Double-fed wind power converter and control method thereof
By using the deviation current between the grid connection point current and the rotor current as a feedforward quantity in the doubly-fed wind turbine, the problems of motor parameter dependence and power closed-loop complexity in traditional methods are solved, achieving more efficient control accuracy and system stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHENZHEN HOPEWIND ELECTRIC CO LTD
- Filing Date
- 2025-12-18
- Publication Date
- 2026-04-24
AI Technical Summary
Traditional doubly fed wind turbine excitation current feedforward control methods rely on motor parameters, leading to errors and system instability caused by parameter changes. At the same time, the power closed-loop control is highly complex, increasing the computational load and parameter sensitivity.
The deviation between the grid connection point current and the rotor current is used as a feedforward quantity and directly introduced into the current loop of the rotor-side converter. This simplifies the power closed-loop control logic, reduces the dependence on motor parameters, and quickly compensates for system disturbances through real-time sampling.
It improves the control accuracy and parameter fault tolerance of the excitation current, simplifies the control algorithm, reduces the amount of computation, improves the system's response speed and stability, and reduces hardware costs.
Smart Images
Figure CN121923232A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of wind power technology, and in particular to a doubly fed wind power converter and its control method. Background Technology
[0002] Doubly fed induction generators (DFIGs) are widely used in wind power generation due to their advantages such as small converter capacity, low cost, and flexible control. The performance of their core control components, the grid-side converter and the rotor-side converter, directly determines the efficiency and power quality of the entire power generation system.
[0003] In traditional rotor-side converter vector control strategies, a field current feedforward method based on motor parameters is typically employed. Specifically, the control system needs to accurately calculate the field current component based on the generator's mutual inductance parameters (Lm) and introduce it as a feedforward quantity into the current loop setpoint. However, this method has significant drawbacks: the generator's mutual inductance parameters can change during actual operation due to factors such as temperature and magnetic saturation, leading to deviations between the factory calibration values and actual values. If the mutual inductance parameters used for the feedforward calculation are inaccurate, the calculated field current feedforward quantity will also contain errors. This forces the system's reactive power closed-loop regulator (usually a PI regulator) to output a compensation quantity to correct this error, increasing the system's regulation burden and potentially causing slower dynamic response, increased overshoot, or even system instability in cases of severe parameter mismatch.
[0004] On the other hand, in the power closed-loop control of doubly-fed induction generator (DFIG) wind turbines, there are two mainstream current sampling schemes: one is to sample the total current at the grid connection point (i.e., the sum of the stator current and the grid-side current), and the other is to sample only the stator current. These two schemes introduce complexity into the power setpoint processing.
[0005] (1) When the power closed-loop feedback uses the stator current, the power setpoint (from the main controller) must be converted into the corresponding stator power setpoint according to the motor operating conditions (such as slip) in order to perform closed-loop control with the stator power feedback value calculated from the stator current.
[0006] (2) When the power closed-loop feedback uses the total current, in order to maintain the consistency of the control target, it is necessary not only to convert the power setpoint to the stator power setpoint, but also to convert the power feedback value from the total power to the stator power before performing closed-loop control.
[0007] This conversion between power input and feedback based on different sampling points increases the complexity and computational load of the control algorithm. Furthermore, the conversion process also relies on motor parameters, introducing additional parameter sensitivity risks. Summary of the Invention
[0008] This application provides a doubly-fed wind power converter and its control method to effectively reduce dependence on motor parameters, improve the control accuracy of excitation current and parameter fault tolerance; at the same time, it simplifies the power closed-loop control logic structure and can adapt to systems with different power closed-loop sampling points.
[0009] This application provides a control method for a doubly-fed wind power converter, the control method comprising:
[0010] Obtain the current at the grid connection point and the rotor current on the rotor side;
[0011] Calculate the deviation current between the current at the grid connection point and the rotor current, and introduce the deviation current as a feedforward quantity into the current loop of the rotor-side converter;
[0012] Based on the current given by the power loop output and the feedforward quantity, a control signal for the rotor-side converter is generated.
[0013] In some examples, the control method includes:
[0014] The current at the grid connection point and the rotor current are transformed by coordinate transformation to obtain the q-axis component of the current at the grid connection point and the q-axis component of the rotor current.
[0015] Calculate the q-axis deviation current between the q-axis component of the current at the grid connection point and the q-axis component of the rotor current, and introduce the q-axis deviation current as the first feedforward quantity into the q-axis current loop of the rotor-side converter.
[0016] Based on the q-axis current given by the reactive power loop output and the first feedforward quantity, a first voltage control command is generated for the rotor-side converter.
[0017] In some examples, the reactive power loop outputs the q-axis current setpoint based on the reactive power setpoint and the reactive power feedback value.
[0018] In some examples, the generation of a first voltage control command for the rotor-side converter based on the q-axis current given by the reactive power loop output and the first feedforward includes:
[0019] The given q-axis current is added to the first feedforward quantity and then compared with the rotor q-axis current feedback. The first voltage control command is then generated through the first PI control loop.
[0020] In some examples, the control method includes:
[0021] The current at the grid connection point and the rotor current are transformed by coordinate transformation to obtain the d-axis component of the current at the grid connection point and the d-axis component of the rotor current.
[0022] Calculate the d-axis deviation current between the d-axis component of the current at the grid connection point and the d-axis component of the rotor current, and introduce the d-axis deviation current as a second feedforward quantity into the d-axis current loop of the rotor-side converter.
[0023] Based on the d-axis current given by the active power loop output and the second feedforward quantity, a second voltage control command is generated for the rotor-side converter.
[0024] In some examples, the active power loop outputs the d-axis current setpoint based on the active power setpoint and the active power feedback value.
[0025] In some examples, the generation of a second voltage control command for the rotor-side converter based on the d-axis current given by the active power loop output and the second feedforward includes:
[0026] The given d-axis current is added to the second feedforward quantity and then compared with the rotor d-axis current feedback. The second voltage control command is then generated through the second PI control loop.
[0027] In some examples, the current at the grid connection point includes either the total current at the grid connection point or the stator current.
[0028] In some examples, the control method further includes:
[0029] Obtain the grid voltage;
[0030] Calculate the current reactive power and / or active power based on the grid voltage and the current at the grid connection point.
[0031] This application also provides a doubly-fed wind power converter, which includes a grid-side converter and a rotor-side converter connected via positive and negative DC buses. The doubly-fed wind power converter also includes a controller configured to perform the steps of the control method for the doubly-fed wind power converter.
[0032] The doubly-fed wind power converter and its control method provided in this application effectively reduce the dependence on motor parameters, improve the control accuracy of excitation current and parameter fault tolerance; at the same time, they simplify the power closed-loop control logic structure and can adapt to systems with different power closed-loop sampling points. Specifically,
[0033] 1. This method abandons the traditional feedforward method based on motor mutual inductance (Lm) to calculate the excitation current, and instead uses a directly measurable physical quantity (the deviation current between the grid connection point current and the rotor current) as the feedforward. This deviation current is physically highly correlated with the required excitation component, thus achieving feedforward compensation without the need for precise motor parameters. This significantly reduces the dependence on motor parameters or the system's sensitivity to parameter changes, thereby improving the robustness of the control.
[0034] 2. If the total current at the sampling point is used for power calculation, the power closed-loop control target is the total system power. Therefore, regardless of the motor's operating conditions, the power setpoint no longer requires complex stator power conversion; the total power setpoint from the main controller can be used directly. This greatly simplifies the control algorithm, reduces computational load, and avoids additional parameter dependencies and potential errors introduced by power conversion.
[0035] 3. Since the feedforward quantity comes directly from real-time sampling, the response speed is fast and it is not affected by parameter drift, enabling more accurate and rapid compensation for system disturbances. This reduces the burden on the reactive power loop PI regulator, allowing it to operate in a more linear region, effectively reducing overshoot, accelerating dynamic response, and enhancing the stability of the entire system.
[0036] 4. The current sampling and subtraction operations involved are easily implemented in existing digital signal processors (DSPs) without incurring expensive additional hardware costs. It is easy to upgrade and deploy software on existing control platforms, making it highly practical for engineering applications. Attached Figure Description
[0037] Figure 1 This is a schematic diagram of a doubly-fed wind power generation system provided in an embodiment of this application;
[0038] Figure 2 This is a schematic diagram of the control method for a doubly-fed wind power converter provided in an embodiment of this application;
[0039] Figure 3 This is a schematic diagram of sampling, coordinate transformation, and power calculation provided in the embodiments of this application;
[0040] Figure 4 This is a schematic diagram of the reactive power control loop provided in an embodiment of this application;
[0041] Figure 5 This is a schematic diagram of the active power control loop provided in an embodiment of this application.
[0042] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0043] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer and more understandable, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.
[0044] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0045] Figure 1 This is a schematic diagram of a doubly fed wind power generation system provided in an embodiment of this application.
[0046] like Figure 1 As shown, a doubly-fed induction generator (DFIG) wind power generation system includes a DFIG generator and a DFIG wind power converter (shown by the dashed line in the figure). The DFIG wind power converter includes a grid-side converter and a machine-side converter (i.e., a rotor-side converter) connected by positive and negative DC buses (i.e., the positive DC bus and the negative DC bus). A DC bus capacitor is also connected between the positive DC bus and the negative DC bus. And chopper circuits, etc.
[0047] For doubly-fed wind power generation systems, there is a total current... Stator current Rotor current and grid-side current When the generator-side converter uses stator voltage-oriented vector control, the d-axis of the synchronous rotating coordinate system is oriented towards the stator voltage vector U. s At that time, combining the voltage equation and flux linkage equation of the doubly-fed motor, and neglecting the stator resistance R... s Under these circumstances, the following formula (1) can be derived:
[0048] In equation (1), , , , These are the d-axis and q-axis components of the stator current and magnetic flux, respectively. , These are the d-axis and q-axis components of the rotor current; Mutual induction; For the self-sensing of the stator; For rotor self-inductance; This refers to the synchronous angular velocity.
[0049] From equation (1), it can be seen that the stator q-axis current and rotor q-axis current Not only does it differ by one intuition And the self-sensing of the stator The relevant conversion coefficients also include a factor derived from the magnetic flux. The generated excitation current component. When the grid-side converter has no output reactive current, the q-axis current of the total current and the stator q-axis current are equal. At this time, the deviation current between the q-axis component of the total current (or stator current) and the rotor q-axis component is... ,Right now or This directly reflects the reactive current required for the system to establish and maintain the magnetic field. The directly sampled and calculated q-axis deviation current is used as a feedforward quantity and introduced into the q-axis current loop of the rotor-side converter for closed-loop control, achieving precise q-axis control.
[0050] In some examples, the doubly-fed wind power converter also includes a controller configured to perform the steps of the control method for the doubly-fed wind power converter, as detailed below.
[0051] Based on this, such as Figure 2 As shown in the figure, this application provides a control method for a doubly-fed wind power converter, the control method including the following steps:
[0052] S11. Obtain the current at the grid connection point and the rotor current on the rotor side;
[0053] S12. Calculate the deviation current between the current at the grid connection point and the rotor current, and introduce the deviation current as a feedforward quantity into the current loop of the rotor-side converter.
[0054] S13. Based on the current given by the power loop output and the feedforward quantity, generate a control signal for the rotor-side converter.
[0055] In some examples, the current at the grid connection point includes either the total current at the grid connection point or the stator current, for example... Figure 1 Total current in Or stator current .
[0056] In some examples, the control method further includes:
[0057] Obtain the grid voltage;
[0058] Calculate the current reactive power and / or active power based on the grid voltage and the current at the grid connection point.
[0059] Please combine Figure 3 To understand this, the sampling module collects the three-phase grid voltage at the grid connection point in real time. Total current or stator current (In practical applications, only one phase needs to be tested) Three-phase rotor current Three-phase grid-side current The image This is the stator voltage.
[0060] The coordinate transformation module transforms the voltage and current signals acquired by the sampling module from a three-phase stationary coordinate system to a two-phase synchronous rotating coordinate system, obtaining the corresponding dq-axis components: (Right now and (and so on) , , .
[0061] The power calculation module calculates based on the total current or stator current. and grid voltage Calculate the reactive power of the current system. and active power As reactive and active power feedback values, the main controller or host computer issues reactive power command. and active power given .
[0062] In some examples, the control method includes:
[0063] The current at the grid connection point and the rotor current are transformed by coordinate transformation to obtain the q-axis component of the current at the grid connection point and the q-axis component of the rotor current.
[0064] Calculate the q-axis deviation current between the q-axis component of the current at the grid connection point and the q-axis component of the rotor current, and introduce the q-axis deviation current as the first feedforward quantity into the q-axis current loop of the rotor-side converter.
[0065] Based on the q-axis current given by the reactive power loop output and the first feedforward quantity, a first voltage control command is generated for the rotor-side converter.
[0066] In some specific examples, the reactive power loop outputs the q-axis current setpoint based on the reactive power setpoint and the reactive power feedback value.
[0067] In some specific examples, the generation of a first voltage control command for the rotor-side converter based on the q-axis current given by the reactive power loop output and the first feedforward includes:
[0068] The given q-axis current is added to the first feedforward quantity and then compared with the rotor q-axis current feedback. The first voltage control command is then generated through the first PI control loop.
[0069] Please combine Figure 4 To understand this, the reactive power loop includes a reactive power regulator and a reactive power PI regulator. The reactive power regulator receives the reactive power command. reactive power given With reactive power feedback After differential operation, the reactive power PI regulator adjusts the output rotor current to obtain the q-axis current setpoint. The current loop controller receives the q-axis current command from the reactive power loop output. and the feedforward amount from the feedforward module ,Right now In actual control, the feedforward quantity is... With q-axis current given The sums are used to form the final current loop composite reference, which is then fed back with the actual rotor current. The comparison is performed, and the first voltage control command is generated by adjusting the first PI regulator, which ultimately drives the rotor-side converter through PWM modulation.
[0070] As can be seen from the above, by improving the feedforward mechanism, the difference between the actual sampled total current (or stator current) q-axis current and the rotor q-axis current is calculated. This difference naturally contains the excitation current information and the stator-rotor current conversion relationship, without relying on any motor parameters for calculation. That is, the system can achieve precise and rapid control of the q-axis current without accurately calculating the excitation current, significantly reducing the dependence on the motor mutual inductance parameter Lm.
[0071] In some examples, the control method includes:
[0072] The current at the grid connection point and the rotor current are transformed by coordinate transformation to obtain the d-axis component of the current at the grid connection point and the d-axis component of the rotor current.
[0073] Calculate the d-axis deviation current between the d-axis component of the current at the grid connection point and the d-axis component of the rotor current, and introduce the d-axis deviation current as a second feedforward quantity into the d-axis current loop of the rotor-side converter.
[0074] Based on the d-axis current given by the active power loop output and the second feedforward quantity, a second voltage control command is generated for the rotor-side converter.
[0075] In some specific examples, the active power loop outputs the d-axis current setpoint based on the active power setpoint and the active power feedback value.
[0076] In some specific examples, the generation of a second voltage control command for the rotor-side converter based on the d-axis current given by the active power loop output and the second feedforward quantity includes:
[0077] The given d-axis current is added to the second feedforward quantity and then compared with the rotor d-axis current feedback. The second voltage control command is then generated through the second PI control loop.
[0078] Please combine Figure 5 To understand this, the stator power, total power, and grid-side power after system per-unit scaling are shown in equation (2) below:
[0079] In this context, the d-axis typically corresponds to the active component, and the q-axis corresponds to the reactive component.
[0080] During normal operation of a doubly-fed induction generator (DFIG), in order to maintain a stable DC bus voltage, the grid-side converter will absorb or output active power from the grid according to changes in active power on the rotor side. It is not zero. This causes a difference between the total power and the stator power.
[0081] (1) When sampling the stator current, there is a conversion deviation between the stator d-axis current and the rotor d-axis current, which is determined by equation (1);
[0082] (2) When sampling the total current, the difference between the total d-axis current and the rotor d-axis current includes not only the conversion deviation between the stator d-axis current and the rotor d-axis current, but also the grid-side d-axis current.
[0083] Therefore, by directly sampling and calculating the d-axis deviation component as a feedforward quantity, and introducing it into the d-axis current loop of the rotor-side converter for closed-loop control, precise d-axis control can be achieved.
[0084] The specific execution process is as follows:
[0085] The power calculation module calculates based on the total current or stator current. and grid voltage Calculate the total active power or stator active power of the current system. As the active power feedback value, the main controller or host computer issues the total active power command. The given value directly corresponds to the total power expected to be delivered to the grid. When using total power closed-loop enable, there is no need to convert the total active power given and feedback into the stator-side power given based on the slip ratio, as is the case with traditional methods.
[0086] Figure 5 The active power loop in the system includes an active power regulator and an active power PI regulator. The active power regulator receives the active power command (…). and active power feedback The d-axis current command of the output rotor current after regulation by the active PI regulator .
[0087] The difference between the d-axis current of the actual sampled total current (or stator current) and the d-axis current of the rotor is obtained. This difference includes the active current information of the grid-side converter and the conversion deviation of the stator and rotor currents.
[0088] The current loop controller receives the d-axis current command from the active power loop. and the feedforward amount from the feedforward module In actual control, the feedforward quantity is... With d-axis current given The sums are used to form the final current loop composite reference, which is then fed back with the actual rotor current. The comparison is performed, and a second voltage control command is generated by adjusting the second PI regulator.
[0089] By introducing d-axis deviation feedforward, the control system only needs to convert the total power command to a stator power command when sampling the stator current; otherwise, no power conversion is required. This is because the feedforward automatically compensates for the difference between the total power and the stator power (mainly reflected in the grid-side converter power), allowing the d-axis command of the rotor current to automatically adapt, ultimately accurately controlling the total active power output of the system. This greatly simplifies the control logic and eliminates the complexity and potential errors caused by power conversion.
[0090] The preferred embodiments of this application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and spirit of this application shall be within the scope of the claims.
Claims
1. A control method for a doubly-fed wind power converter, characterized in that, The control method includes: Obtain the current at the grid connection point and the rotor current on the rotor side; Calculate the deviation current between the current at the grid connection point and the rotor current, and introduce the deviation current as a feedforward quantity into the current loop of the rotor-side converter; Based on the current given by the power loop output and the feedforward quantity, a control signal for the rotor-side converter is generated.
2. The control method according to claim 1, characterized in that, The control method includes: The current at the grid connection point and the rotor current are transformed by coordinate transformation to obtain the q-axis component of the current at the grid connection point and the q-axis component of the rotor current. Calculate the q-axis deviation current between the q-axis component of the current at the grid connection point and the q-axis component of the rotor current, and introduce the q-axis deviation current as the first feedforward quantity into the q-axis current loop of the rotor-side converter. Based on the q-axis current given by the reactive power loop output and the first feedforward quantity, a first voltage control command is generated for the rotor-side converter.
3. The control method according to claim 2, characterized in that, The reactive power loop outputs the q-axis current command based on the reactive power setpoint and the reactive power feedback value.
4. The control method according to claim 2, characterized in that, The first voltage control command for the rotor-side converter is generated based on the q-axis current given by the reactive power loop output and the first feedforward, including: The given q-axis current is added to the first feedforward quantity and then compared with the rotor q-axis current feedback. The first voltage control command is then generated through the first PI control loop.
5. The control method according to any one of claims 1-4, characterized in that, The control method includes: The current at the grid connection point and the rotor current are transformed by coordinate transformation to obtain the d-axis component of the current at the grid connection point and the d-axis component of the rotor current. Calculate the d-axis deviation current between the d-axis component of the current at the grid connection point and the d-axis component of the rotor current, and introduce the d-axis deviation current as a second feedforward quantity into the d-axis current loop of the rotor-side converter. Based on the d-axis current given by the active power loop output and the second feedforward quantity, a second voltage control command is generated for the rotor-side converter.
6. The control method according to claim 5, characterized in that, The active power loop outputs the d-axis current setpoint based on the active power setpoint and the active power feedback value.
7. The control method according to claim 5, characterized in that, The second voltage control command for the rotor-side converter is generated based on the d-axis current given by the active power loop output and the second feedforward quantity, including: The given d-axis current is added to the second feedforward quantity and then compared with the rotor d-axis current feedback. The second voltage control command is then generated through the second PI control loop.
8. The control method according to claim 1, characterized in that, The current at the grid connection point includes the total current at the grid connection point or the stator current.
9. The control method according to claim 1, characterized in that, The control method further includes: Obtain the grid voltage; Calculate the current reactive power and / or active power based on the grid voltage and the current at the grid connection point.
10. A doubly-fed wind power converter, characterized in that, The doubly-fed wind power converter includes a grid-side converter and a rotor-side converter connected via positive and negative DC buses. The doubly-fed wind power converter also includes a controller configured to execute the control method of the doubly-fed wind power converter according to any one of claims 1-9.