Method and device for adaptively adjusting parameters of PID (Proportion Integration Differentiation) controller of network construction converter

Abstract

The invention relates to the technical field of power systems, and discloses a PID controller parameter adaptive adjustment method and device of a network construction converter. The method comprises the following steps: calculating an output error signal and an output error signal change rate of a small signal model based on the small signal model of the network-forming converter, calculating an error gradient by using the output error signal and the change rate thereof, and dynamically updating PID control parameters based on a gradient descent method. When the PID control parameters are updated, whether selection of the PID control parameters can cause instability of a system where the network construction converter is located or not is checked, if yes, the error gradient calculation parameters are adjusted to recalculate the error gradient of the output error signals, if not, updating of the PID controller parameters is stopped, and by adjusting the PID control parameters in a self-adaptive mode, the network construction converter is updated. And the stability of the network-forming converter in a power grid is effectively ensured. The technical problem that in the prior art, an effective technical means for conducting self-adaptive adjustment on the control parameters of the network building converter to maintain stable operation of a power grid system is lacked is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a method and device for adaptively adjusting parameters of a PID controller of a grid-connected converter. Background Art

[0002] A grid-forming inverter (GFI), a device that simulates the inertia of synchronous machines, maintains grid stability by controlling voltage and frequency. To understand its dynamic behavior under disturbances, a small-signal model is often used to linearize the system. The purpose of a small-signal model is to study how the system responds to grid disturbances or load changes. Typically, in small-signal analysis, the system is assumed to be subjected to small perturbations near a stable operating point. By linearizing the control system, a set of transfer functions is derived to describe the system's dynamic characteristics. In a GFI, a proportional-integral-differential (PID) controller is often used to control key parameters such as voltage and current. Currently, how to adaptively adjust the parameters of the PID controller of a GFI to ensure rapid and oscillatory response within the grid system and achieve stable operation remains a pressing technical challenge for those skilled in the art. Summary of the Invention

[0003] The present invention provides a method and device for adaptively adjusting parameters of a PID controller of a grid-connected converter, which is used to solve the technical problem that the prior art lacks effective technical means for adaptively adjusting the control parameters of the grid-connected converter to maintain stable operation of the power grid system.

[0004] In view of this, a first aspect of the present invention provides a method for adaptively adjusting parameters of a PID controller of a grid-connected converter, comprising:

[0005] Construct a small signal model of a grid-connected converter;

[0006] Calculate the output error signal and output error signal change rate of the small signal model in real time;

[0007] Calculating an error gradient of the output error signal based on the output error signal and the rate of change of the output error signal;

[0008] Based on the error gradient, the PID controller parameters are dynamically updated using the gradient descent method;

[0009] Based on the updated PID controller parameters, it is determined whether the system where the grid converter is located will be unstable. If not, the updating of the PID controller parameters is stopped. If so, the error gradient calculation parameters are adjusted to recalculate the error gradient of the output error signal.

[0010] Alternatively, the formula for dynamically updating the PID controller parameters using the gradient descent method is:

[0011]

[0012] in, is the proportional gain of the PID controller at time t+1, is the proportional gain of the PID controller at time t, is the learning rate, is the error function used to control the adjustment direction of the PID controller parameters, is the integral gain of the PID controller at time t+1, is the integral gain of the PID controller at time t, is the differential gain of the PID controller at time t+1, is the differential gain of the PID controller at time t.

[0013] Optionally, the error function used to control the adjustment direction of the PID controller parameters is:

[0014]

[0015] in, is the output error signal of the small signal model.

[0016] Optionally, the error gradient of the output error signal is calculated as:

[0017]

[0018] in, is the error function used to control the adjustment direction of the PID controller parameters, is the output error signal of the small signal model, is the proportional gain of the PID controller, is the integral gain of the PID controller, is the differential gain of the PID controller.

[0019] Optionally, adjusting the error gradient calculation parameters to recalculate the error gradient of the output error signal includes:

[0020] Reduce the learning rate or adjust the calculation parameters of the error gradient of the output error signal to recalculate the error gradient of the output error signal.

[0021] A second aspect of the present invention provides a device for adaptively adjusting parameters of a PID controller of a grid-connected converter, comprising:

[0022] Modeling module, used to build a small signal model of the grid-connected converter;

[0023] Error calculation module, used for real-time calculation of the output error signal and output error signal change rate of the small signal model;

[0024] a gradient calculation module, configured to calculate an error gradient of the output error signal based on the output error signal and a rate of change of the output error signal;

[0025] Parameter update module, used to dynamically update PID controller parameters based on error gradient using gradient descent method;

[0026] The adjustment module is used to determine whether the system in which the grid converter is located will be unstable based on the updated PID controller parameters. If not, the updating of the PID controller parameters is stopped. If so, the error gradient calculation parameters are adjusted to recalculate the error gradient of the output error signal.

[0027] Alternatively, the formula for dynamically updating the PID controller parameters using the gradient descent method is:

[0028]

[0029] in, is the proportional gain of the PID controller at time t+1, is the proportional gain of the PID controller at time t, is the learning rate, is the error function used to control the adjustment direction of the PID controller parameters, is the integral gain of the PID controller at time t+1, is the integral gain of the PID controller at time t, is the differential gain of the PID controller at time t+1, is the differential gain of the PID controller at time t.

[0030] Optionally, the error function used to control the adjustment direction of the PID controller parameters is:

[0031]

[0032] in, is the output error signal of the small signal model.

[0033] Optionally, the error gradient of the output error signal is calculated as:

[0034]

[0035] in, is the error function used to control the adjustment direction of the PID controller parameters, is the output error signal of the small signal model, is the proportional gain of the PID controller, is the integral gain of the PID controller, is the differential gain of the PID controller.

[0036] Optionally, adjusting the error gradient calculation parameters to recalculate the error gradient of the output error signal includes:

[0037] Reduce the learning rate or adjust the calculation parameters of the error gradient of the output error signal to recalculate the error gradient of the output error signal.

[0038] From the above technical solutions, it can be seen that the method for adaptively adjusting the parameters of the PID controller of the grid-connected converter provided by the present invention has the following advantages:

[0039] The present invention provides a method for adaptively adjusting parameters of a PID controller of a grid-type converter. The method calculates the output error signal and the rate of change of the output error signal of the small signal model based on the small signal model of the grid-type converter, calculates the error gradient using the output error signal and its rate of change, and then dynamically updates the PID control parameters based on the gradient descent method. When updating the PID control parameters, it is checked whether the selection of the PID control parameters will cause instability in the system where the grid-type converter is located. If so, the error gradient calculation parameters are adjusted to recalculate the error gradient of the output error signal. If not, the updating of the PID controller parameters is stopped. By adaptively adjusting the PID control parameters, the stability of the grid-type converter in the grid can be effectively guaranteed, and the system can be ensured to respond quickly and without oscillation, thereby achieving stable operation of the system. The method solves the technical problem that the prior art lacks effective technical means for adaptively adjusting the control parameters of the grid-type converter to maintain stable operation of the grid system. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying any creative work.

[0041] Figure 1 A schematic flow chart of a method for adaptively adjusting parameters of a PID controller of a grid-connected converter provided in an embodiment of the present invention;

[0042] Figure 2 The present invention provides a schematic structural diagram of a PID controller parameter adaptive adjustment device for a grid-connected converter provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0044] For easier understanding, see Figure 1 The present invention provides an embodiment of a method for adaptively adjusting control parameters of a grid-connected converter, comprising:

[0045] Step 101: Construct a small signal model of a grid-connected converter.

[0046] It should be noted that when a grid-forming inverter (GFM) is connected to the grid, its small-signal model is used to analyze its dynamic response and stability. The GFM small-signal model system consists of the interaction between the current control loop, the voltage control loop, and the grid connection point. By combining the state-space models of the current control loop, the voltage control loop, and the grid connection point, the state-space model of the entire system can be obtained. The state-space model of the entire system is:

[0047]

[0048] in, is the state vector of the power grid system, including the current change, voltage change and power change, for The first derivative of is the input vector, including the input current and input voltage of the grid-type converter, is the output vector, A is the state coefficient matrix, B is the input coefficient matrix, C is the output coefficient matrix, and D is the transfer coefficient matrix.

[0049] PID controller parameters include proportional gain , integral gain , differential gain Proportional gain Adjust according to the instantaneous value of the error. A large proportional gain can accelerate the response, but may cause oscillation, so it needs to be adjusted dynamically according to the error. Adjust according to the accumulated error. A larger integral gain helps eliminate the steady-state error, but too large a differential gain may cause system instability. Adjusting based on the error change rate helps reduce overshoot and oscillation, ensuring a smoother system response.

[0050] By linearizing the small signal model, the poles of the power system and the controller parameters 、 、 This is relevant to PID controllers. When the controller parameters are too large, the poles of the power grid system may move to the right half plane, causing system instability. To avoid this, the parameters of the PID controller must be adjusted in real time.

[0051] Step 102: Calculate the output error signal and the output error signal change rate of the small signal model in real time.

[0052] It should be noted that the design goal is to minimize the output error of the power grid system and automatically adjust the PID controller parameters according to the feedback of the output error. 、 、 The output error signal of the small signal model is calculated as:

[0053]

[0054] in, is the output error signal of the small signal model, is the reference signal.

[0055] Then calculate the rate of change of the output error signal based on the output error signal .

[0056] Step 103: Calculate the error gradient of the output error signal based on the output error signal and the rate of change of the output error signal.

[0057] It should be noted that the error gradient of the output error signal is calculated based on the output error signal and the rate of change of the output error signal. The calculation formula for the error gradient of the output error signal is:

[0058]

[0059] in, is the error function used to control the adjustment direction of the PID controller parameters, is the output error signal of the small signal model, is the proportional gain of the PID controller, is the integral gain of the PID controller, is the differential gain of the PID controller.

[0060] The partial differential can be seen as two parts. The numerator e(t) is the differential with respect to time t, that is, , the denominator is The differential with respect to time, , then . and Same thing.

[0061] The error gradient expression reflects the relationship between the output error and the PID controller parameters. By calculating the error’s sensitivity to the PID controller parameters (i.e., the gradient), the controller gain can be adjusted to minimize the system error.

[0062] Step 104: Based on the error gradient, dynamically update the PID controller parameters using the gradient descent method.

[0063] It should be noted that an adaptive error indicator is defined to control the error function of the adjustment direction of the PID controller parameters:

[0064]

[0065] in, is the output error signal of the small signal model.

[0066] The parameters of the PID controller are updated using an adaptive algorithm based on gradient descent. The formula for dynamically updating the parameters of the PID controller is:

[0067]

[0068] in, is the proportional gain of the PID controller at time t+1, is the proportional gain of the PID controller at time t, is the learning rate, which determines the step size of parameter update. is the error function used to control the adjustment direction of the PID controller parameters, is the integral gain of the PID controller at time t+1, is the integral gain of the PID controller at time t, is the differential gain of the PID controller at time t+1, is the differential gain of the PID controller at time t.

[0069] Step 105: Based on the updated PID controller parameters, determine whether the system where the grid converter is located is unstable. If not, stop updating the PID controller parameters. If so, adjust the error gradient calculation parameters to recalculate the error gradient of the output error signal.

[0070] It should be noted that after each parameter adjustment, check the poles and zeros of the power system to ensure that the parameter selection of the PID controller will not cause instability in the power system. When there are poles and / or zeros in the right half plane of the zero-pole diagram, the power system is unstable. If instability occurs, adjust the error gradient calculation parameters to recalculate the error gradient of the output error signal. Specifically, reduce the learning rate Alternatively, adjust the parameters of the formula for calculating the error gradient of the output error signal and recalculate the error gradient of the output error signal. If instability does not occur, stop updating the PID controller parameters.

[0071] The following is a specific calculation example:

[0072] Assume that at a certain moment, the output error =0.05, and the error change rate =0.01, .

[0073] Adjust the PID controller parameters by gradient descent method. Set the learning rate =0.1, assuming that the initial PID controller parameters are =10, =5, =2.

[0074] Calculate the output signal error gradient:

[0075]

[0076] Then update the PID controller parameters:

[0077]

[0078] Dynamically adjusting PID controller parameters through an adaptive algorithm effectively ensures the stability of the grid-connected converter in the power grid. Adaptive gain regulation calculates system status and disturbances in real time and adjusts controller gains to ensure fast system response and smooth oscillation, thereby achieving stable system operation.

[0079] The present invention provides a method for adaptively adjusting parameters of a PID controller of a grid-type converter. The method calculates the output error signal and the rate of change of the output error signal of the small signal model based on the small signal model of the grid-type converter, calculates the error gradient using the output error signal and its rate of change, and then dynamically updates the PID control parameters based on the gradient descent method. When updating the PID control parameters, it is checked whether the selection of the PID control parameters will cause instability in the system where the grid-type converter is located. If so, the error gradient calculation parameters are adjusted to recalculate the error gradient of the output error signal. If not, the updating of the PID controller parameters is stopped. By adaptively adjusting the PID control parameters, the stability of the grid-type converter in the grid can be effectively guaranteed, and the system can be ensured to respond quickly and without oscillation, thereby achieving stable operation of the system. The method solves the technical problem that the prior art lacks effective technical means for adaptively adjusting the control parameters of the grid-type converter to maintain stable operation of the grid system.

[0080] For easier understanding, see Figure 2The present invention provides an embodiment of a PID controller parameter adaptive adjustment device for a grid-connected converter, comprising:

[0081] Small signal model building module, used to build the small signal model of the grid-connected converter;

[0082] Modeling module, used to build a small signal model of the grid-connected converter;

[0083] Error calculation module, used for real-time calculation of the output error signal and output error signal change rate of the small signal model;

[0084] a gradient calculation module, configured to calculate an error gradient of the output error signal based on the output error signal and a rate of change of the output error signal;

[0085] Parameter update module, used to dynamically update PID controller parameters based on error gradient using gradient descent method;

[0086] The adjustment module is used to determine whether the system in which the grid converter is located will be unstable based on the updated PID controller parameters. If not, the updating of the PID controller parameters is stopped. If so, the error gradient calculation parameters are adjusted to recalculate the error gradient of the output error signal.

[0087] In one embodiment, the formula for dynamically updating the PID controller parameters using the gradient descent method is:

[0088]

[0089] in, is the proportional gain of the PID controller at time t+1, is the proportional gain of the PID controller at time t, is the learning rate, is the error function used to control the adjustment direction of the PID controller parameters, is the integral gain of the PID controller at time t+1, is the integral gain of the PID controller at time t, is the differential gain of the PID controller at time t+1, is the differential gain of the PID controller at time t.

[0090] In one embodiment, the error function used to control the adjustment direction of the PID controller parameters is:

[0091]

[0092] in, is the output error signal of the small signal model.

[0093] In one embodiment, the error gradient of the output error signal is calculated as:

[0094]

[0095] in, is the error function used to control the adjustment direction of the PID controller parameters, is the output error signal of the small signal model, is the proportional gain of the PID controller, is the integral gain of the PID controller, is the differential gain of the PID controller.

[0096] In one embodiment, adjusting the error gradient calculation parameters to recalculate the error gradient of the output error signal includes:

[0097] Reduce the learning rate or adjust the calculation parameters of the error gradient of the output error signal to recalculate the error gradient of the output error signal.

[0098] The PID controller parameter adaptive adjustment device for the grid-connected converter provided in the present invention is used to execute the PID controller parameter adaptive adjustment method for the grid-connected converter provided in the present invention. Its technical effect has been described in the embodiment of the PID controller parameter adaptive adjustment method for the grid-connected converter provided in the present invention and will not be repeated here.

[0099] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for adaptively adjusting parameters of a PID controller of a grid-connected converter, characterized in that: include: Construct a small signal model of a grid-connected converter; Calculate the output error signal and output error signal change rate of the small signal model in real time; Calculating an error gradient of the output error signal based on the output error signal and the rate of change of the output error signal; Based on the error gradient, the PID controller parameters are dynamically updated using the gradient descent method; Based on the updated PID controller parameters, it is determined whether the system where the grid converter is located will be unstable. If not, the updating of the PID controller parameters is stopped. If so, the error gradient calculation parameters are adjusted to recalculate the error gradient of the output error signal.

2. The method for adaptively adjusting parameters of a PID controller of a grid-connected converter according to claim 1, characterized in that: The formula for dynamically updating the PID controller parameters using the gradient descent method is: in, is the proportional gain of the PID controller at time t+1, is the proportional gain of the PID controller at time t, is the learning rate, is the error function used to control the adjustment direction of the PID controller parameters, is the integral gain of the PID controller at time t+1, is the integral gain of the PID controller at time t, is the differential gain of the PID controller at time t+1, is the differential gain of the PID controller at time t.

3. The method for adaptively adjusting parameters of a PID controller of a grid-connected converter according to claim 2, characterized in that: The error function used to control the adjustment direction of the PID controller parameters is: in, is the output error signal of the small signal model.

4. The method for adaptively adjusting parameters of a PID controller of a grid-connected converter according to claim 2 or 3, characterized in that: The error gradient of the output error signal is calculated as: in, is the error function used to control the adjustment direction of the PID controller parameters, is the output error signal of the small signal model, is the proportional gain of the PID controller, is the integral gain of the PID controller, is the differential gain of the PID controller.

5. The method for adaptively adjusting parameters of a PID controller of a grid-connected converter according to claim 4, characterized in that: Adjust the error gradient calculation parameters to recalculate the error gradient of the output error signal, including: Reduce the learning rate or adjust the calculation parameters of the error gradient of the output error signal to recalculate the error gradient of the output error signal.

6. A PID controller parameter adaptive adjustment device for a grid-connected converter, characterized in that: include: Modeling module, used to build a small signal model of the grid-connected converter; Error calculation module, used for real-time calculation of the output error signal and output error signal change rate of the small signal model; a gradient calculation module, configured to calculate an error gradient of the output error signal based on the output error signal and a rate of change of the output error signal; Parameter update module, used to dynamically update PID controller parameters based on error gradient using gradient descent method; The adjustment module is used to determine whether the system in which the grid converter is located will be unstable based on the updated PID controller parameters. If not, the updating of the PID controller parameters is stopped. If so, the error gradient calculation parameters are adjusted to recalculate the error gradient of the output error signal.

7. The PID controller parameter adaptive adjustment device for a grid-connected converter according to claim 6, characterized in that: The formula for dynamically updating the PID controller parameters using the gradient descent method is: in, is the proportional gain of the PID controller at time t+1, is the proportional gain of the PID controller at time t, is the learning rate, is the error function used to control the adjustment direction of the PID controller parameters, is the integral gain of the PID controller at time t+1, is the integral gain of the PID controller at time t, is the differential gain of the PID controller at time t+1, is the differential gain of the PID controller at time t.

8. The PID controller parameter adaptive adjustment device for a grid-connected converter according to claim 7, characterized in that: The error function used to control the adjustment direction of the PID controller parameters is: in, is the output error signal of the small signal model.

9. The PID controller parameter adaptive adjustment device for a grid-connected converter according to claim 7 or 8, characterized in that: The error gradient of the output error signal is calculated as: in, is the error function used to control the adjustment direction of the PID controller parameters, is the output error signal of the small signal model, is the proportional gain of the PID controller, is the integral gain of the PID controller, is the differential gain of the PID controller.

10. The PID controller parameter adaptive adjustment device for a grid-connected converter according to claim 9, characterized in that: Adjust the error gradient calculation parameters to recalculate the error gradient of the output error signal, including: Reduce the learning rate or adjust the calculation parameters of the error gradient of the output error signal to recalculate the error gradient of the output error signal.

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