CORDIC算法在基于FPGA的旋变解码和PMSM矢量控制中的应用

Application of CORDIC Algorithm in Resolver-to-digital and PMSM Vector-control Based on FPGA

在永磁同步电机(PMSM)矢量控制中,对旋变进行直接解码需要做反正切运算,CLARK-PARK变换需要做正余弦运算,SVPWM的扇区判断以及对电流电压的限幅输出等需要从直角坐标到极坐标的转换,这些运算使用传统方法难以在FPGA中实现。在DSP中通常采用查表方式,往往也难以达到预期精度要求。Coordinate rotation digitalComputer(CORDIC)算法很适合在FPGA中直接进行旋变解码和矢量控制算法运算。论文阐述了CORDIC算法的基本原理,在旋变解码、坐标变换、SVPWM、输出限幅等算法中的应用,并给出了实现方法及运算值与实际值的对比,证明了CORDIC算法具有运算精度高,占用资源少,运算速度快等特点。最后通过一台额定9kW的电动车用永磁同步电机实验验证了算法的正确性和实用性。

In PMSM vector-control, resolver-to-digital needs the arctangent calculations, CLARK-PARK transform needs the sine and cosine calculations, and determining SVPWM sectors and clamp the amplitude of current and voltage vector need to convert the rectangular coordinates into the polar coordinates. All these algorithms are difficult to implement in FPGA with traditional methods. The look-up table often is used in DSP, but it is difficult to meet desired accuracy required frequently. Coordinate rotation digital computer （CORDIC） algorithm is suited to process resolver-to-digital directly and vector-control algorithm in FPGA. Basic theory of CORDIC and application of CORDIC in resolver-to-digital, coordinates convert, SVPWM, and clamp the length of output were discussed in this paper. Operation method and contrast calculation val- ues with real values were provided too. It indicated that the CORDIC algorithm was high accuracy, good per- formance and low consume of LE. At last, the experiment of PMSM for electric motorcar showed all these al- gorithms was correct and useful.