KR20240016054A - Frequency Smoothing Control Method of Wind Turbine with a Small Capacity - Google Patents

Abstract

The disclosed embodiment includes measuring the grid frequency of the power system and determining whether the power system is an over-frequency section or an under-frequency section according to the frequency deviation calculated as the difference between the system frequency and the reference frequency, and determining whether the wind power generator is in a specified maximum frequency section according to the rotor speed. Setting a stall suppression section in each of the over-frequency section and under-frequency section according to the stall margin set so that stall control is not performed at the rotor speed, and smoothing the frequency of the wind generator in response to the frequency deviation before the rotor speed reaches the set stall suppression section. The power deviation to maximum tracking control ratio, which represents the ratio between the power deviation weighted by the control gain that adjusts and the maximum power point tracking control value according to the maximum power point tracking control technique, gradually converges to 0, so that the wind power generator is in the stall suppression section. Including the step of adjusting the control gain to be controlled according to the maximum power point tracking control technique without frequency smoothing, the method can improve the energy absorption ability while preventing the small capacity wind turbine from entering the stall control region in the overfrequency section. and provides a frequency smoothing control method to improve energy dissipation ability without reaching the lowest rotor speed.

Description

Frequency Smoothing Control Method of Wind Turbine with a Small Capacity}

The disclosed embodiments relate to active power control of small-capacity wind power generators, and in a power system to which small-capacity wind power generators are linked, small-capacity wind power generators can be adjusted to adjust the output of small-capacity wind power generators according to frequency changes to contribute to frequency smoothing of the power system. This relates to a frequency smoothing control method for a generator.

Wind power generation is a facility in which blades extract the kinetic energy of the wind to produce electricity, and its output fluctuates as the wind speed fluctuates. In most cases, wind power generators are connected to the power system to supply power.

In the power system, the load continuously fluctuates even during normal times, and the system frequency fluctuates accordingly. The power system operator uses a control device called Automatic Generation Control (AGC) to adjust the frequency fluctuation within a certain range. Using this, a signal is generated and output to adjust the output of the synchronous generator operating in the system. By adjusting the output of the synchronous generator according to the frequency, the frequency is controlled within a certain range.

When a wind power generator is connected to the power system, the frequency of the power system continuously fluctuates due to output fluctuations due to continuous changes in wind speed. In particular, in power systems with a high acceptance rate of wind power generation, when wind speed continuously fluctuates, it is difficult to maintain the frequency in a narrow range when wind power generation performs Maximum Power Point Tracking (MPPT) control. . In this case, more reserve power is needed to maintain a narrow range of frequency fluctuations than the current amount, which increases the operating costs of the power system and causes an increase in electricity bills.

To suppress this problem, a frequency smoothing control technique was proposed to control active power so that the frequency fluctuation range for fluctuating wind speed is alleviated. In the frequency smoothing control technique, the frequency is smoothed by adding or subtracting the output power deviation (ΔP) according to the frequency deviation (Δf) to the maximum power point tracking control value (P _MPPT ), which varies according to the maximum power point tracking control technique. At this time, if the control gain of the output power deviation (ΔP) according to the frequency deviation (Δf) is fixed, the energy absorption and emission capabilities are limited. Therefore, frequency smoothing performance can be improved by using a variable control gain method in which the gain weighted to the frequency deviation (Δf) is variable.

1 and 2 are diagrams for explaining an existing frequency smoothing technique.

In the conventional frequency smoothing technique using variable control gain, as shown in FIG. 1, when the rotor speed is below a certain value (here, 0.9 pu as an example), the output power deviation (ΔP) is compared to While the power deviation to maximum tracking control ratio (ΔP/P _MPPT ), which represents the ratio of the maximum power point tracking control value (P _MPPT ), is proportional to the rotor rotation speed, maximum tracking control is performed when the rotor rotation speed is above a certain value. Adjust the control gain (Gain) so that the ratio (ΔP/P _MPPT ) remains uniform.

This control method using variable control gain can prevent excessive energy emission from wind turbines in the under-frequency section (UFS) because the control gain is set to 0 at the minimum rotor rotation speed (ω _min ). You can. However, because the control gain is used in the same way not only in the low-frequency section but also in the over-frequency section (OFS), kinetic energy absorption is limited in the over-frequency section, which limits frequency control performance.

In order to improve the performance limitations of this over-frequency section, a bivalent control gain method was proposed that divides the over-frequency section and the low-frequency section and uses separate control gains. Figure 3 shows the maximum tracking in the bivalent control gain method. It shows the control ratio (ΔP/P _MPPT ).

However, the bivalent control gain method of FIG. 3 is a large-capacity system that can increase the pitch angle by controlling the pitch of the blades when the rotor rotation speed in the overfrequency section is greater than the maximum rotor speed (ω _max here, for example, 1 p.u.) It is suitable for MW class wind power generators. However, small-capacity wind power generators of tens of KW cannot control the pitch angle due to their structure, so when the rotor speed reaches the maximum rotor speed (ω _max ), the operation of the wind power generator is stopped using stall control. Therefore, in the case of small-capacity wind power generators, the rotor speed must be controlled in advance to prevent it from reaching the maximum rotor speed when performing frequency smoothing control, making it difficult to apply the existing bivalent control gain method as is.

Korea Registered Patent No. 10-21976435 (registered on December 24, 2020)

The purpose of the disclosed embodiments is to provide a frequency smoothing control method that can improve energy absorption ability while preventing a small-capacity wind power generator from entering the stall control region in an overfrequency section.

The purpose of the disclosed embodiments is to provide a frequency smoothing control method that can improve energy dissipation ability while preventing a small-capacity wind turbine from reaching the lowest rotor speed in a low-frequency section.

The frequency smoothing control method according to an embodiment is a method performed by a computing device having one or more processors and a memory that stores one or more programs executed by the one or more processors, and measures the system frequency of the power system to measure the system frequency of the power system. Determining whether the power system is an over-frequency section or an under-frequency section according to a frequency deviation calculated as the difference between the frequency and the reference frequency; Setting a stall suppression section in each of the over-frequency section and the low-frequency section according to a stall margin set so that the wind power generator is not stall controlled at a specified maximum rotor speed depending on the rotor speed; And before the rotor speed reaches the set stall suppression section, the power deviation in which the control gain for adjusting the frequency smoothing of the wind power generator is added to the frequency deviation and the maximum power point tracking control value according to the maximum power point tracking control technique. A step of adjusting the control gain so that the power deviation to maximum tracking control ratio, which represents the ratio between, gradually converges to 0, and the wind generator is controlled according to the maximum power point tracking control technique without frequency smoothing in the stall suppression section. Includes.

The step of setting the stall suppression section includes dividing the overfrequency section from a minimum rotor speed (ω _min ) based on the rotor speed (ω _r ) to a maximum margin rotor speed (ω _max -b) specified by the stall margin. ) to the smoothing section (ω _min < ω _r ≤ ω _max -b) and the section from the maximum margin rotor speed (ω _max -b) to the maximum rotor speed (ω _max ) to the stall suppression section (ω _max -b). < ω _r ≤ ω _max ) can be set separately.

In the step of adjusting the control gain, the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) has a maximum value at the minimum rotor speed (ω _min ) of the smoothing section and gradually decreases to reach the maximum margin rotor. The control gain can be adjusted to be 0 at speed (ω _max -b).

The step of adjusting the control gain is to determine the control gain (Gain _ofs ) in the smoothing section of the overfrequency section according to the rotor speed (ω _r ).

(where f _nom is the reference frequency, k is the proportionality constant for maximum power point tracking (MPPT) starting of the wind power generator, and a is the power deviation for rotor speed (ω _r ) in the overfrequency section to the maximum tracking control ratio (ΔP /P _MPPT ) can be adjusted with a constant proportional to the rate of change.

In the step of setting the stall suppression section, the output power of the wind generator suddenly changes due to the stall control margin (b) at the minimum rotor speed (ω _min ) based on the rotor speed (ω _r ) in the low-frequency section. In order to prevent this, the maximum output section (ω _min < ω _r ≤ ω _max -c) and the maximum output control speed (ω) up to the maximum output control speed (ω _max -c) specified by the set maximum output control margin (c) _max -c) to the maximum margin rotor speed (ω _max -b) specified by the stall margin (ω _max -c < ω _r ≤ ω _max - b) and the maximum margin rotor speed (ω _max The section from -b) to the maximum rotor speed (ω _max ) can be set by dividing it into a stall suppression section (ω _max -b < ω _r ≤ ω _max ).

In the step of adjusting the control gain, the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) is 0 at the minimum rotor speed (ω _min ), increases in the maximum output section, and gradually decreases in the output attenuation section. The control gain can be adjusted to be 0 at the maximum margin rotor speed (ω _max -b).

In the step of adjusting the control gain, the control gain (Gain _ufs ) in the maximum output section of the low frequency section is calculated according to the rotor speed (ω _r ).

(where f _nom is the reference frequency, k is the proportionality constant for maximum power point tracking (MPPT) starting of the wind generator, and d is the maximum tracking control ratio (ΔP/P _MPPT ) to the rotor speed (ω _r ) in the low-frequency section. It can be adjusted with a constant proportional to the rate of change.

In the step of adjusting the control gain, the control gain (Gain _ufs ) in the output attenuation section of the low frequency section is calculated according to the rotor speed (ω _r ).

It can be adjusted.

The step of adjusting the control gain can be adjusted so that the control gain (Gain _ofs ) is maintained at 0 in the stall suppression period.

The frequency smoothing control method further includes the step of smoothing the frequency of the small-capacity wind power generator according to the control gain, and the smoothing of the frequency includes weighting the control gain to the frequency deviation (Δf) to output power deviation ( ΔP) is calculated, and the output power deviation is subtracted from the maximum power point tracking control value (P _MPPT ), which represents the maximum power point that can be output at the rotor speed (ω _r ) according to the maximum power point tracking control technique. A power reference value (P _ref ) is obtained, and the power output from the small-capacity wind power generator can be adjusted according to the active power reference value (P _ref ).

Therefore, the frequency smoothing control method according to the embodiment can improve the energy absorption ability while preventing the small-capacity wind power generator from entering the stall control region in the over-frequency section, and improve the energy emission ability while preventing the small-capacity wind power generator from reaching the minimum rotor speed. By doing so, additional costs for frequency smoothing can be reduced by not using a separate energy storage device, and the operating costs of the power system can be reduced by reducing the additional reserve power that synchronous generators must have for frequency control.

1 and 2 are diagrams for explaining an existing frequency smoothing technique.
Figure 3 shows a frequency smoothing system for a small-capacity wind power generator according to an embodiment.
FIG. 4 shows an example of the detailed configuration of the control gain generation module of FIG. 3.
Figure 5 shows changes in the power deviation required in the overfrequency section versus the maximum tracking control ratio and control gain according to an embodiment.
Figure 6 shows changes in power deviation required in a low frequency section versus maximum tracking control ratio and control gain according to an embodiment.
Figure 7 shows an example of input wind speed applied to a small-capacity wind power generator.
Figure 8 shows an example of measuring grid frequency.
Figures 9 and 10 show the results of comparing rotor speeds according to the frequency smoothing control device of the embodiment.
Figure 11 shows a frequency smoothing control method according to an embodiment.
FIG. 12 is a diagram for explaining a computing environment including a computing device according to an embodiment.

Hereinafter, specific embodiments of one embodiment will be described with reference to the drawings. The detailed description below is provided to provide a comprehensive understanding of the methods, devices and/or systems described herein. However, this is only an example and the present invention is not limited thereto.

In describing one embodiment, if it is determined that a detailed description of the known technology related to the present invention may unnecessarily obscure the gist of an embodiment, the detailed description will be omitted. In addition, the terms described below are terms defined in consideration of functions in the present invention, and may vary depending on the intention or custom of the user or operator. Therefore, the definition should be made based on the contents throughout this specification. The terminology used in the detailed description is intended to describe only one embodiment and should in no way be limiting. Unless explicitly stated otherwise, singular forms include plural meanings. In this description, expressions such as “comprising” or “comprising” are intended to indicate certain features, numbers, steps, operations, elements, parts or combinations thereof, and one or more than those described. It should not be construed to exclude the existence or possibility of any other characteristic, number, step, operation, element, or part or combination thereof. In addition, terms such as "... unit", "... unit", "module", and "block" used in the specification refer to a unit that processes at least one function or operation, which is hardware, software, or hardware. and software.

Figure 3 shows a frequency smoothing system for a small-capacity wind power generator according to an embodiment.

Referring to FIG. 3, the frequency smoothing system according to the embodiment includes a maximum power point tracking control module 11, a frequency smoothing module 12, an active power reference value acquisition module 15, a converter control module 16, and a control gain generation. It may include a module 17.

The maximum power point tracking control module 11 receives the rotor speed (ω _r ) and represents the maximum power point that can be output at the applied rotor speed (ω _r ) according to the maximum power point tracking (MPPT). Outputs the power point tracking control value (P _MPPT ). The maximum power point tracking control module 11 obtains a maximum power point tracking control value (P _MPPT ) that allows the maximum possible power to be output regardless of the grid frequency. Therefore, the power production efficiency of the wind power generator can be maximized, but it causes fluctuations in the grid frequency.

The maximum power point tracking control value (P _MPPT ) can be obtained according to Equation 1.

Here, k is the proportionality constant for maximum power point tracking (MPPT) starting of the small-capacity wind power generator.

The frequency smoothing module 12 prevents the wind power generator from producing power with a large fluctuation range according to the maximum power point tracking control value (P _MPPT ) obtained from the maximum power point tracking control module 11, and the system frequency (f _sys ) Obtain the output power deviation (ΔP) to compensate so that the change is minimal.

The frequency smoothing module 12 may include a frequency deviation output module 13 and a gain weighting module 14. The frequency deviation output module 13 is a frequency representing the difference between the system frequency (f _sys ) and the reference frequency (f _nom ) so that the measured system frequency (f _sys ) can be smoothed by following the reference frequency (f _nom ). Obtain and output the deviation (Δf = f _sys - f _nom ).

However, when the frequency smoothing module 12 performs smoothing considering only the frequency deviation (Δf), the frequency smoothing performance is low due to limited energy absorption and emission capabilities, as described above. In other words, frequency smoothing cannot be performed quickly.

Accordingly, the frequency smoothing module 12 further includes a gain weighting module 14 to improve smoothing performance. The gain weighting module 14 obtains the output power deviation (ΔP = Gain * Δf) by weighting the control gain (Gain) to the frequency deviation (Δf), so that the grid frequency (f _sys ) increases the reference frequency (f _nom ) more quickly. Make it possible to follow.

At this time, the control gain (Gain) is not specified as a fixed value but is varied by the control gain generation module 17. The gain weighting module 14 may vary the control gain (Gain) in response to the gain control signal (GC) applied from the control gain generation module 17. The gain weighting module 14 may be implemented as a proportional controller, for example.

The active power reference value acquisition module 15 subtracts the output power deviation (ΔP) from the maximum power point tracking control value (P _MPPT ) to obtain the active power reference value (P _ref = P), which is the standard for the power produced by the wind generator to follow. Obtain _MPPT - ΔP). The converter control module 16 converts the power produced by the small-capacity wind power generator into grid power according to the obtained active power reference value (P _ref ) and outputs it.

The control gain generation module 17 receives the rotor speed (ω _r ) and based on the pre-specified minimum rotor speed (ω _min ) and maximum rotor speed (ω _max ) and user-specified values (a, b, c). determine the control gain (Gain), and transfer the determined control gain (Gain) to the gain weighting module 14. The gain weighting module 14 weights the determined control gain (Gain) to the frequency deviation (Δf) to output power. Output the deviation (ΔP).

Control gain generation module 17 operates as a frequency smoothing control device in the embodiment.

As mentioned above, the output power deviation (ΔP = Gain * Δf) is changed by the control gain (Gain) for the frequency deviation (Δf), so the frequency smoothing performance of the small-capacity wind power generator is determined by the control gain (Gain). It can be seen as For example, if the control gain (Gain) has a value of 0, the output power deviation (ΔP) becomes 0, and the active power reference value (P _ref = P _MPPT - ΔP) is equal to the maximum power point tracking control value (P _MPPT ). becomes the same. In this case, the wind generator does not perform frequency smoothing and therefore operates under maximum power point tracking (MPPT) control.

Therefore, the control gain generation module 17 adjusts the control gain (Gain) to perform frequency smoothing. At this time, the control gain (Gain) can be determined to be variable so that the small-capacity wind power generator can operate stably in both the over-frequency section and the low-frequency section. In the embodiment, the control gain generation module 17 also uses a control gain method that uses separate control gains by dividing it into an over-frequency section and a low-frequency section, but can be applied to a large-capacity wind power generator capable of controlling the pitch of the blade. 2 Unlike the technique in , the control gain is determined by varying the control gain to be suitable for small-capacity wind power generators using the stall control method.

FIG. 4 shows an example of the detailed configuration of the control gain generation module of FIG. 3, FIG. 5 shows changes in the maximum tracking control ratio and control gain required in the overfrequency section according to the embodiment, and FIG. 6 shows the change in the control gain according to the embodiment. Accordingly, it shows the change in the maximum tracking control ratio and control gain required in the low frequency section.

Referring to FIG. 4, the control gain generation module 17 may include an interval setting module 21, an interval determination module 22, and a gain control module 23.

The section setting module 21 is used to prevent stalls from occurring when the rotor speed (ω _r ) reaches the maximum rotor speed (ω _max ) through smoothing while improving the energy absorption ability of the small-capacity wind power generator in the over-frequency section. While an overfrequency smoothing section is set, a low-frequency smoothing section is set to improve energy dissipation ability while ensuring stable operation in the low-frequency section.

The section setting module 21 obtains and stores the minimum rotor speed (ω _min ) and maximum rotor speed (ω _max ) specified when manufacturing a small-capacity wind power generator. Here, as an example, it is assumed that the minimum rotor speed (ω _min ) is 0.5pu and the maximum rotor speed (ω _max ) is 1p.u. In addition, user-specified values (a, b, c, d) for setting the over-frequency smoothing section and the low-frequency smoothing section can be received and stored together.

Here, a and d are the rate of change of the maximum tracking control ratio (ΔP/P _MPPT ) to the power deviation for the rotor speed (ω _r ) in the over-frequency section and the low-frequency section, respectively, and are values specified by the user depending on the small-capacity wind power generator. . And b is the stall margin to prevent the small-capacity wind power generator from stopping operation due to stall control, and c is the maximum output control margin to ensure that the small-capacity wind power generator can maximize energy emission performance while maintaining a stable state.

Figure 5 (a) shows the required power deviation versus maximum tracking in the overfrequency section in which the system frequency (f _sys ) measured according to an embodiment is greater than the reference frequency (f _nom ) and the frequency deviation (Δf) has a positive value. It represents the control ratio (ΔP/P _MPPT ).

If the frequency deviation (Δf) has a positive value, the active power reference value (P _ref ) has a positive value. Since the output power deviation (ΔP) is subtracted from the maximum power point tracking control value (P _MPPT ), the rotor speed (ω _r ) should be increased so that the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) should gradually decrease.

That is, in the overfrequency section, the wind power generator produces power when the rotor speed (ω _r ) is above the minimum rotor speed (ω _min ), but it can produce power lower than the power according to the maximum power point tracking control value (P _MPPT ). There must be. Therefore, when performing frequency smoothing, the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) has a maximum value at the minimum rotor speed (ω _min ), as shown in (a) of Figure 5, and the rotor speed ( As ω _r ) increases, it should gradually decrease. In this case, the rotor speed (ω _r ) further increases due to the absorbed energy. However, in small-capacity wind power generators, if the rotor speed (ω _r ) exceeds 1 p.u., which is the maximum rotor speed (ω _max ), stall is controlled and the operation is stopped.

Therefore, in order to prevent a small-capacity wind power generator from stopping operation due to stall control, frequency smoothing must be suppressed as much as possible before the rotor speed (ω _r ) reaches the maximum rotor speed (ω _max ) to reduce the absorbed energy. For this purpose, the section setting module 21 may set the stall control margin b (here, 0.1 as an example) in the embodiment.

The stall control margin (b) prevents excessive frequency smoothing by ensuring that the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) becomes zero before the rotor speed (ω _r ) reaches the maximum rotor speed (ω _max ). This is the rotor speed margin to prevent it from performing. That is, in the embodiment, when the rotor speed (ω _r ) reaches the maximum margin rotor speed (ω _max -b) obtained by subtracting the stall control margin (b) from the maximum rotor speed (ω _max ), the power deviation vs. maximum tracking The control gain (Gain) must be determined so that the control ratio (ΔP/P _MPPT ) is 0.

Meanwhile, (a) of FIG. 6 shows the required power deviation vs. maximum tracking in a low-frequency section where the system frequency (f _sys ) measured according to an embodiment is smaller than the reference frequency (f _nom ) and the frequency deviation (Δf) has a negative value. It represents the control ratio (ΔP/P _MPPT ).

If the frequency deviation (Δf) has a negative value, the output power deviation (ΔP) also has a negative value, and the active power reference value (P _ref ) is the value of the output power deviation (ΔP) from the maximum power point tracking control value (P _MPPT ). The absolute value is obtained by adding. Therefore, the rotor speed (ω _r ) must be rapidly reduced so that the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) is rapidly reduced.

However, even in the low-frequency section, the wind power generator produces power if the rotor speed (ω _r ) is higher than the minimum rotor speed (ω _min ), but it must produce power higher than the power according to the maximum power point tracking control value (P _MPPT ). . In other words, it must be able to produce large amounts of power quickly. At this time, at the minimum rotor speed (ω _min ), the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) is set to 0 to prevent over-decleration (OD), and the rotor speed (ω _r ) is set to 0. As it decreases, the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) should gradually decrease. However, even in the low-frequency section, in a small-capacity wind power generator, the rotor speed (ω _r ) should not exceed the maximum rotor speed (ω _max ), so the stall control margin (b) is set, and the section setting module 21 is set to The maximum output control margin (c) can be further set so that the power deviation to maximum tracking control ratio (ΔP/P _MPPT ), which increases with speed (ω _r ), does not change rapidly due to the stall control margin (b).

The section determination module 22 determines the rate of change (a, d) of the maximum tracking control ratio (ΔP/P _MPPT ) to the power deviation for the rotor speed (ω _r ) set in the section setting module 21, and the stall control margin (b). ) and the maximum output control margin (c) to determine the section according to the current rotor speed (ω _r ). The section determination module 22 first determines the over-frequency section and the under-frequency section according to the sign of the frequency deviation (Δf). If it is a low-frequency section, the rotor speed (ω _r ) increases from the minimum rotor speed (ω _min ) to the maximum number of times. Is the maximum output section (ω _min < ω _r ≤ ω _max -c) between the maximum output control speed (ω _max -c) obtained by subtracting the maximum output control margin (c) from the electronic speed (ω _max ), or is the maximum output control The output attenuation section (ω _max -c < ω r ≤ ω max) between the stall control speed (ω _max -b) obtained by subtracting the stall margin (b) from the maximum rotor speed (ω _max ) from the speed (ω _{max -c )} . -b) Determine whether it is.

The gain control module 23 adjusts the gain so that the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) follows Figure 5 (a) and Figure 6 (a) according to the section determined by the section determination module 22. A gain control signal (GC) for adjusting the control gain (Gain) of the weighting module 14 is output.

As shown in Figure 5 (a), in order to increase the energy absorption ability of the small-capacity wind power generator in the overfrequency section and suppress operation stoppage due to stall control, the power deviation for the rotor speed (ω _r ) versus the maximum tracking The control ratio (ΔP/P _MPPT ) should be set as shown in Equation 2.

According to Equation 2, in the overfrequency section, when the rotor speed (ω _r ) is the minimum rotor speed (ω _min ), the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) is set to the largest to increase the energy of the wind turbine. The absorption capacity is maximized, and as the rotor speed (ω _r ) increases, the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) decreases proportionally and becomes 0 at the maximum margin rotor speed (ω _max -b). Set it. Therefore, during frequency smoothing, the rotor speed (ω _r ) was prevented from reaching the maximum rotor speed (ω _max ) as much as possible. That is, the overfrequency section is again divided into a smoothing section (ω _min < ω _r ≤ ω _max -b) according to the rotor speed (ω _r ) and a stall margin (ω _max ) at the maximum rotor speed (ω _max ). The section from the section where b) is subtracted to the maximum rotor speed (ω _max ) is divided into a stall suppression section (ω _max -b < ω _r ≤ ω _max ) to suppress smoothing as much as possible.

And in order to achieve the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) of Equation 2, the control gain (Gain _ofs ) in the overfrequency section can be determined according to Equation 3.

Here, 0.1 is a unit for distinguishing frequencies and represents 0.1Hz.

In Equation 3, kω _r ³ is the maximum power point tracking control value (P _MPPT ), as shown in Equation 1, and the item in [ ] is the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) in Equation 2. represents.

Therefore, if the determined section is an overfrequency section, the gain control module 23 calculates the required overfrequency control gain (Gain _ofs ) according to Equation 3, and the gain weighting module 14 calculates the calculated overfrequency control gain ( The gain control signal (GC) is output to the gain weighting module 14 to weight Gain _ofs ) to the frequency deviation (Δf).

According to Equation 3, the overfrequency control gain (Gain _ofs ) according to the rotor speed (ω _r ) in the overfrequency section is displayed as shown in (b) of FIG. 5.

Meanwhile, as shown in (a) of FIG. 6, even in the low frequency section, smoothing is suppressed as much as possible by setting a stall suppression section (ω _max -b < ω _r ≤ ω _max ). In addition, the remaining sections are divided into the case where the current rotor speed (ω _r ) is the maximum output section (ω _min < ω _r ≤ ω _max -c) and the rotor speed (ω _r ) is the output attenuation section (ω _max -c < ω _r ≤ ω _max -b), the power deviation for rotor speed (ω _r ) to the maximum tracking control ratio (ΔP/P _MPPT ) must be set as shown in Equations 4 and 5.

According to Equations 4 and 5, if the rotor speed (ω _r ) in the low frequency section is the maximum output section (ω _min < ω _r ≤ ω _max -c), the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) is It is set to gradually increase to maximize the wind power generator's energy emission ability, and when the rotor speed (ω _r ) is in the output attenuation section (ω _max -c < ω _r ≤ ω _max -b), the power deviation to maximum tracking control ratio ( ΔP/P _MPPT ) rapidly decreases proportionally until it reaches the stall margin section (ω _max -b < ω _r ≤ ω _max ) set by the stall control margin (b), resulting in the maximum margin rotor speed (ω _max -b ) to 0. Therefore, during frequency smoothing, the rotor speed (ω _r ) was prevented from reaching the maximum rotor speed (ω _max ) as much as possible.

And in order to achieve the power deviation to maximum tracking control ratio (ΔP/P _MPPT ) of Equations 4 and 5, the control gain (Gain _ufs ) in the low frequency section can be determined according to Equations 6 and 7.

In Equations 6 and 7, kω _r ³ is the maximum power point tracking control value (P _MPPT ), as shown in Equation 1, and the items in [ ] are the power deviation to maximum tracking control ratio in Equations 4 and 5, respectively ( ΔP/PMPPT).

Therefore, if the determined section is a low-frequency section, the gain control module 23 calculates the required low-frequency control gain (Gain _ufs ) according to Equations 6 and 7, and the gain weighting module 14 calculates the calculated low-frequency control gain (Gain The gain control signal (GC) is output to the gain weighting module 14 to weight _ufs ) to the frequency deviation (Δf).

According to Equations 6 and 7, the low-frequency control gain (Gain _ufs ) according to the rotor speed (ω _r ) in the low-frequency section is shown as (b) in FIG. 6.

In the illustrated embodiment, each component may have different functions and capabilities in addition to those described below, and may include additional components other than those described below. Additionally, in one embodiment, each component may be implemented using one or more physically separate devices, one or more processors, or a combination of one or more processors and software, and, unlike the example shown, may be implemented in specific operations. It may not be clearly distinguished.

Additionally, the frequency smoothing control device shown in FIG. 4 may be implemented in a logic circuit using hardware, firmware, software, or a combination thereof, and may also be implemented using a general-purpose or special-purpose computer. The device may be implemented using hardwired devices, field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc. Additionally, the device may be implemented as a System on Chip (SoC) including one or more processors and a controller.

In addition, the frequency smoothing control device may be mounted on a computing device or server equipped with hardware elements in the form of software, hardware, or a combination thereof. A computing device or server includes all or part of a communication device such as a communication modem for communicating with various devices or a wired or wireless communication network, a memory for storing data to execute a program, and a microprocessor for executing a program to perform calculations and commands. It can refer to a variety of devices, including:

Figure 7 shows an example of the input wind speed applied to a small-capacity wind power generator, Figure 8 shows an example of measuring the system frequency, and Figures 9 and 10 show the results of comparing the rotor speed according to the frequency smoothing control device of the embodiment. indicates.

In Figures 9 and 10, orange is the result when performing maximum power point tracking (MPPT) control, and green is the result when performing frequency smoothing control. As can be seen in Figures 9 and 10, in the over-frequency section, the output is reduced compared to the maximum power point tracking (MPPT) control, thereby increasing the rotor speed (ω _r ), and in the low-frequency section, the rotor speed (ω r ) increases compared to the maximum power point tracking (MPPT) control. It can be seen that the rotor speed (ω _r ) decreases by increasing the output. Therefore, because more energy is absorbed in the over-frequency section and more energy is emitted in the low-frequency section, the rotor speed section in the embodiment can be wider than the prior art, which allows effective use of the rotor of the wind power generator. It means there is.

Figure 11 shows a frequency smoothing control method according to an embodiment.

Referring to FIG. 11, the frequency smoothing control method of the embodiment first measures the system frequency (f _sys ) (31). Then, the rotor speed (ω _r ) of the small-capacity wind generator is measured (32). When the grid frequency (f _sys ) is measured, the frequency deviation (Δf) is calculated according to the difference between the measured grid frequency (f _sys ) and the reference frequency, and depending on the sign of the calculated frequency deviation (Δf), it is determined whether it is a low frequency section or not. Determine whether it is a frequency section (33).

If it is determined to be an over-frequency section, based on the confirmed rotor speed (ω _r ), within the over-frequency section, whether it is a smoothing section (ω _min < ω _r ≤ ω _max -b) or a stall suppression section (ω _max -b < ω Check the detailed section to see if _r ≤ ω _max (34).

And if the detailed section within the confirmed overfrequency section is the smoothing section (ω _min < ω _r ≤ ω _max -b), the overfrequency control gain (Gain _ofs ) is calculated and set according to Equation 3, and the stall suppression section (ω If _max -b < ω _r ≤ ω _max ), the overfrequency control gain (Gain _ofs ) is set to 0 (35).

On the other hand, if it is determined to be a low-frequency section, based on the confirmed rotor speed (ω _r ), whether the maximum output section (ω _min < ω _r ≤ ω _max -c) or the output attenuation section (ω _max -c < Check the detailed section to see whether it is ω _r ≤ ω _max -b) or the stall suppression section (ω _max -b < ω _r ≤ ω _max ) (36).

And if the detailed section within the confirmed low-frequency section is the maximum output section (ω _min < ω _r ≤ ω _max -c), the low-frequency control gain (Gain _ufs ) is calculated and set according to Equation 6, and the output attenuation section (ω _max - If c < ω _r ≤ ω _max -b), the low frequency control gain (Gain _ufs ) is calculated and set according to Equation 7. And if the stall suppression range is (ω _max -b < ω _r ≤ ω _max ), the low frequency control gain (Gain _ufs ) is set to 0 (35).

Then, a gain control signal (GC) is generated to adjust the control gain (Gain) of the proportional controller according to the set over-frequency control gain (Gain _ofs ) or low-frequency control gain (Gain _ufs ) (38).

When the control gain (Gain) of the proportional controller is adjusted to the over-frequency control gain (Gain _ofs ) or the under-frequency control gain (Gain _ufs ), the adjusted control gain (Gain) is weighted to the frequency deviation (Δf) to produce the output power deviation (ΔP). ) is varied, and frequency smoothing is performed by subtracting the varied output power deviation (ΔP) from the maximum power point tracking control value (P _MPPT ) to obtain an active power reference value (P _ref ).

In FIG. 11, it is described that each process is executed sequentially, but this is only an illustrative explanation, and those skilled in the art can change the order shown in FIG. 11 and execute it without departing from the essential characteristics of the embodiments of the present invention. Alternatively, it can be applied through various modifications and modifications by executing one or more processes in parallel or adding other processes.

The frequency smoothing control method of a small-capacity wind power generator for frequency control according to the embodiment is applicable not only to a double-excited induction generator-based wind power generator (Type C) but also to a full converter-based wind power generator (Type D).

The frequency smoothing control system and method for a small-capacity wind power generator according to the embodiment described above can contribute to frequency smoothing of the power system by adjusting the output of the wind power generator when a small-capacity wind power generator is connected to the power system.

FIG. 12 is a diagram for explaining a computing environment including a computing device according to an embodiment.

In the illustrated embodiment, each component may have different functions and capabilities in addition to those described below, and may include additional components in addition to those not described below. The illustrated computing environment 40 may include a computing device 41 to perform the frequency smoothing control method shown in FIG. 11 . In one embodiment, computing device 41 may be one or more components included in the frequency smoothing control device shown in FIG. 4 .

Computing device 41 includes at least one processor 42, computer-readable storage medium 43, and communication bus 45. Processor 42 may cause computing device 41 to operate according to the above-mentioned example embodiments. For example, the processor 42 may execute one or more programs 44 stored in the computer-readable storage medium 43. The one or more programs 44 may include one or more computer-executable instructions, which, when executed by the processor 42, cause the computing device 41 to operate according to an example embodiment. It can be configured to perform these.

Communication bus 45 interconnects various other components of computing device 41, including processor 42 and computer-readable storage medium 43.

Computing device 41 may also include one or more input/output interfaces 46 and one or more communication interfaces 47 that provide an interface for one or more input/output devices 48 . The input/output interface 46 and communication interface 47 are connected to the communication bus 45. Input/output device 48 may be connected to other components of computing device 41 through input/output interface 46. Exemplary input/output devices 48 include, but are not limited to, a pointing device (such as a mouse or trackpad), a keyboard, a touch input device (such as a touchpad or touch screen), a voice or sound input device, various types of sensor devices, and/or imaging devices. It may include input devices and/or output devices such as display devices, printers, speakers, and/or network cards. The exemplary input/output device 48 is a component constituting the computing device 41 and may be included within the computing device 41, or may be a separate device distinct from the computing device 41 and may be included in the computing device 41. It may be connected.

Although the present invention has been described in detail through representative embodiments above, those skilled in the art will understand that various modifications and other equivalent embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the attached claims.

11: Maximum power point tracking control module
12: Frequency smoothing module
13: Frequency deviation output module
14: Gain weighting module
15: Active power reference value acquisition module
16: Converter control module
17: Control gain generation module
21: Section setting module
22: Section determination module
23: Gain control module

Claims (10)

1. A method performed by a computing device having one or more processors and a memory that stores one or more programs to be executed by the one or more processors, comprising:
Measuring the system frequency of the power system and determining whether the power system is in an over-frequency section or an under-frequency section according to a frequency deviation calculated as the difference between the system frequency and a reference frequency;
Setting a stall suppression section in each of the over-frequency section and the low-frequency section according to a stall margin set so that the wind power generator is not stall controlled at a specified maximum rotor speed depending on the rotor speed; and
Before the rotor speed reaches the set stall suppression section, between the power deviation in which the control gain for adjusting the frequency smoothing of the wind generator is added to the frequency deviation and the maximum power point tracking control value according to the maximum power point tracking control technique. Including the step of adjusting the control gain so that the power deviation to maximum tracking control ratio, which represents the ratio of Frequency smoothing control method for small-capacity wind power generators. The method of claim 1, wherein setting the stall suppression section includes
The _{overfrequency} section is _a smoothing section (ω _{min <} ω _r ≤ ω _max -b) and
Frequency smoothing of a small-capacity wind power generator that sets the section from the maximum margin rotor speed (ω _max -b) to the maximum rotor speed (ω _max ) by dividing it into a stall suppression section (ω _max -b < ω _r ≤ ω _max ). Control method. The method of claim 2, wherein adjusting the control gain includes
The power deviation to maximum tracking control ratio (ΔP/P _MPPT ) has a maximum value at the minimum rotor speed (ω _min ) in the smoothing section and gradually decreases at the maximum margin rotor speed (ω _max -b). A frequency smoothing control method for a small-capacity wind power generator that adjusts the control gain to be 0. The method of claim 3, wherein adjusting the control gain comprises
In the smoothing section of the overfrequency section, the control gain (Gain _ofs ) is calculated according to the rotor speed (ω _r )

(where f _nom is the reference frequency, k is the proportionality constant for maximum power point tracking (MPPT) starting of the wind power generator, and a is the power deviation for rotor speed (ω _r ) in the overfrequency section to the maximum tracking control ratio (ΔP /P _MPPT ) a constant proportional to the rate of change)
Frequency smoothing control method of a small-capacity wind power generator controlled by . The method of claim 1, wherein setting the stall suppression section includes
The maximum output control margin is set to prevent the output power of the wind generator from rapidly changing due to the stall control margin (b) at the minimum rotor speed (ω _min ) based on the rotor speed (ω _r ) in the low-frequency section. The maximum output section (ω _min < ω _r ≤ ω _max -c) up to the maximum output control speed (ω _max -c) specified by (c), and
An output decay section (ω _max -c < ω _r ≤ ω max -b) from the maximum output control speed (ω _max -c) to the maximum margin rotor speed (ω _{max -b} ) specified by the stall margin, and
Frequency smoothing of a small-capacity wind power generator that sets the section from the maximum margin rotor speed (ω _max -b) to the maximum rotor speed (ω _max ) by dividing it into a stall suppression section (ω _max -b < ω _r ≤ ω _max ). Control method. The method of claim 5, wherein adjusting the control gain comprises
The power deviation to maximum tracking control ratio (ΔP/P _MPPT ) is 0 at the minimum rotor speed (ω _min ), increases in the maximum output section, and gradually decreases in the output attenuation section to the maximum margin rotor speed (ω Frequency smoothing control method of a small-capacity wind power generator that adjusts the control gain to be 0 at _max -b). The method of claim 6, wherein adjusting the control gain comprises
In the maximum output section of the low-frequency section, the control gain (Gain _ufs ) is expressed in Equation according to the rotor speed (ω _r )

(where f _nom is the reference frequency, k is the proportionality constant for maximum power point tracking (MPPT) starting of the wind generator, and d is the maximum tracking control ratio (ΔP/P _MPPT ) to the rotor speed (ω _r ) in the low-frequency section. constant proportional to the rate of change)
Frequency smoothing control method of a small-capacity wind power generator controlled by . The method of claim 6, wherein adjusting the control gain comprises
In the output attenuation section of the low-frequency section, the control gain (Gain _ufs ) is calculated according to the rotor speed (ω _r ).

Frequency smoothing control method of a small-capacity wind power generator controlled by . The method of claim 1, wherein adjusting the control gain comprises
A frequency smoothing control method for a small-capacity wind power generator that adjusts the control gain (Gain _ofs ) to be maintained at 0 in the stall suppression section. The method of claim 1, wherein the frequency smoothing control method is
Further comprising smoothing the frequency of the small-capacity wind power generator according to the control gain,
The step of smoothing the frequency is
Calculate the output power deviation (ΔP) by weighting the control gain to the frequency deviation (Δf),
According to the maximum power point tracking control technique, the output power deviation is subtracted from the maximum power point tracking control value (P _MPPT ), which represents the maximum power point that can be output at the rotor speed (ω _r ), and the active power reference value (P _ref ) is obtained. obtains,
A frequency smoothing control method for a small-capacity wind power generator that adjusts the power output from the small-capacity wind power generator according to the active power reference value (P _ref ).