CN110994655A - Centralized coordination control method for distributed power supply - Google Patents
Centralized coordination control method for distributed power supply Download PDFInfo
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- CN110994655A CN110994655A CN201911018422.0A CN201911018422A CN110994655A CN 110994655 A CN110994655 A CN 110994655A CN 201911018422 A CN201911018422 A CN 201911018422A CN 110994655 A CN110994655 A CN 110994655A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E70/00—Other energy conversion or management systems reducing GHG emissions
- Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin
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Abstract
The invention discloses a centralized coordination control method of a distributed power supply, which specifically comprises the following steps: acquiring current charging state parameters of energy storage units in the microgrid system; comparing the acquired current charging state parameters of the energy storage units with the charging state parameters set by the microgrid system; and based on the comparison result, selecting a proper control strategy to perform centralized coordination control on each distributed power supply in the microgrid system. According to the invention, the acquired current charging state parameters of the energy storage unit are compared with the charging state parameters set by the microgrid system, and the schedulability of the microgrid system is improved and the charging balance of the energy storage unit is smoothly realized by switching three control modes.
Description
Technical Field
The invention belongs to the technical field of distributed power supply control, and particularly relates to a centralized coordination control method for a distributed power supply.
Background
Energy is an important material basis for the development of economic society. In recent years, the demand for energy is continuously increasing, fossil energy is increasingly exhausted, the development of nuclear energy is limited, and the energy problem frequently becomes a serious challenge for countries in the world. Meanwhile, the aging of the traditional power system structure and the continuous improvement of the requirement of users on the quality of electric energy enable the development and utilization of renewable energy sources to become a perfect path for social sustainable development. Distributed Generation (DG) has received increasing attention in the 21 st century because of its advantages of environmental protection, high efficiency, flexibility, low investment, etc. However, the outputs of distributed power sources are random and their large number of accesses can contribute a series of uncertainty effects to the distribution grid. The main effects are as follows:
(1) there are many distributed generators (fans, photovoltaics, energy storage) in the microgrid with a frequency converter as an interface, but the frequency converter lacks mechanical parts similar to the rotor of a synchronous generator, resulting in the microgrid lacking inertia. When the micro-grid is disturbed by sudden load change and the like, the voltage and the frequency of the micro-grid are changed rapidly, and the distributed power supply is required to respond rapidly, which provides a challenge for the coordinated control of the distributed power supply.
(2) The new energy generator set exits from the controllable generator set, and other distributed generator sets are needed to inhibit the output fluctuation of the new energy generator set to enable the micro-grid to become the controllable generator set.
The micro-grid is one of effective ways to solve the problems of distributed power generation and grid connection. The distributed load power generation system can operate on a power grid and also can operate on a remote island, and the flexibility and the reliability of load distributed power generation are improved. However, the micro-grids formed by the distributed power supply have various forms and different performances. For example, the new energy power generation has the problems of uncertainty and fluctuation, the stored energy can quickly adjust the charging and discharging power, and the output power fluctuation of the new energy generator set is stabilized. For economic reasons, the energy storage capacity of a microgrid configuration is limited by the installed capacity fraction. In the case of a limited energy storage capacity, the State of charge (SOC) is a problem that must be considered in operation. If the SOC value is too high or too low, the normal operation of the ESSS is affected. Furthermore, when there are multiple energy storage elements in the microgrid, the SOC of the energy storage elements needs to be balanced to avoid severe charging of the energy storage elements. Other deep discharge conditions can affect the stable operation and energy storage life of the microgrid. Therefore, how to coordinate and control the distributed power supplies in the microgrid according to different types of characteristics of the distributed power supplies, fully utilize various distributed power supplies and better realize the control target of the microgrid is a problem which needs to be researched really.
Disclosure of Invention
In order to solve the problems, the invention provides a centralized coordination control method for a distributed power supply, which maintains the energy storage SOC in a proper interval through a switching strategy of an operation mode, and improves the schedulability and stability of the microgrid during grid-connected operation.
In order to achieve the technical purpose and achieve the technical effects, the invention is realized by the following technical scheme:
the invention provides a centralized coordination control method of a distributed power supply, which comprises the following steps:
acquiring current charging state parameters of energy storage units in the microgrid system;
comparing the acquired current charging state parameters of the energy storage units with the charging state parameters set by the microgrid system;
and based on the comparison result, selecting a proper control strategy to perform centralized coordination control on each distributed power supply in the microgrid system.
Optionally, the set charging state parameters include an energy storage minimum charging state parameter, an energy storage normal charging state parameter, and an energy storage maximum charging state parameter.
Optionally, the selecting a suitable control strategy to perform centralized coordination control on each distributed power source in the microgrid system based on the comparison result includes the following steps:
when the obtained current charging state parameter of the energy storage unit is smaller than or equal to the energy storage minimum charging state parameter, a control instruction is sent to each distributed power supply in the microgrid system to control the microgrid to be in a maximum power tracking working mode; and meanwhile, a control instruction is sent to an energy storage unit in the microgrid system to control the microgrid system to be in a self-generating working mode.
Optionally, the output power of each distributed power source and the output power of each energy storage unit are respectively:
PRESi,des＝1
PESS,des＝AGCfeedforward1+AGCfeedback1
in the formula, PRESi,desIs the per-unit value P based on the maximum output power of the distributed power supplyESS,desIs a per unit value with the energy storage capacity of the energy storage unit as a reference value, AGCfeedforward1And AGCfeedback1A feed-forward component and a feedback component representing an automatic generation mode of operation, respectively, and:
AGCfeedback1＝KfpΔPline+KLPI∫ΔPlinedt
in the formula,. DELTA.PlineActive power P for interaction of main network and micro-grid systemlineAnd power scheduling instruction PlinecmdDeviation of (A), SESSiIs the apparent power, P, of the energy storage unitREGiFor the output power, P, of a new-energy generator setsysActive power, K, for microgrid systemsfpAnd KLPIRespectively representing the proportional coefficient and the integral coefficient of a proportional-integral link in an automatic power generation working mode.
Optionally, the selecting a suitable control strategy to perform centralized coordination control on each distributed power source in the microgrid system based on the comparison result includes the following steps:
when the acquired current charging state parameter of the energy storage unit is larger than or smaller than the energy storage normal charging state parameter, a control instruction is sent to each distributed power supply in the microgrid system to control the microgrid system to be in an automatic power generation working mode; and meanwhile, a control instruction is sent to an energy storage unit in the microgrid system to control the microgrid system to be in a hot standby working mode.
Optionally, the output power of each distributed power source and the output power of each energy storage unit are respectively:
PESS,des＝AGCfeedforward2+AGCfeedback2
in the formula, AGCfeedforward2And AGCfeedback2A feedforward component and a feedback component, respectively, of the automatic generation mode of operation, and:
AGCfeedback1＝KfpΔPline+KLPI∫ΔPlinedt
in the formula,. DELTA.PlineActive power P for interaction of main network and micro-grid systemlineAnd power scheduling instruction PlinecmdDeviation of (A), KfpAnd KLPIRespectively representing the proportional coefficient and the integral coefficient of a proportional-integral link in an automatic power generation working mode.
Optionally, the selecting a suitable control strategy to perform centralized coordination control on each distributed power source in the microgrid system based on the comparison result further includes the following steps:
when the sum of the maximum output of all the distributed power supplies is greater than or equal to the sum of the scheduling instructions of the load and the main network interactive power, sending a control instruction to each distributed power supply in the microgrid system, and controlling each distributed power supply to allocate the electric quantity required by the load in an equal proportion according to the maximum output power, wherein the allocation formula is as follows:
optionally, the selecting a suitable control strategy to perform centralized coordination control on each distributed power source in the microgrid system based on the comparison result further includes the following steps:
when the sum of the maximum output of all the distributed power supplies is smaller than the sum of the scheduling instructions of the interactive power of the load and the main network, sending a control instruction to an energy storage unit in the microgrid system, and compensating the difference value between the sum of the maximum output of all the distributed power supplies and the sum of the scheduling instructions of the interactive power of the load and the main network by the energy storage unit; and meanwhile, sending a control instruction to each distributed power supply in the microgrid system, and controlling each distributed power supply to share the electric quantity required by the load in an equal proportion according to the maximum output power.
Optionally, the selecting a suitable control strategy to perform centralized coordination control on each distributed power source in the microgrid system based on the comparison result includes the following steps:
and when the obtained current charging state parameter of the energy storage unit is greater than or equal to the energy storage maximum charging state parameter, sending a control instruction to each distributed power supply and the energy storage unit in the microgrid system, and controlling the distributed power supply and the energy storage unit to be in an automatic power generation working mode.
Optionally, the output power of each distributed power source and the output power of each energy storage unit are respectively:
PESS,des＝PRESi,des＝AGCfeedforward3+AGCfeedback3
in the formula, PRESi,desIs the per-unit value P based on the maximum output power of the distributed power supplyESS,desIs a per unit value with the energy storage capacity of the energy storage unit as a reference value, AGCfeedforward3And AGCfeedback3A feed-forward component and a feedback component representing an automatic generation mode of operation, respectively, and:
AGCfeedback3＝KfpΔPline+KLPI∫ΔPlinedt
in the formula, SESSiIs the apparent power, P, of the energy storage unitRESi,maxIs the maximum output power, P, of the distributed power supplysysActive power, K, for microgrid systemsfpAnd KLPIRespectively representing the proportional coefficient and the integral coefficient of a proportional-integral link in an automatic power generation working mode. Delta PlineActive power P for interaction of main network and micro-grid systemlineAnd power scheduling instruction PlinecmdThe deviation of (2).
Optionally, the method further comprises:
sending a droop control instruction to each distributed power supply to realize one-time adjustment of the frequency of the microgrid;
sending a secondary control instruction to each distributed power supply to realize secondary adjustment of the frequency of the microgrid, wherein the secondary control instruction comprises changing the rated operating point p of the distributed power supplyrefAnd translating the droop curve to change the output of the distributed power supply.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, through the coordination control of the distributed power source (the new energy generator) and the energy storage unit, the dispatching of a power grid can be accepted during the micro-grid parallel operation, and the multi-mode operation can be realized during the parallel operation or the island operation, and the SOC of the energy storage unit is maintained in a proper interval through the switching strategy of the operation mode, so that the dispatching performance and the stability during the micro-grid parallel operation are improved. Compared with the mode of carrying out manual coordination control on the microgrid by the traditional power grid, the method has the advantages that the control mode of the microgrid is improved, the microgrid system has the level of automatic processing, the issuing of the coordination control strategy realizes the effect of regional autonomy, manual verification and verification are not needed, and the efficiency and the reliability are improved.
Drawings
In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the present disclosure taken in conjunction with the accompanying drawings, in which:
fig. 1 is a schematic structural diagram of a microgrid system according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a microgrid system control according to an embodiment of the present invention;
FIG. 3 is a diagram illustrating the switching among mode 1, mode 2 and mode 3 according to an embodiment of the present invention;
FIG. 4(a) is one of the results of switching from mode 2 to mode 1 according to one embodiment of the present invention;
FIG. 4(b) is a second diagram illustrating the result of switching from mode 2 to mode 1 according to an embodiment of the present invention;
FIG. 4(c) is a third diagram illustrating the result of switching from mode 2 to mode 1 according to an embodiment of the present invention;
FIG. 4(d) is a fourth diagram illustrating the result of switching from mode 2 to mode 1 according to an embodiment of the present invention;
FIG. 5(a) is one of the results of switching from mode 2 to mode 3 according to one embodiment of the present invention;
FIG. 5(b) is a second diagram illustrating the result of switching from mode 2 to mode 3 according to an embodiment of the present invention;
FIG. 5(c) is a third diagram illustrating the result of switching from mode 2 to mode 3 according to an embodiment of the present invention;
FIG. 5(d) is a diagram illustrating the result of switching from mode 2 to mode 3 according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of the invention.
The following detailed description of the principles of the invention is provided in connection with the accompanying drawings.
The remaining capacity of the energy storage unit can be represented by the SOC, so that the SOC can be used as a basis for judging charging and discharging of the energy storage unit. One of the methods for calculating the SOC of the energy storage unit is as follows:
in the formula, SOC (0) is the initial value of the energy storage unit SOC, IESSIs the output current of the energy storage unit, SESSIs the capacity of the energy storage unit.
The invention provides a centralized coordination control method of a distributed power supply, which specifically comprises the following steps:
(1) acquiring current charging state parameters of energy storage units in the microgrid system;
in a specific embodiment of the present invention, the microgrid system includes a microgrid central processing unit, and a plurality of distributed power supplies, energy storage units, loads, and other devices connected to the microgrid central processing unit, where the distributed power supplies include: the fan controller and the fan converter, the photovoltaic controller and the photovoltaic converter are connected; the energy storage unit comprises an energy storage converter and an energy storage controller, and is specifically shown in fig. 1;
(2) comparing the acquired current charging state parameters of the energy storage units with the charging state parameters set by the microgrid system;
(3) and based on the comparison result, selecting a proper control strategy to perform centralized coordination control on each distributed power supply in the microgrid system.
In the practical application process, before the centralized coordination control method of the distributed power supply is performed, firstly, the whole microgrid system needs to be checked for grid connection, the on-line of the grid-connected point switches of all new energy devices such as photovoltaic devices, fans and energy storage devices in a microgrid area is checked, whether an RESS system (namely, the distributed power supply) and an ESS system (namely, an energy storage unit) operate normally is checked, and starting functions of AGC (automatic gain control), MPPT (maximum power point tracking) and hot standby mode are respectively deployed in the RESS system and the ESS system. The starting function of the AGC mode (self-generating working mode) is the starting of the automatic power generation control function in the microgrid system, after the starting, the load is distributed to all distributed power supplies according to the principle that the maximum output power is equal in proportion through a microgrid central processing unit, and the distributed power supplies regulate output according to power instructions. The starting function of the MPTT mode (maximum power tracking working mode) is the starting of the maximum power tracking function in the microgrid system, after the starting, the energy storage unit only participates in peak clipping and valley filling of the power grid in the load peak valley period, and the energy storage unit is charged with constant power in the off-peak period. The starting function of the hot standby mode is to start the mode when the output of a distributed power supply (a new energy generator set) in the microgrid system is insufficient, and the effect of microgrid power balance is achieved by controlling the energy storage unit to discharge to compensate the insufficient power generation.
The state of charge parameter that microgrid system set for, record SOC, it includesEnergy storage minimum state of charge parameter SOClowEnergy storage normal charging state parameter SOCnormAnd energy storage maximum state of charge parameter SOChigh。
In a specific embodiment of the invention, the distributed power supply can be selected as a new energy generator set; based on the comparison result, selecting a proper control strategy to perform centralized coordination control on each distributed power supply in the microgrid system comprises the following steps:
when the acquired state of charge parameter SOC of the energy storage unit is less than or equal to the minimum state of charge parameter SOC of the energy storagelow(SOC≤SOClow) When the microgrid system is in an abnormal operation state (mode 1), specifically referring to fig. 3, a control instruction is sent to each distributed power supply in the microgrid system to control the microgrid system to be in a Maximum Power Point Tracking (MPPT) mode; meanwhile, a control instruction is sent to an energy storage unit in the microgrid system to control the energy storage unit to be in a self-generating working mode, the energy storage unit is responsible for controlling the interaction power of the microgrid and a power grid, so that the energy storage unit tracks a scheduling instruction (the scheduling instruction is the power between each transformer substation and a bus gateway issued by related scheduling automation workers in a master station system), and finally the energy storage unit is charged, so that the energy storage unit is prevented from deep discharging, and meanwhile, a larger discharging margin is kept.
Wherein, the output power of each distributed power supply and the energy storage unit is respectively as follows:
PRESi,des＝1
PESS,des＝AGCfeedforward1+AGCfeedback1
in the formula, PRESi,desIs the per-unit value P based on the maximum output power of the distributed power supplyESS,desIs a per unit value with the energy storage capacity of the energy storage unit as a reference value, AGCfeedforward1And AGCfeedback1A feed-forward component and a feedback component representing an automatic generation mode of operation, respectively, and:
AGCfeedback1＝KfpΔPline+KLPI∫ΔPlinedt
in the formula,. DELTA.PlineActive power P for interaction of main network and micro-grid systemlineAnd power scheduling instruction PlinecmdDeviation of (A), KfpAnd KLPIRespectively representing the proportionality and integral coefficients of the proportional-integral link in the automatic power generation mode, PsysFor the total active power demand in the microgrid, SESSiIs the apparent power, P, of the energy storage unitREGiIs the output power, P, of a distributed power supply (new energy generator set)sysActive power of the microgrid system, and:
Psys＝∑PRESi+∑PESSi-Pline+Plinecmd
in the formula, PRESiAnd PESSiActive power output by a distributed power supply (new energy generator) and active power output by an energy storage unit, PlineActive power, P, for interaction of main network and microgrid systemslinecmdAnd giving an active power scheduling instruction for the energy management system.
In a second specific embodiment of the present invention, the selecting a suitable control strategy to perform centralized coordination control on each distributed power source in the microgrid system based on the comparison result includes the following steps:
when the acquired charging state parameter of the energy storage unit is greater than or less than the energy storage normal charging state parameter, that is, the microgrid system is in a normal operation state (mode 2), specifically referring to fig. 3, a control instruction is sent to each distributed power supply in the microgrid system, and in the specific implementation process of the invention, the distributed power supply can be a new energy generator set and is controlled to be in an automatic power generation working mode; and meanwhile, a control instruction is sent to an energy storage unit in the microgrid system to control the microgrid system to be in a hot standby working mode.
The maximum output sum and the minimum output sum of the new energy generator set are respectively assumed to be: pRES,max、PRES,minThe sum of the maximum charging and discharging power of the energy storage unit is-PESS,max、PESS,maxScheduling instruction P of interaction power of microgrid and main network (namely main network)linecmdNormally, the following conditions should be satisfied:
Plinecmd≥PRES,min-Pload
Plinecmd≤PRES,max-Pload
scheduling instruction P of interaction power of microgrid and main network (namely main network)linecmdThe short time (e.g. peak clipping and valley filling time period, generally 3 hours, e.g. 14 o 'clock to 17 o' clock, and 0 o 'clock to 3 o' clock) should satisfy the following conditions:
Plinecmd≥PRES,min-PESS,max-Pload
Plinecmd≤PRES,min+PESS,max-Pload
in the formula, PloadIs the active power of the load.
Wherein, the output power of each distributed power supply and the energy storage unit is respectively as follows:
PESS,des＝AGCfeedforward2+AGCfeedback2
in the formula, AGCfeedforward2And AGCfeedback2A feedforward component and a feedback component, respectively, of the automatic generation mode of operation, and:
AGCfeedback1＝KfpΔPline+KLPI∫ΔPlinedt
in the formula,. DELTA.PlineActive power P for interaction of main network and micro-grid systemlineAnd power scheduling instruction PlinecmdDeviation of (A), KfpAnd KLPIRespectively representing the proportional coefficient and the integral coefficient of a proportional-integral link in an automatic power generation working mode.
Further, the selecting a proper control strategy to perform centralized coordination control on each distributed power supply in the microgrid system based on the comparison result further includes the following steps:
when the sum of the maximum output of all the distributed power supplies is greater than or equal to the sum of scheduling instructions of interactive power (interactive power is provided through a bus in a scheduled power distribution automation master station system and a gateway of the microgrid) of loads (the loads exist in the microgrid, real-time data are accessed into an RESS and ESS system, and the electric quantity data of the loads can be checked) and a main network (a power grid with a voltage level of 35kv and above), sending a control instruction to each distributed power supply in the microgrid system, and controlling each distributed power supply to allocate the electric quantity required by the loads in an equal proportion according to the maximum output power, wherein the allocation formula is specifically as follows:
based on the comparison result, selecting a proper control strategy to perform centralized coordination control on each distributed power supply in the microgrid system, and further comprising the following steps:
when the sum of the maximum output of all the distributed power supplies is smaller than the sum of the scheduling instructions of the interactive power of the load and the main network, sending a control instruction to an energy storage unit in the microgrid system, and compensating the difference value between the sum of the maximum output of all the distributed power supplies and the sum of the scheduling instructions of the interactive power of the load and the main network by the energy storage unit; and meanwhile, sending a control instruction to each distributed power supply in the microgrid system, and controlling each distributed power supply to share the electric quantity required by the load in an equal proportion according to the maximum output power.
In a third specific embodiment of the present invention, the selecting a suitable control strategy to perform centralized coordination control on each distributed power source in the microgrid system based on the comparison result includes the following steps:
when the obtained current charging state parameter of the energy storage unit is greater than or equal to the maximum energy storage charging state parameter, that is, the microgrid system is in an abnormal state (mode three), a control instruction is sent to each distributed power supply and the energy storage unit in the microgrid system, the distributed power supply and the energy storage unit are controlled to be in an automatic generation working mode (AGC mode), the interaction power of the microgrid and the main network is controlled, and the scheduling instruction is tracked, specifically referring to FIG. 3; in this embodiment, the energy storage unit is discharged to prevent the energy storage unit from being deeply charged, and meanwhile, a larger charging margin is kept.
Wherein, the output power of each distributed power supply and the energy storage unit is respectively as follows:
PESS,des＝PRESi,des＝AGCfeedforward3+AGCfeedback3
in the formula, PRESi,desIs the per-unit value P based on the maximum output power of the distributed power supplyESS,desIs a per unit value with the energy storage capacity of the energy storage unit as a reference value, AGCfeedforward3And AGCfeedback3A feed-forward component and a feedback component representing an automatic generation mode of operation, respectively, and:
AGCfeedback3＝KfpΔPline+KLPI∫ΔPlinedt
in the formula, SESSiIs the apparent power, P, of the energy storage unitRESi,maxIs the maximum output power, P, of the distributed power supplysysActive power, K, for microgrid systemsfpAnd KLPIRespectively representing the proportional coefficient and the integral coefficient of a proportional-integral link in an automatic power generation working mode. Delta PlineActive power P for interaction of main network and micro-grid systemlineAnd power scheduling instruction PlinecmdThe deviation of (2).
As shown in fig. 2, the method further comprises:
sending a droop control instruction to each distributed power supply to realize one-time adjustment of the frequency of the microgrid;
sending a secondary control instruction to each distributed power supply to realize secondary adjustment of the frequency of the microgrid, wherein the secondary control instruction comprises changing the rated operating point p of the distributed power supplyrefAnd translating the sag curve, trueThe distributed power supply output is now changed.
Specifically;
the primary adjustment is carried out by a Local Controller (LC) of each distributed power supply, so that the primary adjustment of the frequency of the microgrid is realized; the secondary regulation is responsible for a micro-grid central processing unit (MGCC) and realizes the consideration of main micro-grid interaction power control, the secondary regulation of micro-grid frequency, the distribution of active load, the switching of operation modes and the like.
The primary regulation of the distributed power supply uses conventional droop control as shown in the following equation:
f＝fref+kp(pref-p)
wherein f and frefFrequency and frequency reference values, p and p, respectively, for a distributed power supplyrefThe active power and the active power reference value output by the distributed power supply are respectively. The secondary regulation is carried out by changing the rated operating point p of the distributed power supplyrefOr the slope of the droop curve, changes the distributed power output. However, changing the slope of the droop curve can affect the dynamics of the closed loop system, which can lead to some unpredictable small signal stability problems. Thus, the present invention selectively changes the rated operating point p of the distributed power supplyrefThe translational droop curve changes the distributed power supply output.
Example 2
When a plurality of energy storage units exist in the microgrid system, the highest and the lowest of the charge state parameters of all the energy storage units are used as the operation mode switching judgment conditions, which may cause the conditions of disordered mode switching judgment and unreasonable mode switching. In order to avoid the above situation, the present invention uses the average value of the charge state parameters of all the energy storage units as the determination condition for the operation mode switching, as shown in the following formula. The other cases are similar to the single energy storage case.
In the formula, SESSiCapacity, SOC, of energy storage unit i (i ═ 1,2 … n)iFor the ith to store energyThe state of charge, SOC, of the cell is the calculated average.
Simulation and verification
The invention aims to verify the effectiveness of the proposed centralized coordination control method of the distributed power supply. And (3) carrying out modeling simulation test by using the microgrid system (photovoltaic system, 2 fans and 3 energy storage systems) shown in the figure I. The interaction power of the micro-grid and the main grid (power grid) is positive when the micro-grid flows out, the output power of the energy storage unit is positive, and the value of the mode switching judgment condition (the charging state parameter of the energy storage unit) can be determined according to the actual condition of the micro-grid. The main parameters of the simulation system are shown in table 1.
As can be seen from fig. 4(a), during the discharging process, the energy storage unit can smoothly approach the equilibrium of the SOC. As can be seen from fig. 4(b), the microgrid can more accurately and quickly track the scheduling instruction of the interactive power of the power grid and the microgrid, and the control effect of the interactive power of the power grid and the microgrid is hardly affected in the process that the stored energy tends to be in SOC equilibrium. As can be seen from fig. 4(a) and 4(d), when the microgrid operates in the mode 2, the load is preferentially distributed by the new energy generator set in equal proportion to the maximum output power, and the energy storage unit does not output power; when the interactive power of the power grid and the microgrid rises to 2MW and the maximum sum of the new energy generator sets is smaller than the active power demand of the microgrid, the energy storage unit compensates the shortage power. And when T is 45s, the energy storage unit discharges until the SOC is less than or equal to 40%, and the microgrid operation mode is switched from the mode 2 to the mode 1. As can be seen from fig. 4(b), the switching process does not cause fluctuation of the power interaction between the grid and the microgrid, i.e., the microgrid is smoothly switched from mode 2 to mode 1. When the microgrid operates in the mode 1, as can be seen from fig. 4(d), the new energy generator set operates along the MPPT curve to charge the stored energy.
As can be seen from fig. 5(a), although the SOC of the energy storage unit 3 has reached 85%, the average value of the SOCs of all the energy storage units is less than 80%, and the microgrid still operates in the mode 2. As can be seen from fig. 5(b), the microgrid can more accurately and quickly track the scheduling instruction of the interactive power of the power grid and the microgrid, and the interactive power of the microgrid and the power grid does not fluctuate in the process that the stored energy tends to be balanced by the SOC, that is, the stored energy can smoothly tend to be balanced by the SOC in the charging process. As can be seen from fig. 5(d), when the load of the microgrid is negative, the output of the new energy generator set is reduced to 0, the stored energy absorbs the remaining active power in the microgrid, which may occur in the load valley period, and the power grid performs valley filling by using the microgrid. When t is 41s, the SOC of the stored energy is greater than or equal to 80%, the microgrid operation mode is switched from the mode 2 to the mode 3, and as can be seen from fig. 5(b), no fluctuation of the interaction power between the microgrid and the power grid is caused in the switching process, that is, the microgrid is smoothly switched from the mode 2 to the mode 3. As can be seen from fig. 5(d), when the microgrid operates in the mode 3 and the load of the microgrid is positive, the new energy generator set and the stored energy distribute the load in equal proportion to the maximum output work load, so that the stored energy is discharged.
In summary, when the microgrid operates in the mode 1, the mode 2 or the mode 3, the microgrid can receive power grid scheduling, and can be smoothly switched from the operation mode 2 to the operation mode 1 and the mode 3, that is, the discharge power of the stored energy can be dynamically adjusted along with the change of the deviation of the SOC of the stored energy, so that the stored energy smoothly reaches the balance of the SOC. The feasibility and the accuracy of the method provided by the invention are proved.
The foregoing shows and describes the general principles and broad features of the present invention and advantages thereof. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (11)
1. A centralized coordination control method for distributed power supplies is characterized by comprising the following steps:
acquiring current charging state parameters of energy storage units in the microgrid system;
comparing the acquired current charging state parameters of the energy storage units with the charging state parameters set by the microgrid system;
and based on the comparison result, selecting a proper control strategy to perform centralized coordination control on each distributed power supply in the microgrid system.
2. The centralized coordination control method for distributed power supplies according to claim 1, wherein: the set charging state parameters comprise an energy storage minimum charging state parameter, an energy storage normal charging state parameter and an energy storage maximum charging state parameter.
3. The centralized coordination control method for distributed power supplies according to claim 2, wherein: based on the comparison result, selecting a proper control strategy to perform centralized coordination control on each distributed power supply in the microgrid system comprises the following steps:
when the obtained current charging state parameter of the energy storage unit is smaller than or equal to the energy storage minimum charging state parameter, a control instruction is sent to each distributed power supply in the microgrid system to control the microgrid to be in a maximum power tracking working mode; and meanwhile, a control instruction is sent to an energy storage unit in the microgrid system to control the microgrid system to be in a self-generating working mode.
4. The centralized coordination control method for distributed power supplies according to claim 3, wherein: the output power of each distributed power supply and each energy storage unit is respectively as follows:
PRESi,des＝1
PESS,des＝AGCfeedforward1+AGCfeedback1
in the formula, PRESi,desIs the per-unit value P based on the maximum output power of the distributed power supplyESS,desIs a per unit value with the energy storage capacity of the energy storage unit as a reference value, AGCfeedforward1And AGCfeedback1A feed-forward component and a feedback component representing an automatic generation mode of operation, respectively, and:
AGCfeedback1＝KfpΔPline+KLPI∫ΔPlinedt
in the formula,. DELTA.PlineActive power P for interaction of main network and micro-grid systemlineAnd power scheduling instruction PlinecmdDeviation of (A), SESSiIs the apparent power, P, of the energy storage unitREGiIs the output power of the distributed power supply, PsysActive power, K, for microgrid systemsfpAnd KLPIRespectively representing the proportional coefficient and the integral coefficient of a proportional-integral link in an automatic power generation working mode.
5. The centralized coordination control method for distributed power supplies according to claim 2, wherein: based on the comparison result, selecting a proper control strategy to perform centralized coordination control on each distributed power supply in the microgrid system comprises the following steps:
when the acquired current charging state parameter of the energy storage unit is larger than or smaller than the energy storage normal charging state parameter, a control instruction is sent to each distributed power supply in the microgrid system to control the microgrid system to be in an automatic power generation working mode; and meanwhile, a control instruction is sent to an energy storage unit in the microgrid system to control the microgrid system to be in a hot standby working mode.
6. The centralized coordination control method for distributed power supplies according to claim 5, wherein: the output power of each distributed power supply and each energy storage unit is respectively as follows:
PESS,des＝AGCfeedforward2+AGCfeedback2
in the formula, AGCfeedforward2And AGCfeedback2A feedforward component and a feedback component, respectively, of the automatic generation mode of operation, and:
AGCfeedback1＝KfpΔPline+KLPI∫ΔPlinedt
in the formula,. DELTA.PlineActive power P for interaction of main network and micro-grid systemlineAnd power scheduling instruction PlinecmdDeviation of (A), KfpAnd KLPIRespectively representing the proportionality and integral coefficients of the proportional-integral link in the automatic power generation mode, PsysActive power, P, for microgrid systemsRESi,maxIs the maximum output power, P, of the distributed power supplyREGiIs the output power of the distributed power supply.
7. The centralized coordination control method for distributed power supplies according to claim 5, wherein: based on the comparison result, selecting a proper control strategy to perform centralized coordination control on each distributed power supply in the microgrid system, and the method further comprises the following steps:
when the sum of the maximum output of all the distributed power supplies is greater than or equal to the sum of the scheduling instructions of the load and the main network interactive power, sending a control instruction to each distributed power supply in the microgrid system, and controlling each distributed power supply to allocate the electric quantity required by the load in an equal proportion according to the maximum output power, wherein the allocation formula is as follows:
8. the centralized coordination control method for distributed power supplies according to claim 5, wherein: based on the comparison result, selecting a proper control strategy to perform centralized coordination control on each distributed power supply in the microgrid system, and further comprising the following steps:
when the sum of the maximum output of all the distributed power supplies is smaller than the sum of the scheduling instructions of the interactive power of the load and the main network, sending a control instruction to an energy storage unit in the microgrid system, and compensating the difference value between the sum of the maximum output of all the distributed power supplies and the sum of the scheduling instructions of the interactive power of the load and the main network by the energy storage unit; and meanwhile, sending a control instruction to each distributed power supply in the microgrid system, and controlling each distributed power supply to share the electric quantity required by the load in an equal proportion according to the maximum output power.
9. The centralized coordination control method for distributed power supplies according to claim 2, wherein: based on the comparison result, selecting a proper control strategy to perform centralized coordination control on each distributed power supply in the microgrid system comprises the following steps:
and when the obtained current charging state parameter of the energy storage unit is greater than or equal to the energy storage maximum charging state parameter, sending a control instruction to each distributed power supply and the energy storage unit in the microgrid system, and controlling the distributed power supply and the energy storage unit to be in an automatic power generation working mode.
10. The centralized coordination control method for distributed power supplies according to claim 9, wherein: the output power of each distributed power supply and each energy storage unit is respectively as follows:
PESS,des＝PRESi,des＝AGCfeedforward3+AGCfeedback3
in the formula, PRESi,desIs the per-unit value P based on the maximum output power of the distributed power supplyESS,desIs a per unit value with the energy storage capacity of the energy storage unit as a reference value, AGCfeedforward3And AGCfeedback3A feed-forward component and a feedback component representing an automatic generation mode of operation, respectively, and:
AGCfeedback3＝KfpΔPline+KLPI∫ΔPlinedt
in the formula, SESSiAs apparent of the energy storage unitPower, PRESi,maxIs the maximum output power, P, of the distributed power supplysysActive power, K, for microgrid systemsfpAnd KLPIRespectively representing the proportional coefficient and integral coefficient, delta P, of the proportional-integral link in the automatic power generation modelineActive power P for interaction of main network and micro-grid systemlineAnd power scheduling instruction PlinecmdThe deviation of (2).
11. The centralized coordination control method for distributed power supplies according to claim 1, wherein: the method further comprises the following steps:
sending a droop control instruction to each distributed power supply to realize one-time adjustment of the frequency of the microgrid;
sending a secondary control instruction to each distributed power supply to realize secondary adjustment of the frequency of the microgrid, wherein the secondary control instruction comprises changing the rated operating point p of the distributed power supplyrefAnd translating the droop curve to change the output of the distributed power supply.
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