much different than it is for silicon IGBTs (3 kHz)。 A tradeoff analysis could carried out, but

the targeted benefits will be small and would not likely swing any conclusions reached in this

project。 In addition the trade off study should be carried out for the correct voltage, which will

likely be much higher than the 690 V specified for the baseline turbine。 Designing a high current,

high frequency medium-voltage inductor is a significant design exercise there are no such

products in the market to the author's knowledge。 It is the understanding of the author that

further work of this nature is being done in another NREL concept study in parallel to this

project。

5。 6 promising New Wind Turbine Configurations Using SIC

This project has led to the conclusion that SIC devices will not be exploited to greatest advantage

if they are just used as one-for-one replacements of existing silicon devices in power

electronics rated at 690 V。 However, SIC devices have unique characteristics that can be

exploited to great advantage if the overall configuration is allowed to change。 An existing

baseline wind turbine should not dictate how the SIC devices are used, but rather the unique

characteristics of SIC devices should dictate how the system is configured。 The pertinent SIC

characteristics for wind turbines are high voltage and temperature capability。 Several new

approaches capitalizing on the high-voltage capability are described in this section。 They are not

exhaustive, but rather illustrate some of the new possibilities with SIC devices。 How to capitalize

on the high temperature capability is covered later。

5。6。1 Medium Voltage With Standard Transformer

In this alternative, the baseline converter show in Figure 1 would be made entirely of SIC

MOSFETs (or SIC BJTs) and SIC PN junction diodes (or Schottkys) capable of operating at

2300 VAC and 4, 160 VA。 C, which requires devices that can withstand 5, 500 V and 10, 000 V,

respectively。 The generator feeding this converter in addition to the filter inductor, would also

be rated nominally at 2, 300 VAC or 4, 160 VAC。 The converter would be connected to the grid

through a standard 60 HZ transformer。 The 1。 5 MW of power from the baseline turbine can be

handled by a single inverter bridge that carries only 208 amps and is about one-sixth the size of

that required with silicon IGBTs rated for operation at 690 V rms。 This relatively simple

topology cannot be developed with standard silicon IGBTs and is therefore uniquely enabled by

SIC。

Given DARPA and Navy work now being carried out along with other Peregrine work, the

necessary inverter bridge could be designed and tested during the next two to five years。 It is

impossible to be precise about the reduction in losses due to lack of real test data for high-

forward conduction losses with higher voltage and significant reduction in switching losses。

5。 6。 2 Medium Voltage With High Frequency Transformer

Figure 2 shows in block form the next interesting configuration which contains a high frequency

transformer。 This is a well-know approach to reducing the size of transformers, and is currently

being pursued by the Navy using SIC。 The general strategy is to create smooth DC with a

Rectifier, and then feed the transformer with a high frequency train of square AC pulses created

by an H-bridge。 The width of the pulses can be varied using standard PWM techniques to

regulate the voltage on the output side of the transformer。 The high frequency output is again

rectified into smooth DC, which is inverted using PWM techniques and filtered。 The frequency