Variable-speed pumped storage unit starting method, device and power equipment

Abstract

The present application relates to motor control technology, and provides a starting method, device and power equipment for a variable-speed pumped-storage unit. By connecting a crowbar device to the rotor of the variable-speed unit, the unit operates in an asynchronous motor mode, avoiding out-of-step of the unit caused by too fast acceleration during back-to-back starting and SFC starting, and increasing the starting success rate.

Description

Technical Field

[0001] This application belongs to the technical field of motor control, and particularly relates to a starting method, device and power equipment for a variable-speed pumped-storage unit. Background Technique

[0002] Considering cost, environment, benefits and maturity, pumped storage is currently the most effective, practical and commercially valuable energy storage method in the operation control of large power grids. Since the water head changes greatly during the operation of pumped storage power stations, it directly affects the rotational speed corresponding to the best efficiency of power generation. The speed regulation range of conventional units is small and cannot meet the requirement that the water turbine operates at the optimal rotational speed all the time. Variable-speed units can adjust the rotational speed of the motor within a certain range to adapt to a wider range of water head changes, improve the operation efficiency of the water turbine, and improve the hydraulic performance of the water turbine.

[0003] Pumped storage units need to be started and stopped multiple times every day, and the starting problem plays a very important role in the daily operation of the units. Generally, variable-speed pumped storage units use doubly fed induction generators (DFIGs). In the power generation mode, they can be started through a speed governor, but in the pumping mode, the unit needs to start itself. The current self-starting method is to short-circuit the stator of the doubly fed unit, connect the excitation converter to the rotor of the doubly fed unit, and let it work in the asynchronous motor mode. The unit is started and its speed is increased to the grid connection speed, and then the short-circuit breaker on the stator side is disconnected. Then the excitation converter switches back to the doubly fed motor mode to apply AC excitation to the doubly fed unit, and after the stator working voltage is synchronized with the grid working voltage, the main breaker on the stator side is turned on, and thus the grid connection of the doubly fed unit is completed. However, for high-power doubly fed units, due to the influence of leakage inductance and the limitation of the output working voltage capacity of the excitation converter, the speed cannot be increased to the grid connection speed, and at this time, a back-to-back or static frequency changer (SFC) is needed to start the doubly fed unit.

[0004] Back-to-back starting is a backup starting method for pumped storage units. A conventional unit in this power station or an adjacent power station is used to start the doubly fed unit. The stators of the conventional unit and the doubly fed unit are electrically connected to each other through a starting bus. The conventional unit can be a constant-speed unit or a variable-speed unit. The constant-speed unit includes, but is not limited to, an electrically excited synchronous motor, and the variable-speed unit includes, but is not limited to, a doubly fed induction motor. Taking the constant-speed unit as an example, DC excitation is applied to the rotors of the constant-speed unit and the doubly fed unit respectively. The conventional unit uses the water flow to impact the water turbine to rotate and generate an AC voltage, which is applied to the stator of the doubly fed unit through the starting bus to drive the doubly fed unit to rotate. As the opening of the water turbine guide vane increases, the speed of the conventional unit slowly rises, and the speed of the doubly fed unit also rises synchronously. SFC starting is to use a frequency converter to generate an AC power supply with variable frequency to drive the doubly fed unit. The stator of the doubly fed unit is connected to the output side of the SFC through the starting bus, and DC excitation is applied to the rotor.

[0005] However, since the variable-speed unit has a different structure from the fixed-speed unit, the starting method of the fixed-speed unit cannot be directly used, otherwise it is easy to cause speed oscillation. An AC excitation system and a unit self-starting method for a variable-speed pumped-storage unit in the prior art short-circuit the stator side of the doubly-fed induction motor, and the AC excitation system is connected to the rotor side for self-starting. However, the leakage inductances of the stator and rotor of the motor equivalent to the rotor side are large, which limits the processing ability in the high-speed section, resulting in a long self-starting acceleration time or the inability to reach the grid connection speed. Summary of the Invention

[0006] The purpose of this application is to provide a starting method, device and power equipment for a variable-speed pumped-storage unit, aiming to solve the problem that the variable-speed pumped-storage unit is prone to losing synchronization during rapid starting under the pumping condition.

[0007] In the first aspect, an embodiment of this application provides a starting method for a variable-speed pumped-storage unit, including:

[0008] In response to the unit pumping start command, connect the crowbar device to the unit rotor according to a preset strategy, so that the unit is equivalent to a squirrel-cage asynchronous motor;

[0009] Turn on the drive power device to drive the unit stator, so that the unit speeds up to the grid connection speed.

[0010] In one embodiment, the connecting the crowbar device to the unit rotor according to a preset strategy includes:

[0011] Before the unit speeds up to the grid connection speed, constantly connect the crowbar device to the unit rotor; or

[0012] Before the unit speeds up to the grid connection speed, intermittently connect the crowbar device to the unit rotor according to a preset period.

[0013] In one embodiment, the connecting the crowbar device to the unit rotor according to a preset strategy further includes:

[0014] Detect the operating parameters of the crowbar device;

[0015] Before the unit speeds up to the grid connection speed, and when the operating parameters are less than the corresponding parameter thresholds, connect the crowbar device to the unit rotor.

[0016] In one embodiment, the connecting the crowbar device to the unit rotor according to a preset strategy further includes;

[0017] Before the unit speeds up to the grid connection speed, and when the operating parameters are greater than or equal to the corresponding parameter thresholds, disconnect the connection between the crowbar device and the unit rotor.

[0018] In one embodiment, the operating parameters include at least one of the working current, working voltage, working temperature of the crowbar device, and the unit temperature.

[0019] In one embodiment, before connecting the crowbar device to the unit rotor according to a preset strategy in response to the unit pumping start command, it includes:

[0020] Determine the actual crowbar resistance value corresponding to the maximum starting torque of the unit rotor according to the parameters of the unit and the parameters of the crowbar device;

[0021] Obtain the resistance value range applicable to the unit for the crowbar device under the condition of low voltage ride-through, and the resistance value range includes a resistance lower limit value and a resistance upper limit value;

[0022] Determine the resistance value of the crowbar device according to the resistance value range and the actual crowbar resistance value corresponding to the maximum starting torque.

[0023] In one embodiment, the determining the value of the crowbar device according to the resistance value range and the actual crowbar resistance corresponding to the maximum starting torque includes:

[0024] In the case where the actual crowbar resistance value corresponding to the maximum starting torque is less than the resistance lower limit value, the resistance value of the crowbar device is the resistance lower limit value;

[0025] In the case where the actual crowbar resistance value corresponding to the maximum starting torque is greater than the resistance upper limit value, the resistance value of the crowbar device is the resistance upper limit value;

[0026] In the case where the resistance upper limit value is not less than the actual crowbar resistance value corresponding to the maximum starting torque and the actual crowbar resistance value corresponding to the maximum starting torque is not less than the resistance lower limit value, the resistance value of the crowbar device is the actual crowbar resistance value corresponding to the maximum starting torque.

[0027] In one embodiment, the determining the actual crowbar resistance value corresponding to the maximum starting torque of the unit rotor according to the parameters of the unit and the parameters of the crowbar device includes:

[0028] Obtain the mechanical torque of the unit according to the parameters of the unit and the parameters of the crowbar device;

[0029] Draw the mechanical characteristic curve of the unit according to the expression of the mechanical torque of the unit to obtain the starting torque of the unit;

[0030] Obtain the actual crowbar resistance value corresponding to the maximum starting torque of the unit rotor according to the starting torque of the unit.

[0031] In a second aspect, an embodiment of the present application further provides a starting device for a variable-speed pumped-storage unit, including:

[0032] A control unit, configured to connect a crowbar device to the unit rotor according to a preset strategy in response to a pumping start command of the unit, so that the unit is equivalent to a squirrel-cage induction motor;

[0033] A driving unit, configured to turn on a driving power supply device to drive the stator of the unit, so that the unit speeds up to the grid connection speed.

[0034] In a third aspect, an embodiment of the present application further provides a power device, including an isolation transformer, an excitation transformer, a controller, a memory, and a computer program stored in the memory and executable on the controller, and a crowbar device, a first circuit breaker, a second circuit breaker, a third circuit breaker, a fourth circuit breaker, an excitation current converter, and a frequency converter respectively connected to the controller. A first end of the first circuit breaker, a first end of the second circuit breaker, and a first end of the excitation transformer are commonly connected and connected to the power grid through the isolation transformer. A second end of the first circuit breaker is connected to the stator of the variable-speed pumped-storage unit. A second end of the second circuit breaker is connected to a first end of the frequency converter. A second end of the frequency converter is connected to the stator of the unit through the third circuit breaker. A first end of the excitation current converter is connected to a second end of the isolation transformer through the excitation transformer. A second end of the excitation current converter is connected to the rotor of the variable-speed pumped-storage unit. The crowbar device is connected to the rotor of the unit. A first end of the fourth circuit breaker is connected to the driving unit of the unit, and a second end of the fourth circuit breaker is connected to the stator of the unit. When the controller executes the computer program, the steps of the variable-speed pumped-storage unit starting method described above are implemented.

[0035] The beneficial effects of the embodiment of the present application compared with the related art are as follows:

[0036] In the variable-speed pumped-storage unit starting method of the embodiment of the present application, the crowbar device is connected to the rotor of the variable-speed unit, so that the unit operates in the induction motor mode, avoiding out-of-step of the unit caused by too fast acceleration during back-to-back starting and SFC starting, and increasing the starting success rate. Description of the Drawings

[0037] Figure 1 It is a schematic structural diagram of a power device provided by an embodiment of the present application;

[0038] Figure 2 It is a flowchart of a variable-speed pumped-storage unit starting method provided by an embodiment of the present application;

[0039] Figure 3 It is a circuit structure diagram of a crowbar device provided by an embodiment of the present application;

[0040] Figure 4 The circuit structure diagram of the crowbar device provided by an embodiment of the present application;

[0041] Figure 5 The flow chart of the starting method of the variable-speed pumped-storage unit provided by an embodiment of the present application;

[0042] Figure 6 The steady-state equivalent circuit diagram of the crowbar device connected to the rotor of the unit provided by an embodiment of the present application;

[0043] Figure 7 The mechanical characteristic curve of the starting of the variable-speed pumped-storage unit provided by an embodiment of the present application;

[0044] Figure 8 The module schematic diagram of the starting device of the variable-speed pumped-storage unit provided by an embodiment of the present application;

[0045] Figure 9 The module schematic diagram of the power equipment provided by an embodiment of the present application. Detailed implementation manners

[0046] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0047] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0048] It should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0049] Furthermore, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality of" means two or more unless otherwise specifically defined.

[0050] In some embodiments, the variable-speed (pumped-storage) unit uses a doubly-fed induction motor (DFIG), and there are two starting methods: one is SFC starting, which is the main starting method for the variable-speed unit, and the other is back-to-back starting, which is the backup starting method for the variable-speed unit.

[0051] In electrical equipment, a circuit structure compatible with back-to-back starting and SFC starting is as Figure 1 shown, including an isolation transformer 11, an excitation transformer 12, a crowbar device 13, a first circuit breaker QF1, a second circuit breaker QF2, a third circuit breaker QF3, a fourth circuit breaker QF4, an excitation converter 14, and a frequency converter 15. The first ends of the first circuit breaker QF1, the second circuit breaker QF2, and the first end of the excitation transformer 12 are commonly connected and connected to the grid AC phase through the isolation transformer 11. The second end of the first circuit breaker QF1 is connected to the stator of the variable-speed pumped-storage unit (hereinafter referred to as the variable-speed unit or the unit) 10. The second end of the second circuit breaker QF2 is connected to the first end of the frequency converter 15. The second end of the frequency converter 15 is connected to the stator of the unit through the third circuit breaker QF3. The first end of the excitation converter 14 is connected to the second end of the isolation transformer 11 through the excitation transformer 12. The second end of the excitation converter 14 is connected to the rotor of the variable-speed pumped-storage unit 10. The crowbar device 13 is connected to the rotor of the unit 10. The first end of the fourth circuit breaker QF4 is connected to the driving unit 20, and the second end of the fourth circuit breaker QF4 is connected to the stator of the unit.

[0052] Among them, exemplarily, the driving unit 20 is a constant-speed unit or a variable-speed unit. The constant-speed unit is generally an electrically excited synchronous motor, and the variable-speed unit is generally a doubly-fed induction motor. For example, taking the constant-speed unit as an example, the constant-speed unit uses an electrically excited synchronous motor, and the variable-speed (pumped-storage) unit 10 is a doubly-fed induction motor. The excitation winding terminal of the driving unit 10 is connected to the DC power supply U f . The frequency converter 15 is an SFC frequency converter.

[0053] The purpose of the starting method for the variable-speed pumped-storage unit in the embodiments of this application is that when the unit 10 starts in the pumping condition, the crowbar device 13 is connected to the rotor of the unit, and the unit 10 can be equivalent to a squirrel-cage induction motor. When starting with SFC or back-to-back, the unit is driven in the asynchronous motor mode.

[0054] Active short - circuit control is to control the switching states of the switching tubes of the excitation converter 14, so that the variable - speed unit 10 is in a state of continuous rotor short - circuit or intermittent short - circuit, in order to quickly start the unit 10.

[0055] As Figure 2 shown, an embodiment of the present application provides a starting method for a variable - speed pumped - storage unit, including:

[0056] Step S110, in response to the unit's pumping start command, connect the crowbar device to the unit rotor according to a preset strategy, so that the unit is equivalent to a squirrel - cage induction motor.

[0057] Among them, the crowbar device 13 is connected to the unit rotor, and it is in a parallel relationship with the AC excitation converter 14. The access methods of the crowbar device 13 include full - process access during startup, intermittent access according to periods during startup, intermittent access according to the magnitude of the working current during startup, intermittent access according to the magnitude of the working voltage during startup, intermittent access according to the magnitude of the working temperature during startup, etc.

[0058] Step S120, turn on the drive power supply device to drive the unit stator, so that the unit speed rises to the grid - connection speed.

[0059] The grid - connection speed refers to the unit rotor speed at which the unit can be grid - connected.

[0060] Among them, turning on the drive power supply device means turning on, for example, the frequency converter 15 or the drive unit 20. The drive unit 20 can be a constant - speed unit or a variable - speed unit. The constant - speed unit includes but is not limited to an electrically - excited synchronous motor, and the variable - speed unit includes but is not limited to a doubly - fed induction motor. Taking the constant - speed unit as an example, it is an electrically - excited synchronous motor.

[0061] Exemplarily, during back - to - back startup, the second circuit breaker QF2 and the third circuit breaker QF3 are constantly open, the fourth circuit breaker QF4 is closed, the rotor of the drive unit 20 is excited, the water flow impacts the water turbine of the drive unit 20, driving the unit rotor of the drive unit 20 to rotate, rising from zero speed to the rated speed. The output voltage amplitude and frequency of the unit stator of the drive unit 20 gradually increase, driving the speed of the variable - speed unit 10 to increase. This process is equivalent to constant V / f control; when the speed of the variable - speed unit 10 enters the normal operating speed range, the startup is completed, the fourth circuit breaker QF4 is opened, the movable guide vanes of the water turbine of the drive unit 20 are closed, and the DC exciter stops exciting.

[0062] Exemplarily, during SFC startup, the second circuit breaker QF2 and the third circuit breaker QF3 are constantly closed, the fourth circuit breaker QF4 is constantly open, the frequency converter 15 is started, and the output current drives the speed of the variable - speed unit 10 to increase. When the speed of the variable - speed unit 10 enters the normal operating speed range, the startup is completed, the second circuit breaker QF2 and the third circuit breaker QF3 are opened, the operation of the frequency converter 15 stops, and no voltage is output.

[0063] It is understandable that the crowbar device 13 is a protective electronic circuit device that limits voltage and current. It is installed at the rotor end. Generally, when the stator voltage of the unit drops, the crowbar device 13 is used to absorb the magnetic field energy of the unit 10 and prevent the energy from flowing back into the excitation converter 14, causing system failures. In the embodiment of the present application, when the unit 10 starts up, the crowbar device 13 is connected to the rotor of the unit, which is different from the conventional method. The unit 10 is equivalent to a squirrel-cage induction motor, and the unit 10 can start quickly when operating in the asynchronous motor mode under the starting methods of SFC or back-to-back. Moreover, it can avoid the unit 10 from losing synchronization due to too fast starting acceleration and increase the starting success rate.

[0064] Such as Figure 3 、 Figure 4 As shown, the crowbar device 13 has two circuit structures. Figure 3 What is shown is a three-resistor crowbar device. Figure 4 What is shown is a single-resistor crowbar device. Both methods are internally equipped with switching tubes, and the switching of the crowbar device 13 is realized by controlling the on / off of the switching tubes. Generally, the two crowbar devices 13 have the same effect and can be mutually equivalent. The equivalent relationship is as follows:

[0065] (1)

[0066] Wherein, R c1 is the resistance value of each crowbar resistor in the three-resistor crowbar device, and R c2 is the resistance value of the crowbar resistor in the single-resistor crowbar device. According to the equivalent resistance relationship between the single-resistor crowbar device and the three-resistor crowbar device in formula (1), the resistance value of the single-resistor crowbar device can be obtained.

[0067] In one embodiment, connecting the crowbar device to the rotor of the unit according to the preset strategy in step S110 includes:

[0068] Before the unit 10 accelerates to the grid connection speed, the crowbar device 13 is constantly connected to the rotor of the unit. This can accelerate the acceleration of the unit 10 and start quickly. This method is applicable to the scenario where the heat dissipation performance of the crowbar device 13 is better.

[0069] In one embodiment, connecting the crowbar device to the rotor of the unit according to the preset strategy in step S110 includes:

[0070] Before the unit 10 accelerates to the grid connection speed, the crowbar device 13 is intermittently connected to the rotor of the unit according to a preset period.

[0071] The access period can be freely configured by the user. It can ensure the safety of the system while taking into account the acceleration of the unit 10. This method is applicable to the scenario where the heat dissipation of the crowbar device 13 is average.

[0072] In one embodiment, connecting the crowbar device to the unit rotor according to a preset strategy in step S110 further includes:

[0073] Detecting the operating parameters of the crowbar device 13.

[0074] Before the unit 10 accelerates to the grid connection speed and when the operating parameters are less than the corresponding parameter thresholds, connect the crowbar device 13 to the rotor of the unit 10.

[0075] For example, the operating parameters including at least one of the working current, working voltage, working temperature, and unit temperature of the crowbar device 13 can be detected through a relevant detection circuit.

[0076] In one embodiment, connecting the crowbar device to the unit rotor according to a preset strategy in step S110 further includes;

[0077] Before the unit 10 accelerates to the grid connection speed and when the operating parameters are greater than or equal to the corresponding parameter thresholds, disconnect the connection between the crowbar device 13 and the rotor of the unit 10.

[0078] Exemplarily, a temperature detection sensor is equipped on the crowbar device 13 and is intermittently connected according to the working temperature during the startup process of the variable-speed unit 10. When it is detected that the working temperature exceeds the temperature protection threshold plus the positive hysteresis, the crowbar device 13 is removed. When it is detected that the working temperature is lower than the temperature protection threshold minus the negative hysteresis, the crowbar device 13 is connected. The temperature protection threshold, positive hysteresis, and negative hysteresis can be freely configured by the user. This method is applicable to the occasion where a temperature detection sensor is installed on the crowbar device 13.

[0079] Exemplarily, a current detection sensor is equipped on the crowbar device 13 and is intermittently connected according to the calculated heat accumulation amount during the startup process of the variable-speed unit 10. The heat accumulation formula: .

[0080] Where, R c is the equivalent resistance value of the crowbar device 13, and i is the working current of the crowbar device 13. When the calculated heat accumulation amount exceeds the heat protection threshold plus the positive hysteresis, the crowbar device 13 is removed. When the calculated heat accumulation amount is lower than the heat protection threshold minus the negative hysteresis, the crowbar device 13 is connected. The heat protection threshold, positive hysteresis, and negative hysteresis can be freely configured by the user. This method is applicable to the occasion where a current detection sensor is installed on the crowbar device 13.

[0081] Exemplarily, a voltage detection sensor is equipped on the crowbar device 13 and is intermittently connected according to the calculated heat accumulation amount during the startup process of the variable-speed unit 10. The heat accumulation formula: .

[0082] Where, u cis the operating voltage at both ends of the crowbar device 13. When the calculated heat accumulation amount exceeds the heat protection threshold plus the positive hysteresis, the crowbar device 13 is cut off. When the calculated heat accumulation amount is lower than the heat protection threshold minus the negative hysteresis, the crowbar device 13 is connected. The heat protection threshold, positive hysteresis, and negative hysteresis can be freely configured by the user. This method is applicable to the occasion where a voltage detection sensor is installed on the crowbar device 13.

[0083] Exemplarily, the variable speed unit 10 is equipped with a temperature detection sensor, and it is intermittently connected according to the size of the unit temperature during the startup process of the variable speed unit 10. When it is detected that the unit temperature exceeds the temperature protection threshold plus the positive hysteresis, the crowbar device 13 is cut off; when it is detected that the unit temperature is lower than the temperature protection threshold minus the negative hysteresis, the crowbar device 13 is connected. The temperature protection threshold, positive hysteresis, and negative hysteresis can be freely configured by the user. This method is applicable to the occasion where a temperature detection sensor is installed on the variable speed unit 10.

[0084] Please refer to Figure 5 , in one of the embodiments, before step S110, it further includes:

[0085] Step S210, determine the actual crowbar resistance value corresponding to the maximum starting torque of the unit rotor according to the parameters of the unit and the parameters of the crowbar device.

[0086] Among them, the parameters of the unit 10 are, for example, the number of pole pairs N of the unit p , the stator frequency f s , the stator voltage u s , the stator reactance X s , the rotor reactance X r , the slip s, the stator resistance R s , the stator leakage inductance L s , the reduced rotor leakage inductance L' r , the mutual inductance l between the stator and rotor m , etc. The parameters of the crowbar device 13 are, for example, the crowbar resistance R of the crowbar device c1 , R c2 , etc.

[0087] Among them, first calculate the expression of the mechanical torque of the unit 10, then obtain the expression of the starting torque of the unit 10 according to the expression of the mechanical torque, then obtain the equivalent resistance of the crowbar device 13 corresponding to the maximum starting torque according to the expression of the starting torque, and finally obtain the actual crowbar resistance value corresponding to the maximum starting torque by converting the equivalent resistance of the crowbar device 13 corresponding to the maximum starting torque to the rotor side.

[0088] Step S220, obtain the resistance value range suitable for the crowbar device for the unit in the case of low voltage ride-through, and the resistance value range includes a resistance lower limit value and a resistance upper limit value.

[0089] The low-voltage ride-through requirements of unit 10 are configured according to the unit parameters and application scenarios. For example, the resistance value range of the crowbar device under low-voltage ride-through conditions is R cmin ~R cmax , where R cmin is the lower limit value of the resistance, and R cmax is the upper limit value of the resistance.

[0090] Step S230: Determine the resistance value of the crowbar device according to the resistance value range and the actual crowbar resistance value corresponding to the maximum starting torque.

[0091] Exemplarily, the resistance value of the crowbar device 13 can be within the resistance value range of the crowbar device under low-voltage ride-through conditions. In this way, the crowbar device 13 connected during the startup of the unit 10 can provide a sufficiently large starting torque for the unit 10, and the startup speed can be increased without losing synchronization. On the other hand, during the normal operation of the unit 10, when the stator voltage drops, the crowbar device 13 can absorb the magnetic field energy to prevent the energy from flowing back into the AC excitation converter 14 and causing system failures.

[0092] In one embodiment, step S230 includes:

[0093] When the actual crowbar resistance value R c1_maxT <the lower limit value of the resistance R cmin , the resistance value of the crowbar device 13 is the lower limit value of the resistance R cmin .

[0094] When the actual crowbar resistance value R c1_maxT >the upper limit value of the resistance R cmax , the resistance value of the crowbar device 13 is the upper limit value of the resistance R cmax .

[0095] When the upper limit value of the resistance R cmax ≥the actual crowbar resistance value R corresponding to the maximum starting torque c1_maxT ≥the lower limit value of the resistance R cmin , the resistance value of the crowbar device 13 is the actual crowbar resistance value corresponding to the maximum starting torque.

[0096] Specifically, when the upper limit value of the resistance R cmax ≥the actual crowbar resistance value R corresponding to the maximum starting torque c1_maxT ≥the lower limit value of the resistance R cmin , in order to obtain the maximum starting torque, the actual crowbar resistance value can be directly taken as the resistance value of the crowbar device 13. It can be understood that the resistance value of the crowbar device 13 is the equivalent resistance value of the crowbar device 13.

[0097] In one embodiment, step S210 includes:

[0098] Step A, obtaining the mechanical torque of the unit 10 according to the parameters of the unit 10 and the parameters of the crowbar device 13.

[0099] The steady-state equivalent circuit diagram of the crowbar device 13 connected to the unit rotor is as Figure 6 shown, which is the same as the equivalent circuit of the squirrel-cage induction motor. Figure 1 The rotor resistance increases from R' r to R' r +R' c1 , and the expression of its mechanical torque is as follows:

[0100] (2)

[0101] Wherein, R' r is the reduced rotor resistance, and R' c1 is the equivalent resistance of the crowbar device 13 after reduction.

[0102] Step B, drawing the mechanical characteristic curve of the unit 10 according to the expression of the mechanical torque of the unit 10 to obtain the starting torque of the unit 10.

[0103] Drawing the mechanical characteristic curve according to the mechanical equation, as Figure 7 shown, wherein, s m is the slip corresponding to the maximum torque after the unit rotor is directly short-circuited, s' m is the slip corresponding to the maximum torque after the unit rotor is connected to the crowbar device 13, T m is the maximum torque, and T N is the rated torque. Let s = 1, and the expression of the starting torque can be obtained:

[0104] (3)

[0105] Wherein, X' r is the reduced rotor reactance. According to the expression (3) of the starting torque, it can be seen that as the equivalent resistance of the crowbar device 13 increases, the starting torque first increases and then decreases.

[0106] Step C, obtaining the actual crowbar resistance value corresponding to the maximum starting torque of the unit 10 rotor according to the starting torque of the unit 10.

[0107] Taking the derivative of the expression (3) of the starting torque with respect to the equivalent resistance R' c1 of the crowbar device 13 and making it 0, the equivalent resistance of the crowbar device 13 corresponding to the maximum starting torque can be obtained.

[0108] (4)

[0109] The equivalent resistance of the crowbar device 13 corresponding to the maximum starting torque is converted to the rotor side to obtain the actual crowbar resistance corresponding to the maximum starting torque.

[0110] (5)

[0111] Wherein, N sr is the turns ratio of the stator to the rotor.

[0112] In some embodiments, the starting method further includes the following steps:

[0113] Step S310, in response to the unit 10 accelerating to the grid connection speed, control the disconnection of the crowbar device 13 from the unit rotor.

[0114] Step S320, control the excitation converter 14 to excite and drive the unit rotor, and connect the stator of the unit to the secondary side of the isolation transformer 11 to complete grid connection.

[0115] Specifically, drive to make the working voltage of the unit stator synchronize with the amplitude, frequency, and phase of the grid AC working voltage. Refer to Figure 1 , control the first circuit breaker QF1 to close, the second circuit breaker QF2, the third circuit breaker QF3, and the fourth circuit breaker QF4 to open, and connect the stator of the unit to the secondary side of the isolation transformer 11; at the same time, the second circuit breaker QF2K2 and the fourth circuit breaker QF4K4 can be turned off, and the grid connection process ends.

[0116] Step S330, enter the pumping control stage.

[0117] That is, enter the normal vector control of the excitation converter 14 for the unit 10. The pumping control stage uses normal vector control, and the active power and reactive power are decoupled. The user can freely set the active power set value and the reactive power set value, so that the unit can absorb the grid AC active power for pumped storage and also send reactive power to the grid AC.

[0118] Please refer to Figure 8 , this application embodiment also provides a starting device for a variable-speed pumped storage unit, including:

[0119] A control unit 81, configured to connect the crowbar device 13 to the unit 10 rotor according to a preset strategy in response to a pumping start command of the unit 10, so that the unit 10 is equivalent to a squirrel-cage induction motor;

[0120] A driving unit 82, configured to connect the driving power supply device to drive the stator of the unit 10, so that the unit 10 accelerates to the grid connection speed.

[0121] The specific implementation manners and beneficial effects of the starting device for the variable-speed pumped storage unit can refer to the description of the implementation manners of the above-mentioned starting method for the variable-speed pumped storage unit, and will not be elaborated here.

[0122] Please refer to Figure 1 and Figure 9 Figure 9

[0123] Those skilled in the art can understand that Figure 9 merely examples of the power device 90, which do not constitute a limitation on the power device 90, may include more or fewer components than shown, or combine certain components, or different components. For example, it may also include input / output devices, network access devices, etc.

[0124] The controller 91 may be a central processing unit (CPU), and the controller 91 may also be other general controllers 91, digital signal controllers 91 (Digital Signal Processor, DSP), application specific integrated circuits (ASIC), off-the-shelf programmable gate arrays (Field-Programmable Gate Array, FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general controller 91 may be a microcontroller 91 or any conventional controller 91.

[0125] The memory 92 may be an internal storage unit of the power device 90 in some embodiments, such as the hard disk or memory of the power device 90. The memory 92 may also be an external storage device of the power device 90 in other embodiments, such as a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. equipped on the power device 90. Further, the memory 92 may also include both the internal storage unit and the external storage device of the power device 90. The memory 92 is used to store an operating system, application programs, a Boot Loader, data, and other programs, etc. The memory 92 may also be used to temporarily store the data that has been output or will be output.

[0126] An embodiment of the present application also provides a computer-readable storage medium storing a computer program 921, and when the computer program 921 is executed by the controller 91, the steps in the above method embodiments can be implemented.

[0127] An embodiment of the present application provides a computer program 921 product, and when it runs on a computer, the computer is enabled to execute the steps in the above method embodiments.

[0128] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, to implement all or part of the processes in the above method embodiments of the present application, it can be completed by instructing the relevant hardware through the computer program 921. The computer program 921 can be stored in a computer-readable storage medium. When the computer program 921 is executed by the controller 91, the steps in the above method embodiments can be implemented. Wherein, the computer program 921 includes computer program 921 code, and the computer program 921 code may be in the form of source code, object code, executable file, or some intermediate form, etc. The computer-readable medium may at least include: any entity or device capable of carrying the computer program 921 code to the photographing device / terminal device, a recording medium, a computer memory 92, a ROM (Read-Only Memory, read-only memory 92), a RAM (Random Access Memory, random access memory 92), a CD-ROM (Compact Disc Read-Only Memory, read-only optical disc), magnetic tape, floppy disk, and optical data storage device, etc. The computer-readable storage medium mentioned in the present application may be a non-volatile storage medium, in other words, it may be a non-transitory storage medium.

[0129] It should be understood that all or part of the steps of implementing the above embodiments can be implemented by software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product 921. The computer program product includes one or more computer instructions. These computer instructions can be stored in the above-mentioned computer-readable storage medium.

[0130] In the above embodiments, the descriptions of the respective embodiments have their own emphases. For parts not described or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0131] Those of ordinary skill in the art can realize that the units and algorithm steps of the examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. A professional technician can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application.

[0132] In the embodiments provided in this application, it should be understood that the disclosed device / electronic device and method can be implemented in other ways. For example, the device / electronic device embodiments described above are only illustrative. For example, the division of modules or units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces. The indirect couplings or communication connections of the device or unit can be electrical, mechanical, or other forms.

[0133] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place, or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0134] The above embodiments are only used to illustrate the technical solutions of this application, rather than to limit it; although this application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included in the protection scope of this application.

Claims

1. A starting method for a variable-speed pumped-storage unit, characterized in that, Including: Determine the actual crowbar resistance value corresponding to the maximum starting torque of the unit rotor according to the parameters of the unit and the parameters of the crowbar device; Obtain the resistance value range applicable to the unit in the case of low voltage ride-through for the crowbar device, where the resistance value range includes a resistance lower limit value and a resistance upper limit value; Determine the resistance value of the crowbar device according to the resistance value range and the actual crowbar resistance corresponding to the maximum starting torque; In response to the unit pumping start command, connect the crowbar device to the unit rotor according to a preset strategy, so that the unit is equivalent to a squirrel-cage induction motor; Turn on the drive power device to drive the unit stator to make the unit speed up to the grid connection speed.

2. The startup method according to claim 1, wherein The connecting the crowbar device to the unit rotor according to a preset strategy includes: Before the unit speeds up to the grid connection speed, constantly connect the crowbar device to the unit rotor; or Before the unit speeds up to the grid connection speed, intermittently connect the crowbar device to the unit rotor according to a preset period.

3. The startup method according to claim 1, wherein The connecting the crowbar device to the unit rotor according to a preset strategy further includes: Detect the operating parameters of the crowbar device; Before the unit speeds up to the grid connection speed and when the operating parameters are less than the corresponding parameter thresholds, connect the crowbar device to the unit rotor.

4. The startup method according to claim 3, characterized in that The connecting the crowbar device to the unit rotor according to a preset strategy further includes; Before the unit speeds up to the grid connection speed and when the operating parameters are greater than or equal to the corresponding parameter thresholds, disconnect the connection between the crowbar device and the unit rotor.

5. The startup method according to claim 3 or 4, characterized in that, The operating parameters include at least one of the working current, working voltage, working temperature of the crowbar device and the unit temperature.

6. The starting method according to claim 1, wherein The determining the resistance value of the crowbar device according to the resistance value range and the actual crowbar resistance corresponding to the maximum starting torque includes: When the actual crowbar resistance value corresponding to the maximum starting torque is less than the resistance lower limit value, the resistance value of the crowbar device is equal to the resistance lower limit value; When the actual crowbar resistance value corresponding to the maximum starting torque is greater than the resistance upper limit value, the resistance value of the crowbar device is equal to the resistance upper limit value; When the resistance upper limit value is not less than the actual crowbar resistance value corresponding to the maximum starting torque and the actual crowbar resistance value corresponding to the maximum starting torque is not less than the resistance lower limit value, the resistance value of the crowbar device is the actual crowbar resistance value corresponding to the maximum starting torque.

7. The startup method according to claim 1, characterized in that, The determining the actual crowbar resistance value corresponding to the maximum starting torque of the unit rotor according to the parameters of the unit and the parameters of the crowbar device includes: Obtain the mechanical torque of the unit according to the parameters of the unit and the parameters of the crowbar device; Draw the mechanical characteristic curve of the unit according to the expression of the mechanical torque of the unit to obtain the starting torque of the unit; Obtain the actual crowbar resistance value corresponding to the maximum starting torque of the unit rotor according to the starting torque of the unit.

8. A starting device for a variable-speed pumped-storage unit, characterized in that, Including: A control unit for determining the actual crowbar resistance value corresponding to the maximum starting torque of the unit rotor according to the parameters of the unit and the parameters of the crowbar device; Obtain the resistance value range of the crowbar device applicable to the unit under low-voltage ride-through conditions, where the resistance value range includes a lower resistance limit value and an upper resistance limit value; determine the resistance value of the crowbar device according to the resistance value range and the actual crowbar resistance value corresponding to the maximum starting torque; in response to the unit pumping start command, connect the crowbar device to the unit rotor according to a preset strategy, so that the unit is equivalent to a squirrel-cage induction motor. A drive unit for turning on the drive power supply device to drive the unit stator and raise the unit speed to the grid connection speed.

9. An electrical device, characterized in that, It includes an isolation transformer, an excitation transformer, a controller, a memory, and a computer program stored in the memory and operable on the controller, as well as a crowbar device, a first circuit breaker, a second circuit breaker, a third circuit breaker, a fourth circuit breaker, an excitation converter, and a frequency converter respectively connected to the controller. The first ends of the first circuit breaker, the second circuit breaker, and the first end of the excitation transformer are commonly connected and connected to the power grid through the isolation transformer. The second end of the first circuit breaker is connected to the unit stator of the variable-speed pumped-storage unit. The second end of the second circuit breaker is connected to the first end of the frequency converter. The second end of the frequency converter is connected to the unit stator through the third circuit breaker. The first end of the excitation converter is connected to the second end of the isolation transformer through the excitation transformer. The second end of the excitation converter is connected to the unit rotor of the variable-speed pumped-storage unit. The crowbar device is connected to the unit rotor. The first end of the fourth circuit breaker is connected to the driving unit, and the second end of the fourth circuit breaker is connected to the unit stator. When the controller executes the computer program, it realizes the steps of the variable-speed pumped-storage unit starting method according to any one of claims 1 to 7.

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