CN112986813B - Relay detection circuit and detection method of single-phase grid-connected photovoltaic inverter - Google Patents
Relay detection circuit and detection method of single-phase grid-connected photovoltaic inverter Download PDFInfo
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- CN112986813B CN112986813B CN202110246310.1A CN202110246310A CN112986813B CN 112986813 B CN112986813 B CN 112986813B CN 202110246310 A CN202110246310 A CN 202110246310A CN 112986813 B CN112986813 B CN 112986813B
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Abstract
The invention discloses a relay detection circuit of a single-phase grid-connected photovoltaic inverter and a detection method thereof, wherein the relay detection circuit comprises: an input capacitance; the auxiliary relay and the resistor are sequentially connected in series between the first direct current input end and the second direct current input end; the input end of the H6 bridge circuit is respectively connected with the first direct current input end and the second direct current input end, and the output end of the H6 bridge circuit is respectively connected with the live wire and the zero wire; the main relay and the auxiliary relay are connected between the output end of the H6 bridge circuit and the power grid in series, a first sampling point is arranged between the main relay K2 and the auxiliary relay, and a second sampling point is arranged between the auxiliary relay and the power grid; a driving unit which controls the auxiliary relay, the main relay, the auxiliary relay, and the H6 bridge circuit to be closed or opened; and the detection unit judges whether the main relay and the auxiliary relay are closed or opened or not based on the sampling values of the first sampling point and the second sampling point. Compared with the prior art, the invention can ensure that the relay can be detected in a sticking state.
Description
[ technical field ] A method for producing a semiconductor device
The invention relates to the field of relay detection of inverters, in particular to a relay detection circuit of a single-phase grid-connected photovoltaic inverter and a detection method thereof.
[ background of the invention ]
Photovoltaic inverters (PV inverters or solar inverters) can convert variable dc voltage generated by Photovoltaic (PV) solar panels into mains frequency Alternating Current (AC) and can be fed back to commercial power transmission systems or used for off-grid power grids. Photovoltaic inverters are one of the important system Balances (BOS) in photovoltaic array systems, and can be used with general ac powered equipment.
However, when the relay of the photovoltaic inverter is detected, the problem that the single contact of the relay is stuck and cannot be detected exists, so that the power grid cannot be cut off by the relay in the installation and debugging process, and the personal safety is damaged.
Therefore, there is a need to provide a new technical solution to overcome the above problems.
[ summary of the invention ]
The technical problem to be solved by the invention is to provide a relay detection circuit of a single-phase grid-connected photovoltaic inverter and a detection method thereof, which can ensure that a relay can be detected in a sticking state, thereby preventing personal safety from being damaged because the relay cannot cut off a power grid in the installation and debugging process.
In order to solve the above problem, according to a first aspect of the present invention, there is provided a relay detection circuit of a single-phase grid-connected photovoltaic inverter, including: an input capacitor Cdc connected between the first dc input P and the second dc input N of the photovoltaic inverter; the auxiliary relay K1 and the resistor R are sequentially connected in series between the first direct current input end P and the second direct current input end N; an H6 bridge circuit, two input ends of which are respectively connected with the first direct current input end P and the second direct current input end N, two output ends A and B of which are respectively connected with a live wire L and a zero line N, wherein the H6 bridge circuit is used for converting direct current into alternating current; the H6 bridge circuit comprises a main relay K2 and an auxiliary relay K3, wherein the main relay K2 and the auxiliary relay K3 are connected in series between two output ends A and B of the H6 bridge circuit and a power grid through a live wire L and a zero wire N, a first sampling point Q1 is arranged between the main relay K2 and the auxiliary relay K3, and a second sampling point Q2 is arranged between the auxiliary relay K3 and the power grid;
the driving unit outputs driving signals to control the auxiliary relay K1, the main relay K2 and the auxiliary relay K3 to be closed or opened and control the output end of the H6 bridge circuit to open or close open-loop voltage; and the detection unit is used for judging whether the main relay K2 and the auxiliary relay K3 are closed or opened or not based on the sampling values of the first sampling point Q1 and the second sampling point Q2.
According to another aspect of the present invention, the present invention provides a detection method for a relay detection circuit of a single-phase grid-connected photovoltaic inverter, including: the driving unit controls the main relay K2, the auxiliary relay K3 and the auxiliary relay K1 to be switched off, and controls each power switch tube in the H6 bridge circuit to be switched off so as not to generate open-loop voltage at the output end of the H6 bridge circuit; the detection unit 140 calculates an effective value RlyVoltRms1 of the first sampling point Q1, where the effective value RlyVoltRms1 is referred to as a first effective value of the first sampling point Q1, and if the first effective value RlyVoltRms1 is greater than a first voltage threshold, it is determined that at least one of contacts of the live line L and the zero line N of the auxiliary relay K3 is stuck; if the first effective value RlyVoltRms1 is equal to the power grid voltage, judging that the contacts of the live wire L and the zero wire N of the auxiliary relay K3 are stuck; the driving unit controls the main relay K2 and the auxiliary relay K3 to be disconnected, controls the auxiliary relay K1 to be closed, and controls each power switch tube in the H6 bridge circuit to be closed, so that open-loop voltage is not generated at the output end of the H6 bridge circuit; the detection unit 140 calculates an effective value RlyVoltRms2 of the first sampling point Q1, where the effective value RlyVoltRms2 is referred to as a second effective value of the first sampling point Q1, and if an absolute value of a difference between the first effective value RlyVoltRms1 and the second effective value RlyVoltRms2 of the first sampling point Q1 is greater than a first voltage threshold, it is determined that a contact of the zero line N of the sub relay K3 is stuck; the driving unit controls the main relay K2, the auxiliary relay K3 and the auxiliary relay K1 to be disconnected, and controls each power switch tube in the H6 bridge circuit to be opened so as to generate open-loop voltage at the output end of the H6 bridge circuit; the detection unit 140 calculates an effective value RlyVoltRms3 of the first sampling point Q1, where the effective value RlyVoltRms3 is referred to as a third effective value of the first sampling point Q1, and if the third effective value RlyVoltRms3 of the first sampling point Q1 is greater than a first voltage threshold, it is determined that at least one of contacts of the live line L and the zero line N of the main relay K2 is stuck; if the third effective value RlyVoltsrms 3 is equal to the open-loop voltage, judging that the contacts of the live wire L and the zero line N of the main relay K2 are stuck; the driving unit controls the main relay K2 to be closed, controls the auxiliary relay K3 and the auxiliary relay K1 to be disconnected, and controls each power switch tube in the H6 bridge circuit to be opened so as to generate open-loop voltage at the output end of the H6 bridge circuit; the detection module 140 calculates an effective value RlyVoltRms4 of the first sampling point Q1, where the effective value RlyVoltRms4 is referred to as a fourth effective value of the first sampling point Q1, and if the fourth effective value RlyVoltRms4 of the first sampling point Q1 is smaller than a second voltage threshold, it is determined that at least one of contacts of a live line L and a zero line N of the main relay K2 cannot be closed; the driving unit controls the main relay K2 to be switched off, controls the auxiliary relay K3 to be switched on, controls the auxiliary relay K1 to be switched off, and controls each power switch tube in the H6 bridge circuit to be switched off so as not to generate open-loop voltage at the output end of the H6 bridge circuit; the detection unit 140 calculates an effective value RlyVoltRms5 of the first sampling point Q1, where the effective value RlyVoltRms5 is referred to as a fifth effective value of the first sampling point Q1, and if the fifth effective value RlyVoltRms5 of the first sampling point Q1 is smaller than a second voltage threshold, it is determined that at least one of contacts of the live line L and the zero line N of the main relay K2 cannot be closed.
Compared with the prior art, the method and the device have the advantages that the open-loop voltage is switched on or off at the output end of the H6 bridge circuit, and the relays K, K2 and K3 are controlled to be switched off or on, so that the sticking faults of the relays K2 and K3 can be detected, the relays K2 and K3 can be ensured to be detected in the sticking state, and the harm to the personal safety caused by the fact that the relays cannot cut off the power grid in the installation and debugging process is prevented.
Other objects, features and advantages of the present invention will be described in detail in the following detailed description of the preferred embodiments, which proceeds with reference to the accompanying drawings.
[ description of the drawings ]
The present invention will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which:
fig. 1 is a circuit schematic diagram of a relay detection circuit of a single-phase grid-connected photovoltaic inverter according to an embodiment of the invention;
FIG. 2 is a timing diagram of the driving signals CK1, CK2, CK3, CK4 shown in FIG. 1 according to an embodiment of the present invention;
FIG. 3 is a waveform diagram of a portion of a signal in the relay detection circuit shown in FIG. 1 in one embodiment of the present invention;
fig. 4 is a waveform diagram of the voltage at the first sampling point before and after the auxiliary relay K1 is closed in the relay detection circuit shown in fig. 1 according to an embodiment of the present invention.
[ detailed description ] embodiments
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least an implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. The terms "plurality" or "a plurality" in the present invention mean two or more. "and/or" in the present invention means "and" or ".
Fig. 1 is a schematic circuit diagram of a relay detection circuit of a single-phase grid-connected pv inverter according to an embodiment of the present invention. The relay detection circuit of the single-phase grid-connected photovoltaic inverter shown in fig. 1 includes an auxiliary relay K1, an input capacitor (or inverter capacitor) Cdc, a resistor R, an H6 bridge circuit 110, a grid-inlet filter 120, a main relay K2, an auxiliary relay K3, a driving unit 130, and a detection unit 140.
The input capacitor Cdc is connected between the first dc input end P and the second dc input end N of the photovoltaic inverter. The auxiliary relay K1 and the resistor R are sequentially connected in series between the first direct current input end P and the second direct current input end N of the photovoltaic inverter. Two input ends of the H6 bridge circuit 110 are respectively connected with a first direct current input end P and a second direct current input end N of the photovoltaic inverter, two output ends a and B thereof are respectively connected with a live wire L and a zero wire N, and the H6 bridge circuit 110 is used for converting direct current into alternating current. Main relay K2 and auxiliary relay K3 establish ties between two output A of H6 bridge circuit 110, B and electric wire netting AC (or load) through live wire L and zero line N, and main relay K2 and auxiliary relay K3 all include two contacts, connect respectively on live wire L and zero line N, wherein, be provided with first sampling point Q1 between main relay K2 and the auxiliary relay K3, be provided with second sampling point Q2 between auxiliary relay K3 and the electric wire netting AC (or load). The driving unit 130 outputs driving signals CK1, CK2, CK3, and CK4, wherein the driving signals CK1, CK2, and CK3 respectively control the auxiliary relay K1, the main relay K2, and the auxiliary relay K3 to be turned on or off, and the driving signal CK4 controls the output terminal of the H6 bridge circuit to open or close the open-loop voltage. The detection unit 140 determines whether the main relay K2 and the sub relay K3 are closed or opened based on the sampling values of the first sampling point Q1 and the second sampling point Q2.
In the embodiment shown in fig. 1, the H6 bridge circuit 110 includes a power switch tube S1, a power switch tube S2, a power switch tube S3, a power switch tube S4, a power switch tube S5, and a power switch tube S6. The power switching tube S1 and the power switching tube S2 are sequentially connected between a first direct current input P and a second direct current input N of the photovoltaic inverter, and a connection node between the power switching tube S1 and the power switching tube S2 is connected with a first output end a of the H6 bridge circuit 110; the power switch tube S3 and the power switch tube S4 are sequentially connected between the first dc input P and the second dc input N of the photovoltaic inverter, and a connection node between the power switch tube S3 and the power switch tube S4 is connected to the second output B of the H6 bridge circuit 110; the power switch tube S5 and the power switch tube S6 are sequentially connected in series between the two output ends a and B of the H6 bridge circuit 110.
In the embodiment shown in fig. 1, the driving signal output by the driving unit 130 includes a first driving signal CK1, a second driving signal CK2, a third driving signal CK3 and a fourth driving signal CK4, wherein the first driving signal CK1 is connected to the control terminal of the auxiliary relay K1 to control the auxiliary relay K1 to be closed or opened; the second driving signal CK2 is connected with the control end of the main relay K2 to control the main relay K2 to be closed or opened; the third driving signal CK3 is connected with the control end of the auxiliary relay K3 to control the auxiliary relay K3 to be closed or opened; the fourth driving signal CK4 is not a single signal, and is an inverted signal for driving the power switching tubes S1, S2, S3, S4, S5, and S6 in the H6 bridge circuit 110 to be turned on or off, and is connected to the control terminals of the power switching tubes S1, S2, S3, S4, S5, and S6 in the H6 bridge circuit 110, respectively, so as to control the power switching tubes S1, S2, S3, S4, S5, and S6 in the H6 bridge circuit 110 to be turned on or off, so that the output terminal of the H6 bridge circuit 110 is turned off or off with an open-loop voltage.
Referring to fig. 2, it is a timing diagram of the driving signals CK1, CK2, CK3, CK4 shown in fig. 1 according to an embodiment of the present invention, wherein the driving signal CK1 is the auxiliary relay driving, the driving signal CK2 is the main relay driving, the driving signal CK3 is the auxiliary relay driving, and the driving signal CK4 is the open-loop driving of the H6 bridge circuit 110. In the embodiment shown in fig. 2, when the drive signals CK1, CK2, CK3, and CK4 are at a high level, the corresponding relays or open-loop voltages are closed, and when the drive signals CK1, CK2, CK3, and CK4 are at a low level, the corresponding relays or open-loop voltages are opened. In another embodiment, the drive signals CK1, CK2, CK3, CK4 are low to close the corresponding relay or open loop voltage, and the drive signals CK1, CK2, CK3, CK4 are high to open the corresponding relay or open loop voltage.
As shown in fig. 1, the network-in filter 120 is connected between the second sampling point Q2 and the power grid AC, the network-in filter 120 includes a first filter inductor L1, a second filter inductor L2 and a filter capacitor Co, one end of the first filter inductor L1 is connected to the second sampling point Q2 through the live line L, and the other end is connected to one end of the power grid AC; one end of a second filter inductor L2 is connected with a second sampling point Q2 through a zero line N, and the other end of the second filter inductor L2 is connected with the other end of the power grid AC; the filter capacitor Co is connected between the other end of the first filter inductor L1 and the other end of the second filter inductor L2.
The following describes a detection method of the relay detection circuit of the single-phase grid-connected photovoltaic inverter shown in fig. 1 specifically based on fig. 2.
Step1: the driving signals CK2 and CK3 are both at a low level to respectively control the main relay K2 and the auxiliary relay K3 to be switched off, the driving signal CK1 is at a low level to control the auxiliary relay K1 to be switched off, and the driving signal CK4 is at a low level to control the power switching tubes S1 to S6 in the H6 bridge circuit 110 to be switched off, so that an open-loop voltage is not generated at the output end of the H6 bridge circuit 110; the detection unit 140 calculates an effective value RlyVoltRms1 and an average value RlyVoltAvr1 of the first sampling point Q1 through DSP (Digital Signal process), where the effective value RlyVoltRms1 may be referred to as a first effective value of the first sampling point Q1, and if the first effective value RlyVoltRms1 is greater than a first voltage threshold, for example, the first voltage threshold is 30V, that is, rlyVoltRms1 is greater than 30V, it is determined (or proved) that at least one of contacts of the live line L and the neutral line N of the auxiliary relay K3 is stuck; if the effective value RlyVoltRms1 is equal to the current power grid AC voltage (or the current mains voltage), it is determined (or proved) that the effective value RlyVoltRms1 has a suspended voltage or the contacts of the live line L and the zero line N of the auxiliary relay K3 are stuck.
Step2: the driving signals CK2 and CK3 are both at a low level to respectively control the main relay K2 and the auxiliary relay K3 to be switched off, the driving signal CK1 is at a high level to control the auxiliary relay K1 to be switched on, and the driving signal CK4 is at a low level to control the power switching tubes S1 to S6 in the H6 bridge circuit 110 to be switched off, so that an open-loop voltage is not generated at the output end of the H6 bridge circuit 110; the detection unit 140 calculates an effective value rlyvolts rms2 and an average value rlyvolts avr2 of the first sampling point Q1 through the DSP, where the effective value rlyvolts rms2 may be referred to as a second effective value of the first sampling point Q1, and if an absolute value of a difference between the first effective value rlyvolts rms1 and the second effective value rlyvolts rms2 of the first sampling point Q1 is greater than a first voltage threshold, for example, the first voltage threshold is 30V, that is, | rlyvolts avr 2-rlyvolts avr1| >30V, it is determined (or proved) that a contact of the zero line N of the auxiliary relay K3 is stuck.
Step3: the driving signals CK2 and CK3 are both at a low level to respectively control the main relay K2 and the auxiliary relay K3 to be turned off, the driving signal CK1 is at a low level to control the auxiliary relay K1 to be turned off, and the driving signal CK4 is at a high level to control the power switching tubes S1 to S6 in the H6 bridge circuit 110 to be turned on, so as to generate an open-loop voltage at the output end of the H6 bridge circuit, for example, the inverter outputs an open-loop voltage having the same frequency and the same phase as the grid AC voltage or the mains voltage at the output end of the H6 bridge circuit 110); the detection unit 140 calculates an effective value RlyVoltRms3 of the first sampling point Q1 through the DSP, where the effective value RlyVoltRms3 may be referred to as a third effective value of the first sampling point Q1, and if the third effective value RlyVoltRms3 of the first sampling point Q1 is greater than a first voltage threshold, for example, the first voltage threshold is 30V, that is, rlyVoltRms3>30V, it is determined (or proved) that at least one of contacts of the live line L and the zero line N of the main relay K2 is stuck; if the effective value rlyvoltmms 3 is equal to the current open-loop voltage (or the current mains voltage), it is determined (or proved) that the effective value rlyvoltmms 3 has a floating voltage or the contacts of the live line L and the zero line N of the main relay K2 are stuck.
Step4: the driving signal CK2 is at a high level to control the main relay K2 to be closed, the driving signal CK3 is at a low level to control the auxiliary relay K3 to be opened, the driving signal CK1 is at a low level to control the auxiliary relay K1 to be opened, and the driving signal CK4 is at a high level to control each power switch tube in the H6 bridge circuit 110 to be opened, so as to generate an open-loop voltage at the output end of the H6 bridge circuit; the detection module 140 calculates an effective value RlyVoltRms4 of the first sampling point Q1, where the effective value RlyVoltRms4 may be referred to as a fourth effective value of the first sampling point Q1, and if the fourth effective value RlyVoltRms4 of the first sampling point Q1 is smaller than a second voltage threshold, for example, the second voltage threshold is 60V, that is, rlyVoltRms4 is smaller than 60V, it is determined (or proved) that at least one of contacts of the live line L and the neutral line N of the main relay K2 cannot be closed.
Step5: the driving signal CK2 is at a low level to control the main relay K2 to be turned off, the driving signal CK3 is at a high level to control the auxiliary relay K3 to be turned on, the driving signal CK1 is at a low level to control the auxiliary relay K1 to be turned off, and the driving signal CK4 is at a low level to control each power switch tube in the H6 bridge circuit 110 to be turned off, so that an open-loop voltage is not generated at the output end of the H6 bridge circuit; the detection unit 140 calculates an effective value rlyvolts rms5 of the first sampling point Q1 through the DSP, where the effective value rlyvolts rms5 may be referred to as a fifth effective value of the first sampling point Q1, and if the fifth effective value rlyvolts rms5 of the first sampling point Q1 is smaller than a second voltage threshold, for example, the second voltage threshold is 60V, that is, rlyvolts rms5 is smaller than 60V, it is determined (or proved) that at least one of contacts of the live line L and the neutral line N of the main relay K2 cannot be closed.
It should be noted that, the detection process of the relay detection circuit of the single-phase grid-connected photovoltaic inverter shown in fig. 1 can be executed only when the PV voltage (photovoltaic voltage) and the AC voltage (grid voltage) are both normal (or at the operating voltage 10), and therefore the valid value of the second sampling point Q2 is the current mains voltage (or AC voltage).
Referring to fig. 3, a waveform diagram of a partial signal in the relay detection circuit shown in fig. 1 according to an embodiment of the present invention is shown, in which CH1 is an open-loop voltage, CH2 is a first sampling point voltage, and CH3 is a main relay driver.
Referring to fig. 4, a waveform diagram of voltages at first sampling points before and after closing of the auxiliary relay K1 in the relay detection circuit shown in fig. 1 according to an embodiment of the present invention is shown, wherein RlyVoltAvr1 in Step1 is calculated based on the voltage sampling at the first sampling point before closing, and RlyVoltAvr2 in Step2 is calculated based on the voltage sampling at the first sampling point after closing.
In summary, according to the relay detection circuit and the detection method of the single-phase grid-connected photovoltaic inverter of the present invention, open-loop voltage is applied to the output terminal of the H6 bridge circuit 110 to control the relays K, K2, and K3 to be turned off or on, so that the sticking faults of the relays K2 and K3 can be detected, and the relays K2 and K3 can be detected in a sticking state, thereby preventing the safety of a human body from being damaged due to the fact that the relays cannot cut off a power grid during installation and debugging.
In the present invention, the terms "connected", connected, "connected" and "connecting" mean electrically or communicatively connected, or directly or indirectly connected, unless otherwise specified. As used herein, "coupled" refers to indirect or direct electrical connections, which may be through one or more electrical devices (e.g., resistors, capacitors, inductors, etc.).
The foregoing description has disclosed fully preferred embodiments of the present invention. It should be noted that those skilled in the art can make modifications to the embodiments of the present invention without departing from the scope of the appended claims. Accordingly, the scope of the appended claims is not to be limited to the specific embodiments described above.
Claims (9)
1. The utility model provides a relay detection circuitry of single-phase grid-connected photovoltaic inverter which characterized in that, it includes:
an input capacitor Cdc connected between the first dc input P and the second dc input N of the photovoltaic inverter;
the auxiliary relay K1 and the resistor R are sequentially connected in series between the first direct current input end P and the second direct current input end N;
an H6 bridge circuit, two input ends of which are respectively connected with the first direct current input end P and the second direct current input end N, two output ends A and B of which are respectively connected with a live wire L and a zero line N, wherein the H6 bridge circuit is used for converting direct current into alternating current;
the H6 bridge circuit comprises a main relay K2 and an auxiliary relay K3, wherein the main relay K2 and the auxiliary relay K3 are connected in series between two output ends A and B of the H6 bridge circuit and a power grid through a live wire L and a zero wire N, a first sampling point Q1 is arranged between the main relay K2 and the auxiliary relay K3, and a second sampling point Q2 is arranged between the auxiliary relay K3 and the power grid;
the driving unit outputs driving signals to control the auxiliary relay K1, the main relay K2 and the auxiliary relay K3 to be closed or opened and control the output end of the H6 bridge circuit to open or close open-loop voltage;
a detection unit that determines whether the main relay K2 and the sub relay K3 are closed or opened based on the sampling values of the first sampling point Q1 and the second sampling point Q2,
the driving signals include a first driving signal CK1, a second driving signal CK2, a third driving signal CK3, and a fourth driving signal CK4,
the first driving signal CK1 is connected with the control end of the auxiliary relay K1 to control the auxiliary relay K1 to be switched on or switched off;
the second driving signal CK2 is connected with the control end of the main relay K2 to control the main relay K2 to be switched on or switched off;
the third driving signal CK3 is connected with the control end of the auxiliary relay K3 to control the auxiliary relay K3 to be switched on or switched off;
the fourth driving signal CK4 is respectively connected to the control ends of the power switching tubes in the H6 bridge circuit to control the power switching tubes in the H6 bridge circuit to be turned on or off, so that the output end of the H6 bridge circuit is turned off or closed by an open-loop voltage,
the driving unit controls the main relay K2, the auxiliary relay K3 and the auxiliary relay K1 to be switched off, and controls each power switch tube in the H6 bridge circuit to be switched off so as not to generate open-loop voltage at the output end of the H6 bridge circuit; the detection unit calculates an effective value RlyVoltsRms 1 of a first sampling point Q1, the effective value RlyVoltsRms 1 is called a first effective value of the first sampling point Q1, and if the first effective value RlyVolts 1 is larger than a first voltage threshold value, it is judged that at least one of contacts of a live wire L and a zero wire N of the auxiliary relay K3 is stuck; if the first effective value RlyVoltRms1 is equal to the voltage of the power grid, judging that the contacts of the live wire L and the zero wire N of the auxiliary relay K3 are stuck;
the driving unit controls the main relay K2 and the auxiliary relay K3 to be disconnected, controls the auxiliary relay K1 to be closed, and controls each power switch tube in the H6 bridge circuit to be closed, so that open-loop voltage is not generated at the output end of the H6 bridge circuit; the detection unit 140 calculates an effective value RlyVoltRms2 of the first sampling point Q1, where the effective value RlyVoltRms2 is referred to as a second effective value of the first sampling point Q1, and if an absolute value of a difference between the first effective value RlyVoltRms1 and the second effective value RlyVoltRms2 of the first sampling point Q1 is greater than a first voltage threshold, it is determined that a contact of the zero line N of the sub relay K3 is stuck;
the driving unit controls the main relay K2, the auxiliary relay K3 and the auxiliary relay K1 to be disconnected, and controls each power switch tube in the H6 bridge circuit to be opened so as to generate open-loop voltage at the output end of the H6 bridge circuit; the detection unit 140 calculates an effective value RlyVoltRms3 of the first sampling point Q1, where the effective value RlyVoltRms3 is referred to as a third effective value of the first sampling point Q1, and if the third effective value RlyVoltRms3 of the first sampling point Q1 is greater than a first voltage threshold, it is determined that at least one of contacts of the live line L and the zero line N of the main relay K2 is stuck; if the third effective value RlyVoltRms3 is equal to the open-loop voltage, judging that the contacts of the live wire L and the zero wire N of the main relay K2 are stuck;
the driving unit controls the main relay K2 to be closed, controls the auxiliary relay K3 and the auxiliary relay K1 to be disconnected, and controls each power switch tube in the H6 bridge circuit to be opened so as to generate open-loop voltage at the output end of the H6 bridge circuit; the detection unit calculates an effective value RlyVoltRms4 of the first sampling point Q1, the effective value RlyVoltRms4 is called a fourth effective value of the first sampling point Q1, and if the fourth effective value RlyVoltRms4 of the first sampling point Q1 is smaller than a second voltage threshold value, it is judged that at least one of contacts of a live wire L and a zero wire N of the main relay K2 cannot be closed;
the driving unit controls the main relay K2 to be switched off, controls the auxiliary relay K3 to be switched on, controls the auxiliary relay K1 to be switched off, and controls each power switch tube in the H6 bridge circuit to be switched off so as not to generate open-loop voltage at the output end of the H6 bridge circuit; the detection unit 140 calculates an effective value RlyVoltRms5 of the first sampling point Q1, where the effective value RlyVoltRms5 is referred to as a fifth effective value of the first sampling point Q1, and if the fifth effective value RlyVoltRms5 of the first sampling point Q1 is smaller than a second voltage threshold, it is determined that at least one of contacts of the live line L and the zero line N of the main relay K2 cannot be closed.
2. The relay detection circuit of the single-phase grid-connected photovoltaic inverter according to claim 1,
the H6 bridge circuit comprises a power switch tube S1, a power switch tube S2, a power switch tube S3, a power switch tube S4, a power switch tube S5 and a power switch tube S6,
the power switch tube S1 and the power switch tube S2 are sequentially connected between the first direct current input P and the second direct current input end N, and a connecting node between the power switch tube S1 and the power switch tube S2 is connected with a first output end A of the H6 bridge circuit;
the power switch tube S3 and the power switch tube S4 are sequentially connected between the first direct current input P and the second direct current input end N, and a connecting node between the power switch tube S3 and the power switch tube S4 is connected with the second output end B of the H6 bridge circuit;
and the power switch tube S5 and the power switch tube S6 are sequentially connected in series between the first output end A and the second output end B of the H6 bridge circuit.
3. The relay detection circuit of the single-phase grid-connected photovoltaic inverter according to claim 1,
it also comprises a network filter connected between said second sampling point Q2 and the network,
the network filter comprises a first filter inductor L1, a second filter inductor L2 and a filter capacitor Co,
one end of the first filter inductor L1 is connected with the second sampling point Q2 through a live wire L, and the other end of the first filter inductor L1 is connected with one end of the power grid;
one end of the second filter inductor L2 is connected with the second sampling point Q2 through a zero line N, and the other end of the second filter inductor L2 is connected with the other end of the power grid;
the filter capacitor Co is connected between the other end of the first filter inductor L1 and the other end of the second filter inductor L2.
4. The relay detection circuit of the single-phase grid-connected photovoltaic inverter according to claim 1,
the main relay K2 and the auxiliary relay K3 respectively comprise two contacts which are respectively connected to the live wire L and the zero line N.
5. The detection method of the relay detection circuit of the single-phase grid-connected photovoltaic inverter as claimed in any one of claims 1 to 4, characterized by comprising the following steps:
the driving unit controls the main relay K2, the auxiliary relay K3 and the auxiliary relay K1 to be switched off, and controls each power switch tube in the H6 bridge circuit to be switched off so as not to generate open-loop voltage at the output end of the H6 bridge circuit; the detection unit 140 calculates an effective value RlyVoltsRms 1 of the first sampling point Q1, the effective value RlyVoltsRms 1 is called a first effective value of the first sampling point Q1, and if the first effective value RlyVoltsRms 1 is larger than a first voltage threshold value, it is determined that at least one of contacts of a live wire L and a zero wire N of the auxiliary relay K3 is stuck; if the first effective value RlyVoltRms1 is equal to the power grid voltage, judging that the contacts of the live wire L and the zero wire N of the auxiliary relay K3 are stuck;
the driving unit controls the main relay K2 and the auxiliary relay K3 to be disconnected, controls the auxiliary relay K1 to be closed, and controls each power switch tube in the H6 bridge circuit to be closed, so that open-loop voltage is not generated at the output end of the H6 bridge circuit; the detection unit 140 calculates an effective value RlyVoltRms2 of the first sampling point Q1, where the effective value RlyVoltRms2 is referred to as a second effective value of the first sampling point Q1, and if an absolute value of a difference between the first effective value RlyVoltRms1 and the second effective value RlyVoltRms2 of the first sampling point Q1 is greater than a first voltage threshold, it is determined that a contact of the zero line N of the sub relay K3 is stuck;
the driving unit controls the main relay K2, the auxiliary relay K3 and the auxiliary relay K1 to be switched off, and controls each power switch tube in the H6 bridge circuit to be switched on so as to generate open-loop voltage at the output end of the H6 bridge circuit; the detection unit 140 calculates an effective value RlyVoltRms3 of the first sampling point Q1, where the effective value RlyVoltRms3 is referred to as a third effective value of the first sampling point Q1, and if the third effective value RlyVoltRms3 of the first sampling point Q1 is greater than a first voltage threshold, it is determined that at least one of contacts of the live line L and the zero line N of the main relay K2 is stuck; if the third effective value RlyVoltRms3 is equal to the open-loop voltage, judging that the contacts of the live wire L and the zero wire N of the main relay K2 are stuck;
the driving unit controls the main relay K2 to be closed, controls the auxiliary relay K3 and the auxiliary relay K1 to be disconnected, and controls each power switch tube in the H6 bridge circuit to be opened so as to generate open-loop voltage at the output end of the H6 bridge circuit; the detection module 140 calculates an effective value RlyVoltRms4 of the first sampling point Q1, where the effective value RlyVoltRms4 is referred to as a fourth effective value of the first sampling point Q1, and if the fourth effective value RlyVoltRms4 of the first sampling point Q1 is smaller than a second voltage threshold, it is determined that at least one of contacts of a live line L and a zero line N of the main relay K2 cannot be closed;
the driving unit controls the main relay K2 to be switched off, controls the auxiliary relay K3 to be switched on, controls the auxiliary relay K1 to be switched off, and controls each power switch tube in the H6 bridge circuit to be switched off so as not to generate open-loop voltage at the output end of the H6 bridge circuit; the detection unit 140 calculates an effective value RlyVoltRms5 of the first sampling point Q1, where the effective value RlyVoltRms5 is referred to as a fifth effective value of the first sampling point Q1, and if the fifth effective value RlyVoltRms5 of the first sampling point Q1 is smaller than a second voltage threshold, it is determined that at least one of contacts of the live line L and the zero line N of the main relay K2 cannot be closed.
6. The method for detecting the relay detection circuit of the single-phase grid-connected photovoltaic inverter as claimed in claim 5,
the first voltage threshold is 30V;
the second voltage threshold is 60V.
7. The method for detecting the relay detection circuit of the single-phase grid-connected photovoltaic inverter as claimed in claim 5,
when the relay is detected, the photovoltaic voltage and the power grid voltage are normal.
8. The method for detecting the relay detection circuit of the single-phase grid-connected photovoltaic inverter as claimed in claim 5,
if the first effective value RlyVoltRms1 is equal to the power grid voltage, judging that the first effective value RlyVoltRms1 has a suspended voltage;
if the third effective value RlyVoltRms3 is equal to the power grid voltage, the third effective value RlyVoltRms3 is also judged to have a suspended voltage.
9. The method for detecting the relay detection circuit of the single-phase grid-connected PV inverter as claimed in claim 5, wherein,
and the open-loop voltage at the output end of the H6 bridge circuit and the voltage of the power grid have the same frequency and the same phase.
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