FPGA realization of multilevel space vector PWM using non-orthogonal moving reference frame

Abstract

This paper presents the implementation of Space Vector PWM algorithm using non-orthogonal moving reference frame for diode-clamped multilevel inverter in Field Programmable Gate Array (FPGA). In this algorithm, the non-orthogonal reference voltage is obtained according to the sector where the Reference Voltage (V*) lies. From the triangle identification inside hexagon, the Nearest Three Vectors (NTV) are determined using the information of the sector and triangle where V* is located. The duty cycles are calculated by a set of simple equations. The switching pattern is generated through coefficients referred to by the triangle number where V* lies. The softwares Quartus II®, ModelSim® and MatLab® were used to describe the algorithm in hardware description language, to check, test and simulate it. Fix-pointed 16-bit signed patterns were used for calculus. A 10 MHz clock was used to obtain the switching time, whereas the PWM works with a 50 MHz clock, in order to improve the PWM generation accuracy. The synchronism between switching time calculation and the PWM signal generation was carried out by a state machine. Altera® Cyclone® II FPGA Starter Development Kit with EP2C20F484C7N FPGA, was used to generate the V* and develop the proposed algorithm. The experimental results obtained with the three-level and simulation results with DCI five-level inverter were satisfactory, validating the FPGA algorithm implementation. This algorithm can be extended to topologies of generic-ordered DCI multilevel inverters, very slightly altering its computational efforts.