Method for calculating power instantaneous value during fault period of land converter station in offshore wind plant

Abstract

The invention provides a method for calculating a power instantaneous value during a fault period of a land converter station in an offshore wind plant, and the method comprises the steps: determining a fault phase and the position information of a fault point under the condition that the land converter station has a single-phase grounding fault, and enabling the fault point to be located in a transmission line between the land converter station and a land AC system, determining the input impedance of the fault point, the output current and the power factor of the land converter station and the alternating-current network voltage phasor of the land alternating-current system according to the position information, determining the three-phase voltage of the fault point according to the fault phase, the input impedance, the output current and the alternating-current network voltage phasor, and determining the three-phase voltage of the land converter station according to the output current, the power factor and the three-phase voltage of the fault point. And calculating an alternating current output power instantaneous value of the land converter station. By implementing the method disclosed by the invention, the real-time calculation of the output power of the land converter station during the fault period can be realized, and the accuracy of the obtained alternating current output power instantaneous value can be effectively improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of offshore wind power generation, and in particular to a method for calculating instantaneous power value during a failure of a land converter station in an offshore wind farm. Background Art

[0002] For offshore wind power connected to the flexible direct current grid system, when the output power is blocked due to a fault in the receiving AC power grid, the wind farm will continue to inject power into the flexible direct current system during the fault, which may cause a power surplus problem and further cause DC overvoltage, seriously threatening the safe and stable operation of the system. Therefore, it is necessary to determine the output power of the converter station in a timely manner, so as to evaluate the impact of the fault on the power system and take appropriate measures.

[0003] In the related art, when calculating the output power of a converter station, the accuracy of the obtained output power cannot be guaranteed. Summary of the invention

[0004] The present disclosure aims to solve one of the technical problems in the related art at least to some extent.

[0005] To this end, the purpose of the present disclosure is to propose a method, device, computer equipment and storage medium for calculating the instantaneous value of power during a land converter station failure in an offshore wind farm, which can realize real-time calculation of the output power during a land converter station failure and effectively improve the accuracy of the instantaneous value of the obtained AC output power.

[0006] To achieve the above-mentioned purpose, a method for calculating instantaneous power value during a fault of a land converter station in an offshore wind farm proposed in an embodiment of the first aspect of the present disclosure includes:

[0007] In the event of a single-phase grounding fault at a land converter station, determine the fault phase and location information of the fault point, wherein the fault point is located on the transmission line between the land converter station and the land AC system, and the land converter station and the land AC system belong to an offshore wind power flexible direct current grid-connected system;

[0008] Determining the input impedance of the fault point according to the location information;

[0009] Determining the output current and power factor of the land converter station and the AC grid voltage phasor of the land AC system;

[0010] Determine the three-phase voltage at the fault point according to the fault phase, the input impedance, the output current and the AC grid voltage phasor;

[0011] The instantaneous value of the AC output power of the land converter station is calculated according to the output current, the power factor and the three-phase voltage at the fault point.

[0012] To achieve the above-mentioned purpose, a device for calculating instantaneous power value during a fault of a land converter station in an offshore wind farm proposed in a second aspect of the present disclosure includes:

[0013] The first determination module is used to determine the fault phase and the location information of the fault point when a single-phase grounding fault occurs in the land converter station, wherein the fault point is located on the transmission line between the land converter station and the land AC system, and the land converter station and the land AC system belong to the offshore wind power flexible direct current grid-connected system;

[0014] A second determination module, configured to determine the input impedance of the fault point according to the location information;

[0015] A second determination module is used to determine the output current and power factor of the land converter station and the AC grid voltage phasor of the land AC system;

[0016] A fourth determination module, configured to determine the three-phase voltage at the fault point according to the fault phase, the input impedance, the output current and the AC grid voltage phasor;

[0017] A calculation module is used to calculate the instantaneous value of the AC output power of the land converter station according to the output current, the power factor and the three-phase voltage at the fault point.

[0018] The computer device proposed in the third aspect embodiment of the present disclosure includes: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the method for calculating the instantaneous value of power during a land converter station fault in an offshore wind farm proposed in the first aspect embodiment of the present disclosure is implemented.

[0019] The fourth aspect embodiment of the present disclosure proposes a non-temporary computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, it implements the method for calculating the instantaneous value of power during a land converter station failure in an offshore wind farm as proposed in the first aspect embodiment of the present disclosure.

[0020] The fifth aspect embodiment of the present disclosure proposes a computer program product. When the instructions in the computer program product are executed by a processor, the method for calculating the instantaneous value of power during a land converter station failure in an offshore wind farm proposed in the first aspect embodiment of the present disclosure is executed.

[0021] The instantaneous power value calculation method, device, computer equipment and storage medium provided by the present disclosure during the fault period of the land converter station in the offshore wind farm, in the case of a single-phase grounding fault in the land converter station, the fault phase and the location information of the fault point are determined, wherein the fault point is located in the transmission line between the land converter station and the land AC system, and the land converter station and the land AC system belong to the offshore wind power flexible direct current grid-connected system, according to the location information, the input impedance of the fault point is determined, the output current and power factor of the land converter station, and the AC grid voltage phasor of the land AC system are determined, according to the fault phase, input impedance, output current and AC grid voltage phasor, the three-phase voltage at the fault point is determined, and according to the output current, power factor and three-phase voltage at the fault point, the instantaneous value of the AC output power of the land converter station is calculated. By implementing the method disclosed in the present disclosure, the real-time calculation of the output power during the fault period of the land converter station can be realized, and the accuracy of the obtained instantaneous value of the AC output power can be effectively improved.

[0022] Additional aspects and advantages of the present disclosure will be given in part in the following description and in part will be obvious from the following description or learned through practice of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and / or additional aspects and advantages of the present disclosure will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0024] Figure 1 It is a flow chart of a method for calculating instantaneous power value during a fault of a land converter station in an offshore wind farm proposed in an embodiment of the present disclosure;

[0025] Figure 2 It is a flow chart of a method for calculating instantaneous power value during a fault of a land converter station in an offshore wind farm proposed in another embodiment of the present disclosure;

[0026] Figure 3 It is a flow chart of a method for calculating instantaneous power value during a fault of a land converter station in an offshore wind farm proposed in another embodiment of the present disclosure;

[0027] Figure 4 is a simplified circuit diagram of a flexible DC system under AC fault conditions proposed in the present disclosure;

[0028] Figure 5 It is a composite sequence network diagram of a system under a single-phase grounding fault proposed in the present disclosure;

[0029] Figure 6 It is a structural schematic diagram of a power instantaneous value calculation device during a land converter station failure in an offshore wind farm proposed in an embodiment of the present disclosure;

[0030] Figure 7A block diagram of an exemplary computer device suitable for implementing embodiments of the present disclosure is shown. DETAILED DESCRIPTION

[0031] Embodiments of the present disclosure are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present disclosure, and are not to be construed as limitations of the present disclosure. On the contrary, the embodiments of the present disclosure include all changes, modifications, and equivalents that fall within the spirit and connotation of the appended claims.

[0032] Figure 1 It is a flow chart of a method for calculating instantaneous power value during a failure of a land converter station in an offshore wind farm proposed in an embodiment of the present disclosure.

[0033] Among them, it should be noted that the executor of the method for calculating the instantaneous value of power during the failure of the land converter station in the offshore wind farm in this embodiment is a device for calculating the instantaneous value of power during the failure of the land converter station in the offshore wind farm. The device can be implemented by software and / or hardware. The device can be configured in a computer device. The computer device can include but is not limited to a terminal, a server, etc. For example, the terminal can be a mobile phone, a handheld computer, etc.

[0034] like Figure 1 As shown, the method for calculating the instantaneous power value during the fault of the land converter station in the offshore wind farm includes:

[0035] S101: When a single-phase grounding fault occurs in a land converter station, determine the fault phase and location information of the fault point, wherein the fault point is located in the transmission line between the land converter station and the land AC system, and the land converter station and the land AC system belong to the offshore wind power flexible direct current grid-connected system.

[0036] The fault phase refers to the phase where the ground fault occurs in a single-phase ground fault scenario, for example, it can be phase A, phase B or phase C, and there is no limitation on this.

[0037] The fault point may refer to a location where a ground fault occurs.

[0038] The location information can be used to indicate the location of the fault point in the transmission line.

[0039] In the embodiment of the present disclosure, when a single-phase grounding fault occurs in a land converter station, determining the fault phase and the location information of the fault point can provide reliable trigger conditions for the execution of the embodiment of the present disclosure, and the obtained location information of the fault phase and the fault point can provide reliable data support for subsequent calculation processes.

[0040] S102: Determine the input impedance of the fault point according to the location information.

[0041] In the power system, when a fault occurs, a node of the circuit is formed at the fault point. The input impedance of the node is used to describe the response ability of the node to the external power supply or fault current.

[0042] It is understandable that impedance also exists in the transmission line, and the input impedance of the corresponding fault point may also be different depending on the position of the fault point in the transmission line. Therefore, in the embodiment of the present disclosure, the input impedance of the fault point can be determined based on the location information, thereby effectively improving the adaptability of the obtained input impedance to personalized application scenarios.

[0043] S103: Determine the output current and power factor of the land converter station and the AC grid voltage phasor of the land AC system.

[0044] The power factor refers to the ratio of actual power to apparent power, usually expressed as cosφ. A reasonable power factor value, such as 0.8 or 1, can be assumed based on actual conditions, and there is no restriction on this.

[0045] It can be understood that the output current of the land converter station and the AC grid voltage phasor of the land AC system have a high correlation with the voltage at the fault point. Therefore, in the embodiment of the present disclosure, when determining the output current and power factor of the land converter station and the AC grid voltage phasor of the land AC system, it can provide reliable data support for the subsequent determination of the three-phase voltage at the fault point.

[0046] S104: Determine the three-phase voltage at the fault point according to the fault phase, input impedance, output current and AC grid voltage phasor.

[0047] The three-phase voltage at the fault point may include, for example, a phase A voltage, a phase B voltage, and a phase C voltage at the fault point.

[0048] In the embodiments of the present disclosure, when determining the three-phase voltage at the fault point based on the fault phase, input impedance, output current and AC grid voltage phasor, it can be based on a pre-trained machine learning model, or it can also be based on engineering or mathematical methods, without limitation.

[0049] S105: Calculate the instantaneous value of the AC output power of the land converter station according to the output current, power factor and three-phase voltage at the fault point.

[0050] That is to say, in the embodiment of the present disclosure, after obtaining the output current, power factor and three-phase voltage at the fault point based on the above steps, the instantaneous value of the AC output power of the land converter station can be calculated based on the output current, power factor and three-phase voltage at the fault point.

[0051] In this embodiment, when a single-phase grounding fault occurs at a land converter station, the fault phase and the location information of the fault point are determined, wherein the fault point is located in the transmission line between the land converter station and the land AC system, and the land converter station and the land AC system belong to the offshore wind power flexible direct current grid-connected system. According to the location information, the input impedance of the fault point is determined, the output current and power factor of the land converter station, and the AC grid voltage phasor of the land AC system are determined, and the three-phase voltage at the fault point is determined according to the fault phase, input impedance, output current and AC grid voltage phasor, and the instantaneous value of the AC output power of the land converter station is calculated according to the output current, power factor and three-phase voltage at the fault point. By implementing the method disclosed in the present invention, the real-time calculation of the output power during the fault of the land converter station can be realized, and the accuracy of the instantaneous value of the AC output power obtained can be effectively improved.

[0052] Figure 2 It is a flow chart of a method for calculating the instantaneous value of power during a failure of a land converter station in an offshore wind farm proposed in another embodiment of the present disclosure.

[0053] like Figure 2 As shown, the method for calculating the instantaneous power value during the fault of the land converter station in the offshore wind farm includes:

[0054] S201: When a single-phase grounding fault occurs in a land converter station, determine the fault phase and the location information of the fault point, wherein the fault point is located in the transmission line between the land converter station and the land AC system, and the land converter station and the land AC system belong to the offshore wind power flexible direct current grid-connected system.

[0055] The description of S201 can be specifically referred to the above embodiment, which will not be repeated here.

[0056] S202: Determine the first impedance and the second impedance of the offshore wind power system connected to the flexible direct current grid, wherein the first impedance is the impedance of the transmission line, and the second impedance is the internal impedance of the onshore AC system.

[0057] In the embodiment of the present disclosure, the onshore AC system can be equivalent to having an internal impedance Z S voltage source.

[0058] S203: Determine a third impedance according to the location information and the first impedance, wherein the third impedance is a line impedance between the fault point in the transmission line and the onshore AC system.

[0059] For example, assuming the first impedance is Z L , NM is the transmission line of the onshore converter station, where the N terminal is connected to the converter station, the M terminal is connected to the onshore AC system, and x is the percentage of the distance from the fault point F to the M terminal on the NM line. The corresponding third impedance is xZ L .

[0060] S204: Determine the positive-sequence input impedance, negative-sequence input impedance and zero-sequence input impedance of the fault point according to the second impedance and the third impedance, wherein the positive-sequence input impedance, the negative-sequence input impedance and the zero-sequence input impedance are combined as the input impedance.

[0061] It can be understood that in a single-phase to ground fault, one phase conductor is grounded while the other two phases continue to operate normally. In this case, the frequency and phase of the positive sequence current and voltage remain the same, so the positive sequence impedance does not change. However, the frequency and phase of the negative sequence and zero sequence currents change because the grounding causes an unbalanced condition. The negative sequence current represents the negative sequence short circuit or ground current component in the power system, while the zero sequence current represents the zero sequence short circuit or ground current component in the power system. The negative sequence and zero sequence impedances describe the system's ability to respond to asymmetrical fault conditions. Therefore, in a single-phase to ground fault, the standard impedance is equal to the positive sequence impedance, while the negative sequence impedance and zero sequence impedance reflect the system's response to the negative and zero sequence currents.

[0062] It should be noted that the values ​​of standard impedance, positive sequence impedance, negative sequence impedance and zero sequence impedance may be different for different fault types and system configurations. The specific impedance calculation can be analyzed in detail based on the system parameters and fault conditions.

[0063] That is to say, in the embodiment of the present disclosure, when a single-phase grounding fault occurs in a land converter station, after determining the fault phase and the location information of the fault point, the first impedance and the second impedance in the offshore wind power flexible direct current grid-connected system can be determined, wherein the first impedance is the impedance of the transmission line, and the second impedance is the internal impedance of the onshore AC system. According to the location information and the first impedance, the third impedance is determined, wherein the third impedance is the line impedance between the fault point in the transmission line and the onshore AC system. According to the second impedance and the third impedance, the positive-sequence input impedance, negative-sequence input impedance and zero-sequence input impedance of the fault point are determined, wherein the positive-sequence input impedance, the negative-sequence input impedance and the zero-sequence input impedance are combined as the input impedance, thereby effectively improving the practicality and reliability of the obtained input impedance.

[0064] S205: Determine the output current and power factor of the land converter station, and the AC grid voltage phasor of the land AC system.

[0065] S206: Determine the three-phase voltage at the fault point according to the fault phase, input impedance, output current and AC grid voltage phasor.

[0066] The description of S205 and S206 can be specifically referred to the above embodiment, which will not be repeated here.

[0067] S207: Determine the phase difference information of the land converter station.

[0068] The phase difference information can be used to describe the phase difference between the three-phase output current of the land converter station and the reference phase.

[0069] In the disclosed embodiment, when the phase difference information of the land converter station is determined, reliable reference information can be provided for the subsequent calculation of the three-phase output current of the land converter station.

[0070] S208: Calculate the three-phase output current of the land converter station according to the output current and phase difference information.

[0071] For example, in the embodiment of the present disclosure, when calculating the three-phase output current of the land converter station according to the output current and the phase difference information, it can be based on the following steps:

[0072] Assume that the output current of the converter station is I abc , the output current of phase A is I a , the output current of phase B is I b , the output current of phase C is I c These output currents can be calculated using the following formula:

[0073] I a =I abc *cos(θ a )

[0074] I b =I abc *cos(θ b )

[0075] Ic=I abc *cos(θ c )

[0076] Among them, θ a ,θ b and θ c Indicates the phase difference between each phase and the reference position.

[0077] According to this formula, the output current of each phase can be calculated based on the known output current value and phase difference of the converter station.

[0078] S209: Calculate the instantaneous value of the AC output power based on the power factor, the three-phase voltage at the fault point, and the three-phase output current.

[0079] That is to say, in the embodiments of the present disclosure, the phase difference information of the land converter station can be determined, and the three-phase output current of the land converter station can be calculated based on the output current and the phase difference information. The instantaneous value of the AC output power can be calculated based on the power factor, the three-phase voltage at the fault point and the three-phase output current. Therefore, the reliability of the calculation process of the instantaneous value of the AC output power can be effectively improved.

[0080] In this embodiment, by determining the first impedance and the second impedance in the flexible direct current grid-connected system of offshore wind power, wherein the first impedance is the impedance of the transmission line, and the second impedance is the internal impedance of the onshore AC system, the third impedance is determined according to the location information and the first impedance, wherein the third impedance is the line impedance between the fault point in the transmission line and the onshore AC system, and the positive-sequence input impedance, negative-sequence input impedance and zero-sequence input impedance of the fault point are determined according to the second impedance and the third impedance, wherein the positive-sequence input impedance, the negative-sequence input impedance and the zero-sequence input impedance are combined as the input impedance, thereby effectively improving the practicality and reliability of the obtained input impedance. By determining the phase difference information of the land converter station, the three-phase output current of the land converter station is calculated according to the output current and the phase difference information, and the instantaneous value of the AC output power is calculated based on the power factor, the three-phase voltage at the fault point and the three-phase output current, thereby effectively improving the reliability of the calculation process of the instantaneous value of the AC output power.

[0081] Figure 3 It is a flow chart of a method for calculating the instantaneous value of power during a failure of a land converter station in an offshore wind farm proposed in another embodiment of the present disclosure.

[0082] like Figure 3 As shown, the method for calculating the instantaneous power value during the fault of the land converter station in the offshore wind farm includes:

[0083] S301: When a single-phase grounding fault occurs in a land converter station, determine the fault phase and the location information of the fault point, wherein the fault point is located in the transmission line between the land converter station and the land AC system, and the land converter station and the land AC system belong to the offshore wind power flexible direct current grid-connected system.

[0084] S302: Determine the first impedance and the second impedance of the offshore wind power system connected to the flexible direct current grid, wherein the first impedance is the impedance of the transmission line, and the second impedance is the internal impedance of the onshore AC system.

[0085] S303: Determine a third impedance according to the location information and the first impedance, wherein the third impedance is a line impedance between the fault point in the transmission line and the onshore AC system.

[0086] S304: Determine the positive-sequence input impedance, negative-sequence input impedance and zero-sequence input impedance of the fault point according to the second impedance and the third impedance, wherein the positive-sequence input impedance, the negative-sequence input impedance and the zero-sequence input impedance are combined as the input impedance.

[0087] S305: Determine the output current and power factor of the land converter station, and the AC grid voltage phasor of the land AC system.

[0088] The description of S301 - S305 can be specifically referred to the above embodiment, which will not be repeated here.

[0089] S306: Determine a positive-sequence fault voltage, a negative-sequence fault voltage, and a zero-sequence fault voltage according to the input impedance, the output current, and the AC grid voltage phasor.

[0090] Among them, the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage may refer to the voltages of the fault point in the positive-sequence network, the negative-sequence network and the zero-sequence network respectively.

[0091] Optionally, in some embodiments, the positive-sequence fault current, negative-sequence fault current and zero-sequence fault current of the fault point are equal, and the sum of the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage is zero. When determining the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage according to the input impedance, the output current and the AC power grid voltage phasor, it is possible to determine the first association information between the negative-sequence fault voltage, the negative-sequence fault current and the negative-sequence input impedance, determine the second association information between the zero-sequence fault voltage, the zero-sequence fault current and the zero-sequence input impedance, and determine the positive-sequence fault current, the positive-sequence fault voltage, the negative-sequence fault current and the zero-sequence fault current according to the first association information and the second association information. The third correlation information between the input impedance and the zero-sequence input impedance is used to determine the fourth correlation information between the AC power grid voltage phasor, the output current, the positive-sequence fault current, the positive-sequence input impedance and the positive-sequence fault voltage. The positive-sequence fault voltage is calculated based on the third correlation information and the fourth correlation information. The positive-sequence fault current is calculated based on the positive-sequence fault voltage and the third correlation information. The negative-sequence fault voltage is calculated based on the positive-sequence fault current and the first correlation information. The zero-sequence fault voltage is calculated based on the positive-sequence fault current and the second correlation information. Thus, the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage can be calculated quickly and accurately.

[0092] For example, Figure 4 As shown, Figure 4 This is a simplified circuit diagram of the flexible direct current system under AC fault according to the present disclosure. In the figure, NM is the transmission line of the onshore converter station, and x is the percentage of the distance from the fault point F to the M end on the NM line. T Z is the short-circuit impedance of the transformer connected to the onshore converter station; L is the line impedance. The positive-sequence fault current, negative-sequence fault current and zero-sequence fault current of the fault point are equal, and the sum of the positive-sequence fault voltage, negative-sequence fault voltage and zero-sequence fault voltage is zero, which can be expressed based on formula (1):

[0093]

[0094] Among them, V and I are voltage and current phasors, arrows indicate positive direction, subscripts "M, N, F" are electrical quantities at M, N, F respectively; subscripts "1, 2, 0" represent positive, negative, and zero sequence components respectively. ES is the voltage phasor of the AC grid.

[0095] For example, if the A phase is grounded, Figure 5 As shown, Figure 5 It is a composite sequence network diagram of a system under a single-phase grounding fault proposed in the present disclosure.

[0096] It can be understood that, affected by the negative sequence current suppression of the converter station and the connection mode of the connecting transformer, the negative sequence and zero sequence currents on the converter station side (N side) are both zero. According to the negative sequence and zero sequence networks, the negative sequence voltage expression (i.e., the above-mentioned first associated information) and the zero sequence voltage expression (i.e., the above-mentioned second associated information) at the fault point F can be obtained respectively as follows:

[0097] V F2 =-I M2 ·(Z S2 +xZ L2 )=-I F2 ·(Z S2 +xZ L2 ) (2)

[0098] V F0 =-I M0 ·(Z S0 +xZ L0 )=-I F0 ·(Z S0 +xZ L0 ) (3)

[0099] Define the negative sequence input impedance Z at the fault point ff2 =Z S2 +xZ L2 , zero-sequence input impedance Z at fault point ff0 =Z S0 +xZ L0 .

[0100] Substituting equations (2) and (3) into (1), we can obtain equation 4 (i.e. the third associated information mentioned above), where the positive sequence fault current I F1 :

[0101]

[0102] According to the positive sequence network, we can get Formula 5 (i.e. the fourth association information mentioned above):

[0103] E S =(I F1 -I N1 )·(Z S1 +xZ L1)+V F1 (5)

[0104] Define Z M1 =Z S1 +xZ L1 , Substituting equation (4) into (5), we can get the positive sequence fault voltage V F1 :

[0105]

[0106] Since the positive sequence fault current, negative sequence fault current and zero sequence fault current are equal, the negative sequence and zero sequence fault voltages can be obtained by combining formulas (2), (3), (4) and (6).

[0107] S307: Determine the three-phase voltage at the fault point according to the fault phase, the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage.

[0108] Optionally, in some embodiments, the three-phase voltage at the fault point includes: a fault phase voltage, a first non-fault phase voltage and a second non-fault phase voltage, the value of the fault phase voltage is zero, and when determining the three-phase voltage at the fault point according to the fault phase, the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage, the conversion relationship between the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage and the three-phase voltage at the fault point can be determined, and the first non-fault phase voltage and the second non-fault phase voltage can be calculated and determined according to the conversion relationship, the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage. Thus, the three-phase voltage at the fault point can be accurately and quickly determined based on the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage, thereby effectively improving the reliability of the obtained three-phase voltage at the fault point.

[0109] In the embodiment of the present disclosure, after the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage are determined, the three-phase voltage at the fault point can be obtained according to the symmetrical component method:

[0110]

[0111] In the formula, a=e j120° ,a 2 =e j240° .

[0112] The converter station only outputs positive sequence current during the fault period and can be equivalent to a positive sequence current source. If the converter station still controls its power factor to 1.0 during the fault period, the output current I N1 With positive sequence fault voltage V F1 Since the fault occurred at the converter station exit, it can be considered that the length of the NM line is close to zero, and Z L1,2,3 =0. Considering that the AC main grid is a large power grid, it can be equivalent to an ideal voltage source. Assume I N1 and VF1 The phase of E S The phase difference is 90°. And because Z M1 Very small, the fault point voltage V F The output current I of the converter station N1 The influence of is very small, so formula (7) can be simplified as:

[0113]

[0114] That is to say, in the embodiments of the present disclosure, the positive-sequence fault voltage, negative-sequence fault voltage and zero-sequence fault voltage can be determined based on the input impedance, output current and AC power grid voltage phasor, and the three-phase voltage at the fault point can be determined based on the fault phase, positive-sequence fault voltage, negative-sequence fault voltage and zero-sequence fault voltage. As a result, the accuracy of the obtained three-phase voltage at the fault point can be effectively improved.

[0115] S308: Calculate the instantaneous value of the AC output power of the land converter station according to the output current, power factor and three-phase voltage at the fault point.

[0116] The description of S308 can be specifically referred to the above embodiment, which will not be repeated here.

[0117] In this embodiment, the positive-sequence fault voltage, negative-sequence fault voltage and zero-sequence fault voltage are determined according to the input impedance, output current and AC grid voltage phasor, and the three-phase voltage at the fault point is determined according to the fault phase, positive-sequence fault voltage, negative-sequence fault voltage and zero-sequence fault voltage, thereby effectively improving the accuracy of the obtained three-phase voltage at the fault point. The positive-sequence fault current, negative-sequence fault current and zero-sequence fault current at the fault point are equal, and the sum of the positive-sequence fault voltage, negative-sequence fault voltage and zero-sequence fault voltage is zero. When the positive-sequence fault voltage, negative-sequence fault voltage and zero-sequence fault voltage are determined according to the input impedance, output current and AC grid voltage phasor, the first association information between the negative-sequence fault voltage, negative-sequence fault current and negative-sequence input impedance can be determined, and the second association information between the zero-sequence fault voltage, zero-sequence fault current and zero-sequence input impedance can be determined. According to the first association information and the second association information, the positive-sequence fault current, the positive-sequence fault voltage, the negative-sequence input impedance and the zero-sequence fault voltage are determined. The third correlation information between the positive-sequence fault current and the zero-sequence input impedance is used to determine the fourth correlation information between the AC power grid voltage phasor, the output current, the positive-sequence fault current, the positive-sequence input impedance and the positive-sequence fault voltage. The positive-sequence fault voltage is calculated according to the third correlation information and the fourth correlation information. The positive-sequence fault current is calculated according to the positive-sequence fault voltage and the third correlation information. The negative-sequence fault voltage is calculated according to the positive-sequence fault current and the first correlation information. The zero-sequence fault voltage is calculated according to the positive-sequence fault current and the second correlation information. Thus, the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage can be calculated quickly and accurately. The three-phase voltage at the fault point includes: a fault phase voltage, a first non-fault phase voltage and a second non-fault phase voltage. The value of the fault phase voltage is zero. When determining the three-phase voltage at the fault point according to the fault phase, the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage, the conversion relationship between the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage and the three-phase voltage at the fault point can be determined. According to the conversion relationship, the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage, the first non-fault phase voltage and the second non-fault phase voltage are calculated and determined. Thus, the three-phase voltage at the fault point can be accurately and quickly determined based on the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage, thereby effectively improving the reliability of the obtained three-phase voltage at the fault point.

[0118] For example, in the embodiment of the present disclosure, the AC grid voltage E S The phase is zero phase. Since the output current of the converter station is a three-phase balanced current, the current amplitude is set to I N , then the three-phase output current of the converter station can be expressed as:

[0119]

[0120] According to the instantaneous power theory, equations (8) and (9) are converted from phasor form to time domain form and substituted into equation (10) to obtain the instantaneous value of the AC output power during the converter station fault period:

[0121]

[0122] Figure 6 It is a structural schematic diagram of a power instantaneous value calculation device during a land converter station failure in an offshore wind farm proposed in an embodiment of the present disclosure.

[0123] like Figure 6 As shown, the power instantaneous value calculation device 60 during the fault of the land converter station in the offshore wind farm includes:

[0124] The first determination module 601 is used to determine the fault phase and the location information of the fault point when a single-phase grounding fault occurs in the land converter station, wherein the fault point is located on the transmission line between the land converter station and the land AC system, and the land converter station and the land AC system belong to the offshore wind power flexible direct current grid-connected system;

[0125] A second determination module 602 is used to determine the input impedance of the fault point according to the location information;

[0126] The second determination module 603 is used to determine the output current and power factor of the land converter station and the AC grid voltage phasor of the land AC system;

[0127] The fourth determination module 604 is used to determine the three-phase voltage at the fault point according to the fault phase, input impedance, output current and AC grid voltage phasor;

[0128] The calculation module 605 is used to calculate the instantaneous value of the AC output power of the land converter station according to the output current, the power factor and the three-phase voltage at the fault point.

[0129] It should be noted that the aforementioned explanation of the method for calculating the instantaneous value of power during a land converter station failure in an offshore wind farm is also applicable to the device for calculating the instantaneous value of power during a land converter station failure in an offshore wind farm of this embodiment, and will not be repeated here.

[0130] In this embodiment, when a single-phase grounding fault occurs at a land converter station, the fault phase and the location information of the fault point are determined, wherein the fault point is located in the transmission line between the land converter station and the land AC system, and the land converter station and the land AC system belong to the offshore wind power flexible direct current grid-connected system. According to the location information, the input impedance of the fault point is determined, the output current and power factor of the land converter station, and the AC grid voltage phasor of the land AC system are determined, and the three-phase voltage at the fault point is determined according to the fault phase, input impedance, output current and AC grid voltage phasor, and the instantaneous value of the AC output power of the land converter station is calculated according to the output current, power factor and three-phase voltage at the fault point. By implementing the method disclosed in the present invention, the real-time calculation of the output power during the fault of the land converter station can be realized, and the accuracy of the instantaneous value of the AC output power obtained can be effectively improved.

[0131] Figure 7 A block diagram of an exemplary computer device suitable for implementing embodiments of the present disclosure is shown. Figure 7 The computer device 12 shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present disclosure.

[0132] like Figure 7 As shown, the computer device 12 is in the form of a general-purpose computing device. The components of the computer device 12 may include, but are not limited to: one or more processors or processing units 16, a system memory 28, and a bus 18 that connects various system components (including the system memory 28 and the processing unit 16).

[0133] The bus 18 represents one or more of several types of bus structures, including a memory bus or memory controller, a peripheral bus, a graphics acceleration port, a processor or a local bus using any of a variety of bus structures. For example, these architectures include but are not limited to Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MAC) bus, Enhanced ISA bus, Video Electronics Standards Association (VESA) local bus and Peripheral Component Interconnection (PCI) bus.

[0134] The computer device 12 typically includes a variety of computer system readable media. These media can be any available media that can be accessed by the computer device 12, including volatile and non-volatile media, removable and non-removable media.

[0135] The memory 28 may include computer system readable media in the form of volatile memory, such as random access memory (RAM) 30 and / or cache memory 32. The computer device 12 may further include other removable / non-removable, volatile / non-volatile computer system storage media. By way of example only, the storage system 34 may be used to read and write non-removable, non-volatile magnetic media ( Figure 7 Not shown, often called a "hard drive").

[0136] although Figure 7 Not shown in the figure, a disk drive for reading and writing a removable non-volatile disk (e.g., a "floppy disk"), and an optical disk drive for reading and writing a removable non-volatile optical disk (e.g., a compact disc read only memory (hereinafter referred to as: CD-ROM), a digital versatile disc read only memory (hereinafter referred to as: DVD-ROM) or other optical media) may be provided. In these cases, each drive may be connected to the bus 18 via one or more data medium interfaces. The memory 28 may include at least one program product having a set (e.g., at least one) of program modules that are configured to perform the functions of the various embodiments of the present disclosure.

[0137] A program / utility 40 having a set (at least one) of program modules 42 may be stored, for example, in the memory 28, such program modules 42 including but not limited to an operating system, one or more application programs, other program modules, and program data, each of which or some combination may include an implementation of a network environment. The program modules 42 generally perform the functions and / or methods of the embodiments described in the present disclosure.

[0138] The computer device 12 may also communicate with one or more external devices 14 (e.g., keyboard, pointing device, display 24, etc.), one or more devices that enable a human body to interact with the computer device 12, and / or any device that enables the computer device 12 to communicate with one or more other computing devices (e.g., network card, modem, etc.). Such communication may be performed via an input / output (I / O) interface 22. In addition, the computer device 12 may also communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network, such as the Internet) via a network adapter 20. As shown, the network adapter 20 communicates with other modules of the computer device 12 via a bus 18. It should be understood that, although not shown in the figure, other hardware and / or software modules may be used in conjunction with the computer device 12, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage systems.

[0139] The processing unit 16 executes various functional applications and data processing by running the programs stored in the system memory 28, such as implementing the method for calculating the instantaneous power value during a failure of a land converter station in an offshore wind farm mentioned in the above-mentioned embodiment.

[0140] In order to implement the above embodiments, the present disclosure also proposes a non-temporary computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, it implements the method for calculating the instantaneous value of power during a land converter station failure in an offshore wind farm as proposed in the aforementioned embodiments of the present disclosure.

[0141] In order to implement the above embodiments, the present disclosure also proposes a computer program product. When the instruction processor in the computer program product is executed, it executes the method for calculating the instantaneous value of power during a land converter station failure in an offshore wind farm proposed in the above embodiments of the present disclosure.

[0142] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. The present disclosure is intended to cover any variations, uses, or adaptations of the present disclosure that follow the general principles of the present disclosure and include common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The description and examples are to be considered exemplary only, and the true scope and spirit of the present disclosure are indicated by the following claims.

[0143] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

[0144] It should be noted that, in the description of the present disclosure, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present disclosure, unless otherwise specified, the meaning of "plurality" is two or more.

[0145] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present disclosure includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present disclosure belong.

[0146] It should be understood that the various parts of the present disclosure can be implemented in hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0147] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0148] In addition, each functional unit in each embodiment of the present disclosure may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0149] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0150] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0151] Although the embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present disclosure. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present disclosure.

Claims

1. A method for calculating the instantaneous power value during a fault of a land converter station in an offshore wind farm. It is characterized in that include: In the event of a single-phase grounding fault at a land converter station, determine the fault phase and location information of the fault point, wherein the fault point is located on the transmission line between the land converter station and the land AC system, and the land converter station and the land AC system belong to an offshore wind power flexible direct current grid-connected system; Determining the input impedance of the fault point according to the location information; Determining the output current and power factor of the land converter station and the AC grid voltage phasor of the land AC system; Determine the three-phase voltage at the fault point according to the fault phase, the input impedance, the output current and the AC grid voltage phasor; The instantaneous value of the AC output power of the land converter station is calculated according to the output current, the power factor and the three-phase voltage at the fault point.

2. The method according to claim 1, It is characterized in that The step of determining the input impedance of the fault point according to the position information includes: Determine a first impedance and a second impedance in the offshore wind power flexible direct current grid-connected system, wherein the first impedance is the impedance of the transmission line, and the second impedance is the internal impedance of the onshore alternating current system; Determine a third impedance according to the location information and the first impedance, wherein the third impedance is a line impedance between the fault point in the transmission line and the land AC system; The positive-sequence input impedance, negative-sequence input impedance and zero-sequence input impedance of the fault point are determined according to the second impedance and the third impedance, wherein the positive-sequence input impedance, the negative-sequence input impedance and the zero-sequence input impedance are combined as the input impedance.

3. The method according to claim 2, It is characterized in that The determining of the three-phase voltage at the fault point according to the fault phase, the input impedance, the output current and the AC grid voltage phasor comprises: Determining a positive-sequence fault voltage, a negative-sequence fault voltage and a zero-sequence fault voltage according to the input impedance, the output current and the AC grid voltage phasor; The three-phase voltage at the fault point is determined according to the fault phase, the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage.

4. The method according to claim 3, It is characterized in that The positive-sequence fault current, negative-sequence fault current and zero-sequence fault current of the fault point are equal, and the sum of the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage is zero; Wherein, determining the positive sequence fault voltage, the negative sequence fault voltage and the zero sequence fault voltage according to the input impedance, the output current and the AC grid voltage phasor comprises: Determining first association information between the negative-sequence fault voltage, the negative-sequence fault current and the negative-sequence input impedance; Determining second association information between the zero-sequence fault voltage, the zero-sequence fault current and the zero-sequence input impedance; Determine third association information among the positive-sequence fault current, the positive-sequence fault voltage, the negative-sequence input impedance and the zero-sequence input impedance according to the first association information and the second association information; Determining fourth association information between the AC grid voltage phasor, the output current, the positive-sequence fault current, the positive-sequence input impedance and the positive-sequence fault voltage; Calculating the positive sequence fault voltage according to the third associated information and the fourth associated information; Calculating the positive-sequence fault current according to the positive-sequence fault voltage and the third associated information; Calculating the negative sequence fault voltage according to the positive sequence fault current and the first associated information; The zero-sequence fault voltage is calculated according to the positive-sequence fault current and the second associated information.

5. The method according to claim 3, It is characterized in that The three-phase voltage at the fault point includes: a fault phase voltage, a first non-fault phase voltage and a second non-fault phase voltage, and the value of the fault phase voltage is zero; Wherein, determining the three-phase voltage at the fault point according to the fault phase, the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage includes: Determine the conversion relationship between the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage and the three-phase voltage at the fault point; The first non-fault phase voltage and the second non-fault phase voltage are calculated and determined according to the conversion relationship, the positive-sequence fault voltage, the negative-sequence fault voltage and the zero-sequence fault voltage.

6. The method according to claim 1, It is characterized in that The calculating the instantaneous value of the AC output power of the land converter station according to the output current, the power factor and the three-phase voltage at the fault point comprises: Determining phase difference information of the land converter station; Calculating the three-phase output current of the land converter station according to the output current and the phase difference information; The instantaneous value of the AC output power is calculated based on the power factor, the three-phase voltage at the fault point and the three-phase output current.

7. A device for calculating instantaneous power value during a fault of a land converter station in an offshore wind farm, It is characterized in that include: The first determination module is used to determine the fault phase and the location information of the fault point when a single-phase grounding fault occurs in the land converter station, wherein the fault point is located on the transmission line between the land converter station and the land AC system, and the land converter station and the land AC system belong to the offshore wind power flexible direct current grid-connected system; A second determination module, configured to determine the input impedance of the fault point according to the location information; A second determination module is used to determine the output current and power factor of the land converter station and the AC grid voltage phasor of the land AC system; A fourth determination module, configured to determine the three-phase voltage at the fault point according to the fault phase, the input impedance, the output current and the AC grid voltage phasor; A calculation module is used to calculate the instantaneous value of the AC output power of the land converter station according to the output current, the power factor and the three-phase voltage at the fault point.

8. A computer device, It is characterized in that include: at least one processor; as well as a memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method according to any one of claims 1 to 6.

9. A non-transitory computer-readable storage medium storing computer instructions, It is characterized in that in, The computer instructions are used to cause the computer to execute the method according to any one of claims 1 to 6.

10. A computer program product, It is characterized in that The invention comprises a computer program which, when executed by a processor, implements the steps of the method according to any one of claims 1 to 6.

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