Xiu Yang

Simulation and Analysis of Two-Level Photovoltaic Grid-Connected System

As the power output of the photovoltaic (PV) cell changes with the insolation changing, PV cell temperature and cell voltage changing, it is necessary to control the operating voltage to draw the maximum power of the PV cell in order to increase system efficiency. Two-level three phase grid-connected PV system is designed. The forestage BOOST chopper adopt Incremental conductance algorithm to implement Maximum Power Point Tracking; The controller for the inverter system contains inner current loop and external voltage loop. According to the proposed control schemes, the phase and frequency of grid-connected current is the same as grid voltage, with the result of unity of the power, factor for power grid. The PV grid-connected system is built by MATLAB/SIMULINK, and the simulation results show that the proposed control schemes are validated.

Microgrid Multi-objective Economic Operation Optimization Considering Reactive Power

In order to solve the multi-objective energy optimization problem with conflicting sub-objectives, fuzzy optimization theory is used in this chapter. The optimization model of multi-objective economic-operated combined heat and power (CHP) microgrid system considering heating income is established in this chapter. The microsources can provide both active and reactive power in the model. A typical microgrid consists of a wind turbine, a photovoltaic, a storage battery, a microturbine, a fuel cell, and heating and electric loads. The maximum fuzzy satisfaction degree method is adopted to transform the multi-objective optimization problem into a nonlinear single-objective optimum problem. The improved genetic algorithm is used to optimize microsources’ active and reactive output and the satisfaction degree of multi-objective optimization for grid-connected mode considering spot price. And the single-objective and multi-objective optimal values are comparatively analyzed. Simulation results show that multi-objective model is more precise than single-objective model in reflecting the actual operation characteristics of microgrid and the better environmental benefits can be reached at operation cost as low as possible in this model. So the validity of the proposed model and algorithm is proved.

Separation Criterion Based on Apparent Impedance Angle

In order to improve the criterion based on apparent impedance angle, the electrical parameters in the process of asynchronous oscillation based on the two-machine equivalent system are analyzed, and oscillation center is studied in the paper. In order to detect oscillation period correctly, the voltage and the active power is utilized. Moreover, the integration of reactive power is used to determine oscillation center. The simulation of New England 10 machine system shows that the criterion based on apparent impedance angle can distinguish asynchronous oscillation effectively, and oscillation period can be detected by voltage and active power. Also, the simulation indicates that oscillation center can be captured by reactive power.

Optimization Allocation of Standalone Microgrid Capacity Based on the Complementary Characteristic of Wind and Solar

For the optimal sizing problem of solar-wind-diesel-battery hybrid microgrid, the economic model of optimal sizing was built with the objective that takes daily costs of equipment, operation and maintenance, fuels, environment protection into account. Meanwhile the blackout penalty fee and wasted energy penalty fee also are included in the economic model. The optimal capacity configurations of different power sources in the system were solved by genetic algorithm under optimal investment condition and considering constraints of the reliability of power supply, the complementary of wind and solar, battery charge and discharge times. The reasonableness of the proposed models is verified by case study results.

Control Strategy of the Hybrid Energy Storage System for Leveling Off Fluctuating Power Output of Stand-Alone Photovoltaic System

Hybrid energy storage system (HESS) including battery and super-capacitor can take advantages of both high energy density and high power density. In the stand-alone PV micro-grid, in which two buck/boost bidirectional converters are connected to the DC bus directly, a novel energy management scheme is proposed. After filtering the fluctuating power of the HESS, charge and discharge currents of the battery are controlled by hysteresis control method, the super-capacitor supplies the difference of the power. To leveling off the fluctuating power output of photovoltaic system and control the voltage of the DC bus, a new control strategy applied to the bidirectional converter of the super capacitor is put forward. The feed-forward loops of input voltage, load current and output voltage are introduced to improve the response speed and stability of the system. Results of the simulation show the effectiveness of the proposed energy management and control strategy.

The Application of Ucosφ Out of Step Criterion to the East China Power Grid

This paper analysis the characteristics of two-machine equivalent system in out of step state. According to variation in the out of step state, study the out of step criterion of .Use change area to determine whether the system is out of step, The criterion is simple and clear, and the concept is clear. It can distinguish the acceleration step and deceleration of step, and automatically adapt to system changes in the structure and Operation mode. The minimum voltage amplitude of the device installed is used for capture the oscillation center .The 2012 East China Power Grid, region A fleet out of step mode is simulated analyzed, It is verify that the criterion of accuracy and adaptability in the East China Power Grid.

Research of Interruptible Load Management Model via Incentive Compatibility

In this paper interruptible load management model via incentive compatibility is researched. Simulated the interruptible load capacity and disruption of economic compensation of the interruptible load management with using MATLAB and compare the cost of interruptible load management and construction of standby units, find that interruptible load management can reduce the cost of electricity companies. But it should be noted that when the interrupt the load is too large, the implementation of interruptible load management will increase the operating costs of the utilities.

Simulation Study of Harmonics and Reactive Power in Three-Phase Full-Bridge Controlled Rectifier Circuit with Resistance-Inductance Load

In order to evaluate the harm and impact of power electronic devices on the grid and provide numerical basis for specific design of the corresponding compensated devices, the harmonics and reactive power of three-phase full-bridge controlled rectifier circuit with resistance-inductance load are studied in this paper. Firstly, the harmonics and power factor of the ac side current are analyzed theoretically; the harmonics contents and power factor are calculated. Secondly, the model of three-phase full-bridge controlled rectifier circuit is built in Matlab/Simulink, and the simulation analysis of the ac side power factor and harmonics is achieved, the simulated values are similar to the theoretical values. The results show that the complex calculations of harmonics and power factor can be completed simply and intuitively using simulation study, the simulation study is efficient and accurate.

Adaptive optimal fuzzy control of asymmetric nonlinear Chua's circuit chaos systems

This paper deals with the chaos phenomenon of asymmetric nonlinear Chuas circuit for wind power generation systems. The Takagi-Sugeno (T-S) fuzzy model of asymmetric nonlinear Chuas circuit chaos system is built. Based on the optimal theory, the extreme sensitivity in the state trajectory with respect to the initial conditions is exhibited and an adaptive optimal fuzzy controller is designed in the form of linear matrix inequality (LMI). Thus the chaos of asymmetric nonlinear Chuas circuit with parametric uncertainties is eliminated. The simulation results show that the adaptive optimal fuzzy control system adopting the designed method has good performance and robust capability.