Alternating current and direct current excitation device for excitation system of pumped storage unit

Abstract

The invention discloses an alternating current and direct current excitation device for a pumped storage unit excitation system, which comprises a direct current excitation loop, an alternating current excitation loop, a field suppression switch and a rotor loop, and is characterized in that the direct current excitation loop and the alternating current excitation loop are connected in parallel, the output end after parallel connection is connected with one end of the field suppression switch, and the other end of the field suppression switch is connected with the rotor loop; a connection path of the alternating current excitation loop comprises an alternating current power supply, an alternating current switch, a fuse F1, a transformer and a rectifier bridge, and a connection path of the direct current excitation loop comprises a direct current power supply, a direct current switch, a fuse F2, a divider resistor R1 and a diode. Isolation and mutual crossing prevention of an alternating current circuit and a direct current circuit are achieved through a rectifier bridge of the alternating current excitation loop and a diode of the direct current excitation loop, automatic mode switching is achieved in cooperation with an excitation regulator, seamless switching to the alternating current excitation loop can be achieved when the direct current excitation loop breaks down, and it is guaranteed that the pumped storage unit is reliably started when a power grid is dispatched emergently.

Description

Technical Field

[0001] This invention relates to the field of excitation system technology for pumped storage units, and in particular to AC / DC excitation devices for excitation systems of pumped storage units. Background Technology

[0002] The excitation system of a pumped-storage hydroelectric power unit is a core component ensuring stable operation and efficient energy conversion. It maintains stable terminal voltage by adjusting the excitation current of the rotor windings to control the generator's output terminal voltage, ensuring that the grid voltage fluctuates within permissible limits. It dynamically responds to grid demands, rapidly adjusting the excitation current to compensate for reactive power and support grid voltage recovery during load surges or grid faults. It also provides reactive power compensation, improves the grid power factor, and stabilizes system voltage. In the event of grid failure, a portion of the excitation system can provide initial excitation to the unit, assisting in black start. In pumped-storage hydroelectric power units, the excitation system is not only a "regulator" of voltage and reactive power but also a "guardian" of stable grid operation. Its rapid response and multi-functional control capabilities enable pumped-storage power stations to play a crucial role in peak shaving, frequency regulation, and emergency backup scenarios.

[0003] Currently, pumped storage units mainly use thyristor automatic excitation devices, and their excitation methods have the following technical bottlenecks:

[0004] Limitations of residual voltage excitation: The residual magnetic voltage of a high-voltage generator (≥800kW) is too low (usually <5V) after being converted by the secondary side of the rectifier transformer, which cannot trigger the thyristor to conduct, resulting in self-excitation failure.

[0005] Risks associated with a single external power source: DC excitation relies on batteries: When the DC circuit fails (such as a damaged switch or a broken cable), the unit completely loses its starting capability; AC excitation relies on plant power: When the power grid is completely dark, the AC power supply disappears, making it impossible to meet the black start requirements.

[0006] Traditional AC / DC excitation uses independent circuits, which has problems such as high device redundancy and complex control logic. Furthermore, crosstalk between AC and DC power supplies may damage the equipment. Summary of the Invention

[0007] To overcome the above problems, the purpose of this invention is to provide an AC / DC excitation device for the excitation system of pumped storage units. This device adopts a dual AC / DC circuit design. The DC excitation uses a 220V battery as the main power source, while the AC excitation uses 10.5kV plant power stepped down by a transformer as a backup power source. The AC and DC circuits are isolated and prevented from interfering with each other through the rectifier bridge of the AC excitation circuit and the diodes of the DC excitation circuit. With the help of the excitation regulator, the mode can be automatically switched. In the event of a fault in the DC excitation circuit, it can seamlessly switch to the AC excitation circuit, ensuring reliable startup of the pumped storage unit during emergency grid dispatch.

[0008] The technical solution adopted in this invention is:

[0009] An AC / DC excitation device for the excitation system of a pumped storage unit includes a DC excitation circuit, an AC excitation circuit, a demagnetizing switch, and a rotor circuit. The DC excitation circuit and the AC excitation circuit are connected in parallel, and the output terminal of the parallel circuit is connected to one end of the demagnetizing switch, while the other end of the demagnetizing switch is connected to the rotor circuit.

[0010] The connection path of the AC excitation circuit is AC power supply, AC switch, fuse F1, transformer, rectifier bridge. The connection path of the DC excitation circuit is DC power supply, DC switch, fuse F2, voltage divider resistor R1, diode. The output of the AC excitation circuit after passing through the rectifier bridge is connected in parallel with the output of the DC excitation circuit. The parallel output is connected to one end of the demagnetizing switch.

[0011] As a further description of the present invention, the AC power supply adopts the AC power of a 10.5kV / 50Hz pumped storage power station, and the DC power supply adopts a 220V / 100A DC battery.

[0012] As a further description of the present invention, the rectifier bridge of the AC excitation circuit adopts a six-pulse rectifier bridge, and the transformer of the AC excitation circuit is a step-down transformer with a turns ratio of 10.5kV / 600V.

[0013] As a further description of the present invention, a voltage divider resistor R1 is connected after the positive circuit fuse F2 of the DC excitation circuit, and a diode is connected after the voltage divider resistor R1. The diode of the DC excitation circuit is designed to conduct in one direction.

[0014] As a further description of the present invention, a freewheeling resistor R2 is connected in parallel on the rotor circuit winding side.

[0015] As a further description of the present invention, the DC power supply capacity of the DC excitation circuit is greater than or equal to 120% of the energy required for the start-up of the pumped storage unit.

[0016] As a further description of the present invention, it also includes a voltage judgment module and an excitation regulator. In the voltage judgment module, the DC excitation exit threshold is ≥10% of the rated value of the generator terminal voltage and the AC excitation exit threshold is ≥15% of the rated value. When the excitation regulator detects that the DC current of the DC excitation circuit is less than 5A for more than 3 seconds, it automatically switches to AC excitation.

[0017] As a further description of the present invention, the DC excitation circuit is the excitation mode under normal operating conditions, and the AC excitation circuit is the auxiliary excitation mode when the DC circuit fails.

[0018] As a further description of the present invention, the resistance range of the voltage divider resistor R1 is: The power is greater than or equal to 5kW.

[0019] As a further description of the present invention, the resistance value of the freewheeling resistor R2 is... The power is 10kW.

[0020] The beneficial effects of this invention are:

[0021] This invention relates to an AC / DC excitation device for the excitation system of pumped storage units, comprising a DC excitation circuit, an AC excitation circuit, a demagnetizing switch, and a rotor circuit. The device adopts a dual AC / DC circuit design. The DC excitation uses a 220V battery as the main power source, while the AC excitation uses 10.5kV plant power stepped down by a transformer as a backup power source. The AC / DC circuits are isolated and prevented from interfering with each other through the rectifier bridge of the AC excitation circuit and the diodes of the DC excitation circuit. With the help of the excitation regulator, automatic mode switching is achieved. In the event of a fault in the DC excitation circuit, it can seamlessly switch to the AC excitation circuit, ensuring reliable startup of the pumped storage unit during emergency grid dispatch.

[0022] This invention relates to an AC / DC excitation device for the excitation system of a pumped storage unit. The rectifier bridge of the AC excitation circuit adopts a six-pulse rectifier bridge, and the diodes of the DC excitation circuit are designed for unidirectional conduction. When DC excitation is used, the six-pulse rectifier bridge reverses to cut off the AC side. When AC excitation is used, the diodes of the DC excitation circuit reverse to cut off the DC side, thus preventing AC and DC circuits from interfering with each other.

[0023] This invention relates to an AC / DC excitation device for the excitation system of a pumped storage unit. A voltage divider resistor R1 is connected after the positive circuit fuse F2 of the DC excitation circuit to stabilize the voltage of the DC excitation circuit and ensure the stable operation of the unit. A freewheeling resistor R2 is connected in parallel on the rotor circuit winding side. When fuse F1 or fuse F2 blows due to overcurrent, the freewheeling resistor R2 can absorb magnetic field energy, suppress excitation inrush current, and ensure the normal and stable operation of the unit. Attached Figure Description

[0024] Figure 1 This is a circuit diagram of the AC / DC excitation device for the excitation system of a pumped-storage unit proposed in this invention;

[0025] Figure 2 This is a flowchart illustrating the switching logic of the AC / DC excitation device for the excitation system of a pumped-storage unit proposed in this invention.

[0026] Explanation of reference numerals in the attached figures

[0027] 1-DC excitation circuit,

[0028] 11-DC power supply

[0029] 12-DC switch,

[0030] 13-Fuse F2,

[0031] 14-Voltage divider resistor R1,

[0032] 15-Diode,

[0033] 2- AC excitation circuit,

[0034] 21- AC power supply,

[0035] 22-AC switch,

[0036] 23-Fuse F1,

[0037] 24-Transformer

[0038] 25-Rectifier bridge,

[0039] 3-Demagnetizing switch,

[0040] 4-Rotor circuit,

[0041] 5-Freewheeling resistor R2. Detailed Implementation

[0042] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0043] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0044] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0045] This invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of this invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not adhering to the usual scale. Furthermore, the schematic diagrams are merely examples and should not be construed as limiting the scope of protection of this invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.

[0046] Furthermore, in the description of this invention, it should be noted that the terms "upper," "lower," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used solely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. In addition, the terms "first," "second," or "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0047] Unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" in this invention should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; similarly, they can refer to mechanical connections, electrical connections, or direct connections, or indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0048] like Figures 1-2 As shown, it illustrates a specific embodiment of the present invention:

[0049] Example 1

[0050] The AC / DC excitation device for the excitation system of pumped storage units includes a DC excitation circuit 1, an AC excitation circuit 2, a demagnetizing switch 3, and a rotor circuit 4. The DC excitation circuit 1 and the AC excitation circuit 2 are connected in parallel, and the output end of the parallel circuit is connected to one end of the demagnetizing switch 3. The other end of the demagnetizing switch 3 is connected to the rotor circuit 4.

[0051] The connection path of the AC excitation circuit 2 is AC power supply 21, AC switch 22, fuse F123, transformer 24, rectifier bridge 25. The connection path of the DC excitation circuit 1 is DC power supply 11, DC switch 12, fuse F213, voltage divider resistor R114, diode 15. The output of the AC excitation circuit 2 after passing through the rectifier bridge 25 is connected in parallel with the output of the DC excitation circuit 1. The parallel output is connected to one end of the demagnetizing switch 3.

[0052] Specifically, the AC power supply 21 uses 10.5kV / 50Hz AC power for pumped storage power stations, and the DC power supply 11 uses a 220V / 100A DC battery.

[0053] Specifically, the rectifier bridge 25 of the AC excitation circuit 2 adopts a six-pulse rectifier bridge, and the transformer 24 of the AC excitation circuit 2 is a step-down transformer with a turns ratio of 10.5kV / 600V.

[0054] Specifically, a voltage divider resistor R114 is connected after the positive circuit fuse F213 of the DC excitation circuit 1, and a diode 15 is connected after the voltage divider resistor R114. The diode 15 of the DC excitation circuit 1 is designed to conduct in one direction.

[0055] In this embodiment, as Figure 1 As shown, the device adopts a dual AC / DC circuit design. The DC excitation uses a 220V battery as the main power source, while the AC excitation uses 10.5kV plant power stepped down by transformer 24 as a backup power source. The AC and DC circuits are isolated and prevented from interfering with each other through the rectifier bridge 25 of the AC excitation circuit 2 and the diode 15 of the DC excitation circuit 1. With the help of the excitation regulator, the mode can be automatically switched. In the event of a fault in the DC excitation circuit, it can seamlessly switch to the AC excitation circuit, ensuring the reliable start-up of the pumped storage unit during emergency grid dispatch.

[0056] In this embodiment, as Figure 1 As shown, the DC switch 12 in the DC excitation circuit 1 is used to control the on / off state of the DC excitation circuit 1. The voltage divider resistor R114 is used to stabilize the voltage of the DC excitation circuit 1 and ensure the stable operation of the unit. The AC switch 22 in the AC excitation circuit 2 is used to control the on / off state of the AC excitation circuit 2. The transformer 24 is used to step down the AC voltage. The rectifier bridge 25 is used to convert the AC voltage to DC voltage. The AC / DC excitation device as a whole adopts dual power input of AC and DC, and its output terminals are shared. The core components can be represented by Table 1 below:

[0057] Table 1. Components of AC / DC excitation devices used in the excitation system of pumped-storage units

[0058] Component categories DC excitation circuit AC excitation circuit Common components power supply 220V / 100A DC battery 10.5kV / 50Hz AC power supply for industrial use Excitation transformer Path devices Voltage divider resistor, DC excitation switch Step-down transformer, AC excitation switch Thyristor rectifier bridge Control module Fuse F2 Fuse F1 Excitation regulator core components Diode unidirectional conduction Six-pulse rectifier bridge Anti-reverse-feeding diode group

[0059] In this embodiment, the rectifier bridge 25 of the AC excitation circuit 2 adopts a six-pulse rectifier bridge, and the diode 15 of the DC excitation circuit 1 is designed for unidirectional conduction. When DC excitation is used, the six-pulse rectifier bridge reverses to block the AC side. When AC excitation is used, the diode 15 of the DC excitation circuit reverses to block the DC side, thus preventing AC and DC circuits from interfering with each other.

[0060] In this embodiment, the pumped storage unit adopts an excitation system design with DC excitation circuit 1 and AC excitation circuit 2 connected in parallel. This design can fully utilize the advantages of both circuits, improving the unit's start-up performance, operational reliability, and adjustment flexibility. Specifically, this is reflected in the following aspects:

[0061] First point: Fast and reliable unit startup, suitable for pumped storage units in pumping / power generation mode;

[0062] DC excitation circuit: It can provide a stable and controllable initial excitation current, ensuring that the unit can reliably establish a magnetic field at low speeds (such as pump start-up or back-to-back start-up). It is suitable for low-speed or zero-speed operating conditions (such as the SFC inverter start-up stage), avoiding output instability caused by excessively low frequency AC excitation.

[0063] AC excitation circuit: When the unit speed approaches the rated value (such as in generator mode), it automatically switches to AC excitation and uses the terminal voltage for self-excitation, reducing the dependence on external DC power supply.

[0064] Connecting the DC excitation circuit and the AC excitation circuit in parallel enables seamless switching, achieving a smooth transition from DC to AC and avoiding excitation interruption.

[0065] Second point: Adaptable to complex operating conditions;

[0066] In pumping mode, the DC circuit provides constant excitation at the initial stage of pump startup (low speed), overcoming the limitation of AC excitation not working properly due to low frequency.

[0067] The AC circuit is taken over after the speed increases, which improves efficiency.

[0068] Under power generation conditions, the AC circuit utilizes the generator terminal voltage for self-excitation, reducing energy consumption; the DC circuit serves as a backup, enhancing black start capability.

[0069] Thirdly, high reliability and redundant design;

[0070] To improve fault tolerance, if the DC circuit fails (such as a rectifier failure), the AC circuit can take over immediately, and vice versa, thus preventing the unit from shutting down due to excitation failure.

[0071] It supports black start. When the power grid is completely dark, the DC circuit can be provided with initial excitation by an independent power source such as DC power supply 11, so as to achieve start-up without external power.

[0072] Fourthly, dynamic performance optimization;

[0073] With a fast response, the DC circuit provides precise excitation control during the unit's acceleration phase, reducing start-up time; the AC circuit optimizes reactive power regulation during steady-state operation.

[0074] Suppressing oscillations: Parallel control can dampen the unique hydraulic-mechanical-electromagnetic coupling oscillations (such as low-frequency oscillations) of pumped storage units.

[0075] Fifthly, energy efficiency and economy;

[0076] Reduce the DC power supply capacity, use DC excitation only during the startup phase, and reduce the need for large rectifiers.

[0077] AC self-excitation-driven operation: During normal operation, it relies on the terminal voltage to reduce long-term energy consumption.

[0078] Sixth, harmonics and electromagnetic compatibility are improved;

[0079] When the DC circuit uses a thyristor rectifier, the AC circuit can be configured with a filter to reduce harmonics injected into the power grid during the startup phase.

[0080] To avoid the DC bias magnetization effect on the rotor windings caused by a pure DC excitation system, thus extending the motor's lifespan.

[0081] In summary, in this embodiment, the AC / DC excitation device significantly improves the start-up capability, adaptability, and reliability of pumped storage units through the combination of low-speed reliable excitation, high-speed efficient operation, and redundant backup. It is especially suitable for pumped storage applications with frequent start-stop and multi-condition switching.

[0082] Example 2

[0083] Specifically, a freewheeling resistor R25 is connected in parallel on the winding side of the rotor circuit 4.

[0084] In this embodiment, as Figure 1 As shown, a freewheeling resistor R25 is connected in parallel on the rotor circuit winding side. When fuse F1 or fuse F2 blows due to overcurrent, the freewheeling resistor R25 can absorb magnetic field energy, suppress excitation inrush current, and ensure the normal and stable operation of the unit.

[0085] Example 3

[0086] Specifically, the capacity of the DC power supply 11 of the DC excitation circuit 1 is greater than or equal to 120% of the energy required for the pumped storage unit to start up.

[0087] In this embodiment, the DC power supply 11 of the DC excitation circuit 1 is designed to have a capacity of ≥120% of the unit's starting energy requirement, which ensures the reliability of the unit's start-up, mainly in the following aspects:

[0088] Covering the worst operating conditions: Pumped storage units may face low speed and high torque requirements during startup, especially in pumping mode, or abnormal situations such as voltage dips in the power grid. A 120% capacity margin ensures that the DC power supply can still provide sufficient excitation current when there are voltage fluctuations, temperature changes, or equipment aging, thus avoiding startup failure due to insufficient energy.

[0089] To address the increased cold-state resistance of the rotor, where higher voltage / current is required to establish the rated magnetic field under low-temperature conditions, a margin design is used to compensate for this difference.

[0090] The DC power supply capacity is set to be greater than or equal to 120% of the energy required for the pumped storage unit to start up, following the N-1 principle of redundancy safety design. If a module of the DC power supply fails (such as a single bridge arm of the rectifier is damaged), the remaining capacity can still meet 100% of the start-up requirements, avoiding system paralysis caused by a single point of failure. It has black start capability. When the grid is completely dark, the DC power supply needs to independently support the unit to start from zero (such as relying on batteries). The extra 20% capacity can cover the capacity decay caused by long-term discharge.

[0091] This design provides energy buffering during dynamic processes, suppressing transient shocks. There may be current surges during unit startup (such as the inductive effect of the excitation winding). The margin design prevents the power supply from tripping due to instantaneous overload protection. To meet the coordination requirements of the static inverter, during the frequency conversion startup phase, the DC power supply needs to work with the static inverter to adjust the excitation. The additional capacity provides a margin for frequency / voltage regulation.

[0092] In this embodiment, such a design can extend the equipment life, reduce the DC power supply load rate, and reduce power supply heat generation and stress by operating at less than 80% capacity (120% design value) for a long time, thereby improving the life of components. At the same time, the reserved capacity provides compatibility for possible parameter upgrades of the unit (such as increased excitation current requirements).

[0093] In this embodiment, during the pumping operation of a pumped storage power station, the pump mode needs to overcome hydrostatic resistance, and the initial torque requirement may exceed the design value. The extra capacity ensures the rapid establishment of the magnetic field. When the grid voltage drops to 80%, the DC power supply needs to provide a larger current for a short period of time to maintain excitation. The margin avoids voltage collapse. In multiple continuous start-up conditions, that is, the unit needs to start and stop multiple times in a short period of time (such as frequency regulation requirements), 120% capacity can reduce the pressure of power supply recharge time.

[0094] In summary, in this embodiment, a 120% capacity margin is the safety baseline for the DC excitation circuit design of the pumped storage unit. Over-matching is used to address uncertainties and balance reliability, economy, and technical risks.

[0095] Specifically, it also includes a voltage judgment module and an excitation regulator. In the voltage judgment module, the DC excitation exit threshold is ≥10% of the rated value at the generator terminal voltage, and the AC excitation exit threshold is ≥15% of the rated value. When the excitation regulator detects that the DC current of the DC excitation circuit 1 is less than 5A for more than 3 seconds, it automatically switches to AC excitation.

[0096] Specifically, the DC excitation circuit 1 is the excitation mode under normal operating conditions, and the AC excitation circuit 2 is the auxiliary excitation mode when the DC circuit fails.

[0097] In this embodiment, as Figure 2 As shown, this is the switching logic when the AC / DC excitation device is in use. It can control the excitation device through the voltage judgment module and the excitation regulator so that it can meet the excitation requirements of the pumped storage unit.

[0098] In DC excitation mode, when the terminal voltage is greater than or equal to 10% of the rated value, the DC switch 12 is disconnected and switched to the extreme transformer;

[0099] In AC excitation mode, when the generator terminal voltage is greater than or equal to 15% of the rated value, disconnect AC switch 22 and switch it to the main excitation cabinet.

[0100] In this embodiment, the specific operation procedure under DC excitation mode is as follows:

[0101] Initial state: DC switch 12 is closed, AC switch 22 is open, and the relay is energized;

[0102] Excitation setup: 220V DC current is limited by voltage divider resistor R15 → diode conducts unidirectionally → rotor winding is excited;

[0103] Voltage detection: When the terminal voltage is ≥10% of the rated value, the terminal voltage is determined by the signal from the voltage transformer, triggering the thyristor to conduct;

[0104] Power switching: Disconnect DC switch 12 and switch to power supply from the transformer at the generator end;

[0105] Fault redundancy: If the DC circuit is abnormal (current continuously <5A), an alarm will be triggered and a prompt to switch to AC mode will be displayed.

[0106] In this embodiment, the specific operation procedure in AC excitation mode is as follows:

[0107] Mode switching: Manually modify the excitation regulator parameters or switch automatically after detecting a DC fault;

[0108] Power conversion: 10.5kV AC → step-down transformer → 600V AC output;

[0109] Rectification trigger: The rotor is powered through the full-bridge rectifier bridge → power is supplied via the thyristor;

[0110] Exit conditions: When the terminal voltage is ≥15% of the rated value → disconnect AC switch 22 → switch to main excitation cabinet;

[0111] Protection mechanism: Fuse F1 blows during overcurrent, and freewheeling resistor R2 absorbs magnetic field energy.

[0112] In this embodiment, the specific application of the doubly-fed asynchronous generator in the variable-speed unit is as follows:

[0113] Black start preparation stage: DC power supply 11 of DC excitation circuit 1 charges the bus, and unlocks the grid-side converter after the voltage reaches the rated value.

[0114] Adjust the output voltage during the AC excitation control phase. The amplitude and phase of the speed are adjusted to accelerate the rotational speed from rest to the target value.

[0115] ,

[0116] in:

[0117] The torque coefficient,

[0118] This is the compensation constant.

[0119] During the grid connection phase, the stator electromotive force is matched with the grid parameters and the grid connection switch is closed to switch to grid-connected mode.

[0120] Example 4

[0121] Specifically, the resistance range of the voltage divider resistor R11 4 is: The power is greater than or equal to 5kW.

[0122] Specifically, the resistance value of the freewheeling resistor R25 is... The power is 10kW.

[0123] In this embodiment, the voltage divider resistor is used to regulate the excitation voltage or limit the initial excitation current. If its resistance is too small, the excitation current will be too large, exceeding the design value, causing the rotor windings to overheat and potentially damaging the insulation over long-term operation. It can also cause overload of the excitation power supply, such as the rectifier, triggering protection actions. Furthermore, if the excitation voltage drops too quickly, it may not be able to establish a stable excitation voltage during the initial startup phase, affecting the speed of magnetic field establishment. If its resistance is too large, it will result in insufficient excitation current; a large voltage divider resistor will limit the excitation current, leading to slow magnetic field establishment, prolonging the unit's startup time, and affecting the pumped storage unit's rapid response capability. Insufficient excitation may be provided at low speeds, leading to startup failure. Finally, excessively large voltage divider resistors can reduce the efficiency of the excitation power supply, increasing unnecessary power loss and reducing system energy efficiency.

[0124] In pumped storage units, the optimal value of the voltage divider resistor is usually calculated based on the excitation voltage requirement and the maximum allowable excitation current.

[0125] ,

[0126] in: Indicates the output voltage of the excitation power supply;

[0127] Indicates the rotor winding voltage drop;

[0128] This represents the target excitation current.

[0129] At the same time, the temperature coefficient must be considered to avoid excessive changes in resistance with temperature.

[0130] In this embodiment, the freewheeling resistor is used to provide an energy discharge path for the rotor windings when the excitation system is turned off or malfunctions, preventing overvoltage damage to the equipment. If its resistance is too small, the current discharge will be too rapid, causing the rotor current to decay quickly, potentially leading to induced high voltage. Insufficient demagnetization time may affect the smooth shutdown of the unit (e.g., mechanical shock during generator braking). Overheating of the resistor may also cause it to burn out. Conversely, if the resistance is too large, the rotor energy cannot be released quickly, potentially causing rotor overvoltage risks, prolonging unit downtime, affecting the rapid switching capability of the pumped storage unit, and resulting in residual magnetic fields that could affect the safety of subsequent startups or maintenance.

[0131] In pumped storage units, the optimal value of the freewheeling resistor is usually calculated based on the rotor winding inductance and the target demagnetization time.

[0132] In this embodiment, the actual resistance and power values ​​of the voltage divider resistor 14 and the freewheeling resistor 5 are clearly specified according to the actual usage specifications of the pumped storage unit excitation system, so as to ensure the reliable and effective operation of the AC / DC excitation device.

[0133] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

[0134] Many other changes and modifications can be made without departing from the concept and scope of this invention. It should be understood that this invention is not limited to the specific embodiments, and the scope of this invention is defined by the appended claims.

Claims

1. An AC-DC excitation device for the excitation system of pumped storage units, characterized in that, It comprises a direct current excitation starting circuit (1), an alternating current excitation starting circuit (2), a de-excitation switch (3) and a rotor circuit (4), the direct current excitation starting circuit (1) and the alternating current excitation starting circuit (2) are connected in parallel, one end of the de-excitation switch (3) is connected to the output end after parallel connection, the other end of the de-excitation switch (3) is connected to the rotor circuit (4); The connection path of the alternating current excitation starting circuit (2) comprises an alternating current power supply (21), an alternating current switch (22), a fuse F1 (23), a transformer (24) and a rectifier bridge (25), the connection path of the direct current excitation starting circuit (1) comprises a direct current power supply (11), a direct current switch (12), a fuse F2 (13), a voltage dividing resistor R1 (14) and a diode (15), the output part of the alternating current excitation starting circuit (2) after the rectifier bridge (25) is connected in parallel with the output of the direct current excitation starting circuit (1), and one end of the de-excitation switch (3) is connected to the parallel output.

2. The AC-DC excitation device for the pumped storage unit excitation system according to claim 1, characterized by, The alternating current power supply (21) adopts 10.5kV / 50Hz alternating current used by pumped storage power station, and the direct current power supply (11) adopts 220V / 100A direct current storage battery.

3. The AC-DC excitation device for the pumped storage unit excitation system according to claim 1, characterized by, The rectifier bridge (25) of the alternating current excitation starting circuit (2) adopts a six-pulse rectifier bridge, and the transformer (24) of the alternating current excitation starting circuit (2) is a step-down transformer with a transformation ratio of 10.5kV / 600V.

4. The AC-DC excitation device for the pumped storage unit excitation system according to claim 1, characterized by, The positive circuit fuse F2 (13) of the direct current excitation starting circuit (1) is connected with the voltage dividing resistor R1 (14), the voltage dividing resistor R1 (14) is connected with the diode (15), and the diode (15) of the direct current excitation starting circuit (1) is designed to be unidirectionally conductive.

5. The AC-DC excitation device for the pumped storage unit excitation system according to claim 1, characterized by, The rotor circuit (4) is connected in parallel with a freewheeling resistor R2 (5) on the winding side.

6. The AC-DC excitation device for the pumped storage unit excitation system according to claim 1, characterized by, The capacity of the direct current power supply (11) of the direct current excitation starting circuit (1) is greater than or equal to 120% of the energy required for starting the pumped storage unit.

7. The AC-DC excitation device for the pumped storage unit excitation system according to claim 1, characterized by, It further comprises a voltage judgment module and an excitation regulator, the exit threshold of the direct current excitation starting circuit (1) in the voltage judgment module is greater than or equal to 10% of the rated voltage, and the exit threshold of the alternating current excitation starting circuit (2) is greater than or equal to 15% of the rated voltage, and the excitation regulator automatically switches to the alternating current excitation starting circuit (2) when detecting that the direct current of the direct current excitation starting circuit (1) is less than 5A for more than 3 seconds.

8. The AC-DC excitation device for the pumped storage unit excitation system according to claim 1, characterized by, The direct current excitation starting circuit (1) is a normal working condition excitation starting mode, and the alternating current excitation starting circuit (2) is an auxiliary excitation starting mode when the direct current circuit fails.

9. The AC-DC excitation device for the pumped storage unit excitation system according to claim 4, characterized by, The resistance value of the voltage division resistor R1 (14) is in the range of , and the power is greater than or equal to 5 kW.

10. The AC-DC excitation device for the pumped storage unit excitation system according to claim 5, characterized by, The value of the freewheeling resistor R2 (5) is 10 kW.

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