A system and method for maintaining grid frequency stability

Abstract

The present application belongs to the field of electric power, and particularly relates to a system and method for maintaining the stability of power grid frequency, which comprises an advance prediction module, a frequency monitoring module, a classified transmission module, an energy storage module and an electric energy incorporation module. The frequency of the expected output current is calculated by obtaining the wind turbine data; the current frequency of the wind power channel is monitored, and the current is distributed and guided to be transmitted; the current is integrated according to the frequency; the current within a certain frequency range is uniformly frequency-modulated; the current after the uniform frequency modulation is stored; the stored electric energy is incorporated into the power grid; the current frequency size output by the wind turbine is predicted in advance according to the rotating speed, so that the adjustment preparation can be made, the frequency modulation time is shortened, the current of the same range is integrated and frequency-modulated, the frequency modulation work efficiency is improved, the current of different sizes is frequency-modulated in a targeted manner, and the influence of the current of different frequencies on the stability of the power grid is effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electric power, and particularly relates to a system and method for keeping the stability of power grid frequency. BACKGROUND

[0002] Wind power generation refers to converting the kinetic energy of wind into electric energy. Wind energy is a clean and renewable energy source, and has been used by people for a long time. Wind power generation is very environmentally friendly, and the amount of wind energy is huge, so it is increasingly valued by countries around the world. China is rich in wind energy resources, and the exploitable wind energy reserves are about 1 billion kW.

[0003] During wind power generation, the wind speed at the location of each wind turbine is different due to different positions, which means that the rotational speed of the wind blade is also different, resulting in different frequencies of electric current. If electric currents with different frequencies are simultaneously merged into a power grid, it will cause the frequency of the power grid to fluctuate, which will affect the normal operation of the power grid. SUMMARY

[0004] In order to solve or improve the above problems, the present application provides a system and method for keeping the stability of power grid frequency, and the specific technical solutions are as follows:

[0005] The present application provides a system for keeping the stability of power grid frequency, comprising: an advance prediction module for obtaining wind turbine data to calculate the frequency of predicted output current; a frequency monitoring module for monitoring the current frequency of a wind power channel and comparing it with the frequency of predicted output current, and performing the distribution and guided transmission of current; a classified transmission module for integrating current according to frequency; a unified frequency modulation module for uniformly modulating current within a certain frequency range; an energy storage module for storing current modulated by the unified frequency modulation module; an electric energy merging module for merging stored electric energy into a power grid; the advance prediction module is connected to the frequency monitoring module, the frequency monitoring module is connected to the classified transmission module, the classified transmission module is connected to the unified frequency modulation module, the unified frequency modulation module is connected to the energy storage module, and the energy storage module is connected to the electric energy merging module.

[0006] Preferably, the advance prediction module comprises: a rotational speed sensor for monitoring the rotational speed of the wind blade of a wind turbine; a frequency pre-judgment calculation unit for calculating the frequency of predicted output current according to the rotational speed; and a preliminary frequency modulation unit for dispatching corresponding wind power channels according to the frequency of predicted output current; the rotational speed sensor is connected to the frequency pre-judgment calculation unit, and the frequency pre-judgment calculation unit is connected to the preliminary frequency modulation unit.

[0007] Preferably, the frequency monitoring module comprises: a current frequency detector for detecting the actual current frequency of the wind power channel; a comparison unit for comparing the actual current frequency with the frequency of the predicted output current to determine the predicted error; and a distribution guiding unit for distributing and guiding the current according to the actual current frequency; the current frequency detector is connected with the comparison unit and the distribution guiding unit, and the comparison unit is connected with the frequency prediction calculation unit.

[0008] Preferably, the classified delivery module comprises: a same-frequency integration unit for integrating the current of the same frequency range; a multi-channel delivery unit for delivering the current of different frequencies; and an electric quantity metering unit for counting the total electric quantity delivered by each channel; the same-frequency integration unit is connected with the distribution guiding unit and the multi-channel delivery unit, and the electric quantity metering unit is connected with the multi-channel delivery unit.

[0009] Preferably, the unified frequency modulation module comprises: a multi-channel frequency increasing unit for increasing the frequency of the low-frequency current to 50 Hz through a frequency modulator; a multi-channel frequency decreasing unit for decreasing the frequency of the high-frequency current to 50 Hz through a frequency modulator; an electric energy integration unit for integrating the current after unified frequency modulation; and an AC-DC conversion unit for converting the integrated alternating current into direct current; the multi-channel frequency increasing unit and the multi-channel frequency decreasing unit are connected with the multi-channel delivery unit, the multi-channel delivery unit is connected with the electric energy integration unit, and the electric energy integration unit is connected with the AC-DC conversion unit.

[0010] Preferably, the energy storage module comprises: a battery unit for storing the direct current converted by the AC-DC conversion unit; an electric energy metering unit for counting the electric quantity stored in the battery unit; a DC-AC conversion unit for converting the direct current in the battery unit into alternating current; and an electric energy leading-out unit for leading the alternating current converted by the DC-AC conversion unit into the power grid.

[0011] The battery unit is connected with the AC-DC conversion unit and the DC-AC conversion unit, the DC-AC conversion unit is connected with the electric energy leading-out unit, and the electric energy metering unit is connected with the battery unit.

[0012] The application provides a method for maintaining the stability of the power grid frequency, comprising: collecting the rotating speed of the wind turbine to calculate the predicted frequency; distributing and guiding the current according to the wind power current frequency of the specific wind channel, integrating the current belonging to a certain frequency range to perform unified frequency modulation, and converting the current after frequency modulation into direct current; converting the direct current obtained by frequency modulation into alternating current, and leading the alternating current into the power grid.

[0013] Preferably, the calculated predicted frequency comprises: the predicted frequency f=np / 60, wherein n is the rotating speed of the wind blade driving the generator, and p is the number of magnetic pole pairs of the generator.

[0014] Preferably, the integrating the current belonging to a certain frequency range for unified frequency modulation comprises: increasing the low-frequency current to 50HZ, and decreasing the high-frequency current to 50HZ.

[0015] Preferably, the converting the direct current obtained by the frequency modulation into alternating current, and incorporating the alternating current into the power grid comprises: converting the stored delivery direct current obtained by the conversion into alternating current, and incorporating the alternating current into the power grid.

[0016] The beneficial effects of the present application are: through the advance prediction module, the wind turbine data is acquired to calculate the frequency of the predicted output current; the frequency monitoring module monitors the current frequency of the wind power channel and compares it with the frequency of the predicted output current, and performs current distribution and delivery; the classified delivery module integrates the current according to the frequency; the unified frequency modulation module uniformly modulates the current belonging to a certain frequency range; the energy storage module stores the current after the unified frequency modulation; the energy incorporation module incorporates the stored energy into the power grid; the current frequency of the wind turbine output is predicted in advance according to the rotating speed, so that the adjustment preparation can be made, the frequency modulation time is shortened, the currents with the same frequency range are integrated and modulated, the working efficiency of the frequency modulation is improved, the currents with different sizes are modulated, and the influence of the currents with different frequencies on the stability of the power grid is effectively reduced. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a schematic diagram of a system for maintaining the stability of the power grid according to the present application;

[0018] Figure 2 is a schematic diagram of a method for maintaining the stability of the power grid according to the present application;

[0019] Figure 3 is a schematic diagram of a flow for maintaining the stability of the power grid according to the present application. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0021] It should be understood that the terms "comprises" and "comprising," when used in this specification and the following claims, indicate the presence of the described features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0022] It should also be understood that the terms used in the specification and the appended claims are intended to describe particular embodiments and do not intend to limit the present application. As used in the specification and the appended claims, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0023] It should further be understood that the term "and / or" used in the specification and the appended claims means one or more of the associated listed items as well as all possible combinations of the items and includes the combinations.

[0024] To solve or improve the problems raised by the background, the present application provides a system for maintaining the stability of power grid frequency, as shown in Figure 1 The system for maintaining the stability of power grid frequency comprises: an advance prediction module for obtaining wind power generator data to calculate the frequency of predicted output current; a frequency monitoring module for monitoring the current frequency of the wind power channel and comparing it with the frequency of the predicted output current to guide the distribution and transmission of the current; a classified transmission module for integrating the current according to the frequency; a unified frequency modulation module for uniformly modulating the current belonging to a certain frequency range; an energy storage module for storing the current uniformly modulated; and an electric energy incorporation module (if the specific structure is relatively simple, it can be an electric energy incorporation unit rather than a complex functional module) for incorporating the stored electric energy into the power grid; the advance prediction module is connected to the frequency monitoring module, the frequency monitoring module is connected to the classified transmission module, the classified transmission module is connected to the unified frequency modulation module, the unified frequency modulation module is connected to the energy storage module, and the energy storage module is connected to the electric energy incorporation module.

[0025] The wind power frequency stabilization subsystem and the information transmission unit, the wind power frequency stabilization subsystem comprises an advance prediction module, a frequency monitoring module, a classified transmission device (i.e. a classified transmission module), a unified frequency modulation module, an energy storage module and an electric energy incorporation module, the advance prediction module and the frequency monitoring module are connected to each other through the information transmission unit, the frequency monitoring module and the classified transmission device are connected to each other through the information transmission unit, the classified transmission device and the unified frequency modulation module are connected to each other through the electric quantity transmission wire, the unified frequency modulation module and the energy storage module are connected to each other through the electric quantity transmission wire, and the energy storage module and the electric energy incorporation unit are connected to each other through the electric quantity transmission wire;

[0026] The transmission mode of the information transmission unit includes any one of baseband transmission, frequency band transmission and wideband transmission.

[0027] The advance prediction module comprises a rotating speed sensor for monitoring the rotating speed of the wind blade of the wind driven generator, and a frequency pre-judgment calculation unit for calculating the frequency of the predicted output current according to the rotating speed, and a preliminary frequency modulation unit for dispatching the corresponding wind power channel according to the frequency of the predicted output current. The rotating speed sensor is connected with the frequency pre-judgment calculation unit, and the frequency pre-judgment calculation unit is connected with the preliminary frequency modulation unit.

[0028] The advance prediction module comprises a wind speed sensor, a frequency pre-judgment calculation unit, a preliminary frequency modulation unit and a rotating speed sensor. The wind speed sensor is used for monitoring the wind speed in front of the wind driven generator, the rotating speed sensor is used for monitoring the rotating speed of the wind blade of the wind driven generator, the frequency pre-judgment calculation unit performs pre-judgment calculation on the frequency of the output current under the rotating speed according to the data of the rotating speed sensor, and the preliminary frequency modulation unit dispatches the wind power channel according to the frequency calculated by the frequency pre-judgment unit. The wind speed sensor and the rotating speed sensor are connected with the frequency pre-judgment calculation unit through the information transmission unit, and the frequency pre-judgment calculation unit is connected with the preliminary frequency modulation unit through the information transmission unit. Through monitoring the wind speed, the actual rotating speed can be compared, and the frequency of the output current can be corrected according to the comparison result.

[0029] The frequency monitoring module comprises a current frequency detector for detecting the actual current frequency of the wind power channel, a comparison unit for comparing the actual current frequency with the frequency of the predicted output current to judge the prediction error, and a distribution guiding unit for distributing and guiding the current according to the actual current frequency. The current frequency detector is connected with the comparison unit and the distribution guiding unit, and the comparison unit is connected with the frequency pre-judgment calculation unit.

[0030] The frequency monitoring module comprises a current frequency detector, a comparison unit and a distribution guiding unit. The current frequency detector is used for detecting the wind power current frequency of the channel, the comparison unit is used for comparing the current frequency detected by the current frequency detector with the predicted frequency of the frequency pre-judgment calculation unit to judge the prediction error, and the distribution guiding unit is used for distributing and guiding the current according to the frequency detected by the current frequency detector. The current frequency detector is connected with the comparison unit and the distribution guiding unit through the information transmission unit, and the comparison unit is connected with the frequency pre-judgment calculation unit through the information transmission unit. According to the prediction error, the actual current distribution result can be corrected.

[0031] The classified conveying module comprises a same frequency integration unit for integrating currents of the same frequency range, a multi-channel conveying unit for conveying currents of different frequencies, and an electric quantity metering unit for counting the total electric quantity conveyed by each channel.

[0032] The unified frequency modulation module comprises a multi-channel frequency increasing unit for increasing the frequency of low-frequency currents to 50HZ by a frequency modulator, a multi-channel frequency decreasing unit for decreasing the frequency of high-frequency currents to 50HZ by a frequency modulator, an electric energy integration unit for integrating the currents after unified frequency modulation, and an AC / DC conversion unit for converting the integrated alternating current into direct current.

[0033] The energy storage module comprises a battery unit for storing the direct current converted by the AC / DC conversion unit, an electric energy metering unit for counting the electric quantity stored in the battery unit, a DC / AC conversion unit for converting the direct current in the battery unit into alternating current, and an electric energy leading-out unit for incorporating the alternating current converted by the DC / AC conversion unit into the power grid.

[0034] The method for keeping the stability of the power grid frequency comprises the following steps: S1, collecting the rotating speed of the wind turbine to calculate a predicted frequency; S2, distributing and guiding the current according to the wind power current frequency of a specific wind channel, integrating the current belonging to a certain frequency range for unified frequency modulation, converting the modulated current into direct current, and converting the direct current into alternating current and incorporating the alternating current into the power grid; and S3, converting the direct current obtained by the frequency modulation into alternating current and incorporating the alternating current into the power grid.

[0035] The predicted frequency f is calculated as f = np / 60, wherein n is the rotating speed of the wind turbine and p is the number of magnetic poles of the generator.

[0036] The current belonging to a certain frequency range is integrated for unified frequency modulation, which comprises increasing the frequency of low-frequency currents to 50HZ and decreasing the frequency of high-frequency currents to 50HZ.

[0037] The direct current obtained by the frequency modulation is converted into alternating current, and the alternating current is incorporated into the power grid, which comprises converting the stored conveying direct current into alternating current and incorporating the alternating current into the power grid.

[0038] The flow of maintaining the stability of the power grid frequency is shown as follows: Figure 3

[0039] The first step is to predict the frequency in advance

[0040] The wind speed in front of the wind turbine is monitored by a wind speed sensor, the rotational speed of the wind turbine blade is monitored by a rotational speed sensor, and the frequency of the output current at this rotational speed is calculated by the frequency prediction calculation unit according to the data of the rotational speed sensor. The calculation formula is: f=np / 60, where n is the rotational speed of the wind turbine blade, and p is the number of magnetic poles of the generator.

[0041] The second step is to classify the frequency adjustment

[0042] The current frequency detector detects the wind power current frequency of the channel, the distribution guide unit distributes and guides the current according to the frequency detected by the current frequency detector, and the same frequency integration unit is used to integrate the current with the same frequency range. The multi-channel frequency increasing unit is used to increase the low-frequency current to 50HZ through the frequency converter, the multi-channel frequency decreasing unit is used to decrease the high-frequency current to 50HZ through the frequency converter, the power integration unit is used to integrate the current after frequency adjustment, and the AC-DC conversion unit is used to convert the integrated AC power into DC power.

[0043] The third step is to integrate into the power grid

[0044] The battery unit is used to store the DC power converted by the AC-DC conversion unit, the DC power in the battery is converted into AC power by the DC-AC conversion unit, and the power is integrated into the power grid through the power export unit.

[0045] The rotational speed of the wind turbine blade is monitored by a rotational speed sensor, the frequency of the output current at this rotational speed is calculated by the frequency prediction calculation unit according to the data of the rotational speed sensor, and the frequency of the output current of the wind turbine is predicted in advance according to the rotational speed, so that the frequency adjustment guide unit is prepared, the frequency adjustment time is shortened, the same frequency integration unit integrates the current with the same frequency range, the same frequency is uniformly adjusted, the frequency adjustment efficiency is improved, the multi-channel frequency increasing unit and the multi-channel frequency decreasing unit are used to adjust the frequency of the current with different sizes, and the influence of the current with different frequencies on the stability of the power grid is effectively reduced.

[0046] ​Those skilled in the art can understand that the units of the examples described in combination with the embodiments disclosed in the present embodiment can be realized in electronic hardware, computer software or a combination of both, and the components of the examples have been described in general in the above description in order to clearly illustrate the interchangeability of hardware and software. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. The skilled person can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0047] The present application realizes primary frequency modulation by frequency modulation device, and improves the response speed of the unit to the given power instruction by adding inertia control in the wind turbine unit after distribution by the wind energy management platform; and combines secondary frequency modulation to meet the power reserve capacity requirement, controls the system according to the region for secondary frequency modulation, and obtains a reasonable distribution scheme; through the wireless communication technology of the energy management platform, the distributed installation of the energy management platform is facilitated, the installation cycle is short, the harness is broken, the maintenance is convenient, and the expansion capacity is strong; by coordinating the rotor speed control and pitch angle control of the wind turbine unit, the wind turbine unit can well respond to the change of the power grid frequency, and has the frequency modulation capacity similar to the conventional unit.

[0048] In the embodiments provided in the present application, it should be understood that the division of units is only a logical functional division, and another division mode can be used in actual implementation, for example, a plurality of units can be combined into one unit, one unit can be split into a plurality of units, or some features can be ignored, etc.

[0049] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the description of the present application.

Claims

1. A system for maintaining the stability of the frequency of an electrical grid, characterized in that, The application relates to a wind power current distribution system, which comprises the following modules: an advance prediction module for acquiring wind power generator data to calculate the frequency of predicted output current; a frequency monitoring module for monitoring the current frequency of a wind power channel and comparing the current frequency with the frequency of predicted output current to guide the distribution and transmission of current; a classification transmission module for integrating current according to frequency; a unified frequency modulation module for uniformly modulating current belonging to a certain frequency range; an energy storage module for storing the current uniformly modulated; an electric energy integration module for integrating the stored electric energy into a power grid; the advance prediction module is connected with the frequency monitoring module, the frequency monitoring module is connected with the classification transmission module, the classification transmission module is connected with the unified frequency modulation module, the unified frequency modulation module is connected with the energy storage module, and the energy storage module is connected with the electric energy integration module. The advance prediction module comprises: a rotating speed sensor for monitoring the rotating speed of wind blades of a wind power generator; a frequency pre-judgment calculation unit for calculating the frequency of predicted output current according to the rotating speed; and a preliminary frequency modulation unit for dispatching corresponding wind power channels according to the frequency of predicted output current. The frequency monitoring module comprises: a current frequency detector for detecting the actual current frequency of the wind power channel; a comparison unit for comparing the actual current frequency with the frequency of predicted output current to judge the predicted error; and a distribution and guidance unit for distributing and guiding the transmission of current according to the actual current frequency. The classification transmission module comprises: a same-frequency integration unit for integrating current of the same frequency range; a multi-channel transmission unit for transmitting current of different frequencies; and an electric quantity metering unit for counting the total electric quantity of each channel transmission. The unified frequency modulation module comprises: a multi-channel frequency increasing unit for increasing the frequency of low-frequency current to 50HZ through a frequency modulator; a multi-channel frequency decreasing unit for decreasing the frequency of high-frequency current to 50HZ through a frequency modulator; an electric energy integration unit for integrating the current uniformly modulated; and an AC-DC conversion unit for converting the integrated alternating current into direct current. The energy storage module comprises: a battery unit for storing the direct current converted by the AC-DC conversion unit; an electric energy metering unit for counting the electric quantity stored in the battery unit; and a DC-AC conversion unit for converting the direct current in the battery unit into alternating current. ​ ​ 2. The system for maintaining grid frequency stability of claim 1, wherein, ​ ​ ​ ​ ​ 3. The system for maintaining grid frequency stability of claim 2, wherein, ​ ​ ​ ​ ​ 4. The system for maintaining grid frequency stability of claim 3, wherein, ​ ​ ​ ​ ​ 5. The system for maintaining grid frequency stability of claim 4, wherein, ​ ​ ​ ​ ​ ​ 6. The system for maintaining grid frequency stability of claim 5, wherein, ​ ​ ​ ​ An electric energy export unit is configured to incorporate the AC power converted by the AC / DC conversion unit into a power grid. The battery unit is connected to the AC / DC conversion unit and the DC / AC conversion unit, the DC / AC conversion unit is connected to the electric energy export unit, and the electric energy metering unit is connected to the battery unit.

7. A method of maintaining the stability of the frequency of an electrical grid, characterized in that, The method comprises: Collecting the rotating speed of the wind turbine to calculate the frequency of the expected output current; Monitoring the current frequency of the wind power channel and comparing it with the frequency of the expected output current; According to the wind power current frequency of the specific wind power channel, the current is distributed and guided to be transmitted, the current within a certain frequency range is integrated for unified frequency modulation, the current after the unified frequency modulation is stored, the current after the frequency modulation is converted into DC power, and the DC power is converted into AC power; The AC power is incorporated into a power grid.

8. The method of maintaining grid frequency stability of claim 7, wherein, The calculation of the frequency of the expected output current comprises: The frequency f of the expected output current is np / 60, wherein n is the rotating speed of the wind turbine, and p is the number of magnetic poles of the generator.

9. The method of maintaining grid frequency stability of claim 7, wherein, The integration of the current within a certain frequency range for unified frequency modulation comprises: The low-frequency current is increased to 50 Hz, and the high-frequency current is decreased to 50 Hz.

10. The method of maintaining grid frequency stability of claim 7, wherein, The conversion of the DC power obtained by the frequency modulation into AC power and the incorporation of the AC power into a power grid comprise: The stored DC power obtained by the conversion is converted into AC power again, and the AC power is incorporated into a power grid.

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