An Adaptive Linear Active Disturbance Rejection Control Method and System Based on High-Voltage DC Transmission System

Abstract

The present invention discloses an adaptive linear active disturbance rejection control method and system based on a high-voltage direct current transmission system. The method includes the following steps: performing gain processing on the active disturbance rejection linear controller to obtain an adaptive active disturbance rejection linear controller; realizing the control of the inverse converter in the DC system based on the adaptive active disturbance rejection linear controller to complete the DC grid connection operation; the present invention adjusts the parameters of the LADRC controller to achieve flexible control of the system, improve the system response speed and stability, and avoid equipment damage caused by excessive oscillation of the system.

Description

Technical Field

[0001] The present invention relates to the field of control technology, and in particular, to an adaptive linear active disturbance rejection control system and method based on a high voltage direct current (HVDC) transmission system. Background Art

[0002] Currently, in China, a large number of new energy power generations are transmitted through line-commutated converter high voltage direct current (LCC-HVDC). HVDC transmission has the advantages of large transmission capacity, low loss, rapid and flexible power regulation, and the ability to achieve asynchronous networking. It plays an increasingly important role in long-distance power transmission and grid interconnection. At the same time, the rapidly developing flexible HVDC transmission in recent years has unique application advantages in aspects such as wind power generation and island power supply. Therefore, HVDC transmission has achieved rapid development and wide application worldwide.

[0003] Since the sending-end AC grid of LCC-HVDC is generally located in remote areas and the sending-end AC grid is weak, the new energy power generation base, the sending-end weak AC grid, and the LCC-HVDC transmission system will be mutually coupled, and system oscillations are likely to occur at both the sending end and the receiving end of the new energy power generation LCC-HVDC transmission. Since the instability of the new energy power generation system oscillation will lead to serious power losses and equipment damage, relevant institutions have conducted a large number of investigations to improve the stability of the new energy power generation system. However, system oscillation accidents still occur frequently in the case of a weak grid at the sending end of the new energy power generation LCC-HVDC transmission. Therefore, the system oscillation problem in the case of a weak grid at the sending end of the new energy power generation LCC-HVDC transmission requires extensive attention and research.

[0004] When the load of the new energy power generation LCC-HVDC system suddenly changes, serious voltage oscillations will occur in the LCC-HVDC DC transmission line. Therefore, the stability of the receiving-end weak grid system of the new energy power generation LCC-HVDC transmission can be improved by suppressing the voltage oscillations at the receiving end of the LCC-HVDC. Therefore, it is urgent to improve the response speed and stability of the HVDC transmission system from the control level. Therefore, it is of great significance to explore the control method of the HVDC transmission system. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide an adaptive linear active disturbance rejection control system and method based on a HVDC transmission system to improve the stability and response speed of the HVDC transmission system.

[0006] Technical solution: The present invention aims to provide an adaptive linear active disturbance rejection control method and system based on a high-voltage direct current (HVDC) transmission system. The method includes the following steps: performing gain processing on the active disturbance rejection linear controller to obtain an adaptive active disturbance rejection linear controller; and realizing the control of the inverter in the DC system based on the adaptive active disturbance rejection linear controller to complete the DC grid connection operation.

[0007] Further, the step of performing gain processing on the active disturbance rejection linear controller to obtain an adaptive active disturbance rejection linear controller includes the following steps:

[0008] (1) Calculating the output control quantity of the linear error state feedback controller (LESF);

[0009] (2) By collecting the DC voltage value supplied by the HVDC transmission system in real time, comparing it with the given voltage value, and passing through the control to output the system bandwidth ω of the actual HVDC transmission system c ;

[0010] (3) Calculating the state variables z1, z2, and z3 of the linear extended state observer (LESO);

[0011] (4) Comparing the output signal of the LSEF and the z3 signal of the LESO, and using the gain of the controller to perform disturbance compensation on the processed signal, and inputting the disturbance-compensated signal into the PWM signal generator to generate a signal, generating a PWM wave signal with a certain duty cycle.

[0012] Further, the specific step (1) is as follows: determining the output control quantity of the linear error state feedback controller LESF through the system bandwidth, and the formula is as follows:

[0013] u0 = k p (R - z1) - k d z2

[0014] where u0 is the output control quantity of the LSEF, R is the input value given by the system, z1 and z2 are the state variables observed by the linear extended state observer LESO, and k p , k d are the gains of the controller, and the formula is as follows:

[0015] k d = 2ω c ,

[0016] where ts is the system adjustment time.

[0017] Further, the specific step (2) is as follows, and the formula is as follows:

[0018]

[0019] Among them, ω c is the actual system bandwidth output after control, ω c0 is the system bandwidth, and k a , k b are adaptive adjustment coefficients, and Δu is the output voltage deviation;

[0020] When the system is in the normal working state, the system bandwidth takes ω c0 , and when the system is working under no-load or light-load conditions, the optimal value of the current state can be reselected through the automatic adjustment coefficient.

[0021] Furthermore, the specific content of step (3) is as follows: The parameters of the linear extended state observer LESO are determined by using the characteristic equation pole placement method, and the formula is as follows:

[0022]

[0023] Among them, z1, z2, and z3 are state variables respectively; β1, β2, and β3 are observer gains, and the formula is as follows:

[0024] β1 = 3ω0, β2 = 3ω0 2 , β3 = ω0 3

[0025] ω0 is the observation bandwidth; ω c is the system bandwidth of the high-voltage direct current transmission system.

[0026] The present invention also provides a direct current transmission system control system according to the above-mentioned high-voltage direct current transmission system control method based on adaptive linear auto-disturbance rejection, including a controller design module and a direct current transmission system control module; the controller design module is used to perform gain processing on the auto-disturbance rejection linear controller to obtain an adaptive auto-disturbance rejection linear controller; the direct current transmission system control module realizes the control of the inverse converter in the direct current system based on the adaptive auto-disturbance rejection linear controller to complete the direct current grid connection operation.

[0027] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: By adjusting the parameters of the LADRC controller, the system can be flexibly and controllably adjusted, the system response speed and stability are improved, and the equipment damage caused by excessive oscillation of the system is avoided. Description of the Drawings

[0028] Figure 1 is the principle block diagram of the present invention;

[0029] Figure 2 is the direct current voltage change curve diagram of the inverter in the direct current transmission system under the constant voltage control method in comparison with the control method of the present invention and the traditional PI control method;

[0030] Figure 3 The curve diagram of the DC voltage variation in the system after the load of the sending - end AC power grid suddenly changes, under the comparison between the control method described in this invention and the traditional PI control method. Specific embodiments

[0031] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0032] As Figure 1 shown, an adaptive linear active disturbance rejection control method and system based on a high - voltage DC transmission system are provided in an embodiment of the present invention. The method includes the following steps: Gain processing is performed on the active disturbance rejection linear controller to obtain an adaptive active disturbance rejection linear controller; Based on the adaptive active disturbance rejection linear controller, the control of the inverse converter in the DC system is realized to complete the DC grid - connection operation.

[0033] The gain processing is performed on the active disturbance rejection linear controller to obtain an adaptive active disturbance rejection linear controller, including the following steps:

[0034] (1) Calculate the output control quantity of the linear error state feedback controller LESF; Specifically: Determine the output control quantity of the linear error state feedback controller LESF through the system bandwidth. The formula is as follows:

[0035] u0 = k p (R - z1)-k d z2

[0036] where u0 is the output control quantity of LSEF, R is the input value given by the system, z1 and z2 are the state variables observed by the linear extended state observer LESO, and k p 、k d are the gains of the controller. The formula is as follows:

[0037] k d = 2ω c ,

[0038] where ts is the system adjustment time.

[0039] (2) By collecting the DC voltage value supplied by the high - voltage DC transmission system in real - time, comparing it with the given voltage value, and passing through the control to output the actual system bandwidth ω of the high - voltage DC transmission system c ; Specifically, the formula is as follows:

[0040]

[0041] where ω c is the actual system bandwidth output after control, ω c0 is the system bandwidth, and ka 、k b is the adaptive adjustment coefficient, and Δu is the output voltage deviation;

[0042] When the system is in normal operation, the system bandwidth is taken as ω c0 , and when the system operates under no-load or light-load conditions, the optimal value of the current state can be reselected through the automatic adjustment coefficient.

[0043] (3) Calculate the state variables z1, z2, and z3 of the linear extended state observer LESO; specifically: Use the characteristic equation pole placement method to determine the parameters of the linear extended state observer LESO, and the formula is as follows:

[0044]

[0045] Among them, z1, z2, and z3 are the state variables respectively; β1, β2, and β3 are the observer gains, and the formula is as follows:

[0046] β1 = 3ω0, β2 = 3ω0 2 , β3 = ω0 3

[0047] ω0 is the observation bandwidth; ω c is the system bandwidth of the high-voltage direct current transmission system.

[0048] (4) Compare the output signal of the LSEF and the z3 signal of the LESO, and use the gain of the controller to perform disturbance compensation on the processed signal. Input the signal after disturbance compensation into the PWM signal generator to generate a signal, generating a PWM wave signal with a certain duty cycle.

[0049] Use the controller gain b0 to perform disturbance compensation on the difference between the output signal of the LESF and the z3 signal of the LESO. The signal after disturbance compensation is input into the PWM signal generator. At this time, a PWM wave signal with a certain duty cycle will be generated. Use this signal to complete the control of the inverter, realizing the DC grid connection operation. At the same time, collect the DC voltage, determine the system bandwidth, and use the LESF and LESO for processing again to complete the linear active disturbance rejection control, realizing the adaptive linear active disturbance rejection control, and controlling the converter of the inverter station to complete the DC grid connection operation.

[0050] Figure 2It is a curve comparison diagram of DC voltage under the traditional PI control method and the control method described in the present invention. The inverter control module is set. First, the simulation of the traditional PI control method is carried out. The module in the constant voltage control of the inverter is set as the PI module, the voltage reference value is 220 kV, the parameters of the PI module are Kp = 1 / 500e3 and Ki = 200 / 500e3, and the simulation time is set to 0.5 s to observe the DC voltage change curve. Replace the PI module with the packaged A-LADRC module, adjust the parameters until the DC voltage curve is stable, and compare the curves of the two control methods. It can be concluded that the control method proposed in the present invention is significantly better than the traditional PI control method. From the perspective of the oscillation amplitude, the oscillation amplitude of the control method described in the present invention is small and the number of oscillation links is small; from the perspective of the response speed, the response speed of the present invention is fast, approaching stability at 0.04 s, while the PI control is significantly slower.

[0051] Figure 3 It is a curve comparison diagram of DC voltage under two control methods when the load of the DC transmission system undergoes a sudden change. Set the simulation of the DC transmission system. Set the current to step at 0.2 s on the rectifier side, and the DC current reference value steps from 1000 A to 1500 A, and then observe the response speed of the DC voltage and the system stability under the two control methods. Figure 3 It is a curve diagram of the DC voltage change in the step part. From Figure 3 it can be seen that the control method described in the present invention enables the system to respond faster to faults and the system is more stable. It can be obtained from the curve diagram that compared with the traditional PI control method, the control method described in the present invention has a better oscillation suppression effect on load mutations, a faster response speed, and the voltage quality is improved.

[0052] The embodiment of the present invention also provides a control system for a DC transmission system according to the above-mentioned control method for a high-voltage DC transmission system based on adaptive linear active disturbance rejection, including a controller design module and a DC transmission system control module; the controller design module is used to perform gain processing on the active disturbance rejection linear controller to obtain an adaptive active disturbance rejection linear controller; the DC transmission system control module is based on the adaptive active disturbance rejection linear controller to realize the control of the inverter in the DC system and complete the DC grid connection operation.

Claims

1. A control method for a high-voltage direct current transmission system based on adaptive linear active disturbance rejection, characterized in that, Including the following steps: The gain of the active disturbance rejection linear controller is processed to obtain an adaptive active disturbance rejection linear controller, including the following steps: (1) Calculate the output control quantity of the linear error state feedback controller LESF; (2) By collecting the DC voltage value supplied by the HVDC transmission system in real time, comparing it with the given voltage value, and through control, output the system bandwidth of the actual HVDC transmission system w c ; (3)Calculate the state variables of the Linear Extended State Observer (LESO) z 1、 z 2、 z 3; specifically: The pole placement method of the characteristic equation is used to determine the parameters of the Linear Extended State Observer (LESO), and the formula is as follows: ； Among them, z 1、 z 2、 z 3 are state variables respectively; b 1、 b 2、 b 1, 2, and 3 are observer gains, and the formula is as follows: ； Among them, w 0 is the observation bandwidth; w c is the system bandwidth of the HVDC transmission system; (4) Compare the output signal of the LSEF with the z3 signal of the LESO, and use the gain of the controller to compensate for the disturbance of the processed signal. Input the signal after disturbance compensation into the PWM signal generator to generate a signal and produce a PWM wave signal with a certain duty cycle; Based on the adaptive active disturbance rejection linear controller, the control of the inverter in the DC system is realized to complete the DC grid connection operation.

2. The control method of a high-voltage direct current power transmission system based on adaptive linear active disturbance rejection according to claim 1, wherein, The specific content of the step (1) is: determine the output control quantity of the linear error state feedback controller LESF through the system bandwidth, and the formula is as follows: ； Among them, u 0 is the output control quantity of LSEF, R is the input value given by the system, z 1, z 2 is the initial state variable of the linear extended state observer LESO, k p , k d are the gains of the controller, and the formula is as follows: ； Among them, w c is to control the output of the actual system bandwidth, w c0 is the system bandwidth, k a 、k b is the adaptive adjustment coefficient, ∆ u is the output voltage deviation; When the system is in a normal working state, the system bandwidth is taken as w c0 , when the system is operating under no-load or light-load conditions, the optimal value of the current state can be reselected through the automatic adjustment coefficient.

3. A control method for a HVDC transmission system based on adaptive linear active disturbance rejection according to claim 2, characterized in that, The specific content of the step (2) is, and the formula is as follows: ； Among them, w c is the actual system bandwidth after control output, w c0 is the system bandwidth, k a 、k b is the adaptive adjustment coefficient, ∆ u is the output voltage deviation; When the system is in a normal working state, the system bandwidth takes w c0 , and when the system is working under no-load or light-load conditions, the optimal value of the current state can be re-selected through the automatic adjustment coefficient.

4. The control system of a high-voltage direct current transmission system control method based on adaptive linear active disturbance rejection according to any one of claims 1-3, characterized in that, Including a controller design module and a DC power transmission system control module; the controller design module is used to process the gain of the active disturbance rejection linear controller to obtain an adaptive active disturbance rejection linear controller; the DC power transmission system control module realizes the control of the inverter in the DC system based on the adaptive active disturbance rejection linear controller to complete the DC grid connection operation.

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