*Theoretical and Practical Design Approach of Wireless Power Systems DOI: http://dx.doi.org/10.5772/intechopen.95749*

example), followed by the active PFC/THDC rectifier supplying the voltage source inverter (VSI). For both cases (low or high power) the VSI is sourcing primary/ transmitting coil with relevant compensation. This configuration of power electronic system (**Figure 19** – orange blocks) is providing low ripple input current with sinusoidal character, low THDi, excellent power factor and controllable output voltage. Therefore, it is not required to implement another dc/dc converter stage within the system [29–31].

The recommended topologies are summarized in **Figure 19** according to system dedicated power level.

The concept of power electronic system for the secondary side also differs based on the type of the load, and level of the power delivery. Basically, it consists of secondary side coil equipped by relevant compensation, passive or active rectifier and dc/dc converter stage providing required functionality of the charger.

Finally, the system connection to the grid considering all the power levels established as WPT categories by SAE TIR J2954 is seen in conceptual layout shown in **Figure 20**, valid especially for central Europe [32–35].

A more detailed example above described solution, which could meet all necessary technical requirements on high power applications and simultaneously having excellent operational properties, is seen in **Figure 21**.

**Figure 20.**

resistance of the coil (*Cp* = 5 pF, *L* = 0.1 mH, *R* = 1 Ω). As can be seen from the figure, when reaching the natural resonant frequency of the *fr-self circuit* »225 MHz, the quality factor is equal to zero and at the same time the inductive character of the reactance changes to capacitive character. For this reason, we always try to operate

**4. Practical design approach for industrial wireless power transfer**

Electrical engineers responsible for the design of the wireless transfer chargers must consider standard grid network connection during design process. Because many issues are nowadays address on the quality of the supply grid, the main goal during design of any power electronic system is to achieve the best performance related to the power factor parameter at any power consumption of the system. In addition to this fact, it is also required to have fully symmetrical 3-phase current

> ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi P *<sup>μ</sup>*¼<sup>2</sup>*<sup>i</sup>* 2 *ac*ð Þ *μ*

100 (54)

*iac*ð Þ<sup>1</sup>

Regarding above mentioned facts, each power electronic system, which must undergo strict normative given on the qualitative indicators of the grid variables, must be equipped with input active or passive power factor corrector (PFC) and total harmonic distortion correction (THDC). These blocks are consequently followed by diode rectifier, dc/dc converter (step-up or step-down) and the voltage source inverter. Such power electronic system configuration is robust and verified by many similar applications (mostly power supplies and battery chargers). The main negative drawback of such concept lies in higher price and build-in dimensions along with the increase in power rating. This topology should therefore be recommended for low or medium power WPT chargers (**Figure 19** – blue blocks). Second group of WPT chargers considering the value of power delivery is medium to high power concepts. Here it is recommended to use the configuration composed of input filter (inductive – designed as distribution transformer for

*Power electronics configuration on the primary side of the wireless power charger indicating differences related*

q

the coil at a frequency much lower than the self-resonant frequency.

*Wireless Power Transfer – Recent Development, Applications and New Perspectives*

**charging system**

**Figure 19.**

**62**

*to the level of the power transfer.*

**4.1 Power electronic system configuration**

with as low total harmonic distortion as possible [25–28].

*THDi* ¼

*WPT system categories – Connection to the grid.*

**Figure 21.** *Recommended system configuration for high power application.*

operating frequency, we can determine the voltage drop and the current through the coil from the required power. It is necessary to design an effective winding cross

*Theoretical and Practical Design Approach of Wireless Power Systems*

*DOI: http://dx.doi.org/10.5772/intechopen.95749*

The coil has 22 turns, the calculation parameters being as follows. The self-

In this case, we will focus on the WPT 1 category with an output of 3.7 kW. The experimental workplace consists of a programmable power supply, electronic load, precision power analyzer, oscilloscope, input inverter, output rectifier, additional resistors and the compensated LC circuit WPT itself. The measuring workplace is connected according to the functional diagram, see **Figure 24**. The determining factor in the selection of power components was the ability to work with a switching frequency from 200 kHz upwards. For this reason, a solution based entirely on SiC elements was chosen. The inverter is built on 1200 V JFET modules FF45R12J1W1\_B11 (Infineon) with a type current of 45 A. Due to the low values of switching times of these modules, which are actually in the order of tens of nanoseconds, it is possible to minimize the effect of inverter dead times. The rectifier is based on a 1200 V diode SiC module APTDC20H1201G (Microsemi) with a type

inductance has a value *L* = 147 μH and the active resistance is *R* = 0.19 Ω.

Regarding the available conductor cross-sections, a copper wire (2200 mutually insulated conductors) with a total cross-section of *Sv* = 19.63 mm2 was selected. The winding produced in this way eliminates the effect of the skin effect and the resulting resistance of the coil is therefore only affected by the phenomenon of

section for this.

proximity.

**4.3 Experimental set-up**

current of 20 A.

**Figure 24.**

**65**

*Block diagram of the laboratory experimental set-up.*

**Figure 22.** *Recommended system configuration of secondary side for high power application.*

#### **Figure 23.** *Proposed coupling coil (left) and its magnetic field (right).*

Here the distribution transformer is presented as the grid source, followed by active rectifier, which is responsible for regulation of PF and THDi. Then full bridge inverter is used as VSI and supplies primary side coupling section.

The secondary side of the system shown in **Figure 21** is drawn in more detail in **Figure 22**. The secondary side coupling system is followed by full-bridge diode rectifier with filtering capacitor CS. Then the dc/dc step-down converter (SD) providing required charging algorithm (mostly CC&CV) is supplying the on-board battery pack.

Previously described concepts are representing the mostly used configurations of power electronic systems required for the design of the wireless power chargers suited for industrial and/or automotive applications.
