CN109660117B - Power electronic transformer starting control method - Google Patents
Power electronic transformer starting control method Download PDFInfo
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- CN109660117B CN109660117B CN201811598795.5A CN201811598795A CN109660117B CN 109660117 B CN109660117 B CN 109660117B CN 201811598795 A CN201811598795 A CN 201811598795A CN 109660117 B CN109660117 B CN 109660117B
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- 238000000034 method Methods 0.000 title claims abstract description 23
- 238000010304 firing Methods 0.000 abstract description 2
- 238000010586 diagram Methods 0.000 description 5
- 230000002457 bidirectional effect Effects 0.000 description 2
- 230000010363 phase shift Effects 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/36—Means for starting or stopping converters
Abstract
The invention discloses a power electronic transformer starting control method, which realizes the starting of a direct current side through a starting circuit connected in parallel with the direct current side of a power electronic transformer, wherein a topological structure of the starting circuit is formed by sequentially connecting a three-phase uncontrolled rectifier, a charging circuit mechanical switch K4, a three-phase voltage regulator and a starting resistor in series to a power supply of a power distribution cabinet, and a starting resistor bypass switch K5 is connected in parallel with the starting resistor; firstly, unlocking a DAB circuit in a power electronic transformer topology; a mechanical switch K4 of the charging circuit is switched on; starting a resistor bypass switch K5 to switch on; switching on the AC side switch; unlocking an H bridge in the power electronic transformer topology; the charging circuit mechanical switch K4 is turned off; turning off the firing resistor bypass switch K5; switching on a direct current mechanical switch at the direct current side; and closing the direct current solid-state switch on the direct current side. The invention realizes the smooth starting of the direct current side power electronic transformer through the auxiliary charging circuit by designing the overall sequential control flow of the power electronic transformer.
Description
Technical Field
The invention belongs to the technical field of power electronic control, and particularly relates to a starting control method of a 10kV alternating current/750V direct current power electronic transformer.
Background
The power electronic transformer can be started from an alternating current side and a direct current side, but for a 10kV alternating current/750V direct current power electronic transformer, starting a cascaded H bridge from the 10kV alternating current side is inconvenient, a 10kV resistor and a 10kV contactor need to be configured on the alternating current side, and equipment cost is increased. When a 750V dc distribution network is not established, an auxiliary charging circuit needs to be added for starting from a dc side, and improper control of a sequential control flow of the charging circuit may cause problems that a power electronic transformer cannot be started normally or a circuit is burnt by excessive inrush current, and the like.
Disclosure of Invention
In order to solve the above problems, the present invention provides a power electronic transformer start control method, which realizes smooth start of a dc-side power electronic transformer through an auxiliary charging circuit.
The invention adopts the following technical scheme that the starting control method of the power electronic transformer comprises a starting circuit which is connected in parallel with the direct current side of the power electronic transformer, wherein the starting circuit comprises the following components: the starting circuit topology structure is formed by sequentially connecting the three-phase uncontrolled rectifier, the charging circuit mechanical switch, the three-phase voltage regulator and the starting resistor to the power supply of the power distribution cabinet in series, and the starting resistor bypass switch is connected with the starting resistor in parallel;
the power electronic transformer starting control method comprises the following steps:
s1: unlocking a DAB circuit in the power electronic transformer topology;
s2: switching on a mechanical switch of the charging circuit;
s3: starting a resistor bypass switch to switch on;
s4: switching on the AC side switch;
s5: unlocking an H bridge in the power electronic transformer topology;
s6, disconnecting the mechanical switch of the charging circuit;
s7: turning off the starting resistor bypass switch;
s8: switching on a direct current mechanical switch at the direct current side;
s9: and closing the direct current solid-state switch on the direct current side.
Preferably, the DAB circuit unlocking signal in step S1 is a 50% duty cycle PWM modulated wave.
Preferably, in the step S3, after the voltage at the mechanical switch of the circuit to be charged reaches the set value, the resistance bypass switch is turned on.
Preferably, the H-bridge unlocking signal in step S5 is a sine-modulated wave that is subjected to carrier phase shift processing.
Preferably, the withstand voltage value U of the mechanical switch of the charging circuit is selected by the method that the withstand voltage value U satisfies that the output voltage of the three-phase uncontrolled rectifier bridge is less than the voltage of the direct-current port.
Preferably, the starting resistance R has a value in the range of 5 Ω to 50 Ω.
Preferably, the set value is selected in relation to the withstand voltage value U of the mechanical switch of the charging circuit, and the specific set value is U minus a set threshold, and the threshold is 20V.
The invention has the following beneficial effects: the invention relates to a starting control method of a power electronic transformer, which realizes smooth starting of a direct-current side power electronic transformer through an auxiliary charging circuit. The invention divides the DC side bus voltage equally (two sets of auxiliary charging circuits, and +750V and-750V are respectively and independently decoupled for operation), enlarges the power supply voltage grade, forms bipolar DC power supply, can realize energy bidirectional flow, and ensures the balance of bipolar DC voltage and effective and reliable operation; the power electronic transformer starting sequence control process provided by the invention provides reliable guarantee for the safe and stable starting of the power electronic transformer;
drawings
Fig. 1 is a flowchart of a power electronic transformer start-up control method according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a power electronic transformer and a starting circuit topology thereof according to an embodiment of the present invention;
FIG. 3 is a DAB circuit topology diagram;
FIG. 4 is an H-bridge circuit topology;
fig. 5 is a dc solid state switching circuit topology.
Detailed Description
The technical solution of the present invention is further explained with reference to the embodiments according to the drawings.
FIG. 1 is a flowchart of a method for controlling the start-up of a 10kV AC/750V DC power electronic transformer according to an embodiment of the present invention; fig. 2 is a schematic diagram of a topology structure of a 10kV ac/750V dc power electronic transformer and a starting circuit thereof according to an embodiment of the present invention. The power electronic transformer in fig. 2 is a common topology and will not be described herein.
A power electronic transformer start-up control method, comprising a start-up circuit (i.e. a valve tower charging circuit in the figure) connected in parallel to a 750V dc side of a power electronic transformer, the start-up circuit comprising: the starting circuit topology structure comprises a three-phase uncontrolled rectifier, a charging circuit mechanical switch K4 (or a charging circuit mechanical switch K4 ', two auxiliary charging circuits in the figure, 750V and 750V are independently decoupled and operated respectively), a three-phase voltage regulator, a starting resistor bypass switch K5 and a power distribution cabinet power supply, wherein the three-phase uncontrolled rectifier, the charging circuit mechanical switch K4 (or the charging circuit mechanical switch K4'), the three-phase voltage regulator and the starting resistor are sequentially connected in series to the power distribution cabinet power supply, and the starting resistor bypass switch K5 and the starting resistor are connected in parallel;
in this embodiment, the +750V valve tower start-up is only used as an example for illustration.
The voltage withstanding value U of the charging circuit mechanical switch K4 is selected by satisfying the output voltage of the three-phase uncontrolled rectifier bridge (namely, the voltage withstanding value U is selected by the following method
) Slightly less than the dc port voltage, the withstand voltage U in this embodiment is set to 500V, and is boosted to 707V at most, and is less than 750V of the dc port voltage, the general switch withstand voltage is 380V, and the withstand voltage of the charging circuit mechanical switch K4 in this embodiment is 500V.
The starting resistor R ranges from 5 omega to 50 omega.
In this embodiment, the starting resistor R is 10 Ω, the voltage withstanding value of the charging circuit mechanical switch K4 is 500V, the three-phase voltage regulator is 500V/380V, the voltage withstanding value of the starting resistor bypass switch K5 is 380V, and the power supply of the power distribution cabinet is a three-phase 380V power supply.
The power electronic transformer starting control method comprises the following steps:
s1: unlocking a bidirectional full-bridge direct-current converter (DAB) in the power electronic transformer topology; the DAB topology structure diagram is shown in fig. 3, two sides of the high-frequency transformer of the core equipment in DAB are respectively provided with an H-bridge, which respectively invert the direct current into high-frequency voltage and rectify the high-frequency voltage into low-voltage side direct current.
As a preferred embodiment, the DAB unlocking signal in step S1 is a 50% duty cycle PWM modulated wave, the V1, V4, V5 and V8 unlocking signals in DAB in fig. 2 are a same set of 50% duty cycle pulses, and the V2, V3, V6 and V7 unlocking signals are opposite to the V1, V4, V5 and V8 unlocking signal pulses.
S2: the charging circuit mechanical switch K4 is switched on (if the valve tower is started at-750V, the charging circuit mechanical switch K4 'is switched on, and similarly, the charging circuit mechanical switch K4 in the following steps is replaced by the charging circuit mechanical switch K4');
s3: starting a resistor bypass switch K5 to switch on;
in a preferred embodiment, in the step S3, after the voltage at the mechanical switch K4 of the circuit to be charged reaches the set value, the resistor bypass switch K5 is turned on.
The set value is selected in relation to the withstand voltage U of the charging circuit mechanical switch K4, and in this embodiment, the specific set value is U minus the set threshold, and the threshold is 20V, which is acceptable for the inrush current device itself due to the voltage difference within 20V.
S4: a switch on-off K1 of a 10kV alternating-current side switch;
s5: unlocking an H bridge in the power electronic transformer topology; the topological structure diagram of the H-bridge is shown in fig. 4, and the H-bridge is the simplest structure in the power sub-module of the power electronic transformer and is used for converting high-voltage alternating current into direct current through the cascaded H-bridge.
As a preferred embodiment, the H-bridge unlocking signal in step S5 is a sine-modulated wave that is subjected to carrier phase shift processing.
S6, disconnecting the charging circuit mechanical switch K4;
s7: turning off the firing resistor bypass switch K5;
s8: a direct current mechanical switch K3 on the direct current side of 750V is switched on;
s9: and a direct current solid-state switch K2 on the direct current side of 750V is closed. A dc solid state switch topology is shown in fig. 5. The solid-state switch adopts an IGBT as a power electronic switch, has a fault rapid isolation function, and can cut off a direct current port within 50 us.
It should be noted that the topologies shown in fig. 3, fig. 4 and fig. 5 are all prior art in the art, and are not described herein again.
The control principle is as follows: firstly, on the direct current side, the voltage on the direct current side is increased to a set value without impact by using a starting resistor and a 10kV side alternating current switch, and then the complete machine is started by using 10kV side H bridge unlocking.
The above description is only a preferred embodiment of the present invention, which is used to illustrate the technical solution of the present invention, but not to limit the same; it should be noted that: modifications to the technical solutions described in the foregoing embodiments, or equivalents of some of the technical features thereof, are possible without departing from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (7)
1. A power electronic transformer starting control method is characterized by comprising a starting circuit connected in parallel to a direct current side of a power electronic transformer, wherein the starting circuit comprises: the starting circuit topology structure is formed by sequentially connecting the three-phase uncontrolled rectifier, the charging circuit mechanical switch, the three-phase voltage regulator and the starting resistor to the power supply of the power distribution cabinet in series, and the starting resistor bypass switch is connected with the starting resistor in parallel;
the power electronic transformer starting control method comprises the following steps:
s1: unlocking a DAB circuit in the power electronic transformer topology;
s2: switching on a mechanical switch of the charging circuit;
s3: starting a resistor bypass switch to switch on;
s4: switching on the AC side switch;
s5: unlocking an H bridge in the power electronic transformer topology;
s6, disconnecting the mechanical switch of the charging circuit;
s7: turning off the starting resistor bypass switch;
s8: switching on a direct current mechanical switch at the direct current side;
s9: and closing the direct current solid-state switch on the direct current side.
2. A power electronic transformer start-up control method as claimed in claim 1, wherein the DAB circuit unlock signal in step S1 is a 50% duty cycle PWM modulated wave.
3. The power electronic transformer starting control method according to claim 1, wherein in step S3, after the voltage at the mechanical switch of the circuit to be charged reaches a set value, the starting resistance bypass switch is closed.
4. The power electronic transformer starting control method according to claim 1, wherein the H-bridge unlocking signal in step S5 is a sine-modulated wave after being phase-shifted by a carrier.
5. A power electronic transformer start-up control method according to claim 1, characterized in that the withstand voltage U of the charging circuit mechanical switch is selected in such a way that the withstand voltage U satisfies that the output voltage of the three-phase uncontrolled rectifier bridge is less than the dc port voltage.
6. A power electronic transformer start-up control method according to claim 1, characterized in that the value range of the start-up resistance is 5 Ω to 50 Ω.
7. A power electronic transformer starting control method according to claim 3, characterized in that the set value is selected in relation to the voltage withstand value of the mechanical switch of the charging circuit, the specific set value is the voltage withstand value of the mechanical switch of the charging circuit minus a set threshold value, and the threshold value is 20V.
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| CN201811598795.5A CN109660117B (en) | 2018-12-26 | 2018-12-26 | Power electronic transformer starting control method |
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| CN110829819A (en) * | 2019-11-26 | 2020-02-21 | 国网江苏省电力有限公司南通供电分公司 | Power electronic transformer starting control method |
| CN113556032B (en) * | 2020-04-24 | 2022-08-26 | 国网江苏省电力有限公司电力科学研究院 | Starting method of power unit of power electronic transformer |
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