阅读说明：本技术 一种光储充微网系统及其控制方法 (Light storage and charging micro-grid system and control method thereof ) 是由 何少强 廖琛琛 刘程宇 于 2020-06-24 设计创作，主要内容包括：本发明提供了一种光储充微网系统及其控制方法,该光储充微网系统包括光伏发电单元、储能单元、光伏控制器、储能变流器和并离网切换单元,所述光伏发电单元通过光伏控制器与直流母线连接,所述储能电池、储能变流器分别与直流母线连接,充电桩直接挂在直流母线上,形成直流组网；所述储能变流器通过并离网切换单元与电网、负载连接,形成交流组网；所述光伏控制器用于控制光伏发电单元给储能单元充电；所述并离网切换单元用于实现储能变流器并网和离网的状态切换。采用本发明的技术方案,减少了能量损失,提高了经济性,实现了并离网无缝切换,保障了系统供电质量；并在电网停电或异常波动时,可全自动实现离网运行,保障光储充业务不间断开展。(The invention provides a light storage and charging microgrid system and a control method thereof, wherein the light storage and charging microgrid system comprises a photovoltaic power generation unit, an energy storage unit, a photovoltaic controller, an energy storage converter and a grid-connected and off-grid switching unit, the photovoltaic power generation unit is connected with a direct-current bus through the photovoltaic controller, an energy storage battery and the energy storage converter are respectively connected with the direct-current bus, and a charging pile is directly hung on the direct-current bus to form a direct-current networking; the energy storage converter is connected with a power grid and a load through a grid-connected and off-grid switching unit to form an alternating current networking; the photovoltaic controller is used for controlling the photovoltaic power generation unit to charge the energy storage unit; and the grid-connected and grid-disconnected switching unit is used for realizing the state switching of grid connection and grid disconnection of the energy storage converter. By adopting the technical scheme of the invention, the energy loss is reduced, the economy is improved, the grid-connected and off-grid seamless switching is realized, and the power supply quality of the system is ensured; and when the power grid is powered off or fluctuates abnormally, the off-grid operation can be automatically realized, and the uninterrupted development of the optical storage and charging service is ensured.)

1. The utility model provides a light stores up and fills microgrid system which characterized in that: the system comprises a photovoltaic power generation unit, an energy storage unit, a photovoltaic controller, an energy storage converter and a grid-connected and off-grid switching unit, wherein the photovoltaic power generation unit is connected with a direct current bus through the photovoltaic controller; the energy storage converter is connected with a power grid and a load through a grid-connected and off-grid switching unit to form an alternating current networking;

the photovoltaic controller is used for controlling the photovoltaic power generation unit to charge the energy storage unit;

and the grid-connected and grid-disconnected switching unit is used for realizing the state switching of grid connection and grid disconnection of the energy storage converter.

2. The light storage and charging microgrid system of claim 1, wherein: the energy storage converter comprises an internal inversion unit, the off-grid switching unit comprises an inversion contactor, a load circuit breaker, a power grid contactor and a power grid circuit breaker, the internal inversion unit is connected with the inversion contactor, the inversion contactor is connected with a load through the load circuit breaker, and the inversion contactor is connected with an alternating current power grid through a series circuit of the power grid contactor and the power grid circuit breaker.

3. The light storage and charging microgrid system of claim 2, wherein: the energy storage converter comprises an energy storage control module, the energy storage unit comprises an energy storage battery and a capacity calculation module, the energy storage control module is electrically connected with the capacity calculation module, the internal inversion unit, the inversion contactor and the power grid contactor, and the energy storage control module controls the action of the internal inversion unit, the inversion contactor and the power grid contactor according to the capacity of the energy storage battery fed back by the capacity calculation module.

4. The light storage and charging microgrid system of claim 3, wherein: the energy storage control module controls the grid-connected and off-grid switching unit to act according to the capacity of the energy storage battery fed back by the capacity calculation module and/or the current clock as the peak value or the valley value of the electricity price, so that the system is in a grid-connected or off-grid state;

when the energy storage unit is in an off-grid state, the internal inversion unit converts the direct current of the energy storage unit into alternating current to be output and supplies the alternating current to a load;

when the energy storage control module is in a grid-connected state, the energy storage control module controls the internal inversion unit to work or stop according to the capacity of the energy storage unit;

when the internal inversion unit is stopped, the power grid supplies power to the load;

when the internal inversion unit works, a power grid supplies power to a load, and the internal inversion unit rectifies alternating current of the power grid into direct current for output so as to charge the energy storage unit.

5. The light storage and charging microgrid system of claim 4, wherein: the energy storage control module comprises a signal processor, and an enabling end of the signal processor is electrically connected with the inversion contactor and the power grid contactor through a signal amplifying circuit respectively to control the on-off of each switch; the signal processor is electrically connected with the internal inversion unit and controls the internal inversion unit to work or stop;

the signal amplification circuit comprises a primary signal amplification circuit and a secondary signal amplification circuit.

6. The light storage and charging microgrid system of claim 4, wherein: the photovoltaic controller controls the output of the electric energy of the photovoltaic power generation unit according to the capacity of the energy storage battery fed back by the capacity calculation module; the charging pile comprises a charging pile control module, and the charging pile control module controls external output of the charging pile according to the capacity of the energy storage battery fed back by the capacity calculation module.

7. The method for controlling the optical storage and charging microgrid system according to claim 6, characterized by comprising:

when the capacity of the energy storage battery is smaller than the allowable upper limit value of the system, the photovoltaic controller controls the photovoltaic unit to charge the energy storage battery;

when the capacity of the energy storage battery is larger than the allowable upper limit value of the system, the photovoltaic controller stops working to prevent the energy storage battery from being overcharged;

when the capacity of the energy storage battery is larger than the allowable lower limit value of the system, the charging pile control module controls the charging pile to output outwards;

when the capacity of the energy storage battery is smaller than the system allowable lower limit value, the charging pile control module controls the charging pile to stop outputting, so that the energy storage battery is prevented from being overdischarged;

when the capacity of the energy storage battery is larger than a first system set value, the energy storage control module controls the off-grid switching unit to be switched to an off-grid state, and the internal inversion unit converts direct current of the energy storage battery into alternating current to be output and supplies power to a load;

when the capacity of the energy storage battery is smaller than a first system set value and larger than a second system set value, the energy storage control module controls the grid-connected switching unit to be switched to a grid-connected state and controls the internal inversion unit to stop, and the load is powered by a power grid;

when the capacity of the energy storage battery is smaller than a second system set value, the energy storage control module controls the grid-connected switching unit to be switched to a grid-connected state, and the internal inversion unit rectifies the alternating current and direct current of the power grid to charge the energy storage battery; the load is powered by the grid.

8. The method for controlling the optical storage and charging microgrid system according to claim 7, characterized in that: the system allowable upper limit value is the same as or different from a first system set value, and the system allowable lower limit value is the same as or different from a second system set value; the allowable upper limit value of the system is 90% -98% of the rated capacity of the energy storage battery, and the allowable lower limit value of the system is 3% -10% of the rated capacity of the energy storage battery; the first system set value is 90% -98% of the rated capacity of the energy storage battery, and the second system set value is 3% -10% of the rated capacity of the energy storage battery.

9. The method for controlling the optical storage and charging microgrid system according to claim 8, characterized in that: when the power grid is in power failure or abnormally fluctuates, the energy storage control module controls the grid-connected and off-grid switching unit to be switched to an off-grid state, and the direct current of the energy storage battery is converted into alternating current to be output through the internal inversion unit and supplied to a load.

10. The method for controlling the optical storage and charging microgrid system according to any one of claims 7 to 9, characterized in that: the energy storage control module adjusts the phase and amplitude of the output voltage of the internal inversion unit according to the voltage of the power grid and executes synchronous tracking control;

when the off-grid power supply voltage/grid-connected power supply voltage and the grid voltage have the same phase and the same amplitude, all switches in the grid-connected and off-grid switching unit are closed, the load is jointly supplied with power by the energy storage battery and the grid, and meanwhile, the energy storage control module controls switching from an off-grid voltage source loop model to a grid-connected current source loop model or switching from the grid-connected current source loop model to the off-grid voltage source loop model;

and in a combined power supply stage after a set time, the energy storage control module controls the internal inversion unit to stop, the internal inversion unit exits from a power supply state, and the load is transited to supply power to a power grid or supply power to an energy storage battery.

Technical Field

The invention belongs to the field of new energy and power electronics, and particularly relates to a light storage and charging micro-grid system and a control method thereof.

Background

Under the current large trend background of automobile electrification, the charging pile is used as a supporting facility of a new energy automobile, and the demand is strong. However, in the design and construction process of various charging stations, the power distribution capacity often becomes the bottleneck of the scale of the power station, and even the charging service cannot be developed due to the limited power distribution. Fortunately, due to the rapid cost reduction of photovoltaic power generation and lithium battery energy storage and the development of control technology, the comprehensive application of light storage and charging becomes possible, and the solar photovoltaic battery has economical efficiency. The photovoltaic power generation subsystem can solve the problem that the power distribution capacity of a charging station is limited; the energy storage subsystem can solve photovoltaic power supply and fill electric pile power consumption mobility and randomness problem.

The conventional optical charging and storage system mostly adopts a common alternating current bus scheme as shown in fig. 1. The scheme has the following problems:

(1) photovoltaic power generation equipment adopts traditional photovoltaic inverter to organize the network from the interchange side, and when system load (fill electric pile promptly) was less than photovoltaic power generation power, the surplus energy need fill to energy storage battery system through energy storage converter, just so has two kinds of defects: A. the extra energy loss of a photovoltaic energy charging loop needs to be increased by more than 2% through a photovoltaic grid-connected inverter and an energy storage bidirectional converter. B. When the power grid of charging station appears and cuts off the power supply or the trouble, even illumination resource is abundant, the photovoltaic energy still can't charge the utilization, causes economic loss.

(2) The charging pile adopts a traditional two-stage topological circuit; the preceding stage AC-DC rectification, the subsequent DC voltage regulation and isolation conversion also need to be networked from the AC side. This solution also has two drawbacks: A. the additional energy loss is increased by more than 1 percent by converting the alternating current into the direct current in a plurality of stages; B. when the power grid outage appears, even battery power is enough, fill electric pile still unable use, cause economic loss.

There are also a few demonstration projects or researches using a common dc bus scheme as shown in fig. 2, and the core devices can be networked on the dc side. However, the scheme has very serious application problems: the photovoltaic energy storage system is characterized in that only main energy conversion equipment such as a photovoltaic charging controller, a charging pile and a bidirectional energy storage converter is considered, and the power utilization problem of infrastructure equipment such as air conditioning refrigeration, illumination and monitoring for supporting normal operation of the energy storage system is not considered, the infrastructure equipment is the premise of ensuring normal operation of main equipment of the system, and the equipment basically needs to be supplied with alternating current. In the current implementation process, electricity is taken from a public power grid (as shown in fig. 3), and the scheme has two defects, so that the demonstration project cannot be popularized commercially:

(1) when the power grid has a power failure or fluctuates abnormally, even if the photovoltaic and the charging pile can be used, the light storage and charging system still cannot be used due to the fact that power supply of infrastructure equipment cannot be guaranteed.

(2) When the energy storage battery is fully charged, on one hand, the photovoltaic power generation is limited for preventing the energy storage battery from being overcharged; on the other hand, the power is still taken from the power grid to supply power to the infrastructure equipment, so that energy waste is caused, and the economy is influenced.

Disclosure of Invention

Aiming at the technical problems, the invention discloses a light storage and charging micro-grid system and a control method thereof, which adjust the control mode of the input side of the traditional charging pile, meet the requirement of direct current input, realize direct current side networking, reduce energy loss and improve the economy.

In contrast, the technical scheme adopted by the invention is as follows:

a light storage and charging microgrid system comprises a photovoltaic power generation unit, an energy storage unit, a photovoltaic controller, an energy storage converter and a grid-connected and off-grid switching unit, wherein the photovoltaic power generation unit is connected with a direct-current bus through the photovoltaic controller, the energy storage battery and the energy storage converter are respectively connected with the direct-current bus, and a charging pile is directly hung on the direct-current bus to form a direct-current networking; the energy storage converter is connected with a power grid and a load through a grid-connected and off-grid switching unit to form an alternating current networking;

the photovoltaic controller is used for controlling the photovoltaic power generation unit to charge the energy storage unit and carrying out direct current conversion;

and the grid-connected and grid-disconnected switching unit is used for realizing the state switching of grid connection and grid disconnection of the energy storage converter.

Wherein, the load is infrastructure equipment such as air conditioner refrigeration, illumination, control. By adopting the technical scheme, the traditional system is improved aiming at the comprehensive application field of light storage and charging, and is subdivided into the system power supply and the load equipment, the direct current equipment such as a photovoltaic controller and a charging pile is networked from the direct current side, the alternating current equipment such as infrastructure equipment is networked from the alternating current side, the requirements of different power consumption are considered, the energy loss is reduced, and the economical efficiency is improved.

As a further improvement of the present invention, the energy storage converter includes an internal inverter unit, the grid-connected/off-grid switching unit includes an inverter contactor, a load circuit breaker, a grid contactor, and a grid circuit breaker, the internal inverter unit is connected to the inverter contactor, the inverter contactor is connected to the load through the load circuit breaker, and the inverter contactor is connected to the ac grid through a series circuit of the grid contactor and the grid circuit breaker.

As a further improvement of the present invention, the energy storage converter includes an energy storage control module, the energy storage unit includes an energy storage battery and a capacity calculation module, the energy storage control module is electrically connected to the capacity calculation module, the internal inversion unit, the inversion contactor, and the grid contactor, and controls the operation of the internal inversion unit, the inversion contactor, and the grid contactor according to the capacity of the energy storage battery fed back by the capacity calculation module. The load circuit breaker and the power grid circuit breaker are manually controlled and are kept in a closed state when the system works.

As a further improvement of the invention, the energy storage control module controls the grid-connected and off-grid switching unit to act according to the capacity of the energy storage battery fed back by the capacity calculation module and/or the current clock is the peak value or the valley value of the electricity price, so that the system is in a grid-connected or off-grid state;

when the energy storage unit is in an off-grid state, the internal inversion unit converts the direct current of the energy storage unit into alternating current to be output and supplies the alternating current to a load;

when the energy storage control module is in a grid-connected state, the energy storage control module controls the internal inversion unit to work or stop according to the capacity of the energy storage unit;

when the internal inversion unit is stopped, the power grid supplies power to the load;

when the internal inversion unit works, a power grid supplies power to a load, and the internal inversion unit rectifies alternating current of the power grid into direct current for output so as to charge the energy storage unit.

As a further improvement of the present invention, the energy storage control module includes a signal processor, and each enable end of the signal processor is electrically connected to the inverter contactor and the grid contactor through a signal amplification circuit, respectively, to control the on/off of each switch; and the signal processor is electrically connected with the internal inversion unit and controls the internal inversion unit to work or stop.

Furthermore, the signal amplification circuit comprises a primary signal amplification circuit and a secondary signal amplification circuit.

Further, the primary signal amplifying circuit comprises resistors R335 to R339, a capacitor C140, a transistor Q10, and a transistor Q11, wherein one end of the resistor R35 is connected to the signal processor, the other end of the resistor R35 is connected to one end of the capacitor C140, one end of the resistor R336, and the B electrode of the transistor Q10, and the other end of the capacitor C140, the other end of the resistor R336, and the E electrode of the transistor Q10 are grounded; the C pole of the triode Q10 is connected with a 15V power supply through a resistor R338 and is connected with the B pole of the triode Q11 through a resistor R339, the C pole of the triode Q11 outputs a level signal and is grounded through a resistor R337, and the E pole of the triode Q11 is connected with the 15V power supply;

the secondary signal amplifying circuit comprises a resistor R37, a resistor R38, a resistor R42, a capacitor C29, a triode Q6, a relay K2 and a diode D9; one end of the resistor R37 is connected with the C pole of the triode Q11, the other end of the resistor R37 is connected with one end of the resistor R38, one end of the capacitor C29 and the B pole of the triode Q6, the other end of the resistor R38, the other end of the capacitor C29 and the E pole of the triode Q6 are grounded, the C pole of the triode Q6 is connected with one end of the coil of the relay K2 and the anode of the diode D9, the cathode of the diode D9 is connected with the other end of the coil of the relay K2, and the diode R42 is connected with a 15V power supply; and the contact of the relay K2 is electrically connected with the corresponding inverter contactor and the corresponding power grid contactor.

As a further improvement of the invention, the photovoltaic controller controls the output of the electric energy of the photovoltaic power generation unit according to the capacity of the energy storage battery fed back by the capacity calculation module;

the charging pile comprises a charging pile control module, and the charging pile control module controls external output of the charging pile according to the capacity of the energy storage battery fed back by the capacity calculation module.

The invention also discloses a control method of the light storage and charging microgrid system, which comprises the following steps:

when the capacity of the energy storage battery is smaller than the allowable upper limit value of the system, the photovoltaic controller controls the photovoltaic unit to charge the energy storage battery;

when the capacity of the energy storage battery is larger than the allowable upper limit value of the system, the photovoltaic controller stops working to prevent the energy storage battery from being overcharged;

when the capacity of the energy storage battery is larger than the allowable lower limit value of the system, the charging pile control module controls the charging pile to output outwards;

when the capacity of the energy storage battery is smaller than the system allowable lower limit value, the charging pile control module controls the charging pile to stop outputting, so that the energy storage battery is prevented from being overdischarged;

when the capacity of the energy storage battery is larger than a first system set value, the energy storage control module controls the off-grid switching unit to be switched to an off-grid state, and the internal inversion unit converts direct current of the energy storage battery into alternating current to be output and supplies power to a load;

when the capacity of the energy storage battery is smaller than a first system set value and larger than a second system set value, the energy storage control module controls the grid-connected switching unit to be switched to a grid-connected state and controls the internal inversion unit to stop, and the load is powered by a power grid;

when the capacity of the energy storage battery is smaller than a second system set value, the energy storage control module controls the grid-connected switching unit to be switched to a grid-connected state, and the internal inversion unit rectifies the alternating current and direct current of the power grid to charge the energy storage battery; the load is powered by the grid.

As a further improvement of the present invention, the system allowable upper limit value is the same as or different from the first system set value, and the system allowable lower limit value is the same as or different from the second system set value; the allowable upper limit value of the system is 90% -98% of the rated capacity of the energy storage battery, and the allowable lower limit value of the system is 3-10% of the rated capacity of the energy storage battery; the first system set value is 90% -98% of the rated capacity of the energy storage battery, and the second system set value is 3-10% of the rated capacity of the energy storage battery.

As a further improvement of the invention, when the power grid is in power failure or abnormally fluctuates, the energy storage control module controls the grid-connected and off-grid switching unit to be switched to an off-grid state, and the internal inversion unit converts the direct current of the energy storage battery into alternating current to be output and supplied to a load.

Specifically, when the power grid is in power failure or abnormally fluctuates, the following scheme is implemented:

when the capacity of the energy storage battery is larger than a first system set value, the energy storage control module controls the off-grid switching unit to be switched to an off-grid state, and the internal inversion unit converts direct current of the energy storage battery into alternating current to be output and supplies power to a load;

when the capacity of the energy storage battery is smaller than a first system set value and larger than a second system set value, the energy storage control module controls the grid-connected and off-grid switching unit to be switched to an off-grid state, and the internal inversion unit converts direct current of the energy storage battery into alternating current to be output and supplies power to a load;

and when the capacity of the energy storage battery is smaller than a second system set value, the photovoltaic controller, the charging pile and the internal inversion unit are stopped.

As a further improvement of the present invention, the energy storage control module adjusts the phase and amplitude of the output voltage of the internal inverter unit according to the grid voltage, and performs synchronous tracking control;

when the off-grid power supply voltage/grid-connected power supply voltage and the grid voltage have the same phase and the same amplitude, all switches in the grid-connected and off-grid switching unit are closed, the load is jointly supplied with power by the energy storage battery and the grid, and meanwhile, the energy storage control module controls switching from an off-grid voltage source loop model to a grid-connected current source loop model or switching from the grid-connected current source loop model to the off-grid voltage source loop model;

and in a combined power supply stage after a certain time, the energy storage control module controls the internal inversion unit to stop, the internal inversion unit exits from a power supply state, and the load is transited to supply power to a power grid or supply power to an energy storage battery.

Compared with the prior art, the invention has the beneficial effects that:

firstly, by adopting the technical scheme of the invention, the grid-connected and off-grid change-over switch unit is added in the traditional energy storage bidirectional converter, so that the off-grid operation can be fully automatically realized when the power grid is in power failure or abnormally fluctuates, and the uninterrupted development of the optical storage charging service is ensured.

Secondly, the technical scheme of the invention adjusts the control mode of the input side of the traditional charging pile aiming at the field of comprehensive application of light storage and charging, abandons the circuit structure of the traditional photovoltaic grid-connected inverter, and replaces the traditional photovoltaic controller with high efficiency (for direct current conversion), so as to meet the direct current input, realize direct current side networking, reduce the energy loss, and improve the economical efficiency by networking the alternating current type equipment (infrastructure equipment) from the alternating current side.

Thirdly, according to the technical scheme, a control method of the grid-connected and off-grid switching process of the energy storage converter is refined, grid-connected and off-grid seamless switching is achieved, and the power supply quality of the system is guaranteed.

Drawings

Fig. 1 is a schematic structural diagram of a common ac bus optical storage and charging system in the prior art.

Fig. 2 is a schematic structural diagram of a common dc bus optical storage and charging system in the prior art.

Fig. 3 is a diagram of a prior art conventional infrastructure equipment power scheme of the present invention.

Fig. 4 is a schematic structural diagram of an optical storage and charging microgrid system according to the present invention.

Fig. 5 is a schematic diagram of an off-grid switching unit of an optical storage and charging microgrid system according to the present invention.

Fig. 6 is a circuit diagram of an energy storage control module of the optical storage and charging microgrid system.

Detailed Description

Preferred embodiments of the present invention are described in further detail below.

As shown in fig. 4, a light storage and charging microgrid system comprises a photovoltaic power generation unit, an energy storage unit, a photovoltaic controller, an energy storage converter and a grid-connected and off-grid switching unit, wherein the photovoltaic power generation unit is connected with a direct current bus through the photovoltaic controller, the energy storage battery and the energy storage converter are respectively connected with the direct current bus, and a charging pile is directly hung on the direct current bus to form a direct current networking; the energy storage converter is connected with a power grid and a load through the grid-connected and off-grid switching unit; the photovoltaic controller is used for controlling the photovoltaic power generation unit to charge the energy storage unit; and the grid-connected and grid-disconnected switching unit is used for realizing the state switching of grid connection and grid disconnection of the energy storage converter. Firstly, system power supply and load equipment are subdivided, direct current equipment (such as photovoltaic controllers and charging piles) are networked from a direct current side, and alternating current equipment (infrastructure equipment) is networked from an alternating current side. Wherein, the load is infrastructure equipment such as air conditioner refrigeration, illumination, control.

The energy storage converter comprises an internal inversion unit, and the internal inversion unit comprises a DC/AC inversion circuit. As shown in fig. 5, the grid-connected and off-grid switching unit includes an inverter contactor, a load circuit breaker, a grid contactor and a grid circuit breaker, the internal inverter unit is connected with the inverter contactor, the inverter contactor is connected with a load through the load circuit breaker, and the inverter contactor is connected with an alternating current grid through a series circuit of the grid contactor and the grid circuit breaker.

The energy storage converter comprises an energy storage control module, the energy storage unit comprises an energy storage battery and a capacity calculation module, the energy storage control module is electrically connected with the capacity calculation module, the internal inversion unit, the inversion contactor and the power grid contactor, and the energy storage control module controls the action of the internal inversion unit, the inversion contactor and the power grid contactor according to a signal fed back by the capacity calculation module.

As a specific embodiment, as shown in fig. 6, the energy storage control module includes a signal processor, and an enable end of the signal processor is electrically connected to the inverter contactor and the grid contactor through a signal amplification circuit, respectively, to control opening and closing of each switch; and the signal processor is electrically connected with the internal inversion unit and controls the internal inversion unit to work or stop.

The signal amplification circuit comprises a primary signal amplification circuit and a secondary signal amplification circuit. The primary signal amplifying circuit comprises resistors R335-R339, a capacitor C140, a triode Q10 and a triode Q11, one end of the resistor R35 is connected with the signal processor, the other end of the resistor R35 is connected with one end of the capacitor C140, one end of the resistor R336 and the B pole of the triode Q10, and the other end of the capacitor C140, the other end of the resistor R336 and the E pole of the triode Q10 are grounded; the C pole of the triode Q10 is connected with a 15V power supply through a resistor R338 and is connected with the B pole of the triode Q11 through a resistor R339, the C pole of the triode Q11 outputs a level signal and is grounded through a resistor R337, and the E pole of the triode Q11 is connected with the 15V power supply; the secondary signal amplifying circuit comprises a resistor R37, a resistor R38, a resistor R42, a capacitor C29, a triode Q6, a relay K2 and a diode D9; one end of the resistor R37 is connected with the C pole of the triode Q11, the other end of the resistor R37 is connected with one end of the resistor R38, one end of the capacitor C29 and the B pole of the triode Q6, the other end of the resistor R38, the other end of the capacitor C29 and the E pole of the triode Q6 are grounded, the C pole of the triode Q6 is connected with one end of the coil of the relay K2 and the anode of the diode D9, the cathode of the diode D9 is connected with the other end of the coil of the relay K2, and the diode R42 is connected with a 15V power supply; and the contact of the relay K2 is electrically connected with the inverter contactor and the power grid contactor.

The circuit adopts a signal processor as a control chip to realize the control of the system, and the implementation circuit of each contactor of the off-grid switching unit can adopt the following three-level structure scheme:

a first stage: the DSP sends out instructions according to control requirements;

and a second stage: the first-stage signal amplifying circuit amplifies signals and realizes logic level; (high level, corresponding to switch closed)

And a third stage: and the secondary signal amplifying circuit is used for amplifying the signal again and realizing isolation. (physical isolation of control terminal from Electrical terminal)

Furthermore, the energy storage control module controls the grid-connected and off-grid switching unit to act according to the capacity of the energy storage battery fed back by the capacity calculation module, so that the system is in a grid-connected or off-grid state;

when the energy storage unit is in an off-grid state, the internal inversion unit converts the direct current of the energy storage unit into alternating current to be output and supplies the alternating current to a load;

when the energy storage control module is in a grid-connected state, the energy storage control module controls the internal inversion unit to work or stop according to the capacity of the energy storage unit;

when the internal inversion unit is stopped, the power grid supplies power to the load;

when the internal inversion unit works, a power grid supplies power to a load, and the internal inversion unit rectifies alternating current of the power grid into direct current for output so as to charge the energy storage unit.

The photovoltaic controller controls the output of the electric energy of the photovoltaic power generation unit according to the capacity of the energy storage battery fed back by the capacity calculation module; the charging pile comprises a charging pile control module, and the charging pile control module controls external output of the charging pile according to the capacity of the energy storage battery fed back by the capacity calculation module.

The control method of the light storage and charging microgrid system comprises the following steps:

when the power grid is normal, the operation logics of the devices are as follows:

a photovoltaic controller: and as long as the capacity of the energy storage battery is smaller than the allowable upper limit value of the system, the photovoltaic controller charges the battery according to the maximum power tracking algorithm. When the battery capacity is larger than the allowable upper limit value of the system, the photovoltaic controller stops working to prevent the battery from being overcharged.

Charging pile: as long as the residual capacity of the energy storage battery is greater than the system allowable lower limit value, the charging pile can be put into operation to carry out charging business on the electric automobile. When the residual capacity of the battery is smaller than the allowable lower limit value of the system, the charging pile stops working, and the battery is prevented from being overdischarged.

An energy storage converter: the operation strategy of the energy storage converter is the core of the control scheme of the embodiment, and the stable control or the economic optimal control of the system can be realized by controlling the operation state of the energy storage converter:

when the residual capacity of the energy storage battery is larger than a first system set value, the internal grid-connected and off-grid switching unit of the energy storage converter is switched to an off-grid state, and the direct current of the energy storage battery is converted into alternating current through the internal inversion unit to be output. The system infrastructure devices are powered by energy storage batteries.

When the residual capacity of the energy storage battery is smaller than the first system set value but larger than the second system set value, the grid-connected switching unit in the energy storage converter is switched to a grid-connected state, and the inversion unit in the energy storage converter is stopped. The system infrastructure devices are powered by the grid.

When the residual capacity of the energy storage battery is smaller than a second system set value, the grid-connected and off-grid switching unit in the energy storage converter is switched to a grid-connected state, and the internal inversion unit rectifies the alternating current and the direct current of the power grid to charge the energy storage battery. The system infrastructure devices are powered by the grid.

In summary, the control method of the system can be summarized as shown in table 1 below.

TABLE 1

Capacity of battery	Photovoltaic controller	Charging pile	Energy storage converter	Infrastructure equipment
					>95％	Stopping charging	Allow for	Off grid discharge	Battery powered
5％～95％	Charging of electricity	Allow for	Shutdown	Power supply of electric network
					<5％	Charging of electricity	Shutdown	Grid-connected charging	Power supply of electric network

Wherein the system allowable upper limit value and the first system set value can be set to be the same or different, and the system allowable lower limit value and the second system set value can be the same or different. Further, the system allows the upper limit value to be the same as the first system set value, and is 95%, 98%, 90% or other of the rated capacity of the energy storage battery.

The system allowable lower limit value may be set to be the same as or different from the second system set value. Further, the system allows the lower limit value to be the same as the second system set value, and is 5%, 10%, 3% or other of the rated capacity of the energy storage battery.

In this embodiment, the system allowable upper limit and the first system setting value are 95%, and the system allowable lower limit and the second system setting value are 5%.

The system working logic is that the grid-connected and off-grid working state of the energy storage converter is switched based on the capacity of the energy storage battery. In the implementation process, the switching can also be carried out based on the item-based time-of-use electricity price. For example, during the peak period of the electricity price, the energy storage converter is controlled to be in an off-grid state, and during the valley period of the electricity price, the energy storage converter is controlled to be in a grid-connected state.

When the power grid is in power failure or abnormally fluctuates, the internal grid-connected and off-grid switching unit of the energy storage converter is switched to be in an off-grid state, and the direct current of the energy storage battery is converted into alternating current through the internal inversion unit to be output. The system infrastructure devices are powered by energy storage batteries. Therefore, when the power grid is powered off or abnormal fluctuation occurs, the light storage and charging system is guaranteed to operate uninterruptedly.

Specifically, as shown in fig. 2, when the power grid fails or fluctuates abnormally, the following scheme is implemented:

when the capacity of the energy storage battery is larger than a first system set value, the energy storage control module controls the off-grid switching unit to be switched to an off-grid state, and the internal inversion unit converts direct current of the energy storage battery into alternating current to be output and supplies power to a load;

when the capacity of the energy storage battery is smaller than a first system set value and larger than a second system set value, the energy storage control module controls the grid-connected and off-grid switching unit to be switched to an off-grid state, and the internal inversion unit converts direct current of the energy storage battery into alternating current to be output and supplies power to a load;

and when the capacity of the energy storage battery is smaller than a second system set value, the photovoltaic controller, the charging pile and the internal inversion unit are stopped.

TABLE 2

Capacity of battery	Photovoltaic controller	Charging pile	Energy storage converter	Infrastructure equipment
					>95％	Stopping charging	Allow for	Off grid discharge	Battery powered
5％～95％	Charging of electricity	Allow for	Off grid discharge	Battery powered
					<5％	Shutdown	Shutdown	Shutdown	Shutdown

Furthermore, to ensure the power supply quality of the infrastructure equipment, the control process of switching the energy storage converter between the off-grid state and the grid-connected state according to the embodiment may be subdivided into: phase tracking, joint power supply, independent power supply and three stages. The following example is to switch off-grid battery power supply to grid-connected power supply:

voltage tracking: and the infrastructure equipment continuously executes synchronous tracking control according to the phase and amplitude of the inversion output voltage of the grid voltage micro-rectification energy storage converter under the state of power supply by a battery.

Joint power supply: and after the same phase and the same amplitude of the off-grid power supply voltage and the grid voltage are confirmed, all switches in the off-grid switching unit are closed, the infrastructure equipment is supplied with power jointly by a battery and the grid, and meanwhile, the software control algorithm of the energy storage converter is switched from the off-grid voltage source loop model to the grid-connected current source loop model.

Independent power supply: after a short combined power supply stage (such as 10ms), the inversion unit in the energy storage converter is shut down, the power supply state is quitted, and the infrastructure equipment is transited to supply power to the power grid.

Similarly, the control process of switching from the grid-connected state to the off-grid state is also divided into three stages, synchronous transition is realized, and the power supply reliability of the infrastructure equipment is improved.

According to the technical scheme of the embodiment, aiming at the comprehensive application field of light storage and charging, the control mode of the input side of the traditional charging pile is adjusted, direct current input is met, direct current side networking is realized, energy loss is reduced, and the economy is improved; the circuit structure of the traditional photovoltaic grid-connected inverter is abandoned, and the photovoltaic controller with high efficiency is replaced, so that the direct current input is met, the direct current side networking is realized, the energy loss is reduced, and the economy is improved; a grid-connected and off-grid change-over switch unit is additionally arranged in a traditional energy storage bidirectional converter, so that off-grid operation can be automatically realized when a power grid is in power failure or abnormally fluctuated, and uninterrupted development of optical storage and charging services is guaranteed. The technical scheme of the embodiment refines a control method of the parallel-grid and off-grid switching process of the energy storage converter, realizes the parallel-grid and off-grid seamless switching, and guarantees the power supply quality of the system.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.