Inverter and grid-connected relay service life monitoring method

Abstract

The invention discloses an inverter and a grid-connected relay service life monitoring method. The inverter comprises an inverter circuit, a grid-connected relay, a controller, a voltage sampling circuit, a current sampling circuit and a grid-connected relay driving circuit, when it is monitored that the service life of the grid-connected relay expires, the controller issues a grid-connected relay breaking instruction and gives out an alarm that the service life of the grid-connected relay expires, and the grid-connected relay driving circuit drives the grid-connected relay to be broken according to the grid-connected relay breaking instruction issued by the controller. According to the inverter and the grid-connected relay service life monitoring method, the service life condition of the grid-connected relay can be monitored, and when the service life of the grid-connected relay expires, the breaking instruction is issued to enable the photovoltaic system to be separated from the power grid, so that the situation that the grid-connected relay continues to work and fails, and then the safety of the photovoltaic system and the power grid is threatened is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation, and in particular to a method for monitoring the service life of an inverter and a grid-connected relay. Background Art

[0002] The grid-connected relay is a connecting switch between the inverter voltage inside the inverter and the grid voltage. Its core function is to protect the safety of the photovoltaic system and the grid. It can promptly and effectively disconnect the connection between the two when the photovoltaic system or the grid is abnormal.

[0003] However, existing inverters have the problem that the grid-connected relay continues to work after exceeding its service life, causing failure, thereby threatening the safety of the photovoltaic storage system and the power grid. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for monitoring the service life of an inverter and a grid-connected relay, so as to solve the problem that the grid-connected relay continues to work when its service life exceeds the limit, resulting in failure and thus threatening the safety of the photovoltaic storage system and the power grid.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] In a first aspect, an inverter is provided, comprising an inverter circuit, a grid-connected relay, a controller, a voltage sampling circuit, a current sampling circuit and a grid-connected relay driving circuit; the inverter circuit is used to invert direct current and output alternating current, the grid-connected relay is connected between the output end of the inverter circuit and a power grid, the voltage sampling circuit samples the voltage across the grid-connected relay and transmits the voltage signal to the controller, the current sampling circuit samples the load current of the grid-connected relay and transmits the current signal to the controller; when it is monitored that the service life of the grid-connected relay has expired, the controller issues a grid-connected relay disconnection instruction and issues a grid-connected relay service life expiration alarm, and the grid-connected relay driving circuit drives the grid-connected relay to disconnect according to the grid-connected relay disconnection instruction issued by the controller.

[0007] Preferably, when the service life of the grid-connected relay is monitored to expire, the controller sends a grid-connected relay disconnection instruction and issues a grid-connected relay service life expiration alarm, including: the controller calculates the grid-connected relay's pull-in delay, and when the controller calculates that the grid-connected relay's pull-in delay exceeds the time limit, sends the grid-connected relay disconnection instruction and issues a grid-connected relay service life expiration alarm.

[0008] Preferably, when the controller calculates that the closing delay of the grid-connected relay exceeds the time limit, it sends a grid-connected relay disconnection instruction and issues an alarm for the expiration of the service life of the grid-connected relay, including: before the inverter is started each time, the controller calculates the closing delay of the grid-connected relay Tr0, Tr1, Tr2, Tr3, ..., Trn, where Tri is the closing delay of the i-th closing of the grid-connected relay, i = 0, 1, 2, 3, ..., n; when Trn-Tr0 is greater than TrL, the controller sends a grid-connected relay disconnection instruction and issues an alarm for the expiration of the service life of the grid-connected relay, where TrL is the allowable variation limit of the closing delay of the grid-connected relay.

[0009] Preferably, when the service life of the grid-connected relay is monitored to expire, the controller sends a grid-connected relay disconnection instruction and issues an alarm that the service life of the grid-connected relay has expired, including: the controller accumulates the number of times the grid-connected relay is attracted, and when the controller calculates that the number of times the grid-connected relay is attracted exceeds the number limit, the controller sends a grid-connected relay disconnection instruction and issues an alarm that the service life of the grid-connected relay has expired.

[0010] Preferably, when the service life of the grid-connected relay is monitored to expire, the controller sends a grid-connected relay disconnection instruction and issues an alarm that the service life of the grid-connected relay has expired, including: the controller accumulates the total energization time of the grid-connected relay, and when the controller calculates that the total energization time of the grid-connected relay exceeds the energization time limit, the controller sends a grid-connected relay disconnection instruction and issues an alarm that the service life of the grid-connected relay has expired.

[0011] Preferably, the grid-connected relay adopts an electromagnetic relay, and the grid-connected relay includes a coil, an iron core, an armature and a contact spring; the pull-in time limit is the minimum value of the life of the coil, the iron core and the contact spring of the grid-connected relay.

[0012] Preferably, when it is monitored that the service life of the grid-connected relay has expired, the controller sends a grid-connected relay disconnection instruction and issues an alarm that the service life of the grid-connected relay has expired, including: the controller accumulates the number of on-load disconnections of the grid-connected relay, and when the number of on-load disconnections of the grid-connected relay exceeds the on-load breaking capacity of the grid-connected relay, the controller sends a grid-connected relay disconnection instruction and issues an alarm that the service life of the grid-connected relay has expired.

[0013] Preferably, the controller accumulates the number of on-load disconnections of the grid-connected relay. When the number of on-load disconnections of the grid-connected relay exceeds the on-load breaking capacity of the grid-connected relay, the controller issues a disconnection instruction for the grid-connected relay and issues an alarm for the expiration of the service life of the grid-connected relay, including: the controller accumulates the number of disconnections of the grid-connected relay under different load currents Xn_I1, Xn_I2, ..., Xn_Im, Xn_Ik is the number of disconnections of the grid-connected relay under the kth current level, k=1,2,...,m; when at least one of the inequalities Xn_I1>Yn_I1, Xn_I2>Yn_I2, ..., Xn_Im>Yn_Im holds, the controller issues a disconnection instruction for the grid-connected relay and issues an alarm for the expiration of the service life of the grid-connected relay, Yn_Ik is the on-load breaking capacity of the grid-connected relay under the kth current level.

[0014] Preferably, the grid-connected relay adopts a dual relay system, and the dual relay system includes a main relay and a slave relay connected in series.

[0015] In a second aspect, a method for monitoring the service life of a grid-connected relay is provided, which is applied to an inverter, wherein the inverter includes an inverter circuit, a grid-connected relay, a controller, a voltage sampling circuit, a current sampling circuit and a grid-connected relay driving circuit; the method for monitoring the service life of the grid-connected relay includes: when it is monitored that the service life of the grid-connected relay has expired, the controller issues a grid-connected relay disconnection instruction and issues a grid-connected relay service life expiration alarm; the grid-connected relay driving circuit drives the grid-connected relay to disconnect according to the grid-connected relay disconnection instruction issued by the controller;

[0016] Among them, when it is detected that the grid-connected relay meets at least one of the following conditions, it is determined that the service life of the grid-connected relay has expired: the grid-connected relay's pick-up delay exceeds the time limit; the grid-connected relay's pick-up times exceed the times limit; the grid-connected relay's total pick-up time exceeds the pick-up time limit; the grid-connected relay's on-load breaking times exceed the grid-connected relay's on-load breaking capacity.

[0017] The above-mentioned inverter and grid-connected relay service life monitoring method can monitor the service life of the grid-connected relay. When its service life expires, a disconnection command is issued to disconnect the photovoltaic system from the power grid, thereby preventing the grid-connected relay from continuing to work and causing failure, thereby threatening the safety of the photovoltaic system and the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0019] Figure 1 is a structural block diagram of an inverter in one embodiment of the present invention;

[0020] Figure 2 It is a logical schematic diagram of monitoring the service life of a grid-connected relay according to the present invention. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] An embodiment of the present application provides an inverter that can monitor the service life of a grid-connected relay. When the service life of the grid-connected relay expires, a disconnection command is issued to disconnect the photovoltaic system from the power grid, thereby preventing the grid-connected relay from continuing to work and causing failure, thereby threatening the safety of the photovoltaic system and the power grid.

[0023] like Figure 1 As shown, the inverter includes an inverter circuit, a grid-connected relay, a controller, a voltage sampling circuit, a current sampling circuit and a grid-connected relay driving circuit; the inverter circuit is used to output AC power after inverting direct current; the grid-connected relay is connected between the output end of the inverter circuit and the power grid; the voltage sampling circuit samples the voltage at both ends of the grid-connected relay and transmits the voltage signal to the controller; the current sampling circuit samples the load current of the grid-connected relay and transmits the current signal to the controller; the controller issues a grid-connected relay closing instruction when the inverter is grid-connected and issues a grid-connected relay disconnecting instruction when the inverter is normally shut down or fails; the grid-connected relay driving circuit drives the grid-connected relay to close and disconnect according to the instructions issued by the controller.

[0024] In this embodiment, the grid-connected relay adopts a dual relay system, which includes a main relay and a slave relay connected in series. Figure 1 As shown, K1 and K3 are the main relays of the grid-connected relay, and K2 and K4 are the slave relays of the grid-connected relay. Of course, in other embodiments, the grid-connected relay may also adopt a single relay system.

[0025] In this embodiment, the grid-connected relay is an electromagnetic relay, which includes a coil, an iron core, an armature and a contact spring. The electromagnetic effect is generated by energizing the coil to drive the armature to move, thereby changing the on-off state of the circuit.

[0026] In this embodiment, the current sampling circuit uses a Hall sensor to sample the load current of the grid-connected relay. Figure 1 As shown, SH1 and SH2 are current sampling Hall sensors. Of course, in other embodiments, the current sampling circuit may also adopt other existing technologies to implement the sampling of the on-load current of the grid-connected relay.

[0027] The controller is the main control unit of the entire inverter, which can read the voltage across the grid-connected relay, issue grid-connected relay closing and disconnecting instructions, store and calculate data, accumulate the number of times the grid-connected relay is closed, accumulate the total time the grid-connected relay is closed, read the load current of the relay, accumulate the number of times the grid-connected relay is disconnected, issue alarm instructions, etc., thereby monitoring the service life of the grid-connected relay. When it is monitored that the service life of the grid-connected relay has expired, the controller issues a grid-connected relay disconnecting instruction and issues an alarm for the expiration of the service life of the grid-connected relay. The grid-connected relay drive circuit drives the grid-connected relay to disconnect according to the grid-connected relay disconnecting instruction issued by the controller.

[0028] like Figure 2 As shown, at least one of the following four approaches is used to monitor the service life of the grid-connected relay:

[0029] (1) The controller calculates the on-off delay of the grid-connected relay. When the controller calculates that the on-off delay of the grid-connected relay exceeds the time limit, it issues a disconnection command for the grid-connected relay and issues an alarm indicating that the service life of the grid-connected relay has expired.

[0030] Specifically, the inverter will perform a self-test of the grid-connected relay's pickup delay before each startup. The pickup delay refers to the time from the issuance of the grid-connected relay's pickup command to the change in the voltage across the grid-connected relay. The controller calculates the grid-connected relay's pickup delay Tr0, Tr1, Tr2, Tr3...Trn, where Tri is the grid-connected relay's pickup delay for the i-th time, i=0,1,2,3...n; and then calculates the values ​​of Tr1-Tr0, Tr2-Tr0, Tr3-tr0...Trn-Tr0; when Trn-Tr0 is greater than TrL, the controller issues a grid-connected relay disconnection command and issues an alarm, with the alarm content being "the grid-connected relay's service life has expired". Among them, TrL is the allowable variation limit of the grid-connected relay's pickup delay when it is working normally, which is tested by aging the grid-connected relay.

[0031] (2) The controller accumulates the number of times the grid-connected relay is closed. When the controller calculates that the number of times the grid-connected relay is closed exceeds the limit, it issues a disconnection command for the grid-connected relay and an alarm indicating that the service life of the grid-connected relay has expired.

[0032] Specifically, during the operation of the inverter, the controller accumulates the number of times the grid-connected relay is closed N. When N is greater than M, the controller issues a disconnection command for the grid-connected relay and issues an alarm, the alarm content of which is "the service life of the grid-connected relay has expired". Among them, M is the limit of the number of times the grid-connected relay can be closed within its mechanical life, which is tested by aging the grid-connected relay.

[0033] (3) The controller accumulates the total energizing time of the grid-connected relay. When the controller calculates that the total energizing time of the grid-connected relay exceeds the energizing time limit, it issues a disconnection command for the grid-connected relay and an alarm indicating that the service life of the grid-connected relay has expired.

[0034] Specifically, during the operation of the inverter, the controller accumulates the total energizing time Ta of the grid-connected relay. When Ta is greater than Tb, the controller issues a disconnection command for the grid-connected relay and issues an alarm, which states that the service life of the grid-connected relay has expired. Tb is obtained through the aging grid-connected relay test. During the aging grid-connected relay test, the service life of the coil, iron core, and contact spring of the grid-connected relay is tested separately when the grid-connected relay is energized. The minimum value of the three lifespans is recorded as Tb.

[0035] (4) The controller accumulates the number of on-load disconnections of the grid-connected relay. When the number of on-load disconnections of the grid-connected relay exceeds the on-load disconnection capacity of the grid-connected relay, the controller issues a disconnection command for the grid-connected relay and issues an alarm indicating that the service life of the grid-connected relay has expired.

[0036] Specifically, during the operation of the inverter, the controller accumulates the number of disconnections Xn_Ix of the grid-connected relay under the load current Ix; when Xn_Ix is greater than Yn_Ix, the controller issues a disconnection command for the grid-connected relay and issues an alarm, the alarm content of which is "the service life of the grid-connected relay has expired". Among them, Yn_Ix is the load disconnection capacity of the grid-connected relay under the load current Ix tested by aging the grid-connected relay.

[0037] In some preferred embodiments, the load current Ix can be divided into multiple levels according to the load capacity of the grid-connected relay. For example, the load capacity of 15A can be divided into three current levels of 0-5A, 5-10A, and 10-15A. During the operation of the inverter, the controller accumulates the number of disconnections of the grid-connected relay under different load currents Xn_I1, Xn_I2, ...Xn_Im, Xn_Ik is the number of disconnections of the grid-connected relay under the kth current level, k=1, 2, ...m; when at least one of the inequalities Xn_I1>Yn_I1, Xn_I2>Yn_I2, ...Xn_Im>Yn_Im is established, the controller issues a disconnection instruction for the grid-connected relay and issues an alarm, the alarm content of which is "the service life of the grid-connected relay has expired". Among them, Yn_Ik is the load disconnection capacity of the grid-connected relay under the kth current level, which can be obtained through the aging grid-connected relay test, k=1, 2, ...m.

[0038] The inverter provided in the embodiment of the present invention can monitor the service life of the grid-connected relay. When its service life expires, it issues a disconnection command to disconnect the photovoltaic system from the power grid, thereby preventing the grid-connected relay from continuing to work and causing failure, thereby threatening the safety of the photovoltaic system and the power grid.

[0039] The embodiment of the present application also provides a method for monitoring the service life of a grid-connected relay, which is applied to an inverter, wherein the inverter includes an inverter circuit, a grid-connected relay, a controller, a voltage sampling circuit, a current sampling circuit, and a grid-connected relay driving circuit. The method for monitoring the service life of a grid-connected relay includes:

[0040] S1: When the service life of the grid-connected relay is detected to have expired, the controller sends a disconnection command for the grid-connected relay and issues an alarm indicating that the service life of the grid-connected relay has expired;

[0041] S2: The grid-connected relay driving circuit drives the grid-connected relay to disconnect according to the grid-connected relay disconnection instruction issued by the controller.

[0042] When it is detected that the grid-connected relay meets at least one of the following conditions, it is determined that the service life of the grid-connected relay has expired:

[0043] The pickup delay of the grid-connected relay exceeds the time limit;

[0044] The number of times the grid-connected relay is closed exceeds the limit;

[0045] The total energizing time of the grid-connected relay exceeds the energizing time limit;

[0046] The number of on-load breaking operations of the grid-connected relay exceeds the on-load breaking capacity of the grid-connected relay.

[0047] The service life of the grid-connected relay is monitored by using the grid-connected relay service life monitoring method provided in this embodiment. The specific monitoring process can be referred to Figure 2 The four paths shown will not be repeated here.

[0048] The grid-connected relay service life monitoring method provided in the embodiment of the present invention can monitor the service life of the grid-connected relay. When its service life expires, a disconnection command is issued to disconnect the photovoltaic system from the power grid, thereby preventing the grid-connected relay from continuing to work and causing failure, thereby threatening the safety of the photovoltaic system and the power grid.

[0049] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0050] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. An inverter, characterized in that: It includes an inverter circuit, a grid-connected relay, a controller, a voltage sampling circuit, a current sampling circuit and a grid-connected relay driving circuit; the inverter circuit is used to output AC power after inverting DC power, the grid-connected relay is connected between the output end of the inverter circuit and the power grid, the voltage sampling circuit samples the voltage across the grid-connected relay and transmits the voltage signal to the controller, the current sampling circuit samples the load current of the grid-connected relay and transmits the current signal to the controller; when it is monitored that the service life of the grid-connected relay has expired, the controller sends a grid-connected relay disconnection instruction and issues a grid-connected relay service life expiration alarm, and the grid-connected relay driving circuit drives the grid-connected relay to disconnect according to the grid-connected relay disconnection instruction sent by the controller.

2. The inverter according to claim 1, characterized in that: When it is monitored that the service life of the grid-connected relay has expired, the controller sends a grid-connected relay disconnection instruction and issues a grid-connected relay service life expiration alarm, including: the controller calculates the grid-connected relay's pull-in delay, and when the controller calculates that the grid-connected relay's pull-in delay exceeds the time limit, the controller sends a grid-connected relay disconnection instruction and issues a grid-connected relay service life expiration alarm.

3. The inverter according to claim 2, characterized in that: When the controller calculates that the grid-connected relay's closing delay exceeds the time limit, the controller issues a grid-connected relay disconnection instruction and issues a grid-connected relay service life expiration alarm, including: before the inverter is started each time, the controller calculates the grid-connected relay's closing delay Tr0, Tr1, Tr2, Tr3, ..., Trn, where Tri is the grid-connected relay's closing delay for the i-th time, i = 0, 1, 2, 3, ..., n; when Trn-Tr0 is greater than TrL, the controller issues a grid-connected relay disconnection instruction and issues a grid-connected relay service life expiration alarm, where TrL is the allowable change limit of the grid-connected relay's closing delay.

4. The inverter according to claim 1, characterized in that: When it is monitored that the service life of the grid-connected relay has expired, the controller sends a grid-connected relay disconnection instruction and issues an alarm for the expiration of the service life of the grid-connected relay, including: the controller accumulates the number of times the grid-connected relay is attracted, and when the controller calculates that the number of times the grid-connected relay is attracted exceeds the number limit, the controller sends a grid-connected relay disconnection instruction and issues an alarm for the expiration of the service life of the grid-connected relay.

5. The inverter according to claim 1, characterized in that: When the service life of the grid-connected relay is monitored to expire, the controller sends a grid-connected relay disconnection instruction and issues an alarm for the expiration of the service life of the grid-connected relay, including: the controller accumulates the total energization time of the grid-connected relay, and when the controller calculates that the total energization time of the grid-connected relay exceeds the energization time limit, the controller sends a grid-connected relay disconnection instruction and issues an alarm for the expiration of the service life of the grid-connected relay.

6. The inverter according to claim 5, characterized in that: The grid-connected relay adopts an electromagnetic relay, and the grid-connected relay includes a coil, an iron core, an armature and a contact spring; the pull-in time limit is the minimum value of the life of the coil, the iron core and the contact spring of the grid-connected relay.

7. The inverter according to claim 1, characterized in that: When it is monitored that the service life of the grid-connected relay has expired, the controller sends a grid-connected relay disconnection instruction and issues an alarm that the service life of the grid-connected relay has expired, including: the controller accumulates the number of on-load disconnections of the grid-connected relay, and when the number of on-load disconnections of the grid-connected relay exceeds the on-load breaking capacity of the grid-connected relay, the controller sends a grid-connected relay disconnection instruction and issues an alarm that the service life of the grid-connected relay has expired.

8. The inverter according to claim 7, characterized in that: The controller accumulates the number of on-load disconnections of the grid-connected relay. When the number of on-load disconnections of the grid-connected relay exceeds the on-load disconnecting capacity of the grid-connected relay, the controller issues a disconnection instruction for the grid-connected relay and issues an alarm for the expiration of the service life of the grid-connected relay, including: the controller accumulates the number of disconnections of the grid-connected relay under different load currents Xn_I1, Xn_I2, ..., Xn_Im, Xn_Ik is the number of disconnections of the grid-connected relay under the kth current level, k=1, 2, ..., m; when at least one inequality Xn_I1>Yn_I1, Xn_I2>Yn_I2, ..., Xn_Im>Yn_Im is established, the controller issues a disconnection instruction for the grid-connected relay and issues an alarm for the expiration of the service life of the grid-connected relay, wherein Yn_Ik is the on-load disconnecting capacity of the grid-connected relay under the kth current level.

9. The inverter according to any one of claims 1 to 8, characterized in that: The grid-connected relay adopts a double relay system, and the double relay system includes a main relay and a slave relay connected in series.

10. A method for monitoring the service life of a grid-connected relay, which is applied to an inverter, characterized in that: The inverter includes an inverter circuit, a grid-connected relay, a controller, a voltage sampling circuit, a current sampling circuit and a grid-connected relay driving circuit; The grid-connected relay service life monitoring method comprises: When the service life of the grid-connected relay is detected to have expired, the controller sends a disconnection command for the grid-connected relay and issues an alarm indicating that the service life of the grid-connected relay has expired; The grid-connected relay driving circuit drives the grid-connected relay to disconnect according to the grid-connected relay disconnection instruction issued by the controller; When it is detected that the grid-connected relay meets at least one of the following conditions, it is determined that the service life of the grid-connected relay has expired: The pickup delay of the grid-connected relay exceeds the time limit; The number of times the grid-connected relay is closed exceeds the limit; The total energizing time of the grid-connected relay exceeds the energizing time limit; The number of on-load breaking operations of the grid-connected relay exceeds the on-load breaking capacity of the grid-connected relay.

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