A multi-mode start-up control loop and method for an excitation system

Abstract

The application discloses a kind of excitation system multi-mode starting control loop and method, the control loop includes: synchronous generator G, electric brake circuit, excitation starting circuit, the electric brake circuit includes electric brake power supply, electric brake transformer ZDB, electric brake alternating current circuit breaker S103, rectifier bridge SCR and direct current magnetic field circuit breaker S101, the electric brake power supply is connected to electric brake alternating current circuit breaker S103 by electric brake transformer ZDB, then to rectifier bridge SCR;The direct current that the rectifier bridge SCR rectifies after output is connected to the rotor of synchronous generator G through direct current magnetic field circuit breaker S101;The excitation starting circuit includes AC excitation power supply, diode rectifier bridge, excitation contactor K1, fuse F01 and F02;The application guarantees the success rate of each mode starting for the first time, and eliminates the hidden trouble brought by temporary change of external loop for test under test mode.

Description

Technical Field

[0001] This invention relates to a multi-mode start-up control loop and method for an excitation system, belonging to the field of power system stability and control technology. Background Technology

[0002] Generator sets frequently require zero-start voltage and current ramp-up tests under separately excited conditions. Hydropower units, due to their frequent start-up and shutdown cycles, require the excitation system to be activated to assist in electrical braking shutdown when the generator is in the low-speed range, in order to shorten the unit's low-speed operating time. After the thyristor switches from the off-state to the on-state and the trigger signal is removed, a minimum current, i.e., the holding current, is needed to maintain conduction. However, for large hydropower generators, due to their large rotor inductance and large rotor time constant, the rotor time constant has a significant resistance to current. During electric braking, the initial current is not sufficient to meet the thyristor holding current, leading to freewheeling failure. In separately excited tests, the AC side of the thyristor is connected to the separately excited power supply. The trigger angle of the thyristor is gradually changed through the excitation regulator, causing the power cabinet output current to increase from small to large. When the current is small, the thyristor has difficulty conducting with freewheeling, and the rotor current is almost zero. As the trigger angle gradually decreases, a sudden increase in rotor current occurs. Summary of the Invention

[0003] This invention provides a multi-mode start-up control loop and method for an excitation system, which solves the problems disclosed in the background art.

[0004] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0005] In a first aspect, the present invention provides a multi-mode start-up control circuit for an excitation system, comprising: a synchronous generator G, an electric braking circuit, and an excitation starting circuit, wherein:

[0006] The electric braking circuit includes an electric braking power supply, an electric braking transformer ZDB, an electric braking AC circuit breaker S103, a rectifier bridge SCR, and a DC field circuit breaker S101. The electric braking power supply is connected to the electric braking AC circuit breaker S103 through the electric braking transformer ZDB, and then to the rectifier bridge SCR. The DC power output by the rectifier bridge SCR after rectification is connected to the rotor of the synchronous generator G through the DC field circuit breaker S101.

[0007] The excitation circuit includes an AC excitation power supply, a diode rectifier bridge, an excitation contactor K1, and fuses F01 and F02. The AC excitation power supply is converted into DC power through the diode rectifier bridge and then connected to the rotor ends of the synchronous generator G through the excitation contactor K1 and fuses F01 and F02.

[0008] The synchronous generator G is connected to the generator output circuit breaker GCB, then to the main transformer ZB, and finally to the power line to complete the power generation.

[0009] Furthermore, the excitation circuit also includes a freewheeling resistor switch K2 and a freewheeling resistor Rx. The freewheeling resistor Rx is connected in series with the freewheeling resistor switch K2 and then connected in parallel to both ends of the rotor of the synchronous generator G, and is also connected to the front end of fuses F01 and F02.

[0010] Furthermore, it also includes an excitation regulator. The first input terminal of the excitation regulator collects analog signals of the generator terminal voltage and stator current of the synchronous generator G. The second input terminal of the excitation regulator collects analog signals of the rotor current of the synchronous generator G at the position where the currents of the AC circuit breaker S102 and the electric braking AC circuit breaker S103 intersect. The output terminal of the excitation regulator outputs corresponding trigger pulses to the rectifier bridge SCR.

[0011] Furthermore, it also includes an excitation transformer LCB, whose high-voltage side is connected between the synchronous generator G terminal and the outlet circuit breaker GCB, and the anode voltage on the low-voltage side is connected to the rectifier bridge SCR through the AC circuit breaker S102.

[0012] Furthermore, the synchronous generator G has demagnetizing units connected in parallel on both sides of its rotor for demagnetizing.

[0013] In a second aspect, the present invention provides a control method for a multi-mode start-up control loop of an excitation system according to any one of the foregoing claims, comprising:

[0014] When the normal start-up conditions for self-excitation are met, when the excitation regulator receives the excitation start command, it closes the DC field circuit breaker S101 and the AC circuit breaker S102, closes the freewheeling resistor switch K2, and delays to determine whether the excitation circuit contactor K1 needs to be engaged. Then, the generator starts up. First, the excitation circuit outputs the excitation current to the rotor of the synchronous generator G, thereby inducing the corresponding terminal voltage on the AC side of the synchronous generator. After the excitation regulator collects the terminal voltage and rotor current, it calculates and outputs the corresponding trigger pulse to the rectifier bridge SCR. The rectifier bridge SCR rectifies the DC current to the rotor of the synchronous generator. After successful excitation, the excitation circuit contactor K1 and the freewheeling resistor switch K2 are disconnected, and the start-up is completed.

[0015] Furthermore, including:

[0016] When the conditions for electric braking are met, the DC field circuit breaker S101, the electric braking AC circuit breaker S103, and the short-circuit switch GEB are closed, and the freewheeling resistor switch K2 is closed. When the excitation regulator receives the electric braking command, the excitation regulator collects the stator current analog signal and the rotor current analog signal of the synchronous generator G and calculates the corresponding trigger pulse to the rectifier bridge SCR. The rectifier bridge SCR rectifies the DC current to the rotor of the synchronous generator G, thus completing the electric braking process.

[0017] Furthermore, including:

[0018] When performing a generator short-circuit characteristic test, the excitation regulator determines that the test conditions are met. Then, the DC field circuit breaker S101 and the AC circuit breaker S102 on the low-voltage side of the excitation transformer are closed, and the freewheeling resistor switch K2 is closed. The excitation regulator collects the generator terminal voltage and rotor current and calculates the corresponding trigger pulses for the rectifier bridge SCR. The rectifier bridge SCR rectifies the DC current to the rotor. When the rotor current is less than the set first threshold, the freewheeling resistor circuit contactor K2 is engaged. When the rotor current is greater than the set second threshold, the freewheeling resistor is disengaged, and the separately excited test begins and is completed.

[0019] Furthermore, including:

[0020] When performing a static test on the excitation system, the excitation regulator receives the terminal voltage and rotor current input through the instrument when the test conditions are met. It then activates the separately excited power supply circuit S103 and the freewheeling resistor circuit contactor K2, without needing to activate the DC field circuit breaker S101. The excitation regulator receives the manually input trigger angle signal, calculates the corresponding trigger pulse, and sends it to the rectifier bridge SCR. The rectifier bridge SCR rectifies the DC current to the freewheeling resistor Rx, thus conducting and completing the static test.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0022] This invention provides a multi-mode start-up control circuit and method for an excitation system. The excitation regulator pre-determines whether the start-up conditions for each mode are met and informs the monitoring system. Then, the monitoring system issues commands to the excitation system, ensuring a high success rate for start-up in each mode. At the same time, it eliminates the hidden dangers caused by temporary modifications to the external circuit for testing in the test mode. Without changing the wiring, it can reliably start up in four modes: self-excitation start-up mode, electric braking mode, separately excited test mode, and static test mode. This solves the problem of excitation failure caused by the large rotor time constant of large hydro-generators. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the present invention;

[0024] Figure 2This is a diagram illustrating the signal transmission process in self-excited mode.

[0025] Figure 3 This is a diagram illustrating the signal transmission process in electric braking mode.

[0026] Figure 4 Diagram of signal transmission process under externally excited test mode;

[0027] Figure 5 This is a diagram illustrating the signal transmission process under static test mode.

[0028] Figure 6 This is a schematic diagram of the start-up process in self-excited mode;

[0029] Figure 7 This is a schematic diagram of the starting process in electric braking mode. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] Example 1, see Figure 1This embodiment describes a multi-mode start-up control circuit for an excitation system. The excitation regulator collects analog signals of the terminal voltage and stator current of the synchronous generator G. The high-voltage side of the excitation transformer LCB is connected between the synchronous generator terminals and the output circuit breaker. The anode voltage on the low-voltage side is connected to the rectifier bridge SCR through the AC circuit breaker S102. The electric braking power supply is connected to the electric braking AC circuit breaker S103 through the electric braking transformer ZDB, and then to the rectifier bridge SCR. The excitation regulator collects the analog signal of the rotor current at the point where the currents of the AC circuit breaker S102 and the electric braking AC circuit breaker S103 intersect. The excitation regulator outputs a trigger pulse after control calculation to drive the rectifier bridge SCR for rectification. The DC output of the rectified rectifier bridge SCR is connected to the synchronous generator rotor through the DC field circuit breaker S101. Parallel demagnetizing units are also required on both sides of the rotor for demagnetization. Simultaneously, the synchronous generator requires an initial power supply when starting, called the excitation unit. The excitation unit here uses AC excitation. The AC excitation power supply is converted to DC power by a diode rectifier bridge, and then connected to both ends of the rotor via excitation contactor K1, fuses F01 and F02. A freewheeling resistor switch K2 and a freewheeling resistor Rx circuit are connected in parallel before the fuses. After the synchronous generator G is started and meets the grid connection requirements, the generator terminals of synchronous generator G are connected to the generator output circuit breaker GCB, then to the main transformer, and finally to the power line to complete the power generation.

[0033] Example 2: This example provides a control method for the multi-mode start-up control loop of the excitation system according to any one of Examples 1, including:

[0034] See Figure 2 The signal transmission process diagram in self-excited mode shows that, under the condition of self-excited start-up, the DC field circuit breaker S101 and AC circuit breaker S102 are closed, and the freewheeling resistor switch K2 is closed. After a delay, it is determined whether the excitation circuit contactor K1 needs to be engaged. Then, the generator is started. First, the excitation circuit outputs the excitation current to the rotor, thereby inducing the corresponding terminal voltage on the AC side of the synchronous generator. After the excitation regulator collects the terminal voltage and rotor current, it calculates and outputs the corresponding trigger pulse to the rectifier bridge. The rectifier bridge rectifies the DC current to the rotor. After successful excitation, the excitation circuit contactor K1 and the freewheeling resistor switch K2 are disconnected.

[0035] See Figure 3 The signal transmission process diagram under electric braking mode shows that, under the condition of electric braking, the DC field circuit breaker S101, the electric braking AC circuit breaker S103, and the short-circuit switch GEB are closed, and the freewheeling resistor switch K2 is closed. Upon receiving the electric braking command and meeting the conditions, the excitation regulator collects the stator current and rotor current and calculates the corresponding trigger pulses for the rectifier bridge. The rectifier bridge rectifies the DC current to the rotor, completing the electric braking process.

[0036] See Figure 4The signal transmission process diagram under the separately excited test mode is shown. During the generator short-circuit characteristic test, the DC field circuit breaker S101 and the AC circuit breaker S102 on the low-voltage side of the excitation transformer are closed, along with the freewheeling resistor switch K2. Under the condition that the conditions are met, the excitation regulator collects the generator terminal voltage and rotor current and calculates the corresponding trigger pulses for the rectifier bridge. The rectifier bridge rectifies the DC current to the rotor. When the rotor current is less than the set threshold 3, the freewheeling resistor circuit contactor K2 is engaged; when the rotor current is greater than the set threshold 4, the freewheeling resistor is disengaged, thus starting and completing the separately excited test.

[0037] See Figure 5 The signal transmission process diagram in static test mode is as follows: to perform a static test on the excitation system, the excitation regulator inputs the terminal voltage and rotor current through the instrument, and connects the separately excited power supply circuit S103 and the freewheeling resistor circuit contactor K2. There is no need to connect the DC field circuit breaker S101. The trigger angle is manually input, and the regulator calculates the corresponding trigger pulse to the rectifier bridge. The rectifier bridge rectifies the DC current to the load (freewheeling resistor Rx) to carry out and complete the static test.

[0038] See Figure 6 The following is a schematic diagram of the start-up process in the self-excited mode. In standby mode, upon receiving a remote or local start-up command, the excitation regulator determines that the test mode switching pressure plate is 0, closes the DC field circuit breaker S101 and the AC circuit breaker S102, and opens the AC circuit breaker S103 and the AC side short-circuit switch. The regulator checks for inverter commands or fault signals, closes the freewheeling resistor switch K2, and then delays for 5 seconds to determine whether the start-up circuit contactor K1 needs to be engaged. If the conditions are met, the regulator sends a pulse. If the start-up requirements are met, the excitation is successful; otherwise, the excitation fails.

[0039] See Figure 7 The diagram shows the start-up process in electric braking mode. In standby mode, upon receiving a remote or local start-up command, the excitation regulator determines that the test mode switching pressure plate is 0, closes the DC magnetic field circuit breaker S101, the electric braking AC circuit breaker S103, and the AC side short-circuit switch GEB, opens the AC circuit breaker S102, closes the freewheeling resistor switch K2, and the regulator checks for inverter commands or fault signals. After the electric braking conditions are met, the regulator sends a pulse and enters the electric braking state.

[0040] This invention provides a multi-mode start-up control circuit and method for an excitation system. The excitation regulator pre-determines whether the start-up conditions for each mode are met and informs the monitoring system. Then, the monitoring system issues instructions to the excitation system, ensuring the success rate of start-up in each mode. At the same time, it eliminates the hidden dangers caused by temporary modifications to the external circuit for testing in the test mode.

[0041] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A multi-mode energizing control loop for an excitation system, characterized by, include: Synchronous generator G, electric braking circuit, and excitation circuit, wherein: The electric braking circuit includes an electric braking power supply, an electric braking transformer ZDB, an electric braking AC circuit breaker S103, a rectifier bridge SCR, and a DC field circuit breaker S101. The electric braking power supply is connected to the electric braking AC circuit breaker S103 through the electric braking transformer ZDB, and then to the rectifier bridge SCR. The DC power output by the rectifier bridge SCR after rectification is connected to the rotor of the synchronous generator G through the DC field circuit breaker S101. The excitation circuit includes an AC excitation power supply, a diode rectifier bridge, an excitation contactor K1, and fuses F01 and F02. The AC excitation power supply is converted into DC power through the diode rectifier bridge and then connected to the rotor ends of the synchronous generator G through the excitation contactor K1 and fuses F01 and F02. The synchronous generator G is connected to the generator output circuit breaker GCB, then to the main transformer ZB, and finally to the line to complete the power generation. It also includes an excitation transformer LCB, whose high-voltage side is connected between the synchronous generator G terminal and the outlet circuit breaker GCB, and the anode voltage on the low-voltage side is connected to the rectifier bridge SCR through the AC circuit breaker S102.

2. The multi-mode energizing control loop of claim 1, wherein, The excitation circuit also includes a freewheeling resistor switch K2 and a freewheeling resistor Rx. The freewheeling resistor Rx is connected in series with the freewheeling resistor switch K2 and then connected in parallel to the two ends of the rotor of the synchronous generator G, and is also connected to the front end of fuses F01 and F02.

3. The multi-mode energizing control loop of claim 2, wherein, It also includes an excitation regulator. The first input terminal of the excitation regulator collects analog signals of the generator terminal voltage and stator current of the synchronous generator G. The second input terminal of the excitation regulator collects analog signals of the rotor current of the synchronous generator G at the position where the currents of the AC circuit breaker S102 and the electric braking AC circuit breaker S103 intersect. The output terminal of the excitation regulator outputs corresponding trigger pulses to the rectifier bridge SCR.

4. The multi-mode energizing control loop of claim 1, wherein, The synchronous generator G has demagnetizing units connected in parallel on both sides of its rotor for demagnetizing.

5. A method of controlling a multi-mode start-up control loop of an excitation system according to any one of claims 3-4, characterized in that, include: When the normal start-up conditions for self-excitation are met, when the excitation regulator receives the excitation start command, it closes the DC field circuit breaker S101 and the AC circuit breaker S102, closes the freewheeling resistor switch K2, and determines after a delay whether the excitation circuit contactor K1 needs to be engaged. Then, the generator starts up. First, the excitation circuit outputs the excitation current to the rotor of the synchronous generator G, thereby inducing the corresponding terminal voltage on the AC side of the synchronous generator. After the excitation regulator collects the terminal voltage and rotor current, it calculates and outputs the corresponding trigger pulse to the rectifier bridge SCR. The rectifier bridge SCR rectifies the DC current to the rotor of the synchronous generator. After successful excitation, the excitation circuit contactor K1 and the freewheeling resistor switch K2 are disconnected, and the start-up is completed.

6. The control method of a multi-mode energizing control loop of an excitation system according to claim 5, characterized in that, include: When the conditions for electric braking are met, the DC field circuit breaker S101, the electric braking AC circuit breaker S103, and the short-circuit switch GEB are closed, and the freewheeling resistor switch K2 is closed. When the excitation regulator receives the electric braking command, the excitation regulator collects the stator current analog signal and the rotor current analog signal of the synchronous generator G and calculates the corresponding trigger pulse to the rectifier bridge SCR. The rectifier bridge SCR rectifies the DC current to the rotor of the synchronous generator G, thus completing the electric braking process.

7. The control method of the multi-mode energizing control loop of the excitation system according to claim 5, characterized in that, include: When performing a generator short-circuit characteristic test, the excitation regulator determines that the test conditions are met. Then, the DC field circuit breaker S101 and the AC circuit breaker S102 on the low-voltage side of the excitation transformer are closed, and the freewheeling resistor switch K2 is closed. The excitation regulator collects the generator terminal voltage and rotor current and calculates the corresponding trigger pulses for the rectifier bridge SCR. The rectifier bridge SCR rectifies the DC current to the rotor. When the rotor current is less than the set first threshold, the freewheeling resistor circuit contactor K2 is engaged. When the rotor current is greater than the set second threshold, the freewheeling resistor is disengaged, and the separately excited test begins and is completed.

8. The control method of the multi-mode energizing control loop of the excitation system according to claim 5, characterized in that, include: When performing a static test on the excitation system, the excitation regulator receives the terminal voltage and rotor current input through the instrument when the test conditions are met. It then activates the separately excited power supply circuit S103 and the freewheeling resistor circuit contactor K2, without needing to activate the DC field circuit breaker S101. The excitation regulator receives the manually input trigger angle signal, calculates the corresponding trigger pulse, and sends it to the rectifier bridge SCR. The rectifier bridge SCR rectifies the DC current to the freewheeling resistor Rx, thus conducting and completing the static test.

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