A method for controlling a photovoltaic rapid shutdown system, an inverting system, and a photovoltaic rapid shutdown system. In the photovoltaic rapid shutdown system, the inverting system determines whether the photovoltaic rapid shutdown system is to enter a safe mode, introduces fluctuations onto a direct-current bus in the photovoltaic rapid shutdown system in response to the photovoltaic rapid shutdown system being not to enter the safe mode, and otherwise does not introduce the fluctuations onto the direct-current bus. A shutdown device for a photovoltaic module determines according to an output parameter thereof whether an electrical parameter on the direct-current bus connected to the shutdown device meets a preset condition, controls itself to be turned on or maintains itself being on in response to the electrical parameter meeting the preset condition, and otherwise controls itself to be turned off or maintains itself being off.