*4.1. No-Load Condition Control*

Two separate controls work at the same time in the developed IPT. These are no-load condition control and charge control. Before starting charging, the presence of the load is tested. For this, the duty cycle of switches Q1 and Q2 is set to *Dtest* so that the output voltage of the two-switch forward converter is equal to *VF*\_*test*. At this moment, the current of the forward converter *IF*, is measured. If *I<sup>F</sup>* is not less than *IF*\_*max*1, the system is kept in the load-test section. *IF*\_*max*<sup>1</sup> is the limit current value for the primary side's safe operation. If *I<sup>F</sup>* = *IF*\_*max*1, this could be for two reasons. First, it could be a secondary side open circuit. In the other case, there may be a fully charged battery on the secondary side. In both cases, it is kept as *V<sup>F</sup>* = *VF*\_*test*. The no-load condition control also works during the charging process. Thus, if the load is disconnected during charging, the primary side is protected. The no-load condition control is shown as Section-I in the control algorithm (Figure 5). *Energies* **2022**, *15*, x FOR PEER REVIEW 8 of 16

**Figure 5.** Flow chart of the control algorithm for wireless charging. **Figure 5.** Flow chart of the control algorithm for wireless charging.

*4.2. CC‐CV Control Strategy*

Figure 5 as Section 3.

**5. Simulation and Experimental Results**

completed.

This part is shown as Section 2 in the control algorithm.

is gradually increased starting from the ௧௦௧ value, after the no‐load condition

When ி ൌ ி\_௦௧, and ி has not reached ி\_௦௦ yet, the equivalent impedance value of the battery is quite low and charging has started in CC mode. The nature of SS topology tends to keep the secondary side current constant. The secondary side output voltage increases with the increase in state of charge (SOC). At this moment, if it is on the primary side, ி will increase. The charging process continues in CC mode until the ி ൌ ி\_௦௦ଵ condition is met. When ி ൌ ி\_௦௦ଵ, the charging process has reached the stage of switching to CV mode in CC mode. This part of the control strategy is shown in

In the CV mode of the charging process, the equivalent resistance of the battery bank tends to rise rapidly. The limit current value must be reduced to the second peak current level (ி\_௦௦ଶ) so that ி current does not quickly reach the maximum value. As the charging process continues, ி tends to increase. After this point, ி is reduced to prevent the increase in ி. For this, is gradually reduced. At each step, it is checked whether ி reaches the second peak current value. This loop continues until ி ൌ ி\_௦௧ (Section 4). If this condition is met, the battery is now full and the charging process is

Thus, ி\_௦௧ ൌ 60 value to be applied for charging in constant current mode is reached.
