The invention relates to the field of new energy, in particular to a dual power supply system. With the rapid development of urbanization, the mains supply using load is continuously increased, energy consumption of electricity consumption in cities, particularly road illumination is greatly improved, public illumination consumes electricity greatly, and annual electricity consumption accounts for about 15% of the national total power generation. In 2016, coal-fired power consumption in annual illumination electricity consumption in China reached about 650 billion kilowatt-hour, and fire coal consumed for coal-fired electricity generation reaches about 250 million tons. In current market, 99% or above of public illumination is achieved by adopting mains supply street lamps, one important cause for production of air pollution and haze weather is that too much fire coal is used for electricity generation, reduction of the electricity consumption of coal-fired power generation is the key measure for reducing air pollution, and the technical problem which urgently needs to be solved in the current traditional mains supply field is how to transform a current traditional mains supply system to be a new system powered by mains supply and new energy.