The fourwire voltage source inverters have become an advisable interfaced converter between the source and loads. However, the switching state of the Finite Control Set Model Predictive control does not change regularly in each cycle, which results in variable switching frequency of the inverter switch and large ripple of the output power. In addition, the direction and size of the inverter output voltage are fixed under the traditional FCSMPC control, which may not reach the boundary within the whole control track. Therefore, this paper proposes an online duty cycle modulation predictive control based on capacitor split four wire inverter. This strategy takes into account the advantages of fast dynamic response of FCSMPC and fixed switching frequency of modulation strategy, so the controller can achieve fixed switching frequency and zero error tracking at low sampling rates.

In order to further reduce the cost of wind power, employing 15 MW or even higher capacity wind turbine has been the major development trend in the future wind energy market. This paper has developed the soil structure interaction model of the IEA 15 MW monopile wind turbine using a set of linear springs by improving the capability of FAST due to the demand of investigating the SSI effect on the dynamic responses of nextgeneration large offshore wind turbines. The nacelle vibration and bending moment of the support structure under normal power production and extreme conditions are obtained. The results indicate that the ignorance of SSI effect significantly underestimates the towertop and mudline bending moments under power production load cases. The SSI effect has an insignificant influence on the dynamic responses of the wind turbine under the extreme conditions. Specifically, the fatigue damage of the support structure at the mudline is only predicted with an error lower than 3% under the 50year return period extreme condition. Nonetheless, the SSI effect has a dominant influence for the low wind speed conditions. The tower top and mudline bending moments are underestimated by 37.6% and 20.1%, respectively, if the SSI effect is ignored. The axial mode of the foundation is activated, resulting in an intense nacelle vibration and a huge increase to the fatigue damage of the support structure. The study has verified that the SSI effect is mandatorily considered in the design of large offshore wind turbine structures.

In order to solve the problem of unified setting of yaw control parameters of wind turbines and the delay of yaw startup of wind operation, a yaw control parameter optimization method based on wind direction fluctuation characteristic evaluation and multiobjective particle swarm optimization algorithm was proposed. The yaw control parameters under different wind speed ranges were optimized by taking the power generation of the unit and the rotation Angle of the engine room under yaw control as optimization objectives. A yaw control strategy optimization method based on VMDEEMD –LSTM –LSSVM wind condition prediction model is proposed. Through predicting the average wind speed in a period of time, the optimized yaw control parameters are set in advance, and through predicting the wind direction, whether yaw starts in advance to the wind action is judged and controlled. The results of example analysis show that this strategy can effectively improve the power generation of wind turbines and reduce the cabin rotation Angle under yaw control, which is beneficial to the economic benefit of wind farms.

The key regulatory role of trace elements(TEs) in anaerobic digestion systems has been established, but their intrinsic effects and mechanisms have not yet been fully elucidated. This study investigates the biological effects of TEs on biogas fermentation by examining the dynamic distribution of TEs under different inoculum/substrate (I/S) conditions in an anaerobic digestion system. It aims to clarify the interaction between the chemical form of TEs and the key influencing factors and microbial communities in the anaerobic fermentation process. Results from the 10 batches of experimental anaerobic digestion of glucose showed an 80.7% enhancement in cumulative methane production with the addition of TEs at an I/S ratio of 1.5. Among the three TEs (Fe, Co and Ni) added, the different chemical forms of elemental Fe showed the strongest correlation with pH, alkalinity, volatile fatty acids and ammonia nitrogen content in anaerobic digestion. The pH value was notably correlated with the four chemical forms of Fe. When the anaerobic digestion system operates stably, the relative abundance of Methanosaeta was the highest (53.8%), while the relative abundance of Methanosarcina was the highest (34.0%) when the anaerobic digestion system operates abnormally.

In this paper, Miscanthus lutarioriparius (ML) cellulose was used as the raw material to produce bioethanol by a fedbatch synchronous saccharification and fermentation process. The effects of initial substrate concentration, final substrate concentration, and feeding times on ethanol yield were analyzed. The orthogonal experiments were used to optimize the process, and the optimal process parameters were obtained as follows: Initial substrate concentration was 17.5%, and the batch feeding was conducted twice until the final substrate concentration was 32.5%. Under these conditions, the highest ethanol content could reach to 70.15 g/L, which increased by 23.36% compared to the synchronous saccharification and fermentation process without fedbatch. The material balance analysis was conducted on the basis of the optimal process. The structure of ML cellulose before and after fermentation was characterized by scanning electron microscopy, fourier transform infrared spectroscopy, and Xray diffraction. The results showed that the enzymatic saccharification and fermentation process would change the internal structure of ML cellulose, break the hydrogen bond or covalent bond, and increase the crystallinity of the substrate.

To promote the realization of the "dual carbon" goal, the distributed new energy in different regions of the virtual power plant is coordinated and optimized through lowcarbon power generation. A multi region virtual power plant coordinated and optimized scheduling technology based on the Grey Wolf Optimization Algorithm is proposed. Firstly, construct an operational optimization model with the best economic benefits, connecting virtual power plants in different regions with distributed new energy, and jointly scheduling wind and solar power generation units and carbon capture units; Secondly, due to the difficulty in solving, strong nonlinearity, and high dimensionality of the constructed model, the advantages of the Grey Wolf Optimization Algorithm such as high search efficiency, fast convergence speed, and few optimization parameters are utilized to optimize the model. At the same time, an improved Grey Wolf Optimization Algorithm is proposed to improve the algorithm's global optimization ability and solve the problem of premature and local optima in the later stage of the algorithm; Finally, through simulation verification, the proposed method can achieve optimal scheduling of virtual power plants in different regions, reducing carbon emissions and net costs.

Aiming at the optimal economic operation of energy management strategy for multi port configuration of AC/DC flexible interconnection system, this article proposes an optimization method for multi port AC/DC flexible joint energy control system based on improved Pelican algorithm, which is based on photovoltaic power generation curve, high fit between peak and valley electricity price ranges, and energy storage control. Construct an optimization model for a multi terminal oral DC flexible joint energy control system, with constraints on DC bus voltage, power control unit capacity, and power balance, to comprehensively consider the minimum network loss, optimal economy, and optimal energy storage charging/discharging state. Based on the Pelican optimization algorithm, the model constructed is solved by introducing random mass disturbance behavior to improve the global search ability of the algorithm and prevent the model from getting stuck in local optima during solution. After simulation verification, the method proposed in the article can achieve optimal scheduling of multi terminal oral DC flexible joint energy control system.

In order to guarantee capacity adequacy for the power system with a high penetration of renewable energy resources, it is necessary to establish a capacity market mechanism that is compatible with the energy market. From the perspective of investment decisionmaking, this paper analyzes the efficiency of capacity market mechanism in the power system with high proportion of renewable energy by studying supplier's investment behavior in capacity energy market with high integration of renewable energy. Firstly, a threelayer optimization model is established for the investment decision problem, including unit decisionmaking, capacity market and energy market model. Then since the model is difficult to solve directly, a phased loop iterative solution algorithm is proposed, being able to solve the problem with the capacity and energy market decoupled. Finally, based on the actual data of a certain provincial network, this paper uses the proposed method to compare the effects of energyonly market and capacityenergy market on capacity adequacy for the power system with a high proportion of renewable energy.

This research investigated the effects of adding zerovalent iron (ZVI), activated carbon (AC) and magnetite (Mt)on the performance and microbiological properties of twophase anaerobic digestion of food waste. The results indicated that the addition of ZVI in the acidogenic reactor with AC and Mt in the methanogenic reactor showed the best effect on the anaerobic digestion performance. In the acidogenic reactor, the addition of ZVI increased the total volatile fatty acid concentration by 46.4%~47.9% compared with the control group, which provided better initial condition for the methanogenic reactor and significantly shortened the retardation time.In the methanogenic reactor, the addition of AC and Mt improved the stability of system, and the cumulative methane production was increased by 28.1%~68.4% compared with the control group.

Bifacial photovoltaic modules are designed to generate electricity by absorbing both front and rear irradiance at the same time, which enhances the power generation compared to monofacial photovoltaic modules. In this paper, a twomode power control strategy is proposed based on bifacial photovoltaic modules. Firstly, the modified equivalent irradiation model is used to construct a parametric model of the electrical characteristics of bifacial photovoltaic modules; according to the power output characteristics of bifacial photovoltaic modules and then based on the judgement of irradiance, a twomode control strategy with the maximum power output and the power reserve control is proposed; finally, the model is used to experiment and simulate the 365 W crystalline silicon bifacial photovoltaic module. The experimental results show that the relative error between the predicted power and the measured power is less than 3.5%, and the relative error of the voltage at the maximum power point under the measured condition is 0.3%. The twomode power control strategy can achieve the realtime active power reserve without increasing the energy storage, in which the maximum active standby capacity at the transient equivalent irradiance of 1006 W/m² is 69 W, and at the transient equivalent irradiance of 1031 W/m² is 78 W.