CN110378597B - Photovoltaic power generation equipment fault current online calculation method and device - Google Patents
Photovoltaic power generation equipment fault current online calculation method and device Download PDFInfo
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Abstract
The method for calculating the fault current of the photovoltaic power generation equipment on line only needs to calculate based on electrical information at two ends of a line, iterative calculation is not needed in the calculation process, calculation time can be obviously shortened for a photovoltaic power generation unit power distribution network containing high permeability and dispersedly accessed, real-time performance is higher, and the technical problems that the existing method for analyzing the fault of the photovoltaic power generation unit is long in calculation time and the requirement of a power grid fault analysis task on high real-time performance is difficult to meet are solved.
Description
Technical Field
The application relates to the technical field of electric power operation and maintenance, in particular to a method and a device for online calculation of fault current of photovoltaic power generation equipment.
Background
In recent years, as the development technology of renewable energy is matured, more and more photovoltaic power generation devices are connected to a power grid system, become an important component of a power system, and play an extremely important role in a future power grid.
Because the photovoltaic power generation unit adopts a large number of power electronic control elements, the photovoltaic power generation unit has the characteristics of strong nonlinearity and strong coupling, the power output is strongly correlated with the environment, and the output current has intermittence and volatility, so that the fault analysis and calculation become very complicated after the photovoltaic power generation unit is connected to a power grid. The existing photovoltaic power generation unit fault analysis method adopts a node voltage method, namely, the photovoltaic power generation unit is equivalent to a current source model controlled by voltage, and iterative computation is carried out by utilizing an admittance matrix. However, the iterative calculation method has long calculation time and is difficult to meet the requirement of high real-time performance of a power grid fault analysis task.
Disclosure of Invention
The application provides a method and a device for on-line calculation of fault current of photovoltaic power generation equipment, which are used for solving the technical problems that the conventional method for analyzing the faults of the photovoltaic power generation units is long in calculation time and cannot meet the requirement of high real-time performance of a power grid fault analysis task.
In view of this, a first aspect of the present application provides an online calculating method for a fault current of a photovoltaic power generation device, including:
acquiring electrical information of a pilot line MN according to preset power grid topology information, wherein the electrical information comprises: the three-phase voltage value and the three-phase current value of the M side of the bus, the three-phase voltage value and the three-phase current value of the N side of the bus and equipment parameters of each photovoltaic power generation equipment in the circuit MN are obtained;
calculating a first positive sequence voltage value of each public connection point taking the bus M side as a reference through a first preset formula according to the three-phase voltage value and the three-phase current value of the bus M side and the equipment parameters of each photovoltaic power generation equipment, wherein the first preset formula is as follows:
in the formula (I), the compound is shown in the specification,
is the three-phase voltage value of the bus M,
is the three-phase current value of the bus M, Z is the positive sequence impedance of the line,
a first positive sequence voltage at the ith common connection point,
the output current value of the jth photovoltaic power generation equipment with the bus M side as a reference is represented;
according to the three-phase voltage value and the three-phase current value of the N side of the bus and the equipment parameters of each photovoltaic power generation equipment, calculating a second positive sequence voltage value of each public connection point by taking the N side of the bus as a reference through a second preset formula, wherein the second preset formula is as follows:
in the formula (I), the compound is shown in the specification,
is the three-phase voltage value of the bus N,
is the three-phase current value of the bus N, Z is the positive sequence impedance of the line,
a second positive sequence voltage at the ith common connection point,
the output current value of the jth photovoltaic power generation equipment with the bus N side as a reference is represented;
calculating a voltage difference module value of a first positive sequence voltage value and a second positive sequence voltage value of each common connection point, determining the common connection point corresponding to the minimum voltage module value, and calculating an actual positive sequence voltage value of each common connection point through a third preset formula, wherein the third preset formula is as follows:
in the formula (I), the compound is shown in the specification,
is the actual positive sequence voltage value, k, of the ith common connection point*The serial number of the common connection point corresponding to the minimum voltage modulus difference value is used as the serial number of the common connection point;
obtaining a fault current calculation value of each photovoltaic power generation device through a preset fault current calculation formula according to the actual positive sequence voltage value of each common connection point and the device parameter of each photovoltaic power generation device, wherein the fault current calculation formula is as follows:
in the formula (I), the compound is shown in the specification,
the value of the fault current of the jth photovoltaic power generation device,
is the active current output value of the jth photovoltaic power generation device,
is the reactive current output value, I, of the jth photovoltaic power generation plantq_initialRated reactive current, K, output for normal operation of PVCsupportIs the current support factor, PMPPT_PVCTracking the power value for the maximum power point of the photovoltaic power generation device, Iq_REFFor the reactive current output reference value, I, of a photovoltaic power plantd_REFFor photovoltaic power generationThe active current of the device outputs a reference value.
Preferably, the device parameters of the photovoltaic power generation device specifically include: rated capacity, maximum allowable current output coefficient, current support coefficient, rated line voltage, rated current value, maximum overload current and maximum power point tracking power value.
Preferably, the calculating a voltage difference module value of the first positive sequence voltage value and the second positive sequence voltage value of each common connection point, and determining the common connection point corresponding to the minimum voltage module value specifically includes:
calculating the voltage difference module value of the first positive sequence voltage value and the second positive sequence voltage value of each common connection point through a preset minimum voltage difference module value calculation formula, and determining the common connection point corresponding to the minimum voltage module value;
wherein, the minimum voltage difference module value calculation formula is as follows:
in the formula (I), the compound is shown in the specification,
is the minimum voltage difference modulus.
Preferably, the output current value of the jth photovoltaic power generation device in the first preset formula with the bus M side as a reference
The calculation method specifically comprises the following steps:
in the formula Iq_initialRated reactive current output when the PVC normally operates;
is the first positive-sequence voltage value,
a reference value is output for the active current of the photovoltaic power plant,
outputting a reference value for the reactive current of the photovoltaic power generation equipment,
is the active current output value of the photovoltaic power generation equipment,
is the reactive current output value of the photovoltaic power generation equipment,
tracking the power value for the maximum power point of the photovoltaic power plant,
is the rated current value of the photovoltaic power generation equipment,
is the maximum overcurrent of the photovoltaic power generation device.
Preferably, the output current value of the jth photovoltaic power generation device in the second preset formula with the N side of the bus as a reference
The calculation method specifically comprises the following steps:
in the formula Iq_initialRated reactive current output when the PVC normally operates;
is the first positive-sequence voltage value,
a reference value is output for the active current of the photovoltaic power plant,
outputting a reference value for the reactive current of the photovoltaic power generation equipment,
is the active current output value of the photovoltaic power generation equipment,
is the reactive current output value of the photovoltaic power generation equipment,
tracking the power value for the maximum power point of the photovoltaic power plant,
is the rated current value of the photovoltaic power generation equipment,
is the maximum overcurrent of the photovoltaic power generation device.
The second aspect of the present application provides an online calculating device for a fault current of a photovoltaic power generation device, including:
the parameter acquisition unit is used for acquiring the electrical information of the pilot line MN according to preset power grid topology information, wherein the electrical information comprises: the three-phase voltage value and the three-phase current value of the M side of the bus, the three-phase voltage value and the three-phase current value of the N side of the bus and equipment parameters of each photovoltaic power generation equipment in the circuit MN are obtained;
the first positive sequence voltage calculation unit is configured to calculate, according to the three-phase voltage value and the three-phase current value of the bus M side and the device parameters of each photovoltaic power generation device, a first positive sequence voltage value of each common connection point with the bus M side as a reference through a first preset formula, where the first preset formula is:
in the formula (I), the compound is shown in the specification,
is the three-phase voltage value of the bus M,
is the three-phase current value of the bus M, Z is the positive sequence impedance of the line,
a first positive sequence voltage at the ith common connection point,
the output current value of the jth photovoltaic power generation equipment with the bus M side as a reference is represented;
the second positive sequence voltage calculation unit is configured to calculate, according to the three-phase voltage value and the three-phase current value of the N side of the bus and the device parameters of each photovoltaic power generation device, a second positive sequence voltage value of each common connection point based on the N side of the bus by using a second preset formula, where the second preset formula is:
in the formula (I), the compound is shown in the specification,
is the three-phase voltage value of the bus N,
is the three-phase current value of the bus N, Z is the positive sequence impedance of the line,
a second positive sequence voltage at the ith common connection point,
the output current value of the jth photovoltaic power generation equipment with the bus N side as a reference is represented;
the actual positive sequence voltage calculating unit is configured to calculate a voltage difference module value between a first positive sequence voltage value and a second positive sequence voltage value of each common connection point, determine the common connection point corresponding to the minimum voltage module value, and calculate an actual positive sequence voltage value of each common connection point through a third preset formula, where the third preset formula is:
in the formula (I), the compound is shown in the specification,
is the actual positive sequence voltage value, k, of the ith common connection point*The serial number of the common connection point corresponding to the minimum voltage modulus difference value is used as the serial number of the common connection point;
a fault current calculation unit, configured to obtain a fault current calculation value of each photovoltaic power generation device according to the actual positive sequence voltage value of each common connection point and the device parameter of each photovoltaic power generation device through a preset fault current calculation formula, where the fault current calculation formula is:
in the formula (I), the compound is shown in the specification,
the value of the fault current of the jth photovoltaic power generation device,
for the active current output value of the jth photovoltaic power generation equipment，
Is the reactive current output value, I, of the jth photovoltaic power generation plantq_initialRated reactive current, K, output for normal operation of PVCsupportIs the current support factor, PMPPT_PVCTracking the power value for the maximum power point of the photovoltaic power generation device, Iq_REFFor the reactive current output reference value, I, of a photovoltaic power plantd_REFAnd outputting a reference value for the active current of the photovoltaic power generation equipment.
Preferably, the device parameters of the photovoltaic power generation device specifically include: rated capacity, maximum allowable current output coefficient, current support coefficient, rated line voltage, rated current value, maximum overload current and maximum power point tracking power value.
Preferably, the calculating a voltage difference module value of the first positive sequence voltage value and the second positive sequence voltage value of each common connection point, and determining the common connection point corresponding to the minimum voltage module value specifically includes:
calculating the voltage difference module value of the first positive sequence voltage value and the second positive sequence voltage value of each common connection point through a preset minimum voltage difference module value calculation formula, and determining the common connection point corresponding to the minimum voltage module value;
wherein, the minimum voltage difference module value calculation formula is as follows:
in the formula (I), the compound is shown in the specification,
is the minimum voltage difference modulus.
Preferably, the output current value of the jth photovoltaic power generation device in the first preset formula with the bus M side as a reference
The calculation method specifically comprises the following steps:
in the formula Iq_initialRated reactive current output when the PVC normally operates;
is the first positive-sequence voltage value,
a reference value is output for the active current of the photovoltaic power plant,
outputting a reference value for the reactive current of the photovoltaic power generation equipment,
is the active current output value of the photovoltaic power generation equipment,
is the reactive current output value of the photovoltaic power generation equipment,
tracking the power value for the maximum power point of the photovoltaic power plant,
is the rated current value of the photovoltaic power generation equipment,
is the maximum overcurrent of the photovoltaic power generation device.
Preferably, the output current value of the jth photovoltaic power generation device in the second preset formula with the N side of the bus as a reference
The calculation method specifically comprises the following steps:
in the formula Iq_initialRated reactive current output when the PVC normally operates;
is the first positive-sequence voltage value,
a reference value is output for the active current of the photovoltaic power plant,
outputting a reference value for the reactive current of the photovoltaic power generation equipment,
is the active current output value of the photovoltaic power generation equipment,
is the reactive current output value of the photovoltaic power generation equipment,
tracking the power value for the maximum power point of the photovoltaic power plant,
is the rated current value of the photovoltaic power generation equipment,
is the maximum overcurrent of the photovoltaic power generation device.
According to the technical scheme, the embodiment of the application has the following advantages:
the application provides an online calculation method for fault current of photovoltaic power generation equipment, which comprises the following steps: acquiring electrical information of a pilot line MN according to preset power grid topology information; calculating a first positive sequence voltage value of each public connection point by taking the bus M side as a reference through a first preset formula according to the three-phase voltage value and the three-phase current value of the bus M side and the equipment parameters of each photovoltaic power generation equipment; calculating a second positive sequence voltage value of each common connection point by taking the N side of the bus as a reference through a second preset formula according to the three-phase voltage value and the three-phase current value of the N side of the bus and the equipment parameters of each photovoltaic power generation equipment; calculating a voltage difference module value of a first positive sequence voltage value and a second positive sequence voltage value of each public connection point, determining the public connection point corresponding to the minimum voltage module value, and calculating an actual positive sequence voltage value of each public connection point through a third preset formula; and obtaining a fault current calculation value of each photovoltaic power generation device through a preset fault current calculation formula according to the actual positive sequence voltage value of each common connection point and the device parameter of each photovoltaic power generation device.
According to the photovoltaic power generation equipment fault current on-line calculation method, calculation is carried out only on the basis of electrical information at two ends of a line, iterative calculation is not needed in the calculation process, calculation time can be obviously shortened for a photovoltaic power generation unit power distribution network with high permeability and decentralized access, real-time performance is higher, and the technical problems that an existing photovoltaic power generation unit fault analysis method is long in calculation time and cannot meet the requirement of a power grid fault analysis task on high real-time performance are solved.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
Fig. 1 is a schematic flowchart of an embodiment of a method for online calculating a fault current of a photovoltaic power generation device according to the present application;
fig. 2 is a schematic diagram of a power distribution network provided by the present application;
FIG. 3 is a schematic diagram of another power distribution network provided by the present application;
FIG. 4 shows a PVC in the online calculation method for the fault current of the photovoltaic power generation equipment provided by the present application1And PVC2Comparing the calculated value of the fault current with the actual value;
fig. 5 is a schematic structural diagram of an embodiment of an online calculating device for a fault current of a photovoltaic power generation apparatus provided by the present application.
Detailed Description
The embodiment of the application provides a method and a device for online calculation of fault current of photovoltaic power generation equipment, which are used for solving the technical problems that the conventional method for analyzing the faults of the photovoltaic power generation units is long in calculation time and cannot meet the requirement of high real-time performance of a power grid fault analysis task.
In order to make the objects, features and advantages of the present invention more apparent and understandable, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the embodiments described below are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Referring to fig. 1 to 4, a first aspect of the present application provides an online calculating method of a fault current of a photovoltaic power generation device, including:
Wherein the electrical information includes: the three-phase voltage value and the three-phase current value of the M side of the bus, the three-phase voltage value and the three-phase current value of the N side of the bus and equipment parameters of each photovoltaic power generation equipment in the circuit MN are obtained;
in addition, please refer to fig. 2, the preset grid topology information of this embodiment includes: the method comprises the following steps: (1) line positive sequence impedance Z between Points of Common Coupling (PCC) of photovoltaic power generation unitsiI.e. Z0、Z1、…、Zn(the subscript "n" of all symbols in this invention indicates the number of PVCs on the line MN). In addition, Z is0For the 1 st common connection point PCC between the M side of the line MN and the head end of the line1Line positive sequence impedance in between; znFor the n-th point of common coupling PCC of the end of the linenAnd the line positive sequence impedance between the N side; z1For 1 st point of common coupling PCC1With 2 nd point of common coupling PCC2The positive sequence impedance of the lines in between, the meaning of the other symbols, and so on.
(2) The pre-input important control parameters for each PVC include: rated capacity P of each PVCrated_PVCSuch as Prated_PVC_1、Prated_PVC_2、…、Prated_PVC_n(ii) a Maximum allowable current output coefficient K of each PVCmax_PVCE.g. Kmax_PVC_1、Kmax_PVC_2、…、Kmax_PVC_n(ii) a Current support coefficient K of each PVC in fault Low Voltage Ride Through (LVRT) processsupportE.g. Ksupport_1、Ksupport_2、…、Ksupport_n(ii) a Rated line voltage V of common coupling point PCC corresponding to each PVCrated_PCCE.g. Vrated_PCC_1、Vrated_PCC_2、…、Vrated_PCC_n. Respectively calculating the rated current value I of each PVC by using the parametersrated_PVC_iAnd maximum overload current I allowed to be outputmax_PVC_iI.e. by
Imax_PVC_i＝Kmax_PVC_i×Irated_PVC_i(1≤i≤n)。
102, calculating a first positive sequence voltage value of each public connection point taking the bus M side as a reference through a first preset formula according to the three-phase voltage value and the three-phase current value of the bus M side and equipment parameters of each photovoltaic power generation device, wherein the first preset formula is as follows:
in the formula (I), the compound is shown in the specification,
is the three-phase voltage value of the bus M,
is the three-phase current value of the bus M, Z is the positive sequence impedance of the line,
a first positive sequence voltage at the ith common connection point,
the output current value of the jth photovoltaic power generation equipment with the bus M side as a reference is represented;
wherein the calculated value of the output current of any PVC calculated from the M side
The general calculation method of (1) is as follows:
in the formula Iq_initialRated reactive current output when the PVC normally operates;
is the first positive sequence voltage value, and the second positive sequence voltage value,
a reference value is output for the active current of the photovoltaic power plant,
outputting a reference value for the reactive current of the photovoltaic power generation equipment,
is the active current output value of the photovoltaic power generation equipment,
is the reactive current output value of the photovoltaic power generation equipment,
tracking the power value for the maximum power point of the photovoltaic power plant,
is the rated current value of the photovoltaic power generation equipment,
is the maximum overcurrent of the photovoltaic power generation device.
103, calculating a second positive sequence voltage value of each common connection point with the bus N side as a reference through a second preset formula according to the three-phase voltage value and the three-phase current value of the bus N side and the equipment parameters of each photovoltaic power generation equipment, wherein the second preset formula is as follows:
in the formula (I), the compound is shown in the specification,
is the three-phase voltage value of the bus N,
is the three-phase current value of the bus N, Z is the positive sequence impedance of the line,
a second positive sequence voltage at the ith common connection point,
the output current value of the jth photovoltaic power generation equipment with the bus N side as a reference is represented;
calculated value of output Current of any one PVC calculated from N side
The general calculation method of (1) is as follows:
in the formula Iq_initialRated reactive current output when the PVC normally operates;
is the first positive sequence voltage value, and the second positive sequence voltage value,
a reference value is output for the active current of the photovoltaic power plant,
outputting a reference value for the reactive current of the photovoltaic power generation equipment,
is the active current output value of the photovoltaic power generation equipment,
is the reactive current output value of the photovoltaic power generation equipment,
tracking the power value for the maximum power point of the photovoltaic power plant,
is the rated current value of the photovoltaic power generation equipment,
is the maximum overcurrent of the photovoltaic power generation device.
And 104, calculating a voltage difference module value of the first positive sequence voltage value and the second positive sequence voltage value of each public connection point, determining the public connection point corresponding to the minimum voltage module value, and calculating the actual positive sequence voltage value of each public connection point through a third preset formula.
Respective node voltages calculated from the M side
And electrical compaction measurement on bus M
Form a vector group
Respective node voltages calculated from N-side
And electrical compaction measurement on bus N
Form a vector group
Calculating the modulus of the difference between the corresponding elements of the two sets of vectors, and finding out the position number corresponding to the grid point with the minimum voltage difference modulus
Wherein, the minimum voltage difference module value calculation formula is as follows:
in the formula (I), the compound is shown in the specification,
is the minimum voltage difference modulus.
Wherein the third preset formula is as follows:
in the formula (I), the compound is shown in the specification,
is the actual positive sequence voltage value, k, of the ith common connection point*The serial number of the common connection point corresponding to the minimum voltage modulus difference value;
(1) for the PVC between the bus M and the kth PCC, the actual positive sequence voltage value of the PCC is corresponding to
Is equal to
(2) For the PVC between the bus N and the kth PCC, it corresponds to the positive sequence voltage actual value of the PCC
Is equal to
(3) For k × PCC, its positive sequence voltage actual value
105, obtaining a fault current calculation value of each photovoltaic power generation device through a preset fault current calculation formula according to the actual positive sequence voltage value of each common connection point and the device parameter of each photovoltaic power generation device
Wherein, the fault current calculation formula is as follows:
in the formula (I), the compound is shown in the specification,
the value of the fault current of the jth photovoltaic power generation device,
is the active current output value of the jth photovoltaic power generation device,
is the reactive current output value, I, of the jth photovoltaic power generation plantq_initialRated reactive current, K, output for normal operation of PVCsupportIs the current support factor, PMPPT_PVCTracking the power value for the maximum power point of the photovoltaic power generation device, Iq_REFFor the reactive current output reference value, I, of a photovoltaic power plantd_REFAnd outputting a reference value for the active current of the photovoltaic power generation equipment.
According to the photovoltaic power generation equipment fault current on-line calculation method provided by the embodiment, calculation is performed only on the basis of electrical information at two ends of a line, iterative calculation is not needed in the calculation process, calculation time can be obviously shortened for a photovoltaic power generation unit power distribution network with high permeability and decentralized access, real-time performance is higher, and the technical problems that an existing photovoltaic power generation unit fault analysis method is long in calculation time and cannot meet the requirement of a power grid fault analysis task on high real-time performance are solved.
Taking the 10kV distribution network shown in fig. 3 as an example, M and N in the figure are respectively a head-end bus and a tail-end bus of a line MN, and PCC1 and PCC2 are respectively common connection points of two PVCs. The impedance parameter of the line is 0.118+ j0.356 omega/km, the line MN is connected with two PVCs in a grid mode, the corresponding two PCCs cut the line MN into 3 sections, and the lengths of the two sections are 1.5km, 2.5km and 2.0km respectively; the rated capacities of the PVC1 and the PVC2 are both 3.0 MW; when the power grid normally operates, the two PVC do not output reactive current; points of failure f1 and f2 are located on the line between PCC1 and PCC2, PCC2, respectively.
The embodiment also provides another online calculation method for the fault current of the photovoltaic power generation equipment, which comprises the following steps:
step S1: powering on a relay protection device;
step S2: according to the characteristics of the power grid where the relay protection device is located, power grid topology information is input in advance, the power grid topology shown in fig. 2 is taken as an example, the system comprises two PVCs (polyvinyl chloride), two PCCs (policy charging controllers), and the positive sequence impedance of a line section is Z0＝0.177+j0.534Ω、Z1＝0.295+j0.0.890Ω、Z2＝0.236+j0.712Ω。
Step S3: according to the installation condition of PVC on the circuit MN, the important control parameters of each PVC are input into the relay protection device in advance, and the method comprises the following steps: rated capacity P of each PVCrated_PVCI.e. Prated_PVC_1＝3MW、Prated_PVC_23 MW; maximum allowable current output coefficient K of each PVCmax_PVCI.e. Kmax_PVC_1＝2.0、Kmax_PVC_22.0; current support coefficient K of each PVC in fault low voltage ride through LVRT processsupportI.e. Ksupport_1＝2.0、Ksupport_22.0; rated line voltage V of common coupling point PCC corresponding to each PVCrated_PCCAre all 10 kV. Respectively calculating the rated current value I of each PVC by using the parametersrated_PVC_iAnd maximum overload current I allowed to be outputmax_PVC_iI.e. by
Imax_PVC_i＝2×Irated_PVC_i(1≤i≤2)。
Step S4: the relay protection device collects the electric quantities of the voltage transformer and the current transformer which are arranged on two sides of the line MN in real time, namely the three-phase voltage of the bus M
And three-phase current
And three-phase voltage of bus N
And three-phase current
Through the pilot channel of circuit MN, the electric information volume that circuit MN both ends were gathered is interacted in real time, includes: the amount of voltage and current on both sides of the line MN.
Step S5: based on a photovoltaic power generation system quasi-real-time monitoring system, the latest MPPT power value P of each PVC before relay protection starting when a fault occurs is obtainedMPPT_PVCSuch as PMPPT_PVC_1、PMPPT_PVC_2。
Step S6: calculating the positive sequence voltage of each PCC on the line MN from the M side by using the three-phase voltage and the current magnitude collected by the M side of the line
(the symbol subscript "i" denotes the ith PCC), the calculation is as follows:
in the formula (I), the compound is shown in the specification,
represents the calculated value of the output current of the jth PVC calculated from the M side, and the calculated value of the output current of any PVC calculated from the M side
The general calculation method of (1) is as follows:
in the formula Iq_initialRated for output during normal operation of PVCWork current;
the values are calculated for the PCC positive sequence voltage calculated from the M side.
Step S7: calculating the positive sequence voltage of each PCC on the line MN from the N side by using the three-phase voltage and the current magnitude collected by the N side of the line
(the symbol subscript "i" denotes the ith PCC), the calculation is as follows:
in the formula (I), the compound is shown in the specification,
represents the calculated output current value of the jth PVC calculated from the N side, and the calculated output current value of any PVC calculated from the N side
The general calculation method of (1) is as follows:
in the formula (I), the compound is shown in the specification,
calculating a value for PCC positive sequence voltage calculated from N-side
Step S8: respective node voltages calculated from the M side
And electrical compaction measurement on bus M
Form a vector group
Respective node voltages calculated from N-side
And electrical compaction measurement on bus N
Form a vector group
Calculating the modulus of the difference between the corresponding elements of the two sets of vectors, and finding out the position number corresponding to the grid point with the minimum voltage difference modulus
Step S9: based on the obtained PCC location number, i.e. k*Individual PCC, positive sequence voltage actual value to each common connection point PCC
Namely, it is
(1) For the position of the bus M and the k*PVC between PCCs corresponding to actual value of positive sequence voltage of the PCCs
Is equal to
(2) For the position of the bus N and the k*PVC between PCCs corresponding to actual value of positive sequence voltage of the PCCs
Is equal to
(3) For the k-th*PCC of positive sequence voltage actual value
Step S10: according to the latest MPPT power value P of each PVC directly obtainedMPPT_PVCCalculating the actual value of each PCC positive sequence voltage and the control parameters of each PVC which are input into the relay protection device in advance, and estimating the fault current value of each PVC in real time
Namely, it is
Please refer to the schematic comparison diagram of fig. 4, which lists 4 different failure examples:
example 1:
when the system normally operates, the active power output by the four PVC are all 3.0MW, the reactive power is 0, and the relay protection device finishes the steps S1-S3 when the power grid normally operates. At fault point f1A phase a metallic ground short fault occurs. Starting a relay protection device, and collecting corresponding electric quantity in steps S4 and S5; on this basis, the fault currents of the two PVCs are calculated through steps S6-S10. PVC (polyvinyl chloride)1And PVC2The comparison of the calculated current value with the actual value is shown in fig. 4. As can be seen from fig. 4, the calculated value is highly matched with the actual value, regardless of the current amplitude or current phase angle.
Example 2:
when the system normally operates, the active power output by the four PVC are all 3.0MW, the reactive power is 0, and the relay protection device finishes the steps S1-S3 when the power grid normally operates. At fault point f1The a-phase ground short circuit fault occurs, and the transition resistance is 1.0 Ω. Starting a relay protection device, and collecting corresponding electric quantity in steps S4 and S5; on the basis, the fault currents of two PVCs are calculated to be 0.1937-16.6 degrees kA and 0.2219-29.2 degrees kA respectively through steps S6-S10, and the actual fault currents of the two PVCs are 0.1896-16.9 degrees kA and 0.2219-29.2 degrees kA respectively0.2174 & lt-29.6 DEG kA. By comparing the calculated value with the actual value, the online real-time calculation method for the PVC is high in accuracy.
Example 3:
when the system normally operates, the active power output by the four PVC are all 3.0MW, the reactive power is 0, and the relay protection device finishes the steps S1-S3 when the power grid normally operates. At fault point f2A BC two-phase short circuit fault occurs, and the transition resistance is 1.0 Ω. Starting a relay protection device, and collecting corresponding electric quantity in steps S4 and S5; on the basis, the fault currents of two PVCs are calculated to be 0.2143-18.8 degrees kA and 0.3111-32.4 degrees kA respectively through steps S6-S10, and the actual fault currents of the two PVCs are 0.2100-18.4 degrees kA and 0.3057-31.9 degrees kA respectively. By comparing the calculated value with the actual value, the online real-time calculation method for the PVC is high in accuracy.
Example 4:
when the system normally operates, the active power output by the four PVC are all 3.0MW, the reactive power is 0, and the relay protection device finishes the steps S1-S3 when the power grid normally operates. At fault point f2A BC two-phase short circuit fault occurs, and the transition resistance is 10 Ω. Starting a relay protection device, and collecting corresponding electric quantity in steps S4 and S5; on the basis, the fault currents of two PVCs are calculated to be 0.1769-15.6 degrees kA and 0.1924-24.8 degrees kA respectively through steps S6-S10, and the actual fault currents of the two PVCs are 0.1729-15.3 degrees kA and 0.1883-24.3 degrees kA respectively. By comparing the calculated value with the actual value, the online real-time calculation method for the PVC is high in accuracy.
The above is a detailed description of an embodiment of the online calculating method for the fault current of the photovoltaic power generation equipment provided by the present application, and the following is a detailed description of an embodiment of the online calculating device for the fault current of the photovoltaic power generation equipment provided by the present application.
Referring to fig. 5, an embodiment of the present application provides an online calculating apparatus for a fault current of a photovoltaic power generation device, including:
the parameter obtaining unit 201 is configured to obtain electrical information of the pilot line MN according to preset power grid topology information, where the electrical information includes: the three-phase voltage value and the three-phase current value of the M side of the bus, the three-phase voltage value and the three-phase current value of the N side of the bus and equipment parameters of each photovoltaic power generation equipment in the circuit MN are obtained;
the first positive sequence voltage calculation unit 202 is configured to calculate, according to the three-phase voltage value and the three-phase current value of the bus M side and the device parameters of each photovoltaic power generation device, a first positive sequence voltage value of each common connection point with the bus M side as a reference through a first preset formula, where the first preset formula is:
in the formula (I), the compound is shown in the specification,
is the three-phase voltage value of the bus M,
is the three-phase current value of the bus M, Z is the positive sequence impedance of the line,
a first positive sequence voltage at the ith common connection point,
the output current value of the jth photovoltaic power generation equipment with the bus M side as a reference is represented;
a second positive sequence voltage calculating unit 203, configured to calculate, according to the three-phase voltage value and the three-phase current value of the bus N side and the device parameters of each photovoltaic power generation device, a second positive sequence voltage value of each common connection point using the bus N side as a reference through a second preset formula, where the second preset formula is:
in the formula (I), the compound is shown in the specification,
is the three-phase voltage value of the bus N,
is the three-phase current value of the bus N, Z is the positive sequence impedance of the line,
a second positive sequence voltage at the ith common connection point,
the output current value of the jth photovoltaic power generation equipment with the bus N side as a reference is represented;
the actual positive sequence voltage calculating unit 204 is configured to calculate a voltage difference module value between a first positive sequence voltage value and a second positive sequence voltage value of each common connection point, determine the common connection point corresponding to the minimum voltage module value, and calculate an actual positive sequence voltage value of each common connection point according to a third preset formula, where the third preset formula is:
in the formula (I), the compound is shown in the specification,
is the actual positive sequence voltage value, k, of the ith common connection point*The serial number of the common connection point corresponding to the minimum voltage modulus difference value;
the fault current calculation unit 205 is configured to obtain a fault current calculation value of each photovoltaic power generation device according to the actual positive sequence voltage value of each common connection point and the device parameter of each photovoltaic power generation device through a preset fault current calculation formula, where the fault current calculation formula is:
in the formula (I), the compound is shown in the specification,
the value of the fault current of the jth photovoltaic power generation device,
is the active current output value of the jth photovoltaic power generation device,
is the reactive current output value, I, of the jth photovoltaic power generation plantq_initialRated reactive current, K, output for normal operation of PVCsupportIs the current support factor, PMPPT_PVCTracking the power value for the maximum power point of the photovoltaic power generation device, Iq_REFFor the reactive current output reference value, I, of a photovoltaic power plantd_REFAnd outputting a reference value for the active current of the photovoltaic power generation equipment.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The terms "first," "second," "third," "fourth," and the like in the description of the application and the above-described figures, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes. The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.
Claims (10)
1. A photovoltaic power generation equipment fault current online calculation method is characterized by comprising the following steps:
acquiring electrical information of a pilot line MN according to preset power grid topology information, wherein the electrical information comprises: the three-phase voltage value and the three-phase current value of the M side of the bus, the three-phase voltage value and the three-phase current value of the N side of the bus and equipment parameters of each photovoltaic power generation equipment in the circuit MN are obtained;
calculating a first positive sequence voltage value of each public connection point taking the bus M side as a reference through a first preset formula according to the three-phase voltage value and the three-phase current value of the bus M side and the equipment parameters of each photovoltaic power generation equipment, wherein the first preset formula is as follows:
in the formula (I), the compound is shown in the specification,
is the three-phase voltage value of the bus M,
is the three-phase current value of the bus M, Z is the positive sequence impedance of the line,
a first positive sequence voltage at the ith common connection point,
the output current value of the jth photovoltaic power generation equipment with the bus M side as a reference is represented;
according to the three-phase voltage value and the three-phase current value of the N side of the bus and the equipment parameters of each photovoltaic power generation equipment, calculating a second positive sequence voltage value of each public connection point by taking the N side of the bus as a reference through a second preset formula, wherein the second preset formula is as follows:
in the formula (I), the compound is shown in the specification,
is the three-phase voltage value of the bus N,
is the three-phase current value of the bus N, Z is the positive sequence impedance of the line,
a second positive sequence voltage at the ith common connection point,
the output current value of the jth photovoltaic power generation equipment with the bus N side as a reference is represented;
calculating a voltage difference module value of a first positive sequence voltage value and a second positive sequence voltage value of each common connection point, determining the common connection point corresponding to the minimum voltage module value, and calculating an actual positive sequence voltage value of each common connection point through a third preset formula, wherein the third preset formula is as follows:
in the formula (I), the compound is shown in the specification,
is the actual positive sequence voltage value, k, of the ith common connection point*The serial number of the common connection point corresponding to the minimum voltage modulus difference value is used as the serial number of the common connection point;
obtaining a fault current calculation value of each photovoltaic power generation device through a preset fault current calculation formula according to the actual positive sequence voltage value of each common connection point and the device parameter of each photovoltaic power generation device, wherein the fault current calculation formula is as follows:
in the formula (I), the compound is shown in the specification,
the value of the fault current of the jth photovoltaic power generation device,
is the active current output value of the jth photovoltaic power generation device,
is the reactive current output value, I, of the jth photovoltaic power generation plantq_initialRated reactive current, K, output for normal operation of PVCsupportIs the current support factor, PMPPT_PVCTracking the power value for the maximum power point of the photovoltaic power generation device, Iq_REFFor the reactive current output reference value, I, of a photovoltaic power plantd_REFA reference value is output for the active current of the photovoltaic power plant,
the rated line voltage of the jth common coupling point PCC,
is the rated current value of the jth photovoltaic power generation device,
the maximum overload current of the jth photovoltaic power generation device is n, and the number of the PVC on the line MN is n.
2. The method according to claim 1, wherein the equipment parameters of the photovoltaic power generation equipment specifically include: rated capacity, maximum allowable current output coefficient, current support coefficient, rated line voltage, rated current value, maximum overload current and maximum power point tracking power value.
3. The method according to claim 1, wherein the calculating a voltage difference module value between a first positive sequence voltage value and a second positive sequence voltage value of each common connection point, and the determining the common connection point corresponding to the minimum voltage module value specifically comprises:
calculating the voltage difference module value of the first positive sequence voltage value and the second positive sequence voltage value of each common connection point through a preset minimum voltage difference module value calculation formula, and determining the common connection point corresponding to the minimum voltage module value;
wherein, the minimum voltage difference module value calculation formula is as follows:
in the formula (I), the compound is shown in the specification,
is the minimum voltage difference modulus.
4. The method according to claim 2, wherein the output current value of the jth photovoltaic power generation device in the first preset formula with reference to the side of the bus M
The calculation method specifically comprises the following steps:
in the formula Iq_initialRated reactive current output when the PVC normally operates;
is the first positive-sequence voltage value,
a reference value is output for the active current of the photovoltaic power plant,
outputting a reference value for the reactive current of the photovoltaic power generation equipment,
is the active current output value of the photovoltaic power generation equipment,
is the reactive current output value of the photovoltaic power generation equipment,
tracking the power value for the maximum power point of the photovoltaic power plant,
for rated current of photovoltaic power generation equipmentThe value of the one or more of the one,
is the maximum overcurrent of the photovoltaic power generation device.
5. The method according to claim 2, wherein the output current value of the jth photovoltaic power generation device in the second preset formula with reference to the N side of the bus bar
The calculation method specifically comprises the following steps:
in the formula Iq_initialRated reactive current output when the PVC normally operates;
is the first positive-sequence voltage value,
a reference value is output for the active current of the photovoltaic power plant,
outputting a reference value for the reactive current of the photovoltaic power generation equipment,
is the active current output value of the photovoltaic power generation equipment,
is the reactive current output value of the photovoltaic power generation equipment,
is a photovoltaicThe maximum power point of the power generation device tracks the power value,
is the rated current value of the photovoltaic power generation equipment,
is the maximum overcurrent of the photovoltaic power generation device.
6. An online calculating device for fault current of photovoltaic power generation equipment is characterized by comprising:
the parameter acquisition unit is used for acquiring the electrical information of the pilot line MN according to preset power grid topology information, wherein the electrical information comprises: the three-phase voltage value and the three-phase current value of the M side of the bus, the three-phase voltage value and the three-phase current value of the N side of the bus and equipment parameters of each photovoltaic power generation equipment in the circuit MN are obtained;
the first positive sequence voltage calculation unit is configured to calculate, according to the three-phase voltage value and the three-phase current value of the bus M side and the device parameters of each photovoltaic power generation device, a first positive sequence voltage value of each common connection point with the bus M side as a reference through a first preset formula, where the first preset formula is:
in the formula (I), the compound is shown in the specification,
is the three-phase voltage value of the bus M,
is the three-phase current value of the bus M, Z is the positive sequence impedance of the line,
is the ithA first positive sequence voltage of the common connection point,
the output current value of the jth photovoltaic power generation equipment with the bus M side as a reference is represented;
the second positive sequence voltage calculation unit is configured to calculate, according to the three-phase voltage value and the three-phase current value of the N side of the bus and the device parameters of each photovoltaic power generation device, a second positive sequence voltage value of each common connection point based on the N side of the bus by using a second preset formula, where the second preset formula is:
in the formula (I), the compound is shown in the specification,
is the three-phase voltage value of the bus N,
is the three-phase current value of the bus N, Z is the positive sequence impedance of the line,
a second positive sequence voltage at the ith common connection point,
the output current value of the jth photovoltaic power generation equipment with the bus N side as a reference is represented;
the actual positive sequence voltage calculating unit is configured to calculate a voltage difference module value between a first positive sequence voltage value and a second positive sequence voltage value of each common connection point, determine the common connection point corresponding to the minimum voltage module value, and calculate an actual positive sequence voltage value of each common connection point through a third preset formula, where the third preset formula is:
in the formula (I), the compound is shown in the specification,
is the actual positive sequence voltage value, k, of the ith common connection point*The serial number of the common connection point corresponding to the minimum voltage modulus difference value is used as the serial number of the common connection point;
a fault current calculation unit, configured to obtain a fault current calculation value of each photovoltaic power generation device according to the actual positive sequence voltage value of each common connection point and the device parameter of each photovoltaic power generation device through a preset fault current calculation formula, where the fault current calculation formula is:
in the formula (I), the compound is shown in the specification,
the value of the fault current of the jth photovoltaic power generation device,
is the active current output value of the jth photovoltaic power generation device,
is the reactive current output value, I, of the jth photovoltaic power generation plantq_initialRated reactive current, K, output for normal operation of PVCsupportIs the current support factor, PMPPT_PVCTracking the power value for the maximum power point of the photovoltaic power generation device, Iq_REFFor the reactive current output reference value, I, of a photovoltaic power plantd_REFA reference value is output for the active current of the photovoltaic power plant,
the rated line voltage of the jth common coupling point PCC,
is the rated current value of the jth photovoltaic power generation device,
the maximum overload current of the jth photovoltaic power generation device is n, and the number of the PVC on the line MN is n.
7. The apparatus according to claim 6, wherein the device parameters of the photovoltaic power generation device specifically include: rated capacity, maximum allowable current output coefficient, current support coefficient, rated line voltage, rated current value, maximum overload current and maximum power point tracking power value.
8. The apparatus according to claim 6, wherein the calculating a voltage difference module value between the first positive sequence voltage value and the second positive sequence voltage value of each common connection point, and the determining the common connection point corresponding to the minimum voltage module value specifically comprises:
calculating the voltage difference module value of the first positive sequence voltage value and the second positive sequence voltage value of each common connection point through a preset minimum voltage difference module value calculation formula, and determining the common connection point corresponding to the minimum voltage module value;
wherein, the minimum voltage difference module value calculation formula is as follows:
in the formula (I), the compound is shown in the specification,
is the minimum voltage difference modulus.
9. The apparatus according to claim 7, wherein the output current value of the jth photovoltaic power generation device in the first preset formula is based on the side of the bus bar M
The calculation method specifically comprises the following steps:
in the formula Iq_initialRated reactive current output when the PVC normally operates;
is the first positive-sequence voltage value,
a reference value is output for the active current of the photovoltaic power plant,
outputting a reference value for the reactive current of the photovoltaic power generation equipment,
is the active current output value of the photovoltaic power generation equipment,
is the reactive current output value of the photovoltaic power generation equipment,
tracking the power value for the maximum power point of the photovoltaic power plant,
is the rated current value of the photovoltaic power generation equipment,
is the maximum overcurrent of the photovoltaic power generation device.
10. The apparatus according to claim 7, wherein the output current value of the jth photovoltaic power generation device in the second preset formula based on the N side of the bus bar is used as a reference
The calculation method specifically comprises the following steps:
in the formula Iq_initialRated reactive current output when the PVC normally operates;
is the first positive-sequence voltage value,
a reference value is output for the active current of the photovoltaic power plant,
outputting a reference value for the reactive current of the photovoltaic power generation equipment,
is the active current output value of the photovoltaic power generation equipment,
is the reactive current output value of the photovoltaic power generation equipment,
for maximum power point tracking of photovoltaic power generation equipmentThe value of the rate is,
is the rated current value of the photovoltaic power generation equipment,
is the maximum overcurrent of the photovoltaic power generation device.
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