An electrical power generating system is disclosed, which includes a generator GS operable to generate a variable voltage AC power supply, a booster BO operable to increase the voltage of the output of the generator thereby to provide a DC voltage, a voltage sensor VSa, and control means operable to monitor the DC voltage and to provide a feedback control signal to the generator whereby to vary the variable voltage power supply so as to counter a tendency of the DC voltage to vary. The system also comprises electrical energy storage means RC1; BP1 connected across the DC voltage so as to be charged by the DC voltage, and bistable switching means Tcc, Tcs, Tbc, Tbs and associated control means CS; BS. The bistable switching means are normally in one state in which they are operable to make the connection of the electrical energy storage means across the DC voltage to enable the electrical energy storage means to be charged and to interrupt a connection between the electrical energy storage means and the input of the booster means. The bistable switching means are also operable in its other state to isolate the electrical energy storage means from the DC voltage and to make said connection of the electrical energy storage means with the input of the booster means, whereby to enable discharge of electrical energy from said electrical energy storage means into the booster means. The control means associated with the bistable switching means are responsive to the monitored DC voltage and are operable in response to a fall in the DC voltage to a certain reference level to switch the bistable means from its normal one state to the other state whereby to discharge electrical energy to augment the variable voltage power supply and thereby to counter the sensed fall in said DC voltage.