3 Phase SCR (thyristor) for duct heater

Hi,

One of my project require to use thyristor for duct heater, but my client requirement is 1.thyristor should modulate output power through zero crossing and phase angle control 2. active harmonics filter to minimize THD to less than 5% 3. thyristor and active harmonics filter is compatible with high impedance netral earthing system, otherwise provide isolating transformer. below are the specifications
Voltage 415/3/50HZ, (high impedance neutral earthing system)
Control 4-20mA.
heater - 15KW.
Someone please give me solution on this to choose correct SCR controller, if possible please suggest any brand .

Thanks In advance.

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