This dissertation proposes the method for predicting noise generated during power conversion in a single-phase inverter and transmitted to the input power stage. A single-phase inverter has two switching legs, and first, the noise in a DC-DC buck converter with one switching leg is analyzed and a prediction method is proposed. In this dissertation, a noise analysis and prediction method by extending this prediction method to a single-phase inverter with two switching legs is proposed.
First, this dissertation proposes the high-frequency mathematical model for the common mode noise voltage of a DC-DC buck converter. The high-frequency equivalent circuit considering the parasitic impedance is proposed, and then the impedance path of the common mode noise is analyzed using this high-frequency equivalent circuit. The common mode noise source generated by the switching device is divided into trapezoidal and ringing voltage noise sources and mathematically modeled. For high accuracy at high-frequency, a mathematical model of common mode noise sources including the difference between rise and fall time is proposed using Fourier transform. The common mode noise voltage is modeled by multiplying the impedance path and the noise source. In the results of the simulation, the mathematical model and experiment, the resonance frequency and the magnitude matched with less than 5% error. Through this, the common mode noise is predicted accurately using the high-frequency mathematical model proposed in the dissertation.
Second, the prediction method of differential mode noise transmitted to the input power of a grid single-phase inverter in a high-frequency model is proposed. A high-frequency equivalent circuit model considering the parasitic impedance is proposed for differential mode noise analysis on the input stage during single-phase inverter switching operation. This dissertation presents a method to measure the parasitic impedance included in the DC link capacitor and insulated-gate bipolar transistor (IGBT) using the gain phase method of a network analyzer and extract the parasitic impedance included in the DC bus plate and PCB track using Q3D. A mathematical analysis is proposed by applying the double integral Fourier form to the current noise sources, and a method for obtaining differential mode noise by analyzing the impedance path is proposed. The switching of IGBT is modeled as the noise current source that reflects the pulse width modulation (PWM) duty change using the double integral Fourier form. The impedance path of differential mode noise transmitted to the input is mathematically analyzed on the high-frequency equivalent circuit. The differential mode noise voltage affecting the input is modeled by multiplying the impedance path of differential mode noise and the noise source current. The validity of the proposed high-frequency equivalent circuit model and the mathematical analysis is verified by the less than 5% error in the resonant frequency of the derived differential mode noise voltage and the resonant frequency measured experimentally.
Lastly, the methods for common mode noise prediction for a grid single-phase inverter in a high-frequency model is proposed. The high-frequency detailed circuit of the inverter is proposed by measuring or extracting all parasitic impedance of the interconnection devices and IGBT. A mathematical analysis is proposed by applying the double integral Fourier form to the current and voltage noise sources, and a method for obtaining common mode noise by analyzing the impedance path is proposed. The high-frequency equivalent circuit of the single-phase inverter is derived from the detailed circuit to reduce the time of the simulation. Based on the theory analyzed through the mathematical model of common mode noise, the IGBT is replaced with the noise source that reflects the PWM duty change. The common mode noise spectrum is simulated and compared to an actual experiment to verify the validity of the proposed method. As a result, the resonance points are matched among the mathematical model, simulation, and experiment. The resonance of the mathematical model is 91dBuV at 7.6MHz, that of the detailed circuit is 94dBuV at 7.4MHz, that of the equivalent circuit is 95dBuV at 7.5MHz, and that of the actual experiment is 95dBuV at 7.6MHz. In particular, in this dissertation, the validity is verified by comparing and analyzing the models of all the above processes together.