WO2023039775A1 - 一种光伏系统、继电器检测方法及电源系统 - Google Patents

一种光伏系统、继电器检测方法及电源系统 Download PDF

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Publication number
WO2023039775A1
WO2023039775A1 PCT/CN2021/118637 CN2021118637W WO2023039775A1 WO 2023039775 A1 WO2023039775 A1 WO 2023039775A1 CN 2021118637 W CN2021118637 W CN 2021118637W WO 2023039775 A1 WO2023039775 A1 WO 2023039775A1
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WIPO (PCT)
Prior art keywords
voltage
relay
filter capacitor
phase
grid
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Application number
PCT/CN2021/118637
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English (en)
French (fr)
Inventor
鲁力
辛凯
于心宇
刘云峰
Original Assignee
华为数字能源技术有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Application filed by 华为数字能源技术有限公司 filed Critical 华为数字能源技术有限公司
Priority to EP21957064.5A priority Critical patent/EP4386400A1/en
Priority to PCT/CN2021/118637 priority patent/WO2023039775A1/zh
Publication of WO2023039775A1 publication Critical patent/WO2023039775A1/zh
Priority to US18/598,117 priority patent/US20240213767A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/20—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for electronic equipment
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
    • G01R19/16576—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing DC or AC voltage with one threshold
    • G01R19/1658—AC voltage or recurrent signals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/327—Testing of circuit interrupters, switches or circuit-breakers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/001—Methods to deal with contingencies, e.g. abnormalities, faults or failures
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
    • H02S50/00—Monitoring or testing of PV systems, e.g. load balancing or fault identification
    • H02S50/10—Testing of PV devices, e.g. of PV modules or single PV cells
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/02—Details
    • H02H3/05—Details with means for increasing reliability, e.g. redundancy arrangements
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

Definitions

  • the present application relates to the technical field of power systems, in particular to a photovoltaic system, a relay detection method and a power supply system.
  • the photovoltaic system includes a photovoltaic array and an inverter, wherein the inverter not only includes a power conversion circuit, but also includes a relay, and the power conversion circuit is connected to the grid through the relay.
  • the controller of the inverter can control the switch state of the relay to realize functions such as photovoltaic grid connection, photovoltaic off-grid, and photovoltaic system protection. Therefore, whether the state of the relay is normal has a significant impact on the photovoltaic system.
  • the relay may be abnormal in practical applications, that is, the relay does not disconnect successfully after receiving the disconnect command, but remains closed, for example, the relay has a failure such as sticking and cannot be successfully disconnected.
  • the reliability of the solutions for detecting whether the relay is faulty is poor, and there may be missed detections.
  • the relay is faulty and sticky, but the relay sticking is not detected, which brings great hidden dangers to the photovoltaic system.
  • the application provides a photovoltaic system, a relay detection method and a power supply system, which can accurately detect whether a relay is faulty, so that when the relay is faulty, a fault alarm is issued in time.
  • the application provides a photovoltaic system, including: an inverter, a filter capacitor, a relay, and a controller; the input end of the inverter is used to connect to the photovoltaic array, the output end of the inverter is connected to the first end of the relay, and the second end of the relay The two terminals are used to connect to the AC grid; the output terminal of the inverter is connected to the filter capacitor; the controller is used to send a disconnection command to the relay when the voltage of the filter capacitor is the same frequency and phase as the voltage of the AC grid, and the filter capacitor When the phase of the voltage is within the preset phase range, stop driving the switching tube in the inverter, and when it is detected that the effective value of the difference between the voltage of the filter capacitor and the voltage of the AC grid is less than the preset value, a relay failure alarm message is sent, wherein When the phase of the voltage of the filter capacitor is within a preset phase range, the voltage of the filter capacitor is greater than or equal to a preset threshold.
  • the controller in the photovoltaic system provided by this application only seals the inverter within the preset phase range of the voltage of the filter capacitor, so as to ensure that the voltage of the filter capacitor is at a relatively large value, and the voltage of the filter capacitor is equivalent to the AC power grid
  • the voltage of the AC grid to ground is raised, thereby avoiding being detected as a short circuit of the AC grid to ground, so that the fault of the relay can be detected.
  • the controller provided in the present application is specifically configured to obtain the phase of the voltage of the filter capacitor through the phase of the voltage of the AC power grid. It can be seen that this technical solution can directly obtain the voltage of the filter capacitor through the voltage of the AC grid, avoiding adding a voltage detection circuit on the side of the filter capacitor, thereby reducing the cost of the photovoltaic system provided by the present application.
  • the controller provided in the present application is specifically configured to phase-lock the phase voltage of any phase of the AC grid to obtain the phase of the AC grid voltage.
  • a relay sticking warning is issued, so that the fault can be dealt with in time.
  • the controller provided in the present application is specifically used for the phase of the voltage of the filter capacitor to stop driving the switching tube in the inverter at a peak value of the voltage of the filter capacitor.
  • the controller stops driving the switching tube in the inverter at the peak value of the voltage of the filter capacitor, so that the voltage of the filter capacitor can be kept at the peak value, that is, the voltage of the filter capacitor can be kept at a maximum value, thereby pulling up the AC power grid.
  • the voltage of the ground thereby avoiding being detected as a short circuit to the ground of the AC grid, so that the failure of the relay can be truly detected.
  • the relay provided in this application includes: a first-level relay and a second-level relay; the first-level relay and the second-level relay are connected in series between the output end of the inverter and the AC grid; It is specifically used to send a closing command to the first-level relay, and send an opening command to the second-level relay.
  • the effective value of the difference between the voltage of the filter capacitor and the voltage of the AC grid is less than the preset value, send the second-level Relay failure warning information.
  • the relay includes a first-level relay and a second-level relay, the detection of the relay can detect the first-level relay and the second-level relay respectively, thereby improving detection accuracy.
  • the relay provided in this application includes: a first-level relay and a second-level relay; the first-level relay and the second-level relay are connected in series between the output end of the inverter and the AC grid;
  • the device is specifically used to send a closing command to the second-level relay when sending an opening command to the first-level relay, and when the effective value of the difference between the voltage of the filter capacitor and the AC grid voltage is less than the preset value, send the first-level Relay failure warning information.
  • the controller when any of the three phases of the AC power grid in this application is grounded, the controller is used to further use After driving the switching tube of any phase in the inverter, it is judged that the effective value of the difference between the voltage of the filter capacitor and the voltage of the AC grid continues to be smaller than the preset value, and then send any phase relay failure alarm information.
  • Phase V represents any one of the three phases.
  • the AC grid voltage corresponding to V is 0 because phase V is grounded.
  • the switching tube in the inverter is stopped, and the voltage of the filter capacitor corresponding to V is a stable DC voltage.
  • the collected voltage of the filter capacitor is also 0. It can be seen that the effective value of the difference between the AC grid voltage corresponding to V and the voltage of the filter capacitor is zero, that is, less than the preset value of 30V.
  • the effective value of the difference between the effective value of the AC grid voltage corresponding to the ground phase (V phase) and the voltage of the filter capacitor is also zero, and the relay will Misdiagnosed as adhesions.
  • the switching tube of the V-phase of the inverter is driven to act, the inverter outputs alternating current, and the voltage of the V-phase filter capacitor is an alternating voltage. Therefore, when the relay switch corresponding to V is normally turned off, the voltage of the filter capacitor corresponding to V collected by the photovoltaic system is an effective voltage value.
  • the voltage difference between the two ends of the V-phase relay is the voltage value of the filter capacitor minus 0, that is, the difference between the AC grid voltage corresponding to the V-phase relay and the voltage of the filter capacitor is the voltage value of the filter capacitor, which is greater than the preset value, and the V-phase relay judged to be in normal condition.
  • the V-phase relay when the V-phase relay is normally disconnected, the V-phase relay is judged to be normal, that is, the technical solution can prevent the relay from being misdiagnosed as adhesion.
  • the controller provided by this application is also used to drive any one of the three phases in the inverter after the effective value of the difference between the voltage of the filter capacitor and the AC grid voltage is less than the preset value
  • the photovoltaic system provided in the embodiment of the present application may not send relay sticking fault alarm information after judging that any phase relay in the relay is sticking. It is to drive the action of the switching tube in the inverter corresponding to the adhesion in the inverter.
  • the fault alarm information of the adhesion of the relay is sent , can improve the accuracy and reliability of relay fault detection.
  • the application also provides a relay detection method, which is applied to a photovoltaic system, and the photovoltaic system includes an inverter, a filter capacitor and a relay; the input end of the inverter is used to connect to a photovoltaic array, and the output end of the inverter is connected to a relay
  • the first terminal of the relay is connected to the AC grid; the output terminal of the inverter is connected to the filter capacitor; the method includes: when the voltage of the filter capacitor and the AC grid voltage have the same frequency and phase, send a disconnection command to the relay ;Stop driving the switching tube action in the inverter within the preset phase range of the voltage of the filter capacitor; when it is detected that the effective value of the difference between the voltage of the filter capacitor and the voltage of the AC grid is less than the preset value, a relay fault alarm is sent Information; wherein when the phase of the voltage of the
  • the relay detection method provided in the embodiment of the present application further includes: obtaining the phase of the voltage of the filter capacitor according to the phase of the AC grid voltage. Specifically, it may be: phase-lock the phase voltage of any phase of the AC grid to obtain the phase of the AC grid voltage.
  • the phase of the voltage of the filter capacitor stops driving the switching tube in the inverter within the preset phase range, specifically including: the phase of the voltage of the filter capacitor corresponds to the phase of the filter capacitor The peak value of the voltage stops driving the switching tube in the inverter.
  • the relay provided in the embodiment of the present application includes: a first-level relay and a second-level relay; the first-level relay and the second-level relay are connected in series between the output end of the inverter and the AC power grid ;
  • Send a disconnection command to the relay including: when sending a closing command to the first-level relay, send a disconnection command to the second-level relay, when it is detected that the effective value of the difference between the voltage of the filter capacitor and the AC grid voltage is less than the preset
  • the relay failure warning information is sent, including: when the effective value of the difference between the filter capacitor voltage and the AC grid voltage is less than the preset value, the second-stage relay failure warning information is sent.
  • the relay provided in the embodiment of the present application includes: a first-level relay and a second-level relay; the first-level relay and the second-level relay are connected in series between the output end of the inverter and the AC power grid ; Send a disconnection command to the relay, including: when sending a disconnection command to the first-level relay, send a closing command to the second-level relay; when it is detected that the effective value of the difference between the voltage of the filter capacitor and the AC grid voltage is less than the preset When the value is lower than the value, the relay failure warning information is sent, including: when the effective value of the difference between the filter capacitor voltage and the AC grid voltage is less than the preset value, the first-level relay failure warning information is sent.
  • the method further includes: driving an inverter The switching tube of any phase in the relay acts, and when it is judged that the effective value of the difference between the voltage of the filter capacitor and the voltage of the AC grid continues to be less than the preset value, then send any phase relay failure alarm information
  • the method further includes: driving the switching tube of any one of the three phases in the inverter to act, When the effective value of the difference between the voltage of the filter capacitor and the voltage of the AC power grid continues to be smaller than the preset value, the relay failure alarm information of any phase is sent.
  • the present application also provides a photovoltaic system, including: an inverter, a filter capacitor, a relay, and a controller; the input end of the inverter is used to connect the photovoltaic array, and the inverter The output terminal of the inverter is connected to the first terminal of the relay, and the second terminal of the relay is connected to the AC grid; the output terminal of the inverter is connected to the filter capacitor; At the same time, a disconnect command is sent to the relay to drive the switching tube of any of the three phases in the inverter; when the effective value of the difference between the voltage of the filter capacitor and the voltage of the AC grid is less than the preset value, the switch of any phase is sent Relay failure warning information.
  • the present application also provides a power supply system, including: an inverter, a filter capacitor, a relay, and a controller;
  • the output terminal of the inverter is connected to the first terminal of the relay, and the second terminal of the relay is connected to the AC grid; the output terminal of the inverter is connected to the filter capacitor;
  • the relay sends a disconnection command and stops driving the switching tube in the inverter when the phase of the filter capacitor voltage is within the preset phase range, it detects that the effective value of the difference between the filter capacitor voltage and the AC grid voltage is less than the preset
  • relay failure alarm information is sent, wherein when the phase of the voltage of the filter capacitor is within the preset phase range, the voltage of the filter capacitor is greater than or equal to the preset threshold.
  • the photovoltaic system includes an inverter, a filter capacitor, a relay, and a controller; the filter capacitor is connected to the output terminal of the inverter, and the relay is connected between the output terminal of the inverter and the AC grid. , such as adhesion fault; the controller seals the switching tube in the inverter, that is, stops driving the switching tube in the inverter, the inverter stops output power, and then judges whether the voltage difference between the two ends of the relay is greater than the preset value , to determine whether the relay is stuck, where the voltage on the side of the relay close to the inverter is the voltage of the filter capacitor, and the voltage on the side of the relay close to the AC grid is the voltage of the AC grid.
  • the controller only seals the inverter within the preset phase range of the voltage of the filter capacitor, so as to ensure that the voltage of the filter capacitor is at a relatively large value, and the voltage of the filter capacitor is equivalent to the AC grid side.
  • the voltage on the capacitor is relatively large, which increases the voltage of the AC grid to ground, so as to avoid being detected as a short circuit of the AC grid to ground, so as to truly detect the sticking of the relay.
  • FIG. 1 is a schematic diagram of a photovoltaic system provided by an embodiment of the present application
  • Fig. 2 is a circuit diagram of a photovoltaic system provided by the embodiment of the present application.
  • FIG. 3 is a schematic diagram of another photovoltaic system provided by the embodiment of the present application.
  • Fig. 4 is an equivalent circuit diagram of a photovoltaic system provided by the embodiment of the present application.
  • FIG. 5 is an equivalent circuit diagram of another photovoltaic system provided by the embodiment of the present application.
  • Fig. 6 is a circuit diagram of another photovoltaic system provided by the embodiment of the present application.
  • Fig. 7 is a circuit diagram of a V-phase grounded photovoltaic system provided by the embodiment of the present application.
  • FIG. 8 is a flowchart of a relay detection method provided in an embodiment of the present application.
  • FIG. 9 is a flow chart of another relay detection method provided in the embodiment of the present application.
  • FIG. 10 is a schematic diagram of a power supply system provided by an embodiment of the present application.
  • Words such as “first” and “second” in the following descriptions are used for description purposes only, and should not be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Thus, a feature defined as “first”, “second”, etc. may expressly or implicitly include one or more of that feature. In the description of the present application, unless otherwise specified, "plurality" means two or more.
  • orientation terms such as “upper” and “lower” may include, but are not limited to, definitions relative to the schematic placement orientations of components in the drawings. It should be understood that these directional terms may be relative concepts, They are used for description and clarification relative to, which may change accordingly according to changes in the orientation in which parts of the figures are placed in the figures.
  • connection should be understood in a broad sense, for example, “connection” can be a fixed connection, a detachable connection, or an integral body; it can be a direct connection, or It can be connected indirectly through an intermediary.
  • connection can be a fixed connection, a detachable connection, or an integral body; it can be a direct connection, or It can be connected indirectly through an intermediary.
  • coupled may be an electrical connection for signal transmission.
  • Coupling can be a direct electrical connection, or an indirect electrical connection through an intermediary.
  • the embodiment of the present application relates to a photovoltaic system.
  • the photovoltaic system includes an inverter and a relay.
  • the input end of the inverter is connected to a DC power supply, and the output end of the inverter is connected to an AC grid through a relay.
  • the relay is integrated in the inverter. in the cabinet. For the safety protection of actual work, the inverter can be reliably disconnected from the AC grid.
  • the relay includes two stages connected in series, that is, the first stage relay and the second stage relay.
  • the basic structure of a photovoltaic system provided by the embodiment of the present application will be introduced below by taking the relay including the first-level relay and the second-level relay as an example.
  • FIG. 1 this figure is a schematic diagram of a photovoltaic system provided by an embodiment of the present application.
  • the photovoltaic system provided by the embodiment of this application includes: an inverter 100, a first-stage relay 200, and a second-stage relay 300.
  • the first-stage relay 200 includes three The phases are respectively K1, K3 and K5, and the three phases included in the second stage relay 300 are respectively K2, K4 and K6.
  • the input end of the inverter 100 is used for connecting a direct current power source DC.
  • the embodiment of the present application does not limit the specific form of the direct current power supply DC, and takes the direct current power supply DC as a photovoltaic array as an example for illustration.
  • the output end of the inverter 100 is connected to the first end of the first stage relay 200, the second end of the first stage relay 200 is connected to the first end of the second stage relay 300, and the second end of the second stage relay 300 is used to connect AC grid.
  • K1, K3 and K5 in the first-stage relay 200 can be controlled by the same switch signal, that is, act synchronously, and K2, K3, and K5 in the second-stage relay 300 K4 and K6 can also be controlled by the same switch signal, ie synchronous action.
  • K1, K3 and K5 in the first stage relay 200 can be controlled by different switch signals
  • K2, K4 and K6 in the second stage relay 300 can also be controlled by different switch signals
  • the following is to determine whether the relay fails to be effectively disconnected when receiving the disconnection command, that is, disconnect the inverter from the AC power grid Connection, take relay adhesion as an example to introduce, and take three-phase switches in a primary relay to act simultaneously as an example.
  • this figure is a circuit diagram of a photovoltaic system provided by an embodiment of the present application.
  • the photovoltaic system provided by the embodiment of the present application includes: an inverter 100 , a first-stage relay 200 , a second-stage relay 300 and a filter capacitor 400 .
  • the positive input terminal and the negative input terminal of the inverter 100 are respectively connected to the DC positive bus BUS+ and the DC negative bus BUS- of the DC power supply.
  • the output end of the inverter 100 is connected to the first end of the first stage relay 200, the second end of the first stage relay 200 is connected to the first end of the second stage relay 300, and the second end of the second stage relay 300 is used to connect In the AC power grid, a filter capacitor 400 is connected between the DC midpoint of the input end of the inverter 100 and the output end.
  • the inverter 100, the first-stage relay 200 and the second-stage relay 300 may all be integrated inside the cabinet of the inverter.
  • the photovoltaic system provided by the embodiment of the present application can detect whether the relay is faulty, for example, whether the relay is stuck, that is, whether the controller has sent a disconnection command to the relay, but the relay is not disconnected.
  • the solution provided by the embodiment of the present application will be introduced below by taking the detection of whether a relay is stuck as an example.
  • FIG. 3 is a schematic diagram of another photovoltaic system provided by an embodiment of the present application.
  • the photovoltaic system provided in the embodiment of the present application includes: an inverter 100 , a filter capacitor 400 , a relay 600 and a controller 500 .
  • the input end of the inverter 100 is used to connect to the photovoltaic array, the output end of the inverter 100 is connected to the first end of the relay 600, and the second end of the relay 600 is used to connect to the AC grid; the output end of the inverter 100 is connected to the filter capacitor 400.
  • the technical solution provided by the embodiment of the application is to block the wave when the voltage on the filter capacitor is large, instead of using random wave blocking, and then increase the voltage of the AC grid to the ground, so that it will not be detected as a short circuit of the AC grid to the ground.
  • the relay When adhesions occur, they can be reliably detected.
  • the controller 500 is configured to send a disconnection instruction to the relay 600 when the voltage of the filter capacitor 400 has the same frequency and phase as the AC grid voltage, and stop driving the inverter when the phase of the voltage of the filter capacitor 400 is within a preset phase range
  • a fault alarm message of the relay 600 is sent, wherein the phase of the voltage of the filter capacitor 400 is at the preset phase
  • the voltage of the filter capacitor 400 is greater than or equal to the preset threshold value.
  • the preset threshold value can be selected according to the needs, and the voltage peak value close to the filter capacitor can be selected, that is, the voltage on the filter capacitor is guaranteed to be relatively large when the wave is blocked.
  • the embodiment of the present application does not limit the specific value of the preset value, which can be set according to the needs of the actual product, as long as it can reliably detect whether the relay is stuck.
  • the preset value can be 30V.
  • the voltage difference between the two ends of the relay is greater than When the voltage is 30V, it is judged that the relay is normal and no sticking occurs; when the voltage difference between the two ends of the relay is less than 30V, it is judged that the relay is stuck and abnormal, and a fault alarm message is sent, and the relay needs to be repaired or replaced.
  • the technical solution provided above can send a disconnection command to the relay to be detected after the voltage of the filter capacitor is controlled to have the same frequency and phase as the AC grid voltage, and then randomly stop the drive signal of the inverter, that is, wave blocking, The switching tube in the inverter is no longer driven to act.
  • the relay to be detected When the relay to be detected is successfully disconnected after receiving the disconnect command, that is, the state of the relay is normal and no adhesion occurs, and the voltage of the filter capacitor is the voltage corresponding to the preset phase. At this time, the difference between the voltage of the filter capacitor and the voltage of the AC grid The effective value of is greater than the preset value.
  • the relay to be detected is not disconnected after receiving the disconnection command, that is, the state of the relay is abnormal and sticking occurs, at this time, the effective value of the difference between the voltage of the filter capacitor and the voltage of the AC grid is smaller than the preset value.
  • the controller only seals the inverter within the preset phase range of the voltage of the filter capacitor, so as to ensure that the voltage of the filter capacitor is at a relatively large value, and the voltage of the filter capacitor is equivalent to AC
  • the controller due to the large voltage on the filter capacitor, the voltage of the AC grid to the ground is raised, thereby avoiding being detected as a short circuit to the ground of the AC grid, so that the relay is actually detected to be stuck.
  • the preset phase range in the embodiment of the present application is the preset phase range corresponding to the larger voltage value of the filter capacitor. For example, the wave is blocked near the peak voltage of the filter capacitor. Determine the phase of the AC voltage to correspond to the voltage near the peak.
  • the embodiment of the present application provides a photovoltaic system.
  • the preset phase range in the embodiment of the present application may include a phase range corresponding to a voltage value of the filter capacitor greater than the preset capacitor voltage.
  • this figure is an equivalent circuit diagram of a photovoltaic system provided by an embodiment of the present application.
  • each phase-to-ground PE of the AC grid is respectively determined by the three-phase-to-ground impedances Za, Zb, and Zc.
  • the equivalent impedance Zcx of the inverter side will be connected in parallel to the PE terminal of the AC grid C.
  • Zcx is connected in parallel to both ends of Zc. Therefore, the AC grid
  • the impedance of C relative to ground becomes smaller.
  • the voltage on the filter capacitor is large, the wave is blocked, so that the voltage Ucx on the filter capacitor is applied in parallel Impedance, thereby pulling up the voltage of C relative to ground, and then judging whether the relay is stuck.
  • the photovoltaic system provided by the embodiment of this application can stop driving the switching tube in the inverter within the preset phase range of the voltage of the filter capacitor, so as to ensure that when the detection relay is stuck, the voltage Ucx of the filter capacitor is relatively large, that is, Ucx remains relatively high. large value.
  • Ucx pulls up the voltage of C relative to ground, so the photovoltaic system provided by the implementation of this application can make the voltage of the AC grid voltage to the ground greater than the voltage short-circuit threshold, and will not judge the occurrence of a short-circuit fault to the ground of the AC grid, so that it can truly detect whether the relay is stuck. even.
  • the controller 500 stops driving the switching tubes in the inverter 100 at random, that is, the wave is blocked randomly, the wave may be blocked when the voltage of the filter capacitor is small. If the relay is stuck, the voltage of the filter capacitor is equivalent to phase C, but the voltage of the filter capacitor is small, and the voltage of C relative to the ground will still be less than the voltage short-circuit threshold, and the AC power grid is detected to be short-circuited to the ground. At this time, the relay is normal by default. Relay sticking will be detected.
  • this figure is an equivalent circuit diagram of another photovoltaic system provided by an embodiment of the present application.
  • the voltages of the three phases of the AC grid provided by the embodiment of the present application to the ground PE are determined by the impedances Za, Zb and Zc of the three phases to the ground respectively.
  • the adhesion of the relay causes the impedance of the AC grid relative to PE to decrease, which in turn causes the voltage of the AC grid to decrease.
  • the voltage of the AC grid voltage to the ground is less than the voltage short-circuit threshold, it will be judged that the AC grid has a ground-to-ground short circuit fault.
  • the photovoltaic system will no longer judge whether the relay is stuck, and the default relay state is normal, so the relay sticking will not be detected.
  • the technical solution provided by the embodiment of the present application to randomly stop driving the switching tubes in the inverter will cause the relay to stick but cannot be detected. Therefore, the technical solution provided by the embodiment of the present application is based on the Stop driving the switching tube in the inverter within the preset phase range of the voltage, so that the voltage on the filter capacitor is relatively large, so that when the relay is stuck in the detection, the situation that the voltage of the AC power grid to the ground is less than the voltage short-circuit threshold is avoided, and the realization of Reliable detection of stuck relays.
  • the controller provided in the embodiment of the present application is specifically used to stop driving the switching tube in the inverter when the phase of the AC grid voltage is within the preset phase range. action. Since the AC grid voltage and the filter capacitor have the same frequency and phase, that is, the phase of the AC grid voltage is the same as the phase of the filter capacitor, the voltage phase of the filter capacitor can be judged by detecting the phase of the AC grid voltage without additional hardware The detection circuit can stop driving the switch tube in the inverter when the phase of the AC grid voltage is within the preset phase range.
  • the controller provided in the embodiment of the present application is specifically used to phase-lock the AC grid voltage to obtain the phase of the AC grid voltage. Since the phase of the voltage of the filter capacitor is at the same frequency as the phase of the AC grid voltage In the same phase, therefore, the phase of the AC grid voltage can be stopped within the preset phase range to drive the switching tube in the inverter to act.
  • the solution provided by the embodiment of the present application can phase-lock the AC grid voltage to obtain the phase of the AC grid voltage, so that when the limit of the AC grid voltage is within the preset phase range, the switching tube in the inverter will be stopped.
  • other means may be used to stop the operation of the switching tube in the inverter, which is not limited in this embodiment of the present application.
  • FIG. 6 is a circuit diagram of another photovoltaic system provided by the embodiment of the present application.
  • the relay provided in the embodiment of the present application includes: a first-level relay 200 and a second-level relay 300 .
  • the first stage relay 200 and the second stage relay 300 are connected in series.
  • the controller 500 is specifically configured to send a closing command to the first-stage relay 200 and an opening command to the second-stage relay 300, and when the effective value of the difference between the voltage of the filter capacitor 400 and the voltage of the AC power grid is less than a preset value, Send the fault warning information of the second-level relay 300; it is also specifically used to send the closing command to the second-level relay 300 when sending the opening command to the first-level relay 200, and the difference between the voltage of the filter capacitor 400 and the AC grid voltage When the effective value is less than the preset value, a fault warning message of the first stage relay 200 is sent.
  • the photovoltaic system includes a first-stage relay and a second-stage relay
  • the two-stage relays should be opened respectively, for example, when the first-stage relay is opened, the second-stage relay should be closed.
  • the AC grid voltage in the embodiment of the present application includes three phases, namely A phase, B phase and C phase, and the phase difference between the three phase voltages is 120 degrees.
  • the relay in the embodiment of the present application also includes three switches, and the first stage relay 200 includes a first switch K1 , a third switch K3 and a fifth switch K5 .
  • the second stage relay 300 includes a second switch K2, a fourth switch K4 and a sixth switch K6.
  • the three switches in the first-level relay or the second-level relay (hereinafter referred to as the relay) in the embodiment of the present application can share the same signal receiving end.
  • the three switches in the relay in the embodiment of the present application can be integrated.
  • the controller provided in the embodiment of the present application is specifically used to phase-lock the phase voltage of any phase of the AC grid to obtain the phase of the AC grid voltage, and the phase of the AC grid voltage is within the preset phase range Stop driving the switching tube in the inverter. It should be understood that after the embodiment of the present application phase-locks the phase voltage of any phase of the AC power grid, when the corresponding switch is detected to be stuck, it can be judged that the relay has stuck, and a relay sticking warning is issued, so that the entire relay will be replaced.
  • the controller provided in the embodiment of the present application is specifically used to phase-lock the phase voltage of any phase of the AC grid, obtain the phase of the AC grid voltage, and obtain the phase of the filter capacitor according to the phase of the AC grid voltage.
  • the phase of the voltage when the phase of the voltage of the filter capacitor corresponds to the peak value of the voltage of the filter capacitor, stop driving the switching tube in the inverter to act.
  • V-phase can be any of the three phases of the AC grid.
  • One phase or any phase the following uses C-phase grounding as an example to specifically introduce the situation that the solution provided by the embodiment of the present application is applied to a V-phase grounding photovoltaic system.
  • FIG. 7 is a circuit diagram of a V-phase grounded photovoltaic system provided by an embodiment of the present application.
  • the AC grid voltage in the photovoltaic system includes the following three phases: A phase, B phase and C phase.
  • phase C is connected to PE, that is, phase C is grounded.
  • the sampling method of the AC grid voltage is DC blocking sampling, that is, the sampling AC grid voltage is AC voltage, and the voltage of the filter capacitor is non-DC blocking sampling.
  • the relay failure alarm information is not sent, that is, no alarm is given first, but Drive the switching tube of the V phase in the inverter to act.
  • the effective value of the difference between the voltage of the filter capacitor and the voltage of the AC grid continues to be less than the preset value, it is finally judged that the relay is stuck, and the relay fault alarm message is sent. This can Prevent relays from being misdiagnosed as stuck when their state is normal.
  • phase V phase C
  • the AC grid voltage corresponding to C is 0 because phase C is grounded.
  • the switching tube in the inverter is stopped, and the voltage of the filter capacitor corresponding to C is a stable DC voltage.
  • the collected voltage of the filter capacitor is also 0. It can be seen that the effective value of the difference between the AC grid voltage and the voltage of the filter capacitor corresponding to C is zero, that is, less than the preset value of 30V.
  • the controller provided in the embodiment of the present application is also used to continue the phase inverter when the V-phase of the AC grid is grounded and the V-phase relay is judged to be stuck.
  • the V-phase switching tube emits waves to drive the V-phase switching tube in the inverter to act.
  • a V-phase relay fault alarm message is sent, for example Adhesion occurs.
  • the switch tube of the V-phase of the inverter when the switch tube of the V-phase of the inverter is driven to act, the inverter outputs AC power, and the voltage of the V-phase filter capacitor is the AC voltage. Therefore, when the relay switch corresponding to V is normally turned off, the voltage of the filter capacitor corresponding to V collected by the photovoltaic system is the effective value of the voltage. Therefore, the voltage difference between the two ends of the V-phase relay is the voltage value of the filter capacitor minus 0, that is, the difference between the AC grid voltage corresponding to the V-phase relay and the voltage of the filter capacitor is the voltage value of the filter capacitor, which is greater than the preset value, and the V-phase relay judged to be in normal condition. In the technical solution provided by the embodiment of the present application, when the V-phase relay is normally disconnected, the V-phase relay is judged to be normal, that is, the technical solution can prevent the relay from being misdiagnosed as adhesion.
  • the implementation method introduced above is for the detection of relay sticking when the V phase is grounded, that is, the wave is sent after the wave is closed.
  • this method is also applicable to non-V phase grounding, so that it can be more reliable to detect whether the relay is stuck, that is, After the waves are blocked, no alarm is detected if there is adhesion. Instead, waves are sent for one or more phases of the adhesion to verify whether the adhesion actually occurs. That is, the controller provided in the embodiment of the present application is also used to judge the first When the phase relay is stuck, it will drive the switching tube of the first phase in the inverter to act.
  • the first phase relay When the effective value of the difference between the voltage of the filter capacitor and the AC grid voltage is less than the preset value, the first phase relay is abnormal; the first phase It is any one of the three phases of the AC grid. That is to say, in the solution provided by the embodiment of the present application, when the relay of any phase is stuck, the above-mentioned re-judgment action can be performed to prevent the relay from being misdiagnosed as stuck when the state is normal. In the photovoltaic system provided by the embodiment of the present application, when it is judged that any phase in the relay is stuck (not limited to the V phase), it may also not send relay failure alarm information after judging that the phase is stuck, that is, no alarm, but It is to drive the switching tube action of this phase in the inverter. When the effective value of the difference between the filter capacitor voltage and the AC grid voltage is less than the preset value, the relay fault alarm information is sent, which can improve the accuracy and accuracy of relay fault detection. reliability.
  • the embodiment of the present application provides a photovoltaic system
  • the photovoltaic system only seals the inverter within the preset phase range of the voltage of the filter capacitor, so as to ensure that the voltage of the filter capacitor is at a relatively large value
  • the voltage of the filter capacitor is equivalent to the side of the AC grid. Due to the large voltage on the filter capacitor, the voltage of the AC grid to the ground is raised, thereby avoiding being detected as a short circuit of the AC grid to the ground, so that the relay is actually detected.
  • the switch tube in the inverter can be activated to detect the relay again, so as to prevent the relay from being misdiagnosed as stuck when the relay is in a normal state.
  • the embodiment of the present application also provides another photovoltaic system, that is, when judging whether the relay in the photovoltaic system is stuck, it can be applied to V-phase grounding, or it can be applied to V-phase non-grounding , the following will be introduced by taking this scheme applicable to V-phase grounding as an example.
  • the controller can send waves to the switching tube in the inverter, and then judge whether the effective value of the difference between the voltage of the filter capacitor and the voltage of the AC grid is less than a preset value to judge whether the relay is stuck.
  • the controller of the photovoltaic system sends a disconnection command to the relay when the voltage of the filter capacitor is the same frequency and phase as the AC grid voltage, and sends a wave to the switching tube of any of the three phases in the inverter, that is, drives the switching tube to act , to charge the filter capacitor, and when the effective value of the difference between the voltage of the filter capacitor and the voltage of the AC power grid continues to be smaller than the preset value, a relay failure alarm message of any phase is sent. .
  • the photovoltaic system provided in the embodiment of the present application includes: an inverter, a filter capacitor, a relay, and a controller.
  • the input terminal of the inverter is used to connect to the photovoltaic array, the output terminal of the inverter is connected to the first terminal of the relay, and the second terminal of the relay is connected to the AC grid; the output terminal of the inverter is connected to the filter capacitor.
  • the controller is used to send a disconnection command to the relay when the voltage of the filter capacitor is the same frequency and phase as the AC grid voltage, to drive the switching tube of any of the three phases in the inverter to act, and to judge the voltage of the filter capacitor and the AC grid Whether the effective value of the voltage difference is less than the preset value, if so, send any phase relay failure alarm information.
  • phase V The photovoltaic system provided by the embodiment of the present application will be introduced below by taking phase V as an example to represent any phase.
  • the controller After the controller sends waves, there is an AC voltage on the filter capacitor, and the AC grid voltage is 0 because the V phase is grounded.
  • the relay When the relay is normally disconnected, the effective value of the difference between the filter capacitor voltage and the AC grid voltage is greater than the preset value.
  • the photovoltaic system judges that the working status of the relay is normal. If the relay is stuck, the filter capacitor is grounded through the connected relay through the V phase, the voltage of the filter capacitor is 0, and the voltage of the AC grid is also 0 due to the grounding of the V phase, the effective difference between the voltage of the filter capacitor and the voltage of the AC grid The value is also 0, and if 0 is less than the preset value, the photovoltaic system will judge that the relay is stuck.
  • the photovoltaic system provided in the embodiment of the present application can also be used to determine when any phase in the relay is stuck (not limited to V phase), to drive the switching tube of the phase in the inverter to act, and when the relay is stuck, the filter capacitor It is connected to the AC grid through a relay, and the voltage of the filter capacitor is close to the voltage of the AC grid.
  • the relay is in normal operation, the voltage of the filter capacitor is close to the voltage output by the inverter, and there is a certain difference with the voltage of the AC grid. Therefore, When the effective value of the difference between the voltage of the filter capacitor and the AC grid voltage is less than a preset value, the photovoltaic system can also determine that the relay is stuck.
  • the embodiments of the present application also provide a relay detection method, which will be described in detail below with reference to the accompanying drawings.
  • this figure is a flow chart of a relay detection method provided by an embodiment of the present application.
  • the relay detection method is applied to a photovoltaic system.
  • the photovoltaic system includes an inverter, a filter capacitor, a relay, and a controller; the input end of the inverter is used to connect the photovoltaic array, and the output end of the inverter is connected to the first end of the relay.
  • the second end of the inverter is connected to the AC grid; the output end of the inverter is connected to the filter capacitor; as shown in Figure 8, the relay detection method provided by the embodiment of the present application includes the following steps:
  • S802 Stop driving the switching tube in the inverter within the preset phase range of the voltage of the filter capacitor.
  • the controller only seals the inverter within the preset phase range of the voltage of the filter capacitor, so as to ensure that the voltage of the filter capacitor is at a relatively large value, and the voltage of the filter capacitor is equivalent to AC
  • the controller due to the large voltage on the filter capacitor, the voltage of the AC grid to the ground is raised, thereby avoiding being detected as a short circuit to the ground of the AC grid, so that the relay is actually detected to be stuck.
  • stopping the action of driving the switching tube in the inverter within the preset phase range of the voltage of the filter capacitor includes: stopping when the phase of the AC grid voltage is within the preset phase range Drive the switching tube action in the inverter.
  • the operation of switching tubes in the inverter is stopped, including: phase-locking the AC grid voltage to obtain the AC grid voltage
  • the phase of the AC grid voltage stops driving the switching tube in the inverter within the preset phase range.
  • the AC grid voltage is phase-locked to obtain the phase of the AC grid voltage, and the phase of the AC grid voltage stops driving the switching tube in the inverter within a preset phase range. It includes: phase-locking the phase voltage of any phase of the AC grid to obtain the phase of the AC grid voltage, and the phase of the AC grid voltage stops driving the switching tube in the inverter within a preset phase range.
  • the phase voltage of any phase of the AC grid is phase-locked to obtain the phase of the AC grid voltage, and the phase of the AC grid voltage stops driving the inverter within the preset phase range.
  • the action of the switching tube including: phase-locking the phase voltage of any phase of the AC grid, obtaining the phase of the AC grid voltage, obtaining the phase of the voltage of the filter capacitor according to the phase of the AC grid voltage, and filtering the corresponding phase of the voltage of the filter capacitor
  • the peak value of the capacitor voltage stops driving the switching tube in the inverter to act.
  • the relay in the embodiment of the present application includes: a first-level relay and a second-level relay; and the first-level relay and the second-level relay are connected in series.
  • the control relay is disconnected, including: when the voltage of the filter capacitor is the same frequency and phase as the AC grid voltage, the control relay of the first stage is disconnected;
  • the effective value of the difference between the voltage and the AC grid voltage is less than the preset value, it is judged that the relay is stuck, including: when the effective value of the difference between the voltage of the filter capacitor and the AC grid voltage is less than the preset value, it is judged that the second-stage relay is stuck.
  • the control relay when the voltage of the filter capacitor is the same frequency and phase as the AC grid voltage, the control relay is disconnected, and also includes: when the voltage of the filter capacitor is the same frequency and phase as the AC grid voltage, the control relay of the first stage is disconnected; when When the effective value of the difference between the voltage of the filter capacitor and the voltage of the AC grid is less than the preset value, it is judged that the relay is stuck. level relay sticking.
  • the solutions provided in the embodiments of the present application can be applied to a photovoltaic system where the power grid side is not grounded, and can also be applied to a photovoltaic system whose V-phase is grounded.
  • the V phase can be any of the three phases of the AC power grid.
  • the following describes in detail the application of the solution provided by the embodiment of the present application to any phase-grounded photovoltaic system. Systematic relay detection method.
  • this figure is a flow chart of another relay detection method provided by the embodiment of the present application.
  • S902 Stop driving the switching tube in the inverter within the preset phase range of the voltage of the filter capacitor.
  • the sampling method of the AC grid voltage is DC blocking sampling, that is, the sampling AC grid voltage is AC voltage, and the voltage of the filter capacitor is non-DC blocking sampling.
  • phase V represents any one of the three phases.
  • the inverter When the switching tube of phase V of the inverter is driven to operate, the inverter outputs AC power, and the voltage of the filter capacitor of phase V is AC voltage. Therefore, when the relay switch corresponding to V is normally turned off, the voltage of the filter capacitor corresponding to V collected by the photovoltaic system is an effective voltage value. Therefore, the voltage difference between the two ends of the V-phase relay is the effective voltage value minus 0, that is, the difference between the AC grid voltage corresponding to the V-phase relay and the voltage of the filter capacitor is an effective voltage value, which is greater than the preset value, and the V-phase relay is judged is in normal condition.
  • the V-phase relay when the V-phase relay is normally disconnected, the V-phase relay is judged to be in a normal state, that is, the technical solution can prevent the relay from being misdiagnosed as adhesion.
  • the method provided in the embodiment of the present application further includes: when judging that the first phase relay is stuck, driving the switching tube of the first phase in the inverter to act, and when the voltage of the filter capacitor and the AC grid When the effective value of the voltage difference is less than the preset value, the first phase relay is abnormal; the first phase is any one of the three phases of the AC grid.
  • the embodiment of the present application provides a relay detection method
  • the controller corresponding to the relay can stop driving the switching tube in the inverter when the voltage value of the filter capacitor is large, so as to ensure When detecting the connection, the voltage of the filter capacitor is fixed at the phase with a larger voltage value, so as to prevent the voltage of the AC grid voltage from being lower than the voltage short-circuit threshold, thereby preventing the system from judging that the fault is a short circuit from the AC grid to ground, and the relay is stuck but not detected. out of the situation.
  • the switch tube in the inverter can be activated to detect the relay again, so as to prevent the relay from being misdiagnosed as stuck when the relay is in a normal state.
  • the embodiment of the present application also provides a power supply system, which will be described in detail below with reference to the accompanying drawings.
  • the technical solution for detecting whether the relay is stuck provided by the embodiment of the present application is not only applicable to photovoltaic systems, but also applicable to other power systems with inverters and relays, as long as the input terminal of the inverter is connected to a DC power supply.
  • FIG. 10 this figure is a schematic diagram of a power supply system provided by an embodiment of the present application.
  • the power supply system provided by the embodiment of the present application includes: an inverter 100 , a filter capacitor 400 , a relay 600 and a controller 500 .
  • the input terminal of the inverter 100 is used to connect the DC power supply 700, the output terminal of the inverter 100 is connected to the first terminal of the relay 600, and the second terminal of the relay 600 is connected to the AC grid; the output terminal of the inverter 100 is connected to the filter capacitor 400 .
  • the controller 500 is configured to send a disconnection instruction to the relay 600 when the voltage of the filter capacitor 400 has the same frequency and phase as the AC grid voltage, and stop driving the inverter when the phase of the voltage of the filter capacitor 400 is within a preset phase range
  • a fault alarm message of the relay 600 is sent, wherein the phase of the voltage of the filter capacitor 400 is at the preset phase When within the range, the voltage of the filter capacitor 400 is greater than or equal to the preset threshold.
  • the embodiment of the present application does not limit the specific type of the DC power supply.
  • the source of the DC power supply can be: wind power generation, hydropower generation, and energy storage power station, in addition to the photovoltaic array introduced in the above embodiments.
  • the controller provided in the embodiment of the present application only seals the inverter within the preset phase range of the voltage of the filter capacitor, so as to ensure that the voltage of the filter capacitor is at a relatively large value, and the voltage of the filter capacitor is equivalent to the side of the AC power grid , due to the large voltage on the filter capacitor, the voltage of the AC grid to the ground is raised to avoid being detected as a short circuit to the ground of the AC grid, so that the relay is actually detected to be stuck.
  • the controller in the power supply system provided by the embodiment of the present application can stop driving the switching tube in the inverter when the voltage value of the filter capacitor is large, so as to ensure that the filtering
  • the voltage of the capacitor is at a large value to prevent the voltage of the AC grid voltage from being lower than the voltage short-circuit threshold.
  • the default relay is normal, causing the relay to stick but miss detection. Due to the technical solution provided by the embodiment of the present application, the voltage of the filter capacitor is sufficiently large, so when the relay is stuck, the relay sticking can be accurately detected.

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Abstract

本申请公开了一种光伏系统、继电器检测方法及电源系统，该光伏系统包括逆变器、滤波电容、继电器和控制器；其中滤波电容连接在逆变器的输出端，继电器连接在逆变器的输出端和交流电网之间，在进行继电器的故障检测时，例如黏连，控制器对逆变器进行封波，停止驱动逆变器中的开关管，逆变器停止输出功率，然后判断继电器两端的电压差是否大于预设值，来确定继电器是否故障，当故障时发送故障告警信息。控制器只在滤波电容的电压的预设相位范围内对逆变器进行封波，保证滤波电容的电压处于较大值，滤波电容的电压等效到交流电网侧，由于滤波电容上的电压较大，拉高交流电网对地的电压，从而避免被检测为交流电网对地短路，从而准确检测继电器故障。

Description

一种光伏系统、继电器检测方法及电源系统 技术领域
本申请涉及电力系统技术领域，尤其涉及一种光伏系统、继电器检测方法及电源系统。
背景技术
光伏系统包括光伏阵列和逆变器，其中，逆变器除了包括功率变换电路以外，还包括继电器，功率变换电路通过继电器与电网相连。其中，逆变器的控制器可以控制继电器的开关状态来实现光伏并网、光伏离网、光伏系统保护等作用。因此继电器的状态是否正常对光伏系统具有重大的影响。
继电器在实际应用中可能会出现异常，即继电器接收到断开指令后没有成功断开，而保持闭合的状态，例如继电器出现黏连等不能成功断开的故障。
目前，检测继电器是否故障的方案均可靠性较差，可能出现漏检的情况，例如继电器发生故障黏连了，但是未检测出继电器黏连，使光伏系统存在较大的隐患。
发明内容
本申请提供了一种光伏系统、继电器检测方法及电源系统，能够准确检测继电器是否故障，从而在继电器故障时，及时发出故障告警。
本申请提供一种光伏系统，包括：逆变器、滤波电容、继电器和控制器；逆变器的输入端用于连接光伏阵列，逆变器的输出端连接继电器的第一端，继电器的第二端用于连接交流电网；逆变器的输出端连接滤波电容；控制器，用于在滤波电容的电压与交流电网电压频率相同且相位相同时向继电器发送断开指令，并在滤波电容的电压的相位在预设相位范围内时停止驱动逆变器中开关管动作后，检测到滤波电容的电压与交流电网电压的差值的有效值小于预设值时，发送继电器故障告警信息，其中滤波电容的电压的相位在预设相位范围内时滤波电容的电压大于等于预设阈值。
由此可知，为了避免对逆变器进行封波时，交流电网对地的电压太小，导致逆变器故障被检测为交流电网对地短路。本申请提供的光伏系统中的控制器只在滤波电容的电压的预设相位范围内对逆变器进行封波，从而保证滤波电容的电压处于较大值，滤波电容的电压等效到交流电网侧，由于滤波电容上的电压较大，拉高了交流电网对地的电压，从而避免被检测为交流电网对地短路，从而可以检测出继电器发生故障。
作为一种可能的实施方式，本申请提供的控制器，具体用于通过交流电网电压的相位获得滤波电容的电压的相位。由此可知，该技术方案可以直接通过交流电网的电压获得滤波电容电压，避免了在滤波电容侧新增电压检测电路，从而使得本申请提供光伏系统的成本减少。
作为一种可能的实施方式，本申请提供的控制器，具体用于对交流电网任一相的相电压进行锁相，获得交流电网电压的相位。本申请实施例对交流电网任一相的相电压进行锁相后，当检测出该相对应的继电器黏连，发出继电器黏连警告，以使故障得到及时处理。
作为一种可能的实施方式，本申请提供的控制器，具体用于滤波电容的电压的相位在滤波电容的电压的峰值处停止驱动逆变器中的开关管动作。控制器在滤波电容的电压的峰值出停止驱动逆变器中的开关管的动作，可以使得滤波电容的电压保持在峰值，即使得滤 波电容的电压保持在极大值，从而拉高交流电网对地的电压，进而避免被检测为交流电网对地短路，使得继电器发生故障可以被真正检测到。
作为一种可能的实施方式，本申请提供的继电器包括：第一级继电器和第二级继电器；第一级继电器和第二级继电器串联连接在逆变器的输出端和交流电网之间；控制器，具体用于向第一级继电器发送闭合指令时，向第二级继电器发送断开指令，在滤波电容的电压与交流电网电压的差值的有效值小于预设值时，发送第二级继电器故障告警信息。当继电器包含第一级继电器和第二级继电器时，对于继电器的检测可以分别检测第一级继电器和第二级继电器，提高检测的准确度。
作为一种可能的实施方式，本申请提供的继电器包括：第一级继电器和第二级继电器；第一级继电器和第二级继电器串联连接在逆变器的输出端和交流电网之间；控制器，具体用于向第一级继电器发送断开指令时，向第二级继电器发送闭合指令，在滤波电容的电压与交流电网电压的差值的有效值小于预设值时，发送第一级继电器故障告警信息。
作为一种可能的实施方式，本申请中的交流电网三相中任一相接地时，控制器用于在滤波电容的电压与交流电网电压的差值的有效值小于预设值之后，还用于驱动逆变器中任一相的开关管动作，判断滤波电容的电压与交流电网电压的差值的有效值继续小于预设值时，再发送任一相相继电器故障告警信息。
以V相表示三相中的任一相，在V相接地的前提下，V相对应的交流电网电压由于V相接地因此为0。本申请实施例提供的技术方案在测量滤波电容的电压之前，停止驱动逆变器中的开关管动作，V相对应的滤波电容的电压为稳定的直流电压。又由于V相对应的滤波电容的电压为非隔直采样，因此采集的滤波电容的电压也为0。由此可知，V相对应的交流电网电压和滤波电容的电压的差值的有效值为零，即小于预设值30V。因此若采用上述的方案检测继电器是否黏连，在继电器正常断开时，接地相(V相)对应的交流电网电压的有效值和滤波电容的电压的差值的有效值也为零，继电器将被误诊为黏连。当驱动逆变器V相的开关管动作时，逆变器输出交流电，V相滤波电容的电压为交流电压。因此在V相对应的继电器开关正常断开时，光伏系统采集的V相对应的滤波电容的电压为有效的电压值。从而V相继电器两端的电压差为滤波电容的电压值减去0，即V相继电器对应的交流电网电压和滤波电容的电压的差值为滤波电容的电压值，大于预设值，V相继电器被判断为状态正常。本申请实施例提供的技术方案在V相继电器正常断开时，V相继电器被判断为正常，即该技术方案可以避免继电器被误诊为黏连。
作为一种可能的实施方式，本申请提供的控制器，在滤波电容的电压与交流电网电压的差值的有效值小于预设值之后，还用于驱动逆变器中三相中任一相的开关管动作；在滤波电容的电压与交流电网电压的差值的有效值继续小于预设值时，再发送任一相的继电器故障告警信息。例如故障为继电器黏连，本申请实施例提供的光伏系统，在判断继电器中的任一相继电器黏连时，也可以在判断该相继电器黏连后，不发送继电器黏连故障告警信息，而是驱动逆变器中黏连相对应的逆变器中的开关管动作，当滤波电容的电压与交流电网电压的差值的有效值小于预设值时，才发送继电器黏连的故障告警信息，可以提高继电器故障检测的准确性和可靠性。
根据上述实施例提供的光伏系统，以上系统的优点同样适用于方法部分，在此不再赘述。本申请还提供了一种继电器检测方法，该方法应用于光伏系统，光伏系统包括逆变器、滤波电容和继电器；逆变器的输入端用于连接光伏阵列，逆变器的输出端连接继电器的第一端，继电器的第二端连接交流电网；逆变器的输出端连接滤波电容；该方法包括：当滤波电容的电压与交流电网电压频率相同且相位相同时，向继电器发送断开指令；在滤波电容的电压的预设相位范围内停止驱动逆变器中的开关管动作；当检测到滤波电容的电压与交流电网电压的差值的有效值小于预设值时，发送继电器故障告警信息；其中滤波电容的电压的相位在预设相位范围内时滤波电容的电压大于等于预设阈值。
作为一种可能的实施方式，本申请实施例提供的继电器检测方法还包括：通过交流电网电压的相位获得滤波电容的电压的相位。具体可以为：对交流电网任一相的相电压进行锁相，获得交流电网电压的相位。
作为一种可能的实施方式，本申请实施例提供的滤波电容的电压的相位在预设相位范围内停止驱动逆变器中的开关管动作，具体包括：滤波电容的电压的相位对应滤波电容的电压的峰值处停止驱动逆变器中的开关管动作。
作为一种可能的实施方式，本申请实施例提供的继电器包括：第一级继电器和第二级继电器；第一级继电器和第二级继电器串联连接在逆变器的输出端和交流电网之间；向继电器发送断开指令，包括：向第一级继电器发送闭合指令时，向第二级继电器发送断开指令，当检测到滤波电容的电压与交流电网电压的差值的有效值小于预设值时，发送继电器故障告警信息，包括：在滤波电容的电压与交流电网电压的差值的有效值小于预设值时，发送第二级继电器故障告警信息。
作为一种可能的实施方式，本申请实施例提供的继电器包括：第一级继电器和第二级继电器；第一级继电器和第二级继电器串联连接在逆变器的输出端和交流电网之间；向继电器发送断开指令，包括：向第一级继电器发送断开指令时，向第二级继电器发送闭合指令；当检测到滤波电容的电压与交流电网电压的差值的有效值小于预设值时，发送继电器故障告警信息，包括：在滤波电容的电压与交流电网电压的差值的有效值小于预设值时，发送第一级继电器故障告警信息。
作为一种可能的实施方式，在交流电网三相中任一相接地时，在滤波电容的电压与交流电网电压的差值的有效值小于预设值之后，该方法还包括：驱动逆变器中任一相的开关管动作，判断滤波电容的电压与交流电网电压的差值的有效值继续小于预设值时，再发送任一相相继电器故障告警信息
作为一种可能的实施方式，在滤波电容的电压与交流电网电压的差值的有效值小于预设值之后，该方法还包括：驱动逆变器中三相中任一相的开关管动作，在滤波电容的电压与交流电网电压的差值的有效值继续小于预设值时，再发送任一相的继电器故障告警信息。
根据上述实施例提供的光伏系统和继电器检测方法，本申请还提供了一种光伏系统，包括：逆变器、滤波电容、继电器和控制器；逆变器的输入端用于连接光伏阵列，逆变器的输出端连接继电器的第一端，继电器的第二端连接交流电网；逆变器的输出端连接滤波电容；控制器，用于在滤波电容的电压与交流电网电压频率相同且相位相同时向继电器发 送断开指令，驱动逆变器中三相中任一相的开关管动作；在滤波电容的电压与交流电网电压的差值的有效值小于预设值时，发送任一相的继电器故障告警信息。
根据上述实施例提供的光伏系统和继电器检测方法，本申请还提供了一种电源系统，包括：逆变器、滤波电容、继电器和控制器；逆变器的输入端用于连接直流电源，逆变器的输出端连接继电器的第一端，继电器的第二端连接交流电网；逆变器的输出端连接滤波电容；控制器用于在滤波电容的电压与交流电网电压频率相同且相位相同时向继电器发送断开指令，并在滤波电容的电压的相位在预设相位范围内时停止驱动逆变器中开关管动作后，检测到滤波电容的电压与交流电网电压的差值的有效值小于预设值时，发送继电器故障告警信息，其中滤波电容的电压的相位在预设相位范围内时滤波电容的电压大于等于预设阈值。
本申请提供的技术方案具有以下优点：
该光伏系统包括逆变器、滤波电容、继电器和控制器；其中滤波电容连接在逆变器的输出端，继电器连接在逆变器的输出端和交流电网之间，在进行继电器的故障检测时，例如黏连故障；控制器对逆变器中的开关管进行封波，即停止驱动逆变器中的开关管，逆变器停止输出功率，然后判断继电器两端的电压差是否大于预设值，来确定继电器是否黏连，其中继电器靠近逆变器一侧的电压为滤波电容的电压，继电器靠近交流电网一侧的电压为交流电网的电压。但是，当继电器真正黏连时，容易判断为交流电网对地短路，此时默认继电器正常没有黏连，不再检测继电器，会造成继电器黏连被漏检，为了解决该技术问题，本申请提供的技术方案，控制器只在滤波电容的电压的预设相位范围内对逆变器进行封波，从而保证滤波电容的电压处于较大值，滤波电容的电压等效到交流电网侧，由于滤波电容上的电压较大，拉高了交流电网对地的电压，从而避免被检测为交流电网对地短路，从而真正检测出继电器发生黏连。
附图说明
图1为本申请实施例提供的一种光伏系统的示意图；
图2为本申请实施例提供的一种光伏系统的电路图；
图3为本申请实施例提供的另一种光伏系统的示意图；
图4为本申请实施例提供的一种光伏系统的等效电路图；
图5为本申请实施例提供的另一种光伏系统的等效电路图；
图6为本申请实施例提供的另一种光伏系统的电路图；
图7为本申请实施例提供的一种V相接地的光伏系统的电路图；
图8为本申请实施例提供的一种继电器检测方法的流程图；
图9为本申请实施例提供的另一种继电器检测方法的流程图；
图10为本申请实施例提供的一种电源系统的示意图。
具体实施方式
以下说明中的“第一”、“第二”等用词仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”等的特征可以明示或者隐含地包括一个或者更多该特征。在本申请的描述中，除非另有说明，“多 个”的含义是两个或两个以上。
此外，本申请中，“上”、“下”等方位术语可以包括但不限于相对附图中的部件示意置放的方位来定义的，应当理解到，这些方向性术语可以是相对的概念，它们用于相对于的描述和澄清，其可以根据附图中部件附图所放置的方位的变化而相应地发生变化。
在本申请中，除非另有明确的规定和限定，术语“连接”应做广义理解，例如，“连接”可以是固定连接，也可以是可拆卸连接，或成一体；可以是直接相连，也可以通过中间媒介间接相连。此外，术语“耦接”可以是实现信号传输的电性连接的方式。“耦接”可以是直接的电性连接，也可以通过中间媒介间接电性连接。
本申请实施例涉及一种光伏系统，该光伏系统包括逆变器和继电器，逆变器的输入端连接直流电源，逆变器的输出端通过继电器连接交流电网，一般继电器集成在逆变器的机柜中。为了实际工作的安全保护，能够可靠将逆变器和交流电网断开，一般继电器包括串联的两级，即第一级继电器和第二级继电器。
下面以继电器包含第一级继电器和第二级继电器为例介绍本申请实施例提供的一种光伏系统的基本架构。
参见图1，该图为本申请实施例提供的一种光伏系统的示意图。
本申请实施例提供的光伏系统，包括：逆变器100、第一级继电器200和第二级继电器300，以三相逆变器和三相交流电网为例，第一级继电器200包括的三相分别为K1、K3和K5，第二级继电器300包括的三相分别为K2、K4和K6。
逆变器100的输入端用于连接直流电源DC。本申请实施例不限定直流电源DC的具体形式，以直流电源DC为光伏阵列为例进行说明。
逆变器100的输出端连接第一级继电器200的第一端，第一级继电器200的第二端连接第二级继电器300的第一端，第二级继电器300的第二端用于连接交流电网。
作为一种可能的实施方式，本申请实施例提供的光伏系统，第一级继电器200中的K1、K3和K5可以受同一个开关信号控制，即同步动作，第二级继电器300中的K2、K4和K6也可以受同一个开关信号控制，即同步动作。作为另一种可能的实施方式，第一级继电器200中的K1、K3和K5可以受不同的开关信号控制，第二级继电器300中的K2、K4和K6也可以受不同的开关信号控制，本申请实施例对此不做限定。
为了简化本申请实施例提供的技术方案，方便对本申请实施例提供的技术方案的理解，下面对于继电器是否故障在收到断开指令时不能有效断开，即断开逆变器与交流电网的连接，以继电器黏连为例进行介绍，以一级继电器中的三相开关同时动作为例进行介绍。
参见图2，该图为本申请实施例提供的一种光伏系统的电路图。
本申请实施例提供的光伏系统包括：逆变器100、第一级继电器200和第二级继电器300和滤波电容400。
逆变器100的正输入端和负输入端分别连接直流电源的直流正母线BUS+和直流负母线BUS-。
逆变器100的输出端连接第一级继电器200的第一端，第一级继电器200的第二端连 接第二级继电器300的第一端，第二级继电器300的第二端用于连接交流电网，逆变器100输入端的直流中点和输出端之间连接滤波电容400。在实际应用中逆变器100、第一级继电器200和第二级继电器300可以均集成在逆变器的机柜内部。
当检测继电器是否存在黏连等故障时，需要控制一级继电器闭合，控制被检测的一级继电器断开，判断被检测的一级继电器的两端的电压是否大于预设值，当大于预设值时，判断被检测的继电器未发生黏连，反之判断黏连。对于两级串联的继电器，下面为了更好地理解本申请实施例提供的光伏系统，本实施例统称为继电器来介绍本申请实施例提供的技术方案。
本申请实施例提供的光伏系统可以检测继电器是否发生了故障，例如继电器是否发生了黏连，即是否存在控制器已经向继电器发送了断开指令，但继电器未断开的情况。为了更好地理解本申请实施例提供的方案，下面将以检测继电器是否发生了黏连为示例，介绍本申请实施例提供的方案。
参见图3，该图为本申请实施例提供的另一种光伏系统的示意图。
本申请实施例提供的光伏系统，包括：逆变器100、滤波电容400、继电器600和控制器500。
逆变器100的输入端用于连接光伏阵列，逆变器100的输出端连接继电器600的第一端，继电器600的第二端用于连接交流电网；逆变器100的输出端连接滤波电容400。
本申请实施例中为了避免逆变器随机封波时，滤波电容上的电压较小，如果继电器发生黏连，但是判断为交流电网对地短路，而造成继电器黏连被漏检，因此，本申请实施例提供的技术方案是在滤波电容上的电压较大时封波，而不采用随机封波，进而拉高交流电网对地的电压，不会被检测为交流电网对地短路，当继电器发生黏连时，可以被可靠检测出来。
控制器500，用于在滤波电容400的电压与交流电网电压频率相同且相位相同时向继电器600发送断开指令，并在滤波电容400的电压的相位在预设相位范围内时停止驱动逆变器100中开关管动作后，检测到滤波电容400的电压与交流电网电压的差值的有效值小于预设值时，发送继电器600故障告警信息，其中滤波电容400的电压的相位在预设相位范围内时滤波电容400的电压大于等于预设阈值，预设阈值可以根据需要来选择，选择靠近滤波电容的电压峰值即可，即封波时保证滤波电容上的电压较大。
本申请实施例不限定预设值的具体数值，可以根据实际产品的需要来设置，只要可以可靠检测出继电器是否黏连即可，例如，预设值可以为30V，当继电器两端的电压差大于30V时，判断继电器正常未发生黏连；当继电器两端的电压差小于30V时，判断继电器发生黏连，出现异常，发送故障告警信息，需要对继电器进行检修或更换。
应该理解，上述提供的技术方案可以在控制滤波电容的电压与交流电网电压频率相同且相位相同后，向待检测的继电器发送断开指令，然后随机停止逆变器的驱动信号，即封波，不再驱动逆变器中开关管动作。
当待检测的继电器接收到断开指令成功断开时，即继电器的状态正常未发生黏连，滤波电容的电压为预设相位对应的电压，此时滤波电容的电压和交流电网电压的差值的有效 值大于预设值。当待检测的继电器接收到断开指令后未断开时，即继电器的状态异常发生黏连，此时滤波电容的电压和交流电网电压的差值的有效值小于预设值。
本申请实施例提供的技术方案，控制器只在滤波电容的电压的预设相位范围内对逆变器进行封波，从而保证滤波电容的电压处于较大值，滤波电容的电压等效到交流电网一侧，由于滤波电容上的电压较大，拉高了交流电网对地的电压，从而避免被检测为交流电网对地短路，从而真正检测出继电器发生黏连。
本申请实施例中的预设相位范围为滤波电容的电压值较大对应的预设相位范围，例如在滤波电容的电压峰值附近进行封波，由于滤波电容上的电压为交流电压，因此可以通过判断交流电压的相位来对应峰值附近的电压。
本申请实施例提供光伏系统中，作为一种可能的实施方式本申请实施例中的预设相位范围可以包括，大于预设电容电压的滤波电容的电压值对应的相位范围。
下面结合光伏系统的等效电路图对本申请实施例提供的继电器检测的工作原理进行介绍。
参见图4，该图为本申请实施例提供的一种光伏系统的等效电路图。
本申请实施例提供的交流电网每相对地PE的电压分别由三相对地阻抗Za、Zb和Zc决定。下面以C相为例进行介绍，当继电器黏连时，逆变器侧等效阻抗Zcx会并联在交流电网C相对PE端，如图4所示，Zcx并联在Zc两端，因此，交流电网C相对地阻抗变小，但是，为了拉高C相对地电压不会检测为短路故障，本申请实施例中在滤波电容上的电压较大时封波，这样滤波电容上的电压Ucx施加在并联阻抗上，从而拉高C相对地电压，进而来判断继电器是否黏连。
本申请实施例提供的光伏系统，可以在滤波电容的电压预设相位范围内停止驱动逆变器中开关管动作，从而保证检测继电器黏连时，滤波电容的电压Ucx较大，即Ucx保持较大的值。Ucx拉高C相对地电压，因此本申请实施提供的光伏系统可以使交流电网电压对地的电压大于电压短路阈值，不会判断交流电网发生对地短路故障，从而可以真正检测出继电器是否发生黏连。
如果控制器500随机停止驱动逆变器100中的开关管动作，即随机封波，可能在滤波电容的电压较小时封波。如果继电器黏连，滤波电容的电压等效到C相，但是滤波电容的电压较小，C相对地电压还是会小于电压短路阈值，检测出交流电网对地短路，此时默认继电器正常，而不会检出继电器黏连。
下面将结合光伏系统的等效电路图分析随机封波漏检继电器黏连的原因。
参见图5，该图为本申请实施例提供的另一种光伏系统的等效电路图。
本申请实施例提供的交流电网三相分别对地PE的电压由三相分别对地阻抗Za、Zb和Zc决定。
下面继续以C相继电器发生黏连为例进行分析，当继电器黏连时，逆变器侧等效阻抗Zcx会并联在交流电网对PE端，如图5所示，Zcx和Zc并联，减小了C相对PE的阻抗。
继电器黏连导致交流电网相对PE的阻抗减小，进而导致交流电网电压减小，当交流电网电压对地的电压小于电压短路阈值，则会判断交流电网发生对地短路故障。由于交流电 网对地短路故障时，光伏系统将不再判断继电器是否黏连，默认继电器状态正常，因此继电器黏连不会被检出。
由此可知，本申请实施例提供的随机停止驱动逆变器中的开关管动作的技术方案会出现继电器黏连但无法被检出的情况，因此本申请实施例提供的技术方案在滤波电容的电压的预设相位范围内停止驱动逆变器中的开关管动作，使滤波电容上的电压较大，从而在继电器黏连检测时，避免出现交流电网对地电压小于电压短路阈值的情况，实现继电器黏连的可靠检测。
上述内容主要介绍本申请实施例提供的方案的原理，下面将结合具体地实施例介绍本申请实施例的具体实施方案。
为了简化对滤波电容的电压的获取，作为一种可能的实施方式，本申请实施例提供的控制器，具体用于交流电网电压的相位在预设相位范围内停止驱动逆变器中的开关管动作。由于交流电网电压与滤波电容的电压频率相同且相位相等，即交流电网电压的相位与滤波电容的相位相同，因此可以通过检测交流电网电压的相位来判断滤波电容的电压相位，不需要额外的硬件检测电路，便可以在交流电网电压的相位在预设相位范围内停止驱动逆变器中的开关管动作。
作为一种可能的实施方式，本申请实施例提供的控制器，具体用于对交流电网电压进行锁相，获得交流电网电压的相位，由于滤波电容的电压的相位与交流电网电压的相位同频同相，因此，可以交流电网电压的相位在预设相位范围内停止驱动逆变器中的开关管动作。本申请实施例提供的方案可以对交流电网电压进行锁相，获得交流电网电压的相位，以使在交流电网电压的限位在预设相位范围内时，停止驱动逆变器中开关管动作。本申请实施例也可以通过其他手段在交流电网电压的限位在预设相位范围内时，停止驱动逆变器中开关管动作，本申请实施例在此不做限定。
参见图6，该图为本申请实施例提供的另一种光伏系统的电路图。
如图6所示，本申请实施例提供的继电器包括：第一级继电器200和第二级继电器300。第一级继电器200和第二级继电器300串联连接。
控制器500，具体用于向第一级继电器200发送闭合指令时，向第二级继电器300发送断开指令，滤波电容400的电压与交流电网电压的差值的有效值小于预设值时，发送第二级继电器300故障告警信息；还具体用于向第一级继电器200发送断开指令时，向第二级继电器300发送闭合指令，在滤波电容400的电压与交流电网电压的差值的有效值小于预设值时，发送第一级继电器200故障告警信息。应该理解，当本申请实施例提供光伏系统包含第一级继电器和第二级继电器时，应该分别断开两级继电器，例如断开第一级继电器时，闭合第二级继电器。
如图6所示，本申请实施例中的交流电网电压包括三相，即A相、B相和C相，三相电压之间相位相差120度。相应地，本申请实施例中的继电器也包括三个开关，第一级继电器200包括第一开关K1、第三开关K3和第五开关K5。第二级继电器300包括第二开关K2、第四开关K4和第六开关K6。
为了方便对继电器进行控制，本申请实施例中的第一级继电器或第二级继电器(以下 简称继电器)中的三个开关可以同用同一个信号接收端。为了简化安装，本申请实施例中的继电器中的三个开关可以为一个整体，当继电器的三个开关中任何一个开关在接收到断开信号后没有断开时，即任何一个开关黏连时，则判断该继电器黏连，将更换整个继电器。
作为一种可能的实施方式，本申请实施例提供的控制器，具体用于对交流电网任一相的相电压进行锁相，获得交流电网电压的相位，交流电网电压的相位在预设相位范围内停止驱动逆变器中的开关管动作。应该理解，本申请实施例对交流电网任一相的相电压进行锁相后，当检测出该相对应的开关黏连，即可以判断继电器发生了黏连，发出继电器黏连警告，使得整个继电器将被更换。
为了尽量保证在对继电器黏连的检测时，滤波电容的电压被固定在电压值较大的相位，避免交流电网电压对地的电压小于电压短路阈值，从而避免系统判断故障为交流电网对地短路。作为一种可能的实施方式，本申请实施例提供的控制器，具体用于对交流电网任一相的相电压进行锁相，获得交流电网电压的相位，根据交流电网电压的相位获得滤波电容的电压的相位，在滤波电容的电压的相位对应滤波电容的电压的峰值处，停止驱动逆变器中的开关管动作。应该理解，本申请实施例在滤波电容的电压相位对应滤波电容的电压的峰值处，停止驱动逆变器中的开关管动作，可以使得滤波电容的电压被固定在电压的最大值，从而尽可能地避免交流电网电压对地的电压小于电压短路阈值，从而避免系统判断为交流电网对地短路故障。
本申请以上实施例提供的方案可以应用于电网侧不接地的光伏系统，下面介绍对于电网侧V相接地的光伏系统检测继电器黏连的方案，V相可以为交流电网的三相中的任一相任一相，下面以C相接地作为示例，具体介绍本申请实施例所提供的方案应用于V相接地的光伏系统的情况。
参见图7，该图为本申请实施例提供的一种V相接地的光伏系统电路图。
如图7所示，本申请实施例提供的光伏系统中的交流电网电压包括以下三相：A相、B相和C相。其中，C相与PE相连，即C相接地。交流电网电压的采样方式为隔直采样，即采样的交流电网电压为交流电压，滤波电容的电压为非隔直采样。
本申请实施例中，为了能够准确判断V相的继电器是否发生黏连，当交流电网的V相接地且判断V相继电器黏连时，不发送继电器故障告警信息，即先不告警，而是驱动逆变器中V相的开关管动作，当滤波电容的电压与交流电网电压的差值的有效值继续小于预设值时，才最终判断继电器发生黏连，发送继电器故障告警信息，如此可以避免继电器在状态正常时被误诊为黏连。
在V相(C相)接地的前提下，C相对应的交流电网电压由于C相接地因此为0。本申请实施例提供的技术方案在测量滤波电容的电压之前，停止驱动逆变器中的开关管动作，C相对应的滤波电容的电压为稳定的直流电压。又由于C相对应的滤波电容的电压为非隔直采样，因此采集的滤波电容的电压也为0。由此可知，C相对应的交流电网电压和滤波电容的电压的差值的有效值为零，即小于预设值30V。因此若采用上述的方案检测继电器是否黏连，在继电器正常断开时，接地相(C相)对应的交流电网电压的有效值和滤波电容的电压的差值的有效值也为零，继电器将被误诊为黏连。
为了解决上述的技术问题，作为一种可能的实施方式，本申请实施例提供的控制器，还用于在交流电网的V相接地且判断V相继电器黏连时，继续相逆变器中V相的开关管发波，驱动逆变器中V相的开关管动作，当滤波电容的电压与交流电网电压的差值的有效值小于预设值时，发送V相继电器故障告警信息，例如出现了黏连。
应该理解，当驱动逆变器V相的开关管动作时，逆变器输出交流电，V相滤波电容的电压为交流电压。因此在V相对应的继电器开关正常断开时，光伏系统采集的V相对应的滤波电容的电压为电压的有效值。从而V相继电器两端的电压差为滤波电容的电压值减去0，即V相继电器对应的交流电网电压和滤波电容的电压的差值为滤波电容的电压值，大于预设值，V相继电器被判断为状态正常。本申请实施例提供的技术方案在V相继电器正常断开时，V相继电器被判断为正常，即该技术方案可以避免继电器被误诊为黏连。
以上介绍的实现方式是针对V相接地时继电器黏连的检测，即封波后再发波，另外该方式也适用于非V相接地，这样可以更加可靠检测出继电器是否黏连，即封波后检测出黏连了不告警，而是针对黏连的一相或多相继续发波，验证是否真正发生黏连，即本申请实施例提供的控制器，还用于在判断第一相继电器黏连时，驱动逆变器中的第一相的开关管动作，当滤波电容的电压与交流电网电压的差值的有效值小于预设值时，第一相继电器异常；第一相为交流电网的三相中的任一相。即本申请实施例所提供的方案，还可以在任一相继电器黏连时，执行上述的再次判断的动作以避免继电器在状态正常时被误诊为黏连。本申请实施例提供的光伏系统，在判断继电器中的任意一相黏连时(不限定于V相)，也可以在判断该相黏连后，不发送继电器故障告警信息，即不告警，而是驱动逆变器中该相的开关管动作，当滤波电容的电压与交流电网电压的差值的有效值小于预设值时，才发送继电器故障告警信息，可以提高继电器故障检测的准确性和可靠性。
综上所述，本申请实施例提供了一种光伏系统，该光伏系统只在滤波电容的电压的预设相位范围内对逆变器进行封波，从而保证滤波电容的电压处于较大值，滤波电容的电压等效到交流电网侧，由于滤波电容上的电压较大，拉高了交流电网对地的电压，从而避免被检测为交流电网对地短路，从而真正检测出继电器发生黏连。同时，本申请实施例还可以在继电器黏连时，启动逆变器中的开关管动作，从而再次对继电器进行检测，避免继电器在状态正常时被误诊为黏连。
根据上述实施例提供的光伏系统，本申请实施例还提供了另一种光伏系统，即判断光伏系统中的继电器是否黏连时，可以适用于V相接地，也可以适用于V相不接地，下面以该方案适用于V相接地为例进行介绍。控制器可以向逆变器中的开关管发波，然后判断滤波电容的电压与交流电网电压的差值的有效值是否小于预设值来判断继电器是否黏连故障。即该光伏系统的控制器在滤波电容的电压与交流电网电压频率相同且相位相同时向继电器发送断开指令，向逆变器中三相任一相的开关管发波，即驱动开关管动作，给滤波电容充电，在滤波电容的电压与交流电网电压的差值的有效值继续小于预设值时，再发送任一相的继电器故障告警信息。。
本申请实施例提供的光伏系统，包括：逆变器、滤波电容、继电器和控制器。
逆变器的输入端用于连接光伏阵列，逆变器的输出端连接继电器的第一端，继电器的 第二端连接交流电网；逆变器的输出端连接滤波电容。
控制器，用于滤波电容的电压与交流电网电压频率相同且相位相同时向继电器发送断开指令，驱动逆变器中的三相任一相的开关管动作，判断滤波电容的电压与交流电网电压的差值的有效值是否小于预设值时，如果是则发送任一相继电器故障告警信息。
下面以V相代表任一相作为示例，介绍本申请实施例提供的光伏系统。
控制器发波之后，滤波电容上有交流电压，交流电网电压由于V相接地为0，当继电器正常断开时，滤波电容的电压与交流电网电压的差值的有效值大于预设值，光伏系统判断继电器的工作状态正常。如果继电器黏连，滤波电容通过黏连的继电器通过V相接地，滤波电容的电压为0，交流电网电压由于V相接地也为0，滤波电容的电压与交流电网电压的差值的有效值也为0，0小于预设值，则光伏系统判断继电器黏连。
本申请实施例提供的光伏系统，也可以用于判断继电器中的任意一相黏连时(不限定于V相)，驱动逆变器中该相的开关管动作，当继电器黏连时滤波电容和交流电网通过继电器连接，滤波电容的电压接近于交流电网的电压，当继电器工作状态正常时，滤波电容的电压接近于逆变器输出的电压，与交流电网的电压存在一定的差值，因此当滤波电容的电压与交流电网电压的差值的有效值小于预设值时，光伏系统也可以判断继电器黏连。
基于以上实施例提供的一种光伏系统，本申请实施例还提供了一种继电器检测方法，下面结合附图进行详细说明。
参见图8，该图为本申请实施例提供的一种继电器检测方法的流程图。
该继电器检测方法应用于光伏系统，光伏系统包括逆变器、滤波电容、继电器和控制器；逆变器的输入端用于连接光伏阵列，逆变器的输出端连接继电器的第一端，继电器的第二端连接交流电网；逆变器的输出端连接滤波电容；如图8所示，本申请实施例提供的继电器检测方法，包括以下步骤：
S801：当滤波电容的电压与交流电网电压频率相同且相位相同时，向继电器发送断开指令。
S802：在滤波电容的电压的预设相位范围内停止驱动逆变器中的开关管动作。
S803：当检测到滤波电容的电压与交流电网电压的差值的有效值小于预设值时，发送继电器故障告警信息。
本申请实施例提供的技术方案，控制器只在滤波电容的电压的预设相位范围内对逆变器进行封波，从而保证滤波电容的电压处于较大值，滤波电容的电压等效到交流电网一侧，由于滤波电容上的电压较大，拉高了交流电网对地的电压，从而避免被检测为交流电网对地短路，从而真正检测出继电器发生黏连。
作为一种可能的实施方式，本申请实施例中在滤波电容的电压的预设相位范围内停止驱动逆变器中的开关管动作，包括：在交流电网电压的相位在预设相位范围内停止驱动逆变器中的开关管动作。
作为一种可能的实施方式，本申请实施例中在交流电网电压的相位在预设相位范围内停止驱动逆变器中的开关管动作，包括：对交流电网电压进行锁相，获得交流电网电压的相位，交流电网电压的相位在预设相位范围内停止驱动逆变器中的开关管动作。
作为一种可能的实施方式，本申请实施例中对交流电网电压进行锁相，获得交流电网电压的相位，交流电网电压的相位在预设相位范围内停止驱动逆变器中的开关管动作，包括：对交流电网任一相的相电压进行锁相，获得交流电网电压的相位，交流电网电压的相位在预设相位范围内停止驱动逆变器中的开关管动作。
作为一种可能的实施方式，本申请实施例中对交流电网任一相的相电压进行锁相，获得交流电网电压的相位，交流电网电压的相位在预设相位范围内停止驱动逆变器中的开关管动作，包括：对交流电网任一相的相电压进行锁相，获得交流电网电压的相位，根据交流电网电压的相位获得滤波电容的电压的相位，在滤波电容的电压的相位对应滤波电容的电压的峰值处停止驱动逆变器中的开关管动作。
作为一种可能的实施方式，本申请实施例中继电器包括：第一级继电器和第二级继电器；第一级继电器和第二级继电器串联连接。当滤波电容的电压与交流电网电压频率相同且相位相同时，控制继电器断开，包括：当滤波电容的电压与交流电网电压频率相同且相位相同时控制第一级继电器断开；当滤波电容的电压与交流电网电压的差值的有效值小于预设值时，判断继电器黏连，包括：滤波电容的电压与交流电网电压的差值的有效值小于预设值时，判断第二级继电器黏连；当滤波电容的电压与交流电网电压频率相同且相位相同时，控制继电器断开，还包括：当滤波电容的电压与交流电网电压频率相同且相位相同时控制第一级继电器断开；当滤波电容的电压与交流电网电压的差值的有效值小于预设值时，判断继电器黏连，还包括：滤波电容的电压与交流电网电压的差值的有效值小于预设值时，第二级继电器黏连。
本申请实施例所提供的方案可以应用于电网侧不接地的光伏系统，也可以应用于V相接地的光伏系统。本申请实施例提供的V相接地的光伏系统中V相可以为交流电网的三相中的任一相，下面具体介绍本申请实施例所提供的方案应用于任一相相接地的光伏系统的继电器检测方法。
参见图9，该图为本申请实施例提供的另一种继电器检测方法流程图。
本申请实施例提供的继电器检测方法，包括：
S901：当滤波电容的电压与交流电网电压频率相同且相位相同时，向继电器发送断开指令。
S902：在滤波电容的电压的预设相位范围内停止驱动逆变器中的开关管动作。
S903：检测滤波电容的电压与交流电网电压。
S904：当滤波电容的电压与交流电网电压的差值的有效值小于预设值时，驱动逆变器中三相中任一相的开关管动作。
S905：判断滤波电容的电压与交流电网电压的差值的有效值继续小于预设值时，再发送任一相的继电器故障告警信息。
交流电网电压的采样方式为隔直采样，即采样的交流电网电压为交流电压，滤波电容的电压为非隔直采样。
下面以V相代表三相中的任一相，当驱动逆变器V相的开关管动作时，逆变器输出交流电，V相滤波电容的电压为交流电压。因此在V相对应的继电器开关正常断开时，光伏 系统采集的V相对应的滤波电容的电压为有效的电压值。从而V相继电器两端的电压差为有效的电压值减去0，即V相继电器对应的交流电网电压和滤波电容的电压的差值为有效的电压值，大于预设值，V相继电器被判断为状态正常。本申请实施例提供的技术方案在V相继电器正常断开时，V相继电器被判断为状态正常，即该技术方案可以避免继电器被误诊为黏连。
作为一种可能的实施方式，本申请实施例提供的方法还包括：在判断第一相继电器黏连时，驱动逆变器中的第一相的开关管动作，当滤波电容的电压与交流电网电压的差值的有效值小于预设值时，第一相继电器异常；第一相为交流电网的三相中的任一相。
综上所述，本申请实施例提供了一种继电器检测方法，该继电器对应的控制器可以在滤波电容的电压值较大时停止驱动逆变器中的开关管动作，从而保证在对继电器黏连的检测时，滤波电容的电压被固定在电压值较大的相位，避免交流电网电压对地的电压小于电压短路阈值，从而避免系统判断故障为交流电网对地短路，继电器黏连但未检出的情况。同时，本申请实施例还可以在继电器黏连时，启动逆变器中的开关管动作，从而再次对继电器进行检测，避免继电器在状态正常时被误诊为黏连。
基于以上实施例提供的光伏系统和继电器检测方法，本申请实施例还提供了一种电源系统，下面结合附图进行详细说明。本申请实施例提供的检测继电器是否黏连的技术方案不仅适用于光伏系统，也适用于其他带有逆变器和继电器的电源系统，只要逆变器的输入端连接的直流电源即可。
参见图10，该图为本申请实施例提供的一种电源系统的示意图。
本申请实施例提供的电源系统，包括：逆变器100、滤波电容400、继电器600和控制器500。
逆变器100的输入端用于连接直流电源700，逆变器100的输出端连接继电器600的第一端，继电器600的第二端连接交流电网；逆变器100的输出端连接滤波电容400。
控制器500，用于在滤波电容400的电压与交流电网电压频率相同且相位相同时向继电器600发送断开指令，并在滤波电容400的电压的相位在预设相位范围内时停止驱动逆变器100中开关管动作后，检测到滤波电容400的电压与交流电网电压的差值的有效值小于预设值时，发送继电器600故障告警信息，其中滤波电容400的电压的相位在预设相位范围内时滤波电容400的电压大于等于预设阈值。本申请实施例不限定直流电源的具体类型，例如直流电源的来源除了以上实施例介绍的光伏阵列以外，还可以为：风力发电、水利发电和储能电站等。
本申请实施例提供的控制器只在滤波电容的电压的预设相位范围内对逆变器进行封波，从而保证滤波电容的电压处于较大值，滤波电容的电压等效到交流电网一侧，由于滤波电容上的电压较大，拉高了交流电网对地的电压，避免被检测为交流电网对地短路，从而真正检测出继电器发生黏连。
综上所述，本申请实施例提供的电源系统中的控制器可以在滤波电容的电压值较大时停止驱动逆变器中的开关管动作，从而保证在对继电器黏连的检测时，滤波电容的电压处于较大值，避免交流电网电压对地的电压小于电压短路阈值，检测出对地短路故障而默认 继电器正常，造成继电器黏连了但漏检。由于本申请实施例提供的技术方案，滤波电容的电压足够大，因此，当继电器黏连时，可以准确检测出继电器黏连。
应当理解，在本申请中，“至少一个(项)”是指一个或者多个，“多个”是指两个或两个以上。
本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的精神和范围。

Claims (18)

  1. 一种光伏系统，其特征在于，包括：逆变器、滤波电容、继电器和控制器；
    所述逆变器的输入端用于连接光伏阵列，所述逆变器的输出端连接所述继电器的第一端，所述继电器的第二端用于连接交流电网；
    所述逆变器的输出端连接所述滤波电容；
    所述控制器，用于在所述滤波电容的电压与交流电网电压频率相同且相位相同时向所述继电器发送断开指令，并在所述滤波电容的电压的相位在预设相位范围内时停止驱动所述逆变器中开关管动作后，检测到所述滤波电容的电压与所述交流电网电压的差值的有效值小于预设值时，发送继电器故障告警信息，其中所述滤波电容的电压的相位在所述预设相位范围内时所述滤波电容的电压大于等于预设阈值。
  2. 根据权利要求1所述的光伏系统，其特征在于，所述控制器，还用于通过所述交流电网电压的相位获得所述滤波电容的电压的相位。
  3. 根据权利要求2所述的光伏系统，其特征在于，所述控制器，具体用于对所述交流电网任一相的相电压进行锁相，获得所述交流电网电压的相位。
  4. 根据权利要求1-3任一项所述的光伏系统，其特征在于，所述控制器，具体用于所述滤波电容的电压的相位在所述滤波电容的电压的峰值处停止驱动所述逆变器中的开关管动作。
  5. 根据权利要求1-4任一项所述的光伏系统，其特征在于，所述继电器包括：第一级继电器和第二级继电器；
    所述第一级继电器和所述第二级继电器串联连接在所述逆变器的输出端和所述交流电网之间；
    所述控制器，具体用于向所述第一级继电器发送闭合指令时，向所述第二级继电器发送断开指令，在所述滤波电容的电压与所述交流电网电压的差值的有效值小于所述预设值时，发送所述第二级继电器故障告警信息。
  6. 根据权利要求1-4任一项所述的光伏系统，其特征在于，所述继电器包括：第一级继电器和第二级继电器；
    所述第一级继电器和所述第二级继电器串联连接在所述逆变器的输出端和所述交流电网之间；
    所述控制器，具体用于向所述第一级继电器发送断开指令时，向所述第二级继电器发送闭合指令，在所述滤波电容的电压与所述交流电网电压的差值的有效值小于所述预设值时，发送所述第一级继电器故障告警信息。
  7. 根据权利要求1-6任一项所述的光伏系统，其特征在于，所述交流电网三相中任一相接地时，所述控制器用于在所述滤波电容的电压与所述交流电网电压的差值的有效值小于所述预设值之后，还用于驱动所述逆变器中所述任一相的开关管动作，判断所述滤波电容的电压与所述交流电网电压的差值的有效值继续小于所述预设值时，再发送所述任一相相继电器故障告警信息。
  8. 根据权利要求1-6任一项所述的光伏系统，其特征在于，所述控制器用于在所述滤波 电容的电压与所述交流电网电压的差值的有效值小于所述预设值之后，还用于驱动所述逆变器中三相中任一相的开关管动作，判断所述滤波电容的电压与所述交流电网电压的差值的有效值继续小于所述预设值时，再发送所述任一相的继电器故障告警信息。
  9. 一种继电器检测方法，其特征在于，所述方法应用于光伏系统，所述光伏系统包括逆变器、滤波电容和继电器；所述逆变器的输入端用于连接光伏阵列，所述逆变器的输出端连接所述继电器的第一端，所述继电器的第二端连接交流电网；所述逆变器的输出端连接所述滤波电容，所述方法包括：
    当所述滤波电容的电压与交流电网电压频率相同且相位相同时，向所述继电器发送断开指令；
    在所述滤波电容的电压的预设相位范围内停止驱动所述逆变器中的开关管动作；其中，所述滤波电容的电压的相位在所述预设相位范围内时所述滤波电容的电压大于等于预设阈值
    检测到所述滤波电容的电压与所述交流电网电压的差值的有效值小于预设值时，发送继电器故障告警信息。
  10. 根据权利要求9所述的方法，其特征在于，还包括：通过所述交流电网电压的相位获得所述滤波电容的电压的相位。
  11. 根据权利要求10所述的方法，其特征在于，所述通过所述交流电网电压的相位获得所述滤波电容的电压的相位，具体包括：对所述交流电网任一相的相电压进行锁相，获得所述交流电网电压的相位。
  12. 根据权利要求9-11任一项所述的方法，其特征在于，所述在所述滤波电容的电压的预设相位范围内停止驱动所述逆变器中的开关管动作，包括：
    所述滤波电容的电压的相位对应所述滤波电容的电压的峰值处停止驱动所述逆变器中的开关管动作。
  13. 根据权利要求9-12任一项所述的方法，其特征在于，所述继电器包括：第一级继电器和第二级继电器；
    所述第一级继电器和所述第二级继电器串联连接在所述逆变器的输出端和所述交流电网之间；
    所述向所述继电器发送断开指令，具体包括：
    向所述第一级继电器发送闭合指令时，向所述第二级继电器发送断开指令；
    所述检测到所述滤波电容的电压与所述交流电网电压的差值的有效值小于预设值时，发送继电器故障告警信息，具体包括：
    在所述滤波电容的电压与所述交流电网电压的差值的有效值小于预设值时，发送所述第二级继电器故障告警信息。
  14. 根据权利要求9-12任一项所述的方法，其特征在于，所述继电器包括：第一级继电器和第二级继电器；
    所述第一级继电器和所述第二级继电器串联连接在所述逆变器的输出端和所述交流电网之间；
    所述向所述继电器发送断开指令，具体包括：
    向所述第一级继电器发送断开指令时，向所述第二级继电器发送闭合指令；
    所述检测到所述滤波电容的电压与所述交流电网电压的差值的有效值小于预设值时，发送继电器故障告警信息，具体包括：
    在所述滤波电容的电压与所述交流电网电压的差值的有效值小于预设值时，发送所述第一级继电器故障告警信息。
  15. 根据权利要求9-14任一项所述的方法，其特征在于，在所述交流电网三相中任一相接地时，在所述滤波电容的电压与所述交流电网电压的差值的有效值小于预设值之后，还包括：
    驱动所述逆变器中所述任一相的开关管动作，判断所述滤波电容的电压与所述交流电网电压的差值的有效值继续小于所述预设值时，再发送所述任一相相继电器故障告警信息
  16. 根据权利要求9-14任一项所述的方法，其特征在于，在所述滤波电容的电压与所述交流电网电压的差值的有效值小于所述预设值之后，还包括：
    驱动所述逆变器中三相中任一相的开关管动作，在所述滤波电容的电压与所述交流电网电压的差值的有效值继续小于所述预设值时，再发送所述任一相的继电器故障告警信息。
  17. 一种光伏系统，其特征在于，包括：逆变器、滤波电容、继电器和控制器；
    所述逆变器的输入端用于连接光伏阵列，所述逆变器的输出端连接所述继电器的第一端，所述继电器的第二端连接交流电网；
    所述逆变器的输出端连接所述滤波电容；
    所述控制器，用于在所述滤波电容的电压与交流电网电压频率相同且相位相同时向所述继电器发送断开指令，驱动所述逆变器中三相中任一相的开关管动作；在所述滤波电容的电压与所述交流电网电压的差值的有效值小于预设值时，发送所述任一相的继电器故障告警信息。
  18. 一种电源系统，其特征在于，包括：逆变器、滤波电容、继电器和控制器；
    所述逆变器的输入端用于连接直流电源，所述逆变器的输出端连接所述继电器的第一端，所述继电器的第二端连接交流电网；
    所述逆变器的输出端连接所述滤波电容；
    所述控制器，用于在所述滤波电容的电压与交流电网电压频率相同且相位相同时向所述继电器发送断开指令，并在所述滤波电容的电压的相位在预设相位范围内时停止驱动所述逆变器中开关管动作后，检测到所述滤波电容的电压与所述交流电网电压的差值的有效值小于预设值时，发送继电器故障告警信息，其中所述滤波电容的电压的相位在所述预设相位范围内时所述滤波电容的电压大于等于预设阈值。
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