De Xin Li

Analysis on Thermal Economy and Peak-Shaving Capability for Combined Heat and Power (CHP) Unit in Varying Operating Conditions

Based on the principle of featured through-current area being constant, calculation model for parameters of regenerative steam extraction of CHP unit in different heating conditions is developed in this paper through using FROTRAN software. The generated output and thermal economy of the CHP unit are calculated by using the method of equivalent enthalpy drop, and the accuracy of the model is verified. With the purpose to analyze the rationality of different calculation methods, the distribution ratio of coal consumption for heat supply and coal consumption rate for power generation are calculated through method of equivalent enthalpy drop, heat quantity method and method of actual enthalpy drop under the same operating condition. Moreover, according to the operation test on the unit, the highest and lowest generated output of the CHP under various loads of heat supply are determined, which will provide a basis to the subsequent thermoelectric units in participating in peak shaving of power grid.

Short-Term Prediction of Wind Power Output Based on Markov Chain

Wind power short-term predicting technology has a great significance in process of wind power decision-making. Recent years, the technology had been studied extensively in industry. Markov chain model has strong adaptability, forecast accuracy higher and other else advantages, which is suitable for wind power short-term prediction. This paper have set up one step Markov prediction model and based on which predicting short-term wind power output, and taken the historical power data of an actual wind farm in Jilin Province as an example to simulate and analyze. The paper also have proposed and used RMSE, MXPE, MAPE error analysis indicators to analyze simulation results of different status spaces. The results showed that when the status space is 60 the prediction accuracy of the method is best.

Research on Detection Method of Power Quality for Wind Power Connected to Grid

Owing to the fluctuating and the randomness of wind speed, the influences of large-scale wind power integration on the grid should not be ignored. The output fluctuation of wind farm has serious effect on power quality, causing the problems like voltage flicker and harmonic, it will pose a threat on the safe and stable operation of power grid. This paper mainly analyzed the influence mechanism of wind power integration on power quality and studied the detection method of power quality. The effectiveness of the proposed method was verified by the simulation of real operation data of a wind farm in Jilin Province. The method presented in this paper will provide a reference for the establishment of Chinas wind power testing system and has important engineering significance.

Design and Application of Distributed Solar Power Quality Detection System

This paper studies the stand-alone PV systems, including modeling and simulation of photovoltaic cells based on a battery charge and discharge algorithm design, simulation and design portion of the push-pull boost, simulation and design of single-phase inverter system through experimental platform was build, complete functional test of each module. After considering comprehensive choice as to interfere with observation control method in this paper, based on the principle of interference observation, simulation model in Matlab, through its simulation results and did not join algorithm results were compared and found can effectively increase the output power of the photovoltaic cell.

Active Power Optimization Considering both Generation Cost and Network Loss

In order to improve the calculation efficiency, active power and reactive power are usually optimized separately in optimal power flow considering the decoupling characteristic. However, this would decrease the economy performance of power system. This paper proposed a weighting factor to formulate a multi-objective model, combining the generation cost and system network loss together. The optimization problem is performed using genetic algorithms and quadratic programming respectively. Finally, the feasibility and efficiency of the proposed model are verified with the IEEE 14 Bus test system.

Research on the Capacity of In-Depth Peak Regulation of Large-Scale Heat Supply Unit Based on Characteristics of Thermal Storage of Heat Supply Network and Buildings

Against the backdrop that wind power is always abandoned in heat supply period in winter after wind power is taken into power grid in northern areas of China and there exists a big proportion of large-scale heat supply units in power grid, a method for in-depth peak regulation of large-scale heat supply unit based on characteristics of thermal storage of heat supply network and buildings is put forward in this paper, and a mathematical model for in-depth peak regulation is established. The calculation in a case indicates that the change of heat production of large-scale heat supply unit will not affect the quality of heat supply to a certain extent. During heat supply period, thermal load of heat supply network shall be moderately lowered to coordinate with the in-depth peak regulation when power grid is at its low ebb, and heat supply shall be moderately decreased based on characteristics of thermal storage of heat supply network and buildings when the peak regulation capacity of power grid is very limited, which indicates that it is feasible and practical to help power grid go through its low ebb with the peak regulation capacity gained here. Through the mathematical model established in this paper, time of thermal storage and thermal release as well as such units capacity of in-depth peak regulation can be calculated, which provides a scientific basis for dispatcher of power grid to conduct in-depth peak regulation of heat supply unit.

Analysis of Low Voltage Ride-Through Capability for Variable Speed Wind Turbines Using Experimental and Measured Data

With an increasing amount of wind energy installed, the behavior of wind turbines during grid disturbances becomes more and more important. This paper introduces the basic structures of doubly-fed wind turbines and direct-drive permanent magnet synchronous wind turbines and analyses the capability of low voltage ride through (LVRT) of the wind turbines. Finally this paper elaborates the principle and the procedures of the LVRT tests. The results of the tests show that: Doubly-fed wind turbines and direct-drive permanent magnet synchronous wind turbines are equipped with LVRT capability. The turbines are able to operate normally without disconnection and provide reactive power to support grid restoration during the dip. The direct-drive permanent magnet synchronous wind turbines are superior to the doubly-fed wind turbines on LVRT since a full-power converter is used.

The Influence on Reactive Voltage of Large Scale Wind Power Connected to Grid

Large scale wind power integration has influenced the safety of power system. Taking wind power integration in Jilin as example, the paper describes the influencing factors of large scale wind power integration on reactive power of the grid in detail firstly, then analyze the reactive voltage in four typical ways, and discuss the impact of the wind power fluctuations on the grid reactive voltage.

Co-Optimization of Output and Reserve with Significant Penetration of Renewables

Co-optimization of output and reserve is necessary in order to provide maximum benefit to both consumers and producers. Once renewable generation sources like wind or solar begin to make up a large proportion of the generation mix, this co-optimization becomes much more difficult since the output of renewable sources is not well-known in advance. In this paper, a uniform reliability level is used as a constraint in the process of output and reserve. The proposed model is tested on the modified 5-bus PJM system. The co-optimization is performed by sequential quadratic programming techniques. The results show that the co-optimization results are strongly related to the uncertainties of wind power, the reliability level of the system, and the reliability of generators when wind makes up a significant portion of the generation mix.

Detection Method and Control Strategy of Active Power for Wind Farm Connected into Grid

As one of main clean energies, wind power has been developed fast, but the fluctuations of active power at a wind farm is a huge challenge for the grid system, thus it is essential for wind farm connected into grid to detection the active power. This paper studied control strategies and detection methods of the active power at a wind farm. Simulation results showed the effective detection of active power at a wind farm can improve the characteristics of the grid and the ability of wind farm to regulate the grid and increase the scheduled ability of wind farm.