Black start DC excitation regulator and control method thereof applied to black start system

Abstract

The application belongs to the technical field of black start control of power grid system, and particularly discloses a black start DC excitation regulator and a control method thereof applied to a black start system. The black start DC excitation regulator comprises a rate limiter and a PID controller. The black start DC excitation power source outputs an excitation step signal to a signal input end of the rate limiter. An output signal of the rate limiter is compared with a terminal voltage of a feedback machine, and a difference value is output to a signal input end of the PID controller. An output signal of the PID controller is sent to a generator terminal. The control method comprises the following steps: constructing a black start system; starting initial excitation of the black start DC excitation power source, and adjusting the terminal voltage of the generator through the black start DC excitation regulator; switching to an AC excitation adjustment mode; starting a load, and operating the black start system. The application shortens the excitation time of the black start system with zero start-up and voltage rise, and improves the probability of one-time successful excitation. The application is suitable for black start control of a power grid.

Description

Technical Field

[0001] This invention belongs to the field of black start control technology for power grid systems, specifically a black start DC excitation regulator and its control method applied to black start systems. Background Technology

[0002] Black start refers to a targeted operational measure that, after the entire power grid or system has been shut down due to a fault and power has been lost within the system, restores the entire power system without relying on the assistance of other networks. This is achieved by starting up units with self-starting capabilities within the system, thereby driving units without self-starting capabilities to gradually expand the scope of power system restoration and ultimately restore the entire power system.

[0003] Therefore, the speed and measures of black start are crucial for power grids or regional power systems. Generally, priority is given to hydropower units with large grid capacity and black start capability for black start. The principle of black start path planning is to reduce the length of the starting path, the number of operational steps, and the changes in voltage levels, prioritizing paths with lower charging power. However, in some areas, the power grid structure is weak, the power supply structure is simple, and there are fewer large-capacity hydropower units with black start capability. In these cases, the relevant principles of path planning cannot be followed in the early planning stage of black start path. There are situations where the path from the black start power source to the second batch of starting power sources is long and involves voltage level changes. In long-distance black start systems, due to the high internal resistance of the equivalent power source, linear resonance problems can occur when closing long unloaded lines, leading to black start failure.

[0004] To avoid the aforementioned problems, the power grid can adopt a zero-start boosting starting scheme using a black-start power supply with power lines and main transformers. During the system's zero-start boosting process, the excitation stage of the starting power supply is crucial. Currently, large generator sets generally use a self-excited static thyristor rectifier excitation system. There are three excitation methods for this system: residual voltage excitation, DC excitation power supply excitation, and AC power supply excitation. In the event of a complete blackout in the power grid, the AC system loses power and cannot use AC power supply excitation. In residual voltage excitation, if the generator speed reaches its rated value, the residual terminal voltage is too low to drive the synchronization circuit, pulse triggering circuit, and rectifier bridge thyristor circuit in the excitation regulator, leading to excitation failure. If a DC excitation power supply is used directly for initial excitation, the excitation step signal should not be too large to ensure stability during the excitation process. Generally, the set value of the generator's DC excitation voltage is about 20% to 30% of the terminal voltage. Then, switching to the automatic excitation regulator for boosting extends the excitation time to some extent. However, the excitation time provided by this method is only suitable for the generator's normal start-up. If the AC grid system loses power and the time it takes for the generator to rise from its starting speed to 90% of its rated terminal voltage is too long, it will lead to an unsuccessful black start excitation. After the first black start excitation failure, the entire power grid may fail to recover due to insufficient emergency power supply capacity. Summary of the Invention

[0005] The purpose of this invention is to provide a black-start DC excitation regulator and its control method for use in black-start systems, so as to shorten the excitation time of zero-start voltage boost in black-start systems and increase the probability of successful excitation on the first attempt.

[0006] To achieve the above objectives, the present invention employs the following technical methods:

[0007] A black-start DC excitation regulator is disclosed, which is connected in series with the black-start DC excitation power supply side. The black-start DC excitation regulator includes a ratio limiter and a PID controller. The ratio limiter has a change rate limit, which does not exceed the no-load saturation coefficient of the generator. The ratio limiter limits the change rate of the input signal by limiting the change rate limit, thereby mitigating the impact of the step signal. The black-start DC excitation power supply outputs an excitation step signal to the signal input terminal of the ratio limiter. The output signal of the ratio limiter is compared with the feedback terminal voltage, and the difference is output to the signal input terminal of the PID controller. The output signal of the PID controller is sent to the generator terminal to adjust the generator terminal voltage to the set value of the first stage generator terminal voltage.

[0008] As a limitation, PID controllers include proportional, integral, and derivative types.

[0009] The transfer function of the PID controller is:

[0010]

[0011] In the above formula, G(s) is the transfer function of the PID controller, Kp is the proportional coefficient of the proportional element of the PID controller, Ti is the integral time coefficient of the integral element of the PID controller, and Td is the derivative time constant of the derivative element of the PID controller.

[0012] The present invention also provides a control method for applying the above-mentioned black-start DC excitation regulator to a black-start system, comprising the following steps performed in sequence:

[0013] S1. Construct a black boot system;

[0014] S2. The generator set operates through a black start process. When the speed reaches 100%, the black start system begins zero-start voltage boosting. The black start DC excitation power supply is used for initial excitation. The black start DC excitation power supply outputs an excitation step signal to the ratio limiter. The ratio limiter limits the rate of change of the input signal by setting a change rate limit to mitigate the impact of the step signal. The change rate limit does not exceed the no-load saturation coefficient of the generator. The output signal of the ratio limiter is compared with the feedback terminal voltage, and the difference is output to the PID controller. The PID controller acts on the generator terminal to adjust the generator terminal voltage to the set value of the first stage terminal voltage.

[0015] S3. Switch to AC excitation regulation mode, and the generator terminal voltage will automatically rise to the generator terminal control voltage value;

[0016] S4. Start the load and run the black boot system.

[0017] As a limitation, PID controllers include proportional, integral, and derivative types.

[0018] The transfer function of the PID controller is:

[0019]

[0020] In the above formula, G(s) is the transfer function of the PID controller, Kp is the proportional coefficient of the proportional element of the PID controller, Ti is the integral time coefficient of the integral element of the PID controller, and Td is the derivative time constant of the derivative element of the PID controller. In step S2, adjusting the generator terminal voltage to the set value of the first stage terminal voltage by the PID controller specifically involves: adjusting the proportional coefficient Kp of the proportional element, the integral time coefficient Ti of the integral element, and the derivative time constant Td of the derivative element. Through the coordinated adjustment of the proportional coefficient Kp of the proportional element, the integral time coefficient Ti of the integral element, and the derivative time constant Td of the derivative element, the DC excitation current of the generator rotor winding increases, and according to the principle of electromagnetic induction, the generator generates an induced electromotive force E. q The corresponding increase, combined with formula U G =E q -jI G X d Further adjust the generator terminal voltage to the set value of the first stage terminal voltage; Formula U G =E q -jI G X d In the middle, E q To generate an induced electromotive force for the generator, U G I is the generator terminal voltage. G X is the generator terminal current. dThis is the direct-axis reactance of the generator.

[0021] As a further limitation: In step S2, the proportional coefficient Kp of the proportional element, the integral time coefficient Ti of the integral element, and the derivative time constant Td of the derivative element of the PID controller are specifically adjusted as follows: The Ziegler-Nichols method is used to obtain the Kp, Ti, and Td of the PID controller. First, Ti is set to infinity and Td is 0. Then, Kp is increased until the system oscillates during black start. The Kp value at this critical state is recorded as Kcr, and the oscillation period is Tcr. Finally, based on the second tuning rule of Ziegler-Nichols, that is, Kp = 0.6Kcr, Ti = 0.5Tcr, and Td = 0.125Tcr, the values ​​of Kp, Ti, and Td are tuned.

[0022] As a further limitation: the method for obtaining the terminal control voltage value in step S3 is as follows: under the premise of knowing the measured parameters of the line involved in the black start planning path, the unloaded line capacitance effect is used to obtain the terminal control voltage value in the direction of power supply from the reasonable voltage requirement at the end of the line to the black start planning path.

[0023] As a limitation, the construction of the black boot system in step S1 includes the following steps performed sequentially:

[0024] S11. Preparations for confirming the status of the generator-transformer unit involved in the black start system;

[0025] S12, the black start system involves the plant completing switching operations and channel isolation;

[0026] S13. Close the generator disconnect switch and circuit breaker of the black start system generator;

[0027] S14. Confirm that the zero-start boost black start system is connected and the channel is isolated;

[0028] S15. When a black start system involves a substation modifying its black start protection settings, or when the reclosing circuit of the line belonging to the black start system is shut down, a black start system is formed.

[0029] The beneficial effects achieved by this invention, due to the adoption of the above-described solution, compared with the prior art, are as follows:

[0030] This invention provides a black-start DC excitation regulator and its control method applied to a black-start system. By connecting a black-start DC excitation regulator in series in the black-start excitation power supply system, a ratio limiter mitigates the impact of the excitation step signal, and a PID controller adjusts the generator voltage to the set value of the first stage generator terminal voltage, shortening the excitation time of zero-start voltage boost and increasing the probability of successful excitation on the first attempt. The invention employs the principle of the no-load line capacitance effect voltage method to deduce the generator terminal control voltage value from the control voltage at the end of the line, avoiding the overvoltage phenomenon at the end of the long no-load line during black-start when the AC excitation voltage rises to near the rated generator terminal voltage due to communication signal delay.

[0031] This invention is applicable to black start control after a power outage in a power grid system. Attached Figure Description

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0033] Figure 1 This is a schematic diagram of the structure of the black-start DC excitation regulator connected in series with the black-start excitation power supply system in Embodiment 1 of the present invention;

[0034] Figure 2 This is a logic block diagram of the black-start DC excitation regulator of Embodiment 1 of the present invention;

[0035] Figure 3 This is Embodiment 2 of the present invention, which is a black start system for pumped storage units based on PSCAD with zero-start pressure increase.

[0036] Figure 4 This is a flowchart of the zero-start-up and pressure-boosting black start process of a pumped storage unit based on PSCAD, as shown in Embodiment 2 of the present invention.

[0037] Figure 5 This is the black-start planning path for Embodiment 2 of the present invention;

[0038] Figure 6 This is a schematic diagram of the equivalent impedance and voltage of the i-th bus in Embodiment 2 of the present invention;

[0039] Figure 7 This is a simulation waveform diagram of the excitation voltage, excitation current and terminal voltage of the zero-start-up booster generator of the pumped storage unit based on PSCAD in an embodiment of the present invention.

[0040] Figure 8 This is a simulation waveform diagram of the voltage and current of the pumped storage unit at zero start-up based on PSCAD in an embodiment of the present invention. Detailed Implementation

[0041] The present invention will be further described below with reference to the embodiments. However, those skilled in the art should understand that the present invention is not limited to the following embodiments. Any improvements and equivalent changes made based on the specific embodiments of the present invention are within the scope of protection of the claims of the present invention.

[0042] Example 1: A black-start DC excitation regulator

[0043] A black-start DC excitation regulator, connected in series with the DC excitation power supply side, is shown in the schematic diagram below. Figure 1 As shown; the black-start DC excitation regulator includes a ratio limiter and a PID controller. The ratio limiter has a rate-of-change limit set within it, which does not exceed the generator's no-load saturation coefficient. The ratio limiter restricts the rate of change of the input signal by limiting the rate of change of the input signal, thus mitigating the impact of step signals. The PID controller types include proportional, integral, and derivative elements. The logic block diagram of the black-start DC excitation regulator is shown below. Figure 2 As shown;

[0044] The transfer function of the PID controller is:

[0045]

[0046] In the above formula, G(s) is the transfer function of the PID controller, Kp is the proportional coefficient of the proportional element of the PID controller, Ti is the integral time coefficient of the integral element of the PID controller, and Td is the derivative time constant of the derivative element of the PID controller.

[0047] The black start DC excitation power supply outputs an excitation step signal to the signal input terminal of the ratio limiter. The output signal of the ratio limiter is compared with the feedback terminal voltage, and the difference is output to the signal input terminal of the PID controller. The output signal of the PID controller is sent to the generator terminal to adjust the generator terminal voltage to the set value of the first stage generator terminal voltage.

[0048] Example 2: A control method for applying a black-start DC excitation regulator to a black-start system

[0049] A complete black start control system for pumped storage units was built using PACAD software, combined with actual production operation scenarios. Figure 3 As shown, it includes a synchronous generator, an AC excitation system, an AC / DC excitation system switching device, a speed regulation system, and a black-start DC excitation regulator as described in Example 1.

[0050] The model parameters for the unit's synchronous generator are: rated active power of 300MW, stator voltage of 18kV, rated power factor of 0.9, rated speed of 500r / min, and generator-specific inertia of 3600kg / m. 2The rotor winding resistance is 0.1722Ω, Xd = 1.08pu, Xd' = 0.3pu, Xd" = 0.22pu, Xq = 0.75pu, Xq' = 0.75pu, Xq" = 0.21pu.

[0051] After the black-start DC excitation regulator of Example 1 is applied to the black-start control system of a pumped-storage unit, the black-start control method of the pumped-storage unit black-start control system is as follows: Figure 4 As shown, the steps are performed sequentially:

[0052] S1. Construct a black boot system; specifically, this includes the following steps performed sequentially:

[0053] S11. Preparations for confirming the status of the generator-transformer unit involved in the black start system;

[0054] In this embodiment, all units of pumped storage station A are disconnected and shut down. The AVC, AGC and primary frequency regulation functions of unit #1, which serves as the black start power source, are deactivated. The station automatically performs channel isolation and modifies the protection settings of unit #1 generator-transformer group. The plant's automatic transfer switch has been deactivated. The plant is in normal operating mode. The primary equipment is capable of being shut down and powered on, and the secondary equipment can be normally put into and taken out of service.

[0055] S12, the black start system involves the plant completing switching operations and channel isolation;

[0056] In this embodiment, the first batch of starting power supply E thermal power plant #1 unit is disconnected and shut down, and the AVC, AGC and primary frequency regulation functions of E power plant #1 unit are deactivated. Channel isolation and modification of the protection settings of the #1 generator-transformer unit are carried out automatically. The plant's automatic transfer switch has been deactivated. The plant is in normal operating mode, primary equipment is capable of power outage and restoration, and secondary equipment can be normally put into and taken out of service. The 500kV B substation, 220kV A substation, 220kV C substation, and 220kV D substation perform switching operations according to the dispatch order, forming a black start system according to the black start planning path adjustment method. The black start planning path is as follows: Figure 5 As shown, the system includes a 500kV transformer and a long no-load charging line of nearly 100km. The line from the starting power supply at the sending end through the busbars of each substation to the high-voltage busbar at the receiving end adopts a π-type equivalent line.

[0057] S13. Close the generator disconnect switch and circuit breaker of the black start system generator;

[0058] In this embodiment, the pumped storage system closes the #1 generator outlet 8011 power disconnect switch and 801 switch;

[0059] S14. Confirm that the zero-start boost black start system is connected and the channel is isolated;

[0060] In this embodiment, it is confirmed that the pumped storage power plant #1 generator-transformer unit, 500kV line 1, B substation 500kV #1 bus, B substation #2 main transformer, B substation 220kV #2 bus, 220kV line 2, C substation 220kV #1 bus, C substation #1 main transformer, 220kV line 3, D substation 220kV #1 bus, 220kV line 4, E thermal power plant 220kV #2 bus, and E thermal power plant #1 start-up and standby transformer are connected and completely isolated from other equipment;

[0061] S15. The black start system involves the modification of black start protection settings in the substations, and the reclosing of the lines belonging to the black start system is taken out of operation, forming a black start zero start boost system.

[0062] In this embodiment, the black start system involves modifying the black start protection settings of the substation, and the reclosing of the line to which the black start system belongs is taken out of operation, thus forming a black start zero-start boost system.

[0063] S2. The generator set operates through a black start process. When the speed reaches 100%, the black start system starts zero-start voltage boosting. The black start DC excitation power supply is used for initial excitation. The black start DC excitation power supply outputs an excitation step signal to the ratio limiter. The ratio limiter limits the rate of change of the input signal by setting a change rate limit value to mitigate the impact of the step signal. The output signal of the ratio limiter is compared with the feedback terminal voltage. The difference is output to the PID controller. The PID controller acts on the generator terminal to adjust the generator terminal voltage to the set value of the first stage generator terminal voltage.

[0064] In this embodiment, the pumped storage unit #1 operates through a standardized black start process. Once the speed reaches 100%, the black start system begins zero-start voltage boosting. The pumped storage unit #1 utilizes a DC excitation system for excitation. The black start DC excitation power supply outputs an excitation step signal to the ratio limiter of the black start DC excitation regulator. The ratio limiter restricts the rate of change of the input signal by setting a change rate limit, mitigating the impact of the step signal. The change rate limiter does not exceed the no-load saturation coefficient. In this embodiment, the saturation coefficient of the generator at its rated stator voltage is 0.25. The ratio limiter in this embodiment... The ratio limit is set to 0.2. The output signal of the ratio limiter is compared with the feedback terminal voltage, and the difference is output to the PID controller. The PID controller acts on the generator terminal. The proportional coefficient Kp of the proportional element, the integral time coefficient Ti of the integral element, and the derivative time constant Td of the derivative element of the PID controller are adjusted. Through the coordinated adjustment of the proportional coefficient Kp of the proportional element, the integral time coefficient Ti of the integral element, and the derivative time constant Td of the derivative element, the DC excitation current of the generator rotor winding increases. According to the principle of electromagnetic induction, the generator generates an induced electromotive force E. q The corresponding increase, combined with formula UG =E q -jI G X d Further adjust the generator terminal voltage to the set value of the first stage terminal voltage; Formula U G =E q -jI G X d In the middle, E q To generate an induced electromotive force for the generator, U G I is the generator terminal voltage. G X is the generator terminal current. d The direct-axis reactance of the generator; in this embodiment, the first stage terminal voltage is set to 0.7pu (12.6kV);

[0065] The specific steps for tuning the proportional coefficient Kp of the proportional element, the integral time coefficient Ti of the integral element, and the derivative time constant Td of the derivative element of the PID controller are as follows: The Ziegler-Nichols method is used to determine Kp, Ti, and Td of the PID controller. First, Ti is set to infinity and Td to 0. Then, Kp is increased until the system oscillates during black start. The critical state Kp value is recorded as Kcr, and the oscillation period is Tcr. Finally, based on the second Ziegler-Nichols tuning rule, i.e., Kp = 0.6Kcr, Ti = 0.5Tcr, and Td = 0.125Tcr, the values ​​of Kp, Ti, and Td are tuned. In this embodiment, Kcr = 180 and Tcr = 4; therefore, Kp = 30, Ti = 2, and Td = 0.25.

[0066] S3. Switch to AC excitation regulation mode. The generator terminal voltage will automatically rise to the generator terminal control voltage value of 0.98pu (17.8kV). During the zero-start voltage rise process of the black start system, the pumped storage power station is responsible for adjusting the voltage to ensure that the 500kV and 220kV voltages of each station along the black start system are within the qualified range, and that the high-voltage side voltage of the Huhu pumped storage power station is around 525kV, and the 220kV voltage of each station along the black start system is around 230kV.

[0067] The method for determining the generator terminal control voltage value is as follows: Given the measured parameters of the lines involved in the black-start planning path, the unloaded line capacitance effect is used to deduce the generator terminal control voltage value backward from the reasonable voltage requirement at the end of the line towards the pumped storage power station A in the black-start planning path; the black-start planning path is as follows: Figure 5As shown, the system includes a 500kV transformer and a long unloaded charging line of nearly 100km. The line from the sending-end starting power supply, through the busbars of each substation, to the receiving-end high-voltage busbar uses a π-type equivalent line. In this type of line, the capacitance is concentrated on the corresponding busbar. Therefore, the equivalent impedance of each busbar along the line, looking towards the sending end, can be calculated recursively from the receiving end N. The equivalent impedance of the i-th busbar is as follows: Figure 6 As shown, the voltages of the sending-end busbar nodes and other busbar nodes are recursively calculated from the sending end to the receiving end according to the following formula:

[0068] U1=U

[0069] …

[0070]

[0071] …

[0072]

[0073] according to Figure 4 The black start planning path is to ensure that the 220kV voltage of the E thermal power plant at the end of the line is maintained at 230kV after zero start-up. The voltage on the high-voltage side of the pumped storage power station A step-up transformer is calculated to be around 525kV after zero start-up and voltage stabilization. Since the transformer ratio of the step-up station is 522.5 / 18kV, the control voltage value of the generator terminal voltage is 17.8±0.2kV.

[0074] S4. Start the load and run the black start system;

[0075] In this embodiment, the pumped storage unit #1 operated under plant service load and remained stable for 10 minutes.

[0076] The controllable load of substation C is 20MW. To ensure the system frequency remains at 50±0.5Hz, the load at each startup must not exceed 7MW. During this phase, the pumped storage power station is responsible for frequency and voltage regulation. After the startup load is completed, the system will operate stably for 10 minutes.

[0077] The E thermal power plant uses the #1 standby transformer to start the #1 unit's plant service system, starting one auxiliary machine, such as the primary air fan, coal mill, induced draft fan, forced draft fan, feedwater pump, etc. During this process, the pumped storage power station #1 unit is responsible for the frequency adjustment of the black start test system, and the system frequency adjustment range is 50±0.5Hz.

[0078] The E thermal power plant's #1 unit's plant auxiliary system started normally. After the #1 unit met the conditions for parallel connection with the black start system, the 2011 disconnect switch was closed, and the 201 switch was used to connect in parallel with the black start system synchronously, thus forming the black start system.

[0079] The output of Unit #1 at Power Plant E will be gradually increased to a total of 20MW, including the plant's auxiliary power load and the controllable load of Substation C, with the load increase rate not exceeding 7MW / minute. During this phase, the pumped storage Unit #1 will control the 500kV bus voltage of the plant's black start system at 525kV, and the Unit #1 at Power Plant E will control the 220kV bus voltage of the plant's black start system at 230kV.

[0080] The black boot system runs continuously for 15 minutes, after which the first batch of power supplies from the black boot system shuts down.

[0081] The black-start DC excitation regulator of Example 1 was applied to the black-start system of a pumped storage unit for grid black-start, and the resulting zero-start boost simulation waveform is shown below. Figure 7 and Figure 8 As shown.

[0082] Figure 7 In the equation, EFD, IFD, and VG_rms represent the per-unit values ​​of the excitation voltage, excitation current, and turbine terminal voltage of pumped storage station A, respectively; according to Figure 7 Analysis shows that the pumped storage system starts up from 2 seconds with DC excitation power, and within 5 seconds, the generator terminal voltage is boosted from 0 to 0.7 pu via the black DC excitation regulator. During this process, the maximum excitation voltage is 2.5 times the reference value, and the maximum excitation current is 0.783 times the reference value, meeting the unit's operating requirements. This embodiment of the DC excitation system avoids over-excitation caused by large step excitation signals to a certain extent. The black start system's zero-start voltage boosting process, i.e., the pumped storage power station's generator terminal voltage boosting from 0 to 17.87 kV, also only requires 15 seconds. Typically, the black start system with line zero-start voltage boosting process requires at least 60 seconds. This embodiment significantly shortens the excitation voltage boosting time.

[0083] Figure 8 In Chinese, Uchouxu is... Figure 4 The effective value of the 500kV side line voltage of pumped storage station A, UB500 and UB220 are Figure 4 The effective values ​​of the line voltage on the 500kV and 220kV sides of station B, UE220 is Figure 4 The effective value of the 220kV side line voltage of the ZhongE thermal power plant, and Ia, Ib, and Ic are the instantaneous values ​​of the three-phase excitation current of the transformer at Station B. According to... Figure 8 The waveform diagram of the transformer excitation current in Bilibili shows that during the black start and zero-start voltage rise process, the maximum instantaneous value of the transformer excitation current is only 0.0073 times the rated value, and no inrush current phenomenon occurs. Figure 8 The voltage waveform diagram of the 220kV side of the ZhongE thermal power plant shows that the voltage at the end of the system during the zero-start voltage rise process is within a reasonable range, with the maximum value not exceeding 231kV, which meets the voltage control requirements. The capacitor effect voltage control valve avoids the problem of excessively high voltage at the end of the long line under no-load conditions.

Claims

1. A black-start DC excitation regulator, characterized in that, The black-start DC excitation regulator is connected in series with the black-start DC excitation power supply side. The black-start DC excitation regulator includes a ratio limiter and a PID controller. The ratio limiter has a change rate limit, which does not exceed the generator's no-load saturation coefficient. The ratio limiter limits the change rate of the input signal by limiting the change rate limit, thus mitigating the impact of the step signal. The black-start DC excitation power supply outputs an excitation step signal to the signal input terminal of the ratio limiter. The output signal of the ratio limiter is compared with the feedback terminal voltage, and the difference is output to the signal input terminal of the PID controller. A PID controller consists of a proportional element, an integral element, and a derivative element. The proportional coefficient Kp of the proportional element, the integral time coefficient Ti of the integral element, and the derivative time constant Td of the derivative element have a synergistic adjustment effect. The output signal of the PID controller is sent to the generator. Through the coordinated adjustment of the proportional coefficient Kp of the proportional element, the integral time coefficient Ti of the integral element, and the derivative time constant Td of the derivative element, the DC excitation current of the generator rotor winding increases. According to the principle of electromagnetic induction, the induced electromotive force generated by the generator increases accordingly, and this is combined with the formula U... G =E q -jI G X d Adjust the generator terminal voltage to the set value of the first stage terminal voltage; Among them, E q To generate an induced electromotive force for the generator, U G I is the generator terminal voltage. G X is the generator terminal current. d This is the direct-axis reactance of the generator.

2. The black-start DC excitation regulator according to claim 1, characterized in that, The transfer function of the PID controller is: In the above formula, G(s) is the transfer function of the PID controller, Kp is the proportional coefficient of the proportional element of the PID controller, Ti is the integral time coefficient of the integral element of the PID controller, and Td is the derivative time constant of the derivative element of the PID controller.

3. A control method for a black-start system, characterized in that, The black-start system includes the black-start DC excitation regulator as described in claim 1 or 2, and the control method of the black-start system includes the following steps performed sequentially: S1. Construct a black boot system; S2. The generator set operates through a standardized black start process. When the speed reaches 100%, the black start system begins zero-start voltage boosting. The black start DC excitation power supply is used for initial excitation. The black start DC excitation power supply outputs an excitation step signal to the ratio limiter. The ratio limiter limits the rate of change of the input signal by setting a change rate limit to mitigate the impact of the step signal. The change rate limit does not exceed the no-load saturation coefficient of the generator. The output signal of the ratio limiter is compared with the feedback terminal voltage, and the difference is output to the PID controller. The PID controller acts on the generator to adjust the generator terminal voltage to the set value of the first stage terminal voltage. S3. Switch to AC excitation regulation mode, and the generator terminal voltage will automatically rise to the generator terminal control voltage value; S4. Start the load and run the black start system.

4. The control method for a black-start system according to claim 3, characterized in that, A PID controller includes a proportional element, an integral element, and a derivative element; The transfer function of the PID controller is: In the above formula, G(s) is the transfer function of the PID controller, Kp is the proportional coefficient of the proportional element of the PID controller, Ti is the integral time coefficient of the integral element of the PID controller, and Td is the derivative time constant of the derivative element of the PID controller. In step S2, the PID controller adjusts the generator terminal voltage to the set value of the first stage terminal voltage by: adjusting the proportional coefficient Kp of the proportional element, the integral time coefficient Ti of the integral element, and the derivative time constant Td of the derivative element. Through the coordinated adjustment of the proportional coefficient Kp of the proportional element, the integral time coefficient Ti of the integral element, and the derivative time constant Td of the derivative element, the DC excitation current of the generator rotor winding increases, and according to the principle of electromagnetic induction, the generator generates an induced electromotive force E. q The corresponding increase, combined with formula U G =E q -jI G X d Adjust the generator terminal voltage to the set value of the first stage terminal voltage; Formula U G =E q -jI G X d In the middle, E q To generate an induced electromotive force for the generator, U G I is the generator terminal voltage. G X is the generator terminal current. d This is the direct-axis reactance of the generator.

5. The control method for a black-start system according to claim 4, characterized in that, In step S2, the proportional coefficient Kp of the proportional element, the integral time coefficient Ti of the integral element, and the derivative time constant Td of the derivative element of the PID controller are specifically adjusted as follows: The Ziegler-Nichols method is used to obtain Kp, Ti, and Td of the PID controller. First, Ti is set to infinity and Td to 0. Then, Kp is increased until the system oscillates during black start. The critical state Kp value is recorded as Kcr, and the oscillation period is Tcr. Finally, based on the second Ziegler-Nichols tuning rule, i.e., Kp = 0.6Kcr, Ti = 0.5Tcr, and Td = 0.125Tcr, the values ​​of Kp, Ti, and Td are tuned.

6. A control method for a black-start system according to claims 3-5, characterized in that, The method for obtaining the generator terminal control voltage value in step S3 is as follows: Under the premise of knowing the measured parameters of the lines involved in the black start planning path, the generator terminal control voltage value is calculated by using the unloaded line capacitance effect and working backward from the reasonable voltage requirement at the end of the line to the power supply direction of the black start planning path.

7. The control method for a black-start system according to claim 3, characterized in that, Step S1, which involves constructing the black boot system, includes the following steps performed sequentially: S11. Preparations for confirming the status of the generator-transformer unit involved in the black start system; S12, the black start system involves the plant completing switching operations and channel isolation; S13. Close the generator disconnect switch and circuit breaker of the black start system generator; S14. Confirm that the zero-start boost black start system is connected and the channel is isolated; S15. When a black start system involves a substation modifying its black start protection settings, or when the reclosing circuit of the line belonging to the black start system is shut down, a black start system is formed.

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