Anti-reflux control method for wind power generation system

Abstract

The invention belongs to the technical field of wind power generation, and particularly discloses an anti-countercurrent control method for a wind power generation system, which comprises the following steps that: a fan controller monitors whether any phase of countercurrent flow power appears in a power grid in real time through an anti-countercurrent measuring device; adjusting active and reactive power output of a fan according to the total power factor of the power grid, and adjusting a final power limit value by an inverter, so that the power factor of the power grid is kept within a set range; and the fan controller looks up the table and calculates the theoretical rotating speed of the fan at the current moment according to the set final power limit value, and the fan controller tracks the rotating speed according to the theoretical rotating speed so as to ensure that the fan is kept in the optimal rotating speed interval. By means of measurement and monitoring, output power control, countercurrent prevention control, system monitoring and optimization and the like, the problems of the wind power generation system in the aspects of operation efficiency, power factors and power countercurrent are solved, the operation efficiency and reliability of the wind power generation system are improved, and meanwhile stable operation of a power grid is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and in particular to a backflow prevention control method for a wind power generation system. Background Art

[0002] With the continuous improvement of wind power generation technology and the reduction of costs, more and more parks and buildings have begun to use wind power generation systems as their secondary energy supply. This method can reduce dependence on the power grid and reduce electricity bills, while also contributing to environmental protection and promoting the development of sustainable energy. Due to the small transformer capacity of some industrial parks or buildings, the limited current margin of the grid-connected cables, or the saturation of the installed capacity of the regional power generation system, the power company requires the subsequent construction of wind power systems to achieve irreversible power generation, that is, to achieve self-supply and self-use of wind power generation systems, converting wind energy into electrical energy to meet the load requirements of the park or building without injecting excess electrical energy into the grid.

[0003] The anti-backflow of wind power generation system means that the wind power generation system does not inject excess power into the power grid, but converts wind energy into electricity to meet the load requirements of the park or building. The main advantages of anti-backflow are:

[0004] 1. Reduce dependence on the power grid: Prevent wind power generation systems from injecting excess electricity into the power grid, reducing dependence on the power grid, thereby improving the safety and stability of the power grid.

[0005] 2. Reduce the load pressure on the power grid: Since the wind power generation system no longer injects excess electricity into the power grid, it can reduce the load pressure on the power grid and reduce the operating costs of the power grid.

[0006] 3. Improve the operating efficiency of wind power generation systems: After achieving backflow prevention, the wind power generation system can better adapt to local load requirements, improve its operating efficiency, and also extend the life of the generator set.

[0007] 4. Promote the large-scale application of renewable energy: Anti-backflow technology helps solve the coordination problem between renewable energy and the power grid, promote the large-scale application of renewable energy, and promote the development of sustainable energy.

[0008] The existing technology mainly monitors the load power by installing a backflow prevention device on the grid side, and dispatches the power generation through the power controller system. Install an electric meter at the total load point of the transformer or the high-power branch to monitor the current direction, and feed back the measured value to the wind turbine main control system through 485 communication or DL / T645 communication. The main control system dynamically adjusts the power generation of the wind power generation system according to the load demand. When the load demand decreases, the power control system will reduce the power generation to avoid power backflow.

[0009] The existing anti-backflow devices mainly have the following problems:

[0010] 1. Communication line length limitation: When the industrial park is large, as the communication distance increases, the bandwidth attenuation of 485 communication will also increase, resulting in a decrease in communication rate. According to the 485 communication standard, the maximum communication distance is usually around 1200 meters. Exceeding this distance may cause signal attenuation and data transmission errors.

[0011] 2. Communication interference problem: When 485 communication cables are laid together with the main circuit cables of the photovoltaic wind turbine grid, electromagnetic interference will occur, affecting the transmission quality and stability of the communication signal.

[0012] 3. Difficulty in installing transformers: ① Current transformers are usually located in high-voltage lines or on low-voltage busbars, and require power outages for installation. Related equipment and systems need to be shut down for maintenance and cannot operate normally. The installation time is too long, which has a greater impact on production tasks and may even cause order delays or losses. ② The size specifications of low-voltage power busbars in different parks are inconsistent, and transformers with different perforation sizes need to be purchased and installed separately, increasing the cost of equipment procurement, spare parts storage and maintenance. ③ When using split or fixed current transformers for installation, the wiring process is cumbersome and the construction is difficult.

[0013] The existing anti-backflow control mainly has the following problems:

[0014] 1. System stability and reliability: The power load of heavy-duty industrial parks usually shows obvious fluctuations and peaks in a specific time period. While preventing the reverse power from being too high, it is necessary to reasonably control and balance the peak and valley loads to avoid reverse flow to the power grid. A reasonable power filtering algorithm adjustment strategy needs to be implemented.

[0015] 2. Operation strategy under low load: During periods when wind resources are abundant and the power demand of a park or building is low, it is necessary to track the load power through speed control and operate the motor within a reasonable speed range to reduce mechanical wear, increase service life, reduce fan vibration and noise, enhance system stability, and reduce noise impact on the environment.

[0016] 3. Low power factor problem: Wind power generation systems may cause the power factor of the power grid to decrease. The main reason is that the power generated by the wind turbine system is AC power, and its power factor is usually close to 1, which means that the ratio between active power and apparent power is high. For industrial loads, the active power provided by the system is consumed, but the reactive power is not effectively compensated. The decrease in power factor is an important issue for power companies because they need to maintain the stable operation of the power grid and ensure that the power factor is within a reasonable range. When the power factor is lower than the specified threshold, the industrial park may face fines.

[0017] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0018] The purpose of the present invention is to solve the technical problems existing in the background technology. To this end, a backflow prevention control method for a wind power generation system is provided.

[0019] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0020] A backflow prevention control method for a wind power generation system, comprising:

[0021] The fan controller uses the anti-reverse flow measurement device to monitor in real time whether there is reverse flow of power in any phase of the A phase, B phase, and C phase of the power grid. If reverse flow of power is detected, the fan limit power is calculated;

[0022] The wind turbine controller measures the total power factor of the power grid in real time through the anti-backflow measurement device, and adjusts the active and reactive power output of the wind turbine according to the measurement results. The inverter adjusts the final power limit to keep the power factor of the power grid within the set range;

[0023] The fan controller looks up the table and calculates the theoretical speed of the fan at the current moment according to the set final power limit. The fan controller tracks the speed according to the theoretical speed to ensure that the fan remains in the optimal speed range.

[0024] The following is a technical solution further defined by the present invention, in which the wind turbine controller obtains the real-time monitoring value of the power grid through the optical fiber to 485 communication module.

[0025] The following is a technical solution further limited by the present invention. The real-time monitoring power value obtained is calculated. First, three times the minimum power is calculated, and then three times the minimum power is compared with the target reverse flow power to determine whether there is a reverse flow in the power grid. If the calculated difference is positive, it indicates that there is a reverse flow. If the difference is negative or zero, it indicates that there is no reverse flow.

[0026] The following is a technical solution further defined by the present invention. If there is a reverse flow in the power grid, the fan limit power P is calculated. limit :

[0027] P limit =K 1 *P last +(1-K 1 )*(p grnd +P wind -P target )

[0028] Plimit : fan limit power;

[0029] P last : The previous fan limit power;

[0030] K 1 : fan limit power gain;

[0031] P grid : Anti-backflow device measures single-phase minimum power*3;

[0032] P wind : Real-time output power of the fan;

[0033] P target : Target reverse flow power.

[0034] The following is a technical solution further defined by the present invention: the wind turbine limit power gain K 1 is a coefficient, when K 1 The larger the value, the more sensitive the system is to the change of reverse power. 1 The smaller it is, the less sensitive the system is to the changes in reverse power.

[0035] The following is a technical solution further defined by the present invention. If the power factor of the power grid is lower than a set threshold, the wind turbine controller performs the operation of power factor compensation reactive power:

[0036] Firstly, determine the reverse current power limit value and the power factor active power limit value, and find the minimum value between them;

[0037] The current reactive power value is obtained, and the minimum value and reactive power value are sent to the inverter as parameters. The inverter adjusts the output power and the final limit power according to the received instructions.

[0038] The following is a technical solution further defined by the present invention: if the power factor of the power grid is higher than or equal to a set threshold, at this time, the wind turbine controller performs the operation of the final limit power: maintaining the original output power and the final limit power.

[0039] The following is a technical solution further limited by the present invention. According to the final limit power and the speed power curve of the fan, the speed range corresponding to the power is determined, and a table is looked up to determine whether the fan remains in the optimal speed range. If the fan remains in the optimal speed range, the fan maintains its original working operation. If the fan is not in the optimal speed range, the theoretical speed of the fan at the current moment is calculated.

[0040] The following is a technical solution further defined by the present invention. The theoretical speed N of the fan at the current moment is limit :

[0041] N limit =Ntarget +K 2 *N nome

[0042] N limit : Fan speed limit;

[0043] N target : The fan speed power curve table looks up the target speed;

[0044] K 2 : Fan speed gain;

[0045] N nome : Rated speed of fan.

[0046] The following is a further technical solution of the present invention, which gradually increases the fan speed gain K 2 value, and observe whether the fan speed is within the optimal speed range each time, until a K value that keeps the fan within the optimal speed range is found. 2 value.

[0047] Compared with the prior art, the present invention has the following technical effects:

[0048] The present invention solves the problems of wind power generation system in terms of operating efficiency, power factor and power reverse flow through measurement and monitoring, output power control, anti-reverse flow control, system monitoring and optimization, improves the operating efficiency and reliability of the wind power generation system, and ensures the stable operation of the power grid.

[0049] The present invention is further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0051] Figure 1 It is a connection schematic diagram of the anti-backflow power grid system in the present invention;

[0052] Figure 2 It is a principle block diagram of the anti-backflow control device in the present invention;

[0053] Figure 3 It is a schematic diagram of the method principle of the present invention;

[0054] Figure 4 It is a schematic flow chart of the method of the present invention. DETAILED DESCRIPTION

[0055] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0056] like Figure 1 and 2 As shown, this embodiment provides an anti-backflow power grid system and an anti-backflow control device, which can monitor and control the backflow problem between the wind power generation system and the power grid, solve the communication interference and slow communication problems of the anti-backflow device, ensure the positive flow of electric energy, and maintain the stable operation of the power grid.

[0057] like Figure 3 and 4 As shown, this embodiment provides a method for preventing reverse flow control of a wind power generation system, which prevents reverse flow problems between the wind power generation system and the power grid, and suppresses the occurrence of power oscillation, thereby improving the stability and reliability of the system, while ensuring the safe operation of the power grid. Through measurement and monitoring, output power control, reverse flow control, and system monitoring and optimization, the problems of wind power generation system in terms of operating efficiency, power factor, and power reverse flow are solved, the operating efficiency and reliability of the wind power generation system are improved, and the stable operation of the power grid is guaranteed.

[0058] A backflow prevention power grid system is composed of a park power grid, a power distribution room, industrial loads, a wind turbine generator set, a backflow prevention control device, a backflow prevention communication optical fiber, etc. The backflow prevention control device is composed of a fan controller, a backflow prevention measurement device, a power grid, etc.

[0059] The anti-backflow measurement device measures the industrial load bus power and provides real-time feedback to the fan controller.

[0060] In order to meet the application requirements of different parks, the following three measurement points are recommended for power monitoring:

[0061] ① High-voltage side total load power measurement point: measure the total load power of the high-voltage side power grid of the industrial park system; this measurement point is suitable for newly built or under-construction industrial parks and buildings.

[0062] ② Low-voltage side total load power measurement point: measure the total load power of the low-voltage side grid of the industrial park system. This measurement point is suitable for most industrial parks and buildings, where the construction and renovation projects are relatively small. The anti-backflow device is used to measure the total bus power, which can achieve the highest power generation efficiency of the wind turbine.

[0063] ③ Low-voltage side bus main power trunk node measurement point: measure the bus main power trunk node of the low-voltage side grid of the wind power generation system. This measurement point is suitable for large industrial parks and buildings. It is particularly useful when the total industrial load is much larger than the installed capacity and the wind turbine main control is far away from the main distribution room. The nearest high-power load point can be selected for measurement, thereby saving engineering construction costs.

[0064] Through these measurement points, the load system can be fully monitored and the electric energy can be measured, the system operation status can be understood in real time, and possible problems can be discovered in time. The load system's current, voltage, power, power factor and other parameters can be monitored to timely discover faults or abnormalities in the system. In addition, these measurement points can also provide strong support for the optimization of the load system and the calculation of power generation benefits. By analyzing the measurement data, the working status and load characteristics of the load system can be understood, the system control strategy can be optimized, and the system efficiency and economy can be improved. At the same time, the measurement data can also be used to calculate the power generation benefits, evaluate the power generation capacity and predict the power generation income, providing an important reference for the company's business decision-making.

[0065] The anti-backflow control device consists of a fan controller, optical fiber, communication module TCP-485, smart meter, Rogowski coil mutual inductor, power grid, etc.

[0066] Wind turbine controller: The main control system of a wind turbine. When the power generated by a wind turbine exceeds the power grid's demand, it limits or adjusts the generator's output to ensure that too much power is not injected into the power grid, thereby maintaining stable operation of the power grid.

[0067] Optical fiber: The transmission medium between the fan controller and the anti-backflow measurement device has strong anti-interference ability and is not affected by electromagnetic interference. It supports a larger bandwidth and faster transmission speed.

[0068] Communication module TCP-485: Interface conversion device between optical fiber communication and RS-485 communication, used in scenarios with long-distance transmission and strong anti-interference ability. It can achieve reliable and stable signal transmission and improve the anti-interference and reliability of the system.

[0069] Smart meter: 485 communication smart meter is an energy metering device equipped with a communication module, which can realize remote data transmission and communication functions. 485 connected to the communication module, the communication smart meter transmits power usage data, power load conditions and other related information in real time, allowing the wind turbine control system to be remotely monitored and managed.

[0070] Rogowski coil transformer: a sensor device used to measure AC current. It has the characteristics of small size, light weight, portable installation and strong applicability. Compared with the traditional iron core transformer, the Rogowski coil adopts a slender coil structure, which is smaller in size and weight. The Rogowski coil is flexible and can be directly put on the conductor of the measured current, which is easy to install. Choose the appropriate Rogowski coil diameter according to the needs to meet the requirements of most power grid busbar sizes on the market.

[0071] A backflow prevention control method for a wind power generation system, comprising:

[0072] The wind turbine controller uses the anti-reverse flow measurement device to monitor in real time whether there is any reverse flow of power in any phase of the power grid, namely, phase A, phase B, and phase C. If reverse flow of power is detected, the wind turbine limit power is calculated. The calculation process can help determine the reverse flow power that the wind turbine should limit, effectively monitor and control the reverse flow, and ensure that the wind turbine operates within an acceptable range.

[0073] The wind turbine controller measures the total power factor of the power grid in real time through the anti-backflow measurement device, and adjusts the active and reactive power output of the wind turbine according to the measurement results. The inverter adjusts the final power limit to keep the power factor of the power grid within the set range. By dynamically adjusting the power output of the wind turbine, the controller can ensure that the power factor of the power grid operates in an ideal working state, effectively optimize the impact of the wind turbine on the power grid, and improve the stability and efficiency of the power grid.

[0074] The fan controller looks up the table and calculates the theoretical speed of the fan at the current moment according to the set final power limit. The fan controller tracks the speed according to the theoretical speed to ensure that the fan remains in the optimal speed range. This control method can make the fan always run at the optimal speed during the working process, and maximize the efficiency of the fan.

[0075] Specifically:

[0076] 1. The fan controller obtains the real-time monitoring value of the grid power through the optical fiber to 485 communication module.

[0077] 2. The real-time monitoring power value obtained is calculated. First, three times the minimum power is calculated, and then three times the minimum power is compared with the target reverse flow power to determine whether the grid power has reverse flow. If the calculated difference is positive, it means that there is reverse flow, and the power calculation process is performed, that is, the fan limit power P is calculated. limit :

[0078] P limit =K 1 *P last +(1-K 1 )*(P grid +Pwind -P target ) (1)

[0079] P limit : fan limit power;

[0080] P last : The previous fan limit power;

[0081] K 1 : fan limit power gain;

[0082] P grid : Anti-backflow device measures single-phase minimum power*3;

[0083] P wind : Real-time output power of the fan;

[0084] P target : Target reverse flow power.

[0085] Formula (1) is the anti-backflow power scheduling formula, which describes a power scheduling method, where K 1 is a coefficient, which is adjusted by K 1 The size of can control the degree of smoothing. 1 When the coefficient is large, the system is more sensitive to the change of reverse flow power, and the effect of smoothing will be more obvious; 1 When the coefficient is small, the system is relatively insensitive to the change of reverse flow power, and the effect of smoothing will be weakened. Therefore, the anti-reverse flow power scheduling formula can be obtained by using a suitable K 1 The coefficient is set to smooth the reverse flow power, thereby reducing the instantaneous change and oscillation of power and improving the stability and reliability of the system.

[0086] If the difference is negative or zero, it means there is no reverse flow, and the power factor detection process is performed.

[0087] 3. The real-time monitoring power factor value obtained will be used to determine whether the power factor of the power grid reaches the target setting; if the power factor of the power grid is lower than the set threshold, it means that the power factor of the power grid is insufficient. At this time, the fan controller performs the power factor compensation reactive power operation to improve the power factor of the power grid. Specifically: first determine the reverse power limit value and the power factor active limit value, and find the minimum value between them; this minimum value will be used as a reference value for power scheduling. Next, obtain the current reactive power value, and send the minimum value and reactive power value as parameters to the inverter to perform power scheduling operations. The inverter adjusts the output power and the final limit power according to the received instructions to ensure that the reverse power does not exceed the limit and reaches the required power factor to complete the power scheduling.

[0088] If the power factor of the grid is higher than or equal to the set threshold, it means that the power factor of the grid has reached the requirement. At this time, the fan controller performs the final limit power operation: maintaining the original output power and the final limit power.

[0089] 4. According to the final limit power and the speed power curve of the fan, determine the speed range corresponding to the power, and check the table to determine whether the fan is kept in the optimal speed range. If the fan is kept in the optimal speed range, the fan will keep working as before. If the fan is not in the optimal speed range, calculate the theoretical speed N of the fan at the current moment. limit :

[0090] N limit =N target +K 2 *N nome (2)

[0091] N limit : Fan speed limit;

[0092] N target : The fan speed power curve table looks up the target speed;

[0093] K 2 : Fan speed gain;

[0094] N nome : Rated speed of fan.

[0095] Formula (2) is the motor speed limit formula. This formula describes a speed limit method. According to the speed power curve of the fan, the speed range corresponding to the optimal speed range (also known as the highest speed efficiency range) can be determined. According to the speed range of the optimal speed range, K is gradually adjusted. 2 Usually, one can start from a smaller K 2 value, and gradually increase K 2 Each time, observe whether the fan speed is within the optimal speed range until a suitable K value is found that can keep the fan within the optimal speed range. 2 value, so that the fan remains in the optimal speed range, reducing mechanical wear and fan noise, and improving the fan's energy efficiency and service life.

[0096] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, all equivalent changes made according to the shape, structure and principle of the present invention without departing from the content of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preventing backflow in a wind power generation system, characterized in that: include: The fan controller uses the anti-reverse flow measurement device to monitor in real time whether there is reverse flow of power in any phase of the A phase, B phase, and C phase of the power grid. If reverse flow of power is detected, the fan limit power is calculated; The wind turbine controller measures the total power factor of the power grid in real time through the anti-backflow measurement device, and adjusts the active and reactive power output of the wind turbine according to the measurement results. The inverter adjusts the final power limit to keep the power factor of the power grid within the set range; The fan controller looks up the table and calculates the theoretical speed of the fan at the current moment according to the set final power limit. The fan controller tracks the speed according to the theoretical speed to ensure that the fan remains in the optimal speed range.

2. A wind power generation system backflow prevention control method according to claim 1, characterized in that: The fan controller obtains the real-time monitoring value of the grid power through the optical fiber to 485 communication module.

3. A backflow prevention control method for a wind power generation system as claimed in claim 2, characterized in that: The real-time monitoring power value obtained is calculated. First, three times the minimum power is calculated, and then three times the minimum power is compared with the target reverse flow power to determine whether there is a reverse flow in the power grid. If the calculated difference is positive, it means there is a reverse flow. If the difference is negative or zero, it means there is no reverse flow.

4. A backflow prevention control method for a wind power generation system according to claim 1, characterized in that: If there is reverse flow in the power grid, calculate the wind turbine limit power P limit : P limit =K1*P last +(1-K1)*(P grid +P wind -P target ) P limit : fan limit power; P last : The previous fan limit power; K1: fan limit power gain; P grid : Anti-backflow device measures single-phase minimum power*3; P wind : Real-time output power of the fan; P target : Target reverse flow power.

5. A backflow prevention control method for a wind power generation system as claimed in claim 4, characterized in that: The fan limit power gain K1 is a coefficient. The larger K1 is, the more sensitive the system is to the change of reverse flow power. The smaller K1 is, the less sensitive the system is to the change of reverse flow power.

6. A backflow prevention control method for a wind power generation system according to claim 1, characterized in that: If the power factor of the grid is lower than the set threshold, the fan controller will perform the power factor compensation reactive power operation: Firstly, determine the reverse current power limit value and the power factor active power limit value, and find the minimum value between them; The current reactive power value is obtained, and the minimum value and reactive power value are sent to the inverter as parameters. The inverter adjusts the output power and the final limit power according to the received instructions.

7. A backflow prevention control method for a wind power generation system according to claim 1, characterized in that: If the power factor of the power grid is higher than or equal to the set threshold, the wind turbine controller performs the final limit power operation: maintain the original output power and the final limit power.

8. A backflow prevention control method for a wind power generation system as claimed in claim 6 or 7, characterized in that: According to the final limit power and the speed power curve of the fan, the speed range corresponding to the power is determined, and the table is looked up to determine whether the fan remains in the optimal speed range. If the fan remains in the optimal speed range, the fan maintains its original working operation. If the fan is not in the optimal speed range, the theoretical speed of the fan at the current moment is calculated.

9. A backflow prevention control method for a wind power generation system as claimed in claim 8, characterized in that: The theoretical speed of the fan at the current moment N limit : N limit =N target +K2*N nome N limit : Fan speed limit; N target : The fan speed power curve table looks up the target speed; K2: fan speed gain; N nome : Rated speed of fan.

10. A backflow prevention control method for a wind power generation system according to claim 9, characterized in that: Gradually increase the fan speed gain K2 value, and observe each time whether the fan speed is within the optimal speed range, until a K2 value that keeps the fan in the optimal speed range is found.

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