As wind plants become larger, Ride-Through Technology is critical. However, there are different forms of Ride-Through Technology (RTT).  It is becoming quite clear that no grid is infinite and transmission systems are positively and negatively impacted by distributed generation. This was clear in 2000 when over 200 MW of Zond Z48 and Z50 wind turbines (each rated at 0.75 MW) would nearly instantly trip offline while at full generation due to the converter taking the wind turbines offline when the voltage would go below 90 percent.  Zond, at the time had not stated a strategy to control the wind turbine below this voltage. Also, utility engineers at the time thought that the wind turbine would behave like a synchronous machine and could provide fault current during a fault that caused the voltage would dip.  To make things worse, in 1999 the Z50 and Z48 wind turbine would trip in less time it took a breaker or re-closure to open.       

     In 1999 and 2000, Thomas Wilkins working closely with the staff of Utility, Zond Energy Systems, Zond O&M, Zond Constructors and Trace Technologies, proposed a new idea, just let the wind turbine Ride-Through. It was known that the converter technology at the time could control the rotor current by phase. What was needed was some inventive ideas along with hardware and software modifications so it was proposed and accepted that the wind turbine controller and converter would be modified so that the wind turbine could provide High Voltage Ride Through (HVRT) and Low Voltage Ride Through (LVRT) with a form of dynamic voltage stabilization by feeding reactive current during the disturbance; the disturbance being a fault or loss of generation.

   In 2000, for HVRT, WTG was modified and the Trace Converter was programmed to change the reactive output of the stator to consume capacitive VARS in order to reduce the voltage at the mains of the wind turbine. When the voltage would increase above a given set point the WTG would dynamically change its reactive output to reduce the voltage at the mains. The reduced the chances of a cascade of wind turbines on the collector system tripping off line.

    In 2000, for LVRT, the WTG was modified and the Trace Converter was programmed to limit the current to a maximum value as the voltage dropped and dynamically change its reactive output during the voltage excursion. The design of these first revisions of Ride-Though was down to just below 70 percent rated voltage.  The consequence of limiting the current to a maximum value decreased the output power and the electrical torque. The result was that the wind turbine hub would speed up. However it was realized that the inertia of the hub was so large that the speed of the hub was controllable since the blades could pitch out before an overspeed occurred.   

   In the year 2000 the following functional features were implemented at Lake Benton I and Lake Benton II Wind Farms named either indirectly by specification or directly called out:

Ride-Through

Low voltage Ride-Through

High voltage Ride-Through

Single and multiple point dynamic voltage stabilization

Low voltage reactive adjust

Fault persistence reactive adjust

High voltage reactive adjust

High voltage persistence reactive adjust

WTG local & plant reactive control

Plant coordinated capacitor bank and WTG reactive control

Collector system capacitor bank and WTG reactive control

WTG current limiting during fault

Reactive-ineffective fault persistence trip

Reactive-ineffective high voltage trip

Clear-fault reactive adjust

Clear high voltage reactive adjust

Immediate under-voltage trip (below 70 %)

Ride-Through with re-closure and breaker trip coordination

Current limiting during a low voltage event

Power limiting during a low voltage event

High Voltage limiting during a cascade or load shed