On the Minimal Loading of Sensorless Series-Series Compensated Inductive WPT Link Operating at Load Independent Voltage Output Frequency Without Feedback

Abstract

It is well-known that continuous conduction mode (CCM) operation at certain frequency yields nearly load-independent voltage gain in practical series-series compensated inductive wireless power transfer links (SS-IWPTL). Such an operation is usually referred to as "load independent voltage output" (LIVO). Residual load dependence is due to the presence of non-zero equivalent series resistances in both transmitter and receiver. On the other hand, it has been shown that voltage gain remains load-dependent at the same operating frequency in discontinuous conduction mode (DCM) irrespectively of equivalent series resistances values. Consequently, the output voltage of SS-IWPTL operated at LIVO frequency resides within a range with lower bound corresponding to rated load and upper bound corresponding to zero loading for a given input voltage. The upper bound expression (typically attained in CCM) is derived using the first harmonic approximation (FHA) based equivalent circuit and is well-established by previous works. On the contrary, derivation of the lower bound (achieved in DCM) requires differential equation (DE) based analysis and was barely treated in the literature. The paper demonstrates that lumped capacitance of receiving side coil and input capacitance of receiving side rectifier must be taken into account during DEbased analysis since they impose significant receiving side voltage oscillations, which may give rise to safety issues. In order to damp these oscillations and keep the output DC voltage below a predetermined limit, minimal loading should be applied at the SS-IWPTL output, creating an RCD-snubber equivalent. Guidelines for the minimal load sizing are derived in the paper analytically. Simulations and experiments based on a 400V, 1kW SS-IWPTL operating at LIVO frequency demonstrate excellent matching, validating the proposed analysis. INDEX TERMS Inductive wireless power transfer, series-series compensation, load-independent voltage output, zero load operation.

Output Voltage and Resistance Assessment of Load-Independent-Voltage-Output Frequency Operating Inductive Wireless Power Transfer Link Utilizing Input DC-Side Measurements Only

“…This is due to the fact that the simulation model does not include parasitic capacitances of the coils and the diode bridge since they do not affect the first harmonic behavior. In general, if parasitics are brought into the model, the results look much more similar [20]. Here, the first harmonics only are of interest, and it is shown that the first harmonic approximations are quite similar in simulations and experiments.…”

“…where P O denotes the load power, P O,B signifies load power level corresponding to the bound between CCM and DCM, P O,MIN represents minimum allowed IWPTL load power [20] On the other hand, the relation between the output voltage and load power relation is highly nonlinear yet well-defined analytically in DCM regime (second row of Equation ( 36)). Nevertheless, the relation between the rows of Equation ( 36) is injective (one-to-one), and hence DCM-related output voltage may be estimated from its corresponding CCM counterpart.…”

“…The system is fed from IT61517D ITECH high-voltage DC power supply (ITECH, New Taipei City 23586, Taiwan) and loaded by Maynuo M9715 DC (Maynuo, Nanjing, Jiangsu 20019, China) electronic load, functioning in constant-power mode. IWPT link DC output is terminated by a 20 kΩ resistor to realize the minimum allowed load of P O,MIN = 9 W[20]. System Parameter Values.…”

Predicting Receiver Characteristics without Sensors in an LC–LC Tuned Wireless Power Transfer System Using Machine Learning

“…Equation ( 8) represents the relationship between the circuit elements to achieve resonance. The parameters I in (9) and V C1 (10) were used for ML training. The coupling value was varied to affect the mutual inductance according to Equation (5) in order to simulate different coupling states between the Tx and Rx.…”

“…Research about Rx-side sensorless WPT systems has been undertaken in [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. The study in [ 15 ] proposes a machine learning (ML) assisted method that estimates the power delivered to the Rx by using only measurements at the Tx-side.…”