Subsynchronous oscillation suppression method and device for distributed power supply access
By introducing fractional-order sliding mode control method in the power system, the sliding mode surface is constructed and the fractional-order exponential approach law is used, the problem of sub-synchronous oscillation suppression in distributed power access is solved, and higher stability and robustness are achieved.
Patent Information
- Application Number
- CN202510133953.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-06
- Publication Date
- 2025-03-28
Smart Images
Figure CN119726808A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of power systems, and in particular to a subsynchronous oscillation suppression method of fractional-order sliding mode control. Background Art
[0002] With the development of global renewable energy and the widespread application of power electronics technology, modern power systems are gradually shifting towards the "double high" characteristics of high proportion of renewable energy access and high proportion of power electronic equipment application. While this shift improves energy efficiency and reduces carbon emissions, it also triggers a series of new technical challenges, especially the subsynchronous oscillation problem of power systems.
[0003] Current status of existing technology research: Traditional sliding mode control method: As a nonlinear control technology, sliding mode control has been widely used in oscillation suppression of power systems due to its strong robustness and high tolerance to system uncertainty. By designing the sliding surface and reaching law, traditional sliding mode control can achieve fast response and oscillation suppression to a certain extent. However, the inherent chattering problem of sliding mode control seriously affects the stability and control accuracy of the system.
[0004] Improved method of integer-order sliding mode control: In order to solve the chattering problem of sliding mode control, some studies have proposed improved integer-order sliding mode control methods. For example, by replacing the sign function in the traditional reaching law with a smooth function, or by introducing a variable gain sliding mode control strategy, these improvements have achieved certain results in reducing chattering. However, integer-order sliding mode control has limited design freedom and still performs poorly when dealing with complex nonlinearities and high-frequency oscillations.
[0005] Oscillation suppression of distributed power access technology: In the context of distributed power access, the grid-connected operation mode of photovoltaic, wind power generation and energy storage systems has brought new oscillation characteristics to the power system, intensifying the problems of nonlinearity, wide-band oscillation and multi-modal coupling. At present, the oscillation suppression method based on traditional PI control is still the mainstream of engineering applications, but its robustness to system parameter changes and external disturbances is weak, and the control effect is not ideal when dealing with subsynchronous oscillation problems caused by small disturbances.
[0006] The main problems of the existing technology: Traditional PI control has limited effect on suppressing subsynchronous oscillations under small disturbance conditions and cannot meet the high requirements of modern power systems for stability and robustness.
[0007] Although integer-order sliding mode control has a certain anti-disturbance capability, it still has obvious shortcomings in reducing chattering and improving control flexibility.
[0008] Current research lacks a control strategy that can simultaneously improve the control system's degrees of freedom, effectively reduce the jitter amplitude, and enhance robustness to external disturbances and parameter changes.
[0009] In summary, the technical problems existing in the prior art are summarized as follows: How to design an efficient and robust control method in the power system with distributed power generation access to quickly and effectively suppress subsynchronous oscillations caused by small disturbances, while reducing jitter problems and improving system stability is an important issue that needs to be urgently solved by existing technologies. Summary of the invention
[0010] In order to solve the technical problem of how to design an efficient and robust control method in a power system connected to distributed power sources to quickly and effectively suppress subsynchronous oscillations caused by small disturbances, reduce jitter problems, and improve system stability, the technical solution provided by the present invention is: A subsynchronous oscillation suppression method for distributed power access, comprising: The step of constructing a sliding surface, wherein the sliding surface is constructed by taking the error between the reference value and the actual value of the current of the target system as a state variable and combining a proportional coefficient and an integral coefficient; The step of designing a sliding mode reaching law by introducing a fractional-order exponential reaching law, wherein the fractional-order exponential reaching law is used to dynamically adjust a sliding mode control reaching speed; The expression of the fractional exponential reaching law is: ; in, is the order of fractional calculus , is the reaching law coefficient; for and The derivative of is the control gain coefficient of the fractional-order reaching law, which is used to adjust the reaching speed; It is a sign function, indicating positive or negative, and is used to indicate the approach direction.
[0011] The steps of dynamically generating the output control signal of the converter based on the sliding mode control result of the fractional-order exponential reaching law and combining the equivalent inductance, resistance and synchronous speed of the target system.
[0012] Furthermore, the construction of the distributed system model includes setting the outer loop integral coefficient of the AC / DC converter to 185, the inner loop proportional coefficient to 0.75, and the equivalent inductance parameter to 0.054H.
[0013] Furthermore, in the construction of the sliding surface, the proportional coefficient and the integral coefficient range from 0.1 to 1.0.
[0014] Furthermore, the fractional order exponent of the sliding mode reaching law ranges from 0.5 to 1.0.
[0015] Furthermore, the method further includes: verifying the suppression effect of the fractional-order sliding mode controller by changing the range of the inductance parameter to 0.025H to 0.04H.
[0016] A subsynchronous oscillation suppression device for distributed power access, comprising: A module for constructing a sliding surface, wherein the sliding surface is constructed by taking the error between the reference value and the actual value of the current of the target system as a state variable, and combining a proportional coefficient and an integral coefficient; A module for designing a sliding mode reaching law by introducing a fractional-order exponential reaching law, wherein the fractional-order exponential reaching law is used to dynamically adjust the sliding mode control reaching speed; Based on the sliding mode control results of the fractional-order exponential reaching law, combined with the equivalent inductance, resistance and synchronous speed of the target system, a module is used to dynamically generate the output control signal of the converter.
[0017] A computer storage medium is used to store a computer program. When the computer program is read by a computer, the computer executes the method described.
[0018] A computer includes a processor and a storage medium. When the processor reads a computer program stored in the storage medium, the computer executes the method described.
[0019] The computer program product, as a computer program, implements the method described when the computer program is executed.
[0020] Compared with the prior art, the technical solution provided by the present invention is beneficial in that: The introduction of fractional-order calculus operators to form fractional-order exponential reaching laws enables the sliding mode controller to have the ability to remember historical information and global characteristics. Compared with the traditional integer-order sliding mode control method, the fractional-order operator can provide more dynamic adjustment freedom in the control system, thereby effectively reducing the vibration amplitude near the sliding surface. This feature significantly improves the stability and control accuracy of the system, especially under small disturbance conditions.
[0021] The designed fractional-order sliding surface selects the error between the reference value and the actual value as the state variable, and combines the global characteristics of fractional-order calculus to enable the system to converge to the sliding surface at a faster speed. Compared with traditional PI control, this fast convergence characteristic can not only suppress subsynchronous oscillations more efficiently, but also avoid the problem of continued or aggravated oscillations caused by the long response time of traditional methods.
[0022] The fractional-order exponential reaching law is introduced into the sliding mode reaching law design. By dynamically adjusting the reaching speed, the problem of insufficient robustness of traditional sliding mode control in strong nonlinear and high-frequency oscillation scenarios is effectively solved. The fractional-order exponential reaching law can show stronger anti-interference ability in multi-mode coupling systems. Compared with the existing variable gain sliding mode control, its adaptability to parameter changes and external disturbances is significantly enhanced.
[0023] The converter control strategy based on the fractional-order exponential reaching law is adopted, and the outer loop of power control and the inner loop of current of fractional-order sliding mode control are coordinated to ensure that the grid-side current can quickly track the command value. Compared with traditional PI control and basic sliding mode control, this method has more significant oscillation suppression effect under grid-connected conditions, especially showing superior control performance in multivariable disturbance scenarios.
[0024] It is suitable for use in subsynchronous oscillation suppression. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 It is a grid-connected structure for distributed power sources.
[0026] Figure 2 It is a control block diagram of the converter based on fractional-order sliding mode control.
[0027] Figure 3 It is the active power of the grid when the outer loop integral coefficient is changed.
[0028] Figure 4 It is the active power of the grid when the inductance parameters are changed.
[0029] Figure 5 It is the grid-connected reactive power when the inductance parameters and the outer loop integral parameters are changed at the same time.
[0030] Among them, 1 represents a DC bus, 2 represents a doubly-fed induction wind turbine, 3 represents a back-to-back converter, 4 represents a photovoltaic array, 5 represents a Boost circuit, 6 represents a power grid, 7 represents a bidirectional DC / DC converter, and 8 represents an energy storage terminal. DETAILED DESCRIPTION
[0031] In order to make the advantages and benefits of the technical solution provided by the present invention more clearly reflected, the technical solution provided by the present invention is now further described in detail with reference to the accompanying drawings, specifically: Embodiment 1: This embodiment provides a subsynchronous oscillation suppression method for distributed power supply access, including: The step of constructing a sliding surface, wherein the sliding surface is constructed by taking the error between the reference value and the actual value of the current of the target system as a state variable and combining a proportional coefficient and an integral coefficient; The step of designing a sliding mode reaching law by introducing a fractional-order exponential reaching law, wherein the fractional-order exponential reaching law is used to dynamically adjust a sliding mode control reaching speed; The expression of the fractional exponential reaching law is: ; in, is the order of fractional calculus , is the reaching law coefficient; for and The derivative of is the control gain coefficient of the fractional-order reaching law, which is used to adjust the reaching speed; It is a sign function, indicating positive or negative, and is used to indicate the approach direction.
[0032] The steps of dynamically generating the output control signal of the converter based on the sliding mode control result of the fractional-order exponential reaching law and combining the equivalent inductance, resistance and synchronous speed of the target system.
[0033] The construction of the distributed system model includes setting the outer loop integral coefficient of the AC / DC converter to 185, the inner loop proportional coefficient to 0.75, and the equivalent inductance parameter to 0.054H.
[0034] In the construction of sliding surface, the proportional coefficient and integral coefficient range from 0.1 to 1.0.
[0035] The fractional order exponent of the sliding mode reaching law ranges from 0.5 to 1.0.
[0036] The method also includes the step of verifying the suppression effect of the fractional-order sliding mode controller by changing the range of the inductance parameter to 0.025H to 0.04H.
[0037] Implementation method 2: This implementation method further limits the technical solution provided in implementation method 1, specifically: Step 1: Build a distributed system model and introduce small disturbances Firstly, a distributed simulation model with a doubly-fed induction wind power generation system, a photovoltaic system and an energy storage system connected to the grid is built. The unstable area of the system is determined through eigenvalue analysis, and small external disturbances are introduced to cause subsynchronous oscillation problems. Detailed description: According to Figure 1 The system architecture shown is used to establish a grid-connected model containing photovoltaic power generation, wind power generation and energy storage systems; Among them, the grid-connected models include: Double-fed induction wind power generation system Includes wind turbines and related control equipment that convert wind energy into electrical energy.
[0038] The AC power is converted into DC power by the back-to-back converter 3 and adapted to the subsequent DC bus 1 .
[0039] Back to back inverter 3 Realize bidirectional conversion between DC and AC: One end is connected to the power generation system (such as a wind turbine) through an AC / DC converter; The other end is connected to the grid 6 through a DC / AC converter to achieve grid-connected operation.
[0040] The back-to-back converter 3 has the function of adjusting voltage, frequency and power factor at the same time.
[0041] Photovoltaic power generation system A photovoltaic array 4 is included for converting light energy into direct current.
[0042] The DC output of the photovoltaic array 4 is connected to the DC bus 1 after the voltage level is adjusted by the boost or buck circuit of the Boost circuit 5 .
[0043] Energy storage terminal 8 It includes an energy storage battery and a bidirectional DC / DC converter 7 for storing and releasing energy.
[0044] The energy storage system is connected to the DC bus 1 via a bidirectional DC / DC converter 7 , which plays the role of peak shaving and valley filling and stabilizing the power grid 6 .
[0045] DC bus 1 The core node connecting photovoltaic power generation, wind power generation and energy storage systems is used to collect the direct current generated by each distributed power source.
[0046] The DC bus 1 provides a stable voltage platform and supplies power to the subsequent converters.
[0047] Grid interface The alternating current output by the DC / AC converter passes through a transformer and a filter device and is then connected to the power grid 6 .
[0048] The access points support the stable operation of the grid 6 by controlling power flows (e.g. reactive power regulation).
[0049] The outer loop integral coefficient of the system AC / DC converter is set to 185, the inner loop proportional coefficient is set to 0.75, and the equivalent inductance parameter is set to 0.054H to ensure that the system is in a small disturbance unstable state determined by the characteristic value analysis. On this basis, by changing the atmospheric conditions (such as irradiance and wind speed), converter control parameters or electrical parameters, the subsynchronous oscillation phenomenon with a system oscillation frequency range of more than ten to more than forty is induced, providing simulation input for the subsequent controller design.
[0050] Step 2: Design a fractional-order sliding mode controller By introducing fractional-order calculus operators to construct fractional-order exponential reaching laws, a sliding mode controller is designed to quickly suppress subsynchronous oscillations and ensure that the grid-side current quickly tracks the command value. Detailed description: The design process of the sliding mode controller is divided into the following sub-steps: Step 2-1: Design the sliding surface The sliding surface takes the current error as the state variable and its expression is: in , , is the command current value, which serves as the target tracking signal of the system; It is the actual current value, used to indicate the current current status.
[0051] , is the proportionality coefficient, , is the integration coefficient; The sliding surface is a function of the system parameters and is used to control the d-axis current; The sliding surface is a function of the system parameters and is used to control the q-axis current; Indicates time; The grid-connected system is realized by designing the sliding surface Shaft current and Independent control of shaft current.
[0052] Step 2-2: Design a fractional exponential reaching law The fractional-order calculus operator is introduced into the sliding mode reaching law, and its expression is: in is the order of fractional calculus , is the reaching law coefficient; for and The derivative of is the control gain coefficient of the fractional-order reaching law, which is used to adjust the reaching speed; It is a sign function, indicating positive or negative, and is used to indicate the approach direction.
[0053] The chattering problem near the sliding surface is effectively reduced through the fractional order reaching law, thus improving the stability of the control system.
[0054] Step 2-3: Design the controller output The output signal of the controller is designed as:
[0055] in, : Proportional coefficient in sliding surface construction, used to adjust the amplification factor of the error signal.
[0056] : Combining proportional control and integral control in a sliding mode controller.
[0057] : Sign function, used to indicate the positive or negative nature of the input signal and determine the approach direction of the system.
[0058] : Gain coefficient in the fractional-order reaching law, used to control the speed of sliding mode reaching.
[0059] :Fractional-order calculus operator, used to construct the fractional-order exponential reaching law, reflecting the system's memory and global characteristics of the error signal.
[0060] : is the reaching law parameter, and It also represents the speed of approaching the sliding surface. The larger it is, the faster it reaches the sliding surface, but the greater the chattering.
[0061] : System equivalent inductance, used to describe the current dynamic response characteristics of the system.
[0062] : The equivalent resistance of the system.
[0063] : The current state of the system, as one of the core input variables of sliding mode control.
[0064] : Time derivative of the reference current in the axial direction.
[0065] : The synchronous angular velocity of the system.
[0066] : The total output voltage control signal of the axis.
[0067] :system The actual current value in the axial direction.
[0068] The converter parameters are adjusted through control signals to achieve fast current tracking and oscillation suppression.
[0069] Step 3: Build a simulation system and verify the suppression effect The sliding mode controller based on the fractional-order exponential reaching law is applied to the simulation system to verify its effectiveness in suppressing subsynchronous oscillations under small disturbances. Detailed description: In the constructed simulation system, the fractional-order sliding mode controller is integrated into the control architecture of the converter. By changing the integral parameters of the converter outer loop, the inductance parameters, and adjusting the combination of the two at the same time, the oscillation suppression effect under different parameters is verified, and compared with the traditional PI control and integer-order sliding mode control. The simulation results show that the fractional-order sliding mode controller can significantly reduce the fluctuation amplitude of the active power and reactive power of the grid-connected system, make the system quickly stabilize, and show stronger robustness under multivariable disturbances.
[0070] Implementation Method 3: Combination Figure 1-5 This embodiment is described in detail by using specific examples to further describe the technical solution provided above. Specifically: Step 1: First, establish a distributed system with a double-fed induction wind power generation system, a photovoltaic system, and an energy storage system connected to the grid. Use the eigenvalue analysis method to analyze the converter control parameters and the stability range of the system electrical parameters, and set the system parameters to a small disturbance unstable state. By changing the system parameters and atmospheric conditions such as irradiance and wind speed, the subsynchronous oscillation problem of the system under small disturbances is induced.
[0071] Step 1-1) Figure 1 As shown in the figure, a simulation model is built according to the actual system. Step 1-2) Set the AC / DC converter outer loop integral coefficient to 185, the inner loop proportional coefficient to 0.75, and the equivalent inductance parameter to 0.054H. According to the characteristic value analysis and simulation verification, the system is in a small disturbance unstable state. Small disturbances are introduced by changing the converter control parameters and electrical parameters.
[0072] Step 2: Introduce fractional-order sliding mode control into the converter control strategy; the converter outer loop adopts power control, and the current inner loop control adopts fractional-order sliding mode control structure. The control goal is to ensure that the grid-side current can quickly track the command current value. Select the error between the reference value and the actual value as the state variable, design the sliding surface, introduce the fractional-order calculus operator in the sliding mode reaching law design, form the fractional-order exponential reaching law, and design a sliding mode controller based on the fractional-order exponential reaching law. The control block diagram is as follows: Figure 2 shown.
[0073] Figure 2 middle, : Proportional coefficient in sliding surface construction, used to adjust the amplification factor of the error signal.
[0074] : Combining proportional control and integral control in a sliding mode controller.
[0075] : Sign function, used to indicate the positive or negative nature of the input signal and determine the approach direction of the system.
[0076] : Gain coefficient in the fractional-order reaching law, used to control the speed of sliding mode reaching.
[0077] :Fractional-order calculus operator, used to construct the fractional-order exponential reaching law, reflecting the system's memory and global characteristics of the error signal.
[0078] : is the reaching law parameter, and It also represents the speed of approaching the sliding surface. The larger it is, the faster it reaches the sliding surface, but the greater the chattering.
[0079] : System equivalent inductance, used to describe the current dynamic response characteristics of the system.
[0080] : The equivalent resistance of the system.
[0081] : The current state of the system, as one of the core input variables of sliding mode control.
[0082] : Time derivative of the reference current in the axial direction.
[0083] : The synchronous angular velocity of the system.
[0084] : The total output voltage control signal of the axis.
[0085] :system The actual current value in the axial direction.
[0086] Step 3: Build a simulation system containing a converter based on the fractional-order exponential reaching law, and verify the rationality and suppression effect of the designed controller under the condition of small system disturbance; In this step, a converter based on the fractional-order exponential reaching law is used to suppress the oscillation problem of the system when the system is unstable under small interference and subsynchronous oscillation occurs. By changing the outer loop integral parameters and inductance parameters of the grid-connected converter and changing the outer loop integral coefficient and inductance parameters at the same time, the suppression effects of traditional PI control, integer-order sliding mode control, and fractional-order sliding mode control are compared, as shown in the figure below. Figure 3 , Figure 4 , Figure 5 As shown, the fractional-order sliding mode control can be used to suppress subsynchronous oscillations under distributed power generation.
[0087] The technical solution provided by the present invention is further described in detail above through several specific implementation modes in order to highlight the advantages and benefits of the technical solution provided by the present invention. However, the several specific implementation modes described above are not intended to be used as limitations on the present invention. Any reasonable modification and improvement of the present invention, combination of implementation modes and equivalent substitution within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A method for suppressing subsynchronous oscillation for distributed power access, characterized in that: include: The step of constructing a sliding surface, wherein the sliding surface is constructed by taking the error between the reference value and the actual value of the current of the target system as a state variable and combining a proportional coefficient and an integral coefficient; The step of designing a sliding mode reaching law by introducing a fractional-order exponential reaching law, wherein the fractional-order exponential reaching law is used to dynamically adjust a sliding mode control reaching speed; The expression of the fractional exponential reaching law is: ； in, is the order of fractional calculus , is the reaching law coefficient; for and The derivative of is the control gain coefficient of the fractional-order reaching law, which is used to adjust the reaching speed; is a sign function, indicating positive or negative, used to indicate the approach direction; The steps of dynamically generating the output control signal of the converter based on the sliding mode control result of the fractional-order exponential reaching law and combining the equivalent inductance, resistance and synchronous speed of the target system.
2. A subsynchronous oscillation suppression method for distributed power access according to claim 1, characterized in that: The construction of the distributed system model includes setting the outer loop integral coefficient of the AC / DC converter to 185, the inner loop proportional coefficient to 0.75, and the equivalent inductance parameter to 0.054H.
3. A subsynchronous oscillation suppression method for distributed power access according to claim 1, characterized in that: In the construction of sliding surface, the proportional coefficient and integral coefficient range from 0.1 to 1.
0.
4. A method for suppressing subsynchronous oscillation for distributed power access according to claim 1, characterized in that: The fractional order exponent of the sliding mode reaching law ranges from 0.5 to 1.
0.
5. A method for suppressing subsynchronous oscillation for distributed power access according to claim 1, characterized in that: Also includes: The step of verifying the suppression effect of the fractional-order sliding mode controller by changing the range of the inductance parameter from 0.025H to 0.04H.
6. A subsynchronous oscillation suppression device for distributed power supply access, characterized in that: include: A module for constructing a sliding surface, wherein the sliding surface is constructed by taking the error between the reference value and the actual value of the current of the target system as a state variable, and combining a proportional coefficient and an integral coefficient; A module for designing a sliding mode reaching law by introducing a fractional-order exponential reaching law, wherein the fractional-order exponential reaching law is used to dynamically adjust the sliding mode control reaching speed; Based on the sliding mode control results of the fractional-order exponential reaching law, combined with the equivalent inductance, resistance and synchronous speed of the target system, a module is used to dynamically generate the output control signal of the converter.
7. A computer storage medium for storing a computer program, characterized in that: When the computer program is read by a computer, the computer executes the method of claim 1 .
8. A computer, comprising a processor and a storage medium, characterized in that: When the processor reads the computer program stored in the storage medium, the computer executes the method of claim 1 .
9. A computer program product, being a computer program, characterized in that When the computer program is executed, the method of claim 1 is implemented.