Active frequency supporting method for converter power supply and related device

Abstract

The invention belongs to the technical field of converter power supply frequency support control, and discloses a converter power supply active frequency support method and a related device, and the method comprises the steps: enabling a converter power supply to actively change the current reference power according to a step change type when a power grid operates normally, and injecting step power disturbance to the power grid; the frequency response of the power grid is caused based on the injected step power disturbance, and the inertia coefficient of the power grid is estimated; when power disturbance occurs in the power grid, calculating a self-adaptive reference power adjusting quantity according to the inertia coefficient of the power grid; the converter power supply adjusts the current reference power based on the adaptive reference power adjusting quantity, and injects adaptive frequency support power into the power grid; according to the method, the current reference power is adjusted based on the self-adaptive reference power adjusting quantity, so that the frequency supporting power can be provided more timely and accurately, the increase of the frequency deviation is effectively inhibited, the risk of out-of-limit of the frequency deviation is reduced, and the stability of the power grid frequency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of converter power frequency support control, and particularly relates to an active frequency support method and related device for converter power supplies. Background Art

[0002] With the large-scale access of new energy power supplies with converters as interfaces to the power grid, converter power supplies using constant power control cannot provide frequency support power when the power grid is disturbed, significantly weakening the power grid's frequency support ability; if a disturbance occurs, the power grid frequency will change rapidly in a short period of time; when the frequency deviation exceeds the maximum frequency deviation of the power grid guide track, forced trigger of generator tripping and load shedding events will occur; for this reason, standards such as "Power System Safety and Stability Guide" (GB 38755-2019), "Technical Regulations and Test Guidelines for Primary Frequency Regulation of Grid-connected Power Supplies" (GBT 40595 2021), etc. clearly state that when the power grid is disturbed, converter power supplies should provide frequency support power to suppress the power grid frequency deviation and ensure the safe and stable operation of the power system.

[0003] Currently, traditional converter power frequency support strategies include droop control, virtual synchronous machine control, virtual inertia control, frequency rate of change droop control, etc. The basic principle is to make the converter power supply provide frequency support power proportional to the frequency deviation or the frequency rate of change, equivalently increasing the inertia damping of the power grid, thereby improving the power grid's frequency support ability; however, under the above frequency support strategies, the magnitude of the frequency support power provided by the converter power supply is closely related to the magnitude of the power grid frequency deviation; for small disturbances, the frequency support power required by the converter power supply is small and can be achieved under relatively small power grid frequency deviation conditions; however, when the power grid is subjected to large disturbances, only when the power grid frequency deviation is large can the converter power supply provide sufficient frequency support power, resulting in the frequency deviation being prone to exceed the allowable value specified by the power grid guide; for this reason, some scholars have proposed variable parameter frequency support strategies such as variable droop coefficient control and variable inertia damping control to improve the frequency support ability of traditional converter power frequency support strategies under large disturbances; however, the above variable parameter frequency support strategies require real-time changes in the control parameter magnitudes, and their change ranges and change rules are difficult to determine in advance, and it is impossible to ensure that the converter power supply can effectively suppress the power grid frequency deviation under different large disturbance conditions. Summary of the Invention

[0004] Aiming at the technical problems existing in the prior art, the present invention provides an active frequency support method and related device for converter power supplies to solve the technical problems that the existing variable parameter frequency support strategies need to real-time change the control parameter magnitudes, and their change ranges and change rules are difficult to determine in advance, and it is impossible to ensure that the converter power supply can effectively suppress the power grid frequency deviation under different large disturbance conditions.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: The present invention provides a method for active frequency support of a converter power supply, including: When the power grid operates normally, the converter power supply actively changes the current reference power in a step change pattern and injects a step power disturbance into the power grid; based on the injected step power disturbance, the frequency response of the power grid is caused, and the inertia coefficient of the power grid is estimated; When a power disturbance occurs in the power grid, an adaptive reference power adjustment amount is calculated according to the inertia coefficient of the power grid; the converter power supply adjusts the current reference power based on the adaptive reference power adjustment amount and injects an adaptive frequency support power into the power grid.

[0006] Further, the process of the converter power supply actively changing the current reference power in a step change pattern is as follows:

[0007] Wherein, is the reference power after the converter power supply actively changes the current reference power in a step change pattern; is the current reference power of the converter power supply; is the reference power change amount actively changed by the converter power supply in a step change pattern.

[0008] Further, the process of estimating the inertia coefficient of the power grid by causing the frequency response of the power grid based on the injected step power disturbance is as follows:

[0009] Wherein, is the inertia coefficient of the power grid; is the reference power change amount actively changed by the converter power supply in a step change pattern; is the maximum power grid frequency change rate measured when injecting a step power disturbance into the power grid.

[0010] Further, when a power disturbance occurs in the power grid, the process of calculating the adaptive reference power adjustment amount according to the inertia coefficient of the power grid includes: According to the mathematical expression of the power grid frequency index, calculate the critical disturbance power corresponding to when the steady-state frequency deviation of the power grid increases to the maximum steady-state frequency deviation allowed by the power grid guide, and obtain the critical disturbance power; According to the maximum frequency change rate of the measured frequency in the initial stage of the power disturbance in the power grid, the inertia coefficient of the power grid, the current reference power of the converter power supply, and the rated power of the converter power supply, calculate the adaptive reference power adjustment amount.

[0011] Further, the calculation process of the critical disturbance power is as follows:

[0012] Among them, is the critical disturbance power; is the coefficient related to the damping effect of the converter power supply; is the grid damping coefficient; is the governor coefficient; is the maximum steady-state frequency deviation allowed by the grid code; The calculation process of the adaptive reference power adjustment amount is as follows:

[0013] Among them, is the adaptive reference power adjustment amount; is the grid inertia coefficient; is the maximum frequency change rate of the measured frequency in the initial stage of the power disturbance in the grid; is the rated power of the converter power supply; is the current reference power of the converter power supply.

[0014] Furthermore, the process by which the converter power supply adjusts the current reference power based on the adaptive reference power adjustment amount includes: Compare the adaptive reference power adjustment amount with the critical disturbance power, and correct the current reference power of the converter power supply according to the comparison result.

[0015] Furthermore, the process of comparing the adaptive reference power adjustment amount with the critical disturbance power and correcting the current reference power of the converter power supply according to the comparison result is as follows: When the absolute value of the adaptive reference power adjustment amount is greater than or equal to the critical disturbance power, the adaptive reference power adjustment amount is superimposed on the current reference power of the converter power supply; when the absolute value of the adaptive reference power adjustment amount is less than the critical disturbance power, the current reference power of the converter power supply remains unchanged; Specifically, the reference power of the converter power supply after correction is as follows:

[0016] Among them, is the reference power of the converter power supply after correction; is the current reference power of the converter power supply; is the adaptive reference power adjustment amount; is the critical disturbance power.

[0017] Furthermore, after the converter power supply adjusts the current reference power based on the adaptive reference power adjustment amount and injects the adaptive frequency support power into the grid, it also includes: When the secondary frequency regulation of the power grid starts and the power grid frequency begins to recover, the converter power supply starts to withdraw from the frequency support state; Among them, the operation of the converter power supply starting to withdraw from the frequency support state includes: when the converter power supply receives a new reference power issued by the power grid dispatching center, removing the adaptive reference power adjustment amount; or the converter power supply actively withdraws from the frequency support state according to the power grid frequency recovery state; Specifically, during the process of the converter power supply starting to withdraw from the frequency support state, the reference power of the converter power supply is as follows:

[0018] Among them, is the reference power of the converter power supply during the withdrawal stage; is the new reference power issued by the power grid dispatching center; is the current reference power of the converter power supply; is the rated frequency of the power grid; is the measured frequency of the power grid; is the power grid frequency at the steady state of frequency regulation; is the adaptive reference power adjustment amount.

[0019] The present invention also provides a converter power supply active frequency support system, including: An estimation module, when the power grid is operating normally, the converter power supply actively changes the current reference power in a step change pattern and injects a step power disturbance into the power grid; based on the injected step power disturbance, causing the frequency response of the power grid, and estimating the power grid inertia coefficient; A frequency support module, when a power disturbance occurs in the power grid, calculates an adaptive reference power adjustment amount according to the power grid inertia coefficient; the converter power supply adjusts the current reference power based on the adaptive reference power adjustment amount and injects an adaptive frequency support power into the power grid.

[0020] The present invention also provides an electronic device, including: A processor, suitable for executing a computer program; A computer-readable storage medium, in which a computer program is stored, and when the computer program is executed by the processor, it executes the active frequency support method of the converter power supply.

[0021] Compared with the prior art, the beneficial effects of the present invention are: The active frequency support method for the converter power supply provided by the present invention can provide frequency support power more timely and accurately by adjusting the current reference power based on the adaptive reference power adjustment amount, effectively suppressing the increase of frequency deviation, reducing the risk of frequency deviation exceeding the limit, and improving the stability of the grid frequency. Specifically, the converter power supply adjusts the current reference power based on the adaptive reference power adjustment amount and injects the adaptive frequency support power into the grid. Without simply relying on the magnitude of the frequency deviation to determine the frequency support power, it can more flexibly inject the adaptive frequency support power into the grid according to the actual situation, effectively avoiding the problem that insufficient frequency support power cannot be provided due to the frequency deviation not being large enough, thus effectively improving the frequency support ability under grid disturbances. Secondly, by adjusting the current reference power based on the adaptive reference power adjustment amount, the converter can adjust the output power in real time according to the actual operating state and disturbance conditions of the grid. At the same time, there is no need to change complex control parameters in real time. Only the adaptive reference power adjustment amount needs to be calculated according to the grid inertia coefficient, and then the current reference power of the converter power supply can be adaptively adjusted, thus simplifying the frequency support process and more effectively coping with different large disturbance conditions to ensure that the grid frequency deviation is effectively suppressed. In addition, the adaptive reference power adjustment amount is calculated based on the estimated grid inertia coefficient, enabling the converter power supply to adjust the output power more accurately according to the dynamic characteristics of the grid. Compared with the traditional variable parameter frequency support strategy that requires real-time change of the control parameter magnitude and whose change range and rules are difficult to determine in advance, the present invention can more reliably suppress the grid frequency deviation under different large disturbance conditions and significantly enhance the frequency regulation ability of the converter under large disturbances.

[0022] The active frequency support system, electronic device and computer-readable storage medium for the converter power supply provided by the present invention have all the advantages of the above-mentioned active frequency support method for the converter power supply. Brief Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0024] Figure 1 It is a flowchart of the active frequency support method for the converter power supply provided in Embodiment 1; Figure 2 It is a schematic diagram of the active frequency support method for the converter power supply in Embodiment 1; Figure 3 It is a schematic diagram of the adaptive reference power in Embodiment 1; Figure 4It is the circuit topology and control structure diagram of the converter power grid-connected test system in Embodiment 1; Figure 5 It is the test result diagram for implementing the active frequency support method of the converter power supply described in Embodiment 1; Figure 6 It is the comparative test result under the complex disturbance condition of the power grid in Embodiment 1; Figure 7 It is the structure block diagram of the active frequency support system for the converter power supply provided in Embodiment 2; Figure 8 It is the structure block diagram of the electronic device provided in Embodiment 3. Specific implementation manners

[0025] In order to make the technical problems, technical solutions and beneficial effects solved by the present application clearer and more understandable, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application; obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present application.

[0026] The present invention provides an active frequency support method for a converter power supply, including the following steps: Step 100: When the power grid is operating normally, the converter power supply actively changes the current reference power in a step change pattern and injects a step power disturbance into the power grid; based on the injected step power disturbance, the frequency response of the power grid is caused, and the inertia coefficient of the power grid is estimated.

[0027] Step 200: When a power disturbance occurs in the power grid, calculate the adaptive reference power adjustment amount according to the inertia coefficient of the power grid; the converter power supply adjusts the current reference power based on the adaptive reference power adjustment amount and injects the adaptive frequency support power into the power grid.

[0028] In the active frequency support method for the converter power supply provided by the present invention, the converter power supply adjusts the current reference power based on the adaptive reference power adjustment amount, so that the converter power supply can adaptively adjust the reference power under various complex working conditions, thereby effectively ensuring the power grid frequency stability under various disturbance conditions; at the same time, the present invention can adaptively adjust the magnitude of the reference power according to the magnitude of the power disturbance without changing the original control parameters of the converter power supply; secondly, the present invention only needs local information to complete the frequency support, with a small amount of calculation, and has the feasibility of being applied in the local control of the converter power supply; in addition, since the reference power is an essential part of the existing converter power supply control, the converter power supply frequency support method described above can be applied to most of the existing converter power supply frequency control methods, with good versatility.

[0029] The following uses some specific embodiments to further explain the active frequency support method for the converter power supply provided by the present invention: Embodiment 1 As shown in the Figure 1 accompanying drawings, Embodiment 1 of the present invention provides an active frequency support method for a converter power supply, including the following steps: Step 1. When the power grid is operating normally, the converter power supply actively changes the current reference power in a step change pattern and injects a step power disturbance into the power grid; based on the injected step power disturbance, the frequency response of the power grid is caused, and the grid inertia coefficient is estimated.

[0030] Specifically, when the power grid is operating normally, at every preset time interval, the converter power supply actively changes the current reference power in a step change pattern, so that the output power of the converter power supply changes stepwise to inject a step power disturbance into the power grid and cause the power grid frequency response; where the preset time interval is determined according to the actual frequency support requirement; the process of the converter power supply actively changing the current reference power in a step change pattern is as follows:

[0031] where, is the reference power after the converter power supply actively changes the current reference power in a step change pattern; is the current reference power of the converter power supply; is the reference power change amount actively changed by the converter power supply in a step change pattern.

[0032] After the converter power supply actively changes the current reference power and injects a step power disturbance into the power grid, detect the maximum change rate of the power grid frequency to obtain the maximum power grid frequency change rate measured when injecting the step power disturbance into the power grid; according to the reference power change amount actively changed by the converter power supply in a step change pattern and the maximum power grid frequency change rate measured when injecting the step power disturbance into the power grid, estimate the grid inertia coefficient; where the estimation process of the grid inertia coefficient is as follows:

[0033] where, is the grid inertia coefficient; is the reference power change amount actively changed by the converter power supply in a step change pattern; is the maximum power grid frequency change rate measured when injecting the step power disturbance into the power grid.

[0034] Step 2: When the power grid sends a power disturbance, calculate the adaptive reference power adjustment amount according to the power grid inertia coefficient; the converter power supply adjusts the current reference power based on the adaptive reference power adjustment amount and injects the adaptive frequency support power into the power grid to suppress the power grid frequency deviation.

[0035] The specific process is as follows: Step 21: According to the mathematical expression of the power grid frequency index, calculate the critical disturbance power corresponding to when the steady-state frequency deviation of the power grid increases to the maximum steady-state frequency deviation allowed by the power grid guidelines, and obtain the critical disturbance power; among them, the calculation process of the critical disturbance power is as follows:

[0036] Among them, is the critical disturbance power, that is, the critical disturbance power corresponding to when the steady-state frequency deviation of the power grid increases to the maximum steady-state frequency deviation allowed by the power grid guidelines; is the coefficient related to the damping effect of the converter power supply; is the damping coefficient of the power grid; is the governor coefficient; is the maximum steady-state frequency deviation allowed by the power grid guidelines.

[0037] Step 22: According to the maximum frequency change rate of the measured frequency in the initial stage of the power grid power disturbance, the power grid inertia coefficient, the current reference power of the converter power supply, and the rated power of the converter power supply, calculate the adaptive reference power adjustment amount; among them, the calculation process of the adaptive reference power adjustment amount is as follows:

[0038] Among them, is the adaptive reference power adjustment amount; is the maximum frequency change rate of the measured frequency in the initial stage of the power grid power disturbance; is the rated power of the converter power supply.

[0039] It should be noted that when the power grid suffers a large disturbance, if the reference power of the converter power supply can be quickly adjusted so that its adjustment amount is close to the disturbance power, the converter power supply will quickly provide a frequency support power equivalent to the disturbance power, thereby quickly suppressing the frequency deviation of the power grid; therefore, in this Embodiment 1, the idea of superimposing the disturbance power on the current reference power is used to achieve fast frequency support after the power grid is disturbed; however, since the magnitude of the grid disturbance load is difficult to measure and cannot be directly applied to the frequency control of the converter power supply, in this Embodiment 1, the disturbance estimated value is used instead of the actual disturbance load for calculation; specifically, based on the mathematical relationship between the maximum frequency change rate and the disturbance power, the measured grid frequency change rate after the disturbance is used to estimate the disturbance power, and an adaptive reference power adjustment amount is obtained, and then the adaptive reference power adjustment amount is superimposed on the current reference power of the converter power supply, so as to achieve the purpose of fast frequency support; in addition, the reference power of the converter power supply is within its output power constraint.

[0040] Step 23: Compare the adaptive reference power adjustment amount with the critical disturbance power, and correct the current reference power of the converter power supply according to the comparison result to obtain the corrected reference power of the converter power supply; specifically, when the absolute value of the adaptive reference power adjustment amount is greater than or equal to the critical disturbance power, that is , then superimpose the adaptive reference power adjustment amount on the current reference power of the converter power supply; when the absolute value of the adaptive reference power adjustment amount is less than the critical disturbance power, that is , then keep the current reference power of the converter power supply unchanged.

[0041] Among them, the corrected reference power of the converter power supply is as follows:

[0042] Among them, is the corrected reference power of the converter power supply; is the current reference power of the converter power supply; is the adaptive reference power adjustment amount; is the critical disturbance power.

[0043] Step 24: The converter power supply outputs an adaptive frequency support power based on the corrected reference power of the converter power supply and injects it into the power grid; for example, when the absolute value of the adaptive reference power adjustment amount exceeds the critical disturbance power, the adaptive reference power adjustment amount is superimposed on the current reference power of the converter power supply, and at this time, the converter power supply outputs an adaptive frequency support power based on the corrected reference power of the converter power supply; among them, the adaptive frequency support power is as follows:

[0044] Among them, is the output power of the converter power supply; is the frequency modulation power provided before the converter power supply adaptively adjusts the reference power.

[0045] Step 3: When the secondary frequency modulation of the power grid starts and the power grid frequency begins to recover, the converter power supply starts to withdraw from the frequency support state.

[0046] Specifically, the operation of the converter power supply starting to withdraw from the frequency support state includes two methods; one is that when the converter power supply receives a new reference power issued by the power grid dispatching center, the adaptive reference power adjustment amount is removed; the other is that the converter power supply actively withdraws from the frequency support state according to the power grid frequency recovery state.

[0047] Among them, during the process of the converter power supply starting to withdraw from the frequency support state, the reference power of the converter power supply is as follows:

[0048] Among them, is the reference power of the converter power supply during the withdrawal stage; is the new reference power issued by the power grid dispatching center; is the current reference power of the converter power supply; is the rated frequency of the power grid; is the measured frequency of the power grid; is the power grid frequency at the steady state of frequency modulation; is the adaptive reference power adjustment amount.

[0049] It should be noted that after using the adaptive reference power adjustment amount to correct the current reference power of the converter power supply, the converter power supply injects adaptive frequency support power into the power grid. As the power grid frequency gradually enters the quasi-steady state, it indicates that the power grid frequency has left the dangerous period; subsequently, the secondary frequency modulation of the power grid starts and gradually restores the frequency to the rated state. At this time, the converter power supply should gradually withdraw from the frequency support state; there are two optional withdrawal methods: 1) The converter power supply waits for the power grid dispatching center to update the reference power. When it receives the new reference power, the adaptive reference power adjustment amount is removed; 2) When the secondary frequency modulation of the power grid starts and the power grid frequency begins to recover, the adaptive reference power adjustment amount is replaced with an exit power that gradually decreases as the power grid frequency recovers, so that the frequency support power injected by the converter power supply into the power grid gradually decreases to zero; thus, the frequency support process of the converter power supply is completed.

[0050] Frequency support principle: The principle of the active frequency support method of the converter power supply described in this Embodiment 1 is as shown in the appendix Figure 1As shown; when the power grid is operating normally, the converter power supply actively changes the reference power in a step-change pattern, injects a step power disturbance into the power grid, and uses the induced power grid frequency response to estimate the power grid inertia coefficient; when the power grid is disturbed, calculate the adaptive reference power adjustment amount according to the disturbance situation and the estimated power grid inertia coefficient; when the absolute value of the adaptive reference power adjustment amount is greater than or equal to the critical disturbance power, then superimpose the adaptive reference power adjustment amount on the current reference power of the converter power supply, so as to adaptively adjust the reference power of the converter power supply to suppress the power grid frequency deviation and ensure the safe and stable operation of the power grid frequency; it should be noted that the attached Figure 2 The existing converter control structure in [reference] includes a power control loop, a current control loop, and SPWM modulation; since the reference power is an important and indispensable part of converter control, the converter power supply frequency support method described in Embodiment 1 of the present invention meets the requirement of being directly applicable to the existing converter power supply frequency control, such as droop control and virtual synchronous machine control, and has strong versatility.

[0051] In Embodiment 1 of the present invention, the converter power supply actively changes the current reference power to estimate the power grid inertia coefficient; specifically, when the power grid is operating normally, at every preset time interval, the converter power supply actively changes the reference power in a step-change pattern, making its output power change step by step, which is equivalent to injecting a step power disturbance into the power grid and causing a power grid frequency response; the converter detects the maximum change rate of the power grid frequency caused by the change of the reference power to estimate the power grid inertia coefficient; it should be noted that during the normal operation of the power grid, the converter power supply actively changes the reference power to cause a frequency response of the power grid, and then uses the maximum power grid frequency change rate measured when injecting a step power disturbance into the power grid to estimate the power grid inertia coefficient, providing basic data for the converter frequency support when the power grid is disturbed later.

[0052] In Embodiment 1 of the present invention, when a power disturbance occurs in the power grid, calculate the adaptive reference power adjustment amount according to the power grid inertia coefficient; the converter power supply adjusts the current reference power based on the adaptive reference power adjustment amount and injects an adaptive frequency support power into the power grid, that is, the process of realizing the adaptive reference power frequency support is as shown in the attached Figure 3 As shown; specifically, it includes the calculation of the adaptive reference power adjustment amount, the calculation of the recovery power, and the generation of the mode switching signal, and the process is as follows: When the grid frequency deviation exceeds the maximum frequency deviation specified in the grid guidelines, a generator load shedding event will be forcibly triggered. Therefore, when the steady-state frequency deviation increases to the allowable value specified in the grid guidelines, the disturbance to the grid is the critical disturbance power that just triggers the generator load shedding event. At this time, the critical disturbance power can be calculated based on the mathematical relationship between the steady-state frequency deviation and the disturbance power. When the grid suffers a large disturbance, if the reference power of the converter power supply can be quickly adjusted so that its adjustment amount is close to the disturbance power, the converter power supply will be able to quickly provide a frequency support power equivalent to the disturbance power, thereby quickly suppressing the grid frequency deviation. Therefore, when the grid suffers a large disturbance, the disturbance power can be superimposed on the original reference power. Since the size of the grid disturbance load is difficult to measure and cannot be directly applied to the converter frequency control, it is necessary to use a disturbance estimate instead of the actual disturbance load for calculation. In this embodiment 1, based on the mathematical relationship between the maximum frequency change rate and the disturbance power, it can be seen that the measured grid frequency change rate after the disturbance is used to estimate the adaptive reference power adjustment amount.

[0053] After the calculation of the adaptive reference power adjustment amount is completed, the critical disturbance power is compared with the adaptive reference power adjustment amount to determine whether to correct the current reference power of the converter power supply; if , the adaptive reference power adjustment amount is superimposed on the current reference power of the converter power supply, and the reference power of the converter power supply is corrected to ;if , the current reference power of the converter power supply is maintained unchanged; if the adaptive reference power adjustment amount exceeds the critical disturbance power, the adaptive reference power adjustment amount is superimposed on the current reference power of the converter power supply, and the output power of the converter power supply is .

[0054] When the reference power of the converter power supply is corrected to Afterwards, the frequency of the power supply of the converter is supported and the grid frequency enters a quasi-steady state; as the grid frequency gradually enters a quasi-steady state, it indicates that the grid frequency has left the dangerous period, and then the secondary frequency modulation of the grid is started and the frequency is gradually restored to the rated state. At this time, the power supply of the converter should exit the frequency support state; there are two optional exit methods: 1) The power supply of the converter waits for the grid dispatching center to update the reference power, and when the new reference power is received, the adaptive reference power adjustment amount is removed; 2) When the secondary frequency modulation of the grid is started and the frequency of the grid begins to recover, the adaptive reference power adjustment amount is replaced with the exit power that gradually decreases as the grid frequency recovers, so that the frequency support power injected by the converter power supply to the grid gradually decreases to zero; at this point, the frequency support process of the converter power supply is completed.

[0055] In order to facilitate the control of the operating mode of the converter, the mode control signal is used in this embodiment 1. T Perform operation mode control, such asFigure 3 As shown; specifically, before the power grid is disturbed, the converter power supply is in the normal operation mode, and at this time, the value of the mode control signal T is 0; when the power grid is disturbed, the converter power supply estimates the adaptive reference power adjustment amount and compares it with the critical disturbance power. If it satisfies , then the reference power of the converter power supply is corrected to , and at this time, the value of the mode control signal T is 1; for the first exit method, the converter power supply waits for the power grid dispatching center to update the reference power. When a new reference power is received, the adaptive reference power adjustment amount is removed, and at this time, the value of the mode control signal T is 0; for the second exit method, when the power grid frequency gradually stabilizes and the secondary frequency regulation of the power grid starts to restore the frequency, the adaptive reference power adjustment amount is replaced with an exit power that gradually decreases as the power grid frequency recovers. At this time, the value of the mode control signal T is 2; when the power grid frequency returns within the dead zone of primary frequency regulation, the exit power is set to zero, and the converter power supply returns to the normal operation mode, that is, the mode control signal T is 0.

[0056] Effectiveness verification test: The following is to build a converter power supply grid-connected test system and conduct tests under various conditions to verify the effectiveness of the converter power supply active frequency support method described in Embodiment 1; among them, the circuit topology and control structure diagram of the converter power supply grid-connected test system are as shown in the appendix Figure 4 as shown.

[0057] As shown in the appendix Figure 5 shown, the appendix Figure 5 gives the test result diagram of implementing the converter power supply active frequency support method described in Embodiment 1; it can be seen from the appendix Figure 5 that before the power grid is disturbed, the converter power supply operates in the droop mode, and its current reference power is P 0; at this time, according to the mathematical expression of the power grid frequency index, calculate the critical disturbance power corresponding to when the steady-state frequency deviation of the power grid increases to the maximum steady-state frequency deviation allowed by the power grid guide; according to the maximum frequency change rate of the measured frequency in the initial stage of the power grid power disturbance, calculate the adaptive reference power adjustment amount. Since the adaptive reference power adjustment amount is greater than the critical disturbance power, the converter power supply quickly superimposes the adaptive reference power adjustment amount on the current reference power before the disturbance; subsequently, the output power of the converter power supply increases rapidly, and the power grid frequency rises rapidly, effectively suppressing the transient and steady-state frequency deviations of the power grid; as the secondary frequency regulation of the power grid starts, the power grid frequency begins to recover. At this time, the converter power supply replaces the adaptive reference power adjustment amount with the exit power; as the power grid frequency deviation gradually decreases, the output power of the converter power supply gradually returns to the current reference powerP 0; Subsequently, the converter power supply returns to the state before the disturbance; thus, the process of the converter power supply frequency support ends.

[0058] In this Embodiment 1, by comparing the frequency modulation effects of non-frequency modulation, droop control, and the active frequency support method of the converter power supply, two power disturbances, one small and one large, are set successively to verify the effectiveness of the active frequency support method of the converter power supply described in this Embodiment 1, as shown in the appendix Figure 6 ; among them, in the appendix Figure 6 , the black, blue, and red curves respectively represent the grid frequency and the converter output power curves when the converter does not participate in frequency modulation, adopts droop control, and adopts the active frequency support method of the converter power supply.

[0059] It can be seen from the appendix Figure 6 that for the first small disturbance, the transient and steady-state frequency deviations of the grid under the three controls are all within the maximum frequency deviation specified by the grid guidelines; it should be noted that when the adaptive reference power adjustment amount is less than the critical disturbance power, the active frequency support method of the converter power supply does not correct the current reference power of the converter power supply; therefore, the frequency and power curves obtained by the active frequency support method of the converter power supply and the droop control methods are the same; for the second large disturbance, when the converter power supply does not perform frequency modulation, the transient and steady-state frequency deviations are 0.45 Hz and 0.37 Hz respectively; when the converter power supply adopts droop control, the transient and steady-state frequency deviations are 0.29 Hz and 0.23 Hz respectively; when the converter power supply adopts the active frequency support method of the converter power supply, the transient and steady-state frequency deviations are 0.16 Hz and 0.07 Hz respectively; the experimental results prove that the frequency modulation performance of the converter frequency support method described in this Embodiment 1 is superior to the existing frequency support strategies and can effectively solve the problem of grid frequency stability.

[0060] The active frequency support method of the converter power supply described in this Embodiment 1, through the frequency support method of the adaptive reference power, can provide frequency support power more timely and accurately, effectively suppress the increase of the frequency deviation, reduce the risk of the frequency deviation exceeding the limit, and improve the stability of the grid frequency.

[0061] Embodiment 2 As shown in the appendix Figure 7 , this Embodiment 2 provides an active frequency support system for a converter power supply, including an estimation module and a frequency support module.

[0062] An estimation module is used to actively change the current reference power in a step - change pattern by the converter power supply and inject a step - power disturbance into the power grid when the power grid is operating normally; based on the injected step - power disturbance, the frequency response of the power grid is caused, and the inertia coefficient of the power grid is estimated. A frequency support module is used to calculate an adaptive reference - power adjustment amount according to the inertia coefficient of the power grid when a power disturbance occurs in the power grid; the converter power supply adjusts the current reference power based on the adaptive reference - power adjustment amount and injects an adaptive frequency - support power into the power grid.

[0063] Optionally, the active frequency - support system of the converter power supply described in Embodiment 2 further includes an exit module; the exit module is used to make the converter power supply start to exit the frequency - support state when the secondary frequency regulation of the power grid starts and the power - grid frequency begins to recover.

[0064] Embodiment 3 As shown in the Figure 8 accompanying drawings, Embodiment 3 provides an electronic device, including: a memory for storing a computer program; a processor for implementing the steps of the active - frequency - support method of the converter power supply when executing the computer program; or, the processor implements the functions of each module in the above - mentioned active - frequency - support system of the converter power supply when executing the computer program.

[0065] Exemplarily, the computer program can be divided into one or more modules / units, and the one or more modules / units are stored in the memory and executed by the processor to complete the present invention. The one or more modules / units can be a series of computer - program instruction segments capable of completing preset functions, and the instruction segments are used to describe the execution process of the computer program in the electronic device.

[0066] The electronic device can be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The electronic device may include, but is not limited to, a processor and a memory. Those skilled in the art can understand that the above are examples of the electronic device, which do not constitute a limitation on the electronic device and may include more components than the above, or combine some components, or different components. For example, the electronic device may further include input - output devices, network - access devices, a bus, etc.

[0067] The so - called processor may be a central processing unit, or may also be other general - purpose processors, digital - signal processors, application - specific integrated circuits, field - programmable gate arrays or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general - purpose processor may be a microprocessor or the processor may also be any conventional processor, etc. The processor is the control center of the electronic device, connecting various parts of the entire electronic device through various interfaces and circuits.

[0068] The memory can be used to store the computer programs and / or modules. By running or executing the computer programs and / or modules stored in the memory, and invoking the data stored in the memory, the processor realizes various functions of the electronic device.

[0069] The memory may mainly include a program storage area and a data storage area. Among them, the program storage area can store an operating system, application programs required for at least one function (such as functions like data measurement and processing, parameter calculation, etc.).

[0070] For the active frequency support method of the converter power supply provided by the present invention, the converter power supply adjusts the current reference power based on the adaptive reference power adjustment amount and injects the adaptive frequency support power into the power grid, so that the converter power supply can estimate the disturbance magnitude according to the measured frequency information under various complex working conditions, and adaptively adjust the reference power, which can effectively ensure the power grid frequency stability under various disturbance conditions; the size of the reference power is adaptively adjusted according to the disturbance magnitude, without changing the original control parameters of the converter power supply.

[0071] In the present invention, frequency support can be completed only with local information, with a small amount of calculation, and it has the feasibility of being applied in the local control of the converter power supply; since the reference power is an essential part of the existing converter power supply control, the proposed frequency support method can be applied to most existing converter controls, and has good generality.

[0072] In summary, the converter power supply frequency support method described in the present invention can significantly improve the frequency support ability of the converter power supply under large disturbances, has a better frequency deviation suppression effect, and does not require changing control parameters, and has relatively practical engineering application value and can be applied to various converter controls.

[0073] The above embodiments are only one of the implementation manners that can realize the technical solution of the present invention. The scope of protection required by the present invention is not only limited by this embodiment, but also includes any changes, substitutions and other implementation manners that are easily conceivable by those skilled in the art within the technical scope disclosed by the present invention.

Claims

1. An active frequency support method for a converter power supply, characterized in that Including: When the power grid operates normally, the converter power supply actively changes the current reference power in the form of a step change and injects a step power disturbance into the power grid. Based on the injected step power disturbance, the frequency response of the power grid is caused, and the inertia coefficient of the power grid is estimated. When a power disturbance occurs in the power grid, according to the inertia coefficient of the power grid, an adaptive reference power adjustment amount is calculated; the converter power supply adjusts the current reference power based on the adaptive reference power adjustment amount and injects an adaptive frequency support power into the power grid.

2. The active frequency support method for a converter power supply according to claim 1, characterized in that, The process of the converter power supply actively changing the current reference power in the form of a step change is as follows: Among them, is the reference power after the converter power supply actively changes the current reference power according to the step change pattern; is the current reference power of the converter power supply; is the reference power change amount actively changed by the converter power supply according to the step change pattern.

3. The active frequency support method for a converter power supply according to claim 1, characterized in that The process of estimating the inertia coefficient of the power grid based on the injected step power disturbance, which causes the frequency response of the power grid, is as follows: Among them, is the grid inertia coefficient; is the reference power change amount actively changed by the converter power supply according to the step change pattern; is the maximum grid frequency change rate measured when injecting a step power disturbance into the grid.

4. The active frequency support method for a converter power supply according to claim 1, wherein When a power disturbance occurs in the power grid, the process of calculating the adaptive reference power adjustment amount according to the inertia coefficient of the power grid includes: According to the mathematical expression of the power grid frequency index, calculate the critical disturbance power corresponding to when the steady-state frequency deviation of the power grid increases to the maximum steady-state frequency deviation allowed by the power grid guide, and obtain the critical disturbance power. According to the maximum frequency change rate of the measured frequency in the initial stage of the power disturbance in the power grid, the inertia coefficient of the power grid, the current reference power of the converter power supply, and the rated power of the converter power supply, calculate the adaptive reference power adjustment amount.

5. A method for active frequency support of a converter power supply according to claim 4, characterized in that, The calculation process of the critical disturbance power is as follows: Among them, is the critical disturbance power; is the coefficient related to the damping effect of the converter power supply; is the grid damping coefficient; is the governor coefficient; is the maximum steady-state frequency deviation allowed by the grid code; The calculation process of the adaptive reference power adjustment amount is as follows: Among them, is the adaptive reference power adjustment amount; is the grid inertia coefficient; is the maximum frequency change rate of the measured frequency in the initial stage of power disturbance occurrence in the power grid; is the rated power of the converter power supply; is the current reference power of the converter power supply.

6. The active frequency support method for a converter power supply according to claim 4, characterized in that, The process of the converter power supply adjusting the current reference power based on the adaptive reference power adjustment amount includes: Compare the adaptive reference power adjustment amount with the critical disturbance power, and correct the current reference power of the converter power supply according to the comparison result.

7. A method for actively frequency supporting a converter power supply according to claim 6, characterized in that The process of comparing the adaptive reference power adjustment amount with the critical disturbance power and correcting the current reference power of the converter power supply according to the comparison result is as follows: When the absolute value of the adaptive reference power adjustment amount is greater than or equal to the critical disturbance power, superimpose the adaptive reference power adjustment amount on the current reference power of the converter power supply; when the absolute value of the adaptive reference power adjustment amount is less than the critical disturbance power, keep the current reference power of the converter power supply unchanged. Specifically, the reference power of the converter power supply after correction is as follows: Among them, is the reference power of the corrected converter power supply; is the current reference power of the converter power supply; is the adaptive reference power adjustment amount; is the critical disturbance power.

8. The active frequency support method for a converter power supply according to claim 4, wherein After the converter power supply adjusts the current reference power based on the adaptive reference power adjustment amount and injects an adaptive frequency support power into the power grid, it further includes: When the secondary frequency regulation of the power grid starts and the power grid frequency begins to recover, the converter power supply starts to withdraw from the frequency support state. Among them, the operation of the converter power supply starting to withdraw from the frequency support state includes: when the converter power supply receives a new reference power issued by the power grid dispatching center, remove the adaptive reference power adjustment amount; or the converter power supply actively withdraws from the frequency support state according to the power grid frequency recovery state. Specifically, during the process of the converter power supply starting to withdraw from the frequency support state, the reference power of the converter power supply is as follows: Among them, is the reference power of the converter power supply in the exit stage; is the new reference power issued by the power grid dispatching center; is the current reference power of the converter power supply; is the rated frequency of the power grid; is the measured frequency of the power grid; is the power grid frequency at the steady state of frequency modulation; is the adaptive reference power adjustment amount.

9. A converter power supply active frequency support system, characterized in that, Including: An estimation module, used for when the power grid operates normally, the converter power supply actively changes the current reference power in the form of a step change and injects a step power disturbance into the power grid; based on the injected step power disturbance, causing the frequency response of the power grid and estimating the inertia coefficient of the power grid. A frequency support module, which is used to calculate an adaptive reference power adjustment amount according to the grid inertia coefficient when a power disturbance occurs in the power grid; the converter power supply adjusts the current reference power based on the adaptive reference power adjustment amount and injects an adaptive frequency support power into the power grid.

10. An electronic device, characterized in that, It includes: A processor, which is suitable for executing a computer program; A computer-readable storage medium, in which a computer program is stored, and when the computer program is executed by the processor, it executes the active frequency support method of the converter power supply according to any one of claims 1-8.

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