Direct-current bus control method and device of direct-current coupling photovoltaic energy storage system
By combining competition mechanisms and droop control, the problems of communication occupancy, SOC balancing, and voltage instability in DC-coupled photovoltaic energy storage systems are solved, achieving stable and efficient utilization of the DC bus.
Patent Information
- Application Number
- CN202610130844.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-30
- Publication Date
- 2026-05-15
AI Technical Summary
Existing DC bus control methods for DC-coupled photovoltaic energy storage systems suffer from problems such as occupying a large number of communication channels, failing to achieve SOC equalization among energy storage clusters, frequently limiting PV power generation capacity, and instability under harsh operating conditions.
A competitive mechanism is adopted to control PV string power generation, load power consumption, and energy storage charging and discharging. A competitive control threshold related to DC bus voltage is designed. By combining the control of grid-connected and off-grid inverters with load, and combined with droop control, the SOC balance between energy storage clusters is achieved, and the bus voltage is adjusted within a reasonable range.
It achieves maximum power generation from PV strings, full utilization of load power, stability of DC bus voltage, and ensures that parallel battery clusters can respond normally to power commands and achieve SOC balance.
Smart Images
Figure CN122051910A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a DC bus control method, and more particularly to a DC bus control method and apparatus for a DC-coupled photovoltaic energy storage system. Background Technology
[0002] Both photovoltaic (PV) and energy storage systems generate direct current (DC), and charging stations, data centers, and other power-consuming equipment also receive DC power. DC-coupled systems significantly simplify DC / AC and AC / DC conversion, improving system conversion efficiency. Therefore, new energy DC power generation / consumption systems are developing rapidly. A common DC-coupled PV-energy storage system is as follows: Figure 1 As shown in the diagram. The PV strings can be new energy power generation devices such as photovoltaics, wind power, and hydropower; energy storage can be various charging and discharging devices such as batteries and supercapacitors; and the load can be various loads such as charging piles, motors, and grid-connected / off-grid inverters. The specific power generation, energy storage, and power consumption equipment and their quantities are not limited by the diagram. Because the DC-coupled system has multiple power generation and power consumption devices and grid-connected / off-grid inverters connected to the DC bus, the system is complex. Therefore, its control system must achieve multi-objective control to ensure normal power generation from the PV strings and other power generation devices, minimizing power limitations. Each parallel energy storage device must respond to a unified power command and adjust its input or output power according to SOC differences. It must also adjust the load power consumption based on the system's power generation status, ensuring stable DC bus voltage and avoiding drastic fluctuations under various operating conditions.
[0003] Existing DC bus control methods for DC-coupled photovoltaic-storage systems achieve the aforementioned control objectives through rapid and extensive information exchange, with a conventional approach employing preliminary droop control. However, existing methods all have limitations. Some require a large number of high-speed communication channels, some cannot perform SOC balancing between energy storage clusters, some frequently limit PV power generation capacity, and some cause instability of the DC bus under harsh operating conditions. Summary of the Invention
[0004] Purpose of the invention: To address the above problems, this invention proposes a DC bus control method and device for a DC-coupled photovoltaic energy storage system. It does not restrict PV string power generation unless necessary, and can realize the full utilization of photovoltaic power, the full utilization of load power, and the stable DC bus voltage. The parallel battery clusters can not only respond normally to power commands, but also balance the SOC.
[0005] Technical Solution: The technical solution adopted in this invention is a DC bus control method for a DC-coupled photovoltaic energy storage system. This method uses a competitive mechanism to control PV string power generation, load power consumption, and energy storage charging and discharging; it controls the bus voltage to not exceed the upper limit of the PV string bus voltage reference value; and it combines the control of the grid-connected / off-grid inverter with the load. In the competitive mechanism, the bus voltage reference values of each competitive control loop satisfy the following: the upper limit of the PV string bus voltage reference value is greater than the upper limit of the load bus voltage reference value; the upper limit of the load bus voltage reference value is greater than the upper limit of the energy storage droop control voltage reference value; and the lower limit of the load bus voltage reference value is less than the lower limit of the energy storage droop control voltage reference value.
[0006] Controlling the bus voltage to not exceed the upper limit of the PV string bus voltage reference value includes: taking the PV string voltage reference value and the upper limit of the PV string bus voltage reference value as inputs, and outputting the PV string current reference value through the PV side voltage competition loop.
[0007] The PV-side voltage competition loop includes two voltage loops and a comparison module; the upper limit of the voltage reference value of the PV string and the upper limit of the bus voltage reference value of the PV string are respectively passed through the two voltage loops, and the smaller value output by the two voltage loops is taken as the PV string current reference value output.
[0008] Load control includes: increasing load power or starting a specified load when the bus voltage exceeds the upper limit of the load bus voltage reference value; decreasing load power or shutting down a specified load when the bus voltage is lower than the lower limit of the load bus voltage reference value; and adjusting the energy storage charging and discharging power using droop control.
[0009] The load power current is adjusted by the load-side competition loop, including: the upper limit of the load bus voltage reference value and the load power, which are respectively passed through the voltage loop and the power loop, and the larger value of the output is taken as the first output; the lower limit of the load bus voltage reference value is output through the voltage loop as the second output; and the smaller value between the first output and the second output is taken as the load current reference value.
[0010] Automatic power balancing control of multiple parallel battery clusters is achieved using droop control, with the droop formula as follows:
[0011] ;
[0012] In the formula, This is the reference value for the DC bus voltage. This is the base value for the droop control voltage. This is the droop coefficient for droop control. This refers to the actual charge and discharge power. This is the base value for droop control power;
[0013] The charging power corresponding to the upper limit of the energy storage droop control voltage reference value shall not be less than the absolute value of the maximum allowable charging power; the discharging power corresponding to the lower limit of the energy storage droop control voltage reference value shall not be less than the absolute value of the maximum allowable discharging power.
[0014] Under droop control, the charging and discharging power of a single battery cluster is adjusted by regulating the droop control power base value through the power loop.
[0015] Under droop control, the DC bus voltage is regulated by adjusting the droop control voltage base value through a voltage loop.
[0016] This invention proposes a computer program product, including a computer program and / or instructions, which, when executed by a processor, implement the DC bus control method of the DC-coupled photovoltaic energy storage system.
[0017] This invention proposes a DC bus control device for a DC-coupled photovoltaic energy storage system, including a system coordination controller. When the system coordination controller executes the computer program, it implements the DC bus control method for the DC-coupled photovoltaic energy storage system.
[0018] Beneficial effects: Compared with the prior art, the present invention has the following advantages: 1. It adopts a competitive mechanism to control the power generation, energy storage charging and discharging, and load power consumption of PV strings, and designs a competitive control threshold related to DC bus voltage to promote the PV strings to generate as much power as possible and avoid the DC bus voltage being too high or too low; 2. The parallel energy storage cluster adopts droop control, which automatically adjusts the charging and discharging power according to the DC bus voltage to maintain the DC bus voltage within a reasonable range; 3. It achieves system optimization control by adjusting the droop control parameters, achieves SOC equalization control by adjusting the power base value, and achieves optimal control of the DC bus voltage value by adjusting the voltage base value. Attached Figure Description
[0019] Figure 1 This is an example of a DC-coupled photovoltaic-storage system;
[0020] Figure 2 This is a schematic diagram of the DC bus competition control voltage threshold described in this invention;
[0021] Figure 3 This is a block diagram of the PV-side voltage competition loop described in this invention;
[0022] Figure 4 This is a block diagram of a load-related voltage contention loop;
[0023] Figure 5 This is a schematic diagram of the droop control power / voltage range;
[0024] Figure 6 This is a module diagram of individually adjusting battery power in the droop control described in this invention;
[0025] Figure 7 This is a module diagram of the unified adjustment of DC bus voltage in the droop control described in this invention. Detailed Implementation
[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.
[0027] The DC bus control method for the DC-coupled photovoltaic energy storage system described in this invention includes: using a competitive mechanism to control PV string power generation, load power consumption, and energy storage charging and discharging; controlling the bus voltage to not exceed the upper limit of the PV string bus voltage reference value; and combining the control of the off-grid inverter and the load. Load control includes: when the bus voltage is within the normal range, the load consumes normal power, where normal power refers to the power consumed by the required load during normal operation, i.e., the load power without adjusting the load power; when the bus voltage exceeds the upper limit of the load bus voltage reference value, increasing the load power current or starting a designated load; when the bus voltage is lower than the lower limit of the load bus voltage reference value, decreasing the load power current or shutting down a designated load; and adjusting the energy storage charging and discharging power using droop control. The following sections provide specific details:
[0028] S1 employs a competitive mechanism to control PV string power generation, load power consumption, and energy storage charging and discharging; it controls the bus voltage to not exceed the upper limit of the PV string bus voltage reference value.
[0029] A competitive mechanism is employed to control PV string power generation, load power consumption, and energy storage charging and discharging. A competitive control relationship related to the DC bus voltage is designed, i.e., the bus voltage reference value for each competitive control loop, such as... Figure 2 As shown, This indicates the upper limit of the reference value for the PV string bus voltage. This indicates the upper limit of the reference value for the load bus voltage. This indicates the upper limit of the reference value for the energy storage droop control voltage. This indicates the lower limit of the reference value for the energy storage droop control voltage. This represents the lower limit of the load bus voltage reference value. The thresholds conform to the relationship shown in the figure: the upper limit of the PV string bus voltage reference value. Greater than the upper limit of the load bus voltage reference value The upper and lower limits of the load bus voltage reference value completely cover the upper and lower limits of the energy storage droop control voltage reference value: the upper limit of the load bus voltage reference value. Greater than the upper limit of the energy storage droop control voltage reference value Lower limit of load bus voltage reference value Less than the lower limit of the energy storage droop control voltage reference value .
[0030] Control the bus voltage to not exceed the upper limit of the PV string bus voltage reference value, such as Figure 3 As shown, the voltage reference value of the PV string is... and the upper limit of the reference value of the PV string bus voltage As input, the PV string current reference value is output through the PV-side voltage contention loop. Specifically, the voltage reference value of the PV string. and the upper limit of the reference value of the PV string bus voltage After passing through two voltage loops, the smaller value of the two voltage loop outputs is taken as the reference value for the PV string current. This output enables a voltage contention loop on the PV side.
[0031] S2, the control of the grid-connected and off-grid inverters (applicable to both grid-connected and off-grid inverters) and the load is combined. The load control includes: when the bus voltage is within the normal range, the load consumes normal power; when the bus voltage exceeds the upper limit of the load bus voltage reference value, the load power is increased or the specified load is started; when the bus voltage is lower than the lower limit of the load bus voltage reference value, the load power is reduced or the specified load is shut down.
[0032] Inverters connected to or off the grid are also considered loads connected to the DC bus (except that the load power can be negative), and controlled together with other ordinary DC loads. For power-adjustable loads, the load consumes normal power when the bus voltage is within the normal range, and the load consumes normal power when the bus voltage is too high. Or too low At this time, the load power is adjusted up or down through the load-side competition ring (it can also start or stop a portion of the load). For example... Figure 4 As shown, the upper limit of the load bus voltage reference value and load power After passing through the voltage loop and power loop respectively, the larger output value is taken as the first output, which is the lower limit of the load bus voltage reference value. The output through the voltage loop is used as the second output; the smaller value between the first and second outputs is taken as the load current reference value. .
[0033] S3 uses droop control to regulate the energy storage charging and discharging power.
[0034] Automatic power balancing control for multiple parallel battery clusters is achieved using droop control. The calculation formula for droop control is as follows:
[0035] ;
[0036] In the formula, This is the reference value for the DC bus voltage. This is the base value for the droop control voltage. This is the droop coefficient for droop control. This represents the actual charge / discharge power; a positive value indicates discharge. The reference value for droop control power is positive, and negative values represent discharge. The charging power corresponding to the upper limit of the energy storage droop control voltage reference value shall not be less than the absolute value of the maximum allowable charging power; the discharge power corresponding to the lower limit of the energy storage droop control voltage reference value shall not be less than the absolute value of the maximum allowable discharge power.
[0037] like Figure 5 As shown, the voltage droop range should be at the upper limit of the energy storage droop control voltage reference value. and lower limit between.
[0038] Under droop control, the charging and discharging power of each battery cluster is the same. However, for reasons such as SOC balancing, it may be necessary to change the charging and discharging power of a specific battery cluster individually. This is done by adjusting the droop control power base value. To achieve this. For example... Figure 6 The diagram shown is a module diagram for individually adjusting battery power in droop control. This is a reference value for charging and discharging power.
[0039] DC bus voltage under droop control It will vary with the charging and discharging power within a certain range, in order to achieve steady state. At its optimal value, the droop control voltage base value can be adjusted. To achieve, to regulate This requires all battery clusters to execute at the same time and with the same voltage step. A scheme for uniformly adjusting the DC bus voltage under droop control is as follows: Figure 7 As shown, This is the reference value for the DC bus voltage.
[0040] Example 2:
[0041] In one embodiment, a computer program product is provided, including a computer program and / or instructions that, when executed by a processor, implement the DC bus control method of the DC-coupled photovoltaic energy storage system.
[0042] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.
[0043] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.
[0044] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.
[0045] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.
[0046] Example 3:
[0047] The DC bus control device for the DC-coupled photovoltaic energy storage system of the present invention includes a system coordination controller, which controls the PV string current reference value through the respective controllers of each DC-DC and DC-AC circuit. Load current reference value And the charging and discharging current of the battery clusters. Specifically, the reference value for PV string current. Control is achieved through the controller of the DC-DC circuit on the string side of each PV group. Load current reference value. Control is achieved through a controller in the load-side DC-DC or DC-AC circuit. The charging and discharging current of the battery clusters is controlled by a controller in the DC-DC circuit of each battery cluster.
Claims
1. A DC bus control method for a DC-coupled photovoltaic energy storage system, characterized in that: This method employs a competitive mechanism to control PV string power generation, load power consumption, and energy storage charging and discharging; controls the bus voltage to not exceed the upper limit of the PV string bus voltage reference value; and combines the control of the grid-connected / off-grid inverter with the load; in the competitive mechanism, the bus voltage reference value of each competitive control loop satisfies the following: the upper limit of the PV string bus voltage reference value is greater than the upper limit of the load bus voltage reference value; The upper limit of the load bus voltage reference value is greater than the upper limit of the energy storage droop control voltage reference value, and the lower limit of the load bus voltage reference value is less than the lower limit of the energy storage droop control voltage reference value.
2. The DC bus control method for a DC-coupled photovoltaic energy storage system according to claim 1, characterized in that: Controlling the bus voltage to not exceed the upper limit of the PV string bus voltage reference value includes: taking the PV string voltage reference value and the upper limit of the PV string bus voltage reference value as inputs, and outputting the PV string current reference value through the PV side voltage competition loop.
3. The DC bus control method for a DC-coupled photovoltaic energy storage system according to claim 2, characterized in that: The PV-side voltage competition loop includes two voltage loops and a comparison module; the upper limit of the voltage reference value of the PV string and the upper limit of the bus voltage reference value of the PV string are respectively passed through the two voltage loops, and the smaller value output by the two voltage loops is taken as the PV string current reference value output.
4. The DC bus control method for a DC-coupled photovoltaic energy storage system according to claim 1, characterized in that: Load control includes: increasing load power or starting a specified load when the bus voltage exceeds the upper limit of the load bus voltage reference value; decreasing load power or shutting down a specified load when the bus voltage is lower than the lower limit of the load bus voltage reference value; and adjusting the energy storage charging and discharging power using droop control.
5. The DC bus control method for a DC-coupled photovoltaic energy storage system according to claim 1, characterized in that: The load power current is adjusted by the load-side competition loop, including: the upper limit of the load bus voltage reference value and the load power, which are respectively passed through the voltage loop and the power loop, and the larger value of the output is taken as the first output; the lower limit of the load bus voltage reference value is output through the voltage loop as the second output; and the smaller value between the first output and the second output is taken as the load current reference value.
6. The DC bus control method for a DC-coupled photovoltaic energy storage system according to claim 1, characterized in that: Automatic power balancing control of multiple parallel battery clusters is achieved using droop control, with the droop formula as follows: ； In the formula, This is the reference value for the DC bus voltage. This is the base value for the droop control voltage. This is the droop coefficient for droop control. This refers to the actual charge and discharge power. This is the base value for droop control power; The charging power corresponding to the upper limit of the energy storage droop control voltage reference value shall not be less than the absolute value of the maximum allowable charging power; the discharging power corresponding to the lower limit of the energy storage droop control voltage reference value shall not be less than the absolute value of the maximum allowable discharging power.
7. The DC bus control method for a DC-coupled photovoltaic energy storage system according to claim 1, characterized in that: Under droop control, the charging and discharging power of a single battery cluster is adjusted by regulating the droop control power base value through the power loop.
8. The DC bus control method for a DC-coupled photovoltaic energy storage system according to claim 1, characterized in that: Under droop control, the DC bus voltage is regulated by adjusting the droop control voltage base value through a voltage loop.
9. A computer program product, comprising a computer program and / or instructions, characterized in that, When the computer program and / or instructions are executed by the processor, they implement the DC bus control method of the DC-coupled photovoltaic energy storage system as described in any one of claims 1 to 8.
10. A DC bus control device for a DC-coupled photovoltaic energy storage system, comprising a system coordination controller, characterized in that: When the system co-controller executes the computer program, it implements the DC bus control method of the DC-coupled photovoltaic energy storage system as described in any one of claims 1 to 8.