Energy storage system and control method thereof

Abstract

The application discloses an energy storage system and a control method thereof. The energy storage system comprises an energy storage converter and an energy storage battery. The control method comprises the following steps: acquiring a grid voltage and a grid frequency; determining a first power corresponding to the grid voltage according to the grid voltage and a preset relationship curve of the grid voltage and power; determining a second power corresponding to the grid frequency according to the grid frequency and a preset relationship curve of the grid frequency and power; determining a charging and discharging power of the energy storage converter according to the first power and the second power, and controlling the charging and discharging operation of the energy storage converter with the charging and discharging power. The preset relationship curve of the grid voltage and power and the preset relationship curve of the grid frequency and power are used to determine the power corresponding to the grid voltage and the grid frequency, and then the charging and discharging power of the energy storage converter is determined, and the charging and discharging operation of the energy storage converter is controlled with the charging and discharging power. In this way, the energy storage converter can timely discharge to the grid when the load suddenly changes, and the diesel generator is prevented from dragging the net.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to an energy storage system and its control method. Background Technology

[0002] In oilfield operations, multiple generators are typically connected in parallel. When a sudden increase in load occurs, instability in the parallel connection can easily lead to grid disconnection. By configuring an intelligent voltage-stabilized energy storage system for oilfield drilling, timely discharge to the grid can be initiated when a sudden load change is detected, preventing sudden load changes in the generators and avoiding grid disconnection.

[0003] In existing energy storage systems, charging and discharging strategies are primarily implemented through commands issued by a host computer, making it impossible to automatically switch operating states based on current DC-side parameters. However, this charging and discharging strategy is not suitable for oilfield drilling energy storage systems. Summary of the Invention

[0004] This application aims to provide an energy storage system and its control method to provide a charging and discharging strategy suitable for oilfield drilling energy storage systems.

[0005] This application provides a control method for an energy storage system, the energy storage system including an energy storage converter and an energy storage battery; the control method includes:

[0006] Obtain the grid voltage and grid frequency;

[0007] Based on the preset relationship curve between the grid voltage and the grid power, determine the first power corresponding to the grid voltage; based on the preset relationship curve between the grid frequency and the grid frequency, determine the second power corresponding to the grid frequency.

[0008] Based on the first power and the second power, the charging and discharging power of the energy storage converter is determined, and the charging and discharging operation of the energy storage converter is controlled by the charging and discharging power.

[0009] Another aspect of this application provides an energy storage system, including an energy storage converter and an energy storage battery;

[0010] It also includes a controller configured to acquire grid voltage and grid frequency; determine a first power corresponding to the grid voltage based on a preset relationship curve of grid voltage and power; determine a second power corresponding to the grid frequency based on the preset relationship curve of grid frequency and power; determine the charging and discharging power of the energy storage converter based on the first power and the second power, and control the charging and discharging operation of the energy storage converter with the charging and discharging power.

[0011] The energy storage system and control method provided in this application determine the power corresponding to the grid voltage and grid frequency through preset relationship curves of grid voltage and power and preset relationship curves of grid frequency and power, and then determine the charging and discharging power of the energy storage converter, and control the charging and discharging operation of the energy storage converter with the charging and discharging power; thus, it can discharge to the grid in a timely manner when the load changes suddenly, avoiding the diesel generator from dragging the grid. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of an energy storage system provided in an embodiment of this application;

[0013] Figure 2 This is a schematic diagram of the control method for the energy storage system provided in the embodiments of this application;

[0014] Figure 3 This is a schematic diagram of the preset relationship curve between grid voltage and power provided in the embodiments of this application;

[0015] Figure 4 This is a schematic diagram of the preset relationship curve between power grid frequency and power provided in the embodiments of this application;

[0016] Figure 5 This is a schematic diagram of the working state switching of the energy storage system provided in the embodiments of this application.

[0017] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer and more understandable, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.

[0019] In the description of this application, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," and "right," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0020] Figure 1 This is a schematic diagram of an energy storage system provided in an embodiment of this application.

[0021] like Figure 1As shown, the energy storage system includes energy storage batteries, PCS (energy storage converter), transformer, incoming line cabinet, BMS (battery management system), and EMS (energy management system).

[0022] The power grid can charge the energy storage battery through the PCS. The energy storage battery can discharge to the power grid through the PCS.

[0023] The power grid is connected to the generator set. The power grid is connected to the energy storage battery in sequence through the incoming switchboard, transformer, and PCS.

[0024] In one example, the PCS includes a DC / AC converter and a DC bus capacitor. The DC power converted by the DC / AC converter can charge the energy storage battery through the DC bus capacitor. Furthermore, a DC / DC converter can also be placed between the DC bus capacitor and the energy storage battery.

[0025] Energy storage batteries include supercapacitors, lithium batteries, and so on.

[0026] The BMS acquires information about the energy storage battery, such as temperature and voltage, and feeds it back to the PCS (End of Charge (EOC), End of Discharge (EOD), battery voltage, etc.) and EMS.

[0027] EMS can obtain information from PCS and issue commands to PCS, such as charging and discharging control, real-time data exchange, etc.; EMS can also obtain information from incoming line cabinets, such as real-time power consumption, transformer temperature protection, etc.

[0028] Figure 2 This is a schematic diagram of the control method for the energy storage system provided in the embodiments of this application.

[0029] like Figure 2 As shown, the method includes the following steps:

[0030] S11. Obtain the grid voltage and grid frequency;

[0031] S12. Determine the first power corresponding to the grid voltage based on the preset relationship curve of grid voltage and power; determine the second power corresponding to the grid frequency based on the preset relationship curve of grid frequency and power.

[0032] S13. Determine the charging and discharging power of the energy storage converter based on the first power and the second power, and control the charging and discharging operation of the energy storage converter with the charging and discharging power.

[0033] In one example, a preset relationship curve between grid voltage and power can be referenced. Figure 3 As shown.

[0034] from Figure 3As can be seen from the preset relationship curve between grid voltage and power, when the grid voltage V grid Given the voltage V0 corresponding to full-load power P0 and the voltage V corresponding to zero power comp Between these points, the power P and the grid voltage V grid The relationship increases linearly; when the grid voltage V grid Voltage V corresponding to power greater than zero comp At that time, the power P is a constant value P. charge .

[0035] In a specific example, P charge It can be 50kW, and the full-load power P0 can be 630kW.

[0036] In another example, a preset relationship curve between grid frequency and power can be referenced. Figure 4 As shown.

[0037] from Figure 4 As can be seen from the preset relationship curve between grid frequency and power, when the grid frequency f grid Given the frequency f0 corresponding to full load power P1 and the frequency f corresponding to zero power comp Between these points, the power P and the grid frequency f grid The relationship increases linearly; when the grid frequency f grid Frequency f corresponding to power greater than zero comp At that time, the power P is a constant value P. charge .

[0038] In a specific example, P charge It can be 50kW, and the full-load power P1 can be 630kW.

[0039] In one example, determining the charging and discharging power of the energy storage converter based on the first power and the second power includes:

[0040] If both the first power and the second power are discharge power, then the negative of the maximum absolute value of the two is taken as the discharge power of the energy storage converter.

[0041] If one of the first power and the second power is a discharge power and the other is a charging power, then only the discharge power value of the two is taken as the discharge power of the energy storage converter.

[0042] If both the first power and the second power are charging power, then the maximum value of the two charging power is taken as the charging power of the energy storage converter.

[0043] by Figure 3 or Figure 4 Let's take an example to illustrate:

[0044]

[0045] P vgrid According to Figure 3 The preset relationship curve between grid voltage and power is shown, which determines the power corresponding to the grid voltage. P fgrid According to Figure 4 The preset relationship curve between grid frequency and power is shown, and the power corresponding to the determined grid frequency is specified.

[0046] In one example, the acquisition of grid voltage and grid frequency further includes, prior to:

[0047] Obtain the DC-side capacitor voltage of the energy storage converter;

[0048] Based on the DC-side capacitor voltage, determine whether the energy storage system has entered a charging / discharging state;

[0049] If the energy storage system enters a charging / discharging state, then the steps of obtaining the grid voltage and grid frequency are performed.

[0050] In one example, determining whether the energy storage system has entered a charging / discharging state based on the DC-side capacitor voltage includes:

[0051] If the DC-side capacitor voltage is between the supplementary voltage and the float charge voltage, the energy storage system is controlled to switch to the charging and discharging state.

[0052] In one example, determining whether the energy storage system has entered a charging / discharging state based on the DC-side capacitor voltage further includes:

[0053] If the DC-side capacitor voltage is between the fault voltage and the replenishment voltage, then the energy storage system is controlled to switch to forced replenishment mode;

[0054] If the DC-side capacitor voltage is lower than the fault voltage, the energy storage system is controlled to switch to a fault state.

[0055] In a specific example, the float charge voltage can be 830V. The replenishment voltage is a multiple of the rated voltage, for example, 1.5 times the rated voltage. The fault voltage is lower than the replenishment voltage, for example, 1.45 times the rated voltage.

[0056] When the DC-side capacitor voltage is between the compensation voltage and the float charge voltage, the system is in a normal charging and discharging state; when the DC-side capacitor voltage is between the fault voltage and the compensation voltage, the system automatically enters a forced compensation state; when the DC-side capacitor voltage is lower than the fault voltage, it automatically enters a fault state.

[0057] The following combination Figure 5 The process of switching operating states of an energy storage system is explained below:

[0058] When a device malfunctions and sends a signal to the EMS (Energy Management System), such as a fault report from the PCS (Power Control System); or when the EMS's DI (Digital Identifier) ​​fault signal terminal receives a signal; or when the DC-side capacitor voltage enters the fault range (i.e., the DC-side capacitor voltage is lower than the fault voltage, with an acknowledgment time of, for example, 20ms), the energy storage system automatically enters a fault state. The fault state ends when the EMS is automatically or manually reset.

[0059] When the DC-side capacitor voltage falls below the replenishment voltage (confirmation time is, for example, 20ms), the energy storage system automatically enters forced replenishment mode. Once in forced replenishment mode, as long as it does not enter a fault state, the EMS will continuously send a charging command for 20 seconds, i.e., it will be in charging mode for 20 seconds, during which time it cannot discharge.

[0060] After 20 seconds of charging, the forced charging state ends or enters a fault state.

[0061] When the energy storage system is in a discharging state, the discharging state ends when the grid voltage returns to normal, enters a fault state, or enters a forced recharging state.

[0062] When the energy storage system is in a charging state, the charging state ends if it is interrupted by other states.

[0063] Furthermore, another embodiment of this application also provides an energy storage system, which can be referred to the foregoing.

[0064] The energy storage system shown also includes a controller; the controller is configured to acquire grid voltage and grid frequency; determine a first power corresponding to the grid voltage according to a preset relationship curve of grid voltage and power; determine a second power corresponding to the grid frequency according to the preset relationship curve of grid frequency and power; determine the charging and discharging power of the energy storage converter according to the first power and the second power, and control the charging and discharging operation of the energy storage converter with the charging and discharging power.

[0065] In this example, the controller can be integrated into the BMS, PCS, or EMS; preferably, it is integrated into the EMS, which sends the determined charging and discharging power of the energy storage converter to the PCS to control the charging and discharging operation of the energy storage converter. The controller can also be a standalone module.

[0066] Furthermore, embodiments of this application also provide a computer-readable storage medium storing at least one line of program code, which is loaded and executed by a processor to implement the charging terminal control method of the energy storage system described above.

[0067] The preferred embodiments of this application have been described above with reference to the accompanying drawings, but this does not limit the scope of the claims. Any modifications, equivalent substitutions, and improvements made by those skilled in the art without departing from the scope and spirit of this application shall be within the scope of the claims.

Claims

1. A control method for an energy storage system, the energy storage system comprising an energy storage converter and an energy storage battery; characterized in that, The control method includes: Obtain the grid voltage and grid frequency; Based on the preset relationship curve between the grid voltage and the grid power, determine the first power corresponding to the grid voltage; based on the preset relationship curve between the grid frequency and the grid frequency, determine the second power corresponding to the grid frequency. Based on the first power and the second power, the charging and discharging power of the energy storage converter is determined, and the charging and discharging operation of the energy storage converter is controlled by the charging and discharging power. Determining the charging and discharging power of the energy storage converter based on the first power and the second power includes: If both the first power and the second power are discharge power, then the negative of the maximum absolute value of the two is taken as the discharge power of the energy storage converter. If one of the first power and the second power is a discharge power and the other is a charging power, then only the discharge power value of the two is taken as the discharge power of the energy storage converter. If both the first power and the second power are charging power, then the maximum value of the two charging power is taken as the charging power of the energy storage converter.

2. The control method according to claim 1, characterized in that, When the grid voltage is between the voltage corresponding to zero power and the voltage corresponding to full load power, the first power is the discharge power; when the grid voltage is greater than the voltage corresponding to zero power, the first power is the charging power.

3. The control method according to claim 2, characterized in that, When the grid voltage is between the voltage corresponding to full load power and the voltage corresponding to zero power, the first power increases linearly with the grid voltage; when the grid voltage is greater than the voltage corresponding to zero power, the first power is a constant value.

4. The control method according to claim 1, characterized in that, When the grid frequency is between the frequency corresponding to zero power and the frequency corresponding to full load power, the second power is the discharge power; when the grid frequency is greater than the frequency corresponding to zero power, the second power is the charging power.

5. The control method according to claim 4, characterized in that, When the grid frequency is between the frequency corresponding to full load power and the frequency corresponding to zero power, the second power increases linearly with the grid frequency; when the grid frequency is greater than the frequency corresponding to zero power, the second power is a constant value.

6. The control method according to claim 1, characterized in that, The acquisition of grid voltage and grid frequency, prior to this, also includes: Obtain the DC-side capacitor voltage of the energy storage converter; Based on the DC-side capacitor voltage, determine whether the energy storage system has entered a charging / discharging state; If the energy storage system enters a charging / discharging state, then the steps of obtaining the grid voltage and grid frequency are performed.

7. The control method according to claim 6, characterized in that, The step of determining whether the energy storage system has entered a charging / discharging state based on the DC-side capacitor voltage includes: If the DC-side capacitor voltage is between the supplementary voltage and the float charge voltage, the energy storage system is controlled to switch to the charging and discharging state.

8. The control method according to claim 7, characterized in that, The step of determining whether the energy storage system has entered a charging / discharging state based on the DC-side capacitor voltage further includes: If the DC-side capacitor voltage is between the fault voltage and the replenishment voltage, then the energy storage system is controlled to switch to forced replenishment mode; If the DC-side capacitor voltage is lower than the fault voltage, the energy storage system is controlled to switch to a fault state.

9. An energy storage system, characterized in that, Including energy storage converters and energy storage batteries; It also includes a controller configured to acquire grid voltage and grid frequency; and to determine a first power corresponding to the grid voltage based on a preset relationship curve between the grid voltage and power. Based on the preset relationship curve between the grid frequency and power, the second power corresponding to the grid frequency is determined; based on the first power and the second power, the charging and discharging power of the energy storage converter is determined, and the charging and discharging operation of the energy storage converter is controlled by the charging and discharging power. Determining the charging and discharging power of the energy storage converter based on the first power and the second power includes: If both the first power and the second power are discharge power, then the negative of the maximum absolute value of the two is taken as the discharge power of the energy storage converter. If one of the first power and the second power is a discharge power and the other is a charging power, then only the discharge power value of the two is taken as the discharge power of the energy storage converter. If both the first power and the second power are charging power, then the maximum value of the two charging power is taken as the charging power of the energy storage converter.

Images