# Robust Optimal Tracking Control of a Full-Bridge DC-AC Converter
## 4 Simulation and Experimental Results  
The commercial optimization software, for example HEEDS-MDO, can be used to design the optimization of engineering problems. However, based on the current funding considerations and the currently available software resources, the MATLAB/Simulink is used to simulate the full-bridge DC-AC converter controlled by the proposed strategy and a typical TA. Figure 3 displays the simulated block diagram of the full-bridge DC-AC converter with the control strategy. Likewise, the circuitry of the proposed full-bridge DC-AC converter has been implemented using a dSPACE DS1102 controller board (dSPACE GmbH, Paderborn, Germany) based on a Texas Instruments digital signal processor, substantiating the applicability of the proposed strategy. The photo of the experimental setup is displayed in Figure 4. The system parameters of the full-bridge DC-AC converter are listed in Table 1. It should be noted that the component values can be selected as proposed in [83; 84; 85] below. (i) Pick the switching frequency [84; 85]: In order to reduce the size of the filter, it is necessary to elect a sufficiently high switching frequency, and in the case of metal-oxide-semiconductor field-effect transistor switches, it is often elected amidst 20 and 40 kHz. (ii) Pick a coefficient related to the cutoff frequency of the LC filter [83]: When the factor is small, the switching frequency and the fundamental frequency have large attenuation and small amplification, respectively. The minimum value of the factor can be calculated, and the modulation value is preferably 0.95 or less. (iii) Pick a factor related to both switching frequency and inductance ripple current [83]: The ripple current of the inductance is preferably in the range of 20% to 40%. Then, both L and C component values are calculated from the picked coefficients of (8), (20), (25), and (26) of [83]. Figure 3: Simulated block diagram of full-bridge DC-AC converter with the control strategy. The simulated output-waveshapes of the full-bridge DC-AC converters shown in Figures 5 and 6 are respectively divided into the proposed strategy and the typical TA under TRIAC (triode for alternating current)-controlled loads (at 90/270 firing angles, changing from no load to full load of 12 ohm). The proposed strategy displays a smaller voltage dip and speedier recovery time than the typical TA. For the sake of examining the performance of the full-bridge DC-AC converter at highly non-linear load situations, Figure 7 depicts the simulated output-waveshape of the full-bridge DC-AC converter at a rectified load (\(C_{d}=200\) uF and \(R_{d}=30\) ohm) using the proposed strategy. The output-voltage has a good sine form, and its voltage % THD can reach 0.14%, which is less than 5% of the IEEE standard. Figure 8 represents a typical TA subject to the situation of a rectified load (\(C_{d}=200\) uF and \(R_{d}=30\) ohm), the simulated output-waveshape of the full-bridge DC-AC converter exposures of an unsatisfactory contortion and a quite high voltage %THD of 13.57% yields. Thereby, the proposed strategy completely enhances the steady-state performance of the full-bridge DC-AC converter, even under severe non-linear loading. Table 2 gives the simulated output-voltage dip and %THD for TRIAC-controlled loads and rectified loads, respectively. Based on the above response under different load conditions, we can further understand that the output LC filter tends to cause current stress in the full-bridge DC-AC converter under transient conditions, and the load current may also increase current stress. When there is a high inductive load, the design of the filter ratio has been proposed in the (20) of the literature [84], and it is suggested that the middle range between the upper and lower boundaries can be used for inductive loads. In addition, if the converter is connected to an inductive load, the power factor and efficiency of the output sine voltage are unsatisfactory.