The voltage error is fed to a compensation controller which generates the magnitude control
Signal for the sinusoidal PWM generator. Via a synchronization
Network, a phase control signal is also fed to the sinusoidal
PWM generator, which in turn provides the gating signals for
The power inverter

See image
http://s.eeweb.com/resized/images/remote/http_s.eeweb.com/members/yang_yang/discussions/2012/11

http://s.eeweb.com/members/yang_yang/discussions/2012/11/06/electric-spring-setup-1352218318.png