Research On Sigma-Delta Modulation Technology And Its Application In The Inverter

When Sigma-Delta modulation technology,similar to PWM and other modulation techniques,is a method of converting analog signals into digital(switching)signals.The uniqueity of Sigma-Delta modulation lies in the closed-loop modulation,which makes the Sigma-Delta modulation with noise shaping characteristics,combined with oversampling,Sigma-Delta modulation can achieve high signal to noise ratio and high resolution advantages.So when Sigma-Delta modulation is applied to Class D amplifiers,it can be made close to linear power;when Sigma-Delta modulation is applied to data converters,it can achieve extremely high resolution and accuracy.The closed-loop characteristics of Sigma-Delta modulation technology have been widely used in digital power amplifier,data conversion and other fields.However,SigmaDelta modulation technology is rarely used in the field of inverter as a kind of excellent modulation method.Therefore,based on the inverter application,this paper studies the effect of Sigma-Delta modulation on the performance of the inverter.Firstly,the development of Sigma-Delta modulation technology is introduced,and its modulation principle and modulation process are described.The mathematic model of Sigma-Delta modulator is established,the principle of noise shaping is analyzed,and it is explained that oversampling and noise shaping can improve Sigma-Delta The reason why the increase of the order of the Sigma-Delta modulator can improve the performance of the modulator,but at the same time reduce the stability of the system.Then,based on the inverter application,a Sigma-Delta modulator with midpoint feedback of the bridge arm is proposed.The mathematic model is established and the lowfrequency component of the arm-delta modulation can be suppressed by Sigma-Delta modulation.The frequency domain characteristics of the error are low frequency odd harmonics as the main components,so the Sigma-Delta modulation can effectively suppress the deadband error through the midpoint feedback of the bridge arm and verify the conclusion by simulation.And can inhibit the dead-band error is PWM and other open-loop modulator does not have the characteristics.Finally,the comparison between Sigma-Delta modulation and traditional modulation mode PWM,delta modulation and hysteresis control structure and performance is compared.The conclusion is as follows: Sigma-Delta modulation is compared in high frequency application(wide bandgap device)PWM modulation is more advantageous,Sigma-Delta modulation is better than Delta modulation,Sigma-Delta modulation and hysteresis control compared to a more stable performance.So Sigma-Delta modulation technology applied to the inverter is of great potential.