CN105652117B - DC/DC converter-based full-power-cycle test circuit for DC power grid - Google Patents
DC/DC converter-based full-power-cycle test circuit for DC power grid Download PDFInfo
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- CN105652117B CN105652117B CN201511009842.4A CN201511009842A CN105652117B CN 105652117 B CN105652117 B CN 105652117B CN 201511009842 A CN201511009842 A CN 201511009842A CN 105652117 B CN105652117 B CN 105652117B
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention provides a DC/DC converter-based full-power cycle test circuit of a DC power grid, which comprises: the DC/DC converter comprises a DC voltage source, an AC power source and a DC/DC converter; two sides of the DC/DC converter are respectively provided with a direct current voltage source; the other side of the direct voltage source connected to the DC/DC converter is connected to an alternating current power source. The invention realizes the bidirectional power transmission and the reversal of the voltage polarity of the bus, thereby examining the electrical characteristics of the test sample in the aspects of full voltage, full current, four quadrants and the like.
Description
Technical Field
The invention relates to a power electronic system, in particular to a DC power grid full-power circulation test circuit based on a DC/DC converter.
Background
The construction of a high-voltage direct-current transmission system and a network thereof becomes an important development direction in the power field in the world, countries such as india and brazil plan the construction of an extra-high-voltage direct-current transmission project, russian plans realize western power transmission through a direct-current transmission technology, and european Super Grid (Super Grid) plans and us 2030 Grid plans (Grid 2030), and the construction plans of a direct-current power Grid are proposed.
At present, China is the country where direct current transmission projects are established and operated most in the world, and flexible direct current transmission projects are also under accelerated construction. Since the first flexible direct-current transmission project was put into operation in 2011, China successively completes the interconnection multi-terminal flexible direct-current transmission project of Zhoushan island and the grid-connected multi-terminal flexible direct-current transmission project of the wind farm in south Australia, and the building door flexible direct-current project in the implementation stage provides convenience for building a multi-terminal direct-current power grid and a direct-current power grid in the future.
The high-voltage DC/DC converter is used as key equipment in a direct current network, is used for realizing power interaction among networks, construction of a hierarchical direct current power grid, direct current collection, sending out, isolation and network fault suppression of a wind power plant, effectively solves the problems of large capacitive current, low operation reliability and the like of the conventional alternating current grid-connected system, can provide emergency power support, reduces the construction cost of an additional standby power supply, reduces the power generation cost of renewable energy sources, improves the operation reliability of the direct current network, promotes the development and application of the renewable energy sources such as offshore wind power and the like, and makes contribution to the creation of a low-carbon, environment-friendly and green sustainable development society.
The function and reliability of the DC/DC converter as a connecting device of direct current lines or networks with different voltage levels directly relate to the efficiency and safety of a direct current power grid. Because a direct current line or a network relates to high-capacity electric energy conversion, a DC/DC converter with higher voltage and current levels is needed, the working mechanism is complex, the development difficulty is high, only a few mechanisms develop the development work of a small-capacity experimental prototype at present, the difference from the actual engineering application requirement is large, and the related research work of a test method is still in a blank state.
Disclosure of Invention
In order to overcome the above defects in the prior art, the present invention provides a test circuit for full power cycle of DC power grid based on DC/DC converter, which includes: the DC/DC converter comprises a DC voltage source, an AC power source and a DC/DC converter; two sides of the DC/DC converter are respectively provided with a direct current voltage source; the other side of the direct voltage source connected to the DC/DC converter is connected to an alternating current power source.
Four contacts are respectively arranged on two sides of the DC/DC converter. The AC power supply includes: the circuit breaker branch circuit is formed by connecting an alternating-current voltage source and two circuit breakers in series; one end of the alternating voltage source is connected with the middle point of the circuit breaker branch circuit, and the other end of the alternating voltage source is grounded.
The direct current voltage source includes: the device comprises a transformer, a three-phase rectifier bridge, a smoothing reactor, two capacitors and two isolating switches; the three-phase rectifier, the smoothing reactor and the two capacitors are sequentially connected to form a series circuit; the middle point of the capacitor series branch is grounded, and two ends of the capacitor series branch are respectively connected with the two isolating switches; the secondary side of the transformer is connected with the three-phase rectifier bridge, and the primary side of the transformer is connected with the branch circuit of the circuit breaker.
In a normal working mode, when one three-phase rectifier operates in a rectifying mode, the other three-phase rectifier operates in an inverting mode, and the isolating switch selects the contacts at the two ends of the DC/DC converter, power is transmitted from the direct-current voltage source at one side of the DC/DC converter to the direct-current voltage source at the opposite side of the DC/DC converter, the polarity of the direct-current bus of the capacitor series branch at one end of the smoothing reactor is positive, and the polarity of the direct-current bus of the capacitor series branch at one end of the three-phase rectifier is negative.
When the running states of the two three-phase rectifiers are interchanged and the position of the isolating switch is kept unchanged, the power transmission direction is reversed, and the polarity of the direct current bus of the capacitor series branch circuit is reversed simultaneously. When the running states of the two three-phase rectifiers are unchanged and the isolating switch selects the middle contact of the DC/DC converter, the transmission direction of the power is reversed again, and the polarity of the direct current bus is kept unchanged.
Compared with the closest prior art, the technical scheme provided by the invention has the following beneficial effects:
1. the invention adopts two capacitors C connected in series, selectively grounds the midpoint of the capacitors to form positive and negative voltages, and uses a DC/DC converter to satisfy a direct current power grid with positive and negative symmetry;
2. the test circuit can realize power bidirectional transmission, also realizes the reversal of the voltage polarity of the bus, and can evaluate the electrical characteristics of the test sample in full voltage, full current and four quadrants.
3. The current converters on the two sides of the test circuit are respectively in a rectification state and an inversion operation state, energy output by the power supply is injected from the rectification side and is fed back to the power supply from the inversion side, so that full power circulation of the circuit is realized, the alternating current power supply only needs to supplement energy lost in the test circuit, the power consumption of the test is greatly reduced, the operation cost is saved, and the economic and environment-friendly performance is high.
Drawings
Fig. 1 is a circuit diagram of a full power test of a direct current power grid of the invention.
Detailed Description
The test circuit of the present invention is described in further detail below with reference to fig. 1.
The method is mainly performed by aiming at a full-power cycle test method of the DC/DC converter for the direct-current power grid. Fig. 1 shows a schematic diagram of the test circuit, which mainly comprises an ac power supply, a dc voltage source 1, a dc voltage source 2 and a test sample. The alternating current power supply part comprises a ground E, an alternating current voltage source AC, circuit breakers QF1 and QF2, and is a basic power supply of the whole test circuit and provides an energy source for the test circuit. The direct-current voltage source 1 comprises a transformer TM1, a three-phase rectifier bridge U1, a smoothing reactor L1, two series capacitors C1, isolating switches QS1 and QS2, the primary side of a transformer TM1 is connected with an alternating-current power supply through a circuit breaker, the secondary side of the transformer TM1 is connected with the rectifier bridge U1, the rectifier bridge U1 rectifies alternating current transmitted by the alternating-current power supply and outputs the alternating current into direct current, the capacitor C1 is charged through the smoothing reactor L1 to form direct-current voltage with small fluctuation amplitude, the middle points of the two capacitors are grounded, and the direct-current voltage is symmetric in positive and negative. The dc voltage source 2 is structurally and functionally identical to the dc voltage source 1, except for the voltage levels. The test part is a tested DC/DC converter which is respectively connected with the DC output ends of the DC voltage source 1 and the DC voltage source 2 through isolating switches.
The dc bus voltage polarity and power transmission direction are determined by the inverter operating mode in combination with the selected contact positions of the disconnectors QS1, QS2, QS3 and QS 4. Under a normal working mode, a three-phase rectifier bridge U1 performs rectification operation, a three-phase rectifier bridge U2 performs inversion operation, isolating switches QS1, QS2, QS3 and QS4 respectively select contacts 1, 3, 5 and 7, power is transmitted from the +/-Ud 1 side of a DC/DC converter to the +/-Ud 2 side, and the polarity of a direct-current bus is positive, negative and positive; if the three-phase rectifier bridge U1 operates in an inversion mode and the three-phase rectifier bridge U2 operates in a rectification mode, the power and the polarity of the direct-current bus are simultaneously reversed; if the three-phase rectifier bridge U1 runs in an inverted mode, the three-phase rectifier bridge U2 runs in a rectified mode, and meanwhile the four isolating switches are switched to the contact positions of 2, 4, 6 and 8 respectively, power is reversed, and the polarity of the direct-current bus is kept unchanged.
When a test is started, firstly disconnecting switches QS1, QS2, QS3 and QS4 are switched on and are respectively arranged at the positions of contacts 1, 3, 5 and 7, then circuit breakers QF1 and QF2 are switched on to unlock and start a converter U1, a bridge arm of a DC/DC converter close to the side of a three-phase rectifier bridge U1 is unlocked and precharged, a test DC/DC converter is started after a capacitor C1 is charged to a certain voltage level, a three-phase rectifier bridge U2 is unlocked and operates in an inversion mode after the capacitor C2 is stably charged, the trigger angle of the three-phase rectifier bridge U2 is adjusted to enable the loop current level to reach a test requirement value, then the trigger angles of the three-phase rectifier bridge U1 and the three-phase rectifier bridge U2 are adjusted simultaneously to maintain the direct current value unchanged until the test voltage reaches the test requirement value, and a.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (1)
1. A DC power grid full power cycle test circuit based on a DC/DC converter is characterized by comprising: the DC/DC converter comprises a DC voltage source, an AC power source and a DC/DC converter;
two sides of the DC/DC converter are respectively provided with one direct-current voltage source;
the other side of the direct-current voltage source connected with the DC/DC converter is connected with the alternating-current power supply;
four contacts are respectively arranged on two sides of the DC/DC converter;
the alternating current power supply includes: the circuit breaker branch circuit is formed by connecting the alternating-current voltage source and two circuit breakers in series;
one end of the alternating current voltage source is connected with the middle point of the circuit breaker branch circuit, and the other end of the alternating current voltage source is grounded;
the direct current voltage source includes: the device comprises a transformer, a three-phase rectifier bridge, a smoothing reactor, two capacitors and two isolating switches;
the three-phase rectifier, the smoothing reactor and the two capacitors are sequentially connected to form a series circuit;
the middle point of the capacitor series branch is grounded, and two ends of the capacitor series branch are respectively connected with the two isolating switches;
the secondary side of the transformer is connected with the three-phase rectifier bridge, and the primary side of the transformer is connected with the breaker branch;
in a normal operation mode, when one three-phase rectifier is in rectification operation and the other three-phase rectifier is in inversion operation, and the isolating switch selects contacts at two ends of the DC/DC converter, power is transmitted from a direct-current voltage source at one side of the DC/DC converter to a direct-current voltage source at the opposite side of the DC/DC converter, the polarity of a direct-current bus of the capacitor series branch at one end of the smoothing reactor is positive, and the polarity of a direct-current bus of the capacitor series branch at one end of the three-phase rectifier is negative;
when the running states of the two three-phase rectifiers are exchanged and the position of the isolating switch is kept unchanged, the power transmission direction is reversed, and the polarity of the direct current bus of the capacitor series branch circuit is simultaneously reversed;
when the running states of the two three-phase rectifiers are unchanged and the isolating switch selects the middle contact of the DC/DC converter, the transmission direction of the power is reversed again, and the polarity of the direct current bus is kept unchanged.
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| CN201511009842.4A CN105652117B (en) | 2015-12-29 | 2015-12-29 | DC/DC converter-based full-power-cycle test circuit for DC power grid |
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| CN201511009842.4A CN105652117B (en) | 2015-12-29 | 2015-12-29 | DC/DC converter-based full-power-cycle test circuit for DC power grid |
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| CN105652117B true CN105652117B (en) | 2020-10-27 |
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| CN108614168B (en) * | 2016-12-12 | 2020-07-07 | 北京天诚同创电气有限公司 | Full-power test method for power generation field converter |
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