Transient overvoltage suppression method and device in power system fault recovery process

Abstract

The invention provides a transient overvoltage suppression method and device in a power system fault recovery process, and the method comprises the steps: judging whether the terminal voltage of a flexible DC conversion unit is greater than a first threshold value or not when a power system is in a low-voltage fault ride-through state; under the condition that the terminal voltage is greater than or equal to a first threshold value, calculating a difference value between the output phases of the flexible direct current conversion unit and the synchronous power supply to obtain a target power angle difference; under the condition that the target power angle difference is greater than or equal to a second threshold value, controlling the power system to enter an overvoltage suppression state; and updating the target power angle difference under the condition that the terminal voltage of the flexible direct current conversion unit is within a preset range, and controlling the power system to exit the overvoltage suppression state under the condition that the updated target power angle difference is smaller than a third threshold value. According to the method, the problem of transient overvoltage of the flexible direct current conversion unit caused by uncontrollability of a synchronous power supply and coupling characteristics of power and voltage in a flexible direct current limiting mode in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power system fault recovery, and in particular to a method for suppressing transient overvoltage in a power system fault recovery process. Background Art

[0002] In order to increase the channel utilization hours and the frequency and voltage support capacity of the sending system, large-scale new energy bases often use the method of bundling with a small amount of local synchronous power sources for transmission. However, due to the uncontrollability of the output power of the synchronous power source and the coupling characteristics of power and voltage in the flexible DC current limiting mode, when the fault is restored, the synchronous power source accelerates and the power angle with the flexible DC is greatly pulled apart, which will cause the power flowing into the flexible DC to exceed the rated value during the fault recovery process, that is, power overload occurs, and then current saturation causes voltage control failure. In summary, in the power system where new energy and synchronous power sources are bundled and transmitted, it is easy to have a flexible DC transient overvoltage phenomenon caused by active power surplus during the AC fault recovery process.

[0003] Existing renewable energy transient overvoltage suppression mainly targets the overvoltage caused by excess reactive power when renewable energy is transmitted via traditional DC. This is achieved by increasing the strength of the grid at the connection point by adding phase-shifting phases or STATCOM and other devices. Flexible DC transient overvoltage suppression considers controlling the transient overvoltage caused by excess reactive power when pure renewable energy is transmitted via flexible DC.

[0004] To sum up, in the prior art, when solving the transient overvoltage phenomenon of flexible direct current, the problem is considered from the perspective of excess reactive power in the power system. In fact, the transient overvoltage phenomenon of the power system transmitted by renewable energy and synchronous power sources in a bundle is mainly caused by active power overload. That is, the prior art lacks a transient overvoltage suppression method for the power system fault recovery process that is suitable for the power system transmitted by renewable energy and synchronous power sources in a bundle. Summary of the invention

[0005] The main purpose of the present application is to provide a method, device, computer-readable storage medium and power system for suppressing transient overvoltage in a power system fault recovery process, so as to at least solve the problem of transient overvoltage in a flexible DC converter unit caused by the uncontrollability of a synchronous power supply and the coupling characteristics of power and voltage in a flexible DC current limiting mode in the prior art.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present application, a transient overvoltage suppression method in a power system fault recovery process is provided, the power system comprising at least a flexible DC converter unit and a synchronous power supply, the method comprising: when the power system is in a low-voltage fault ride-through state, judging whether the terminal voltage of the flexible DC converter unit is greater than a first threshold value; when the terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold value, calculating the difference between the output phase of the flexible DC converter unit and the output phase of the synchronous power supply to obtain a target power angle difference; when the target power angle difference is greater than or equal to a second threshold value, controlling the power system to enter an overvoltage suppression state, the overvoltage suppression state suppresses the overvoltage phenomenon of the power system by collaboratively controlling the voltage and output frequency of the flexible DC converter unit; when the terminal voltage of the flexible DC converter unit is within a preset range, updating the target power angle difference, and when the updated target power angle difference is less than a third threshold value, controlling the power system to exit the overvoltage suppression state.

[0007] Optionally, the second threshold is based on a first preset formula Calculated, where A is the second threshold, K is the safety factor, and the safety factor is used to characterize the safety degree between the flexible DC converter unit and the synchronous power supply, P nmmc is the rated power of the flexible DC converter unit, P renew0 is the new energy output power before the fault, U nmmc is the rated voltage of the flexible DC converter unit, U nsg is the rated voltage of the synchronous power supply.

[0008] Optionally, the third threshold is based on a second preset formula Calculated, where B is the third threshold, K is the safety factor, and the safety factor is used to characterize the safety degree between the flexible DC converter unit and the synchronous power supply, P nmmc is the rated power of the flexible DC converter unit, U nmmc is the rated voltage of the flexible DC converter unit, U nsg is the rated voltage of the synchronous power supply.

[0009] Optionally, controlling the power system to enter an overvoltage suppression state includes: performing voltage control on the terminal voltage of the flexible DC converter unit based on the rated voltage of the flexible DC converter unit, the voltage control being used to reduce the voltage of the flexible DC converter unit and recover it within a preset time period; performing phase control on the set output frequency of the flexible DC converter unit based on the output power of the flexible DC converter unit before failure and obtaining the expected output power of the flexible DC converter unit after failure recovery, the phase control being used to increase the output frequency of the flexible DC converter unit to reduce the active power output by the synchronous power supply.

[0010] Optionally, the terminal voltage of the flexible DC converter unit is controlled based on the rated voltage of the flexible DC converter unit, including: calculating the product of the rated voltage of the flexible DC converter unit and a first preset coefficient to determine a target voltage; reducing the terminal voltage of the flexible DC converter unit to the target voltage and controlling the terminal voltage of the flexible DC converter unit to increase at a target change rate until the terminal voltage of the flexible DC converter unit is equal to the rated voltage of the flexible DC converter unit, and the target change rate is determined according to the rated power of the flexible DC converter unit and the output power of the flexible DC converter unit before failure.

[0011] Optionally, the target change rate is negatively correlated with a difference between a rated power of the flexible DC converter unit and an output power of the flexible DC converter unit before a fault occurs.

[0012] Optionally, the set output frequency of the flexible DC converter unit is phase-controlled based on the output power of the flexible DC converter unit before the fault and the expected output power after the fault of the flexible DC converter unit is recovered, including: calculating the product of the rated power of the flexible DC converter unit and a second preset ratio to obtain a target power; when the expected output power of the flexible DC converter unit after the fault is recovered is greater than the target power and less than the rated power of the flexible DC converter unit, the set output frequency of the flexible DC converter unit is increased by the target frequency until the terminal voltage of the flexible DC converter unit is equal to the rated voltage of the flexible DC converter unit, and the target frequency is determined by proportional operation based on the expected output power of the flexible DC converter unit after the fault is recovered and the output power of the flexible DC converter unit before the fault.

[0013] Optionally, the target frequency is obtained by converting a difference between an output power of the flexible DC converter unit before a fault and an expected output power of the flexible DC converter unit after the fault is recovered using a third preset coefficient.

[0014] Optionally, the method further includes: controlling the power system to enter the low voltage fault ride-through state when the terminal voltage of the flexible DC converter unit is less than or equal to a fourth threshold, and the fourth threshold is less than the first threshold.

[0015] According to another aspect of the present application, a transient overvoltage suppression device for a power system fault recovery process is provided, the power system comprising at least a flexible DC converter unit and a synchronous power supply, the device comprising: a first acquisition unit, used to determine whether the terminal voltage of the flexible DC converter unit is greater than a first threshold value when the power system is in a low-voltage fault ride-through state; a first control unit, used to calculate the difference between the output phase of the flexible DC converter unit and the output phase of the synchronous power supply to obtain a target power angle difference when the terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold value; a second control unit, used to control the power system to enter an overvoltage suppression state when the target power angle difference is greater than or equal to a second threshold value, the overvoltage suppression state suppressing the overvoltage phenomenon of the power system by cooperatively controlling the voltage and output frequency of the flexible DC converter unit; a third control unit, used to update the target power angle difference when the terminal voltage of the flexible DC converter unit is within a preset range, and control the power system to exit the overvoltage suppression state when the updated target power angle difference is less than a third threshold value.

[0016] According to another aspect of the present application, a computer-readable storage medium is provided, wherein the computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute any one of the methods described.

[0017] According to another aspect of the present application, there is provided a power system, comprising: one or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and the one or more programs include methods for executing any one of the described methods.

[0018] Applying the technical solution of the present application, in the transient overvoltage suppression method of the fault recovery process of the above-mentioned power system, first, when the above-mentioned power system is in a low-voltage fault ride-through state, it is determined whether the terminal voltage of the above-mentioned flexible DC converter unit is greater than a first threshold value; then, when the terminal voltage of the above-mentioned flexible DC converter unit is greater than or equal to the above-mentioned first threshold value, the difference between the output phase of the above-mentioned flexible DC converter unit and the output phase of the above-mentioned synchronous power supply is calculated to obtain a target power angle difference; thereafter, when the above-mentioned target power angle difference is greater than or equal to a second threshold value, the above-mentioned power system is controlled to enter an overvoltage suppression state, and the above-mentioned overvoltage suppression state suppresses the overvoltage phenomenon of the above-mentioned power system by coordinated control of the voltage and output frequency of the above-mentioned flexible DC converter unit; finally, when the terminal voltage of the above-mentioned flexible DC converter unit is within a preset range, the above-mentioned target power angle difference is updated, and when the updated target power angle difference is less than a third threshold value, the above-mentioned power system is controlled to exit the above-mentioned overvoltage suppression state. The present application spontaneously identifies the operating conditions of the power system during the transient process of the end of low-voltage fault ride-through. When the power system is running at high power and the overvoltage risk is high, the output voltage of the flexible DC converter unit is reduced, the voltage capacity is reserved, and the output frequency of the flexible DC converter unit is increased to reduce the power angle difference to reduce the active power output of the synchronous power supply, thereby reducing the output power of the synchronous power supply during the transient process of the end of the fault ride-through. The flexible DC transient overvoltage phenomenon in the transient process of the fault ride-through of the new energy and synchronous power bundled island transmission system is suppressed, and the transient overvoltage problem of the flexible DC converter unit caused by the uncontrollability of the synchronous power supply and the coupling characteristics of power and voltage under the flexible DC current limiting mode in the prior art is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic flow chart of a transient overvoltage suppression method in a power system fault recovery process provided in accordance with an embodiment of the present application is shown;

[0020] Figure 2 A schematic diagram of the structure of a system for bundling new energy and synchronous power supply and transmitting via a flexible DC island is shown according to an embodiment of the present application;

[0021] Figure 3 A logic schematic diagram of a flexible direct current transient overvoltage suppression provided according to an embodiment of the present application is shown;

[0022] Figure 4 A structural block diagram of a transient overvoltage suppression device for a power system fault recovery process provided in accordance with an embodiment of the present application is shown. DETAILED DESCRIPTION

[0023] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0024] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0025] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0026] As introduced in the background technology, in the prior art, the new energy and synchronous power sources are bundled and transmitted through the flexible DC island system, which is prone to flexible DC transient overvoltage caused by active power surplus during the AC fault recovery process. In order to solve the transient overvoltage problem of the flexible DC converter unit caused by the uncontrollability of the synchronous power source and the coupling characteristics of power and voltage in the flexible DC current limiting mode in the prior art, the embodiments of the present application provide a transient overvoltage suppression method, device, computer-readable storage medium and power system in the fault recovery process of a power system.

[0027] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0028] In this embodiment, a transient overvoltage suppression method for a power system fault recovery process running on a mobile terminal, a computer terminal or a similar computing device is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in an order different from that shown here.

[0029] Figure 1FIG. 1 is a flow chart of a transient overvoltage suppression method in a power system fault recovery process according to an embodiment of the present application. Figure 1 As shown, the method comprises the following steps:

[0030] Step S201, when the power system is in a low voltage fault ride-through state, determining whether the terminal voltage of the flexible DC converter unit is greater than a first threshold;

[0031] Specifically, when the above power system is in a low voltage fault ride-through state, the terminal voltage U of the flexible DC converter station is obtained. t And determine whether the terminal voltage of the flexible DC converter unit is greater than the first threshold (low voltage ride through exit threshold U LVTR ) to determine whether to exit the above low voltage fault ride-through state.

[0032] It can be understood that the present application is provided with a configuration that, when a fault is detected in the power system (including but not limited to a low-voltage fault, etc.), the power system is controlled to enter the above-mentioned low-voltage fault ride-through state, and exit the low-voltage fault ride-through state when the voltage recovers to a preset value (i.e., the above-mentioned first threshold), and further determines whether to enter the overvoltage suppression state to suppress overvoltage in the power system.

[0033] In the specific implementation process, Figure 2 As shown, the above power system is a new energy and synchronous power bundled island transmission system. It includes a flexible DC converter unit and a synchronous power supply, and the above synchronous power supply includes conventional power supplies such as thermal power.

[0034] Step S202, when the terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold, calculating the difference between the output phase of the flexible DC converter unit and the output phase of the synchronous power supply to obtain a target power angle difference;

[0035] Specifically, when the terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold (low voltage ride-through exit threshold U LVTR ), the fault recovery process is switched on. To avoid the flexible DC transient overvoltage phenomenon in the above power system due to the large power angle difference, the present application sets the phase θ corresponding to the terminal voltage to be obtained. mmc , and obtain the synchronous power supply phase θ at the end of the synchronous power supply fault ride-through through communication sg , and then calculate the difference between the output phase of the flexible DC converter unit and the output phase of the synchronous power supply to obtain the target power angle difference θ sg -θ mmc .

[0036] Step S203, when the target power angle difference is greater than or equal to a second threshold, controlling the power system to enter an overvoltage suppression state, wherein the overvoltage suppression state suppresses the overvoltage phenomenon of the power system by collaboratively controlling the voltage and output frequency of the flexible DC converter unit;

[0037] Specifically, a judgment is made based on the target power angle difference and the second threshold value A. When the target power angle difference is greater than or equal to the second threshold value, it is determined that the power angle difference between the flexible DC converter unit and the synchronous power supply is sufficient to cause a power overload of the conventional power supply, and there is a risk of transient overvoltage.

[0038] When it is determined that there is a risk of transient overvoltage, the voltage and output frequency of the flexible DC converter unit are controlled to increase the overvoltage capacity while reducing the output active power of the synchronous power supply to avoid transient overvoltage.

[0039] Furthermore, when the target power angle difference is less than the second threshold, it is determined that the power angle difference between the flexible DC converter unit and the synchronous power supply is insufficient to cause a conventional power overload, there is no risk of transient overvoltage, the overvoltage suppression state is not entered, and the control logic of the normal operation of the power system is maintained.

[0040] Step S204: when the terminal voltage of the flexible DC converter unit is within a preset range, updating the target power angle difference; when the updated target power angle difference is less than a third threshold, controlling the power system to exit the overvoltage suppression state.

[0041] Specifically, when the fault recovery process is completed and the voltage returns to the normal range, that is, the voltage deviation from the normal operation of the circuit is within the allowable range, the power angle difference at the current moment is re-detected, and the above target power angle difference θ between the flexible DC converter unit and the synchronous power supply is sg -θ mmc When it is less than the third threshold B, it is determined that the power angle difference between the flexible DC converter unit and the synchronous power supply is insufficient to cause a power overload of the conventional power supply, and there is no transient overvoltage risk, so the overvoltage suppression state is exited.

[0042] Through this embodiment, first, when the above-mentioned power system is in a low-voltage fault ride-through state, it is determined whether the terminal voltage of the above-mentioned flexible DC converter unit is greater than a first threshold value; then, when the terminal voltage of the above-mentioned flexible DC converter unit is greater than or equal to the above-mentioned first threshold value, the difference between the output phase of the above-mentioned flexible DC converter unit and the output phase of the above-mentioned synchronous power supply is calculated to obtain a target power angle difference; thereafter, when the above-mentioned target power angle difference is greater than or equal to a second threshold value, the above-mentioned power system is controlled to enter an overvoltage suppression state, and the above-mentioned overvoltage suppression state suppresses the overvoltage phenomenon of the above-mentioned power system by collaboratively controlling the voltage and output frequency of the above-mentioned flexible DC converter unit; finally, when the terminal voltage of the above-mentioned flexible DC converter unit is within a preset range, the above-mentioned target power angle difference is updated, and when the updated target power angle difference is less than a third threshold value, the above-mentioned power system is controlled to exit the above-mentioned overvoltage suppression state. The present application spontaneously identifies the operating conditions of the power system during the transient process of the end of low-voltage fault ride-through. When the power system is running at high power and the overvoltage risk is high, the output voltage of the flexible DC converter unit is reduced, the voltage capacity is reserved, and the output frequency of the flexible DC converter unit is increased to reduce the power angle difference to reduce the active power output of the synchronous power supply, thereby reducing the output power of the synchronous power supply during the transient process of the end of the fault ride-through. The flexible DC transient overvoltage phenomenon in the transient process of the fault ride-through of the new energy and synchronous power bundled island transmission system is suppressed, and the transient overvoltage problem of the flexible DC converter unit caused by the uncontrollability of the synchronous power supply and the coupling characteristics of power and voltage under the flexible DC current limiting mode in the prior art is solved.

[0043] In one embodiment, the second threshold is based on a first preset formula Calculated, where A is the second threshold, K is the safety factor, and the safety factor is used to characterize the safety level between the flexible DC converter unit and the synchronous power supply, P nmmc is the rated power of the above flexible DC converter unit, P renew0 is the new energy output power before the above fault, U nmmc is the rated voltage of the flexible DC converter unit, U nsg is the rated voltage of the above synchronous power supply.

[0044] Specifically, Figure 3 As shown, the rated power P of the flexible DC converter unit is obtained. nmmc , obtain the new energy output power P before the fault renew0 , get the rated voltage U of the flexible DC converter unit nmmc , get the rated voltage U of the synchronous power supply nsg , substituting the above parameters into the above formula, we can obtain the second threshold value A.

[0045] In a specific implementation, the above K value derivation process is as follows:

[0046] According to the power transmission relationship between synchronous power supply and flexible DC Derivation, considering flexible DC overvoltage (1.3U nmmc ), synchronous power supply normal voltage (1.05U nsg ), the corresponding synchronous power transmission power According to the formula, the critical value of the power angle difference is derived as:

[0047]

[0048] Considering the safety margin to be α (generally 5% to 10% based on conventional standards), the above formula is rewritten based on the safety margin:

[0049]

[0050] Therefore, the criterion is proposed: if the power angle difference between the flexible DC and the synchronous power supply satisfies The flexible DC adopts the normal control mode.

[0051] In the above specific embodiments, 1.3 and 1.05 are both typical values ​​that comply with the standards. In the actual application of different power systems, the values ​​can be taken within the standard requirements according to the actual working conditions and control requirements. This application does not limit the values.

[0052] In one embodiment, the third threshold is based on the second preset formula Calculated, where B is the third threshold, K is the safety factor, and the safety factor is used to characterize the safety level between the flexible DC converter unit and the synchronous power supply, P nmmc is the rated power of the flexible DC converter unit, U nmmc is the rated voltage of the flexible DC converter unit, U nsg is the rated voltage of the above synchronous power supply.

[0053] Specifically, Figure 3 As shown, the rated power P of the flexible DC converter unit is obtained. nmmc , get the rated voltage U of the flexible DC converter unit nmmc , get the rated voltage U of the synchronous power supply nsg , substituting the above parameters into the above formula, we can obtain the third threshold value B.

[0054] In order to prevent the above-mentioned transient overvoltage phenomenon of the flexible DC, in an optional implementation manner, the above-mentioned step S203 includes:

[0055] Step S2031, performing voltage control on the terminal voltage of the flexible DC converter unit based on the rated voltage of the flexible DC converter unit, wherein the voltage control is used to reduce the voltage of the flexible DC converter unit and restore it within a preset time period;

[0056] Specifically, the actual terminal voltage of the flexible DC converter unit is controlled based on the rated voltage of the flexible DC converter unit to reduce the terminal voltage of the flexible DC converter unit, reserve capacity for voltage increase in a subsequent fault recovery process, and avoid transient overvoltage.

[0057] Step S2032, performing phase control on the set output frequency of the flexible DC converter unit based on the output power of the flexible DC converter unit before the fault and the expected output power after the fault recovery of the flexible DC converter unit. The phase control is used to increase the output frequency of the flexible DC converter unit to reduce the active power output by the synchronous power supply.

[0058] Specifically, the set output frequency of the flexible DC converter unit is obtained to obtain the first frequency fn, and the output power P of the flexible DC converter unit before the failure is obtained. 0mmc , obtain the expected output power P after the above flexible DC converter unit fault is restored mmc The output power of the flexible DC converter unit before the fault and the expected output power after the fault recovery of the flexible DC converter unit are obtained to increase the set output frequency of the flexible DC converter unit to reduce the active power output of the synchronous power supply, thereby avoiding the transient overvoltage phenomenon caused by the active power surplus.

[0059] In order to avoid the above transient overvoltage phenomenon, in an optional implementation, the above step S2031 includes:

[0060] Step S20311, calculating the product of the rated voltage of the flexible DC converter unit and the first preset coefficient to determine the target voltage;

[0061] In one embodiment, the first preset coefficient is set to 0.8. Figure 3 As shown, the voltage module obtains the fourth voltage 0.8U according to the product of the rated voltage of the flexible DC converter unit and the first preset coefficient. n .

[0062] Step S20312, reducing the terminal voltage of the above-mentioned flexible DC converter unit to the above-mentioned target voltage and controlling the terminal voltage of the above-mentioned flexible DC converter unit to increase at a target change rate until the terminal voltage of the above-mentioned flexible DC converter unit is equal to the rated voltage of the above-mentioned flexible DC converter unit, and the above-mentioned target change rate is determined according to the rated power of the above-mentioned flexible DC converter unit and the output power of the above-mentioned flexible DC converter unit before the failure.

[0063] Specifically, Figure 3 As shown, the above target change rate is determined as the slope K r , and then adjust the terminal voltage of the flexible DC converter unit to the fourth voltage 0.8U n , with a slope K r , restore to U n .

[0064] In the above embodiment, 0.8 is not a fixed coefficient, and can be set within the scope of national standards. By setting the transient voltage and recovery power, the present application realizes the expansion and automatic recovery of transient overvoltage capacity.

[0065] In one embodiment, the target change rate is negatively correlated with a difference between the rated power of the flexible DC converter unit and the output power of the flexible DC converter unit before a failure.

[0066] Specifically, the output power P of the flexible DC converter unit before the fault is obtained 0mmc , get the rated power P of the flexible DC converter unit nmmc , the first deviation value ΔP1 is obtained by calculating the difference between the rated power of the flexible DC converter unit and the output power of the flexible DC converter unit before the failure according to the target change rate. Figure 3 As shown, the voltage module pre-stores a curve corresponding to the relationship between the first deviation value and the target change rate, that is, the preset curve, and the target change rate is obtained by querying the corresponding first deviation value.

[0067] Through the above embodiments, the present application achieves slow recovery under high power and fast recovery under low power to ensure that the total voltage recovery time does not exceed 200ms.

[0068] In order to implement the above phase control, in an optional implementation manner, the above step S2032 includes:

[0069] Step S20321, calculating the product of the rated power of the flexible DC converter unit and the second preset ratio to obtain the target power;

[0070] Specifically, in one embodiment, the second preset coefficient is set to 0.9, such as Figure 3As shown, the phase module obtains the target power 0.9P according to the product of the rated power of the flexible DC converter unit and the second preset ratio. nmmc .

[0071] Step S20322, when the expected output power of the flexible DC converter unit after recovery from fault is greater than the target power and less than the rated power of the flexible DC converter unit, the set output frequency of the flexible DC converter unit is increased by the target frequency until the terminal voltage of the flexible DC converter unit is equal to the rated voltage of the flexible DC converter unit, and the target frequency is determined by proportional calculation based on the expected output power of the flexible DC converter unit after recovery from fault and the output power of the flexible DC converter unit before fault.

[0072] Specifically, when the expected output power of the flexible DC converter unit after fault recovery is greater than the target power and less than the rated power of the flexible DC converter unit, the additional frequency f is obtained by the proportional controller. add , that is, the above target frequency, superimposed on the rated frequency f n The above adjusted frequency f is obtained * . Control the flexible DC converter unit to output with adjusted frequency.

[0073] In one embodiment, the target frequency is obtained by converting the difference between the output power of the flexible DC converter unit before the failure and the expected output power of the flexible DC converter unit after the failure is recovered using a third preset coefficient.

[0074] Specifically, Figure 3 As shown, the output power P of the flexible DC converter unit before failure is obtained. 0mmc , obtain the expected output power P after the above flexible DC converter unit fault is restored mmc , the output power of the flexible DC converter unit before the fault and the expected output power of the flexible DC converter unit after the fault is restored are calculated to obtain a second deviation value ΔP2. Figure 3 As shown, according to the second deviation value, the third preset coefficient k can be determined ip , calculate the product of the third preset coefficient and the second deviation value to obtain the target frequency f add .

[0075] In the above real-time example, after determining the control signal U of the flexible DC substation, U is decomposed into U by dq. * d and U * q , for U n Perform dq decomposition and get U d and Uq Then the voltage is controlled, and the corresponding current I and current I n Perform dq decomposition to obtain I * d and I * q and I d and I q Perform current control and feedforward control through the decoupling link, and finally perform coordinate transformation according to the frequency and feedforward output to obtain the final output voltage E abc , ensure E abc Less than the threshold.

[0076] In order to ensure the operation of the power system, in an optional implementation manner, the method further includes:

[0077] Step S601: When the terminal voltage of the flexible DC converter unit is less than or equal to a fourth threshold, controlling the power system to enter the low voltage fault ride-through state, and the fourth threshold is less than the first threshold.

[0078] Specifically, the terminal voltage U of the flexible DC converter station is obtained t , when the terminal voltage of the above-mentioned flexible DC converter unit is in a low voltage abnormal state, that is, the terminal voltage of the above-mentioned flexible DC converter unit is less than or equal to the fourth threshold, the above-mentioned power system is controlled to enter the above-mentioned low voltage fault ride-through state.

[0079] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0080] The embodiment of the present application also provides a transient overvoltage suppression device for a power system fault recovery process. It should be noted that the transient overvoltage suppression device for a power system fault recovery process of the embodiment of the present application can be used to execute the transient overvoltage suppression method for a power system fault recovery process provided by the embodiment of the present application. The device is used to implement the above-mentioned embodiments and preferred implementation modes, and those that have been described will not be repeated. As used below, the term "module" can implement a combination of software and / or hardware for a predetermined function. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceived.

[0081] The following is an introduction to the transient overvoltage suppression device for the power system fault recovery process provided in an embodiment of the present application.

[0082] Figure 4is a structural block diagram of a transient overvoltage suppression device in a power system fault recovery process according to an embodiment of the present application. Figure 4 As shown, the device comprises:

[0083] A first acquisition unit 10 is used to determine whether the terminal voltage of the flexible DC converter unit is greater than a first threshold when the power system is in a low voltage fault ride-through state;

[0084] Specifically, when the above power system is in a low voltage fault ride-through state, the terminal voltage U of the flexible DC converter station is obtained. t And determine whether the terminal voltage of the flexible DC converter unit is greater than the first threshold (low voltage ride through exit threshold U LVTR ) to determine if there is an overvoltage risk.

[0085] In the specific implementation process, Figure 2 As shown, the above power system is a new energy and synchronous power bundled island transmission system. It includes a flexible DC converter unit and a synchronous power supply, and the above synchronous power supply includes conventional power supplies such as thermal power.

[0086] A first control unit 20 is configured to calculate a difference between an output phase of the flexible DC converter unit and an output phase of the synchronous power supply to obtain a target power angle difference when the terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold value;

[0087] Specifically, when the terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold (low voltage ride-through exit threshold U LVTR ), the fault recovery process is switched on. To avoid the flexible DC transient overvoltage phenomenon in the above power system due to the large power angle difference, the present application sets the phase θ corresponding to the terminal voltage to be obtained. mmc , and obtain the synchronous power supply phase θ at the end of the synchronous power supply fault ride-through through communication sg , and then calculate the difference between the output phase of the flexible DC converter unit and the output phase of the synchronous power supply to obtain the target power angle difference θ sg -θ mmc .

[0088] A second control unit 30 is used to control the power system to enter an overvoltage suppression state when the target power angle difference is greater than or equal to a second threshold value, wherein the overvoltage suppression state suppresses the overvoltage phenomenon of the power system by collaboratively controlling the voltage and output frequency of the flexible DC converter unit;

[0089] Specifically, a judgment is made based on the target power angle difference and the second threshold value A. When the target power angle difference is greater than or equal to the second threshold value, it is determined that the power angle difference between the flexible DC converter unit and the synchronous power supply is sufficient to cause a power overload of the conventional power supply, and there is a risk of transient overvoltage.

[0090] When it is determined that there is a risk of transient overvoltage, the voltage and output frequency of the flexible DC converter unit are controlled to increase the overvoltage capacity while reducing the output active power of the synchronous power supply to avoid transient overvoltage.

[0091] Furthermore, when the target power angle difference is less than the second threshold, it is determined that the power angle difference between the flexible DC converter unit and the synchronous power supply is insufficient to cause a conventional power overload, there is no risk of transient overvoltage, the overvoltage suppression state is not entered, and the control logic of the normal operation of the power system is maintained.

[0092] The third control unit 40 is used to update the target power angle difference when the terminal voltage of the flexible DC converter unit is within a preset range, and control the power system to exit the overvoltage suppression state when the updated target power angle difference is less than a third threshold.

[0093] Specifically, when the fault recovery process is completed and the voltage returns to the normal range, that is, the voltage deviation from the normal operation of the circuit is within the allowable range, the power angle difference at the current moment is re-detected, and the above target power angle difference θ between the flexible DC converter unit and the synchronous power supply is sg -θ mmc When it is less than the third threshold B, it is determined that the power angle difference between the flexible DC converter unit and the synchronous power supply is insufficient to cause a power overload of the conventional power supply, and there is no transient overvoltage risk, so the overvoltage suppression state is exited.

[0094] Through this embodiment, the first acquisition unit determines whether the terminal voltage of the above-mentioned flexible DC converter unit is greater than the first threshold value when the above-mentioned power system is in a low-voltage fault ride-through state; the first control unit calculates the difference between the output phase of the above-mentioned flexible DC converter unit and the output phase of the above-mentioned synchronous power supply when the terminal voltage of the above-mentioned flexible DC converter unit is greater than or equal to the above-mentioned first threshold value, and obtains the target power angle difference; the second control unit controls the above-mentioned power system to enter the overvoltage suppression state when the above-mentioned target power angle difference is greater than or equal to the second threshold value, and the above-mentioned overvoltage suppression state suppresses the overvoltage phenomenon of the above-mentioned power system by coordinated control of the voltage and output frequency of the above-mentioned flexible DC converter unit; the third control unit updates the above-mentioned target power angle difference when the terminal voltage of the above-mentioned flexible DC converter unit is within a preset range, and controls the above-mentioned power system to exit the above-mentioned overvoltage suppression state when the updated target power angle difference is less than the third threshold value. The present application spontaneously identifies the operating conditions of the power system during the transient process of the end of low-voltage fault ride-through. When the power system is running at high power and the overvoltage risk is high, the output voltage of the flexible DC converter unit is reduced, the voltage capacity is reserved, and the output frequency of the flexible DC converter unit is increased to reduce the power angle difference to reduce the active power output of the synchronous power supply, thereby reducing the output power of the synchronous power supply during the transient process of the end of the fault ride-through. The flexible DC transient overvoltage phenomenon in the transient process of the fault ride-through of the new energy and synchronous power bundled island transmission system is suppressed, and the transient overvoltage problem of the flexible DC converter unit caused by the uncontrollability of the synchronous power supply and the coupling characteristics of power and voltage under the flexible DC current limiting mode in the prior art is solved.

[0095] In one embodiment, the second threshold is based on a first preset formula Calculated, where A is the second threshold, K is the safety factor, and the safety factor is used to characterize the safety level between the flexible DC converter unit and the synchronous power supply, P nmmc is the rated power of the above flexible DC converter unit, P renew0 is the new energy output power before the above fault, U nmmc is the rated voltage of the flexible DC converter unit, U nsg is the rated voltage of the above synchronous power supply.

[0096] Specifically, Figure 3 As shown, the rated power P of the flexible DC converter unit is obtained. nmmc , obtain the new energy output power P before the fault renew0 , get the rated voltage U of the flexible DC converter unit nmmc , get the rated voltage U of the synchronous power supply nsg , substituting the above parameters into the above formula, we can obtain the second threshold value A.

[0097] In a specific implementation, the above K value derivation process is as follows:

[0098] According to the power transmission relationship between synchronous power supply and flexible DC Derivation, considering flexible DC overvoltage (1.3U nmmc ), synchronous power supply normal voltage (1.05U nsg ), the corresponding synchronous power transmission power According to the formula, the critical value of the power angle difference is derived as:

[0099]

[0100] Considering the safety margin to be α (generally 5% to 10% based on conventional standards), the above formula is rewritten based on the safety margin:

[0101]

[0102] Therefore, the criterion is proposed: if the power angle difference between the flexible DC and the synchronous power supply satisfies The flexible DC adopts the normal control mode.

[0103] In the above specific embodiments, 1.3 and 1.05 are both typical values ​​that comply with the standards. In the actual application of different power systems, the values ​​can be taken within the standard requirements according to the actual working conditions and control requirements. This application does not limit the values.

[0104] In one embodiment, the third threshold is based on the second preset formula Calculated, where B is the third threshold, K is the safety factor, and the safety factor is used to characterize the safety level between the flexible DC converter unit and the synchronous power supply, P nmmc is the rated power of the flexible DC converter unit, U nmmc is the rated voltage of the flexible DC converter unit, U nsg is the rated voltage of the above synchronous power supply.

[0105] Specifically, Figure 3 As shown, the rated power P of the flexible DC converter unit is obtained. nmmc , get the rated voltage U of the flexible DC converter unit nmmc , get the rated voltage U of the synchronous power supply nsg , substituting the above parameters into the above formula, we can obtain the third threshold value B.

[0106] In order to prevent the above-mentioned transient overvoltage phenomenon of the flexible DC, in an optional implementation manner, the above-mentioned second control unit includes:

[0107] A first control module, configured to perform voltage control on a terminal voltage of the flexible DC converter unit based on a rated voltage of the flexible DC converter unit, wherein the voltage control is configured to reduce the voltage of the flexible DC converter unit and restore the voltage within a preset time period;

[0108] Specifically, the actual terminal voltage of the flexible DC converter unit is controlled based on the rated voltage of the flexible DC converter unit to reduce the terminal voltage of the flexible DC converter unit, reserve capacity for voltage increase in a subsequent fault recovery process, and avoid transient overvoltage.

[0109] The second control module is used to perform phase control on the set output frequency of the above-mentioned flexible DC converter unit based on the output power of the above-mentioned flexible DC converter unit before the failure and the expected output power after the failure of the above-mentioned flexible DC converter unit is recovered. The above-mentioned phase control is used to increase the output frequency of the above-mentioned flexible DC converter unit to reduce the active power output by the above-mentioned synchronous power supply.

[0110] Specifically, the set output frequency of the flexible DC converter unit is obtained to obtain the first frequency fn, and the output power P of the flexible DC converter unit before the failure is obtained. 0mmc , obtain the expected output power P after the above flexible DC converter unit fault is restored mmc The output power of the flexible DC converter unit before the fault and the expected output power after the fault recovery of the flexible DC converter unit are obtained to increase the set output frequency of the flexible DC converter unit to reduce the active power output of the synchronous power supply, thereby avoiding the transient overvoltage phenomenon caused by the active power surplus.

[0111] In order to avoid the above transient overvoltage phenomenon, in an optional implementation, the above first control module includes:

[0112] A first calculation submodule, used for calculating the product of the rated voltage of the flexible DC converter unit and a first preset coefficient to determine a target voltage;

[0113] In one embodiment, the first preset coefficient is set to 0.8. Figure 3 As shown, the voltage module obtains the fourth voltage 0.8U according to the product of the rated voltage of the flexible DC converter unit and the first preset coefficient. n .

[0114] The first control submodule is used to reduce the terminal voltage of the above-mentioned flexible DC converter unit to the above-mentioned target voltage and control the terminal voltage of the above-mentioned flexible DC converter unit to increase at a target change rate until the terminal voltage of the above-mentioned flexible DC converter unit is equal to the rated voltage of the above-mentioned flexible DC converter unit, and the above-mentioned target change rate is determined according to the rated power of the above-mentioned flexible DC converter unit and the output power of the above-mentioned flexible DC converter unit before failure.

[0115] Specifically, Figure 3 As shown, the above target change rate is determined as the slope K r , and then adjust the terminal voltage of the flexible DC converter unit to the fourth voltage 0.8U n , with a slope K r , restore to U n .

[0116] In the above embodiment, 0.8 is not a fixed coefficient, and can be set within the scope of national standards. By setting the transient voltage and recovery power, the present application realizes the expansion and automatic recovery of transient overvoltage capacity.

[0117] In one embodiment, the target change rate is negatively correlated with a difference between the rated power of the flexible DC converter unit and the output power of the flexible DC converter unit before a failure.

[0118] Specifically, the output power P of the flexible DC converter unit before the fault is obtained 0mmc , get the rated power P of the flexible DC converter unit nmmc , the first deviation value ΔP1 is obtained by calculating the difference between the rated power of the flexible DC converter unit and the output power of the flexible DC converter unit before the failure according to the target change rate. Figure 3 As shown, the voltage module pre-stores a curve corresponding to the relationship between the first deviation value and the target change rate, that is, the preset curve, and the target change rate is obtained by querying the corresponding first deviation value.

[0119] Through the above embodiments, the present application achieves slow recovery under high power and fast recovery under low power to ensure that the total voltage recovery time does not exceed 200ms.

[0120] In order to implement the above phase control, in an optional implementation manner, the above second control module includes:

[0121] A second calculation submodule, used for calculating the product of the rated power of the flexible DC converter unit and the second preset ratio to obtain a target power;

[0122] Specifically, in one embodiment, the second preset coefficient is set to 0.9, such as Figure 3As shown, the phase module obtains the target power 0.9P according to the product of the rated power of the flexible DC converter unit and the second preset ratio. nmmc .

[0123] The third calculation submodule is used to increase the set output frequency of the above-mentioned flexible DC converter unit by the above-mentioned target frequency until the terminal voltage of the above-mentioned flexible DC converter unit is equal to the rated voltage of the above-mentioned flexible DC converter unit when the expected output power after the above-mentioned flexible DC converter unit is recovered from the fault is greater than the above-mentioned target power and less than the rated power of the above-mentioned flexible DC converter unit, and the above-mentioned target frequency is determined by proportional calculation based on the expected output power after the above-mentioned flexible DC converter unit is recovered from the fault and the output power of the above-mentioned flexible DC converter unit before the fault.

[0124] Specifically, when the expected output power of the flexible DC converter unit after fault recovery is greater than the target power and less than the rated power of the flexible DC converter unit, the additional frequency f is obtained by the proportional controller. add , that is, the above target frequency, superimposed on the rated frequency f n The above adjusted frequency f is obtained * . Control the flexible DC converter unit to output with adjusted frequency.

[0125] In one embodiment, the target frequency is obtained by converting the difference between the output power of the flexible DC converter unit before the failure and the expected output power of the flexible DC converter unit after the failure is recovered using a third preset coefficient.

[0126] Specifically, Figure 3 As shown, the output power P of the flexible DC converter unit before failure is obtained. 0mmc , obtain the expected output power P after the above flexible DC converter unit fault is restored mmc , the output power of the flexible DC converter unit before the fault and the expected output power of the flexible DC converter unit after the fault is restored are calculated to obtain a second deviation value ΔP2. Figure 3 As shown, according to the second deviation value, the third preset coefficient k can be determined ip , calculate the product of the third preset coefficient and the second deviation value to obtain the target frequency f add .

[0127] In the above real-time example, after determining the control signal U of the flexible DC substation, U is decomposed into U by dq. * d and U * q , for U n Perform dq decomposition and get U d and Uq Then the voltage is controlled, and the corresponding current I and current I n Perform dq decomposition to obtain I * d and I * q and I d and I q Perform current control and feedforward control through the decoupling link, and finally perform coordinate transformation according to the frequency and feedforward output to obtain the final output voltage E abc , ensure E abc Less than the threshold.

[0128] In order to ensure the operation of the power system, in an optional implementation manner, the above device further includes:

[0129] A fourth control unit is used to control the power system to enter the low-voltage fault ride-through state when the terminal voltage of the flexible DC converter unit is less than or equal to a fourth threshold, and the fourth threshold is less than the first threshold.

[0130] Specifically, the terminal voltage U of the flexible DC converter station is obtained t , when the terminal voltage of the above-mentioned flexible DC converter unit is in a low voltage abnormal state, that is, the terminal voltage of the above-mentioned flexible DC converter unit is less than or equal to the fourth threshold, the above-mentioned power system is controlled to enter the above-mentioned low voltage fault ride-through state.

[0131] The transient overvoltage suppression device for the power system fault recovery process includes a processor and a memory. The first acquisition unit, the first control unit, the second control unit, and the third control unit are all stored in the memory as program units, and the processor executes the program units stored in the memory to implement corresponding functions. The modules are all located in the same processor; or, the modules are located in different processors in any combination.

[0132] The processor includes a kernel, which calls the corresponding program unit from the memory. One or more kernels can be set to suppress transient overvoltage during the fault ride-through process by adjusting kernel parameters.

[0133] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM, and the memory includes at least one memory chip.

[0134] An embodiment of the present invention provides a computer-readable storage medium, which includes a stored program, wherein when the program is running, the device where the computer-readable storage medium is located is controlled to execute the transient overvoltage suppression method of the power system fault recovery process.

[0135] Specifically, the transient overvoltage suppression method in the power system fault recovery process includes:

[0136] Step S201, when the power system is in a low voltage fault ride-through state, determining whether the terminal voltage of the flexible DC converter unit is greater than a first threshold;

[0137] Step S202, when the terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold, calculating the difference between the output phase of the flexible DC converter unit and the output phase of the synchronous power supply to obtain a target power angle difference;

[0138] Step S203, when the target power angle difference is greater than or equal to a second threshold, controlling the power system to enter an overvoltage suppression state, wherein the overvoltage suppression state suppresses the overvoltage phenomenon of the power system by collaboratively controlling the voltage and output frequency of the flexible DC converter unit;

[0139] Step S204: when the terminal voltage of the flexible DC converter unit is within a preset range, updating the target power angle difference; when the updated target power angle difference is less than a third threshold, controlling the power system to exit the overvoltage suppression state.

[0140] An embodiment of the present invention provides a processor, which is used to run a program, wherein the transient overvoltage suppression method of the power system fault recovery process is executed when the program is running.

[0141] Specifically, the transient overvoltage suppression method in the power system fault recovery process includes:

[0142] Step S201, when the power system is in a low voltage fault ride-through state, determining whether the terminal voltage of the flexible DC converter unit is greater than a first threshold;

[0143] Step S202, when the terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold, calculating the difference between the output phase of the flexible DC converter unit and the output phase of the synchronous power supply to obtain a target power angle difference;

[0144] Step S203, when the target power angle difference is greater than or equal to a second threshold, controlling the power system to enter an overvoltage suppression state, wherein the overvoltage suppression state suppresses the overvoltage phenomenon of the power system by collaboratively controlling the voltage and output frequency of the flexible DC converter unit;

[0145] Step S204: when the terminal voltage of the flexible DC converter unit is within a preset range, updating the target power angle difference; when the updated target power angle difference is less than a third threshold, controlling the power system to exit the overvoltage suppression state.

[0146] An embodiment of the present invention provides a power system, the power system comprising a processor, a memory, and a program stored in the memory and executable on the processor, and when the processor executes the program, at least the following steps are implemented:

[0147] Step S201, when the power system is in a low voltage fault ride-through state, determining whether the terminal voltage of the flexible DC converter unit is greater than a first threshold;

[0148] Step S202, when the terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold, calculating the difference between the output phase of the flexible DC converter unit and the output phase of the synchronous power supply to obtain a target power angle difference;

[0149] Step S203, when the target power angle difference is greater than or equal to a second threshold, controlling the power system to enter an overvoltage suppression state, wherein the overvoltage suppression state suppresses the overvoltage phenomenon of the power system by collaboratively controlling the voltage and output frequency of the flexible DC converter unit;

[0150] Step S204: when the terminal voltage of the flexible DC converter unit is within a preset range, updating the target power angle difference; when the updated target power angle difference is less than a third threshold, controlling the power system to exit the overvoltage suppression state.

[0151] The present application also provides a computer program product, which, when executed on a data processing device, is suitable for executing a program for initializing at least the following method steps:

[0152] Step S201, when the power system is in a low voltage fault ride-through state, determining whether the terminal voltage of the flexible DC converter unit is greater than a first threshold;

[0153] Step S202, when the terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold, calculating the difference between the output phase of the flexible DC converter unit and the output phase of the synchronous power supply to obtain a target power angle difference;

[0154] Step S203, when the target power angle difference is greater than or equal to a second threshold, controlling the power system to enter an overvoltage suppression state, wherein the overvoltage suppression state suppresses the overvoltage phenomenon of the power system by collaboratively controlling the voltage and output frequency of the flexible DC converter unit;

[0155] Step S204: when the terminal voltage of the flexible DC converter unit is within a preset range, updating the target power angle difference; when the updated target power angle difference is less than a third threshold, controlling the power system to exit the overvoltage suppression state.

[0156] Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0157] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0158] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0159] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0160] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0161] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0162] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0163] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0164] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0165] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0166] 1) The transient overvoltage suppression method of the power system fault recovery process of the present application, first, when the above-mentioned power system is in a low-voltage fault ride-through state, determine whether the terminal voltage of the above-mentioned flexible DC converter unit is greater than a first threshold value; then, when the terminal voltage of the above-mentioned flexible DC converter unit is greater than or equal to the above-mentioned first threshold value, calculate the difference between the output phase of the above-mentioned flexible DC converter unit and the output phase of the above-mentioned synchronous power supply to obtain a target power angle difference; thereafter, when the above-mentioned target power angle difference is greater than or equal to a second threshold value, control the above-mentioned power system to enter an overvoltage suppression state, and the above-mentioned overvoltage suppression state suppresses the overvoltage phenomenon of the above-mentioned power system by coordinated control of the voltage and output frequency of the above-mentioned flexible DC converter unit; finally, when the terminal voltage of the above-mentioned flexible DC converter unit is within a preset range, update the above-mentioned target power angle difference, and when the updated target power angle difference is less than a third threshold value, control the above-mentioned power system to exit the above-mentioned overvoltage suppression state. The present application spontaneously identifies the operating conditions of the power system during the transient process of the end of low-voltage fault ride-through. When the power system is running at high power and the overvoltage risk is high, the output voltage of the flexible DC converter unit is reduced, the voltage capacity is reserved, and the output frequency of the flexible DC converter unit is increased to reduce the power angle difference to reduce the active power output of the synchronous power supply, thereby reducing the output power of the synchronous power supply during the transient process of the end of the fault ride-through. The flexible DC transient overvoltage phenomenon in the transient process of the fault ride-through of the new energy and synchronous power bundled island transmission system is suppressed, and the transient overvoltage problem of the flexible DC converter unit caused by the uncontrollability of the synchronous power supply and the coupling characteristics of power and voltage under the flexible DC current limiting mode in the prior art is solved.

[0167] 2) The transient overvoltage suppression device of the power system fault recovery process of the present application, the first acquisition unit determines whether the terminal voltage of the flexible DC converter unit is greater than the first threshold value when the power system is in a low-voltage fault ride-through state; the first control unit calculates the difference between the output phase of the flexible DC converter unit and the output phase of the synchronous power supply when the terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold value to obtain the target power angle difference; the second control unit controls the power system to enter the overvoltage suppression state when the target power angle difference is greater than or equal to the second threshold value, and the overvoltage suppression state suppresses the overvoltage phenomenon of the power system by coordinated control of the voltage and output frequency of the flexible DC converter unit; the third control unit updates the target power angle difference when the terminal voltage of the flexible DC converter unit is within a preset range, and controls the power system to exit the overvoltage suppression state when the updated target power angle difference is less than the third threshold value. The present application spontaneously identifies the operating conditions of the power system during the transient process of the end of low-voltage fault ride-through. When the power system is running at high power and the overvoltage risk is high, the output voltage of the flexible DC converter unit is reduced, the voltage capacity is reserved, and the output frequency of the flexible DC converter unit is increased to reduce the power angle difference to reduce the active power output of the synchronous power supply, thereby reducing the output power of the synchronous power supply during the transient process of the end of the fault ride-through. The flexible DC transient overvoltage phenomenon in the transient process of the fault ride-through of the new energy and synchronous power bundled island transmission system is suppressed, and the transient overvoltage problem of the flexible DC converter unit caused by the uncontrollability of the synchronous power supply and the coupling characteristics of power and voltage under the flexible DC current limiting mode in the prior art is solved.

[0168] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for suppressing transient overvoltage in a power system fault recovery process, characterized in that: The power system comprises at least a flexible DC converter unit and a synchronous power supply, and the method comprises: When the power system is in a low voltage fault ride-through state, determining whether the terminal voltage of the flexible DC converter unit is greater than a first threshold; When the terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold, a difference between an output phase of the flexible DC converter unit and an output phase of the synchronous power supply is calculated to obtain a target power angle difference; When the target power angle difference is greater than or equal to a second threshold, the power system is controlled to enter an overvoltage suppression state, wherein the overvoltage suppression state suppresses the overvoltage phenomenon of the power system by collaboratively controlling the voltage and output frequency of the flexible DC converter unit; When the terminal voltage of the flexible DC converter unit is within a preset range, the target power angle difference is updated, and when the updated target power angle difference is less than a third threshold, the power system is controlled to exit the overvoltage suppression state.

2. The method according to claim 1, characterized in that The second threshold is based on the first preset formula Calculated, where A is the second threshold, K is the safety factor, and the safety factor is used to characterize the safety degree between the flexible DC converter unit and the synchronous power supply, P nmmc is the rated power of the flexible DC converter unit, P renew0 is the new energy output power before the fault, U nmmc is the rated voltage of the flexible DC converter unit, U nsg is the rated voltage of the synchronous power supply.

3. The method according to claim 1, characterized in that The third threshold is based on the second preset formula Calculated, where B is the third threshold, K is the safety factor, and the safety factor is used to characterize the safety degree between the flexible DC converter unit and the synchronous power supply, P nmmc is the rated power of the flexible DC converter unit, U nmmc is the rated voltage of the flexible DC converter unit, U nsg is the rated voltage of the synchronous power supply.

4. The method according to claim 1, characterized in that: Controlling the power system to enter an overvoltage suppression state includes: Performing voltage control on the terminal voltage of the flexible DC converter unit based on the rated voltage of the flexible DC converter unit, wherein the voltage control is used to reduce the voltage of the flexible DC converter unit and restore it within a preset time period; The set output frequency of the flexible DC converter unit is phase-controlled based on the output power of the flexible DC converter unit before the fault and the expected output power after the fault of the flexible DC converter unit is recovered. The phase control is used to increase the output frequency of the flexible DC converter unit to reduce the active power output by the synchronous power supply.

5. The method according to claim 4, characterized in that The method of controlling the terminal voltage of the flexible DC converter unit based on the rated voltage of the flexible DC converter unit includes: Calculating the product of the rated voltage of the flexible DC converter unit and a first preset coefficient to determine a target voltage; The terminal voltage of the flexible DC converter unit is reduced to the target voltage and the terminal voltage of the flexible DC converter unit is controlled to increase at a target change rate until the terminal voltage of the flexible DC converter unit is equal to the rated voltage of the flexible DC converter unit, and the target change rate is determined according to the rated power of the flexible DC converter unit and the output power of the flexible DC converter unit before failure.

6. The method according to claim 5, characterized in that The target change rate is negatively correlated with a difference between the rated power of the flexible DC converter unit and the output power of the flexible DC converter unit before a fault occurs.

7. The method according to claim 4, characterized in that The method performs phase control on the set output frequency of the flexible DC converter unit based on the output power of the flexible DC converter unit before the failure and the expected output power of the flexible DC converter unit after the failure is recovered, including: Calculating the product of the rated power of the flexible DC converter unit and the second preset ratio to obtain a target power; When the expected output power of the flexible DC converter unit after recovery from fault is greater than the target power but less than the rated power of the flexible DC converter unit, the set output frequency of the flexible DC converter unit is increased by the target frequency until the terminal voltage of the flexible DC converter unit is equal to the rated voltage of the flexible DC converter unit, and the target frequency is determined by proportional calculation based on the expected output power of the flexible DC converter unit after recovery from fault and the output power of the flexible DC converter unit before fault.

8. The method according to claim 7, characterized in that The target frequency is obtained by converting the difference between the output power of the flexible DC converter unit before the fault and the expected output power of the flexible DC converter unit after the fault is recovered using a third preset coefficient.

9. The method according to claim 1, characterized in that: The method further comprises: When the terminal voltage of the flexible DC converter unit is less than or equal to a fourth threshold, the power system is controlled to enter the low voltage fault ride-through state, and the fourth threshold is less than the first threshold.

10. A transient overvoltage suppression device for a power system fault recovery process, characterized in that: The power system at least includes a flexible DC converter unit and a synchronous power supply, and the device includes: A first acquisition unit, configured to determine whether a terminal voltage of the flexible DC converter unit is greater than a first threshold when the power system is in a low voltage fault ride-through state; a first control unit, configured to calculate a difference between an output phase of the flexible DC converter unit and an output phase of the synchronous power supply to obtain a target power angle difference when a terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold; a second control unit, configured to control the power system to enter an overvoltage suppression state when the target power angle difference is greater than or equal to a second threshold value, wherein the overvoltage suppression state suppresses the overvoltage phenomenon of the power system by collaboratively controlling the voltage and output frequency of the flexible DC converter unit; The third control unit is used to update the target power angle difference when the terminal voltage of the flexible DC converter unit is within a preset range, and control the power system to exit the overvoltage suppression state when the updated target power angle difference is less than a third threshold.

11. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein when the program is executed, the device where the computer-readable storage medium is located is controlled to execute the method according to any one of claims 1 to 9.

12. A power system, characterized in that: include: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and the one or more programs include methods for executing any one of claims 1 to 9.

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