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In order to reduce the cost and the size of a single-phase to three-phase power converter, an electrolytic capacitor-less single-phase to three-phase inverter is proposed. As the system does not have energy storage, such as an electrolytic capacitor, it results in source current harmonics due to the spatial harmonics of the motor. Adding an inductor for filtering the source current harmonics increases the cost and size of the system. In order to improve the source current waveform without adding passive components, it is necessary to reduce the source current harmonics via inverter control. However, when the inverter control reduces the source current harmonics, voltage saturation of the inverter causes source current distortion. At the rated speed and load, the voltage saturation region amounts to 40–50% of the source period, and the source current harmonics do not meet the guideline of IEC 61000-3-2. This paper proposes a direct dc-link current control (DDCCC) considering voltage saturation and the dq -axis current reference calculation for applying the DDCCC, which reduces the source current harmonics below the guideline. The effectiveness of the proposed method is verified through experiments. [ABSTRACT FROM PUBLISHER]

We investigate a thermally isolated quantum many-body system with an external control represented by a step protocol of a parameter. The propagator at each step of the parameter change is described by thermodynamic quantities under some assumptions. For the time evolution of such systems, we formulate a path integral over the trajectories in the thermodynamic state space. In particular, for quasistatic operations, we derive an effective action of the thermodynamic entropy and its canonically conjugate variable. Then, the symmetry for the uniform translation of the conjugate variable emerges in the path integral. This leads to the entropy as a Noether invariant in quantum mechanics.