As well as their main function of converting AC power to DC power or vice-versa, HVDC stations will produce or absorb reactive power. The reactive power characteristics of LCC and VSC stations are very different and are treated separately. An LCC converter has an inherent lagging power factor, due to the firing angle delay and commutation period. Its consumption of reactive power normally has to be balanced by on-site sources of reactive power, such as AC filters, shunt capacitors and other devices. The maximum switchable size of such sources is limited by the maximum permitted reactive power interchange with the AC system at any DC power level and by the maximum permitted voltage step on switching. A reactive power controller takes into account all the various requirements regarding reactive balance and harmonic power quality and determines the appropriate power levels at which filters and other elements are switched in and out. VSC converters can inherently control their transfer of active and reactive power independently, within certain limits. Furthermore, the harmonic generation of the MMC type of VSC is very low and either no filter or only a very small damping filter is required. The reactive power exchange with the network may therefore be controlled continuously according to the requirements of the network operator.