# A Transformer-Less Buck-Boost Grid-Tied Inverter with Low Leakage-Current and High Voltage-Gain
## 5 Experimental Results

Table 3: Component parameters of the laboratory prototype. Figure 10: The experimental waveforms of the output voltage \(v_{o}\) and the gate-driving signals under the condition of 100 V input voltage and 500 W load. (\(v_{o}\): 200 V/div; \(V_{gs}\): 20 V/div; time: 5 ms/div). inductor \(L_{3}\), which can effectively increase voltage gain. Figure 13 shows the simulation waveforms of the output voltage \(v_{o}\) and the leakage current under the condition of 100 V input voltage and 500 W load. These waveforms prove that the proposed inverter can effectively suppress the leakage current of the PV panel. Moreover, the laboratory prototype is further measured with 200 V input voltage to verify its suitability for a wide range of input voltage applications. Figure 14 illustrates the experimental waveforms of the output voltage \(v_{o}\) and the driving signals of the switches  
Figure 11: The experimental waveforms of the input voltage \(V_{in}\), the output voltage \(v_{o}\), and the output current \(i_{o}\) under the condition of 100 V input voltage and 500 W load (\(V_{in}\), \(v_{o}\): 100 V/div; \(i_{o}\): 5 A/div; time: 5 ms/div). Figure 12: Under the condition of 100 V input voltage and 500 W load, the experimental waveforms of the output voltage \(v_{o}\) and the inductor currents \(i_{L1}\), \(i_{L3}\): (**a**) complete AC period (\(v_{o}\): 200 V/div; \(i_{L1}\), \(i_{L3}\): 10 A/div; time: 5 ms/div); (**b**) zoom-in on the peak of the output voltage (\(v_{o}\): 200 V/div; \(i_{L1}\), \(i_{L3}\): 10 A/div; time: 20 \(\upmu\)s/div). Figure 13: The simulation waveforms of the output voltage \(v_{o}\) and the leakage current \(i_{ leakage}\) under the condition of 100 V input voltage and 500 W load (\(v_{o}\): 100 V/div; \(i_{ leakage}\): 100 mA/div; time: 5 ms/div). \(S_{Bu1}\), \(S_{Bol}\), and \(S_{1}\). The modulation method is similar to that at 100 V input, but the operation time of the step-down mode becomes longer, and the operation time of the step-up mode becomes shorter. Figure 15 illustrates the experimental waveforms of the input voltage \(V_{in}\), the output voltage \(v_{o}\) and the output current \(i_{o}\) under the condition of 200 V input voltage and 500 W load. As can be seen, \(v_{o}\) and \(i_{o}\) are also low-distortion and close to the ideal sinusoidal wave, which indeed verifies the feasibility for the applications with wide-range input voltage. Figure 16 illustrates the experimental waveforms of the output voltage \(v_{o}\), and the inductor currents \(i_{L1}\), \(i_{L3}\) under the same conditions. At Figure 16a, due to the higher input voltage, the peak of inductor currents is lower than those at 100 V input voltage. Figure 16b illustrates zoom-in waveforms of the inductor currents \(i_{L1}\), \(i_{L3}\) on the peak of output voltage. It can be seen that the inductor \(L_{1}\) is still charging alone and discharging in series with the inductor \(L_{3}\). Figure 17 illustrates the simulation waveforms of the output voltage \(v_{o}\) and leakage current under the condition of 200 V input voltage and 500 W load. It can be seen that the leakage current can still be effectively suppressed under 200 V input voltage. The measured odd-order harmonics and total harmonic distortion (THD) of the inverter output under 100 V and 200 V input voltages are collected in Table 4. The data meet the requirements of international electrical standards; it is able to verify the feasibility of the investigated inverter. Figure 18 illustrates the experimental efficiency curves of the laboratory prototype, in which the efficiency is up to 95% at 100 V input and 96.7% at 200 V input, respectively. These results further confirm that high conversion efficiency can be achieved by the investigated inverter with a single stage of energy processing. Figure 19 shows the picture with the experimental test bench.