A photovoltaic power generation system, the system comprising: at least two photovoltaic panels (1602, 1604) each having a dc power output; a power conditioning unit having a dc power input and an ac mains power supply output for delivering an ac mains supply; wherein said dc power outputs of said at least two photovoltaic panels are connected in parallel with one another to said dc power input of said power conditioning unit; said photovoltaic panels are all substantially matched such that said photovoltaic panels have substantially the same size/type/power rating wherein said power conditioning unit comprises a dc-to-dc converter having an input coupled to said dc power input and having an output coupled to a dc link of said power conditioning unit, a dc-to-ac converter having an input coupled to said dc link and having an output coupled to said ac mains power supply output, and an energy storage capacitor (Cdc) coupled to said dc link; and wherein said power conditioning unit is configured to perform maximum power point tracking (MPPT) responsive to a level of power flowing into said dc power input, wherein said level of power flowing into said dc power input is sensed at said dc link, and wherein said power conditioning unit comprises a controller coupled to control said dc-to-ac converter to perform said maximum power point tracking (MPPT); and wherein said controller has a sense input coupled to said energy storage capacitor to sense at said energy storage capacitor a signal responsive to a level of power flowing into said dc power input of said power conditioning unit, and wherein said controller is configured to perform said MPPT by controlling said dc-to-ac converter to control power injected into said ac mains power supply responsive to said level of power flowing into said dc input of said power conditioning unit sensed at said dc link, and characterised in that said controller is configured to use exclusively the level of voltage fluctuations on the energy storage capacitor coupled to the dc link via the sense input without using the current values on the dc link to control the amount of power being extracted from the dc power output and the amount of power being injected into said ac mains power supply. at least two photovoltaic panels (1602, 1604) each having a dc power output; a power conditioning unit having a dc power input and an ac mains power supply output for delivering an ac mains supply; wherein said dc power outputs of said at least two photovoltaic panels are connected in parallel with one another to said dc power input of said power conditioning unit; said photovoltaic panels are all substantially matched such that said photovoltaic panels have substantially the same size/type/power rating wherein said power conditioning unit comprises a dc-to-dc converter having an input coupled to said dc power input and having an output coupled to a dc link of said power conditioning unit, a dc-to-ac converter having an input coupled to said dc link and having an output coupled to said ac mains power supply output, and an energy storage capacitor (Cdc) coupled to said dc link; and wherein said power conditioning unit is configured to perform maximum power point tracking (MPPT) responsive to a level of power flowing into said dc power input, wherein said level of power flowing into said dc power input is sensed at said dc link, and wherein said power conditioning unit comprises a controller coupled to control said dc-to-ac converter to perform said maximum power point tracking (MPPT); and wherein said controller has a sense input coupled to said energy storage capacitor to sense at said energy storage capacitor a signal responsive to a level of power flowing into said dc power input of said power conditioning unit, and wherein said controller is configured to perform said MPPT by controlling said dc-to-ac converter to control power injected into said ac mains power supply responsive to said level of power flowing into said dc input of said power conditioning unit sensed at said dc link, and characterised in that said controller is configured to use exclusively the level of voltage fluctuations on the energy storage capacitor coupled to the dc link via the sense input without using the current values on the dc link to control the amount of power being extracted from the dc power output and the amount of power being injected into said ac mains power supply.