CN214280955U - Medium-voltage photovoltaic inverter system and photovoltaic power generation system - Google Patents

Abstract

The utility model is suitable for a photovoltaic technology field provides a medium voltage photovoltaic inverter system and photovoltaic power generation system, and medium voltage photovoltaic inverter system includes contravariant unit, current sampling unit, step up transformer, high-pressure filtering unit, and the switch that is incorporated into the power networks; the input end of the inversion unit is connected with the direct current bus, and the output end of the inversion unit is connected with the primary side of the boosting transformer; the secondary side of the boosting transformer is connected with the high-voltage filtering unit and one side of the grid-connected switch, and the other side of the grid-connected switch is connected to the medium-voltage power system; the current sampling unit is connected to the primary side or the secondary side of the step-up transformer. The utility model discloses in the medium voltage photovoltaic inverter system that provides, the problem of the no-load loss of step up transformer among the current medium voltage photovoltaic inverter system has been solved.

Description

Medium-voltage photovoltaic inverter system and photovoltaic power generation system

Technical Field

The utility model belongs to the technical field of the photovoltaic, especially, relate to a middling pressure photovoltaic inverter system and photovoltaic power generation system.

Background

With the continuous development of the photovoltaic industry, the power grade and the system grade of the inverter are continuously increased. In order to increase the safety of the system and reduce the system loss, the attention of the inverter industry to the medium voltage system is increasing.

Referring to fig. 5 and 6, a conventional medium voltage inverter system specifically includes two units, i.e., a low voltage side inverter system and a medium voltage side step-up transformer system. The low-voltage side system mainly comprises an inverter, an inverter inductor L1, an inductive current sampling Hall1, a filter capacitor C1, a low-voltage output frame circuit breaker CB1 or a low-voltage alternating current fuse F1 and an alternating current load switch SW 1. The medium-voltage side system mainly comprises a step-up transformer T1 and a high-voltage switch CB 2. The existing high-voltage switch CB2 is a very large device, and generally needs a great force to be closed, and meanwhile, the voltage of the medium-voltage power grid is high (the voltage is in KV level, such as 10KV, 20KV, 35KV and the like), so that certain danger exists, and therefore, on-site personnel are not allowed to easily open and close the high-voltage switch CB2, and at the moment, the high-voltage switch CB2 is in a long-term closed state.

However, the medium-voltage inverter system has certain disadvantages, and due to the particularity of the photovoltaic system, under the condition that light is weak at night or on cloudy days, the photovoltaic system cannot generate electric energy and is in a standby state, and at the moment, the inverter system does not work, but because the high-voltage switch CB2 is always in a closed state, the step-up transformer T1 continuously operates at no-load at night, and at the moment, great no-load loss exists. Meanwhile, in the grid-connected power generation process of the medium-voltage inverter system, when the medium-voltage grid is powered off, the primary side leakage inductance of the booster transformer T1 can enable the output port of the inverter to generate high voltage, so that the inverter can be possibly damaged. Meanwhile, the traditional inverter system and the booster transformer system are produced by each manufacturer independently and do not interfere with each other, the traditional inverter system and the booster transformer system are connected in a wiring mode through the voltage inverter system in an electrical connection mode, so that the integration degree is low, and a large number of low-voltage devices are used in the traditional medium-voltage inverter system, so that a series of problems such as high cost are caused.

SUMMERY OF THE UTILITY MODEL

An object of the embodiment of the utility model is to provide a medium voltage photovoltaic inverter system aims at solving the problem of the no-load loss of step up transformer among the current medium voltage photovoltaic inverter system.

The embodiment of the utility model provides a realize like this, a medium voltage photovoltaic inverter system, include:

the system comprises an inversion unit, a current sampling unit, a boosting transformer, a high-voltage filtering unit and a grid-connected switch;

the input end of the inversion unit is connected with the direct current bus, and the output end of the inversion unit is connected with the primary side of the boosting transformer;

the secondary side of the boosting transformer is connected with the high-voltage filtering unit and one side of the grid-connected switch, and the other side of the grid-connected switch is connected to a medium-voltage power system;

the current sampling unit is connected to a primary side or a secondary side of the step-up transformer.

Furthermore, the grid-connected switch is a high-voltage output frame circuit breaker, or a high-voltage alternating current load switch is combined with a high-voltage alternating current fuse;

the high-voltage alternating current fuse is connected with the secondary side of the boosting transformer, and the high-voltage alternating current load switch is connected with the grid-connected switch.

Furthermore, the boosting transformer adopts a star-delta connection mode.

Furthermore, the step-up transformer comprises a main iron core, an auxiliary iron core, a primary side winding and a secondary side winding, wherein the primary side winding is wound on a wound iron core formed by the main iron core and the auxiliary iron core, and the secondary side winding is wound on the main iron core.

Furthermore, the system further comprises a filter inductor connected between the inverter unit and the primary side of the step-up transformer.

Furthermore, the current sampling unit is a hall current sensor.

Further, the inverter unit is a two-level inverter, a three-level inverter, or a five-level inverter.

Furthermore, the inverter unit is a three-phase full-bridge IGBT inverter.

The utility model discloses another embodiment still provides a photovoltaic power generation system, the system includes:

a photovoltaic system;

the medium-voltage photovoltaic inverter system is connected with the photovoltaic system; and

and the medium-voltage power system is connected with the medium-voltage photovoltaic inverter system.

The medium-voltage photovoltaic inverter system provided by the embodiment of the utility model incorporates the medium-voltage components necessary in the traditional medium-voltage inverter system into the inverter part, so that the inversion unit, the step-up transformer and the grid-connected switch are integrated into a whole, at the moment, the medium-voltage photovoltaic inversion system does not need a low-voltage output frame circuit breaker or a low-voltage AC fuse matched with an AC load switch in the traditional inverter system, therefore, the medium-voltage grid connection can be realized only by controlling the on-off of the grid connection switch, at the moment, at night or on cloudy days, when the inversion unit is in a standby state, the step-up transformer is disconnected from the medium-voltage power system by controlling the off of the grid connection switch, therefore, the energy of the medium-voltage power system can not be consumed in a standby state, the no-load loss of the booster transformer in the standby state is eliminated, and the problem of no-load loss of the booster transformer in the conventional medium-voltage photovoltaic inverter system is solved. Meanwhile, the medium-voltage photovoltaic inverter system does not need a low-voltage output frame circuit breaker or a low-voltage alternating current fuse wire in a traditional inverter system to be matched with an alternating current load switch, and compared with a mode of controlling the on-off of the low-voltage output frame circuit breaker and the on-off of a high-voltage switch in a traditional scheme, the system integration degree is effectively improved, and the system cost is saved. Meanwhile, the inverter unit, the step-up transformer and the grid-connected switch are integrated into a whole, so that the current of the step-up transformer is brought into a system regulation loop, and the problem that the inverter is damaged by high voltage caused by power failure of a traditional medium-voltage power grid is solved; meanwhile, leakage inductance generated by the step-up transformer can be used as a filter inductance, so that the cost of the filter inductance can be saved for the medium-voltage photovoltaic inverter system, and the system cost is saved.

Drawings

Fig. 1 is a schematic structural diagram of a medium-voltage photovoltaic inverter system according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a medium-voltage photovoltaic inverter system according to another embodiment of the present invention;

fig. 3 is a schematic structural diagram of a medium-voltage photovoltaic inverter system according to another embodiment of the present invention;

fig. 4 is a schematic structural diagram of a step-up transformer in a medium-voltage photovoltaic inverter system according to still another embodiment of the present invention;

FIG. 5 is a schematic diagram of a conventional medium voltage photovoltaic inverter system;

fig. 6 is a schematic structural diagram of another existing medium-voltage photovoltaic inverter system.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "fixed" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The utility model integrates the inversion unit, the current sampling unit, the step-up transformer, the high-voltage filtering unit and the grid-connected switch, so that the low-voltage output frame circuit breaker in the traditional inverter system is reduced, and the system cost is saved; the medium-voltage grid connection can be realized by controlling the on-off of the grid connection switch, so that the step-up transformer and the medium-voltage power system can be disconnected by controlling the off of the grid connection switch at night or on cloudy days, the energy of the medium-voltage power system cannot be consumed in a standby state, the no-load loss of the step-up transformer in the standby state is eliminated, and the problem of no-load loss of the step-up transformer in the conventional medium-voltage photovoltaic inverter system is solved; meanwhile, as the current of the step-up transformer is brought into a system regulation loop, the total current of the system can be collected through the current sampling unit, and corresponding safety protection is carried out, so that the problem that the inverter is damaged by high voltage caused by the outage of a traditional medium-voltage power grid is solved; meanwhile, leakage inductance generated by the step-up transformer can be used as a filter inductance, so that the cost of the filter inductance can be saved for the medium-voltage photovoltaic inverter system, and the system cost is saved.

Example one

Please refer to fig. 1, which is a schematic structural diagram of a medium voltage photovoltaic inverter system according to an embodiment of the present invention, for convenience of description, only showing a portion related to an embodiment of the present invention, the medium voltage photovoltaic inverter system according to an embodiment of the present invention includes:

the system comprises an inversion unit 20, a current sampling unit 30, a boosting transformer 40, a high-voltage filtering unit 50 and a grid-connected switch 60;

the input end of the inversion unit 20 is connected to the dc bus, the output end of the inversion unit 20 is connected to the primary side of the step-up transformer 40, and the inversion unit 20 is configured to invert the dc power of the dc bus into ac power and output the ac power to the step-up transformer 40;

the secondary side of the step-up transformer 40 is connected with the high-voltage filtering unit 50 and one side of the grid-connected switch 60, the other side of the grid-connected switch 60 is connected to the medium-voltage power system, and the step-up transformer 40 is used for outputting the alternating current output by the inverting unit 20 to the grid-connected switch 60 after being stepped up;

the current sampling unit 30 is connected to the primary side or the secondary side of the step-up transformer 40.

Wherein, in the embodiment of the utility model provides an in, this middling pressure photovoltaic inverter system is applied to photovoltaic power generation system, and its photovoltaic power generation system includes: photovoltaic systems, medium voltage photovoltaic inverter systems, and medium voltage power systems (i.e., medium voltage grids), wherein the photovoltaic systems are configured to output current when operated under solar radiation, and the higher the solar irradiance, the output power of the photovoltaic module is correspondingly higher, and when the photovoltaic module is used, the photovoltaic system is the photovoltaic module, such as a solar battery and the like, the direct current output by the photovoltaic component during working is connected into a medium-voltage photovoltaic inverter system, and further, when in specific use, the photovoltaic system can also comprise a confluence unit which is connected with a plurality of photovoltaic modules and is used for inputting the direct current output by each photovoltaic module into the medium-voltage photovoltaic inverter system after confluence, at the moment, the input direct current is inverted into alternating current through the medium-voltage photovoltaic inversion system, and the alternating current is boosted to meet the required specification of the medium-voltage power system and then is connected to the medium-voltage power system.

Referring to fig. 1, in an embodiment of the present invention, the inverter unit 20, the current sampling unit 30, the step-up transformer 40, the high-voltage filtering unit 50, and the grid-connected switch 60 adopt an integrated design, that is, in this embodiment, it incorporates the existing conventional box transformer step-up transformer system into the conventional inverter system to realize an integrated design, at this time, the input end of the inverter unit 20 is connected with the dc bus (that is, the dc output by the photovoltaic module), the output end of the inverter unit 20 is connected with the primary side of the step-up transformer 40, wherein the inverter unit 20 is a three-phase full-bridge IGBT inverter, for performing high-frequency chopping on the dc at the input end thereof, so as to chop the dc into an ac current, and output the ac current from the output end thereof. The inverter unit 20 converts the dc power into ac power, which is specifically low-voltage ac power, for example, 600V to 690V. Further, the inverter unit 20 in fig. 1 only illustrates a circuit structure on one phase line, and it can be understood that the circuit structures on the other two phase lines are the same as those in the above-mentioned figure, and are not described herein again. Further, in the topology form of the inverting unit 20, the inverting unit 20 may be a two-level inverter, a three-level inverter, or a five-level inverter, which is set according to actual use requirements, and is not specifically limited herein.

Wherein, in the utility model discloses an embodiment, step-up transformer 40's primary side is connected with inverter unit 20's output, step-up transformer 40's secondary side is connected with high-voltage filter unit 50 and grid-connected switch 60 one side, also the secondary side of step-up transformer 40 passes through grid-connected switch 60 and links to each other with medium voltage electric power system, step-up transformer 40 is used for stepping up to high voltage alternating current to the low voltage alternating current that inverter unit 20 input this moment, and confirm whether insert to medium voltage electric power system through grid-connected switch 60's control, it is specific, the voltage after step-up transformer 40 of this embodiment is the KV level, for example 10KV, 20KV, 35KV etc., it sets up according to the required voltage of actual medium voltage electric power system, do not specifically limit here.

Further, the step-up transformer 40 adopts a star-delta connection mode, that is, the primary side of the step-up transformer 40 adopts a star connection, and the secondary side adopts a delta connection, and as shown in fig. 4, the step-up transformer 40 includes a main iron core, an auxiliary iron core, a primary side winding and a secondary side winding, the primary side winding is wound on the wound iron core formed by the main iron core and the auxiliary iron core, the secondary side winding is wound on the main iron core, at this time, the step-up transformer 40 is wound by adding the auxiliary iron core, so that the leakage inductance of the step-up transformer 40 can be increased, and then the leakage inductance generated by the step-up transformer 40 is used as the filter inductance of the medium voltage photovoltaic inverter system. At this time, the leakage inductance generated by the step-up transformer 40 with the auxiliary iron core is used as the filter inductance, so that the cost of the filter inductance can be saved in the medium-voltage photovoltaic inverter system.

Further, in an embodiment of the present invention, the high voltage filter unit 50 is a high voltage filter capacitor C1, one end of the high voltage filter capacitor C1 is connected to the secondary side of the step-up transformer 40 and the grid-connected switch 60, and the other end of the high voltage filter capacitor C1 is grounded. Further, as shown in fig. 2 and fig. 3, in another embodiment of the present invention, the photovoltaic inverter system further includes a filter inductor 70, the filter inductor 70 is connected between the inverter unit 20 and the primary side of the step-up transformer 40, and the step-up transformer 40 can adopt the transformer T1 with the auxiliary iron core as described above, and can also adopt an existing conventional transformer. When the step-up transformer 40 adopts the transformer T1 with the auxiliary iron core, the leakage inductance generated by the step-up transformer 40 is used as a part of the filter inductance of the medium-voltage photovoltaic inverter system, and the step-up transformer 40 and the set filter inductance 70 jointly form the whole filter inductance of the medium-voltage photovoltaic inverter system, and at this time, the leakage inductance generated by the step-up transformer 40 can replace a part of the filter inductance, so that the inductance cost can be reduced. When the boost transformer 40 is a conventional transformer, the filter inductor of the medium-voltage photovoltaic inverter system is formed by the filter inductor 70. At this time, the high-voltage filter capacitor C1 and the leakage inductance and/or the filter inductance generated by the step-up transformer 40 form an LC filter circuit, and the high-voltage filter capacitor is disposed at the rear end of the step-up transformer 40, so that the LC filter circuit can be used for integrally filtering a medium-voltage photovoltaic inverter system formed by the inverter unit 20 and the step-up transformer 40.

Further, one side of grid-connected switch 60 is connected to the secondary side of step-up transformer 40, and the other side of grid-connected switch 60 is connected to the medium-voltage power system. In an embodiment of the present invention, as shown in fig. 2, the grid-connected switch 60 includes a high-voltage ac fuse F1 and a high-voltage ac load switch SW 1; the high-voltage ac fuse F1 is connected to the secondary side of the step-up transformer 40, and the high-voltage ac load switch SW1 is connected to the grid-connection switch 60. Wherein the high voltage load switch SW1 needs to be equipped with a high voltage AC fuse F1 because it has no load sharing capability. In other embodiments of the present invention, as shown in fig. 3, the grid-connected switch 60 can also be a high-voltage output frame circuit breaker CB1, wherein the high-voltage output frame circuit breaker CB1 has a load sharing capability, so that the circuit breaker can also be directly used. That is, the grid-connected switch 60 is any one of the high-voltage output frame circuit breaker CB1 or the high-voltage ac load switch SW1 combined with the high-voltage ac fuse F1, and is set according to actual use requirements, which is not limited herein.

Further, in an embodiment of the present invention, as shown in fig. 1 to fig. 3, the current sampling unit 30 is disposed on the primary side of the step-up transformer 40, and the current sampling unit 30 is connected to the output end of the inverter unit 20 and the step-up transformer 40 or the filter inductor L1, respectively, wherein it should be noted that in other embodiments of the present invention, the current sampling unit 30 can be disposed on the secondary side of the step-up transformer 40, that is, the current sampling unit 30 is connected to the primary side or the secondary side of the step-up transformer 40, and the current sampling unit 30 is mainly used for detecting the total current amount in the medium voltage photovoltaic inverter system, and the current detection is not affected by the primary side or the secondary side of the step-up transformer 40, so in this embodiment, the position relationship of the current sampling unit 30 is not specifically limited, and is specifically set according to the actual use requirement, further, the current sampling unit 30 is a HALL current sensor HALL.

Further, in an embodiment of the present invention, the photovoltaic inverter system further includes a voltage detection circuit for respectively detecting the voltage of the photovoltaic module, the voltage of the step-up transformer 40, the voltage of the medium voltage power system, and the like.

The operation mode of the medium-voltage photovoltaic inverter system is as follows: firstly, collecting the voltage of a photovoltaic assembly, starting an inverter unit 20 voltage source to start inversion when detecting that the voltage of the photovoltaic assembly meets the starting requirement, simultaneously sampling the voltage of a booster transformer 40 and the voltage of a medium-voltage power system, and controlling a grid-connected switch 60 to be closed to start grid-connected power generation when the amplitude and the phase of the two meet the grid-connected requirement. And when the voltage of the photovoltaic module does not meet the grid-connected requirement, the grid-connected switch 60 is disconnected, so that the medium-voltage power system and the medium-voltage photovoltaic inverter system are thoroughly disconnected. The grid connection requirement is that the phase, phase sequence and amplitude of the line voltage at the high-voltage side of the step-up transformer 40 are the same as those of the line voltage of the medium-voltage power system.

In this embodiment, because the necessary medium-voltage component in the conventional medium-voltage inverter system is incorporated into the inverter part, so that the inverter unit, the step-up transformer and the grid-connected switch are integrated into a whole, at this time, the medium-voltage photovoltaic inverter system does not need a low-voltage output frame circuit breaker or a low-voltage ac fuse wire in the conventional inverter system to cooperate with an ac load switch, and therefore, only the grid-connected medium-voltage switch is needed in this embodiment. Meanwhile, the step-up transformer with the auxiliary iron core is adopted, so that leakage inductance generated by the step-up transformer can be used for replacing a part of filter inductance, and the cost of the inductance can be effectively reduced.

Meanwhile, medium-voltage grid connection is realized by controlling the on-off of the grid connection switch, and at night or on cloudy days, when the photovoltaic module is not in a standby state without the power generation inversion unit, the grid connection switch is controlled to be switched off, so that the step-up transformer is switched off from the medium-voltage power system, the energy of the medium-voltage power system cannot be consumed in the standby state, the no-load loss of the step-up transformer in the standby state is eliminated, and the problem of no-load loss of the step-up transformer in the conventional medium-voltage photovoltaic inversion system is solved.

Meanwhile, the medium-voltage component and the inversion component in the traditional medium-voltage photovoltaic inversion system respectively detect respective current and voltage, so that when the medium-voltage grid is powered off, the primary side leakage inductance of the boosting transformer can enable the output port of the inverter to generate high voltage, but the inversion component does not effectively detect the high voltage generated by the medium-voltage component, and the inverter can be possibly damaged The problem of damaging a step-up transformer does not exist in full protection, namely when a grid-connected switch is disconnected, so that the problem that the inverter is damaged by high voltage caused by the outage of a traditional medium-voltage power grid is solved.

Example two

The second embodiment of the present invention also provides a photovoltaic power generation system, for convenience of description, only show and the embodiment of the present invention relates to a relevant part, the embodiment of the present invention provides a middle photovoltaic power generation system including: a photovoltaic system; a medium voltage photovoltaic inverter system as described in embodiment one connected to a photovoltaic system; and a medium voltage power system (i.e., a medium voltage grid) connected to the medium voltage photovoltaic inverter system.

Wherein the photovoltaic system is used for outputting corresponding current when the photovoltaic system works and is irradiated by sunlight, and the higher the sunlight irradiance is, the higher the output power of the photovoltaic component is, when in specific use, the photovoltaic system is a photovoltaic component, such as a solar battery, and the direct current output by the photovoltaic component when in work is accessed to an inversion unit of a medium-voltage photovoltaic inversion system, furthermore, when in specific use, the photovoltaic system also comprises a confluence unit which is connected with a plurality of photovoltaic components and is used for converging the direct current output by each photovoltaic component and inputting the converged direct current into the input end of the inversion unit, when the voltage of the photovoltaic component is detected to meet the starting requirement, the voltage source of the inversion unit starts inversion, and the inversion unit inverts the input direct current into low-voltage alternating current (such as between 600V and 690V) and outputs the low-voltage alternating current to a step-up transformer, and the step-up transformer steps up the low-voltage alternating current and correspondingly determines whether to be connected to the medium-voltage power system or not according to the control of the grid-connected switch when the low-voltage alternating current is stepped up to meet the specification (the voltage is in KV level, such as 10KV, 20KV, 35KV and the like) required by the medium-voltage power system. And controlling a grid-connected switch to be closed to start grid-connected power generation when the amplitude and the phase of the sampled voltage of the step-up transformer and the voltage of the medium-voltage power system meet grid-connected requirements. And when the voltage of the photovoltaic module does not meet the grid-connected requirement, the grid-connected switch is disconnected, so that the medium-voltage power system and the medium-voltage photovoltaic inverter system are thoroughly disconnected.

In the embodiment, the inverter unit, the step-up transformer and the grid-connected switch are integrated into a whole by incorporating the necessary medium-voltage component in the traditional medium-voltage inverter system into the inverter part, and at the moment, the medium-voltage photovoltaic inverter system does not need a low-voltage output frame circuit breaker or a low-voltage alternating current fuse wire in the traditional inverter system to be matched with an alternating current load switch any more, so that medium-voltage grid connection can be realized only by controlling the on-off of the grid-connected switch, and at night or on a cloudy day, when the inverter unit is in a standby state, the step-up transformer is disconnected with the medium-voltage power system by controlling the on-off of the grid-connected switch, so that the energy of the medium-voltage power system cannot be consumed in the standby state, the no-load loss of the step-up transformer during standby is eliminated, and the problem of no-load loss of the step-up transformer in the traditional medium-voltage photovoltaic inverter system is solved. Meanwhile, the medium-voltage photovoltaic inverter system does not need a low-voltage output frame circuit breaker or a low-voltage alternating current fuse wire in a traditional inverter system to be matched with an alternating current load switch, and compared with a mode of controlling the on-off of the low-voltage output frame circuit breaker and the on-off of a high-voltage switch in a traditional scheme, the system integration degree is effectively improved, and the system cost is saved. Meanwhile, the inverter unit, the step-up transformer and the grid-connected switch are integrated into a whole, so that the current of the step-up transformer is brought into a system regulation loop, and the problem that the inverter is damaged by high voltage caused by power failure of a traditional medium-voltage power grid is solved.

The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, as any modifications, equivalents, improvements and the like made within the spirit and principles of the present invention are intended to be included within the scope of the present invention.

Claims (9)

1. A medium voltage photovoltaic inverter system, the system comprising:

the system comprises an inversion unit, a current sampling unit, a boosting transformer, a high-voltage filtering unit and a grid-connected switch;

the input end of the inversion unit is connected with the direct current bus, and the output end of the inversion unit is connected with the primary side of the boosting transformer;

the secondary side of the boosting transformer is connected with the high-voltage filtering unit and one side of the grid-connected switch, and the other side of the grid-connected switch is connected to a medium-voltage power system;

the current sampling unit is connected to a primary side or a secondary side of the step-up transformer.

2. The medium voltage photovoltaic inverter system of claim 1, wherein the grid-tie switch is a high voltage output frame circuit breaker, or a high voltage ac load switch in combination with a high voltage ac fuse;

the high-voltage alternating current fuse is connected with the secondary side of the boosting transformer, and the high-voltage alternating current load switch is connected with the grid-connected switch.

3. The medium voltage photovoltaic inverter system of claim 1 wherein the step-up transformer is star-delta connected.

4. The medium voltage photovoltaic inverter system according to claim 3, wherein the step-up transformer includes a main core, an auxiliary core, a primary side winding and a secondary side winding, the primary side winding is wound around a winding core formed by the main core and the auxiliary core, and the secondary side winding is wound around the main core.

5. The medium voltage photovoltaic inverter system of claim 1, further comprising a filter inductor connected between the inverter unit and the primary side of the step-up transformer.

6. The medium voltage photovoltaic inverter system of claim 1, wherein the current sampling unit is a hall current sensor.

7. The medium voltage photovoltaic inverter system of claim 1, wherein the inverter unit is a two-level inverter, a three-level inverter, or a five-level inverter.

8. The medium voltage photovoltaic inverter system of claim 1, wherein the inverter unit is a three-phase full bridge IGBT inverter.

9. A photovoltaic power generation system, characterized in that the system comprises:

a photovoltaic system;

the medium voltage photovoltaic inverter system of any one of claims 1-8 connected to the photovoltaic system; and

and the medium-voltage power system is connected with the medium-voltage photovoltaic inverter system.

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