A wind turbine generator control system includes relatively fast regulation of voltage near the individual generators with relatively slower overall reactive power regulation at a substation or wind farm level. The variable gain amplifier includes a first differential amplifier, a second differential amplifier, a combining circuit, and a current control circuit. Moreover, the piece goods, after being picked up on the pick-up platform, are secured by force andor shape against slipping off or falling down until they are unloaded, and the loaded goods being put down automatically by the apparatus at the intended location.