Control method for wind driven generator to follow optimal power coefficient conforming to aerodynamics
By using a wind turbine controller and MPPT algorithm, the generator speed is adjusted in real time, solving the problem that the wind turbine speed cannot track the optimal tip speed ratio, and achieving efficient power generation under different wind speed conditions.
Patent Information
- Application Number
- CN202510887573.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-30
- Publication Date
- 2025-10-31
AI Technical Summary
The speed of existing wind turbines cannot track the optimal tip speed ratio in real time, which prevents them from maximizing power output. Furthermore, the control methods rely on human experience and have a narrow range of adaptability to wind speeds.
A wind turbine controller is used to establish a stable DC bus voltage through an active inverter and a DC converter. Combined with the MPPT algorithm, the generator speed is adjusted in real time to achieve active tracking of wind speed and ensure that the tip speed ratio is at the optimal point.
It enables wind turbines to automatically track the optimal power point under different wind speed conditions, improving power generation efficiency, avoiding long-term debugging and manual intervention, and is highly adaptable.
Smart Images
Figure CN120879736A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for controlling the power coefficient of an electric motor, specifically to a method for controlling a wind turbine to follow a control method that conforms to the optimal power coefficient for aerodynamics. Background Technology
[0002] The ratio of the tip speed (linear velocity) of the outermost blade of a wind turbine to the wind speed is called the tip speed ratio. At a given wind speed, achieving the optimal tip speed ratio means generating the maximum electrical energy at that turbine rotational speed. To ensure that the wind turbine always fully utilizes wind energy and achieves maximum power generation at a given wind speed, the turbine rotational speed (proportional to the generator rotational speed) should continuously adjust to the wind speed to maintain the tip speed ratio at its optimal point.
[0003] Current technology involves the generator's rotational speed being passively driven by the wind. The generator is driven by two torques: 1) wind energy (positive torque) and 2) generator power output (negative torque). The balance point of these two torques determines the generator's rotational speed. The positive torque accelerates the impeller, while the negative torque decelerates it. When the positive and negative torques are equal, the rotational speed stabilizes. However, this "stabilized" speed is often not the optimal tip speed ratio, meaning the turbine's maximum power cannot be achieved. The negative torque occurs passively during this process. The generator's controller passively monitors the generator's output voltage, current, and frequency. When the voltage increases, it absorbs more current, indirectly increasing the negative torque to reach a new balance point. Often, a wind turbine has a voltage-current curve, and the current is adjusted according to the voltage. This curve often doesn't align with the optimal tip speed ratio curve. Furthermore, this curve can only be determined manually. Therefore, most manufacturers set this curve based on experience. This curve can only work within a relatively narrow wind speed range. Therefore, it is necessary to design a wind turbine generator control method that can actively adjust the generator speed under different wind speeds, and ultimately track the optimal tip speed ratio in real time, so that the wind turbine can be in the state of maximum power generation for a long time. Summary of the Invention
[0004] To address the problems existing in the prior art, the present invention provides a control method for wind turbines to follow the optimal power coefficient that conforms to aerodynamics, thereby solving the above-mentioned technical problems.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a control method for wind turbines to follow the optimal power coefficient in aerodynamics, wherein the control method employs the following wind turbine controller;
[0006] The wind turbine controller includes an input terminal and an output terminal. The input terminal is connected to the wind turbine generator, and the output terminal is connected to the power grid or load. In the middle is a constant voltage circuit, which can be provided by a DC-DC converter or by an active inverter at the output terminal.
[0007] The input terminal is set as an active inverter, where the generator output voltage corresponding to the inverter at the input terminal is variable, and the inverter at the output terminal can operate in active inverter mode to establish a stable DC bus voltage; the DC-DC converter can also be used to establish a stable DC bus voltage.
[0008] When the input inverter generates negative torque in the generator (generating state), the inverter charges the bus voltage. At this time, the output inverter discharges the bus voltage to supply power to the grid, or the DC converter charges the battery. This is the operating state of the wind turbine during the power generation process.
[0009] When the input inverter generates positive torque in the generator, the input inverter discharges to the bus voltage. At this time, the output inverter charges the bus voltage. Then, the output inverter draws power from the grid, or the DC inverter charges the bus voltage. This is the motor operating state generated when the wind turbine adjusts according to the wind speed and temporarily controls the generator speed.
[0010] In both of the above operating states, the bus voltage must be maintained at a stable level. This function is accomplished by the output inverter or DC-DC converter.
[0011] The specific method for automatically tracking wind speed using the aforementioned fan controller is as follows:
[0012] Step S1: At the current wind turbine speed, the generator is controlled by the input inverter to operate in speed control mode. At this time, the current power is calculated by measuring the DC current and voltage of the bus. Then, by finely adjusting the motor speed, the power P2 and P3 are measured, and the generator is operated at the higher power.
[0013] Step S2: Repeat the method in S1. This process is the MPPT (Maximum Power Point Tracking) algorithm process, until at a certain wind turbine speed, fine-tuning downwards and upwards can no longer find a greater power output. This is the maximum power point.
[0014] Furthermore, when the wind speed is greater than the design wind speed, the control terminal monitors the engine power. When the generator reaches the rated power, if the power generation continues to increase, the MPPT algorithm changes direction and looks for the point where the power decreases until the power is maintained near the rated power.
[0015] Furthermore, in extremely strong winds, the MPPT algorithm rapidly adjusts the fan speed so that the negative torque received by the fan is greater than the positive torque, thus accelerating the fan's deceleration until the fan stops.
[0016] Furthermore, when the wind speed is low, the wind turbine cannot start on its own. In this case, the active inverter is used to start the generator. Then, the MPPT algorithm is activated. When the wind speed is low, the MPPT algorithm will reduce the speed of the generator until the maximum power is obtained at a certain speed. If the maximum power cannot balance the mechanical loss of the wind turbine, then the wind turbine will stop. When the wind speed is high, the maximum power is greater than the mechanical loss of the wind turbine, and the current power is maintained to continue generating electricity.
[0017] Furthermore, the specific implementation method of the MPPT algorithm is as follows:
[0018] At the current rotational speed, measure the current power P1.
[0019] Step 1: First, adjust the speed using Speed + Δspeed.
[0020] Step 2: Measure the input power of the controller, stabilize for 30 seconds, and obtain the power P3;
[0021] Step 3: Speed adjustment, Speed-Δspeed
[0022] Step 4: Measure the input power of the controller, stabilize for 30 seconds, and obtain the power P2;
[0023] Step 5: If power P3 > power P2 and P3 > P1, adjust to the new speed: Speed = Speed + Δspeed
[0024] Step 6: If power P2 > power P3, and P2 > P1, adjust to the new speed Speed = Speed
[0025] -Δspeed
[0026] Step 7: If power P1 > power P2 and P1 > P3, maintain the current speed Speed = Speed
[0027] Return to step 1 and repeat, where Speed is the current motor speed, and Δ speed The speed change is represented by P1, P2, and P3, which are the output power of the generator at different speeds. Speed regulation methods can include voltage speed regulation, current speed regulation, frequency speed regulation, and vector control.
[0028] Furthermore, it also includes a bidirectional DC / DC converter and an energy storage battery.
[0029] This bidirectional DC / DC converter is used to establish a stable DC bus voltage when the wind turbine is operating off-grid.
[0030] When in off-grid mode, the energy storage battery is added to the system to act as a voltage source. By adjusting the PWM value of the DC / DC converter, the bus voltage is adjusted, thereby stabilizing the bus voltage.
[0031] The beneficial effects of this invention are: this method ensures that the fan operates at its optimal aerodynamic power point at all times. It avoids lengthy manual data testing and machine debugging, and changes in operating conditions allow the control software to automatically track the optimal tip speed ratio. This enables large-scale on-site installation and immediate achievement of maximum operating power. Attached Figure Description
[0032] Figure 1 A schematic diagram of the controller implemented in the grid-connected state for the MPPT algorithm of the present invention;
[0033] Figure 2 A schematic diagram of the controller implemented by the MPPT algorithm of the present invention in the off-grid energy storage state;
[0034] Figure 3 This is a schematic diagram of the power coefficient versus tip speed ratio of the present invention. Detailed Implementation
[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.
[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.
[0037] like Figure 1 As shown in Embodiment 1, the wind turbine controller consists of two parts: an input terminal and an output terminal. The input terminal is the end connected to the wind turbine generator, and the output terminal is the end connected to the power grid (if operating in grid-connected mode) or the load (if operating off-grid). Generally, the input terminal is a passive rectifier that converts the AC voltage output from the generator into DC voltage. The output terminal is an inverter that converts the DC voltage back to AC voltage. Between the rectifier and the output inverter is the DC bus voltage.
[0038] See Figure 1In grid-connected mode, because the input is a passive rectifier, the generator can only function as a generator; that is, the controller can only generate negative torque on the generator. To actively adjust the generator speed, it's necessary to generate positive and negative torque on the generator as needed. Therefore, the passive rectifier at the input needs to be replaced with an active inverter.
[0039] If the controller's input is replaced with an active inverter, then the DC bus voltage corresponding to the inverter needs to be stable. Since the generator output voltage corresponding to the input inverter is variable, the task of maintaining the DC bus voltage can only be accomplished by the output inverter or DC-DC converter.
[0040] The output inverter is an active inverter, so the hardware remains the same; only the software is modified. Since the output inverter draws grid voltage, which is relatively stable, it is feasible to use it to establish a stable DC bus voltage.
[0041] When the input inverter generates negative torque in the generator, the inverter charges the bus voltage. In order to ensure the stability of the bus voltage, the output inverter discharges the bus voltage, which in turn supplies power to the grid. This is the power generation process, and the wind turbine operates in this state most of the time.
[0042] When the input inverter generates positive torque in the generator, it discharges to the bus voltage. Similarly, the output inverter can only charge to the bus voltage, at which point it draws power from the grid. The generator is essentially operating as a motor. This is the working state that occurs when the generator speed is temporarily controlled as the wind turbine adjusts its speed according to the wind speed. This is also the key technology of this invention. Theoretically, this is a method of using two bidirectional inverters back-to-back, completing both motor control and energy flow control functions.
[0043] In addition, the current wind speed is measured or estimated using the MPPT (Maximum Power Operating Point Tracking) algorithm, with reference to... Figure 3 As shown, operating point 1 is the operating point that generates maximum power. At this tip speed ratio, only one fan speed can produce maximum power. The specific method for finding the maximum power point is as follows: 1. At the current fan speed, the generator operates in speed control mode. 2. Simultaneously, calculate the current power by measuring the DC current and voltage of the bus. Then, by fine-tuning the motor speed, adjusting it upwards and downwards, measure the power at the other two speeds, select the speed with the higher power, and operate at that speed. Repeat the above process until at a certain fan speed, fine-tuning downwards and upwards no longer yields a greater power output; this point is the maximum power point. This process can be completed without an anemometer.
[0044] When the wind speed is greater than the design wind speed, the software is constantly monitoring the generator power. Therefore, once the generator reaches its rated power, if the power generation continues to increase, the MPPT algorithm changes direction and looks for a point where the power decreases until the power is maintained near the rated power.
[0045] In extremely strong winds, the MPPT algorithm can quickly adjust the fan speed, ensuring that the negative torque received by the fan is greater than the positive torque. This accelerates the fan's deceleration until it stops, effectively preventing potential damage to the fan in strong winds.
[0046] The MPPT method can also operate in light winds: When the wind is very weak, the wind turbine won't start. In this case, the active inverter is used to start the generator (which acts as a motor), and then the MPPT algorithm is activated: 1. If the wind speed is too low, MPPT will reduce the generator speed until it reaches maximum power at a certain speed. If this maximum power cannot compensate for the wind turbine's mechanical losses, the wind turbine will stop. 2. If the wind speed is high enough, it will maintain the current power output and continue generating electricity. This achieves two things: 1. In a very low wind speed, the wind generally cannot push the wind turbine, so it has no chance to generate electricity. With this function, the active inverter starts the wind turbine, giving it a chance to attempt power generation at a lower wind speed and maintain stable power generation. 2. If the power generated at this wind speed cannot compensate for the system's mechanical losses, the wind turbine will automatically stop and continue to attempt power generation.
[0047] The specific implementation method of the MPPT algorithm is as follows:
[0048] At the current rotational speed, measure the current power P1.
[0049] Step 1: First, adjust the speed using Speed + Δspeed.
[0050] Step 2: Measure the input power of the controller, stabilize for 30 seconds, and obtain the power P3;
[0051] Step 3: Speed adjustment, Speed-Δspeed
[0052] Step 4: Measure the input power of the controller, stabilize for 30 seconds, and obtain the power P2;
[0053] Step 5: If power P3 > power P2 and P3 > P1, adjust to the new speed: Speed = Speed + Δspeed
[0054] Step 6: If power P2 > power P3, and P2 > P1, adjust to the new speed Speed = Speed
[0055] -Δspeed
[0056] Step 7: If power P1 > power P2 and P1 > P3, maintain the current speed Speed = Speed
[0057] Return to step 1 and repeat, where Speed is the current motor speed, and Δ speed The speed change is represented by P1, P2, and P3, which are the output power of the generator at different speeds. Speed regulation methods can include voltage speed regulation, current speed regulation, frequency speed regulation, and vector control.
[0058] In this embodiment 2, when in off-grid mode, the function of stabilizing the bus voltage can be achieved by adding a bidirectional DC / DC converter and an energy storage battery. During off-grid operation, the energy storage battery is added to the system. (See...) Figure 2 Its function is to store energy in the battery during normal power generation. When the load power exceeds the power generation power, the battery will discharge to maintain the balance between power generation power + battery discharge power = load power.
[0059] exist Figure 2 The topology consists of three parts: an input inverter, an output inverter, and a bidirectional DC / DC converter. Since the output inverter's output is the load, it can only output power in one direction and lacks the function of stabilizing the bus voltage. The bidirectional DC / DC converter then assumes this function. It utilizes the battery's voltage source characteristic, adjusting the PWM magnitude of the DC / DC converter to regulate the bus voltage, thereby stabilizing it. Any bidirectional DC / DC converter combined with a battery can perform this function.
[0060] In this way, the input inverter functions the same as in grid-connected applications, and its MPPT power is also the same. The output inverter becomes a unidirectional inverter, and its control method is relatively simpler. The control objective of the DC / DC bidirectional converter is to adjust the bus voltage. With this arrangement, the wind turbine following the optimal power coefficient control method of this patent also holds true in off-grid and energy storage applications.
[0061] The beneficial effects of this invention are: it ensures that the fan operates at its optimal aerodynamic power point at all times, avoiding lengthy manual data testing and machine debugging (which typically takes a year). Furthermore, changes in operating conditions allow the control software to automatically track the optimal tip speed ratio. This enables large-scale on-site installation and immediate achievement of maximum operating power.
[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A control method for a wind turbine to follow a direction that conforms to the optimal power coefficient in aerodynamics, characterized in that, The control method uses the following fan controller; The wind turbine controller includes an input terminal and an output terminal. The input terminal is connected to the wind turbine generator, and the output terminal is connected to the power grid or load. In the middle is a constant voltage circuit, which can be provided by a DC-DC converter or by an active inverter at the output terminal. The input terminal is set as an active inverter, where the generator output voltage corresponding to the inverter at the input terminal is variable, and the inverter at the output terminal can operate in active inverter mode to establish a stable DC bus voltage. The DC converter can also be used to establish a stable DC bus voltage. When the input inverter generates negative torque in the generator, the inverter charges the bus voltage. At this time, the output inverter discharges the bus voltage, thereby supplying power to the grid or charging the energy storage battery. This is the operating state of the wind turbine during the power generation process. When the input inverter generates positive torque in the generator, the input inverter discharges to the bus voltage. At this time, the output inverter charges the bus voltage, or the energy storage battery charges the bus voltage through the DC converter. At this time, the output inverter draws power from the grid, or the energy storage battery discharges. This is the working state that occurs when the wind turbine adjusts according to the wind speed and temporarily controls the speed of the generator. In both of the above operating states, the bus voltage must be kept at a stable voltage. This function is accomplished by the output inverter or DC-DC converter. The specific method for automatically tracking wind speed using the aforementioned fan controller is as follows: Step S1: At the current wind turbine speed, the generator operates in speed control mode. At this time, the current power is calculated by measuring the DC current of the bus. Then, by finely adjusting the motor speed up and down, the power P2 and P3 are measured, and the generator is operated at the higher power. Step S2: Repeat the method in S1. This process is the MPPT algorithm process, until at a certain fan speed, fine-tuning downwards and upwards can no longer find a greater power output. This is the maximum power point.
2. The control method for a wind turbine generator to follow the optimal power coefficient according to claim 1, characterized in that, When the wind speed is greater than the design wind speed, the control terminal monitors the engine power. When the generator reaches the rated power, if the power generation continues to increase, the MPPT algorithm changes direction and looks for the point where the power decreases until the power is maintained near the rated power.
3. The control method for a wind turbine generator to follow the optimal power coefficient according to claim 1, characterized in that, In extremely strong winds, the MPPT algorithm quickly adjusts the fan speed to produce a negative torque, thus accelerating the fan's deceleration until it stops.
4. The control method for a wind turbine following an optimal power coefficient according to claim 1, characterized in that, When the wind is weak, the wind turbine cannot start on its own. At this time, the active inverter is used to start the generator. Then the MPPT algorithm is started. When the wind speed is low, the MPPT algorithm will reduce the speed of the generator until the maximum power is obtained at a certain speed. If the maximum power cannot balance the mechanical loss of the wind turbine, then the wind turbine will stop. When the maximum power is greater than the mechanical loss of the wind turbine, the current power is maintained and the generator continues to generate electricity.
5. The control method for a wind turbine generator to follow the optimal power coefficient according to claim 1, characterized in that, The specific implementation method of the MPPT algorithm is as follows: At the current rotational speed, measure the current power P1. Step 1: First, adjust the speed using Speed + Δspeed. Step 2: Measure the input power of the controller, stabilize for 30 seconds, and obtain the power P3; Step 3: Speed adjustment, Speed-Δspeed Step 4: Measure the input power of the controller, stabilize for 30 seconds, and obtain the power P2; Step 5: If power P3 > power P2 and P3 > P1, adjust to the new speed: Speed = Speed + Δspeed Step 6: If power P2 > power P3, and P2 > P1, adjust to the new speed: Speed = Speed - Δspeed Step 7: If power P1 > power P2 and P1 > P3, maintain the current speed Speed = Speed Return to step 1 and repeat, where Speed is the current motor speed, and Δ speed The speed change is represented by P1, P2, and P3, which are the output power of the generator at different speeds. Speed regulation methods can include voltage speed regulation, current speed regulation, frequency speed regulation, and vector control.
6. The control method for a wind turbine generator to follow the optimal power coefficient according to claim 1, characterized in that, It also includes a bidirectional DC / DC converter and an energy storage battery. This bidirectional DC / DC converter is used to establish a stable DC bus voltage when the wind turbine is operating off-grid. When in off-grid mode, the output of the inverter is the load, and it outputs power in one direction without stabilizing the DC bus voltage. At this time, the energy storage battery will be added to the system to act as a voltage source. By adjusting the PWM value of the DC / DC converter, the bus voltage is adjusted, thereby stabilizing the bus voltage.
7. The control method for a wind turbine generator to follow the optimal power coefficient according to claim 1, characterized in that, It also includes an active inverter at the output end, which is a bidirectional inverter that operates in voltage regulation mode at the input end when connected to the grid.