Grid-connected/off-grid seamless switching control method and device for renewable energy hydrogen production system

The invention discloses a renewable energy hydrogen production system grid-connected/off-grid seamless switching control method and device considering harmonic suppression. Firstly, according to different harmonic characteristics and control targets of the renewable energy hydrogen production system in two operation modes, an impedance adjustment control strategy suitable for an island mode and a harmonic compensation control strategy suitable for a grid-connected mode are provided. And then, a method for improving a voltage outer loop and a phase-locked loop is introduced into the energy storage converter with the isolated network voltage and frequency established, and smooth transition of the bus voltage of the renewable energy hydrogen production system in the switching process is achieved. According to the method, seamless switching between grid-connected/island working modes of the renewable energy hydrogen production system can be realized under a nonlinear hydrogen production load and a harmonic power