CN113131498A - Independent micro-grid control method - Google Patents

Abstract

The invention discloses an independent micro-grid control method, which divides a single set of SOC for energy storage; when the bus tie switch is disconnected, averaging the SOC of the energy storage devices under the same bus to determine the value of the SOC of the equivalent energy storage devices under each bus, and regarding the sub-microgrid under one bus as an independent microgrid; when the bus coupler is closed, determining the SOC of the equivalent energy storage devices under each bus, and determining the SOC of the equivalent energy storage devices of the independent micro-grid according to the SOC difference of the equivalent energy storage devices under each bus; according to the interval where the equivalent SOC of the independent microgrid is located, the equivalent energy storage SOC is located in the safety interval by adjusting the distributed power supply and the load.

Description

Independent micro-grid control method

Technical Field

The invention belongs to the technical field of micro-grid control, and particularly relates to an independent micro-grid control method.

Background

Currently, an independent micro-grid integrating various distributed power sources and energy storage systems has become a flexible, reliable and economical power supply mode, which can effectively solve the problem of power supply in remote areas such as islands, mountainous areas, and the like. Because a large power grid is not used for providing support, a voltage source type micro source needs to be arranged in an independent micro power grid to provide voltage and frequency reference for a system, and power balance between a distributed power source and a load is realized. In the past, when an independent micro-grid is designed to operate, a diesel generator with mature technology and reliable operation is commonly used as a main voltage source type micro-source in the micro-grid. However, due to the problems of fossil energy crisis, environmental pollution and the like, an energy storage device which is more economical and environment-friendly is urgently needed to replace a diesel generator as a main voltage source type micro source of a system. When a distributed power supply in an independent microgrid is not matched with a load for a long time, an energy storage device serving as a main voltage source type microgrid is easily in a continuous charging or discharging State for a long time, and once the State Of Charge (SOC) Of the energy storage device exceeds a design limit value, the energy storage device is forced to quit operation, and finally the whole microgrid is stopped.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides an independent microgrid control method which can prevent an energy storage device SOC serving as a main voltage source in an independent microgrid from running out of limit, so that the whole microgrid system is powered down.

The independent micro-grid described herein includes energy storage, distributed power sources including wind power, photovoltaic, and diesel generators, and loads including electrical and thermal loads.

The technical scheme adopted by the invention is as follows

The invention provides an independent microgrid control method, which comprises the following steps:

dividing the SOC for single set of energy storage;

when the bus tie switch is disconnected, averaging the SOC of the energy storage devices under the same bus to determine the value of the SOC of the equivalent energy storage devices under each bus, and regarding the sub-microgrid under one bus as an independent microgrid;

when the bus coupler is closed, determining the SOC of the equivalent energy storage devices under each bus, and determining the SOC of the equivalent energy storage devices of the independent micro-grid according to the SOC difference of the equivalent energy storage devices under each bus;

and according to the interval where the equivalent SOC of the independent micro-grid is located, the equivalent energy storage SOC is located in a safety interval by adjusting the distributed power supply and the load.

The method comprises the following specific steps:

in a normal operation state, neglecting system loss, and the relation formula required to be satisfied in the system operation process is as follows:

P_BSD-P_BSC＝P_Load-P_DG (1)

the normal state is a state of power balance in the microgrid which meets the formula (1); if the power in the microgrid does not satisfy the formula (1), an abnormal operation state such as a ground fault may exist.

P in formula (1)_BSD、P_BSCIndicating discharge, charge power of stored energy, P_LoadRepresenting the power consumed by the load, P_DGRepresenting the distributed power source output power. The power balance equation should hold when the system is operating steadily.

Since the charging and discharging states of the stored energy cannot occur simultaneously at each moment, P is set_BS＝P_BSD-P_BSCFor storing power (the same energy storage device cannot exhibit the characteristics of charging and discharging for the outside, at any time P_BSD、P_BSCAt least one will be 0), when P is_BSWhen the output power is more than or equal to 0, the energy storage output power is represented; when P is present_BS<And 0 represents the stored energy absorbed power. Setting P_LD＝P_Load-P_DGRepresents the equivalent load power of the system (independent micro-grid system) when P_LDWhen the load power is more than or equal to 0, the load power is more than the output power of the distributed power supply; when P is present_LD<And when 0, the distributed power supply output power is larger than the load power.

Dividing a single set of energy storage SOC interval according to the energy storage operation design limit requirement;

by setting SOC_min、SOC_low、SOC_high、SOC_maxWith equal parameters, the energy storage of a single set is originally 0,100 percent]Is divided into 5 sections, which are respectively [0, SOC_min]、[SOC_min,SOC_low]、[SOC_low,SOC_high]、[SOC_high,SOC_max]、[SOC_max,100％]After the interval to which the energy storage SOC belongs is judged, the energy storage SOC is indirectly adjusted by adjusting the distributed power supply and the load in the independent microgrid; as all the single set of energy storage intervals in the power grid are divided identically, the SOC division intervals of the single set of energy storage can represent the equivalent energy storage division intervals of the independent micro-power grid.

SOC_min、SOC_maxRespectively the minimum and maximum values of the energy storage SOC, SOC_min、SOC_maxThe method is determined by considering the energy storage operation life and the operation limit in the design stage, and is not easily changed in the operation stage after the determination; SOC_low、SOC_highRespectively a low value and a high value of the energy storage SOC, and is used for determining an adjustment dead zone (namely a safety interval, the main station can not adjust the energy storage SOC) of the energy storage SOC, and the adjustable SOC is predicted according to the load and the power of the distributed power supply (the information is given by the main station system) in an operation stage_low、SOC_highSo as to improve the economical efficiency and the reliability of the operation of the independent micro-grid system.

When the SOC of the stored energy is in [ SOC ]_low,SOC_high]And meanwhile, the master station is an adjustment dead zone of the energy storage SOC and does not control the change of the energy storage SOC. Wherein [ SOC_high,SOC_max]、[SOC_min,SOC_low]And [ SOC ]_low,SOC_high]The interval constitutes an SOC normal operation interval (i.e., [ SOC ]_high,SOC_max]、[SOC_min,SOC_low]And [ SOC ]_low,SOC_high])，[SOC_max,100％]For the upper limit interval of the energy storage SOC, [0, SOC_min]For the lower limit interval of the energy storage SOC, if the diesel engine needs to be considered to be started and stopped, the SOC can be set at 0_min]Adding a critical value SOC corresponding to the starting of the firewood in the interval_DEWhen the SOC is lower than the SOC_DEIs strong and strongThe firewood is started.

When the SOC of the stored energy is in [ SOC ]_high,SOC_max]When the charging power is increased, the charging power of the stored energy is reduced by means of increasing the load and reducing the DG (DG is a distributed power supply) output; when the SOC of the stored energy is in [ SOC ]_max,100％]In the process, the emergency control that the energy storage SOC is higher than the upper limit is required, the energy storage is controlled to discharge with smaller power mainly by means of reducing DG output so as to reduce the SOC, and the SOC is required to be controlled to [ SOC ] in order to avoid frequent conversion of the energy storage between charging and discharging modes_low,SOC_high]Only when the interval is reached, emergency control of the SOC beyond the upper limit is exited; when the SOC of the stored energy is in [ SOC ]_min,SOC_low]When the system is used, the lower limit of the SOC of the stored energy is required to be prevented and controlled, and the discharge power of the stored energy is reduced by means of increasing DG output, reducing load and the like; when the SOC of the stored energy is at 0, SOC_min]When the micro-grid is in use, emergency control is needed to be carried out when the energy storage SOC is lower, measures such as load reduction, firewood generation and the like are adopted (firewood generation is not a clean energy source and is avoided as much as possible, photovoltaic power and wind power are lower only in the micro-grid, and the SOC of the energy storage is in a state of 0 and SOC_min]When the diesel engine is started, the reduction rate of the energy storage SOC is reduced, the micro-grid breakdown caused by the low-SOC offline of the energy storage is avoided), the energy storage is controlled to be charged with smaller power so as to improve the SOC, and the SOC is controlled to be in a state from [ SOC ] to [ SOC ] in order to avoid frequent conversion of the energy storage between a charging mode and a discharging mode_low,SOC_high]In the interval, the emergency control in which the SOC is lower is exited.

Determining an equivalent energy storage SOC value of the independent micro-grid according to the system sectional bus and the on/off position of the bus coupler switch;

when a plurality of sections of buses in the independent micro-grid operate in a splitting mode, the system is equivalent to a plurality of independent island micro-grids, the operation of the plurality of independent island micro-grids is not affected, and meanwhile, the operating conditions of energy storage devices on the same bus are considered to be similar (the energy storage function is to provide voltage and frequency reference for the micro-grid and is a main voltage source of the system), the operating conditions are required to be similar in the voltage source, otherwise, circulation current can be generated to cause large loss of the energy storage system), at the moment, mutually independent control strategies can be adopted, and the independent micro-grid control based on the energy storage SOC is realized on each island micro-grid; when multiple sections of buses in the independent micro-grid operate in parallel, the system is equivalent to a single island sub-micro-grid comprising multiple sections of buses, the lower SOC value of each section of bus is sent, and in order to avoid conflict of control instructions, the overall equivalent energy storage SOC value of the system is confirmed according to the lower energy storage SOC value of each section of bus;

taking an example of parallel operation of two sections of buses, after acquiring energy storage SOC values of the two sections of buses respectively, A) firstly defining the larger of the energy storage SOC values of the two sections of buses as B_SOCThe smaller SOC is S_SOCDefining the difference value SOC_dif＝B_SOC-S_SOC. When SOC is reached_dif<And D, considering that the difference between the two sets of stored SOC is not large, and the two sets of stored SOC are only possibly in the same interval or adjacent intervals (the intervals are shown in FIG. 2). When SOC is reached_dif>And D, considering that the difference between the two sets of stored SOC is large and the two sets of stored SOC are possibly in non-adjacent sections. Wherein D is a positive integer and should be smaller than the minimum segment interval of the SOC (i.e. the one with the smallest width of five segment intervals);

B) when SOC is reached_dif<And D, taking the energy storage condition close to the critical value (namely the nearest interval segment boundary) as the basis for determining the SOC segment control. If B is_SOC>SOC_maxThen, the system SOC E is judged [ SOC ∈ [ ]_max,100％](ii) a If SOC_max>B_SOC>SOC_highThen, the system SOC E is judged [ SOC ∈ [ ]_high,SOC_max](ii) a If S_SOC<SOC_minThen, the system SOC is determined to be [0, SOC ∈_min](ii) a If SOC_low>S_SOC>SOC_minThen, the system SOC E is judged [ SOC ∈ [ ]_min,SOC_low]. If none of the above conditions belong to, judging that the SOC is in [ SOC ]_low,SOC_high]Interval, not controlling the SOC of the system;

C) when SOC is reached_dif>D, the distribution of SOC of two systems is 6, if B_SOC>SOC_high，S_SOC∈[SOC_low,SOC_high]Locking S_SOCAnd (4) storing energy, and discharging the stored energy with high SOC as much as possible. If S_SOC<SOC_low，B_SOC∈[SOC_low,SOC_high]Then is locked B_SOCEnergy storage, early triggering of low SOC protection measures of the system, so that S_SOCIs improved. If B is_SOC>SOC_high，S_SOC<SOC_lowThen according to P_LDDetermine the specific logic if P_LD>0, when the system is heavily loaded, then S is locked_SOCSo that B is_SOCPut energy back to [ SOC ]_low,SOC_high]After the interval, operating according to the existing logic; if P_LD<0, at the moment, the system generates power again and is locked B_SOCSo that S_SOCEnergy absorption, return to [ SOC ]_low,SOC_high]An interval. If the above situation does not exist, it is known that one of the following three states is present: (1) b is_SOC,S_SOC>SOC_high；(2)B_SOC,S_SOC<SOC_low；(3)B_SOC,S_SOC∈[SOC_low,SOC_high]. May be in accordance with the SOC_dif<Controlling the strategy of D;

when more than two sections of buses run in parallel in the system, the equivalent SOC values of any two sections of buses can be obtained first, then the obtained equivalent SOC values and the third section of buses use A) -C) method to obtain the equivalent SOC values containing the three sections of buses, and the like until the equivalent SOC values of all parallel running sub-micro-grids in the independent micro-grid are contained.

After obtaining the energy storage SOC in the independent microgrid, indirectly controlling the energy storage SOC according to a specific region to which the energy storage SOC belongs and a formulated flow, wherein the contents are as follows:

when the output of the distributed power supply in the independent micro-grid is excessive, the stored energy is continuously charged, and the SOC exceeds the SOC_highEnter [ SOC ]_high,SOC_max]Intervals, measures that can be taken include: (1) starting a limited load, (2) increasing heat storage and power supply to store heat (possibly load is cut off or limited power, which are limited loads), wherein the heat storage needs to consume electric energy to generate heat energy, the heat storage and power supply is electric energy provided for heat storage, and (3) reducing the generated power of a distributed power supply, wherein the control priority of the regulating means is (1) → (2) → (3), wherein → "represents highThus, "the process" is carried out. The final control target is to limit the energy storage charging to the lowest charging power value P_{BSC_low}，(P_{BSC_low}For the control parameter during the operation of the system, interface adjustment can be opened) if the variation (the variation between two control periods) SOC' of the energy storage SOC is judged to be smaller than the first threshold k₁I.e. SOC' is less than or equal to k₁Then the low priority policy need not be entered. Wherein k is₁Is a small positive number, k₁Should be slightly larger than P_{BSC_low}SOC increase amount due to charging. If the SOC' is not more than k by the steps₁If yes, alarming;

if the energy storage SOC continuously rises, when the energy storage SOC exceeds the SOC_maxEnter [ SOC ]_max,100％]During the interval, the measure can be taken that the energy storage P is enabled by further reducing the power of the distributed power supply_BS>P_{BSD_low}I.e. greater than the lowest discharge power of the stored energy, and gradually increasing the reduction of the distributed power supply. If the variation SOC' of the SOC is judged to be less than or equal to-k₂Then the increase and decrease of the power of the distributed power source is stopped. Until the SOC is at [ SOC ]_low,SOC_high]And stopping the corresponding control flow. Wherein the second threshold value k₂Is a small positive number, k₂Should be slightly larger than P_{BSD_low}SOC reduction amount due to discharge. If the SOC' is less than or equal to-k by the steps₂If yes, alarming;

when the power output of the distributed power supply in the independent micro-grid is insufficient, the stored energy is continuously discharged, and if the SOC of the stored energy is positioned in [ SOC ]_min,SOC_low]Measures that may be taken include: (1) releasing the power limit on the distributed power source, (2) reducing or turning off the regenerative power supply, (3) cutting down the load power, the priority is (1) → (2) → (3), wherein "→" means "higher than". The control objective is to limit the energy storage discharge to a low power value P_{BSD_low}If the variation of the energy storage SOC is judged to be larger than-k₃I.e. SOC'>-k₃Then the low priority policy need not be entered. Wherein the third threshold value k₃Is a small positive number, k₃Should be slightly less than P_{BSD_low}SOC reduction amount due to discharge. If SOC cannot be caused through the steps'>-k₃If yes, alarming;

when the energy storage SOC is lower than the SOC_minGo to [0, SOC_min]In the interval, the stored energy P can be obtained by further reducing the load_BS<-P_{BSC_low}I.e., greater than the minimum charging power, and gradually decreases the amount of load reduction. If judging the variation SOC of the SOC'>k₄The load reduction is stopped. Until the SOC is at [ SOC ]_low,SOC_high]And stopping the corresponding control flow. Wherein k is₄Is a small positive number, k₄Should be slightly less than P_{BSC_low}SOC increase amount due to charging. If the steps cannot be passed, making SOC'>k₄If the diesel engine is started, the diesel engine compensates the system power shortage, and if the diesel engine is started, the SOC cannot be reached'>k₄If yes, alarming;

when the energy storage SOC is in [ SOC ]_low,SOC_high]And in the process, the energy storage SOC is not indirectly controlled, and the power limitation on the distributed power supply and the load is cancelled. If the obtained energy storage SOC does not belong to one of the 5 regions, the SOC monitoring is considered to be wrong, and an alarm signal is given.

SOC_min、SOC_maxThe long-term operation parameters are determined by the design operation characteristics of the battery; SOC_low、SOC_highThe parameters are short-term operation parameters, and can be flexibly adjusted according to the predicted values of DG and load power in the operation process. The adjusting method comprises the following steps:

parameter SOC_low、SOC_highIs selected in dependence on the system payload P in the future time period t_LDIf P is judged_LD*t<-k₅If the distributed power supply is excessive, the SOC is reduced_highTo prevent overcharge in advance and reduce SOC_lowTo consume more energy; judgment of P_LD*t>k₆When the load is excessive, the SOC is raised_highTo reserve more power and raise SOC_lowTo prevent overdischarge in advance. P_LD*t∈[-k₅,k₆]Then, the SOC is maintained_highAnd SOC_lowAnd is not changed. The fifth threshold k5 and the sixth threshold k6 are positive numbers and can be selected according to operation experienceAnd (6) selecting.

Has the advantages that: the control method of the independent micro-grid is formulated based on the SOC state of the energy storage device serving as a main voltage source in the independent micro-grid system, long-term grid-connected operation of the energy storage system is achieved, the operation safety and reliability of the independent micro-grid are improved, the interval division range of the energy storage SOC can be flexibly adjusted according to the distributed power supply and the load power prediction result, and the operation economy of the independent micro-grid system is further improved. Specifically, the method comprises the following steps:

when the energy management of the independent micro-grid is carried out based on the energy storage SOC, the power supply requirement of the load is firstly met, the maximum consumption of the power of the distributed power supply is realized, namely, the load power supply priority principle is met, the energy use experience of a user is improved, and the power difference between the load and the distributed power supply is stabilized through the charge-discharge control of the energy storage. And the energy storage is ensured to have the tendency of charging as much as possible, and the load limit power value is reduced under the emergency condition.

The independent micro-grid operation regulation and control strategy based on the energy storage SOC belongs to a post-verification strategy, namely control logic is not based on power prediction information of a distributed power supply and a load, control on the energy storage SOC is completed only through a heuristic process, the control logic is simple and clear, and programs are conveniently implemented;

besides the operation regulation strategy of the independent micro-grid, in order to further improve the economical efficiency and reliability of the operation of the independent micro-grid system, the operation interval division of the energy storage SOC is flexibly regulated by combining a distributed power supply and load prediction information.

Drawings

FIG. 1 is a schematic diagram of the main steps of the independent microgrid control method of the present invention;

FIG. 2 is a schematic diagram of an energy storage SOC partition bay;

FIG. 3 is a flow chart of obtaining an equivalent energy storage SOC of the system;

FIG. 4 is an independent micro-grid main regulation strategy logic diagram based on an energy storage SOC;

fig. 5 is a flow chart of energy storage SOC interval division based on load and distributed power supply prediction information.

Detailed Description

The invention is further described with reference to the accompanying drawings.

As shown in fig. 1 to 5, the present invention provides an independent microgrid control method, including:

dividing a single set of energy storage SOC interval according to the energy storage operation design limit requirement;

when the bus-coupled switch is disconnected, for adjacent energy storage devices under the same bus, due to the fact that the operation conditions are similar, the value of the SOC of the equivalent energy storage device under each bus can be determined by a method of averaging the SOCs of the adjacent energy storage devices under the same bus, and the sub-micro-grids under each bus are independently controlled;

when the bus coupler is closed, for the energy storage devices under different buses, due to the fact that the operating condition difference is large, the SOC of the equivalent energy storage device under each bus needs to be determined, and then the SOC value of the equivalent energy storage device of the independent micro-grid is determined according to the difference of the SOC of the equivalent energy storage device under each bus and the algorithm flow;

judging the area of the equivalent energy storage SOC in the independent microgrid, combining the existing adjustable distributed power supply and load resources in the microgrid, and according to the established control flow, realizing indirect control on the energy storage SOC in the independent microgrid by adjusting the distributed power supply and the load, and ensuring that the energy storage SOC is in a safe area;

and adjusting the set range of a single set of energy storage SOC interval according to the load and the power prediction information of the distributed power supply, so as to achieve the optimal control of the system.

And carrying out day-ahead scheduling on each controllable device and each energy storage device in the multi-energy complementary system according to the optimization solution result.

Referring to fig. 2, the energy storage SOC control principle and the interval division method of the present invention are:

under a general state, a relational expression which needs to be satisfied in the operation process of the system is as follows:

P_BSD-P_BSC＝P_Load-P_DG (1)

p in formula (1)_BSD、P_BSCRepresenting stored energyDischarge, charge power, P_LoadRepresenting the power consumed by the load, P_DGRepresenting the distributed power source output power. The power balance equation should hold when the system is operating steadily.

Since the charging and discharging states of the stored energy cannot occur simultaneously at each moment, P is set_BS＝P_BSD-P_BSCFor the power of stored energy, when P_BSWhen the output power is more than or equal to 0, the energy storage output power is represented; when P is present_BS<And 0 represents the stored energy absorbed power. Setting P_LD＝P_Load-P_DGRepresents the equivalent load power of the system, when P_LDWhen the load power is more than or equal to 0, the load power is more than the output power of the distributed power supply; when P is present_LD<And when 0, the distributed power supply output power is larger than the load power.

When the island micro-grid is used for energy control, the power supply requirement of the load is firstly met, and then the maximum consumption of the DG power is realized, namely the cost for reducing the load is higher than the cost for reducing the power of the distributed power supply. Under the condition that the premise is met, the power difference between the load and the DG is stabilized through energy storage charge and discharge control. And the stored energy is ensured to have the tendency of charging as much as possible, and the load limiting power value under the emergency condition is reduced.

As shown in FIG. 2, the SOC for energy storage is divided into 5 segments, only when the SOC is at [ SOC ]_high,SOC_max]，[SOC_min,SOC_low]，[SOC_max,100％]，[0,SOC_min]During intervals, energy management indirectly adjusts the SOC of energy storage by adjusting distributed power sources and loads. When the SOC of the stored energy is in [ SOC ]_low,SOC_high]And meanwhile, the master station is an adjustment dead zone of the energy storage SOC and does not control the change of the energy storage SOC. Wherein [ SOC_high,SOC_max]、[SOC_min,SOC_low]And [ SOC ]_low,SOC_high]The interval constitutes an SOC normal operation interval, [ SOC_max,100％]For the upper limit interval of the energy storage SOC, [0, SOC_min]The lower limit interval of the energy storage SOC is set.

When the SOC of the stored energy is in [ SOC ]_high,SOC_max]In time, it is necessary to perform preventive control for the upper limit of the energy storage SOC to be exceeded byThe charging power of the stored energy is reduced by means of increasing the load and reducing the DG output; when the SOC of the stored energy is in [ SOC ]_max,100％]In the process, the emergency control that the energy storage SOC is higher than the upper limit is required, the energy storage is controlled to discharge with smaller power mainly by means of reducing DG output so as to reduce the SOC, and the SOC is required to be controlled to [ SOC ] in order to avoid frequent conversion of the energy storage between charging and discharging modes_low,SOC_high]Only when the interval is reached, emergency control of the SOC beyond the upper limit is exited; when the SOC of the stored energy is in [ SOC ]_min,SOC_low]When the system is used, the lower limit of the SOC of the stored energy is required to be prevented and controlled, and the discharge power of the stored energy is reduced by means of increasing DG output, reducing load and the like; when the SOC of the stored energy is at 0, SOC_min]In the process, emergency control is required to be carried out when the energy storage SOC is lower, the energy storage is controlled to be charged with lower power by means of load reduction and firewood starting so as to improve the SOC, and the SOC is required to be controlled to be from [ SOC ] to [ SOC ] in order to avoid frequent conversion of the energy storage between charging and discharging modes_low,SOC_high]In the interval, the emergency control in which the SOC is lower is exited.

For example, the SOC of energy storage can be adjusted_maxAnd SOC_minSet to 80% and 20%, respectively, SOC_maxAnd SOC_minThe manual settings for the design phase are generally not changed during operation. SOC_highAnd SOC_lowThe SOC dead zone range is limited and can be adjusted according to specific operation time period requirements.

If the diesel engine needs to be started and stopped, the control can be carried out at the above [0, SOC ]_min]And a critical SOC value corresponding to the starting of the diesel engine is added in the interval.

Referring to fig. 3, the process of acquiring the equivalent energy storage SOC of the system of the present invention is as follows:

when the independent micro-grid system comprises a plurality of sections of buses, determining an equivalent SOC value of the independent micro-grid at the moment according to the on-off state of the bus coupler switch;

when the bus tie switch is disconnected, the system is equivalent to a plurality of independent island sub-micro-grids, the operation of each island sub-micro-grid is subjected to complementary influence, and at the moment, a plurality of sets of mutually independent control strategies can be adopted to perform segmented control on the energy storage SOC. If the bus coupler switch is closed, the energy storage devices connected to the buses of all the sections in the system respectively upload respective SOC values;

taking an example of parallel operation of two segments of buses, after acquiring energy storage SOC values of the two segments of buses respectively, firstly defining the larger of the energy storage SOC values of the two segments of buses as B_SOCThe smaller SOC is S_SOCDefining the difference value SOC_dif-＝B_SOC-S_SOC. When SOC is reached_dif<When D, the SOC difference of the two sets of energy storage is not large, and the two sets of energy storage only can be in the same section or adjacent sections. When SOC is reached_dif>And D, considering that the difference between the two sets of stored SOC is large and the two sets of stored SOC are possibly in non-adjacent sections. Where D is a positive integer and should be smaller than the minimum segment interval of the SOC.

When SOC is reached_dif<And D, taking the energy storage condition close to the critical value as a basis for determining the SOC sectional control. If B is_SOC>SOC_maxThen, the system SOC E is judged [ SOC ∈ [ ]_max,100％](ii) a If SOC_max>B_SOC>SOC_highThen, the system SOC E is judged [ SOC ∈ [ ]_high,SOC_max](ii) a If S_SOC<SOC_minThen, the system SOC is determined to be [0, SOC ∈_min](ii) a If SOC_low>S_SOC>SOC_minThen, the system SOC E is judged [ SOC ∈ [ ]_min,SOC_low]. If none of the above conditions belong to, judging that the SOC is in [ SOC ]_low,SOC_high]Interval, not controlling the SOC of the system;

when SOC is reached_dif>D, the distribution of SOC of two systems is 6, if B_SOC>SOC_high，S_SOC∈[SOC_low,SOC_high]Locking S_SOCAnd (4) storing energy, and discharging the stored energy with high SOC as much as possible. If S_SOC<SOC_low，B_SOC∈[SOC_low,SOC_high]Then is locked B_SOCEnergy storage, early triggering of low SOC protection measures of the system, so that S_SOCIs improved. If B is_SOC>SOC_high，S_SOC<SOC_lowThen according to P_LDDetermine the specific logic if P_LD>0, when the system is heavily loaded, then S is locked_SOCSo that B is_SOCPut energy back to [ SOC ]_low,SOC_high]After the interval, operating according to the existing logic; if P_LD<0, at the moment, the system generates power again and is locked B_SOCSo that S_SOCEnergy absorption, return to [ SOC ]_low,SOC_high]An interval. If the above situation does not exist, it is known that one of the following three states is present: (1) b is_SOC,S_SOC>SOC_high；(2)B_SOC,S_SOC<SOC_low；(3)B_SOC,S_SOC∈[SOC_low,SOC_high]. May be in accordance with the SOC_dif<Controlling the strategy of D;

when more than two sections of buses run in parallel in the system, the equivalent SOC values of any two sections of buses can be obtained firstly, then the obtained equivalent SOC values and the third section of buses are used for obtaining the equivalent SOC values containing the three sections of buses by using the method of claim 7, and the like is repeated until the equivalent SOC values of all sub-microgrids running in parallel in the independent microgrid are contained.

Referring to fig. 4, the logic flow of the independent micro-grid master regulation and control strategy based on the energy storage SOC of the system of the present invention is as follows:

when the output of the distributed power supply in the independent micro-grid is excessive, the stored energy is continuously charged, and the SOC exceeds the SOC_highEnter [ SOC ]_high,SOC_max]Intervals, measures that can be taken include: (1) starting a limited load, (2) increasing the heat storage and power supply to store heat, and (3) reducing the generated power of the distributed power supply, the control priority of the regulating means is (1) → (2) → (3), wherein "→" means "higher than". The final control target is to limit the energy storage charging to the lowest power value P_{BSC_low}If the variation of the energy storage SOC is judged to be less than k₁I.e. SOC' is less than or equal to k₁Then the low priority policy need not be entered. Wherein k is₁A positive, small value, a first threshold value k₁Should be slightly larger than P_{BSC_low}The SOC increase due to charging (not more than 2% of the energy storage capacity). If the SOC' is not more than k by the steps₁And then an alarm is given.

If the energy storage SOC continuously rises, when the energy storage SOC exceeds the SOC_maxEnter [ SOC ]_max,100％]Interval(s)Then, measures may be taken to enable the stored energy P by further reducing the power of the distributed power supply_BS>P_{BSD_low}I.e., greater than the minimum discharge power, and gradually increasing the distributed power supply reduction amount. If the variation SOC' of the SOC is judged to be less than or equal to-k₂Then the increase and decrease of the power of the distributed power source is stopped. Until the SOC is at [ SOC ]_low,SOC_high]And stopping the corresponding control flow. Wherein the second threshold value k₂Is a small integer, k₂Should be slightly larger than P_{BSD_low}SOC reduction caused by discharge (not more than 2% of energy storage capacity). If the above steps can not be passed, making SOC' less than or equal to-k₂And then an alarm is given.

When the power output of the distributed power supply in the independent micro-grid is insufficient, the stored energy is continuously discharged, and if the SOC of the stored energy is positioned in [ SOC ]_min,SOC_low]Measures that may be taken include: (1) releasing the power limit on the distributed power source, (2) reducing or turning off the regenerative power supply, (3) cutting down the load power, the priority is (1) → (2) → (3), wherein "→" means "higher than". The control objective is to limit the energy storage discharge to a low power value P_{BSD_low}If the variation of the energy storage SOC is judged to be larger than-k₃I.e. SOC'>-k₃Then the low priority policy need not be entered. Wherein the third threshold value k₃Is a small positive number, k₃Should be slightly less than P_{BSD_low}SOC reduction caused by discharge (not more than 2% of energy storage capacity). If the steps cannot be passed, making SOC'>-k₃And then an alarm is given.

When the energy storage SOC is lower than the SOC_minGo to [0, SOC_min]In the interval, the stored energy P can be obtained by further reducing the load_BS<-P_{BSC_low}I.e., greater than the minimum charging power, and gradually decreases the amount of load reduction. If judging the variation SOC of the SOC'>k₄The load reduction is stopped. Until the SOC is at [ SOC ]_low,SOC_high]And stopping the corresponding control flow. Wherein k is₄A small positive integer, a fourth threshold value k₄Should be slightly less than P_{BSC_low}SOC increase due to charging (not exceeding energy storage capacity)2%) of the total weight of the steel sheet. If the steps cannot be passed, making SOC'>k₄If the diesel engine is started, the diesel engine compensates the system power shortage, and if the diesel engine is started, the SOC cannot be reached'>k₄And then an alarm is given.

When the energy storage SOC is in [ SOC ]_low,SOC_high]And in the process, the energy storage SOC is not indirectly controlled, and the power limitation on the distributed power supply and the load is cancelled. If the obtained energy storage SOC does not belong to one of the 5 regions, the SOC monitoring is considered to be wrong, and an alarm signal is given.

Referring to fig. 5, the energy storage SOC interval division flowchart based on the load and the distributed power prediction information is as follows:

SOC_min、SOC_maxthe long-term operation parameters are determined by the design operation characteristics of the battery; SOC_low、SOC_highThe method is a short-term operation parameter, and can flexibly adjust the DG (distributed generation) and the predicted value of the load power in the operation process;

parameter SOC_low、SOC_highIs selected in dependence on the system payload P in the future time period t_LDIf P is judged_LD*t<-k₅If the distributed power supply is excessive, the SOC is reduced_highTo prevent overcharge in advance and reduce SOC_lowTo consume more energy; judgment of P_LD*t>k₆When the load is excessive, the SOC is raised_highTo reserve more power and raise SOC_lowTo prevent overdischarge in advance. P_LD*t∈[-k₅,k₆]Then, the SOC is maintained_highAnd SOC_lowAnd is not changed. The fifth threshold k5 and the sixth threshold k6 are positive numbers and can be selected according to operation experience.

The embodiments are only for illustrating the technical idea of the present invention, and the technical idea of the present invention is not limited thereto, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the scope of the present invention.

Claims (10)

1. An independent microgrid control method, characterized by comprising:

dividing the SOC for single set of energy storage;

when the bus tie switch is disconnected, averaging the SOC of the energy storage devices under the same bus to determine the value of the SOC of the equivalent energy storage devices under each bus, and regarding the sub-microgrid under one bus as an independent microgrid;

when the bus coupler is closed, determining the SOC of the equivalent energy storage devices under each bus, and determining the SOC of the equivalent energy storage devices of the independent micro-grid according to the SOC difference of the equivalent energy storage devices under each bus;

and according to the interval where the equivalent SOC of the independent micro-grid is located, the equivalent energy storage SOC is located in a safety interval by adjusting the distributed power supply and the load.

2. The independent microgrid control method according to claim 1, wherein the partitioning of the energy storage SOC is specifically:

storing energy of a single set of energy [0,100%]The SOC interval of (1) is divided into 5 sections, which are respectively [0, SOC ] from low to high_min]、[SOC_min,SOC_low]、[SOC_low,SOC_high]、[SOC_high,SOC_max]、[SOC_max,100％](ii) a Therein, SOC_min、SOC_maxRespectively the minimum and maximum values of the energy storage SOC, SOC_low、SOC_highRespectively a low value and a high value of the energy storage SOC.

3. The independent microgrid control method of claim 2, characterized in that when the bus tie switch is closed, determining the SOC of the equivalent energy storage devices under each bus, then determining the SOC of the equivalent energy storage devices of the independent microgrid according to the SOC difference of the equivalent energy storage devices under each bus, and controlling the independent microgrid according to the interval where the SOC is located comprises:

A) when the bus tie switch is closed and two sections of buses run in parallel, after the energy storage SOC values of the two sections of buses are respectively obtained, firstly, the larger energy storage SOC value of the two sections of buses is defined as B_SOCThe smaller the stored energy SOC is S_SOCDefining the difference value SOC_dif＝B_SOC-S_SOC；

B) When SOC is reached_dif<When D, the energy storage SOC close to the critical value of the SOC interval is taken as the equivalent SOC, and if B is not, the equivalent SOC is obtained_SOC>SOC_maxAnd then judging that the system SOC belongs to the SOC_max,100％](ii) a If SOC_max>B_SOC>SOC_highThen, the system SOC E is judged [ SOC ∈ [ ]_high,SOC_max](ii) a If S_SOC<SOC_minThen, the system SOC is determined to be [0, SOC ∈_min](ii) a If SOC_low>S_SOC>SOC_minThen, the system SOC E is judged [ SOC ∈ [ ]_min,SOC_low](ii) a If none of the above conditions belong to, judging that the SOC is in [ SOC ]_low,SOC_high]An interval;

C) when SOC is reached_dif>When D is, if B is_SOC>SOC_high，S_SOC∈[SOC_low,SOC_high]Locking S_SOCStoring energy, and discharging the stored energy with high SOC as much as possible; if S_SOC<SOC_low，B_SOC∈[SOC_low,SOC_high]Then is locked B_SOCEnergy storage, early triggering of low SOC protection measures of the system, so that S_SOCIs promoted if B_SOC>SOC_high，S_SOC<SOC_lowThen according to P_LDDetermine the specific logic if P_LD>0, when the system is heavily loaded, then S is locked_SOCSo that B is_SOCPut energy back to [ SOC ]_low,SOC_high]After the interval, operating according to the existing logic; if P_LD<0, at the moment, the system generates power again and is locked B_SOCSo that S_SOCEnergy absorption, return to [ SOC ]_low,SOC_high]An interval; if the above situation does not exist, it is known that one of the following three states is present: (1) b is_SOC,S_SOC>SOC_high；(2)B_SOC,S_SOC<SOC_low；(3)B_SOC,S_SOC∈[SOC_low,SOC_high](ii) a According to SOC_dif<D, wherein P_LDThe system equivalent load power is D is a positive integer and is smaller than the minimum subsection interval of the SOC;

if more than two sections of buses run in parallel in the system, obtaining equivalent SOC values of any two sections of buses, then obtaining the equivalent SOC values of the three sections of buses by using the obtained equivalent SOC values and the third section of buses according to the method of A) -C), and repeating the steps until the equivalent SOC values of all the buses running in parallel in the independent micro-grid are included.

4. The independent microgrid control method of claim 2, wherein enabling the equivalent energy storage SOC to be in a safety interval by adjusting the distributed power supplies and loads according to the interval in which the equivalent SOC of the independent microgrid is located comprises:

when the equivalent energy storage SOC of the independent micro-grid is in [ SOC ]_low,SOC_high]When the time is long, the change is not controlled;

when the equivalent energy storage SOC of the independent micro-grid is in [ SOC ]_high,SOC_max]When the upper limit is exceeded, the upper limit is prevented and controlled;

when the equivalent energy storage SOC of the independent micro-grid is in [ SOC ]_max,100％]When the emergency control is performed, emergency control is performed on the emergency control;

when the equivalent energy storage SOC of the independent micro-grid is in [ SOC ]_min,SOC_low]When the lower limit is exceeded, preventive control is performed;

when the equivalent energy storage SOC of the independent micro-grid is at 0, SOC_min]The lower limit of the emergency control is set to be smaller.

5. The independent microgrid control method of claim 4, characterized in that when the equivalent energy storage SOC of the independent microgrid is in [ SOC ]_high,SOC_max]The measures taken to perform the upper limit-exceeding preventive control include: (1) starting a limited load, (2) increasing heat storage and power supply for heat storage, and (3) reducing the generated power of a distributed power supply; the control priority of the above regulation means is (1) → (2) → (3), wherein "→" means "higher than"; the final control target is to limit the energy storage charging to the energy storage minimum charging power value P_{BSC_low}If the variation SOC' between two control cycles of the equivalent energy storage SOC of the independent micro-grid is smaller than a first threshold k₁I.e. SOC' is less than or equal to k₁Then the lower priority policy does not need to be entered; if the SOC' is less than or equal to k by the method₁And then an alarm is given.

6. The independent microgrid control method of claim 5, characterized in that if the equivalent energy storage SOC of the independent microgrid continuously rises, when the energy storage SOC exceeds the SOC_maxEnter [ SOC ]_max,100％]When the interval is over, the measures taken by the emergency control comprise: further reducing the power of the distributed power supply to enable the stored energy P_BS>P_{BSD_low}Namely, the power is larger than the lowest discharge power of the stored energy, and the reduction of the distributed power supply is gradually increased; if the variation of SOC is less than or equal to-k₂Stopping increasing and reducing the electric quantity of the distributed power supply until the SOC is in [ SOC ]_low,SOC_high]Stopping the corresponding control flow; wherein P is_BSFor storing energy, P_{BSD_low}To store the lowest discharge power, k₂A second threshold value, which takes a positive value slightly greater than P_{BSD_low}The SOC reduction caused by discharge can not be made to be less than or equal to-k by the method₂And then an alarm is given.

7. The independent microgrid control method of claim 4, characterized in that when the equivalent energy storage SOC of the independent microgrid is in [ SOC ]_min,SOC_low]The lower limit preventive control is performed by taking measures including: (1) releasing power limits on the distributed power supply, (2) reducing or turning off the regenerative power supply, (3) cutting off the load power, with the priority being (1) → (2) → (3), wherein "→" means "higher than"; the control target is to limit the energy storage discharge to the lowest discharge power value P_{BSD_low}If the variation of the energy storage SOC is judged to be larger than-k₃I.e. SOC'>-k₃Then the lower priority policy does not need to be entered; wherein the third threshold value k₃Is a positive number, k₃Is slightly less than P_{BSD_low}SOC ' reduction due to discharge if SOC ' cannot be obtained by the above method '>-k₃And then an alarm is given.

8. The independent microgrid control method of claim 7, characterized in that when the independent microgrid equivalent energy storage SOC is in [0, SOC_min]The measures taken for emergency control of the lower limit are as follows: further reducing the load so that the stored energy P_BS<-P_{BSC_low}I.e. greater than the lowest charging power, and gradually reducing the reduction amount of the load; if judging the variation SOC of the SOC'>k₄Then the load shedding is stopped until the SOC is at [ SOC ]_low,SOC_high]Stopping the corresponding control flow; wherein the fourth threshold value k₄Is a positive number, k₄Should be slightly less than P_{BSC_low}SOC increase amount due to charging; if SOC cannot be made by the method'>k₄If the diesel engine is started, the diesel engine compensates the system power shortage, and if the diesel engine is started, the SOC cannot be reached'>k₄Then alarm, wherein P_BSFor energy storage power.

9. The independent microgrid control method of claim 2, further comprising adjusting a set range of a single set of energy storage SOC intervals according to load and power prediction information of the distributed power supply.

10. The independent microgrid control method according to claim 9, characterized in that the adjusting of the set range of a single set of energy storage SOC intervals according to the load and the power prediction information of the distributed power supply is specifically: setting a fifth threshold k₅And a sixth threshold value k₆If P is_LD×t∈[-k₅,k₆]The distributed power is considered to be excessive by lowering the SOC_highTo prevent overcharge in advance and reduce SOC_lowTo consume more energy; if P_LD×t>k₆The system equivalent load is considered to be excessive, and the SOC is increased_highTo reserve more power and raise SOC_lowTo prevent overdischarge in advance; if P_LD×t∈[-k₅,k₆]Then, the SOC is maintained_highAnd SOC_lowUnchanged, wherein, P_LDIndicating that the system is equivalently negativeAnd (4) the charge power.

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