Ladder Time Stepwise Inertia Coordinated Control Method of Multiple Wind Farms to Suppress System Frequency Secondary Drop

Currently,both regulated and deregulated power trading exist in China’s power system,which has caused imbalanced funds in the electricity market.In this paper,a simulation analysis of the electricity market with wind energy resources is conducted,and the calculation methods of unbalanced funds are investigated systematically.In detail,the calculation formulas of unbalanced funds are illustrated based on their definition,and a two-track electricity market clearing model is established.Firstly,the concept of the dual-track system is explained,and the specific calculation formulas of various types of unbalanced funds are provided.Next,considering the renewable energy consumption,the market clearing model based on DC power flow is constructed and solved;by combining fitting methods of mid-and long-term curves,the unbalanced funds are calculated based on clearing results and formulas.

Development Trend of Energy and Key Points of Ecological Environment Protection in China's "14^(th) Five-Year Plan" Period

From the changes of total primary energy consumption and primary energy consumption structure,installed capacity and power generation of secondary energy(electricity),etc.,the development characteristics of China's energy structure in the"13^(th) Five-Year Plan"period was comprehensively studied.Combined with the complexity of the international situation,the diversification of the domestic energy system,the intelligence of the energy industry,etc.,the situation and challenges faced by China's energy development were deeply discussed in the four aspects of energy security,energy low-carbon transformation,energy system efficiency,and energy technology level.From the angle of ecological environment protection,the development of energy in the"14^(th) Five-Year Plan"period in China was analyzed,and some policies and measures were put forward.

Design of a Multifrequency Signal Parameter Estimation Method for the Distribution Network Based on HIpST

The application of traditional synchronous measurement methods is limited by frequent fluctuations of electrical signals and complex frequency components in distribution networks.Therefore,it is critical to find solutions to the issues of multifrequency parameter estimation and synchronous measurement estimation accuracy in the complex environment of distribution networks.By utilizing the multifrequency sensing capabilities of discrete Fourier transform signals and Taylor series for dynamic signal processing,a multifrequency signal estimation approach based on HT-IpDFT-STWLS(HIpST)for distribution networks is provided.First,by introducing the Hilbert transform(HT),the influence of noise on the estimation algorithm is reduced.Second,signal frequency components are obtained on the basis of the calculated signal envelope spectrum,and the interpolated discrete Fourier transform(IpDFT)frequency coarse estimation results are used as the initial values of symmetric Taylor weighted least squares(STWLS)to achieve high-precision parameter estimation under the dynamic changes of the signal,and the method increases the number of discrete Fourier.Third,the accuracy of this proposed method is verified by simulation analysis.Data show that this proposed method can accurately achieve the parameter estimation of multifrequency signals in distribution networks.This approach provides a solution for the application of phasor measurement units in distribution networks.

Multi-energy Storage System Model Based on Electricity Heat and Hydrogen Coordinated Optimization for Power Grid Flexibility

Based on decreasing the flexibility of the power grid through the integration of large-scale renewable energy,a multi-energy storage system architectural model and its coor-dination operational strategy with the same flexibility as in the pumped storage power station and battery energy storage system(BESS)are studied.According to the new energy fluctuation characteristics and the different peak valley parameters in the power grid,this paper proposes a electricity heat hydrogen multi-energy storage system(EHH-MESS)and its coordination and optimization operational model to reduce the curtailment of wind power and photovoltaic(PV)to the power grid and improve the flexibility of the power grid.Finally,this paper studied the simulation model of an energy storage optimization control strategy after the multi-energy storage system is connected to the distribution networks,and analyzed three operational modes of the multi-energy storage system.The simulation results show that the EHH-MESS proposed in this paper has a better power grid regulation flexibility and economy,and can be used to replace the battery energy storage system based on MATLAB.

A Model of Electro-thermal Hybrid Energy Storage System for Autonomous Control Capability Enhancement of Multi-energy Microgrid

In view of the problem of low self-service capability of the microgrid due to the high operating cost and low capacity of the traditional battery energy storage system.In this paper,an electrothermal hybrid energy storage model based on electricity,hydrogen and thermal energy conversion and storage is introduced,and a microgrid autonomous operational strategy is proposed.First,the addition of the power to hydrogen transfer equipment in the traditional combined heat and power(TCHP)system without battery energy storage is studied,and a micro gas turbine,electric to hydrogen transfer equipment and electric boiler based electrothermal energy storage system(ETSS)model is established.Aiming at the lowest comprehen-sive operating cost of multiple energy sources in a microgrid and maximizing the consumption of curtailed wind,the multi-objective scheduling model of an electrothermal hybrid energy storage system is established,then the multi-energy autonomous operational strategy of a microgrid is proposed.Lastly,the simulation of a multi-energy microgrid in Northeast China is taken as an example.The results of the simulation showed that compared with a combined heat and power microgrid system considering conventiona battery energy storage,a multi-energy microgrid system using electrothermal hybrid energy storage has better flexibility and economy,and can improve wind power accommodation.

Availability estimation of wind power forecasting and optimization of day-ahead unit commitment

Due to the uncertainty of the accuracy of wind power forecasting,wind turbines cannot be accurately equated with dispatchable units in the preparation of a dayahead dispatching plan for power grid.A robust optimization model for the uncertainty of wind power forecasting with a given confidence level is established.Based on the forecasting value of wind power and the divergence function of forecasting error,a robust evaluation method for the availability of wind power forecasting during given load peaks is established.A simulation example is established based on a power system in Northeast China and an IEEE 39-node model.The availability estimation parameters are used to calculate the equivalent value of wind power of the conventional unit to participate in the dayahead dispatching plan.The simulation results show that the model can effectively handle the challenge of uncertainty of wind power forecasting,and enhance the consumption of wind power for the power system.

A Robust Control Strategy to Improve Transient Stability for AC-DC Interconnected Power System with Wind Farms

In view of the variable parameters that affect the transient stability of electromagnetic torque and mechanical torque balance in AC-DC system,and the uncertainty of wind power in large-scale interconnection of wind farm.This paper proposes a linear parameter varying(LPV)robust feedback control method for transient stability of interconnected systems.The proposed LPV robust feedback control method uses the DC channel power control and the mechanical power in the interconnected system as the control target to improve the transient stability of the interconnected system with wind farm channel.Firstly,aiming at the strong nonlinear characteristics of the interconnected system,the power balance and the wind power output uncertainty in the transient process,the transient process is designed as a linear model of variable parameters.Then,the H∞robust output feedback controller is designed according to the LPV model.The transient stability control strategy topology and transfer function of the interconnected system are proposed.Finally,the proposed scheme is verified by an interconnected system formed by four equal-value grids through AC and DC lines in a digital simulation platform.The results show that the LPV robust feedback control model proposed in this paper has better response characteristics and transient stability control effects for interconnected systems with wind power weak sendingend system.

Effects of Mn-doping on the structure and electrical properties of Sm-PMN-PT piezoceramics

MnO_(2)-modified Pb_(0.9625)Sm_(0.025)(Mg_(1/3)Nb_(2/3))_(0.71)Ti_(0.2)9O_(3) ceramics were prepared via a solid-state reaction approach.Results of detailed characterizations revealed that the addition of MnO_(2) has influence on the grain size,and all samples exhibit a pure perovskite structure.As the content of manganese increases,the volume of tetragonal phase increases.The ceramics with 1.5 mol.%MnO_(2) show a high electro-strain of 0.151%at 2 kV/mm.Therefore,this study provides a new insight into the role of MnO_(2) addition in tailoring the electrical properties of the Sm-PMN-PT ceramics by acceptor doping.

Short-Term Electricity Price Forecasting Using Random Forest Model with Parameters Tuned by Grey Wolf Algorithm Optimization

Accurately forecasting short-term electricity prices is of great significance to electricity market participants.Compared with the time series forecasting methods,machine learning forecasting methods can consider more external factors.The forecasting accuracy of machine learning models is greatly affected by the parameters,meanwhile,the manual selection of parameters usually cannot guarantee the accuracy and stability of the forecasting.Therefore,this paper proposes a random forest(RF)electricity price forecasting model based on the grey wolf optimizer(GWO)to improve the accuracy of forecasting.Among them,RF has a good ability to deal with the problem of non-linear and unstable electricity prices.The optimization of model parameters by GWO can overcome the instability of the forecasting accuracy of manually tune parameters.On this basis,the short-term electricity prices of the PJM power market in four seasons are separately predicted.Experimental results show that the RF algorithm can better predict the short-term electricity price,and the optimization of the RF forecasting model by GWO can effectively improve the accuracy of the RF forecasting model.

Cu(Ⅱ)and ammonium adsorption from dairy cattle breeding sewage by phosphorus-modified dairy cow manure hydrochar

To realize the synergistic treatment of dairy cow manure solids and dairy cattle breeding sewage,this study produced phosphorus-modified hydrochar by dairy cow manure solids impregnated with potassium phosphate(K_(3)PO_(4)).And then,the adsorption characteristics of Cu(Ⅱ)and ammonium(NH_(4)^(+))in dairy cattle breeding sewage under different dosages and adsorption time conditions of modified hydrochar were explored.The results show that the specific surface area and total pore volume of the hydrochar were increased by phosphorus-modified.The adsorption amount of hydrochar per unit-mass decreased with the increase in the dosage.With the increase in the dosage,the adsorption capacity of Cu(Ⅱ)decreased from the initial 26.16 mg/g to 3.38 mg/g.The adsorption of Cu(Ⅱ)and NH_(4)^(+)in sewage by hydrochar was mainly chemical adsorption,which was mainly affected by chelation and ion exchange.This adsorption was more inclined to single-molecular layer adsorption.Both the pH values and the ionic strength influenced the competitive adsorption between Cu(Ⅱ)and NH_(4)^(+).The higher the pH value was,the greater the adsorption amount,and the stronger the adsorption capacity by hydrochar.Moreover,the increase in the ionic strength decreases the adsorption capacity of hydrochar.