Current Issue : January - March Volume : 2018 Issue Number : 1 Articles : 5 Articles
Grid-connected LCL-filtered inverters are commonly\nused for distributed power generators. The LCL\nresonance should be treated properly. Recently, many\nstrategies have been used to damp the resonance, but the\nrelationships between different damping strategies have not\nbeen thoroughly investigated. Thus, this study analyses the\nessential mechanisms of LCL-resonance damping and\nreviews state-of-the-art resonance damping strategies.\nExisting resonance damping strategies are classified into\nthose with single-state and multi-state feedback. Singlestate\nfeedback strategies damp the LCL resonance using\nfeedback of a voltage or current state at the resonance\nfrequency. Multi-state feedback strategies are summarized\nas zero-placement and pole-placement strategies, where the\nzero-placement strategy configures the zeros of a novel\nstate combined by multi-state feedback, while the poleplacement\nstrategy aims to assign the closed-loop poles\nfreely. Based on these mechanisms, an investigation of\nsingle-state and multi-state feedback is presented, including\ndetailed comparisons of the existing strategies. Finally,\nsome future research directions that can improve LCL-filtered\ninverter performance and minimize their implementation\ncosts are summarized....
The economic dispatch problem of a virtual power plant (VPP) is becoming non-convex\nfor distributed generators� characteristics of valve-point loading effects, prohibited operating zones,\nand multiple fuel options. In this paper, the economic dispatch model of VPP is established and then\nsolved by a distributed randomized gradient-free algorithm. To deal with the non-smooth objective\nfunction, its Gauss approximation is used to construct distributed randomized gradient-free oracles\nin optimization iterations. A projection operator is also introduced to solve the discontinuous variable\nspace problem. An example simulation is implemented on a modified IEEE-34 bus test system, and\nthe results demonstrate the effectiveness and applicability of the proposed algorithm...
This paper proposes an energy and reserve joint dispatch model based on a robust\noptimization approach in real-time electricity markets, considering wind power generation\nuncertainties as well as zonal reserve constraints under both normal and N-1 contingency conditions.\nIn the proposed model, the operating reserves are classified as regulating reserve and spinning reserve\naccording to the response performance. More specifically, the regulating reserve is usually utilized to\nreduce the gap due to forecasting errors, while the spinning reserve is commonly adopted to enhance\nthe ability for N-1 contingencies. Since the transmission bottlenecks may inhibit the deliverability of\nreserve, the zonal placement of spinning reserve is considered in this paper to improve the reserve\ndeliverability under the contingencies. Numerical results on the IEEE 118-bus test system show the\neffectiveness of the proposed model....
Stochastic noises have a great adverse effect on the prediction accuracy of electric power load. Modeling online\nand filtering real-time can effectively improve measurement accuracy. Firstly, pretreating and inspecting statistically\nthe electric power load data is essential to characterize the stochastic noise of electric power load. Then, set order\nfor the time series model by Akaike information criterion (AIC) rule and acquire model coefficients to establish\nARMA (2,1) model. Next, test the applicability of the established model. Finally, Kalman filter is adopted to process\nthe electric power load data. Simulation results of total variance demonstrate that stochastic noise is obviously\ndecreased after Kalman filtering based on ARMA (2,1) model. Besides, variance is reduced by two orders, and every\ncoefficient of stochastic noise is reduced by one order. The filter method based on time series model does reduce\nstochastic noise of electric power load, and increase measurement accuracy....
This paper presents a method to determine transmission power based on power amplifier\n(PA) operations in order to improve the energy efficiency (EE) of a large-scale (LS) Multiple Input\nMultiple Output (MIMO)-OFDM system, which is a multi-carrier multiple antenna system with a\nlarge amount of transmitter (TX) antennas. Regarding the EE improvement, we propose two kinds\nof PA operation schemes: increasing the effective TX power (ITXP) and reducing the PA power\nconsumption (RPC) assuming that a reduction of peak-to-average power ratio is applied in the\nappropriate manner. Closed-form expressions of relative EE are derived for both schemes, and the\nrelative EE of the ITXP scheme is shown to depend on the precoding method that is applied to\nreduce the inter-user interference, while that of the RPC scheme is independent of the precoding\nmethod. The relative EE difference between the ITXP and the RPC schemes is also shown to rely on\nthe occupation ratio of the PA power consumption over the total power consumption. Thus, the EE\ncan remarkably improve by selecting the appropriate scheme based on the circumstances. The results\nof a simulation also validate the derived closed-form expression of the relative EE....
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