CN117955075A - Neutral point grounding type medium-voltage direct-current transformer and micro-grid - Google Patents
Neutral point grounding type medium-voltage direct-current transformer and micro-grid Download PDFInfo
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Abstract
The invention discloses a middle-point grounding type medium-voltage direct-current transformer and a micro-grid, which comprise a plurality of low-voltage side power units and medium-voltage side power units which are connected by adopting grouping isolation transformation, wherein the input ends of the plurality of low-voltage side power units are connected in parallel, and the output ends of the plurality of medium-voltage side power units are connected in series; the output ends of the plurality of medium-voltage side power units are divided into an anode output end and a cathode output end through an anode unit series group and a cathode unit series group; the cathodes of the positive electrode unit series group are connected with the anodes of the negative electrode unit series group, and the connection point of the positive electrode unit series group and the negative electrode unit series group is grounded through a grounding inductor; the invention ensures that the midpoint voltage to ground of the direct-current transformer is approximately zero, the voltage to ground of the positive pole or the negative pole of the direct-current transformer is only half of the voltage of the full bus, the cost and the volume are reduced, the working voltage of the micro-grid can be improved, the transmission loss is reduced, and the transmission distance of the micro-grid is improved under the same voltage-withstanding capability as the prior art.
Description
Technical Field
The invention relates to the technical field of electric energy conversion, in particular to a midpoint grounding type medium-voltage direct current transformer and a micro-grid.
Background
The off-grid medium-voltage direct-current micro-grid can directly couple new energy power generation with direct-current load, avoid adverse effect on the grid, and reduce the requirement on a grid access point.
At present, a new energy power generation station is generally at a certain distance from a direct current load, and the transmission distance is longer as the medium voltage level is higher, the application range is wider, so that after the new energy power generation voltage is boosted by using a direct current transformer, the transmission distance of a micro-grid can be increased, and the transmission loss is reduced.
In the prior art, a high-resistance grounding mode is adopted in a direct-current transformer, the middle point is not grounded, the positive electrode and the negative electrode of the direct-current transformer are grounded through the same large-resistance resistor respectively, and when the positive electrode or the negative electrode is grounded at a single point or electric leakage caused by insulation reduction occurs, the voltage of the other electrode to the ground is the full bus voltage. Therefore, the ground insulation level of the whole direct-current transformer in the prior art should be designed according to the voltage of the whole bus, so that the voltage-resistant level of the direct-current transformer and micro-grid equipment is high in requirement, and the manufacturing cost is high.
Disclosure of Invention
The invention aims to provide a neutral point grounded medium-voltage direct-current transformer and a micro-grid, which are used for solving the technical problems of high voltage-resistant level requirement and high cost of direct-current transformers and micro-grid equipment in the prior art.
In order to solve the technical problems, the invention specifically provides the following technical scheme:
The neutral point grounded type medium-voltage direct-current transformer comprises a plurality of low-voltage side power units and medium-voltage side power units which are connected by adopting grouping isolation transformation, wherein the input ends of the low-voltage side power units are connected in parallel, and the output ends of the medium-voltage side power units are connected in series;
the output ends of the plurality of the medium-voltage side power units are divided into an anode output end and a cathode output end through an anode unit series group and a cathode unit series group;
The cathodes of the positive electrode unit series group are connected with the anodes of the negative electrode unit series group, and the connection point of the positive electrode unit series group and the negative electrode unit series group is grounded through a grounding inductor.
As a preferable scheme of the invention, the positive output end formed by the positive unit series connection group is connected with a positive output inductor in series, and the negative output end formed by the negative unit series connection group is connected with a negative output inductor in series.
As a preferable scheme of the invention, the positive electrode output end and the negative electrode output end are respectively grounded through a lightning protection assembly, and the lightning protection assembly comprises a main lightning arrester and a reverse conduction valve group which are connected in parallel between the positive electrode output end and the grounding electrode and between the negative electrode output end and the grounding electrode.
As a preferred aspect of the present invention, the reverse pilot valve group includes a piezoresistor and a diode valve group connected in series;
The positive electrode of the diode valve bank is grounded between the positive electrode output end and the grounding electrode, and the negative electrode of the diode valve bank is connected with the positive electrode output end through the piezoresistor;
And an anode of the diode valve bank between the negative electrode output end and the grounding electrode is connected with the negative electrode output end, and a cathode of the diode valve bank is grounded through the piezoresistor.
As a preferable scheme of the invention, the diode valve group comprises a plurality of diodes connected in series, each diode is connected with a static voltage equalizing resistor and a dynamic voltage equalizing component in parallel, and the piezoresistor is also connected with the static voltage equalizing resistor in parallel;
Wherein, the dynamic voltage equalizing component comprises a resistor and a capacitor which are connected in series.
As a preferable scheme of the invention, diodes are connected in parallel at two ends of the static equalizing resistor, and the conducting direction of the diodes is the same as that of the diodes of the diode valve group in the same reverse conducting valve group.
As a preferable mode of the invention, the rated voltage of the piezoresistor is 0.1 times of the highest unipolar operation voltage of the medium-voltage side power unit, and the residual voltage of the piezoresistor is 0.2 times of the highest unipolar operation voltage of the medium-voltage side power unit.
In order to solve the technical problem, the invention also provides a micro-grid based on the neutral point grounding type medium voltage direct current transformer, which comprises the following components:
a plurality of direct current transformers and a medium voltage direct current protection device connected with the plurality of direct current transformers through a direct current transmission line;
the medium-voltage direct current protection device is provided with a plurality of ports, and each port is provided with an anode port, a cathode port and a grounding port;
The positive electrode port is connected with the positive electrode output end of the direct current transformer, the negative electrode port is connected with the negative electrode output end of the direct current voltage, and the grounding port and the grounding end of the direct current transformer share a grounding electrode.
As a preferable scheme of the invention, the direct current transformer is divided into a near-end direct current transformer and a far-end direct current transformer according to the connection distance;
the grounding terminals of the near-end direct current transformers share the same grounding electrode, the far-end direct current transformers are grouped based on mutual distances, the far-end direct current transformers in the same group are commonly connected with one grounding electrode, and the grounding port of the medium-voltage direct current protection device and the grounding terminal of the near-end direct current transformer share the same grounding electrode.
As a preferable scheme of the invention, the positive electrode port of the medium-voltage direct current protection device is connected with the grounding port through a lightning protection component, and the negative electrode port of the medium-voltage direct current protection device is connected with the grounding port through the lightning protection component.
Compared with the prior art, the invention has the following beneficial effects:
the neutral point between the positive electrode output end and the negative electrode output end of the direct current transformer is grounded through the grounding inductor, the change rate of the inductance current is in direct proportion to the voltage difference between the two ends of the inductor, so that the voltage difference between the two ends of the inductor is approximately zero in a steady state, namely, when the inductance current is unchanged, the midpoint grounding voltage of the direct current transformer is approximately zero, the positive electrode or the negative electrode grounding voltage of the direct current transformer is only half of the full bus voltage, the insulation requirement on the direct current transformer is remarkably reduced, and the manufacturing cost and the volume are reduced;
And under the same pressure-resistant capability as the prior art, the working voltage of the micro-grid system can be improved, the transmission loss is reduced, and the transmission distance of the micro-grid is improved.
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 will be apparent to those of ordinary skill in the art that the drawings in the following description are exemplary only and that other implementations can be obtained from the extensions of the drawings provided without inventive effort.
Fig. 1 is a mounting structure diagram of a lightning protection component of a medium voltage dc transformer according to embodiment 1 of the present invention;
FIG. 2 is a schematic diagram of the assembly connection structure of the valve block according to embodiment 1 of the present invention;
FIG. 3 is a schematic diagram showing the connection structure of the pressure-sensitive component according to embodiment 1 of the present invention
Fig. 4 is a schematic structural diagram of a micro-grid according to embodiment 2 of the present invention;
Fig. 5 is a mounting structure diagram of a lightning protection component of the medium voltage dc protection device according to embodiment 2 of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
As shown in fig. 1, the invention provides a medium-voltage direct-current transformer with a grounded middle point, which comprises a plurality of low-voltage side power units and medium-voltage side power units which are connected by adopting grouping isolation transformation, wherein the input ends of the plurality of low-voltage side power units are connected in parallel, the output ends of the plurality of medium-voltage side power units are connected in series, and an output inductance is respectively connected in series with an anode output end formed by an anode unit series group and a cathode output end formed by a cathode unit series group.
The output ends of the plurality of medium-voltage side power units are divided into an anode output end and a cathode output end through an anode unit series group and a cathode unit series group.
The cathodes of the positive electrode unit series group are connected with the anodes of the negative electrode unit series group, and the connection point of the positive electrode unit series group and the negative electrode unit series group is grounded through a grounding inductor.
It should be noted that the input and the output are conventionally defined in terms of power flow direction.
When the medium-voltage direct-current transformer is used as a boosting direct-current transformer, the low-voltage side is an input end, and the medium-voltage side is an output end;
the medium-voltage direct-current transformer is used as a step-down direct-current transformer, the medium-voltage side is used as an input end, and the low-voltage side is used as an output end;
the medium voltage dc transformer is used as a bidirectional dc transformer, and its input terminal may be selected as the low voltage side or the medium voltage side, and its output terminal may be selected as the low voltage side or the medium voltage side.
However, since the present embodiment focuses on the structure and method of the dc transformer, the same structure and method of the dc transformer are different in definition of the input terminal and the output terminal when used for boosting and for reducing. In order to avoid redundancy, in the description herein, the input and output terminals are described according to a step-up dc transformer as an example, and when the dc transformer is used for dc step-down, the definition of "input" and "output" may be structurally reversed, where "input" and "output" in this embodiment do not represent the limitation on the power flow direction.
One example of a medium voltage dc transformer with a neutral point grounded is: the midpoint of the DC transformer is grounded through an inductor.
In the prior art, the midpoint of the direct current transformer is not grounded, and the anode and the cathode of the direct current transformer are grounded through the same resistor with large resistance. When the positive electrode or the negative electrode is grounded at a single point or when electric leakage caused by insulation reduction occurs, the voltage of the other electrode to the ground is the full bus voltage. The ground insulation level of the whole dc transformer in the prior art should be designed according to the full bus voltage.
In the embodiment, the midpoint of the dc transformer is grounded through the grounding inductor, and the change rate of the inductor current is proportional to the voltage difference between the two ends of the inductor due to the working principle of the inductor. Therefore, in a steady state, namely when the current of the inductor is unchanged, the voltage difference between two ends of the inductor is approximately zero, the voltage to the ground of the middle point of the direct current transformer is approximately zero, the voltage to the ground of the positive electrode or the negative electrode of the direct current transformer is only half of the voltage of the full bus, the insulation requirement on the direct current transformer is obviously reduced, and the manufacturing cost and the volume are reduced.
Since it is generally not desirable to have a large current continuously flowing into the ground electrode, this embodiment proposes that the dc transformer detects the current on the ground inductance during normal operation, and dynamically adjusts the outputs of the series group of positive cells and the series group of negative cells so that the current approaches 0.
Specifically, when the current flowing into the grounding electrode on the grounding inductor is positive, the output voltage of the positive electrode unit series group is reduced, and the output voltage of the negative electrode unit series group is increased, so that the grounding inductor is subjected to negative voltage, and the positive current flowing into the grounding electrode on the grounding inductor is reduced;
When the current flowing into the grounding electrode on the grounding inductor is negative, the output voltage of the positive electrode unit series group is increased, the output voltage of the negative electrode unit series group is reduced, and the grounding inductor is subjected to positive voltage, so that the absolute value of the negative current flowing into the grounding electrode on the grounding inductor is reduced.
The neutral point between the positive electrode output end and the negative electrode output end of the direct current transformer is grounded through the grounding inductor, the change rate of the inductance current is in direct proportion to the voltage difference between the two ends of the inductor, so that the voltage difference between the two ends of the inductor is approximately zero in a steady state, namely, when the inductance current is unchanged, the midpoint grounding voltage of the direct current transformer is approximately zero, the positive electrode or the negative electrode grounding voltage of the direct current transformer is only half of the full bus voltage, the insulation requirement on the direct current transformer is remarkably reduced, and the manufacturing cost and the volume are reduced.
Therefore, the direct-current transformer provided by the embodiment is also applicable to a system which does not need lightning protection, and can also achieve the purpose of reducing the insulation requirement of equipment, thereby reducing the volume and the manufacturing cost.
For the system and the equipment which need lightning protection, the direct current transformer with the midpoint grounded through the inductor needs to additionally consider the overvoltage problem caused by lightning strike and the discharging problem of lightning strike current.
Another embodiment is a medium voltage dc transformer with a neutral point grounded: the positive output end and the negative output end of the direct current transformer are respectively grounded through the lightning protection component.
The lightning protection assembly comprises a main lightning arrester and a reverse conduction valve group which are connected in parallel between the positive electrode output end and the grounding electrode and between the negative electrode output end and the grounding electrode.
Wherein the rated voltage of the main lightning arrester is 1.1 times of the highest unipolar working voltage of the medium-voltage side power unit.
The components and the structure of the reverse guide valve group are shown in figure 2, the reverse guide valve group comprises a piezoresistor and a diode valve group which are connected in series, the anode of the diode valve group between the output end of the positive electrode and the grounding electrode is grounded, and the cathode of the diode valve group is connected with the output end of the positive electrode through the piezoresistor.
The anode of the diode valve bank between the cathode output end and the grounding electrode is connected with the cathode output end, and the cathode of the diode valve bank is grounded through a piezoresistor.
The diode valve group comprises a plurality of diodes which are connected in series, and each diode is connected with a static voltage equalizing resistor and a dynamic voltage equalizing component in parallel; wherein the dynamic voltage equalizing assembly comprises a resistor and a capacitor connected in series.
The piezoresistor of the reverse conducting valve group is also connected with a static equalizing resistor in parallel.
In addition, as shown in fig. 3, in this embodiment, a lightning protection diode may be connected in parallel to the varistor, so as to avoid serious heat generation of the varistor when lightning current with the same polarity as that of the diode flows through the lightning protection valve bank. Meanwhile, when no lightning wave exists, the normal operation of the system is not affected.
Further, the rated voltage of the piezoresistor is 0.1 times of the highest unipolar operation voltage of the medium-voltage side power unit, and the residual voltage of the piezoresistor is 0.2 times of the highest unipolar operation voltage of the medium-voltage side power unit.
The potential of the direct current transformer with the midpoint grounded through the inductor is directly related to the ground, so that the mode of respectively adding the diode lightning protection valve group to the ground by the positive electrode and the negative electrode of the embodiment can be adopted.
The existing lightning protection device is characterized in that a metal oxide lightning arrester is respectively arranged on the anode and the cathode in a pair. Under the current lightning protection device, when negative polarity lightning wave hits the positive pole, positive pole voltage and negative pole voltage can jump to the negative residual voltage of arrester simultaneously, and the lightning current can flow through DC transformer's power unit to lead to equipment overcurrent to shut down, even lead to burning out the power unit.
In this embodiment, the neutral point between the positive output end and the negative output end of the dc transformer is grounded through an inductor, and the lightning protection component is matched, so that the voltage-resistant level requirement of the whole micro-grid device can be reduced, the transmission loss is reduced, and the transmission distance of the micro-grid is increased.
The working principle of the midpoint grounded medium-voltage direct-current transformer combined with the lightning protection component for protection is as follows:
when the direct-current transformer detects current on the grounding inductor in normal operation, the output of the positive electrode unit series group and the negative electrode unit series group is dynamically regulated to enable the current to be close to 0;
When the positive electrode or the negative electrode is short-circuited to the ground, the grounding inductance is used for limiting the rising speed of the short-circuit current, the direct-current transformer detects the short-circuit current and performs locking protection, and the short-circuit protection time is generally 0.5ms. The working voltage of the main lightning arrester is 1.1 times of the highest working voltage of the single pole, and the residual voltage is about 2.2 times of the highest working voltage of the single pole, so that the short-time working voltage acts on the main lightning arrester, and the reverse-conduction valve group cannot be damaged.
When the positive pole receives the lightning wave with positive polarity, the main lightning arrester of the positive pole discharges to the ground, and the residual voltage is 2.2 times of the highest working voltage of the monopole.
It should be further specifically noted that, when the positive electrode receives a lightning wave with positive polarity, one of the discharge protection modes of the lightning protection assembly is: the residual voltage of the main lightning arrester of the positive electrode discharges to the ground through the positive electrode output inductance of the direct current transformer, the positive electrode unit series group and the grounding inductance.
At this time, the voltage of the positive series unit group is 0.7 to 1 times of the highest working voltage of the monopole, so that the total voltage of the grounding inductor and the positive output inductor is instantaneously raised to about 1.2 to 1.5 times of the monopole working voltage, and the voltage acts on the grounding inductor to generate impact current. The current is generally small because the inductance value of the grounding inductance is large, so that the positive electrode unit series group is not damaged.
The second discharging protection mode of the lightning protection component is as follows: the residual voltage of the positive main lightning arrester is discharged to the ground through a reverse conducting valve bank which is connected with the output end of the negative electrode in parallel through a direct-current transformer.
At this time, the voltage of the negative electrode series unit group is 0.7 to 1 times of the unipolar maximum working voltage, so the total voltage on the piezoresistor connected in series by the positive electrode output inductance, the negative electrode output inductance and the inverse pilot valve group at the negative electrode output end is 0.2 to 0.8 times of the unipolar maximum working voltage. The residual voltage of the piezoresistor is 0.2 times of the highest working voltage of the single pole, so that the voltages acting on the positive output inductor and the negative output inductor are about 0 to 0.6 times of the highest working voltage of the single machine, the current is small, and the positive unit series group and the negative unit series group are not damaged.
In summary, when the positive pole receives the positive lightning wave, the direct current transformer can safely operate.
When the positive pole receives negative polarity lightning wave, the diode valve group of the positive pole reverse conducting valve group is conducted to directly inject the lightning wave into the grounding electrode, and the series piezoresistor limits the positive pole voltage to be near the highest voltage of minus 0.2 times of the monopole, so that the direct current transformer cannot be stopped in an overcurrent way, and the power unit cannot be burnt.
The discharge protection mode specifically comprises the following steps: the residual voltage of the positive main lightning arrester discharges to the ground through the positive output inductance of the direct-current transformer, the positive unit series group and the grounding inductance.
At this time, the voltage of the positive electrode series unit group is 0.7 to 1 times of the highest working voltage of the single pole, so that the total voltage of the grounding inductor and the positive electrode output inductor is instantaneously raised to about 0.8 to 1.1 times of the highest working voltage of the single pole, and the voltage acts on the grounding inductor to generate impact current. The current is generally small because the inductance value of the grounding inductance is large, so that the positive electrode unit series group is not damaged.
Because the voltage of the negative electrode series unit group is 0.7 to 1 times of the unipolar working voltage, the negative electrode voltage is about-1.6 to-2.2 times of the unipolar working voltage, the negative electrode main lightning arrester is not fully conducted, and no large grounding current flows through the positive and negative electrode unit series group.
In summary, when the positive pole receives the negative-polarity lightning wave, the direct-current transformer can safely operate.
The process of receiving the lightning wave by the negative electrode is similar to that of the positive electrode, and thus, a description thereof will not be repeated in this embodiment.
The invention adopts the special lightning protection component to prevent lightning current from flowing through the power unit of the direct current transformer, thereby causing the equipment to be stopped due to overcurrent and even burning the power unit, and effectively improving the safe operation level.
Therefore, the invention can improve the safe operation level of the direct current transformer and reduce the voltage withstand level requirement of the direct current transformer.
Example 2
The medium-voltage dc transformer with the grounded midpoint in the above embodiment 1 can be connected to a micro-grid formed by the medium-voltage dc protection device, and the micro-grid has a structure and a connection mode as shown in fig. 4, and includes:
the system comprises a plurality of direct current transformers and a medium voltage direct current protection device connected with the plurality of direct current transformers through a direct current transmission line.
The medium-voltage direct current protection device is provided with a plurality of ports, each port is provided with an anode port, a cathode port and a grounding port, the anode port is connected with the anode output end of the direct current transformer, the cathode port is connected with the cathode output end of the direct current voltage, and the grounding port and the grounding end of the direct current transformer share a grounding electrode.
The direct current transformers are divided into a near-end direct current transformer and a far-end direct current transformer according to the connection distance, wherein the grounding ends of a plurality of near-end direct current transformers share the same grounding electrode, the grounding ends of single far-end direct current transformers are respectively and independently connected with one grounding electrode, and the grounding port of the medium-voltage direct current protection device and the grounding end of the near-end direct current transformer share the same grounding electrode.
In this embodiment, the positive electrode port of the medium voltage dc protection device is connected to the ground port through a lightning protection component, and the negative electrode port of the medium voltage dc protection device is connected to the ground port through a lightning protection component.
The lightning protection assembly installed in the medium voltage direct current protection device has the same structure as the lightning protection assembly connected with the medium voltage direct current transformer with the middle point grounded in the embodiment 1, and is used for realizing the protection effect of the medium voltage direct current protection device, and the installation mode of the lightning protection assembly of the medium voltage direct current protection device is specifically shown in fig. 5.
Compared with the prior art, the lightning protection voltage-withstanding requirement of the micro-grid of the embodiment is reduced by half, and under the same voltage-withstanding capability as the prior art (the voltage of the positive electrode or the negative electrode of the direct-current transformer to the ground is the full bus voltage), the system working voltage can be improved, the transmission loss is reduced, and the transmission distance of the micro-grid is increased.
The above embodiments are only exemplary embodiments of the present application and are not intended to limit the present application, the scope of which is defined by the claims. Various modifications and equivalent arrangements of this application will occur to those skilled in the art, and are intended to be within the spirit and scope of the application.
Claims (10)
1. The neutral point grounded type medium-voltage direct-current transformer is characterized by comprising a plurality of low-voltage side power units and medium-voltage side power units which are connected by adopting grouping isolation transformation, wherein the input ends of the low-voltage side power units are connected in parallel, and the output ends of the medium-voltage side power units are connected in series;
the output ends of the plurality of the medium-voltage side power units are divided into an anode output end and a cathode output end through an anode unit series group and a cathode unit series group;
The cathodes of the positive electrode unit series group are connected with the anodes of the negative electrode unit series group, and the connection point of the positive electrode unit series group and the negative electrode unit series group is grounded through a grounding inductor.
2. A medium voltage DC transformer with a grounded middle point as set forth in claim 1, wherein,
The positive output end formed by the positive unit series group is connected with a positive output inductor in series, and the negative output end formed by the negative unit series group is connected with a negative output inductor in series.
3. A medium voltage DC transformer with a grounded middle point as set forth in claim 1, wherein,
The positive electrode output end and the negative electrode output end are respectively grounded through a lightning protection assembly, and the lightning protection assembly comprises a main lightning arrester and a reverse-conduction valve group which are connected in parallel between the positive electrode output end and the grounding electrode and between the negative electrode output end and the grounding electrode.
4. A medium voltage DC transformer with a grounded midpoint according to claim 3,
The reversing pilot valve group comprises a piezoresistor and a diode valve group which are connected in series;
The positive electrode of the diode valve bank is grounded between the positive electrode output end and the grounding electrode, and the negative electrode of the diode valve bank is connected with the positive electrode output end through the piezoresistor;
And an anode of the diode valve bank between the negative electrode output end and the grounding electrode is connected with the negative electrode output end, and a cathode of the diode valve bank is grounded through the piezoresistor.
5. A medium voltage DC transformer with a grounded middle point as claimed in claim 4, wherein,
The diode valve group comprises a plurality of diodes which are connected in series, each diode is connected with a static voltage equalizing resistor and a dynamic voltage equalizing component in parallel, and the piezoresistor is also connected with the static voltage equalizing resistor in parallel;
Wherein, the dynamic voltage equalizing component comprises a resistor and a capacitor which are connected in series.
6. A medium voltage DC transformer with a grounded middle point as claimed in claim 5, wherein,
Diodes are connected in parallel at two ends of the static equalizing resistor, and the conducting direction of the diodes is the same as that of the diodes of the diode valve group in the same reverse conducting valve group.
7. A medium voltage DC transformer with a grounded middle point as claimed in claim 4 or 6, wherein,
The rated voltage of the piezoresistor is 0.1 times of the highest unipolar working voltage of the medium-voltage side power unit, and the residual voltage of the piezoresistor is 0.2 times of the highest unipolar working voltage of the medium-voltage side power unit.
8. A micro-grid based on a medium voltage dc transformer with neutral point grounded according to any of claims 1-7, comprising:
a plurality of direct current transformers and a medium voltage direct current protection device connected with the plurality of direct current transformers through a direct current transmission line;
the medium-voltage direct current protection device is provided with a plurality of ports, and each port is provided with an anode port, a cathode port and a grounding port;
The positive electrode port is connected with the positive electrode output end of the direct current transformer, the negative electrode port is connected with the negative electrode output end of the direct current voltage, and the grounding port and the grounding end of the direct current transformer share a grounding electrode.
9. A micro-grid based on a medium voltage DC transformer with a neutral point grounded as claimed in claim 8, wherein,
The direct current transformer is divided into a near-end direct current transformer and a far-end direct current transformer according to the connection distance;
the grounding terminals of the near-end direct current transformers share the same grounding electrode, the far-end direct current transformers are grouped based on mutual distances, the far-end direct current transformers in the same group are commonly connected with one grounding electrode, and the grounding port of the medium-voltage direct current protection device and the grounding terminal of the near-end direct current transformer share the same grounding electrode.
10. A micro-grid based on a medium voltage DC transformer with a neutral point grounded as claimed in claim 9,
The positive electrode port of the medium-voltage direct current protection device is connected with the grounding port through a lightning protection assembly, and the negative electrode port of the medium-voltage direct current protection device is connected with the grounding port through the lightning protection assembly.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410137932.4A CN117955075A (en) | 2024-02-01 | 2024-02-01 | Neutral point grounding type medium-voltage direct-current transformer and micro-grid |
Applications Claiming Priority (1)
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| CN117374899A (en) * | 2023-10-20 | 2024-01-09 | 中科智寰(北京)科技有限公司 | DC power grid feed-in protection device with lightning protection function |
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| CN101872969A (en) * | 2010-07-14 | 2010-10-27 | 吉林省电力有限公司电力科学研究院 | Capacitive grounding current distributed compensation method and device for medium-voltage power supply system |
| CN106684850A (en) * | 2016-12-13 | 2017-05-17 | 国家电网公司 | Grounding system for neutral point in high-voltage transformer |
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