CN115459334A - Rural photovoltaic flexible direct-current power distribution network system and method - Google Patents
Rural photovoltaic flexible direct-current power distribution network system and method Download PDFInfo
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- 230000005611 electricity Effects 0.000 claims description 76
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- 238000005485 electric heating Methods 0.000 claims description 11
- 238000004146 energy storage Methods 0.000 claims description 9
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- 238000006243 chemical reaction Methods 0.000 claims description 5
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- 238000005457 optimization Methods 0.000 description 5
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- 238000013082 photovoltaic technology Methods 0.000 description 2
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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
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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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
- H02J3/007—Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources
- H02J3/0075—Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources for providing alternative feeding paths between load and source according to economic or energy efficiency considerations, e.g. economic dispatch
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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
- H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
- H02J3/14—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by switching loads on to, or off from, network, e.g. progressively balanced loading
- H02J3/144—Demand-response operation of the power transmission or distribution network
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/28—Arrangements for balancing of the load in a network by storage of energy
- H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—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
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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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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- 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
- H02J2310/00—The network for supplying or distributing electric power characterised by its spatial reach or by the load
- H02J2310/50—The network for supplying or distributing electric power characterised by its spatial reach or by the load for selectively controlling the operation of the loads
- H02J2310/56—The network for supplying or distributing electric power characterised by its spatial reach or by the load for selectively controlling the operation of the loads characterised by the condition upon which the selective controlling is based
- H02J2310/58—The condition being electrical
- H02J2310/60—Limiting power consumption in the network or in one section of the network, e.g. load shedding or peak shaving
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- 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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- Engineering & Computer Science (AREA)
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- Supply And Distribution Of Alternating Current (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
Abstract
The application relates to a rural photovoltaic flexible direct current power distribution network system and a method, wherein the system comprises: a first transfer switch and a second transfer switch; a DC/DC converter, a bidirectional DC/DC converter and a unidirectional DC/DC converter; the photovoltaic panel system comprises a first group of photovoltaic panels and a second group of photovoltaic panels, wherein the first group of photovoltaic panels are connected with a heating wire through a DC/DC converter, a first change-over switch to form a first photovoltaic panel system, and the second group of photovoltaic panels supply power to indoor electric equipment through a bidirectional DC/DC converter to form a second photovoltaic panel system; one end of the DC/AC converter and one end of the transformer are connected with one path of the village bus, and the other end of the DC/AC converter and the other end of the transformer are connected with a power grid. Therefore, the problems that the capacity expansion requirement of the transformer of the existing photovoltaic power distribution system is large, the investment cost is high and the like are solved.
Description
Technical Field
The application relates to the technical field of renewable energy utilization and micro-grid, in particular to a rural photovoltaic flexible direct-current power distribution network system and method.
Background
The rural area has a wide roof area and is suitable for developing a photovoltaic technology, the power consumption of the rural area is small, the annual power consumption of most of farmers does not exceed 3000 kW.h, and the photovoltaic installation potential of the rural area is far lower.
Photovoltaic power generation is less limited by regions, and has the advantages of safety, reliability, no noise, low pollution, capability of generating and supplying power on site without consuming fuel and erecting a power transmission line, short construction period and the like.
However, photovoltaic power generation is unstable, photovoltaic power is difficult to be effectively consumed, and the existing photovoltaic power distribution system has large capacity expansion requirement of a transformer and high investment cost, which is not beneficial to popularization and application of photovoltaic technology.
Disclosure of Invention
The application provides a rural photovoltaic flexible direct-current power distribution network system and a method, and aims to solve the problems that an existing photovoltaic power distribution system is large in transformer capacity expansion requirement, high in investment cost and the like.
An embodiment of a first aspect of the present application provides a village photovoltaic flexible direct current distribution network system, including: a first transfer switch and a second transfer switch; a DC/DC converter, a bidirectional DC/DC converter and a unidirectional DC/DC converter; the first group of photovoltaic panels are connected through the DC/DC converter, the first change-over switch and the heating wires to form a first photovoltaic panel system, and the second group of photovoltaic panels supply power to indoor electric equipment through the bidirectional DC/DC converter to form a second photovoltaic panel system, wherein the first photovoltaic panel system and the second photovoltaic panel system are connected through the second change-over switch; the system comprises a DC/AC converter and a transformer, wherein one end of the DC/AC converter and one end of the transformer are connected with one path of a village bus, the other end of the DC/AC converter and the other end of the transformer are connected with a power grid, the other path of the village bus is connected with a platform area power storage device through the bidirectional DC/DC converter and is connected with other platform area power utilization devices through the unidirectional DC/DC converter, so that the switching states of the first change-over switch and the second change-over switch are controlled according to the heating requirement in winter or the living power utilization requirement, the power utilization requirement of the platform area on rainy days is met by the platform area power storage device while the power utilization requirement is met by an indoor battery, and the power sent into the power grid by the platform area is adjusted by combining a bus voltage control strategy, so that the power is stably interacted with the power grid.
Optionally, in an embodiment of the present application, the method further includes: the bidirectional electric meter is arranged between one end of the DC/DC bidirectional converter and the village bus so as to calculate electricity selling income and electricity buying expense.
Optionally, in an embodiment of the present application, an associated bus voltage control system is composed of the DC/DC converter, the bidirectional DC/DC converter and the unidirectional DC/DC converter, for connecting the first transfer switch and disconnecting the second transfer switch when the heating demand is met, sending the power of the first group of photovoltaic panels to an electric heating device for heating, sending the power of the second group of photovoltaic panels indoors to meet the load of the electric device, and sending the surplus power to a platform area for economic benefit; when the electricity demand is the life electricity demand, the second change-over switch is connected, the first change-over switch is disconnected, the electricity of the first group of photovoltaic panels is sent to the indoor to meet the load of the electricity utilization equipment, and the surplus electricity is directly sent to the platform district together with the electricity generated by the second group of photovoltaic panels through the bidirectional DC/DC converter to obtain economic benefits.
Optionally, in an embodiment of the present application, the bus voltage control strategy is divided into three layers, where a first layer is balanced operation when an absolute value of a voltage change rate is smaller than a first preset percentage; the second layer is that the absolute value of the voltage change rate is larger than the first preset percentage and smaller than a second preset percentage, and the priority of energy storage regulation is highest; the third layer is used for controlling the load, the energy storage and the photovoltaic side output power at the same time, wherein the absolute value of the voltage change rate is larger than a third preset percentage and smaller than a fourth preset percentage.
The embodiment of the second aspect of the application provides a village photovoltaic flexible direct current distribution network method, which comprises the following steps: detecting actual requirements of rural areas; when the actual demand is detected to be the winter heating demand or the domestic power demand, the on-off states of the first change-over switch and the second change-over switch are controlled, so that the indoor battery is utilized to meet the power demand, meanwhile, the power storage equipment of the transformer area is utilized to meet the power demand of the transformer area on rainy days, and the power sent into the power grid by the transformer area is adjusted by combining a bus voltage control method, so that the power is enabled to be in stable interaction with the power grid.
Optionally, in an embodiment of the present application, the method further includes: calculating electricity selling income and electricity buying expense based on the bidirectional electricity meter so as to use recommended electricity utilization information based on the electricity selling income and the electricity buying expense.
Optionally, in an embodiment of the present application, the controlling the switching states of the first transfer switch and the second transfer switch to meet the power demand of the power grid on rainy days by using the power storage device of the power grid while using the indoor battery to meet the power demand, and adjusting the power sent by the power grid to the power grid by the power grid in combination with the bus voltage control method to enable the power grid to smoothly interact with the power grid includes: when the winter heating is needed, connecting the first change-over switch, disconnecting the second change-over switch, sending the power of the first group of photovoltaic panels to electric heating equipment for heating, sending the power of the second group of photovoltaic panels to the indoor to meet the load of electric equipment, and sending redundant power to a platform area to obtain economic benefits; when the domestic electricity demand is met, the second change-over switch is connected, the first change-over switch is disconnected, the power of the first group of photovoltaic panels is sent to the indoor to meet the load of the electricity utilization equipment, and the surplus power is directly sent to a platform district together with the second group of photovoltaic panels through the bidirectional DC/DC converter to generate power so as to obtain economic benefits.
Thus, the embodiments of the present application have the following advantageous effects:
the embodiment of the application comprises the following steps: a first transfer switch and a second transfer switch; a DC/DC converter, a bidirectional DC/DC converter and a unidirectional DC/DC converter; the first group of photovoltaic panels are connected with the heating wires through the DC/DC converter, the first change-over switch to form a first photovoltaic panel system, and the second group of photovoltaic panels supply power to indoor electric equipment through the bidirectional DC/DC converter to form a second photovoltaic panel system; the photovoltaic power generation system comprises a DC/AC converter and a transformer, wherein one end of the DC/AC converter and one end of the transformer are connected with one path of a village bus, and the other end of the DC/AC converter and the other end of the transformer are connected with a power grid, so that photovoltaic power generation in a transformer area is preferentially consumed by peasant households and power utilization equipment in the transformer area, redundant power is sequentially transmitted into the power grid through flexible adjustment, the power utilization of the transformer area is completely provided by the photovoltaic power generation, power support does not need to be obtained from the power grid, the power is transmitted to the power grid, rural consumers of the power are changed into a virtual power plant, and the capacity expansion requirements and investment cost of the transformer are effectively reduced. Therefore, the problems that the capacity expansion requirement of the transformer of the existing photovoltaic power distribution system is large, the investment cost is high and the like are solved.
Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.
Drawings
The foregoing and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is an illustration of an example of a rural photovoltaic flexible dc distribution network system according to an embodiment of the application;
fig. 2 is a schematic diagram of a logic architecture of a rural photovoltaic flexible dc power distribution network system according to an embodiment of the present application;
fig. 3 is a flowchart of a method for a rural photovoltaic flexible direct current power distribution network according to an embodiment of the application.
Description of reference numerals: a rural photovoltaic flexible direct-current power distribution network system-10; the photovoltaic power generation system comprises a first transfer switch-100, a second transfer switch-101, a DC/DC converter-200, a bidirectional DC/DC converter-201, a unidirectional DC/DC converter-202, a first group of photovoltaic panels-300, a second group of photovoltaic panels-301, a DC/AC converter-400, a transformer-500 and a bidirectional electric meter-600.
Detailed Description
Reference will now be made in detail to embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present application and should not be construed as limiting the present application.
The rural photovoltaic flexible direct current power distribution network system and the method of the embodiment of the application are described below with reference to the attached drawings. To the problem mentioned in the above-mentioned background art, the application provides a rural photovoltaic flexible direct current distribution network system, including equipment such as photovoltaic board, DC/DC converter, DC/AC converter, through being connected with the electric wire netting, make the photovoltaic power generation in platform district be preferentially absorbed by peasant household and the consumer in platform district, unnecessary electric power sends into the electric wire netting in order through flexible regulation again, thereby realize that the power consumption in platform district is provided by photovoltaic power generation completely, solve the heating and the domestic power demand of peasant household, need not obtain electric power support from the electric wire netting, carry electric power to the electric wire netting simultaneously, change rural consumer from electric power into a virtual power plant, compare present photovoltaic distribution system simultaneously, effectively reduced transformer dilatation demand and investment cost. Therefore, the problems that the capacity expansion requirement of the transformer of the existing photovoltaic power distribution system is large, the investment cost is high and the like are solved.
Specifically, fig. 1 is a block schematic diagram of a rural photovoltaic flexible direct current distribution network system according to an embodiment of the present application.
As shown in fig. 1, the rural photovoltaic flexible dc distribution network system 10 includes: the photovoltaic system comprises a first change-over switch 100, a second change-over switch 101, a DC/DC converter 200, a bidirectional DC/DC converter 201, a unidirectional DC/DC converter 202, a first group of photovoltaic panels 300, a second group of photovoltaic panels 301, a DC/AC converter 400 and a transformer 500.
Wherein a first change-over switch 100 and a second change-over switch 101.
A DC/DC converter 200, a bidirectional DC/DC converter 201, and a unidirectional DC/DC converter 202.
The first group of photovoltaic panels 300 and the second group of photovoltaic panels 301 are connected through a DC/DC converter, a first change-over switch and a heating wire to form a first photovoltaic panel system, and the second group of photovoltaic panels supplies power to indoor electric equipment through a bidirectional DC/DC converter to form a second photovoltaic panel system, wherein the first photovoltaic panel system and the second photovoltaic panel system are connected through a second change-over switch.
The system comprises a DC/AC converter 400 and a transformer 500, wherein one end of the DC/AC converter and one end of the transformer are connected with one path of a village bus, the other end of the DC/AC converter and the other end of the transformer are connected with a power grid, the other path of the village bus is connected with a platform area power storage device through bidirectional DC/DC conversion and is connected with other platform area power utilization devices through a unidirectional DC/DC converter, the switching states of a first change-over switch and a second change-over switch are controlled according to winter heating requirements or living power utilization requirements, the power utilization requirements of the platform area on rainy days are met by utilizing an indoor battery, and meanwhile, the power sent into the power grid by the platform area is adjusted by combining a bus voltage control strategy, so that the power is enabled to be smoothly interacted with the power grid.
It should be noted that the embodiments of the present application include a first transfer switch, a second transfer switch, a DC/DC converter with MPPT (Maximum Power Point Tracking) algorithm, a first group of photovoltaic panels, a second group of photovoltaic panels, a DC/AC converter, a transformer, a bidirectional DC/DC converter, a unidirectional DC/DC converter, and a related bus voltage control system.
From this, the embodiment of this application can have different operation mode in heating season and non-heating season, has greatly satisfied peasant household heating demand and domestic power consumption demand, simultaneously through bus voltage control, adjusts the power curve of platform district morning, realizes interacting steadily with the electric wire netting, compares with traditional photovoltaic system, and the dilatation volume of transformer is little or even need not the dilatation, reduces investment cost.
Optionally, in an embodiment of the present application, an associated bus voltage control system is composed of the DC/DC converter 200, the bidirectional DC/DC converter 201 and the unidirectional DC/DC converter 202, so as to connect the first transfer switch 100 and disconnect the second transfer switch 102 when the demand for heating is needed, send the power of the first group of photovoltaic panels 300 to the electric heating equipment for heating, send the power of the second group of photovoltaic panels 301 to the indoor to satisfy the load of the electric equipment, and send the surplus power to the platform area to obtain economic benefit; when the electricity demand is for life, the second change-over switch 101 is connected, the first change-over switch 100 is disconnected, the electricity of the first group of photovoltaic panels 300 is sent indoors to meet the load of the electric equipment, and the surplus electricity is directly sent to the platform district together with the electricity generated by the second group of photovoltaic panels 301 through the bidirectional DC/DC converter 201 to obtain economic benefit.
It should be noted that, in the embodiments of the present application, the photovoltaic panels are divided into two groups, wherein the first group of photovoltaic panels is used for winter heating.
Specifically, the photovoltaic panels of the first group of photovoltaic panels are connected with the electric heating equipment through a DC/DC converter with an MPPT algorithm and a first conversion switch, so that a photovoltaic heating system is formed. In the heating season, all the electric power generated by the photovoltaic panel enters the electric heating equipment for heating of farmers. The electric heating equipment has certain heat storage capacity, such as heating wires, so as to ensure the heating effect of farmers at night and in rainy days.
The second group of photovoltaic panels are divided into two paths through the DC/DC converter, one path is directly connected with a village bus through an ammeter, and the other path supplies power to indoor electric equipment through the bidirectional DC/DC converter, so that the electric power of the second group of photovoltaic panels is transmitted indoors to meet the load of the electric equipment, and the redundant electric power is transmitted to a transformer area to obtain economic benefit.
It should be noted that the above-mentioned change-over switch is used for changing the operation mode of the distribution network system in different seasons. In heating seasons such as winter, the first change-over switch is connected, the second change-over switch is disconnected at the same time, the photovoltaic heating system starts to operate, and the electric power of the first group of photovoltaic panels is transmitted to the electric heating equipment for heating; in non-heating seasons, the second change-over switch is connected, the first change-over switch is disconnected, the photovoltaic heating system stops running, the power of the first group of photovoltaic panels is used for meeting the indoor domestic power demand, redundant power and the power generated by the second group of photovoltaic panels are sent to the transformer area together, and the power distribution network runs direct current all the time.
Meanwhile, a second transfer switch is arranged indoors, so that the two groups of photovoltaic panel systems can be connected together. One path of the village bus is connected with a 10KV power grid through a DC/AC converter and a transformer, and the other path of the village bus is connected with power storage equipment of the transformer area through a bidirectional DC/DC converter and is connected with other power utilization equipment of the transformer area through a unidirectional DC/DC converter.
It can be understood that the distribution network system of this application embodiment uses electric power all to come from the photovoltaic board, does not get the electricity from the electric wire netting, has really realized zero carbon operation.
Optionally, in an embodiment of the present application, the rural photovoltaic flexible dc distribution network system 10 provided in the embodiment of the present application further includes: and the bidirectional electric meter 600 is arranged between one end of the DC/DC bidirectional converter 201 and a village bus, so that electricity selling income and electricity buying expense are calculated.
It should be noted that the rural photovoltaic flexible direct-current power distribution network system provided by the application further comprises a bidirectional electric meter, the bidirectional electric meter is arranged between one end of the DC/DC bidirectional converter and the village bus, and when farmers in the transformer area transmit power to the transformer area on a sunny day, the electricity selling yield is calculated through metering of the electric meter. When electricity is taken from the power storage equipment in the transformer area in rainy days, the electricity is measured by an ammeter, and the electricity purchasing cost is calculated. The cost metering mode is utilized to encourage farmers to increase the own electricity storage capacity and reduce the electricity consumption in rainy days, thereby effectively reducing the design capacity and investment cost of the electricity storage equipment in the transformer area.
Therefore, the embodiment of the application solves the problems of rural domestic electricity utilization and heating, saves the heating and electricity utilization cost of farmers, and can increase the income of the farmers through electricity selling.
Optionally, in an embodiment of the present application, the bus voltage control strategy is divided into three layers, where the first layer is balanced operation when the absolute value of the voltage change rate is smaller than a first preset percentage; the second layer is that the absolute value of the voltage change rate is greater than a first preset percentage and less than a second preset percentage, and the priority of energy storage regulation is highest; the third layer is used for controlling the load, the energy storage and the photovoltaic side output power at the same time, wherein the absolute value of the voltage change rate is larger than a third preset percentage and smaller than a fourth preset percentage.
The control method of the power distribution network system in the embodiment of the application adopts a bus voltage control system, the control system is composed of a DC/DC converter with an MPPT algorithm, a bidirectional DC/DC converter, a unidirectional DC/DC converter, an indoor battery and a transformer area power storage device, the starting and stopping of a load, the battery charging and discharging power and the power generation power are controlled by the aid of the bus voltage signal, and an additional controller is not needed.
In the embodiment of the application, the voltage level of the platform area bus is 750V, the voltage level of the wire connected with the platform area bus is also 750V, the voltage level indoors is 220V, and the microgrid bus voltage control is divided into the following three layers:
a first layer: the absolute value of the voltage change rate is less than 2 percent, and the balance operation is carried out;
a second layer: the absolute value of the voltage change rate is more than 2 percent and less than 5 percent, and the energy storage regulation is preferentially controlled;
and a third layer: the absolute value of the voltage change rate is more than 5% and less than 10%, and the load, the energy storage and the photovoltaic side output power are controlled simultaneously.
It should be noted that the power storage device in the platform area may be a conventional energy storage battery, or may be a large-sized electric farm implement or an electric vehicle, but the current of the power storage device needs to be over 100Ah, and a bidirectional charging and discharging protocol is opened. The control principle of the power storage equipment in the transformer area is to meet the power consumption requirement of the transformer area in rainy days and cloudy days, and the charging and discharging power of the transformer area is adjusted in sunny days, so that the power transmitted into a power grid by the transformer area is kept stable.
The control principle of the indoor battery is to meet the power demand of farmers at night.
The control of the generated power is that when the bus voltage is less than 102% of the rated value, the DC/DC converter connected with the photovoltaic panel operates in the MPPT mode; when the bus voltage is higher than 102% of the rated value, the DC/DC converter connected to the photovoltaic panel operates in a constant voltage control mode.
The control of the battery is not carried out when the bus voltage is between 98% -102% of the rated value; when the bus voltage is between 95% and 98% of the rated value, the battery discharges; when the bus voltage is lower than the rated value by 95%, the battery discharges with the maximum current; similarly, when the bus voltage is between 102% -105% of the nominal value, the battery is charged; when the bus voltage is above the rated value of 105%, the battery is charged with the maximum current.
The control of the load is to divide the electrical appliances in peasant household into two types, one is the non-transferable load, such as the electrical appliances with unchangeable running time, such as an electric cooker, lighting, a television and the like; the other is an electric appliance which can transfer loads, such as a washing machine, an electric kettle, an air conditioner and the like, and the running time of the electric appliance can be properly adjusted without influencing the normal life of people. The operation of the load is controlled, namely the power on and off of the socket capable of transferring the load are controlled by the bus voltage. When the bus voltage is between 95% and 105% of the rated value, the control is not carried out; disconnecting a portion of the receptacle that can transfer the load when the bus voltage is between 90% and 95% of the rated value; when the bus voltage is lower than the rated value by 90%, all the sockets capable of transferring load loads are disconnected; when the bus voltage is 105% above the rated value, all sockets that can transfer load are turned on.
It should be noted that the photovoltaic installed capacity, the electric storage device capacity and the control strategy of the power distribution network system in the embodiment of the present application are calculated by establishing an optimization model, taking stable interaction with the power grid as a target function, taking the power demand of the distribution grid at night and in rainy days as a constraint condition, and using an optimization algorithm.
The power utilization requirements of farmers at night are met by utilizing the indoor battery, and the power utilization requirements of the transformer area on rainy days are met by utilizing the transformer area power storage equipment, so that power is not taken from a power grid all the year round; meanwhile, the power transmitted into the power grid by the transformer area is adjusted by combining a bus voltage control method, so that the transformer area and the power grid are in a stable interaction operation mode,
in addition, the embodiment of the application realizes the stable interaction of the transformer area and the power grid through the flexible control of the bus voltage, so that a rural power distribution network system becomes a virtual power plant outputting power outwards, and meanwhile, the capacity expansion cost of a transformer is saved.
The following application will explain a rural photovoltaic flexible direct-current power distribution network system through a specific embodiment by combining with an actual situation.
Scenario 1: on a sunny day in a non-heating season, the first conversion switch is turned off, the second conversion switch is connected, the first group of photovoltaic panels outputs current at the maximum power point through the DC/DC converter under the MPPT algorithm optimization, electric energy is consumed by indoor electric equipment including electric appliances and electric storage equipment, redundant electric power is transmitted to a transformer area through the bidirectional DC/DC converter together with electric power generated by the second group of photovoltaic panels, and the electric quantity transmitted to the transformer area is measured by the bidirectional electric meter and used for calculating electricity selling cost;
scenario 2: in cloudy and rainy days in non-heating seasons, the first change-over switch is turned off, the second change-over switch is connected, the electricity storage equipment in the transformer area discharges electricity and is sent to a village bus, the electricity is sent to the households of peasant households through the bidirectional ammeter and the bidirectional DC/DC converter to meet the requirements of household appliances, and electricity is taken from the electricity storage equipment in the transformer area and is metered through the bidirectional ammeter to be used for calculating electricity purchasing cost;
scenario 3: on a sunny day in a heating season, the first change-over switch is connected, the second change-over switch is turned off, the first group of photovoltaic panels outputs current at the maximum power point through the DC/DC converter under the MPPT algorithm optimization, and the current is sent to the electric heating equipment for room heating. The second group of photovoltaic panels output current at the maximum power point under the MPPT algorithm optimization through the DC/DC converter, one part of the current is sent to peasant households through the bidirectional DC/DC converter to meet the power consumption requirement of an electric appliance, and the rest current is metered by the bidirectional ammeter and sent to a transformer area, and meanwhile electricity selling cost is metered;
scenario 4: in rainy days in the heating season, the first change-over switch is connected, the second change-over switch is turned off, the platform area electricity storage equipment discharges electricity and is sent to a village bus, the electricity is sent to peasant households through the bidirectional ammeter and the bidirectional DC/DC converter to only meet the requirements of household appliances, the heating requirements of the peasant households are met by heat storage of the electricity utilization equipment, electricity storage electric energy is not supplied to the electricity heating equipment, electricity is taken from the platform area electricity storage equipment and is metered through the bidirectional ammeter to be used for calculating electricity purchasing cost;
scenario 5: at night in a non-cloudy rainy day, the first change-over switch turns off the switch, the second change-over switch is connected, the indoor battery discharges electricity to meet the requirements of farmers for household appliances, but the battery can not supply electricity to heating equipment;
the bus voltage control process of the system is as follows:
the method comprises the following steps that electric energy generated by a photovoltaic panel is consumed by electric equipment at first and then is sent to a village bus, when the power received by a transformer substation area is larger than a set value, the voltage of the bus is increased, the electricity storage equipment of the transformer substation area starts to be charged, a transferable load electric appliance in the house starts to run, an indoor battery also starts to be charged and is used for consuming redundant electric quantity, and a DC/DC converter runs in a constant voltage control mode; when the power received by the transformer area is smaller than a set value, the bus voltage is reduced, the transformer area power storage equipment starts to discharge, the indoor transferable load electrical appliance stops running, and the DC/DC converter runs the MPPT mode for supplementing the electric quantity; therefore, stable interaction between the transformer area and the power grid is realized.
Furthermore, the electricity selling cost and the electricity buying cost of the peasant household are settled every month, and the peasant household is encouraged to increase the electricity storage capacity of the peasant household by using a cost metering mode and reduce electricity consumption in rainy days, so that the design capacity and the investment cost of electricity storage equipment in a transformer area are effectively reduced.
According to the rural photovoltaic flexible direct-current power distribution network system provided by the embodiment of the application, rural photovoltaic flexible direct-current power distribution network system which is stably interacted with a power grid is realized through a battery operation control strategy by using photovoltaic power generation on the roof of a peasant household as a power energy source of a platform area and combining an indoor battery and a platform area concentrated power storage device to guarantee the power utilization requirement of the platform area at night and on rainy days. The system comprises a photovoltaic panel, a DC/DC converter, a DC/AC converter, a transformer, a bus voltage control system and the like, photovoltaic power generation in a transformer area is preferentially consumed by farmers and electric equipment in the transformer area through connection with a power grid, and redundant power is sequentially transmitted to the power grid through flexible adjustment. The embodiment of this application can effectively realize that the power consumption in platform district is provided by photovoltaic power generation completely to solve peasant household's heating and life power consumption demand, need not to acquire electric power support from the electric wire netting, to electric wire netting transmission electric power simultaneously, become a virtual power plant with rural consumer from electric power. In addition, the transformer implemented by the method has small capacity expansion requirement and even does not need capacity expansion, and the investment cost is further reduced.
The rural photovoltaic flexible direct current distribution network method provided by the embodiment of the application is described by referring to the attached drawings.
Fig. 3 is a flowchart of a method for a rural photovoltaic flexible dc power distribution network according to an embodiment of the present application.
As shown in fig. 3, the method for the rural photovoltaic flexible direct current distribution network comprises the following steps:
in step S301, the actual demand in the rural area is detected.
In step S302, when the actual demand is detected to be a winter heating demand or a domestic power demand, the switching states of the first transfer switch and the second transfer switch are controlled to meet the power demand by using the indoor battery, to meet the power demand of the platform area on rainy days by using the platform area power storage device, and to adjust the power sent to the power grid by the platform area by combining the bus voltage control method, so that the power is smoothly interacted with the power grid.
Optionally, in an embodiment of the present application, the method further includes: and calculating the electricity selling income and the electricity buying expense based on the bidirectional electricity meter so as to use the recommended electricity utilization information based on the electricity selling income and the electricity buying expense.
Optionally, in an embodiment of the present application, controlling the on-off states of the first transfer switch and the second transfer switch to meet the power demand by the indoor battery, and meeting the power demand of the power distribution platform in rainy days by the power storage device of the power distribution platform, and adjusting the power sent to the power grid by the power distribution platform in combination with the bus voltage control method to enable the power to smoothly interact with the power grid includes: when the solar energy power generation system meets the winter heating requirement, the first change-over switch is connected, the second change-over switch is disconnected, the electric power of the first group of photovoltaic panels is sent to electric heating equipment for heating, the electric power of the second group of photovoltaic panels is sent to the indoor to meet the load of electric equipment, and the redundant electric power is sent to a platform area to obtain economic benefit; when the demand is the electricity demand of living, the second change-over switch is connected, the first change-over switch is disconnected, the electricity of the first group of photovoltaic panels is sent to the indoor to meet the load of the electric equipment, and the surplus electricity is directly sent to the platform district together with the electricity generated by the second group of photovoltaic panels through the bidirectional DC/DC converter to obtain economic benefits.
It should be noted that the foregoing explanation of the rural photovoltaic flexible dc power distribution network system embodiment is also applicable to the rural photovoltaic flexible dc power distribution network method of the embodiment, and details are not repeated here.
According to the method for the rural photovoltaic flexible direct-current power distribution network, the actual requirements of the rural area are detected; when the actual demand is detected to be the winter heating demand or the domestic power demand, the on-off states of the first change-over switch and the second change-over switch are controlled, so that the indoor battery is utilized to meet the power demand, meanwhile, the power storage equipment of the transformer area is utilized to meet the power demand of the transformer area in rainy days, and the power transmitted into the power grid by the transformer area is adjusted by combining a bus voltage control method, so that the power is stably interacted with the power grid, the power consumption of the transformer area is completely provided by photovoltaic power generation, the power support does not need to be obtained from the power grid, the power is transmitted to the power grid, rural consumers of the secondary power are changed into a virtual power plant, and the capacity expansion demand and the investment cost of the transformer are effectively reduced.
Claims (7)
1. The utility model provides a flexible direct current distribution network system of rural photovoltaic which characterized in that includes:
a first transfer switch and a second transfer switch;
a DC/DC converter, a bidirectional DC/DC converter and a unidirectional DC/DC converter;
the first group of photovoltaic panels are connected through the DC/DC converter, the first change-over switch and the heating wires to form a first photovoltaic panel system, and the second group of photovoltaic panels supply power to indoor electric equipment through the bidirectional DC/DC converter to form a second photovoltaic panel system, wherein the first photovoltaic panel system and the second photovoltaic panel system are connected through the second change-over switch;
DC/AC converter and transformer, the one end of DC/AC converter and transformer links to each other with one of village bus, the other end of DC/AC converter and transformer links to each other with the electric wire netting, wherein, another way of village bus is passed through two-way DC/DC conversion is connected with platform district power storage equipment and is passed through one-way DC/DC converter links to each other with other platform district consumer, with according to winter heating demand or life power consumption demand control first change over switch with the on off-off state of second change over switch, when utilizing indoor battery to satisfy the power demand, utilize platform district power storage equipment satisfies the power demand of platform district in overcast and rainy day to and combine bus voltage control strategy, adjust the platform district and send into the power of electric wire netting, make it with the electric wire netting is steady mutual.
2. The system of claim 1, further comprising:
the bidirectional electric meter is arranged between one end of the DC/DC bidirectional converter and the village bus so as to calculate electricity selling income and electricity buying expense.
3. The system of claim 1, wherein the DC/DC converter, the bi-directional DC/DC converter and the unidirectional DC/DC converter constitute an associated bus voltage control system for connecting the first transfer switch and disconnecting the second transfer switch when required for the heating, sending power of the first group of photovoltaic panels to an electric heating device for heating, and sending power of the second group of photovoltaic panels indoors to meet a load of the electric device, and sending surplus power to a platform area for economic benefit; when the electricity demand is living, the second change-over switch is connected, the first change-over switch is disconnected, the electricity of the first group of photovoltaic panels is sent to the indoor to meet the load of electric equipment, and the surplus electricity is directly sent to a platform district together with the electricity generated by the second group of photovoltaic panels through the bidirectional DC/DC converter to obtain economic benefits.
4. The system of claim 1, wherein the bus voltage control strategy is divided into three layers, the first layer being balanced operation with the absolute value of the rate of change of voltage being less than a first predetermined percentage; the second layer is that the absolute value of the voltage change rate is greater than the first preset percentage and less than a second preset percentage, and the priority of energy storage regulation is highest; the third layer is used for controlling the load, the energy storage and the photovoltaic side output power at the same time, wherein the absolute value of the voltage change rate is larger than a third preset percentage and smaller than a fourth preset percentage.
5. A rural photovoltaic flexible direct current distribution network method, characterized in that the rural photovoltaic flexible direct current distribution network system according to any one of claims 1-4 is adopted, wherein the method comprises the following steps:
detecting actual requirements of rural areas;
when the actual demand is detected to be the winter heating demand or the domestic power demand, the on-off states of the first change-over switch and the second change-over switch are controlled, so that the indoor battery is utilized to meet the power demand, meanwhile, the power storage equipment of the transformer area is utilized to meet the power demand of the transformer area on rainy days, and the power sent into the power grid by the transformer area is adjusted by combining a bus voltage control method, so that the power is enabled to be in stable interaction with the power grid.
6. The method of claim 5, further comprising:
calculating a power selling profit and a power buying fee based on a bidirectional electric meter to use recommended power utilization information based on the power selling profit and the power buying fee.
7. The method of claim 5, wherein said controlling the switching states of said first transfer switch and said second transfer switch to meet power demand by said district power storage device on rainy days while meeting power demand by an indoor battery, and regulating the power delivered by the district to said grid to smoothly interact with said grid in conjunction with a bus voltage control method comprises:
when the winter heating is required, connecting the first change-over switch, disconnecting the second change-over switch, sending the power of the first group of photovoltaic panels to electric heating equipment for heating, sending the power of the second group of photovoltaic panels to the indoor to meet the load of electric equipment, and sending redundant power to a platform area to obtain economic benefit;
when the domestic electricity demand is met, the second change-over switch is connected, the first change-over switch is disconnected, the power of the first group of photovoltaic panels is sent to the indoor to meet the load of the electricity utilization equipment, and the surplus power is directly sent to a platform district together with the second group of photovoltaic panels through the bidirectional DC/DC converter to generate power so as to obtain economic benefits.
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