motor speed to increase by controlling the guide vane opening through the governor, which specifically includes the following steps:

[0086] Step S 31 . When the current motor speed is less than p % of the rated speed, for example p can be taken as 10, an open-loop control method is adopted. The top-level controller sends an opening command to the governor, and the governor controls the guide vane opening to slowly open at a slope related to the speed, for example, slowly open at a rate of 1° / second, and controls the excitation current to reach the rated excitation current following the motor speed.

[0087] During this process, it is necessary to calculate the guide vane opening at the current moment. The calculation method for the guide vane opening at the current moment is as follows:

[0088] ,

[0089] wherein, 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 relatively small positive number such as 0.01, is the rated speed, is the guide vane step coefficient, is the maximum guide vane opening.

[0090] During this process, it is necessary to calculate the current excitation current. The calculation method for the current excitation current is as follows:

[0091] ,

[0092] wherein, is the current excitation current, is the rated excitation current, is a coefficient from 0 to 1, is the current motor speed, is the rated speed.

[0093] Step S 32 . Current motor speed SPD is greater than the rated speed by p %, the hysteresis control switching logic is adopted to switch the guide vane control mode to the closed-loop control. Refer to the attached instruction manual Figure 2 , when, the guide vane control mode is switched from the open-loop control mode to the closed-loop control; when, the guide vane control mode is switched from the closed-loop control to the open-loop control mode. The hysteresis control switching logic can avoid the problem of frequent switching of the control mode caused by the fluctuation of the motor speed near .

[0094] Then, the top-level controller gives the speed-up curve as the command value of the closed-loop control to control the motor to accelerate stably and quickly, as shown in the attached instruction manual Figure 3 .

[0095] Among them, the command value of the closed-loop control specifically refers to:

[0096] ,

[0097] wherein, is the command value of the closed-loop control, is the current time, For the time of switching to closed-loop control shown in the appendix of the specification Figure 3 and the time for the motor speed shown in the appendix of the specification to reach stability For the appendix of the specification Figure 3 and the time for the motor speed shown in the appendix of the specification to reach stability

[0098] Step S 33 . In the closed-loop control mode, the motor speed continuously rises. When the current motor speed rises to w % of the rated voltage of the DC side w which can be taken as 50, close the machine-side circuit breaker, and through the short-time 2-fold forced excitation function of the excitation device (generally, the maximum forced excitation multiple is 2 times and lasts for 10 s), make the terminal voltage of the motor rise and reach the rated value, so that the DC side voltage rises along the set curve until the DC voltage reaches the rated value

[0099] Step S 34 . Refer to Figure 4 in the appendix of the specification t At time 3, after the DC voltage reaches the rated voltage, close the grid-side circuit breaker, and the grid-side converter is put into operation to control the DC voltage in the closed-loop to a stable state

[0100] Step S4. Judge the currently required operating state. If it is the power generation state, the machine-side converter enters the power control mode to complete the startup; if it is the pumping state, close the guide vane, the machine-side converter enters the braking deceleration state. After the motor speed drops to 0, it drives the pump-turbine to speed up in the reverse direction and enters the pumping working condition mode to complete the startup

[0101] Embodiment 5

[0102] As another preferred embodiment of the present invention, the present invention includes a full-power pumped-storage unit converter startup device, including a memory and a processor. The processor is used to execute the instructions stored in the memory to implement the full-power pumped-storage unit converter startup control method described in any one of the above Embodiments 1-4

[0103] In summary, after those of ordinary skill in the art read the documents of the present invention, all other corresponding transformation schemes that can be made without creative mental labor according to the technical solutions and technical concepts of the present invention fall within the scope protected by the present invention

Claims

1. A starting control method for a full-power variable-speed pumped storage unit converter, characterized in that: Including 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 off state; Step S2. Control the excitation device to generate an initial excitation current; Step S3. Control the opening of the guide vane through the governor to control the speed increase of the motor, specifically including the following steps: Step S 31 . When the current motor speed is less than p % of the rated speed, an open-loop control method is adopted. The guide vane opening is slowly opened with a speed-related slope through the speed governor, and the excitation current is controlled to follow the motor speed to reach the rated excitation current; where p is 10; Step S 32 . When the current motor speed is greater than p % of the rated speed, the hysteresis control switching logic is adopted to switch the guide vane control mode to closed-loop control. Using the given speed-up curve as the command value of the closed-loop control, the motor is controlled to stably and rapidly speed up to 70% of the rated speed; Step S 33 . When the current motor speed rises to w % of the rated voltage of the DC side, close the machine-side circuit breaker, and make the terminal voltage of the motor reach the rated value through the short-time strong excitation function of the excitation device, so that the DC voltage reaches the rated value; Step S 34 . After the DC voltage reaches the rated value, close the grid-side circuit breaker, and the grid-side converter is put into operation, and the DC voltage is closed-loop controlled to a stable state; Step S4. Judge the currently required operating state. If it is the power generation state, the machine-side converter enters the power control mode to complete the start; if it is the pumping state, close the guide vane, the machine-side converter enters the braking deceleration state, and after the motor speed drops to 0, it drives the pump-turbine to speed up in the reverse direction and enters the pumping working condition mode to complete the start.

2. The starting control method of the converter of a full-power variable-speed pumped storage unit according to claim 1, characterized in that: The specific hysteresis control switching logic refers to: When [condition], the guide vane control mode switches from the open-loop control mode to the closed-loop control; When [condition], the guide vane control mode switches from the closed-loop control to the open-loop control mode.

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 exciting current, is the rated exciting current, is a coefficient from 0 to 1.

4. A starting control method for a full-power variable-speed pumped storage unit converter according to claim 1, characterized in that: The said step S 31 further includes calculating the guide vane opening at the current moment, and the calculation method of the guide vane opening at the current moment is as follows: ， Wherein, 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 further includes calculating a current exciting current, and the calculation method of the current exciting current is as follows: ， Wherein, is the current excitation current, is the rated excitation current, is a coefficient from 0 to 1, is the current motor speed, is the rated speed.

6. The starting control method of the full-power variable-speed pumped storage unit converter according to claim 1, characterized in that: The command value of the closed-loop control specifically refers to: ， In the formula, is the command value of the closed-loop control, t is the current time, t 1 is the time to switch to the closed-loop control, t 2 is the time when the motor speed reaches stability.

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