A method of operating an impedance injection module, IIM, the IIM comprising: a plurality of impedance injection units, IIUs; at least a control module; the method of operating comprising: controlling, by the control module, the plurality of impedance injection units IIUs to form multiple connection configurations in sequence, each connection configuration comprising one IIU or multiple IIUs in series, parallel or combination thereof; forming an impedance injection module; coupling the impedance injection module to a high-voltage transmission line; extracting power from the impedance injection module from the high voltage transmission line for its operation; and generating, by the control module through the multiple connection configurations of IIUs in sequence, a plurality of rectangular impedance injection waveforms during operation that are synchronized over time such that when combined and injected on to the high-voltage transmission line, produce a pseudo-sinusoidal waveform, the method being characterized in that it further comprises: synchronizing one or more local clocks (404A, 404B) associated with the control module and the plurality of IIUs to a system clock or to a global clock, for controlling the generating and injecting of the impedance injection waveforms; wherein synchronizing one or more local clocks (404A, 404B) to the system clock is using a sub-cyclic communication link communicably coupling the intelligent control module to the system clock. a plurality of impedance injection units, IIUs; at least a control module; the method of operating comprising: controlling, by the control module, the plurality of impedance injection units IIUs to form multiple connection configurations in sequence, each connection configuration comprising one IIU or multiple IIUs in series, parallel or combination thereof; forming an impedance injection module; coupling the impedance injection module to a high-voltage transmission line; extracting power from the impedance injection module from the high voltage transmission line for its operation; and generating, by the control module through the multiple connection configurations of IIUs in sequence, a plurality of rectangular impedance injection waveforms during operation that are synchronized over time such that when combined and injected on to the high-voltage transmission line, produce a pseudo-sinusoidal waveform, controlling, by the control module, the plurality of impedance injection units IIUs to form multiple connection configurations in sequence, each connection configuration comprising one IIU or multiple IIUs in series, parallel or combination thereof; forming an impedance injection module; coupling the impedance injection module to a high-voltage transmission line; extracting power from the impedance injection module from the high voltage transmission line for its operation; and generating, by the control module through the multiple connection configurations of IIUs in sequence, a plurality of rectangular impedance injection waveforms during operation that are synchronized over time such that when combined and injected on to the high-voltage transmission line, produce a pseudo-sinusoidal waveform, the method being characterized in that it further comprises: synchronizing one or more local clocks (404A, 404B) associated with the control module and the plurality of IIUs to a system clock or to a global clock, for controlling the generating and injecting of the impedance injection waveforms; wherein synchronizing one or more local clocks (404A, 404B) to the system clock is using a sub-cyclic communication link communicably coupling the intelligent control module to the system clock. synchronizing one or more local clocks (404A, 404B) associated with the control module and the plurality of IIUs to a system clock or to a global clock, for controlling the generating and injecting of the impedance injection waveforms; wherein synchronizing one or more local clocks (404A, 404B) to the system clock is using a sub-cyclic communication link communicably coupling the intelligent control module to the system clock.