A simple approach to calculate active power of electrosurgical units

Abstract Introduction: Despite of more than a hundred years of electrosurgery, only a few electrosurgical equipment manufacturers have developed methods to regulate the active power delivered to the patient, usually around an arbitrary setpoint. In fact, no manufacturer has a method to measure the active power actually delivered to the load. Measuring the delivered power and computing it fast enough so as to avoid injury to the organic tissue is challenging. If voltage and current signals can be sampled in time and discretized in the frequency domain, a simple and very fast multiplication process can be used to determine the active power. Methods This paper presents an approach for measuring active power at the output power stage of electrosurgical units with mathematical shortcuts based on a simple multiplication procedure of discretized variables – frequency domain vectors – obtained through Discrete Fourier Transform (DFT) applied on time-sampled voltage and current vectors. Results Comparative results between simulations and a practical experiment are presented – all being in accordance with the requirements of the applicable industry standards. Conclusion An analysis is presented comparing the active power analytically obtained through well-known voltage and current signals against a computational methodology based on vector manipulation using DFT only for time-to-frequency domain transformation. The greatest advantage of this method is to determine the active power of noisy and phased out signals with neither complex DFT or ordinary transform methodologies nor sophisticated computing techniques such as convolution. All results presented errors substantially lower than the thresholds defined by the applicable standards.

摘要与引言：尽管电外科技术已历经百余年发展，但仅有少数电外科设备制造商开发出了可调节输出至患者的有功功率（active power）的方法，且通常仅基于任意设定值进行功率调节。事实上，目前尚无制造商能够实现对实际输送至负载的有功功率的精准测量。准确测量实际输送功率并快速完成计算以避免对人体生物组织造成损伤，是一项极具挑战性的任务。若可对电压与电流信号进行实时采样，并在频域完成离散化处理，即可通过简洁且极高效的乘法运算确定有功功率。

研究方法：本文提出了一种针对电外科设备输出功率级有功功率的测量方案，该方法基于对离散化变量——频域向量——的简易乘法运算，而这些离散化变量可通过对时域采样得到的电压、电流向量施加离散傅里叶变换（Discrete Fourier Transform，DFT）获取，同时辅以数学简化手段。

研究结果：本文给出了仿真实验与实际物理实验的对比结果，所有结果均符合对应行业标准的要求。

研究结论：本文通过分析对比了两种有功功率计算路径：其一为基于经典电压、电流信号的解析计算法，其二为仅将离散傅里叶变换（DFT）用于时域-频域转换、基于向量运算的计算方法。本方法的最大优势在于，即便面对存在噪声与相位偏移的信号，也无需采用复杂的DFT或常规变换手段，亦无需使用卷积等复杂计算技术，即可完成有功功率的测定。所有测试结果的误差均显著低于相关行业标准规定的阈值。