Abstract : Addressing the shortcomings of current oilfield heating power supply control systems, such as their simplistic and crude design and inability to automatically adjust output frequency, a novel variable frequency heating power supply for oilfields is designed. The design of its main parameters and the selection criteria for components are presented. This paper utilizes frequency tracking and phase-shift control technology to ensure the power supply output frequency tracks the load resonant frequency, guaranteeing optimal heating efficiency. Experiments show that this power supply device can effectively improve heating efficiency and ensure energy-saving and economical operation. Keywords : Variable frequency drive; Heating; Power supply; Phase-shift control 1 Introduction China possesses abundant heavy oil reserves, with proven reserves alone reaching over a billion tons. Heavy oil, characterized by its high viscosity, high pour point, and high wax content (the so-called "three highs"), presents significant challenges to extraction and transportation. Heavy oil extraction primarily relies on thermal methods such as steam injection, steam drive, reservoir combustion, hot water drive, and electric heating. Among these, the hollow sucker rod electric heating method offers significant advantages, including uniform heating, low investment, and low operating costs. However, conventional hollow rod heating power supplies use a 50Hz power frequency. Low frequency and poor skin effect heating result in low heating efficiency, low effective capacity utilization, and a high susceptibility to three-phase imbalance and inconvenient operation. Currently, medium-frequency heating power supplies for oilfields partially solve these problems, but in practical applications, they still suffer from simple control and the inability to automatically adjust the power output frequency according to load changes. These commonly used medium-frequency heating power supplies adjust the frequency appropriately at the beginning of heating, selecting the frequency corresponding to the maximum current as the operating frequency to make the load approximately work in a resonant state to ensure maximum heating efficiency. However, due to the influence of temperature and environmental factors during heating, the inductance of the hollow sucker rod and cable changes, inevitably disrupting the load's resonant operating state and reducing the power supply's heating efficiency. Furthermore, determining the operating frequency by adjusting the current for each monitoring cycle not only increases the workload of personnel but also reduces work efficiency. To address these issues, this paper proposes a novel variable frequency heating power supply for oilfields. It utilizes frequency tracking and phase-shift control technology to make the power supply output frequency track changes in the load's resonant frequency, thereby enabling the system to achieve optimal operating conditions and energy-saving effects. 2. Analysis of Variable Frequency Heating Principle The heating element of the variable frequency power supply for oilfields consists of the core sucker rod and the cable inside the hollow sucker rod. When alternating current passes through the cable and the hollow sucker rod, heat is generated, achieving conductive heating of the heavy oil. The hollow sucker rod is the main heating element. On the one hand, the skin effect of the steel hollow sucker rod is much stronger than that of the copper cable, and the impedance of the hollow sucker rod is much greater than that of the copper cable. On the other hand, the steel hollow sucker rod is in an alternating electric field. As the power supply output frequency increases, the magnetic induction intensity of the current increases, and the heating caused by the hysteresis effect cannot be ignored. [b][align=center]For more details, please click: A New Type of Variable Frequency Heating Power Supply Design for Oilfields[/align][/b]