Fault networking operation control method and system under SVI power grid voltage phase jump

Abstract

The invention discloses a fault networking operation control method and system under SVI power grid voltage phase jump. The control method comprises the steps of frozen active integral output, equivalent internal potential phase compensation and transient over-current suppression. And if the difference value between the power grid voltage angular frequency and the self-generated angular frequency is greater than a threshold triggering mark position 1, restoring to 0 after keeping for a set time. When the mark position is 1, 1) the active integral output is frozen, so that the self-generated angular frequency keeps the angular frequency unchanged at the moment before the fault; and 2) equivalent internal potential phase angle compensation: calculating a difference value between a power grid phase angle and a self-generated phase angle in real time, generating a compensation phase angle, and further generating an equivalent internal potential phase angle. During the fault ride-through period, transient overcurrent is suppressed, according to the overcurrent multiple, the original virtual impedance set multiple is increased, and / or additional virtual impedance is input and multiplied by inductive current to obtain compensation voltage, and virtual impedance and current inner loop control is carried out after the compensation voltage and the grid-connected voltage are subtracted from the remolded internal potential instantaneous value at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field of fault ride-through of new energy inverters, and more specifically, relates to a fault network operation control method and system under SVI power grid voltage phase jump. Background Art

[0002] In recent years, the scale of installed capacity of new energy in my country has expanded rapidly, and photovoltaic, wind power, energy storage and other fields have flourished. Flexible and efficient power electronic inverters have become the key interface for the grid connection of new energy equipment. However, the lack of inertia and damping makes it difficult to support the frequency and voltage of the power grid. The high proportion of new energy equipment connected to the grid through it will seriously threaten the stability of the power grid. SVI (Self-synchronous Voltage-source Inverters) can achieve fast synchronization at an extremely low short-circuit ratio by simulating the characteristics of synchronous machines, and introduce damping and active droop control and reactive power control to support grid frequency regulation and voltage regulation respectively. It has received widespread attention from both inside and outside the industry. However, traditional grid-building technologies are often applied to normal grid voltage conditions and lack the ability to operate stably under grid fault conditions. Faced with large disturbances such as grid voltage faults, SVI will encounter transient stability problems similar to synchronous machines.

[0003] In recent years, the industry has made a lot of progress in the research on improving the network construction capability during power grid faults, but there are still some shortcomings. On the one hand, many studies only consider the grid voltage amplitude drop scenario during the grid fault, and ignore the grid voltage phase jump. In fact, the jump of the grid voltage amplitude and phase will cause the voltage difference between the inverter output voltage and the grid to be too large, which will then cause the problem of overcurrent and power imbalance. Ignoring the phase angle jump problem will make many existing fault ride-through strategies difficult to apply to actual engineering practice; on the other hand, the research on voltage source operation control under fault ride-through is not comprehensive. The control strategy research on the network construction technology during the fault period focuses on the switching of the voltage source to the current source mode during the fault period, directly controlling the reactive and active currents to achieve the effect of supporting voltage and current limiting, and there are problems such as the instability of the phase-locked loop in the weak grid scenario. In addition, there is a transient overcurrent problem in the low voltage ride-through control, and high voltage ride-through is rarely involved. In summary, the improvement and breakthrough of the SVI voltage source operation control technology during the fault ride-through period is crucial to the safety and stability of the new energy grid connection. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a method and system for controlling the operation of a fault network under a phase jump of an SVI power grid voltage. The method and system can realize the stable operation of the SVI in a voltage source mode when the amplitude and phase angle of the power grid voltage jump, and effectively suppress transient overcurrent spikes, thereby improving the grid-connected friendliness and absorption level of new energy generator sets.

[0005] The present invention adopts the following technical solution.

[0006] A first aspect of the present invention provides a method for controlling the operation of a fault network under a voltage phase jump of an SVI power grid, comprising the following steps: Detect the deviation between the self-generated angular frequency and the grid angular frequency. If the deviation exceeds the threshold, The self-generated angular frequency Maintain the angular frequency before the fault and detect the deviation between the self-generated phase angle and the grid phase angle. If the deviation exceeds the threshold, compensate the equivalent internal potential phase. time After that, according to the grid connection point voltage, during low voltage ride-through or high voltage ride-through, the active power command is adjusted and the internal potential is reshaped; During the entire fault ride-through period, it is detected whether overcurrent occurs. If the grid-connected phase current amplitude reaches a set multiple of the rated current, transient overcurrent suppression control is performed by adjusting the virtual impedance.

[0007] Preferably, the first flag is set , indicating whether the deviation between the self-generated angular frequency and the grid angular frequency exceeds the threshold, which is expressed by the following formula: (12) Where: It is the first sign; is the self-generated angular frequency; is the grid voltage angular frequency; is the angular frequency deviation threshold; First Logo From 0 to 1, the start time Timing, the first sign From 0 to 1 hold time Then restore to 0.

[0008] Preferably, a freezing link is configured in the active power-frequency control loop to freeze the self-generated angular frequency output by the active power droop integral link under set conditions. , the first mark The output signal of the freezing link is taken after the logical negation operation; Output signal of the freeze phase Deviation from actual SVI active power Multiply them together to get the SVI active power deviation taking into account the freezing phase, which is expressed as follows: (13) Where: To take into account the SVI active power deviation during the freezing phase; is the actual SVI active power deviation.

[0009] Preferably, calculating in real time the absolute value of the grid voltage phase deviation from the self-generated phase and comparing it with a threshold value comprises: If the first sign During the period of setting 1, , that is, there is a non-negligible phase jump, and the equivalent internal potential compensation amount If detected , no phase compensation is required; Grid voltage phase angle Phase angle with self-generation The difference is adjusted by phase angle dead zone and PI to generate compensation phase angle , expressed as follows: (14) Where: To compensate the phase angle; is the phase angle deviation threshold; is the grid connection point voltage phase angle; Self-generated phase angle for active power control; is the PI link transfer function.

[0010] Preferably, the first mark After resetting to 0, the fault ride-through control is continued for the possible grid voltage amplitude jump, including: taking the active power instruction during non-fault ride-through as the reference, adjusting the active power instruction during fault ride-through according to the set ratio, which is expressed by the following formula: (15) (16) Where: It is the active power instruction during non-fault crossing. It is the active power instruction during fault crossing; P eF is the grid-connected active power during the fault period, P e is the grid-connected active power before the fault; δ is the power angle before the fault, δ F is the power angle during the fault period; It is the active reference adjustment coefficient of high voltage ride through; It is the active reference adjustment coefficient of low voltage ride through; is the grid connection point voltage before the fault, is the grid connection point voltage during the fault period, is the grid voltage before the fault, is the grid voltage during the fault period, is the per unit value of the grid connection point voltage.

[0011] Preferably, the fault ride-through control is continued for the possible grid voltage amplitude jump, and further includes: internal potential reshaping for maintaining the voltage source characteristics during the fault ride-through and avoiding power imbalance, which is expressed by the following formula: (17) Where: is the equivalent internal potential amplitude of the SVI reshaped under fault; is the self-generated equivalent internal potential amplitude before the fault; is an intermediate variable; U gN is the rated voltage of the power grid; k c It is the ratio of the maximum overcurrent allowed by the inverter to the rated current; I g is the grid-connected current; Z eqF is the total impedance from the SVI converter port to the grid during the fault period; Z eq is the total impedance from the SVI converter port to the grid before the fault; k F is the voltage drop depth.

[0012] Preferably, a second flag is set , indicating whether a transient overcurrent occurs; if an overcurrent multiple is detected If it is greater than or equal to the multiple threshold, the second flag Set from 0 to 1; if an overcurrent multiple is detected If the value is less than the multiple threshold, the second flag Maintain the value to 0, expressed as follows: (18) (19) Where: For the second sign; is the overcurrent multiple; is the absolute value of the three-phase current amplitude of the grid, is the rated current; is the multiple threshold; Second sign When set from 0 to 1, transient overcurrent suppression control is started.

[0013] Preferably, the transient overcurrent suppression control includes: Using only additional virtual impedance or increasing the original virtual impedance; or A method of combining the use of additional virtual impedance and the increase of original virtual impedance.

[0014] Preferably, the method of increasing the original virtual impedance includes: According to the overcurrent multiple, the original virtual impedance is increased to the set multiple, which is expressed as the following formula: (20) Where: is the increased virtual reactance, is a complex variable, is the increased virtual resistance, is the virtual impedance after enlargement; is the original virtual reactance, is the original virtual resistance, is the original virtual impedance; The corresponding virtual reactance increase coefficient is obtained by real-time table lookup according to the overcurrent multiple; Ways to add virtual impedance include: Real-time sampling of inverter output current and with additional virtual impedance After multiplication, the compensation voltage is obtained , to reshape the instantaneous value of the internal potential At the same time, subtract the compensation voltage and grid voltage After the voltage deviation is obtained, virtual impedance and current inner loop control are performed to obtain the current inner loop control reference value, which is expressed as the following formula: (twenty one) Where: is the compensation voltage; Output current for the inverter; is the original virtual reactance, is the original virtual resistance, is the original virtual impedance; It is the reference value of the current inner loop control; is the instantaneous value of the reshaped internal potential, is the compensation voltage, is the grid voltage; is the additional virtual reactance, To add a virtual resistor, is an additional virtual impedance.

[0015] Preferably, the method of combining the additional virtual impedance and the increase of the original virtual impedance includes: real-time sampling of the inverter output current and with additional virtual impedance After multiplication, the compensation voltage is obtained , to reshape the instantaneous value of the internal potential At the same time, subtract the compensation voltage and grid voltage After the voltage deviation is obtained, virtual impedance and current inner loop control are performed to obtain the current inner loop control reference value, which is expressed as the following formula: (twenty two) Where: It is the reference value of the current inner loop control; is the instantaneous value of the reshaped internal potential, is the grid voltage, is the inverter output current, is the additional virtual reactance, To add a virtual resistor, is the additional virtual impedance, For the second sign; is the original virtual reactance, is the original virtual resistance, is the virtual reactance increase factor.

[0016] A second aspect of the present invention provides a control system for fault networking operation under SVI power grid voltage phase jump, and the method for controlling fault networking operation under SVI power grid voltage phase jump comprises: The detection unit is used to detect the deviation between the self-generated angular frequency and the grid angular frequency. If the deviation exceeds the threshold, The self-generated angular frequency Maintain the angular frequency before the fault and detect the deviation between the self-generated phase angle and the grid phase angle. If the deviation exceeds the threshold, compensate the equivalent internal potential phase. Adjustment unit for time After that, according to the grid connection point voltage, during low voltage ride-through or high voltage ride-through, the active power command is adjusted and the internal potential is reshaped; The detection unit is used to detect whether overcurrent occurs during the entire fault ride-through period. If the grid-connected phase current amplitude reaches a set multiple of the rated current, transient overcurrent suppression control is performed by adjusting the virtual impedance.

[0017] Preferably, the control system further comprises: an active power-frequency control loop and a reactive power-voltage control loop; The flag unit outputs a first flag signal and a second flag signal; the first signal indicates that the deviation between the self-generated angular frequency and the grid angular frequency exceeds a threshold value, and is used to start the output control of the frozen active power droop integral link, and to start the equivalent internal potential phase compensation control in the case of a phase jump; the second signal indicates the occurrence of a transient overcurrent, and is used to start the transient overcurrent control, and suppress the transient overcurrent by adjusting the virtual impedance; The active power-frequency control loop includes an active power droop integral link and a freezing link. The active power droop integral link outputs a self-generated angular frequency. The freezing link freezes the output of the active droop integration link based on the first flag signal.

[0018] Preferably, the first flag signal is set from 0 to 1, indicating whether the deviation between the self-generated angular frequency and the grid angular frequency exceeds a threshold value, and the holding time Then restore to 0; The first flag signal passes through the NOT gate to generate an output signal of the freezing link; The output signal of the freezing link is multiplied by the actual SVI active power deviation to obtain the SVI active power deviation taking the freezing link into account.

[0019] Preferably, the system further comprises: a phase compensation link, which is used to determine whether there is a non-negligible phase jump during the period when the first flag signal is set to 1; if there is a non-negligible phase jump, the grid voltage phase angle is used to compensate for the non-negligible phase jump. Phase angle with self-generation The difference is adjusted by phase angle dead zone and PI to generate compensation phase angle .

[0020] Preferably, the system further comprises: an active power instruction ratio adjustment link, which is used to implement fault ride-through control for possible grid voltage amplitude jumps, and to generate active power reference adjustment coefficients for non-fault ride-through, high voltage ride-through, and low voltage ride-through, respectively.

[0021] Preferably, the system further comprises: an internal potential reshaping link, which is used to reshape the internal potential according to a set algorithm, maintain the voltage source characteristics during fault ride-through, and avoid power imbalance.

[0022] Preferably, the system further comprises: a transient overcurrent suppression control module; The second flag signal is set from 0 to 1, indicating that a transient overcurrent occurs, and the transient overcurrent suppression control module starts the transient overcurrent suppression control; The transient overcurrent suppression control module includes: an additional virtual impedance link and an original virtual impedance adjustment link; The additional virtual impedance link or the original virtual impedance adjustment link is put into operation separately, or the additional virtual impedance link and the original virtual impedance adjustment link are put into operation in combination to implement transient overcurrent suppression control.

[0023] The third aspect of the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is loaded into the processor, the fault network operation control method under the SVI power grid voltage phase jump is implemented.

[0024] A fourth aspect of the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the fault network operation control method under the voltage phase jump of the SVI power grid.

[0025] Compared with the prior art, the beneficial effects of the present invention include at least: (1) The proposed SVI control system calculates the absolute value of the difference between the grid angular frequency and the self-generated angular frequency in real time , the absolute value of the difference between the grid phase and the self-generated phase , the active frequency loop is switched and controlled to realize the equivalent internal potential phase compensation during the fault period. On the basis of the grid voltage amplitude jump fault, the grid voltage phase jump fault is further considered to ensure that the SVI still performs fault ride-through in the voltage source mode, providing transient support for the grid.

[0026] (2) By calculating the ratio of phase current to rated current in real time ,according to The deviation from the threshold is used to calculate the transient process in real time and to switch the virtual impedance, which can effectively suppress the overcurrent fault during the transient process of fault ride-through.

[0027] The present invention can ensure the stable operation of the new energy generator set under power grid failure, and improve the grid compatibility of the new energy generator set and the level of new energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1The main grid-connected circuit and control topology diagram of the SVI system of the present invention; Figure 2 Freeze the active integral output and generate the sw1 diagram for the present invention; Figure 3 This is the equivalent internal potential phase compensation diagram of the present invention; Figure 4 For the virtual impedance 1 of the present invention and the generation of sw2 diagram; Figure 5 Additional virtual impedance output diagram for the present invention; Figure 6 In order to consider the phase angle jump in this embodiment, the low voltage fault crosses into the fault simulation waveform; Figure 7 In order to consider the phase angle jump in this embodiment, the low voltage fault ride-through simulates the waveform when exiting the fault; Figure 8 In order to consider the phase angle jump in this embodiment, the high voltage fault crosses into the fault simulation waveform; Fig. 9 In order to consider the phase angle jump in this embodiment, the high voltage fault is crossed through and the waveform is simulated when the fault is exited; Fig.10 This is the fault-travel control flow chart. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The described embodiments are only embodiments of a part of the present invention, not all embodiments. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0030] Embodiment 1 of the present invention provides a method for controlling the operation of a fault network under a phase jump of an SVI power grid voltage, which at least includes: a control strategy for coping with a phase angle jump of a power grid and a transient overcurrent suppression strategy. Among them, the control strategy for coping with a phase angle jump of a power grid includes: freezing active integral output control and equivalent internal potential phase compensation control; the transient overcurrent suppression strategy includes: adjusting the original virtual impedance and the additional virtual impedance. Specifically, the method for controlling the operation of a fault network under a phase jump of an SVI power grid voltage includes the following steps: like Figure 1 As shown, the SVI main circuit topology includes: DC power supply , inverter, LC filter and control module; wherein the DC side port of the inverter is connected to the DC power supply The inverter three-phase AC port is connected to the PCC grid connection point after passing through the LC filter and the grid-connected switch. The control module includes: an active-frequency control loop and a reactive-voltage control loop; the active-frequency control loop outputs a self-generated angular frequency and self-generated phase angle , the reactive-voltage control loop output self-generated equivalent internal potential amplitude .

[0031] It is understandable that by collecting the SVI AC grid-connected point voltage and inverter output current Information, calculate instantaneous active power and reactive power, grid voltage angular frequency , grid voltage phase .

[0032] Specifically, the reactive-voltage control loop outputs the self-generated equivalent internal potential amplitude before the fault , expressed as follows: (twenty three)

[0033] Where: is the self-generated equivalent internal potential amplitude before the fault; is the reactive power integral coefficient, is a complex variable; is the reactive power-voltage droop coefficient; Output reactive power reference value for SVI, is the average value of SVI output reactive power; is the grid voltage amplitude, is the voltage amplitude at the grid connection point.

[0034] Active power-frequency control loop outputs self-generated angular frequency and self-generated phase angle , expressed as follows: (twenty four) (25) Where: Self-generated phase angle for active power control; is the self-generated angular frequency; is a complex variable; is the virtual rotor inertia; is the rated angular frequency; It is the active power instruction during non-fault crossing; is the grid-connected active power before the fault; is the active power-frequency droop coefficient.

[0035] As one of the outstanding essential features of the present invention, the control strategy for dealing with grid phase angle jumps includes: detecting the deviation between the self-generated angular frequency and the grid angular frequency, and if the deviation exceeds a threshold, The self-generated angular frequency The angular frequency before the fault is maintained unchanged and the deviation between the self-generated phase angle and the grid phase angle is detected. If the deviation exceeds the threshold, the equivalent internal potential phase is compensated.

[0036] Preferably but not restrictively, the control strategy for dealing with the grid phase angle jump includes: setting a first flag , characterizes whether the deviation between the self-generated angular frequency and the grid angular frequency exceeds the threshold, specifically including: calculating the grid voltage angular frequency in real time and self-generated angular frequency The absolute value of the difference, that is, the voltage angular frequency deviation , when the voltage angular frequency deviation Greater than or equal to the set angular frequency deviation threshold When the first flag is triggered Set from 0 to 1 and keep it for a period of time After the restoration is set to 0; when the first flag After restoring to 0, if it is detected again , then the first flag is triggered again Set from 0 to 1 and keep it for a period of time After recovery, set to 0, keep time It is an adjustable parameter that can be adjusted according to the actual project and is usually no more than tens of milliseconds.

[0037] More specifically, if Figure 2 As shown, the absolute value of the deviation between the grid voltage angular frequency and the self-generated angular frequency is calculated in real time and expressed as follows: (26) Where: is the voltage angular frequency deviation, i.e., the absolute value of the deviation between the grid voltage angular frequency and the self-generated angular frequency; is the self-generated angular frequency; is the grid voltage angular frequency.

[0038] If a voltage angular frequency deviation is detected If the value is greater than or equal to the angular frequency deviation threshold, the first flag is triggered to be set from 0 to 1. Specifically, it is expressed as follows: (27)

[0039] Where: It is the first sign; is the angular frequency deviation threshold.

[0040] Trigger the first flag From 0 to 1 hold time After recovery, it is set to 0, the first flag After resetting to 0, return to continue comparing the voltage angular frequency deviation with the set angular frequency deviation threshold. Assignment.

[0041] It can be understood that the active power-frequency control loop includes an active power droop integral link and a freezing link, and the active power droop integral link outputs a self-generated angular frequency The freezing link is used to freeze the output of the active droop integral link under set conditions. Specifically, Figure 2 As shown, the first sign During the period of setting 1, the freezing link outputs a freezing signal, which makes the self-generated angular frequency output by the active droop integral link Maintain the angular frequency at the moment before the fault unchanged.

[0042] Further preferably but not limiting, the first mark The output signal of the freeze link after the logical NOT operation is expressed as the following formula: (28)

[0043] Where: It is the first sign; Take the logical NOT operation for the first flag, that is, the output signal of the freezing link.

[0044] Freeze the output signal of the link Deviation from actual SVI active power Multiply them together to get the SVI active power deviation taking into account the freezing phase, which is expressed as follows:

[0045] Where: To take into account the SVI active power deviation during the freezing phase; is the actual SVI active power deviation.

[0046] As one of the outstanding essential features of the present invention, the active power droop integral link is improved based on the SVI active power deviation taking into account the freezing link. Output self-generated angular frequency After, the first sign During the period of setting 1, the signal output by the freezing link Set to 0 to control the SVI active power deviation taking into account the freezing phase is 0, thus realizing the self-generated angular frequency output of the active droop integral link Maintain the angular frequency at the moment before the fault unchanged.

[0047] First Logo During the period when the first flag is set to 1, the equivalent internal potential phase compensation control is further performed. During the period of setting to 1, determine whether there is a phase jump that cannot be ignored. If there is a phase jump that cannot be ignored, calculate the equivalent internal potential compensation amount and generate the equivalent internal potential phase angle.

[0048] More specifically, if Figure 3 As shown, the grid voltage is sampled in real time and the grid voltage phase angle is calculated. , real-time sampling of the self-generated phase angle generated by the active-frequency control loop , grid voltage phase angle Phase angle with self-generation The difference is adjusted by phase angle dead zone and PI to generate compensation phase angle , compensation phase angle Phase angle with self-generation The equivalent internal potential phase angle is generated after summing .

[0049] Preferably but not restrictively, determining whether there is a non-negligible phase jump includes: calculating in real time the absolute value of the grid voltage phase and the self-generated phase deviation, and comparing it with a threshold. Specifically, if the first flag During the period of setting 1, , that is, there is a non-negligible phase jump, and the equivalent internal potential compensation amount If detected , no phase compensation is required.

[0050] Grid voltage phase angle Phase angle with self-generation The difference is adjusted by phase angle dead zone and PI to generate compensation phase angle ; In the first sign During the period of setting to 0, the compensation phase angle does not work, which is expressed by the following formula: (29) Where: To compensate the phase angle; is the grid connection point voltage phase angle; Self-generated phase angle for active power control; is the phase angle deviation threshold; is the PI link transfer function.

[0051] Compensation phase angle Phase angle with self-generation The equivalent internal potential phase angle is generated after summing , thereby achieving phase compensation during the fault, which is expressed as follows: (30) Where: is the equivalent internal potential phase angle; To compensate the phase angle; is the self-generated phase angle.

[0052] That is, the first sign After setting to 1, the self-generated phase angle In the next Time is the self-generated angular frequency before the fault The integral output compensates the phase angle Phase angle with self-generation The equivalent internal potential phase angle is generated after summing , thereby achieving phase compensation during faults.

[0053] It is worth noting that in tens of milliseconds Phase compensation has been achieved for the grid voltage phase jump during the time period. After the time period, the first sign Reset to 0 and continue to implement fault ride-through control for possible grid voltage amplitude jumps, including: active power instruction during fault ride-through and reshaping of the SVI equivalent internal potential.

[0054] The active power command during non-fault ride-through is used as a reference, and the active power command during fault ride-through is adjusted according to the set ratio. Specifically, during fault ride-through, the active power reference command is expressed by the following formula: (31) (32) Where: It is the active power instruction for non-fault ride-through; when the grid-connected point voltage per unit value is detected to be 0.9pu ≤ When ≤1.1pu, continue to use the active power instruction during non-fault ride-through; It is the active power instruction during fault crossing; It is the active reference adjustment coefficient of high voltage ride through, that is, when the grid connection point voltage standard value is detected When ≥1.1pu, during the whole process of high voltage ride through, the active power command is: = × ; It is the active reference adjustment coefficient of low voltage ride-through; that is, when the grid-connected point voltage per unit value 0 ≤ When ≤0.9pu, during the whole process of low voltage ride-through, the active power command is: = × ; is the grid connection point voltage before the fault, is the grid connection point voltage during the fault period, is the grid voltage before the fault, is the grid voltage during the fault period, is the grid-connected active power during the fault period, is the grid-connected active power before the fault, is the power angle before the fault, is the power angle during the fault period.

[0055] During the fault ride-through period, in order to maintain the voltage source characteristics during the fault ride-through period and avoid power imbalance, the internal potential is reshaped. The equivalent reshaped internal potential is expressed by the following formula: (33) Where: is the equivalent internal potential amplitude of the SVI reshaped under fault; is the self-generated equivalent internal potential amplitude before the fault; is an intermediate variable; is the rated voltage of the power grid; is the grid-connected current; is the total impedance from the SVI converter port to the grid during the fault period, Z eq is the total impedance from the SVI converter port to the grid before the fault; It is the ratio of the maximum overcurrent allowed by the inverter to the rated current; It is the voltage drop depth, which takes a positive sign for low voltage ride-through and a negative sign for high voltage ride-through.

[0056] As one of the outstanding essential features of the present invention, the transient overcurrent suppression strategy includes: real-time calculation of the absolute value of the grid-connected phase current amplitude Rated current of times, when Greater than threshold When the second flag is triggered Set from 0 to 1, the second flag During the period of being set to 1, transient overcurrent suppression control is started, and transient overcurrent is suppressed by adjusting the original virtual impedance and / or the additional virtual impedance.

[0057] Preferably but not restrictively, the transient overcurrent suppression strategy specifically includes: Real-time calculation of overcurrent multiples, that is, the absolute value of the grid-connected phase current amplitude is a multiple of the rated current, expressed as follows: (34) Where: It is the overcurrent multiple, that is, the ratio of the absolute value of the three-phase grid-connected current amplitude to the rated current; is the absolute value of the three-phase current amplitude of the grid, is the rated current.

[0058] like Figure 4 As shown, if an overcurrent multiple is detected If it is greater than or equal to the multiple threshold, the second flag Set from 0 to 1; if an overcurrent multiple is detected If the value is less than the multiple threshold, the second flag Maintain the value to 0, expressed as follows: (35) Where: For the second sign; is the overcurrent multiple; is the multiple threshold.

[0059] If the second sign When set from 0 to 1, transient overcurrent suppression control is started.

[0060] Further preferably but not limitatively, the transient overcurrent suppression control includes: using an additional virtual impedance or increasing the original virtual impedance alone; or using an additional virtual impedance and increasing the original virtual impedance in combination.

[0061] Specifically, the methods of increasing the original virtual impedance include: Figure 4 As shown, according to the overcurrent multiple, the original virtual impedance is increased to the set multiple, which is expressed by the following formula: (36) Where: is the increased virtual reactance, is a complex variable, is the increased virtual resistance, is the virtual impedance after enlargement; is the original virtual reactance, is the original virtual resistance, is the original virtual impedance; is the virtual reactance increase factor.

[0062] Preferably, but not limited to, by looking up a table, according to the overcurrent multiple The size of the virtual reactance increase coefficient corresponding to the real-time table , and with the original virtual impedance Further preferably but not restrictively, the table lookup method includes but is not limited to function calculation, step calculation or interpolation.

[0063] That is, the instantaneous value of the reshaped internal potential Subtract grid voltage After the voltage deviation is obtained, virtual impedance and current inner loop control are performed to obtain the current inner loop control reference value, which is expressed as the following formula: (37) Where: It is the reference value of the current inner loop control; is the instantaneous value of the reshaped internal potential; is the grid voltage; is the original virtual reactance, is the original virtual resistance, is the original virtual impedance.

[0064] The methods of adding virtual impedance include: Figure 5 As shown, the additional virtual impedance output diagram of the present invention is used to sample the inverter output current in real time. and with additional virtual impedance After multiplication, the compensation voltage is obtained , the instantaneous value of the reshaped internal potential is At the same time, subtract the compensation voltage and grid voltage After the voltage deviation is obtained, virtual impedance and current inner loop control are performed to obtain the current inner loop control reference value, which is expressed as the following formula: (38) Where: is the compensation voltage; Output current for the inverter; is the original virtual reactance, is the original virtual resistance, is the original virtual impedance; It is the reference value of the current inner loop control; is the instantaneous value of the reshaped internal potential, is the compensation voltage, is the grid voltage; is the additional virtual reactance, To add a virtual resistor, is an additional virtual impedance.

[0065] Figure 1 The transient overcurrent suppression strategy presented in the paper combines the two methods of increasing the original virtual impedance and the additional virtual impedance. The combination of the additional virtual impedance and the increase of the original virtual impedance includes: real-time sampling of the inverter output current and with additional virtual impedance After multiplication, the compensation voltage is obtained , to reshape the instantaneous value of the internal potential At the same time, subtract the compensation voltage and grid voltage After the voltage deviation is obtained, virtual impedance and current inner loop control are performed to obtain the current inner loop control reference value, which is expressed as the following formula: (39) Where: It is the reference value of the current inner loop control; is the instantaneous value of the reshaped internal potential, is the grid voltage, is the inverter output current, is the additional virtual reactance, To add a virtual resistor, is the additional virtual impedance, is the second sign, For compensation voltage, if the second mark Set to 1 to perform voltage compensation, the second flag If set to 0, voltage compensation will not be performed; is the original virtual reactance, is the original virtual resistance, is the virtual reactance increase coefficient, that is is the original virtual impedance, is the increased virtual impedance.

[0066] Embodiment 2 of the present invention provides a fault network operation control system under SVI power grid voltage phase jump, and the fault network operation control method under SVI power grid voltage phase jump described in embodiment 1 is implemented, including: The detection unit is used to detect the deviation between the self-generated angular frequency and the grid angular frequency. If the deviation exceeds the threshold, The self-generated angular frequency Maintain the angular frequency before the fault and detect the deviation between the self-generated phase angle and the grid phase angle. If the deviation exceeds the threshold, compensate the equivalent internal potential phase. Adjustment unit for time After that, according to the grid connection point voltage, during low voltage ride-through or high voltage ride-through, the active power command is adjusted and the internal potential is reshaped; The detection unit is used to detect whether overcurrent occurs during the entire fault ride-through period. If the grid-connected phase current amplitude reaches a set multiple of the rated current, transient overcurrent suppression control is performed by adjusting the virtual impedance.

[0067] Preferably but not limitatively, the control system further comprises: an active power-frequency control loop and a reactive power-voltage control loop; The flag unit outputs a first flag signal and a second flag signal; the first signal indicates that the deviation between the self-generated angular frequency and the grid angular frequency exceeds a threshold value, and is used to start the output control of the frozen active power droop integral link, and to start the equivalent internal potential phase compensation control in the case of a phase jump; the second signal indicates the occurrence of a transient overcurrent, and is used to start the transient overcurrent control, and suppress the transient overcurrent by adjusting the virtual impedance; The active power-frequency control loop includes an active power droop integral link and a freezing link. The active power droop integral link outputs a self-generated angular frequency. The freezing link freezes the output of the active droop integration link based on the first flag signal.

[0068] Preferably but not restrictively, the first flag signal is set from 0 to 1, indicating whether the deviation between the self-generated angular frequency and the grid angular frequency exceeds a threshold value, and the holding time Then restore to 0; The first flag signal passes through the NOT gate to generate an output signal of the freezing link; The output signal of the freezing link is multiplied by the actual SVI active power deviation to obtain the SVI active power deviation taking the freezing link into account.

[0069] Preferably but not restrictively, the system further comprises: a phase compensation link, which is used to determine whether there is a non-negligible phase jump during the period when the first flag signal is set to 1; if there is a non-negligible phase jump, the grid voltage phase angle is used to compensate for the non-negligible phase jump. Phase angle with self-generation The difference is adjusted by phase angle dead zone and PI to generate compensation phase angle .

[0070] Preferably but not restrictively, the system further comprises: an active power instruction ratio adjustment link, which is used to implement fault ride-through control for possible grid voltage amplitude jumps, and to generate active power reference adjustment coefficients for non-fault ride-through, high voltage ride-through, and low voltage ride-through, respectively.

[0071] Preferably but not restrictively, the system further comprises: an internal potential reshaping link for reshaping the internal potential according to a set algorithm to maintain voltage source characteristics during fault ride-through and avoid power imbalance.

[0072] Preferably but not limitatively, the system further comprises: a transient overcurrent suppression control module; The second flag signal is set from 0 to 1, indicating that a transient overcurrent occurs, and the transient overcurrent suppression control module starts the transient overcurrent suppression control; The transient overcurrent suppression control module includes: an additional virtual impedance link and an original virtual impedance adjustment link; The additional virtual impedance link or the original virtual impedance adjustment link is put into operation separately, or the additional virtual impedance link and the original virtual impedance adjustment link are put into operation in combination to implement transient overcurrent suppression control.

[0073] Embodiment 3 of the present invention provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is loaded into the processor, the fault network operation control method under the SVI power grid voltage phase jump described in Embodiment 1 is implemented.

[0074] Embodiment 4 of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the fault network operation control method under the SVI power grid voltage phase jump according to embodiment 1 is implemented.

[0075] In order to more clearly introduce the outstanding substantive features of the present invention and the significant progress it brings to the prior art, an application example of the present invention is introduced below. The present invention can realize the stable operation of SVI in voltage source mode when the grid voltage phase angle jumps, and effectively suppress transient overcurrent spikes, thereby improving the grid connection friendliness and consumption level of new energy generator sets.

[0076] The implementation effect of the present invention is further demonstrated below, and the effectiveness of the present invention is verified by simulation based on Matlab / Simulink simulation.

[0077] Figure 6 and Figure 7 This is the waveform to verify the low voltage ride-through control strategy in this example. When the fault enters and exits, the grid voltage amplitude and phase both jump. At 0.02s, the grid voltage drops from 1p.u. to 0.1pu. When the fault enters, the grid phase jumps +30°, and the grid connection point voltage decreases. The SVI operates stably in voltage source mode during the fault, and the grid phase jumps -30° when the fault exits. During the fault entry and fault recovery stages, the three-phase currents are all less than 1.5pu, and the SVI operates stably in voltage source mode.

[0078] Figure 8 and Fig. 9 This is the waveform for verifying the high voltage ride-through control strategy in this example. When the fault enters and exits, the grid voltage amplitude and phase both jump. At 0.02s, the grid voltage rises from 1p.u. to 1.28pu. When the fault enters, the grid phase jumps +30°, and the grid connection point voltage increases. The SVI operates stably in voltage source mode during the fault, and the grid phase jumps -30° when the fault exits. During the fault entry and fault recovery stages, the three-phase currents are all less than 1p.u., and the SVI operates stably in voltage source mode.

[0079] Fig.10 This is the fault ride-through control flow chart of the present invention. First, the grid voltage angular frequency is calculated in real time. and self-generated angular frequency The absolute value of the deviation, when detected , the first sign = 1, freeze the active droop integral link output to 0, and maintain the self-generated angular frequency at the first mark Set the value to 1 to maintain constant. Time. Real-time calculation of the absolute value of the grid voltage phase and the self-generated phase deviation, the first sign If detected during the period of setting 1 , that is, there is a non-negligible phase jump, and the equivalent internal potential compensation amount If detected , no phase compensation is required. Maintain After time, the first sign Set to 0, need to determine whether it exists again If yes, repeat the above steps until .time It is an adjustable parameter that can be adjusted according to the actual project and is usually no more than tens of milliseconds.

[0080] The active power command during non-fault ride-through is ; When the grid voltage per unit value is detected to be 0 ≤ ≤ 0.9 . . During the whole process of low voltage ride-through, the active power command is: = × ; When the grid voltage per unit value is detected ≥ 1.1 . . During the whole process of high voltage ride through, the active power command is: = × ; During fault ride-through, the internal potential is reshaped to maintain the voltage source characteristics during fault ride-through and avoid power imbalance.

[0081] At the same time, by detecting the current amplitude of the grid connection point , real-time calculation of grid-connected point current amplitude With current rating The ratio of the overcurrent multiple = / , when an overcurrent multiple is detected When the transient overcurrent suppression strategy is triggered, the second flag is triggered On the one hand, according to the overcurrent multiple The size is checked in real time to increase the original virtual impedance coefficient , the table lookup method includes but is not limited to function calculation, step calculation or interpolation, etc.; on the other hand, real-time sampling of the inverter output current , and with additional virtual impedance ( + ) is multiplied to obtain the compensation voltage , the instantaneous value of the reshaped internal potential is At the same time, subtract the compensation voltage and grid voltage After the voltage deviation is obtained, virtual impedance and current inner loop control are performed, such as Figure 1 As shown, a combination of the two is adopted to suppress transient overcurrent, which is expressed by the following formula: (40) Where: It is the reference value of the current inner loop control; is the instantaneous value of the reshaped internal potential; is the grid voltage; Output current for the inverter; is the additional virtual reactance, is a complex variable, To add a virtual resistor, is the additional virtual impedance; For the second sign; is the original virtual reactance, is the original virtual resistance, is the original virtual impedance; The virtual reactance is increased by a multiple.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A fault network operation control method under SVI power grid voltage phase jump, characterized in that: The following steps are involved: Detect the deviation between the self-generated angular frequency and the grid angular frequency. If the deviation exceeds the threshold, The self-generated angular frequency Maintain the angular frequency before the fault and detect the deviation between the self-generated phase angle and the grid phase angle. If the deviation exceeds the threshold, compensate the equivalent internal potential phase. time After that, according to the grid connection point voltage, during low voltage ride-through or high voltage ride-through, the active power command is adjusted and the internal potential is reshaped; During the entire fault ride-through period, it is detected whether overcurrent occurs. If the grid-connected phase current amplitude reaches a set multiple of the rated current, transient overcurrent suppression control is performed by adjusting the virtual impedance.

2. A method for controlling fault network operation under voltage phase jump of an SVI power grid according to claim 1, characterized in that: Set the first flag , indicating whether the deviation between the self-generated angular frequency and the grid angular frequency exceeds the threshold, which is expressed by the following formula: （1） Where: It is the first sign; is the self-generated angular frequency; is the grid voltage angular frequency; is the angular frequency deviation threshold; First Logo From 0 to 1, the start time Timing, the first sign From 0 to 1 hold time Then restore to 0.

3. A method for controlling fault network operation under voltage phase jump of an SVI power grid according to claim 2, characterized in that: A freezing link is configured in the active power-frequency control loop to freeze the self-generated angular frequency output by the active power droop integral link under set conditions. , the first mark The output signal of the freezing link is taken after the logical negation operation; Output signal of the freeze phase Deviation from actual SVI active power Multiply them together to get the SVI active power deviation taking into account the freezing phase, which is expressed as follows: （2） Where: To take into account the SVI active power deviation during the freezing phase; is the actual SVI active power deviation.

4. A method for controlling fault network operation under voltage phase jump of an SVI power grid according to claim 2 or 3, characterized in that: The absolute value of the grid voltage phase deviation from the self-generated phase is calculated in real time and compared with the threshold value, including: If the first sign During the period of setting 1, , there is a non-negligible phase jump, and the equivalent internal potential compensation If detected , no phase compensation is required; Grid voltage phase angle Phase angle with self-generation The difference is adjusted by phase angle dead zone and PI to generate compensation phase angle , expressed as follows: （3） Where: To compensate the phase angle; is the phase angle deviation threshold; is the grid connection point voltage phase angle; Self-generated phase angle for active power control; is the PI link transfer function.

5. A method for controlling fault network operation under voltage phase jump of an SVI power grid according to claim 2 or 3, characterized in that: First Logo After resetting to 0, the fault ride-through control is continued for the possible grid voltage amplitude jump, including: taking the active power instruction during non-fault ride-through as the reference, adjusting the active power instruction during fault ride-through according to the set ratio, which is expressed by the following formula: （4） （5） Where: It is the active power instruction during non-fault crossing. It is the active power instruction during fault crossing; P eF is the grid-connected active power during the fault period, P e is the grid-connected active power before the fault; δ is the power angle before the fault, δ F is the power angle during the fault period; It is the active reference adjustment coefficient of high voltage ride through; It is the active reference adjustment coefficient of low voltage ride through; is the grid connection point voltage before the fault, is the grid connection point voltage during the fault period, is the grid voltage before the fault, is the grid voltage during the fault period, is the per unit value of the grid connection point voltage.

6. A method for controlling fault network operation under voltage phase jump of an SVI power grid according to claim 2 or 3, characterized in that: Continuing to implement fault ride-through control for possible grid voltage amplitude jumps, it also includes: internal potential reshaping for maintaining voltage source characteristics during fault ride-through and avoiding power imbalance, which is expressed by the following formula: （6） Where: is the equivalent internal potential amplitude of the SVI reshaped under fault; is the self-generated equivalent internal potential amplitude before the fault; is an intermediate variable; U gN is the rated voltage of the power grid; k c It is the ratio of the maximum overcurrent allowed by the inverter to the rated current; I g is the grid-connected current; Z eqF is the total impedance from the SVI converter port to the grid during the fault period; Z eq is the total impedance from the SVI converter port to the grid before the fault; k F is the voltage drop depth.

7. A method for controlling fault network operation under voltage phase jump of an SVI power grid according to claim 2 or 3, characterized in that: Set the second flag , indicating whether a transient overcurrent occurs; if an overcurrent multiple is detected If it is greater than or equal to the multiple threshold, the second flag Set from 0 to 1; if an overcurrent multiple is detected If the value is less than the multiple threshold, the second flag Maintain the value to 0, expressed as follows: （7） （8） Where: For the second sign; is the overcurrent multiple; is the absolute value of the three-phase current amplitude of the grid, is the rated current; is the multiple threshold; Second sign When set from 0 to 1, transient overcurrent suppression control is started.

8. A method for controlling fault network operation under voltage phase jump of an SVI power grid according to claim 7, characterized in that: Transient overcurrent suppression control includes: A method of using additional virtual impedance alone or a method of increasing the original virtual impedance; Alternatively, a method of combining additional virtual impedance and increasing original virtual impedance is used.

9. A method for controlling fault network operation under voltage phase jump of an SVI power grid according to claim 8, characterized in that: Ways to increase the original virtual impedance include: According to the overcurrent multiple, the original virtual impedance is increased to the set multiple, which is expressed as the following formula: （9） Where: is the increased virtual reactance, is a complex variable, is the increased virtual resistance, is the virtual impedance after enlargement; is the original virtual reactance, is the original virtual resistance, is the original virtual impedance; The corresponding virtual reactance increase coefficient is obtained by real-time table lookup according to the overcurrent multiple; Ways to add virtual impedance include: Real-time sampling of inverter output current and with additional virtual impedance After multiplication, the compensation voltage is obtained , to reshape the instantaneous value of the internal potential At the same time, subtract the compensation voltage and grid voltage After the voltage deviation is obtained, virtual impedance and current inner loop control are performed to obtain the current inner loop control reference value, which is expressed as the following formula: （10） Where: is the compensation voltage; Output current for the inverter; is the original virtual reactance, is the original virtual resistance, is the original virtual impedance; It is the reference value of the current inner loop control; is the instantaneous value of the reshaped internal potential, is the compensation voltage, is the grid voltage; is the additional virtual reactance, To add a virtual resistor, is an additional virtual impedance.

10. The method for controlling the operation of a fault network under voltage phase jump of an SVI power grid according to claim 8, characterized in that: The combined use of additional virtual impedance and the increase of original virtual impedance include: real-time sampling of inverter output current and with additional virtual impedance After multiplication, the compensation voltage is obtained , to reshape the instantaneous value of the internal potential At the same time, subtract the compensation voltage and grid voltage After the voltage deviation is obtained, virtual impedance and current inner loop control are performed to obtain the current inner loop control reference value, which is expressed as the following formula: （11） Where: It is the reference value of the current inner loop control; is the instantaneous value of the reshaped internal potential, is the grid voltage, is the inverter output current, is the additional virtual reactance, To add a virtual resistor, is the additional virtual impedance, For the second sign; is the original virtual reactance, is the original virtual resistance, is the virtual reactance increase factor.

11. A control system for fault networking operation under voltage phase jump of an SVI power grid, which runs the fault networking operation control method under voltage phase jump of an SVI power grid according to any one of claims 1 to 10, characterized in that: include: The detection unit is used to detect the deviation between the self-generated angular frequency and the grid angular frequency. If the deviation exceeds the threshold, The self-generated angular frequency Maintain the angular frequency before the fault and detect the deviation between the self-generated phase angle and the grid phase angle. If the deviation exceeds the threshold, compensate the equivalent internal potential phase. Adjustment unit for time After that, according to the grid connection point voltage, during low voltage ride-through or high voltage ride-through, the active power command is adjusted and the internal potential is reshaped; The detection unit is used to detect whether overcurrent occurs during the entire fault ride-through period. If the grid-connected phase current amplitude reaches a set multiple of the rated current, transient overcurrent suppression control is performed by adjusting the virtual impedance.

12. The SVI power grid voltage phase jump fault network operation control system according to claim 11, characterized in that: The control system further comprises: an active power-frequency control loop and a reactive power-voltage control loop; The flag unit outputs a first flag signal and a second flag signal; the first signal indicates that the deviation between the self-generated angular frequency and the grid angular frequency exceeds a threshold value, and is used to start the output control of the frozen active power droop integral link, and to start the equivalent internal potential phase compensation control in the case of a phase jump; the second signal indicates the occurrence of a transient overcurrent, and is used to start the transient overcurrent control, and suppress the transient overcurrent by adjusting the virtual impedance; The active power-frequency control loop includes an active power droop integral link and a freezing link. The active power droop integral link outputs a self-generated angular frequency. The freezing link freezes the output of the active droop integration link based on the first flag signal.

13. The SVI power grid voltage phase jump fault network operation control system according to claim 12, characterized in that: The first flag signal is set from 0 to 1, indicating whether the deviation between the self-generated angular frequency and the grid angular frequency exceeds the threshold value. Then restore to 0; The first flag signal passes through the NOT gate to generate an output signal of the freezing link; The output signal of the freezing link is multiplied by the actual SVI active power deviation to obtain the SVI active power deviation taking the freezing link into account.

14. The SVI power grid voltage phase jump fault network operation control system according to claim 13, characterized in that: The system also includes: a phase compensation link, which is used to determine whether there is a non-negligible phase jump during the period when the first flag signal is set to 1; if there is a non-negligible phase jump, the grid voltage phase angle is used to Phase angle with self-generation The difference is adjusted by phase angle dead zone and PI to generate compensation phase angle .

15. The SVI power grid voltage phase jump fault network operation control system according to claim 13, characterized in that: The system also includes: an active power instruction ratio adjustment link, which is used to implement fault ride-through control for possible grid voltage amplitude jumps, and generate active power reference adjustment coefficients for non-fault ride-through, high voltage ride-through, and low voltage ride-through respectively.

16. The SVI power grid voltage phase jump fault network operation control system according to claim 13, characterized in that: The system also includes: an internal potential reshaping link, which is used to reshape the internal potential according to a set algorithm to maintain the voltage source characteristics during fault ride-through and avoid power imbalance.

17. The SVI power grid voltage phase jump fault network operation control system according to claim 12, characterized in that: The system further comprises: a transient overcurrent suppression control module; The second flag signal is set from 0 to 1, indicating that a transient overcurrent occurs, and the transient overcurrent suppression control module starts the transient overcurrent suppression control; The transient overcurrent suppression control module includes: an additional virtual impedance link and an original virtual impedance adjustment link; The additional virtual impedance link or the original virtual impedance adjustment link is put into operation separately, or the additional virtual impedance link and the original virtual impedance adjustment link are put into operation in combination to implement transient overcurrent suppression control.

18. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the computer program is loaded into the processor, the fault network operation control method under the voltage phase jump of the SVI power grid according to any one of claims 1 to 10 is implemented.

19. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the fault network operation control method under voltage phase jump of the SVI power grid according to any one of claims 1 to 10 is implemented.

Images