This chapter focuses on the analysis of the mathematical model of the single-phase inverter and the suppression of its electromagnetic radiation. The high-frequency switching of solar inverter leads to the generation of a large amount of high-frequency harmonics in the output voltage, which can cause electromagnetic interference to the surrounding equipment. Therefore, it is necessary to study the model of solar inverter and find effective methods to suppress the electromagnetic radiation.
1. Introduction
The single-phase inverter is a typical nonlinear system, and the study of its mathematical model is the theoretical basis for the control design of solar inverter. The output voltage of solar inverter contains a large number of high-frequency harmonics, which can cause electromagnetic radiation and interfere with the normal operation of other equipment.
2. Mathematical Model of Single-Phase Inverter
2.1 Equivalent Model of Inverter Bridge
The solar inverter bridge is equivalent to a proportional link, and its output voltage is controlled by the switching signals of the power devices.
2.2 Output Filter Model
The output filter is used to filter out the high-frequency harmonics in the output voltage of the solar inverter and improve the quality of the output waveform.
2.3 Model of Single-Phase Inverter
The state space average model of the single-phase inverter is established by combining the equivalent model of solar inverter bridge and the output filter model.
2.4 Closed-Loop Control Model of Single-Phase Inverter
The closed-loop control model of the single-phase inverter is established by adding the voltage and current feedback loops to the model of the single-phase inverter.
3. Output Harmonic Analysis of Single-Phase Inverter
3.1 Time Domain Analysis
The output voltage of the two-state inverter is analyzed in the time domain, and the sampling points of the output voltage are determined by the intersection points of the modulation wave and the carrier wave.
3.2 Frequency Domain Analysis
The double Fourier series expansion is used to analyze the output voltage of solar inverter in the frequency domain, and the amplitudes of the harmonics are calculated.
3.3 Simulation Study
The simulation model of the single-phase inverter is established, and the output voltage spectrum is simulated and analyzed.
4. Electromagnetic Radiation Suppression Based on Frequency Hopping Modulation
4.1 Principle of Frequency Modulation
The principle of frequency modulation is introduced, and the relationship between the frequency deviation and the modulation signal is explained.
4.2 Principle of Frequency Hopping Modulation Inverter
The working principle of the frequency hopping modulation solar inverter is explained, and the way to reduce the amplitude of the carrier signal by spreading the spectrum is described.
4.3 Output Harmonic Analysis of Frequency Hopping Modulation Solar Inverter
The output harmonic analysis of the frequency hopping modulation solar inverter is carried out, and the distribution of the harmonic spectrum is studied.
4.4 Simulation Analysis and Experimental Results
The simulation and experimental results show that the frequency hopping modulation solar inverter can effectively reduce the amplitude of the harmonics and suppress the electromagnetic radiation.
In summary, this chapter analyzes the mathematical model of the single-phase inverter and the output harmonic characteristics, and proposes a method of using frequency hopping modulation to suppress the electromagnetic radiation. The simulation and experimental results verify the effectiveness of this method.
The following is a summary of the key points in tabular form:
| Topic | Key Points |
|---|---|
| Mathematical Model of Single-Phase Inverter | – Equivalent model of solar inverter bridge – Output filter model – State space average model – Closed-loop control model |
| Output Harmonic Analysis of Single-Phase Inverter | – Time domain analysis – Frequency domain analysis – Simulation study |
| Electromagnetic Radiation Suppression Based on Frequency Hopping Modulation | – Principle of frequency modulation – Principle of frequency hopping modulation solar inverter – Output harmonic analysis of frequency hopping modulation solar inverter – Simulation analysis and experimental results |