Designing a High-Voltage Bidirectional Square Wave
simulate this circuit &ndash; Schematic created using CircuitLab

An idea of the circuit. 


use a separating transformer to boost the voltage.
Use a MOSFET H-Bridge  with appropriate HV gate drive circuit.
Use a current feedback measurement to determine the load current
USe a MCU that controls the bridge in PWM mode at high switching frequency, chopper like. It depends on the load type, how to maintain the current setpoint.