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If you are happy with linear power supply then here is a nice project of (almost) 0-30V - 10A power supply ..
If you would like to reduce the output current you can omit Q4/R8 and Q5/R9 ..
And, for 220V ac you will need to select proper step-down transformer rated for that voltage .. https://www.uoguelph.ca/~antoon/circ/ps3010/ps3010a.html