Building a numeric potentiometer for AC current
I will interpret this as an AC electronic/active load, basically a "resistor emulator" for AC. I'm thinking about several solutions:


Oldskool


Several relays, switching resistors of values in powers of 2 in parallel or in series. Basically a 4-bit number, and each bit controls a resistor. Say you have 4 relays, and resistors of 1,2,4,8 ohms. 

If they're in series you can make any value between 1 and 15 ohms.

If they're in parallel, then the binary number controls the inverse of the resistor value, which is basically the current.


Simple PWm


In this case we would generate a PWM signal, switching a low value resistor in circuit with an AC switch (like a pair of back to back FETs). 

Current is proportional to V/R multiplied by the duty cycle, which makes this an adjustable resistor.

Add a LC for smoothing...