Method for the determination of a control scheme for a neutral point clamped voltage source converter with at least 3 levels, in particular as a shunt active power filter, with a topology of three bridge legs between each of three phases (R,S,T) of a grid and a neutral point, each leg comprising at least four active switches (T1-T4), wherein there is provided a clamping carrier modulator synchronized with the grid for the control of no-switching intervals, said method comprising at least the following steps: i) analyzing the waveform of the grid and/or a load voltage (I LR) and determining windows of 120° within the voltage cycle of the grid/load, wherein the windows are centered around the positive and negative peak maximum of the grid/load voltage waveform, said windows defining the allowed period for no-switching of the corresponding bridge leg; ii) operating or simulating the operation of the voltage source converter with a clamping carrier modulator frequency equal to the third harmonic frequency of the grid/load, wherein, if within said window, as a function of the clamping carrier modulator the switching of the corresponding bridge leg is interrupted and clamped, then analyzing the balance in the operating junction temperatures and/or power losses across the active switches and analyzing the total losses of the voltage source converter; iii) operating or simulating the operation of the voltage source converter with a clamping carrier modulator frequency equal to the ninth harmonic frequency of the grid/load, wherein, if within said window, as a function of the clamping carrier modulator the switching of the corresponding bridge leg is interrupted and clamped, then analyzing the balance in the operating junction temperatures and/or power losses across the active switches and the total losses of the voltage source converter; iv) comparing the balance and the total losses of steps ii) and iii) and selecting either the clamping carrier modulator frequency according to step ii) or step iii) showing, as primary criterion, the better balance and, as secondary criterion, the lower total losses; v) operating or simulating the operation of the voltage source converter with the selected clamping carrier modulator frequency, wherein as a function of the clamping carrier modulator the switching of the corresponding bridge leg is interrupted and clamped in as far as within said window, while iteratively changing at least one of the following operating parameters of the voltage source converter: switching frequency, DC-link voltage reference, duty cycle of clamping carrier modulator, phase shift of the clamping carrier modulator relative to the grid, and optimising the balance in the operating junction temperatures and/or power losses across the active switches and the total losses of the voltage source converter as a function of the adjustment of these operating parameters until reaching optimum operation parameters for the control scheme. i) analyzing the waveform of the grid and/or a load voltage (I LR) and determining windows of 120° within the voltage cycle of the grid/load, wherein the windows are centered around the positive and negative peak maximum of the grid/load voltage waveform, said windows defining the allowed period for no-switching of the corresponding bridge leg; ii) operating or simulating the operation of the voltage source converter with a clamping carrier modulator frequency equal to the third harmonic frequency of the grid/load, wherein, if within said window, as a function of the clamping carrier modulator the switching of the corresponding bridge leg is interrupted and clamped, then analyzing the balance in the operating junction temperatures and/or power losses across the active switches and analyzing the total losses of the voltage source converter; iii) operating or simulating the operation of the voltage source converter with a clamping carrier modulator frequency equal to the ninth harmonic frequency of the grid/load, wherein, if within said window, as a function of the clamping carrier modulator the switching of the corresponding bridge leg is interrupted and clamped, then analyzing the balance in the operating junction temperatures and/or power losses across the active switches and the total losses of the voltage source converter; iv) comparing the balance and the total losses of steps ii) and iii) and selecting either the clamping carrier modulator frequency according to step ii) or step iii) showing, as primary criterion, the better balance and, as secondary criterion, the lower total losses; v) operating or simulating the operation of the voltage source converter with the selected clamping carrier modulator frequency, wherein as a function of the clamping carrier modulator the switching of the corresponding bridge leg is interrupted and clamped in as far as within said window, while iteratively changing at least one of the following operating parameters of the voltage source converter: switching frequency, DC-link voltage reference, duty cycle of clamping carrier modulator, phase shift of the clamping carrier modulator relative to the grid, and optimising the balance in the operating junction temperatures and/or power losses across the active switches and the total losses of the voltage source converter as a function of the adjustment of these operating parameters until reaching optimum operation parameters for the control scheme.