CN109375099B - Fault detection method for grid-connected relay of photovoltaic inverter - Google Patents
Fault detection method for grid-connected relay of photovoltaic inverter Download PDFInfo
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Abstract
The invention discloses a fault detection method of a grid-connected relay of a photovoltaic inverter, which comprises the following steps: the sampling circuit detection is used for judging whether the power grid voltage sampling circuit is abnormal or not; the impedance grounding detection is used for judging whether the condition of the fire wire impedance grounding exists or not; if the live wire impedance grounding exists, Relay detection under the impedance grounding condition is carried out for Relay abnormity detection under the live wire impedance grounding condition; if the condition of live wire impedance grounding does not exist, Relay detection under the non-impedance grounding condition is carried out for Relay abnormity detection under the non-live wire impedance grounding condition; and Relay contact impedance detection is used for detecting whether Relay contact impedance is too large. The method can distinguish the inverter grid-connected relay fault from the abnormal condition causing the false alarm of the grid-connected relay fault, ensure the rapid positioning of the fault reason and ensure the reliable grid connection of the machine.
Description
Technical Field
The invention relates to the field of grid-connected relays of photovoltaic inverters, in particular to a fault detection method of a grid-connected relay of a photovoltaic inverter.
Background
With the continuous development of the photovoltaic industry, the requirements for the reliable and stable operation of a photovoltaic power generation system are higher and higher. Safety regulations generally require that the photovoltaic inverter has two groups of series-connected grid-connected relays in order to ensure that the photovoltaic inverter can be reliably disconnected at the time of a fault, and whether the two groups of relays can be reliably disconnected and closed needs to be detected before the inverter is connected to the grid. At present, the conventional detection method only judges whether the grid-connected relay is normal by detecting the voltage of a power grid and the inversion voltage, and the method has a large blind area. Faults such as sampling circuit abnormity, live wire impedance grounding and the like easily cause false alarm of grid-connected relay faults. The difficulty of relay fault detection is greatly improved, the maintenance cost is increased, and meanwhile, due to the fact that the inverter is stopped due to false alarm, the power generation amount of the system is reduced, and the benefit of a client is damaged.
Disclosure of Invention
In order to solve the problem of false alarm of the inverter grid-connected relay, the invention aims to provide a fault detection method of the photovoltaic inverter grid-connected relay, which can distinguish the fault of the inverter grid-connected relay from the abnormal condition causing the false alarm of the fault of the grid-connected relay, ensure the rapid positioning of the fault reason and ensure the reliable grid connection of a machine.
In order to achieve the purpose, the invention adopts the technical scheme that:
a fault detection method of a grid-connected Relay of a photovoltaic inverter (referred to herein as a Relay for short) including a main Relay connected to an inverter side and an auxiliary Relay connected to a grid side or a load side of three phases, the main Relay and the auxiliary Relay of each phase being connected in series with each other, the fault detection method comprising:
the sampling circuit detection is used for judging whether the power grid voltage sampling circuit is abnormal or not;
the impedance grounding detection is used for judging whether the condition of the fire wire impedance grounding exists or not; if the live wire impedance grounding exists, Relay detection under the impedance grounding condition is carried out for Relay abnormity detection under the live wire impedance grounding condition; if the condition of live wire impedance grounding does not exist, Relay detection under the non-impedance grounding condition is carried out for Relay abnormity detection under the non-live wire impedance grounding condition;
and Relay contact impedance detection is used for detecting whether Relay contact impedance is too large.
If the sampling circuit detects and judges that the power grid voltage sampling circuit is not abnormal, the impedance grounding detection is carried out; and if the Relay abnormity detection of the live line impedance grounding condition or the Relay abnormity detection of the non-live line impedance grounding condition does not detect the Relay abnormity, carrying out the Relay contact impedance detection.
Further, the sampling circuit detection comprises the following steps:
calculating three-phase grid voltage sampling Ugrid_a_sample，Ugrid_b_sample，Ugrid_c_sampleSum of Uzero_avgEffective value of (U)zero_rms；
Judging whether m (m) exists in n power grid periods<n) times satisfy Uzero_rms>Uzero_setOtherwise, reporting the abnormal fault of the hardware of the sampling circuit, and if so, carrying out impedance grounding detection.
Further, the impedance grounding detection comprises the following steps:
calculating the effective value U of the inversion voltage between the main Relay and the auxiliary Relay of the three phasesinv_a，Uinv_b，Uinv_cSequencing the three-phase inversion voltage to obtain Uinv_max，Uinv_mid，Uinv_min；
Judge Uinv_midWhether it satisfies Umin_set<Uinv_mid<Umax_setIf the impedance grounding condition is met, Relay detection is carried out under the impedance grounding condition, if the impedance grounding condition is not met, the next step is carried out, wherein Umin_set、Umax_setRespectively represent the minimum inversion voltage set value (e.g., 0.3U)grid) Maximum inverter voltage set point (e.g., 0.7U)grid）；
Calculating three-phase auxiliary Relay terminal voltage Urelay_a，Urelay_b，Urelay_c；
Judging at least two secondary Relay terminal voltages Urelay_x<k1*UgridIf yes, a Relay fault is reported, otherwise, the next step is executed, wherein Urelay_xIs selected from Urelay_a，Urelay_b，Urelay_c，k1Is a proportionality coefficient (e.g., 0.3), UgridIs the grid voltage;
judging that only one phase of secondary Relay terminal voltage U existsrelay_x<k1*UgridAnd three-phase inversion voltage Uinv_x<k2*UgridIf yes, executing the next step, otherwise, executing Relay detection under the non-impedance grounding condition, wherein Uinv_xIs selected from Uinv_a，Uinv_b，Uinv_c， k2A scaling factor (e.g., 0.7);
subtracting the sampling voltage of the fault phase power grid from the three-phase inversion sampling voltage to obtain a new three-phase inversion sampling voltage, and calculating to obtain an inversion voltage effective value U from the new inversion sampling voltageinv_a，Uinv_b，Uinv_cAnd performing Relay detection under the non-impedance grounded condition, wherein Ugrid_yTo satisfy U in the previous steprelay_x<k1*UgridThe grid voltage of that phase.
Further, the Relay detection under the non-impedance grounding condition comprises the following steps:
judge Urelay_x<c1*UgridIf yes, reporting a Relay fault, otherwise, carrying out the next step, wherein c1A scaling factor (e.g., 0.3);
according to the network voltage UgridThe instruction turns on PWM to generate open-loop voltage and judge Uinv_x>c2*UgridIf yes, reporting a Relay fault, otherwise, carrying out the next step, wherein c2A scaling factor (e.g., 0.7);
closing the auxiliary Relay, and judging Uinv_x<c2*UgridIf yes, reporting a Relay fault, otherwise, carrying out the next step;
closing the main Relay and carrying out the next step;
turn off PWM and judge Uinv_x<c2*UgridIf yes, a Relay fault is reported, otherwise, the Relay contact impedance detection is carried out.
Further, the Relay detection under the impedance grounding condition comprises the following steps:
judging the absolute value of the difference between two three-phase inversion voltage effective values>UminReporting a Relay fault; judging the absolute value of the difference between two three-phase inversion voltage effective values<UminAnd the number of times that the product of instantaneous values of two-phase inversion voltages in the period of the power grid is less than zero>Count reporting Relay failure, otherwise, proceeding to the next step, wherein UminAt the minimum setting voltage, Count is the setting Count value (e.g., 20 times);
according to the network voltage UgridThe PWM is instructed to be started to generate open-loop voltage, and the absolute value of the difference value of every two effective values of the three-phase inverter voltage is judged>UminReporting a Relay fault; judging the absolute value of the difference between two three-phase inversion voltage effective values<UminAnd the number of times that the product of instantaneous values of two-phase inversion voltages in the period of the power grid is less than zero>Counting, reporting a Relay fault, and otherwise, performing the next step;
closing the minor Relay, and judgingAbsolute value of pairwise difference of effective values of Relay voltages>UminReporting a Relay fault; judging the absolute value of the difference between two inverter voltage effective values>UminAnd the number of times that the product of instantaneous values of two-phase inversion voltages in the period of the power grid is less than zero>Counting, reporting a Relay fault, and otherwise, performing the next step;
closing the main Relay and carrying out the next step;
turn off PWM and judge Uinv_x<c2*UgridIf yes, reporting a Relay fault, otherwise, detecting the Relay contact impedance, wherein Uinv_xIs selected from Uinv_a，Uinv_b，Uinv_c，c2Is a proportionality coefficient, UgridIs the grid voltage.
Further, the Relay contact impedance detection comprises the following steps:
machine synchronization, judgment Urelay_x>k3*UgridIf yes, a Relay fault is reported, wherein k3Is a scaling factor (e.g., 0.2).
In a specific embodiment, the method specifically comprises the following steps:
s1, calculating three-phase grid voltage sampling Ugrid_a_sample，Ugrid_b_sample，Ugrid_c_sampleSum of Uzero_avgEffective value of (U)zero_rms；
S2, judging whether m (m) exists in n power grid periods<n) times satisfy Uzero_rms>Uzero_setOtherwise, reporting the hardware abnormal fault of the sampling circuit, if so, performing the following step S3 (performing the impedance grounding detection);
s3, calculating the effective value U of the inverter voltage between the main Relay and the auxiliary Relay of the three phasesinv_a，Uinv_b，Uinv_cSequencing the three-phase inversion voltage to obtain Uinv_max，Uinv_mid，Uinv_min；
S4, judging Uinv_midWhether it satisfies Umin_set<Uinv_mid<Umax_setIf the impedance grounding condition is satisfied, the following step 9b (Relay detection under the impedance grounding condition) is performed, but the impedance grounding condition is not satisfiedIf so, the following step S5 is performed, wherein Umin_set、Umax_setRespectively represent the minimum inversion voltage set value (0.3U)grid) Maximum inversion voltage set value (0.7U)grid）；
S5, calculating three-phase auxiliary Relay terminal voltage Urelay_a，Urelay_b，Urelay_c；
S6, judging at least two secondary Relay terminal voltages Urelay_x<k1*UgridIf yes, a Relay fault is reported, otherwise, the following step S7 is executed, wherein Urelay_xIs selected from Urelay_a，Urelay_b，Urelay_c，k1Is a proportionality coefficient (0.3), UgridIs the grid voltage;
s7, judging that only one secondary Relay terminal voltage U existsrelay_x<k1*UgridAnd three-phase inversion voltage Uinv_x<k2*UgridIf yes, then step S8 is performed, otherwise step 9a is performed to perform Relay detection of the non-impedance grounding condition, where Uinv_xIs selected from Uinv_a，Uinv_b，Uinv_c， k2Is a proportionality coefficient (0.7);
s8, subtracting the sampling voltage of the fault phase network from the sampling voltage of the three-phase inversion to obtain a new sampling voltage of the three-phase inversion, and calculating to obtain an effective value U of the inversion voltage from the new sampling voltage of the inversioninv_a，Uinv_b，Uinv_cPerforming the following step 9a, wherein Ugrid_yTo satisfy U in the previous steprelay_x<k1*UgridThe grid voltage of that phase;
s9a, judgment Urelay_x<c1*UgridIf yes, a Relay fault is reported, otherwise, the following step 10a is executed, wherein c1Is a proportionality coefficient (0.3);
s10a, according to the power grid voltage UgridThe instruction turns on PWM to generate open-loop voltage and judge Uinv_x>c2*UgridIf yes, reporting a Relay fault, otherwise, executing the following step 11a, wherein c2Is a proportionality coefficient (0.7);
s11a, closing the auxiliary Relay, and judging Uinv_x<c2*UgridIf yes, reporting a Relay fault, otherwise, executing the following step 12 a;
s12a, closing the main Relay, and executing the following step 13 a;
s13a, turning off PWM and judging Uinv_x<c2*UgridIf yes, reporting a Relay fault, otherwise, executing the following step 14;
s9b, judging the absolute value of the difference of every two effective values of the three-phase inverter voltage>UminReporting a Relay fault; judging the absolute value of the difference between two three-phase inversion voltage effective values<UminAnd the number of times that the product of instantaneous values of two-phase inversion voltages in the period of the power grid is less than zero>Count reporting Relay failure, otherwise, performing the following step 10b, wherein UminThe minimum setting voltage value and the Count is the setting Count value (20 times);
s10b, according to the power grid voltage UgridThe PWM is instructed to be started to generate open-loop voltage, and the absolute value of the difference value of every two effective values of the three-phase inverter voltage is judged>UminReporting a Relay fault; judging the absolute value of the difference between two three-phase inversion voltage effective values<UminAnd the number of times that the product of instantaneous values of two-phase inversion voltages in the period of the power grid is less than zero>Count, report Relay trouble, otherwise carry out the following step 11 b;
s11b, closing the auxiliary Relay, and judging the absolute value of the pairwise difference of effective values of Relay voltages>UminReporting a Relay fault; judging the absolute value of the difference between two inverter voltage effective values>UminAnd the number of times that the product of instantaneous values of two-phase inversion voltages in the period of the power grid is less than zero>Count, report Relay trouble, otherwise carry out the following step 12 b;
s12b, closing the main Relay, and executing the following step 13 b;
s13b, turning off PWM and judging Uinv_x<c2*UgridIf yes, reporting a Relay fault, otherwise, executing the following step 14;
s14, machine synchronization and U judgmentrelay_x>k3*UgridIf yes, a Relay fault is reported, wherein k3Is a proportionality coefficient (0.2)）。
Compared with the prior art, the invention has the following advantages by adopting the scheme:
the fault detection method can effectively distinguish the false alarm of the relay detection fault caused by sampling circuit abnormity, live wire grounding and impedance grounding, can quickly locate the fault reason and quickly take corresponding measures, not only reduces the power generation loss caused by machine halt due to false alarm, but also can quickly locate and solve problems, reduce maintenance cost and better serve customers.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a schematic diagram of a hardware system to which the fault detection method of the present invention is applied;
fig. 2 is a flow chart of a fault detection method according to the present invention.
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the advantages and features of the invention may be more readily understood by those skilled in the art. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Fig. 1 shows a hardware system of a photovoltaic inverter, and the fault detection method provided by the invention is used for detecting whether a relay of the hardware system has a fault and a fault reason. Referring to fig. 1, the Grid-connected Relay includes three-phase main relays and three-phase auxiliary relays, wherein each main Relay is electrically connected to an Inverter side (Inverter), each auxiliary Relay is electrically connected to a Grid side (Grid) or a load side, and the main relays and the auxiliary relays of each phase are connected in series. And a power grid voltage sampling circuit and an inverter voltage sampling circuit are respectively arranged on the output side of the auxiliary Relay of each phase and between the main Relay and the auxiliary Relay.
The invention discloses a fault detection method of a grid-connected relay of a photovoltaic inverter, which comprises the following steps: detecting by a sampling circuit; detecting impedance grounding; relay detection under the impedance grounding condition; relay detection under a non-impedance grounding condition; relay contact impedance detection. The sampling circuit detects whether the power grid voltage sampling circuit is abnormal or not; the impedance grounding detection is used for judging whether a condition of live wire impedance grounding exists or not; relay detection under the impedance grounding condition is used for Relay abnormality detection under the live wire impedance grounding condition; the Relay detection logic under the non-impedance grounding condition is used for Relay abnormality detection under the non-live wire impedance grounding condition; relay contact impedance detection is used for detecting whether Relay has the problem of excessive contact impedance.
Referring to a flow chart shown in fig. 2, the method for detecting the fault of the grid-connected relay of the photovoltaic inverter specifically comprises the following steps:
A. the sampling circuit detects:
s1, calculating three-phase grid voltage sampling Ugrid_a_sample，Ugrid_b_sample，Ugrid_c_sample(obtained by processing sampling values of the inverter grid voltage sampling circuit by an ADC (analog to digital converter) module of the DSP chip) sum Uzero_avgEffective value of (U)zero_rms；
S2, judging whether m (m) exists in n power grid periods<n) times satisfy Uzero_rms>Uzero_setOtherwise, reporting the hardware abnormal fault of the sampling circuit, if so, entering step S3.
B. Impedance grounding detection:
s3, calculating the effective value U of the inverter voltage between the main Relay and the auxiliary Relay of the three phasesinv_a,Uinv_b,Uinv_cSorting U of three-phase inversion voltageinv_max，Uinv_mid，Uinv_min；
S4, judging Uinv_midWhether it satisfies Umin_set<Uinv_mid<Umax_setIf the requirement is met, the method goes to stepStep S9b, if not, the process goes to step S5;
s5, calculating the effective value U of the voltage at the three-phase auxiliary Relay terminalrelay_a，Urelay_b，Urelay_c；
S6, cutting off voltage U of at least two secondary relaysrelay_x<k1*UgridIf yes, a Relay fault is reported, otherwise, the step S7 is carried out;
s7, judging that only one secondary Relay terminal voltage (assumed as a phase) U existsrelay_a<k1*UgridAnd three-phase inversion voltage Uinv_x<k2*UgridIf yes, go to step S8, otherwise go to step S9 a;
s8, subtracting the sampling voltage of the fault phase network from the sampling voltage of the three-phase inversion to obtain a new sampling voltage of the three-phase inversion (for example, assuming that U is satisfied in step S7)relay_a<k1*UgridThe phase a is a fault phase), the inversion voltage effective value U is obtained by calculating the new inversion sampling voltageinv_a，Uinv_b，Uinv_cThe process proceeds to step S9 a.
C. Relay test under non-impedance conditions:
s9a, judgment Urelay_x<c1*UgridReporting a Relay fault, otherwise, entering a step S10 a;
s10a, according to the grid voltage Ugrid command, opening PWM to generate open-loop voltage, and judging Uinv_x>c2*UgridReporting a Relay fault, otherwise, entering a step S11 a;
s11a, closing the auxiliary Relay, and judging Uinv_x<c2*UgridIf yes, a Relay fault is reported, otherwise, the step S12a is carried out;
s12a, closing the main Relay, and entering the step S13 a;
s13a, turning off PWM and judging Uinv_x<c2*UgridIf yes, a Relay fault is reported, otherwise, the step S14 is entered.
D. Relay test under impedance conditions:
s9b, judging the absolute value of the pairwise difference of the effective values of the three-phase inverter voltages>UminReport reason of RelayA barrier; judging the absolute value of the difference between the effective values of the three-phase inverter voltages<UminAnd the number of times that the product of two-phase instantaneous values in the period of the power grid is less than zero>Count, report Relay fault, otherwise go to step S10 b;
s10b, according to the grid voltage Ugrid command, opening PWM to generate open-loop voltage, and judging the absolute value of pairwise difference of effective values of three-phase inverter voltage>UminIf yes, a Relay fault is reported; judging the absolute value of the difference between the effective values of the three-phase inverter voltages<UminAnd the number of times that the product of two-phase instantaneous values in the period of the power grid is less than zero>Count, reporting Relay fault, otherwise entering step S11 b;
s11b, closing the auxiliary Relay, and judging the absolute value of pairwise difference of effective values of Relay voltages>UminReporting a Relay fault; judging the absolute value of the difference between two inverter voltage effective values>UminAnd the number of times that the product of two-phase instantaneous values in the period of the power grid is less than zero>Count, reporting Relay fault, otherwise entering step S12 b;
s12b, closing the main Relay, and entering the step S13 b;
s13b, turning off PWM and judging Uinv_x<c2*UgridIf yes, a Relay fault is reported, otherwise, the step S14 is entered.
E. Relay contact impedance detection:
s14: machine synchronization, judgment Urelay_x>k3*UgridIf yes, a Relay fault is reported.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and are preferred embodiments, which are intended to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (4)
1. A fault detection method for a grid-connected Relay of a photovoltaic inverter is disclosed, wherein the grid-connected Relay comprises a three-phase main Relay connected with an inversion side and an auxiliary Relay connected with a power grid side or a load side, and the main Relay and the auxiliary Relay of each phase are connected in series, and the fault detection method is characterized by comprising the following steps:
detecting and judging whether the power grid voltage sampling circuit is abnormal or not through the sampling circuit, and if the power grid voltage sampling circuit is judged to be abnormal, executing impedance grounding detection;
judging whether a condition of live wire impedance grounding exists through impedance grounding detection;
if the live wire impedance grounding condition exists, Relay detection under the impedance grounding condition is executed, and Relay abnormity detection under the live wire impedance grounding condition is realized;
if the condition of live wire impedance grounding does not exist, Relay detection under the non-impedance grounding condition is executed, and Relay abnormity detection under the non-live wire impedance grounding condition is realized;
if Relay abnormity detection of the live line impedance grounding condition or Relay abnormity detection of the non-live line impedance grounding condition does not detect Relay abnormity, Relay contact impedance detection is executed to detect whether Relay contact impedance is too large;
wherein the impedance grounding detection comprises the following steps:
calculating the effective value U of the inversion voltage between the main Relay and the auxiliary Relay of the three phasesinv_a，Uinv_b，Uinv_cSequencing the three-phase inversion voltage to obtain Uinv_max，Uinv_mid，Uinv_min；
Judge Uinv_midWhether it satisfies Umin_set<Uinv_mid<Umax_setIf the impedance grounding condition is met, Relay detection is carried out under the impedance grounding condition, if the impedance grounding condition is not met, the next step is carried out, wherein Umin_set、Umax_setRespectively representing a minimum inversion voltage set value and a maximum inversion voltage set value;
calculating three-phase auxiliary Relay terminal voltage Urelay_a，Urelay_b，Urelay_c；
Judging at least two secondary Relay terminal voltages Urelay_x<k1*UgridIf yes, reporting a Relay fault, otherwise, executing the next step, wherein Urelay_xIs selected from Urelay_a，Urelay_b，Urelay_c，k1Is a proportionality coefficient, UgridIs the grid voltage;
judging that only one phase of secondary Relay terminal voltage U existsrelay_x<k1*UgridAnd three-phase inversion voltage Uinv_x>k2*UgridIf yes, executing the next step, otherwise, executing Relay detection under the non-impedance grounding condition, wherein Uinv_xIs selected from Uinv_a，Uinv_b，Uinv_c， k2Is a proportionality coefficient;
subtracting the sampling voltage of the fault phase power grid from the three-phase inversion sampling voltage to obtain a new three-phase inversion sampling voltage, and calculating to obtain an inversion voltage effective value U from the new inversion sampling voltageinv_a，Uinv_b，Uinv_cPerforming Relay detection under the non-impedance grounding condition;
the Relay detection under the impedance grounding condition comprises the following steps:
judging the absolute value of the difference between two three-phase inversion voltage effective values>UminReporting a Relay fault; judging the absolute value of the difference between two three-phase inversion voltage effective values<UminAnd the number of times that the product of instantaneous values of two-phase inverter voltages in the period of the power grid is less than zero>Count reporting Relay failure, otherwise, proceeding to the next step, wherein UminThe minimum set voltage value is obtained, and the Count is a set Count value;
according to the network voltage UgridThe PWM is instructed to be started to generate open-loop voltage, and the absolute value of the difference value of every two effective values of the three-phase inverter voltage is judged>UminReporting a Relay fault; judging the absolute value of the difference between two three-phase inversion voltage effective values<UminAnd the number of times that the product of instantaneous values of two-phase inverter voltages in the period of the power grid is less than zero>Counting, reporting a Relay fault, and otherwise, performing the next step;
closing the auxiliary Relay, and judging the absolute value of the difference between every two Relay voltage effective values>UminReporting a Relay fault; judging the absolute value of the difference between two inverter voltage effective values>UminAnd the number of times that the product of instantaneous values of two-phase inverter voltages in the period of the power grid is less than zero>Count reporting Relay faultOtherwise, the next step is carried out;
closing the main Relay and carrying out the next step;
turn off PWM and judge Uinv_x<c2*UgridIf yes, reporting a Relay fault, otherwise, detecting the Relay contact impedance, wherein Uinv_xIs selected from Uinv_a，Uinv_b，Uinv_c，c2Is a proportionality coefficient;
the Relay detection under the non-impedance grounding condition comprises the following steps:
judge Urelay_x<c1*UgridIf yes, reporting a Relay fault, otherwise, carrying out the next step, wherein c1Is a proportionality coefficient;
according to the network voltage UgridThe instruction turns on PWM to generate open-loop voltage and judge Uinv_x>c2*UgridIf yes, reporting a Relay fault, otherwise, carrying out the next step;
closing the auxiliary Relay, and judging Uinv_x<c2*UgridIf yes, reporting a Relay fault, otherwise, carrying out the next step;
closing the main Relay and carrying out the next step;
turn off PWM and judge Uinv_x<c2*UgridIf yes, a Relay fault is reported, otherwise, the Relay contact impedance detection is carried out.
2. The fault detection method of claim 1, wherein the sampling circuit detection comprises the steps of:
calculating three-phase grid voltage sampling Ugrid_a_sample，Ugrid_b_sample，Ugrid_c_sampleSum of Uzero_avgEffective value of (U)zero_rms；
Judging whether m times of meeting U exists in n power grid periodszero_rms>Uzero_setOtherwise, reporting the abnormal fault of the hardware of the sampling circuit, and if so, carrying out impedance grounding detection; wherein m is<n。
3. The fault detection method according to claim 1, wherein the Relay contact impedance detection comprises the steps of:
machine synchronization, judgment Urelay_x>k3*UgridIf yes, reporting a Relay fault, wherein Urelay_xSelected from three-phase secondary Relay terminal voltage Urelay_a，Urelay_b，Urelay_c，k3Is a proportionality coefficient, UgridIs the grid voltage.
4. The fault detection method according to claim 1, characterized by comprising in particular the steps of:
s1, calculating three-phase grid voltage sampling Ugrid_a_sample，Ugrid_b_sample，Ugrid_c_sampleSum of Uzero_avgEffective value of (U)zero_rms；
S2, judging whether m times of meeting U exists in n power grid periodszero_rms>Uzero_setOtherwise, reporting the abnormal fault of the hardware of the sampling circuit, if so, performing the following step S3; wherein m is<n；
S3, calculating the effective value U of the inverter voltage between the main Relay and the auxiliary Relay of the three phasesinv_a，Uinv_b，Uinv_cSequencing the three-phase inversion voltage to obtain Uinv_max，Uinv_mid，Uinv_min；
S4, judging Uinv_midWhether it satisfies Umin_set<Uinv_mid<Umax_setIf yes, the following step S9b is performed, and if not, the following step S5 is performed, wherein Umin_set、Umax_setRespectively representing a minimum inversion voltage set value and a maximum inversion voltage set value;
s5, calculating three-phase auxiliary Relay terminal voltage Urelay_a，Urelay_b，Urelay_c；
S6, judging at least two secondary Relay terminal voltages Urelay_x<k1*UgridIf yes, a Relay fault is reported, otherwise, the following step S7 is executed, wherein Urelay_xIs selected from Urelay_a，Urelay_b，Urelay_c，k1Is a proportionality coefficient, UgridIs the grid voltage;
s7, judging that only one secondary Relay terminal voltage U existsrelay_x<k1*UgridAnd three-phase inversion voltage Uinv_x>k2*UgridIf yes, the following step S8 is executed, otherwise, the following step S9a is executed, wherein Uinv_xIs selected from Uinv_a，Uinv_b，Uinv_c， k2Is a proportionality coefficient;
s8, subtracting the sampling voltage of the fault phase network from the sampling voltage of the three-phase inversion to obtain a new sampling voltage of the three-phase inversion, and calculating to obtain an effective value U of the inversion voltage from the new sampling voltage of the inversioninv_a，Uinv_b，Uinv_cStep S9a is performed, wherein Ugrid_yTo satisfy U in step S7relay_x<k1*UgridThe grid voltage of that phase;
s9a, judgment Urelay_x<c1*UgridIf yes, a Relay fault is reported, otherwise, the following step S10a is executed, wherein c1Is a proportionality coefficient;
s10a, according to the power grid voltage UgridThe instruction turns on PWM to generate open-loop voltage and judge Uinv_x>c2*UgridIf yes, a Relay fault is reported, otherwise, the following step S11a is executed, wherein c2Is a proportionality coefficient;
s11a, closing the auxiliary Relay, and judging Uinv_x<c2*UgridIf yes, a Relay fault is reported, otherwise, the following step S12a is executed;
s12a, closing the main Relay, and executing the following step S13 a;
s13a, turning off PWM and judging Uinv_x<c2*UgridIf yes, a Relay fault is reported, otherwise, the following step S14 is executed;
s9b, judging the absolute value of the difference of every two effective values of the three-phase inverter voltage>UminReporting a Relay fault; judging the absolute value of the difference between two three-phase inversion voltage effective values<UminAnd the number of times that the product of instantaneous values of two-phase inverter voltages in the period of the power grid is less than zero>Report of CountFailure, otherwise the following step 10b is performed, wherein UminThe minimum set voltage value is obtained, and the Count is a set Count value;
s10b, according to the power grid voltage UgridThe PWM is instructed to be started to generate open-loop voltage, and the absolute value of the difference value of every two effective values of the three-phase inverter voltage is judged>UminReporting a Relay fault; judging the absolute value of the difference between two three-phase inversion voltage effective values<UminAnd the number of times that the product of instantaneous values of two-phase inverter voltages in the period of the power grid is less than zero>Count, reporting Relay fault, otherwise executing the following step S11 b;
s11b, closing the auxiliary Relay, and judging the absolute value of the pairwise difference of effective values of Relay voltages>UminReporting a Relay fault; judging the absolute value of the difference between two inverter voltage effective values>UminAnd the number of times that the product of instantaneous values of two-phase inverter voltages in the period of the power grid is less than zero>Count, reporting Relay fault, otherwise executing the following step S12 b;
s12b, closing the main Relay, and executing the following step S13 b;
s13b, turning off PWM and judging Uinv_x<c2*UgridIf yes, a Relay fault is reported, otherwise, the following step S14 is executed;
s14, machine synchronization and U judgmentrelay_x>k3*UgridIf yes, a Relay fault is reported, wherein k3Is a scaling factor.
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| CN109946599B (en) * | 2019-03-28 | 2021-08-27 | 爱士惟新能源技术(江苏)有限公司 | Method and device for detecting relay before grid connection of photovoltaic three-phase inverter and storage medium |
| CN110346708B (en) * | 2019-06-13 | 2021-04-16 | 爱士惟新能源技术(扬中)有限公司 | Relay fault detection method for photovoltaic grid-connected and off-grid inverter |
| CN110261689B (en) * | 2019-06-26 | 2021-04-20 | 爱士惟新能源技术(江苏)有限公司 | Relay detection method for photovoltaic inverter BUS voltage unbalance and live wire grounding |
| CN110736924A (en) * | 2019-11-12 | 2020-01-31 | 爱士惟新能源技术(江苏)有限公司 | Relay sampling detection circuit and method for grid-connected inverters |
| CN111521928B (en) * | 2020-04-28 | 2023-03-31 | 阳光电源股份有限公司 | Grid-connected switch failure detection method and system of three-phase inverter |
| CN112986813B (en) * | 2021-03-05 | 2023-03-21 | 苏州海鹏科技有限公司 | Relay detection circuit and detection method of single-phase grid-connected photovoltaic inverter |
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