Generator de-excitation control device, control method and generator

Abstract

The invention discloses a generator de-excitation control device and method and a generator, and belongs to the technical field of generator excitation. The generator de-excitation control device comprises a first de-excitation unit connected with an excitation winding; the second field suppression unit is connected between the first field suppression unit and the excitation winding; the first switch unit is connected between the first de-excitation unit and the second de-excitation unit; the second switch unit is connected between the second de-excitation unit and the first switch unit; the control unit controls the first de-excitation unit to be connected with the excitation winding and performs constant-voltage inversion de-excitation on the excitation winding; the second switch unit is controlled to be disconnected, so that the excitation winding is disconnected from the first de-excitation unit; and after the second field suppression unit is connected with the excitation winding, flexible energy-shifting field suppression is carried out on the excitation winding. According to the field suppression control device, multiple field suppression is carried out on the excitation winding through the first field suppression unit, the second field suppression unit and the second switch unit, and the field suppression control device is suitable for large-energy field suppression work of a large generator.

Description

Technical Field

[0001] Embodiments of the present application relate to the technical field of generator excitation, and in particular to a generator deexcitation control device, a control method and a generator. Background Art

[0002] When a short circuit or grounding accident occurs inside or outside the generator, the demagnetization device can exhaust the magnetic field energy stored in the rotor excitation winding of the generator as soon as possible, thereby preventing the accident from expanding and reducing losses. For large generator sets, the fault current is higher and the rotor winding energy storage is greater. Therefore, the demagnetization device of large generator sets must meet higher reliability, safety and speed. At present, the energy transfer type demagnetization device that uses a combination of a demagnetization switch and a demagnetization resistor has high reliability, but the demagnetization switch is prone to generate a high arc voltage when it is disconnected, which will damage the generator. Summary of the invention

[0003] The embodiment of the present application aims to provide a generator demagnetization control device to solve the technical problem of low safety of demagnetization devices in the prior art. Another embodiment of the present application aims to provide a generator demagnetization control method to solve the technical problem of low safety of demagnetization devices in the prior art.

[0004] In order to solve the above technical problems, the embodiments of the present application disclose the following technical solutions:

[0005] In a first aspect, a generator demagnetization control device is provided, which is used to perform demagnetization protection on an excitation winding, comprising:

[0006] a first demagnetization unit, wherein the first demagnetization unit is connected to the excitation winding;

[0007] a second demagnetization unit, wherein the second demagnetization unit is connected between the first demagnetization unit and the excitation winding;

[0008] A first switch unit, wherein the first switch unit is connected between the first demagnetization unit and the second demagnetization unit;

[0009] a second switch unit, wherein the second switch unit is connected between the second demagnetization unit and the first switch unit;

[0010] a control unit, the control unit being configured to control the first switch unit to be turned on so that the first demagnetization unit is connected to the excitation winding and performs constant voltage inversion demagnetization on the excitation winding; and control the second switch unit to be turned off so that the excitation winding is disconnected from the first demagnetization unit;

[0011] The second demagnetization unit is configured to perform flexible energy transfer demagnetization on the excitation winding after being connected to the excitation winding.

[0012] In combination with the first aspect, the first demagnetization unit includes a capacitor, one end of the capacitor is connected to the excitation winding through the first switch unit and the second demagnetization unit, and the other end of the capacitor is connected to the excitation winding through the first switch unit, the second switch unit and the second demagnetization unit.

[0013] In combination with the first aspect, the second demagnetization unit includes a first diode, a nonlinear resistor and a fuse, one end of the first diode is connected to one end of the excitation winding, the other end of the first diode is connected to the nonlinear resistor through the fuse, and the other end of the nonlinear resistor is connected to the other end of the excitation winding.

[0014] In combination with the first aspect, the generator demagnetization control device also includes a rectifier unit, the rectifier unit includes a three-level voltage source converter, the three-phase AC side of the three-level voltage source converter is connected to the generator end power supply, the DC side of the three-level voltage source converter is connected to the first demagnetization unit, and the control side of the three-level voltage source converter is connected to the control unit.

[0015] In a second aspect, a generator demagnetization control method is provided for demagnetization protection of an excitation winding, the method comprising the following steps:

[0016] Controlling the first switch unit to be turned on so that the first demagnetization unit performs constant voltage inversion demagnetization on the excitation winding;

[0017] In response to the voltage value across the first demagnetization unit being greater than the threshold voltage of the second demagnetization unit, the second demagnetization unit is turned on and performs flexible energy transfer demagnetization on the excitation winding;

[0018] In response to the constant voltage inverter demagnetization and the flexible energy transfer demagnetization both failing to be demagnetized, the second switch unit is controlled to be disconnected to disconnect the excitation winding from the generator circuit.

[0019] In combination with the second aspect, the method of controlling the first switch unit to be turned on so that the first demagnetization unit performs constant voltage inversion demagnetization on the excitation winding includes:

[0020] The control unit sends a first unlocking signal to the first switch unit, so that the first demagnetization unit is connected to the excitation winding after being unlocked;

[0021] The control unit sends a second unlocking signal to the rectifying unit to unlock the rectifying unit;

[0022] Wherein, the excitation current in the excitation winding flows to the first demagnetization unit to achieve energy charging;

[0023] The first demagnetization unit releases energy through the rectifier unit to perform the constant voltage inversion demagnetization on the excitation winding.

[0024] In combination with the second aspect, in response to the voltage value across the first demagnetization unit being greater than the threshold voltage of the second demagnetization unit, the method in which the second demagnetization unit is turned on and performs flexible energy transfer demagnetization on the excitation winding includes:

[0025] When the voltage value across the first demagnetization unit is greater than the threshold voltage of the second demagnetization unit, the control unit sends a first locking signal to lock the rectifying unit;

[0026] When the voltage across the first demagnetization unit is greater than the on-voltage of the second demagnetization unit, all the excitation current in the excitation winding is transferred to the second demagnetization unit, and the excitation current is consumed by the heat of the second demagnetization unit to achieve the flexible energy transfer demagnetization.

[0027] In combination with the second aspect, before controlling the first switch unit to be turned on so that the first demagnetization unit performs constant voltage inversion demagnetization on the excitation winding, the method further includes:

[0028] When the generator is abnormal, the control unit sends a second locking signal to the first switch unit to lock the first switch unit;

[0029] By blocking the first switch unit, the power unit is stopped from supplying energy to the excitation winding.

[0030] In combination with the second aspect, in response to the constant voltage inverter demagnetization and the flexible energy transfer demagnetization both failing to demagnetize, the method of controlling the second switch unit to disconnect to disconnect the excitation winding from the generator circuit includes:

[0031] The control unit determines the excitation current;

[0032] In response to the excitation current being always greater than a current threshold, the control unit controls the second switch unit to be turned off, so as to disconnect the excitation winding from the generator circuit.

[0033] In a third aspect, a generator is provided, comprising:

[0034] The machine-side power supply and field winding, and

[0035] A generator demagnetization control device as described in any one of the first aspects, wherein a plurality of the generator demagnetization control devices are connected between the machine-end power supply and the excitation winding, and are used to perform demagnetization control on the excitation winding when an internal circuit short circuit or an external ground fault occurs in the generator; or, the generator uses a method as described in any one of the second aspects to perform demagnetization control on the excitation winding.

[0036] One of the above technical solutions has the following advantages or beneficial effects:

[0037] Compared with the prior art, a demagnetization control device of a generator of the present application is used for demagnetization protection of an excitation winding, and includes: a first demagnetization unit, the first demagnetization unit is connected to the excitation winding; a second demagnetization unit, the second demagnetization unit is connected between the first demagnetization unit and the excitation winding; a first switch unit, the first switch unit is connected between the first demagnetization unit and the second demagnetization unit; a second switch unit, the second switch unit is connected between the second demagnetization unit and the first switch unit; a control unit, the control unit is configured to control the first switch unit to be turned on, so that the first demagnetization unit is connected to the excitation winding and performs constant voltage inverter demagnetization on the excitation winding; and control the second switch unit to be turned off, so that the excitation winding is disconnected from the first demagnetization unit; the second demagnetization unit is configured to perform flexible energy transfer demagnetization on the excitation winding after being connected to the excitation winding. The demagnetization control device provided by the present application performs multiple demagnetization on the excitation winding through the first demagnetization unit, the second demagnetization unit and the second switch unit, and is suitable for large-energy demagnetization work of large generators, and has high safety.

[0038] Compared with the prior art, a generator demagnetization control method of the present application is used for demagnetization protection of the excitation winding, and the method includes the following steps: controlling the first switch unit to be turned on so that the first demagnetization unit performs constant voltage inverter demagnetization on the excitation winding; in response to the voltage value across the first demagnetization unit being greater than the threshold voltage of the second demagnetization unit, the second demagnetization unit is turned on and performs flexible energy transfer demagnetization on the excitation winding; in response to the failure of both constant voltage inverter demagnetization and flexible energy transfer demagnetization, the second switch unit is controlled to be disconnected to disconnect the excitation winding from the generator circuit. The demagnetization control method provided by the present application performs multiple demagnetization on the excitation winding through constant voltage inverter demagnetization, flexible energy transfer demagnetization and demagnetization switch, and is suitable for large-energy demagnetization work of large generators with high safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The technical solution and other beneficial effects of the present application will be made apparent by describing in detail the specific implementation methods of the present application in conjunction with the accompanying drawings.

[0040] Figure 1 A schematic diagram of module connections of a generator demagnetization control device provided in an embodiment of the present application;

[0041] Figure 2 A schematic diagram of the circuit connection of the generator demagnetization control device provided in an embodiment of the present application;

[0042] Figure 3 A schematic diagram of the circuit connection of the generator demagnetization control device provided in an embodiment of the present application;

[0043] Figure 4 A schematic diagram of a circuit equivalent of a generator demagnetization control device provided in an embodiment of the present application;

[0044] Figure 5 A schematic diagram of signal changes in a circuit of a generator demagnetization control device provided in an embodiment of the present application;

[0045] Figure 6 A schematic diagram of the method steps of the generator demagnetization control method is provided for the embodiment of the present application;

[0046] Figure 7 A schematic diagram of module connections of a generator provided in some embodiments of the present application. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. In the description of the present application, it is necessary to understand that the orientation or position relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. is based on the orientation or position relationship shown in the drawings, which 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 cannot be understood as a limitation to the present application. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0048] The relevant technical personnel of this application have noticed that when a short circuit or grounding accident occurs inside or outside the generator, the demagnetization system can exhaust the magnetic field energy storage in the rotor excitation winding of the generator as soon as possible, thereby preventing the accident from expanding and reducing losses. For large generator sets, the fault current is higher and the rotor winding energy storage is huge. A complete demagnetization device for large generator sets must meet higher reliability, safety and speed. For example, reliability includes that the demagnetization circuit can be reliably put into operation under normal or abnormal conditions; safety includes that the demagnetization voltage does not affect the safety of the generator and the safety of the excitation equipment, while minimizing the loss of the demagnetization switch and the demagnetization resistor; speed includes that under the premise of ensuring safe demagnetization, the demagnetization voltage is always maintained at a high value during the demagnetization process to accelerate the transfer or consumption of magnetic field energy.

[0049] At present, the most widely used and mature demagnetization system is a transfer energy demagnetization system formed by a combination of a demagnetization switch and a demagnetization resistor. It has a simple structure and high reliability. However, when applied to large generator sets, the following problems still exist:

[0050] 1. The arc voltage generated by the demagnetization switch when it is disconnected in large and medium-sized generator sets is relatively high, and the arc voltage and breaking capacity of the DC demagnetization switch are limited by the manufacturing process. When used in large units, it is difficult to select and the price is expensive;

[0051] 2. When the unit is shut down due to a fault or the reverse power protection is used for normal shutdown of a large unit, the demagnetization switch trips on load and the energy consumption of the demagnetization resistor will affect the life of the demagnetization device, which is not conducive to the safety of the demagnetization device;

[0052] Therefore, some embodiments of the present application provide a generator demagnetization system, comprising a plurality of groups of parallel flexible excitation power units, each group of flexible excitation power units is composed of a front-stage three-level voltage-type converter and a rear-stage five-level DC chopper, and the front-stage three-level voltage-type converter and the rear-stage five-level DC chopper are connected through the intermediate DC bus support capacitor. According to the special topological structure of the flexible excitation power unit circuit, high reliability, high safety and rapidity of large motor demagnetization are achieved.

[0053] The specific implementation methods of the present application are described below by way of examples:

[0054] like Figures 1 to 5As shown, an embodiment of the present application provides a generator demagnetization control device for performing demagnetization protection on an excitation winding, comprising: a first demagnetization unit, the first demagnetization unit is connected to the excitation winding; a second demagnetization unit, the second demagnetization unit is connected between the first demagnetization unit and the excitation winding; a first switch unit, the first switch unit is connected between the first demagnetization unit and the second demagnetization unit; a second switch unit, the second switch unit is connected between the second demagnetization unit and the first switch unit; a control unit, the control unit is configured to control the first switch unit to be turned on, so that the first demagnetization unit is connected to the excitation winding and performs constant voltage inversion demagnetization on the excitation winding; and to control the second switch unit to be turned off, so that the excitation winding is disconnected from the first demagnetization unit; the second demagnetization unit is configured to perform flexible energy transfer demagnetization on the excitation winding after being connected to the excitation winding.

[0055] The specific working process and principle include: when a short circuit occurs inside the generator or a ground fault occurs outside, the relay is turned on to relay the circuit of the generator. At this time, when the control unit detects a generator fault, it sends a first unlocking signal, and the first unlocking signal is configured to turn on the first switch unit to achieve the connection between the first demagnetization unit and the excitation winding. The first demagnetization unit can realize constant voltage inverter demagnetization of the excitation winding; when the control unit detects that the voltage value at both ends of the first demagnetization unit is greater than the threshold voltage of the second demagnetization unit, it means that the energy storage of the first demagnetization unit has reached the upper limit, so the second demagnetization unit is connected to the excitation winding, so as to perform flexible energy transfer demagnetization on the excitation winding. At this time, the excitation winding mainly releases the stored energy to the second demagnetization unit, so as to achieve rapid release of the energy of the excitation winding; when the voltage value at both ends of the first demagnetization unit is always greater than the threshold voltage of the second demagnetization unit and lasts for more than a certain time, it means that both constant voltage inverter demagnetization and flexible energy transfer demagnetization are invalid, and the control unit disconnects the connection between the excitation winding and the generator circuit by controlling the second switch unit, so as to achieve mechanical demagnetization of the excitation winding.

[0056] In the embodiments of the present application, it should be noted that when the constant voltage inverter demagnetization or the flexible energy transfer demagnetization works effectively, the excitation current in the excitation winding circuit will be quickly exhausted, and the process generally lasts for 1-2s. Therefore, when the voltage value at both ends of the first demagnetization unit is greater than the threshold voltage of the second demagnetization unit for 1-2s, it indicates that the constant voltage inverter demagnetization and the flexible energy transfer demagnetization have failed and failed to effectively demagnetize the excitation winding. In some embodiments, in addition to judging the working state of the constant voltage inverter demagnetization and the flexible energy transfer demagnetization by the voltage value at both ends of the first demagnetization unit, it can also be judged by the magnitude of the excitation current in the excitation winding circuit. If the excitation current fails to decrease for 1-2s, it indicates that the constant voltage inverter demagnetization and the flexible energy transfer demagnetization have failed to demagnetize.

[0057] In an embodiment of the present application, the excitation winding is located on the rotating part (rotor) of the generator, usually a coil or winding wound around a rotating shaft for generating a magnetic field. The main purpose of the excitation winding is to generate a stable and constant magnetic field, thereby generating a current in the generator. The generated current will generate a magnetic field on the generator rotor, and an induced current will be generated through the wires in the stator winding (stator coil). The current source of the excitation winding can be a DC power supply, usually powered by an external power supply or a self-excited generator. The current source used and the control method of the excitation winding depend on the type and design of the generator. The current of the excitation winding can be adjusted by the excitation regulation unit to control the output voltage and current of the generator.

[0058] In the embodiment of the present application, the main function of the excitation regulating unit is to control the current in the excitation winding according to the load demand of the generator and the requirements of the power system. By adjusting the current of the excitation winding, the excitation regulating unit can achieve the following goals: 1) Regulate the output voltage of the generator: By controlling the current of the excitation winding, the output voltage of the generator can be adjusted to keep it at the desired level; 2) Stabilize the voltage and frequency of the power system: The excitation regulating unit can adjust the current of the excitation winding in time according to the load changes of the power system to keep the voltage and frequency of the power system stable; 3) Respond to the dispatching instructions of the power system: According to the dispatching instructions of the power system, the excitation regulating unit can adjust the current of the excitation winding to meet the needs of the system, such as participating in reactive power control, frequency response, etc.

[0059] In the embodiment of the present application, the control unit is mainly used for the device or system responsible for monitoring, operating and controlling the generator, and has the function of monitoring and controlling the operation of the generator to ensure the safe and stable operation of the generator. The main functions of the control unit include: monitoring generator parameters: the control unit monitors various parameters of the generator, such as voltage, current, frequency, temperature, etc., through sensors and measuring devices. The monitoring of these parameters can provide real-time understanding of the operating status of the generator and detect any abnormal or fault conditions; regulating the output of the generator: the control unit adjusts the current of the excitation winding, the speed of the rotor or other control methods according to the load demand and the requirements of the power system to achieve the regulation of the output voltage, frequency and power of the generator. Thereby ensuring that the output of the generator meets the required power system requirements. Protection and safety functions: the control unit is responsible for monitoring the status of the generator during operation and taking corresponding protection measures for any abnormal conditions or fault events. For example, overload, short circuit, overtemperature, etc. can be monitored, and measures can be taken to protect the safety of generator equipment and personnel. Communication and connection functions: the control unit can communicate and connect with other systems or devices, such as communicating with the monitoring system, data acquisition system or remote control center of the power system. It can realize remote monitoring, remote control and data transmission of the generator, facilitating operation and maintenance management and remote troubleshooting.

[0060] like Figure 2 and Figure 3 As shown, in an embodiment of the present application, the first demagnetization unit includes a capacitor, one end of the capacitor is connected to the excitation winding through the first switch unit and the second demagnetization unit, and the other end of the capacitor is connected to the excitation winding through the first switch unit, the second switch unit and the second demagnetization unit. Specifically, the energy in the excitation winding is consumed by the capacitor, thereby achieving a demagnetization effect. Usually, the anode and cathode of the capacitor are respectively connected to the positive terminal and the negative terminal of the excitation winding, thereby constructing a parallel circuit to connect the capacitor to the excitation winding. Before the excitation winding releases energy to the capacitor, first, the excitation source needs to be disconnected, that is, the power supply to the excitation winding is stopped. This can prevent the magnetic field from continuing to be generated and energy from being provided to the excitation winding. The excitation winding can then charge the capacitor, thereby releasing the stored energy, thereby reducing or eliminating the strength of the magnetic field.

[0061] In the embodiment of the present application, the capacitor includes a first capacitor C1 and a second capacitor C2, which are connected in series with the rectifier unit and the first switch unit. In some other embodiments of the present application, the capacitor may also be composed of one capacitor or multiple capacitors, and the specific number of capacitors can be selected according to actual conditions, and the embodiments of the present application are not further listed here.

[0062] like Figure 2 and Figure 3 As shown, in the embodiment of the present application, the second demagnetization unit includes a first diode, a nonlinear resistor and a fuse, one end of the first diode is connected to one end of the excitation winding, the other end of the first diode is connected to the nonlinear resistor through the fuse, and the other end of the nonlinear resistor is connected to the other end of the excitation winding. Specifically, after the three-level power converter pulse is locked, the nonlinear resistor is connected to the positive and negative ends of the excitation winding to achieve flexible energy transfer demagnetization of the excitation winding. Figure 4 As shown, the generator excitation winding is equivalent to a large inductive load. When the excitation winding charges the capacitor, it is equivalent to a current with the same magnitude as the excitation current I f The same current source, where the voltage of the current source is U f Under the action of the current source, the capacitor voltage U dc It rises in a straight line. When the capacitor voltage U dc The threshold voltage U of the nonlinear resistor d0 When the currents are equal, the capacitor begins to discharge through the nonlinear resistor, and a current I gradually begins to be generated in the nonlinear resistor. M , while the excitation current I f Gradually decreases; when the capacitor voltage U dc Greater than the nonlinear resistance's on-state voltage UMD After that, the current I in the nonlinear resistor M The increase speed is faster; when the capacitor voltage U dc Continue to rise and equal to the rated voltage U of the nonlinear resistor M0 When the current in the nonlinear resistor is M reaches its maximum value, at which point the excitation current I f will be transferred to the nonlinear resistor until the excitation current I f Therefore, by connecting the nonlinear resistor, the energy consumption in the excitation winding can be transferred from the capacitor charging to the heat consumption of the nonlinear resistor to complete the flexible energy transfer demagnetization process. In the whole process, the energy transfer is stable and smooth, without arc and switching loss. The changes in voltage and circuit size during the energy transfer process are as follows: Figure 5 shown.

[0063] In an embodiment of the present application, the nonlinear resistor includes a zinc oxide resistor, which is a resistor made of zinc oxide material. The zinc oxide resistor is a nonlinear resistor whose resistance value changes with the change of voltage or current. The basic structure of the zinc oxide resistor is to make zinc oxide powder into a graphite fused shape, and fix two electrode leads at both ends of the fused block. The zinc oxide fused block has certain resistance properties, and its resistance value will change with the change of voltage or current in the working environment. Zinc oxide resistors can also be generally used for overcurrent protection, overvoltage protection, current limiting and other applications of power supply lines. When the current or voltage in the circuit exceeds the rated value of the zinc oxide resistor, the resistance value of the zinc oxide resistor will increase rapidly, thereby limiting the current flowing through the zinc oxide resistor and protecting other electronic components from damage.

[0064] like Figure 2 and Figure 3 As shown, in the embodiment of the present application, the first diode acts as a switch. In the forward biased (on) state, the first diode allows current to flow through; in the reverse biased (off) state, the first diode does not allow current to flow through, thereby limiting the flow direction of the excitation current If.

[0065] like Figure 2 and Figure 3 As shown, in the embodiment of the present application, the fuse is used to prevent circuit overload. When the current carried by the nonlinear resistance circuit exceeds the rated current of the fuse, the fuse will immediately disconnect the circuit to avoid dangers such as equipment damage or fire caused by excessive current.

[0066] like Figures 1 to 3As shown, in an embodiment of the present application, the first switch unit includes a five-level DC chopper, and the five-level DC chopper receives a first unlocking signal; the control unit is configured to send a first locking signal, and the first locking signal is configured to disconnect the connection between the first switch unit and the excitation winding. Specifically, when an internal short circuit or an external grounding fault occurs in the generator, after the relay starts the relay protection action, the excitation regulator sends a first locking signal to the first switch unit through the control unit, and the first switch unit is locked under the control of the first locking signal, thereby terminating the generator power unit from continuing to supply energy to the excitation winding, thereby avoiding the continuous increase of energy in the excitation winding. After the first switch unit is locked, the control unit sends a first unlocking signal again, and the first unlocking signal is used to unlock the five-level DC chopper, so as to connect the capacitor and the excitation winding. It should be noted that the first switch unit includes a plurality of interconnected IGBTs (Insulated Gate Bipolar Transistor, insulated gate bipolar transistors), wherein the first unlocking signal can only unlock a certain number of internal IGBTs as long as the excitation winding can be connected to the first demagnetization unit. After the excitation winding is connected to the first demagnetization unit, it can discharge to the first demagnetization unit. The first demagnetization unit stores the energy in the excitation winding to achieve constant voltage inversion demagnetization of the excitation winding, that is, constant voltage demagnetization.

[0067] In some embodiments of the present application, due to the effect of the excitation winding inductance, the generator excitation current I f The flow direction and size remain unchanged ( Figure 2 , Figure 3 and Figure 4 The direction of the arrow in the figure is the direction of current flow), the excitation current I f From the positive pole of the excitation winding, through the five-level DC chopper and the capacitor, back to the negative pole, thus forming a loop. Therefore, the excitation winding charges the capacitor, and the capacitor voltage U across the capacitor is dc The control unit increases according to the capacitor voltage U dc Compared with the threshold voltage of the second demagnetization unit, if the capacitor voltage U dc If the voltage of the first demagnetization unit is greater than or equal to the threshold voltage of the second demagnetization unit, the control unit sends a first unlocking signal to the rectifier unit, and the rectifier unit is turned on under the control of the first unlocking signal, so that the capacitor is connected to the generator end power supply through the rectifier unit, so that the DC side voltage of the rectifier unit is kept at a constant value. At this time, the excitation winding discharges to the generator end power supply, and the excitation current I f It descends at a constant speed, thereby achieving constant voltage inverter demagnetization of the excitation winding.

[0068] like Figures 1 to 3As shown, in an embodiment of the present application, the rectifier unit includes a three-level voltage source converter, the three-phase AC side of the three-level voltage source converter is connected to the generator end power supply, the DC side of the three-level voltage source converter is connected to the first demagnetization unit, and the control side of the three-level voltage source converter is connected to the control unit to receive a second unlocking signal and a second locking signal; wherein the second unlocking signal is configured to unlock the rectifier unit so that the first demagnetization unit is connected to the generator end power supply; and the second locking signal is configured to lock the rectifier unit so that the first demagnetization unit is disconnected from the generator end power supply.

[0069] Specifically, in the embodiment of the present application, at the same time or after the excitation winding is connected to the capacitor (i.e., the first demagnetization unit), the control unit sends a second unlocking signal, and the second unlocking signal is configured to turn on the three-level voltage source converter, and the three-level voltage source converter is configured to connect the capacitor to the generator end power supply. The generator end power supply can be regarded as a voltage source. After the generator end power supply is connected to the capacitor, the capacitor can release energy to the generator end power supply, that is, indirectly connect the generator end power supply to the excitation winding, thereby improving the demagnetization effect of the excitation winding.

[0070] In an embodiment of the present application, in order to enable the excitation winding to release energy to the nonlinear resistor (i.e., the second demagnetization unit), the control unit sends a second locking signal; the second locking signal is configured to lock the three-level voltage source converter to disconnect the capacitor from the generator-end power supply, thereby indirectly disconnecting the excitation winding from the generator-end power supply.

[0071] like Figure 6 As shown, the embodiment of the present application provides a generator demagnetization control method for demagnetization protection of the excitation winding, and the method includes the following steps:

[0072] S1: Control the first switch unit to be turned on, so that the first demagnetization unit performs constant voltage inversion demagnetization on the excitation winding.

[0073] In an embodiment of the present application, before the control unit sends a first unlocking signal, the operating state of the generator is monitored by the excitation regulation unit. When it is found that the generator is in an abnormal state, the excitation regulation unit sends a generator abnormality signal to the control unit; wherein the abnormal state of the generator includes a short circuit inside the generator or a ground fault outside the generator, at which time the relay performs relay protection; after receiving the generator abnormality signal, the control unit sends a first locking signal to the first switch unit, and the first locking signal is configured to cut off the connection between the first switch unit and the excitation winding to terminate the energy supply of the excitation winding, thereby avoiding unnecessary losses.

[0074] In an embodiment of the present application, after the first switch unit is turned off, the control unit sends a first unlocking signal again, and the first unlocking signal is configured to unlock the locked first switch unit, and the excitation winding is connected to the first demagnetization unit through the first switch unit. It should be noted that the first switch unit includes a plurality of interconnected IGBTs, wherein the first unlocking signal can only unlock a certain number of internal IGBTs as long as the excitation winding can be connected to the first demagnetization unit. After the excitation winding is connected to the first demagnetization unit, it can discharge to the first demagnetization unit, and the first demagnetization unit stores the energy in the excitation winding to achieve constant voltage inverter demagnetization of the excitation winding, that is, constant voltage demagnetization.

[0075] In some embodiments of the present application, when the communication between the excitation winding and the first demagnetization unit requires one or more IGBTs to be realized, the control unit can turn on the one or more IGBTs by issuing a first unlocking signal.

[0076] In an embodiment of the present application, at the same time or after the excitation winding is connected to the first demagnetization unit, the control unit sends a second unlocking signal, and the second unlocking signal is configured to turn on the rectifier unit, and the rectifier unit is configured to connect the first demagnetization unit to the generator end power supply. The excitation current in the excitation winding flows to the first demagnetization unit to achieve energy charging; the first demagnetization unit releases energy through the rectifier unit to perform constant voltage inversion demagnetization on the excitation winding. The generator end power supply can be regarded as a voltage source. After the generator end power supply is connected to the first demagnetization unit, the first demagnetization unit can release energy to the generator end power supply, that is, indirectly connect the generator end power supply to the excitation winding, thereby improving the demagnetization effect of the excitation winding.

[0077] S2: In response to the voltage value across the first demagnetization unit being greater than the threshold voltage of the second demagnetization unit, the second demagnetization unit is controlled to be turned on and perform flexible energy transfer demagnetization on the excitation winding.

[0078] In an embodiment of the present application, the control unit is used to monitor the voltage and current at various locations in the internal circuit of the generator. When the control unit detects that the voltage value at both ends of the first demagnetization unit is greater than the threshold voltage of the second switching unit, it means that the energy storage of the first demagnetization unit has reached an upper limit, and the first demagnetization unit can no longer demagnetize the excitation winding by storing energy. Therefore, the second demagnetization unit is required to perform flexible energy transfer demagnetization on the excitation winding; when the voltage value at both ends of the first demagnetization unit is greater than the turn-on voltage of the second demagnetization unit, the excitation current in the excitation winding is completely transferred to the second demagnetization unit, and the excitation current consumes heat through the second demagnetization unit to achieve flexible energy transfer demagnetization.

[0079] In an embodiment of the present application, in order to enable the excitation winding to release energy to the second demagnetization unit, the control unit sends a second locking signal; the second locking signal is configured to lock the rectifier unit to disconnect the first demagnetization unit from the generator end power supply, that is, indirectly disconnect the excitation winding from the generator end power supply.

[0080] S3: In response to the failure of both the constant voltage inverter demagnetization and the flexible energy transfer demagnetization, the second switch unit is controlled to be disconnected to disconnect the excitation winding from the generator circuit.

[0081] In an embodiment of the present application, the control unit judges the voltage value or the excitation current in the first demagnetization unit circuit; in response to the voltage value being always greater than the voltage threshold, or the excitation current being always greater than the current threshold, the control unit controls the second switch unit to disconnect, so as to disconnect the connection between the excitation winding and the generator circuit. Specifically, the control unit compares the voltage value at both ends of the first demagnetization unit with the threshold voltage of the second demagnetization unit. When the voltage value at both ends of the first demagnetization unit is always greater than the threshold voltage of the second demagnetization unit and lasts for more than a certain period of time, or the control unit monitors that the excitation current in the excitation winding circuit has not decreased for more than a certain period of time, it indicates that both the constant voltage inverter demagnetization and the flexible energy transfer demagnetization have failed. The control unit disconnects the excitation winding from the generator circuit by controlling the second switch unit, thereby achieving mechanical demagnetization of the excitation winding.

[0082] In the embodiment of the present application, it should be noted that when the constant voltage inverter demagnetization or flexible energy transfer demagnetization is normally performing demagnetization work, the excitation current in the excitation winding circuit will decrease or be quickly exhausted within 1-2 seconds. Therefore, when the voltage value at both ends of the first demagnetization unit is greater than the threshold voltage of the second demagnetization unit for 1-2 seconds, it means that the excitation current has not decreased, and it also means that the constant voltage inverter demagnetization or flexible energy transfer demagnetization has failed to effectively demagnetize the excitation winding. At this time, effective demagnetization can be achieved by controlling the second switch unit to cut off the excitation winding from the generator circuit.

[0083] In some embodiments, in addition to judging the working status of constant voltage inverter demagnetization and flexible energy transfer demagnetization by the voltage value at both ends of the first demagnetization unit, it can also be judged by the size of the excitation current in the excitation winding circuit. If the excitation current fails to decrease for 1-2 seconds, it means that both the constant voltage inverter demagnetization and the flexible energy transfer demagnetization have failed. At this time, effective demagnetization can be achieved by controlling the second switch unit to cut off the excitation winding from the generator circuit.

[0084] like Figure 7As shown, an embodiment of the present application also provides a generator, which includes a machine-end power supply and an excitation winding, and a plurality of generator demagnetization control devices as provided in any of the above embodiments, wherein the plurality of generator demagnetization control devices are connected between the machine-end power supply and the excitation winding, and are used to perform demagnetization control on the excitation winding when an internal circuit short circuit or an external ground fault occurs in the generator.

[0085] The above is a detailed introduction to a generator demagnetization control device, a control method and a generator provided in the embodiments of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solution and its core idea of ​​the present application. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A generator demagnetization control device, used for demagnetization protection of excitation winding, characterized in that: include: a first demagnetization unit, wherein the first demagnetization unit is connected to the excitation winding; a second demagnetization unit, wherein the second demagnetization unit is connected between the first demagnetization unit and the excitation winding; A first switch unit, wherein the first switch unit is connected between the first demagnetization unit and the second demagnetization unit; a second switch unit, wherein the second switch unit is connected between the second demagnetization unit and the first switch unit; a control unit, the control unit being configured to control the first switch unit to be turned on so that the first demagnetization unit is connected to the excitation winding and performs constant voltage inversion demagnetization on the excitation winding; and control the second switch unit to be turned off so that the excitation winding is disconnected from the first demagnetization unit; The second demagnetization unit is configured to perform flexible energy transfer demagnetization on the excitation winding after being connected to the excitation winding.

2. The generator deexcitation control device according to claim 1, characterized in that: The first demagnetization unit includes a capacitor, one end of the capacitor is connected to the excitation winding through the first switch unit and the second demagnetization unit, and the other end of the capacitor is connected to the excitation winding through the first switch unit, the second switch unit and the second demagnetization unit.

3. The generator deexcitation control device according to claim 1, characterized in that: The second demagnetization unit includes a first diode, a nonlinear resistor and a fuse, one end of the first diode is connected to one end of the excitation winding, the other end of the first diode is connected to the nonlinear resistor through the fuse, and the other end of the nonlinear resistor is connected to the other end of the excitation winding.

4. The generator deexcitation control device according to claim 1, characterized in that: The generator demagnetization control device also includes a rectifier unit, which includes a three-level voltage source converter. The three-phase AC side of the three-level voltage source converter is connected to the generator end power supply, the DC side of the three-level voltage source converter is connected to the first demagnetization unit, and the control side of the three-level voltage source converter is connected to the control unit.

5. A generator demagnetization control method for demagnetization protection of excitation winding, characterized in that: The method comprises the following steps: Controlling the first switch unit to be turned on so that the first demagnetization unit performs constant voltage inversion demagnetization on the excitation winding; In response to the voltage value across the first demagnetization unit being greater than the threshold voltage of the second demagnetization unit, the second demagnetization unit is turned on and performs flexible energy transfer demagnetization on the excitation winding; In response to the constant voltage inverter demagnetization and the flexible energy transfer demagnetization both failing to be demagnetized, the second switch unit is controlled to be disconnected to disconnect the excitation winding from the generator circuit.

6. The generator deexcitation control method according to claim 5, characterized in that: The method of controlling the first switch unit to be turned on so that the first demagnetization unit performs constant voltage inversion demagnetization on the excitation winding includes: The control unit sends a first unlocking signal to the first switch unit, so that the first demagnetization unit is connected to the excitation winding after being unlocked; The control unit sends a second unlocking signal to the rectifying unit to unlock the rectifying unit; Wherein, the excitation current in the excitation winding flows to the first demagnetization unit to achieve energy charging; The first demagnetization unit releases energy through the rectifier unit to perform the constant voltage inversion demagnetization on the excitation winding.

7. The generator deexcitation control method according to claim 6, characterized in that: The method of turning on the second demagnetization unit and performing flexible energy transfer demagnetization on the excitation winding in response to the voltage value across the first demagnetization unit being greater than the threshold voltage of the second demagnetization unit comprises: When the voltage value across the first demagnetization unit is greater than the threshold voltage of the second demagnetization unit, the control unit sends a first locking signal to lock the rectifying unit; When the voltage across the first demagnetization unit is greater than the on-voltage of the second demagnetization unit, all the excitation current in the excitation winding is transferred to the second demagnetization unit, and the excitation current is consumed by the heat of the second demagnetization unit to achieve the flexible energy transfer demagnetization.

8. The generator deexcitation control method according to claim 7, characterized in that: Before controlling the first switch unit to be turned on so that the first demagnetization unit performs constant voltage inversion demagnetization on the excitation winding, the method further includes: When the generator is abnormal, the control unit sends a second locking signal to the first switch unit to lock the first switch unit; By blocking the first switch unit, the power unit is stopped from supplying energy to the excitation winding.

9. The generator deexcitation control method according to claim 8, characterized in that: The method of controlling the second switch unit to disconnect in response to both the constant voltage inverter demagnetization and the flexible energy transfer demagnetization failing to demagnetize, so as to disconnect the excitation winding from the generator circuit, comprises: The control unit determines the excitation current; In response to the excitation current being always greater than a current threshold, the control unit controls the second switch unit to be turned off, so as to disconnect the excitation winding from the generator circuit.

10. A generator, characterized in that: include: The machine-side power supply and field winding, and A generator demagnetization control device according to any one of claims 1 to 4, wherein a plurality of the generator demagnetization control devices are connected between the machine-end power supply and the excitation winding, and are used to perform demagnetization control on the excitation winding when an internal circuit short circuit or an external ground fault occurs in the generator; or The generator uses the method described in any one of claims 5 to 9 to perform demagnetization control on the excitation winding.

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