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4.3

6

Table 4-3.

Compare Register Values vs Sector Number

Sector Determination Algorithm

T o d e t e r m i n e t h e s e c t o r w h i c h a g i v e n s t a t o r v o l t a g e b e l o n g s t o , s o m e a l g o r i t h m s h a v e b e e n t proposed in the literature which generally require many arithmetic operations and are based on h e c o o r d i n a t e s o f i n t h e C o n c o r d i a p l a n e o r i n t h e a - b - c p h a s e s p a c e . W h e n t h i s v o l t a g e i s s V deduced from a V/f control principle, its modulus Vsm is computed by the V/f law recalled in the previous application note, and its phase θ is deduced from ωs by a discrete-time integrator. To implement this sector determination algorithm efficiently, we manage θ and k instead of θ in a s V

dedicated integrator shown on Fig. 6. The sector number k is the output of a modulo six counter , a n d i s c o n f i n e d t o l i e b e t w e e n 0 a n d π θ π (see Fig. 7). activated each time θ exceeds 3 3

Figure 4-5.

Sector determination algorithm

Application Note

7546A–AVR–12/05

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