Excitation system of synchronous generator

Abstract

The utility model discloses an excitation system of a synchronous generator. The excitation system comprises a reverse excitation control unit and a digital voltage regulator. The reverse excitation control unit comprises a central microprocessor, a power supply module, a CAN communication transceiver, a voltage sampling module, a current sampling module, an IGBT module and an excitation output module during sudden load unloading; the output end of the power supply module is connected with the central microprocessor; one end of the CAN communication transceiver is bidirectionally connected with the central microprocessor; the input and output ends of the voltage sampling module and the current sampling module are respectively connected with the voltage and current signal output ends of the generator and the central microprocessor; the input end of the IGBT module is connected with the central microprocessor; the input end of the excitation output module is connected with the output end of the IGBT module during sudden load unloading, and the output end of the excitation output module is connected with an exciter stator coil of the generator during sudden load unloading. According to the utility model, the transient performance grade of the generator when the load is suddenly unloaded is effectively improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a kind of excitation system of synchronous generator. BACKGROUND

[0002] When generator is in doing sudden load and sudden unloading transient performance test, or generator is in actual load process and encounters sudden load and sudden unloading, reverse excitation system will effectively improve the transient performance of synchronous generator, and the synchronous generator using reverse excitation system can make its transient response improve a performance grade. Reverse excitation system can be used in large quantities in the synchronous generator of 500KW and above power section, as an effective supplement of generator automatic voltage control, accurately control the rapid uprush of voltage waveform of generator under sudden load and sudden unloading.

[0003] The existing excitation control of synchronous generator is generally to realize the automatic control of terminal voltage of generator through analog automatic voltage regulator (abbreviated as AVR) or digital automatic voltage regulator (abbreviated as DVR).

[0004] Compared with reverse excitation system, the existing AVR and DVR voltage regulator are to automatically control the terminal voltage of generator by changing the size of forward excitation current or voltage. The terminal voltage regulation accuracy of existing analog AVR regulator is low, and the general accuracy is ±1%; the regulation accuracy of digital DVR regulator is high, and the general accuracy is ±0.2%. In terms of transient performance, AVR and DVR can effectively improve the transient response performance of generator, but compared with AVR, DVR is more obvious in improving the transient response performance of generator, so the generator of current data center adopts digital automatic voltage regulator DVR. However, AVR or obvious DVR voltage regulator has a significant disadvantage, that is, when synchronous generator encounters transient load, when encountering load unloading or 100% load unloading, the terminal voltage of synchronous generator rises (or voltage uprush) very badly in the moment of load unloading, so that after the generator unloads the load, the terminal voltage rises too fast, the transient performance cannot reach G3 performance grade (G3 grade requires that voltage uprush is not more than +20% of rated value), the transient performance parameter will be downgraded to G2 grade (G2 grade requires that voltage uprush is not more than +25% of rated value), or the voltage uprush is too much, and even downgraded to G1 grade (G1 grade requires that voltage uprush is not more than +35% of rated value). The too high voltage uprush will cause the downgrading of transient performance of synchronous generator in actual application or the decrease of acceptance grade, which is extremely unfavorable for the operation and procurement of synchronous generator in data center. UTILITY MODEL CONTENTS

[0005] The excitation system of the synchronous generator can effectively solve the deficiency of the digital voltage regulator in controlling the excitation system, and effectively improve the transient performance level of the synchronous generator when the load is suddenly unloaded.

[0006] The utility model discloses a kind of purposes in overcoming the defects of prior art and provide a synchronous generator's excitation system, it can effectively solve the deficiency of digital voltage regulator in controlling excitation system, effectively improve the transient performance level of synchronous generator when the load is suddenly unloaded.

[0007] The reverse excitation control unit includes a central microprocessor, a power module, a CAN communication transceiver, a voltage sampling module, a current sampling module, an IGBT module, and an excitation output module during sudden load discharge.

[0008] The input end of the power module is connected with a working power supply, and the output end of the power module is connected with the central microprocessor.

[0009] One end of the CAN communication transceiver is bidirectionally connected with the central microprocessor.

[0010] The input end of the voltage sampling module is connected with the voltage signal output end of the generator, and the output end of the voltage sampling module is connected with the central microprocessor.

[0011] The input end of the current sampling module is connected with the current signal output end of the generator, and the output end of the current sampling module is connected with the central microprocessor.

[0012] The input end of the IGBT module is connected with the central microprocessor.

[0013] The input end of the excitation output module during sudden load discharge is connected with the output end of the IGBT module, and the output end of the excitation output module during sudden load discharge is connected with the exciter stator coil of the generator.

[0014] The power input end of the digital automatic voltage regulator is connected with a working power supply. The CAN communication end of the digital automatic voltage regulator is bidirectionally connected with the other end of the CAN communication transceiver of the reverse excitation control unit. The voltage sampling end of the digital automatic voltage regulator is connected with the voltage signal output end of the generator. The current sampling end of the digital automatic voltage regulator is connected with the current signal output end of the generator. The excitation output end of the digital automatic voltage regulator is connected with the exciter stator coil of the generator.

[0015] The synchronous generator's excitation system has the following characteristics: the reverse excitation control unit and the digital automatic voltage regulator form a new excitation control system, and the reverse excitation control unit and the digital automatic voltage regulator communicate and exchange data through a CAN bus. BRIEF DESCRIPTION OF DRAWINGS

[0016] Fig. 1 is a schematic diagram of the synchronous generator's excitation system of the utility model;

[0017] Fig. 2 is a schematic diagram of the reverse excitation control unit in the synchronous generator's excitation system of the utility model;

[0018] Fig. 3 is a wiring diagram of the synchronous generator's excitation system of the utility model. DETAILED DESCRIPTION

[0019] The utility model will be further described below with reference to the drawings.

[0020] Please refer to Figs. 1 to 3 The synchronous generator's excitation system of the utility model comprises a reverse excitation control unit 100 and a digital automatic voltage regulator 200.

[0021] The reverse excitation control unit 100 comprises a central microprocessor 10, a power module 11, a CAN communication transceiver 12, a voltage sampling module 13, a current sampling module 14, an IGBT module 15 and an excitation output module 16 during sudden load shedding, wherein,

[0022] The input end of the power module 11 is connected with the working power from the permanent magnet generator in the generator 300, and the output end of the power module 11 is connected with the central microprocessor 10;

[0023] One end of the CAN communication transceiver 12 is bidirectionally connected with the central microprocessor 10; the CAN communication transceiver 12 is used for conversion and transmission of current, voltage and other signals, data exchange between the reverse excitation unit 100 and the digital automatic voltage regulator 200 and the receiving and sending process of control triggering and shutting off the forward excitation;

[0024] The input end of the voltage sampling module 13 is connected with the voltage signal output end of the generator, the output end of the voltage sampling module 13 is connected with the central microprocessor 10; the voltage sampling module 13 is used for real-time sampling of the voltage signal of the generator 300, and is used for judging one of the bases of the load sudden unloading and one of the main bases of the reverse excitation trigger output;

[0025] The input end of the current sampling module 14 is connected with the current signal output end of the generator 300, the output end of the current sampling module 14 is connected with the central microprocessor 10; the current sampling module 14 is used for real-time sampling of the current signal of the generator 300, and is used for judging one of the bases of the load sudden unloading and one of the main bases of the reverse excitation trigger output;

[0026] The input end of the IGBT (Insulated Gate Bipolar Transistor) module 15 is connected with the central microprocessor 10; the IGBT module 15 is the main component of the reverse excitation control unit 100. The IGBT module 15 does not output when the load runs stably; when the load sudden unloading is detected, the IGBT module 15 outputs the reverse excitation to the generator 300 through the sudden unloading load excitation output module 16, so as to weaken the main magnetic field of the generator 300, and make the three-phase terminal voltage of the generator 300 rapidly drop, and when the three-phase terminal voltage drops to the rated voltage, the reverse excitation is cut off, and the reverse excitation is no longer output to the generator;

[0027] The input end of the sudden unloading load excitation output module 16 is connected with the output end of the IGBT module 15, the output end of the sudden unloading load excitation output module 16 is connected with the exciter stator coil of the generator 300; the sudden unloading load excitation output module 16 is used for trigger output of the reverse excitation signal, and the reverse excitation signal is used for controlling the magnetic field of the exciter stator of the generator 300, so as to control the size of the three-phase terminal voltage of the generator 300.

[0028] The central microprocessor (CPU) is the core processing component of the reverse excitation control unit 100, which is used for real-time sampling of the parameters of the generator 300 in the load sudden unloading, accurate calculation and control of the size of the reverse excitation parameter, and smooth output of the reverse excitation parameter through the PID closed loop control, so that the voltage output of the generator 300 is more smooth and more easy to control.

[0029] The power input end of the digital automatic voltage regulator 200 is connected with a working power supply; the CAN communication end of the digital automatic voltage regulator 200 is bidirectionally connected with the other end of the CAN communication transceiver 12 of the reverse excitation control unit 100, the voltage sampling end of the digital automatic voltage regulator 200 is connected with the voltage signal output end of the generator 300; the current sampling end of the digital automatic voltage regulator 200 is connected with the current signal output end of the generator 300; and the excitation output end of the digital automatic voltage regulator 200 is connected with the exciter stator coil of the generator 300.

[0030] The reverse excitation control unit 100 controls and improves the load dump performance of the generator, monitors the parameters in real time when the load is dumped, and only triggers the output of reverse excitation when the load is dumped.

[0031] The digital automatic voltage regulator 200 is a core control component when the generator is normally working, and the digital automatic voltage regulator 200 always outputs forward excitation and automatically controls the terminal voltage of the generator. When the generator 300 performs the load dump operation, the reverse excitation control unit 100 outputs reverse excitation, and the forward excitation output by the digital automatic voltage regulator 200 is temporarily cut off, so that the rise of the terminal voltage of the generator 300 during the load dump is accurately suppressed.

[0032] The synchronous generator 300 receives the excitation signals from the digital automatic voltage regulator 200 or the reverse excitation control unit 100. When the forward excitation is strengthened, the terminal voltage of the generator 300 rises; when the reverse excitation is strengthened, the terminal voltage of the generator 300 can be accurately controlled to rapidly drop, so that the rapid rebound of the terminal voltage of the generator 300 is suppressed, and the electrical performance of the generator 300 during the transient load dump is improved.

[0033] The load 400 is connected to the output terminal of the generator. The complex load 400 is not always smooth, the load 400 suddenly rises or drops, and the possibility of sudden load dump of the load 400 always exists. The system is used for accurately controlling the sudden rise or overshoot of the voltage of the generator 300 during the load dump of the load 400, making the output voltage of the generator 300 controllable and stable, and making the load performance meet the acceptance index of G3 level.

[0034] The working principle of the excitation system of the synchronous generator is as follows:

[0035] When the generator 30 is running normally and smoothly, the excitation parameters of the conventional operation are automatically controlled and output by the digital automatic voltage regulator 200 (DVR), and the digital automatic voltage regulator 200 outputs positive excitation to the generator 300. The digital automatic voltage regulator 200 detects the three-phase voltage of the generator 300 in real time, and can also detect the phase current of the generator 300. When it is detected that the terminal voltage of the loaded generator 300 is lower than the rated set value, the digital automatic voltage regulator 200 will increase the output of the positive excitation, so as to automatically maintain the terminal voltage of the generator 300 near the rated voltage. When the load gradually decreases, the positive excitation does not need to be a large value to maintain the rated voltage of the generator 300, at this time the digital automatic voltage regulator 200 will automatically reduce the excitation to the generator 300, and vice versa, the positive excitation value of the generator 300 will be gradually increased. If the reverse excitation system is not used at this time, when the sudden load occurs, due to the inertia effect, the positive excitation of the generator 300 still maintains and does not automatically shut off after the generator 300 loses the load instantaneously, and the digital automatic voltage regulator 200 cannot control and suppress the rise of the terminal voltage in time, at this time the terminal voltage overshoots.

[0036] The function of reverse excitation control unit 100: when the generator 300 is running normally under the conventional smooth 100% load, the reverse excitation control unit 100 monitors the line voltage and phase current of the generator 300 in real time, but does not trigger the output of the reverse excitation of IGBT module 15, at this time the forward excitation of digital automatic voltage regulator 200 is normal, and the reverse excitation is cut off and not output. There is real-time CAN communication between reverse excitation control unit 100 and DVR digital voltage regulator 200 for data exchange and comparison. When the generator 300 encounters a large load dump, the digital automatic voltage regulator 200 cannot instantaneously reduce the excitation to suppress the instantaneous rise of the terminal voltage due to inertia. At this time, the reverse excitation control unit 100 compares the detected current and voltage with the parameter values when the load is stable. When the current is detected to decrease significantly and the voltage is detected to rise significantly, the reverse excitation control unit 100 will output reverse excitation to the generator 300. Almost at the same time, the reverse excitation control unit 100 will send control signals to the digital automatic voltage regulator 200 through the CAN communication transceiver 12. At this time, the digital automatic voltage regulator 200 will instantaneously shut off the forward excitation. By timely shutting off the forward excitation and accurately outputting the reverse excitation, the voltage surge on the generator 300 is offset or reduced. After the generator 300 receives the reverse excitation, the terminal voltage surge is rapidly suppressed, and the terminal voltage of the generator 300 smoothly decreases and quickly falls to near the rated voltage. At this time, the IGBT module 15 in the reverse excitation control unit 100 will instantaneously shut off the output of the reverse excitation, and at the same time, a forward excitation control signal will be sent to the digital automatic voltage regulator 200 through the CAN communication transceiver 12 to make the forward excitation trigger to restore the normal control of the digital automatic voltage regulator 200. At this time, the forward excitation is normally output, and the reverse excitation is cut off.

[0037] When the generator 300 encounters a large load dump again, the above control process will be repeated. Generally, the IGBT module 15 in the reverse excitation control unit 100 will only trigger the reverse excitation and output it to the generator 300 when the load is dumped, and the reverse excitation can timely suppress the rise of the terminal voltage of the generator 300.

[0038] According to the parameter performance calculation formula of the generator 300 load dump:

[0039] Load sudden unloading transient voltage deviation % = (highest surge voltage - rated voltage) ÷ rated voltage × 100% From the above formula, the rated voltage is a constant value, the smaller the surge voltage when the load is suddenly unloaded, the smaller the transient voltage deviation value, and the better the electrical performance of the generator when the load is suddenly unloaded by 100%. The reverse excitation system just suppresses the recoil voltage of the generator when the load is suddenly unloaded, thereby reducing the transient voltage deviation value of the generator and improving the electrical performance of the generator when the load is suddenly unloaded. The generator can also meet the high performance requirements of G3 level under the condition of load sudden unloading, and finally meets the stringent requirements of customers on the load sudden unloading performance of the generator.

[0040] The excitation system of the synchronous generator of the utility model, compared with the generator controlled by the digital automatic voltage regulator 200 without using the reverse excitation control unit 100, through actual test, it is found that the generator using the reverse excitation control unit 100, when the load is suddenly unloaded, the surge voltage is more easily controlled, and the sudden unloading transient voltage deviation value can be reduced by about 7-10% percentage points, and the electrical performance of the generator when the load is suddenly unloaded is obviously improved.

[0041] The above examples are only for illustrating the utility model, and are not limited to the utility model. Those skilled in the art can make various transformations or modifications without departing from the spirit and scope of the utility model. Therefore, all equivalent technical solutions should belong to the scope of the utility model, which should be limited by the claims.

Claims

1. An excitation system of a synchronous generator comprising a field-reversing control unit and a digital automatic voltage regulator; characterized in that, The reverse excitation control unit comprises a central microprocessor, a power module, a CAN communication transceiver, a voltage sampling module, a current sampling module, an IGBT module and an excitation output module during sudden load shedding. An input end of the power module is connected with a working power supply, and an output end of the power module is connected with the central microprocessor. One end of the CAN communication transceiver is bidirectionally connected with the central microprocessor. An input end of the voltage sampling module is connected with a voltage signal output end of the generator, and an output end of the voltage sampling module is connected with the central microprocessor. An input end of the current sampling module is connected with a current signal output end of the generator, and an output end of the current sampling module is connected with the central microprocessor. An input end of the IGBT module is connected with the central microprocessor. An input end of the excitation output module during sudden load shedding is connected with an output end of the IGBT module, and an output end of the excitation output module during sudden load shedding is connected with an exciter stator coil of the generator. A power input end of the digital automatic voltage regulator is connected with a working power supply; a CAN communication end of the digital automatic voltage regulator is bidirectionally connected with the other end of the CAN communication transceiver of the reverse excitation control unit; a voltage sampling end of the digital automatic voltage regulator is connected with a voltage signal output end of the generator; a current sampling end of the digital automatic voltage regulator is connected with a current signal output end of the generator; and an excitation output end of the digital automatic voltage regulator is connected with an exciter stator coil of the generator.

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