The Research On The Cascaded Multicell High-Voltage Inverter

In recent years, high-voltage variable-frequency drive systems develop rapidly, and arealready widely used in many industries. They can help us to enhance the productionefficiency and save the energy.Of all the topologies of the high-voltage inverter, cascaded multicell is the widely usedone, which has the advantages of a simple control, high reliability and small harmonic. Thecontrol and modulation strategies of cascaded multicell inverter mainly arestepped-waveform technique, Multicarrier PWM strategy with carrier disposition, carrierphase-shifted sinusoidal PWM (CPS-SPWM) technique, and sampling time staggered spacevector pulse width modulation (STS-SVPWM) technique. The study on STS-SVPWMtechnique is made.Cascaded multicell inverter has plenty of space vectors with considerable levels. It isvery complicated to apply conventional SVPWM strategy and needs more computationresources. Thinking in a different way, we can treat it as many traditional two-levelinverters that are organized in series. STS-SVPWM technique which is based on traditionalSVM can be applied on it. The paper analyses two kings of phase-difference space vectormodulation (PD-SVM) methods. A simulation using MATLAB/SIMULINK is made andthe result shows that the±π PD-SVM method has the advantage of high efficiency of DCvoltage and good quality of output wave, while the±2π/3PD-SVM method can eliminatecommon voltage.Finally, The paper introduced the hardware and software design of the main controlsystem. The paper presents a method using field programmable gate array(FPGA) toimplement a PWM pulse generator for8cells cascaded inverter. A simulation using QuartusⅡ is made, and the simulation result verifies the presented method.