Analysis of optical storage direct flexible power distribution system

New demand for distribution regulation mode under the development of new energy

Power system is a large-scale nonlinear time-varying energy balance system . The traditional power grid uses an accurate, real-time and controllable traditional power generation system , To match a basically measurable power system , And rolling adjustment during actual operation , It can realize the safe and reliable operation of power system . But the large-scale access of new energy has fundamentally changed “ The source moves with the load ” The mode of operation of . In the power system with high proportion of new energy , Due to the randomness of new energy 、 Volatility has a huge impact ,“ It's hot and windless ”“ Clouds come without light ”, The power generation output cannot be controlled in real time as required . After a large number of distributed new energy sources are connected at the power side , The accuracy of power load forecasting has also decreased significantly . It means , Neither the power generation side nor the user side can be controlled accurately in real time , The traditional technical means and production mode have been unable to meet the operation requirements of the new energy grid with a high proportion , Therefore, the adjustable capacity of demand side load is very important .
“ Light storage is straight and soft ” This new type of power distribution , The distributed power supply is connected , And connected with the flexible ( elastic ) load , It is the best carrier to realize demand response . Besides , The peak value of photovoltaic power generation is synchronized with the peak value of power load for public buildings in terms of daily distribution and quarterly distribution ,“ Light storage is straight and soft ” It has also become the best technical means to realize distributed generation and load local balance . adopt “ Light storage is straight and soft ” Adjustable capacity to maximize load transfer , Realize the interaction between distributed power and load in the construction Park , Even gather flexible and adjustable resources in the park , Participate in electrical auxiliary services , Promote the power grid from “ The source moves with the load ” towards “ Source load interaction ” shift .

Typical optical storage direct flexible power distribution system

The typical optical storage direct flexible power distribution system is shown in the figure below ：

In this system “ light ” Refers to building roof photovoltaic power generation , adopt DC／DC( DC to DC converter ) Access 375 V DC bus .“ Store ” It refers to passing through the DC bus DC／DC Connected 、 A battery pack arranged at one or more locations , And several charging piles arranged in the adjacent parking lot connected by the DC bus , These charging piles are used to charge the electric vehicle battery in the parking lot ／ discharge .“ straight ” It refers to the realization of DC power supply , Including power and charging equipment 375 V Direct , And by DC／DC Converted for low-power electrical appliances 48 V DC branch .375 V The DC bus passes through AC／DC( AC to DC converter ) Communicate with 380 V External power grid connection , Input electricity from the external power grid to meet the power demand of the building .“ The soft ” It refers to the influence of this system on the power grid , It is not a rigid load whose power supply must be equal to the power consumption on the load side at this time , Instead, the power taken from the power grid can be adjusted in a large range according to the supply-demand relationship of the power grid . From the grid side , This power consumption system becomes the flexible load of the power grid .
The realization of flexibility is mainly through the “ Demand side response ” Realization , Each equipment can automatically change its instantaneous power consumption according to the supply-demand relationship of the power grid —— Including... Of each battery “ Demand side response ”, The batteries and electric vehicle batteries connected in the system can be charged according to the supply and demand of the power grid ／ Discharge power —— To change AC／DC The electric power entering the system from the external power grid . Therefore, the ultimate goal of the optical storage direct flexible distribution system is to change the building power system from the current rigid load to flexible load , The power consumption can be adjusted at any time according to the supply-demand relationship of the power system , It does not depend on the power consumption of each electric equipment in the system at that time .

The regulation principle of optical storage direct flexible power distribution system

Take the picture above as an example , We added some annotations to help understand . among ① Represents the interface with the external communication network AC/DC;② Represents the interface with photovoltaic cells DC/DCP;③ Represents the interface with the battery DC/DCB;④ Represents the interface with other electrical terminals DC/DCT;⑤ Represents the interface with electric vehicles DC/DCc light . These interfaces are intelligent converters with programmable controllers , The control logic of the whole system is discussed below .

The power system is based on the power supply and demand relationship of the power grid , The power consumption of the optical storage direct flexible distribution system at a certain time is required to be P0, here AC／DC Constant output power P0, The input power of DC bus is P0+PV, among Pv Input power for photovoltaic power generation . Because the power of each electric equipment and power storage device changes automatically with the change of DC bus voltage , Therefore, when the total power of all electrical equipment including battery and charging pile is equal to P0+PV when , If the DC bus voltage is at the required upper limit voltage Vmax And lower limit voltage Vmin Between , The system maintains balance . When a consumer tries to increase power , Make the total power higher than P0+PV when , DC bus voltage drops , At this time, each electric equipment will automatically reduce its own power consumption according to the voltage drop , Battery 、 The charging point also reduces the charging current according to the voltage drop , It is even converted to supplying part of the power to the system through discharge . such , As the DC bus voltage drops , The power taken by the system from the external power grid continues to decline , Eventually rebalance to P0+PV. conversely , If each consumer tries to reduce power , Thus, the total power is lower than P0+PV, The bus voltage will rise , Each electric equipment will automatically increase its own power consumption according to the rise of voltage , Battery 、 The charging point will also automatically increase the charging power , such , The power taken from the external network will be rebalanced at P0 On .
The power supply of external power grid and photovoltaic power generation P0+PV Too big , The power of each electric equipment and charging device is too small , The DC bus voltage reaches the allowable upper limit Vmax, At this point, it is necessary to pass AC／DC Reduce the electric power introduced from the external power grid P0 And regulating photovoltaic power generation DC／DC, Through part “ Abandon the light ” Stabilize the bus voltage at Vmax; When the power supply of external power grid and photovoltaic power generation is too small , Less than the total power of each electric equipment at that time , When the power storage devices have no power to discharge ,AC／DC The power supply will be increased , Maintain the DC bus voltage at Vmin, To ensure basic electricity demand . In both cases , The power taken by the system from the external power grid will be less than or greater than the required power P0 The phenomenon of , At this time, the optical storage, direct and flexible distribution system cannot obtain power from the external power grid in strict accordance with the required power . Whether this kind of working condition will occur depends on the adjustable power of each electric equipment in the system , It also depends on the battery set by the system and the battery capacity of the electric vehicle connected at that time .

Classification of flexible load in optical storage direct flexible distribution system

Under the regulation mode of the distribution system, the electric appliances in the building can be divided into three categories according to the regulation performance and regulation mode ： Translation delay type 、 Variable power type 、 Severable type .
The translation delay type equipment includes both the heat storage tank 、 Air conditioning ice ／ Water storage system 、 The refrigerator 、 freezer 、 Washing machine 、 Sewage pump, etc , And rechargeable electronic and electrical equipment with battery . Use AI Technology through the study of DC bus voltage changes in a day , Identify the time periods of the day that require more electricity and avoid electricity as much as possible ; By learning the operation rules of the equipment itself , Obtain the required continuous operation duration and start stop time ratio . Based on this information, the optimal operation plan for one day can be formulated , Avoid running during periods of power shortage , Try to adjust the equipment to use electricity during the period of power surplus .
Variable power type equipment includes electric equipment that can adjust power through frequency conversion or other means , Such as split air conditioner 、 Multi connected air conditioner 、 Fan 、 Water pump 、 Variable frequency escalator 、 Elevator, etc . These devices have their own control and adjustment devices , The power consumption can be changed by frequency conversion or other means . In the optical storage direct flexible power distribution system , DC bus voltage can be measured , The correction factor of operating power is determined according to the voltage . DC bus voltage is high , Then the correction factor will be high , It can increase the power consumption 10％; When the DC bus voltage is low , The correction factor is low , That is, reduce the speed or reduce the actual power consumption by other means .
The disconnectable load is cut off after the bus voltage drops to the preset value , To reduce the power consumption of the system .
The above description of the control strategy is only a simple principle , The control strategy details of each product are related to the regulation characteristics of the product itself , It needs to be independently researched and developed by the manufacturer , The difference of its performance can become the competitive point of similar products . A good regulation strategy will not affect the function and use effect of the product itself , It also has the performance of flexible adjustment of power consumption , Thus, the system flexibility can be increased or the demand for battery capacity can be reduced under the same system flexibility .

The above content only makes a simple analysis of the typical model of the optical storage direct flexible distribution system , To help you understand the types and functions of flexible loads . In fact, for a large building , It can be divided into several optical storage units , These units are interconnected 、 Coordinate with each other , Make full use of their energy storage capacity and regulation capacity . And multiple buildings in a region can also be connected by building optical storage direct and flexible micro networks . Optical storage, direct and flexible power distribution will lead the construction industry 、 Building power distribution 、 Power system and terminal products are integrated with each other . meanwhile , New industries emerged through mutual penetration , It has also developed rapidly under the background of double carbon , From Gree's “ Light storage empty ” Go to Huawei's antuoshan Guangchu zhirou park , Both show their growing influence , It's both a challenge and an opportunity .