Stator overvoltage protection circuit and multi-unit parallel power generation system

Abstract

The utility model relates to the technical field of power generation, discloses a stator overvoltage protection circuit and a multi-unit parallel power generation system, and aims to solve the problem of poor accuracy of the protection mode of the existing multi-unit parallel power generation system. The rotating speed acquisition module, the rotor current acquisition module and the machine-end circuit breakers are arranged in one-to-one correspondence with the machine sets, the machine-end voltage acquisition module, the rotating speed acquisition module and the rotor current acquisition module are respectively connected with the control module, and the control module is respectively connected with the control ends of the machine-end circuit breakers. Each generator set is connected with the power grid through the switch end of the corresponding generator end circuit breaker, and the control module controls the generator end circuit breaker of the corresponding generator set to be switched off when monitoring that the generator end voltage is greater than a voltage threshold value and the rotating speed of a certain generator set is greater than a rotating speed threshold value or the rotor current is greater than a current threshold value. The overvoltage protection device improves the accuracy of overvoltage protection, and is suitable for a multi-unit parallel power generation system.

Description

Technical Field

[0001] This utility model relates to the field of power generation technology, specifically to a stator overvoltage protection circuit and a multi-unit parallel power generation system. Background Technology

[0002] Typically, each unit in a power generation system needs to be equipped with stator overvoltage protection to prevent insulation breakdown and short-circuit faults caused by overvoltage in the stator circuit. The specific solution involves collecting the terminal voltage to determine if it exceeds a specific value. If the terminal voltage exceeds this value, the unit needs to be disconnected and demagnetized, or it can be shut down directly.

[0003] In power generation systems, such as hydropower or thermal power systems, when two or more generating units are connected in parallel via a main wiring configuration, the terminal voltage of each unit is the same due to the direct parallel connection. If the terminal voltage of one unit rises for some reason, the terminal voltage of the other units connected in parallel will also rise. If the voltage exceeds a set value, the stator overvoltage protection of each unit will trip and shut down, causing all parallel units to stop. This situation, where a single unit's overvoltage fault causes other parallel units to trip, can expand the scope of the accident and cause unnecessary power generation losses.

[0004] To address stator overvoltage faults in multi-unit parallel power generation systems and reduce power generation losses due to unnecessary tripping, the common practice is to use a time-delay coordination method. For example, in a two-unit parallel power generation system, the stator overvoltage protection delay for Unit 1 can be set to 0.1 seconds, and for Unit 2, it can be set to 0.3 seconds. If the overvoltage is caused by a fault in Unit 1, it will trip first due to its shorter delay, thus disconnecting Unit 1 from the grid, allowing Unit 2 to continue generating power normally. However, if the fault is in Unit 2, the fault-free Unit 1 will also trip first due to its shorter delay, followed by Unit 2. Therefore, for two-unit parallel connections, using a time-delay coordination method to achieve selective stator overvoltage protection has only a 50% probability of correct operation, indicating poor accuracy. Utility Model Content

[0005] This invention aims to solve the problem of poor accuracy in the protection methods of existing multi-unit parallel power generation systems, and proposes a stator overvoltage protection circuit and a multi-unit parallel power generation system.

[0006] The technical solution adopted by this utility model to solve the above-mentioned technical problems is:

[0007] In a first aspect, this utility model provides a stator overvoltage protection circuit for use in a multi-unit parallel power generation system. It includes a control module and a generator terminal voltage acquisition module, as well as a speed acquisition module, a rotor current acquisition module, and a generator terminal circuit breaker, each corresponding to a generator unit. The generator terminal voltage acquisition module, speed acquisition module, and rotor current acquisition module are respectively connected to the signal input terminal of the control module. The first signal output terminal of the control module is respectively connected to the control terminal of each generator terminal circuit breaker. Each generator unit is connected to the power grid through the switching terminal of its corresponding generator terminal circuit breaker. The control module is configured to control the generator terminal circuit breaker of the corresponding generator unit to open when it detects that the generator terminal voltage is greater than a voltage threshold and the speed of a generator unit is greater than a speed threshold or the rotor current is greater than a current threshold.

[0008] Furthermore, it also includes a field deactivation switch that corresponds to each generator unit. The second signal output terminal of the control module is connected to the control terminal of each field deactivation switch. The excitation winding of each generator unit is connected to the excitation power supply through the switch terminal of the corresponding field deactivation switch. The control module is also configured to control the field deactivation switch of the corresponding generator unit to open at the same time as controlling the circuit breaker of the corresponding generator unit to open.

[0009] Furthermore, it also includes an alarm module, the third signal output terminal of the control module is connected to the alarm module, and the control module is also configured to control the alarm module to issue a corresponding alarm while controlling the circuit breaker of the corresponding unit to open.

[0010] Furthermore, the alarm module is an audible and visual alarm.

[0011] Furthermore, the terminal voltage acquisition module is a voltage sensor, the speed acquisition module is a speed sensor, a Hall element, a rotary encoder, a photoelectric sensor or an electromagnetic sensor, and the rotor current acquisition module is a current sensor.

[0012] Secondly, this utility model provides a multi-unit parallel power generation system, including the stator overvoltage protection circuit as described in the first aspect.

[0013] Furthermore, the multi-unit parallel power generation system is a hydropower generation system or a thermal power generation system.

[0014] The beneficial effects of this utility model are as follows: The stator overvoltage protection circuit and multi-unit parallel power generation system provided by this utility model, by adding a corresponding speed acquisition module and rotor current acquisition module to each unit, can identify the overvoltage unit based on the acquired speed and rotor current when the terminal voltage is abnormal. Then, the abnormal unit is selectively disconnected to achieve selective tripping, thereby improving the accuracy of overvoltage protection, ensuring that other units can continue to generate electricity normally, and achieving the effect of reducing the scope of the accident and reducing power generation losses. Attached Figure Description

[0015] Figure 1 A schematic diagram of a stator overvoltage protection circuit provided for an embodiment;

[0016] Figure 2 A logic diagram of a stator overvoltage protection circuit provided for an embodiment;

[0017] Figure 3 A schematic diagram of another stator overvoltage protection circuit provided in the embodiment;

[0018] Figure 4 A logic diagram of another stator overvoltage protection circuit provided for an embodiment. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the accompanying drawings of this embodiment will be used as a reference below.

[0020] The technical solution of this utility model is applicable to multi-unit parallel power generation systems, such as hydropower or thermal power generation systems. Currently, for stator overvoltage faults in multi-unit parallel power generation systems, the common practice is to use a delayed coordination method to reduce power generation losses caused by unnecessary tripping. The inventors have discovered that this overvoltage protection method suffers from low accuracy.

[0021] Based on this, the technical solution of this utility model is proposed. In this utility model, the stator overvoltage protection circuit includes a control module and a generator terminal voltage acquisition module, as well as a speed acquisition module, a rotor current acquisition module, and a generator terminal circuit breaker that are configured one-to-one with the generator set. The generator terminal voltage acquisition module, speed acquisition module, and rotor current acquisition module are respectively connected to the signal input terminal of the control module. The first signal output terminal of the control module is respectively connected to the control terminal of each generator terminal circuit breaker. Each generator set is connected to the power grid through the switching terminal of the corresponding generator terminal circuit breaker. The control module is configured to control the generator terminal circuit breaker of the corresponding generator set to open when the generator terminal voltage is detected to be greater than the voltage threshold and the speed of a certain generator set is greater than the speed threshold or the rotor current is greater than the current threshold.

[0022] Based on existing technology, this invention adds a corresponding speed acquisition module and rotor current acquisition module to each generator unit. The speed acquisition module is used to collect the speed of the corresponding generator unit, and the rotor current acquisition module is used to collect the rotor current of the corresponding generator unit. When the terminal voltage is abnormal, the overvoltage generator unit is identified based on the collected speed and rotor current of the generator unit. Then, the abnormal generator unit is selectively disconnected to achieve selective tripping, thereby improving the accuracy of overvoltage protection, ensuring that other generator units can continue to generate electricity normally, and achieving the effect of reducing the scope of the accident and reducing power generation losses.

[0023] The technical solutions in this embodiment will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments.

[0024] Figure 1 A schematic diagram of a stator overvoltage protection circuit is shown. Please refer to [link / reference]. Figure 1 The circuit includes a control module and a generator terminal voltage acquisition module, as well as a speed acquisition module, a rotor current acquisition module, and a generator terminal circuit breaker, each corresponding to a generator unit. The generator terminal voltage acquisition module, speed acquisition module, and rotor current acquisition module are respectively connected to the signal input terminal of the control module. The first signal output terminal of the control module is respectively connected to the control terminal of each generator terminal circuit breaker. Each generator unit is connected to the power grid through the switching terminal of the corresponding generator terminal circuit breaker. The control module is configured to control the generator terminal circuit breaker of the corresponding generator unit to open when it detects that the generator terminal voltage is greater than the voltage threshold and the speed of a certain generator unit is greater than the speed threshold or the rotor current is greater than the current threshold.

[0025] In this embodiment, the terminal voltage acquisition module can be a voltage sensor, the speed acquisition module can be a speed sensor, a Hall element, a rotary encoder, a photoelectric sensor or an electromagnetic sensor, and the rotor current acquisition module can be a current sensor.

[0026] Hall effect sensors, based on the Hall effect, can accurately measure changes in magnetic fields and convert them into motor speed information, such as the DH188 / DH220. Rotary encoders are sensors that directly measure rotational motion; by calculating the number or period of pulses, the motor speed can be determined. Photoelectric sensors are detection devices based on photoelectric components; when measuring motor speed, the photoelectric sensor can be fixed to the motor shaft, and the motor speed is determined by calculating the frequency of the signal. Electromagnetic sensors are detection devices based on the principle of electromagnetic induction; when measuring motor speed, the electromagnetic sensor is fixed to the motor shaft, and the speed is calculated by calculating the frequency of the signal generated when a magnetic material passes through the sensor.

[0027] In a multi-unit parallel power generation system, since multiple units are directly connected in parallel and each unit has the same terminal voltage, only one terminal voltage acquisition module is needed. This module collects the terminal voltage of any one unit and sends it to the control module. However, the rotational speeds and rotor currents of the multiple units may differ. Therefore, corresponding speed acquisition modules and rotor current acquisition modules are required for each unit to identify units experiencing overvoltage. Specifically, the speed acquisition module collects the rotational speed of the corresponding unit and sends it to the control module, while the rotor current acquisition module collects the rotor current of the corresponding unit and sends it to the control module.

[0028] Please see Figure 2 The implementation logic of the stator overvoltage protection circuit provided in this embodiment is as follows:

[0029] The control module receives the terminal voltage, the corresponding speed and rotor current of each unit, and compares whether the terminal voltage is greater than the voltage threshold, the speed is greater than the speed threshold, and the rotor current is greater than the current threshold. When the terminal voltage is greater than the voltage threshold, and the speed or rotor current of a certain unit is greater than the speed threshold or the current threshold, the unit is determined to be an overvoltage unit. At this time, the corresponding terminal circuit breaker of the unit is controlled to open, realizing the disconnection of the overvoltage unit, that is, separating the overvoltage unit from the grid.

[0030] The voltage threshold, speed threshold, and current threshold can be set according to actual conditions. In this embodiment, the voltage threshold is 1.3 times the rated voltage of the generator terminal, the speed threshold is 1.05 times the rated speed, and the current threshold is 1.05 times the rated rotor current.

[0031] As can be seen from the above process, the function of the control module is to compare voltage, speed, and current, and to control the switching of the circuit breaker at the machine terminal. Therefore, the control module can be implemented using simple digital circuits such as comparators, OR gates, and AND gates, without the need for a computer program. Of course, the control module can also be a controller loaded with a computer program. This computer program is used to compare voltage, speed, and current, and to control the switching of the circuit breaker at the machine terminal. This is a conventional computer program in the art and is not an improvement on this embodiment, so it will not be described in detail here.

[0032] Please see Figure 3 In this embodiment, the stator overvoltage protection circuit may further include a field-depleting switch that corresponds to each generator set. The second signal output terminal of the control module is connected to the control terminal of each field-depleting switch. The excitation winding of each generator set is connected to the excitation power supply through the switch terminal of the corresponding field-depleting switch. The control module is also configured to control the field-depleting switch of the corresponding generator set to open at the same time as controlling the circuit breaker of the corresponding generator set to open.

[0033] After the generator set is disconnected from the power grid, the electromotive force is no longer constrained by the grid, which may generate excessively high voltage, damaging the unit's insulation and the power grid equipment. To prevent this from happening, this embodiment performs a demagnetization operation simultaneously with the unit's disconnection.

[0034] Specifically, in this embodiment, upon determining that the unit is an overvoltage unit, the circuit breaker at the overvoltage unit's terminal is opened, and simultaneously the field deactivation switch of the overvoltage unit is opened, disconnecting the excitation winding from the excitation power supply circuit. This eliminates the magnetic field in the overvoltage unit, causing the electromotive force to drop to zero, thereby effectively reducing the transient voltage after separation and protecting the safety of the unit and grid equipment.

[0035] Based on the stator overvoltage protection circuit described above, this embodiment can be further extended with a delay in practical applications to further ensure the safety of the generator unit and grid equipment. Please refer to [reference needed]. Figure 4 When the generator terminal voltage exceeds the voltage threshold, and the rotational speed of a particular generator exceeds the rotational speed threshold or the rotor current exceeds the current threshold, the generator is identified as an overvoltage generator. If the duration of this state is greater than or equal to t1 but less than t2, the corresponding generator terminal circuit breaker and demagnetizing switch are disconnected to demagnetize the generator. If the duration of the generator terminal voltage exceeding the voltage threshold is greater than or equal to t2, the corresponding generator terminal circuit breakers and demagnetizing switches for all generators are disconnected to demagnetize all generators. This prevents the generators from failing to return to normal operation after being demagnetized, further ensuring the safety of the generators and grid equipment. t1 and t2 can be set according to actual conditions; for example, t1 can be 0.1 seconds and t2 can be 0.3 seconds.

[0036] It should be noted that when the control module is a combined digital circuit, delay processing can be achieved by adding a timer. When the control module is a controller, only a timing-related computer program needs to be added. This program is also a conventional computer program in this field and is not an improvement on this embodiment, so it will not be described in detail here.

[0037] In this embodiment, the stator overvoltage protection circuit may further include an alarm module. The third signal output terminal of the control module is connected to the alarm module. The control module is also configured to control the alarm module to issue a corresponding alarm while controlling the circuit breaker of the corresponding unit to open.

[0038] The alarm module can be an audible and visual alarm. In practical applications, when a unit is determined to be overvoltage, the alarm module can be used to issue a corresponding alarm to the staff, so that the staff can be informed of the unit's status in a timely manner and check and maintain it promptly.

[0039] In summary, the stator overvoltage protection circuit provided in this embodiment, based on existing technology, adds corresponding speed acquisition modules and rotor current acquisition modules to each unit. When the terminal voltage is abnormal, it identifies the overvoltage unit based on the acquired speed and rotor current, and then selectively disconnects the abnormal unit to achieve selective tripping. This improves the accuracy of overvoltage protection, ensures that other units can continue to generate electricity normally, and reduces the scope of the accident and power generation losses.

[0040] Based on the above technical solution, this embodiment also proposes a multi-unit parallel power generation system, including the stator overvoltage protection circuit as described in this embodiment.

[0041] It is understood that since the multi-unit parallel power generation system described in this embodiment includes the stator overvoltage protection circuit described in the embodiment, the system disclosed in the embodiment is relatively simple to describe because it corresponds to the circuit disclosed in the embodiment. For relevant parts, please refer to the circuit description, which will not be repeated here.

[0042] It should be noted that the present invention provides only a specific structure of a stator overvoltage protection circuit and a multi-unit parallel power generation system. The relevant modules involved are all hardware system modules or functional modules that combine computer software programs or protocols with hardware in the prior art. The computer software programs or protocols involved in these functional modules are technologies known to those skilled in the art and are not improvements to this system, so they will not be described in detail here. The improvement of this system lies in the interaction or connection relationship between the modules, that is, in improving the overall structure of the system to solve the corresponding technical problems to be solved by this system.

Claims

1. A stator overvoltage protection circuit, applied in a multi-unit parallel power generation system, characterized in that, The system includes a control module and a generator terminal voltage acquisition module, as well as a speed acquisition module, a rotor current acquisition module, and a generator terminal circuit breaker, each corresponding to a generator unit. The generator terminal voltage acquisition module, speed acquisition module, and rotor current acquisition module are connected to the signal input terminal of the control module, and the first signal output terminal of the control module is connected to the control terminal of each generator terminal circuit breaker. Each generator unit is connected to the power grid through the switching terminal of the corresponding generator terminal circuit breaker. The control module is configured to control the generator terminal circuit breaker of the corresponding generator unit to open when it detects that the generator terminal voltage is greater than a voltage threshold and the speed of a generator unit is greater than a speed threshold or the rotor current is greater than a current threshold.

2. The stator overvoltage protection circuit according to claim 1, characterized in that, It also includes a field deactivation switch that corresponds to each generator unit. The second signal output terminal of the control module is connected to the control terminal of each field deactivation switch. The excitation winding of each generator unit is connected to the excitation power supply through the switch terminal of the corresponding field deactivation switch. The control module is also configured to control the field deactivation switch of the corresponding generator unit to open at the same time as controlling the circuit breaker of the corresponding generator unit to open.

3. The stator overvoltage protection circuit according to claim 1, characterized in that, It also includes an alarm module, the third signal output terminal of the control module is connected to the alarm module, and the control module is also configured to control the alarm module to issue a corresponding alarm while controlling the circuit breaker of the corresponding unit to open.

4. The stator overvoltage protection circuit according to claim 3, characterized in that, The alarm module is an audible and visual alarm.

5. The stator overvoltage protection circuit according to claim 1, characterized in that, The terminal voltage acquisition module is a voltage sensor, the speed acquisition module is a speed sensor, Hall element, rotary encoder, photoelectric sensor or electromagnetic sensor, and the rotor current acquisition module is a current sensor.

6. A multi-unit parallel power generation system, characterized in that, Includes the stator overvoltage protection circuit as described in any one of claims 1 to 5.

7. The multi-unit parallel power generation system according to claim 6, characterized in that, The multi-unit parallel power generation system is either a hydropower generation system or a thermal power generation system.

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