The Development of a 1 kW Mid-Range Wireless Power Transfer Platform for Autonomous Guided Vehicle Applications Using an LCC-S Resonant Compensator

Abstract

This study presents the development, simulation, and hardware implementation of a 48 V, 1 kW mid-range wireless power transfer (WPT) platform for autonomous guided vehicle (AGV) charging in industrial applications. The system uses an LCC-S compensation topology, selected for its ability to maintain a constant output voltage and deliver high efficiency even under load variations at a typical coil distance of 15 cm. It can also operate at different distances by adjusting the compensator circuit. A proportional–integral (PI) controller is implemented for current regulation, offering a practical, low-cost solution well suited to industrial embedded systems. Compared to advanced control strategies, the PI controller provides sufficient accuracy with minimal computational demand, enabling reliable operation in real-world environments. Current adjustment can be dynamically carried out in response to real-time changes and continuously monitored based on the AGV battery’s state of charge (SOC). Simulation and experimental results validate the system’s performance, achieving over 80% efficiency and demonstrating its feasibility for scalable, robust AGV charging in Industry 4.0 Manufacturing Settings.

1. Introduction

Nowadays, technology is an essential component of everyday life. The advancement of devices that improve convenience and efficiency has attracted significant attention. A crucial innovation with substantial potential to revolutionize lifestyles is the “wireless electric power transmitter”, also known as wireless power transmission (WPT) [1,2]. This technology eliminates the constraints associated with wired connections, which increases usability to improve the performance of the electrical system. Generally, wireless power transmitters are designed for multiple applications, ranging from small electronic devices [3], such as smartphones, wireless headphones, and smartwatches, to larger hardware such as electric vehicles [4,5,6] and residential electrical appliances. They are also applied in the industrial, medical, and smart home technology sectors. This technology extends typical enhancements in convenience. However, it also enables long-term cost reduction and reduces waste generated by electrical cables while enhancing safety in their application, especially in situations where electrical systems require high safety standards, such as in hospitals and industrial facilities.

Recently, WPT is increasingly used in industrial automation as a reliable, maintenance-free solution for charging AGVs. As shown in Figure 1, AGVs are vital in logistics, warehousing, and smart manufacturing, where efficient, autonomous charging is essential. Traditional plug-in systems suffer from wear and alignment issues, reducing operational uptime. In contrast, WPT offers contactless energy transfer, supporting opportunity and dynamic charging without human intervention. Typical AGV WPT systems operate around 1 kW using high-frequency AC to induce voltage via inductive or resonant coupling. Compensation topologies such as Series–Series (SS) [7], Series–Parallel (SP) [8], Parallel–Series (PS) [9], or Parallel–Parallel (PP) [10] are employed to improve efficiency and misalignment tolerance. Additionally, modern systems integrate wireless communication for real-time SOC-based control, enabling adaptive charging under varying conditions. Advanced control strategies [11], including Model Predictive Control [12,13,14,15], Sliding-Mode Control [16,17,18], Fuzzy Logic Control [19,20], and Hamiltonian-based approaches [21,22,23], are actively explored to enhance current regulation and system stability, particularly under the nonlinear dynamics of lithium-ion battery loads. As factories focus more on automation and reliability, WPT has become an important technology that supports fast, efficient, and maintenance-free charging for AGVs.

2. Overview of Wireless Power Transfer

Wireless power transfer is a technology that allows energy to be delivered without physical contact, and it is widely used in electric vehicles (EVs) and industrial systems. To improve efficiency and maintain stable power delivery, resonant inductive coupling is often combined with compensation topologies. This paper provides a brief overview of WPT and highlights how different compensator circuits affect system performance. A comparison of commonly used compensation methods is provided in

Table 1. Compensator topology comparison.

Topology	Advantages	Disadvantages
SS (Series–Series)	- Simple structure - Easy to design and control - Good voltage gain at resonance	- Output depends on load - Poor regulation - Sensitive to coil misalignment
SP (Series–Parallel)	- Load-independent voltage source behavior - Better voltage regulation	- Cannot achieve ZVS easily - High circulating current - Poor efficiency at light load
PS (Parallel–Series)	- Load-independent current source - Suitable for constant current applications	- Requires large capacitors - Difficult to maintain ZVS - Sensitive to misalignment
PP (Parallel–Parallel)	- Output current relatively stable under load variations - Constant current profile possible	- Poor ZVS conditions - Complex tuning - High component stress
LCC-S (LCC-Series)	- Output current relatively stable under load variations - Constant current profile possible	- More complex structure - Requires precise tuning - Slightly higher cost and size

.

2.1. Resonant Compensation Topologies in Wireless Power Transfer for AGVs

In the framework of WPT for AGVs, the choice of compensation topology directly impacts power transfer efficiency, control complexity, and system robustness—particularly under varying load conditions, which are common in industrial environments. Traditional compensation topologies, such as SS, SP, PS, and PP, offer simple configurations but suffer from limitations in terms of load-dependent behavior, inefficient power conversion at high power levels, and limited soft-switching capability. Among these, the LCC-Series (LCC-S) topology offers significant practical advantages. It provides load-independent input impedance, enabling the inverter to operate under well-defined, controlled conditions. The topology also supports zero-voltage switching (ZVS) across a wide range of load variations, significantly reducing switching losses and improving system efficiency. Its voltage-source characteristic at the receiver makes it especially compatible with downstream dc-to-dc converters for battery charging, such as Buck or bidirectional converters, without requiring complex matching networks.

In terms of control, LCC-S is well suited for integration with simple and reliable control strategies such as the PI controller, which allows for effective current regulation with minimal computational burden. This is particularly important in industrial deployments where cost, hardware simplicity, and reliability are paramount. Compared to more advanced strategies like model MPC or Hamiltonian control, PI controllers offer easy implementation, low tuning overhead, and robust responses—making them ideal for embedded microcontroller-based AGV systems. Overall, while basic topologies may be suited for tightly controlled or low-power environments, the LCC-S compensator emerges as the most practical and scalable solution for real-world AGV wireless charging. Its combination of high efficiency, misalignment tolerance, and control simplicity aligns with the operational demands of modern smart factories and supports continuous, maintenance-free AGV operation under Industry 4.0 frameworks.

2.2. The LCC-S Resonant Compensator Analysis

2.2.1. The WPT with an LCC-S Resonant Tank

The LCC-S Wireless Power Transfer (WPT) [24,25,26,27] shown in Figure 2 is a highly efficient wireless power transmission technique. The WPT system uses the principle of magnetic induction and a resonance compensation network to optimize energy transmission over a specified distance. The LCC-S topology employs a configuration combining an inductor and a capacitor to achieve a resonant frequency which enhances power transmission stability and minimizes energy loss.

The main factors are the primary side (transmitter, Tx), which includes a high-frequency ac power source and an LCC compensation network to produce an alternating magnetic field, and the secondary side (receiver, Rx), which employs winding to support power and compensation with a single capacitor. Consequently, this simplifies the circuit, thus lowering expenses and providing substantial benefits, such as improved performance, increased durability against misalignment, and decreased size and weight. Thus, this is suitable for use in electric vehicles, medical devices, and industrial automation.

Normally, wireless power transmission typically employs various kinds of resonant tanks. However, the output depends on the transmitted power, the distance between coils, and the transmission control in either a unidirectional or bidirectional setup. Figure 3a,b show a simplified circuit for determining system gain, while the secondary circuit can be represented to calculate the equivalent circuit on the primary side.

Understanding the advantages of the LCC-S topology is crucial. This type of resonant tank shows distinct resonant conditions compared to other resonant types. Equations (1)–(3) demonstrate that if the variable meets the specified resonant conditions, we can determine the values of other variables such as a compensation inductor, and the capacitor can be compensated in the system.

$$j\omega L_r+{\displaystyle \frac{1}{j\omega C_r}}=0$$

(1)

$$j\omega L_p+{\displaystyle \frac{1}{j\omega C_p}}+{\displaystyle \frac{1}{j\omega C_r}}=0$$

(2)

$$j\omega L_s+{\displaystyle \frac{1}{j\omega C_s}}=0$$

(3)

The calculation of the system gain [28,29,30] in wireless power transmission systems is necessary. Equation (4) demonstrates that the system voltage gain is dependent upon the ratio of mutual inductance to the compensated inductor. Thus, this system will remain unaffected by load fluctuations, offering a distinct advantage over other types of resonant tanks.

$$Gain={\displaystyle \frac{M}{L_r}}$$

(4)

where

M = Mutual Inductance

L_r = Compensated Inductance

2.2.2. The Current Regulated dc-to-dc Buck Converter

To achieve the required power, we employ a dc-to-dc Buck converter for charging control. Figure 4 illustrates a converter system that regulates switching devices to operate with a duty cycle limited to 50%. Regulation is carried out based on monitoring the current entering the battery, with feedback control being implemented using the current as the setpoint. Additionally, the selection of the controller is a critical aspect of this research. A comparison of the PI controller with other controllers is presented in

Table 2. Comparison of PI controller and advanced controllers.

Aspect	PI Controller	Modern Controllers (MPC, Adaptive, SMC, Fuzzy)
Implementation Complexity	Simple, easy to implement in low-end microcontrollers	Complex, requires advanced algorithms and more computation
Cost	Low cost (minimal hardware/software)	Higher cost due to processing, memory, or sensor requirements
Tuning	Manual tuning	Self-tuning (Adaptive), rule-based (Fuzzy), or predictive (MPC)
Robustness to Nonlinearity	Weak—performance drops with battery nonlinearity or misalignment	Strong—effectively handles system nonlinearity and parameter variation
Suitability for Real-Time Dynamic Charging	Limited—may overshoot or be unstable with rapid SOC changes	Excellent—tracks dynamic charging profiles (e.g., fast charging from 0 to 20 A)
Industrial Use Case Readiness	Common in low-cost applications with stable operation	Used in advanced, high-performance systems (but still maturing for WPT)

. It can be observed that the main advantages of the PI controller lie in its simplicity and lower unit cost. In contrast, advanced control topologies offer greater robustness when dealing with nonlinear loads such as batteries. From this analysis, it can be concluded that the use of a PI controller in this study is acceptable, provided that the Kp and Ki values are properly tuned to maintain a well-damped current response without overshoot. However, the PI controller still has limitations, particularly in handling current step-up conditions during on-load operations.

3. Simulations of the Proposed Wireless System

The design includes two parts: Initially, wireless power transmission is implemented using the LCC-S compensator, which employs a high-frequency inverter to transmit a square wave signal to the transmission (Tx) coil. Moreover, the gain calculation is performed by scripting in MATLAB/Mfile version 2020a to acquire various parameter values. The LCC-S resonant compensator offers the advantage of eliminating concerns regarding connection to the rectifier’s output. Secondly, the research team selected a dc-to-dc Buck converter for battery charging control.

3.1. Simulation of WPT with LCC-S Resonant Tank

The simulation of this proposed system will be carried out following specified conditions. A rectangular power platform of the same size and shape is used, as shown in Figure 5. The preliminary design determines the size of the AGV and the location of the main power transmission. Here, the power transmission coil base is specified according to

Table 3. Coil specifications.

Parameter	Value
Primary/secondary self-inductance	32.66/32.56 µH
Mutual inductance	5.4 µH
Operating distance	15 cm
Coil type/size	Rectangular/30 cm × 30 cm

, and the transmission rating is determined according to

Table 4. Overall system parameters.

Parameter	Value
Input Voltage	200 V ± 5%
Output Voltage	120 V ± 5%
Output Power	1 kW ± 5%
Switching Frequency	85k Hz ± 1%

, respectively.

The simulation starts with the supply of a 200 Vdc input voltage to the high-frequency inverter, operating at a frequency of 85 kHz, in accordance with SAE J2954 standards [31], using a square wave signal to power the transmission coil (Tx). Subsequently, the resonant tank will function to control the output voltage as calculated. The results are presented in

Table 5. Compensation circuit component parameters.

Compensators	Value
Lr	8.56 μH ± 2%
Cr	409.25 nF ± 2%
Co	40.85 μF ± 2%
Cp	149.61 nF ± 2%
Cs	109.56 nF ± 2%

, which displays the compensatory values in the LCC-S compensators, designed to maintain the output voltage at approximately 120 V. The voltage is then supplied to a dc-to-dc converter to regulate the charging current.

3.2. Simulation of dc-to-dc Buck Regulator Converter

This paper proposes the use of a dc-to-dc Buck converter for simulating battery charging control, as shown in Figure 6. The principles and explanation for its selection were outlined in a previous section. The research team will demonstrate a simulation in which the converter is connected to a WPT using an LCC-S resonant tank. The design and operation of the feedback control circuit is illustrated in Figure 7. This system uses a current to deliver feedback; then, the PI controller attempts to minimize the error to near zero in comparison to the setpoint current.

Normally, a dc-to-dc Buck converter is controlled by two switching devices, which operate at offset intervals corresponding to half the period. Therefore, charging control must be carried out by shifting the duty cycle as specified.

The simulation was conducted using MATLAB/Simulink version 2020a. The obtained results are validated using the simulation outcomes. Figure 8 illustrates the increase in the battery terminal voltage as a result of applying different current setpoints under closed-loop control. The charging process begins at 0 A, with the initial voltage measured at approximately 51.8 V, corresponding to an 80% state of charge (SOC) for a 48 V, 100 Ah battery. As the charging current is increased to 10 A and subsequently to 20 A, the terminal voltage increases to 52.15 V and 52.3 V, respectively.

4. Hardware Implementation Analysis

This section presents the hardware implementation of a 1 kW, 48 V WPT system, as shown in Figure 9, for AGV charging in industrial applications. The system uses an LCC-S compensation topology to maintain a constant output voltage at a coil distance of 15 cm. A low-cost PI controller is implemented on a microcontroller to efficiently regulate the current, offering a practical solution for real-time industrial control. The experimental results confirm stable performance and over 80% efficiency, validating the system’s feasibility for real-world applications.

The hardware implementation setup, as shown in Figure 10, was evaluated in a laboratory environment. A Kikusui PAT500-16T DC power unit (Kikusui Electronics Corporation, Yokohama, Japan) provides the input power to the WPT system. The inverter, which converts the dc input to ac, employs GaN-based MOSFETs, namely TP65H070G4PS 650V/29A (Transphorm Inc., Goleta, CA, USA), as switching devices. Compared to conventional MOSFETs, GaN switches offer a more compact form factor and significantly higher power density.

The inverter is controlled using a C2000 series digital signal processor, TMS320F28335 (Texas Instruments Incorporated, Dallas, TX, USA), which handles system regulation and coordination. The setup includes integrated protection features, such as overvoltage and overcurrent protection, to ensure reliable and safe operation. The resulting high-frequency ac signal is transmitted through an LCC compensator and a coil system configured to allow for adjustable distances between the coils. On the secondary side, a compensator capacitor is connected. Based on preliminary calculations, the output voltage is monitored and regulated to a target value of 120 V, which serves as the input for the battery charging control unit of a 48 V, 100 Ah battery pack. The control system operates in Constant Current Mode (CCM) during the charging process.

The charging control system is designed using a dc-to-dc Buck converter, employing two switching devices for current feedback based on the battery current. A digital signal controller regulates the current to the desired level, with configurable settings ranging from 0 to the rated current. The input voltage utilized in this system benefits from the advantages of the LCC-S resonant compensator. Figure 11a–c illustrate the battery charging operation at an approximate power ranging from 500 to 1000 W, monitored using a Yokogawa DLM3000 oscilloscope (Yokogawa Electric Corporation, Musashino, Japan), with the data recorded and saved in CSV format. The current response, regulated by a PI controller with proportional gains set to Kp = 1.45 and Ki = 300, demonstrates satisfactory performance. The charging current exhibits no overshoot, and the settling time remains within acceptable limits for lithium-based battery charging applications. Figure 11d illustrates a step-up in the battery charging current, increasing from 10 A to 20 A (corresponding to ~500 W to ~1000 W). It can be observed that the current remains well-regulated at the desired level despite maintaining the same Kp and Ki values. This indicates that the charging system does not require any retuning under load variation conditions.

Based on the power levels at various operating points, this study provides additional data on battery charging across different current levels. A graph is presented to show the relationship between the charging current and system efficiency, ranging from 1 A to the rated 20 A, as shown in Figure 12. Additionally, a thermal image captured with a FLUKE TiS20+ camera (Fluke Corporation, Everett, WA, USA) during 1 kW operation is included in Figure 13 to illustrate the system’s thermal behavior. The GaN MOSFET exhibited the highest temperature at approximately 47 °C, followed by the heatsink at 45 °C, the TI TMS320F28335, and the power regulator, while the ambient temperature during the measurement was 25 °C. The efficiency measurements at 1 kW indicate 94.19% efficiency for the inverter, 98.36% for the wireless coil, 97.07% for the rectifier circuit, and 93.97% for the dc-to-dc charging unit.

In summary, the hardware implementation of the proposed 1 kW mid-range WPT system for AGV charging confirms the practical viability of the LCC-S resonant topology combined with a PI-controlled dc-to-dc Buck converter. According to Figure 14, the charging current remains well-regulated across a wide range—from 0 A to 20 A—without the need for controller retuning, highlighting the robustness of the implemented PI controller. A well-damped transient response with a settling time of approximately 2 ms was achieved, ensuring safe and reliable charging suitable for lithium-based AGV batteries. Moreover, the integration of wireless communication for dynamic current adjustment further enhances the system’s industrial applicability. These hardware results validate the proposed WPT architecture as a practical and scalable solution for maintenance-free AGV charging in factory environments.

5. Conclusions

This study presents the comprehensive development of a 1 kW mid-range wireless power transfer (WPT) system for autonomous guided vehicle (AGV) charging, covering system design, simulation, and hardware implementation. An LCC-S resonant compensator was chosen for its ability to maintain stable power transfer across load variations, making it suitable for demanding industrial environments. The simulation results show that during the charging process, the battery voltage rises from 51.8 V to 52.3 V as the current increases from 0 A to 20 A, corresponding to an increase in the state of charge (SOC) for a 48 V, 100 Ah battery. These results confirm proper system behavior and compatibility with dynamic charging profiles.

Hardware validation demonstrates that the system achieves over 80% power transfer efficiency at a coil gap of 15 cm. The PI-controlled dc-to-dc Buck converter effectively regulates the charging current from 0 A to 20 A with no need for retuning. The transient response is well-damped, with a settling time of approximately 2 ms and no overshoot, ensuring safe and stable charging. The use of GaN-based switches and a TMS320F28335 digital signal controller contributes to the system’s high-frequency performance and scalability. Future work will focus on enhancing misalignment resilience, improving thermal design, and extending the platform for multi-vehicle (multi-AGV) dynamic charging, thus promoting greater autonomy and operational uptime in industrial AGV fleets.