The virtual synchronous generator (VSG) technology of inverter is widely used to provide the inertia and damping support for power system. However, an additional measurement device PLL (phase-locked loop) is required in the virtual synchronous generator grid connection to track the voltage phase, amplitude, and frequency, which restricts the flexible output of the distributed power generation system. To tackle this challenge, a method for grid-connected control of virtual synchronous generator based on virtual impedance is proposed. It is assumed that there is a virtual power exchange between the synchronous machine and the power grid when the virtual synchronous generator is off-grid, the virtual impedance is developed to calculate the virtual current, and when the virtual current is zero, the output voltage of the VSG can be synchronized with the voltage of the power grid, thereby seamlessly switching between off-grid and grid-connected VSG. A semiphysical simulation platform is built based on RT-LAB; simulation and experimental results show that the proposed grid synchronization control strategy of the VSG can achieve seamless transform between different VSG modes, which is simpler than the conventional synchronization control, while having a good active and reactive power tracing performance.
With the rapid development of laser technology, information technology, and materials, the detection of trace gas has been taken to a new level. Advanced analytical methods were invented, for example, gas chromatography, mass spectrometry, chemical sensors, absorption spectrum, and so forth. With the detailed data gathered from new high-tech equipment, we can predict and diagnose diseases such as diabetic ketoacidosis, irritable bowel syndrome, lung cancer and so on. However, there is still a large amount of exhaled gas that has not been discovered, which means that breath analysis of exhaled gas is a very promising field in the future. Non-invasive breath diagnosis and monitoring technology have attracted huge attention from all over the world. Using exhaled gas to diagnose and monitor human disease has numerous advantages for being non-invasive, convenient and environment friendly.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.