CN110011344A - A kind of energy-storage system and its control method - Google Patents

Abstract

The invention relates to an energy storage system, comprising: a sampling module, connected to a converter module, for acquiring a sampling signal; a control module, connected to the sampling module, for sending a charging signal or a discharging signal according to the feedback and the sampling signal; the converter module, Connected to the control module, used to convert AC to DC and then step down according to the charging signal, or to convert DC to AC after boosted according to the discharge signal; the energy storage control module, connected to the converter module, used for balanced control of DC distribution; The energy module is connected to the energy storage control module to store or provide DC. The invention amplifies the DC voltage of the iron-zinc flow battery and then inverts it into an AC voltage signal and then integrates it into the power grid; the control strategy can be reasonably selected according to different usage scenarios, the output of new energy power generation is smoothed to a large extent, and the power grid is improved. It ensures the safe and reliable operation of the system and improves the economy and safety of power grid operation.

Description

An energy storage system and its control method

technical field

The invention belongs to the technical field of energy storage, and in particular relates to an energy storage system and a control method thereof.

Background technique

Energy storage technology is the key core technology of energy systems such as distributed generation technology, microgrid and smart grid. Common energy storage technologies include pumped hydropower stations, compressed air, superconducting magnets, batteries, and flow batteries. Among them, the flow battery is a new type of high-capacity redox electrochemical energy storage device. Unlike conventional batteries, the active material of the flow battery is not on the electrode, but is dissolved in the electrolyte, which is the composition of the electrolyte. It is characterized by high capacity, wide application area and long cycle life. It is a new energy product.

In the power grid, the zinc-iron flow battery energy storage technology has the characteristics of low cost, high safety and environmental friendliness, and has a good application prospect. In order to smoothly connect the zinc-iron flow battery to the power grid, it is necessary to ensure that the output voltage signal and current signal of the zinc-iron flow battery are stable. Unable to connect to the power grid smoothly, resulting in reduced power supply quality and poor economical and safe power grid operation.

SUMMARY OF THE INVENTION

In order to solve the technical defects and deficiencies existing in the prior art, the embodiments of the present application provide an energy storage system and a control method thereof. The technical problem to be solved by the present invention is realized by the following technical solutions:

An embodiment of the present invention provides an energy storage system, including:

The sampling module, connected to the converter module, is used to obtain the sampling signal;

a control module, connected to the sampling module, for sending a charging signal or a discharging signal according to the feedback and the sampling signal;

a converter module, connected to the control module, and configured to convert the alternating current into direct current and then step down according to the charging signal, or convert the direct current into alternating current after boosting the voltage according to the discharging signal;

an energy storage control module, connected to the converter module, for balanced control of the distribution of the direct current;

An energy storage module, connected to the energy storage control module, for storing or providing direct current.

In an embodiment of the present invention, the sampling signal includes a current sampling signal and a voltage sampling signal.

In one embodiment of the present invention, the control module includes: at least one EIA-485 communication interface, at least one RJ-45 Ethernet interface, at least one CAN interface, at least one optical fiber interface, at least one RS-232 printing interface and At least one RS-485 timing interface.

In an embodiment of the present invention, the feedback includes one or more of active power tracking, peak clipping and valley filling, planning curve, frequency and voltage regulation, fluctuation stabilization, power distribution, and SOC adjustment.

In an embodiment of the present invention, the converter module includes:

A DC filter circuit, connected to the energy storage control module, for reducing DC common mode interference;

a booster circuit, connected to the DC filter circuit, for boosting the DC voltage;

a CL filter circuit, connected to the booster circuit, for filtering out high-frequency components in the DC;

a conversion circuit, connected to the CL filter circuit, for converting the alternating current into direct current and then reducing the voltage, or converting the direct current into alternating current after boosting the voltage;

The LCL filter circuit is connected to the conversion circuit for reducing high-frequency harmonics in the alternating current;

The AC filter circuit is connected to the LCL filter circuit for suppressing high-frequency interference in the AC.

In an embodiment of the present invention, the converter module further includes: multiple groups of bypass switches connected between the DC filter circuit and the energy storage control module; and the LCL filter circuit and the energy storage control module between the AC filter circuits; and, the output end of the AC filter circuit.

In an embodiment of the present invention, the DC boost circuit is a non-isolated Buck circuit or an isolated Buck circuit.

In an embodiment of the present invention, the conversion circuit is a three-phase full-bridge IGBT conversion circuit.

In an embodiment of the present invention, the energy storage module is a zinc-iron flow battery.

Another embodiment of the present invention provides a control method for an energy storage system, including:

Get the sampled signal;

Send a charging signal or a discharging signal according to the feedback and the sampling signal;

Converting the alternating current to direct current according to the charging signal and then reducing the voltage, or boosting the direct current and converting it to alternating current according to the discharging signal;

Balance control of DC distribution;

Store or provide DC.

It can be seen from the above that the energy storage system proposed in the embodiment of the present application uses the converter module to amplify the DC voltage of the zinc-iron flow battery, and then inverts the amplified DC voltage into an AC voltage and then integrates it into the power grid; through the control module Control strategies can be reasonably selected according to different usage scenarios to smooth the output of new energy power generation to a large extent, improve the power supply quality of the power grid, ensure the safe and reliable operation of the system, and improve the economy and safety of power grid operation.

Other aspects and features of the present invention will become apparent from the following detailed description with reference to the accompanying drawings. It should be understood, however, that the drawings are designed for illustrative purposes only and are not intended to limit the scope of the invention, since reference should be made to the appended claims. It should also be understood that unless otherwise indicated, the drawings are not necessarily to scale, and are merely intended to conceptually illustrate the structures and processes described herein.

Description of drawings

1 is a schematic structural diagram of an energy storage system according to an embodiment of the present application;

2 is a schematic diagram of peak shaving and valley filling in an energy storage system provided by an embodiment of the present application;

3 is a schematic diagram of a planning curve in an energy storage system provided by an embodiment of the present application;

4 is a schematic diagram of auxiliary frequency regulation in an energy storage system provided by an embodiment of the present application;

5 is a schematic diagram of auxiliary voltage regulation in an energy storage system provided by an embodiment of the present application;

6 is a schematic diagram of smoothing fluctuations in an energy storage system provided by an embodiment of the present application;

7 is a schematic diagram of power distribution during charging in an energy storage system according to an embodiment of the present application;

8 is a schematic diagram of power distribution during discharge in an energy storage system according to an embodiment of the present application;

FIG. 9 is a schematic diagram of SOC adjustment in an energy storage system provided by an embodiment of the present application;

10 is a circuit diagram of a converter module in an energy storage system provided by an embodiment of the present application;

FIG. 11 is a schematic flowchart of a control method of an energy storage system provided by an embodiment of the present application.

Detailed ways

In order to make the above objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Please refer to FIG. 1 , which is a schematic structural diagram of an energy storage system provided by an embodiment of the present application.

An energy storage system provided by this embodiment includes:

The sampling module, connected to the converter module, is used to obtain the sampling signal;

The control module, connected to the sampling module, is used for sending a charging signal or a discharging signal according to the feedback and sampling signals;

The converter module, connected to the control module, is used to convert the AC into DC and then step down according to the charging signal, or convert the DC to AC after boosting according to the discharge signal;

The energy storage control module is connected to the converter module for balanced control of the DC distribution;

The energy storage module is connected to the energy storage control module to store or provide DC.

Specifically, the energy storage system provided in the embodiment of the present application is applied to the power grid, and can convert the surplus AC power on the power grid at night or on weekdays into DC power, then reduce the voltage and store it in the energy storage module, and feed it back to the power grid when the power grid is insufficient. The power grid is used to balance the peaks and valleys of the power grid, and the control module can reasonably select control strategies according to different usage scenarios, that is, different feedbacks, so as to realize the functions of charge/discharge management of the energy storage module, smoothing of the AC side load power, and island operation. At the same time, applying the energy storage system proposed in this application to intermittent new energy power generation systems such as wind energy, solar energy, and tide can smooth the output of new energy power generation to a large extent, improve the power supply quality of the microgrid, and enable large-scale renewable energy generation. The renewable energy system is safely and reliably integrated into the power grid, which truly embodies the "green power transformation".

In a specific embodiment, the sampling signal includes a current sampling signal and a voltage sampling signal.

Specifically, the sampling module is connected to the converter module and the control module, and is used to acquire current sampling signals and voltage sampling signals in the converter module and the power grid in real time, and transmit the above-mentioned sampling signals to the control module. The control module will provide different feedbacks according to different usage scenarios, including one or more of the above active power tracking, peak cutting and valley filling, planning curve, frequency regulation and voltage regulation, fluctuation suppression, power distribution and SOC adjustment, combined with the above The voltage sampling signal and the current sampling signal, select the control strategy reasonably, send the charging signal or the discharging signal to the converter module, the converter module will convert the AC power into DC power according to the discharge signal, and then store the voltage in the energy storage module, or according to the discharge signal. The charging signal boosts the DC power and converts it into AC power, which is sent to the grid through the transformer.

In a specific embodiment, the control module further includes: at least one EIA-485 communication interface, at least one RJ-45 Ethernet interface, at least one CAN interface, at least one optical fiber interface, at least one RS-232 printing interface and at least one RS-232 interface -485 time synchronization interface.

Specifically, the control module adopts PCS-9567C with powerful functions of measurement and control, communication and energy management, standard 4U chassis structure, which is characterized by: high-performance and high-reliability UAPC hardware platform, friendly man-machine interface; powerful optional The plug-in can meet various needs of the site; the fully enclosed chassis, the strong and weak currents are strictly separated, the traditional backplane wiring method is cancelled, and corresponding anti-interference measures are also taken in the software design, which greatly improves the anti-interference ability of the device. The external electromagnetic radiation also meets the relevant standards; the flexible background communication mode is equipped with RJ-45 Ethernet interface, EIA-485, CAN and other communication interfaces (also optional super five lines or optical fiber), which is convenient for the realization of various communication methods , convenient for communication access with sampling module, converter module, energy storage control module and other auxiliary equipment; adapt to high-altitude applications <6000 meters; with internal high-speed bus and intelligent I/O, flexible device hardware configuration, with universal, Easy to extend and easy to maintain. It has convenient on-site device testing functions, including remote signaling test, export transmission test and telemetry signal test. A variety of time synchronization methods can be selected: the time synchronization interface can support a variety of GPS time synchronization methods, including IRIG-B, SNTP and other time synchronization methods and IEEE1588V2 high-precision network synchronization time synchronization methods; perfect event recording function, can record 64 times Alarm report, 64 fault recording waveforms, 1024 self-check reports, 1024 displacement reports, 1024 latest remote control reports.

The specific electrical parameters are shown in the table below:

1) AC current

2) AC voltage

3) AC and DC sampling

enter ±15V ±600mA maximum input allowed -35V～35V -2A～2A Sampling accuracy 0.5% (7.5V) 0.5% (200mA) input resistance 19.02kΩ 0.5Ω

4) DC sampling

enter 0～5V 0～20mA Sampling accuracy 0.5% (5V) 0.5% (20mA) input resistance 20kΩ 235Ω

5) Device power supply

Adopt standard GB/T 8367-1987 (idt IEC 60255-11:2008) Rated voltage 110Vdc, 220Vdc, 220VAC input range 88～264Vdc, 88～264VAC ripple ≤15% of rated voltage

6) Switch input

7) Switch output

8) Mechanical structure

9) Environmental condition parameters

Adopt standard GB/T 14047-1993 (idt IEC 60225-1:2009) range of working temperature -20℃～+55℃ Storage temperature range -40℃～+70℃ transport temperature range -40℃～+70℃ Relative humidity 5%～95%, no condensation or freezing inside the device

10) Communication method and port

a) Communication method

show liquid crystal standard communication RS485, RJ45 Ethernet, CAN, LC fiber, RS232 printing, time synchronization

b) EIA-485 interface

c) Ethernet interface

d) CAN interface

Transmission rate 1Mbps Transmission standard IS011898 Transmission distance ＜40 meters Protocol CAN bus protocol Wiring form shielded twisted pair

e) Optical fiber interface

characteristic glass fiber terminal SC Optical cable type Multimode Typical transmission distance ＜2km

f) print interface

g) Time synchronization interface

PCS-9567C can realize the following functions in application:

Measurement and control function:

1) With 6-way AC voltage and 6-way AC current (1A or 5A optional) sampling input;

2) With 6 channels of AC and DC 3 channels of ±15V voltage input and 3 channels of ±600mA current sampling input;

3) With 12 channels of DC 0-20mA or 0-5V (selectable by jumper) sampling input;

4) With 25 channels of custom remote signal input;

5) With 11 remote control independent control split/close out nodes;

6) Event and SOE records;

Communication function:

1) Communication to the next

a) Support Modbus, DLT645, GOOSE, CAN and other protocols;

b) Support communication with PCS, BMS, electricity meter and other auxiliary equipment;

c) With 12 RJ-45 network ports (each network port can be replaced with LC optical fiber interface as needed) to support ModbusTCP/GOOSE protocol;

d) It has 5 EIA-485/RS-232 serial ports (can be selected by jumper), and supports serial port protocols such as serial port Modbus and DLT645;

e) It has 4 standard CAN interfaces and supports standard CAN bus protocol.

2) On-the-spot communication

a) Support IEC104, IEC61850, IEC103, Modbus and other protocols, support network communication with EMS and monitoring background,

b) With 3 R-J45 network ports;

c) With 2-way EIA-485 communication interface;

d) With 1 RS232 printing interface;

e) With 1 channel RS485 time synchronization interface;

f) Using a large-capacity database, it supports up to 50,000 points, and the relevant data can be viewed on the LCD.

g) Editing and synthesis of forwarding information.

Energy Management Features:

1) Active power tracking

The energy storage module can quickly respond to dispatching instructions and realize the role of auxiliary power regulation. The power tracking control of this controller can be selected through the fixed value control word to support remote mode or local mode. The remote mode means that the controller controls the charging and discharging power of the energy storage according to the active command value sent by the main station (SCADA monitoring system); discharge power. The coordinated control device controls the active power output of the energy storage system by detecting the current output active power and the received power command in real time, so as to quickly and accurately respond to the dispatch command.

2) Cut peaks and fill valleys

Due to its fast response characteristics, the energy storage module has excellent peak regulation performance. It can be used as a power source to release electricity during peak periods of electricity consumption, and absorb electricity as a load during low electricity consumption periods, improving the economy and safety of grid operation.

As shown in Figure 2, the controller can choose to support remote mode or local mode through the fixed value control word. The remote mode means that the controller controls the charging and discharging power of the energy storage according to the peak and valley values sent by the master station (SCADA monitoring system); Can charge and discharge power. When the output power is greater than the peak power, the energy storage system charges and absorbs the peak power; when the output power is less than the valley power, the energy storage system discharges to fill the valley power.

3) Planning curve

The function of the planned curve is to control the output of the energy storage system so that the charging and discharging plan can be arranged according to the predetermined planning curve. As shown in Figure 3, the controller plan curve control can be selected to support remote mode or local mode through the fixed value control word. Remote mode means that the controller controls the energy storage charging and discharging power according to the planned curve power value sent by the master station (SCADA monitoring system); Energy storage charge and discharge power.

4) Frequency modulation and voltage regulation

Energy storage can assist power grid frequency regulation, and improve the frequency regulation effect by using its fast response characteristics. At the same time, the energy storage system can also output reactive power and play the role of auxiliary voltage regulation.

As shown in Figure 4, the frequency of the power grid depends on the balance between the generation active power and the load active power. When the generation active power is greater than the load active power, the system frequency increases; when the generation active power is less than the load active power, the system frequency decline. The energy storage system assists in adjusting the active power of the generation through active-frequency (P-F) droop control, so that it is balanced with the active power of the load in real time, thereby stabilizing the system frequency. When the system frequency decreases, the energy storage system discharges to increase the active output; when the system frequency increases, the energy storage system charges to reduce the active output.

As shown in Figure 5, the voltage of the power grid depends on the balance between the generation reactive power and the load reactive power. When the generated reactive power is greater than the load reactive power, the system voltage rises; when the generated reactive power is less than the load reactive power When the power is increased, the system voltage drops. The energy storage system assists in regulating the reactive power of generation through reactive-voltage (Q-V) droop control, so that it is balanced with the reactive power of the load in real time, thereby stabilizing the system voltage. When the system voltage drops, the energy storage system emits reactive power; when the system voltage rises, the energy storage system absorbs reactive power.

5) Smooth out fluctuations

Photovoltaic, wind power and other new energy power generation have large intermittency and volatility, which seriously affects the performance of their grid-connected power generation. More and more studies use the energy storage capacity of energy storage batteries to smooth the power fluctuations of new energy power generation through battery charging and discharging.

As shown in Figure 6, the smoothing fluctuation control is divided into the first-order filtering control mode and the power fluctuation limiting control mode according to the algorithm, which can be set by the control word. The first-order filter control strategy is to perform first-order low-pass filtering according to the output power of the power supply. For the power components that change rapidly and do not meet the fluctuation limit requirements, the energy storage system is used to eliminate them, so the rest is a smooth power component with small fluctuations. . The power fluctuation limit control strategy is to detect the output power of the power supply in real time, and count its fluctuation in a certain period of time. If the power fluctuation component exceeds the fluctuation limit set by the device, the energy storage system will charge and discharge to suppress the fluctuation. The device can be set by a fixed value, so that the control target can meet the power fluctuation limit of different time scales.

6) Power distribution and SOC adjustment

For energy storage units with larger capacity, the charge and discharge characteristics of each battery pack are not the same, and their SOC values are not exactly the same. In order to ensure balanced charge and discharge of each battery pack and prolong battery life, the coordinated control device sets a power balance distribution strategy and an SOC adjustment control strategy.

As shown in FIG. 7 and FIG. 8 , the controller obtains the SOC state of each battery group, and for each charging and discharging power, it is allocated to each battery group in proportion according to the SOC of each battery group. When charging, the battery pack with a small SOC is preferentially charged, and the charging power is high; when discharging, the battery pack with a large SOC is preferentially discharged, and the discharging power is high.

In order to make each battery group of the energy storage system have a suitable SOC value, and respond to each charge and discharge command, as shown in Figure 9, SOC adjustment control is carried out on the premise of not affecting the operation of other functional modules. The control strategy of charging and discharging keeps the SOC within a reasonable range.

Specifically, the sampling module will monitor the current signal and voltage signal in the circuit of the converter module in real time, obtain the voltage sampling signal and the current sampling signal and transmit them to the control module in time. feedback, including one or more of the above-mentioned active power tracking, peak clipping and valley filling, planning curve, frequency and voltage regulation, fluctuation stabilization, power distribution and SOC adjustment, and then combine the above-mentioned voltage sampling signal and current sampling signal to send a charging signal Or the discharge signal is sent to the converter module, and the converter module will convert the AC power into DC power according to the discharge signal, and then store it in the energy storage module, or boost the DC power and convert it into AC power according to the charging signal, and transmit it to the AC power through the transformer. go to the grid.

In a specific embodiment, the converter module includes:

The DC filter circuit is connected to the energy storage control module to reduce the DC common mode interference;

The booster circuit is connected to the DC filter circuit for boosting the DC voltage;

The CL filter circuit is connected to the booster circuit to filter out the high frequency components in the DC;

The conversion circuit, connected to the CL filter circuit, is used to convert AC to DC and then step down, or to convert DC to AC after boosting;

The LCL filter circuit is connected to the conversion circuit to reduce the high frequency harmonics in the AC;

The AC filter circuit, connected to the LCL filter circuit, is used to suppress high-frequency interference in the AC.

In a specific embodiment, the converter module further includes: multiple groups of bypass switches connected between the DC filter circuit and the energy storage control module; and between the LCL filter circuit and the AC filter circuit; and the AC filter circuit 's output.

In a specific embodiment, the DC boost circuit is a non-isolated Buck circuit or an isolated Buck circuit.

In a specific embodiment, the conversion circuit is a three-phase full-bridge IGBT conversion circuit.

Specifically, as shown in FIG. 10 , the converter module adopts a PCS energy storage converter, and its main circuit includes one DC/AC conversion circuit and three DC/DC DC boosting (reversely bucking) circuits. The DC/AC conversion circuit is composed of a single three-phase full-bridge IGBT conversion circuit. The AC side is connected to the grid or transformer, and the DC side is connected to the high-voltage side of the three-way DC/DC boost circuit. The low-voltage side of the three-way DC/DC boost circuit is connected to a zinc-iron flow battery. An AC filter circuit, namely an AC EMI filter, is arranged on the AC side of the DC/AC conversion circuit to suppress high-frequency interference in the AC power; a DC filter circuit, namely a DC filter, is arranged on the low-voltage side of each DC/DC booster circuit. EMI filter to reduce DC common mode interference from zinc-iron flow batteries. There is a CL filter circuit, namely a CL filter, on the high-voltage side of each DC/DC booster circuit, which can filter out the high frequency in the DC current generated by each module and reduce the stability of the output current and voltage; The DC side of the conversion circuit is also equipped with a CL filter, which can filter out the medium and high frequency of the DC current generated by the DC/AC conversion circuit when the zinc-iron flow battery is charged, thereby improving the life of the zinc-iron flow battery; One LCL filter is connected to each phase on the AC side. Each group of LCL filters shares one set of capacitors and one set of inductors, which can reduce the high-frequency harmonic current on the AC side and reduce the interference of unstable parameters of the power grid.

A voltage sampling circuit is provided at the confluence of the low-voltage side and the low-voltage side of each DC/DC booster circuit; a current sampling circuit is provided at the confluence of the high-voltage side of each DC/DC booster circuit. The DC side of the DC/AC conversion circuit is also provided with a voltage and current sampling circuit; the AC side of the DC/AC conversion circuit is provided with a voltage sampling circuit; at the same time, a current circuit is provided in each IGBT circuit. The above sampling circuit is used to realize the interconnection between the energy storage module, the energy storage control module and the control module, so as to ensure the generation of the energy storage module and the stable operation of the converter module.

The converter module of the embodiment of the present application adopts a three-way 100kW DC/DC booster circuit to adapt to the characteristics of low voltage and high current of the large-capacity zinc-iron flow battery, and the product upgrade is convenient. The low-voltage end of each DC/DC booster circuit can accept 138V-228V output (or charging) energy storage battery, and the three-way DC/DC booster circuit can accept a current of 2391A in parallel. Therefore, the conversion of the zinc-iron flow battery with low voltage, high current and large capacity energy storage is realized. The three-way DC/DC boost circuit raises the DC low voltage at the end of the energy storage battery to a DC high voltage of 650V, and then converts it into a 315V three-phase AC power through the DC/AC conversion circuit, and then passes through the 315/400V isolation transformer to achieve the load. Powered or charged with utility power.

The LCL filter on the AC side can greatly reduce the high-frequency harmonics on the AC side, and at the same time, it can also reduce the influence of unstable factors of the power grid, and improve the stability of the equipment. The AC side EMI filter can not only suppress the influence of high-frequency interference in the power grid on the equipment, but also suppress the interference of the equipment on the power grid. The CL filter on the DC side can filter out the high-frequency components in the DC current, reduce the ripple of the output current and voltage, and improve the life of the energy storage battery. The DC side EMI filter can reduce the common mode interference on the DC side and improve the stability of the device.

The sampling circuit in the embodiment of the present application can be amicably interconnected with the control module and the converter module. It can realize the steady-state control function to ensure the safe and reliable operation of the system, and formulate corresponding control strategies according to different scenarios. It has the characteristics of fast response and excellent peak regulation performance. It can be used as a power source to release electricity during peak periods of electricity consumption, and absorb electricity as a load during low electricity consumption periods, improving the economy and safety of grid operation.

The working process of the energy storage system will be described in detail below:

(1) Charging process

When the control module detects that there is excess power in the grid, it switches the energy storage system to the charging mode. In the charging mode, the high voltage side of the DC/DC boost circuit is the input terminal, and the low voltage side is the output terminal. The output electric energy of the electric energy application system is stepped down by the DC/DC booster circuit, and then AC-DC converted by the DC/AC conversion circuit, and then transmitted to the zinc-iron flow battery to realize the charging of the zinc-iron flow battery.

In the process of charging the zinc-iron flow battery, the energy storage control module, that is, the battery management unit, will perform thermal management, power balancing and charging management according to the state of the zinc-iron flow battery; at the same time, the DC/DC boost circuit According to the status of the zinc-iron flow battery in its own energy storage module, adjust the voltage on the low-voltage side to make the charging voltage of the zinc-iron flow battery stable; and cooperate with other DC/DC boost circuits in the energy storage system to ensure energy storage. The transmission voltage and transmission power of the system are stable.

(2) Discharge process

When the control module detects that the power grid needs the zinc-iron flow battery to provide electric energy and the energy storage system has electric energy that can be discharged, the energy storage system is switched to the discharge mode. In the discharge mode, the low-voltage side of the DC/DC booster circuit is the input end, and the high-voltage side is the output end; the electric energy stored in the zinc-iron flow battery is transmitted to the DC/DC booster circuit, and the booster circuit is boosted by the DC/DC booster circuit. After pressure treatment, the DC/AC conversion circuit performs DC-AC conversion and then transmits it to the power grid to realize the discharge process of the zinc-iron flow battery.

During the discharge process of the zinc-iron flow battery, the energy storage control module, that is, the battery management unit, performs thermal management, power balance and discharge management on the battery pack according to the monitored state of the battery pack; The state of the zinc-iron flow battery in the energy storage module adjusts the output voltage of the high-voltage side. The higher the voltage of the high-voltage side of the DC/DC booster circuit, the greater the output energy; The smaller, the smaller the output energy. And, together with other DC/DC boost circuits in the energy storage system, the transmission voltage and transmission power of the energy storage system are guaranteed to be stable.

In a specific embodiment, the converter module PCS has a reliable and comprehensive protection method during operation. Once a fault or abnormality is detected, the PCS will stop working and send an alarm signal. The protection is divided into hardware protection and software protection. Among them, the hardware protection includes IGBT over-temperature and over-current protection, and DC bus voltage protection. Software protection includes the following contents.

(1) DC overvoltage and undervoltage protection: PCS allows the maximum input voltage of the DC side to be 350V. When the converter detects that the input voltage is higher than this limit value, the converter will disconnect the energy storage device from the grid within 0.2-1s When the PCS detects that the DC voltage is lower than the set undervoltage value, the converter will protect and stop, and send out the corresponding alarm information.

(2) DC overcurrent protection: PCS can monitor the DC side current in real time. When the current value exceeds the set value, the converter will disconnect the energy storage device from the power grid within 0.2-1s, and issue a corresponding alarm message. Its constant value setting needs to be matched with the battery charge and discharge limit current.

(3) DC reverse connection protection: PCS detects the DC incoming line voltage of the converter module in real time. When the converter detects the positive and negative connection of the incoming line, it will automatically trip the grid-connected contactor and the DC circuit breaker will trip. After the positive polarity is connected, the converter can work normally.

(4) AC over/under voltage protection: During the grid-connected operation of the converter, the allowable deviation of the grid voltage at the grid interface is ±10% of the rated value. When the grid voltage exceeds the specified range, the converter stops working and stops working. The corresponding alarm information is displayed on the LCD screen of the control device.

(5) AC over/under frequency protection: During the grid-connected operation of the converter, the allowable range of the grid frequency is 48.5Hz-51.5Hz. When the grid frequency exceeds the specified range, the converter will stop working, and the LCD will display on the control device. The corresponding alarm information is displayed on the screen.

(6) AC overcurrent protection: During the grid-connected operation of the converter, when the grid is short-circuited, the converter can limit the AC output current to within 120% of the rated value, and at the same time disconnect the energy storage device from the grid within 60s open, and send out the corresponding alarm message.

In a specific embodiment, the energy storage module may be a zinc-iron flow battery.

Specifically, zinc-iron flow batteries have good application prospects in large-scale flow batteries due to their low electrolyte cost, high safety, and environmental friendliness. At present, typical energy storage inverters are mostly used in lithium batteries, so it is very important to develop an energy storage converter compatible with zinc-iron flow batteries.

As shown in FIG. 11 , the present invention provides a control method for an energy storage system on the basis of the foregoing embodiment, including:

Send a charging signal or a discharging signal to the converter module according to the feedback;

Convert AC power to DC power according to the discharge signal and then step down, or boost the DC power and convert it to AC power according to the charging signal;

store or provide DC electrical energy;

Balance control of DC power.

The energy storage system proposed in the embodiment of the present application uses a converter module to amplify the DC voltage signal of the zinc-iron flow battery, and then inverts the amplified DC voltage signal into an AC voltage signal and then integrates it into the power grid; Reasonable selection of control strategies for different usage scenarios can largely smooth the output of new energy power generation, improve the power supply quality of the power grid, ensure the safe and reliable operation of the system, and improve the economy and safety of power grid operation.

The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be considered that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deductions or substitutions can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (10)

1. a kind of energy-storage system characterized by comprising

Sampling module connects unsteady flow module, for obtaining sampled signal；

Control module connects the sampling module, believes for sending charging signals according to feedback and the sampled signal or discharging Number；

Unsteady flow module connects the control module, for being depressured after exchange is converted to direct current according to the charging signals or root Exchange will be converted to after DC boosting according to the discharge signal；

Energy storage control module connects the unsteady flow module, the distribution for Balance route direct current；

Energy-storage module connects the energy storage control module, for storing or providing direct current.

2. energy-storage system according to claim 1, which is characterized in that the sampled signal includes current sampling signal and electricity Press sampled signal.

3. energy-storage system according to claim 1, which is characterized in that the control module includes: at least one EIA-485 Communication interface, at least one RJ-45 Ethernet interface, at least one CAN interface, at least one optical fiber interface, at least one RS- 232 printing interfaces and at least one RS-485 clock synchronization interface.

4. energy-storage system according to claim 1, which is characterized in that the feedback is filled out including active power tracking, peak clipping Paddy, Plan Curve, frequency modulation and voltage modulation, stabilize fluctuation, power distribution and SOC adjustment one of or it is a variety of.

5. energy-storage system according to claim 1, which is characterized in that the unsteady flow module includes:

DC filtering circuit connects the energy storage control module, for reducing DC common-mode interference；

Booster circuit connects the DC filtering circuit, for improving DC voltage；

CL filter circuit connects the booster circuit, for filtering out the radio-frequency component in direct current；

Conversion circuit connects the CL filter circuit, for will exchange be converted to direct current after be depressured, or will be converted after DC boosting For exchange；

LCL filter circuit connects the conversion circuit, for reducing the high-frequency harmonic in exchange；

Ac filter circuit connects the LCL filter circuit, for inhibiting the High-frequency Interference in exchange.

6. energy-storage system according to claim 5, which is characterized in that the unsteady flow module further include: multiple groups by-pass switch, It is connected between the DC filtering circuit and the energy storage control module；And the LCL filter circuit exchanges filter with described Between wave circuit；And the output end of the ac filter circuit.

7. energy-storage system according to claim 5, which is characterized in that the DC voltage booster circuit is non-isolation type Buck electricity Road or isolated form Buck circuit.

8. energy-storage system according to claim 5, which is characterized in that the conversion circuit is three phase full bridge IGBT conversion electricity Road.

9. energy-storage system according to claim 1, which is characterized in that the energy-storage module is zinc-iron flow battery.

10. a kind of control method of energy-storage system characterized by comprising

Obtain sampled signal；

Charging signals or discharge signal are sent according to feedback and the sampled signal；

It is depressured after exchange is converted to direct current according to the charging signals, or will be converted after DC boosting according to the discharge signal For exchange；

The distribution of Balance route direct current；

Storage provides direct current.