Series Operation Of Converter

Series Operation Of Converter

A single phase series converter is the converter in which two or more converters are connected in series in order to share the voltage and improve the power factor.It is normally used for high voltage application.

The figure below shows the two full more coverts connected in series to each other. Let α₁ and α₂ be the firing angle of converter 1 and converter 2 respectively. And the figure of the waveforms shows the output voltage, the input voltage to the converters , and input current from the supply when both the converters are operating with a highly inductive load.

From the waveform diagram fig_2, we can follow that the path of conduction for output voltage is (for positive cycle of voltage source)

Secondary Voltage Source1 –T₁ – Load(Highly Inductive) – T₂^’ - Secondary Voltage Source 2 - T₁^’ -T₂ – Secondary Voltage Source

For the negative cycle of voltage from a secondary source.

Secondary Voltage Source1 –T₃ – Load(Highly Inductive) – T₂^’ - Secondary Voltage Source 2 - T₁^’ –T₄ – Secondary Voltage Source

V_dc1 = 2V_m/π (cos α₁ )The average dc voltage is

V_dc2 = 2V_m/π (cos α₂ )

Average D.C voltage across the load is the sum of d.c voltage across two converter:

V_output = V_{dc1 +} V_dc2

= 2*V_m/π (cos α₁ + cos α₂ )

For fully conductive state, α₁ = 0 (Converter-1 is fully conducted), 0 ≤ α₂ ≤ 180, and the output voltage is

V_output = (2*V_m*(1 + cos α₂ ))/ π

And in the inversion mode,Converter-2 is fully retarded(i.e α₂ = 0 , 0 ≤ α₁ ≤ 180) and the resultant average voltage is (2*V_m*( cos α_{1 - 1} ))/ π and its waveform is shown below: