A New Energy Flexible DC Island Operation and Joint Fault Ride-Through Method and Device

Abstract

The present invention discloses a method and device for combined fault ride-through of a new energy flexible DC island operation. The present invention calculates the maximum active power of the flexible DC during fault ride-through constrained by the maximum DC voltage withstand capacity of the flexible DC, the minimum active power of each new energy source during fault ride-through constrained by the maximum DC voltage withstand capacity of the new energy source, and the total minimum active power of all new energy sources during fault ride-through. Combining the real-time operation states of the flexible DC and the new energy sources and considering the accommodation of the new energy sources, the parameters in the voltage reduction method are given, and the voltage reduction method with determined parameters is used for combined fault ride-through of the new energy flexible DC island operation after a fault, giving full play to the over-voltage capacity of the flexible DC itself, the fault ride-through control capacity of the new energy sources, and the control capacity of the energy-consuming device, maximizing the new energy accommodation capacity, reducing the investment of the energy-consuming device to improve the economy, and reducing the risk of equipment over-voltage and blocking caused by the fault of the receiving-end converter station or the AC power grid.

Description

Technical Field

[0001] The invention relates to a new energy flexible direct current island operation joint fault ride-through method and device, belonging to the field of power system stability analysis and control. Background Art

[0002] With the construction of a new power system based on new energy, the new energy field will usher in huge development opportunities. Flexible direct current transmission has the advantages of relatively low long-distance transmission cost, independent control of active and reactive power, and island and multi-terminal access. It is considered to be an important form of future new energy grid connection.

[0003] As a new type of power grid, the new energy collection and transmission system through flexible direct current has its own special dynamic characteristics and control: if the receiving end converter station or AC power grid fails, causing power imbalance in the flexible direct current system, these unbalanced powers will charge the flexible direct current MMC submodule capacitors, causing the DC voltage to rise rapidly to the DC voltage protection set value in a few milliseconds to tens of milliseconds, thereby causing the converter station to lock, causing a greater impact on the system. Therefore, the risk of equipment overvoltage and lockout caused by the receiving end converter station or AC power grid failure is an urgent problem to be solved. Summary of the invention

[0004] The present invention provides a new energy flexible direct current island operation joint fault ride-through method and device, which solves the problems disclosed in the background technology.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A new energy flexible direct current island operation joint fault ride-through method, comprising:

[0007] According to the active power sent to the flexible direct current sending end converter station before the fault, the flexible direct current steady-state DC voltage before the fault and the steady-state active power of the renewable energy, the maximum operating active power of the flexible direct current during the fault ride-through period subject to the maximum DC voltage withstand capability of the flexible direct current, the minimum operating active power of each renewable energy unit during the fault ride-through period subject to the maximum DC voltage withstand capability of the renewable energy, and the sum of the minimum operating active powers of all renewable energy units during the fault ride-through period are calculated; wherein, the fault ride-through period is from the moment when the flexible direct current real-time DC voltage after the fault reaches the DC voltage start threshold of the step-down method to the moment when the flexible direct current real-time DC voltage after the fault reaches the DC voltage exit threshold of the step-down method / the moment of safety control generator disconnection;

[0008] According to the active power fed into the VSC-HVDC sending converter station before the fault, the real-time DC voltage of the VSC-HVDC after the fault, the maximum operating active power of the VSC-HVDC during the fault ride-through period, the minimum operating active power of each new energy source during the fault ride-through period, and the total sum of the minimum operating active power of all new energy sources during the fault ride-through period, calculate the AC voltage reference value and the energy-consuming active power of the VSC-HVDC during the fault ride-through period in the step-down method, the control mode and the active current reference value of each new energy source during the fault ride-through period;

[0009] Adopt the step-down method with determined parameters for the combined fault ride-through of the new energy VSC-HVDC island operation after the fault.

[0010] Calculate the maximum operating active power of the VSC-HVDC during the fault ride-through period under the constraint of the maximum DC voltage withstand capacity of the VSC-HVDC. The formula is:

[0011]

[0012]

[0013] Among them, P set_vsc is the maximum operating active power of the VSC-HVDC during the fault ride-through period, C vsc is the equivalent capacitance of the VSC-HVDC, U dc_vscmax is the maximum DC voltage withstand of the VSC-HVDC, U dc_vscstart is the DC voltage start threshold of the step-down method, t start is the duration from the fault occurrence time to the time when the real-time DC voltage of the VSC-HVDC after the fault reaches the DC voltage start threshold of the step-down method, t end is the duration from the fault occurrence time to the time when the new energy is cut off by the security control theory / the theoretical action time of the relay protection action, U dc_vsc0 is the steady-state DC voltage of the VSC-HVDC before the fault, and P is the active power fed into the VSC-HVDC sending converter station before the fault.

[0014] Calculate the minimum operating active power of each new energy source during the fault ride-through period under the constraint of the maximum DC voltage withstand capacity of the new energy source. The formula is:

[0015]

[0016] Among them, P set_ng_i is the minimum operating active power of the i-th new energy source during the fault ride-through period, U dc_ngmax_i is the maximum DC voltage withstand of the i-th new energy source, P ng_i is the steady-state active power of the i-th new energy source before the fault, R chopper_i is the chopper resistance value of the i-th new energy source, t max_i is the longest repeated switching time of the chopper of the i-th new energy source, t start is the duration from the fault occurrence time to the time when the real-time DC voltage of the VSC-HVDC after the fault reaches the DC voltage start threshold of the step-down method, tend It is the duration from the moment of fault occurrence to the moment when the new energy is cut off by the safety control theory / the moment when the relay protection theoretically operates.

[0017] According to the active power fed into the flexible DC sending-end converter station before the fault, the real-time DC voltage of the flexible DC after the fault, the maximum operating active power of the flexible DC during the fault crossing, the minimum operating active power of each new energy during the fault crossing, and the total sum of the minimum operating active power of all new energies during the fault crossing, and considering the consumption of new energy, calculate the AC voltage reference value and the energy-consuming active power of the flexible DC during the fault crossing in the step-down method, and the control mode and the active current reference value of each new energy during the fault crossing, including:

[0018] If the active power fed into the flexible DC sending-end converter station before the fault is less than the maximum operating active power of the flexible DC during the fault crossing, the AC voltage reference value of the flexible DC during the fault crossing is the rated AC voltage of the flexible DC, and the combined fault crossing method for the new energy flexible DC island operation ends;

[0019] If the active power fed into the flexible DC sending-end converter station before the fault is not less than the maximum operating active power of the flexible DC during the fault crossing, determine the operating active power of each new energy during the fault crossing and the total sum of the operating active power of all new energies during the fault crossing according to the maximum operating active power of the flexible DC during the fault crossing, the minimum operating active power of each new energy during the fault crossing, and the total sum of the minimum operating active power of all new energies during the fault crossing;

[0020] Calculate the energy-consuming active power of the flexible DC according to the total sum of the operating active power of all new energies during the fault crossing and the maximum operating active power of the flexible DC during the fault crossing;

[0021] Calculate the AC voltage reference value and the AC voltage drop coefficient of the flexible DC during the fault crossing according to the operating active power of each new energy during the fault crossing;

[0022] If the real-time DC voltage of the flexible DC after the fault is greater than the DC voltage start threshold of the step-down method and greater than the DC voltage exit threshold of the step-down method, the AC voltage reference value of the flexible DC during the fault crossing is the rated AC voltage of the flexible DC multiplied by the AC voltage drop coefficient, the control mode of all new energies during the fault crossing is all active current priority, and the active current reference value of each new energy during the fault crossing is the ratio of the minimum operating active power of each new energy to the terminal AC voltage;

[0023] If the real-time DC voltage of the flexible DC after the fault is less than or equal to the DC voltage start threshold of the step-down method or the DC voltage exit threshold of the step-down method, the AC voltage reference value of the flexible DC during the fault crossing is the rated AC voltage of the flexible DC, and the combined fault crossing method for the new energy flexible DC island operation ends.

[0024] If the active power fed into the VSC-HVDC sending converter station before the fault is not less than the maximum active power of the VSC-HVDC during the fault ride-through period, determine the active power of each new energy source during the fault ride-through period and the total active power of all new energy sources during the fault ride-through period according to the maximum active power of the VSC-HVDC during the fault ride-through period, the minimum active power of each new energy source during the fault ride-through period, and the sum of the minimum active powers of all new energy sources during the fault ride-through period, including:

[0025] If the active power fed into the VSC-HVDC sending converter station before the fault is not less than the maximum active power of the VSC-HVDC during the fault ride-through period, and the maximum active power of the VSC-HVDC during the fault ride-through period is greater than or equal to the sum of the minimum active powers of all new energy sources during the fault ride-through period, the total active power of all new energy sources during the fault ride-through period is the maximum active power of the VSC-HVDC during the fault ride-through period, and calculate the active power of each new energy source during the fault ride-through period according to the minimum active power of each new energy source during the fault ride-through period, the maximum active power of the VSC-HVDC during the fault ride-through period, and the sum of the minimum active powers of all new energy sources during the fault ride-through period;

[0026] If the active power fed into the VSC-HVDC sending converter station before the fault is not less than the maximum active power of the VSC-HVDC during the fault ride-through period, and the maximum active power of the VSC-HVDC during the fault ride-through period is less than the sum of the minimum active powers of all new energy sources during the fault ride-through period, the total active power of all new energy sources during the fault ride-through period is the sum of the minimum active powers of all new energy sources during the fault ride-through period, and the active power of each new energy source during the fault ride-through period is the minimum active power of each new energy source during the fault ride-through period.

[0027] Calculate the active power of each new energy source during the fault ride-through period according to the minimum active power of each new energy source during the fault ride-through period, the maximum active power of the VSC-HVDC during the fault ride-through period, and the sum of the minimum active powers of all new energy sources during the fault ride-through period. The formula is:

[0028]

[0029] where, P set_i is the active power of the i-th new energy source during the fault ride-through period, P set_ng_i is the minimum active power of the i-th new energy source during the fault ride-through period, N is the number of new energy sources, P set_vsc is the maximum active power of the VSC-HVDC during the fault ride-through period, and P set_ng is the sum of the minimum active powers of all new energy sources during the fault ride-through period.

[0030] The formula for calculating the active power consumed by the VSC-HVDC is:

[0031] P vsc_chopper = P set - P set_vsc

[0032] Among them, P vsc_chopper is the active power consumed by the flexible DC system, P set_vsc is the maximum active power of the flexible DC system during the fault ride-through period, and P set is the total active power of all new energy sources during the fault ride-through period.

[0033] According to the active power of each new energy source during the fault ride-through period, calculate the reference value of the flexible DC AC voltage and the flexible DC AC voltage dip coefficient during the fault ride-through period, including:

[0034] According to the active power of each new energy source during the fault ride-through period, calculate the maximum allowable voltage dip value of the new energy machine terminal AC voltage during the fault ride-through period;

[0035] According to the maximum allowable voltage dip value of the new energy machine terminal AC voltage during the fault ride-through period, calculate the reference value of the flexible DC AC voltage during the fault ride-through period;

[0036] According to the reference value of the flexible DC AC voltage and the rated flexible DC AC voltage during the fault ride-through period, calculate the flexible DC AC voltage dip coefficient.

[0037] The formula for calculating the maximum allowable voltage dip value of the new energy machine terminal AC voltage during the fault ride-through period is:

[0038] U ac_ngmax = max(U ac_ngmin_i )

[0039]

[0040] Among them, U ac_ngmax is the maximum allowable voltage dip value of the new energy machine terminal AC voltage during the fault ride-through period, U ac_ngmin_i is the minimum allowable voltage dip value of the i-th new energy machine terminal AC voltage during the fault ride-through period, P set_i is the active power of the i-th new energy source during the fault ride-through period, and i max_i is the maximum tolerable AC current value of the i-th new energy source.

[0041] The formula for calculating the reference value of the flexible DC AC voltage during the fault ride-through period is:

[0042]

[0043] Among them, U ac_vscref is the reference value of the flexible DC AC voltage during the fault ride-through period, U ac_ngmax is the maximum allowable voltage dip value of the new energy machine terminal AC voltage during the fault ride-through period, P set_i is the active power of the i-th new energy source during the fault ride-through period, and R ng_i is the resistance of the outgoing line of the i-th new energy source.

[0044] The formula for calculating the flexible DC-AC voltage dip coefficient is as follows:

[0045]

[0046] Among them, k is the flexible DC-AC voltage dip coefficient, U ac_vscref is the reference value of the flexible DC-AC voltage during the fault ride-through period, and U ac_vscN is the rated flexible AC voltage.

[0047] A new energy flexible DC island operation combined fault ride-through device includes:

[0048] An active power calculation module, which calculates the maximum operating active power of the flexible DC during the fault ride-through period under the constraint of the maximum DC voltage withstand capacity of the flexible DC, the minimum operating active power of each new energy during the fault ride-through period under the constraint of the maximum DC voltage withstand capacity of the new energy, and the total sum of the minimum operating active power of all new energies during the fault ride-through period, based on the active power sent to the flexible DC sending converter station before the fault, the steady-state flexible DC voltage before the fault, and the steady-state active power of the new energy; among them, the fault ride-through period is from the moment when the real-time flexible DC voltage after the fault reaches the DC voltage start threshold of the step-down method to the moment when the real-time flexible DC voltage after the fault reaches the DC voltage exit threshold of the step-down method / the moment of the safety control and generator tripping;

[0049] A parameter calculation module, which calculates the reference value of the flexible DC AC voltage and the energy-consuming active power during the fault ride-through period in the step-down method, the control mode of each new energy during the fault ride-through period, and the reference value of the active current, based on the active power sent to the flexible DC sending converter station before the fault, the real-time flexible DC voltage after the fault, the maximum operating active power of the flexible DC during the fault ride-through period, the minimum operating active power of each new energy during the fault ride-through period, and the total sum of the minimum operating active power of all new energies during the fault ride-through period;

[0050] A fault ride-through module, which performs the combined fault ride-through of the new energy flexible DC island operation after the fault by using the step-down method with determined parameters.

[0051] The parameter calculation module includes:

[0052] A first comparison and setting module, if the active power sent to the flexible DC sending converter station before the fault is less than the maximum operating active power of the flexible DC during the fault ride-through period, the reference value of the flexible DC AC voltage during the fault ride-through period is the rated flexible AC voltage, and the new energy flexible DC island operation combined fault ride-through device ends the operation;

[0053] A comparison calculation module, if the active power fed into the VSC-HVDC sending converter station before the fault is not less than the maximum active power during the fault ride-through of the VSC-HVDC, determines the active power of each new energy source during the fault ride-through and the total active power of all new energy sources during the fault ride-through according to the maximum active power of the VSC-HVDC during the fault ride-through, the minimum active power of each new energy source during the fault ride-through, and the sum of the minimum active powers of all new energy sources during the fault ride-through;

[0054] A VSC-HVDC energy-consuming active power module calculates the VSC-HVDC energy-consuming active power according to the total active power of all new energy sources during the fault ride-through and the maximum active power of the VSC-HVDC during the fault ride-through;

[0055] A reference value drop coefficient calculation module calculates the reference value of the VSC-HVDC AC voltage and the VSC-HVDC AC voltage drop coefficient during the fault ride-through according to the active power of each new energy source during the fault ride-through;

[0056] A second comparison and setting module, if the real-time DC voltage of the VSC-HVDC after the fault is greater than the DC voltage start threshold of the buck method and greater than the DC voltage exit threshold of the buck method, the reference value of the VSC-HVDC AC voltage during the fault ride-through is the multiple of the rated AC voltage by the VSC-HVDC AC voltage drop coefficient, all new energy control modes during the fault ride-through are active current priority, and the active current reference value of each new energy source during the fault ride-through is the ratio of the minimum active power of each new energy source to the terminal AC voltage;

[0057] A third comparison and setting module, if the real-time DC voltage of the VSC-HVDC after the fault is less than or equal to the DC voltage start threshold of the buck method or the DC voltage exit threshold of the buck method, the reference value of the VSC-HVDC AC voltage during the fault ride-through is the rated AC voltage of the VSC-HVDC, and the new energy VSC-HVDC island operation combined fault ride-through device ends operation.

[0058] A computer-readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to execute the new energy VSC-HVDC island operation combined fault ride-through method.

[0059] A computing device includes one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and are configured to be executed by the one or more processors, and the one or more programs include instructions for executing the new energy VSC-HVDC island operation combined fault ride-through method

[0060] Beneficial effects achieved by the present invention: The present invention calculates the maximum active power of the VSC-HVDC during fault ride-through constrained by the maximum DC voltage withstand capacity of the VSC-HVDC, the minimum active power of each new energy source during fault ride-through constrained by the maximum DC voltage withstand capacity of the new energy source, and the total minimum active power of all new energy sources during fault ride-through. It fully exploits the overvoltage capacity of the VSC-HVDC itself and the fault ride-through control ability of the new energy source. Combining the real-time operating states of the VSC-HVDC and the new energy source, it gives the parameters in the voltage reduction method. By using the voltage reduction method with determined parameters for the combined fault ride-through of the new energy VSC-HVDC island operation after a fault, the risk of equipment overvoltage and blocking caused by the faults of the receiving-end converter station or the AC grid can be reduced. Brief Description of the Drawings

[0061] Figure 1 It is a detailed flowchart of the method of the present invention. Specific Embodiments

[0062] The present invention will be further described below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be used to limit the protection scope of the present invention.

[0063] A combined fault ride-through method for new energy VSC-HVDC island operation includes the following steps:

[0064] Step 1: According to the active power fed into the sending-end converter station of the VSC-HVDC before the fault, the steady-state DC voltage of the VSC-HVDC before the fault, and the steady-state active power of the new energy source, calculate the maximum active power of the VSC-HVDC during fault ride-through constrained by the maximum DC voltage withstand capacity of the VSC-HVDC, the minimum active power of each new energy source during fault ride-through constrained by the maximum DC voltage withstand capacity of the new energy source, and the total minimum active power of all new energy sources during fault ride-through. Among them, the fault ride-through period is from the moment when the real-time DC voltage of the VSC-HVDC after the fault reaches the DC voltage start threshold of the voltage reduction method to the moment when the real-time DC voltage of the VSC-HVDC after the fault reaches the DC voltage exit threshold of the voltage reduction method / the moment of the ATC load shedding; the fault is an AC-DC fault such as a short-circuit fault of the AC system connected to the receiving end of the VSC-HVDC or the locking of the receiving-end converter station of the VSC-HVDC.

[0065] Step 2: According to the active power fed into the sending-end converter station of the VSC-HVDC before the fault, the real-time DC voltage of the VSC-HVDC after the fault, the maximum active power of the VSC-HVDC during fault ride-through, the minimum active power of each new energy source during fault ride-through, and the total minimum active power of all new energy sources during fault ride-through, calculate the AC voltage reference value and the energy-consuming active power of the VSC-HVDC during fault ride-through in the voltage reduction method, and the control mode and the active current reference value of each new energy source during fault ride-through.

[0066] Step 3: Use the voltage reduction method with determined parameters for the combined fault ride-through of the new energy VSC-HVDC island operation after a fault.

[0067] The above method calculates the maximum active power of the VSC-HVDC during the fault ride-through period restricted by the maximum DC voltage withstand capacity of the VSC-HVDC, the minimum active power of each new energy source during the fault ride-through period restricted by the maximum DC voltage withstand capacity of the new energy source, and the total minimum active power of all new energy sources during the fault ride-through period, fully utilizes the overvoltage capacity of the VSC-HVDC itself and the fault ride-through control ability of the new energy source, combines the real-time operating states of the VSC-HVDC and the new energy source, gives the parameters in the step-down method, and uses the step-down method with determined parameters to conduct the combined fault ride-through of the new energy VSC-HVDC island operation after the fault, which can reduce the risks of equipment overvoltage and blocking caused by the faults of the receiving-end converter station or the AC power grid.

[0068] In the above step 1, the active power sent to the sending-end converter station of the VSC-HVDC before the fault, the steady-state DC voltage of the VSC-HVDC before the fault, and the steady-state active power of the new energy source can all be obtained through monitoring. On this basis, the following formula can be used to calculate the maximum active power of the VSC-HVDC during the fault ride-through period restricted by the maximum DC voltage withstand capacity of the VSC-HVDC:

[0069]

[0070]

[0071] Among them, P set_vsc is the maximum active power of the VSC-HVDC during the fault ride-through period, C vsc is the equivalent capacitance of the VSC-HVDC, U dc_vscmax is the maximum DC voltage withstand of the VSC-HVDC, U dc_vsc0 is the steady-state DC voltage of the VSC-HVDC before the fault, U dc_vscstart is the DC voltage start threshold of the step-down method, t start is the duration from the fault occurrence moment to the moment when the real-time DC voltage of the VSC-HVDC after the fault reaches the DC voltage start threshold of the step-down method, t end is the duration from the fault occurrence moment to the moment when the new energy sources are cut off according to the security control theory (usually 180 ms) / the moment when the relay protection theory operates (i.e., the fault clearing moment, usually 100 ms), and P is the active power sent to the sending-end converter station of the VSC-HVDC before the fault.

[0072] The following formula can be used to calculate the minimum active power of each new energy source during the fault ride-through period restricted by the maximum DC voltage withstand capacity of the new energy source:

[0073]

[0074] Among them, P set_ng_i is the minimum active power of the i-th new energy source during the fault ride-through period, U dc_ngmax_i is the maximum DC voltage withstand of the i-th new energy source, P ng_i is the steady-state active power of the i-th new energy source before the fault, R chopper_iis the resistance value of the i-th new energy chopper, t max_i is the longest repeated switching time of the i-th new energy chopper.

[0075] Then the sum of the minimum operating active powers of all new energies during the fault ride-through period is:

[0076]

[0077] Among them, P set_ng is the sum of the minimum operating active powers of all new energies during the fault ride-through period, and N is the number of new energies.

[0078] According to the active power P sent to the HVDC sending-end converter station before the fault obtained by monitoring, the real-time DC voltage of the HVDC after the fault, as well as the maximum operating active power of the HVDC during the fault ride-through period, the minimum operating active power of each new energy during the fault ride-through period, and the sum of the minimum operating active powers of all new energies during the fault ride-through period, considering the new energy accommodation, the reference value of the AC voltage of the HVDC and the energy-consuming active power during the fault ride-through period, the control mode and the reference value of the active current of each new energy during the fault ride-through period can be calculated. The specific method is as follows:

[0079] 1) If the active power P sent to the HVDC sending-end converter station before the fault is less than the maximum operating active power P set_vsc of the HVDC during the fault ride-through period, the reference value U ac_vscref of the AC voltage of the HVDC during the fault ride-through period is the rated AC voltage of the HVDC, and the joint fault ride-through method for the new energy HVDC island operation ends.

[0080] 2) If the active power P sent to the HVDC sending-end converter station before the fault is not less than the maximum operating active power P set_vsc of the HVDC during the fault ride-through period, according to the maximum operating active power P set_vsc of the HVDC during the fault ride-through period, the minimum operating active power of each new energy during the fault ride-through period, and the sum of the minimum operating active powers of all new energies during the fault ride-through period P set_ng , determine the operating active power of each new energy during the fault ride-through period and the sum of the operating active powers of all new energies during the fault ride-through period P set .

[0081] If the active power P sent to the HVDC sending-end converter station before the fault is not less than the maximum operating active power P set_vsc of the HVDC during the fault ride-through period, and the maximum operating active power P set_vsc of the HVDC during the fault ride-through period is greater than or equal to the sum of the minimum operating active powers of all new energies during the fault ride-through period P set_ng , in order to maximize the new energy accommodation capacity, the sum of the operating active powers of all new energies during the fault ride-through period P set is the maximum operating active power P of the HVDC during the fault ride-through periodset_vsc , according to the minimum active power of each new energy source during the fault ride-through period, the maximum active power P of the flexible DC during the fault ride-through period set_vsc and the total minimum active power P of all new energy sources during the fault ride-through period set , calculate the active power of each new energy source during the fault ride-through period, which can be expressed by the formula:

[0082]

[0083] where, P set_i is the active power of the i-th new energy source during the fault ride-through period, and P set_ng_i is the minimum active power of the i-th new energy source during the fault ride-through period.

[0084] If the active power P fed into the flexible DC sending-end converter station before the fault is not less than the maximum active power P of the flexible DC during the fault ride-through period set_vsc and the maximum active power P of the flexible DC during the fault ride-through period set_vsc is less than the total minimum active power P of all new energy sources during the fault ride-through period set_ng , in order to maximize the new energy consumption capacity, the total active power P of all new energy sources during the fault ride-through period set is the total minimum active power P of all new energy sources during the fault ride-through period set_ng , and the active power of each new energy source during the fault ride-through period is the minimum active power of each new energy source during the fault ride-through period.

[0085] 3) According to the total active power P of all new energy sources during the fault ride-through period set and the maximum active power P of the flexible DC during the fault ride-through period set_vsc , calculate the active power consumed by the flexible DC, which can be expressed by the formula:

[0086] P vsc_chopper = P set - P set_vsc

[0087] where, P vsc_chopper is the active power consumed by the flexible DC.

[0088] 4) According to the active power of each new energy source during the fault ride-through period, calculate the reference value of the flexible DC AC voltage and the flexible DC AC voltage drop coefficient during the fault ride-through period.

[0089] Specifically, it can be as follows:

[0090] 41) According to the active power of each new energy source during the fault ride-through period, calculate the maximum allowable voltage drop value of the new energy machine-side AC voltage during the fault ride-through period, which can be expressed by the formula:

[0091] Uac_ngmax = max(U ac_ngmin_i )

[0092]

[0093] where U ac_ngmax is the maximum allowable voltage dip value of the AC voltage at the new energy machine terminal during the fault ride-through period, U ac_ngmin_i is the minimum allowable voltage dip value of the AC voltage at the i-th new energy machine terminal during the fault ride-through period, P set_i is the active power of the i-th new energy operation during the fault ride-through period, i max_i is the maximum tolerable AC current value of the i-th new energy.

[0094] 42) Calculate the reference value of the flexible DC-AC voltage during the fault ride-through period according to the maximum allowable voltage dip value of the AC voltage at the new energy machine terminal during the fault ride-through period. It can be expressed by the formula:

[0095]

[0096] where R ng_i is the resistance of the outgoing line of the i-th new energy.

[0097] 43) Calculate the flexible DC-AC voltage drop coefficient according to the reference value of the flexible DC-AC voltage and the rated flexible DC-AC voltage during the fault ride-through period. It can be expressed by the formula:

[0098]

[0099] where k is the flexible DC-AC voltage drop coefficient, U ac_vscN is the rated flexible DC-AC voltage.

[0100] 5) If the real-time flexible DC voltage U dc_vsc after the fault is greater than the DC voltage start threshold U dc_vscstart of the step-down method and greater than the DC voltage exit threshold U dc_vscend of the step-down method, the reference value U ac_vscref of the flexible DC-AC voltage during the fault ride-through period is the multiple of the rated flexible DC-AC voltage drop coefficient, all new energy control modes during the fault ride-through period are active current priority, and the active current reference value of each new energy during the fault ride-through period is the ratio of the minimum operating active power of each new energy to the AC voltage at the machine terminal, that is U ac_ng_i is the AC voltage at the i-th new energy machine terminal.

[0101] 6) If the real-time flexible DC voltage U dc_vsc after the fault is less than or equal to the DC voltage start threshold U dc_vscstart of the step-down method or the DC voltage exit threshold U dc_vscend of the step-down method, the reference value Uac_vscref is the rated AC voltage of the VSC-HVDC. The method for the combined fault ride-through of the new energy VSC-HVDC island operation ends.

[0102] Based on the determined parameters, the step-down method is adopted for the combined fault ride-through of the new energy VSC-HVDC island operation after a fault.

[0103] In actual application, the specific process of the above method is as Figure 1 described below:

[0104] S1) Monitor the active power P fed into the VSC-HVDC sending converter station before the fault and the steady-state DC voltage U of the VSC-HVDC before the fault dc_vsc0 , and calculate the maximum active power P of the VSC-HVDC during the fault ride-through under the constraint of the maximum DC voltage withstand capacity of the VSC-HVDC set_vsc ;

[0105] S2) If P < P set_vsc , then the reference value U of the VSC-HVDC AC voltage during the fault ride-through ac_vscref is the rated AC voltage of the VSC-HVDC, and this method ends; if P ≥ P set_vsc , go to S3;

[0106] S3) Monitor the steady-state active power of the new energy, and calculate the minimum active power P of each new energy unit during the fault ride-through under the constraint of the maximum DC voltage withstand capacity of the new energy set_ng_i , i = 1,..., N, and calculate the sum P of the minimum active powers of all new energy units during the fault ride-through set_ng ;

[0107] S4) To maximize the new energy accommodation capacity, if P set_vsc ≥ P set_ng , then the sum P of the active powers of all new energy units during the fault ride-through set = P set_vsc ; if P set_vsc <P set_ng , then the sum P of the active powers of all new energy units during the fault ride-through set = P set_ng ;

[0108] S5) In the case of P set = P set_vsc or P set = P set_ng , calculate the active power P of each new energy unit during the fault ride-through set_i , i = 1,..., N;

[0109] S6) According to the total P of the active powers of all new energy units during the fault ride-through set and the maximum active power P of the VSC-HVDC during the fault ride-through set_vsc, calculate the active power P consumed by the VSC-HVDC vsc_chopper ;

[0110] S7) According to the active power P set_i of each new energy source during the fault ride-through period, i = 1,..., N, calculate the maximum allowable voltage dip value U ac_ngmax of the AC voltage at the machine terminal of the new energy source during the fault ride-through period;

[0111] S8) According to the maximum allowable voltage dip value U ac_ngmax of the AC voltage at the machine terminal of the new energy source during the fault ride-through period, calculate the reference value U ac_vscref of the AC voltage of the VSC-HVDC during the fault ride-through period;

[0112] S9) According to the reference value U ac_vscref of the AC voltage of the VSC-HVDC and the rated AC voltage U ac_vscN of the VSC-HVDC during the fault ride-through period, calculate the AC voltage drop coefficient k of the VSC-HVDC;

[0113] S10) Monitor the real-time DC voltage U dc_vsc of the VSC-HVDC after the fault; if U dc_vsc > U dc_vscstart and U dc_vsc > U dc_vscend , U ac_vscref is k times the rated AC voltage, all new energy control modes are active current priority during the fault ride-through period, and the active current reference value of each new energy source during the fault ride-through period is If U dc_vsc ≤ U dc_vscstart or U dc_vsc ≤ U dc_vscend , the reference value U ac_vscref of the AC voltage of the VSC-HVDC during the fault ride-through period is the rated AC voltage of the VSC-HVDC, and the method for the combined fault ride-through of the new energy VSC-HVDC island operation ends.

[0114] The above method gives full play to the overvoltage capacity of the VSC-HVDC itself and the fault ride-through control ability of the new energy source, maximizes the new energy consumption capacity, reduces the risk of equipment overvoltage and blocking caused by the faults of the receiving-end converter station or the AC power grid, and can provide a reference for the planning, design and application of the new energy VSC-HVDC island operation project.

[0115] Based on the same technical solution, the present invention also discloses a software device for the above method, a device for the combined fault ride-through of the new energy VSC-HVDC island operation, including:

[0116] The active power calculation module calculates the maximum operating active power of the HVDC during the fault ride-through period under the constraint of the maximum DC voltage withstand capacity of the HVDC, the minimum operating active power of each new energy source during the fault ride-through period under the constraint of the maximum DC voltage withstand capacity of the new energy source, and the total minimum operating active power of all new energy sources during the fault ride-through period based on the active power fed into the HVDC sending-end converter station before the fault, the steady-state DC voltage of the HVDC before the fault, and the steady-state active power of the new energy source. Wherein, the fault ride-through period is from the moment when the real-time DC voltage of the HVDC after the fault reaches the DC voltage start threshold of the step-down method to the moment when the real-time DC voltage of the HVDC after the fault reaches the DC voltage exit threshold of the step-down method / the moment when the generator is tripped by the AGC control device.

[0117] The parameter calculation module calculates the AC voltage reference value and the energy-consuming active power of the HVDC during the fault ride-through period in the step-down method, the control mode and the active current reference value of each new energy source during the fault ride-through period considering the consumption of new energy sources based on the active power fed into the HVDC sending-end converter station before the fault, the real-time DC voltage of the HVDC after the fault, the maximum operating active power of the HVDC during the fault ride-through period, the minimum operating active power of each new energy source during the fault ride-through period, and the total minimum operating active power of all new energy sources during the fault ride-through period.

[0118] The parameter calculation module includes:

[0119] The first comparison and setting module, if the active power fed into the HVDC sending-end converter station before the fault is less than the maximum operating active power of the HVDC during the fault ride-through period, the AC voltage reference value of the HVDC during the fault ride-through period is the rated AC voltage of the HVDC, and the new energy HVDC island operation combined fault ride-through device ends operation;

[0120] The comparison and calculation module, if the active power fed into the HVDC sending-end converter station before the fault is not less than the maximum operating active power of the HVDC during the fault ride-through period, determines the operating active power of each new energy source during the fault ride-through period and the total operating active power of all new energy sources during the fault ride-through period based on the maximum operating active power of the HVDC during the fault ride-through period, the minimum operating active power of each new energy source during the fault ride-through period, and the total minimum operating active power of all new energy sources during the fault ride-through period.

[0121] The HVDC energy-consuming active power module calculates the HVDC energy-consuming active power based on the total operating active power of all new energy sources during the fault ride-through period and the maximum operating active power of the HVDC during the fault ride-through period.

[0122] The reference value drop coefficient calculation module calculates the AC voltage reference value and the AC voltage drop coefficient of the HVDC during the fault ride-through period based on the operating active power of each new energy source during the fault ride-through period.

[0123] The second comparison setting module: If the flexible DC voltage in real time after a fault is greater than the DC voltage start threshold of the step-down method and greater than the DC voltage exit threshold of the step-down method, during the fault ride-through period, the reference value of the flexible AC voltage is the flexible AC voltage drop coefficient times the rated AC voltage; during the fault ride-through period, all new energy control modes are active current priority; during the fault ride-through period, the reference value of the active current of each new energy source is the ratio of the minimum operating active power of each new energy source to the AC voltage at the machine terminal.

[0124] The third comparison setting module: If the flexible DC voltage in real time after a fault is less than or equal to the DC voltage start threshold of the step-down method or the DC voltage exit threshold of the step-down method, during the fault ride-through period, the reference value of the flexible AC voltage is the rated flexible AC voltage, and the combined fault ride-through device for the new energy flexible DC island operation ends operation.

[0125] The fault ride-through module: Adopts the step-down method with determined parameters for the combined fault ride-through of the new energy flexible DC island operation after a fault.

[0126] The above device gives full play to the overvoltage capacity of the flexible DC itself, the new energy fault ride-through control capacity, and the control capacity of the energy-consuming device, maximally improves the new energy consumption capacity, reduces the investment of the energy-consuming device to improve economy, and reduces the risk of equipment overvoltage and blocking caused by the fault of the receiving-end converter station or the AC power grid.

[0127] Based on the same technical solution, the present invention also discloses a computer-readable storage medium storing one or more programs, the one or more programs including instructions that, when executed by a computing device, cause the computing device to execute the combined fault ride-through method for the new energy flexible DC island operation.

[0128] Based on the same technical solution, the present invention also discloses a computing device, including one or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and are configured to be executed by the one or more processors, and the one or more programs include instructions for executing the combined fault ride-through method for the new energy flexible DC island operation.

[0129] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program codes.

[0130] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and combinations of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable data processing devices to generate a machine, such that the instructions executed by the processors of the computer or other programmable data processing devices produce means for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0131] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including instruction means that implement the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0132] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one flow Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0133] The above are only embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention pending approval.

Claims

1. A combined fault ride-through method for flexible DC island operation of new energy, characterized in that, Including: Calculating the maximum active power of the flexible DC during the fault ride-through (FRT) under the constraint of the maximum DC voltage withstand capacity of the flexible DC, the minimum active power of each new energy source during the FRT under the constraint of the maximum DC voltage withstand capacity of the new energy source, and the total minimum active power of all new energy sources during the FRT, based on the active power fed into the flexible DC sending converter station before the fault, the steady-state DC voltage of the flexible DC before the fault, and the steady-state active power of the new energy source; wherein, the FRT period is from the moment when the real-time DC voltage of the flexible DC reaches the starting threshold of the DC voltage by the voltage reduction method after the fault to the moment when the real-time DC voltage of the flexible DC reaches the withdrawal threshold of the DC voltage by the voltage reduction method / the moment of the ATC generator tripping; Calculating the AC voltage reference value and the energy-consuming active power of the flexible DC during the FRT in the voltage reduction method, the control mode and the active current reference value of each new energy source during the FRT, based on the active power fed into the flexible DC sending converter station before the fault, the real-time DC voltage of the flexible DC after the fault, the maximum active power of the flexible DC during the FRT, the minimum active power of each new energy source during the FRT, and the total minimum active power of all new energy sources during the FRT; Performing the joint FRT of the new energy and the flexible DC during the island operation after the fault by using the voltage reduction method with determined parameters; The above calculating the AC voltage reference value and the energy-consuming active power of the flexible DC during the FRT in the voltage reduction method, the control mode and the active current reference value of each new energy source during the FRT, based on the active power fed into the flexible DC sending converter station before the fault, the real-time DC voltage of the flexible DC after the fault, the maximum active power of the flexible DC during the FRT, the minimum active power of each new energy source during the FRT, and the total minimum active power of all new energy sources during the FRT, includes: If the active power fed into the flexible DC sending converter station before the fault is less than the maximum active power of the flexible DC during the FRT, the AC voltage reference value of the flexible DC during the FRT is the rated AC voltage of the flexible DC, and the method for the joint FRT of the new energy and the flexible DC during the island operation ends; If the active power fed into the flexible DC sending converter station before the fault is not less than the maximum active power of the flexible DC during the FRT, determining the active power of each new energy source during the FRT and the total active power of all new energy sources during the FRT, based on the maximum active power of the flexible DC during the FRT, the minimum active power of each new energy source during the FRT, and the total minimum active power of all new energy sources during the FRT; Calculating the energy-consuming active power of the flexible DC, based on the total active power of all new energy sources during the FRT and the maximum active power of the flexible DC during the FRT; Calculating the AC voltage reference value and the AC voltage drop coefficient of the flexible DC during the FRT, based on the active power of each new energy source during the FRT; If the post-fault flexible DC real-time voltage is greater than the DC voltage start threshold of the step-down method and greater than the DC voltage exit threshold of the step-down method, the flexible AC voltage reference value during the fault ride-through period is the flexible AC voltage drop coefficient times the rated AC voltage, all new energy control modes during the fault ride-through period are active current priority, and the active current reference value of each new energy source during the fault ride-through period is the ratio of the minimum operating active power of each new energy source to the AC voltage at the machine terminal; If the post-fault flexible DC real-time voltage is less than or equal to the DC voltage start threshold of the step-down method or the DC voltage exit threshold of the step-down method, the flexible AC voltage reference value during the fault ride-through period is the rated flexible AC voltage, and the combined fault ride-through method for new energy flexible island operation ends.

2. A new energy flexible DC island operation combined fault ride-through method according to claim 1, characterized in that Calculate the maximum operating active power of the flexible DC during the fault ride-through period constrained by the maximum DC voltage withstand capacity of the flexible DC, and the formula is: Among them, P set_vsc is the maximum active power of the VSC-HVDC during fault ride-through, C vsc is the equivalent capacitance of the VSC-HVDC, U dc_vscmax is the maximum DC voltage withstand of the VSC-HVDC, U dc_vscstart is the DC voltage startup threshold of the voltage reduction method, t start is the duration from the fault occurrence time to the time when the real-time DC voltage of the VSC-HVDC after the fault reaches the DC voltage startup threshold of the voltage reduction method, t end is the duration from the fault occurrence time to the time when the new energy is cut off by the security control theory / the theoretical action time of the relay protection action, U dc_vsc0 is the steady-state DC voltage of the VSC-HVDC before the fault, and P is the active power sent to the sending converter station of the VSC-HVDC before the fault.

3. A new energy flexible DC island operation combined fault ride-through method according to claim 1, characterized in that Calculate the minimum operating active power of each new energy source during the fault ride-through period constrained by the maximum DC voltage withstand capacity of the new energy source, and the formula is: Among them, P set_ng_i is the minimum active power of the i-th new energy during fault ride-through, U dc_ngmax_i is the maximum DC voltage withstand of the i-th new energy, P ng_i is the steady-state active power of the i-th new energy before the fault, R chopper_i is the chopper resistance value of the i-th new energy, t max_i is the longest repeated switching time of the chopper of the i-th new energy, t start is the duration from the fault occurrence time to the time when the flexible DC voltage reaches the starting threshold of the DC voltage reduction method after the fault, t end is the duration from the fault occurrence time to the time when the new energy is cut off according to the security control theory / theoretical action time of the relay protection action.

4. The method for jointly fault ride-through in the operation of a new energy flexible DC island according to claim 1, wherein, If the active power fed into the flexible DC sending-end converter station before the fault is not less than the maximum operating active power of the flexible DC during the fault ride-through period, determine the operating active power of each new energy source during the fault ride-through period and the total operating active power of all new energy sources during the fault ride-through period according to the maximum operating active power of the flexible DC during the fault ride-through period, the minimum operating active power of each new energy source during the fault ride-through period, and the sum of the minimum operating active powers of all new energy sources during the fault ride-through period, including: If the active power fed into the flexible DC sending-end converter station before the fault is not less than the maximum operating active power of the flexible DC during the fault ride-through period, and the maximum operating active power of the flexible DC during the fault ride-through period is greater than or equal to the sum of the minimum operating active powers of all new energy sources during the fault ride-through period, the total operating active power of all new energy sources during the fault ride-through period is the maximum operating active power of the flexible DC during the fault ride-through period, and calculate the operating active power of each new energy source during the fault ride-through period according to the minimum operating active power of each new energy source during the fault ride-through period, the maximum operating active power of the flexible DC during the fault ride-through period, and the sum of the minimum operating active powers of all new energy sources during the fault ride-through period; If the active power fed into the flexible DC sending-end converter station before the fault is not less than the maximum operating active power of the flexible DC during the fault ride-through period, and the maximum operating active power of the flexible DC during the fault ride-through period is less than the sum of the minimum operating active powers of all new energy sources during the fault ride-through period, the total operating active power of all new energy sources during the fault ride-through period is the sum of the minimum operating active powers of all new energy sources during the fault ride-through period, and the operating active power of each new energy source during the fault ride-through period is the minimum operating active power of each new energy source during the fault ride-through period.

5. The method for jointly fault ride-through in the flexible DC island operation of a new energy according to claim 4, wherein, Calculate the operating active power of each new energy source during the fault ride-through period according to the minimum operating active power of each new energy source during the fault ride-through period, the maximum operating active power of the flexible DC during the fault ride-through period, and the sum of the minimum operating active powers of all new energy sources during the fault ride-through period, and the formula is: Among them, P set_i is the active power of the i-th new energy operation during the fault ride-through period, and P set_ng_i is the minimum active power of the i-th new energy operation during the fault ride-through period. N is the number of new energy units, and P set_vsc is the maximum active power of the flexible DC operation during the fault ride-through period, and P set_ng is the sum of the minimum active powers of all new energy operations during the fault ride-through period.

6. The combined fault ride-through method for a new energy flexible DC island operation according to claim 1, wherein The formula for calculating the active power consumed by the flexible DC is: P vsc_chopper = P set -P set_vsc Among them, P vsc_chopper is the active power consumed by the VSC-HVDC system, P set_vsc is the maximum active power of the VSC-HVDC system during the fault ride-through period, and P set is the total active power of all new energy sources during the fault ride-through period.

7. The hybrid fault ride-through method for a new energy flexible DC island operation according to claim 1, wherein Calculate the flexible DC AC voltage reference value and the flexible DC AC voltage drop coefficient during the fault ride-through according to the active power of each new energy source during the fault ride-through, including: Calculate the maximum allowable voltage drop of the AC voltage at the machine terminal of the new energy source during the fault ride-through according to the active power of each new energy source during the fault ride-through; Calculate the flexible DC AC voltage reference value during the fault ride-through according to the maximum allowable voltage drop of the AC voltage at the machine terminal of the new energy source during the fault ride-through; Calculate the flexible DC AC voltage drop coefficient according to the flexible DC AC voltage reference value and the rated flexible DC AC voltage during the fault ride-through.

8. The new energy flexible DC island operation combined fault ride-through method according to claim 7, wherein The formula for calculating the maximum allowable voltage drop of the AC voltage at the machine terminal of the new energy source during the fault ride-through is: U ac_ngmax = max(U ac_ngmin_i ) Among them, U ac_ngmax is the maximum allowable voltage dip value of the AC voltage at the new energy machine terminal during the fault ride-through period, and U ac_ngmin_i is the minimum allowable voltage dip value of the AC voltage at the i-th new energy machine terminal during the fault ride-through period, and P set_i is the active power of the i-th new energy during the fault ride-through period, and i max_i is the maximum tolerable AC current value of the i-th new energy.

9. The new energy flexible DC island operation combined fault ride-through method according to claim 7, wherein The formula for calculating the flexible DC AC voltage reference value during the fault ride-through is: Among them, U ac_vscref is the flexible AC voltage reference value during the fault ride-through period, and U ac_ngmax is the maximum allowable voltage dip value of the new energy machine-side AC voltage during the fault ride-through period. P set_i is the active power of the i-th new energy operation during the fault ride-through period, and R ng_i is the resistance of the outgoing line of the i-th new energy source.

10. The new energy flexible DC island operation combined fault ride-through method according to claim 7, wherein, The formula for calculating the flexible DC AC voltage drop coefficient is: Among them, k is the flexible DC and AC voltage sag coefficient, and U ac_vscref is the flexible DC and AC voltage reference value during the fault ride-through period, and U ac_vscN is the rated flexible DC and AC voltage.

11. A new energy flexible DC island operation combined fault ride-through device, characterized in that, Including: An active power calculation module, which calculates the maximum active power of the flexible DC during the fault ride-through under the constraint of the maximum DC voltage withstand capacity of the flexible DC, the minimum active power of each new energy source during the fault ride-through under the constraint of the maximum DC voltage withstand capacity of the new energy source, and the sum of the minimum active power of all new energy sources during the fault ride-through according to the active power sent to the flexible DC sending converter station before the fault, the steady-state flexible DC voltage before the fault, and the steady-state active power of the new energy source; where the fault ride-through period is from the moment when the real-time flexible DC voltage after the fault reaches the DC voltage start threshold of the step-down method to the moment when the real-time flexible DC voltage after the fault reaches the DC voltage exit threshold of the step-down method / the moment when the generator is tripped by the AGC; A parameter calculation module, which calculates the flexible DC AC voltage reference value and the energy-consuming active power during the fault ride-through in the step-down method, the control mode of each new energy source during the fault ride-through, and the active current reference value according to the active power sent to the flexible DC sending converter station before the fault, the real-time flexible DC voltage after the fault, the maximum active power of the flexible DC during the fault ride-through, the minimum active power of each new energy source during the fault ride-through, and the sum of the minimum active power of all new energy sources during the fault ride-through; A fault ride-through module, which performs joint fault ride-through of the new energy flexible DC island operation after the fault using the step-down method with determined parameters; The above parameter calculation module includes: A first comparison and setting module. If the active power sent to the flexible DC sending converter station before the fault is less than the maximum active power of the flexible DC during the fault ride-through, the flexible DC AC voltage reference value during the fault ride-through is the rated flexible DC AC voltage, and the new energy flexible DC island operation joint fault ride-through device ends operation; A comparison and calculation module. If the active power sent to the flexible DC sending converter station before the fault is not less than the maximum active power of the flexible DC during the fault ride-through, determine the active power of each new energy source during the fault ride-through and the sum of the active power of all new energy sources during the fault ride-through according to the maximum active power of the flexible DC during the fault ride-through, the minimum active power of each new energy source during the fault ride-through, and the sum of the minimum active power of all new energy sources during the fault ride-through; The flexible DC energy-consuming active power module calculates the flexible DC energy-consuming active power according to the sum of the active powers of all new energy sources during the fault ride-through period and the maximum operating active power of the flexible DC during the fault ride-through period; The reference value drop coefficient calculation module calculates the reference value of the flexible DC AC voltage and the flexible DC AC voltage drop coefficient during the fault ride-through period according to the active power of each new energy source during the fault ride-through period; The second comparison and setting module, if the real-time DC voltage of the flexible DC after the fault is greater than the starting threshold of the DC voltage by the step-down method and greater than the exiting threshold of the DC voltage by the step-down method, the reference value of the flexible DC AC voltage during the fault ride-through period is the multiple of the flexible DC AC voltage drop coefficient of the rated AC voltage, all new energy control modes are active current priority during the fault ride-through period, and the reference value of the active current of each new energy source during the fault ride-through period is the ratio of the minimum operating active power of each new energy source to the terminal AC voltage; The third comparison and setting module, if the real-time DC voltage of the flexible DC after the fault is less than or equal to the starting threshold of the DC voltage by the step-down method or the exiting threshold of the DC voltage by the step-down method, the reference value of the flexible DC AC voltage during the fault ride-through period is the rated AC voltage of the flexible DC, and the combined fault ride-through device for the new energy flexible DC island operation ends operation.

12. A computer-readable storage medium storing one or more programs, characterized in that, The one or more programs include instructions that, when executed by a computing device, cause the computing device to perform any of the methods according to claims 1 to 10.

13. A computing device, characterized in that, Comprising: One or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for performing any of the methods according to claims 1 to 10.

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