CROSS REFERENCE TO RELATED APPLICATION

The present application claims the priority to Chinese Patent Application No. 201810973984.X, titled “ACTIVE BYPASS CONTROL DEVICE AND METHOD FOR PHOTOVOLTAIC MODULE”, filed on Aug. 24, 2018 with the Chinese Patent Office, which is incorporated herein by reference in its entirety.

FIELD

The present disclosure relates to the field of power electronics, in particular to an active bypass control device and an active bypass control method for a photovoltaic module.

BACKGROUND

In the field of photovoltaic power generation, in order to prevent the hot spot effect of a photovoltaic module, a bypass diode is usually arranged in a junction box of the photovoltaic module. In a case that a substring in the photovoltaic module is shaded and the power thereof is insufficient, the current is automatically transferred from the substring to the external parallel diode loop, avoiding heat generation of the abnormal substring as a load, while not affecting the power generation of other substrings. In some module-level products, such as a shutdown device and an optimizer, a diode is also connected in parallel with the output port of the photovoltaic module. In the case of device abnormal shutdown, the branch in which the photovoltaic module is located is bypassed, so that the remaining photovoltaic modules in the same substring are not affected.

The current of a conventional photovoltaic module is generally about 10 A, and the current of a double-sided photovoltaic module even reaches 13 A. When entering the bypass mode, the current flows through the parallel diode. Depending on the performance of the diode, the loss usually ranges from 3 W to 6 W. The large power consumption results in the temperature in the conventional junction box being above 150°. The junction box may heat up and bulge under the continuous high temperature. In this case, the life of the diode is reduced, resulting in reduced reliability of the product. Further, in order to improve heat dissipation, a metal piece having a larger area may be required for the diode, or a potting sealant with better thermal conductivity may be used, or a diode with better performance may be selected, which all result in increase of the cost. In addition, the system loss is large, bringing a certain loss to the system power generation.

SUMMARY

There are provided an active bypass control device and an active bypass control method for a photovoltaic module in the present disclosure, to solve problems in the conventional technology of low reliability, high cost and large system loss.

The following technical solutions are provided in the present disclosure.

In a first aspect, an active bypass control device for a photovoltaic module is provided. The active bypass control device includes a power source, a sampling unit, a controller, N first driving circuits, and N first controllable switches, where N is a positive integer, where

an output end of the power source is connected to a power supply end of the controller;

an output end of the sampling unit is connected to an input end of the controller;

each of the N first controllable switches is connected between one of N pairs of bypass ports corresponding to the first controllable switch, and the first controllable switch includes a first switch and a first diode that are antiparallel, the first diode is reversely connected between the pair of bypass ports, and a control end of the first switch is connected to one output end of the controller via one of the N first driving circuits corresponding to the first controllable switch;

the sampling unit is configured to: detect, for each first controllable switch, analog quantity information of the first controllable switch, and output a sampling signal based on the analog quantity information; and

the controller is configured to: determine, based on the sampling signal, whether the analog quantity information of the first controllable switch meets a predetermined bypass condition; and control, in a case that the analog quantity information meets the predetermined bypass condition, the first switch in the first controllable switch to be turned on by using the first driving circuit corresponding to the first controllable switch.

In an embodiment, the controller is further configured to: after controlling the first switch in the first controllable switch to be turned on,

control the first switch to be turned off by using the first driving circuit corresponding to the first controllable switch in a case that a time period during which the first switch is turned on exceeds a first preset time period; and

determine, based on a sampling signal outputted by the sampling unit after performing re-detecting on the first controllable switch, whether the analog quantity information corresponding to the sampling signal meets the predetermined bypass condition

In an embodiment, the controller is further configured to: before determining whether the analog quantity information meets the predetermined bypass condition,

perform software filtering on the sampling signal.

In an embodiment, the analog quantity information is one of a voltage, a current, power, and a branch temperature;

in a case that the analog quantity information is the voltage, the predetermined bypass condition is that, the number of times that a voltage of the first controllable switch is lower than a preset voltage threshold is greater than or equal to a preset number of times, or a time period during which the voltage of the first controllable switch is lower than the preset voltage threshold is greater than or equal to a second preset time period;

in a case that the analog quantity information is the current, the predetermined bypass condition is that, the number of times that a current of the first controllable switch is greater than a preset current threshold is greater than or equal to a preset number of times, or a time period during which the current of the first controllable switch is greater than the preset current threshold is greater than or equal to a second preset time period;

in a case that the analog quantity information is the power, the predetermined bypass condition is that, the number of times that power of the first controllable switch is greater than a preset power threshold is greater than or equal to a preset number of times, or a time period during which the power of the first controllable switch is greater than the preset power threshold is greater than or equal to a second preset time period; and

in a case that the analog quantity information is the branch temperature, the predetermined bypass condition is that, the number of times that a branch temperature of the first controllable switch is higher than a preset temperature threshold is greater than or equal to a preset number of times, or a time period during which the branch temperature of the first controllable switch is greater than the preset temperature threshold is greater than or equal to a second preset time period.

In an embodiment, the first controllable switch is a triode having a body diode or a switch transistor having a body diode; and

the first switch is a relay, a triode or a switch transistor.

In an embodiment, an input end of the power source is connected between two ends of the photovoltaic module.

In an embodiment, the N pairs of bypass ports are arranged between two ends of the photovoltaic module, or the N pairs of bypass ports are arranged between two ends of at least one substring in the photovoltaic module, or the N pairs of bypass ports are arranged between two ends of the photovoltaic module and two ends of at least one substring in the photovoltaic module.

In an embodiment, in a case that the N pairs of bypass ports are arranged between the two ends of the photovoltaic module and the active bypass control device for a photovoltaic module is applied to a shutdown device, the other output end of the controller is connected to a control end of a second controllable switch in the shutdown device via a second driving circuit;

the second controllable switch is connected between the first controllable switch and the photovoltaic module; and

the controller is further configured to:

control the second controllable switch to be turned on by using the second driving circuit in a case that the photovoltaic module is in a normal condition; and

control the second controllable switch to be turned off by using the second driving circuit in a case that the photovoltaic module is in an abnormal condition.

In a second aspect, there is provided an active bypass control method for a photovoltaic module, applied to the active bypass control device for a photovoltaic module described in the first aspect. The active bypass control method includes:

detecting, by the sampling unit for each first controllable switch, analog quantity information of the first controllable switch, and outputting, by the sampling unit, a sampling signal based on the analog quantity information;

determining, by the controller based on the sampling signal, whether the analog quantity information of the first controllable switch meets a predetermined bypass condition; and

controlling, by the controller, the first switch in the first controllable switch to be turned on by using the first driving circuit corresponding to the first controllable switch in a case that the analog quantity information meets the predetermined bypass condition.

In an embodiment, after controlling the first switch in the first controllable switch to be turned on, the active bypass control method further includes:

counting, by the controller, a time period during which the first switch is turned on;

determining, by the controller, whether the time period during which the first switch is turned on exceeds a first preset time period;

controlling, by the controller, the first switch to be turned off by using the corresponding first driving circuit in a case that the time period during which the first switch is turned on exceeds the first preset time period; and

re-detecting, by the sampling unit, analog quantity information of the first controllable switch, and re-outputting, by the sampling unit, a sampling signal based on the analog quantity information.

With the active bypass control device for a photovoltaic module provided in the present disclosure, in the case that the controller determines, based on the sampling signal outputted by the sampling unit, that the analog quantity information of the first controllable switch meets the predetermined bypass condition, the controller controls the first switch in the first controllable switch to be turned on by using the first driving circuit corresponding to the first controllable switch, so that the first diode in the first controllable switch is prevented from having a large power consumption, thereby solving the problems in the conventional technology of low reliability, high cost and large system loss caused by the large power consumption of the first diode.

