Transient overvoltage suppression method and apparatus for power system fault recovery process

Abstract

A transient overvoltage suppression method and apparatus for a power system fault recovery process. The method comprises: when a power system is in a low-voltage fault ride-through state, determining whether a terminal voltage of a high-voltage direct-current conversion unit is greater than a first threshold; when the terminal voltage is greater than or equal to the first threshold, calculating the difference between output phases of the high-voltage direct-current conversion unit and a 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, controlling the power system to enter an overvoltage suppression state; and when the terminal voltage of the high-voltage direct-current conversion 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, controlling the power system to exit the overvoltage suppression state. The described method solves the problem in the existing technology of transient overvoltage of a high-voltage direct-current conversion unit caused by the uncontrollable nature of a synchronous power supply and the coupling characteristics of power and voltage in a high-voltage direct-current current limiting mode.

Description

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

[0001] The present application claims priority to the Chinese patent application No. 202411387208.3, filed on September 30, 2024, and entitled "Transient overvoltage suppression method and device for power system fault recovery process", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of power system fault recovery, in particular to a transient overvoltage suppression method for power system fault recovery process. BACKGROUND

[0003] To improve the channel utilization hours and the frequency voltage support capability of the sending end system, large-scale new energy bases often adopt the mode of bundling with local small synchronous power sources for sending out. However, due to the uncontrollability of the output power of the synchronous power source and the coupling characteristics of power and voltage in the current limiting mode of the flexible direct current, during the fault recovery, the synchronous power source accelerates and the power angle with the flexible direct current is pulled apart, which will cause the power flowing into the flexible direct current to exceed the rated value during the fault recovery process, that is, the phenomenon of power overload occurs, and then the current saturation causes the voltage control to fail. In summary, the power system bundled with new energy and synchronous power sources is prone to the phenomenon of transient overvoltage of flexible direct current caused by active power surplus during the AC fault recovery process.

[0004] The existing new energy transient overvoltage suppression is mainly aimed at the overvoltage caused by reactive power surplus when new energy is sent out through traditional direct current, and is realized by increasing devices such as phase modulators or STATCOM to improve the strength of the grid at the grid connection point. The suppression of transient overvoltage of flexible direct current considers the phenomenon of transient overvoltage caused by reactive power surplus when pure new energy is sent out through flexible direct current.

[0005] In summary, in the prior art, when solving the phenomenon of transient overvoltage of flexible direct current, it is considered from the perspective of reactive power surplus of the power system. In fact, the phenomenon of transient overvoltage of the power system bundled with new energy and synchronous power sources is mainly caused by active power overload, that is, there is a lack of a transient overvoltage suppression method for power system fault recovery process suitable for the power system bundled with new energy and synchronous power sources in the prior art.

[0006] SUMMARY

[0007] The main purpose of the present application is to provide a transient overvoltage suppression method, device, computer readable storage medium and power system for power system fault recovery process, which at least solves the problem of transient overvoltage of the flexible direct current converter unit caused by the uncontrollability of the synchronous power source and the coupling characteristics of power and voltage in the current limiting mode of the flexible direct current in the prior art.

[0008] To achieve the above object, according to one aspect of the present application, a transient overvoltage suppression method for a power system fault recovery process is provided, the power system at least comprising a flexible DC conversion unit and a synchronous power source, the method comprising: judging whether an end voltage of the flexible DC conversion unit is greater than a first threshold value when the power system is in a low-voltage fault ride-through state; calculating a difference between an output phase of the flexible DC conversion unit and an output phase of the synchronous power source to obtain a target power angle difference when the end voltage of the flexible DC conversion unit is greater than or equal to the first threshold value; controlling 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 being achieved by cooperatively controlling a voltage and an output frequency of the flexible DC conversion unit to suppress overvoltage phenomenon of the power system; updating the target power angle difference when the end voltage of the flexible DC conversion unit is within a preset range, and controlling the power system to exit the overvoltage suppression state when the updated target power angle difference is less than a third threshold value.

[0009] Optionally, the second threshold value is calculated according to a first preset formula , wherein A is the second threshold value, K is a safety coefficient, the safety coefficient being used to represent a safety degree between the flexible DC conversion unit and the synchronous power source, P nmmc is a rated power of the flexible DC conversion unit, P renew0 is a new energy output power before the fault, U nmmc is a rated voltage of the flexible DC conversion unit, U nsg is a rated voltage of the synchronous power source.

[0010] Optionally, the third threshold value is calculated according to a second preset formula , wherein B is the third threshold value, K is a safety coefficient, the safety coefficient being used to represent a safety degree between the flexible DC conversion unit and the synchronous power source, P nmmc is a rated power of the flexible DC conversion unit, U nmmc is a rated voltage of the flexible DC conversion unit, U nsg is a rated voltage of the synchronous power source.

[0011] Optionally, the control of the power system into the overvoltage suppression state comprises: voltage control of the terminal voltage of the flexible DC conversion unit based on the rated voltage of the flexible DC conversion unit, the voltage control being used to reduce the voltage of the flexible DC conversion unit and recover within a preset time length; phase control of the set output frequency of the flexible DC conversion unit based on the output power before the failure of the flexible DC conversion unit and the predicted output power after the failure recovery of the flexible DC conversion unit, the phase control being used to increase the output frequency of the flexible DC conversion unit to reduce the active power output by the synchronous power supply.

[0012] Optionally, the voltage control of the terminal voltage of the flexible DC conversion unit based on the rated voltage of the flexible DC conversion unit comprises: calculating the product of the rated voltage of the flexible DC conversion unit and a first preset coefficient to determine a target voltage; reducing the terminal voltage of the flexible DC conversion unit to the target voltage and controlling the terminal voltage of the flexible DC conversion unit to increase at a target rate of change until the terminal voltage of the flexible DC conversion unit is equal to the rated voltage of the flexible DC conversion unit, the target rate of change being determined according to the rated power of the flexible DC conversion unit and the output power before the failure of the flexible DC conversion unit.

[0013] Optionally, the target rate of change is negatively correlated with the difference between the rated power of the flexible DC conversion unit and the output power before the failure of the flexible DC conversion unit.

[0014] Optionally, the phase control of the set output frequency of the flexible DC conversion unit based on the output power before the failure of the flexible DC conversion unit and the predicted output power after the failure recovery of the flexible DC conversion unit comprises: calculating the product of the rated power of the flexible DC conversion unit and a second preset proportion to obtain a target power; in the case that the predicted output power after the failure recovery of the flexible DC conversion unit is greater than the target power and less than the rated power of the flexible DC conversion unit, increasing the set output frequency of the flexible DC conversion unit by a target frequency until the terminal voltage of the flexible DC conversion unit is equal to the rated voltage of the flexible DC conversion unit, the target frequency being determined by proportional operation based on the predicted output power after the failure recovery of the flexible DC conversion unit and the output power before the failure of the flexible DC conversion unit.

[0015] Optionally, the target frequency is obtained by conversion with a third preset coefficient according to the difference between the output power before the failure of the flexible DC conversion unit and the predicted output power after the failure recovery of the flexible DC conversion unit.

[0016] Optionally, the method further includes: in a case where the terminal voltage of the flexible DC conversion unit is less than or equal to a fourth threshold, controlling the power system to enter the low-voltage fault ride-through state, the fourth threshold being less than the first threshold.

[0017] According to another aspect of the present application, there is provided a transient overvoltage suppression device for a power system fault recovery process, the power system comprising at least a flexible DC conversion unit and a synchronous power source, the device comprising: a first acquisition unit configured to determine whether a terminal voltage of the flexible DC conversion unit is greater than a first threshold in a case where 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 conversion unit and an output phase of the synchronous power source to obtain a target power angle difference in a case where the terminal voltage of the flexible DC conversion 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 in a case where the target power angle difference is greater than or equal to a second threshold, the overvoltage suppression state being configured to suppress an overvoltage phenomenon of the power system by performing a coordinated control on a voltage and an output frequency of the flexible DC conversion unit; and a third control unit configured to update the target power angle difference in a case where the terminal voltage of the flexible DC conversion unit is within a preset range, and control the power system to exit the overvoltage suppression state in a case where the updated target power angle difference is less than a third threshold.

[0018] According to still another aspect of the present application, there is provided a computer-readable storage medium comprising a stored program, wherein the program, when executed, controls a device in which the computer-readable storage medium is located to perform any of the methods described above.

[0019] According to yet 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 configured to be executed by the one or more processors, the one or more programs comprising instructions for performing any of the methods described above.

[0020] In the transient overvoltage suppression method for the power system fault recovery process, first, whether the terminal voltage of the flexible DC conversion unit is greater than a first threshold is judged when the power system is in a low-voltage fault ride-through state; then, a difference between an output phase of the flexible DC conversion unit and an output phase of the synchronous power source is calculated to obtain a target power angle difference when the terminal voltage of the flexible DC conversion unit is greater than or equal to the first threshold; subsequently, the power system is controlled to enter an overvoltage suppression state when the target power angle difference is greater than or equal to a second threshold, and the overvoltage suppression state is realized by cooperatively controlling the voltage and the output frequency of the flexible DC conversion unit to suppress the overvoltage phenomenon of the power system; finally, the target power angle difference is updated when the terminal voltage of the flexible DC conversion unit is within a preset range, and the power system is controlled to exit the overvoltage suppression state when the updated target power angle difference is less than a third threshold. In the transient process after the low-voltage fault ride-through ends, the power system operating condition is identified spontaneously, and when the power system is operating at high power and the overvoltage risk is high, the output voltage of the flexible DC conversion unit is reduced to reserve voltage capacity, and the output frequency of the flexible DC conversion unit is increased to reduce the power angle difference and the active power output by the synchronous power source, so as to reduce the output power of the synchronous power source in the transient process after the fault ride-through ends, and the flexible DC transient overvoltage phenomenon in the fault ride-through transient process of the new energy and synchronous power source bundled island sending-out system is suppressed, and the problem of flexible DC conversion unit transient overvoltage 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 is solved. BRIEF DESCRIPTION OF DRAWINGS

[0021] FIG. 1 shows a flowchart of a transient overvoltage suppression method for a power system fault recovery process according to an embodiment of the present application;

[0022] FIG. 2 shows a structure diagram of a new energy and synchronous power source bundled flexible DC island sending-out system according to an embodiment of the present application;

[0023] FIG. 3 shows a logic diagram of a flexible DC transient overvoltage suppression according to an embodiment of the present application;

[0024] FIG. 4 shows a structure block diagram of a transient overvoltage suppression device for a power system fault recovery process according to an embodiment of the present application.

[0025] Among them, the above drawings include the following reference signs:

[0026] 102, processor; 104, memory; 106, transmission device; 108, input and output device. DETAILED DESCRIPTION

[0027] It should be noted that the embodiments and features of the embodiments in the present application can be combined with each other in the case of no conflict. The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0028] In order for those skilled in the technical field to better understand the scheme of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should be within the scope of protection of the present application.

[0029] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily limit to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0030] As introduced in the background, in the prior art, the new energy and synchronous power bundled with the flexible DC island sending out system is prone to have the phenomenon of flexible DC transient overvoltage caused by active power surplus during AC fault recovery. In order to solve the problem of transient overvoltage of the flexible DC converter unit caused by the uncontrollability of the synchronous power and the coupling characteristics of power and voltage in the current limiting mode of the flexible DC in the prior art, the embodiments of the present application provide a transient overvoltage suppression method, device, computer readable storage medium and power system for the process of power system fault recovery.

[0031] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application.

[0032] In the present embodiment, a transient overvoltage suppression method for the process of power system fault recovery 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 drawings can be executed in a computer system such as a set of computer executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from here.

[0033] FIG. 1 is a flow chart of a transient overvoltage suppression method of a power system fault recovery process according to an embodiment of the present application. As shown in FIG. 1, the method comprises the following steps:

[0034] Step S201, when the power system is in a low-voltage fault ride-through state, determining whether the terminal voltage of the flexible DC conversion unit is greater than a first threshold value;

[0035] Specifically, when the power system is in a low-voltage fault ride-through state, the terminal voltage U of the flexible DC conversion station is obtained t . And determine whether the terminal voltage of the flexible DC conversion unit is greater than the first threshold value (low-voltage ride-through exit threshold value U LVTR ) to determine whether to exit the low-voltage fault ride-through state.

[0036] It can be understood that the present application is provided, in the case of monitoring the failure of the power system (including but not limited to low-voltage fault, etc.), control the power system to cut into the low-voltage fault ride-through state, and exit the low-voltage fault ride-through state when the voltage is restored to the preset value (i.e. the first threshold value), further whether to cut into the overvoltage suppression state, to suppress the overvoltage phenomenon of the power system.

[0037] In the specific implementation process, as shown in FIG. 2, the power system is a new energy and synchronous power packed island sending-out system. It includes a flexible DC conversion unit and a synchronous power source, and the synchronous power source includes a conventional power source such as thermal power.

[0038] Step S202, when the terminal voltage of the flexible DC conversion unit is greater than or equal to the first threshold value, calculate the difference between the output phase of the flexible DC conversion unit and the output phase of the synchronous power source to obtain the target power angle difference;

[0039] Specifically, when the terminal voltage of the flexible DC conversion unit is greater than or equal to the first threshold value (low-voltage ride-through exit threshold value U LVTR ), cut into the fault recovery process, in order to avoid the flexible DC transient overvoltage phenomenon of the power system due to the excessive power angle difference, the present application is provided to obtain the phase θ corresponding to the terminal voltage mmc , and the synchronous power source phase θ is obtained through communication when the synchronous power source fault ride-through ends sg , and then calculate the difference between the output phase of the flexible DC conversion unit and the output phase of the synchronous power source to obtain the target power angle difference θ sg -θ mmc .

[0040] Step S203, in the case that the target power angle difference is greater than or equal to the second threshold value, the power system is controlled to enter an overvoltage suppression state, and the overvoltage suppression state is achieved by cooperatively controlling the voltage and output frequency of the flexible HVDC converter unit to suppress the overvoltage phenomenon of the power system.

[0041] Specifically, based on the target power angle difference and the second threshold value A, in the case that 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 HVDC converter unit and the synchronous power source is sufficient to cause the conventional power source power overload, and there is a risk of transient overvoltage.

[0042] In the case that it is determined that there is a risk of transient overvoltage, by controlling the voltage and output frequency of the flexible HVDC converter unit, the overvoltage capacity is increased while the output active power of the synchronous power source is reduced, so as to avoid the transient overvoltage phenomenon.

[0043] Further, in the case that the target power angle difference is less than the second threshold value, it is determined that the power angle difference between the flexible HVDC converter unit and the synchronous power source is not sufficient to cause the conventional power source power overload, and there is no risk of transient overvoltage, so as not to enter the overvoltage suppression state, and the control logic in the normal operation state of the power system is maintained.

[0044] Step S204, in the case that the terminal voltage of the flexible HVDC converter unit is within a preset range, the target power angle difference is updated, and in the case that the updated target power angle difference is less than a third threshold value, the power system is controlled to exit the overvoltage suppression state.

[0045] Specifically, when the fault recovery process is completed, the voltage is restored to the normal range, i.e. the voltage deviation from the normal operation state of the circuit is within the allowable range, the power angle difference at the current time is re-detected, and in the case that the target power angle difference θ sg -θ mmc is less than the third threshold value B, it is determined that the power angle difference between the flexible HVDC converter unit and the synchronous power source is not sufficient to cause the conventional power source power overload, and there is no risk of transient overvoltage, so as to exit the overvoltage suppression state.

[0046] By the embodiment, firstly, when the power system is in a low-voltage fault ride-through state, it is judged whether the terminal voltage of the flexible DC conversion unit is greater than a first threshold value; then, when the terminal voltage of the flexible DC conversion unit is greater than or equal to the first threshold value, a difference between an output phase of the flexible DC conversion unit and an output phase of the synchronous power source is calculated to obtain a target power angle difference; after that, when the target power angle difference is greater than or equal to a second threshold value, the power system is controlled to enter an overvoltage suppression state, and the overvoltage suppression state is realized by cooperatively controlling the voltage and the output frequency of the flexible DC conversion unit to suppress the overvoltage phenomenon of the power system; finally, when the terminal voltage of the flexible DC conversion 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 value, the power system is controlled to exit the overvoltage suppression state. In the transient process at the end of the low-voltage fault ride-through, the power system operating condition is identified spontaneously, and when the power system is running at high power and the overvoltage risk is high, the output voltage of the flexible DC conversion unit is reduced to reserve voltage capacity, and the output frequency of the flexible DC conversion unit is increased to reduce the power angle difference and the active power output of the synchronous power source, so as to reduce the output power of the synchronous power source in the transient process at the end of the fault ride-through, and the flexible DC transient overvoltage phenomenon in the fault ride-through transient process of the new energy and synchronous power bundled island transmission system is suppressed, and the problem of flexible DC transient overvoltage of the flexible DC conversion 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 is solved.

[0047] In an embodiment, the second threshold value is calculated according to a first preset formula , wherein A is the second threshold value, K is a safety factor, the safety factor is used to represent the safety degree between the flexible DC conversion unit and the synchronous power source, P nmmc is the rated power of the flexible DC conversion unit, P renew0 is the new energy output power before the fault, U nmmc is the rated voltage of the flexible DC conversion unit, U nsg is the rated voltage of the synchronous power source.

[0048] Specifically, as shown in FIG. 3, the rated power P nmmc of the flexible DC conversion unit is obtained, the new energy output power P renew0 before the fault is obtained, the rated voltage U nmmc of the flexible DC conversion unit is obtained, the rated voltage U nsg of the synchronous power source is obtained, and the parameters are substituted into the formula to obtain the second threshold value A.

[0049] In a specific implementation, the derivation of the K value is as follows:

[0050] According to the power transmission relationship between the synchronous power supply and the flexible DC Derivation, considering the flexible DC overvoltage (1.3U nmmc ), the normal voltage of the synchronous power supply (1.05U nsg ), the corresponding transmission power of the synchronous power supply According to the formula, the critical value of the power angle difference is:

[0051] Considering the safety redundancy α (generally 5%~10% based on conventional standards), the above formula is rewritten based on the safety redundancy:

[0052] Therefore, the criterion is proposed: if the power angle difference between the flexible DC and the synchronous power supply meets The flexible DC adopts the normal control mode. Wherein,

[0053] In the above specific embodiments, 1.3 and 1.05 are typical values conforming to the standard. In the actual application process of different power systems, the values can be selected within the range required by the standard according to the actual working conditions and control requirements. The application does not limit the values.

[0054] In an embodiment, the third threshold value is calculated according to a second preset formula , wherein B is the third threshold value, K is a safety factor, the safety factor is used to represent 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, and U nsg is the rated voltage of the synchronous power supply.

[0055] Specifically, as shown in FIG. 3, the rated power P nmmc of the flexible DC converter unit is obtained, the rated voltage U nmmc of the flexible DC converter unit is obtained, the rated voltage U nsg of the synchronous power supply is obtained, and the parameters are substituted into the above formula to obtain the third threshold value B.

[0056] In order to prevent the transient overvoltage phenomenon of the flexible DC, in an optional implementation, the step S203 includes:

[0057] In step S2031, the voltage of the flexible DC conversion unit is controlled based on the rated voltage of the flexible DC conversion unit, so as to reduce the voltage of the flexible DC conversion unit and restore the voltage within a preset time length.

[0058] Specifically, the actual terminal voltage of the flexible DC conversion unit is controlled based on the rated voltage of the flexible DC conversion unit, so as to reduce the terminal voltage of the flexible DC conversion unit, reserve capacity for voltage rise in the subsequent fault recovery process, and avoid transient overvoltage phenomenon.

[0059] In step S2032, the set output frequency of the flexible DC conversion unit is phase-controlled based on the output power of the flexible DC conversion unit before the fault and the predicted output power of the flexible DC conversion unit after the fault recovery, so as to increase the output frequency of the flexible DC conversion unit and reduce the active power output by the synchronous power supply.

[0060] Specifically, the set output frequency of the flexible DC conversion unit is obtained as a first frequency fn, the output power of the flexible DC conversion unit before the fault is obtained as P 0mmc , and the predicted output power of the flexible DC conversion unit after the fault recovery is obtained as P mmc The set output frequency of the flexible DC conversion unit is increased based on the output power of the flexible DC conversion unit before the fault and the predicted output power of the flexible DC conversion unit after the fault recovery, so as to reduce the active power output by the synchronous power supply, avoid surplus active power, and cause transient overvoltage phenomenon.

[0061] In order to avoid the transient overvoltage phenomenon, in an optional embodiment, the step S2031 comprises:

[0062] In step S20311, a product of the rated voltage of the flexible DC conversion unit and a first preset coefficient is calculated to determine a target voltage.

[0063] In an embodiment, the first preset coefficient is set to 0.8. As shown in FIG. 3, the voltage module obtains a fourth voltage 0.8U n based on the product of the rated voltage of the flexible DC conversion unit and the first preset coefficient.

[0064] In step S20312, the terminal voltage of the flexible DC conversion unit is reduced to the target voltage, and the terminal voltage of the flexible DC conversion unit is controlled to increase at a target change rate until the terminal voltage of the flexible DC conversion unit is equal to the rated voltage of the flexible DC conversion unit. The target change rate is determined according to the rated power of the flexible DC conversion unit and the output power of the flexible DC conversion unit before the fault.

[0065] Specifically, as shown in FIG. 3, the target change rate is determined as the slope K r , and the end voltage of the flexible DC conversion unit is adjusted to the fourth voltage 0.8U n , and the slope K r , and is restored to U n .

[0066] In the above embodiment, 0.8 is not a fixed coefficient, and is allowed to be set within the range required by the national standard. By setting the transient voltage and the recovery power, the application realizes the expansion of the transient overvoltage capacity and automatic recovery.

[0067] In an embodiment, the target change rate is negatively correlated with the difference between the rated power of the flexible DC conversion unit and the output power of the flexible DC conversion unit before the fault.

[0068] Specifically, the output power P 0mmc of the flexible DC conversion unit before the fault is obtained, the rated power P nmmc of the flexible DC conversion unit is obtained, the difference between the rated power of the flexible DC conversion unit and the output power of the flexible DC conversion unit before the fault is calculated according to the target change rate, and the first deviation ΔP1 is obtained. As shown in FIG. 3, the voltage module pre-stores a curve corresponding to the relationship between the first deviation and the target change rate, i.e., the preset curve, and the target change rate is obtained by querying the corresponding first deviation.

[0069] Through the above embodiment, the application realizes slow recovery at high power and fast recovery at low power to ensure that the total voltage recovery time does not exceed 200 ms.

[0070] In order to realize the above phase control, in an optional implementation, the step S2032 comprises:

[0071] Step S20321, calculating the product of the rated power of the flexible DC conversion unit and the second preset proportion to obtain the target power;

[0072] Specifically, in an embodiment, the second preset coefficient is set to 0.9, and as shown in FIG. 3, the phase module obtains the target power 0.9P nmmc .

[0073] In step S20322, in a case where the predicted output power of the flexible DC conversion unit after the failure recovery is greater than the target power and less than the rated power of the flexible DC conversion unit, the set output frequency of the flexible DC conversion unit is increased by the target frequency proportional to the difference between the predicted output power of the flexible DC conversion unit after the failure recovery and the output power of the flexible DC conversion unit before the failure until the terminal voltage of the flexible DC conversion unit is equal to the rated voltage of the flexible DC conversion unit.

[0074] Specifically, in a case where the predicted output power of the flexible DC conversion unit after the failure recovery is greater than the target power and less than the rated power of the flexible DC conversion unit, the additional frequency f add , i.e., the target frequency, is obtained by the proportional controller, and the target frequency is superimposed on the rated frequency f n to obtain the adjusted frequency f * . The flexible DC conversion unit is controlled to output at the adjusted frequency.

[0075] In an embodiment, the target frequency is obtained by converting the difference between the output power of the flexible DC conversion unit before the failure and the predicted output power of the flexible DC conversion unit after the failure recovery by a third preset coefficient.

[0076] Specifically, as shown in FIG. 3, the output power P 0mmc of the flexible DC conversion unit before the failure is obtained, and the predicted output power P mmc of the flexible DC conversion unit after the failure recovery is obtained. The difference between the output power of the flexible DC conversion unit before the failure and the predicted output power of the flexible DC conversion unit after the failure recovery is calculated to obtain a second deviation ΔP2. As shown in FIG. 3, the third preset coefficient k ip is determined according to the second deviation, and the product of the third preset coefficient and the second deviation is calculated to obtain the target frequency f add .

[0077] In the real-time example, after the control signal U of the flexible DC substation is determined, U * d and U * q are obtained by dq decomposition of U n . Further voltage control is performed, and further dq decomposition of the corresponding current I and current I d is performed to obtain I q n and I * d . * q ​and I d and I q The current control is performed and the feedforward control is performed through the decoupling link, and finally the coordinate transformation is performed according to the frequency and the feedforward output to obtain the final output voltage E abc , and E abc is less than a threshold value.

[0078] In order to ensure the operation of the power system, in an optional embodiment, the above method further comprises:

[0079] Step S601, in the case that the terminal voltage of the flexible DC conversion unit is less than or equal to a fourth threshold value, the power system is controlled to enter the low-voltage fault ride-through state, and the fourth threshold value is less than the first threshold value.

[0080] Specifically, the terminal voltage U t of the flexible DC conversion station is obtained. In the case that the terminal voltage of the flexible DC conversion unit is in a low-voltage abnormal state, i.e., the terminal voltage of the flexible DC conversion unit is less than or equal to a fourth threshold value, the power system is controlled to enter the low-voltage fault ride-through state.

[0081] 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 the logical order is shown in the flowchart, in some cases, the steps shown or described herein can be executed in an order different from that shown herein.

[0082] The embodiments of the present application also provide 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 embodiments of the present application can be used to execute the transient overvoltage suppression method for a power system fault recovery process provided by the embodiments of the present application. The device is used to implement the above embodiments and preferred embodiments, which have been described. As used below, the term "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware, or a combination of software and hardware can also be implemented and conceived.

[0083] The transient overvoltage suppression device for a power system fault recovery process provided by the embodiments of the present application is described below.

[0084] FIG. 4 is a structural block diagram of a transient overvoltage suppression device for a power system fault recovery process according to an embodiment of the present application. As shown in FIG. 4, the device includes:

[0085] The first acquisition unit 10 is configured to determine whether the terminal voltage of the flexible DC conversion unit is greater than a first threshold value when the power system is in a low-voltage fault ride-through state.

[0086] Specifically, in the case that the power system is in a low-voltage fault ride-through state, the terminal voltage U of the flexible DC converter station is acquired t . And it is judged 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 there is an overvoltage risk.

[0087] In the specific implementation process, as shown in FIG. 2, the power system is a new energy and synchronous power source bundled island sending-out system. It includes a flexible DC converter unit and a synchronous power source, and the synchronous power source includes a conventional power source such as a thermal power source.

[0088] The first control unit 20 is configured to, in the case that the terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold, calculate the difference between the output phase of the flexible DC converter unit and the output phase of the synchronous power source to obtain a target power angle difference;

[0089] Specifically, in the case that 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 cut in. In order to avoid the phenomenon of flexible DC transient overvoltage of the power system due to excessive power angle difference, the application sets to acquire the phase θ corresponding to the terminal voltage mmc , and acquires the synchronous power source phase θ sg at the end of the synchronous power source fault ride-through through communication, and then calculates the difference between the output phase of the flexible DC converter unit and the output phase of the synchronous power source to obtain the target power angle difference θ sg - θ mmc .

[0090] The second control unit 30 is configured to, in the case that the target power angle difference is greater than or equal to a second threshold, control the power system to enter an overvoltage suppression state, and the overvoltage suppression state is realized by cooperatively controlling the voltage and output frequency of the flexible DC converter unit to suppress the overvoltage phenomenon of the power system.

[0091] Specifically, based on the target power angle difference and the second threshold A, in the case that the target power angle difference is greater than or equal to the second threshold, it is determined that the power angle difference between the flexible DC converter unit and the synchronous power source is sufficient to cause the power overload of the conventional power source, and there is a risk of transient overvoltage.

[0092] In the case that it is determined that there is a risk of transient overvoltage, by controlling the voltage and output frequency of the flexible DC converter unit, the overvoltage capacity is increased while the output active power of the synchronous power source is reduced, so as to avoid the phenomenon of transient overvoltage.

[0093] Further, in the case that the target power angle difference is less than the second threshold, it is determined that the power angle difference between the flexible DC conversion unit and the synchronous power source is not enough to cause the conventional power source power overload, there is no risk of transient overvoltage, the control logic in the normal operation state of the power system is maintained, and the overvoltage suppression state is not entered.

[0094] The third control unit 40 is configured to update the target power angle difference in the case that the terminal voltage of the flexible DC conversion unit is in the preset range, and control the power system to exit the overvoltage suppression state in the case that the updated target power angle difference is less than the third threshold.

[0095] Specifically, when the fault recovery process ends and the voltage returns to the normal range, that is, the voltage deviation from the normal operation state of the circuit is within the allowable range, the power angle difference at the current time is re-detected, and the target power angle difference θ sg -θ mmc less than the third threshold B, it is determined that the power angle difference between the flexible DC conversion unit and the synchronous power source is not enough to cause the conventional power source power overload, there is no risk of transient overvoltage, and the overvoltage suppression state is exited.

[0096] By the embodiment, the first acquisition unit judges whether the terminal voltage of the flexible DC conversion unit is greater than a first threshold value when the power system is in a low-voltage fault ride-through state; the first control unit calculates a difference between an output phase of the flexible DC conversion unit and an output phase of the synchronous power source to obtain a target power angle difference when the terminal voltage of the flexible DC conversion unit is greater than or equal to the first threshold value; the second control unit controls 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, and the overvoltage suppression state suppresses the overvoltage phenomenon of the power system by cooperatively controlling the voltage and the output frequency of the flexible DC conversion unit; and the third control unit updates the target power angle difference when the terminal voltage of the flexible DC conversion unit is in a preset range, and controls the power system to exit the overvoltage suppression state when the updated target power angle difference is less than a third threshold value. In the transient process at the end of the low-voltage fault ride-through, the application spontaneously identifies the operating condition of the power system, and when the power system is operating at high power and the overvoltage risk is high, the output voltage of the flexible DC conversion unit is reduced to reserve voltage capacity, and the output frequency of the flexible DC conversion unit is increased to reduce the power angle difference and the active power output by the synchronous power source, so as to reduce the output power of the synchronous power source in the transient process at the end of the fault ride-through, and the flexible DC transient overvoltage phenomenon in the fault ride-through transient process of the new energy and synchronous power bundled island transmission system is suppressed, and the problem of flexible DC transient overvoltage of the flexible DC conversion unit caused by the uncontrollability of the synchronous power source and the coupling characteristics of power and voltage in the current-limiting mode of the flexible DC is solved.

[0097] In an embodiment, the second threshold value is calculated according to a first preset formula , wherein A is the second threshold value, K is a safety factor, the safety factor is used to represent the safety degree between the flexible DC conversion unit and the synchronous power source, P nmmc is the rated power of the flexible DC conversion unit, P renew0 is the output power of the new energy before the fault, U nmmc is the rated voltage of the flexible DC conversion unit, and U nsg is the rated voltage of the synchronous power source.

[0098] Specifically, as shown in FIG. 3, the rated power P nmmc of the flexible DC conversion unit is obtained, the output power P renew0 of the new energy before the fault is obtained, the rated voltage U nmmc of the flexible DC conversion unit is obtained, the rated voltage U nsg of the synchronous power source is obtained, and the parameters are substituted into the formula to obtain the second threshold value A.

[0099] In a specific implementation, the derivation of the K value is as follows:

[0100] According to the power transmission relationship between the synchronous power supply and the flexible DC Derivation, considering the flexible DC overvoltage (1.3U nmmc ), the normal voltage of the synchronous power supply (1.05U nsg ), the corresponding transmission power of the synchronous power supply According to the formula, the critical value of the power angle difference is:

[0101] Considering the safety redundancy α (generally 5%~10% based on conventional standards), the above formula is rewritten based on the safety redundancy:

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

[0103] In the above specific embodiments, 1.3 and 1.05 are typical values conforming to the standard. In the actual application process of different power systems, the values can be selected within the range required by the standard according to the actual working conditions and control requirements. The application does not limit the values.

[0104] In an embodiment, the third threshold value is calculated according to a second preset formula , wherein B is the third threshold value, K is a safety factor, the safety factor is used to represent 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, and U nsg is the rated voltage of the synchronous power supply.

[0105] Specifically, as shown in FIG. 3, the rated power P nmmc of the flexible DC converter unit is obtained, the rated voltage U nmmc of the flexible DC converter unit is obtained, the rated voltage U nsg of the synchronous power supply is obtained, and the parameters are substituted into the above formula to obtain the third threshold value B.

[0106] In order to prevent the transient overvoltage phenomenon of the flexible DC, in an optional implementation, the second control unit comprises:

[0107] The first control module is configured to perform voltage control on the terminal voltage of the flexible DC converter unit based on the rated voltage of the flexible DC converter unit, so as to reduce the voltage of the flexible DC converter unit and restore the voltage within a preset time length.

[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, so as to reduce the terminal voltage of the flexible DC converter unit, reserve capacity for voltage rise in a subsequent fault recovery process, and avoid transient overvoltage.

[0109] The second control module is configured to perform 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 predicted output power of the flexible DC converter unit after the fault recovery, so as to increase the output frequency of the flexible DC converter unit and reduce the active power output by the synchronous power supply.

[0110] Specifically, the set output frequency of the flexible DC converter unit is obtained as a first frequency fn, the output power of the flexible DC converter unit before the fault is obtained as P 0mmc , and the predicted output power of the flexible DC converter unit after the fault recovery is obtained as P mmc The set output frequency of the flexible DC converter unit is increased based on the output power of the flexible DC converter unit before the fault and the predicted output power of the flexible DC converter unit after the fault recovery, so as to reduce the active power output by the synchronous power supply, and avoid the surplus of the active power, thereby avoiding transient overvoltage.

[0111] In order to avoid the transient overvoltage, in an optional embodiment, the first control module comprises:

[0112] The first calculation submodule is configured to calculate the product of the rated voltage of the flexible DC converter unit and a first preset coefficient, so as to determine a target voltage.

[0113] In an embodiment, the first preset coefficient is set to 0.8, and as shown in FIG. 3, the voltage module obtains a fourth voltage 0.8U n based on the product of the rated voltage of the flexible DC converter unit and the first preset coefficient.

[0114] The first control submodule is configured to reduce the terminal voltage of the flexible DC converter unit to the target voltage and control 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 the fault.

[0115] Specifically, as shown in FIG. 3, the target change rate is determined as the slope K r , and the end voltage of the flexible DC conversion unit is adjusted to the fourth voltage 0.8U n , and the slope K r , and is restored to U n .

[0116] In the above embodiment, 0.8 is not a fixed coefficient, and is allowed to be set within the range required by the national standard. By setting the transient voltage and the recovery power, the application realizes the expansion of the transient overvoltage capacity and the automatic recovery.

[0117] In an embodiment, the target change rate is negatively correlated with the difference between the rated power of the flexible DC conversion unit and the output power of the flexible DC conversion unit before the fault.

[0118] Specifically, the output power P 0mmc of the flexible DC conversion unit before the fault is obtained, the rated power P nmmc of the flexible DC conversion unit is obtained, the difference between the rated power of the flexible DC conversion unit and the output power of the flexible DC conversion unit before the fault is calculated according to the target change rate, and the first deviation ΔP1 is obtained. As shown in FIG. 3, the voltage module pre-stores a curve corresponding to the relationship between the first deviation and the target change rate, i.e., the preset curve, and the target change rate is obtained by querying the corresponding first deviation.

[0119] Through the above embodiment, the application realizes slow recovery at high power and fast recovery at low power to ensure that the total voltage recovery time does not exceed 200ms.

[0120] In order to realize the above phase control, in an optional implementation, the second control module comprises:

[0121] The second calculation submodule is configured to calculate the product of the rated power of the flexible DC conversion unit and the second preset proportion to obtain a target power;

[0122] Specifically, in an embodiment, the second preset coefficient is set to 0.9, and as shown in FIG. 3, the phase module obtains the target power 0.9P nmmc according to the product of the rated power of the flexible DC conversion unit and the second preset proportion.

[0123] The third calculation sub-module is configured to, in a case where the predicted output power of the flexible DC conversion unit after the fault recovery is greater than the target power and less than the rated power of the flexible DC conversion unit, increase the set output frequency of the flexible DC conversion unit by the target frequency until the terminal voltage of the flexible DC conversion unit is equal to the rated voltage of the flexible DC conversion unit, the target frequency being determined by proportional operation based on the predicted output power of the flexible DC conversion unit after the fault recovery and the output power of the flexible DC conversion unit before the fault.

[0124] Specifically, in a case where the predicted output power of the flexible DC conversion unit after the fault recovery is greater than the target power and less than the rated power of the flexible DC conversion unit, an additional frequency f add , i.e., the target frequency, is obtained by a proportional controller. n The rated frequency f * is added to the target frequency to obtain the adjusted frequency f 0mmc . The flexible DC conversion unit is controlled to output at the adjusted frequency.

[0125] In an embodiment, the target frequency is obtained by converting a difference between the output power of the flexible DC conversion unit before the fault and the predicted output power of the flexible DC conversion unit after the fault recovery by a third preset coefficient.

[0126] Specifically, as shown in FIG. 3, the output power P 0mmc of the flexible DC conversion unit before the fault is obtained, and the predicted output power P mmc of the flexible DC conversion unit after the fault recovery is obtained. A second deviation ΔP2 is obtained by calculating a difference between the output power of the flexible DC conversion unit before the fault and the predicted output power of the flexible DC conversion unit after the fault recovery. As shown in FIG. 3, the third preset coefficient k ip is determined according to the second deviation, and a product of the third preset coefficient and the second deviation is calculated to obtain the target frequency f add .

[0127] In the real-time example, after the control signal U of the flexible DC substation is determined, U * d and U * q are obtained by dq decomposition of U n . Furthermore, voltage control is performed, and I d and I q are obtained by dq decomposition of corresponding currents I and I n . * d * qand I d and I q The current is controlled, and the feedforward control is performed through the decoupling link, and finally the coordinate transformation is performed according to the frequency and the feedforward output to obtain the final output voltage E abc , and E abc is less than a threshold value.

[0128] In order to ensure the operation of the power system, in an optional embodiment, the device further comprises:

[0129] A fourth control unit is configured 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 value, and the fourth threshold value is less than the first threshold value.

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

[0131] The transient overvoltage suppression device for the power system fault recovery process comprises a processor and a memory, and 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 corresponding functions are realized by executing the program units stored in the memory by the processor. The modules are all located in the same processor, or the modules are located in different processors in any combination.

[0132] The processor comprises a core, and the core retrieves the corresponding program unit from the memory. The core can be one or more, and the transient overvoltage phenomenon in the fault ride-through process is suppressed by adjusting the core parameters.

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

[0134] The embodiment of the present application provides a computer readable storage medium, and the computer readable storage medium comprises a stored program, wherein the device in which the computer readable storage medium is located performs the transient overvoltage suppression method for the power system fault recovery process when the program runs.

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

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

[0137] Step S202, when the terminal voltage of the flexible HVDC converter unit is greater than or equal to the first threshold value, calculating a difference between an output phase of the flexible HVDC converter unit and an output phase of the synchronous power source 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 value, controlling the power system to enter an overvoltage suppression state, and the overvoltage suppression state is realized by cooperatively controlling the voltage and the output frequency of the flexible HVDC converter unit to suppress the overvoltage phenomenon of the power system;

[0139] Step S204, when the terminal voltage of the flexible HVDC 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.

[0140] The embodiment of the present application provides a processor for running a program, wherein the processor is used for executing the transient overvoltage suppression method of the power system fault recovery process when the program is running.

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

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

[0143] Step S202, when the terminal voltage of the flexible HVDC converter unit is greater than or equal to the first threshold value, calculating a difference between an output phase of the flexible HVDC converter unit and an output phase of the synchronous power source 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 value, controlling the power system to enter an overvoltage suppression state, and the overvoltage suppression state is realized by cooperatively controlling the voltage and the output frequency of the flexible HVDC converter unit to suppress the overvoltage phenomenon of the power system;

[0145] Step S204, when the terminal voltage of the flexible HVDC 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.

[0146] The embodiment of the present application provides a power system, the power system comprises a processor, a memory and a program stored on the memory and executable on the processor, and at least the following steps are realized when the processor executes the program:

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

[0148] Step S202, calculating a difference value between the output phase of the flexible DC conversion 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 conversion unit is greater than or equal to the first threshold value;

[0149] Step S203, controlling 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, and the overvoltage suppression state is realized by cooperatively controlling the voltage and the output frequency of the flexible DC conversion unit to suppress the overvoltage phenomenon of the power system;

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

[0151] The present application also provides a computer program product, which is adapted to execute the program with at least the following method steps when executed on a data processing device:

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

[0153] Step S202, calculating a difference value between the output phase of the flexible DC conversion 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 conversion unit is greater than or equal to the first threshold value;

[0154] Step S203, controlling 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, and the overvoltage suppression state is realized by cooperatively controlling the voltage and the output frequency of the flexible DC conversion unit to suppress the overvoltage phenomenon of the power system;

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

[0156] It will be apparent to one of ordinary skill in the art that the modules or steps of the application described above can be implemented with a general purpose computing device, which can be centralized on a single computing device or distributed over a network of multiple computing devices, which can be implemented with program code executable by a computing device, which can be stored in a storage device and executed by a computing device, and in some cases, the steps shown or described can be executed in a different order than shown, or can be implemented as separate integrated circuit modules, or as a single integrated circuit module. Thus, the present application is not limited to any particular combination of hardware and software.

[0157] Those skilled in the art will appreciate that embodiments of the present application can be readily used as a method, a system, or a computer program product. Accordingly, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0158] The present application is described herein with reference to the flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processing system or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart illustrations and / or block diagrams block or blocks.

[0159] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instructions which implement the function specified in the flowchart illustrations and / or block diagrams block or blocks.

[0160] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart illustrations and / or block diagrams block or blocks.

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

[0162] Memory can include non-persistent memory and / or volatile memory, such as random access memory (RAM) and / or cache memory, etc. Memory is an example of computer readable media.

[0163] Computer readable media includes permanent and non-permanent, removable and non-removable media implemented in any method or technology for storage of information such as 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 disc read only memory (CD-ROM), digital versatile disc (DVD), or other optical storage, magnetic cassettes, magnetic disks storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information accessible to a computing device. According to the definition herein, computer readable media does not include transitory media, such as modulated data signals and carrier waves.

[0164] It should also be noted that the terms "comprising", "containing", or any other variant thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article or apparatus that comprises a list of elements does not include only those elements in the list, but can also include other elements not expressly listed or inherent to such process, method, article or apparatus. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of additional identical elements in the process, method, article or apparatus that includes the element.

[0165] From the above description, it can be seen that the above-mentioned 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 application first 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. Then, in the case where the terminal voltage of the flexible DC converter unit is greater than or equal to the first threshold value, the difference between the output phase of the flexible DC converter unit and the output phase of the synchronous power source is calculated to obtain the target power angle difference. After that, in the case where the target power angle difference is greater than or equal to the second threshold value, the power system is controlled to enter an overvoltage suppression state, and the overvoltage suppression state is achieved by coordinated control of the voltage and output frequency of the flexible DC converter unit to suppress the overvoltage phenomenon of the power system. Finally, in the case where the terminal voltage of the flexible DC converter unit is within the preset range, the target power angle difference is updated, and in the case where the updated target power angle difference is less than the third threshold value, the power system is controlled to exit the overvoltage suppression state. In the transient process at the end of low-voltage fault ride-through, the application spontaneously identifies the operating conditions of the power system. In the case where 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 to reserve voltage capacity, and the output frequency of the flexible DC converter unit is increased to reduce the power angle difference and reduce the active power output of the synchronous power source, thereby reducing the output power of the synchronous power source in the transient process at the end of fault ride-through. The flexible DC transient overvoltage phenomenon in the fault ride-through transient process of the new energy and synchronous power bundled island transmission system is suppressed, and the problem of transient overvoltage 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 is solved.

[0167] 2) The transient overvoltage suppression device of the power system fault recovery process of the application, the first acquisition unit judges whether the terminal voltage of the flexible DC conversion unit is greater than the first threshold value when the power system is in the low-voltage fault ride-through state; the first control unit calculates the difference between the output phase of the flexible DC conversion unit and the output phase of the synchronous power supply to obtain the target power angle difference when the terminal voltage of the flexible DC conversion unit is greater than or equal to the first threshold value; 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 cooperatively controlling the voltage and output frequency of the flexible DC conversion unit; the third control unit updates the target power angle difference when the terminal voltage of the flexible DC conversion unit is within the 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. In the transient process at the end of low-voltage fault ride-through, the application spontaneously identifies the operating conditions of the power system. In the case of high-power operation of the power system and high overvoltage risk, the output voltage of the flexible DC conversion unit is reduced to reserve voltage capacity, and the output frequency of the flexible DC conversion unit is increased to reduce the power angle difference and the active power output of the synchronous power supply, so as to reduce the output power of the synchronous power supply in the transient process at the end of fault ride-through, so that the flexible DC transient overvoltage phenomenon in the fault ride-through transient process of the new energy and synchronous power bundled island transmission system is suppressed, and the transient overvoltage problem of the flexible DC conversion unit caused by the uncontrollability of the synchronous power supply and the coupling characteristics of power and voltage in the flexible DC current limiting mode in the prior art is solved.

[0168] The above only describes the preferred embodiments of the application and is not intended to limit the application. Those skilled in the art can make various modifications and changes to the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A method of transient overvoltage mitigation for a power system fault restoration process, characterized by, The power system at least comprises a flexible DC conversion unit and a synchronous power source, and the method comprises: When the power system is in a low-voltage fault crossing state, it is determined whether the terminal voltage of the flexible DC conversion unit is greater than a first threshold value; When the terminal voltage of the flexible DC conversion unit is greater than or equal to the first threshold value, a difference between an output phase of the flexible DC conversion unit and an output phase of the synchronous power source is calculated to obtain a target power angle difference; When the target power angle difference is greater than or equal to a second threshold value, the power system is controlled to enter an overvoltage suppression state, and the overvoltage suppression state is realized by cooperatively controlling the voltage and output frequency of the flexible DC conversion unit to suppress the overvoltage phenomenon of the power system; When the terminal voltage of the flexible DC conversion 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 value, the power system is controlled to exit the overvoltage suppression state.

2. The method of claim 1, wherein, The second threshold value is calculated according to a first preset formula , wherein A is the second threshold value, K is a safety coefficient, the safety coefficient is used to represent a safety degree between the flexible DC conversion unit and the synchronous power supply, P nmmc is a rated power of the flexible DC conversion unit, P renew0 is a new energy output power before the fault, U nmmc is a rated voltage of the flexible DC conversion unit, U nsg is a rated voltage of the synchronous power supply.

3. The method of claim 1, wherein, The third threshold value is determined according to a second preset formula is calculated, wherein B is the third threshold value, K is a safety coefficient, the safety coefficient is used to represent a safety degree between the flexible direct current conversion unit and the synchronous power supply, P nmmc is a rated power of the flexible direct current conversion unit, U nmmc is a rated voltage of the flexible direct current conversion unit, U nsg is a rated voltage of the synchronous power supply.

4. The method of claim 1, wherein, The power system is controlled to enter an overvoltage suppression state, comprising: The terminal voltage of the flexible DC conversion unit is controlled based on the rated voltage of the flexible DC conversion unit, and the voltage control is used to reduce the voltage of the flexible DC conversion unit and restore within a preset time length; The set output frequency of the flexible DC conversion unit is controlled based on the output power before the flexible DC conversion unit fails and the expected output power after the flexible DC conversion unit recovers from the failure, and the phase control is used to increase the output frequency of the flexible DC conversion unit to reduce the active power output by the synchronous power source.

5. The method of claim 4, wherein, The terminal voltage of the flexible DC conversion unit is controlled based on the rated voltage of the flexible DC conversion unit, comprising: The product of the rated voltage of the flexible DC conversion unit and a first preset coefficient is calculated to determine a target voltage; The terminal voltage of the flexible DC conversion unit is reduced to the target voltage, and the terminal voltage of the flexible DC conversion unit is controlled to increase at a target change rate until the terminal voltage of the flexible DC conversion unit is equal to the rated voltage of the flexible DC conversion unit, and the target change rate is determined according to the rated power of the flexible DC conversion unit and the output power before the flexible DC conversion unit fails.

6. The method of claim 5, wherein, The target change rate is negatively correlated with the difference between the rated power of the flexible DC conversion unit and the output power before the flexible DC conversion unit fails.

7. The method of claim 4, wherein, The set output frequency of the flexible DC conversion unit is controlled based on the output power before the flexible DC conversion unit fails and the expected output power after the flexible DC conversion unit recovers from the failure, comprising: The product of the rated power of the flexible DC conversion unit and a second preset proportion is calculated to obtain a target power; When the expected output power after the flexible DC conversion unit recovers from the failure is greater than the target power in a case where the output power of the flexible DC conversion unit is less than the rated power of the flexible DC conversion unit, increasing the set output frequency of the flexible DC conversion unit to the target frequency until the terminal voltage of the flexible DC conversion unit equals the rated voltage of the flexible DC conversion unit, the target frequency being determined by proportional operation based on the estimated output power after the flexible DC conversion unit fails and the output power before the flexible DC conversion unit fails.

8. The method of claim 7, wherein, The target frequency is obtained by converting the difference between the output power before the flexible DC conversion unit fails and the estimated output power after the flexible DC conversion unit fails by a third preset coefficient.

9. The method of claim 1, wherein, The method further includes: in a case where the terminal voltage of the flexible DC conversion unit is less than or equal to a fourth threshold value, controlling the power system to enter the low-voltage fault ride-through state, the fourth threshold value being less than the first threshold value.

10. A transient overvoltage suppression device for power system fault restoration procedures, characterized in that, The power system at least includes a flexible DC conversion unit and a synchronous power source, and the device includes: a first obtaining unit configured to, in a case where the power system is in a low-voltage fault ride-through state, judge whether the terminal voltage of the flexible DC conversion unit is greater than a first threshold value; a first control unit configured to, in a case where the terminal voltage of the flexible DC conversion unit is greater than or equal to the first threshold value, calculate a difference between an output phase of the flexible DC conversion unit and an output phase of the synchronous power source to obtain a target power angle difference; a second control unit configured to, in a case where the target power angle difference is greater than or equal to a second threshold value, control the power system to enter an overvoltage suppression state, the overvoltage suppression state being achieved by cooperative control of the voltage and the output frequency of the flexible DC conversion unit to suppress overvoltage phenomenon of the power system; a third control unit configured to, in a case where the terminal voltage of the flexible DC conversion unit is within a preset range, update the target power angle difference, and in a case where the updated target power angle difference is less than a third threshold value, control the power system to exit the overvoltage suppression state.

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

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

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