Wind turbine control strategy conditions l Rural pastoral mechanization The first wind energy utilization technology in 2011 is one of the fastest developing and clean renewable energy technologies. Its main forms of utilization include wind power generation, wind power lifting, and sail navigation aids. . In addition, it can also be complementary to other energy sources and combine both to generate electricity. Wind energy utilization technology is playing an increasingly important role in the energy crisis.

According to different ways of lifting water, modern wind water lifting machines can be divided into two categories: mechanical wind lifting water and wind power pumps. 1. Wind power pumps are new types of wind power water lifting methods that have emerged in recent years. There are two basic types of wind water lifting pumps: One is to pump water for the wind energy storage and electric pump; the other is that the wind generator generates electricity within the effective wind speed range and directly drive the electric pump to lift water. Although the latter saves the storage battery and the inverter system compared with the former, reducing the intermediate links and reducing the cost of the water lifting system to some extent, the control difficulty increases, and there is still no very effective control strategy. Therefore, this paper aims to discuss the control strategy of wind power pumps, hoping to have a certain guiding significance for the realization of real wind power pumps.

1 Structure and composition of wind power pumps Due to the different tasks undertaken by each part of the wind power pump, we can divide it into four parts, namely the wind energy conversion system, the rectification and inverter system, the pump water system and the control system. The main task of the wind energy conversion system is to convert captured wind energy into electrical energy. Its main structure includes wind turbines, generators, etc. The task of the rectifier and inverter system is to further fine tune the electrical energy to make it a qualified electrical energy that can be used, mainly The structure consists of rectifiers, inverters, and accumulators; the main task of the pumping system is to extract groundwater and store it in a reservoir, which is used by the people; the main task of the control system is to assist the safe and effective operation of the wind pump system. At the same time provide protection for each device.

After analyzing the above structure, considering the various needs of users, the wind power pump structure as shown is adopted. It should be noted that in the wind power pump system shown in the figure, the battery is not only a device for storing energy and voltage, but also a standby power source for the pump. When it is not possible to use wind power to lift water and it is necessary to lift water, the water pump is powered to ensure water demand.

2 Wind power pump working condition analysis For the above-mentioned wind power pump system, the wind power generation system in the wind power pump has the load as the water pump. During the normal operation, there is a coupling phenomenon between the motor and the generator of the water pump, which can realize the load. Automatic matching, therefore, its operating conditions are slightly different from the general small wind power system. The following are the operating conditions of the wind pump in the process of gradually increasing wind speed: 2.1 Wind turbine start In the process of gradually increasing the wind speed, when the wind speed reaches the wind turbine cutting speed Vmin, the wind wheel starts to rotate, driving the generator to work. Due to the low output power of the wind turbine in the early stage of start-up, it cannot meet the requirements for use. This part of the energy is only used for battery charging.

2.2 The pump starts With the increase of wind speed, the output power of the wind turbine also increases. When the output reaches the required conditions for starting the water pump, the water pump starts and starts pumping water.

2.3 Normal operation of wind power pump As the wind speed continues to increase, the generator and the water pump motor are in a coupled state. The water pump automatically follows the output of the wind turbine and adjusts its output flow. 13. At this time, if the battery can be charged, the power is not zero. At the same time, the battery can also be charged.

2.4 Shutdown of the wind turbine pump When the wind speed increases to the cut-out speed Vmax, the wind turbine stops working and the water pump no longer lifts water. At this time, if water needs to be pumped, the battery can be used as a power source to start the pump to extract a certain amount of water when the battery is not overcharged.

3 Wind power pump control strategy Since the water pump can automatically track the output of the wind turbine, it is not necessary to consider the power matching problem of the load during operation. Therefore, the key issues in the control of the designed wind power pump system are the start-up control of the pump, the control of the high-winding stop, and the protection control.

3.1 Start-up control strategy of wind power pump water pump In this paper, the control system adopts the structure of parallel connection of battery and inverter. As the terminal voltage during the charge and discharge of the battery does not change much, it is determined to be a fixed value. If the loss is not taken into account, the battery and the inverter can be identified as a constant voltage alternating power supply. Therefore, before the water pump starts, the battery charging current Fm is used to control the pump start signal. Thus, the following control strategy is designed: With the starting current Ip of the pump as the given value, the difference between the charging current and the battery charging current Fm is input to the starting controller, and the control of starting the pump is realized.

3.2 Wind power system control strategy For generators, the output power increases with the increase of wind speed, but if the output power exceeds the maximum output power, the generator will be damaged. Therefore, in order to ensure the normal operation of the wind turbine, a governor mechanism must be used to limit the maximum output power of the generator. For small wind turbines, due to economic considerations, torsional wind wheels are generally used to reduce the windward area of ​​the wind turbine to achieve the purpose of limiting the power output of the generator. There are two common speed limit measures: One is to use the balance between the wind pressure on the wing plate and the tension of the spring to achieve lateral speed control, the other is the eccentric torque and friction The balance between the moments to achieve the wind wheel sideways 4. 3.3 Battery protection control In order to ensure the safe operation of wind power pumps, protection control must be designed for sensitive and vulnerable components. The battery is an important part of this. In a wind power pump, overshoot and overdischarge of the battery will affect its operation safety and service life. Therefore, overcharge and overdischarge protection of the battery must be designed in the wind power pump system. Since the battery terminal voltage Vb can be used to characterize its operating conditions, we can determine the timing of overshoot and over-discharge protection by monitoring the battery terminal voltage. Limit the battery terminal voltage between the maximum and minimum values. When VfVmax is overcharged, the battery is in the state of edge charging. When Vb=Vmin, the load is cut through overdischarge protection, and the battery is in charge or stopped.

In addition to battery protection, there are other electrical components that need protection, such as pump motors.

4 conclusions This paper through the analysis of the simple wind power pump system working conditions, put forward the corresponding control strategy, the purpose is to ensure the safe and effective operation of wind power pumps, draw the following conclusions.

4.1 Compared with the traditional mechanical wind power lifting technology, the lifting of water from the wind power pump solves the problem of large starting torque of mechanical water lifting, enlarges the wind speed range of lifting water, and improves the utilization rate of wind energy. Separation of the wind-fetching place and the water-taken place is realized, making water use more convenient.

4.2 Since the users of wind power pumps are mostly located in remote areas far away from the power grid, taking into account the difficulty of maintenance and the convenience of use, wind power pumps should adopt simple and safe control strategies when designing and controlling them, minimizing costs, reducing maintenance rates, and improving The safety factor increases its service life.

4.3 The most simple wind pump system is designed in this paper, so its use is very simple. However, with a reasonable load control system, the purpose of using other loads while lifting water can be achieved.

The simple, effective and safe control strategy is the most important key technology for realizing or promoting the application of wind power pumps. We have a good practical significance and theoretical guidance for us to discuss.

1 Liu Huimin, Wu Yongzhong, Liu Wei. Wind power lifting and wind power water lifting technology. Renewable energy 2005.3

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