Inverters, methods for shutting down inverters and photovoltaic systems.

Abstract

OCR07AP An inverter is provided; a method for switching off the inverter and the photovoltaic system is implemented. Pulse blocking is carried out. The inverter circuit responds to a short circuit of the negative electrode of the DC source to ground. The switching module is switched off if the initial current of the switching module at a current time point is less than or equal to the preset current at a certain point and the current change trend is a downward trend. Alternatively, the switching module is switched off within a preset time period starting from the time point when the acquired current of the switching module is less than or equal to the preset value if the current change trend is a downward trend.

Claims

OCR07AP1. An inverter comprising an inverter circuit, at least one switching module, and a controller, where the input terminals of the inverter circuit are configured to connect to a DC source, the output terminals of each phase of the inverter circuit are connected to the corresponding switching modules of at least one switching module, and the output terminals of at least one switching module are configured to connect to the power grid. The controller is configured to perform pulse blocking on the inverter circuit in response to a short circuit of the negative electrode of the DC source to ground, where pulse blocking comprises the disabling of the drive pulses for each switching transistor in the inverter circuit, specifying whether the first current of the switching module of at least one switching module at a time point is less than or equal to the first preset current after the inverter circuit experiences pulse blocking, or whether the first preset current is greater than or equal to the safety current of the switching module.Identify the current change trend of the switching module at the current point in time. Respond to the first switching module current being less than or equal to the first preset current and shut down the switching module. Respond to the current change trend being a downward trend or shut down the switching module within a preset time period starting from the time point when the acquired current of the switching module is less than or equal to the preset value when the current change trend of the switching module is identified as a downward trend after the inverter circuit experiences a blocking pulse.

2. Inverter according to claim 1, where, for identifying the current change trend of the switching module as a downward trend, the controller is configured to continuously acquire a certain amount of current of the switching module and identify the current change trend of the switching module as a downward trend, responding to a certain amount of current of the switching module that is decreasing.

3. Inverter according to claim 1,Where the preset value is equal to zero and the preset duration is the first period at which the current of the switching module is zero, the preset value is the current corresponding to the first time point, the first time point is the periodic time point specified by subtracting the first delay period from the time point when the current in the periodic current curve corresponding to the switching module drops to zero, and the first delay period is the duration from the time point when the shut-off signal is sent to the time point when the switching module is actually shut off, where the preset duration is the first period at which the current of the switching module is zero, or the preset value is the current corresponding to the second time point.The second time point is the periodic time point specified by subtracting the second delay period from the time point when the current in the periodic current curve corresponding to the switching module drops to zero, and the second delay period is combined with the period from the time point when the shut-off signal is applied to the switching module to the time point when the switching module is actually switched off, and the power resistance period from the time point corresponding to the maximum impulse current that the switching module can withstand to the time point when the current in the drop-down portion of the periodic current curve drops to zero, and the preset period is the sum of the first period when the current of the switching module is zero and is equal to twice the power resistance period.

4. Inverter according to claim 3, where the first period is calculated by the following equation (Equation), where Delta T represents the first time length from the time point when the current of the switching module drops to zero to the time point closest to when the voltage of the switching module is zero under the condition that the downward trend of the current of the switching module is a downward trend, (Equation), U represents the voltage rating of the phase power corresponding to the switching module,V represents the phase power voltage corresponding to the switching module and f represents the phase power frequency corresponding to the switching module.

5. Inverter according to claim 1, whereby for identifying the trend of current change of the switching module at the current time point, the controller is configured to identify the trend of current change of the switching module at the current time point based on the switching module current obtained before the current time point and / or the acquisition of the second switching module current if the specified time period has expired, and to identify the trend of current change of the switching module based on the relationship between the first and second currents.

6. Inverter according to claim 1,Where, after identifying whether the first current of the switching module of at least one switching module at the current time point is less than or equal to the first preset current, the inverter is further configured to monitor the switching module current, responding to if the first current of the switching module is greater than the first preset current, and shutting down the switching module when it is detected that the switching module current drops to less than or equal to the first preset current.

7. Inverter under claim 1, where the safety current is greater than zero, and after identifying whether the first current of the switching module of at least one switching module at the current time point is less than or equal to the first preset current, the inverter is further configured to identify whether the first current is less than or equal to the second preset current, where the second preset current is less than the safety current, and shutting down the switching module in response to the first current being less than or equal to the second preset current.

8. Inverter under claim 1,Where for at least one switching module, each switching module is equipped with at least two relay switches, and the control terminals of at least two relay switches are connected to the controller, where for closing the switching module, the controller is configured to close one of the at least two relay switches in the switching module.

9. Method for closing the inverter, where the inverter is equipped with the inverter circuit, at least one switching module, and the controller, the input terminals of the inverter circuit are configured to connect to a DC source, the output terminals of each phase of the inverter circuit are connected to the corresponding switching module of at least one switching module, and the output terminals of at least one switching module are configured to connect to the power grid, and the method of assembly with pulse blocking operation on the inverter circuit in response to a short circuit of the negative electrode of the DC source to ground, where pulse blocking is assembled with the shutdown of the driven pulse for each switching transistor in the inverter circuit.Identifying whether the first current of at least one switching module at the current time point is less than or equal to the first preset current after the inverter circuit experiences a blocking pulse, where the first preset current is greater than or equal to the switching module's safety current, identifying the trend of the switching module's current change at the current time point in response to the first current of the switching module being less than or equal to the first preset current, and the switching module shutdown in response to a decreasing current change trend, or the switching module shutdown within a preset time period starting from the time point when the acquired current of the switching module is less than or equal to the preset value, when the trend of the switching module's current change is identified as a decreasing trend after the inverter circuit experiences a blocking pulse.

10. Photovoltaic system assembled with photovoltaic cable and inverter.Where the photovoltaic line is connected to the inlet end of the inverter and configured to supply direct current (DC) power to the inverter, the outlet end of the inverter is configured to connect to the power grid, convert the DC power to alternating current (AC) power and send the AC power to the power grid, and the inverter is at least one of the inverters according to claims 1 through 8 or an inverter in which the method according to claim 9 is used;

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