This paper proposes the solution for decreasing of the reciprocating compressor noise and vibrations, which happens at stoppage. These vibrations and resulting noise are caused by the gas pressure in the cylinder, which impacts the compressor's piston and can reverse the motor at stoppage. To avoid this situation the motor must be stopped, when the gas is not pressurized, i.e., at the desired mechanical position, however motor is not equipped with a mechanical position sensor as the control system utilizes an electrical speed and position estimator. As a rule, it is impossible to estimate the mechanical position using an electrical position, however it has been noticed that at low speeds a detrimental feature of reciprocating compressors – varying load torque can help identify the mechanical position. Load torque impacts the quadrature current, making it oscillate at the mechanical frequency of the motor, so this mechanical frequency and position can be estimated using a Phased Locked Loop (PLL) algorithm, applied to the quadrature current.

中文翻译：

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静压停止的往复式压缩机的机械位置估计

本文提出了减少往复式压缩机噪音和振动（停止时发生）的解决方案。这些振动和由此产生的噪音是由气缸内的气压引起的，气压会影响压缩机的活塞，并可能在停机时使电动机反转。为了避免这种情况，必须在未加压气体时（即，在所需的机械位置）停止电动机，但是由于控制系统利用电速度和位置估计器，因此电动机未配备机械位置传感器。通常，不可能使用电气位置来估算机械位置，但是已经注意到，在低速运行时，往复式压缩机的有害特征–改变负载扭矩可以帮助识别机械位置。负载转矩会影响正交电流，