CN115483690B - Elastic wide-area damping control method and system based on multi-controller switching - Google Patents

Abstract

The invention discloses an elastic wide area damping control method and system based on multi-controller switching, belonging to the field of power system control, wherein the method comprises the following steps: the wide area damping controller connected to the power grid closed loop system detects whether the system communication network is attacked, starts timing when the attack is detected, and sends out strong attack early warning when the attack duration exceeds the time threshold which can be born by the wide area damping controller; when the switching-monitoring controller monitors strong attack early warning, the wide area damping controller which is currently connected to the power grid closed-loop system is cut off, and one of the pre-configured alternative wide area damping controllers with the optimal network state is selected to be connected to the power grid closed-loop system so as to continue oscillation suppression. The plurality of wide area damping controllers are arranged to replace each other, and a new strong attack judging mode is provided, so that the cyclic switching is performed rapidly, and the interval oscillation of the system is effectively restrained while the influence of the strong attack is eliminated.

Description

Elastic wide-area damping control method and system based on multi-controller switching

Technical Field

The present invention belongs to the field of power system control, and more specifically, relates to an elastic wide-area damping control method and system based on multi-controller switching.

Background Art

In order to cope with the increasing risk of cyber attacks, many elastic wide-area damping control methods that can resist cyber attacks are constantly being developed. For scenarios where attacks inject false data into transmitted signals, causing data mutations, most existing elastic wide-area damping control methods detect or repair attacks based on the degree to which the values of wide-area signals are affected by attacks. However, even if there is no attack, various electrical quantities may mutate during grid operation due to physical faults such as short circuits, making it difficult to distinguish between attacks and physical faults in the grid. In addition, attack designers are constantly developing various new types of attacks to simulate physical faults in the grid as much as possible, and inject them when the grid is not disturbed, which will further increase the difficulty of distinguishing between attacks and faults.

Setting up redundant backup is a common practice to improve safety in power systems. However, existing wide-area damping control methods based on redundancy rarely study how to defend against attacks of different intensities, which causes the controller to be frequently switched, causing unnecessary disturbances to the system, and requires the design of more redundant backups, which increases communication consumption and other costs.

In summary, it is of great significance to design a reasonable multi-control switching mechanism to avoid the problem of unstable system operation caused by inappropriate switching of controllers due to the difficulty in effectively distinguishing between attacks and physical failures.

Summary of the invention

In view of the defects of the prior art and the need for improvement, the present invention provides a flexible wide-area damping control method and system based on multi-controller switching, which aims to solve the problem of unstable system operation caused by inappropriate switching of controllers due to the difficulty in effectively distinguishing between attacks and physical failures in the existing flexible wide-area damping control method.

To achieve the above-mentioned purpose, according to one aspect of the present invention, there is provided a flexible wide-area damping control method based on multi-controller switching, comprising: S1, a wide-area damping controller connected to a power grid closed-loop system detects whether the system communication network is attacked, starts timing when an attack is detected, and issues a strong attack warning when the attack duration exceeds the time threshold that it can withstand; S2, when a switching-monitoring controller detects a strong attack warning, the wide-area damping controller currently connected to the power grid closed-loop system is cut off, and a wide-area damping controller with the best network status is selected from pre-configured alternative wide-area damping controllers to be connected to the power grid closed-loop system to continue oscillation suppression.

Furthermore, after S2, it also includes: the switching-monitoring controller marks the state of the wide-area damping controller to be cut off as a failure state, and performs a connectivity test on the wide-area damping controller in the failure state at a preset interval; when the connectivity test passes, the failure state is changed to a dormant state, and the wide-area damping controller in the dormant state is used as a standby wide-area damping controller, and the connectivity test is stopped.

Furthermore, the connectivity test includes: after the preset time, the switching-monitoring controller activates the communication function of the wide area damping controller in the failed state, and communicates with the activated wide area damping controller. If no strong attack is found within the communication set time period, the connectivity test passes, otherwise, the connectivity test fails.

Furthermore, the selection of the one with the best network status to access the power grid closed-loop system in S2 includes: the switching-monitoring controller sends a broadcast, and receives response information returned by each alternative wide-area damping controller according to the received broadcast, and connects the alternative wide-area damping controller corresponding to the earliest received response information to the power grid closed-loop system.

Furthermore, the alternative wide area damping controller is not connected to the system communication network and communicates only when broadcasting.

Furthermore, the switching-monitoring controller stores historical data of the power grid closed-loop system, and the switching-monitoring controller in S2 is also used to transmit the historical data to the wide-area damping controller newly connected to the power grid closed-loop system, so that the wide-area damping controller newly connected to the power grid closed-loop system can identify the current operating state of the system according to the historical data to quickly identify the system model parameters, thereby achieving oscillation suppression.

According to another aspect of the present invention, there is provided an elastic wide-area damping control system based on multi-controller switching, comprising: a switching-monitoring controller and a plurality of wide-area damping controllers, wherein one wide-area damping controller is connected to a power grid closed-loop system, and at least one wide-area damping controller is an alternative wide-area damping controller; the switching-monitoring controller and the plurality of wide-area damping controllers execute the elastic wide-area damping control method based on multi-controller switching as described above.

In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

(1) Distinguishing strong and weak attacks based on attack time solves the problem of being unable to effectively distinguish attacks from physical faults when distinguishing attacks from the perspective of signal amplitude. It improves the accuracy of distinguishing strong and weak attacks, thereby ensuring accurate switching of alternative controllers, avoiding frequent switching or untimely switching that affects system performance, and improving the system's ability to suppress oscillations and operational stability.

(2) A dormant state is proposed as an intermediate state between the working state and the failed state. On the one hand, the wide-area damping controller that was previously attacked by a strong attack will not be abandoned. It can continue to be used after the attack disappears or is cleared, realizing the reuse of the failed controller and improving the utilization efficiency of each candidate controller. It avoids the need to repeatedly set up many candidate controllers. On the other hand, by setting the dormant state and connectivity test, the network is confirmed to be secure before it is put into the working state, avoiding the risk of the failed controller being directly put into operation and causing it to be attacked again.

(3) Considering that the probability of attacks is high during the period when the failed controller is removed, the connectivity test will most likely fail. Therefore, a connectivity test is performed after a preset cool-off period. The purpose is to wait for the attack to disappear or be cleared, thereby improving the efficiency and success rate of the connectivity test.

(4) By designing the alternative wide-area damping controller to communicate only during broadcasting, communication resources can be saved while ensuring the system switching control performance, thus avoiding the problem of doubling the consumption of communication resources caused by the increase in the number of alternative controllers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a flow chart of an elastic wide-area damping control method based on multi-controller switching provided by an embodiment of the present invention;

FIG2 is a schematic structural diagram of an elastic wide-area damping control system based on multi-controller switching provided by an embodiment of the present invention;

3 is a schematic diagram of a process of performing attack detection, weak attack compensation, and strong attack warning by a wide-area damping controller provided by an embodiment of the present invention;

FIG4 is a schematic diagram of multi-controller switching under a strong attack provided by an embodiment of the present invention;

FIG5 is a flowchart of a single wide-area damping controller provided by an embodiment of the present invention;

6A, 6B, and 6C are graphs showing changes in system tie line power and controller output instructions over time after two SNPMs are strongly attacked under three different initial conditions provided by an embodiment of the present invention;

7 is a graph showing the change of controller output instructions and the corresponding working state of each wide-area damping controller over time when two wide-area damping controllers are attacked in succession under continuous faults provided by an embodiment of the present invention;

8 is a comparison diagram of the integral of the absolute error (ITAE) of time multiplied by the power angle δ _1-10 under different wind speed conditions provided by an embodiment of the present invention for the system in four control scenarios.

DETAILED DESCRIPTION

In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

In the present invention, the terms "first", "second", etc. (if any) in the present invention and the accompanying drawings are used to distinguish similar objects but not necessarily to describe a specific order or sequence.

Fig. 1 is a flow chart of an elastic wide-area damping control method based on multi-controller switching provided by an embodiment of the present invention. Referring to Fig. 1 , the method includes operations S1 to S2.

Operation S1, the wide area damping controller connected to the power grid closed-loop system detects whether the system communication network is attacked, starts timing when an attack is detected, and issues a strong attack warning when the attack duration exceeds the time threshold that it can withstand.

Operation S2, when the switching-monitoring controller detects a strong attack warning, it cuts off the wide-area damping controller currently connected to the power grid closed-loop system, and selects one with the best network status from the pre-configured candidate wide-area damping controllers to connect to the power grid closed-loop system to continue oscillation suppression.

According to an embodiment of the present invention, the alternative wide-area damping controller is not connected to the system communication network and communicates only during broadcasting, thereby saving communication resources on the basis of ensuring the system switching control performance and avoiding the problem of doubling of communication resource consumption caused by an increase in the number of alternative controllers.

The operation S2 selects a network state optimal for access to the grid closed-loop system, including: the switching-monitoring controller sends a broadcast, receives response information returned by each candidate wide-area damping controller according to the received broadcast, and connects the candidate wide-area damping controller corresponding to the earliest received response information to the grid closed-loop system.

The switching-monitoring controller stores historical data of the power grid closed-loop system. In operation S2, the switching-monitoring controller is also used to transmit the historical data to the wide-area damping controller of the newly connected power grid closed-loop system, so that the wide-area damping controller of the newly connected power grid closed-loop system can identify the current operating state of the system according to the historical data, so as to quickly identify the system model parameters, thereby achieving oscillation suppression.

Operation S2 also includes: the switching-monitoring controller marks the state of the wide-area damping controller to be cut off as a failure state, and performs a connectivity test on the wide-area damping controller in the failure state at preset intervals; when the connectivity test passes, the failure state is changed to a dormant state, and the wide-area damping controller in the dormant state is used as an alternative wide-area damping controller, and the connectivity test is stopped.

According to an embodiment of the present invention, the connectivity test includes: after a preset time, the switching-monitoring controller activates the communication function of the wide area damping controller in a failed state, and communicates with the activated wide area damping controller. If no strong attack is found within the communication set time period, the connectivity test passes, otherwise, the connectivity test fails.

The elastic wide-area damping control method based on multi-controller switching in this embodiment is described in detail below in conjunction with FIG. 2 to FIG. 8 .

Referring to FIG2 , the flexible wide-area damping control method based on multi-controller switching is applicable to a plurality of wide-area damping controllers based on a secure network prediction control algorithm and a switch-monitor module (MSM). The wide-area damping controller is the secure networked prediction control based modules (SNPM) shown in FIG2 .

SNPM generates a control prediction sequence based on the wide-area signal, and has the ability to detect attacks, distinguish attack intensity, and compensate for weak attacks. When the communication network is not attacked, or the intensity of the attack is weak, the SNPM connected to the power grid closed-loop system can output accurate control signals to suppress low-frequency oscillations. In order to deal with strong attack scenarios that a single SNPM cannot cope with, multiple SNPMs are set up to serve as substitutes for each other, and defense against strong attacks is completed by switching with each other. In this embodiment, for example, three SNPMs are set up, and only one SNPM is connected to the power grid closed-loop system for control at a time, and the redundancy is 3 at this time.

MSM monitors the operating status of multiple SNPMs in real time. When an SNPM connected to the power grid closed-loop system is attacked, it is removed from the power grid closed-loop system and one with the best network condition is selected from other candidate SNPMs to continue to perform the oscillation suppression function.

Refer to Figure 3, which shows the process of SNPM performing attack detection, weak attack compensation and strong attack warning functions. The control prediction generator generates a control prediction sequence based on the wide area signal collected by the synchronized phasor measurement unit (PMU). The sequence and the timestamp are packaged into the data packet. After being processed by the MD5 algorithm and the DES algorithm, if the data packet is attacked during transmission through the communication network, the decrypted timestamp will be different from the original timestamp, and the attack can be discovered by comparison. The data register outputs the most recently received data packet each time. If there is no attack or the attack is a weak attack, the control prediction value at the corresponding time can be found from the data packet, and the controller outputs the control instruction normally; if the attack is a strong attack, the corresponding control prediction value cannot be found in the data packet, and the SNPM issues a strong attack warning.

In this embodiment, three operating states are set for SNPM, namely working state, dormant state and failure state. The SNPM in working state is connected to the closed-loop system of the power grid, and the communication line is connected, so as to play its role in suppressing the interval oscillation of the power system. The SNPM in dormant state is not connected to the closed-loop power system, but is recognized by MSM as trustworthy, so it is used as an alternative SNPM, and its communication is not connected. The SNPM in failure state was connected to the closed-loop system for some time in the past, but it was withdrawn from operation because it was found to be under strong attack. Since it is still possible to be attacked by strong attacks, it is not trustworthy and cannot be used as an alternative SNPM, and its communication is not connected.

Referring to FIG. 4 , a schematic diagram of each stage of switching control in this embodiment is shown when the power grid closed-loop system is subjected to a strong attack. This example includes the following six stages:

Phase 1: SNPM1 is connected to the power system to perform the damping control function, SNPM2 and SNPM3 are in sleep mode, and the communication is suspended.

Phase 2: SNPM1 suffers a strong attack and sends a strong attack warning to MSM.

Phase 3: SNPM1 is cut off from the closed-loop system of the power grid, and MSM broadcasts to SNPM2 and SNPM3 in the dormant state. SNPM2 receives the broadcast information first and responds due to its better network condition. In this phase, the power system is temporarily in an open-loop state, and there is no wide-area damping control measure in the system.

Phase 4: SNPM2 is selected as the first to respond and is connected to the system, and a new closed-loop control is formed. The state of SNPM2 changes from dormant to active; SNPM3 remains dormant; SNPM1 is in an invalid state as it has just been strongly attacked, and enters a cool-down period, waiting for the attack to disappear or be cleared.

Phase 5: The cooling-off period of SNPM1 ends and MSM begins to conduct connectivity tests on it.

Phase 6: SNPM1 passes the connectivity test, and its status changes from failure to sleep, and the system continues to operate normally. It should be noted that the system has been operating normally since Phase 4, and the oscillation can be well suppressed.

Referring to FIG. 5 , there is shown a workflow diagram of a single SNPM, in which the following operations S101 to S115 are performed in a working state.

In operation S101 , the SNPM in a working state collects a wide area signal through a PMU.

In operation S102, a control prediction sequence is generated according to the wide area signal.

In operation S103, the data packet containing the control prediction sequence is encrypted.

In operation S104, the encrypted data packet is transmitted to the driver side through a wide area measurement system (WAMS).

In operation S105, the received data packet is decrypted.

In operation S106, a hash code is used to detect whether the data packet has been subjected to a strong attack during the communication process. If so, the process proceeds to operation S107; otherwise, the process proceeds to operation S111 and ends the operation.

In operation S107, a timer starts counting the attacks received.

In operation S108, if the attack duration exceeds the compensation capability of SNPM, proceed to operation S109; otherwise, proceed to operation S110-operation S111 and then end the operation.

In operation S109, it is determined that the current SNPM has been subjected to a strong attack, and a strong attack warning is issued to the state monitoring and switching control module, and the process proceeds to operation S112.

In operation S110 , a suitable control prediction value is selected from the control sequence according to the attack duration.

In operation S111, a control instruction is output.

In operation S112, the SNPM is cut off from the closed-loop system, and its state is changed from a working state to a failed state.

In operation S113, after the cooling-off period, the SNPM starts to enter the connectivity test. If it passes, it goes to operation S114, otherwise, it re-executes operation S113.

In operation S114, the SNPM enters a sleep state.

In operation S115, the SNPM in the dormant state receives the broadcast information in the next strong attack event. If it is selected after sending a response, it enters the working state and goes to operation S101, otherwise, it returns to operation S114.

Refer to Figures 6A, 6B, and 6C, which respectively show the curves of the system interconnection line power and controller output instructions changing with time after two SNPMs are strongly attacked when SNPM1, SNPM2, and SNPM3 are connected to the closed-loop system at the initial time. Taking Figure 6A as an example, it can be seen that when any two SNPMs are subjected to a strong attack, the system can still effectively suppress the interval oscillation after the failure. By observing the final output signal of the controller, it can be seen that its signal completely coincides with the SNPM connected to the closed-loop system at each stage, indicating that the control method in this embodiment is effectively switched after the strong attack occurs, and the SNPM connected to the closed-loop system is changed, which illustrates the effectiveness of the control method of this embodiment. Figures 6B and 6C also demonstrate the above effects.

Refer to Figure 7, which shows the curve diagram of the controller output command and the corresponding working state of each SNPM changing with time when two SNPMs are attacked successively under continuous faults. As can be seen from Figure 7, SNPM1 is initially connected to the closed-loop system, and it is attacked strongly at t=1.19s and enters a failed state. After the broadcast of the switching gap, SNPM3 is selected to be connected to the closed-loop system. SNPM1 then successively experienced a cooling-off period-connectivity test failure-cooling-off period-connectivity test passing, and then recovered from the failed state to the dormant state. During this period, at t=12.19s, SNPM3 was also attacked strongly. Since SNPM1 had not entered the dormant state at this time, only SNPM2 was selected as an alternative and began to perform damping control. SNPM3 entered a failed state and began to experience a cooling-off period-connectivity test cycle. In the process of the actual control module switching from SNPM1 to SNPM3 and then to SNPM2, the system had two three-phase short-circuit reclosing faults at t=1s and 11s, but the oscillations caused by the faults were effectively suppressed. FIG. 7 well demonstrates the effectiveness of the three operating states and the switching mechanism designed in this embodiment.

Refer to Figure 8, which shows a comparison chart of the integral of the absolute error (ITAE) of the time multiplied by the power angle δ _1-10 of the system in four control scenarios under different wind speed conditions. ITAE is a commonly used indicator reflecting control performance in the field of wide-area stability control. The larger its value, the more violent the system oscillation. It can be seen that from working condition 1 to working condition 5, the wind speed of the wind farm changes from low to high, the corresponding system's tidal current condition worsens, the interval oscillation modal damping ratio decreases, and the oscillation under the condition of no wide-area damping control becomes more violent. Although a single SNPM that is strongly attacked has a certain suppression effect, its performance is still very poor, and it is difficult to effectively suppress oscillations. The elastic wide-area damping control method based on multiple controllers in this embodiment shows a good oscillation suppression effect when a single or two SNPMs are strongly attacked, indicating that it has good adaptability to the operating conditions of the power system.

The embodiment of the present invention also provides an elastic wide-area damping control system based on multi-controller switching, including: a switching-monitoring controller and multiple wide-area damping controllers. Among them, one wide-area damping controller is connected to the power grid closed-loop system, and at least one wide-area damping controller is an alternative wide-area damping controller. The switching-monitoring controller and the multiple wide-area damping controllers perform the elastic wide-area damping control method based on multi-controller switching as shown in Figures 1 to 8.

It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims (5)

1. The elastic wide-area damping control method based on multi-controller switching is characterized by comprising the following steps of:

S1, a wide area damping controller connected to a power grid closed loop system detects whether a system communication network is attacked, when the attack is detected, timing is started, and when the attack duration exceeds a time threshold which can be born by the wide area damping controller, a strong attack early warning is sent;

S2, when the switching-monitoring controller monitors strong attack early warning, cutting off a wide area damping controller which is currently connected with the power grid closed-loop system, and selecting one with the optimal network state from the pre-configured alternative wide area damping controllers to be connected with the power grid closed-loop system so as to continue oscillation suppression;

the step S2 further includes:

the switching-monitoring controller marks the state of the cut wide area damping controller as a failure state, and performs connectivity test on the wide area damping controller in the failure state every preset time;

When the connectivity test is passed, changing the failure state into a dormant state, and taking the dormant wide-area damping controller as an alternative wide-area damping controller to stop the connectivity test;

the connectivity test includes:

after the preset time, the switching-monitoring controller activates the communication function of the wide area damping controller in the failure state and communicates with the activated wide area damping controller, if no strong attack is found in the communication set time period, the connectivity test is passed, otherwise, the connectivity test is not passed.

2. The method for controlling elastic wide area damping based on multi-controller switching as set forth in claim 1, wherein the selecting an access grid closed-loop system with an optimal network state in S2 includes:

and the switching-monitoring controller sends out broadcasting, receives response information returned by each alternative wide-area damping controller according to the received broadcasting, and accesses the alternative wide-area damping controller corresponding to the earliest received response information into the power grid closed-loop system.

3. The multi-controller switching based resilient wide area damping control method of claim 1, wherein the alternative wide area damping controller is not in communication with the system communication network and communicates only on the fly.

4. A multi-controller switching-based elastic wide area damping control method according to any one of claims 1-3, wherein the switching-monitoring controller stores historical data of a closed-loop system of a power grid, and the switching-monitoring controller in S2 is further configured to transmit the historical data to a wide area damping controller of the closed-loop system of the newly accessed power grid, so that the wide area damping controller of the closed-loop system of the newly accessed power grid identifies a current running state of the system according to the historical data, so as to quickly identify system model parameters, thereby implementing oscillation suppression.

5. An elastic wide area damping control system based on multi-controller switching, comprising: the system comprises a switching-monitoring controller and a plurality of wide-area damping controllers, wherein one wide-area damping controller is connected with a power grid closed-loop system, and at least one wide-area damping controller is an alternative wide-area damping controller;

The switch-monitor controller and the plurality of wide area damping controllers perform the multi-controller switching-based elastic wide area damping control method as set forth in any one of claims 1-4.