Damped oscillation control method

Abstract

The invention discloses a control method for damped oscillation, which realizes additional damping control based on an extended PID damping control algorithm and inhibits system oscillation. An extended PID damping control algorithm which can be used for suppressing oscillation is obtained by deforming a general format of extended PID control; and determining additional positions of a system output / feedback signal y and an input / control signal u in the system to be controlled, calculating the size of the control signal u according to the output signal y and the determined control parameters, and adding the control signal u to a control loop to realize damping control. According to the method, a unified expression format of additional damping control is provided, links such as band-pass filtering, proportional gain, phase compensation and amplitude limiting of traditional additional damping control are unified into a mathematical expression format, universality is achieved, the method can be flexibly applied to the conditions of multiple input signals and multiple output signals, the calculated amount is small, design is simple, and the method is suitable for large-scale popularization and application. And the additional damping control capability can be improved.

Description

Technical Field

[0001] The invention belongs to the field of electric power technology, relates to oscillation suppression technology, and in particular to a novel additional damping control method for suppressing oscillation. Background Art

[0002] Vigorously developing new energy power generation is an important measure to promote low-carbon energy transformation and ensure energy security. With the increase in the scale and proportion of new energy installed capacity, the power system presents the characteristics of high proportion of new energy and high proportion of power electronics, and the oscillation problem gradually becomes prominent. Adding damping control strategies to unstable units to suppress system oscillation is of great significance to improving system stability.

[0003] The working principle of traditional additional damping control is to select electrical quantities with obvious oscillation components as output feedback signals, calculate the oscillation frequency, extract the components through filters, and then inject them into the new energy grid-connected system through phase and amplitude modulation to adjust the voltage and current outputs and improve the system damping. The feedback signals of additional damping control often take voltage, current, power, and frequency. The feedback signals are sequentially passed through bandpass filtering, proportional gain, phase compensation, and limiting links. The input position is usually selected on the inner and outer loop controllers of the inverter. The role of the bandpass filter is to extract the oscillation component; the role of the proportional gain and phase compensation is to enable the additional damping signal to better offset the oscillation component; the role of the limiting link is to prevent overshoot of the control quantity and ensure that the controller can be physically realized.

[0004] Traditional additional damping control is widely used in power systems. However, traditional additional damping control belongs to model-driven control and needs to rely on accurate system state equations. The nonlinearity and time-varying nature of the power system, the random uncertainty of the operating state of new energy stations and other factors make it difficult to accurately model the power system, and the adaptability of traditional additional damping control to different operating scenarios is limited. In the traditional additional damping control strategy, each filtering and phase shifting requires N points of data window cycle sampling, and the amount of calculation is much higher than simple algebraic calculation. The phase compensation link increases the control delay, and the amount of calculation for each operation is very large. If the situation of multiple input signals or multiple output signals is considered, the coupling effect and modeling problems of different loops make it difficult for traditional control technology to achieve the modeling of such complex damping control. Existing research has adopted methods such as self-disturbance rejection technology, virtual impedance technology, notch technology, sliding mode control technology, and artificial intelligence to improve the control effect of the additional damping control strategy, but these improvement strategies have not fundamentally improved the structure of the additional damping control, nor have they solved the design problem of the complex damping controller.

[0005] In summary, the proposed unified mathematical expression format for additional damping control has very important engineering value for improving the structure of additional damping controller, enhancing control potential and simplifying the design process.

[0006] Purpose of the Invention

[0007] In order to address the shortcomings of the prior art, the present invention proposes a unified format of additional damping control that can be used to suppress oscillations. The bandpass filtering, proportional gain, phase compensation, limiting and other links of traditional additional damping control are unified into a mathematical expression format. The format has universality and can be flexibly applied to multiple input signals and multiple output signals. The calculation amount is small, the design is simple, and the additional damping control capability can be improved. Summary of the invention

[0008] According to a first aspect of the present application, an extended PID damping control algorithm that can be used for oscillation suppression is provided, which may include the following steps:

[0009] Step 1: Write the unified format of extended PID control;

[0010] The unified format of extended PID control is:

[0011]

[0012] Among them, u(k) is the control signal, y(k) is the output signal, y* is the given value of the system output signal, variable k is the kth point in the discrete signal, and real number k i is the coefficient of each corresponding item, L is the dimension of extended PID control, and i is a variable.

[0013] Step 2: Considering the need for additional damping control, transform equation (1);

[0014] In the damping control process, in order to maintain the stability of the control system, equation (1) is transformed into:

[0015]

[0016] Among them, the dimension L ≥ 2, the real number k i are the coefficients of the corresponding terms, and When the oscillation disappears, the output signal y(k) is constant and the output signal has no effect on the control signal u(k).

[0017] Step 3: Introduce the step size factor to obtain the extended PID damping control algorithm that can be used for oscillation suppression;

[0018] In order to make the control algorithm design more flexible, the step size factor ρ is introduced into equation (1): 0 , construct the relaxed format:

[0019]

[0020] Where 0≤ρ 0 ≤1, step factor ρ 0Its role is to improve the convergence and stability of the control algorithm in some cases.

[0021] By setting ρ 0 With k i , can play the role of limiting and proportional gain; by setting different coefficients for the output signal y(k-i+1) at different historical moments, it can play the role of filtering and phase shifting. In summary, the mathematical expression of formula (3) can realize the function of general traditional damping control.

[0022] According to a second aspect of the present application, an additional damping controller based on an extended PID damping control algorithm is provided, which may include the following steps:

[0023] Step 1: Select the system output signal y;

[0024] In the oscillating system, select the signal with obvious oscillation component as the system output / feedback signal y;

[0025] In the power system, the original signal or processed signal of a voltage, current, power, or frequency electrical quantity signal related to the oscillation can be selected as the output signal y, or the arithmetic result obtained by combining multiple signals can be selected as the output signal y.

[0026] Step 2: Determine the required additional damping controller order and other control parameters;

[0027] According to formula (3), first determine the dimension L of the extended PID damping control, and then determine the coefficient k of each corresponding item according to a certain parameter design method: i (and have ) and step factor ρ 0 (0≤ρ 0 ≤1).

[0028] Step 3: Calculate the size of the control signal u according to the extended PID damping control algorithm;

[0029] According to formula (3), the specific value of the output signal y and various control parameters are substituted to calculate the size of the control signal u.

[0030] Step 4: Select the additional position of the control signal u;

[0031] In the control link of the oscillation system, a place is selected as the additional signal position and the control signal u is added to the link. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the principle block diagram of the extended PID damping controller.

[0033] Figure 2 It is an LRC circuit structure. DETAILED DESCRIPTION

[0034] The embodiments are described in detail below in conjunction with the accompanying drawings.

[0035] Figure 1 The block diagram of the extended PID damping control principle based on equation (3) is shown in Figure 3. A set of historical output information y(k), y(k-1),…, y(k-L+1) is stored in the signal storage to determine the control parameter ρ. 0 and k i After that, the current control signal u(k) is calculated by the control algorithm (3) and input into the controlled system to obtain the output value y(k+1) at a new moment. The control system can work cyclically under the action of the time-delay element and the storage element.

[0036] Considering a general oscillating system, the most common device in an electrical system is a circuit composed of components such as resistors, inductors, and capacitors, such as Figure 2 The general circuit structure shown in the figure consists of a network composed of resistor R, inductor L, and capacitor C. The voltage u o (t) is the output y, u i (t) is the original control of the circuit, in u i (t) Additional extended PID damping control u k (t) as additional damping control.

[0037] The differential equation for this device is:

[0038]

[0039] Under the action of inductance and capacitance, Figure 2 The system is prone to oscillation. When RC is a negative value, the circuit structure is a negative damping system. Once oscillation occurs, it is difficult for the system to recover stability on its own. The use of additional damping strategy plays an important role in suppressing oscillation.

[0040] Experiments show that under appropriate control parameters, the additional damping control based on the extended PID damping control algorithm can effectively suppress system oscillations, and with the increase of the control order L, it is expected to achieve better and better control effects.

[0041] The present invention shows that the additional damping controller based on the extended PID damping control algorithm can effectively solve a class of oscillation problems and realize a unified expression format of damping control. Compared with the traditional additional damping strategy, formula (3) can realize the oscillation suppression function of traditional control, and only simple algebraic calculations are needed in the implementation process, and the amount of calculation is significantly reduced; due to the addition of more control dimensions and available information, the present invention can achieve better control effects. The present invention has universal significance for any oscillation in a physical system.

[0042] The method of the present invention is not only applicable to the second-order LRC electrical oscillation system in the embodiment, but also to other oscillation systems of the second order and above, including but not limited to a second-order system containing a single oscillation and a high-order system containing multiple oscillations.

[0043] The method of the present invention is not only applicable to the power system oscillation scenario in the embodiment, but also applicable to any physical system, including but not limited to the fields of electricity, petrochemical, manufacturing, metallurgy, etc.

[0044] Those skilled in the art should understand that the embodiments of the present invention are only to describe the preferred specific implementation methods of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A damped oscillation control method, based on an extended PID damping algorithm to suppress system oscillation, characterized in that: The method comprises the following steps: Step 1: The extended PID damping control algorithm is obtained by transforming the extended PID control; Step 2: Determine the order of the extended PID damping control algorithm and other control parameters; Step 3: Determine the additional positions of the system output / feedback signal y and the input / control signal u in the system to be controlled; Step 4: According to the output signal y and the given control parameters, the size of the control signal u is calculated and added to the control loop to achieve damping control.

2. The method according to claim 1, characterized in that: The general format of extended PID control is: Among them, u(k) is the control signal, y(k) is the output signal, y* is the given value of the system output signal, variable k is the kth point in the discrete signal, and real number k i is the coefficient of each corresponding item, L is the dimension of extended PID control, and i is a variable.

3. The method according to claim 2, characterized in that: Considering the need for additional damping control, equation (1) is transformed into: Among them, the dimension L ≥ 2, the real number k i are the coefficients of the corresponding terms, and Its purpose is to make the output signal y(k) constant when the oscillation disappears, and the output signal will not affect the u(k) signal, so as to maintain the stability of the control system.

4. The method according to claim 3, characterized in that: By introducing the step size factor, the extended PID damping control algorithm that can represent general damping control is obtained: Among them, 0≤ρ0≤1, the role of the step factor ρ0 is to improve the convergence and stability of the control algorithm in some cases.

5. The method according to claim 4, characterized in that: The damping function is realized by selecting appropriate control parameters; by setting ρ0 and k i , can play the role of limiting and proportional gain; by setting different coefficients k for the output signal y(k-i+1) at different historical moments i , which can play the role of filtering and phase shifting.

6. The method according to claim 4, characterized in that: By determining the parameter L, the dimension of the controller is determined, and the number of historical output signals and the number of other control parameters required are determined.

7. The method according to claim 4, characterized in that: By determining the order L and other control parameters, equation (3) can realize the functions of limiting, gain, filtering, and phase shifting of the general damping controller by algebraic calculation, and can realize the function of suppressing oscillation of the general damping controller, but its damping capacity can be further enhanced by increasing the order and using more historical output signals.

8. The method according to claim 5, characterized in that: The control parameters are set through certain methods, including theoretical calculation method, engineering experience method, adaptive iteration method, parameter optimization method and artificial intelligence method.

9. The method according to claim 1, characterized in that: In an oscillating system, a signal with a more obvious oscillation component is selected as the system output / feedback signal y; a single physical quantity related to the oscillation can be selected as the output signal y, or the arithmetic result obtained by combining multiple signals can be selected as the output signal y.

10. The method according to claim 9, characterized in that: The output signal y is derived from the signal in the oscillation system. The output signal y can be a directly measured physical quantity or a deformation result after mathematical operation of the physical quantity.

11. The method according to claim 1, characterized in that: A suitable position is selected in the oscillation system as an additional position of the control signal u, which can be a single input point or multiple positions as input points.

12. The method according to claim 1, characterized in that: Substitute the specific value of the output signal y and the determined control parameters into equation (3) to calculate the control signal u, which is added to the control loop using the algebraic addition method to achieve damped oscillation.

13. The method according to claim 1, characterized in that: The oscillation suppression method based on the extended PID damping algorithm can be used not only to suppress oscillations of a single frequency, but also to suppress oscillations containing multiple oscillation frequencies.

14. The method according to claim 1, characterized in that: The oscillation suppression method based on the extended PID damping algorithm can be extended to all physical systems of second order and above.

Images