| Power system simulation is one of the most important methods for engineers to study the different phenomena in the system. There are two kinds of simulation methods, the physical and the numerical system simulation methods. Both have their advantages and disadvantages. The hybrid power system simulator has the advantages of both physical and numerical simulator. As the linking part of numerical and physical parts, the power amplifier is one of the most important parts in the electric generator and dynamic load numerical real time models. However, the linear power amplifier specially made is prohibiting expensive. In this paper, a kind of class D amplifier is proposed to replace the linear one. The basic concept of class D amplifier is to convert the input analog signal into a pulse width modulated signal (PWM signal), then the PWM signal is demodulated to reconstruct the analog signal. Usually a low pass filter is used for this purpose. Since PWM signal has only two or three voltage levels, a simple switch mode amplifier can be used to obtain high output power. Class D amplifier is much cheaper and energy saving than its linear counterpart. However, the waveform distortion of class D amplifier is bigger than that of its counterpart. In this paper, the math model of class D amplifier is deduced. And the characters that influence the performance of class D amplifier are analyzed. A prototype class D amplifier which employs DSP chip as the core of the controller has been built to test our theory.
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