WO2021180113A1

WO2021180113A1 - Doubly-fed wind power generation system and power generation method therefor

Info

Publication number: WO2021180113A1
Application number: PCT/CN2021/079933
Authority: WO
Inventors: 张鲁华; 俞庆; 葛昊祥; 马成斌; 储开诚
Original assignee: 上海电气风电集团股份有限公司
Priority date: 2020-03-12
Filing date: 2021-03-10
Publication date: 2021-09-16
Also published as: CN111245020A; CN111245020B

Abstract

Disclosed are a doubly-fed wind power generation system and a power generation method therefor. The doubly-fed wind power generation system comprises a doubly-fed electric motor, a transformer and a current-transforming device, wherein a stator coil of the doubly-fed electric motor is connected to a power grid; a rotor coil of the doubly-fed electric motor is connected to a primary side coil of the transformer; a secondary side coil of the transformer is connected to the power grid by means of the current-transforming device; and the transformer is used for boosting the voltage outputted by the current-transforming device and then supplying the boosted voltage to the rotor coil of the doubly-fed electric motor when the current wind speed is less than a first preset wind speed or when the current wind speed is greater than a second preset wind speed. The present invention can increase the output voltage of a motor-side current transformer, and guarantee effective control of the electric motor by the current transformer at a high rotating speed and a low rotating speed, such that a wind turbine can operate in a wider range of rotating speeds, that is, in a larger space of wind speeds, thereby improving the adaptability of the wind turbine to high wind and low wind working conditions, and improving the utilization rate of the wind turbine.

Description

Double-fed wind power generation system and power generation method

This application claims the priority of the Chinese patent application 202010169124.8 with the filing date of 2020/3/12. This application quotes the full text of the aforementioned Chinese patent application.

Technical field

The invention relates to the field of power electronics and power transmission, in particular to a doubly-fed wind power generation system and a power generation method.

Background technique

Doubly-fed wind power generators are a mainstream model of onshore wind power generation. With its large-scale installation and application, how to increase its wind energy rate has become a research hotspot in the field of doubly-fed wind power generation.

In the prior art, the doubly-fed motor can be connected to the grid, and the voltage required to provide the rotor port of the motor is shown in the following formula:

V _{r_pwm} =|s|*V _ro

Among them, V _{r_pwm} -rotor terminal voltage of doubly-fed motor; s-slip rate; V _ro -rotor open circuit voltage;

The rotor voltage of the doubly-fed motor is _{the product of the open circuit voltage V ro} and the slip rate s. As the slip becomes larger (the absolute value of the slip becomes larger), to maintain the normal operation of the motor, the voltage that needs to be provided to the rotor port of the motor also becomes larger, so it is required at lower wind speeds and ultra-high wind speeds. Provide a higher terminal voltage for the motor rotor port.

When the converter adopts the SVPWM (Space Vector Pulse Width Modulation) control method, the highest line voltage peak value provided by the rotor-side converter for the doubly-fed motor rotor is V _dc , where V _dc is the DC bus voltage.

When the converter adopts SPWM (Pulse Width Modulation) control mode, the highest peak line voltage peak value provided by the rotor-side converter for the rotor of the doubly-fed motor is

It can be seen that the output capacity of the converter is limited by the DC bus voltage. If no other changes are made, if the fan is to run at a higher and lower speed (large slip), it needs to be improved. The DC bus voltage of the converter. However, in practical applications, the DC bus voltage cannot be increased indefinitely. It is restricted by the rating of the power device, and the improvement space is limited. When the wind speed is low or high, the converter cannot provide the required terminal voltage. The fan cannot be connected to the grid.

Summary of the invention

The technical problem to be solved by the present invention is to overcome the shortcomings of the short speed range of grid-connected operation of the doubly-fed machine and the low utilization rate of wind energy in the prior art, and provide a doubly-fed wind power generation system and a power generation method.

The present invention solves the above technical problems through the following technical solutions:

A doubly-fed wind power generation system. The doubly-fed wind power generation system includes a doubly-fed electric machine, a transformer, and a converter;

The stator coil of the doubly-fed motor is connected to the power grid, the rotor coil of the doubly-fed motor is connected to the primary coil of the transformer, and the secondary coil of the transformer is connected to the power grid through the converter device; the original The turns ratio of the side coil and the secondary side coil is k:1, k>1;

The transformer is used for boosting the voltage output by the converter device and supplying it to the doubly-fed motor when the current wind speed is less than a first preset wind speed or when the current wind speed is greater than a second preset wind speed The rotor coil, wherein the second preset wind speed is greater than the first preset wind speed.

Preferably, the turns ratio k is calculated as follows:

Among them, s is the slip rate of the doubly-fed motor corresponding to the first or second preset wind speed, V _ro is the rotor open circuit voltage, V _dc is the DC bus voltage, and k ₀ is the modulation factor. When the converter adopts SVPWM modulation

When using SPWM modulation

Preferably, the converter device includes a rotor-side converter, a DC capacitor, and a grid-side converter, one end of the rotor-side converter is connected to the secondary winding of the transformer, and the rotor-side converter The other end of the grid-side converter is connected to one end of the grid-side converter, and the other end of the grid-side converter is connected to the grid.述DC Capacitor.

Preferably, the doubly-fed wind power generation system includes a first switch module, one end of the first switch module is connected to the secondary winding of the transformer, and the other end of the first switch module is connected to the converter device At one end, the other end of the converter device is connected to the power grid.

Preferably, the doubly-fed wind power generation system includes a second switch module, one end of the second switch module is connected to the rotor coil, and the other end of the second switch module is connected to one end of the converter device.

Preferably, the doubly-fed wind power generation system further includes a wind speed detection module and a control module;

The wind speed detection module is used to detect the current wind speed; the control module is used to control the second switch module to be opened and the first switch module to be closed when the current wind speed is less than the first preset wind speed, The power grid supplies power to the converter device, and the transformer boosts the voltage output by the converter device and supplies it to the rotor coil of the doubly-fed electric machine;

The control module is further configured to control the second switch module to close and the first switch module to open when the current wind speed is not less than the first preset wind speed and not greater than the second preset wind speed , The power grid directly supplies power to the rotor coil of the doubly-fed electric machine through the converter device;

The control module is further configured to control the second switch module to be opened and the first switch module to be closed when the current wind speed is greater than the second preset wind speed, and the power grid to supply power to the converter device , The transformer boosts the voltage output by the converter device and supplies it to the rotor coil of the doubly-fed machine.

A doubly-fed wind power generation method based on the aforementioned doubly-fed wind power generation system;

The doubly-fed wind power generation method includes:

Detect current wind speed;

If the current wind speed is less than the first preset wind speed, the second switch module is controlled to open and the first switch module is closed, the power grid supplies power to the converter device, and the transformer connects the The voltage output by the converter device is boosted and supplied to the rotor coil of the doubly-fed motor;

If the current wind speed is not less than the first preset wind speed and not greater than the second preset wind speed, the second switch module is controlled to be closed and the first switch module is disconnected, and the power grid passes through the The converter device directly supplies power to the rotor coil of the doubly-fed motor;

If the current wind speed is greater than the second preset wind speed, the second switch module is controlled to open and the first switch module is closed, the power grid supplies power to the converter device, and the transformer connects the The voltage output by the converter is boosted and then supplied to the rotor coil of the doubly-fed machine.

The positive progress effect of the present invention is that the doubly-fed wind power generation system provided by the present invention connects the stator coil of the doubly-fed motor to the grid, and the rotor coil of the doubly-fed motor is connected to the primary coil of the transformer. The secondary winding of the converter is connected to the grid through the converter device; when the transformer is switched into operation, the voltage output capacity of the machine-side port of the converter device can be improved, and the converter can effectively control the generator and make the wind turbine It can be connected to the grid to generate electricity in a wider speed range, increasing the power generation capacity of the wind turbine.

Description of the drawings

Fig. 1 is a schematic structural diagram of a doubly-fed wind power generation system according to Embodiment 1 of the present invention.

Fig. 2 is a schematic structural diagram of a doubly-fed wind power generation system according to Embodiment 2 of the present invention.

Detailed ways

The present invention will be further described by way of examples below, but the present invention is not limited to the scope of the described examples.

Example 1

The first embodiment provides a doubly-fed wind power generation system. As shown in FIG. 1, a doubly-fed wind power generation system includes a doubly-fed wind power generation system 1, a transformer 2, and a converter 3;

The stator coil of the doubly-fed motor 1 is connected to the power grid, the rotor coil of the doubly-fed motor 1 is connected to the primary coil of the transformer 2, and the secondary coil of the transformer 2 is connected to the power grid through the converter 3 Connection; the turns ratio of the primary coil and the secondary coil is k:1, k>1;

The transformer 2 is used for boosting the voltage output by the converter device 3 and supplying the double-feedback when the current wind speed is less than a first preset wind speed or when the current wind speed is greater than a second preset wind speed The rotor coil of the motor 1, wherein the second preset wind speed is greater than the first preset wind speed.

Specifically, the first preset wind speed may be the cut-in wind speed of the grid-connected operation of the doubly-fed motor 1. When the unit is operating at a wind speed lower than the cut-in wind speed, the wind turbine is in a sub-synchronous operation state. The second preset wind speed may be the cut-out wind speed of the grid-connected operation of the doubly-fed motor 1. When the unit is operating at a wind speed higher than the cut-out wind speed, the wind turbine is in a super-synchronous operation state.

Preferably, the turns ratio k is calculated as follows:

Among them, s is the slip rate of the doubly-fed motor corresponding to the first or second preset wind speed, V _ro is the open-circuit voltage of the rotor, Vdc is the DC bus voltage, and k0 is the modulation factor. When the converter adopts SVPWM modulation

When using SPWM modulation

In this embodiment, after the transformer 2 is added, the terminal voltage output capability of the converter device 3 can be increased to kV _dc . When the fan speed is higher or lower, the absolute value of the slip rate s is larger. At this time, the rotor voltage V _{r_pwm} required by the motor rotor is higher. After the terminal voltage output capacity of the converter device 3 is improved, it can be Provide a higher voltage for the motor rotor to complete the effective control of the motor by the converter device 3. It can be seen from the foregoing formula that the turns ratio of the coil is determined by the DC bus voltage V _dc , the rotor open circuit voltage V _ro , and the slip rate s. Under the condition of hardware limitation, the turns ratio of the transformer coil can be determined according to the slip rate of the motor operation expected by the user.

Preferably, the transformer 2 may be a conventional power transformer, or a voltage conversion device formed by other technologies (such as a solid-state transformer, a power electronic conversion circuit, etc.).

Preferably, the converter device 3 may include a rotor-side converter 31, a DC capacitor 32, and a grid-side converter 33. One end of the rotor-side converter 31 is connected to the secondary winding of the transformer 2, so The other end of the rotor-side converter 31 is connected to one end of the grid-side converter 33, the other end of the grid-side converter 33 is connected to the grid, and the rotor-side converter 31 and the grid-side converter The DC capacitor 32 is provided on the DC bus between the converters.

In a specific application scenario, for example, when the energy flow direction is from the grid side to the rotor side, the grid-side converter 33 realizes the rectification function, that is, the AC-DC conversion process, and the DC capacitor 32 is used to realize the DC voltage. After the establishment of, the rotor-side converter 31 realizes the function of inversion, that is, the DC-AC conversion process, and then supplies the AC to the rotor coil.

In another specific application scenario, for example, when the energy flow direction is from the rotor side to the grid side, the rotor-side converter 31 realizes the rectification function, that is, the AC-DC conversion process, and the DC capacitor 32 is used to realize With the establishment of the DC voltage, the grid-side converter 33 realizes the function of inversion, that is, the DC-AC conversion process, and then supplies the AC to the grid.

The doubly-fed wind power generation system provided by this embodiment can effectively improve the voltage output capability of the converter's machine-side port, ensure the converter's ability to control the motor, and enable the wind turbine to be connected to the grid within a wide range of grid-connected speeds. The power generation operation ensures the normal power generation of the wind turbine at a lower or higher wind speed, and improves the utilization rate of wind energy.

Example 2

This embodiment 2 provides a doubly-fed wind power generation system, which is a further improvement on the basis of embodiment 1. As shown in FIG. 2, the doubly-fed wind power generation system may further include a first switch module 4, so One end of the first switch module 4 is connected to the secondary coil of the transformer 2, the other end of the first switch module 4 is connected to one end of the converter device 3, and the other end of the converter device 3 is connected to the Power grid.

Further, the doubly-fed wind power generation system may further include a second switch module 5, one end of the second switch module 5 is connected to the rotor coil, and the other end of the second switch module 5 is connected to the converter device 3. One end.

Further, the doubly-fed wind power generation system further includes a wind speed detection module 6 and a control module 7;

Preferably, the wind speed detection module 6 may be an anemometer.

The wind speed detection module 6 is used to detect the current wind speed; the control module 7 is used to control the second switch module 5 to turn off and the first switch when the current wind speed is less than the first preset wind speed The module 4 is closed, the power grid supplies power to the converter device 3, and the transformer 2 boosts the voltage output by the converter device 3 and supplies it to the rotor coil of the doubly-fed motor 1;

The control module 7 is further configured to control the second switch module 5 to be closed and the first switch module 5 when the current wind speed is not less than the first preset wind speed and not greater than the second preset wind speed 4 is disconnected, the power grid directly supplies power to the rotor coil of the doubly-fed electric machine 1 through the converter 3;

The control module 7 is also used to control the second switch module 5 to be turned off and the first switch module 4 to be turned on when the current wind speed is greater than the second preset wind speed, and the power grid changes to the The current device 3 supplies power, and the transformer 2 boosts the voltage output by the converter device 3 and supplies it to the rotor coil of the doubly-fed motor 1.

The operating principle of the doubly-fed wind power generation system is as follows:

The doubly-fed wind power generation method includes:

Detect current wind speed;

If the current wind speed is less than the first preset wind speed, control the second switch module 4 to open and the first switch module 4 to close, the power grid supplies power to the converter device 3, and the transformer 2 Boost the voltage output by the converter device 3 and supply it to the rotor coil of the doubly-fed motor 1;

If the current wind speed is not less than the first preset wind speed and not greater than the second preset wind speed, the second switch module 5 is controlled to be closed and the first switch module 4 is disconnected, and the power grid passes The converter device 3 directly supplies power to the rotor coil of the doubly-fed motor 1;

If the current wind speed is greater than the second preset wind speed, control the second switch module 5 to open and the first switch module 4 to close, the power grid supplies power to the converter device 3, and the transformer 2 The voltage output by the converter device 3 is boosted and then supplied to the rotor coil of the doubly-fed motor 1.

In a non-limiting specific application scenario, for example, the synchronous speed of a doubly-fed motor 1 is n=1500r/min (revolutions/min), the DC bus voltage V _dc ＝1050V, the rotor open circuit voltage V _ro ＝2700V, When the transformer 2 is not used, the lowest grid-connected running speed n _min and the highest grid-connected running speed n _{max of the} doubly-fed motor 1 can be calculated by the following formula:

When the power generation device and method proposed in this invention are used, a step-up transformer 2 with a step-up ratio k=1.3 is connected in series between the rotor of the doubly-fed generator and the rotor-side converter 31,

Then the lowest grid-connected running speed n _min and the highest grid-connected running speed n _{max of} the doubly-fed motor 1 can be calculated by the following formula:

It can be seen that after the addition of the transformer, the speed range of grid-connected operation of the doubly-fed motor 1 has been effectively expanded, so that the wind turbine can still be connected to the grid for power generation at low and high wind speeds, which effectively improves the utilization rate of the wind turbine. .

When the doubly-fed wind power generation system provided in this embodiment is in operation, through the cooperation of the first switch module 4 and the second switch module 5, the transformer 2 can be flexibly connected, which further enhances the wind turbine’s ability to respond to changes in wind speed, and Increased power generation efficiency.

Although the specific embodiments of the present invention are described above, those skilled in the art should understand that these are only examples, and various changes or modifications can be made to these embodiments without departing from the principle and essence of the present invention. Revise. Therefore, the protection scope of the present invention is defined by the appended claims.

Claims

A doubly-fed wind power generation system is characterized in that the doubly-fed wind power generation system includes a doubly-fed electric machine, a transformer, and a converter;

The stator coil of the doubly-fed motor is connected to the power grid, the rotor coil of the doubly-fed motor is connected to the primary coil of the transformer, and the secondary coil of the transformer is connected to the power grid through the converter device; the original The turns ratio of the side coil and the secondary side coil is k:1, k>1;

The transformer is used for boosting the voltage output by the converter device and supplying it to the doubly-fed motor when the current wind speed is less than a first preset wind speed or when the current wind speed is greater than a second preset wind speed The rotor coil, wherein the second preset wind speed is greater than the first preset wind speed.
The doubly-fed wind power generation system according to claim 1, wherein the turns ratio k is calculated in the following manner:

Among them, s is the slip rate of the doubly-fed motor corresponding to the first or second preset wind speed, V ro is the open-circuit voltage of the rotor, V dc is the DC bus voltage, and k 0 is the modulation factor; when the converter adopts SVPWM modulation
When using SPWM modulation
The doubly-fed wind power generation system according to at least one of claims 1-2, wherein the converter device comprises a rotor-side converter, a DC capacitor, and a grid-side converter, and the rotor-side converter One end of the transformer is connected to the secondary winding of the transformer, the other end of the rotor-side converter is connected to one end of the grid-side converter, the other end of the grid-side converter is connected to the grid, and the rotor The DC capacitor is arranged on the DC bus between the side converter and the power grid converter.
The doubly-fed wind power generation system according to at least one of claims 1-3, wherein the doubly-fed wind power generation system comprises a first switch module, and one end of the first switch module is connected to the auxiliary transformer of the transformer. Side coil, the other end of the first switch module is connected to one end of the converter device, and the other end of the converter device is connected to the power grid.
The doubly-fed wind power generation system of claim 4, wherein the doubly-fed wind power generation system comprises a second switch module, one end of the second switch module is connected to the rotor coil, and the second switch module The other end of is connected to one end of the converter device.
The doubly-fed wind power generation system of claim 5, wherein the doubly-fed wind power generation system further comprises a wind speed detection module and a control module;

The wind speed detection module is used to detect the current wind speed; the control module is used to control the second switch module to open and the first switch module to close when the current wind speed is less than the first preset wind speed, The power grid supplies power to the converter device, and the transformer boosts the voltage output by the converter device and supplies it to the rotor coil of the doubly-fed electric machine;

The control module is further configured to control the second switch module to close and the first switch module to open when the current wind speed is not less than the first preset wind speed and not greater than the second preset wind speed , The power grid directly supplies power to the rotor coil of the doubly-fed electric machine through the converter device;

The control module is further configured to control the second switch module to be opened and the first switch module to be closed when the current wind speed is greater than the second preset wind speed, and the power grid to supply power to the converter device , The transformer boosts the voltage output by the converter device and supplies it to the rotor coil of the doubly-fed machine.
A doubly-fed wind power generation method, characterized in that the doubly-fed wind power generation method is based on the doubly-fed wind power generation system according to at least one of the preceding claims 5-6;

The doubly-fed wind power generation method includes:

Detect current wind speed;

If the current wind speed is less than the first preset wind speed, the second switch module is controlled to open and the first switch module is closed, the power grid supplies power to the converter device, and the transformer connects the The voltage output by the converter device is boosted and supplied to the rotor coil of the doubly-fed motor;

If the current wind speed is not less than the first preset wind speed and not greater than the second preset wind speed, the second switch module is controlled to be closed and the first switch module is disconnected, and the power grid passes through the The converter device directly supplies power to the rotor coil of the doubly-fed motor;

If the current wind speed is greater than the second preset wind speed, the second switch module is controlled to open and the first switch module is closed, the power grid supplies power to the converter device, and the transformer connects the The voltage output by the converter is boosted and then supplied to the rotor coil of the doubly-fed machine.