CN207117500U - Two-way five level DCs translation circuit and the generator excited system comprising the circuit - Google Patents

Abstract

The utility model discloses a bidirectional five-level DC conversion circuit and a generator excitation system comprising the circuit. In the five-level chopper circuit of the present utility model, one end of the first, third, and fifth switch tubes is connected to one end of the excitation output, and the other end is respectively connected to the positive end of the DC power supply, connected in series with the seventh diode, and then connected to the middle point of the capacitor series circuit , DC power supply negative terminal; one end of the second, fourth, and sixth switching tubes is connected to the other end of the excitation output, and the other end is respectively connected to the positive terminal of the DC power supply, and the eighth diode is connected in series to the midpoint of the capacitor series circuit and the negative terminal of the DC power supply ; The first to sixth diodes are antiparallel connected to the first to sixth switch tubes respectively. The utility model can realize the bidirectional output of the excitation current while completing the output of the five-level DC chopper excitation voltage and the bidirectional flow of the excitation power, and realize the four-quadrant operation control of the five-level DC conversion circuit.

Description

Bidirectional five-level DC conversion circuit and generator excitation system including the circuit

technical field

The utility model belongs to the technical field of electrical engineering, in particular to a bidirectional five-level DC conversion circuit applied to a generator excitation system and a generator excitation system including the circuit.

Background technique

With the large-scale commissioning of UHV DC and flexible DC and the rapid development of new energy power generation with high penetration rate, power electronic power system is in the field of ultra-low frequency power oscillation, sub-synchronous oscillation, millisecond-level reactive power voltage support and other electromagnetic/electromechanical hybrid systems. Increased operational risk in the field. The excitation system is an important part of the synchronous generator, which has an important impact on the safe and stable operation of the power system. Making full use of the regulation ability of the excitation system is one of the most economical and effective means to improve the stability of the power system.

The conventional excitation system based on the rectification of the semi-controlled device thyristor (SCR) is limited by its slow control speed and can only control the device to be turned on but not to be turned off, so it has been difficult to adapt to the operation requirements of the power electronic grid. Fully controlled devices such as IGBTs can be turned on and off at the same time, so their control response speed and control flexibility have obvious advantages. At present, scholars at home and abroad have proposed to apply the rectifier circuit and chopper circuit composed of fully-controlled devices such as IGBT to the generator excitation system to realize a fully-controlled excitation system. While providing the DC excitation current of the synchronous generator, its AC side It can control the reactive current component, and can quickly control the injection or absorption of reactive power to the synchronous generator. The millisecond-level direct support capability of the reactive power on the AC side can significantly improve the reactive power and voltage control performance and response speed of the unit, and provide means for the suppression technology of broadband low-frequency power oscillation and subsynchronous oscillation.

At present, the topological structure of the fully controlled excitation system can be divided into voltage source type and current source type. Due to the cost, volume and weight of large inductors for energy storage, and the complexity of control, there are few studies on current source fully controlled excitation systems. In the voltage source type fully-controlled excitation circuit, in order to realize the requirements of the excitation system, such as zero-start up-current, energy exchange feedback, etc., the topology of the combination of three-phase fully-controlled rectification and DC-DC chopper circuit is the main one. Among them, the DC-DC chopper circuit is mainly based on the H bridge or H bridge parallel structure, which can output the front-end DC voltage E, 0 and DC voltage -E three-level voltage. DC voltage E. Since the switching tube in the loop is not an ideal device in practice, there are overlaps of current and voltage waveforms in the turn-on and cut-off processes during use, resulting in switching losses of power devices, which increase with the increase in the corresponding voltage change at both ends during operation. , will reduce the overall system efficiency; at the same time, a higher voltage change rate will also bring more serious electromagnetic interference problems; on the DC output side, a large output voltage level change will also affect the quality of the output voltage, making the voltage ripple Increased, the higher the common mode voltage, the greater the damage to the motor shaft current and insulation.

Utility model content

The technical problem to be solved by the utility model is to overcome the above-mentioned defects in the prior art and provide a bidirectional five-level DC conversion circuit applied to the excitation system of a generator to realize five-level DC chopper excitation voltage output and bidirectional excitation power flow, so as to reduce the loss of the switching tube, improve the efficiency of the fully-controlled excitation system, and realize the bidirectional output of the excitation current, so as to realize the four-quadrant operation control of the five-level DC conversion circuit.

In order to achieve the above object, the technical solution adopted by the utility model is as follows: a bidirectional five-level DC conversion circuit, which includes a DC power supply circuit, a first capacitor C1, a second capacitor C2 and a five-level DC chopper circuit;

The five-level DC chopper circuit includes a first switching tube V1, a second switching tube V2, a third switching tube V3, a fourth switching tube V4, a fifth switching tube V5, a sixth switching tube V6, a first diode Tube VD1, second diode VD2, third diode VD3, fourth diode VD4, fifth diode VD5, sixth diode VD6, seventh diode VD7 and eighth diode VD8;

The first capacitor C1 and the second capacitor C2 are connected in parallel to the two ends of the DC power supply circuit after being connected in series, the two ends of the DC power supply circuit are positive voltage terminal P and negative voltage terminal N respectively, and the connection point between the two capacitors is Intermediate voltage terminal M;

One end of the first switching tube V1 is connected to the positive voltage terminal P, and the other end is connected to the first end of the excitation output; one end of the second switching tube V2 is connected to the positive voltage terminal P, and the other end is connected to the second end of the excitation output; One end of the third switching tube V3 is connected to the negative voltage terminal N, and the other end is connected to the first end of the excitation output; one end of the fourth switching tube V4 is connected to the negative voltage terminal N, and the other end is connected to the second end of the excitation output; the fifth The switch tube V5 is connected in series with the seventh diode VD7, one end of the series branch is connected to the intermediate voltage terminal M, and the other end is connected to the first end of the excitation output; the sixth switch tube V6 is connected in series with the eighth diode VD8, the One end of the series branch is connected to the intermediate voltage terminal M, and the other end is connected to the second end of the excitation output;

The first diode VD1, the second diode VD2, the third diode VD3, the fourth diode VD4, the fifth diode VD5, and the sixth diode VD6 are respectively connected in antiparallel to the first Both ends of the switching tube V1 , the second switching tube V2 , the third switching tube V3 , the fourth switching tube V4 , the fifth switching tube V5 , and the sixth switching tube V6 .

As a supplement to the above technical solution, the first switching tube V1, the second switching tube V2, the third switching tube V3, the fourth switching tube V4, the fifth switching tube V5 and the sixth switching tube V6 all use IGBT full control devices .

As a supplement to the above technical solution, the collector of the first switching tube V1 is connected to the positive voltage terminal P, and the emitter is connected to the first end of the excitation output;

The collector of the second switching tube V2 is connected to the positive voltage terminal P, and the emitter is connected to the second excitation output terminal;

The emitter of the third switching tube V3 is connected to the negative voltage terminal N, and the collector is connected to the first end of the excitation output;

The emitter of the fourth switching tube V4 is connected to the negative voltage terminal N, and the collector is connected to the second excitation output terminal;

The emitter of the fifth switching tube V5 is connected to the anode of the seventh diode VD7, the cathode of the seventh diode VD7 is connected to the intermediate voltage terminal M, and the collector of the fifth switching tube V5 is connected to the first end of the excitation output;

The emitter of the sixth switching tube V6 is connected to the anode of the eighth diode VD8, the cathode of the eighth diode VD8 is connected to the intermediate voltage terminal M, and the collector of the sixth switching tube V6 is connected to the second excitation output terminal.

Another object of the present utility model is to provide a generator excitation system including the above-mentioned bidirectional five-level DC conversion circuit, the first switching tube V1, the second switching tube V2, the third switching tube V3, and the fourth switching tube V4 , The control terminals of the fifth switching tube V5 and the sixth switching tube V6 are controlled by the excitation regulator of the generator excitation system.

As a supplement to the above generator excitation system,

1) When the excitation current flows from the first end of the excitation output to the second end of the excitation output:

When the first switching tube V1 and the fourth switching tube V4 are turned on, the circuit output voltage +E;

When the first switching tube V1 and the sixth switching tube V6 are turned on, the circuit output voltage +E/2;

When the first switch tube V1 is turned on, the current continues to flow through the second diode VD2, and the circuit output voltage is 0;

When the fourth switch tube V4 is turned on, the current continues to flow through the third diode VD3, and the circuit also outputs a voltage of 0;

When the sixth switch tube V6 is turned on, the current continues to flow through the third diode VD3 and the eighth diode VD8, and the circuit output voltage is -E/2;

When the current continues to flow through the third diode VD3 and the second diode VD2, the circuit output voltage -E;

2) When the excitation current flows from the second end of the excitation output to the first end of the excitation output:

When the second switching tube V2 and the third switching tube V3 are turned on, the circuit outputs a voltage -E;

When the second switch tube V2 and the fifth switch tube V5 are turned on, the circuit output voltage is -E/2;

When the second switch tube V2 is turned on, the current continues to flow through the first diode VD1, and the circuit output voltage is 0;

When the third switch tube V3 is turned on, the current continues to flow through the fourth diode VD4, and the circuit also outputs a voltage of 0;

When the fifth switch tube V5 is turned on, the current continues to flow through the fourth diode VD4 and the seventh diode VD7, and the circuit output voltage is +E/2;

When the current continues to flow through the first diode VD1 and the fourth diode VD4, the circuit outputs a voltage +E.

The utility model has the following beneficial effects: the bidirectional five-level DC conversion circuit described in the utility model can output E, E/2, 0, -E/2, -E five-level DC according to different conduction control signals The excitation voltage, compared with the typical H-bridge three-level chopping, increases the two-way level output of E/2 and -E/2, and the turn-on and turn-off voltage during operation can be reduced by E/2, thereby reducing the switching power of the switching tube. Loss, improve system efficiency, reduce electromagnetic interference and DC output voltage ripple; at the same time, when a smaller DC excitation voltage output is required, E/2, 0 will increase the turn-on duty cycle compared with E, 0 at the same switching frequency double, which is more conducive to achieving more precise control of the DC output voltage. In addition, while satisfying the bidirectional flow of the excitation power, it can also realize the bidirectional output of the excitation current, and has the capability of four-quadrant operation, which further expands the control flexibility of the five-level DC conversion circuit.

Description of drawings

Fig. 1 is the bidirectional five-level DC conversion circuit diagram of the utility model;

Fig. 2 is a schematic diagram of the chopping waveform of the output voltage of the bidirectional five-level DC conversion circuit of the present invention;

Fig. 3 is a schematic diagram of the utility model applied to a self-parallel excitation system.

Detailed ways

The utility model will be described in detail below in conjunction with the accompanying drawings and specific embodiments of the specification.

As shown in Figure 1, the utility model provides a bidirectional five-level DC conversion circuit applied to the generator excitation system, which consists of a DC power supply circuit, a first capacitor C1, a second capacitor C2 and a five-level DC chopper circuit composition; the five-level DC chopper circuit consists of a first switching tube V1, a second switching tube V2, a third switching tube V3, a fourth switching tube V4, a fifth switching tube V5, a sixth switching tube V6, a A diode VD1, a second diode VD2, a third diode VD3, a fourth diode VD4, a fifth diode VD5, a sixth diode VD6, a seventh diode VD7 and an eighth diode Composed of diode VD8.

The first capacitor C1 and the second capacitor C2 are connected in series and parallel to both ends of the DC power supply circuit. The two ends of the DC power supply circuit are positive voltage terminal P and negative voltage terminal N respectively, and the connection point between the two capacitors is the middle Voltage terminal M.

One end of the first switching tube V1 is connected to the positive voltage terminal P, and the other end is connected to the first end of the excitation output. One end of the second switching tube V2 is connected to the positive voltage terminal P, and the other end is connected to the second end of the excitation output. One end of the third switching tube V3 is connected to the negative voltage terminal N, and the other end is connected to the first end of the excitation output. One end of the fourth switching tube V4 is connected to the negative voltage terminal N, and the other end is connected to the second end of the excitation output. The fifth switch tube V5 is connected in series with the seventh diode VD7, one end of the series branch is connected to the intermediate voltage terminal M, and the other end is connected to the first excitation output terminal. The sixth switch tube V6 is connected in series with the eighth diode VD8, one end of the series branch is connected to the intermediate voltage terminal M, and the other end is connected to the second excitation output terminal.

The first diode VD1, the second diode VD2, the third diode VD3, the fourth diode VD4, the fifth diode VD5 and the sixth diode VD6 are respectively antiparallel connected to the first Both ends of the switching tube V1 , the second switching tube V2 , the third switching tube V3 , the fourth switching tube V4 , the fifth switching tube V5 , and the sixth switching tube V6 .

The first switching tube V1 , the second switching tube V2 , the third switching tube V3 , the fourth switching tube V4 , the fifth switching tube V5 and the sixth switching tube V6 all use full-control devices such as IGBTs.

The collector of the first switching tube V1 is connected to the positive voltage terminal P, and the emitter is connected to the first terminal of the excitation output. The collector of the second switching tube V2 is connected to the positive voltage terminal P, and the emitter is connected to the second excitation output terminal. The emitter of the third switching tube V3 is connected to the negative voltage terminal N, and the collector is connected to the first terminal of the excitation output. The emitter of the fourth switching tube V4 is connected to the negative voltage terminal N, and the collector is connected to the second terminal of the excitation output. The emitter of the fifth switching tube V5 is connected to the anode of the seventh diode VD7, the cathode of the seventh diode VD7 is connected to the intermediate voltage terminal M, and the collector of the fifth switching tube V5 is connected to the first excitation output terminal. The emitter of the sixth switching tube V6 is connected to the anode of the eighth diode VD8, the cathode of the eighth diode VD8 is connected to the intermediate voltage terminal M, and the collector of the sixth switching tube V6 is connected to the second excitation output terminal.

The control terminals of the first switching tube V1, the second switching tube V2, the third switching tube V3, the fourth switching tube V4, the fifth switching tube V5 and the sixth switching tube V6 are controlled by the excitation regulator of the generator excitation system.

As shown in Figure 1, the DC excitation current flows in the direction shown in the figure: when the first switch tube V1 and the fourth switch tube V4 are turned on, the circuit output voltage +E; when the first switch tube V1 and the sixth switch tube V6 When it is turned on, the circuit output voltage +E/2; when the first switch tube V1 is turned on, the current continues to flow through the second diode VD2, and the circuit output voltage is 0; when the fourth switch tube V4 is turned on, the current flows through the third and second diodes The pole tube VD3 continues to flow, and the circuit also outputs 0 voltage; when the sixth switch tube V6 is turned on, the current continues to flow through the third diode VD3 and the eighth diode VD8, and the circuit output voltage is -E/2; when the current passes through The second diode VD2 and the third diode VD3 freewheel, and the circuit outputs a voltage of -E.

In order to balance the wear of carbon brushes and slip rings, after a certain period of operation of the generator set, it is necessary to reverse the polarity of the current injected into the excitation winding, and the conventional excitation is realized through the polarity reversal device. The chopper circuit provided by the embodiment of the utility model adopts a symmetrical structure, and the polarity reversal operation can be realized by changing the control signal of the switch tube. The current can be injected into the excitation winding from the opposite direction of the excitation current shown in Figure 1 to achieve reverse polarity operation: when the second switch V2 and the third switch V3 are turned on, the circuit output voltage -E; when the second switch V2 and the third switch When the fifth switch tube V5 is turned on, the circuit output voltage is -E/2; when the second switch tube V2 is turned on, the current continues to flow through the first diode VD1, and the circuit output voltage is 0; when the third switch tube V3 is turned on, the current The circuit also outputs 0 voltage through the fourth diode VD4; when the fifth switch tube V5 is turned on, the current continues through the fourth diode VD4 and the seventh diode VD7, and the circuit output voltage is +E/2 ; When the current continues to flow through the first diode VD1 and the fourth diode VD4, the circuit output voltage +E.

Using the above chopper output combination, the excitation system control can be designed as follows: use +E/2 and 0 level combination to achieve normal excitation, and adjust between output 0 and rated excitation voltage; use +E/2 and +E level combination The method realizes short-time strong excitation, and adjusts between the output rating and the maximum excitation voltage; adopts the combination of 0 and -E/2 levels for inverter control, and realizes slow de-excitation; adopts the combination of -E/2 and -E levels Carry out inverter control to realize rapid demagnetization and demagnetization. In addition, the reverse pole operation can be designed as follows: use the combination of -E/2 and 0 levels to realize reverse excitation, and adjust the output between 0 and rated excitation voltage; use the combination of -E/2 and -E levels to realize short-term Reverse strong excitation, adjustable from output rating to maximum excitation voltage; use 0 and +E/2 level combination mode for inverter control to realize slow de-excitation of reverse excitation; use +E/2 and +E level Inverter control is carried out in a combined way to realize rapid demagnetization and demagnetization of reverse excitation. The waveform diagram is shown in Figure 2 in turn.

Combined with the self-shunt excitation system, the application of the five-level DC conversion circuit to the generator excitation system is described in detail, as shown in Figure 3: the DC power supply circuit adopts a three-level full-control rectification circuit as an example, and the AC side of the rectification circuit Connect the low-voltage side of the excitation transformer, the high-voltage side of the AC side of the excitation transformer is connected to the generator end, the DC side of the rectifier circuit is connected to the five-level DC conversion circuit, and the excitation voltage output end of the five-level DC conversion circuit is connected to the excitation winding of the generator. When the unit is in normal operation, the excitation system obtains energy from the machine end through the excitation transformer, completes the AC-DC rectification through the three-level full-control rectification circuit to provide DC power, and then outputs stable DC excitation through the DC-DC chopping of the five-level DC conversion circuit voltage, and then provide the excitation current required for the normal operation of the unit; when the excitation of the unit is reversed, the energy flows in the opposite direction, and the energy of the excitation winding passes through the five-level DC conversion circuit, the three-level full-control rectification circuit and the excitation transformer, and is reversed to the machine end. Send, and then realize the rapid shutdown and de-excitation.

The above embodiments are only to illustrate the technical ideas of the utility model, and cannot limit the protection scope of the utility model with this. Any changes made on the basis of the technical solutions according to the technical ideas proposed by the utility model all fall into the scope of the utility model. within the scope of the new protection.

Claims (5)

1. two-way five level DCs translation circuit, it is characterised in that it include dc source provide circuit, the first capacitor C1, Second capacitor C2 and five level DC chopper circuits；

The five level DCs chopper circuit includes first switch pipe V1, second switch pipe V2, the 3rd switching tube V3, the 4th switch Pipe V4, the 5th switching tube V5, the 6th switching tube V6, the first diode VD1, the second diode VD2, the 3rd diode VD3, the 4th Diode VD4, the 5th diode VD5, the 6th diode VD6, the 7th diode VD7 and the 8th diode VD8；

The both ends that dc source provides circuit, dc source are parallel to after the first capacitor C1 and the second capacitor C2 series connection The both ends for providing circuit are respectively positive voltage terminal P and negative voltage side N, and the tie point between two capacitors is medium voltage end M；

One end connection positive voltage terminal P of the first switch pipe V1, other end connection excitation output first end；The second switch Pipe V2 one end connection positive voltage terminal P, other end connection excitation export the second end；One end connection of the 3rd switching tube V3 is negative Voltage end N, other end connection excitation output first end；One end connection negative voltage side N of the 4th switching tube V4, the other end connect Connect excitation and export the second end；The 5th switching tube V5 connects with the 7th diode VD7, among one end connection of the series arm Voltage end M, other end connection excitation output first end；The 6th switching tube V6 connects with the 8th diode VD8, the series connection branch One end connection medium voltage end M on road, other end connection excitation export the second end；

The first diode VD1, the second diode VD2, the 3rd diode VD3, the 4th diode VD4, the 5th diode VD5, the 6th diode VD6 are connected anti-parallel to first switch pipe V1, second switch pipe V2, the 3rd switching tube V3, the 4th opened respectively Close pipe V4, the 5th switching tube V5, the 6th switching tube V6 both ends.

2. two-way five level DCs translation circuit as claimed in claim 1, it is characterised in that described first switch pipe V1, Second switch pipe V2, the 3rd switching tube V3, the 4th switching tube V4, the 5th switching tube V5 and the 6th switching tube V6 are complete using IGBT Control device.

3. two-way five level DCs translation circuit as claimed in claim 1 or 2, it is characterised in that

The colelctor electrode connection positive voltage terminal P of the first switch pipe V1, emitter stage connection excitation output first end；

The colelctor electrode connection positive voltage terminal P of the second switch pipe V2, emitter stage connection excitation export the second end；

The emitter stage connection negative voltage side N of the 3rd switching tube V3, colelctor electrode connection excitation output first end；

The emitter stage connection negative voltage side N of the 4th switching tube V4, colelctor electrode connection excitation export the second end；

The emitter stage of the 5th switching tube V5 is connected with the 7th diode VD7 anode, the 7th diode VD7 negative electrode connection Medium voltage end M, the 5th switching tube V5 colelctor electrode connection excitation output first end；

The emitter stage of the 6th switching tube V6 is connected with the 8th diode VD8 anode, the 8th diode VD8 negative electrode connection Medium voltage end M, the 6th switching tube V6 colelctor electrode connection excitation export the second end.

4. include the generator excited system of any one of the claim 1-3 two-way five level DCs translation circuit, its feature Be, described first switch pipe V1, second switch pipe V2, the 3rd switching tube V3, the 4th switching tube V4, the 5th switching tube V5 and 6th switching tube V6 control terminal is controlled by generator excited system field regulator.

5. generator excited system as claimed in claim 4, it is characterised in that

1）When exciting current flows to excitation from excitation output first end exports the second end：

When first switch pipe V1 and the 4th switching tube V4 are opened, circuit output voltage+E；

When first switch pipe V1 and the 6th switching tube V6 are opened, circuit output voltage+E/2；

When first switch pipe V1 is opened, electric current passes through the second diode VD2 afterflows, circuit output voltage 0；

When the 4th switching tube V4 is opened, electric current passes through the 3rd diode VD3 afterflows, the same output voltage 0 of circuit；

When the 6th switching tube V6 is opened, electric current passes through the 3rd diode VD3 and the 8th diode VD8 afterflows, circuit output electricity Pressure-E/2；

When electric current passes through the 3rd diode VD3 and the second diode VD2 afterflows, circuit output voltage-E；

2）When exciting current exports the second end from excitation flows to excitation output first end：

When second switch pipe V2 and the 3rd switching tube V3 are opened, circuit output voltage-E；

When second switch pipe V2 and the 5th switching tube V5 are opened, circuit output voltage-E/2；

When second switch pipe V2 is opened, electric current passes through the first diode VD1 afterflows, circuit output voltage 0；

When the 3rd switching tube V3 is opened, electric current passes through the 4th diode VD4 afterflows, the same output voltage 0 of circuit；

When the 5th switching tube V5 is opened, electric current passes through the 4th diode VD4 and the 7th diode VD7 afterflows, circuit output electricity Pressure+E/2；

When electric current passes through the first diode VD1 and the 4th diode VD4 afterflows, circuit output voltage+E.