A control method and system for a photovoltaic energy storage system

Abstract

The present invention discloses a control method and system for a photovoltaic storage system. The control method includes: when the sum of the photovoltaic power generation value and the maximum discharge power value of the DC converter is greater than or equal to a first power value, less than the grid dispatching power value, and the photovoltaic power generation value is less than or equal to the first power value, controlling the DC converter to discharge and the discharge power is equal to a first difference between the first power value and the photovoltaic power generation value; when the photovoltaic power generation value is greater than the first power value and the difference between the photovoltaic power generation value and the maximum charging power value of the DC converter is less than or equal to the grid dispatching power value, controlling the DC converter to charge and the charging power is equal to a second difference between the photovoltaic power generation power and the first power value. The control method and system of the present invention can realize the tracking of the maximum power point of the photovoltaic module to effectively utilize the energy of the photovoltaic system.

Description

Technical Field

[0001] The present invention relates to the field of automation control technology, and in particular to a control method and system for a photovoltaic storage system. Background Art

[0002] With the development of photovoltaic technology, PV power generation has matured and installed capacity has increased rapidly. However, due to the intermittent and uncontrollable nature of PV power generation, PV power generation systems suffer from significant fluctuations in output power. If the power output of a PV power generation system is directly fed to the grid without processing, it can cause fluctuations in grid voltage and frequency, impacting the stability of the entire grid.

[0003] The photovoltaic storage system, which combines a photovoltaic system with an energy storage system, can effectively mitigate fluctuations in output power. When the photovoltaic system outputs too much energy, the energy storage system charges, reducing the total output power while avoiding energy waste. When the photovoltaic system's energy is insufficient, the energy storage system discharges to ensure smooth total power output. However, in actual operation, energy storage systems often operate in constant power charging mode or constant power discharging mode. When the energy output of the photovoltaic system changes over time, the energy storage system operating in constant power mode can easily lead to the photovoltaic system's energy not being effectively utilized. It also makes it difficult for the inverter to track the maximum power point of the photovoltaic modules, resulting in energy waste of the photovoltaic modules. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects or problems existing in the background technology, and to provide a control method and system for a photovoltaic storage system so that the working power of the energy storage system can be adjusted in real time to achieve tracking of the maximum power point of the photovoltaic module and effectively utilize the energy of the photovoltaic system.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A control method for a photovoltaic storage system, characterized in that the photovoltaic components in the photovoltaic storage system output power to the inverter in priority to the energy storage system, the inverter and the energy storage side DC converter are communicatively connected, and the inverter is directly connected to the photovoltaic components; a first power value that is less than the grid dispatching power value is set; the control method for the photovoltaic storage system includes: when the sum of the photovoltaic power generation power value and the maximum discharge power value of the DC converter is less than the first power value, controlling the DC converter to discharge and the discharge power is equal to the maximum discharge power value; when the sum of the photovoltaic power generation power value and the maximum discharge power value of the DC converter is greater than or equal to the first power value, less than the grid dispatching power value and the When the photovoltaic power generation power value is less than or equal to the first power value, the DC converter is controlled to discharge and the discharge power is equal to a first difference value obtained by subtracting the photovoltaic power generation power value from the first power value; when the photovoltaic power generation power value is greater than the first power value and the difference between the photovoltaic power generation power value and the maximum charging power value of the DC converter is less than or equal to the grid dispatching power value, the DC converter is controlled to charge and the charging power is equal to a second difference value obtained by subtracting the first power value from the photovoltaic power generation power value; when the difference between the photovoltaic power generation power value and the maximum charging power value of the DC converter is greater than the grid dispatching power value, the DC converter is controlled to charge and the charging power is equal to the maximum charging power value.

[0007] Based on technical solution one, there is also provided technical solution two. In technical solution two, the difference between the grid dispatching power value and the first power value is greater than the fluctuation amplitude when the inverter stably outputs the grid dispatching power value.

[0008] Based on Technical Solution 2, there is also a Technical Solution 3. In Technical Solution 3, the specific method of controlling the discharge power of the DC converter to be equal to the first difference obtained by subtracting the first power value from the photovoltaic power generation power value is as follows: the inverter output power value is obtained at each manually set interval, and the cumulative error between the inverter output power value and the first power value is correspondingly included in the first difference to form a third difference. If the third difference is less than the maximum discharge power value, the DC converter is controlled within the interval so that the discharge power of the energy storage system is equal to the third difference; if the third difference is greater than or equal to the maximum discharge power value, the DC converter is controlled within the interval so that the discharge power of the energy storage system is equal to the maximum discharge power value.

[0009] Based on Technical Solution 3, there is also a Technical Solution 4. In Technical Solution 4, the specific method of controlling the charging power of the DC converter to be equal to the second difference obtained by subtracting the first power value from the photovoltaic power generation power value is as follows: the cumulative error between the inverter output power value and the first power value is correspondingly included in the second difference to form a fourth difference. If the fourth difference is less than the maximum charging power value, the DC converter is controlled within the interval so that the charging power of the energy storage system is equal to the fourth difference; if the fourth difference is greater than or equal to the maximum charging power value, the DC converter is controlled within the interval so that the charging power of the energy storage system is equal to the maximum charging power value.

[0010] Based on Technical Solution One, there is also a Technical Solution Five. In Technical Solution Five, the specific method for controlling the charging of the DC converter and making the charging power equal to the maximum charging power value is as follows: the cumulative error between the grid dispatching power value and the inverter output power value is correspondingly included in the grid dispatching power value to form the inverter set power value, and the inverter adjusts its output power according to its set power value.

[0011] Based on technical solutions one to five, there is also a technical solution six. In technical solution six, when the photovoltaic power generation power value is less than the set second power value, the connection between the photovoltaic module and the inverter is disconnected; the power supply relationship of the energy storage side DC converter and its output power are determined by the working mode of the inverter and the grid dispatching power.

[0012] Technical Solution 7. The present invention also provides a photovoltaic storage system, including a photovoltaic module, an inverter, an energy storage system and a DC converter on the energy storage side; the inverter is communicatively connected to the DC converter; the output end of the photovoltaic module is directly connected to the DC side of the inverter; the energy storage system is connected to the DC bus of the inverter through the DC converter; the photovoltaic storage system is used to execute the control method described in any one of Technical Solutions 1 to 5.

[0013] Based on Technical Solution 6, there is also a Technical Solution 7. In Technical Solution 7, the output end of the photovoltaic module is connected to the DC side of the inverter through a DC circuit breaker; the DC circuit breaker is used to disconnect when the photovoltaic power generation power value is less than a set second power value.

[0014] From the above description of the present invention, it can be seen that compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. In technical solution 1, when the sum of the photovoltaic power generation power value and the maximum discharge power value of the DC converter is less than the first power value, the DC converter is controlled to discharge and the discharge power is equal to the maximum discharge power value, which is conducive to making the output power of the inverter track the maximum power point of the photovoltaic module and making the photovoltaic storage system output as much power to the grid as possible; when the sum of the photovoltaic power generation power value and the maximum discharge power value of the DC converter is greater than or equal to the first power value and less than the grid dispatching power value and the photovoltaic power generation power value is less than or equal to the first power value, the DC converter is controlled to discharge and the discharge power is equal to the first difference obtained by subtracting the photovoltaic power generation power value from the first power value; and when the photovoltaic power generation power value is greater than the first power value and the difference between the photovoltaic power generation power value and the maximum charging power value of the DC converter is less than or equal to the grid dispatching power value, the DC converter is controlled to charge and the charging power is equal to the photovoltaic power generation power value minus the first power value. The second difference obtained by adjusting the power value of the photovoltaic power generation device and the maximum charging / discharging power value of the DC converter enables the DC converter on the energy storage side to track the maximum power point of the photovoltaic module in real time during these stages, and the inverter maintains the first power value to form a stable section during this stage, that is, the output power of the inverter is stable; when the difference between the photovoltaic power generation power value and the maximum charging power value of the DC converter is greater than the grid dispatching power value, the DC converter is controlled to charge and the charging power is equal to the maximum charging power value, which is conducive to reducing the output power of the inverter as much as possible and avoiding waste of photovoltaic module energy; it can be seen that the adoption of this technical solution can adjust the output power and power supply relationship of the DC converter on the energy storage side according to the relationship between the photovoltaic power generation power value and the set first power value, the maximum charging / discharging power value of the DC converter on the energy storage side and the grid dispatching power value, which is conducive to enabling the inverter to keep tracking the maximum power point of the photovoltaic module, thereby realizing effective utilization of the energy of the photovoltaic module.

[0016] 2. In the second technical solution, the difference between the grid dispatching power value and the first power value is greater than the fluctuation amplitude when the inverter stably outputs the grid dispatching power value, so that the power loop of the inverter is always in a saturated state and fails, and the bus voltage loop of the inverter works, so that the inverter can keep tracking the maximum power point of the photovoltaic module, while avoiding the output power of the inverter from coinciding with the grid dispatching power when it fluctuates, thereby achieving the stability of the inverter output power. With this setting, the output power of the inverter can still maintain the stability of the output power and track the maximum power point of the photovoltaic module when it is close to the grid dispatching power, thereby achieving effective utilization of the energy of the photovoltaic module.

[0017] 3. In Technical Solution 3, the cumulative error between the inverter output power value and the first power value is correspondingly included in the first difference to form a third difference, and then the discharge power of the energy storage system is adjusted according to the relationship between the third difference and the maximum discharge power. This not only allows the inverter output power to be maintained at the first power value to form a stable section, but also allows the inverter output power to be used as real-time feedback of the actual discharge power of the energy storage system, making the calculation of the discharge power of the energy storage system more accurate.

[0018] 4. In Technical Solution 4, the cumulative error between the inverter output power value and the first power value is correspondingly included in the second difference to form a fourth difference, and then the charging power of the energy storage system is adjusted according to the relationship between the fourth difference and the maximum charging power. This not only allows the inverter output power to remain at the first power value to form a stable section, but also allows the inverter output power to serve as real-time feedback of the actual charging power of the energy storage system, making the calculation of the energy storage system's charging power more accurate.

[0019] 5. In Technical Solution 5, the cumulative error between the grid dispatching power value and the inverter output power value is correspondingly included in the grid dispatching power value to form the inverter set power value. The inverter adjusts its output power according to its set power value, which is conducive to controlling the output power value of the inverter at this stage to remain at the grid dispatching power value.

[0020] 6. In Technical Solution 6, when the photovoltaic power generation value is less than the set second power value, the connection between the photovoltaic module and the inverter is disconnected; the power supply relationship and output power of the DC converter on the energy storage side are determined by the working mode of the inverter and the grid dispatching power, which avoids the grid energy or energy storage system energy from being fed back into the photovoltaic module when the photovoltaic module is out of power at night or the photovoltaic output power is too low.

[0021] 7. In technical solution seven, the present invention also discloses a photovoltaic storage system that executes the above-mentioned control method. The photovoltaic storage system can adjust the output power and power supply relationship of the energy storage side DC converter according to the relationship between the photovoltaic power generation power value and the set first power value, the maximum charge / discharge power value of the energy storage side DC converter and the grid dispatching power value, which is conducive to enabling the inverter to keep tracking the maximum power point of the photovoltaic module, thereby realizing the effective utilization of the photovoltaic module energy.

[0022] 8. In Technical Solution 8, the setting of the DC circuit breaker is simple and practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 A schematic structural diagram of the optical storage system of the present invention;

[0025] Figure 2 Schematic diagram of the change of the output power of the inverter, photovoltaic power generation value and the output power of the DC converter of the photovoltaic storage system over time;

[0026] Figure 3 for Figure 2 The control loops of stages 3 and 5 in

[0027] Figure 4 for Figure 2 The control loop of stage 4. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are preferred embodiments of the present invention and should not be regarded as excluding other embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] In the claims, description and drawings of the present invention, unless otherwise clearly defined, the use of terms such as "first", "second" or "third" is for the purpose of distinguishing different objects rather than for describing a specific order.

[0030] In the claims, description and drawings of the present invention, if the terms "include", "have" and their variations are used, they are intended to mean "including but not limited to".

[0031] The following describes the optical storage system of this application. Figure 1 This is a schematic diagram of the structure of the solar storage system of this application, see Figure 1 The PV-storage system consists of photovoltaic modules, an inverter, an energy storage system, and a DC converter on the energy storage side. The output of the photovoltaic modules is directly connected to the DC side of the inverter via a DC isolating switch. The energy storage system is connected to the inverter's DC bus via a DC converter. The inverter is a single-stage inverter that communicates with the DC converter. The power output from the DC converter to the inverter is generated by the energy storage system, and the DC converter controls the output power of the energy storage system.

[0032] In this application, the solar-storage system also includes a rectifier bridge stack connected in parallel with the inverter. The rectifier bridge stack primarily provides energy to the busbar to help the inverter start up when the DC disconnector is disconnected, the DC converter on the energy storage side stops operating, and the busbar is depleted of energy. Alternatively, the rectifier bridge stack is activated when the DC converter fails or runs out of energy. In other words, in most situations, the rectifier bridge stack is disconnected from the busbar.

[0033] Photovoltaic modules convert solar energy into electricity, which is then stored internally in the energy storage system. Optionally, the photovoltaic modules alone can output power to the grid, the energy storage system alone can output power to the grid, or both the photovoltaic modules and the energy storage system can output power to the grid together, though this is not a specific limitation. In this application, the photovoltaic modules prioritize outputting power to the inverter. When energy is insufficient, the DC converter controls the energy storage system to supplement the discharge. The photovoltaic power generation value varies over time.

[0034] In this application, the inverter's outer loop includes a power loop and a bus voltage loop. The power loop receives grid power dispatch commands, while the inner loop is a current loop. The DC converter's outer loop includes a power control loop and a bus voltage loop, while the inner loop is a current loop. In this application, the inverter adjusts the energy storage system's output power and power supply relationship via communication commands.

[0035] In this application, it is assumed that the discharge power value of the photovoltaic component at the current moment is Ppv, that is, the photovoltaic power generation power value is Ppv. Ppv is obtained by detection. The detection method belongs to the existing technology and will not be repeated here.

[0036] The grid dispatching power value is A, which is issued by the dispatching center and is changeable in the short term.

[0037] The current working power value of the DC converter on the energy storage side is P dcdc ,Pbat_chargeMax is the maximum charging power value allowed by the energy storage system, and Pbat_DischargeMax is the maximum discharging power value allowed by the energy storage system.

[0038] The inverter output power value is Pfb, and the value of Ppv is obtained through detection. The detection method belongs to the existing technology and will not be repeated here.

[0039] The first power value is Ps_dcdc. The first power value Ps_dcdc is less than the grid dispatching power value A and the difference between the first power value Ps_dcdc and the grid dispatching power value A is greater than the fluctuation amplitude when the inverter steadily outputs the grid power value dispatching value A. In this application, the first power value Ps_dcdc is also greater than the maximum operating power value (Pbat_chargeMax and Pbat_DischargeMax) allowed by the DC converter.

[0040] The control method of the solar storage system includes:

[0041] When the sum of the photovoltaic power generation power value Ppv and the maximum discharge power value Pbat_DischargeMax is less than the first power value Ps_dcdc, the DC converter is controlled to discharge and the discharge power value is equal to the maximum discharge power value Pbat_DischargeMax;

[0042] When the sum of the photovoltaic power generation power value Ppv and the maximum discharge power value Pbat_DischargeMax is greater than or equal to the first power value Ps_dcdc, less than the grid dispatch power value A, and the photovoltaic power generation power value Ppv is less than or equal to the first power value Ps_dcdc, the DC converter is controlled to discharge and the discharge power value is equal to the first difference between the first power value Ps_dcdc and the photovoltaic power generation power value Ppv;

[0043] When the photovoltaic power generation power value Ppv is greater than the first power value Ps_dcdc and the difference between the photovoltaic power generation power value Ppv and the maximum charging power value Pbat_chargeMax is less than or equal to the grid dispatching power value A, the DC converter is controlled to charge and the charging power value is equal to the second difference between the photovoltaic power generation power value Ppv and the first power value Ps_dcdc;

[0044] When the difference between the photovoltaic power generation power value Ppv and the maximum charging power value Pbat_chargeMax is greater than the grid dispatching power value A, the DC converter is controlled to charge and the charging power value is equal to the maximum charging power value Pbat_chargeMax.

[0045] Specifically, there are the following scenarios:

[0046] Scenario 1: Ppv+Pbat_DischargeMax <Ps_dcdc

[0047] The inverter's output power value, Pfb, is the sum of the photovoltaic power generation value, Ppv, and the DC converter's output power value, Pbat_DischargeMax. In this scenario, the inverter's output power value, Pfb, is less than the first power value, Ps_dcdc, and thus less than the grid dispatch power value, A. The photovoltaic power generation value, Ppv, changes over time, and the inverter's output power value, Pfb, changes with the photovoltaic power generation value, Ppv. That is, the inverter's output power value, Pfb, tracks the photovoltaic power generation value, Ppv. The photovoltaic power generation value, Ppv, exists in the following two situations.

[0048] Case 1: When the photovoltaic power value Ppv is less than the set second power value, the photovoltaic module is disconnected from the inverter. At this time, the output power value Pfb of the inverter is equal to the output power value of the DC converter, that is, the maximum discharge power value Pbat_DischargeMax, corresponding to Figure 2 The second power value can be set according to actual needs and is not limited here.

[0049] Therefore, in this scenario, the DC converter must be operated at the maximum discharge power value Pbat_DischargeMax to keep the output power value Pfb of the solar energy storage system at the maximum.

[0050] Case 2: PV module output power value, the inverter output power value Pfb is the sum of the PV power generation power value Ppv and the DC converter output power value Pbat_DischargeMax. At this time, the inverter output power value Pfb changes with the change of the PV power generation power value Ppv, that is, the inverter output power value Pfb tracks the PV power generation power value Ppv, so that the PV storage system outputs the largest possible power value to the grid, corresponding to Figure 2 Phase 2 and Phase 6 of the

[0051] Scenario 2: Ps_dcdc ≤ Ppv + Pbat_DischargeMax

[0052] In this scenario, the output power value Pfb of the inverter is close to the grid dispatching power value A, but because the output power value Pfb of the inverter has a fluctuation amplitude, the output power value Pfb of the inverter may coincide with the grid dispatching power value A when fluctuating. Therefore, the upper and lower fluctuation ranges of the output power value Pfb of the inverter should be staggered with the grid dispatching power value A as much as possible. That is, the difference between the grid dispatching power value A and the first power value Ps_dcdc is greater than the fluctuation amplitude when the inverter stably outputs the grid dispatching power value A. In this scenario, the photovoltaic power generation power value Ppv may be greater than the first power value Ps_dcdc, or it may be less than or equal to the first power value Ps_dcdc. That is, there are the following two situations:

[0053] Case 1: Ppv≤Ps_dcdc

[0054] At this time, the DC converter is controlled to discharge and the discharge power is equal to the first difference value obtained by subtracting the photovoltaic power value Ppv from the first power value Ps_dcdc; specifically, as Figure 3 ​As shown, the inverter output power value Pfb is obtained at every manually set interval, and the cumulative error between the inverter output power value Pfb and the first power value Ps_dcdc is correspondingly included in the first difference to form a third difference. If the third difference is less than the maximum discharge power value Pbat_DischargeMax, the DC converter is controlled within the interval to make the discharge power value of the energy storage system equal to the third difference, and the theoretical set value Pdcdc_ref is output; if the third difference is greater than or equal to the maximum discharge power value Pbat_DischargeMax, the DC converter is controlled within the interval to make the energy storage system discharge power value equal to the third difference, and the theoretical set value Pdcdc_ref is output; if the third difference is greater than or equal to the maximum discharge power value Pbat_DischargeMax, the DC converter is controlled within the interval to make the energy storage system discharge power value equal to the third difference. The system's discharge power value is equal to the maximum discharge power value Pbat_DischargeMax, and the theoretical set value Pdcdc_ref is output. At this point, Pdcdc_ref is still a theoretical set value. The energy storage-side DC converter adjusts its output power based on the set operating power Pdcdc_ref. Specifically, the DC converter calculates the theoretical current value using the theoretical set value Pdcdc_ref in combination with the DC converter's voltage value. By adjusting the DC converter's current loop, the actual current value is obtained, and thus, the actual operating power is obtained in combination with the DC converter's voltage value. The controller PI calculates the cumulative error between the inverter output power value Pfb and the first power value Ps_dcdc. This not only maintains the inverter output power value Pfb at the first power value Ps_dcdc, forming a plateau, but also allows the inverter output power value Pfb to serve as real-time feedback of the energy storage system's actual discharge power value, making the calculation of the energy storage system's discharge power value more accurate.

[0055] Case 2, Ppv>Ps_dcdc,

[0056] At this time, the DC converter is controlled to charge and the charging power value is equal to the second difference obtained by subtracting the first power value Ps_dcdc from the photovoltaic power value Ppv; specifically, as Figure 3As shown, the cumulative error between the inverter output power value Pfb and the first power value Ps_dcdc is correspondingly included in the second difference to form a fourth difference. If the fourth difference is less than the maximum charging power value Pbat_chargeMax, the DC converter is controlled to ensure that the energy storage system's charging power value is equal to the fourth difference within the interval, and the theoretical set value Pdcdc_ref is output. If the fourth difference is greater than or equal to the maximum charging power value Pbat_chargeMax, the DC converter is controlled to ensure that the energy storage system's charging power value is equal to the maximum charging power value Pbat_chargeMax within the interval, and the theoretical set value Pdcdc_ref is output. The DC converter on the energy storage side adjusts its actual output power based on the set operating power Pdcdc_ref, using the same adjustment scheme as in Case 1. The cumulative error between the inverter output power value Pfb and the first power value Ps_dcdc is calculated by a PI controller. This not only maintains the inverter output power value Pfb at the first power value Ps_dcdc to form a stable section, but also allows the inverter output power value Pfb to serve as real-time feedback of the actual charging power value of the energy storage system, making the calculation of the charging power value of the energy storage system more accurate.

[0057] like Figure 2 As shown, when the photovoltaic power generation value Ppv gradually increases, it enters stage 3; when the photovoltaic power generation value Ppv gradually decreases, it enters stage 5. Regardless of stage 3 or stage 5, the output power value Pfb of the inverter is the first power value Ps_dcdc, thus forming a stable segment.

[0058] At the initial moment of phase 3, the DC converter operates at the maximum discharge power value Pbat_DischargeMax, the output power value Pfb of the inverter is equal to the first power value Ps_dcdc, Ppv≤Ps_dcdc, and the output power value P of the DC converter on the energy storage side is dcdc =Ps_dcdc-Ppv.

[0059] Therefore, subsequently, due to the increase of the photovoltaic power generation power value Ppv, the discharge power value of the DC converter decreases. When the photovoltaic power generation power value Ppv increases to be greater than the first power value Ps_dcdc, the DC converter switches to the charging state; subsequently, the output power value P of the DC converter on the energy storage side increases. dcdc =Ppv-Ps_dcdc. As the PV module output power value Ppv continues to increase, the charging power value of the DC converter gradually increases until the charging power value of the DC converter reaches the maximum value; or when the second difference is greater than the maximum charging power value Pbat_chargeMax of the DC converter, the difference is made to correspond to the maximum charging power value Pbat_chargeMax.

[0060] At the initial moment of stage 5, the DC converter operates at the maximum charging power value Pbat_chargeMax, the output power value Pfb of the inverter is equal to the first power value Ps_dcdc, Ppv>Ps_dcdc, P dcdc =Ppv-Ps_dcdc.

[0061] Therefore, subsequently, due to the decrease in the output power value of the photovoltaic module, the charging power value of the DC converter decreases. When the photovoltaic power generation power value Ppv decreases to be equal to the first power value Ps_dcdc, the DC converter switches to the discharge power state. Subsequently, the output power value P of the DC converter on the energy storage side is dcdc =Ps_dcdc-Ppv, as the output power value of the PV module continues to decrease, the discharge power value of the DC converter gradually increases until the discharge power value of the DC converter reaches the maximum value; or when the first difference is greater than the maximum discharge power value Pbat_DischargeMax of the DC converter, the first difference is made to correspond to the maximum discharge power value Pbat_DischargeMax.

[0062] Scenario 3: Ppv-Pbat_chargeMax>A

[0063] In this scenario, the output power value of the photovoltaic storage system exceeds the grid dispatch power value A, which often means that the photovoltaic power generation power value Ppv is too large. At this time, making the DC converter operate at the maximum charging power value Pbat_chargeMax state is conducive to reducing the output power value Pfb of the inverter as much as possible, avoiding the waste of photovoltaic module energy, corresponding to Figure 2 Stage 4 in.

[0064] Specifically, if Figure 4 As shown, the cumulative error between the grid dispatching power value A and the inverter output power value Pfb is correspondingly included in the grid dispatching power value A to form the inverter set power value Pinv_ref. The inverter adjusts its output power value according to its set power value Pinv_ref, so that the output power value Pfb of the inverter is maintained at the grid dispatching power value A during this stage.

[0065] It can be seen that the use of this technical solution can adjust the output power value and power supply relationship of the energy storage side DC converter based on the relationship between the photovoltaic power generation value and the set first power value, the maximum charge / discharge power value of the energy storage side DC converter, and the grid dispatch power value. This is conducive to the inverter maintaining tracking of the maximum power value point of the photovoltaic module, thereby achieving effective utilization of the photovoltaic module energy. The difference between the grid dispatch power value and the first power value is greater than the fluctuation amplitude when the inverter steadily outputs the grid power value dispatch value, causing the inverter's power value loop to remain in a saturated state and fail, and the inverter's bus voltage loop to operate, thereby allowing the inverter to maintain tracking of the maximum power value point of the photovoltaic module. At the same time, it prevents the inverter's output power value from coinciding with the grid dispatch power value when it fluctuates, achieving stability of the inverter's output power value. This setting allows the inverter's output power value to remain stable and track the maximum power value point of the photovoltaic module when the output power value is close to the grid dispatch power value, achieving effective utilization of the photovoltaic module energy.

[0066] The above description and embodiments are intended to explain the scope of protection of the present invention, but do not constitute a limitation thereto. Modifications, equivalent substitutions, or other improvements to the embodiments of the present invention or portions thereof that can be obtained by a person of ordinary skill in the art through logical analysis, reasoning, or limited experimentation based on the teachings of the present invention or the above embodiments, combined with common knowledge, ordinary technical knowledge in the field, and / or prior art, should all be included within the scope of protection of the present invention.

Claims

1. A control method for a solar energy storage system, characterized in that: The photovoltaic components in the photovoltaic storage system output power to the inverter in priority to the energy storage system. The inverter is in communication with the energy storage side DC converter, and the inverter is directly connected to the photovoltaic components. A first power value is set that is less than the grid dispatching power value; the control method of the photovoltaic storage system includes: When the sum of the photovoltaic power generation power value and the maximum discharge power value of the DC converter is less than the first power value, controlling the DC converter to discharge with the discharge power equal to the maximum discharge power value; When the sum of the photovoltaic power generation power value and the maximum discharge power value of the DC converter is greater than or equal to the first power value and less than the grid dispatching power value, and the photovoltaic power generation power value is less than or equal to the first power value, controlling the DC converter to discharge with a discharge power equal to a first difference obtained by subtracting the photovoltaic power generation power value from the first power value; When the photovoltaic power generation power value is greater than the first power value and the difference between the photovoltaic power generation power value and the maximum charging power value of the DC converter is less than or equal to the grid dispatching power value, controlling the DC converter to charge with a charging power equal to a second difference obtained by subtracting the first power value from the photovoltaic power generation power value; When the difference between the photovoltaic power generation power value and the maximum charging power value of the DC converter is greater than the grid dispatching power value, controlling the DC converter to charge and the charging power is equal to the maximum charging power value; The difference between the grid dispatching power value and the first power value is greater than the fluctuation amplitude when the inverter stably outputs the grid dispatching power value; The specific method of controlling the discharge power of the DC converter to be equal to the first difference value obtained by subtracting the first power value from the photovoltaic power generation value is as follows: The inverter output power value is obtained at manually set intervals, and the cumulative error between the inverter output power value and the first power value is correspondingly included in the first difference to form a third difference. If the third difference is less than the maximum discharge power value, the DC converter is controlled within the interval so that the discharge power of the energy storage system is equal to the third difference; if the third difference is greater than or equal to the maximum discharge power value, the DC converter is controlled within the interval so that the discharge power of the energy storage system is equal to the maximum discharge power value.

2. A control method for a solar energy storage system according to claim 1, characterized in that: The specific method for controlling the DC converter charging power to be equal to a second difference value obtained by subtracting the first power value from the photovoltaic power generation value is as follows: the cumulative error between the inverter output power value and the first power value is correspondingly included in the second difference value to form a fourth difference value; if the fourth difference value is less than the maximum charging power value, then controlling the DC converter within the interval so that the charging power of the energy storage system is equal to the fourth difference value; if the fourth difference value is greater than or equal to the maximum charging power value, then controlling the DC converter within the interval so that the charging power of the energy storage system is equal to the maximum charging power value.

3. The control method of a solar energy storage system according to claim 1, wherein: The specific method of controlling the DC converter to charge and ensure that the charging power is equal to the maximum charging power value is as follows: The cumulative error between the grid dispatching power value and the inverter output power value is correspondingly included in the grid dispatching power value to form the inverter set power value, and the inverter adjusts its output power according to its set power value.

4. A control method for a solar energy storage system according to any one of claims 1 to 3, characterized in that: When the photovoltaic power generation value is less than the set second power value, the connection between the photovoltaic module and the inverter is disconnected; the power supply relationship and output power of the DC converter on the energy storage side are determined by the working mode of the inverter and the grid dispatching power.

5. A solar storage system, characterized in that: Including photovoltaic modules, inverters, energy storage systems and energy storage side DC converters; The inverter is communicatively connected to the DC converter; The output end of the photovoltaic module is directly connected to the DC side of the inverter; The energy storage system is connected to the DC bus of the inverter through the DC converter; The photovoltaic storage system is used to execute the control method according to any one of claims 1 to 3.

6. The solar storage system according to claim 5, characterized in that: The output end of the photovoltaic assembly is connected to the DC side of the inverter through a DC circuit breaker; the DC circuit breaker is used to disconnect when the photovoltaic power generation power value is less than a set second power value.

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