A method of controlling a solar power plant comprising photovoltaic modules (PV modules) and a power conversion system arranged to convert the power collected by the PV modules for transmission by means of an electric power transmission system, the conversion system comprises a plurality of DC/DC converters (4a-d), a power collecting grid and a DC/AC inverter, and wherein the PV modules are arranged in arrays (2a-d) of PV modules, each PV array (2a-d) having an interface (3a-d) connected to, and controlled by, a respective one of the DC/DC converters (4a-d), the power collecting grid being arranged to provide an interface between the plurality of DC/DC converters (4a-d) and an input of the DC/AC inverter, the method comprising - monitoring the performance of each PV array (2a-d), and - a first mode of operation comprising: a first step of regulating, wherein the voltage level of each interface between a PV array (2a-d) and the corresponding DC/DC converter (4a-d) is adjusted, which regulating is based on a performance model of the PV array (2a-d) and an efficiency model of each DC /DC converter (4a-d), which efficiency model describes the relationship between the voltage and the power of the respective DC/DC converter, and which regulating includes monitoring the output power of each DC/DC converter (4a-d) during the first step of regulating and using the monitored output power of each DC /DC converter (4a-d) as a feedback for adjusting the voltage level of each interface between PV array (2a-d) and corresponding DC/DC converter (4a-d), a second step of regulating, wherein the voltage level of the power collecting grid, is adjusted, which regulating is based on an efficiency model of the DC/AC inverter, which efficiency model describes the relationship between the voltage and the power of the respective DC/AC converter and which regulating includes monitoring the output power of the DC/AC inverter, during the second step of regulating and using the monitored output power of the DC/AC inverter as a feedback for adjusting the voltage level of the power collecting grid. - monitoring the performance of each PV array (2a-d), and - a first mode of operation comprising: a first step of regulating, wherein the voltage level of each interface between a PV array (2a-d) and the corresponding DC/DC converter (4a-d) is adjusted, which regulating is based on a performance model of the PV array (2a-d) and an efficiency model of each DC /DC converter (4a-d), which efficiency model describes the relationship between the voltage and the power of the respective DC/DC converter, and which regulating includes monitoring the output power of each DC/DC converter (4a-d) during the first step of regulating and using the monitored output power of each DC /DC converter (4a-d) as a feedback for adjusting the voltage level of each interface between PV array (2a-d) and corresponding DC/DC converter (4a-d), a second step of regulating, wherein the voltage level of the power collecting grid, is adjusted, which regulating is based on an efficiency model of the DC/AC inverter, which efficiency model describes the relationship between the voltage and the power of the respective DC/AC converter and which regulating includes monitoring the output power of the DC/AC inverter, during the second step of regulating and using the monitored output power of the DC/AC inverter as a feedback for adjusting the voltage level of the power collecting grid. a first step of regulating, wherein the voltage level of each interface between a PV array (2a-d) and the corresponding DC/DC converter (4a-d) is adjusted, which regulating is based on a performance model of the PV array (2a-d) and an efficiency model of each DC /DC converter (4a-d), which efficiency model describes the relationship between the voltage and the power of the respective DC/DC converter, and which regulating includes monitoring the output power of each DC/DC converter (4a-d) during the first step of regulating and using the monitored output power of each DC /DC converter (4a-d) as a feedback for adjusting the voltage level of each interface between PV array (2a-d) and corresponding DC/DC converter (4a-d), a second step of regulating, wherein the voltage level of the power collecting grid, is adjusted, which regulating is based on an efficiency model of the DC/AC inverter, which efficiency model describes the relationship between the voltage and the power of the respective DC/AC converter and which regulating includes monitoring the output power of the DC/AC inverter, during the second step of regulating and using the monitored output power of the DC/AC inverter as a feedback for adjusting the voltage level of the power collecting grid.