CN208112245U - Power transmission systems, wind turbines and wind farms - Google Patents

Abstract

The utility model discloses a power transmission system, a wind turbine generator set and a wind farm, which are used to transmit power in the form of direct current, reduce the cost of transmission lines and line losses during power transmission, improve line utilization and increase power transmission. distance while avoiding the skin effect present in the line. The power transmission system is used to transmit the electric energy generated by the wind turbine to the power grid. The power transmission system includes: a machine-side rectification module, a grid-side inverter module, a grid-connected module, and a power extraction module, where The machine-side rectification module is used to connect to the wind turbine, the machine-side rectification module, the grid-side inverter module and the grid-connected module are connected in sequence, the grid-connected module is used to connect to the power grid; the input end of the power taking module is connected The output end of the grid-side inverter module is used to connect to the wind turbine generator set.

Description

Power transmission systems, wind turbines and wind farms

technical field

The utility model relates to the technical field of power electronics, in particular to an electronic transmission system, a wind power generating set and a wind farm.

Background technique

The electric energy generated by the wind turbine needs to be connected to the grid for transmission. When the electricity generated by the wind turbine is connected to the grid, the traditional power transmission scheme is a direct-drive AC transmission system or a doubly-fed AC transmission system.

As shown in Fig. 1, Fig. 1 shows the circuit topology of the direct-drive AC power transmission system. In the wind farm 10, after the electric energy generated by each direct drive motor is converted by the converter, the 690-volt low-voltage alternating current is converted into a 35-kilovolt (KV) medium-voltage alternating current through the booster, and then imported into the central The 35KV medium-voltage alternating current in the high-voltage busbar 11 and the medium-voltage busbar 11 is converted into 110KV high-voltage alternating current or 220KV high-voltage alternating current through the booster 12, and finally the 110KV high-voltage alternating current or 220KV high-voltage alternating current is incorporated into the power grid 13. In this solution, since there is reactive power in the AC grid, in order to improve the power transmission capacity of the grid, a static var generator (Static Var Generator, SVG) 14 needs to be installed for reactive power compensation.

As shown in Fig. 2, Fig. 2 shows the circuit topology of the doubly-fed AC power transmission system. In the wind farm 20, after the electric energy generated by each doubly-fed generator is converted by the converter, the 690V low-voltage alternating current is converted into a 35KV medium-voltage alternating current through the booster, and then imported into the medium-voltage busbar 21, The 35KV medium-voltage alternating current in the medium-voltage busbar 21 is converted into 110KV high-voltage alternating current or 220KV high-voltage alternating current through the booster 22 , and finally the 110KV high-voltage alternating current or 220KV high-voltage alternating current is incorporated into the power grid 23 . In this solution, since there is reactive power in the AC grid, in order to improve the power transmission capacity of the grid, a static var generator 24 also needs to be installed for reactive power compensation.

It can be seen from the above that whether it is a direct-drive AC transmission system or a doubly-fed AC transmission system, when the electric energy generated by the wind turbines in the wind farm is integrated into the grid, it is transmitted in the form of alternating current. This method not only has high line cost, poor economy, and short transmission distance; but also when AC power is transmitted, there is a skin effect in the line, the line utilization rate is low, and the loss is high; Changes will cause grid voltage fluctuations; at the same time, SVG needs to be added to the circuit system for reactive power compensation, which increases system costs and losses.

Utility model content

The embodiment of the utility model provides a power transmission system, a wind power generating set and a wind farm, which are used for power transmission in the form of direct current, reduce the cost of the power transmission line and the line loss in the power transmission process, improve the utilization rate of the line, increase Power transmission distance while avoiding the skin effect existing in the line.

In the first aspect, the embodiment of the utility model provides a power transmission system for transmitting the electric energy generated by the wind power generating set to the power grid. The power transmission system includes: a machine-side rectifier module, a grid-side inverter module, a grid-connected module, And the power-taking module, wherein the machine-side rectifier module is used to connect the wind turbine, the machine-side rectifier module, the grid-side inverter module and the grid-connected module are connected in sequence, and the grid-connected module is used to connect to the grid;

The input end of the power-taking module is connected to the grid-side inverter module, and the output end is used to connect to the wind power generating set.

In some embodiments of the first aspect, the power transmission system further includes: a machine-side multi-winding transformer, the primary winding of the machine-side multi-winding transformer is used to connect with the generator of the wind power generating set, and the two The secondary winding is respectively connected to the machine-side rectifier module and the power-taking module.

In some embodiments of the first aspect, the power-taking module includes a multi-winding transformer and a plurality of power units, and the plurality of power units are connected in cascade, and the three-phase AC port of each power unit is respectively connected to a secondary side of the multi-winding transformer The three-phase ports of the windings are connected correspondingly. The primary winding of the multi-winding transformer is connected to a secondary winding of the multi-winding transformer on the machine side. Multiple power units are connected between two DC bus bars, and the DC bus bar is connected to the rectifier module on the machine side. Between the grid-side inverter module.

In some embodiments of the first aspect, each power unit includes a three-phase pulse width modulation (PulseWidth Modulation, PWM) converter, and the three-phase PWM converter includes three inverter bridge arms connected in parallel, and The midpoints of the three inverter bridge arms are respectively correspondingly connected to the three-phase ports of a secondary winding of the multi-winding transformer.

In some embodiments of the first aspect, the power unit further includes a chopper and energy-discharging component connected in parallel with the three-phase PWM converter.

In some embodiments of the first aspect, the chopping and energy-discharging assembly includes: a half-bridge arm connected between the busbars of the power unit, and one end connected to the midpoint of the half-bridge arm, and the other end connected to the positive pole of the power unit The energy-discharging resistor connected to the busbar.

In some embodiments of the first aspect, the machine-side rectification module includes a three-phase rectifier, and the three-phase rectifier includes six rectification bridge arms, and each rectification bridge arm includes a plurality of diodes connected in series, wherein each rectification bridge arm The difference between the sum of the reverse withstand voltage values of multiple diodes included in the diode and the voltage value of the DC bus is greater than a preset voltage threshold, and the DC bus is connected between the machine-side rectifier module and the grid-side inverter module.

In some embodiments of the first aspect, the power transmission system further includes: a DC circuit breaker, connected between the machine-side rectifier module and the grid-side inverter module, for short-circuit protection of the power transmission system; or/and,

The DC smoothing reactor is connected between the rectifier module on the machine side and the inverter module on the grid side, and is used for filtering the direct current output by the rectifier module on the machine side.

In some embodiments of the first aspect, the grid-connected module includes a sequentially connected soft-start switch circuit, a switch assembly, and a grid-side transformer.

In some embodiments of the first aspect, the grid-side inverter module includes a Modular Multilevel Converter (MMC) converter valve.

In the second aspect, the embodiment of the present utility model provides a wind power generating set, and the wind generating set includes the power transmission system provided in the first aspect of the embodiment of the present utility model.

In a third aspect, an embodiment of the present utility model provides a wind farm, and the wind farm includes a plurality of wind power generating sets provided in the second aspect of the present utility model embodiment; or,

The wind farm includes a plurality of wind power generators, bus bars and the power transmission system provided in the first aspect of the embodiment of the present utility model, wherein,

Busbar, connected to each wind turbine;

The power transmission system is connected to the busbar.

The power transmission system, the wind power generating set and the wind farm provided by the embodiment of the utility model, the power transmission system includes: a machine-side rectification module, a grid-side inverter module, a grid-connected module, and a power-taking module, wherein the machine-side rectification module is used for For connecting wind turbines, the rectifier module on the machine side, the inverter module on the grid side and the grid-connected module are connected in sequence. The grid-connected module is used to connect to the grid; generator set.

In the power transmission system provided by the embodiment of the utility model, the grid-side inverter module is connected to the power grid through the grid-connected module, so that the power-taking module can take power from the grid-side inverter module to start the wind turbine. After the wind turbine is started, The electric energy generated by the wind turbine converts AC power into DC power through the machine-side rectifier module, and transmits it to the grid side in the form of DC power. The grid-side inverter module converts DC power into AC power, and then integrates the AC power into the grid through the grid-connected module. In the above process, the electric energy generated by the wind power generating set is transmitted from the machine side to the grid side in the form of direct current. Compared with the transmission in the form of alternating current in the prior art, it can reduce the cost of the transmission line and the line loss in the process of power transmission, and improve Line utilization, increase the power transmission distance, while avoiding the skin effect in the line.

Description of drawings

The utility model can be better understood from the following description of specific embodiments of the utility model in conjunction with the accompanying drawings, wherein the same or similar reference numerals represent the same or similar features.

FIG. 1 is a schematic structural diagram of a circuit topology of a direct drive AC power transmission system in the prior art;

FIG. 2 is a schematic structural diagram of a circuit topology of a doubly-fed AC power transmission system in the prior art;

Fig. 3 is a schematic structural diagram of the circuit topology of the power transmission system provided by the embodiment of the present invention; for the convenience of understanding, a wind power generator is also shown;

4 is a schematic structural diagram of the circuit topology of the power-taking module in the power transmission system provided by the embodiment of the present invention;

Fig. 5 is a schematic structural diagram of the circuit topology of the power unit in the power-taking module provided by the embodiment of the utility model;

6 is a schematic structural diagram of the circuit topology of the machine-side rectifier module in the power transmission system provided by the embodiment of the present invention;

Fig. 7 is a schematic structural diagram of a circuit topology of a wind farm provided by an embodiment of the present invention.

Detailed ways

Features and exemplary embodiments of various aspects of the present invention will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is only to provide a better understanding of the present invention by showing examples of the present invention. The utility model is by no means limited to any specific configuration and algorithm proposed below, but covers any modification, replacement and improvement of elements, components and algorithms without departing from the spirit of the utility model. In the drawings and the following description, well-known structures and techniques are not shown in order to avoid unnecessarily obscuring the present invention.

It should be noted that the machine side mentioned in the embodiment of the utility model refers to the wind turbine side, for example, the machine side rectifier module mentioned in the embodiment of the utility model refers to the rectifier installed on the wind turbine side module. The grid side mentioned in the embodiments of the present utility model refers to the grid side, for example, the grid-side inverter module mentioned in the embodiments of the present utility model refers to the inverter module arranged on the grid side.

The power transmission system, the wind power generating set and the wind farm provided by the embodiment of the utility model will be described in detail below with reference to FIGS. 3 to 7 .

As shown in Figure 3, the power transmission system provided by the embodiment of the utility model is used to transmit the electric energy generated by the wind power generator 30 in the wind power generating set to the power grid 31. The power transmission system includes: machine side rectification module 32, grid side The inverter module 33, the grid-connected module 34, and the power-taking module 35, wherein the machine-side rectifier module 32 is used to connect the wind power generator, and the machine-side rectifier module 32, the grid-side inverter module 33 and the grid-connected module 34 are connected in sequence, The grid-connected module 34 is used to connect to the grid; the input end of the power-taking module 35 is connected to the grid-side inverter module 33 , and the output end is used to connect to the wind power generating set.

Among them, the power-taking module 35 takes power from the grid-side inverter module 33 to start the wind-driven generator 30 in the wind-driven generator set, and the electric energy generated by the wind-driven generator 30 in the wind-driven generator set passes through the machine-side rectifier module 32 and the grid-side inverter. The transformer module 33 and the grid-connected module 34 are transmitted to the grid 31.

During specific implementation, the machine-side rectification module 32 and the power-taking module 35 may be connected to the wind power generator 30 of the wind power generating set through a multi-winding transformer. Specifically, the power transmission system also includes: a machine-side multi-winding transformer 36, the primary winding of the machine-side multi-winding transformer 36 is used to connect with the wind turbine 30 of the wind power generating set, and the two secondary windings of the machine-side multi-winding transformer 36 The side windings are respectively connected to the machine-side rectification module 32 and the power-taking module 35 .

In one embodiment, the power transmission system further includes: a DC circuit breaker 37 connected between the generator-side rectifier module 32 and the grid-side inverter module 33 for short-circuit protection of the power transmission system.

In one embodiment, the power transmission system further includes: a DC smoothing reactor 38 connected between the generator-side rectifier module 32 and the grid-side inverter module 33 for filtering the DC output from the generator-side rectifier module 32 .

In one embodiment, the grid-side inverter module 33 includes an MMC converter valve.

In one embodiment, the grid-connected module 34 includes a soft-start switch circuit 341 , a switch assembly 342 and a grid-side transformer 343 connected in sequence. Wherein, the switch assembly 342 may be a medium voltage circuit breaker.

In practical application, when starting the wind power generating set, the switch assembly 342 in the grid-connected module 34 is closed, and at this time, the power grid 31 transmits power to the wind generating set through the grid-side transformer 343 .

Specifically, since the switch assembly 342 is closed, the grid-side inverter module 33 is connected to the grid 31, and the alternating current in the grid 31 is charged to the grid-side inverter module 33 (or MMC converter valve) through the charging resistor in the soft-start switch circuit 341. When the charging is completed, the switch assembly in the soft start switch circuit 341 is closed, and the AC charging circuit of the charging resistor in the soft start switch circuit 341 is disconnected.

The electric energy stored in the busbar of the grid-side inverter module 33 passes through the DC smoothing reactor 38 and the DC circuit breaker 37, and transmits DC power to the DC busbar. connection line.

The power taking module 35 takes power from the DC bus, and inverts the obtained electric energy into alternating current, and sends power to the wind power generator 30 in the wind power generating set through the power taking winding of the multi-winding transformer 36 on the machine side, so as to meet the requirements of the wind power generator 30. On demand for starting work, the wind turbines 30 in the wind park are started.

After the wind power generator 30 in the wind power generating set starts to work, the 690V AC power generated by the wind power generator 30 is boosted and converted into 35KV AC power. The power winding supplies the AC power of 35KV to the machine-side rectification module 32 .

The generator-side rectifier module 32 converts the 35KV AC power into DC power, and transmits the DC power to the grid-side inverter module 33 through the DC circuit breaker 37 and the DC smoothing reactor 38 in sequence. The grid-side inverter module 33 inverts the DC power into 35KV AC power, and converts the 35KV AC power into 220KV AC power through the grid-side transformer 343, and then merges it into the power grid 31 to realize the conversion of the wind power generated by the wind power generator 30 in the wind power generating set The electrical energy is transmitted to the grid 31 .

During the above-mentioned process of starting the wind turbine 30 in the wind turbine generator set, the power acquisition module 35 needs to acquire power from the DC bus, and convert the acquired electric energy into alternating current, and transfer the power to the The wind turbines 30 in the wind park deliver electricity.

In one implementation, as shown in FIG. 4 , the circuit topology of the power-taking module 35 may include: a multi-winding transformer 351 and multiple power units 352 . Among them, a plurality of power units 352 are connected in cascade, and the three-phase AC port of each power unit 352 is respectively connected to the three-phase port of a secondary winding of the multi-winding transformer 351, and the primary winding of the multi-winding transformer 351 is connected to the machine A secondary winding of the side multi-winding transformer 36 is connected, and multiple power units 352 are connected between two DC buses.

In an example, the multiple power units include M power units, and each power unit 352 includes three electrical ports, which are respectively a DC positive port, a DC negative port, and a three-phase AC port. When connecting multiple power units 352 in cascade, the DC positive port of the first power unit 352 is connected to the DC bus DC+, and the DC negative port of the first power unit 352 is connected to the DC positive port of the second power unit 352; By analogy, the DC positive port of the Mth power unit 352 is connected to the DC negative port of the M-1th power unit 352, and the DC negative port of the Mth power unit 352 is connected to the DC bus DC-.

The three-phase AC ports of the first power unit 352 are respectively connected to the three-phase ports of the first secondary winding of the secondary side of the multi-winding transformer 351; sequentially, the three-phase AC ports of the Mth power unit 352 are respectively connected to the multi-winding The three-phase ports of the Mth secondary winding on the secondary side of the transformer 351 are connected correspondingly; the primary winding of the multi-winding transformer 351 is connected to a secondary winding of the machine-side multi-winding transformer 36 . Wherein, M is a positive integer greater than 1.

In one embodiment, as shown in FIG. 5 , the circuit topology of the power unit 352 may include: a three-phase pulse width modulation PWM converter 3520, which includes three inverters connected in parallel As for the bridge arms, the midpoints of the three inverter bridge arms serve as the three-phase AC ports of the power unit 352 , which are respectively connected to the three-phase ports of a secondary winding of the multi-winding transformer.

The three-phase PWM converter 3520 included in the power unit 352 can invert the direct current in the busbar of the power unit 352 into a three-phase alternating current, which corresponds to the three-phase port of the secondary winding of the corresponding multi-winding transformer 351. The three-phase alternating current in the secondary winding of the multi-winding transformer 351 is rectified into direct current, realizing the bidirectional flow of energy.

In one embodiment, the power unit 352 further includes a chopper and energy removal component 3521 connected in parallel with the three-phase PWM converter 3520 . As shown in FIG. 5 , the chopper and energy removal assembly 3521 includes: a half-bridge arm connected between the busbars of the power unit 352, and a positive busbar with one end connected to the midpoint of the half-bridge arm and the other end connected to the power unit 352 Connected discharge resistor.

The energy unloading and chopping component 3521 can be configured to discharge the energy exceeding the DC bus voltage threshold through the energy unloading resistor in the energy unloading and chopping component 3521 when the DC bus voltage exceeds a preset DC bus voltage threshold. Wherein, the preset DC bus voltage threshold can be freely set according to empirical values.

It should be noted that the half-bridge arm mentioned in the embodiment of the present invention includes two insulated gate bipolar transistors (Insulated Gate Bipolar Transistor, IGBT) connected in series.

In one embodiment, each IGBT included in the bridge arm of the half-bridge may also be connected with an anti-parallel diode.

In one embodiment, the power unit 352 further includes a bus capacitor 3522 and a discharge resistor 3523 connected in parallel with the three-phase PWM converter 3520 . Among them, the busbar capacitor 3522 is used to realize energy storage, and the discharge resistor 3523 is used to realize the discharge of residual electric energy after the wind power generating set stops.

When transmitting the electric energy generated by the wind power generator 30 in the wind power generating set to the grid 31 , the generator-side rectification module 32 is used to convert the 35KV AC power into DC power. The machine-side rectification module 32 may include a three-phase rectifier.

As shown in FIG. 6, the three-phase rectifier includes six rectification bridge arms 321, and each rectification bridge arm includes a plurality of diodes connected in series, wherein the reverse withstand voltage value of the plurality of diodes included in each rectification bridge arm The difference between the sum and the voltage value of the DC bus is greater than the preset voltage threshold. Wherein, the preset voltage threshold can be freely set according to empirical values, for example, the preset voltage threshold is 4500V.

Based on the same concept of the utility model, the embodiment of the utility model also provides a wind power generating set, which includes the power transmission system provided by the above embodiments of the utility model.

The wind power generating set provided by the embodiment of the utility model, because the wind generating set includes the power transmission system provided by the embodiment of the utility model, the electric energy generated by the generator in the wind generating set can be transmitted from the machine side to the grid side in the form of direct current , so as to reduce the cost of the transmission line and the line loss during the power transmission process, improve the line utilization rate, increase the power transmission distance, and avoid the skin effect existing in the line.

Based on the same concept of the utility model, the embodiment of the utility model also provides a wind farm, which includes a plurality of wind power generating sets provided in the above-mentioned embodiments of the utility model.

In the wind farm provided by the embodiment of the present utility model, each wind power generating set includes the power transmission system provided by the embodiment of the present utility model, so that the electric energy generated by each wind generating set in the wind farm can be converted from The machine side is transmitted to the grid side, thereby reducing the cost of the transmission line and the line loss during the power transmission process, improving the line utilization rate, increasing the power transmission distance, and avoiding the skin effect existing in the line.

In addition, the embodiment of the present utility model also provides another wind farm. As shown in FIG. The power transmission system 300 , wherein the busbar 40 is connected to each wind power generator; the power transmission system 300 is connected to the busbar 40 .

Wherein, the wind generator may be a direct-drive AC wind generator or a doubly-fed AC wind generator, which is not limited in the embodiment of the present utility model.

In the wind farm provided by the embodiment of the present utility model, the power transmission system provided by the above-mentioned embodiment of the present utility model is used in the wind farm, so that the electric energy generated by each wind power generator in the wind farm can be transferred from the machine side in the form of direct current Transmission to the grid side, thereby reducing the cost of transmission lines and line loss during power transmission, improving line utilization, increasing power transmission distance, and avoiding the skin effect in the line. At the same time, a confluence bus is used in the wind farm to aggregate the electric energy generated by multiple wind turbines, and after aggregation, centralized transmission is carried out, which effectively saves costs.

Those skilled in the art should understand that the above-mentioned embodiments are illustrative rather than restrictive. Different technical features in different embodiments can be combined to achieve beneficial effects. Those skilled in the art should be able to understand and implement other modified embodiments of the disclosed embodiments on the basis of studying the drawings, specification and claims. In the claims, the term "comprising" does not exclude other means or steps; the indefinite article "a" does not exclude a plurality; the terms "first" and "second" are used to indicate names rather than to indicate any specific Order. Any reference signs in the claims should not be construed as limiting the scope. The functions of several parts appearing in the claims can be realized by a single hardware or software module. The appearance of certain technical features in different dependent claims does not mean that these technical features cannot be combined to obtain beneficial effects.

Claims (11)

1. A power transmission system for transmitting electrical energy generated by a wind power plant to an electrical grid, the power transmission system comprising: the wind power generation system comprises a machine side rectification module, a network side inversion module, a grid-connected module and a power taking module, wherein the machine side rectification module is used for being connected with a wind generating set, the machine side rectification module, the network side inversion module and the grid-connected module are sequentially connected, and the grid-connected module is used for being connected with a power grid;

and the power taking module is used for taking power from the grid side inversion module to start the wind generating set.

2. The system of claim 1, wherein the power transfer system further comprises: and the primary winding of the machine side multi-winding transformer is used for being connected with a generator of the wind generating set, and two secondary windings of the machine side multi-winding transformer are respectively connected with the machine side rectifying module and the electricity taking module.

3. The system of claim 1, wherein the power-taking module comprises a multi-winding transformer and a plurality of power units, the plurality of power units are connected in cascade, a three-phase alternating current port of each power unit is correspondingly connected with a three-phase port of a secondary winding of the multi-winding transformer, a primary winding of the multi-winding transformer is connected with a secondary winding of the machine side multi-winding transformer, the plurality of power units are connected between two direct current buses, and the direct current buses are connected between the machine side rectification module and the grid side inversion module.

4. The system of claim 3, wherein each power unit comprises a three-phase PWM converter, the three-phase PWM converter comprises three inverter bridge arms connected in parallel, and midpoints of the three inverter bridge arms are respectively connected with a three-phase port of a secondary winding of the multi-winding transformer.

5. The system of claim 4, further comprising a chopping and dump assembly in the power unit connected in parallel with the three-phase PWM converter.

6. The system of claim 5, wherein the chopping and de-energizing assembly comprises: the energy-discharging device comprises a half-bridge arm connected between buses of the power unit and an energy-discharging resistor, wherein one end of the energy-discharging resistor is connected to the midpoint of the half-bridge arm, and the other end of the energy-discharging resistor is connected with a positive bus of the power unit.

7. The system according to any one of claims 1-6, wherein the machine side rectification module comprises a three-phase rectifier, the three-phase rectifier comprises six rectification bridge arms, each rectification bridge arm comprises a plurality of diodes connected in series, wherein the sum of the reverse withstand voltage values of the plurality of diodes comprised in each rectification bridge arm is greater than a preset voltage threshold value from the voltage value of a direct current bus connected between the machine side rectification module and the grid side inverter module.

8. The system of any of claims 1-6, wherein the power transmission system further comprises: the direct current breaker is connected between the machine side rectification module and the network side inversion module and is used for carrying out short-circuit protection on the power transmission system; or/and the light source is arranged in the light path,

and the direct current smoothing reactor is connected between the machine side rectification module and the network side inversion module and is used for filtering direct current output by the machine side rectification module.

9. The system according to any of claims 1-6, wherein the grid-side inverter module comprises a modular multi-level MMC converter valve.

10. A wind park according to any of claims 1-9, wherein the wind park comprises a power transmission system according to any of claims 1-9.

11. A wind park, characterized in that it comprises a plurality of wind energy installations according to claim 10; or,

the wind park comprising a plurality of wind generators, a bus bar and a power transmission system according to any one of claims 1-9,

the bus bar is connected with each wind driven generator;

the power transmission system is connected with the bus bar.