# TAB Series-Resonant DC-DC Converter and Multi-Phase-Shift Based Global Optimization Modulation
## 4 Experimental Results and Analysis  
The proposed three-port converter and optimized modulation are verified by the built experimental platform shown in Figure 7a. The modular approach is used to build the experimental platform. We have built some general half-bridge modules with the SiC power switches. The voltage rating of the switches is 650 V. Based on these modules, it is convenient to make up various dc-dc or dc-ac converters. Combining with the schematic of the proposed converter shown in Figure 1, we use six modules to make up the proposed three-port converter in this experiment. Then combining with (4), (8), and (9) the parameters of the resonant tank of port 1 and port 2 are designed according to the requirements of the transmission power level. Combining with (4), (12) and the switching frequency \(f_{s}\), the parameters of the resonant tank of port 3 are designed. The input inductors and bus capacitors of port 1 and port 2 are designed according to the ripple requirements of the input current and the bus voltage. In addition, three dc voltage sources and three resistors are connected in parallel to the three ports, respectively, so that the power can be transferred among the three ports under the bi-direction. The parameters of the experimental platform are listed in Table 1. In order to verify the availability of the proposed modulation when the voltage gain varies in a wide range, the voltages on port 1 and 2 vary from 60 V to 150 V. In addition, to decrease the capacitance and rated voltage of the resonant capacitor used on port 3, an inductor is connected in series in the resonant tank. The total value of the leakage inductance of the transformer on port 3 and the external inductance is 101 \(\mu\)H. The three components construct the resonant tank with the resonant frequency of 50 kHz, which is equal to the switching frequency to realize the power decoupling. All experiments are performed under open-loop conditions. The control is implemented based on DSP + FPGA platform. The specific type of the used DSP and FPGA are TMS320F28377 and Cyclone IV, respectively. First, according to the range of voltage gain and transfer power, the operating state of the converter is selected. On this basis, the control variables are calculated, combined with (25), (32), (34), and (36). The above works are completed by DSP. Then, the calculations of DSP are transferred to FPGA and the driving signals of the switches are generated by FPGA. The block of the control configuration is shown in Figure 7b. According to power flowing direction, there are three types of operation modes, namely the forward mode, backward mode, and hybrid mode. In order to verify the performance of the power decoupling and the optimized modulation in the entire power range, the experimental results of various operation modes are all tested and analyzed separately below. As a comparison, the corresponding experimental results of the conventional TAB resonant converter without the decoupling resonant tank are also tested and shown here. Figure 7: Experimental platform. (**a**) Photograph, (**b**) Control configuration. First, the performance of decoupling of both port 1 and port 2 operating in the forward mode is verified and compared with that of the conventional converter. In order to observe the performance of the power decoupling, the transfer power of port 2 remained constant and that of port 1 is stepped at some time. The corresponding experimental results of the converter and the conventional converter and the proposed one are shown in Figure 8. From Figure 8a, in the conventional converter, when \(i_{1}\) step change occurs, the current of port 2 \(i_{2}\) varies accordingly. This clearly reveals the power coupling problem. From Figure 8b, in the proposed converter, \(i_{2}\) keeps constant during the transient process, that is, the power coupling between port 1 and port 2 is eliminated. In the following, the global optimal modulation in all states is tested and compared with the SPS modulation.