CN110994590A - Voltage sag treatment system based on light storage system and control method thereof - Google Patents
Voltage sag treatment system based on light storage system and control method thereof Download PDFInfo
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- CN110994590A CN110994590A CN201911113728.4A CN201911113728A CN110994590A CN 110994590 A CN110994590 A CN 110994590A CN 201911113728 A CN201911113728 A CN 201911113728A CN 110994590 A CN110994590 A CN 110994590A
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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
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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
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
- H02J7/35—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering with light sensitive cells
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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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- 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
- Y02E70/00—Other energy conversion or management systems reducing GHG emissions
- Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin
Abstract
The invention relates to a voltage sag treatment system based on a light storage system and a control method thereof, wherein the voltage sag treatment system comprises the following steps: the power grid connecting end, the first isolating switch, the thyristor, the second isolating switch and the load connecting end are sequentially connected in series; a bypass switch is connected between a connection point between the power grid connection end and the first isolating switch and a connection point between the load connection end and the second isolating switch; the junction between the thyristor and the second isolating switch, the coupling transformer, the bidirectional converter, the energy storage device, the DC/DC converter and the photovoltaic system are sequentially connected; the controller is used for controlling the DC/DC converter and the bidirectional converter according to the running state of the power grid so as to enable the energy storage device and the photovoltaic system to change the running state; the system is connected to a main circuit between a power grid and a load through a power grid connecting end and a load connecting end, and the technical scheme provided by the invention realizes seamless switching between the photovoltaic/energy storage system and commercial power, so that the electric energy quality of important load users is improved.
Description
Technical Field
The invention relates to the field of electric energy quality, in particular to a voltage sag treatment system based on an optical storage system and a control method thereof.
Background
Technical updating of electric equipment puts higher requirements on power supply quality, and voltage sag is one of the most serious power quality problems with the highest occurrence frequency. Particularly, the short-time voltage dip can cause abnormal work of sensitive loads such as a logic programmable controller, a precision mechanical tool, a semiconductor production line and the like, even damage of equipment, and huge economic loss is brought to enterprises.
At present, a standard GB/T30137-2013 power quality voltage sag and temporary interruption is implemented, and the standard gives relevant definitions of the voltage sag, recommendation indexes, monitoring requirements and the like. According to the standard voltage sag, the voltage sag is defined as the phenomenon that the effective value of the voltage rapidly drops to 90% -10% of the reference voltage and is recovered to be normal after the voltage temporarily lasts for 10 ms-1 min. There are many reasons for voltage sag, and lightning stroke, starting of induction motor, and short-circuit fault are the main reasons for voltage sag. Lightning stroke can cause the action of a protection device, so that voltage sag is caused, the sag influence range caused by the lightning stroke is large, and the duration time generally exceeds 100 ms; the full-voltage starting of the induction motor needs to draw large current from a power supply, so that voltage sag is caused, the duration of the caused voltage sag is long, the sag degree is small, and adverse effects can be eliminated through proper measures. Short-circuit faults occur for a large number of reasons and are harmful and may cause voltage dips in adjacent branches. Voltage sag cannot be avoided and cannot be predicted, so that voltage sag treatment equipment becomes a research hotspot in the field of power quality.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to realize seamless switching between a photovoltaic/energy storage system and a mains supply, thereby improving the electric energy quality of important load users. Furthermore, when the power quality is normal, the photovoltaic is used for peak clipping and valley filling for sensitive load users, so that the power quality is further improved.
The purpose of the invention is realized by adopting the following technical scheme:
in a voltage sag management system based on an optical storage system, the improvement comprising: the power grid system comprises a power grid connecting end, a load connecting end, a bypass switch, a first isolating switch, a second isolating switch, a thyristor, a coupling transformer, a bidirectional converter, an energy storage device, a DC/DC converter, a photovoltaic system and a controller;
the power grid connecting end, the first isolating switch, the thyristor, the second isolating switch and the load connecting end are sequentially connected in series;
the bypass switch is connected between the connection point between the power grid connection end and the first isolating switch and the connection point between the load connection end and the second isolating switch;
the junction between the thyristor and the second isolating switch, the coupling transformer, the bidirectional converter, the energy storage device, the DC/DC converter and the photovoltaic system are sequentially connected;
the controller is used for controlling the DC/DC converter and the bidirectional converter according to the running state of a power grid, so that the energy storage device and the photovoltaic system change the running state;
the system is connected to a main circuit between the power grid and the load through the power grid connecting end and the load connecting end.
Preferably, the bidirectional converter is a bidirectional AC/DC converter.
Preferably, the controller includes:
the monitoring unit is used for monitoring the running state of the power grid; the operating state includes at least any one of: the power grid normally supplies power to the load, voltage sag occurs in the power grid, and the power grid is recovered to be normal;
the first charging unit is used for controlling the DC/DC converter to enable the photovoltaic system to charge the energy storage device when the chargeable capacity of the energy storage device does not reach the upper limit;
the second charging unit is used for controlling the bidirectional converter to enable the power grid to charge the energy storage device when the power grid normally supplies power to a load and the chargeable capacity of the energy storage device does not reach an upper limit;
the power supply unit is used for cutting off the power supply of the power grid to the load when the voltage of the power grid drops temporarily, and controlling the bidirectional converter to enable the energy storage device to supply power to the load;
and the flexible exit unit is used for controlling the bidirectional converter to enable the energy storage device to flexibly exit power supply to the load after the power grid is recovered to be normal.
Further, the first charging unit is specifically configured to: and controlling the DC/DC converter by adopting a grid-connected double closed-loop control strategy to realize that the photovoltaic system charges the energy storage device.
Further, the second charging unit is specifically configured to:
closing the first and second isolation switches;
opening the bypass switch;
and controlling the bidirectional converter to convert three-phase alternating current on a main circuit between a power grid and a load into direct current to charge the energy storage device by adopting a grid-connected double closed-loop control strategy.
Further, the power supply unit is specifically configured to:
opening the first isolating switch and closing the second isolating switch;
opening the bypass switch;
and controlling the bidirectional converter by using an off-grid double closed-loop control strategy to enable the energy storage device to supply power to the load.
Further, the flexible exit unit is specifically configured to:
closing the first and second isolation switches;
opening the bypass switch;
and controlling the bidirectional converter by utilizing a synchronous grid-connected control strategy to enable the energy storage device to flexibly exit, and enabling the power supply to be switched to a power grid by the energy storage device.
In a method of controlling a voltage sag management system based on a light storage system, the improvement comprising:
when the chargeable capacity of the energy storage device does not reach the upper limit, controlling the DC/DC converter to enable the photovoltaic system to charge the energy storage device;
monitoring the running state of the power grid;
when the power grid normally supplies power to the load and the chargeable capacity of the energy storage device does not reach the upper limit, controlling the bidirectional converter to enable the power grid to charge the energy storage device;
when the voltage of the power grid drops temporarily, the power supply of the power grid to the load is cut off, and the bidirectional converter is controlled to enable the energy storage device to supply power to the load;
and when the power grid is recovered to be normal, the bidirectional converter is controlled to enable the energy storage device to flexibly quit power supply to the load.
Preferably, the controlling the DC/DC converter to enable the photovoltaic system to charge the energy storage device includes:
and a grid-connected double closed-loop control strategy is adopted to control the DC/DC converter, so that the photovoltaic system charges the energy storage device.
Preferably, when the load is normally supplied by the power grid, the bidirectional converter is controlled to enable the power grid to charge the energy storage device, and the method includes:
closing the first and second isolation switches;
disconnecting the bypass switch;
and a grid-connected double closed-loop control strategy is adopted to control the bidirectional converter to convert three-phase alternating current on a main circuit between a power grid and a load into direct current to charge the energy storage device.
Preferably, when a voltage sag occurs in the power grid, the power supply of the power grid to the load is cut off, and the bidirectional converter is controlled to enable the energy storage device to supply power to the load, and the method includes:
the first isolating switch is opened, and the second isolating switch is closed;
disconnecting the bypass switch;
and controlling the bidirectional converter by using an off-grid double closed-loop control strategy to enable the energy storage device to supply power to the load.
Preferably, after the power grid returns to normal, the bidirectional converter is controlled to enable the energy storage device to flexibly quit power supply to the load, and the method includes:
closing the first and second isolation switches;
disconnecting the bypass switch;
and controlling the bidirectional converter by utilizing a synchronous grid-connected control strategy to enable the energy storage device to flexibly exit, and enabling the power supply to be turned to a power grid by the energy storage device.
Preferably, when the thyristor, the coupling transformer, the bidirectional converter, the DC/DC converter or the energy storage device fails, the bypass switch is closed, the first isolating switch and the second isolating switch are opened, and the thyristor, the coupling transformer, the bidirectional converter, the DC/DC converter or the energy storage device is overhauled.
In a voltage sag management system based on an optical storage system, a controller, the improvement comprising:
the monitoring unit is used for monitoring the running state of the power grid; the operating state includes at least any one of: the power grid normally supplies power to the load, voltage sag occurs in the power grid, and the power grid is recovered to be normal;
the first charging unit is used for controlling the DC/DC converter to enable the photovoltaic system to charge the energy storage device when the chargeable capacity of the energy storage device does not reach the upper limit;
the second charging unit is used for controlling the bidirectional converter to enable the power grid to charge the energy storage device when the power grid normally supplies power to a load and the chargeable capacity of the energy storage device does not reach an upper limit;
the power supply unit is used for cutting off the power supply of the power grid to the load when the voltage of the power grid drops temporarily, and controlling the bidirectional converter to enable the energy storage device to supply power to the load;
and the flexible exit unit is used for controlling the bidirectional converter to enable the energy storage device to flexibly exit power supply to the load after the power grid is recovered to be normal.
Compared with the closest prior art, the invention has the following beneficial effects:
the technical scheme provided by the invention is suitable for various types of voltage sag, and the traditional method has no universal control method and strategy for single-phase voltage sag, two-phase voltage sag, three-phase unbalanced voltage sag and three-phase balanced voltage sag. The control strategy provided by the invention has better general performance. The thyristor and the coupling transformer are applied to medium voltage class, and the energy storage device and the bidirectional converter are in low voltage state, thereby simplifying operation and maintenance. The photovoltaic/energy storage system and the electric power supply control method have the advantages that automatic control from seconds to hours can be provided by combining with a wide modern energy storage technology, the power supply quality of a power distribution network is effectively improved, and multifunctional coordination control of the energy storage system is realized.
Drawings
FIG. 1 is a schematic structural diagram of a voltage sag management system based on a light storage system;
FIG. 2 is a schematic diagram of the IGBT switch control in the DC/DC converter circuit in the embodiment of the present invention;
FIG. 3 is a control block diagram of an off-grid dual closed-loop control strategy in an embodiment of the present invention;
fig. 4 is a control block diagram of a synchronization grid-connection strategy in the embodiment of the present invention.
Detailed Description
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
With the increasing dependence on electric energy and the rapid increase of electricity demand in modern society, the requirement on power supply quality is higher and higher, and sudden power failure inevitably damages the normal life order of people and the normal operation of society, especially to the load which is particularly important in the first-class load, and once the power supply is interrupted, the power supply can cause great political influence or economic loss. As the main power of the emergency power supply equipment of the power grid, the mobile energy storage power supply system has the advantages of flexibility, mature technology, quick start, environmental friendliness and the like, and plays an increasingly remarkable role in small and medium-sized power utilization places such as political power conservation, urban power grid emergency, major natural disaster resistance, temporary power utilization in power shortage areas and the like.
The issue of voltage sag and short-term interruption management is essentially the compatibility between the supply voltage sag level and the voltage sag tolerance of the consumer, and therefore, the present invention provides a voltage sag management system based on an optical storage system, as shown in fig. 1, including:
the power grid system comprises a power grid connecting end, a load connecting end, a bypass switch, a first isolating switch, a second isolating switch, a thyristor, a coupling transformer, a bidirectional converter, an energy storage device, a DC/DC converter, a photovoltaic system and a controller;
the power grid connecting end, the first isolating switch, the thyristor, the second isolating switch and the load connecting end are sequentially connected in series;
the bypass switch is connected between the connection point between the power grid connection end and the first isolating switch and the connection point between the load connection end and the second isolating switch;
the junction between the thyristor and the second isolating switch, the coupling transformer, the bidirectional converter, the energy storage device, the DC/DC converter and the photovoltaic system are sequentially connected;
the controller is used for controlling the DC/DC converter and the bidirectional converter according to the running state of a power grid, so that the energy storage device and the photovoltaic system change the running state;
the system is connected to a main circuit between the power grid and the load through the power grid connecting end and the load connecting end.
The bidirectional converter is a bidirectional AC/DC converter.
The invention aims to realize seamless switching between a photovoltaic/energy storage system and mains supply, thereby improving the electric energy quality of important load users. Furthermore, when the power quality is normal, the photovoltaic is used for peak clipping and valley filling for sensitive load users, so that the power quality is further improved.
In a preferred embodiment of the present invention, the controller comprises:
the monitoring unit is used for monitoring the running state of the power grid; the operating state includes at least any one of: the power grid normally supplies power to the load, voltage sag occurs in the power grid, and the power grid is recovered to be normal;
the first charging unit is used for controlling the DC/DC converter to enable the photovoltaic system to charge the energy storage device when the chargeable capacity of the energy storage device does not reach the upper limit;
the second charging unit is used for controlling the bidirectional converter to enable the power grid to charge the energy storage device when the power grid normally supplies power to a load and the chargeable capacity of the energy storage device does not reach an upper limit;
the power supply unit is used for cutting off the power supply of the power grid to the load when the voltage of the power grid drops temporarily, and controlling the bidirectional converter to enable the energy storage device to supply power to the load;
and the flexible exit unit is used for controlling the bidirectional converter to enable the energy storage device to flexibly exit power supply to the load after the power grid is recovered to be normal.
Specifically, the first charging unit is specifically configured to: and controlling the DC/DC converter by adopting a grid-connected double closed-loop control strategy to realize that the photovoltaic system charges the energy storage device.
The second charging unit is specifically configured to:
closing the first and second isolation switches;
opening the bypass switch;
and controlling the bidirectional converter to convert three-phase alternating current on a main circuit between a power grid and a load into direct current to charge the energy storage device by adopting a grid-connected double closed-loop control strategy.
The power supply unit is specifically configured to:
opening the first isolating switch and closing the second isolating switch;
opening the bypass switch;
and controlling the bidirectional converter by using an off-grid double closed-loop control strategy to enable the energy storage device to supply power to the load.
The flexible exit unit is specifically configured to:
closing the first and second isolation switches;
opening the bypass switch;
and controlling the bidirectional converter by utilizing a synchronous grid-connected control strategy to enable the energy storage device to flexibly exit, and enabling the power supply to be switched to a power grid by the energy storage device.
Based on the technical scheme, the invention also provides a control method of the voltage sag treatment system based on the light storage system, and the method comprises the following steps:
when the chargeable capacity of the energy storage device does not reach the upper limit, controlling a DC/DC converter to enable a photovoltaic system to charge the energy storage device;
monitoring the running state of the power grid;
when the power grid normally supplies power to a load and the chargeable capacity of the energy storage device does not reach the upper limit, controlling the bidirectional converter to enable the power grid to charge the energy storage device;
when the voltage of the power grid drops temporarily, the power supply of the power grid to the load is cut off, and the bidirectional converter is controlled to enable the energy storage device to supply power to the load;
and when the power grid is recovered to be normal, the bidirectional converter is controlled to enable the energy storage device to flexibly quit power supply to the load.
Specifically, in a preferred embodiment of the present invention, the controlling the DC/DC converter to enable the photovoltaic system to charge the energy storage device includes:
and controlling the DC/DC converter by adopting a grid-connected double closed-loop control strategy to realize that the photovoltaic system charges the energy storage device.
In the process, the commonly used double closed-loop control of the energy storage converter is adopted to realize the on-off state control of the IGBT in the DC/DC converter, so that the electric energy flows from the photovoltaic to the energy storage device, the energy storage device is in a floating charge state, the IGBT in the DC/DC converter controls the floating charge of the energy storage device, and further, the control principle of the IGBT switch in the circuit of the DC/DC converter is shown in fig. 2, and the control method comprises the following steps:
solving a difference value between a photovoltaic voltage feedback signal Udc and a given voltage value Udref, and generating a given current signal Idref of an inner ring through a PI control link; calculating a difference value between a photovoltaic reactive power feedback signal Q and a given reactive value Qref, and generating a given current signal Iqref of an inner ring through a PI control link; respectively subtracting the obtained Idref and Id, and Iqref and Iq, and generating given voltage signals Udref and Uqref through a PI control link; and operating the obtained given voltage signal, the actual voltage signal and the feedforward control signal to obtain voltage control signals Udl and Uql, generating a PWM control signal and controlling the on-off of the IGBT.
In an embodiment of the present invention, when the power grid normally supplies power to the load, the controlling the bidirectional converter to charge the energy storage device by the power grid includes:
closing the first and second isolation switches;
opening the bypass switch;
and controlling the bidirectional converter to convert three-phase alternating current on a main circuit between a power grid and a load into direct current to charge the energy storage device by adopting a grid-connected double closed-loop control strategy.
In the process, a bidirectional converter controls a three-phase alternating current mains supply to be converted into a direct current to charge an energy storage device so as to achieve the purpose of low-current charging, a grid-connected double closed-loop control strategy commonly used by the energy storage converter realizes the on-off state control of an IGBT (insulated gate bipolar translator) in the bidirectional AC/DC converter, so that electric energy flows from a main circuit to the energy storage device, the energy storage device is in a floating charging state, and the control principle of the energy storage device is the same as that of the DC/DC converter, and the energy storage:
voltage feedback signal U of commercial powerdcWith a given voltage value UdrefThe difference between the two signals is used for generating a given current signal I of an inner ring through a PI control linkdref(ii) a Obtaining reactive power feedback signal Q and given reactive value Q of commercial powerrefThe difference between the two signals is used for generating a given current signal I of an inner ring through a PI control linkqref(ii) a Will obtain IdrefAnd Id、IqrefAnd IqRespectively carrying out difference and generating a given voltage signal U through a PI control linkdrefAnd Uqref(ii) a Operating the obtained given voltage signal with the actual voltage signal and the feedforward control signal to obtain a voltage control signal UdlAnd UqlAnd generating a PWM control signal to control the on-off of the IGBT.
In an embodiment of the present invention, when a voltage sag occurs in a power grid, cutting off power supplied to a load by the power grid, and controlling a bidirectional converter to enable an energy storage device to supply power to the load includes:
opening the first isolating switch and closing the second isolating switch;
opening the bypass switch;
and controlling the bidirectional converter by using an off-grid double closed-loop control strategy to enable the energy storage device to supply power to the load.
In the process, when voltage sag occurs in mains supply, the bidirectional converter adopts an off-grid double closed-loop control strategy to control the electric energy of the energy storage device to be converted from direct current to three-phase current to supply power to a load so as to achieve the purpose of voltage sag control, a control block diagram of the bidirectional converter is shown in fig. 3, wherein Up-d, Ug-d, theta and E in the control block diagram respectively represent a grid-connected point voltage d-axis component, a grid voltage d-axis component, a voltage vector position angle and a grid-connected point voltage amplitude. And taking the d axis in the dq coordinate system to coincide with the grid electromotive force, and then the grid electromotive force q axis component Ug _ q is equal to 0. Therefore, the energy storage device only needs to ensure that the d-axis component of the output voltage is the same as the d-axis component of the electromotive force of the power grid, and the position angles of the voltage vectors are the same. After comparing Up-d with Ug-d, adding the voltage amplitude of the grid-connected point and the PI regulator to form a new voltage amplitude of the grid-connected point; the voltage vector position angle is the same as the grid voltage position angle theta. The purpose of the control mode is to ensure that the voltage of the grid-connected point is equal to the voltage amplitude of the power grid, the initial phase is the same and the frequency is the same. When voltage sag occurs, the thyristor is turned off because the passing current is zero, and a thyristor gate signal is changed from 1 to 0; and the energy storage system replaces the commercial power after the fault to supply power to the load, so that the voltage sag management is completed.
In an embodiment of the present invention, when the power grid is recovered to normal, the controlling the bidirectional converter to enable the energy storage device to flexibly quit power supply to the load includes:
closing the first and second isolation switches;
opening the bypass switch;
and controlling the bidirectional converter by utilizing a synchronous grid-connected control strategy to enable the energy storage device to flexibly exit, and enabling the power supply to be switched to a power grid by the energy storage device.
In the process, after the voltage sag is recovered, the bidirectional converter controls the voltage provided by the energy storage device to be gradually reduced, and a power supply party is gradually turned to the mains supply from the energy storage device so as to achieve the purpose of flexibly withdrawing the energy storage device. After comparing Up-d with Ug-d, adding the voltage amplitude of the grid-connected point and the PI regulator to form a new voltage amplitude of the grid-connected point; and after comparing the Ug-q with the Ug-q, adding the Ug-q and the theta through a PI regulator to form a voltage vector angle for regulating the voltage of the grid-connected point. The purpose of the control mode is to enable the grid-connected point voltage to be equal to the grid voltage in amplitude, initial phase and frequency. And after synchronization grid connection is finished, the thyristor is conducted, so that the power grid and the energy storage system are in grid-connected operation, the bidirectional converter controls the output current of the grid-connected point to be slowly reduced until the output current is zero, and the energy storage system is changed to a floating charge working state.
It should be noted that, in the practical application process, when the thyristor, the coupling transformer, the bidirectional converter, the DC/DC converter or the energy storage device has a fault, the bypass switch may be closed, the first isolating switch and the second isolating switch may be opened, and the thyristor, the coupling transformer, the bidirectional converter, the DC/DC converter or the energy storage device may be overhauled.
The invention also provides a controller, which is applied to a voltage sag treatment system based on the light storage system and comprises the following components:
the monitoring unit is used for monitoring the running state of the power grid; the operating state includes at least any one of: the power grid normally supplies power to the load, voltage sag occurs in the power grid, and the power grid is recovered to be normal;
the first charging unit is used for controlling the DC/DC converter to enable the photovoltaic system to charge the energy storage device when the chargeable capacity of the energy storage device does not reach the upper limit;
the second charging unit is used for controlling the bidirectional converter to enable the power grid to charge the energy storage device when the power grid normally supplies power to a load and the chargeable capacity of the energy storage device does not reach an upper limit;
the power supply unit is used for cutting off the power supply of the power grid to the load when the voltage of the power grid drops temporarily, and controlling the bidirectional converter to enable the energy storage device to supply power to the load;
and the flexible exit unit is used for controlling the bidirectional converter to enable the energy storage device to flexibly exit power supply to the load after the power grid is recovered to be normal.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and although the present invention is described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is to be covered by the claims.
Claims (14)
1. A voltage sag management system based on a light storage system, the system comprising: the power grid system comprises a power grid connecting end, a load connecting end, a bypass switch, a first isolating switch, a second isolating switch, a thyristor, a coupling transformer, a bidirectional converter, an energy storage device, a DC/DC converter, a photovoltaic system and a controller;
the power grid connecting end, the first isolating switch, the thyristor, the second isolating switch and the load connecting end are sequentially connected in series;
the bypass switch is connected between the connection point between the power grid connection end and the first isolating switch and the connection point between the load connection end and the second isolating switch;
the junction between the thyristor and the second isolating switch, the coupling transformer, the bidirectional converter, the energy storage device, the DC/DC converter and the photovoltaic system are sequentially connected;
the controller is used for controlling the DC/DC converter and the bidirectional converter according to the running state of a power grid, so that the energy storage device and the photovoltaic system change the running state;
the system is connected to a main circuit between the power grid and the load through the power grid connecting end and the load connecting end.
2. The system of claim 1, wherein the bidirectional converter is a bidirectional AC/DC converter.
3. The system of claim 1, wherein the controller comprises:
the monitoring unit is used for monitoring the running state of the power grid; the operating state includes at least any one of: the power grid normally supplies power to the load, voltage sag occurs in the power grid, and the power grid is recovered to be normal;
the first charging unit is used for controlling the DC/DC converter to enable the photovoltaic system to charge the energy storage device when the chargeable capacity of the energy storage device does not reach the upper limit;
the second charging unit is used for controlling the bidirectional converter to enable the power grid to charge the energy storage device when the power grid normally supplies power to a load and the chargeable capacity of the energy storage device does not reach an upper limit;
the power supply unit is used for cutting off the power supply of the power grid to the load when the voltage of the power grid drops temporarily, and controlling the bidirectional converter to enable the energy storage device to supply power to the load;
and the flexible exit unit is used for controlling the bidirectional converter to enable the energy storage device to flexibly exit power supply to the load after the power grid is recovered to be normal.
4. The system of claim 3, wherein the first charging unit is specifically configured to: and controlling the DC/DC converter by adopting a grid-connected double closed-loop control strategy to realize that the photovoltaic system charges the energy storage device.
5. The system of claim 3, wherein the second charging unit is specifically configured to:
closing the first and second isolation switches;
opening the bypass switch;
and controlling the bidirectional converter to convert three-phase alternating current on a main circuit between a power grid and a load into direct current to charge the energy storage device by adopting a grid-connected double closed-loop control strategy.
6. The system of claim 3, wherein the power unit is specifically configured to:
opening the first isolating switch and closing the second isolating switch;
opening the bypass switch;
and controlling the bidirectional converter by using an off-grid double closed-loop control strategy to enable the energy storage device to supply power to the load.
7. The system of claim 3, wherein the flexible exit unit is specifically configured to:
closing the first and second isolation switches;
opening the bypass switch;
and controlling the bidirectional converter by utilizing a synchronous grid-connected control strategy to enable the energy storage device to flexibly exit, and enabling the power supply to be switched to a power grid by the energy storage device.
8. A method for controlling a voltage sag management system according to any one of claims 1 to 7, wherein the method comprises:
when the chargeable capacity of the energy storage device does not reach the upper limit, controlling the DC/DC converter to enable the photovoltaic system to charge the energy storage device;
monitoring the running state of the power grid;
when the power grid normally supplies power to a load and the chargeable capacity of the energy storage device does not reach the upper limit, controlling the bidirectional converter to enable the power grid to charge the energy storage device;
when the voltage of the power grid drops temporarily, the power supply of the power grid to the load is cut off, and the bidirectional converter is controlled to enable the energy storage device to supply power to the load;
and when the power grid is recovered to be normal, the bidirectional converter is controlled to enable the energy storage device to flexibly quit power supply to the load.
9. The method of claim 8, wherein controlling the DC/DC converter to cause a photovoltaic system to charge the energy storage device comprises:
and controlling the DC/DC converter by adopting a grid-connected double closed-loop control strategy to realize that the photovoltaic system charges the energy storage device.
10. The method of claim 8, wherein controlling the bidirectional converter to cause the grid to charge the energy storage device when the grid is normally supplying power to the load comprises:
closing the first and second isolation switches;
disconnecting the bypass switch;
and controlling the bidirectional converter to convert three-phase alternating current on a main circuit between a power grid and a load into direct current to charge the energy storage device by adopting a grid-connected double closed-loop control strategy.
11. The method of claim 8, wherein the removing the power from the grid to the load and controlling the bidirectional converter to cause the energy storage device to supply power to the load when a voltage sag occurs in the grid comprises:
the first isolating switch is opened, and the second isolating switch is closed;
disconnecting the bypass switch;
and controlling the bidirectional converter by using an off-grid double closed-loop control strategy to enable the energy storage device to supply power to the load.
12. The method of claim 8, wherein controlling the bidirectional converter to flexibly remove the energy storage device from the power supply to the load after the grid returns to normal comprises:
closing the first and second isolation switches;
disconnecting the bypass switch;
and controlling the bidirectional converter by utilizing a synchronous grid-connected control strategy to enable the energy storage device to flexibly exit, and enabling the power supply to be switched to a power grid by the energy storage device.
13. The method of claim 8, wherein when a thyristor, coupling transformer, bidirectional converter, DC/DC converter, or energy storage device fails, closing the bypass switch, opening the first and second isolation switches, and servicing the thyristor, coupling transformer, bidirectional converter, DC/DC converter, or energy storage device.
14. A controller is applied to a voltage sag treatment system based on an optical storage system, and is characterized by comprising:
the monitoring unit is used for monitoring the running state of the power grid; the operating state includes at least any one of: the power grid normally supplies power to the load, voltage sag occurs in the power grid, and the power grid is recovered to be normal;
the first charging unit is used for controlling the DC/DC converter to enable the photovoltaic system to charge the energy storage device when the chargeable capacity of the energy storage device does not reach the upper limit;
the second charging unit is used for controlling the bidirectional converter to enable the power grid to charge the energy storage device when the power grid normally supplies power to a load and the chargeable capacity of the energy storage device does not reach an upper limit;
the power supply unit is used for cutting off the power supply of the power grid to the load when the voltage of the power grid drops temporarily, and controlling the bidirectional converter to enable the energy storage device to supply power to the load;
and the flexible exit unit is used for controlling the bidirectional converter to enable the energy storage device to flexibly exit power supply to the load after the power grid is recovered to be normal.
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