| With the gradual depletion of the fossil energy and environmental pollution becming more and more serious,the development and utilization of traditional energy sources is an urgently need to upgrade.The solar photovoltaic power generation with its renewable,environmental friendly and other features has a significant advantage on the energy-saving emission reduction and reducing the over-dependence on traditional energy.Photovoltaic power generation influences by the change of light intensity,temperature and other environmental factors.The feature of photovoltaic power is randomness,volatility and intermittent.However,the battery energy storage system can control the process of charge and discharge to regulate of output power,stabilize the voltage fluctuation.Constructing the photovoltaic power generation system with battery energy storage system and researching the coordinated control of photovoltaic energy storage systems could ameliorate the integration characteristics of photovoltaic energy storage system.Photovoltaic energy storage systems include photovoltaic array module,storage battery module,grid connected inverter modules and control systems.The PV array is access to the system by mode of bipolar.Regulate the duty ratio of the DC/DC circuit by modified the variable step incremental conductance method to achieving maximum power of the PV array.The battery system is access to DC side and through bidirectional DC/DC converter circuit to connect with the input of grid connected inverter side.Proposed to the battery control strategy and designed protection circuit to avoid energy storage battery over-charge or over-discharge to control system interconnection real-time power.Researching the power distribution network power model then putting forward the droop control model(P-f Q-U)suited for distributed network to keep the inverter output and distribution network node be synchronized.It improved the characteristics of photovoltaic grid connected energy storage system through the control of inverter.This thesis presents a kind of power losses model of distributed photovoltaic energy storage system connected to network accounting of reactive power to improve performance of the distributed photovoltaic energy storage power system based on the load flow analysis of distributed network operation.Comparing the difference of power loss and voltage deviation of the traditional distributed network operation in parallel with photovoltaic energy storage system connected to the network,then put forward the index of active and reactive power losses and set up the model of power losses of photovoltaic energy storage system.The powerof the photovoltaic energy storage system is determined by the optimization analysis according to the distribution network power loss power model for the optimal operation.Taking a single power distribution circuit as an example to analysis the power losses model,compared the results of differrent power losses/voltage fluctuation in different operation states under the index of the power losses.It verifies the correctness and feasibility of the power losses model. |
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