CN212518847U - Excitation system of alternating-current generator - Google Patents
Excitation system of alternating-current generator Download PDFInfo
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- CN212518847U CN212518847U CN202021260006.XU CN202021260006U CN212518847U CN 212518847 U CN212518847 U CN 212518847U CN 202021260006 U CN202021260006 U CN 202021260006U CN 212518847 U CN212518847 U CN 212518847U
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Abstract
The utility model provides an alternator excitation system, including three-phase thyristor full-control rectifier bridge U1, alternator's rotor excitation winding L1 is connected to three-phase thyristor full-control rectifier bridge U1's output, and alternator excitation system still includes resistance R1, electric capacity C1 and the three-phase full wave rectifier bridge U2 that constitutes by the diode. The utility model discloses select three-phase full wave rectifier bridge U2 as three-phase thyristor full controlled rectifier bridge U1's commutation overvoltage absorption circuit, have that components and parts are few, the reliability is high, generate heat characteristics such as few, efficient, because of the capacity of electric capacity improves greatly in the return circuit, loop resistance is also very little, and is strong to commutation overvoltage's suppressive ability.
Description
Technical Field
The utility model relates to a generator excitation technical field especially relates to an alternator excitation system.
Background
The main task of the synchronous generator excitation system is to provide an adjustable direct current voltage for the excitation winding of the generator so as to meet the requirements of normal power generation of the generator and safe operation of a power system. The excitation power supply is taken from the generator end of the generator, transformed by an excitation transformer and then sent to an excitation power unit for rectification, changed into direct current and added to an excitation winding of the generator to provide excitation current required by the normal power generation of the generator. The high-power rectifying device is a key component in the excitation power unit of the synchronous generator, and the reliable operation of the high-power rectifying device is directly related to the safety of the operation of the generator. The thyristor is used as a core element of a high-power rectifying device, and if overvoltage or overcurrent exceeding the rated value of the thyristor is borne, the thyristor can be damaged in a short time. Practice proves that the commutation overvoltage is the most frequent and dangerous overvoltage borne by the thyristor rectifier bridge in normal operation, and if no proper measures are taken for effective suppression, the normal operation of an excitation system is seriously threatened.
The traditional commutation overvoltage protection mostly adopts resistance-capacitance protection, namely, two ends of each rectifying element are connected with a resistance-capacitance absorption network in parallel, so that a follow current path is provided for reverse current flowing through leakage inductance of a transformer, which is formed by a carrier accumulation effect in a thyristor, and Ldi/dt is greatly reduced. The capacitor mainly absorbs peak overvoltage, and the resistor is used for limiting charge and discharge current of the capacitor, so that the capacitor can absorb energy, the damping circuit can vibrate, and the thyristor turn-on loss and current rise rate can be limited. However, the existence of the resistor in the conventional scheme greatly reduces the overvoltage suppression capability of the protection circuit, because although the voltage at two ends of the capacitor cannot change suddenly, the sudden change of the current causes the generated sudden change voltage to be added to the turned-off thyristor, and the effect of suppressing the commutation overvoltage is poor.
SUMMERY OF THE UTILITY MODEL
In view of this, the utility model provides an alternator excitation system to solve traditional synchronous generator excitation system and adopt the poor problem of resistance-capacitance protection suppression commutation overvoltage effect.
The technical scheme of the utility model is realized like this: an excitation system of an alternating-current generator comprises a three-phase thyristor full-control rectifier bridge U1, the output end of the three-phase thyristor full-control rectifier bridge U1 is connected with a rotor excitation winding L1 of the alternating-current generator,
the alternating-current generator excitation system further comprises a resistor R1, a capacitor C1 and a three-phase full-wave rectifier bridge U2 formed by diodes;
the middle point of a first bridge arm of a three-phase thyristor full-control rectifier bridge U1 is connected with the middle point of a first bridge arm of a three-phase full-wave rectifier bridge U2, the middle point of a second bridge arm of a three-phase thyristor full-control rectifier bridge U1 is connected with the middle point of a second bridge arm of a three-phase full-wave rectifier bridge U2, and the middle point of a third bridge arm of a three-phase thyristor full-control rectifier bridge U1 is connected with the middle point of a third bridge arm of a three-phase full-;
the anode of the output end of the three-phase full-wave rectifier bridge U2 is connected with the cathode of the output end of the three-phase full-wave rectifier bridge U2 through a resistor R1, and a capacitor C1 is connected with the resistor R1 in parallel.
Optionally, the excitation system of the ac generator further includes a resistor R2, a resistor R3, a capacitor C2, and a capacitor C3, an anode of an output end of the three-phase full-wave rectifier bridge U2 is connected to an anode of an output end of the three-phase thyristor full-control rectifier bridge U1 through the resistor R2 and the capacitor C2, and a cathode of an output end of the three-phase full-wave rectifier bridge U2 is connected to a cathode of an output end of the three-phase thyristor full-control rectifier bridge U1 through the resistor R3 and the capacitor C3.
Optionally, the resistor R1, the resistor R2, and the resistor R3 are sequentially 2 kilo-ohms, 10 ohms, and the capacitor C1, the capacitor C2, and the capacitor C3 are sequentially 6 μ F, 0.94 μ F, and 0.94 μ F.
Optionally, the alternator excitation system further includes a field suppression resistor R4, a diode D7, a diode D8, a diode D9, a diode D10, and a diac V1;
the negative electrode of the diode D7 is connected with the negative electrode of the diode D10, the positive electrode of the diode D10 is connected with the negative electrode of the diode D8, the positive electrode of the diode D8 is connected with the positive electrode of the diode D9, the negative electrode of the diode D9 is connected with the positive electrode of the diode D7, the common end of the diode D7 and the diode D10 is connected with the common end of the diode D8 and the diode D9 through a diac V1, the positive electrode of the direct current bus of the three-phase thyristor fully-controlled rectifier bridge U1 is connected with the common end of the diode D7 and the diode D9 through a field suppression resistor R4, and the common end of the diode D8 and the diode D10 is connected with the negative electrode of the direct current bus of the three.
Optionally, the demagnetization resistor R4 is a silicon carbide nonlinear resistor.
Optionally, the diac V1 is an avalanche diode.
The utility model discloses an alternator excitation system has following beneficial effect for prior art:
(1) the utility model discloses a three-phase full wave rectifier bridge U2 is as commutation overvoltage absorption circuit of three-phase thyristor full control rectifier bridge U1, has the characteristics such as few components and parts, high reliability, generate heat less, efficient, because the capacity of electric capacity in the return circuit improves greatly, the return circuit resistance is also very little, and is strong to commutation overvoltage's suppressive power; (2) the utility model discloses utilize the circuit that field suppression resistance R4, diode D7, diode D8, diode D9, diode D10 and bidirectional breakdown diode V1 constitute, can consume the positive negative overvoltage that produces between rotor excitation winding L1 and the three-phase thyristor full control rectifier bridge U1, prevent that the excessive pressure from to three-phase thyristor full control rectifier bridge U1 and rotor excitation winding L1's damage.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a circuit diagram of an excitation system of an ac generator according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work all belong to the protection scope of the present invention.
As shown in fig. 1, the ac generator excitation system includes a three-phase thyristor full-control rectifier bridge U1, an output end of the three-phase thyristor full-control rectifier bridge U1 is connected to a rotor excitation winding L1 of the ac generator, and the ac generator excitation system further includes a resistor R1, a capacitor C1, and a three-phase full-wave rectifier bridge U2 formed by diodes; the middle point of a first bridge arm of a three-phase thyristor full-control rectifier bridge U1 is connected with the middle point of a first bridge arm of a three-phase full-wave rectifier bridge U2, the middle point of a second bridge arm of a three-phase thyristor full-control rectifier bridge U1 is connected with the middle point of a second bridge arm of a three-phase full-wave rectifier bridge U2, and the middle point of a third bridge arm of a three-phase thyristor full-control rectifier bridge U1 is connected with the middle point of a third bridge arm of a three-phase full-; the anode of the output end of the three-phase full-wave rectifier bridge U2 is connected with the cathode of the output end of the three-phase full-wave rectifier bridge U2 through a resistor R1, and a capacitor C1 is connected with the resistor R1 in parallel.
The three-phase thyristor fully-controlled rectifier bridge U1 comprises thyristors T1-T6, a first bridge arm is formed by the thyristor T1 and the thyristor T4, a second bridge arm is formed by the thyristor T3 and the thyristor T6, and a third bridge arm is formed by the thyristor T5 and the thyristor T2. The three-phase full-wave rectifier bridge U2 comprises diodes D1-D6, a first leg is formed by a diode D1 and a diode D4, a second leg is formed by a diode D3 and a diode D6, and a third leg is formed by a diode D5 and a diode D2. The embodiment is equivalent to that a three-phase full-wave rectifier bridge U2 is connected in parallel to the input side of the anode of a three-phase thyristor full-controlled rectifier bridge U1 to perform phase-change overvoltage protection on the three-phase thyristor full-controlled rectifier bridge U1, and the output of the three-phase full-wave rectifier bridge U2 is connected in parallel with a resistor R1 and a capacitor C1. The resistor R1 and the capacitor C1 are mainly used for suppressing overvoltage, the capacitor C1 plays a role in filtering, and the resistor R1 is not only a discharge resistor of the capacitor C1, but also a main energy consumption absorption resistor of the whole protection circuit.
The protection principle of the three-phase full-wave rectifier bridge U2 is discussed by taking the commutation process of the thyristor Tl-T3 as an example. Assuming that the reverse current caused by the memory effect at the moment of finishing the commutation of the thyristor Tl and the thyristor T3 is i, the commutation equivalent inductance is La, Lb and Lc, at the moment of finishing the commutation of the thyristor Tl and the thyristor T3, the thyristor T2 is always in the on state, the commutation of the diode D1 and the diode D3 is finished, and the diode D2 is also in the on state, the reverse current flowing through Lb can flow through a loop of B-D-e-C-O, and the reverse current flowing through La can not flow through the loop, so that the potential of a point is lower than the potential of C point due to the back voltage caused by the discontinuous leakage inductance La current, so that the diode D4 is forced to be turned on, and the diode D2 is turned off. Then the whole free-wheeling loop of La and Lb becomes A-O-B-B-d-e-a. This completes the sinking of the reverse current. Due to the symmetry of the three-phase circuit, the phase-changing process of other elements is similar to that, and is not described in detail here. Thus, the three-phase full-wave rectifier bridge U2 of the embodiment is used as a commutation overvoltage absorption circuit of the three-phase thyristor full-control rectifier bridge U1, has the characteristics of few components, high reliability, less heat generation, high efficiency and the like, and has strong suppression capability on commutation overvoltage because the capacity of a capacitor in a loop is greatly improved and the loop resistance is very small.
Further, as shown in fig. 1, the excitation system of the alternator of this embodiment further includes a resistor R2, a resistor R3, a capacitor C2, and a capacitor C3, an anode of an output end of the three-phase full-wave rectifier bridge U2 is connected to an anode of an output end of the three-phase thyristor full-controlled rectifier bridge U1 through a resistor R2 and a capacitor C2, and a cathode of an output end of the three-phase full-wave rectifier bridge U2 is connected to a cathode of an output end of the three-phase thyristor full-controlled rectifier bridge U1 through a resistor R3 and a capacitor C3. The resistor R2 and the capacitor C2, the resistor R3 and the capacitor C3 are used for improving the commutation speed and reducing the commutation overlap angle.
In this embodiment, the resistance-capacitance in the circuit is optimally designed, preferably, the resistor R1, the resistor R2, and the resistor R3 are sequentially 2 kilo-ohms, 10 ohms, and the capacitor C1, the capacitor C2, and the capacitor C3 are sequentially 6 μ F, 0.94 μ F, and 0.94 μ F. According to practical verification, after the resistance-capacitance of the parameters is adopted, the instantaneous value of the excitation voltage output by the system becomes smoother, and the commutation overvoltage burrs are obviously weakened.
Further, as shown in fig. 1, the alternator field system of this embodiment further includes a field suppression resistor R4, a diode D7, a diode D8, a diode D9, a diode D10, and a diac V1;
the negative electrode of the diode D7 is connected with the negative electrode of the diode D10, the positive electrode of the diode D10 is connected with the negative electrode of the diode D8, the positive electrode of the diode D8 is connected with the positive electrode of the diode D9, the negative electrode of the diode D9 is connected with the positive electrode of the diode D7, the common end of the diode D7 and the diode D10 is connected with the common end of the diode D8 and the diode D9 through a diac V1, the positive electrode of the direct current bus of the three-phase thyristor fully-controlled rectifier bridge U1 is connected with the common end of the diode D7 and the diode D9 through a field suppression resistor R4, and the common end of the diode D8 and the diode D10 is connected with the negative electrode of the direct current bus of the three.
The field suppression resistor R4 is a silicon carbide nonlinear resistor, and the diac V1 is an avalanche diode.
When the synchronous generator is shut down, and the field suppression switch is disconnected, electromagnetic energy in a rotor winding of the generator is suddenly disconnected due to a circuit, if the energy is not released and consumed in time, a very large high voltage can be generated, and the field suppression switch is easily burnt and the insulation of the rotor winding is damaged. In this embodiment, when a forward overvoltage is generated between the rotor excitation winding L1 and the three-phase thyristor full-control rectifier bridge U1, if the overvoltage amplitude reaches the breakdown voltage of the diac V1, the diac V1 is broken down and conducted, and the forward overvoltage is consumed by the silicon carbide nonlinear resistor R4 after passing through the diode D7 and the diode D8; when negative overvoltage is generated between the rotor excitation winding L1 and the three-phase thyristor full-control rectifier bridge U1, if the overvoltage amplitude reaches the breakdown voltage of the bidirectional breakdown diode V1, the bidirectional breakdown diode V1 is broken down and conducted, and the negative overvoltage is consumed by the silicon carbide nonlinear resistor R4 after passing through the diode D10 and the diode D9. When the voltage in the circuit drops to the return value of diac V1, diac V1 automatically returns to the high impedance state. Therefore, the embodiment can consume positive and negative overvoltage generated between the rotor excitation winding L1 and the three-phase thyristor fully-controlled rectifier bridge U1, and prevent the overvoltage from damaging the three-phase thyristor fully-controlled rectifier bridge U1 and the rotor excitation winding L1.
The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. The utility model provides an alternator excitation system, includes three-phase thyristor full controlled rectifier bridge U1, and alternator's rotor excitation winding L1 is connected to three-phase thyristor full controlled rectifier bridge U1's output, its characterized in that:
the alternating-current generator excitation system further comprises a resistor R1, a capacitor C1 and a three-phase full-wave rectifier bridge U2 formed by diodes;
the middle point of a first bridge arm of a three-phase thyristor full-control rectifier bridge U1 is connected with the middle point of a first bridge arm of a three-phase full-wave rectifier bridge U2, the middle point of a second bridge arm of a three-phase thyristor full-control rectifier bridge U1 is connected with the middle point of a second bridge arm of a three-phase full-wave rectifier bridge U2, and the middle point of a third bridge arm of a three-phase thyristor full-control rectifier bridge U1 is connected with the middle point of a third bridge arm of a three-phase full-;
the anode of the output end of the three-phase full-wave rectifier bridge U2 is connected with the cathode of the output end of the three-phase full-wave rectifier bridge U2 through a resistor R1, and a capacitor C1 is connected with the resistor R1 in parallel.
2. The alternator excitation system of claim 1 further comprising a resistor R2, a resistor R3, a capacitor C2 and a capacitor C3, wherein the positive terminal of the output terminal of the three-phase full-wave rectifier bridge U2 is connected to the positive terminal of the output terminal of the three-phase thyristor full-controlled rectifier bridge U1 through a resistor R2 and a capacitor C2, and the negative terminal of the output terminal of the three-phase full-wave rectifier bridge U2 is connected to the negative terminal of the output terminal of the three-phase thyristor full-controlled rectifier bridge U1 through a resistor R3 and a capacitor C3.
3. The alternator field system as in claim 2, wherein the resistor R1, the resistor R2, and the resistor R3 are sequentially 2 kilo-ohms, 10 ohms, and the capacitor C1, the capacitor C2, and the capacitor C3 are sequentially 6 μ F, 0.94 μ F, and 0.94 μ F.
4. The alternator field system as in claim 1 further comprising a field suppression resistor R4, a diode D7, a diode D8, a diode D9, a diode D10, and a diac V1;
the negative electrode of the diode D7 is connected with the negative electrode of the diode D10, the positive electrode of the diode D10 is connected with the negative electrode of the diode D8, the positive electrode of the diode D8 is connected with the positive electrode of the diode D9, the negative electrode of the diode D9 is connected with the positive electrode of the diode D7, the common end of the diode D7 and the diode D10 is connected with the common end of the diode D8 and the diode D9 through a diac V1, the positive electrode of the direct current bus of the three-phase thyristor fully-controlled rectifier bridge U1 is connected with the common end of the diode D7 and the diode D9 through a field suppression resistor R4, and the common end of the diode D8 and the diode D10 is connected with the negative electrode of the direct current bus of the three.
5. An alternator field system as in claim 4 wherein said field suppression resistor R4 is a silicon carbide nonlinear resistor.
6. An alternator field system as in claim 4 wherein said diac V1 is an avalanche diode.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202021260006.XU CN212518847U (en) | 2020-06-30 | 2020-06-30 | Excitation system of alternating-current generator |
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| CN202021260006.XU CN212518847U (en) | 2020-06-30 | 2020-06-30 | Excitation system of alternating-current generator |
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| CN212518847U true CN212518847U (en) | 2021-02-09 |
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