Auxiliary power system, crane power system and crane

The invention discloses an auxiliary power system which comprises a first engine, a first oil pump device and a generator, the first oil pump device and the generator are driven by the first engine, and the discharge amount of pressure oil is changed according to the rotating speed of the first engine; the first oil pump device comprises a first oil pump and a second oil pump connected with the first oil pump in series. An oil outlet of the first oil pump is connected with a first quick-change connector of the quick-change device through a first one-way valve. An oil outlet of the second oil pump is connected with a second quick-change connector of the quick-change device through a second one-way valve; the output end of the generator is connected with a third quick-change connector of the quick-change device through a third one-way valve; the input ends of the first oil pump device and the generator are communicated with the loading oil tank; and the loading oil tank is connected with a fourth quick-change c