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Under the background of a green, low carbon economy, it is significant to accurately estimate the future CO2 emissions of countries with significant CO2 emissions for developing the world's green economy. A new Nonlinear Grey Bernoulli and BP neural network combined model (BP-ONGBM (1,1) model) have been proposed to study the CO2 emissions of China, the USA, the European Union, India and Japan. Firstly, the Particle Swarm Optimization (PSO) algorithm is optimized using the Artificial Fish Swarm Algorithm (AFSA). Then, the background value of the ONGBM (1,1) model is dynamically optimized. Based on the linearization of the model, the time response function is derived. Then, the ONGBM (1,1) model is combined with the BP neural network model. An improved PSO algorithm determines the combined weight and the background value coefficient. Finally, according to the observation data from 2010 to 2021 in the Emissions Database for Global Atmospheric Research 2022, the model is established to calculate the CO2 emissions of the selected countries from 2022 to 2026 and compared with the prediction results provided by multiple competitive models. The empirical application shows that the proposed BP-ONGBM (1,1) model is significantly better than other competitive models. [ABSTRACT FROM AUTHOR]

This paper proposes a novel three-phase nine-switch ac/ac converter topology. This converter features sinusoidal inputs and outputs, unity input power factor, and more importantly, low manufacturing cost due to its reduced number of active switches. The operating principle of the converter is elaborated; its modulation schemes are discussed. Simulated semiconductor loss analysis and comparison with the back-to-back two-level voltage source converter are presented. Finally, experimental results from a 5-kVA prototype system are provided to verify the validity of the proposed topology. Index Terms--AC/AC converter, pulsewidth modulation (PWM), reduced switch count topology.

A novel control scheme for permanent-magnet synchronous generator is proposed in this paper, where a current-source converter is employed as the bridge between the generator and the grid for high-power wind energy conversion systems. In these medium voltage (2.3-13.8 kV) level applications, current-source converters not only have inherent advantages, but also present some challenges for controller design due to the dc link choke and filter capacitors. The control strategy is developed to achieve better performances with improved dynamic response. By maintaining the grid-side converter modulation index at the highest possible level, the proposed control scheme reduces the dc link current to a minimum value to reduce converter conduction loss. The system's dynamic performance is further improved by adopting generator-side power feedforward. Simulation and experimental results are provided to verify the proposed control scheme. Index Terms--Current source converter (CSC), permanent-magnet synchronous generator (PMSG), power feedforward control, wind energy conversion.

The development of the brushless doubly-fed induction generator (BDFIG) system and flexible power flow controller for the wind energy conversion is proposed in this paper. The system employs two cascaded induction machines to eliminate the brushes and copper rings in the traditional DFIG. The dynamic model of BDFIG with two machines' rotor electromechanically interconnected is presented and the control strategy for flexible power flow control is developed. The independent control of the active and reactive power flows is achieved by means of a four quadrant power converter under the closed-loop stator flux oriented control scheme. The experimental results obtained verify the proposed controller scheme, which allows wide operational range and reactive power control. Index Terms--Brushless doubly-fed induction generator (BDFIG), maximum power point tracking (MPPT), power flow, wind energy conversion.

A newly developed electrothermal calculation method is implemented to estimate the power loss and working temperature of insulated gate bipolar transistor (IGBT) devices. Based on the measurement of the IGBT's characteristics, the exact estimation of power loss considering the junction temperature is introduced. Then, the thermal network is used to calculate the working temperature. The comparison between experimental and calculation results shows that this method is effective as a designing step with only the time-domain voltage and current data obtained from simulation results. Index Terms--Insulated gate bipolar transistor, junction temperature, power loss.