Abstract: A system and a method of black start for a combined operation of wind power, photovoltaic power, energy storage, and thermal power includes a renewable energy alternating current microgrid module, a power transmission and distribution module, and a thermal power generation module, the power transmission and distribution module is coupled to the renewable energy alternating current microgrid module and the thermal power generation module respectively. The renewable energy alternating current microgrid module includes a photovoltaic unit, a wind power unit, and an energy storage unit. The power transmission and distribution module is configured to transmit the electrical energy generated by the renewable energy alternating current microgrid module to the thermal power generation module. The thermal power generation module is configured to start an auxiliary equipment using the electrical energy transmitted by the power transmission and distribution module.

Abstract: The system for frequency modulation based on Direct Current (DC) controllable load for a high-voltage plant includes a frequency modulator and a DC-controllable load for the high-voltage plant connected to the frequency modulator. The frequency modulator includes a centralized rectifier configured to adjust power of loads in the DC-controllable load in response to a frequency modulation command. The DC-controllable load is configured to respond to an adjustment of the power of loads performed by the centralized rectifier.

Abstract: A sanding tool includes a baseplate assembly, a housing assembly, a drive mechanism, and a fan assembly. The baseplate assembly includes a baseplate. The housing assembly includes a body housing. The housing assembly further includes a functional housing, where a hollow cavity is formed in the functional housing, the functional housing is provided with an inlet and an outlet that communicate with the hollow cavity, the inlet communicates with a dust removal channel of the sanding tool, the outlet is configured to discharge gas in the cavity, and the fan assembly is used for forming a dust removal air path moving towards the inlet. A ratio of an area of a projection of the functional housing on the baseplate to an area of the baseplate is greater than or equal to 0.15 and less than or equal to 0.95.

Abstract: A sanding tool includes a machine body, a power supply, a base plate assembly, a drive mechanism, and a control mechanism. The machine body includes a casing. The base plate assembly includes a base plate. The drive mechanism is disposed in the casing and includes a motor and an output shaft, the motor has a motor shaft rotating around a first axis, the output shaft rotates around a second axis, and the output shaft transmits power to the base plate assembly. The control mechanism is electrically connected to the motor and configured to control the sanding tool to operate. The first axis and the second axis form an included angle and are not in the same plane. A battery pack and the motor are disposed on two sides of the output shaft.