Converter monitoring in a wind turbine application

Statistical Method of Estimating Semiconductor Switching Transition Time Enabling Condition Monitoring of Megawatt Converters

“…By defining the average number of samples (n avg ) during a switching transition with a given t tr and T s as ( 8), equations ( 6) and ( 7) can be written as ( 9) and (10).…”

“…Methods 3 to 10 of Table I require special gate drives or connection to auxilliary terminals of the power modules, and are not relevant for a self-sufficient monitoring system connected to the power terminals of the power modules. The vce on method (method 1 of Table I) was demonstrated in a wind turbine field application for monitoring of both IGBTs and the anti-parallel diodes [10], [11]. vce on is the collector emitter voltage across an IGBT in it's on-state.…”

“…It was shown that vce on can be monitored by connecting a relatively simple, yet robust measurement circuitry to the collector and emitter terminals of the power modules without the need for special gate drives. By use of the same connection points as described in [10], [11] (power terminals of the power module), and by allowing the full collector emitter voltage (vce) to be sampled, monitoring of t tr of an IGBT may be enabled (method 2 of Table I). Being able of monitoring two types of TSEPs in essentially the same circuitry expands the monitoring potential of a CMU.…”

“…For each IGBT/diode pair of the converter, the physical raw collector-emitter voltage (vce raw ) is split into a vce on signal The vce on circuitry enables high ADC resolution in the conduction mode, but saturates when voltage goes beyond ± 5V, as described in [10]. The vce circuitry allows for sampling of the vce voltage in it's full voltage range, yet with lower resolution in absolute voltage.…”

“…RC outputs a voltage (v RC ) which is proportional to the time derivative of the current ( dic /dt), and an integration of the signal must be performed to arrive at i c . The raw rogowski coil voltage is numerically integrated, as described in [10].…”