WO2014051175A1

WO2014051175A1 - Device and method for low voltage ride-through of wind power generator

Info

Publication number: WO2014051175A1
Application number: PCT/KR2012/007825
Authority: WO
Inventors: 강정욱; 채재훈; 정태훈
Original assignee: 주식회사 메가베스
Priority date: 2012-09-27
Filing date: 2012-09-27
Publication date: 2014-04-03

Abstract

The present invention relates to a device and a method for the low voltage ride-through of the systems of a wind power generator, wherein the low voltage ride-through of a wind power generator can be readily carried out using a bidirectional power conversion system and an energy storage system, and improvement in the quality of the wind power generation can be promoted. That is, the present invention is to provide an economical and efficient low voltage-ride through a device resolving the low voltage ride-through of systems by using the discharge capacity of the energy storage system with respect to a new wind power generator (plant) and the existing wind power generator (plant), wherein an energy storage system including a bidirectional power conversion system for charging or discharging electricity generated from a wind power generator connected to the system is provided and operated so as to meet the low voltage ride-through (LVRT) function required for the wind power generator (plant) when a low voltage below a predetermined level is generated in the system and maximize the electricity quality produced from the wind power generation.

Description

Low voltage receiving operation device and method of wind power generator

The present invention relates to a low voltage accommodating operation apparatus and method of a wind power generator, and more particularly, a system low voltage accommodating operation of a wind power generator using a bidirectional power converter and an energy storage device can be easily performed, and to improve wind power generation quality. The present invention relates to a low voltage accommodating driving apparatus and method of a wind power generator.

As is well known, demand for renewable energy is steadily increasing due to the depletion of fossil fuels and global warming. Among them, the installed capacity of wind power is increasing rapidly in the world. The amount of power consumed also means a sharp increase.

However, nature does not supply what humans want, as much as they want, when humans want it, and the amount of power changes rapidly according to the change of nature, which adversely affects the entire power system.

In addition, the increasing share of wind power in the power system requires not only to stop power generation from disturbing the system, but also to cooperate with the system. Code is being legislated.

In particular, the low voltage acceptance operation (LVRT) maintains the connected state without disconnecting the wind power generation from the grid within a predetermined time even when a momentary low voltage condition occurs in the grid, and at a point when the system recovers from the instantaneous low voltage status. It is to send power to the system to perform an operation that contributes to the system recovery.

More specifically, referring to FIG. 1 illustrating the low voltage acceptance operation (LVRT) function required for a wind power generator (small) when an instantaneous low voltage of a system occurs, the low voltage acceptance operation function includes a system voltage of a system at which an instantaneous low voltage of the system is in a steady state. It is the ability to operate for 0.625 seconds up to the% level and maintain the grid connection status when the steady state grid voltage recovers more than 90% for up to 3 seconds.

Conventional known low voltage operation (LVRT) methods use Operation at reduced speed / load, variable dc buses and use of derated converters to operate at high currents. with more variable dc bus and higher currents, Additional capacitors on the dc bus, Active crowbar, Energy discharge, and the torque value applied to the generator Changing methods have been applied, and these methods basically use wind turbines to reduce the amount of power generated or consume the generated energy through loads such as resistors.

However, the conventional low voltage accommodation operation method has a very complicated structure due to the method of responding without stopping the wind generator fundamentally, there is a problem that requires a mechanical or electrical modification for the existing wind turbine. .

In addition, as a conventional low voltage accommodating operation method, a method of sending only a part of the generated energy to the system without stopping the wind power generator and storing the rest in the energy storage device (ESS) may be applied. Because of the need to fit the wind power generation capacity, there is a cost and technical limitations, such as eventually to increase the capacity of the energy storage (ESS).

On the other hand, in the wind power generator using a double excitation generator, the current controller gain value according to the wind turbine inductance conversion before and after the grid connection plays an important role for stable grid input.

Wind generators using the Double Fed Induction Generation (DFIG) control the stator voltage by controlling the rotor current, and the controlled stator voltage is linked to the grid.

As soon as the wind turbine is connected to the grid, the internal parameter values of the generator will fluctuate. This may affect the current controller gain value of the MSC (Machine Side Converter) based on the generator parameters before the grid is energized, resulting in unstable current control. In addition, the current control of the MSC side is unstable as the current control of the rotor becomes unstable due to Low Voltage Ride Through (LVRT) generated by the grid. This can cause equipment burnout.

For reference, the cause of the low voltage acceptance operation (LVRT) is caused by a ground fault in the system and a sudden voltage drop of the system.

As shown in the accompanying FIG. 7, the wind generator using the double-fed induction generation (DFIG) has an output terminal of the wind generator connected to a grid connected to TR.

At this time, if an abnormality occurs in the system and a sudden voltage drop occurs, the stator voltage of the DFIG generator drops sharply, and the wind speed of the rotor increases to make the stator voltage normal. As a result, surplus energy is generated, which leads to an increase in voltage of the MSC and the DC-link stage.

Therefore, additional control methods for processing surplus energy are required, and a method of reducing generator output by controlling torque of a generator according to a grid voltage is disclosed in Korean Patent Laid-Open Publication No. 10-2009-53009 (2009.05.27). In addition, a method for solving the problem by using an active croebar of the DC-link stage is disclosed in Korean Patent Laid-Open Publication No. 10-2008-90006 (2008.10.08).

However, the method of reducing the generator output by controlling the torque of the generator may be the most effective method of reducing the generator output through the pitch control, but the physical response of the pitch to a short low voltage of several hundreds [ms], such as low voltage acceptance operation The disadvantage is that it is too slow.

In addition, the method using the active crowbar should be capable of sufficient energy control to control the surplus energy generated by the crowbar, but there is a problem that the power control semiconductor is burned out due to the energy control limit.

The present invention has been studied in view of the above-mentioned problems in the prior art, the generation of the wind power generator when a low voltage below a certain level in the system stops the power generation at the same time using the power converter and energy storage device (ESS) toward the system It is an object of the present invention to provide an apparatus and method for low voltage acceptance operation of a wind power generator (small) that can satisfy the low voltage acceptance operation (LVRT) regulation required for a wind power generator (small) in a system by supplying it.

Another object of the present invention is to charge and discharge wind energy by using a power converter (PCS) and an energy storage device (ESS) even in a low voltage acceptance operation (LVRT) situation in which there is no low voltage generation below a certain level in the system. By allowing the control to be made, it is possible to mitigate the output fluctuation of the wind power generation, and to contribute to the improvement of wind power quality by supplying reactive power required by the wind power generation.

Wind turbine driving apparatus according to an embodiment of the present invention for achieving the above object is a system for low voltage acceptance operation, the blade is mounted on a rotatable shaft to produce rotational energy from the wind; A generator for generating electric power from the rotational energy of the blades; A power converter for converting the electric power produced by the generator into electric power of a form suitable for supplying a system connected to the wind turbine; A power converter including a DC / DC or an AC / DC bidirectional converter depending on the installation position to randomly charge and discharge the power of the energy storage device; An energy storage device connected to the power converter to supply power to the system when the voltage of the system falls below a predetermined level; Characterized in that configured to include.

Wind turbine driving method according to an embodiment of the present invention for achieving the above object is for the low voltage acceptance operation of the system, when the voltage of the system falls below a certain level, the first generation of the wind turbine at the first point Discontinuing operation and simultaneously applying power supply from the energy storage system to the grid; Preparing power supply from the energy storage device to the system from the first time point to a second time point at which the voltage of the system starts to rise; Starting to supply power from the energy storage device to the system until a third time point, when the voltage of the system is normally restored; Monitoring whether the voltage of the system has returned to a normal state and restarting the wind generator if it is determined that the voltage of the system has returned to the normal state; Supplying power from the energy storage system to the grid until a fourth time point when the output of the wind power generator reaches a normal level; Characterized in that it comprises a.

Wind turbine driving apparatus according to another embodiment of the present invention for achieving the above object is a system for low voltage acceptance operation, the blade is mounted on a rotating shaft to produce rotational energy from the wind, and to generate power from the rotational energy of the blade A wind turbine generator comprising a generator and a power converter for converting the power produced by the generator into a power suitable for supplying the grid, the main switch is installed between the power converter and the grid of the wind turbine, The first energy storage device is connected between the converter and the main switch by the first switch, and the second energy storage device is connected by the second switch between the main switch and the grid.

Wind generator operation method according to another embodiment of the present invention for achieving the above object is for the low voltage acceptance operation of the system, when the voltage of the system falls below a predetermined size, the opening of the main switch installed between the system and the wind turbine and Simultaneously stopping the power generation operation of the wind turbine; The second switch is turned on so that power of the second energy storage device is supplied to the grid during the low voltage receiving operation period; When the grid voltage reaches a steady state, maintaining the first switch on to restart the wind power generator and supplying reactive power from the first energy storage device to the wind power generator; Turning on the main switch and turning off the second switch when the output of the wind power generator reaches a normal level; When the voltage of the system is stabilized and completely turned off from the wind turbine stage to the first switch, the first energy storage device and the second energy storage device may implement an operation for stabilizing power quality.

Through the above problem solving means, the present invention provides the following effects.

According to the present invention, when a low voltage below a certain level occurs in a system in which a wind generator (small) is connected, power generation of the wind generator is stopped, and power is supplied using an energy storage device (ESS) including a power converter (PCS). By supplying to the side, the system can satisfy the low voltage acceptance operation (LVRT) function required for the wind generator (small).

In addition, the energy storage device (ESS) including the power conversion device (PCS) according to the present invention has the advantage that can be applied to the existing wind turbine as well as a new wind generator.

In particular, the present invention can greatly reduce the capacity of the energy storage device (ESS) because it utilizes the discharge capacity of the energy storage device (ESS).

1 is a diagram illustrating a low voltage acceptance operation (LVRT) function required for a wind power generator (small) when a momentary low voltage is generated in a system.

2 is a block diagram illustrating an example of installing an energy storage device (ESS) including a power conversion device (PCS) according to an embodiment of the present invention as a separate device between a wind generator and a grid;

3 is a block diagram of installing an energy storage device (ESS) including a power conversion device (PCS) according to an embodiment of the present invention inside a power converter included in a wind turbine;

4 is a detailed view of a wind turbine including an energy storage device (ESS) including a power conversion device (PCS) according to an embodiment of the present invention;

5 is a graph for explaining a method of discharging power to a grid in an energy storage device including a power conversion device (PCS) according to an embodiment of the present invention;

6 is a flowchart of a method in which a power converter (PCS) receives a command to supply power to a system through an energy storage device according to an embodiment of the present invention;

7 is a schematic view showing a wind power generator using a double excitation method,

8 is a schematic view showing an example of a low voltage accommodating driving device of a wind turbine according to another embodiment of the present invention;

FIG. 9 is a view illustrating an operation of a first switch B1 and a second switch B2 according to an opening of a main switch and a first time with respect to a time axis of the low voltage accommodating and operating device of a wind power generator according to another embodiment of the present invention. And charge and discharge characteristics of the second energy storage devices ESS-1 and ESS-2.

10 is a flowchart illustrating a low voltage acceptance driving method according to another embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Low voltage acceptance operation (LVRT) method of the wind power generator according to the present invention is based on the existing concept that the wind power generator or wind power plant maintains the power generation state for a certain period of time while maintaining a system linkage when a low voltage below a certain level occurs in the system. Rather than focusing on the system, if the system generates a low voltage below a certain level, the grid connection is maintained but the wind turbine is stopped and the system is powered by using an energy storage device (ESS) instead of the wind power generation. The main focus is on meeting the needs.

In addition, the present invention is to provide a system low-voltage receiving operation apparatus that can be applied to the existing wind turbine (small), as well as a new wind generator (small), generated in the wind generator (small) connected to the grid An energy storage device including a two-way power conversion system (PCS) that can charge and discharge electricity is installed between the system and the wind power plant. Another point is to meet the requirements of Low Voltage Ride Through (LVRT), which is required for the system, and to maximize the power quality from wind power generation.

To this end, as shown in the block diagram of the accompanying FIG. 4, the system low voltage acceptance operation apparatus of the wind turbine according to an embodiment of the present invention includes a blade 12 mounted on a rotatable shaft and producing rotational energy from the wind; The generator 14 generates electric power from the rotational energy of the blade 12 and converts the electric power produced by the generator 14 into a power suitable for supplying the system 30 connected to the wind turbine 10. A power converter 16 (PCS: Power Conversion System) including a DC / DC or AC / DC bidirectional converter depending on the installation position to randomly charge and discharge electric power to the energy storage device, It is configured to include an energy storage device 20 (ESS: Energy Storage System) connected to the power converter 22.

The generator 14 generates electric power from the rotational energy of the blade 12, and the generated electric power is in the form of AC, but is not suitable to be directly supplied to the system, so that the power converter 16 generates the generator 14. The power produced by is converted into a power of a form suitable for supplying the system 30 associated with the wind turbine (10).

That is, the power converter 16 is an AC / DC converter 24 for converting the AC power produced by the generator 14 to DC, as shown in the accompanying FIG. DC / AC inverter 26 to convert to appropriate AC power.

In addition, the power converter 16 is not included in the fixed speed type (Fixed Speed Type) according to the characteristics of the wind generator, and corresponds to about 30% of the capacity of the wind generator in the double-fed induction generation (DFIG) Only the power converter capacity is connected to the rotor, and the direct drive method (WRSG: Wound Rotor Synchronous Generator & PMSG: Permanent Magnetic Synchronous Generator) includes power converter capacity capable of handling 100% of the wind turbine capacity.

The power conversion system 22 (PCS: Power Conversion System) includes a DC / DC or AC / DC bi-directional converter depending on the installation location to randomly charge and discharge power to the energy storage device (20).

This bi-directional power conversion system (PCS) is an energy storage device to perform a low voltage acceptance operation (LVRT) function when the power generation of the wind turbine (small) is stopped due to the low voltage state below the predetermined level. A command for supplying power to the system 30 from 20 is received, and control is performed to properly supply power from the energy storage device 20 to the system.

That is, as will be described later, the power conversion system 22 (PCS: Power Conversion System) is authorized to supply power stored in the energy storage device 20 to the system at a first point when the voltage of the system drops below a predetermined size. The power supply is prepared until the second time point at which the system voltage starts to rise, and the power from the energy storage device 20 until the third time point at which the system voltage starts to rise and is restored to a normal state. Start supplying to increase the supply power, and the power of the energy storage device 20 until the fourth time point when the wind turbine 10 is restarted and normally restored after the voltage of the system returns to the normal state. 30) will continue to supply.

In this case, the energy storage device 20 (ESS: Energy Storage System) including the power conversion system 22 (PCS: Power Conversion System) is provided as a separate individual device as shown in Figure 2, excluding the power converter, It may be installed between the wind generator 10 and the system 30.

In other words, when the energy storage device 20 having the power conversion device 22 is combined in the existing power converter, since the retrofitting work and the cost thereof are very expensive, the power conversion device 22 without the retrofitting work is required. It is preferable to directly connect the energy storage device 20 between the power converter 16 and the system 30.

Alternatively, the energy storage system 20 (ESS: Energy Storage System) including the power conversion system 22 (PCS: Power Conversion System) is a power converter 16 included in the wind generator 10, as shown in FIG. Can be installed inside of.

That is, when the energy storage device 20 having the power converter 22 is installed in a new wind turbine, the energy storage device 20 having the power converter 22 is directly combined with the power converter 16. It is installed together with the power converter, the power conversion device 22 output terminal is the AC / DC converter 24 of the power converter 16 in the state that the energy storage device 20 is connected to the input terminal of the power converter 22 Connected between the DC / AC inverters 26.

In addition, when a function of a power converter is added to each DC terminal of the AC / DC converter 24 and the DC / AC inverter 26 in the power converter 16, the power converter 16 without a separate power converter is included. Only the energy storage device 20 may be connected between the AC / DC converter 24 and the DC / AC inverter 26 of the power source, and only the energy storage device may implement a system low voltage acceptance operation of the wind power generator according to the present invention. .

On the other hand, the energy storage device 20 should always store more than a certain level of energy in order to respond to the low-voltage acceptance operation (LVRT) requirements of the system at any time, and additionally the quality of wind power generation through the charge and discharge control of wind energy It is desirable to calculate the overall dose, taking into account the improvement target levels.

In addition, the energy storage device 20 itself includes a battery management system (BMS: Battery Management System) which is a kind of control means for safety management, temperature management, state of charge (SOC) management, communication functions, etc. Connected.

Preferably, the energy storage device 20 is adopted to have a high discharge capacity to supply power to the system side through the discharge within a quick time, lithium ion battery (Li-ion), lithium iron phosphate battery (LiFePO ₄ ), Lithium Manganese Oxide Battery (LiMn ₂ O ₄ ), Lithium Cobalt Oxide Battery (Lithum Cobalt Oxide), Lithium Polymer Battery (Li-ion Polymer), Lithium Air Battery, Ni-MH Battery, Nickel One or more of cadmium batteries (Ni-Cd), NaS batteries and supercapacitors can be used.

Here, a low voltage acceptance operation method based on the above-described system low voltage acceptance operation apparatus of the present invention, that is, a low voltage acceptance operation method performed by applying a command to supply power from the energy storage device to the system to the power conversion apparatus will be described below. Same as

6 is a flowchart illustrating a method according to a preferred embodiment of the present invention for applying a command to supply power to a system from an energy storage device, and FIG. 5 to supply power to the system from an energy storage device. LVRT reference diagram for explaining how to apply a command to the power converter and reference diagram showing the amount of energy discharge.

Once the system is in a steady state other than a low voltage condition below a certain level, the power converter (PCS) frequently issues a command to charge and discharge energy to the energy storage device in order to perform the wind quality stabilization task that has already been granted in addition to the LVRT function. Receive and perform.

In the normal state of the system, a step (S101) of continuously monitoring whether the voltage of the system falls below a predetermined size to determine whether a low voltage situation occurs in the system is performed.

In order to facilitate understanding of the present invention, a time point at which the voltage of the system falls below a predetermined magnitude will be referred to as a first time point.

When the voltage of the system 30 falls below a predetermined size, the wind power generation is stopped according to the wind generator stop algorithm (S102), and at the same time, the discharge of the energy storage device 20 is applied (S103).

In other words, the power converter 22 is discharged and starts to prepare for supply of power from the energy storage device 20 to the grid 30.

More specifically, referring to FIG. 5 comparing the change in the system voltage and the discharge amount of the energy storage device, the time when the voltage of the system 30 falls below a predetermined magnitude, that is, the first time point corresponds to t0. It can be seen that, at this t0, the voltage of the system has dropped to Va. Accordingly, the power converter 22 can supply power from the energy storage device 20 to the system 30 while monitoring the voltage state of the system 30. Get ready.

Thus, as a command is applied to the power converter 22 to supply power from the energy storage device 20 to the system 30, a preparation process for supplying power from the energy storage device 20 to the system 30. As shown in FIG. 5, power supply preparation from the energy storage device to the system must be completed until t1, which is a point in time when the voltage of the system rises (hereinafter, referred to as a second time point).

Next, the step of continuously monitoring whether the voltage of the system 30 starts to rise (S104).

As a result of the monitoring, when the voltage of the system 30 starts to rise, power supply is started from the energy storage device 20 to the system 30, and as shown in FIG. 5, the time point at which the voltage of the system is normally restored (third time point) The amount of discharge of the energy storage device, that is, the amount of power supply supplied from the energy storage device 20 to the system 30 up to t2, is increased (S105).

In this case, when the voltage of the system 30 reaches a somewhat lower voltage Vb level when the steady state before the low voltage is 100%, it is determined that the voltage of the system 30 is restored to the normal state.

Therefore, in the interval between the second time point t1 and the third time point t2, the grid voltage sampling is periodically repeated for a predetermined time. Through this, a slope for recovering the grid voltage is obtained and is proportional to the slope. The discharge amount is increased, and the time to reach the third time point t2 can be predicted to be used for preparing the wind power generator (small).

As described above, the discharge of the energy storage device 20 is continued to monitor whether the voltage of the system 30 returns to the normal state (S106), and when it is determined that the voltage of the system 30 returns to the normal state, the wind power generator 10 ) Is restarted (S107).

In addition, the wind power generator 10 is restarted, and the energy storage device until the output according to the wind power generation reaches a normal level, that is, to the point (normally referred to as the fourth time point) at which power is normally supplied to the system ( Power supply to the system 30 is continued in 20) (S108).

At this time, when the continuous power supply from the energy storage device 20 to the system 30 is made, it is preferable to maintain the power value supplied to the system at a level similar to the power value generated by the wind turbine 10 is restarted, The reason is the imbalance between the value discharged from the energy storage device 20 and the power value supplied from the wind turbine 10 at the moment when the voltage of the system is restored normally and the wind turbine 10 restarts to produce and supply power. This is to alleviate the impact caused.

As shown in FIG. 6, the third time point t2 to the fourth time point t3 are the time taken for the wind power generator 10 to restart to produce power normally, wherein the third time point t2 to the fourth time point ( Since the energy storage device 20 discharges a lot of power in the section between t3), narrowing the range between the sections is effective to reduce the capacity of the energy storage device and also consumes invalidity when the wind turbine is restarted. Power can be supplied from the energy storage device.

Finally, it is determined whether the wind power generator 10 is restarted to produce and supply power normally (S109), and when the power is normally produced and supplied, the discharge of the energy storage device 20, that is, the power supply of the energy storage device 20. In response to the step (S110), the low voltage acceptance operation (LVRT) corresponding to the end is terminated.

As such, according to an embodiment of the present invention, when a low voltage of a predetermined level or less occurs in a system in which a wind generator is linked, the power generation operation of the wind generator is stopped, and the energy storage device 20 including the power converter 22 (PCS). By supplying power to the grid using ESS, it is possible to fully satisfy the low-voltage receiving operation (LVRT) function required for the wind generator (small) in the grid, and also to utilize the discharge capacity of the energy storage system (ESS). ESS capacity can be significantly reduced.

In particular, in the case of the present invention by using the energy storage device 20 having a good instantaneous discharge capacity, it is possible to supply power to the system side through a large amount of discharge in a short time, the capacity of the energy storage device 20 Can be further reduced.

Hereinafter, a low voltage accommodating driving apparatus and method of a wind power generator according to another embodiment of the present invention will be described.

The low voltage accommodating operation apparatus of a wind power generator according to another embodiment of the present invention has an emphasis on solving the low voltage accommodating operation using an energy storage system (ESS) having an interlock structure.

Referring to FIG. 8, which shows a low voltage accommodating and operating device of a wind turbine according to another embodiment of the present invention, an interlock switch (switch) having an interlock structure between the power converter 16 and the grid 30 of the wind turbine 10. The dual energy storage device is connected by.

That is, the main switch A1 is installed between the power converter 16 and the grid 30 of the wind power generator 10, and the first energy storage device ESS-1 between the power converter 16 and the main switch A1. ) Is connected by the first switch (B1), the second energy storage device (ESS-2) is connected by the second switch (B2) between the main switch (A1) and the system (30).

The main switch A1, the first switch B1, and the second switch B2 are arranged in an interlock structure with each other.

In this state, when an abnormality occurs in the grid and a sudden voltage drop occurs, the main switch A1 is turned off, and the first switch B1 is connected to the wind turbine stage, and the second switch B2 is It is connected to the grid stage independently.

Here, a description will be given with reference to FIGS. 9 and 10 attached to a low voltage acceptance operation method of a wind power generator according to another embodiment of the present invention.

9 illustrates the operation of the first switch B1 and the second switch B2 according to the opening of the main switch, and the charge / discharge characteristics of the first and second energy storage devices ESS-1 and ESS-2 with respect to the time axis. 10 is a flowchart illustrating a low voltage accommodation driving method according to another embodiment of the present invention.

First, in order to determine whether a low voltage situation has occurred in the system 30, a step (S201) of continuously monitoring whether the voltage of the system falls below a predetermined size is performed.

When the voltage of the grid 30 falls below a predetermined size, the main switch A1 installed between the grid and the wind turbine is opened (off) (S202).

At the same time, in the state in which the main switch A1 is opened, the second energy storage device ESS-2 connected to the grid terminal by the second switch B2 has discharge characteristics, so that the main switch A1 is discharged. The second energy storage device (ESS-2) becomes a virtual wind power generator to supply power to the grid during the low voltage receiving operation period in order to appear that there is no deviation of the wind turbine on the grid due to the opening.

That is, while the main switch A1 is open, the power from the second energy storage device ESS-2 is supplied to the system during the low voltage receiving operation period through the second switch B2 in the ON state. (S204).

According to the present invention, when the wind generator 10 is restarted after the abnormality caused by the instantaneous voltage drop on the system 30 is solved, the first energy storage device ESS-1 in the ON state of the first switch B1 is turned on. ) To supply the reactive power required to restart the wind power generator 10, and if the wind generator 10 is normally operated, the main switch (A1) is turned on to properly connect the wind generator 10 and the grid (30) (ON).

At this time, the first switch B1 is kept on and the second switch B2 is sequentially opened to continuously charge and discharge the first and second energy storage devices ESS-1 and ESS-2. Will be made.

That is, by monitoring whether the voltage of the system 30 starts to rise (S205), even if it is determined that the system voltage starts to rise, the first energy storage device ESS-1 enters a discharge standby state (S206). The discharge is continued from the energy storage device ESS-2 to the system 30 (S207).

Next, by monitoring whether the voltage of the system 30 has reached the steady state (S208), if it is determined that the steady state has been reached, the main switch A1 is turned on and at the same time, the first switch B1 is kept on. At the same time, the second switch B2 is turned off.

Therefore, when the wind generator 10 is restarted after the abnormality due to the instantaneous voltage drop on the system 30 is solved, the first energy storage device ESS-1 is turned on in the state where the first switch B1 is turned on. Discharge is supplied to the generator 10 by the reactive power required for restart (S209), and at the same time the discharge of the second energy supply device (ESS-2) is continued (S210) and the voltage of the system 30 is stabilized When the wind power generator 10 is normally operated by the reactive power (S211), the main switch A1 is turned on (ON) in order to normally connect the wind power generator 10 and the system 30 (S212).

At this time, the voltage of the system 30 is maintained in a stable state, and after a predetermined time elapses, the main switch A1 is turned on (ON) and the second switch B2 is opened (off), thereby providing the wind generator 10. By forcibly linking the grid in a state in which the system and the system 30 are not synchronized, instantaneous reverse algae occur. In this case, the first energy storage device ESS-1, which continuously charges, serves as a buffer. After a predetermined time, only the wind turbine 10 is connected to the system 30 to supply power.

That is, as the main switch A1 is turned on and the second switch B2 is turned off, the wind turbine 10 and the grid 30 are instantaneously linked, so that the power of the grid 30 is transferred to the wind turbine 10. The reverse algae flowing to the bar is generated, and the reverse algae is buffered in the first energy storage device ESS-1.

On the other hand, even if the wind direction and the wind speed for generating the wind power generator 10 is not maintained at the desired level, the main switch A1 is kept on in the state in which the wind power generator 10 and the system 30 are connected to each other. By turning on the first switch B1 to supply a certain level of reactive power from the first energy storage device ESS-1 to the wind turbine, it is possible to improve the power generation efficiency of the wind turbine 10.

As described above, according to another embodiment of the present invention, through the switching control of the main switch (A1) and the first and second switches (B1, B2) when a low voltage below a certain level in the system in which the wind generator (small) is connected, By charging and discharging the first and second energy storage devices ESS-1 and ESS-2, the low voltage acceptance operation (LVRT) function required for the wind generator (small) in the system can be sufficiently satisfied, and After the low voltage acceptance operation (LVRT) is completed, the energy storage devices can be used for improving the power quality.

[Description of the code]

10: wind power generator

12: blade

14: Generator

16: power converter

20: energy storage device

22: power converter

24: AC / DC converter

26 DC / AC Inverter

30: system

A1: main switch

B1; First switch

B2: second switch

C1: third switch

ESS-1: First Energy Storage Device

ESS-2: Second Energy Storage Device

Claims

The blade 12 mounted on the rotating shaft to generate rotational energy from the wind, the generator 14 to generate electric power from the rotational energy of the blade 12, and the electric power produced by the generator 14 to supply the system 30 In the low-voltage receiving operation apparatus of the wind power generator including the power converter 16 or the power converter 16 for converting into a power of a suitable form below,
An energy storage device 20 having a power conversion device 22 is installed between the generator 14 and the system 30, and in order to randomly charge and discharge the power of the energy storage device, DC / DC or AC / DC bidirectionally. A power converter 22 including a converter is connected between the generator 14 and the grid 30, and when the voltage of the grid 30 is lowered below a predetermined level to the power converter 22, Low voltage receiving operation device of the wind turbine, characterized in that by connecting the energy storage device 20 for supplying power to the system 30 after the operation stops.
The method according to claim 1,
An energy storage device 20 having the power converter 22 is connected between the AC / DC converter 24 and the DC / AC inverter 26 of the power converter 16. Driving device.
The method according to claim 2,
When the function of the power converter is added to each DC terminal of the AC / DC converter 24 and the DC / AC inverter 26 in the power converter 16, the AC / DC converter 24 of the power converter 16 is added. Low voltage accommodating operation device of the wind turbine, characterized in that only the energy storage device 20 is connected between the) and the DC / AC inverter (26).
The method according to claim 1,
When the energy storage device 20 having the power converter 22 is installed in an existing wind turbine installation, the power converter 22 is connected to the power converter 22 while the energy storage device 20 is connected. Low voltage receiving operation apparatus of the wind turbine, characterized in that is connected between the power converter 16 and the grid (30).
The method according to any one of claims 1 to 3,
The energy storage device 20 is adopted as an energy storage device having excellent discharge capability, lithium ion battery (Li-ion), lithium iron phosphate battery (LiFePO 4 ), lithium manganese oxide battery (LiMn 2 O 4 ), Lithium cobalt oxide battery (Lithum Cobalt Oxide), lithium polymer battery (Li-ion Polymer), lithium air battery, nickel-hydrogen battery (Ni-MH), nickel cadmium battery (Ni-Cd), NaS battery and supercapacitor Low voltage receiving operation device of a wind turbine, characterized in that any one or more adopted.
When the voltage of the system 30 falls below a predetermined level, the power supply from the energy storage device 20 to the system 30 is applied while stopping the power generation operation of the wind power generator 10 at the first time of the first drop. Becoming a step;
Preparing power supply from the energy storage device 20 to the system 30 from the first time point to a second time point when the voltage of the system 30 starts to rise;
Starting power supply from the energy storage device 20 to the system 30 until the third time point at which the voltage of the system 30 starts to rise and is normally restored;
Monitoring whether the voltage of the system 30 has returned to the normal state, and restarting the wind turbine 10 if it is determined that the voltage of the system 30 has returned to the normal state;
Supplying power from the energy storage device 20 to the system 30 until a fourth time point at which the output according to the power generation of the wind power generator 10 reaches a normal level;
Low voltage acceptance operation method of the wind turbine comprising a.
The method according to claim 6,
Low voltage acceptance operation method of the wind power generator, characterized in that the power supply from the energy storage device 20 to the system 30 starts at a first point when the voltage of the system drops below a certain level.
The blade 12 mounted on the rotating shaft to generate rotational energy from the wind, the generator 14 to generate electric power from the rotational energy of the blade 12, and the electric power produced by the generator 14 to supply the system 30 In the low-voltage receiving operation apparatus of the wind power generator including the power converter 16 or the power converter 16 for converting into a power of a suitable form below,
Between the power converter 16 and the system 30 of the wind turbine 10 is installed a main switch (A1) that is opened when the voltage of the system 30 falls below a certain level, the operation of the wind generator 10 The first switch B1 connects the first energy storage device ESS-1 between the power converter 16 and the main switch A1 so as to supply reactive power when it is restarted after stopping. A second energy storage device ESS-2 for supplying power to the system 30 when the voltage of the system 30 falls below a predetermined level between the system 30 and the system 30 by the second switch B2. Low voltage receiving operation device of the wind power generator, characterized in that by connecting.
The method according to claim 8,
The first and second energy storage devices ESS-1 and ESS-2 are adopted as energy storage devices having excellent discharge capability, and are lithium ion batteries (Li-ion) and lithium iron phosphate batteries (LiFePO 4). ), Lithium manganese oxide battery (LiMn 2 O 4 ), lithium cobalt oxide battery (Lithum Cobalt Oxide), lithium polymer battery (Li-ion Polymer), lithium air battery, nickel hydrogen battery (Ni-MH), nickel cadmium battery ( Ni-Cd), NaS battery and supercapacitor, the low voltage acceptance operation device characterized in that the adoption of any one or more.
When the voltage of the grid 30 falls below a predetermined size, the main switch A1 installed between the grid 30 and the wind turbine 10 is opened, and the wind turbine stops generating power;
The second switch B2 is turned ON to supply the power of the second energy storage device ESS-2 to the system 30 during the low voltage receiving operation period;
When the voltage of the grid 30 reaches the normal state, the first switch B1 is kept in the on state to restart the wind power generator so that the reactive power for restarting the wind power generator is the first energy storage device ESS-1. Supplying to the wind turbine generator 10;
Turning on the main switch A1 and turning off the second switch B2 when the output of the wind power generator reaches a normal level;
When the voltage of the grid 30 is stabilized, the first switch B1 is turned off from the wind turbine end;
Low voltage receiving operation method of the wind power generator comprising a.
The method according to claim 10,
When the main switch A1 is turned on and the second switch B2 is turned off, and the wind turbine 10 and the grid 30 are instantaneously connected, the power of the grid 30 is transferred to the wind turbine 10. Low voltage receiving operation method of the wind power generator, characterized in that for buffering the reverse current flowing in the first energy storage device (ESS-1).
The method according to claim 10,
If the wind direction and wind speed for generating the wind power generator 10 are not maintained at a desired level, the first energy storage device is turned on by turning on the first switch B1 in a state in which the wind power generator 10 is connected to the grid 30. Low voltage acceptance operation method of the wind turbine, characterized in that a predetermined level of reactive power is supplied from the (ESS-1) to the wind turbine (10).