CN108988388B

CN108988388B - Grid-connected inverter system

Info

Publication number: CN108988388B
Application number: CN201810883083.1A
Authority: CN
Inventors: 张凤岗; 邓超; 李本强; 李克成; 郭晗; 张鹏
Original assignee: Sungrow Shanghai Co Ltd
Current assignee: Sungrow Shanghai Co Ltd
Priority date: 2018-08-06
Filing date: 2018-08-06
Publication date: 2022-05-24
Anticipated expiration: 2038-08-06
Also published as: CN108988388A

Abstract

The invention provides a grid-connected inverter system, wherein a controller of the grid-connected inverter system can be combined with an output signal of a voltage acquisition device to judge whether a grid-connected switching device has a fault or not, so that the state detection of a switch of the grid-connected switching device is realized; and in four switches in the grid-connected switching device, every two switches are controlled by the same control signal output by the controller, so that the occupation of controller resources is reduced compared with the prior art, and the problems in the prior art are solved.

Description

Grid-connected inverter system

Technical Field

The invention relates to the technical field of power electronics, in particular to a grid-connected inverter system.

Background

According to the requirement of a grid-connected standard, a user in the prior art generally uses a single-phase grid-connected inverter, and the configuration of a grid-connected switching device of the single-phase grid-connected inverter is as shown in fig. 1: a total of 4 independent relays (SW1, SW2, SW3 and SW4) are arranged between an alternating-current side filter circuit (a first inductor L1, a second inductor L2 and a capacitor C) of the single-phase inverter and a power grid; wherein, 2 relays SW1, SW2 are connected in series on the L line, and 2 relays SW3, SW4 are connected in series on the N line.

The controller in the single-phase grid-connected inverter generally needs to control the on-off of 4 relays and each power switch tube in a single-phase inverter bridge, and the state detection of the short circuit and/or the open circuit of the 4 relays is realized by combining two collected voltages of V1_ sample and V2_ sample.

However, in the solution shown in fig. 1, each relay needs to be controlled independently, so that more controller resources are occupied.

Disclosure of Invention

The invention provides a grid-connected inverter system and a grid-connected switching device state detection method thereof, which aim to solve the problem that in the prior art, more controller resources are occupied.

In order to achieve the purpose, the technical scheme provided by the application is as follows:

a grid-tied inverter system comprising: the system comprises a controller, a voltage acquisition device, an inverter bridge, an alternating current side filter circuit and a grid-connected switch device; wherein:

the inverter bridge, the alternating current side filter circuit and the grid-connected switching device are sequentially connected, and the other end of the grid-connected switching device is connected with a power grid;

the input end of the voltage acquisition device is connected with the grid-connected switching device;

the grid-connected switching device includes: the first upper switch, the first lower switch, the second upper switch and the second lower switch; the first upper switch and the second upper switch are connected in series to an L line between the AC-side filter circuit and a power grid, and the first lower switch and the second lower switch are connected in series to an N line between the AC-side filter circuit and the power grid; the first upper switch and the first lower switch are controlled by a first control signal output by the controller, and the second upper switch and the second lower switch are controlled by a second control signal output by the controller;

the controller is used for controlling the on-off of each power switch tube in the first upper switch, the first lower switch, the second upper switch, the second lower switch and the inverter bridge, receiving the output signal of the voltage acquisition device, and judging whether the grid-connected switching device fails or not according to the cross correspondence between each signal in the output signal and the first control signal or the second control signal.

Optionally, the first upper switch, the first lower switch, the second upper switch and the second lower switch are four independent single-pole relays.

Or, the first upper switch and the first lower switch are two switches in a first double-pole relay, and the second upper switch and the second lower switch are two switches in a second double-pole relay.

Preferably, the first upper switch and the first lower switch are both connected to the ac-side filter circuit;

and the second upper switch and the second lower switch are connected with a power grid.

Preferably, the voltage acquisition device includes: the voltage acquisition device comprises a first voltage acquisition unit, a second voltage acquisition unit and a third voltage acquisition unit; wherein:

the first voltage acquisition unit is arranged between a point C and a point F, the second voltage acquisition unit is arranged between a point B and a point F, and the third voltage acquisition unit is arranged between a point A and a point E;

or the first voltage acquisition unit is arranged between a point C and a point F, the second voltage acquisition unit is arranged between a point C and a point E, and the third voltage acquisition unit is arranged between a point B and a point D;

or the first voltage acquisition unit is arranged between a point C and a point F, the second voltage acquisition unit is arranged between the point C and the point E, and the third voltage acquisition unit is arranged between a point A and a point E;

or the first voltage acquisition unit is arranged between a point C and a point F, the second voltage acquisition unit is arranged between a point B and a point F, and the third voltage acquisition unit is arranged between a point B and a point D;

the point a is a connection point between the first upper switch and the ac-side filter circuit, the point B is a connection point between the first upper switch and the second upper switch, the point C is a connection point between the second upper switch and the power grid, the point D is a connection point between the first lower switch and the ac-side filter circuit, the point E is a connection point between the first lower switch and the second lower switch, and the point F is a connection point between the second lower switch and the power grid.

Preferably, the controller is configured to control on/off of each power switching tube in the first upper switch, the first lower switch, the second upper switch, the second lower switch, and the inverter bridge, receive an output signal of the voltage acquisition device, and determine whether the grid-connected switching device fails according to the output signal, and specifically configured to:

controlling the on-off of each power switch tube in the first upper switch, the first lower switch, the second upper switch, the second lower switch and the inverter bridge for multiple times, and receiving at least two signals of an output signal of the first voltage acquisition unit, an output signal of the second voltage acquisition unit, an output signal of the third voltage acquisition unit and an output voltage signal of the inverter bridge every time;

and judging whether the first upper switch, the first lower switch, the second upper switch or the second lower switch has faults or not according to the relation between the difference value between the at least two signals and a threshold value each time.

Preferably, the voltage acquisition device includes: the device comprises a first voltage acquisition unit and a second voltage acquisition unit; wherein:

the first voltage acquisition unit is arranged between a point C and a point F, and the second voltage acquisition unit is arranged between a point A and a point F;

or the first voltage acquisition unit is arranged between a point C and a point F, and the second voltage acquisition unit is arranged between a point C and a point D;

the point A is a connection point between the first upper switch and the alternating current side filter circuit, the point C is a connection point between the second upper switch and the power grid, the point D is a connection point between the first lower switch and the alternating current side filter circuit, and the point F is a connection point between the second lower switch and the power grid;

the controller is configured to control on/off of each of the first upper switch, the first lower switch, the second upper switch, the second lower switch, and each of the power switching tubes in the inverter bridge, receive an output signal of the voltage acquisition device, and determine whether the grid-connected switching device fails according to the output signal, and is specifically configured to:

controlling the on-off of each power switch tube in the first upper switch, the first lower switch, the second upper switch, the second lower switch and the inverter bridge for multiple times, and receiving the output signal of the first voltage acquisition unit and the output signal of the second voltage acquisition unit each time;

and judging whether the first upper switch, the first lower switch, the second upper switch or the second lower switch has faults or not according to the relationship between the difference value between the output signal of the first voltage acquisition unit and the output signal of the second voltage acquisition unit and the output voltage signal of the inverter bridge and a threshold value each time.

Preferably, the voltage collecting device further comprises: a third voltage acquisition unit;

the third voltage acquisition unit is arranged between the point A and the point D, or between the point B and the point E;

wherein, point B is a connection point between the first upper switch and the second upper switch, and point E is a connection point between the first lower switch and the second lower switch;

if the third voltage acquisition unit is arranged between the point A and the point D, the controller is further configured to: controlling the on-off of each power switch tube in the first upper switch, the first lower switch, the second upper switch, the second lower switch and the inverter bridge, and receiving an output signal of the third voltage acquisition unit and an output voltage signal of the inverter bridge;

and judging whether the inverter bridge has a fault according to the relation between the difference value between the output signal of the third voltage acquisition unit and the output voltage signal of the inverter bridge and a threshold value.

Preferably, the voltage acquisition device includes: the device comprises a first voltage acquisition unit and two second voltage acquisition units; wherein:

the first voltage acquisition unit is arranged between a point C and a point F, one second voltage acquisition unit is arranged between a point A and the point F, and the other second voltage acquisition unit is arranged between the point C and the point D;

the point a is a connection point between the first upper switch and the ac-side filter circuit, the point C is a connection point between the second upper switch and the power grid, the point D is a connection point between the first lower switch and the ac-side filter circuit, and the point F is a connection point between the second lower switch and the power grid.

the point B is a connection point between the first upper switch and the second upper switch, and the point E is a connection point between the first lower switch and the second lower switch.

Preferably, the voltage acquisition device includes: the voltage acquisition device comprises a first voltage acquisition unit, a second voltage acquisition unit, a third voltage acquisition unit and a fourth voltage acquisition unit; wherein:

the first voltage acquisition unit is arranged between a point C and a point F, the second voltage acquisition unit is arranged between a point B and a point F, the third voltage acquisition unit is arranged between a point A and a point E, and the fourth voltage acquisition unit is arranged between a point C and a point E;

the point a is a connection point between the first upper switch and the ac-side filter circuit, the point B is a connection point between the first upper switch and the second upper switch, the point C is a connection point between the second upper switch and the power grid, the point E is a connection point between the first lower switch and the second lower switch, and the point F is a connection point between the second lower switch and the power grid.

Preferably, the first upper switch and the second lower switch are both connected to the ac-side filter circuit;

the second upper switch and the first lower switch are both connected with a power grid.

Preferably, the voltage acquisition device includes:

the first voltage acquisition unit is arranged between the point C and the point F;

the second voltage acquisition unit is arranged between the point B and the point E;

the point B is a connection point between the first upper switch and the second upper switch, the point C is a connection point between the second upper switch and a power grid, the point E is a connection point between the first lower switch and the second lower switch, and the point F is a connection point between the second lower switch and the power grid;

the controller is configured to control on/off of each of the first upper switch, the first lower switch, the second upper switch, the second lower switch, and the power switching tubes in the inverter bridge, receive an output signal of the voltage acquisition device, and determine whether the grid-connected switching device fails according to the output signal, and specifically configured to:

and judging whether the first upper switch, the first lower switch, the second upper switch or the second lower switch has a fault or not according to the relationship between the difference value between the output signal of the first voltage acquisition unit and the output signal of the second voltage acquisition unit and the output voltage signal of the inverter bridge and a threshold value each time.

the third voltage acquisition unit is arranged between the point A and the point D;

the point A is a connection point between the first upper switch and the alternating current side filter circuit, and the point D is a connection point between the first lower switch and the alternating current side filter circuit;

the controller is further configured to: controlling the on-off of each power switch tube in the first upper switch, the first lower switch, the second upper switch, the second lower switch and the inverter bridge, and receiving an output signal of the third voltage acquisition unit and an output voltage signal of the inverter bridge;

According to the grid-connected inverter system provided by the invention, the controller can be combined with the output signal of the voltage acquisition device to judge whether the grid-connected switching device has a fault, so that the state detection of the on-off state of the grid-connected switching device is realized; and in four switches in the grid-connected switching device, every two switches are controlled by the same control signal output by the controller, so that the occupation of controller resources is reduced compared with the prior art, and the problems in the prior art are solved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a grid-connected switchgear provided in the prior art;

fig. 2a and fig. 2b are schematic structural diagrams of two grid-connected switching devices provided by an embodiment of the invention;

fig. 3a to fig. 3h are schematic diagrams of six structures of a grid-connected switchgear device shown in fig. 2a with a state detection function added according to another embodiment of the present invention;

fig. 4 is a schematic structural diagram of a grid-connected switching device shown in fig. 2b and added with a state detection function according to another embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The invention provides a grid-connected inverter system, which solves the problem that in the prior art, more controller resources are occupied.

Referring to fig. 2a and 2b, the grid-connected inverter system includes: a controller (not shown), a voltage acquisition device (not shown), an inverter bridge, an ac-side filter circuit (such as the first inductor L1, the second inductor L2, and the capacitor C1 shown in fig. 2a and 2 b), and a grid-connected switching device; wherein:

the grid-connected switching device includes: a first upper switch SW1, a first lower switch SW2, a second upper switch SW3 and a second lower switch SW 4; the first upper switch SW1 and the second upper switch SW3 are connected in series to an L line between the ac-side filter circuit and the grid, and the first lower switch SW2 and the second lower switch SW4 are connected in series to an N line between the ac-side filter circuit and the grid; the first upper switch SW1 and the first lower switch SW2 are controlled by a first control signal Driver1 output by the controller, and the second upper switch SW3 and the second lower switch SW4 are controlled by a second control signal Driver2 output by the controller;

the controller is used for controlling the on-off of the first upper switch SW1, the first lower switch SW2, the second upper switch SW3, the second lower switch SW4 and each power switch tube in the inverter bridge, receiving the output signals of the voltage acquisition device, and judging whether the grid-connected switching device has faults or not according to the cross corresponding relation between each signal in the output signals and the first control signal Driver1 or the second control signal Driver 2.

Optionally, the first upper switch SW1, the first lower switch SW2, the second upper switch SW3 and the second lower switch SW4 are four independent single-pole relays;

alternatively, the first upper switch SW1 and the first lower switch SW2 are two switches in the first two-pole relay, and the second upper switch SW3 and the second lower switch SW4 are two switches in the second two-pole relay. At this time, the two double-pole relays replace four single-pole relays in the prior art, so that the structural cost of the grid-connected switching device can be reduced.

As shown in fig. 2a, one end of the first upper switch SW1 is connected to a connection point of a first inductor L1 and a capacitor C1 in the ac-side filter circuit, the other end of the first upper switch SW1 is connected to one end of the second upper switch SW3, and the other end of the second upper switch SW3 is connected to the line L of the power grid; one end of the first lower switch SW2 is connected to a connection point of the second inductor L2 and the capacitor C1 in the ac-side filter circuit, the other end of the first lower switch SW2 is connected to one end of the second lower switch SW4, and the other end of the second lower switch SW4 is connected to the N line of the power grid. The first upper switch SW1 and the first lower switch SW2 are controlled by a first control signal Driver1, and the second upper switch SW3 and the second lower switch SW4 are controlled by a second control signal Driver 2; it can be seen that each control signal corresponds to a pair of up-down switches, and accordingly, the corresponding signal acquisition point in the output signal of the voltage acquisition device needs to be arranged at the crossing position across a certain pair of up-down switches.

As shown in fig. 2b, one end of the first upper switch SW1 is connected to the connection point of the first inductor L1 and the capacitor C1 in the ac-side filter circuit, the other end of the first upper switch SW1 is connected to one end of the second upper switch SW3, and the other end of the second upper switch SW3 is connected to the line L of the power grid; one end of the second lower switch SW4 is connected to a connection point between the second inductor L2 and the capacitor C1 in the ac-side filter circuit, the other end of the second lower switch SW4 is connected to one end of the first lower switch SW2, and the other end of the first lower switch SW2 is connected to the N line of the power grid. The first upper switch SW1 and the first lower switch SW2 are controlled by a first control signal Driver1, and the second upper switch SW3 and the second lower switch SW4 are controlled by a second control signal Driver2, which can be seen that each control signal respectively controls a pair of upper and lower switches arranged in a crossing manner.

According to the grid-connected switching device provided by the embodiment, the controller can be combined with the output signal of the voltage acquisition device to judge whether the grid-connected switching device has a fault according to the cross corresponding relation between each signal in the output signal and the first control signal Driver1 or the second control signal Driver2, so that the state detection of the switch of the grid-connected switching device is realized; and in four switches in the grid-connected switching device, every two switches are controlled by the same control signal output by the controller, so that the occupation of controller resources is reduced compared with the prior art, and the problems in the prior art are solved.

It should be noted that, in order to achieve the short-circuit and/or open-circuit state detection for the switches SW 1-SW 4 and to achieve no current surge when all the switches are closed, another embodiment of the present invention provides several specific grid-connected switching devices based on fig. 2a, as shown in fig. 3 a-3 h.

In fig. 3a to 3h, point a is a connection point between the first upper switch SW1 and the ac side filter circuit, point B is a connection point between the first upper switch SW1 and the second upper switch SW3, point C is a connection point between the second upper switch SW3 and the grid, point D is a connection point between the first lower switch SW2 and the ac side filter circuit, point E is a connection point between the first lower switch SW2 and the second lower switch SW4, and point F is a connection point between the second lower switch SW4 and the grid.

In fig. 3a to 3d, when the controller detects whether the grid-connected switching device has a fault, the controller is specifically configured to:

controlling the on-off of each power switch tube in the first upper switch SW1, the first lower switch SW2, the second upper switch SW3, the second lower switch SW4 and the inverter bridge for multiple times, and receiving at least two signals of an output signal V1_ sample of the first voltage acquisition unit, an output signal V2_ sample of the second voltage acquisition unit, an output signal V3_ sample of the third voltage acquisition unit and an output voltage signal of the inverter bridge every time;

whether the first upper switch SW1, the first lower switch SW2, the second upper switch SW3, or the second lower switch SW4 malfunctions is determined each time according to a relationship between a difference between at least two signals and a threshold.

Specifically, the method comprises the following steps:

referring to fig. 3a, the grid-tie switching device includes:

the first voltage acquisition unit is arranged between the point C and the point F (the output signal is V1_ sample);

the second voltage acquisition unit is arranged between the point B and the point F (the output signal is V2_ sample);

and the third voltage acquisition unit is arranged between the point A and the point E (the output signal is V3_ sample).

In the sampling structure shown in fig. 3a, the specific detection process of the controller is as follows:

the first upper switch SW1, the first lower switch SW2, the second upper switch SW3 and the second lower switch SW4 are controlled to be turned off; receiving and comparing an output signal V1_ sample of the first voltage acquisition unit and an output signal V2_ sample of the second voltage acquisition unit; if the difference value between the first upper switch SW3 and the second upper switch SW3 is larger than the threshold value, the second upper switch SW3 is judged to be normally disconnected, and if the difference value is not larger than the threshold value, the second upper switch SW3 is judged to be in a short circuit sticky state;

controls the first upper switch SW1 and the first lower switch SW2 to be opened, and the second upper switch SW3 and the second lower switch SW4 to be closed; receiving and comparing an output signal V3_ sample of the third voltage acquisition unit with an output signal V2_ sample of the first voltage acquisition unit or the second voltage acquisition unit; if the difference value between the first upper switch SW1 and the second upper switch SW is larger than the threshold value, judging that the first upper switch SW1 can be normally disconnected, and otherwise, judging that the first upper switch SW1 is in a short circuit sticky state; receiving and comparing the output signal V2_ sample of the second voltage acquisition unit with the output signal V1_ sample of the first voltage acquisition unit; if the difference value between the first upper switch SW3 and the second upper switch SW3 is in an abnormal open state, judging that the second upper switch SW3 can be normally closed;

the first upper switch SW1, the first lower switch SW2, the second upper switch SW3 and the second lower switch SW4 are controlled to be switched off, the inverter bridge is controlled to work slowly, and the sinusoidal voltage V _ inv is output; receiving and comparing an output signal V3_ sample of the third voltage acquisition unit with a sinusoidal voltage V _ inv; if the difference value between the first lower switch SW2 and the second lower switch SW is larger than the threshold value, judging that the first lower switch SW2 can be normally disconnected, and otherwise, judging that the first lower switch SW2 is in a short circuit sticky state;

controlling the first upper switch SW1 and the first lower switch SW2 to be closed, and the second upper switch SW3 and the second lower switch SW4 to be opened, and controlling the inverter bridge to keep outputting the sinusoidal voltage V _ inv; receiving and comparing an output signal V2_ sample of the second voltage acquisition unit and an output signal V3_ sample of the third voltage acquisition unit; if the difference value between the first lower switch SW and the second lower switch SW is larger than the threshold value, the second lower switch SW4 can be normally switched off, otherwise, the second lower switch SW4 is in a short circuit sticky state; or receiving and comparing the output signal V2_ sample of the second voltage acquisition unit with the sinusoidal voltage V _ inv; if the difference value between the first lower switch SW and the second lower switch SW is larger than the threshold value, the second lower switch SW4 can be normally switched off, otherwise, the second lower switch SW4 is in a short circuit sticky state; receiving and comparing an output signal V3_ sample of the third voltage acquisition unit with a sinusoidal voltage V _ inv; if the difference value between the first lower switch SW2 and the second lower switch SW2 is in an abnormal open state, judging that the first lower switch SW2 can be normally closed;

the sinusoidal voltage V _ inv output by the inverter bridge is controlled to gradually and slowly change to the same frequency and phase with the output signal V1_ sample of the first voltage acquisition unit, the second upper switch SW3 and the second lower switch SW4 are controlled to be closed, then the inverter bridge is controlled to stop working, and the output signal V3_ sample of the third voltage acquisition unit and the output signal V1_ sample of the first voltage acquisition unit can be received and compared at the moment; if the difference value between the first upper switch SW1 and the second upper switch SW3 is smaller than the threshold value, the first upper switch SW1, the second upper switch SW3 and the second lower switch SW4 are judged to be normally closed, otherwise, the first upper switch SW1, the second upper switch SW3 and the second lower switch SW4 are judged to be in an abnormal open state; or, receiving and comparing an output signal V1_ sample of the first voltage acquisition unit with a sinusoidal voltage V _ inv output by the inverter bridge in a following normal grid-connected working state of the inverter bridge; if the difference value between the two is smaller than the threshold value, all the switches can be normally closed, otherwise, part of the switches are judged to be in an abnormal open circuit state.

Also similar to the structure shown in fig. 3a are: FIG. 3b, FIG. 3c and FIG. 3 d; wherein:

as shown in fig. 3b, the voltage collecting device includes:

the second voltage acquisition unit is arranged between the point C and the point E (the output signal is V2_ sample);

and the third voltage acquisition unit is arranged between the point B and the point D (the output signal is V3_ sample).

In the sampling structure shown in fig. 3b, the specific detection process of the controller is as follows:

the first upper switch SW1, the first lower switch SW2, the second upper switch SW3 and the second lower switch SW4 are controlled to be turned off; receiving and comparing an output signal V1_ sample of the first voltage acquisition unit and an output signal V2_ sample of the second voltage acquisition unit; if the difference value between the first lower switch SW and the second lower switch SW is larger than the threshold value, the second lower switch SW4 can be normally switched off, otherwise, the second lower switch SW4 is in a short circuit sticky state;

controls the first upper switch SW1 and the first lower switch SW2 to be opened, and the second upper switch SW3 and the second lower switch SW4 to be closed; receiving and comparing an output signal V3_ sample of the third voltage acquisition unit with an output signal V2_ sample of the first voltage acquisition unit or the second voltage acquisition unit; if the difference value between the first lower switch SW2 and the second lower switch SW is larger than the threshold value, judging that the first lower switch SW2 can be normally disconnected, and otherwise, judging that the first lower switch SW2 is in a short circuit sticky state; receiving and comparing the output signal V2_ sample of the second voltage acquisition unit with the output signal V1_ sample of the first voltage acquisition unit; if the difference value between the first lower switch and the second lower switch is smaller than the threshold value, the second lower switch SW4 can be normally closed, otherwise, the second lower switch SW4 is in an abnormal open state;

the first upper switch SW1, the first lower switch SW2, the second upper switch SW3 and the second lower switch SW4 are controlled to be switched off, the inverter bridge is controlled to work slowly, and the sinusoidal voltage V _ inv is output; receiving and comparing an output signal V3_ sample of the third voltage acquisition unit with a sinusoidal voltage V _ inv; if the difference value between the first upper switch SW1 and the second upper switch SW is larger than the threshold value, judging that the first upper switch SW1 can be normally disconnected, and otherwise, judging that the first upper switch SW1 is in a short circuit sticky state;

controlling the first upper switch SW1 and the first lower switch SW2 to be closed, and the second upper switch SW3 and the second lower switch SW4 to be opened, and controlling the inverter bridge to keep outputting the sinusoidal voltage V _ inv; receiving and comparing an output signal V2_ sample of the second voltage acquisition unit and an output signal V3_ sample of the third voltage acquisition unit; if the difference value between the first upper switch SW3 and the second upper switch SW3 is larger than the threshold value, the second upper switch SW3 is judged to be normally disconnected, and if the difference value is not larger than the threshold value, the second upper switch SW3 is judged to be in a short circuit sticky state; or receiving and comparing the output signal V2_ sample of the second voltage acquisition unit with the sinusoidal voltage V _ inv; if the difference value between the first upper switch SW3 and the second upper switch SW3 is larger than the threshold value, the second upper switch SW3 is judged to be normally disconnected, and if the difference value is not larger than the threshold value, the second upper switch SW3 is judged to be in a short circuit sticky state; moreover, an output signal V3_ sample and a sinusoidal voltage V _ inv of the third voltage acquisition unit are received and compared; if the difference value between the first upper switch SW1 and the second upper switch SW is smaller than the threshold value, judging that the first upper switch SW1 can be normally closed, otherwise, judging that the first upper switch SW1 is in an abnormal open state;

the sinusoidal voltage V _ inv output by the inverter bridge is controlled to gradually and slowly change to be in the same frequency and phase as the output signal V1_ sample of the first voltage acquisition unit, then the second upper switch SW3 and the second lower switch SW4 are controlled to be closed, then the inverter bridge is controlled to stop working, and at the moment, the output signal V3_ sample of the third voltage acquisition unit and the output signal V1_ sample of the first voltage acquisition unit can be received and compared; if the difference value between the first lower switch SW2 and the second upper switch SW3 is smaller than the threshold value, the first lower switch SW2, the second lower switch SW4 and the second upper switch SW4 are all judged to be normally closed, otherwise, the first lower switch SW2, the second upper switch SW3 and the second lower switch SW4 are judged to be in an abnormal open state; or, receiving and comparing an output signal V1_ sample of the first voltage acquisition unit with a sinusoidal voltage V _ inv output by the inverter bridge in a following normal grid-connected working state of the inverter bridge; if the difference value between the two is smaller than the threshold value, all the switches can be normally closed, otherwise, part of the switches are judged to be in an abnormal open circuit state.

As shown in fig. 3c, the voltage collecting device includes:

In the sampling structure shown in fig. 3c, the specific detection process of the controller is as follows:

controls the first upper switch SW1 and the first lower switch SW2 to be opened, and the second upper switch SW3 and the second lower switch SW4 to be closed; receiving and comparing an output signal V3_ sample of the third voltage acquisition unit with an output signal V2_ sample of the first voltage acquisition unit or the second voltage acquisition unit; if the difference value between the first upper switch SW1 and the second upper switch SW is larger than the threshold value, judging that the first upper switch SW1 can be normally disconnected, and otherwise, judging that the first upper switch SW1 is in a short circuit sticky state; receiving and comparing the output signal V2_ sample of the second voltage acquisition unit with the output signal V1_ sample of the first voltage acquisition unit; if the difference value between the first lower switch and the second lower switch is smaller than the threshold value, the second lower switch SW4 can be normally closed, otherwise, the second lower switch SW4 is in an abnormal open state;

controlling the first upper switch SW1 and the first lower switch SW2 to be closed, and the second upper switch SW3 and the second lower switch SW4 to be opened, and controlling the inverter bridge to keep outputting the sinusoidal voltage V _ inv; receiving and comparing an output signal V2_ sample of the second voltage acquisition unit and an output signal V3_ sample of the third voltage acquisition unit; if the difference value between the first upper switch SW3 and the second upper switch SW3 is larger than the threshold value, the second upper switch SW3 is judged to be normally disconnected, and if the difference value is not larger than the threshold value, the second upper switch SW3 is judged to be in a short circuit sticky state; or receiving and comparing the output signal V2_ sample of the second voltage acquisition unit with the sinusoidal voltage V _ inv; if the difference value between the first upper switch SW3 and the second upper switch SW3 is larger than the threshold value, the second upper switch SW3 is judged to be normally disconnected, and if the difference value is not larger than the threshold value, the second upper switch SW3 is judged to be in a short circuit sticky state; receiving and comparing an output signal V3_ sample of the third voltage acquisition unit with a sinusoidal voltage V _ inv; if the difference value between the first lower switch SW2 and the second lower switch SW2 is in an abnormal open state, judging that the first lower switch SW2 can be normally closed;

the sinusoidal voltage V _ inv output by the inverter bridge is controlled to gradually and slowly change to be in the same frequency and phase as the output signal V1_ sample of the first voltage acquisition unit, then the second upper switch SW3 and the second lower switch SW4 are controlled to be closed, then the inverter bridge is controlled to stop working, and at the moment, the output signal V3_ sample of the third voltage acquisition unit and the output signal V1_ sample of the first voltage acquisition unit can be received and compared; if the difference value between the first upper switch SW1 and the second upper switch SW3 is smaller than the threshold value, the first upper switch SW1, the second upper switch SW3 and the second lower switch SW4 are all judged to be normally closed, otherwise, the first upper switch SW1, the second upper switch SW3 and the second lower switch SW4 are judged to be in an abnormal open state; or, receiving and comparing an output signal V1_ sample of the first voltage acquisition unit with a sinusoidal voltage V _ inv output by the inverter bridge in a following normal grid-connected working state of the inverter bridge; if the difference value between the two is smaller than the threshold value, all the switches can be normally closed, otherwise, part of the switches are judged to be in an abnormal open circuit state.

As shown in fig. 3d, the voltage collecting device includes:

In the sampling structure shown in fig. 3d, the specific detection process of the controller is as follows:

controls the first upper switch SW1 and the first lower switch SW2 to be opened, and the second upper switch SW3 and the second lower switch SW4 to be closed; receiving and comparing an output signal V3_ sample of the third voltage acquisition unit with an output signal V2_ sample of the first voltage acquisition unit or the second voltage acquisition unit; if the difference value between the first lower switch SW2 and the second lower switch SW is larger than the threshold value, judging that the first lower switch SW2 can be normally disconnected, and otherwise, judging that the first lower switch SW2 is in a short circuit sticky state; receiving and comparing the output signal V2_ sample of the second voltage acquisition unit with the output signal V1_ sample of the first voltage acquisition unit; if the difference value between the first upper switch SW3 and the second upper switch SW3 is in an abnormal open state, judging that the second upper switch SW3 can be normally closed;

controlling the first upper switch SW1 and the first lower switch SW2 to be closed, and the second upper switch SW3 and the second lower switch SW4 to be opened, and controlling the inverter bridge to keep outputting the sinusoidal voltage V _ inv; receiving and comparing an output signal V2_ sample of the second voltage acquisition unit and an output signal V3_ sample of the third voltage acquisition unit; if the difference value between the first lower switch SW and the second lower switch SW is larger than the threshold value, the second lower switch SW4 can be normally switched off, otherwise, the second lower switch SW4 is in a short circuit sticky state; or receiving and comparing the output signal V2_ sample of the second voltage acquisition unit with the sinusoidal voltage V _ inv; if the difference value between the first lower switch SW4 and the second lower switch SW4 is larger than the threshold value, the second lower switch SW4 is judged to be normally disconnected, and otherwise the second lower switch SW4 is judged to be in a short circuit sticky state; receiving and comparing an output signal V3_ sample of the third voltage acquisition unit with a sinusoidal voltage V _ inv; if the difference value between the first upper switch SW1 and the second upper switch SW is smaller than the threshold value, judging that the first upper switch SW1 can be normally closed, otherwise, judging that the first upper switch SW1 is in an abnormal open state;

In addition, on the basis of fig. 2a, the voltage collecting device can also be shown in fig. 3e and 3 f; in fig. 3e to 3f, when the controller detects whether the grid-connected switching device has a fault, the controller is specifically configured to:

controlling the on-off of each power switch tube in the first upper switch SW1, the first lower switch SW2, the second upper switch SW3, the second lower switch SW4 and the inverter bridge for multiple times, and receiving an output signal V1_ sample of the first voltage acquisition unit and an output signal V2_ sample of the second voltage acquisition unit each time;

whether the first upper switch SW1, the first lower switch SW2, the second upper switch SW3 or the second lower switch SW4 has a fault is judged according to the relationship between the difference value between the output signal V1_ sample of the first voltage acquisition unit and the output signal V2_ sample of the second voltage acquisition unit and the output voltage signal of the inverter bridge and the threshold value each time.

Specifically, the method comprises the following steps:

referring to fig. 3e, the voltage collecting apparatus includes:

and the second voltage acquisition unit is arranged between the point A and the point F (the output signal is V2_ sample).

Alternatively, referring to fig. 3f, the voltage collecting device comprises:

and the second voltage acquisition unit is arranged between the point C and the point D (the output signal is V2_ sample).

Further, as shown in fig. 3e and 3f, the grid-connected switching device may further include: a third voltage acquisition unit (output signal is V3_ sample); the third voltage acquisition unit is arranged between the point A and the point D, or between the point B and the point E;

and an output signal V3_ sample of the third voltage acquisition unit is output to the controller, so that the controller realizes self-checking of an inverter bridge in the grid-connected inverter system.

In the voltage acquisition devices shown in fig. 3E and 3f, taking the example that the third voltage acquisition unit is disposed between the point B and the point E as an example, the specific detection process of the controller is as follows:

the first upper switch SW1, the first lower switch SW2, the second upper switch SW3 and the second lower switch SW4 are controlled to be switched off, the inverter bridge is controlled to work slowly, and the sinusoidal voltage V _ inv is output; receiving and comparing an output signal V3_ sample of the third voltage acquisition unit with a sinusoidal voltage V _ inv; and if the difference value between the two is smaller than the threshold value, judging that the inverter bridge is normal.

Controlling the first upper switch SW1 and the first lower switch SW2 to be opened, and the second upper switch SW3 and the second lower switch SW4 to be closed, and controlling the inverter bridge to keep outputting the sinusoidal voltage V _ inv; receiving and comparing an output signal V2_ sample of the second voltage acquisition unit with an output signal V1_ sample and a sinusoidal voltage V _ inv of the first voltage acquisition unit respectively; if the difference values obtained in the two comparisons are larger than the threshold value, the first upper switch SW1 and the first lower switch SW2 can be normally switched off, otherwise, the first upper switch SW1 and the first lower switch SW2 are in a short circuit sticky state; receiving and comparing an output signal V3_ sample of the third voltage acquisition unit with an output signal V1_ sample of the first voltage acquisition unit; if the difference between the two is less than the threshold value, it is determined that the second upper switch SW3 and the second lower switch SW4 can be normally closed, otherwise it is determined that the second upper switch SW3 or the second lower switch SW4 is in an abnormal open state;

controlling the first upper switch SW1 and the first lower switch SW2 to be closed, and the second upper switch SW3 and the second lower switch SW4 to be opened, and controlling the inverter bridge to keep outputting the sinusoidal voltage V _ inv; receiving and respectively carrying out output signals V2_ sample of the second voltage acquisition unit with output signals V1_ sample and sinusoidal voltage V _ inv of the first voltage acquisition unit; if the difference obtained in the two comparisons is larger than the threshold value, the second upper switch SW3 and the second lower switch SW4 can be normally switched off, otherwise, the second upper switch SW3 and the second lower switch SW4 are in a short circuit sticky state; receiving and comparing an output signal V3_ sample of the third voltage acquisition unit with a sinusoidal voltage V _ inv; if the difference between the two is greater than the threshold value, it is determined that the first upper switch SW1 and the first lower switch SW2 can be normally closed, otherwise it is determined that the first upper switch SW1 or the first lower switch SW2 is in an abnormal open state.

The sinusoidal voltage V _ inv output by the inverter bridge is controlled to gradually and slowly change to be in the same frequency and phase as the output signal V1_ sample of the first voltage acquisition unit, and then the second upper switch SW3 and the second lower switch SW4 are controlled to be closed; then the inverter bridge is controlled to stop working, and at the moment, if the third voltage acquisition unit is arranged between the point A and the point D, the output signal V3_ sample of the third voltage acquisition unit and the output signal V1_ sample of the first voltage acquisition unit can be received and compared; if the difference value between the two is smaller than the threshold value, all the switches can be normally closed, otherwise, part of the switches are judged to be in an abnormal open circuit state; or, receiving and comparing an output signal V1_ sample of the first voltage acquisition unit with a sinusoidal voltage V _ inv output by the inverter bridge in a following normal grid-connected working state of the inverter bridge; if the difference value between the two is smaller than the threshold value, all the switches can be normally closed, otherwise, part of the switches are judged to be in an abnormal open circuit state.

The grid-connected inverter system provided by this embodiment is directed at the grid-connected switching device shown in fig. 2a, the voltage sampling point of the voltage acquisition device on the line L, N is not at a symmetrical position, but is placed at a crossing position across the relay switch, so that the controller can accurately and effectively judge the short-circuit and open-circuit abnormal states of the relay switch by combining the crossing voltage sampling value with the crossing corresponding relationship between the first control signal and the second control signal. In addition, self-checking of the inverter bridge can be realized through the corresponding voltage acquisition unit.

In fig. 3e and 3f, if there is no third voltage collecting unit, when the controller detects the state of the grid-connected switching device, the output voltage signal of the inverter bridge for judgment may be derived from the output set value of the controller for the inverter bridge.

It should be noted that, on the basis of fig. 2a, the voltage acquisition device may also adopt a manner that the voltage acquisition units in fig. 3a to 3f are combined with each other, for example, the structure shown in fig. 3g may be obtained by combining fig. 3e and 3f, and the structure shown in fig. 3h may be obtained by combining fig. 3a and 3 c;

referring to fig. 3g, the voltage collecting apparatus includes: the first voltage acquisition unit and the two second voltage acquisition units can also comprise a third voltage acquisition unit; the first voltage acquisition unit (output signal is V1_ sample) is arranged between a point C and a point F, one second voltage acquisition unit (output signal is V2_ sample1) is arranged between a point A and the point F, the other second voltage acquisition unit (output signal is V2_ sample2) is arranged between the point C and the point D, and the third voltage acquisition unit (output signal is V3_ sample) is arranged between the point A and the point D, or the point B and the point E;

referring to fig. 3h, the voltage collecting apparatus includes: the voltage acquisition device comprises a first voltage acquisition unit, a second voltage acquisition unit, a third voltage acquisition unit and a fourth voltage acquisition unit; the first voltage acquisition unit (output signal is V1_ sample) is arranged between a point C and a point F, the second voltage acquisition unit (output signal is V2_ sample) is arranged between a point B and the point F, and the third voltage acquisition unit (output signal is V3_ sample) is arranged between a point A and a point E; the fourth voltage acquisition unit (the output signal is V4_ sample) is arranged between the point C and the point E;

the voltage acquisition device shown in fig. 3g can reduce the relay action number in the relay detection process; the voltage acquisition device shown in fig. 3h can also solve the problem of parasitic voltage of the sampling loop by arranging the fourth voltage acquisition unit. Here, only two examples are shown, and in practical applications, various combinations may be performed on the voltage acquisition schemes shown in fig. 3a to 3f, which are not described herein again one by one, and are all within the protection scope of the present application.

The rest of the structure and the principle are the same as the above embodiments, and are not described in detail here.

On the basis of fig. 2b, in order to realize the state detection of the short circuit and/or the open circuit of the switches SW 1-SW 4, another embodiment of the present invention provides a specific grid-connected switching device, as shown in fig. 4, the grid-connected switching device further includes, on the basis of fig. 2 b:

the second voltage acquisition unit is arranged between the point B and the point E (the output signal is V2_ sample);

further, as shown in fig. 4, the grid-connected switching device may further include: a third voltage acquisition unit (output signal is V3_ sample) arranged between the point A and the point D;

the output signal of the third voltage acquisition unit is output to the controller, so that the controller realizes self-checking of an inverter bridge in the grid-connected inverter system;

the point a is a connection point between the first upper switch SW1 and the ac side filter circuit, the point B is a connection point between the first upper switch SW1 and the second upper switch SW3, the point C is a connection point between the second upper switch SW3 and the grid, the point D is a connection point between the first lower switch SW2 and the ac side filter circuit, the point E is a connection point between the first lower switch SW2 and the second lower switch SW4, and the point F is a connection point between the second lower switch SW4 and the grid.

In the sampling structure shown in fig. 4, when the controller detects whether the grid-connected switching device has a fault, the controller is specifically configured to:

Referring to fig. 4, the specific detection process of the controller is as follows:

the first upper switch SW1 and the first lower switch SW2 are controlled to be turned off by a first control signal Driver1, the second upper switch SW3 and the second lower switch SW4 are controlled to be turned off by a second control signal Driver2, the inverter bridge works slowly, and the sinusoidal voltage V _ inv is output. And receiving and comparing an output signal V3_ sample of the third voltage acquisition unit with the sinusoidal voltage V _ inv, if the difference value between the output signal V3_ sample and the sinusoidal voltage V _ inv is smaller than a threshold value, judging that the inverter bridge is normal, otherwise, judging that the inverter bridge is abnormal.

The first upper switch SW1 and the first lower switch SW2 are controlled to be opened through a first control signal Driver1, the second upper switch SW3 and the second lower switch SW4 are controlled to be closed through a second control signal Driver2, the output signal V2_ sample and the sinusoidal voltage V _ inv of the second voltage acquisition unit are received and compared, if the difference value between the two is larger than a threshold value, the first upper switch SW1 is judged to be normally opened, and if not, the first upper switch SW1 is judged to be short-circuit sticky; and receiving and comparing the output signal V2_ sample of the second voltage acquisition unit and the output signal V1_ sample of the first voltage acquisition unit, if the difference value between the two is greater than the threshold value, determining that the first lower switch SW2 can be normally disconnected, otherwise determining that the first lower switch SW2 is short-circuit sticky.

The first upper switch SW1 and the first lower switch SW2 are controlled to be closed through a first control signal Driver1, the second upper switch SW3 and the second lower switch SW4 are controlled to be opened through a second control signal Driver2, the output signal V2_ sample and the sinusoidal voltage V _ inv of the second voltage acquisition unit are received and compared, if the difference value between the two is larger than a threshold value, the second lower switch SW4 is judged to be normally opened, and if not, the second lower switch SW4 is judged to be short-circuit sticky; and receiving and comparing the output signal V2_ sample of the second voltage acquisition unit and the output signal V1_ sample of the first voltage acquisition unit, if the difference value between the two is greater than the threshold value, determining that the second upper switch SW3 can be normally disconnected, otherwise determining that the second upper switch SW3 is short-circuit sticky.

V _ inv is gradually and slowly changed to be in the same frequency and phase as V1_ sample, then the second upper switch SW3 and the second lower switch SW4 are controlled to be closed through a second control signal Driver2, the inverter bridge is controlled to stop working, at the moment, the output signal V3_ sample of the third voltage acquisition unit and the output signal of the first voltage acquisition unit can be received and compared, if the difference value between the output signal V3_ sample and the output signal of the first voltage acquisition unit is smaller than a threshold value, all switches can be normally closed, and if not, part of switches are abnormally opened. Or, under the following normal grid-connected working state of the inverter bridge, receiving and comparing the output signal V1_ sample of the first voltage acquisition unit and the sinusoidal voltage V _ inv output by the inverter bridge, if the difference value between the two is smaller than a threshold value, judging that all switches can be normally closed, otherwise, judging that part of switches are abnormally opened.

For the grid-connected switching device shown in fig. 2b, each control signal controls a pair of upper and lower switches which are arranged in a crossed manner, but the voltage acquisition devices of the grid-connected switching device are arranged at symmetrical positions relative to voltage sampling points on a L, N line, so that the controller can judge the abnormal states of short circuit and open circuit of the relay switch accurately and effectively through the voltage sampling values of the symmetrical points and the cross corresponding relation between the voltage sampling values and the first control signal or the second control signal. In addition, in fig. 4, if there is no third voltage collecting unit, when the controller detects the state of the grid-connected switching device, the output voltage signal of the inverter bridge for judgment may be derived from the output set value of the controller for the inverter bridge.

The rest of the principle is the same as the above embodiments, and is not described in detail here.

It should be noted that, the steps of the controller detection processes provided in the above two embodiments may be mutually referred and interchanged, and the sequence of the steps may also be adjusted according to the specific application environment, and is not limited thereto, and all the steps are within the scope of the present application.

The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make numerous possible variations and modifications to the present teachings, or modify equivalent embodiments to equivalent variations, without departing from the scope of the present teachings, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.

Claims

1. A grid-connected inverter system, comprising: the system comprises a controller, a voltage acquisition device, an inverter bridge, an alternating current side filter circuit and a grid-connected switch device; wherein:

when each control signal respectively controls a pair of upper and lower switches which are arranged in a crossed manner, the voltage acquisition device is arranged at a symmetrical position relative to a voltage sampling point on an L, N line, and the voltage sampling point arranged at the symmetrical position at least comprises a connection point between each upper and lower switch and a power grid;

when each control signal respectively controls a pair of upper and lower switches which are symmetrically arranged, the voltage sampling point of the voltage acquisition device on the L, N line is placed at the cross position crossing the switches;

the controller is used for controlling the on-off of each power switch tube in the first upper switch, the first lower switch, the second upper switch, the second lower switch and the inverter bridge, receiving an output signal of the voltage acquisition device, and judging whether the grid-connected switching device fails or not according to the cross correspondence between each signal in the output signal and the first control signal or the second control signal;

the output signals of the voltage acquisition devices at least come from the voltage acquisition devices arranged between the connection points between the upper switch and the lower switch and the power grid respectively, and the output signals of the voltage acquisition devices at least come from the voltage acquisition devices which are arranged at the cross positions of the cross switches corresponding to voltage sampling points on L, N lines.

2. The grid-connected inverter system according to claim 1, wherein the first upper switch, the first lower switch, the second upper switch, and the second lower switch are four independent single-pole relays.

3. The grid-connected inverter system according to claim 1, wherein the first upper switch and the first lower switch are two switches of a first double pole relay, and the second upper switch and the second lower switch are two switches of a second double pole relay.

4. The grid-connected inverter system according to claim 2 or 3, wherein the first upper switch and the first lower switch are connected to the ac-side filter circuit;

5. The grid-connected inverter system according to claim 4, wherein the voltage acquisition device comprises: the voltage acquisition device comprises a first voltage acquisition unit, a second voltage acquisition unit and a third voltage acquisition unit; wherein:

or the first voltage acquisition unit is arranged between the point C and the point F, the second voltage acquisition unit is arranged between the point C and the point E, and the third voltage acquisition unit is arranged between the point A and the point E;

6. The grid-connected inverter system according to claim 5, wherein the controller is configured to control on/off of each of the first upper switch, the first lower switch, the second upper switch, the second lower switch, and the power switching tubes in the inverter bridge, receive an output signal of the voltage acquisition device, and determine whether the grid-connected switching device fails according to the output signal, and specifically configured to:

7. The grid-connected inverter system according to claim 4, wherein the voltage acquisition device comprises: the device comprises a first voltage acquisition unit and a second voltage acquisition unit; wherein:

8. The grid-connected inverter system according to claim 7, wherein the voltage acquisition device further comprises: a third voltage acquisition unit;

9. The grid-connected inverter system according to claim 4, wherein the voltage acquisition device comprises: the device comprises a first voltage acquisition unit and two second voltage acquisition units; wherein:

10. The grid-connected inverter system according to claim 9, wherein the voltage acquisition device further comprises: a third voltage acquisition unit;

11. The grid-connected inverter system according to claim 4, wherein the voltage acquisition device comprises: the voltage acquisition device comprises a first voltage acquisition unit, a second voltage acquisition unit, a third voltage acquisition unit and a fourth voltage acquisition unit; wherein:

12. The grid-connected inverter system according to claim 4, wherein the voltage acquisition device comprises:

13. The grid-connected inverter system according to claim 12, wherein the voltage collecting device further comprises: a third voltage acquisition unit;