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This paper presents an enhanced control method for a doubly-fed induction generator (DFIG) basedwind-power generation system with series grid-side converter (SGSC) under unbalanced grid voltage conditions. The behaviors of the DFIG system with SGSC during network unbalance are described. By injecting a series control voltage generated from the SGSC to balance the stator voltage, the adverse effects of voltage unbalance upon the DFIG, such as stator and rotor current unbalances, electromagnetic torque and power pulsations can be removed, then the conventional vector control strategy for the rotor-side converter (RSC) remains in full force under unbalanced conditions. Meanwhile, three control targets for the parallel grid-side converter (PGSC) are identified, including eliminating the oscillations in total active power or reactive power, or eliminating negative-sequence current injected to the grid. Furthermore, a precise current reference generation strategy for the PGSC has been proposed for the PGSC to further improve the operation performance of the whole system. Finally, the proposed coordinated control strategy for the DFIG system with SGSC has been validated by the simulation results of a 2 MW DFIG-based wind turbine with SGSC and experimental results on a laboratory-scale experimental rig under small steady-state grid voltage unbalance. Index Terms-wind-power generation, doubly-fed induction generator (DFIG), grid voltage unbalance, series grid-side converter (SGSC), enhanced control NOMENCLATUREThis article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. 2 u s and u g Stator and grid voltage vectors u seires Series injected voltage vector of SGSC referred to stator-side i s, i r Stator and rotor current vectors i series SGSC current vector referred to stator-side i total Total current vector of the DFIG system P s and Q s Stator output active and reactive powers P r and Q r Rotor output active and reactive powers P g and Q g PGSC output active and reactive powers P series and Q series Active and reactive powers through SGSC P total and Q total Total output active and reactive powers of the DFIG system with SGSC T e Electromagnetic torque u dc Common dc-link voltage ω Synchronous angular speed θ g Grid voltage angle s Slip C Common dc-link capacitance Subscripts + andPositive-and negative-sequence components av Average component sin and cos Sine and cosine oscillating components abc Stationary abc-axis dq Synchronous dq-axis s and r Stator and rotor g and series PGSC and SGSC Superscripts + andPositive and negative synchronous reference frames * Reference value ^ Conjugate complex

Residential solid fuel combustion (RSFC) is a key cause of air pollution in China. In these serial studies, field measurements of RSFC from 166 rural households in eastern China were conducted to update the database of emission factors (EFs) and chemical profiles of gaseous and particulate organic pollutants, and the present study focuses on the intermediate volatile organic compounds (IVOCs), which are precursors of secondary organic aerosol (SOA). The results show that the averaged EFs of IVOCs (EFIVOC) for crop straw, fuelwood, and coal are 550.7 ± 397.9, 416.1 ± 249.5, and 361.9 ± 308.0 mg/kg, respectively, which are among the EFIVOC of gasoline vehicle, diesel vehicle, non-road machinery, and heavy fuel oil vessel, and are significantly affected by fuel, stove, and combustion efficiency. The percentages of normal alkanes (n-alkanes), branched alkanes (b-alkanes), polycyclic aromatic hydrocarbons (PAHs), and unresolved complex mixture from RSFC are 3.5 ± 1.6, 8.0 ± 3.7, 17.6 ± 6.7, and 70.9 ± 8.1%, respectively, and the compositions are featured by lower b-alkanes and higher PAHs than those of vehicle sources. The proportions of some individual n-alkanes and PAHs (such as n-C12–n-C15, naphthalene, and its alkyl substituents) can be used as indicators to differentiate RSFC from vehicle sources, while methoxyphenols can be used to distinguish biomass burning from coal combustion. Based on China’s energy statistics, the total IVOC emissions from RSFC in 2014 were 175.9 Gg. These data will help to update the IVOC emission inventory and improve the estimates of SOA production in China.

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