Together with the defined input and output voltage characteristics, the following additional features are desired for this conversion: (a) high conversion efficiency, (b) low mass and volume, (c) low switching stresses and EMI, and (d) high reliability. Among various types of DC/AC power processors, the resonant type inverters offer high efficiency, low mass and volume, simple power and control circuitry, low EMI, and high reliability while providing the required output voltage characteristics. This type of inverter system has been adopted for some near future space applications such as Space Station. Therefore, the DC/AC resonant mode inverters are only considered and discussed for future high power space based applications in this paper. 3.2 Control Methods Since constant output frequency is often required, the output voltage of DC/AC resonant inverters are controlled by employing either of the following two methods: (1) phase-shift control; (2) pulse width control. Each of the above control techniques is briefly discussed below: 3.2.1 Phase-shift Control. Figure 3 shows a block diagram of a DC/AC resonant inverter system to illustrate the basic principle of phase-shift control. In this type of control two resonant inverters are fed by a common input DC source and their outputs are vectorally added by using an output transformer. Both inverters are operated at the same and constant frequency, however, the gating signals of inverter no. 2, as shown in Fig. 3(b), leads the gating signals of inverter no. 1 by a phase angle 0. Assuming that the output voltage levels of each inverter are identical, the combined output voltage of the inverter system is given by:
RkJQdWJsaXNoZXIy MTU5NjU0Mg==