An electrical power system (10, 10i) having a DC bus with a variable voltage setting, the electrical power system comprising: a variable-voltage DC bus; a number N ≥ 2 of electrical machines (G1-G4, M1-M4), each electrical machine connected to the variable-voltage DC bus via one of a corresponding number N of converters (21-24, 31-34), each electrical machine and corresponding converter having an index n = (1,..., N); and a controller configured to select a voltage setting V dc_bus for the variable-voltage DC bus and determine a voltage droop ΔV for the selected voltage setting V dc_bus, and to provide control signals to the converters (21-24, 31-34) to control the voltage setting of the variable-voltage DC bus according to both the selected voltage setting V dc_bus and the voltage droop ΔV, wherein: a number P ≥ 1 of the N electrical machines (G1-G4, M1-M4) are configured as generators (G1-G4) and the corresponding P converters are configured as AC-DC converters, each generator being operable to generate alternating current and to deliver direct current to the variable-voltage DC bus via the corresponding one of the AC-DC converters; a remaining number N - P ≥ 0 of the N electrical machines (G1-G4, M1-M4) are configured as motors (M1-M4) and the corresponding N - P converters are configured as DC-AC converters, each motor being operable to receive alternating current from the variable-voltage DC bus via the corresponding one of the DC-AC converters; and the controller is configured to select a voltage setting V dc_bus greater than or equal to a minimum voltage requirement V dc_min for the bus, the controller being configured to determine the minimum voltage requirement V dc_min using present operating speeds of each of the N electrical machines (G1-G4, M1-M4). a variable-voltage DC bus; a number N ≥ 2 of electrical machines (G1-G4, M1-M4), each electrical machine connected to the variable-voltage DC bus via one of a corresponding number N of converters (21-24, 31-34), each electrical machine and corresponding converter having an index n = (1,..., N); and a controller configured to select a voltage setting V dc_bus for the variable-voltage DC bus and determine a voltage droop ΔV for the selected voltage setting V dc_bus, and to provide control signals to the converters (21-24, 31-34) to control the voltage setting of the variable-voltage DC bus according to both the selected voltage setting V dc_bus and the voltage droop ΔV, wherein: a number P ≥ 1 of the N electrical machines (G1-G4, M1-M4) are configured as generators (G1-G4) and the corresponding P converters are configured as AC-DC converters, each generator being operable to generate alternating current and to deliver direct current to the variable-voltage DC bus via the corresponding one of the AC-DC converters; a remaining number N - P ≥ 0 of the N electrical machines (G1-G4, M1-M4) are configured as motors (M1-M4) and the corresponding N - P converters are configured as DC-AC converters, each motor being operable to receive alternating current from the variable-voltage DC bus via the corresponding one of the DC-AC converters; and the controller is configured to select a voltage setting V dc_bus greater than or equal to a minimum voltage requirement V dc_min for the bus, the controller being configured to determine the minimum voltage requirement V dc_min using present operating speeds of each of the N electrical machines (G1-G4, M1-M4). a number P ≥ 1 of the N electrical machines (G1-G4, M1-M4) are configured as generators (G1-G4) and the corresponding P converters are configured as AC-DC converters, each generator being operable to generate alternating current and to deliver direct current to the variable-voltage DC bus via the corresponding one of the AC-DC converters; a remaining number N - P ≥ 0 of the N electrical machines (G1-G4, M1-M4) are configured as motors (M1-M4) and the corresponding N - P converters are configured as DC-AC converters, each motor being operable to receive alternating current from the variable-voltage DC bus via the corresponding one of the DC-AC converters; and the controller is configured to select a voltage setting V dc_bus greater than or equal to a minimum voltage requirement V dc_min for the bus, the controller being configured to determine the minimum voltage requirement V dc_min using present operating speeds of each of the N electrical machines (G1-G4, M1-M4).