An active power control method for optical storage direct current coupling system

Abstract

The present application relates to a kind of active power control method for light storage direct current coupling system, which is realized by distinguishing direct current energy storage control demand, using different control modes, and on-demand flexible adjustment of energy storage charge and discharge.Compared with prior art, the present application has the advantages of expanding the control function of direct current energy storage, improving the overall utilization efficiency of direct current energy storage system, etc.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, in particular to an active power control method for a photovoltaic energy storage direct current coupling system. BACKGROUND

[0002] The proposal of the "double carbon" plan has led to a continuous increase in the proportion of new energy power generation represented by photovoltaic power generation. Equipping photovoltaic power stations with energy storage systems can smooth photovoltaic power generation output and alleviate the impact of intermittency and uncontrollability on the power grid. At present, in photovoltaic + energy storage systems (hereinafter referred to as photovoltaic energy storage systems), there are mainly two topological structures: direct current coupling and alternating current coupling. Among them, the direct current coupling mode is widely used in small and decentralized photovoltaic energy storage systems due to its advantages such as fewer power conversion links, low energy loss, and less equipment investment. The system schematic diagram is shown in Figure 1 .

[0003] In the direct current coupling mode, the energy storage system is connected to the photovoltaic array through a DC / DC device and synchronously receives the control of the inverter circuit, so it can directly participate in the power output control of the photovoltaic array under the same inverter. The photovoltaic and energy storage systems are closely connected and coupled with each other. However, the energy storage system cannot directly receive external energy storage charging and discharging instructions, making it difficult to realize decoupling control of the photovoltaic array power and the energy storage power, and unable to conveniently implement external control actions such as reducing power prediction deviation and charging and discharging test. The overall power regulation flexibility of the direct current coupling energy storage is poor. SUMMARY

[0004] The purpose of the present application is to overcome the defects of the prior art and provide an active power control method for a photovoltaic energy storage direct current coupling system, which effectively improves the control flexibility of the direct current coupling energy storage.

[0005] The purpose of the present application can be achieved by the following technical solutions:

[0006] According to one aspect of the present application, an active power control method for a photovoltaic energy storage direct current coupling system is provided, which realizes the on-demand flexible adjustment of energy storage charging and discharging by distinguishing the direct current energy storage control requirements and adopting different control modes.

[0007] As a preferred technical solution, the distinguishing of the direct current energy storage control requirements and the adoption of different control modes are specifically:

[0008] When the photovoltaic array is in the AGC power limiting and primary frequency modulation control mode, a closed-loop power mode is adopted;

[0009] When the photovoltaic array is in the maximum power tracking mode MPPT, an energy storage power control mode is adopted.

[0010] As a preferred technical solution, the method specifically includes the following steps:

[0011] Step 1, according to the photovoltaic station AGC and primary frequency operation state, set the active power control mode of the photovoltaic storage direct current coupling system;

[0012] Step 2, in the closed-loop power control mode, the photovoltaic storage cooperates to meet the power regulation requirement of AGC and primary frequency, and the part of the AGC and primary frequency load instruction allocated to the photovoltaic array is taken as a set value, the AC active power at the inverter outlet of the photovoltaic storage coupling system is taken as a measured value, power closed-loop control is carried out, and the control output instruction is the total active power instruction of the inverter;

[0013] Step 3, in the external power control mode, the direct current storage participates in the external control functions such as full-field power prediction, charge-discharge test and station power supply, the external charge-discharge power requirement of the direct current storage is taken as a set value, the storage power is taken as a measured value, the storage power is closed-loop controlled, and the control output instruction is the total active power instruction of the inverter;

[0014] Step 4, the total active power instruction of the inverter is selected according to the active power control mode of the photovoltaic storage direct current coupling system, and the control loop that is not selected tracks the total active power instruction in effect.

[0015] As a preferred technical scheme, the step 1 is specifically:

[0016] When the photovoltaic station AGC is put into operation and is in a photovoltaic power limiting control mode, or the primary frequency is put into operation and the grid frequency changes more than the control dead zone, the photovoltaic storage direct current coupling system is in a closed-loop power control mode; otherwise, the photovoltaic array in the photovoltaic storage system is in an MPPT mode, and the direct current storage is in an external charge-discharge power control mode.

[0017] As a preferred technical scheme, in the step 3, the difference between the photovoltaic array inverter output power and the direct current storage power coupled in the photovoltaic array is taken as a closed-loop control feedforward, so as to reduce the influence of the photovoltaic array power fluctuation on the storage power control.

[0018] As a preferred technical scheme, in the step 3, the discharge instruction of N% of the rated power of the direct current storage is periodically superimposed on the external charge-discharge power requirement instruction of the direct current storage, so that the photovoltaic array is in a maximum power tracking control mode, and the problem of light abandonment caused by the direct current storage power control is avoided.

[0019] As a preferred technical scheme, the N% is 1%.

[0020] As a preferred technical scheme, the time period in the periodicity is 5-10 min.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] 1) The present application realizes flexible control of light storage direct current coupling energy storage, expands the control function of direct current energy storage, and improves the overall utilization efficiency of the direct current energy storage system;

[0023] 2) The present application takes the difference between the output power of the photovoltaic array inverter and the direct current energy storage power coupled in the photovoltaic array as the feedforward of the closed-loop control, reduces the influence of the photovoltaic array power fluctuation on the energy storage power control;

[0024] 3) The present application periodically superimposes a 1% direct current energy storage rated power discharge instruction on the external charging and discharging power demand instruction of the direct current energy storage, and the time period can be 5-10 minutes. The photovoltaic array is in the maximum power tracking control mode, and the light abandonment problem caused by the direct current energy storage power control is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a schematic diagram of a light storage direct current coupling system;

[0026] Figure 2 It is an active power control principle diagram of the light storage direct current coupling system of the present application. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the present application.

[0028] As shown in the figure, a certain 100MW photovoltaic station is equipped with a total capacity of 5.5MW / 11MWh of distributed energy storage batteries, which include 10 sets of 500kW / 1000kWh distributed alternating current energy storage and 4 sets of 125kW / 250kWh distributed direct current coupling energy storage, wherein the active power control method of the light storage direct current coupling system is as follows: Figure 2 (1) According to the AGC and primary frequency modulation operation state of the photovoltaic station, the active power control mode of the light storage direct current coupling system is set. When the photovoltaic station AGC is put into operation and is in the photovoltaic power limiting control mode, or the primary frequency modulation is put into operation and the grid frequency changes more than the control dead zone, the light storage system is in the closed-loop power control mode; otherwise, the photovoltaic array in the light storage system is in the MPPT mode, and the direct current energy storage is in the external charging and discharging power control mode. In the external charging and discharging power control mode, the charging and discharging power instruction of the direct current energy storage is calculated by the coordination controller of the distributed energy storage system.

[0029]

[0030] ​(2) In closed-loop power control mode, the part of AGC and primary frequency modulation load command allocated to photovoltaic array is set as the set value, the AC active power of the photovoltaic array is the measured value, and the total active power command of the inverter is the control output command.

[0031] (3) In external power control mode, the external charging and discharging power demand of the DC energy storage is set as the set value, the DC energy storage power is the measured value, and the total active power command of the inverter is the control output command.

[0032] (4) In step (3), the difference between the photovoltaic array inverter output power and the DC energy storage power coupled in the photovoltaic array is used as the feedforward of closed-loop control to reduce the influence of photovoltaic array power fluctuation on energy storage power control.

[0033] (5) In step (3), a 1kw discharging command is periodically superimposed on the external charging and discharging power demand command of the DC energy storage, and the time period is 10min. The photovoltaic array is in maximum power tracking control mode to avoid the problem of light abandonment caused by DC energy storage power control.

[0034] (6) The total active power command of the inverter is selected according to the active power control mode of the photovoltaic energy storage DC coupling system, and the control loop that is not selected tracks the effective total active power command.

[0035] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An active power control method for a light storage DC coupled system, characterized in that, The method realizes flexible adjustment of the charging and discharging of the energy storage according to the needs by distinguishing the control needs of the direct-current energy storage and adopting different control modes; The different control modes for distinguishing the control needs of the direct-current energy storage are as follows: When the photovoltaic array is in the AGC power limiting and primary frequency modulation control mode, a closed-loop power mode is adopted; When the photovoltaic array is in the maximum power tracking mode MPPT, an energy storage power control mode is adopted; The method specifically comprises the following steps: Step 1: According to the AGC and primary frequency modulation operation state of the photovoltaic station, the active power control mode of the photovoltaic and energy storage direct-current coupling system is set; Step 2: In the closed-loop power control mode, the photovoltaic and energy storage system cooperates to meet the power adjustment needs of the AGC and primary frequency modulation, and the part allocated to the photovoltaic array in the AGC and primary frequency modulation load instruction of the photovoltaic station is taken as the set value, the AC active power at the outlet of the inverter of the photovoltaic and energy storage coupling system is taken as the measured value, and power closed-loop control is performed, and the control output instruction is the total active power instruction of the inverter; Step 3: In the external power control mode, the direct-current energy storage participates in the external control functions of the whole field power prediction, charging and discharging test, and station power supply, and the external charging and discharging power demand of the direct-current energy storage is taken as the set value, the direct-current energy storage power is taken as the measured value, and the closed-loop control of the energy storage power is performed, and the control output instruction is the total active power instruction of the inverter; Step 4: According to the active power control mode of the photovoltaic and energy storage direct-current coupling system, the total active power instruction of the inverter is selected, and the control loop that is not selected tracks the total active power instruction that is in effect.

2. The method for active power control for optical storage DC coupling system according to claim 1, wherein, The step 1 specifically comprises: When the photovoltaic station AGC is in operation and in the photovoltaic power limiting control mode, or the primary frequency modulation is in operation and the grid frequency changes more than the control dead zone, the photovoltaic and energy storage direct-current coupling system is in the closed-loop power control mode; otherwise, the photovoltaic array in the photovoltaic and energy storage system is in the MPPT mode, and the direct-current energy storage is in the external charging and discharging power control mode.

3. The method of claim 1, wherein, In step 3, the difference between the output power of the photovoltaic array inverter and the direct-current energy storage power coupled in the photovoltaic array is taken as the feedforward of the closed-loop control, so as to reduce the influence of the power fluctuation of the photovoltaic array on the energy storage power control.

4. The method of claim 1, wherein, In step 3, the discharging instruction of N% of the rated power of the direct-current energy storage is periodically superimposed on the external charging and discharging power demand instruction of the direct-current energy storage, so that the photovoltaic array is in the maximum power tracking control mode, and the problem of light abandonment caused by the direct-current energy storage power control is avoided.

5. The method of claim 4, wherein, The N% is 1%.

6. The method of claim 4, wherein, The time period in the periodicity is 5-10 minutes.

Images