CN111628572A - User-side direct-current microgrid intelligent response system and method - Google Patents
User-side direct-current microgrid intelligent response system and method Download PDFInfo
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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
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00004—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by the power network being locally controlled
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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
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00032—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for
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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
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- 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
- H02J3/381—Dispersed generators
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
- H02J2300/26—The renewable source being solar energy of photovoltaic origin involving maximum power point tracking control for photovoltaic sources
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E40/70—Smart grids as climate change mitigation technology in the energy generation sector
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/12—Monitoring or controlling equipment for energy generation units, e.g. distributed energy generation [DER] or load-side generation
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- Y04S10/14—Energy storage units
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- Y04S10/00—Systems supporting electrical power generation, transmission or distribution
- Y04S10/50—Systems or methods supporting the power network operation or management, involving a certain degree of interaction with the load-side end user applications
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- Y04S40/00—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them
- Y04S40/12—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment
- Y04S40/126—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment using wireless data transmission
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- Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
- Y04S40/00—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them
- Y04S40/12—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment
- Y04S40/128—Systems for electrical power generation, transmission, distribution or end-user application management characterised by the use of communication or information technologies, or communication or information technology specific aspects supporting them characterised by data transport means between the monitoring, controlling or managing units and monitored, controlled or operated electrical equipment involving the use of Internet protocol
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Abstract
The invention belongs to the field of new energy and power demand side response, and particularly relates to a user side direct-current micro-grid intelligent response system and method, which are ubiquitous power internet of things energy management terminal technical methods. According to the upper computer function source optimization scheme, the response sequence of the source, the load and the storage in the power distribution of the user side direct-current micro-grid is divided, the voltage hierarchical control strategy of the direct-current micro-grid is improved according to the response sequence, and the given power value and the droop characteristic of the source, load and storage interface converter are set. The response sequence of the source, the load and the storage in the microgrid voltage stability and the stable switching of different response sequences of the source, the load and the storage are flexibly set, the demand response instruction is executed, and the bidirectional interaction between the power grid and the user is realized. The micro-grid is controlled to be stable in coordination of the controllable and adjustable load, the source and the storage which are converted into different energy sources, the diversified coupling of different energy forms such as the source, the load and the storage is improved, the clean energy is consumed in place to the maximum extent, the energy utilization rate is improved, and the energy consumption cost is reduced.
Description
Technical Field
The invention belongs to the field of new energy and power demand side response, and particularly relates to a user side direct-current micro-grid intelligent response system and method, which are ubiquitous power internet of things energy management terminal technical methods.
Background
Clean energy represented by wind and light is well developed under the support of policies, but the consumption problem of the power grid operation caused by the fluctuation and randomness of the clean energy restricts the scale of the power grid connected with the clean energy, and the waste of resources caused by the wind and light abandonment is a main contradiction of the clean energy development.
Compared with an alternating-current micro-grid, the direct-current micro-grid can receive clean energy such as wind and light more efficiently and reliably, coordination control is easy, and power balance between a micro source and a load can be achieved by controlling the stability of the direct-current bus voltage.
At present, a voltage hierarchical control strategy is mainly adopted for a direct current micro-grid, and the working mode of each interface converter in a system is determined by detecting the variable quantity of the bus voltage of the direct current micro-grid, so that the stable operation of the direct current micro-grid is realized. However, the voltage hierarchical control strategy cannot realize flexible and accurate distribution of power among the interface converters, and further improvement of the strategy is needed.
In the voltage hierarchical control strategy, a low-voltage load reduction measure is adopted only when the microgrid cannot maintain low-voltage stable operation, the power is continuously adjustable during normal operation, the controllable load does not participate in the voltage stable operation control of the microgrid, and in addition, the voltage hierarchical control strategy does not consider the coupling problem of clean energy and other energy sources, so that the maximum local consumption of the clean energy is not realized.
At present, related research of demand response mainly focuses on a scheduling mechanism and a pricing strategy, user loads have a coupling characteristic, and a control method related to a demand response mode cannot be directly applied to a terminal user direct-current microgrid.
Disclosure of Invention
Aiming at the defects and the improvement requirements in the prior art, the invention provides a user-side direct-current microgrid intelligent response system and method. The invention aims to realize the intelligent response of the upper computer energy optimization scheme at the user side.
The invention is realized by the following technical scheme:
the utility model provides a user side direct current microgrid intelligent response system, includes direct current microgrid and energy intelligent management ware to with the wireless interconnection of distribution network host computer, the direct current microgrid includes: a direct current bus, a power supply, a load and energy storage; wherein, the power, the load and the energy storage are all provided with interface converters; the power supply, the load and the energy storage are respectively connected with the direct current bus through the interface converter; the energy intelligent manager is connected with a power supply, a load and the stored energy through a communication bus and wirelessly interconnected with the upper computer; and the upper computer calculates or formulates an energy optimization configuration scheme of the ubiquitous power Internet of things and transmits the energy optimization configuration scheme to the energy intelligent manager through wireless transmission.
The interface converter comprises a DC/DC or DC/AC controllable interface converter; the upper computer is a power distribution network management user system.
A user side direct current microgrid intelligent response method comprises the following steps:
step 1, receiving an energy optimization scheme of an upper computer, and improving a voltage hierarchical control strategy of the direct-current microgrid;
and step 3, configuring voltage layers where interface converters of different devices are located, realizing distribution of power among the interface converters, strengthening coupling of clean energy and different energy forms at a demand side, and intelligently responding to an upper computer energy optimization scheme.
The application range of the direct-current microgrid voltage hierarchical control strategy in the step 1 is terminal users taking households and buildings as energy units; the energy unit is a carrier which takes a user side direct current micro-grid as energy exchange; the user side direct current micro-grid is formed by combining different types of power supplies, loads in different electric energy conversion modes and energy storage in different energy storage modes; the loads in different electric energy conversion forms are continuously adjustable and can be coupled with other energy sources through the interface converter.
The receiving upper computer function power supply optimization scheme is characterized in that a user side direct current microgrid power supply is divided, and load and energy storage can be continuously regulated and controlled, namely a source, load and storage interface converter response sequence is used for short.
The receiving upper computer energy optimization scheme receives the response sequence of the source converter, the load converter and the storage interface converter, the response sequence is discharged when the given power value of the interface converter in the upper computer energy optimization scheme is met as a condition, and the response of the given power value of the interface converter which is met preferentially is given priority; the given power value of the droop control characteristic of each interface converter is a power distribution value in the optimization scheme; the response of the given power value of the interface converter which is preferentially met is preferentially characterized in that a voltage hierarchical control strategy of the direct-current microgrid is improved, and current flows out of the direct-current bus interface converters to form a group, called load for short, which comprises a power interface converter which is positioned in a bus and used for transmitting power to a power supply, an energy storage interface converter which works in a charging state and a load interface converter; dividing a response sequence according to a power distribution sequence in the optimized distribution scheme, and giving a response first in a priority mode; the method comprises the following steps that current flows into a direct current bus interface converter as a group, called a source for short, the direct current bus interface converter comprises a power interface converter for transmitting power from a power supply to a bus, an energy storage interface converter working in a discharge state and a clean energy interface converter; and sequentially satisfying the condition that the sequencing is performed from high to low load converter power, and inserting the source converter into the sequencing of the load converter.
In the energy optimization scheme of the receiving upper computer, the response sequence of the source, load and storage interface converter is in a (0.90-1.10) pu voltage range, voltage layers are divided according to the total number of the 'source' and 'load' and the reserved boundary number, and the calculation formula is as follows:
n＝[(1.1-0.9)/(d+k+r)]
in the formula, n is the number of dividing layers, d is the number of the current transformers of the 'source' group, k is the number of the current transformers of the 'load' group, r is the number of reserved voltage layers, and [ ] is an integer function; the division of the layers is shown in the voltage hierarchy table:
voltage stratification meter
In the table above, nominal value 1pu is used as a boundary, higher than 1pu is the "load" side, lower than 1pu is the "source" side, and Δ n is the differential pressure level, which can be variable.
In the step 2, a control strategy that the grid side interface converter and the energy storage interface converter fixedly occupy voltage layers near the rated voltage is changed, wherein each voltage layer comprises an interface converter, the interface converters are divided into two groups of 'source' and 'carrier', the interface converters of the 'carrier' group are sequenced, and a response sequence is divided; the division principle is as follows: the response sequence is discharged under the condition that the given power value of the interface converter is met in the optimized distribution scheme, namely the response sequence is divided according to the power distribution sequence in the optimized distribution scheme, the distributed response is prioritized, the level is high, and the response sequence is determined sequentially, and the method comprises the following steps:
determining the highest level; if the micro-grid energy is preferentially on the Internet, distributing the power converter to the layer 1; if the energy of the microgrid is preferentially used for charging the energy storage, distributing the energy storage converter to the layer 1; the microgrid energy is preferentially consumed on site, and the load converter is distributed to the layer 1;
determining the next layer, namely the 2 nd layer, in the rest converters, and keeping the principle unchanged; assuming that the energy storage converter is distributed to the layer 1, and a power supply converter and a load converter are remained; if the residual power meeting the given power value of the energy storage converter is preferentially on line, distributing the power converter to a layer 2; if the residual power is preferentially consumed on the spot, distributing the load converter to the 2 nd layer;
and (3) repeating the step (2) until the final load side interface converter is set.
Further, sequencing the source side interface converters and dividing the priority; the voltage amplitude of a voltage layer at the source side selected by the same bidirectional interface converter is lower than that of a voltage layer at the load side; for a source side interface converter participating in load side power control, inserting the source side interface converter into a voltage layer which is one layer higher than the voltage amplitude of a controlled interface converter under the condition that the power of a load group converter with high priority level to low priority level is sequentially met, and inserting the source side interface converter into the sequence of the load group converter; the 'source' side interface converter which does not participate in the 'load' side power regulation starts voltage reduction sequencing from the first layer (i.e. the (k + 1) th layer) adjacent to the 'load' side, and the method is the same as that of the 'load' side.
The voltage layer where the interface converters of different devices are arranged in the step 3 is used for realizing the distribution of power among the interface converters, strengthening the coupling of clean energy and different energy forms at the demand side, and intelligently responding to the energy optimization scheme of the upper computer, and the method comprises the following steps:
step (1) setting the voltage and power set values of the interface control equipment according to the source, load and storage voltage layers, adopting droop control, and expressing a droop control curve as follows:
udc＝udc.H-idc
＝(udc.H-udc.L)/idc.set
idc.set＝Pdc.set/udc
in the formula udcFor setting the voltage of the interface device, udc.H、udc.LThe upper limit value and the lower limit value of the voltage amplitude interval in the voltage level corresponding table are obtained; is the sag factor, Pdc.setGiven power value i in energy optimization distribution schemedc.setSetting a current set value for the interface equipment; i.e. idcIs the interface device current value.
Step (2) normally operating the direct-current microgrid, and controlling the direct-current microgrid by using an interface converter corresponding to the interval where the bus voltage is located to set udc＝udc.H-idcThe droop characteristic operates to ensure power balance in the system; if the operation power of the interval interface converter is less than Pdc.setSetting values to keep the current operation mode unchanged; if the operation power of the interval interface converter is greater than Pdc.setSetting value, changing the interface converter into constant power Pdc.setIn the (current-limiting) operation mode, the microgrid voltage is controlled by the interface converter corresponding to the next interval when the microgrid voltage is over to the next interval; each voltage interval of the direct-current micro-grid is provided with at least one converter with voltage droop characteristics to control direct-current voltage, and natural smooth switching of voltage stabilization control among converters with different interfaces is realized;
changing the source, load, storage and transportation state and the upper computer energy optimization scheme, resetting the response sequence, and switching the reset response sequence from high to low with the original response sequence;
the slope function is adopted to realize translation switching among different response sequences, and u is converteddc＝udc.H-idcConstant u in sag characteristicdc.HShift to reset correspondenceThe upper voltage limit of the interval, the translation function is as follows:
udc.Hx＝udc.Ha-st
s＝(udc.Ha-udc.Hb)/tset；
in the formula: u. ofdc.HxFor translating given value, udc.Ha、udc.HbResetting the upper limit of the voltage amplitude interval corresponding to the response sequence for the original response sequence; s is the slope of the ramp function, t is the translational switching time, tsetSetting switching time;
after the translation, modifying the droop coefficient and the power given value P in the energy optimization distribution scheme according to the source, load, storage running state and the upper computer energy optimization schemedc.set(ii) a By responding to different permutation combinations of the sequence and stable switching among the different combinations, the accurate distribution of the power of the converter with the required interface is realized, the voltage hierarchical control function is expanded, and the purpose of energy optimization is achieved.
The invention has the following advantages and beneficial effects:
according to the invention, the fixed working mode of the voltage hierarchical control of the direct-current microgrid is changed by setting the response sequence of the interface converters, the network side interface converter is the 1 st layer, the storage battery interface converter is the 2 nd layer and the like; therefore, the power value of each interface converter can be flexibly set and accurately distributed, and the energy optimization distribution scheme of the upper computer can be implemented.
According to the invention, a mode of switching the voltage hierarchical control work of the direct-current microgrid is abandoned, the direct-current bus voltage is taken as an information carrier to be matched with the droop control characteristic of the converter with the unique interface of each voltage layer, and the adjacent interface converters do not need to be added with hysteresis loops, so that the stable control of the microgrid can be switched smoothly and seamlessly; by different permutation and combination of response sequence, the smooth switching between networking and island states is realized.
The invention responds to different sequences and has different energy flow directions and conversion forms, and converts the clean energy which can not be accepted by the power grid into other energy to the maximum extent through the coordination control of the controllable and adjustable interface converters for converting different energy sources, thereby further improving the local consumption capability of the clean energy.
The invention expands the function of voltage layered control by different permutation and combination of response sequence. The energy storage of the user side is maximized before the power grid plans to cut off power, and the like, so that the method is convenient for the user and reduces the energy waste.
The ubiquitous power internet of things conforms to the new trend of current energy development and consumption, can strengthen the coupling of power and other energy sources, improve the comprehensive utilization rate of energy sources, reduce the energy consumption cost of the whole society and construct a comprehensive energy service intelligent ecological platform. The platform construction requires customer response, and a value closed loop is realized. Particularly, around the ubiquitous power internet of things of a user side, diversified coupling of clean energy and different energy forms of a demand side, such as cold, heat, electricity and water, is sought, a demand response instruction is executed, bidirectional interaction between a power grid and a user is realized, and an intelligent coping method is urgently needed by the user side.
Drawings
To facilitate understanding and practice of the invention by those of ordinary skill in the art, the following description is provided in conjunction with the accompanying drawings to provide a further understanding of the invention, and the exemplary embodiments and descriptions thereof are provided to explain the invention and are not to be construed as limiting the invention.
Fig. 1 is a schematic diagram of a user-side dc microgrid structure according to the present invention;
fig. 2 is a schematic diagram of a typical 220V building dc microgrid terminal user structure with various types of loads.
In the figure: the intelligent energy management system comprises an intelligent energy manager 1, a communication bus 2, a direct current bus 3, a power supply 4, a load 5, an energy storage 6, an interface converter 7, an upper computer 8 and a photovoltaic 9.
Detailed Description
The embodiments of the invention will be described in detail below with reference to the accompanying drawings, which can be embodied in many different forms and are defined and covered by the claims. It is specifically intended that the following description be regarded as illustrative in nature and not as restrictive in any way, since it is intended to limit the disclosure to the precise form disclosed and illustrated. Unless specifically stated otherwise, the relative arrangement of components and steps and numerical expressions and values set forth in the embodiments do not limit the scope of the present disclosure. Additionally, techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail but are intended to be part of the specification where appropriate.
Example 1
The invention relates to a user side direct current microgrid intelligent response system and a method, which receive an upper computer energy optimization scheme, improve a direct current microgrid voltage layering control strategy by dividing a user side direct current microgrid power supply, continuously regulating and controlling a load and energy storage response sequence, change the control strategy of 1 and 2 layers that a network side interface converter and an energy storage interface converter fixedly occupy voltage layers near a rated voltage, and flexibly configure the voltage layers where interface converters of different equipment are positioned, thereby realizing flexible and accurate distribution of power among the interface converters, and strengthening the coupling of clean energy and different energy forms at a demand side, thereby intelligently responding to the upper computer energy optimization scheme.
The system comprises a direct-current microgrid and an intelligent manager thereof, and is wirelessly interconnected with an upper computer of a power distribution network, wherein the direct-current microgrid comprises: a direct current bus 3, a power supply 4, a load 5 and an energy storage 6. The power supply 4, the load 5 and the energy storage 6 all comprise interface converters 7; the power supply 4, the load 5 and the energy storage 6 are respectively connected with the direct current bus 3 through an interface converter 7; the energy intelligent manager 1 is connected with the power source 4, the load 5 and the energy storage 6 through the communication bus 2, is wirelessly interconnected with the upper computer 8, receives a power distribution network optimal configuration scheme, and patrols the state of the direct-current micro-grid equipment.
The upper computer is a general name of a power distribution network management user system, the upper computer 8 calculates or formulates an energy optimization configuration scheme of a ubiquitous power internet of things, and the energy optimization configuration scheme is transmitted to the energy intelligent manager 1 through wireless transmission.
The interface converter 7 comprises a DC/DC or DC/AC controllable interface converter.
The invention discloses a user-side direct-current microgrid intelligent response method which is realized by improving a direct-current microgrid voltage hierarchical control strategy and has an application range of terminal users taking households and buildings as energy units. The energy unit is a carrier which takes a user side direct current micro-grid as energy exchange; the user side direct current micro-grid is formed by combining different types of power supplies, loads in different electric energy conversion modes, energy storage in different energy storage modes and the like. The loads in different electric energy conversion forms are continuously adjustable and can be coupled with other energy sources through the interface converter.
The invention relates to a user-side direct-current microgrid intelligent response method which specifically comprises the following steps:
step 1, receiving an energy optimization scheme of an upper computer, and improving a voltage hierarchical control strategy of the direct-current microgrid;
and step 3, configuring voltage layers where interface converters of different devices are located, realizing distribution of power among the interface converters, strengthening coupling of clean energy and different energy forms at a demand side, and intelligently responding to an upper computer energy optimization scheme.
The upper computer function power source optimization scheme in the step 1 is to divide a user side direct current microgrid power source, and continuously regulate and control load and energy storage, which is called a source, load and storage interface converter response sequence for short. The voltage hierarchical control strategy of the direct-current microgrid is improved, power is flexibly and accurately distributed among the interface converters, the continuously adjustable and controllable load response sequence is changed, coupling of clean energy and different energy forms of a demand side is enhanced, and the energy optimization scheme of an upper computer is intelligently responded.
The response sequence of the source, load and storage interface converters is discharged under the condition that the given power value of the interface converter in the upper energy machine optimization scheme is met, and the response of the given power value of the interface converter which is met preferentially is given preferentially.
And the given power value of the droop control characteristic of each interface converter is a power distribution value in an optimization scheme.
The response of the given power value of the interface converter which is preferentially met is preferentially in that a voltage hierarchical control strategy of the direct-current microgrid is improved. The converter for making current flow out of DC bus interface is a group, called load for short, and includes power interface converter for bus to supply power, energy storage interface converter working in charging state and load interface converter. And dividing the response sequence according to the power distribution sequence in the optimized distribution scheme, and giving the response priority preferentially. The energy storage converter comprises a power interface converter for transmitting power from a power supply to a bus and an energy storage interface converter working in a discharge state. And sequentially satisfying the condition that the sequencing is performed from high to low load converter power, and inserting the source converter into the sequencing of the load converter.
Within the voltage range of (0.90-1.10) pu, dividing voltage layers according to the total number of 'sources' and 'loads' and the number of reserved boundaries, wherein the calculation formula is as follows:
n＝[(1.1-0.9)/(d+k+r)]
in the formula, n is the number of dividing layers, d is the number of the current transformers of the source group, k is the number of the current transformers of the load group, r is the number of reserved voltage layers, and [ ] is an integer function. The division of the layers is shown in the voltage hierarchy table:
voltage stratification meter
In the above table, the rated value 1pu is used as a boundary, higher than 1pu is used as a "load" side, lower than 1pu is used as a "source" side, and Δ n is a level voltage difference, which can be a variable, and in order to reduce voltage fluctuation during normal operation, the voltage difference of the layer where the rated voltage is located can be reduced appropriately.
And in the step 2, a control strategy that the grid side interface converter and the energy storage interface converter fixedly occupy a voltage layer near the rated voltage is changed. Each voltage layer only comprises one interface converter, the interface converters are divided into two groups of 'source' and 'load' according to an energy optimization scheme, and the interface converters of the 'load' group are firstly sequenced and response sequences are divided. The division principle is as follows: in the optimization distribution scheme, response sequences are discharged under the condition that given values of the power of the interface converters are met, namely the response sequences are divided according to the power distribution sequences in the optimization scheme, the distribution response is prioritized, the level is high, and the response sequences are determined in sequence. The specific process comprises the following steps:
step (1) first determines the highest level. If the micro-grid energy is preferentially on the Internet, distributing the power converter to the layer 1; if the energy of the microgrid is preferentially used for charging the energy storage, distributing the energy storage converter to the layer 1; the microgrid energy is preferentially consumed on site, and the load converter is distributed to the layer 1;
and (2) secondly, determining the next layer, namely the 2 nd layer, in the rest of the converters, and keeping the principle unchanged. It is assumed that the energy storage converter has been allocated to layer 1, and the power converter and the load converter remain. If the residual power meeting the given power value of the energy storage converter is preferentially on line, distributing the power converter to a layer 2; if the residual power is preferentially consumed on the spot, distributing the load converter to the 2 nd layer;
and (3) repeating the step (2) until the final load side interface converter is set.
Further, the source side interface converters are sorted and prioritized. The division principle is as follows: the voltage amplitude of a voltage layer at the source side selected by the same bidirectional interface converter is lower than that of a voltage layer at the load side; for the source side interface converter participating in the load side power control, under the condition that the power of the load group converters with priority levels from high to low is sequentially met, the source side interface converter can be inserted into a voltage layer with the voltage amplitude higher by one layer than that of the controlled interface converter, and the source side interface converter is inserted into the sequence of the load group converters; the 'source' side interface converter which does not participate in the 'load' side power regulation starts voltage reduction sequencing from the first layer (i.e. the (k + 1) th layer) adjacent to the 'load' side, and the method is the same as that of the 'load' side.
And 3, configuring voltage layers of the interface converters of different devices, realizing the distribution of power among the interface converters, strengthening the coupling of clean energy and different energy forms at the demand side, and intelligently responding to the energy optimization scheme of the upper computer. Setting the voltage and power set values of interface control equipment according to a source voltage layer, a load voltage layer and a storage voltage layer, adopting droop control, and expressing a droop control curve as follows:
udc＝udc.H-idc
＝(udc.H-udc.L)/idc.set
idc.set＝Pdc.set/udc
in the formula udcFor setting the voltage of the interface device, udc.H、udc.LThe upper limit value and the lower limit value of the voltage amplitude interval in the voltage level corresponding table are obtained; is the sag factor, Pdc.setGiven power value i in energy optimization distribution schemedc.setSetting value of interface equipment current idcIs the interface device current value.
Further, the direct-current microgrid is normally operated and controlled by the interface converter corresponding to the interval where the bus voltage is located so as to set udc＝udc.H-idcThe droop characteristic operates to ensure power balance within the system. If the operation power of the interval interface converter is less than Pdc.setSetting values to keep the current operation mode unchanged; if the operation power of the interval interface converter is greater than Pdc.setSetting value, changing the interface converter into constant power Pdc.setAnd in the (current-limiting) operation mode, the microgrid voltage is transited to the next interval and is controlled by the interface converter corresponding to the interval. Therefore, each voltage interval of the direct-current microgrid is provided with at least one converter with the voltage droop characteristic to control direct-current voltage, and natural smooth switching of voltage stabilization control among converters with different interfaces is realized;
furthermore, the source, load, storage and transportation states and the upper computer can reset the response sequence by changing the optimization scheme of the source, the load, the storage and transportation states and the upper computer.
Further, the reset response sequence is switched with the original response sequence from high to low. The slope function is adopted to realize translation switching between different response sequences, namely udc＝udc.H-idcConstant u in sag characteristicdc.HTranslating to the upper limit value of the voltage of the reset corresponding interval, wherein the translation function is as follows:
udc.Hx＝udc.Ha-st
s＝(udc.Ha-udc.Hb)/tset；
in the formula: u. ofdc.HxFor translating given value, udc.Ha、udc.HbResetting the upper limit of the voltage amplitude interval corresponding to the response sequence for the original response sequence; s is the slope of the ramp function, t is the translational switching time, tsetAnd setting switching time.
Further, after translation, according to the source, load, storage running state and the upper computer energy optimization scheme, the droop coefficient and the power given value P in the energy optimization distribution scheme are modifieddc.set。
By responding to different permutation combinations of the sequence and stable switching among the different combinations, the accurate distribution of the power of the converter with the required interface is realized, the voltage hierarchical control function is expanded, and the purpose of energy optimization is achieved.
The scheme for realizing energy optimization is characterized in that stable control of adding controllable and adjustable loads into the microgrid is adopted, the load response sequence is changed, the coupling degree of clean energy and other energy is adjusted, and diversified coupling of different energy forms such as sources, loads and storage is improved.
Furthermore, the source, load and storage response sequences are different, and the flow direction and the conversion form of the energy source are different. By adjusting the load response sequence, the quantity of other energy forms of electric energy conversion can be adjusted, the diversified coupling of the clean energy and different energy forms on the demand side is realized, and the intelligent response of the energy is achieved.
Further, once the response sequence is determined, the converters work independently without mutual communication, and the control is dispersed.
Further, in order to enable the clean energy in the power supply to operate in a Maximum Power Point Tracking (MPPT) mode, the clean energy is set at a highest voltage amplitude layer, and when the voltage of the direct-current micro-grid exceeds a set voltage, the power is reduced to operate.
Example 2
As shown in fig. 2, fig. 2 is a schematic diagram of a typical 220V building dc microgrid terminal user structure with multiple types of loads. Wherein: the direct-current micro-grid is composed of a direct-current bus 3, commercial power, a load 5, a storage battery pack and a photovoltaic 9. Wherein, the power supply 4 selects commercial power, and the energy storage 6 selects a storage battery pack. To fully utilize the photovoltaic, the photovoltaic is listed separately from the power source.
The commercial power, the load 5, the storage battery pack and the photovoltaic 9 all comprise a DC/DC or DC/AC interface converter 7; the commercial power, the load 5, the storage battery pack and the photovoltaic 9 are respectively connected with the direct current bus 3 through an interface converter 7; the energy intelligent manager 1 is connected with commercial power, a load 5, a storage battery pack and a photovoltaic 9 through a communication bus 2, wirelessly interconnected with an upper computer 8, receives a power distribution network optimal configuration scheme, and patrols the state of the direct-current micro-grid equipment. The load 5 comprises a controllable load variable frequency heater, a television, a computer, an electric kettle, an electric cooker and an uncontrollable load for lighting. Specific parameters are as in the user parameter table:
user parameter table
And the upper computer calculates or formulates an energy optimization configuration scheme of the ubiquitous power Internet of things and transmits the energy optimization configuration scheme to the energy intelligent manager through wireless transmission.
The specific energy optimization allocation scheme is as follows: the power generated by the user side to the commercial power and the power of the internet is not more than 4kW, and the battery state SOC of the storage battery is 60%.
After the energy intelligent manager receives the scheme, the system is divided into groups according to the directions of current flowing into and current flowing out of the direct current bus of the interface converter, and the commercial power, the load, the storage battery and the photovoltaic are divided into two groups of source and load:
the 'source': commercial powerRectifying currentStorage battery packDischarge of electricityAnd performing photovoltaic operation;
"carry": commercial powerInversionLoad, accumulator batteryCharging of electricity；
The voltage is divided into 7 layers in the (0.90-1.10) pu range according to the total number of 'source' and 'load' 6 and 1 voltage layer left at the direct current voltage boundary. In order to ensure that voltage fluctuation is small during normal operation and the voltage level difference of a layer where rated voltage is located is small, the voltage level difference is divided into the following layers according to a voltage level control strategy of the direct-current microgrid:
voltage stratification meter
In order to utilize clean energy to the maximum extent and enable the solar photovoltaic power generation system to operate in an MPPT mode, fixedly distributing the 4 th layer with the highest voltage amplitude to the photovoltaic;
further, the "load" group response order is divided. According to the scheme, the photovoltaic power is preferentially connected to the Internet, and the mains supply on the Internet side is suppliedInversionSet to layer 1, power Pdc.set4 kW; accumulator batteryCharging of electricityThe state of the battery SOC is 60%, and in order to maintain the photovoltaic grid, the surplus power is stored in the storage battery preferentially, therefore, the storage battery pack is usedCharging of electricityThe load is set to layer 3 if layer 2 is set.
The "source" group is prioritized. For maximum utilization of the photovoltaic, it has been fixed as the "source" layer 4; for 'source' side accumulator battery participating in 'load' side power controlDischarge of electricityA battery packDischarge of electricityPlugged into the mainsInversionThe voltage layer with one higher voltage amplitude value, namely the layer 2, then the load side storage battery packCharging of electricityThe load is sequentially changed into a 3 rd layer and a 4 th layer, and the commercial power which does not participate in the load side power regulationRectifying currentIs layer 5. According to the principle that each voltage layer can only contain one interface converter, since the photovoltaic and the load are the same voltage layer, the conflict occurs, and the voltage of the photovoltaic is fixed, the voltage layers of the rest "source" and "load" groups are extended to the voltage layer with the lower voltage amplitude, and the result is shown in the following voltage layer table:
voltage stratification meter
Setting droop control curves of all voltage layers according to the layers where the photovoltaic, the load, the storage battery and the commercial power are located:
udc＝udc.H-idc
＝(udc.H-udc.L)/idc.set
idc.set＝Pdc.set/udc
in the formula udcFor setting the voltage of the interface device, udc.H、udc.LThe upper limit value and the lower limit value of the voltage amplitude interval in the priority corresponding table are set; for sag factor, remove commercial powerInversionPdc.setFor limiting power by 4kWThe others are the power limits of each interface device. i.e. idc.setThe interface device current is given. i.e. idcIs the interface device current value.
The calculation result is shown in a droop control curve table:
droop control curve chart
Note that the data in the table is the per-unit value. Voltage reference 220V, power reference is rated power of respective interface equipment
The intelligent response process of the user side direct current microgrid is as follows:
the photovoltaic power generation power is less than the limited power of the internet and is 4kW greater than the limited power of the internet.
The photovoltaic power is less than the limited power of the online 4 kW:
photovoltaic inflow microgrid and storage batteryDischarge of electricityWhen the sum of the discharge power is less than or equal to 4kW, the storage battery packDischarge of electricityOperating at maximum discharge power and constant power, by mains supplyInversionControlling the stability of the direct-current microgrid according to the droop characteristic, wherein the microgrid voltage is positioned in a (0.98-1.0) pu interval;
the voltage of the microgrid rises along with the increase of the photovoltaic inflow microgrid power, and when the photovoltaic inflow microgrid power and the storage battery packDischarge of electricityWhen the sum of the discharge power is more than 4kW, the voltage continues to rise, the voltage of the microgrid enters a (1.0-1.02) pu interval, and the commercial power is suppliedInversionThe constant-power operation with 4kW of power is changed, and the storage battery packDischarge of electricityThe droop characteristic is used for controlling the stability of the direct-current micro-grid, reducing the power output and maintaining the power of the internet to be 4 kW;
photovoltaic power is greater than the online limit power of 4 kW:
when the power of the photovoltaic inflow microgrid is continuously increased and is more than 4kW, the storage battery packDischarge of electricityThe discharge power is reduced to 0, the microgrid voltage continues to rise, the microgrid voltage enters a (1.02-1.05) pu interval, and the storage battery pack in the intervalCharging of electricityThe droop characteristic is used for controlling the stability of the direct-current micro-grid, and the photovoltaic residual power is maintained to be 4kW except that the online power is maintainedThe rate is preferentially stored in the battery.
When storage battery packCharging of electricityState of the battery at SOC>At 80%, the charging power is limited. When the SOC is 95%, the energy manager resets the response sequence according to the battery state. Accumulator batteryCharging of electricityThe load is reduced to the 3 rd layer and the load is increased to the 2 nd layer;
accumulator battery realized by adopting slope functionCharging of electricityAnd switching the translation among different layers of the load. The translation function is as follows:
s＝(udc.Ha-udc.Hb)/tset＝(1.09-1.05)/1＝0.04
udc.Hx＝udc.Ha-st＝1.09-0.04t；
in the formula: u. ofdc.HxFor translating given value, udc.Ha、udc.HbResetting the upper limit of the voltage amplitude interval corresponding to the response sequence for the original response sequence; s is the slope of the ramp function, t is the translational switching time, tsetAnd setting switching time.
Shifting the load from layer 3 to layer 2, i.e. the load sag characteristic udc＝udc.H-idcConstant u indc.HFrom original udc.Ha1.09pu to udc.Hb1.05pu, shift switching time tsetIs 1 second; energy storageCharging of electricityThe hierarchical operation is the same.
Accumulator batteryCharging of electricityAfter the load is stably switched, the power of the internet is kept unchanged at 4kW, and the residual photovoltaic power is converted into energy in other forms through the load interface converter. In the interval (1.02-1.05) pu, the load controls the stability of the direct-current microgrid according to the droop characteristic, and the coupling degree of the clean energy and other energy can be adjusted by changing the response sequence of the load.
In the implementation process of the embodiment, the arrangement and combination of the direct-current microgrid interface converters with different response sequences are designed, so that the direct-current microgrid voltage division control strategy is not only used for stable control of the microgrid, but also accurate distribution of power in the microgrid interface converters can be realized, the upper computer optimization scheme is completed, the voltage of the direct-current microgrid can be guaranteed to operate in a pu interval of (-95% -105%) as far as possible, controllable and adjustable loads are added into the stable control of the microgrid, and the clean energy consumption capability is further improved.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention.
Claims (10)
1. A user side direct current microgrid intelligent response system is characterized in that: including direct current microgrid and energy intelligent management ware to with the wireless interconnection of distribution network host computer, the direct current microgrid includes: the system comprises a direct current bus (3), a power supply (4), a load (5) and an energy storage (6); wherein, the power supply (4), the load (5) and the energy storage (6) are all internally provided with an interface converter (7); the power supply (4), the load (5) and the energy storage (6) are respectively connected with the direct current bus (3) through an interface converter (7); the energy intelligent manager (1) is connected with the power supply (4), the load (5) and the energy storage (6) through the communication bus (2) and is wirelessly interconnected with the upper computer (8); the upper computer (8) calculates or formulates an energy optimization configuration scheme of the ubiquitous power Internet of things, and transmits the energy optimization configuration scheme to the energy intelligent manager (1) through wireless transmission.
2. The system according to claim 1, wherein the system comprises: the interface converter (7) comprises a DC/DC or DC/AC controllable interface converter; the upper computer is a power distribution network management user system.
3. A user side direct current microgrid intelligent response method is characterized by comprising the following steps: the method comprises the following steps:
step 1, receiving an energy optimization scheme of an upper computer, and improving a voltage hierarchical control strategy of the direct-current microgrid;
step 2, changing a control strategy that the grid side interface converter and the energy storage interface converter fixedly occupy a voltage layer near a rated voltage;
and step 3, configuring voltage layers where interface converters of different devices are located, realizing distribution of power among the interface converters, strengthening coupling of clean energy and different energy forms at a demand side, and intelligently responding to an upper computer energy optimization scheme.
4. The intelligent response method for the user-side direct-current microgrid according to claim 3, characterized in that: the application range of the direct-current microgrid voltage hierarchical control strategy in the step 1 is terminal users taking households and buildings as energy units; the energy unit is a carrier which takes a user side direct current micro-grid as energy exchange; the user side direct current micro-grid is formed by combining different types of power supplies, loads in different electric energy conversion modes and energy storage in different energy storage modes; the loads in different electric energy conversion forms are continuously adjustable and can be coupled with other energy sources through the interface converter.
5. The intelligent response method for the user-side direct-current microgrid according to claim 3, characterized in that: the receiving upper computer function power supply optimization scheme is characterized in that a user side direct current microgrid power supply is divided, and load and energy storage can be continuously regulated and controlled, namely a source, load and storage interface converter response sequence is used for short.
6. The intelligent response method for the user-side direct-current microgrid according to claim 3, characterized in that: the receiving upper computer energy optimization scheme receives the response sequence of the source converter, the load converter and the storage interface converter, the response sequence is discharged when the given power value of the interface converter in the upper computer energy optimization scheme is met as a condition, and the response of the given power value of the interface converter which is met preferentially is given priority; the given power value of the droop control characteristic of each interface converter is a power distribution value in the optimization scheme; the response of the given power value of the interface converter which is preferentially met is preferentially characterized in that a voltage hierarchical control strategy of the direct-current microgrid is improved, and current flows out of the direct-current bus interface converters to form a group, called load for short, which comprises a power interface converter which is positioned in a bus and used for transmitting power to a power supply, an energy storage interface converter which works in a charging state and a load interface converter; dividing a response sequence according to a power distribution sequence in the optimized distribution scheme, and giving a response first in a priority mode; the method comprises the following steps that current flows into a direct current bus interface converter as a group, called a source for short, the direct current bus interface converter comprises a power interface converter for transmitting power from a power supply to a bus, an energy storage interface converter working in a discharge state and a clean energy interface converter; and sequentially satisfying the condition that the sequencing is performed from high to low load converter power, and inserting the source converter into the sequencing of the load converter.
7. The intelligent response method for the user-side direct-current microgrid according to claim 3, characterized in that: in the energy optimization scheme of the receiving upper computer, the response sequence of the source, load and storage interface converter is in a (0.90-1.10) pu voltage range, voltage layers are divided according to the total number of the 'source' and 'load' and the reserved boundary number, and the calculation formula is as follows:
n＝[(1.1-0.9)/(d+k+r)]
in the formula, n is the number of dividing layers, d is the number of the current transformers of the 'source' group, k is the number of the current transformers of the 'load' group, r is the number of reserved voltage layers, and [ ] is an integer function; the division of the layers is shown in the voltage hierarchy table:
voltage stratification meter
In the table above, nominal value 1pu is used as a boundary, higher than 1pu is the "load" side, lower than 1pu is the "source" side, and Δ n is the differential pressure level, which can be variable.
8. The intelligent response method for the user-side direct-current microgrid according to claim 3, characterized in that: in the step 2, a control strategy that the grid side interface converter and the energy storage interface converter fixedly occupy voltage layers near the rated voltage is changed, wherein each voltage layer comprises an interface converter, the interface converters are divided into two groups of 'source' and 'carrier', the interface converters of the 'carrier' group are sequenced, and a response sequence is divided; the division principle is as follows: the response sequence is discharged under the condition that the given power value of the interface converter is met in the optimized distribution scheme, namely the response sequence is divided according to the power distribution sequence in the optimized distribution scheme, the distributed response is prioritized, the level is high, and the response sequence is determined sequentially, and the method comprises the following steps:
determining the highest level; if the micro-grid energy is preferentially on the Internet, distributing the power converter to the layer 1; if the energy of the microgrid is preferentially used for charging the energy storage, distributing the energy storage converter to the layer 1; the microgrid energy is preferentially consumed on site, and the load converter is distributed to the layer 1;
determining the next layer, namely the 2 nd layer, in the rest converters, and keeping the principle unchanged; assuming that the energy storage converter is distributed to the layer 1, and a power supply converter and a load converter are remained; if the residual power meeting the given power value of the energy storage converter is preferentially on line, distributing the power converter to a layer 2; if the residual power is preferentially consumed on the spot, distributing the load converter to the 2 nd layer;
and (3) repeating the step (2) until the final load side interface converter is set.
9. The intelligent response method for the user-side direct-current microgrid according to claim 8, characterized in that: sequencing the source side interface converters and dividing the priority; the voltage amplitude of a voltage layer at the source side selected by the same bidirectional interface converter is lower than that of a voltage layer at the load side; for a source side interface converter participating in load side power control, inserting the source side interface converter into a voltage layer which is one layer higher than the voltage amplitude of a controlled interface converter under the condition that the power of a load group converter with high priority level to low priority level is sequentially met, and inserting the source side interface converter into the sequence of the load group converter; the 'source' side interface converter which does not participate in the 'load' side power regulation starts voltage reduction sequencing from the first layer (i.e. the (k + 1) th layer) adjacent to the 'load' side, and the method is the same as that of the 'load' side.
10. The intelligent response method for the user-side direct-current microgrid according to claim 3, characterized in that: the voltage layer where the interface converters of different devices are arranged in the step 3 is used for realizing the distribution of power among the interface converters, strengthening the coupling of clean energy and different energy forms at the demand side, and intelligently responding to the energy optimization scheme of the upper computer, and the method comprises the following steps:
step (1) setting the voltage and power set values of the interface control equipment according to the source, load and storage voltage layers, adopting droop control, and expressing a droop control curve as follows:
udc＝udc.H-idc
＝(udc.H-udc.L)/idc.set
idc.set＝Pdc.set/udc
in the formula udcFor setting the voltage of the interface device, udc.H、udc.LThe upper limit value and the lower limit value of the voltage amplitude interval in the voltage level corresponding table are obtained; is the sag factor, Pdc.setGiven power value i in energy optimization distribution schemedc.setSetting a current set value for the interface equipment; i.e. idcIs the interface device current value.
Step (2) normally operating the direct-current microgrid, and controlling the direct-current microgrid by using an interface converter corresponding to the interval where the bus voltage is located to set udc＝udc.H-idcThe droop characteristic operates to ensure power balance in the system; if the operation power of the interval interface converter is less than Pdc.setSetting values to keep the current operation mode unchanged; if the operation power of the interval interface converter is greater than Pdc.setSetting value, changing the interface converter into constant power Pdc.setIn the (current-limiting) operation mode, the microgrid voltage is controlled by the interface converter corresponding to the next interval when the microgrid voltage is over to the next interval; each voltage interval of the direct-current micro-grid is provided with at least one converter with voltage droop characteristics to control direct-current voltage, and natural smooth switching of voltage stabilization control among converters with different interfaces is realized;
changing the source, load, storage and transportation state and the upper computer energy optimization scheme, resetting the response sequence, and switching the reset response sequence from high to low with the original response sequence;
the slope function is adopted to realize translation switching among different response sequences, and u is converteddc＝udc.H-idcConstant u in sag characteristicdc.HTranslating to the upper limit value of the voltage of the reset corresponding interval, wherein the translation function is as follows:
udc.Hx＝udc.Ha-st
s＝(udc.Ha-udc.Hb)/tset；
in the formula: u. ofdc.HxFor translating given value, udc.Ha、udc.HbResetting the upper limit of the voltage amplitude interval corresponding to the response sequence for the original response sequence; s is the slope of the ramp function, t is the translational switching time, tsetSetting switching time;
after the translation, modifying the droop coefficient and the power given value P in the energy optimization distribution scheme according to the source, load, storage running state and the upper computer energy optimization schemedc.set(ii) a By responding to different permutation combinations of the sequence and stable switching among the different combinations, the accurate distribution of the power of the converter with the required interface is realized, the voltage hierarchical control function is expanded, and the purpose of energy optimization is achieved.
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