CN108923446B - Method for configuring energy storage capacity in photovoltaic/energy storage integrated system - Google Patents
Method for configuring energy storage capacity in photovoltaic/energy storage integrated system Download PDFInfo
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Abstract
The invention relates to a method for configuring energy storage capacity in a photovoltaic/energy storage integrated system, which is technically characterized by comprising the following steps: the method comprises the following steps: step 1, establishing a photovoltaic/energy storage integrated system comprising a lead-acid battery energy storage system and a lead-carbon battery energy storage system by taking a photovoltaic/energy storage system project in a certain place as reference; step 2, making a proper energy management strategy to respectively control the power flow of the lead-acid battery energy storage system and the lead-carbon battery energy storage system; step 3, establishing a lead-acid battery energy storage system and a lead-carbon battery energy storage system which are respectively used for peak clipping and valley filling and fluctuation stabilization, and designing and calculating energy storage capacities under different functional conditions; and 4, after the capacities of the energy storage system when the system respectively performs peak clipping and valley filling and fluctuation stabilizing are obtained, building a corresponding simulation model for simulation. The lead-acid battery and the lead-carbon battery are combined to be used as an energy storage system, and the energy storage system is controlled to carry out peak clipping and valley filling and fluctuation stabilization through a proper energy management strategy.
Description
Technical Field
The invention belongs to the technical field of new energy management, relates to a configuration method of energy storage capacity, and particularly relates to a configuration method of energy storage capacity in a photovoltaic/energy storage integrated system.
Background
After the 70 s in the 20 th century, with the development of modern industry, the global energy crisis and the air pollution problem are increasingly prominent, the traditional fuel energy is reduced day by day, the harm to the environment is increasingly prominent, and about 20 hundred million people in the world can not obtain normal energy supply. In this case, solar energy is a focus of attention due to its unique advantages. Abundant solar radiation energy is an important energy source, is inexhaustible, pollution-free and cheap energy source which can be freely utilized by human beings, and has very wide development and utilization potential. However, as photovoltaic power generation is connected to the power grid in a large scale, various disadvantages of photovoltaic power generation are gradually exposed. Firstly, in the time without illumination, the photovoltaic power station cannot generate electricity or generates little electricity, however, the peak period of the electricity consumption of residents is mostly concentrated in the time period, and the peak clipping and valley filling are carried out by using the energy storage system. Secondly, the power generated by photovoltaic has large fluctuation, which causes large impact on the power grid when being incorporated into the power grid. Again, this requires an energy storage system to smooth out the fluctuations. The energy storage system is added to improve the performance of the photovoltaic power station in various aspects, however, the energy storage system is expensive, and if the capacity of the energy storage system is configured too much, the economic benefit generated by the energy storage system is not enough to offset the investment cost of the energy storage battery.
In foreign countries, for example, germany has now been able to ensure photovoltaic power generation access at a higher rate. In practice, however, such a high rate of photovoltaic access is also supported by the main grid and the power market, so the grid architecture is also very strong, and large-scale power regulation is feasible.
In China, the photovoltaic power generation in China currently accounts for less than 1% of the total capacity of a power grid in China. The photovoltaic permeability is low, and is not enough to obviously influence the power grid, so that photovoltaic power stations are installed in large quantity at present and are not influenced intermittently.
A better way to solve the problem is to use an energy storage system. The energy storage batteries which are commonly used in the market at present are lead-acid batteries and lead-carbon batteries. The lead-acid storage battery is the most economic energy storage system scheme at present, and has the advantages of mature technology, low cost and capability of constructing a large-scale energy storage system. Compared with various energy storage batteries, the lead-acid battery has high cost performance, occupies a dominant position in an energy storage system and an industrial standby power supply, and has short service life. The lead-carbon battery has the advantages of high charging and discharging speed, long cycle life in a shallow charging and discharging state, high-capacity charging and discharging characteristics and the like. Compared with a lead-acid battery, the lead-carbon battery has the advantages that the charging speed is increased by 8 times, and the discharging power is increased by 3 times. The characteristics of the lead-acid battery and the lead-carbon battery show that the lead-acid battery has the lowest cost but a short service life, the lead-carbon battery has more charge and discharge times, can be charged and discharged for many times, has large charge and discharge current and has slightly higher cost.
At present, most of storage batteries used in the domestic existing energy storage system are single in type, namely only lead-acid batteries are used as energy storage units, or only lead-carbon batteries are used as energy storage units, and the specific numerical value of the energy storage capacity required by the energy storage system when fluctuation is stabilized is not considered. Meanwhile, the domestic prior art only considers the service life of the storage battery.
Disclosure of Invention
The invention aims to provide a photovoltaic/energy storage integrated system energy storage capacity configuration method which is scientific, reasonable, effective, practical and beneficial to energy conservation popularization.
The invention solves the practical problem by adopting the following technical scheme:
a method for configuring energy storage capacity in a photovoltaic/energy storage integrated system comprises the following steps:
step 3, establishing a lead-acid battery energy storage system and a lead-carbon battery energy storage system which are respectively used for peak clipping and valley filling and fluctuation stabilization, and designing and calculating energy storage capacities under different functional conditions to enable the capacities to be minimum on the premise of fully playing roles;
and 4, after the capacities of the energy storage system when the system respectively performs peak clipping and valley filling and fluctuation stabilizing are obtained, building a corresponding simulation model for simulation.
Moreover, the photovoltaic/energy storage integrated system in the step 1 comprises a photovoltaic power station system, a lead-acid battery energy storage system, a lead-carbon battery energy storage system, a photovoltaic grid-connected inverter, a three-phase power grid and a load; the photovoltaic power generation unit in the photovoltaic power station system is connected with the alternating current bus through the photovoltaic grid-connected DC/AC inverter and is respectively connected with the three-phase power grid and the load through the alternating current bus; the lead-acid battery energy storage system is composed of lead-acid battery storage battery units, and the lead-acid battery storage battery units are connected with an alternating current bus through a photovoltaic grid-connected DC/AC inverter and are respectively connected with a three-phase power grid and a load through the alternating current bus; the lead-carbon battery energy storage system is composed of lead-carbon battery storage battery units, and the lead-carbon battery storage battery units are connected with an alternating current bus through a photovoltaic grid-connected DC/AC inverter and are respectively connected with a three-phase power grid and a load through the alternating current bus.
Moreover, the specific method of the step 2 is as follows: the method comprises the following steps of drawing a photovoltaic power curve and a load power curve by analyzing certain place sunny illumination data, cloudy illumination data and load capacity, further calculating power required to be provided by a power grid and a power change curve of an energy storage system, formulating an energy management strategy of the photovoltaic/energy storage integrated system according to the curves, wherein the energy management strategy comprises a power calculation formula of the energy storage system and a power calculation formula sent by the power grid:
(1) the power calculation formula of the energy storage system is as follows:
in the formula: pbatIs the charging and discharging power of the storage battery and has the unit of W and PbatWhen the voltage is less than 0, the storage battery is discharged; pPVThe unit is the output power of the photovoltaic power station and is W; pgridThe power generated by the power grid is in W, PgridWhen the power is less than 0, the power is absorbed by the power grid; p is the power consumed by the load in W; epsilon is a threshold value;
(2) the power calculation formula sent by the power grid is as follows:
in the formula: pPVFor photovoltaic power plantsOutput power in units of W; pgridThe power generated by the power grid is in W, PgridWhen the power is less than 0, the power is absorbed by the power grid; p is the power consumed by the load in W; plossThe total loss is given in W.
The specific method of step 3 is: the method specifically comprises a calculation method of the energy storage capacity of the lead-acid battery energy storage system during peak clipping and valley filling and a calculation method of the energy storage capacity of the lead-acid battery energy storage system during fluctuation stabilizing, wherein the calculation methods are as follows:
(1) the calculation formula of the energy storage capacity of the energy storage system of the lead-acid battery during peak clipping and valley filling is as follows:
in the formula: w is the capacity needed by the storage battery during peak clipping and valley filling, and the unit is J; pPVThe unit is the output power of the photovoltaic power station and is W; pgridThe power generated by the power grid is in W, PgridWhen the power is less than 0, the power is absorbed by the power grid; p is the power consumed by the load in W; α is the ratio of the capacity of the battery itself to the capacity actually used; delta is a margin coefficient;
(2) the calculation formula of the energy storage capacity of the lead-carbon battery energy storage system when the fluctuation is stabilized is as follows:
in the formula: w is the capacity needed by the storage battery when the fluctuation is stabilized, and the unit is J; pPVThe unit is the output power of the photovoltaic power station and is W; pfilThe unit is the output power of the photovoltaic power station after filtering and is W; α is the ratio of the capacity of the battery itself to the capacity actually used; delta is a margin coefficient;
moreover, the specific method of the step 4 is as follows: according to the energy storage capacity obtained by calculation, analog simulation research is carried out on Matlab/Simulink software, and the effectiveness of the established model and the energy storage capacity algorithm can be verified according to the power change curve of each subsystem after the energy storage system is added.
The invention has the advantages and beneficial effects that:
1. the invention relates to a method for configuring energy storage capacity in a photovoltaic/energy storage integrated system, which comprises the steps of establishing the photovoltaic/energy storage integrated system by taking a photovoltaic/energy storage system project in a certain place as reference, and constructing an operation schematic diagram of the photovoltaic/energy storage integrated system; according to actual sunny illumination data, cloudy illumination data and load capacity of a certain place, a proper energy management strategy is formulated; respectively calculating respective energy storage capacities for different functions executed by the energy storage system around the established system operation schematic diagram, and summarizing a general algorithm; a corresponding simulation model is built on Matlab/Simulink software, the reasonability of the energy storage capacity required by the energy storage system under different weather and different functional conditions is verified, the effectiveness of the energy storage system in respectively carrying out peak clipping and valley filling and fluctuation stabilizing is verified on reasonable capacity configuration, and the effective and lasting operation of the photovoltaic/energy storage integrated system is realized.
2. The invention provides a method for configuring energy storage capacity in a photovoltaic/energy storage integrated system aiming at two technical problems of peak clipping and valley filling and fluctuation stabilizing which need to be solved when the existing photovoltaic power station is connected to a power grid, wherein a lead-acid battery and a lead-carbon battery are combined to serve as an energy storage system, and the lead-acid battery and the lead-carbon battery are used for controlling the energy storage system to carry out peak clipping and valley filling and fluctuation stabilizing through a proper energy management strategy; specifically, aiming at the condition that the load peak period and the photovoltaic power station power generation peak period are staggered, peak clipping and valley filling are carried out by utilizing a lead-acid battery through energy management; aiming at the condition that the output power of a photovoltaic power station is severely jittered under the cloudy or rainy weather condition, the fluctuation is stabilized by utilizing the lead-carbon battery through energy management.
3. When the lead-acid battery is used as the energy storage system, compared with the prior art, the charging and discharging times of the lead-acid battery are reduced, and the service life of the lead-acid battery is prolonged; when the lead carbon battery is used as the energy storage system, the energy storage capacity of the lead carbon battery is calculated on the premise of combining the power prediction technology and the low-pass filtering method.
4. The invention simultaneously uses the lead-acid battery and the lead-carbon battery to form the energy storage unit, fully exerts the functions of peak clipping and valley filling and fluctuation stabilization on the premise of minimum capacity of the storage battery, and can prolong the service life of the storage battery on the premise of fully utilizing the characteristics of the storage battery.
Drawings
FIG. 1 is a process flow diagram of the present invention;
FIG. 2 is a schematic diagram of the operation of the integrated photovoltaic/energy storage system of the present invention;
FIG. 3 is a graph of a typical photovoltaic array power curve versus a typical daily load for the present invention;
FIG. 4 is a power variation curve diagram of each module under clear illumination conditions when peak clipping and valley filling are performed according to the present invention;
FIG. 5 is a diagram of a lead-acid battery state for peak clipping and valley filling under sunny lighting conditions when peak clipping and valley filling are performed in accordance with the present invention;
FIG. 6 is a diagram of a lead acid battery state for peak clipping and valley filling in cloudy days, according to the present invention;
FIG. 7 is a diagram of a lead-acid battery state for peak clipping and valley filling in a sunny day with an excessively small energy storage capacity when peak clipping and valley filling are performed in accordance with the present invention;
FIG. 8 is a graph of the filtering effect of the illumination curve in cloudy weather according to the present invention;
FIG. 9 is a plot of photovoltaic array power under cloudy climate conditions and its filtered plot in accordance with the present invention;
FIG. 10 is a graph of power variation of modules in cloudy weather with the fluctuation being smoothed in accordance with the present invention;
FIG. 11 is a state diagram of a lead acid battery used for peak clipping and valley filling in cloudy days, while suppressing fluctuations in accordance with the present invention;
fig. 12 is a state diagram of a lead carbon battery for stabilizing wave motion in cloudy weather in accordance with the present invention.
Detailed Description
The embodiments of the invention will be described in further detail below with reference to the accompanying drawings:
a method for configuring energy storage capacity in a photovoltaic/energy storage integrated system, as shown in fig. 1, includes the following steps:
In this embodiment, the photovoltaic/energy storage integrated system in step 1 includes a photovoltaic power station system, a lead-acid battery energy storage system, a lead-carbon battery energy storage system, a photovoltaic grid-connected inverter, a three-phase power grid, and a load; the photovoltaic power generation unit in the photovoltaic power station system is connected with the alternating current bus through the photovoltaic grid-connected DC/AC inverter and is respectively connected with the three-phase power grid and the load through the alternating current bus; the lead-acid battery energy storage system is composed of lead-acid battery storage battery units, and the lead-acid battery storage battery units are connected with an alternating current bus through a photovoltaic grid-connected DC/AC inverter and are respectively connected with a three-phase power grid and a load through the alternating current bus; the lead-carbon battery energy storage system is composed of lead-carbon battery storage battery units, and the lead-carbon battery storage battery units are connected with an alternating current bus through a photovoltaic grid-connected DC/AC inverter and are respectively connected with a three-phase power grid and a load through the alternating current bus;
at present, a photovoltaic/energy storage integrated system can be divided into two types according to the type of a bus bar, namely a common alternating current bus structure and a common direct current bus structure. The common alternating current bus structure has the technical advantages that the photovoltaic power generation unit and the storage battery unit are respectively connected with the alternating current bus through the DC/AC inverter, the system is connected with a power grid through the alternating current bus, and when the power grid fails and other needs occur, the photovoltaic/energy storage system can be separated from the power grid to operate independently. Here, a common alternating current bus system is adopted, and a typical photovoltaic/energy storage integrated system operation schematic diagram is shown in fig. 2.
the specific method of the step 2 comprises the following steps: the method comprises the following steps of drawing a photovoltaic power curve and a load power curve by analyzing certain place sunny illumination data, cloudy illumination data and load capacity, further calculating power required to be provided by a power grid and a power change curve of an energy storage system, formulating an energy management strategy of the photovoltaic/energy storage integrated system according to the curves, wherein the energy management strategy comprises a power calculation formula of the energy storage system and a power calculation formula sent by the power grid:
(1) the power calculation formula of the energy storage system is as follows:
when the sum of the electric quantity output by the photovoltaic power station and the power supplied by the power grid is greater than the load power demand, charging the energy storage battery by the redundant power of the system; when the sum of the power output by the photovoltaic power station and the power supplied by the power grid cannot meet the load power demand, the energy storage battery supplies power to the load. Wherein the power supplied by the grid may be negative, indicating a need to deliver power to the grid. When the difference between the total power output by the photovoltaic array and the demand of the load is small, a threshold value is set for preventing the storage battery from shaking caused by frequent charging and discharging, and when the difference is smaller than the threshold value, the storage battery maintains the state of the previous moment unchanged. The power calculation formula for the energy storage system can be obtained by:
in the formula: pbatIs the charging and discharging power of the storage battery and has the unit of W and PbatWhen the voltage is less than 0, the storage battery is discharged; pPVThe unit is the output power of the photovoltaic power station and is W; pgridThe power generated by the power grid is in W, PgridWhen the power is less than 0, the power is absorbed by the power grid; p is the power consumed by the load in W; ε is the threshold value.
(2) The power calculation formula sent by the power grid is as follows:
whether the power is taken from or delivered to the grid, the power of the grid is preferably kept constant, so that the influence of the system on the grid can be minimized. The power generated by the power grid can be obtained by the following formula:
in the formula: pPVThe unit is the output power of the photovoltaic power station and is W; pgridThe power generated by the power grid is in W, PgridWhen the power is less than 0, the power is absorbed by the power grid; p is the power consumed by the load in W; plossThe total loss is given in W.
In the formula, 24 hours is taken as a period, after a period of time, the charge state of the photovoltaic energy storage system is required to be recovered to an initial value, the total energy for charging the photovoltaic energy storage system is required to be equal to the total energy for discharging, the photovoltaic energy storage system can be operated for a long time without causing the overcharge or overdischarge of a storage battery after the photovoltaic energy storage system is operated for a period of time, and the sum of the total energy of a power grid and the total energy of a photovoltaic array is required to be equal to the total energy consumed by a load or not.
Step 3, establishing a lead-acid battery energy storage system and a lead-carbon battery energy storage system which are respectively used for peak clipping and valley filling and fluctuation stabilization, and designing and calculating energy storage capacities under different functional conditions to enable the capacities to be minimum on the premise of fully playing roles;
the specific method of the step 3 comprises the following steps: the method specifically comprises a calculation method of the energy storage capacity of the lead-acid battery energy storage system during peak clipping and valley filling and a calculation method of the energy storage capacity of the lead-acid battery energy storage system during fluctuation stabilizing, wherein the calculation methods are as follows:
(1) the calculation formula of the energy storage capacity of the energy storage system of the lead-acid battery during peak clipping and valley filling is as follows:
how the capacity of the storage battery is configured has great influence on photovoltaic power generation, the capacity selection is small, a photovoltaic power generation system cannot fully obtain the maximum benefit, and the reliability of a power grid is reduced; the capacity selection is too large, so that the investment is increased, and the storage battery can be in an insufficient charging state for a long time, so that the use effect and the service life of the battery are influenced, and part of economy is lost. In general, an energy storage system for peak clipping and valley filling only performs one complete charge and discharge within 24 hours, so the energy storage capacity of the energy storage system for the lead-acid battery for peak clipping and valley filling can be obtained by the following formula:
in the formula: w is the capacity needed by the storage battery during peak clipping and valley filling, and the unit is J; pPVThe unit is the output power of the photovoltaic power station and is W; pgridThe power generated by the power grid is in W, PgridWhen the power is less than 0, the power is absorbed by the power grid; p is the power consumed by the load in W; α is the ratio of the capacity of the battery itself to the capacity actually used; δ is a margin coefficient, and is usually 1.2.
Wherein, point A and point B are as shown in figure 3, in 24 hours, from point A to point B, the storage battery carries on the primary charging; since the battery is discharged once from point B to point a, the minimum capacity of the battery is the integral of the power charged from point B to the battery at point a.
(2) The calculation formula of the energy storage capacity of the lead-carbon battery energy storage system when the fluctuation is stabilized is as follows:
the power of photovoltaic power generation is susceptible to weather and exhibits large fluctuation, which causes large impact to the power grid when the power grid is incorporated into the power grid, so an energy storage system is needed to stabilize the fluctuation. The photovoltaic power is filtered by utilizing the Butterworth low-pass filter principle, and due to the fact that certain time delay is caused by low-pass filtering, a photovoltaic power generation power prediction technology is introduced, proper prediction time is selected, the time delay caused by the low-pass filtering can be completely or partially eliminated, and therefore the energy storage capacity calculation formula of the lead-carbon battery energy storage system for stabilizing fluctuation can be obtained through the following formula:
in the formula: w is the capacity needed by the storage battery when the fluctuation is stabilized, and the unit is J; pPVThe unit is the output power of the photovoltaic power station and is W; pfilThe unit is the output power of the photovoltaic power station after filtering and is W; α is the ratio of the capacity of the battery itself to the capacity actually used; δ is a margin coefficient, and is usually 1.2. A. thexPoints and BxThe meaning of the dots is shown in fig. 9.
In actual life, when the energy storage capacity is determined, a certain margin needs to be reserved, so the energy storage capacity mentioned above needs to be multiplied by a coefficient, and the coefficient generally takes 1.2. In general, the operating range of the state of charge of the battery is 50% to 100%, so the depth of discharge for peak clipping and valley filling and fluctuation suppression is 50%, i.e., the actual configuration capacity of the battery should be 2 times the used capacity. When the charge state operating range of the storage battery is not 50% -100%, the ratio of the capacity of the storage battery to the actually used capacity is multiplied.
And 4, after the capacities of the energy storage system when the system respectively carries out peak clipping and valley filling and fluctuation stabilizing are obtained, building corresponding simulation models on Matlab/Simulink software, and researching the power flow conditions of a photovoltaic power station, an energy storage battery, a three-phase power grid and a load within 1 day of simulation time, so that the economical efficiency and the effectiveness of the energy storage capacity obtained through calculation are proved.
The specific method of the step 4 comprises the following steps: according to the calculated energy storage capacity, simulation research is carried out on Matlab/Simulink software, the simulation time is 1 day, and FIGS. 4-7 show simulation results of peak clipping and valley filling (without stabilizing fluctuation), wherein FIG. 4 shows power change curves of modules under a clear illumination condition, FIG. 5 shows a lead-acid battery state for peak clipping and valley filling under a clear illumination condition, FIG. 6 shows a lead-acid battery state for peak clipping and valley filling under cloudy weather, and FIG. 7 shows a lead-acid battery state for peak clipping and valley filling under a clear illumination condition when the energy storage capacity is too small. Fig. 8 is a filtering effect of an illumination curve in cloudy weather, and fig. 10 to 12 are simulation results of stabilizing fluctuation, where fig. 10 is a power variation curve of each module in cloudy weather, fig. 11 is a state of a lead-acid battery for peak clipping and valley filling in cloudy weather, and fig. 12 is a state of a lead-acid carbon battery for stabilizing fluctuation in cloudy weather. And the effectiveness of the established model and the energy storage capacity algorithm can be verified according to the power change curve of each subsystem after the energy storage system is added.
As can be seen from the simulation results: according to the configuration technology of the energy storage capacity in the photovoltaic/energy storage integrated system, the energy storage capacity obtained through calculation can be used for effectively carrying out peak clipping and valley filling and stabilizing fluctuation, and the effective and durable operation of the photovoltaic/energy storage integrated system is realized. The following conclusions can be drawn from the simulation results:
as can be seen from fig. 5, in a sunny weather condition, when only peak clipping and valley filling are performed, the storage battery is charged and discharged once a day, and the state is changed at the intersection of the power waveform of the sum of the photovoltaic array and the power grid and the power waveform of the load. When the sum of the photovoltaic array and the power grid power is greater than the load power, the redundant power charges the storage battery; when the sum of the power of the photovoltaic array and the power grid is less than the load power, the lacking power is provided by discharging of the storage battery. The state of charge is close to the maximum value and the minimum value at the intersection point respectively, which shows that the capacity of the storage battery for simulation is reasonably selected; the initial value of the charge state simulation is close to the final value of the charge state simulation at the end of the simulation, and the result shows that the power taken from the power grid is reasonable.
As can be seen from fig. 6, when the climate conditions are changed drastically, the number of charging and discharging of the energy storage system is increased significantly. Because the output power of the photovoltaic array is insufficient under the cloudy condition, the storage battery drains off the electric quantity, the output power of the storage battery is instantly changed into 0, the output power of the power grid is instantly increased at the same moment, and the part of the power supplied by the storage battery to load power is changed into the load power born by the power grid. Obviously, the storage battery itself can be caused great injury by the too frequent charge and discharge of energy storage system, so should surrender photovoltaic fluctuation.
As can be seen from fig. 7, when the energy storage capacity is insufficient, the storage battery may be in a dry charge state or a full charge state. When the storage battery is drained of electric quantity, the power output by the power grid can be instantly increased, and the part which is not enough to supply load power is borne by the power grid; when the storage battery is fully charged, the power output by the power grid is instantly reduced, and the photovoltaic array feeds redundant power to the power grid on the premise of supplying power to the load, so that the waste of electric energy is caused. Therefore, the economic cost can be reduced and unnecessary electric energy loss can be reduced by selecting the proper energy storage capacity.
Fig. 8 introduces a photovoltaic power generation power prediction technique, and performs low-pass filtering on the predicted power curve, and the filtering result is used as a target value of photovoltaic power generation power stabilizing fluctuation. The control method adopts an ultra-short-term photovoltaic power generation power prediction technology, the technology is based on a method combining physics and statistics, numerical weather prediction data is utilized on the basis of a statistical model, and the accuracy is high. Because the power prediction curve is advanced in time compared with the original power curve, the time delay caused by low-pass filtering can be completely or partially eliminated by selecting the proper prediction time. As can be seen from fig. 8, the phase of the illumination curve obtained by filtering the predicted power curve is substantially identical to the phase of the original illumination curve, and the expected effect is achieved.
In fig. 9, the capacity of the energy storage system required to stabilize fluctuation may be calculated according to the intersection point of the filtered illumination curve and the original illumination curve.
Fig. 10 is a power change curve of four modules, namely, a power grid, a photovoltaic power station, a load, and an energy storage system for peak clipping and valley filling, on the premise that the energy storage system for peak clipping and the energy storage system for stabilizing fluctuation are both put into operation in cloudy weather.
As can be seen from fig. 11, because the system has peak clipping, valley filling and fluctuation stabilizing at the same time, the original photovoltaic curve with severe fluctuation becomes smooth, and if the fluctuation is not stabilized, the number of charging and discharging times of the lead-acid battery in one cycle will reach twice, which may seriously affect the service life of the lead-acid battery. Therefore, the photovoltaic power curve can be smoothed by stabilizing fluctuation, the storage battery for peak clipping and valley filling is indirectly protected, and the charging and discharging times of the storage battery are reduced.
As can be seen from fig. 12, the storage battery for stabilizing photovoltaic fluctuation has more charge and discharge times within 24 hours, the lead-acid battery has small charge and discharge current, the number of charge and discharge times per day is limited, the lead-carbon battery has more charge and discharge times, can be charged and discharged for many times rapidly, and the charge and discharge current is large, so that the lead-carbon battery is more suitable for stabilizing fluctuation than the lead-acid battery.
The invention discloses a method for configuring energy storage capacity in a photovoltaic/energy storage integrated system, which can provide reference for energy storage capacity configuration in a photovoltaic power generation system. And (3) making a proper energy management strategy by analyzing the illumination data of a certain place on a sunny day, the illumination data of a cloudy day and the load quantity around the established system operation schematic diagram, establishing energy storage systems respectively used for peak clipping and valley filling and fluctuation stabilizing, designing and calculating energy storage capacity under different functional conditions, and summarizing a general algorithm. After the capacity of the energy storage system is obtained when the system respectively carries out peak clipping and valley filling and fluctuation stabilization, corresponding simulation models are built on Matlab/Simulink software, and power flow conditions of a photovoltaic power station, an energy storage battery, a three-phase power grid and a load are researched within 1 day of simulation time, so that the economical efficiency and the effectiveness of the energy storage capacity obtained through calculation are proved.
It should be emphasized that the examples described herein are illustrative and not restrictive, and thus the present invention includes, but is not limited to, those examples described in this detailed description, as well as other embodiments that can be derived from the teachings of the present invention by those skilled in the art and that are within the scope of the present invention.
Claims (5)
1. A method for configuring energy storage capacity in a photovoltaic/energy storage integrated system is characterized by comprising the following steps: the method comprises the following steps:
step 1, establishing a photovoltaic/energy storage integrated system comprising a lead-acid battery energy storage system and a lead-carbon battery energy storage system by taking a photovoltaic/energy storage system project in a certain place as reference, and constructing an operation schematic diagram of the photovoltaic/energy storage integrated system;
step 2, aiming at illumination data and load data of a certain place under different climatic conditions, an energy management strategy is formulated to respectively control the power flow of a lead-acid battery energy storage system and a lead-carbon battery energy storage system;
step 3, establishing a lead-acid battery energy storage system and a lead-carbon battery energy storage system which are respectively used for peak clipping and valley filling and fluctuation stabilization, and designing and calculating energy storage capacities under different functional conditions to enable the capacities to be minimum on the premise of fully playing roles;
and 4, after the capacities of the energy storage system when the system respectively performs peak clipping and valley filling and fluctuation stabilizing are obtained, building a corresponding simulation model for simulation.
2. The method for configuring the energy storage capacity in the integrated photovoltaic/energy storage system according to claim 1, wherein: the photovoltaic/energy storage integrated system in the step 1 comprises a photovoltaic power station system, a lead-acid battery energy storage system, a lead-carbon battery energy storage system, a photovoltaic grid-connected inverter, a three-phase power grid and a load; the photovoltaic power generation unit in the photovoltaic power station system is connected with the alternating current bus through the photovoltaic grid-connected DC/AC inverter and is respectively connected with the three-phase power grid and the load through the alternating current bus; the lead-acid battery energy storage system is composed of lead-acid battery storage battery units, and the lead-acid battery storage battery units are connected with an alternating current bus through a photovoltaic grid-connected DC/AC inverter and are respectively connected with a three-phase power grid and a load through the alternating current bus; the lead-carbon battery energy storage system is composed of lead-carbon battery storage battery units, and the lead-carbon battery storage battery units are connected with an alternating current bus through a photovoltaic grid-connected DC/AC inverter and are respectively connected with a three-phase power grid and a load through the alternating current bus.
3. The method for configuring the energy storage capacity in the integrated photovoltaic/energy storage system according to claim 1, wherein: the specific method of the step 2 comprises the following steps: the method comprises the following steps of drawing a photovoltaic power curve and a load power curve by analyzing certain place sunny illumination data, cloudy illumination data and load capacity, further calculating power required to be provided by a power grid and a power change curve of an energy storage system, formulating an energy management strategy of the photovoltaic/energy storage integrated system according to the curves, wherein the energy management strategy comprises a power calculation formula of the energy storage system and a power calculation formula sent by the power grid:
(1) the power calculation formula of the energy storage system is as follows:
in the formula: pbatFor charging and discharging batteriesElectric power in W, PbatWhen the voltage is less than 0, the storage battery is discharged; pPVThe unit is the output power of the photovoltaic power station and is W; pgridThe power generated by the power grid is in W, PgridWhen the power is less than 0, the power is absorbed by the power grid; p is the power consumed by the load in W; epsilon is a threshold value;
(2) the power calculation formula sent by the power grid is as follows:
in the formula: pPVThe unit is the output power of the photovoltaic power station and is W; pgridThe power generated by the power grid is in W, PgridWhen the power is less than 0, the power is absorbed by the power grid; p is the power consumed by the load in W; plossThe total loss is given in W.
4. The method for configuring the energy storage capacity in the integrated photovoltaic/energy storage system according to claim 1, wherein: the specific method of the step 3 comprises the following steps: the method specifically comprises a calculation method of the energy storage capacity of the lead-acid battery energy storage system during peak clipping and valley filling and a calculation method of the energy storage capacity of the lead-acid battery energy storage system during fluctuation stabilizing, wherein the calculation methods are as follows:
(1) the calculation formula of the energy storage capacity of the energy storage system of the lead-acid battery during peak clipping and valley filling is as follows:
in the formula: w is the capacity needed by the storage battery during peak clipping and valley filling, and the unit is J; pPVThe unit is the output power of the photovoltaic power station and is W; pgridThe power generated by the power grid is in W, PgridWhen the power is less than 0, the power is absorbed by the power grid; p is the power consumed by the load inIs W; α is the ratio of the capacity of the battery itself to the capacity actually used; delta is a margin coefficient;
(2) the calculation formula of the energy storage capacity of the lead-carbon battery energy storage system when the fluctuation is stabilized is as follows:
in the formula: w is the capacity needed by the storage battery when the fluctuation is stabilized, and the unit is J; pPVThe unit is the output power of the photovoltaic power station and is W; pfilThe unit is the output power of the photovoltaic power station after filtering and is W; α is the ratio of the capacity of the battery itself to the capacity actually used; δ is a margin coefficient.
5. The method for configuring the energy storage capacity in the integrated photovoltaic/energy storage system according to claim 1, wherein: the specific method of the step 4 comprises the following steps: according to the energy storage capacity obtained by calculation, analog simulation research is carried out on Matlab/Simulink software, and the effectiveness of the established model and the energy storage capacity algorithm can be verified according to the power change curve of each subsystem after the energy storage system is added.
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