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By modeling the typical electromechanical transient of grid-tied PWM inverters, this paper firstly proves that PWM inverters and Rotational Synchronous Generators (RSGs) are similar in physical mechanism and equivalent in mathematical model, and the concept of Static Synchronous Generator (SSG) is thereby developed. Furthermore, the rationality and feasibility of migrating the concepts, tools and...
In this paper, a detailed mathematical presentation of Photovoltaic (PV) generation system, as well as its simulation model based on MATLAB / Simulink is established first. Its inverter-based simplified models, i.e. the switching-function equivalent model and average model, are simulated and compared quantitatively from different aspects. Simulation results reveal that the switching-function equivalent...
Three-phase PWM inverters function as energy converters and grid-connected power generators in renewable energy generation systems, and its dynamic and stability characteristics affect the security and reliability of the entire generator sets and even the connected grid. The three-phase PWM inverters based on the VSG (Virtual Synchronous Generator) technology, which is referred to as the Static synchronous...
In this paper, a thermal model used to determine the cell temperature of a photovoltaic (PV) module is developed. This model takes into account the ambient temperature and wind velocity to predict the performance of a PV module. The validity and utility of the proposed model are assessed by comparing the simulation result with that of the experiment. Finally, it is shown how this model can be effectively...
This paper focuses on the optimal design of Moving Average Filter (MAF). The necessary and sufficient condition for MAF to filter out a group of harmonics with specified orders simultaneously is deduced based on the presented model. Accordingly, the enhanced MAF (EMAF) algorithm is proposed and used for the fast open-loop phase locking of the distorted grid. Compared with the Cascaded Delayed Signal...
Phase synchronization results in distorted grid contain a certain amount of oscillations, failing to meet the requirement of high-performance grid-connected power converters. Moving Average Filter (MAF) and Delayed Signal Cancellation (DSC), as well as their derivations, i.e. Cascaded MAF (CMAF) and Cascaded DSC (CDSC), are main solutions to this problem. In this paper, the mathematical models of...
Fast and accurate detection of instantaneous reactive current in single-phase power system is a pre-requisite for the precise control of STATCOM (Static Synchronous Compensator). A major solution is based on the construction of virtual orthogonal signal in rotational coordinate transformation; however, conventional methods show weaknesses in the speed of detection and the ability of noise and harmonic...
Fast and accurate grid synchronization is essential for grid-connected converter control. The existing phase locking schemes are divided into two categories: closed-loop phase locking (CLPL) and open-loop phase locking (OLPL). OLPL methods show good steady-state performance and strong robustness to the variations and imbalance of the grid, however, the dynamic response is not fast enough due to their...
The conventional mathematic model of PV (Photovoltaic) cells contains logarithmic terms, which is not conducive to derivation calculation in small-signal modeling. The parameters of PV system are coupling due to its double-loop control method, and it's hard to precisely choose controller parameters. To solve these two problems above, this paper is based on PV system connected to an infinite power...
In this paper1, we present the architecture, design, and simulation of an intelligent system for Temperature Monitoring used in metropolitan heating. The system consists of several TelosB-compatible motes, a Nokia uSDCard, and a smart phone. We use TelosB Motes to collect temperature data, and to transport the data to the smart phone. The uSDCard, as the middle layer, connects the smart phone with...
Range-Free algorithms, appealing to people for their cost-efficiency, suffer from the precision problem. Some methods try to combine received signal strength indication (RSSI) with range-free localization algorithms to improve the accuracy, but RSSI is sensitive to the radio irregularity. Based on the well known RIM model, we present a new method of RSSI calibration, namely MRIRC, to mitigate the...
AOTF (Acousto-Optic Tunable Filter) imaging spectrometer is used for hyperspectral imaging. Due to the improvement of AOTF imaging spectral technique, the image acquisition task suited to AOTF faces stricter requirement. The image acquisition system not only has the ability of images collection but also has the ability of portable lightweight, high-speed electronic tunable, low power consumption and...
The temperature system of the HTHP equipment has time-lap, time-variant and non-liner characteristics. It is hard to realize precise tracking control using the traditional PID control. A new temperature control strategy called PID subsection tracking control is developed to track the arbitrary temperature curve for the HTHP equipment. The control software designed based on LABVIEW can realize multi...
Congestion has always been a serious problem for all kinds of communication networks. Wireless sensor networks (WSN) face special difficulties in dealing with congestion due to their unique requirements and constraints. Various congestion control schemes for WSN have been proposed recently. These schemes try to solve the problem either at the MAC layer or through a cross-layer approach. This paper...
For large scale unstructured astronomical data documents, the simple index method often results in high communication cost and slow query processing. Based on the characteristics of domain specific astronomical data and the quantitative tracing and analyzing results, a query terms similarity calculation formula is provided. An index clustering algorithm is designed to generate many small clusters...
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