**4. Results**

In this section, a system experiment setup was built, and the proposal was compared against the traditional method. The algorithm is realized by the DSP (TMS320F28335) and FPGA (Xilinx XC6SLX9). The experimental parameters are shown in Table 4. Figure 11 shows the control diagram of the proposal. The phase angle θ is detected to generate the reference current. The output *m* of the PR (Proportional Resonant) regulator is used as the input of the new modulation method. The new modulation method judges the positive or negative of *m* and selects the corresponding switching sequence. The specific switching sequence selection is shown in Figure 12, where *Ts* represents the switching period.


**Table 4.** Experimental parameters.

**Figure 11.** System control block diagram.

**Figure 12.** Switching sequence selection for new modulation method.

The experimental results for the conventional current-type inverter are shown in Figure 13. The output current *Iinv* is unipolar, and the grid current *Ig* is sinusoidal. Figure 13b shows the voltages *VPO*, *VNO* and the common-mode voltage *VCM*. The leakage current *Ileakage* waveform is shown in Figure 13c, and the maximum leakage current is 2 A. The switching-frequency variation of the common-mode voltage causes the leakage current to far exceed the 300 mA. As shown in Figure 13d, for the gating signal waveforms of the switches *S*1–*S*4, the switch *S*1 and the switch *S*3 operate at the power frequency, and the switch *S*2 and the switch *S*4 operate at a high frequency.

**Figure 13.** Results with conventional current-type inverter. (**a**) Output current *Iinv*, common-mode voltage *VCM*, grid current *Ig*; (**b**) *VPO*, *VNO*, common-mode voltage *VCM*; (**c**) Leakage current *Ileakage*, common-mode voltage *VCM*; (**d**) Switches *S*1–*S*4 gating signal waveforms.

The output current *Iinv* and the grid current *Ig* are shown in Figure 14a. From Figure 14d, the switches *S*1-*S*4 operate in power frequency, which reduces the switching loss. Figure 14b is the experimental result of the voltages *VPO*, *VNO* and the common-mode voltage *VCM*. The common-mode voltage is the half-grid voltage, ignoring the effect of the fundamental-frequency component of the common-mode voltage on the high-frequency common-mode behavior. According to Equation (5), the leakage current is able to be attenuated. The experimental waveform of the leakage current *Ileakage* is shown in Figure 14c. The maximum value of the leakage current is 144 mA, which meets the standard and is less than 300 mA, which is satisfactory in terms of the VDE-0126-1-1.

**Figure 14.** Results with new current-source inverter. (**a**) Output current*Iinv*, common-mode voltage *VCM*, grid current *Ig*; (**b**) *VPO*, *VNO*, common-mode voltage *VCM*; (**c**) Leakage current *Ileakage*, common-mode voltage *VCM*; (**d**) Switches *S*1–*S*6 gating signal waveforms.
