A method for state of charge management of an energy storage device of a light storage system

Abstract

The application provides a kind of optical storage system energy storage device state of charge management method, it is related to optical storage system control technical field, solve the optical storage system with initiative support ability and through energy storage device control direct current bus voltage, energy storage device overcharge / overdischarge leads to state of charge out of limit, simple cut off energy storage easy to cause system instability problem.The technical scheme is: set energy storage state of charge safety range and hierarchical limit threshold, build upper and lower limit management strategy.Lower limit side according to state of charge dynamic adjustment active droop coefficient, when out of limit, utilize photovoltaic power small power charging recovery;Upper limit side cut off energy storage, switch photovoltaic control target to maintain direct current bus voltage stability, balance photovoltaic and net side power, guarantee energy storage safety and system stability.

Description

Technical Field

[0001] This application belongs to the field of photovoltaic energy storage system control technology, and relates to a method for managing the state of charge of a photovoltaic energy storage device. Background Technology

[0002] As the proportion and installed capacity of new energy sources such as wind and solar power connected to the grid via inverters continue to expand, the future power system will be a "dual-high" system characterized by a high proportion of renewable energy and a high proportion of power electronic equipment. When voltage and frequency disturbances occur in the grid, inverters used in solar and other new energy applications may experience a mismatch between the system's required output power and the output power of the new energy sources. Therefore, energy storage devices are needed to buffer this power imbalance.

[0003] When configuring energy storage in a photovoltaic (PV) system, a suitable coupling method needs to be selected based on the structure of the PV power generation unit. Firstly, the energy storage device can be connected to the AC side of the PV system via an inverter, known as AC coupling. Besides AC coupling, the energy storage device can also be connected to the DC bus, known as DC coupling. DC coupling can be further divided into two types: direct connection of the energy storage to the DC bus and connection via an inverter.

[0004] In photovoltaic-storage systems, the control strategies for grid-side converters are mainly divided into grid-following control and grid-connected control. Grid-following control relies on the grid voltage synchronization signal (such as a phase-locked loop) and connects to the grid as a current source. It lacks autonomous voltage and frequency regulation capabilities, but can adjust active power through additional active power droop control to participate in primary frequency regulation, providing a certain frequency support capability, i.e., based on the grid frequency deviation (Δ... f Adjust active power (Δ) P 0), the expression is Δ P 0=- k p ×Δ f The grid-connected control system simulates the operating characteristics of a synchronous generator, autonomously establishing voltage and frequency, and connecting to the grid as a voltage source. It possesses stronger active support capabilities, able to achieve frequency support directly through the active power droop factor without relying on external commands, and also based on the grid frequency deviation (Δ). f Autonomous adjustment of active power (Δ) P The expression is Δ P =- k p ×Δ f Thus, it directly participates in a frequency modulation.

[0005] To ensure normal system operation, photovoltaic (PV) power generation systems with a DC bus require DC bus voltage stability control. Currently, DC bus control methods can be broadly categorized into three types: the first maintains DC bus voltage by adjusting PV power to match the output power of the grid-side converter; the second maintains DC bus voltage by adjusting the output power of the grid-side converter to match the PV power; and the third maintains DC bus voltage by controlling the charging / discharging of energy storage devices to buffer the power imbalance between PV power and grid-side converter output power. The method of controlling DC bus voltage by adjusting PV power is mostly used in PV systems without energy storage; the method of controlling DC bus voltage by adjusting grid-side power relies on the grid-side response speed and is suitable for grid-connected control applications with faster grid-side response; the method of controlling DC bus voltage through energy storage devices has a fast response speed and is suitable for grid-connected control applications with slower grid-side response, and can also be used in applications where grid-connected control is employed.

[0006] The state of charge (SOC) of an energy storage device is an important indicator for measuring its remaining capacity. It represents the ratio of the device's current remaining capacity to its fully charged capacity, usually expressed as a percentage, with a value ranging from 0% to 100%. Because energy storage devices need to charge and discharge according to different operating conditions, there is a possibility that overcharging or over-discharging can cause the SOC to exceed the safe operating range. Therefore, SOC management methods are needed to ensure the safety of energy storage devices.

[0007] In a photovoltaic-energy storage system where the DC bus voltage is controlled by an energy storage device, the system disconnects the energy storage device from the system once its state of charge reaches or exceeds a safe range, preventing it from charging / discharging. However, simply disconnecting the energy storage device from the system may cause the DC bus voltage to run away from control, ultimately leading to system instability, because the energy storage device needs to control the DC bus voltage.

[0008] The energy storage device of a photovoltaic energy storage system with active support capability and control of DC bus voltage through energy storage device may cause the state of charge to exceed the safe operating range due to overcharging or over-discharging. If the energy storage device is simply disconnected from the system, although the safety of the energy storage device can be guaranteed, it is easy to cause system instability. Summary of the Invention

[0009] This invention provides a method for managing the state of charge (SOC) of an energy storage device in a photovoltaic-storage system. The technical problem it solves is that in photovoltaic-storage systems with active support capabilities and DC bus voltage control via the energy storage device, the energy storage device is prone to exceeding the safe operating range due to overcharging or over-discharging. Simply disconnecting the energy storage device can lead to DC bus voltage runaway and system instability. The invention aims to improve the adaptability and reliability of photovoltaic-storage systems under complex power grid conditions.

[0010] To achieve the above objectives, this application employs the following technical means: In a first aspect, this application provides a method for managing the state of charge (SOC) of an energy storage device in a photovoltaic-energy storage system, comprising: By setting the safe operating range and graded limit thresholds for the state of charge (SOC) of energy storage devices, a collaborative control mechanism is constructed between the lower limit management strategy and the upper limit management strategy for SOC. The graded limit thresholds include the variable active power droop coefficient activation threshold (SOC) located above the safe lower limit of SOC. lim1 and governor off threshold SOC lim2 ; The specific state-of-charge (SOC) management strategy is as follows: when the energy storage device's state of charge drops to its maximum charge (SOC)... lim1 At that time, based on the state of charge and SOC lim2 The difference dynamically reduces the active power droop factor of the grid-side converter, balancing the output power of the photovoltaic array with that of the grid-side converter to suppress the decline in state of charge; when the state of charge drops to SOC... lim2 When the active power droop factor is set to 0 and the system frequency support function is turned off; when the state of charge is below the safe lower limit SOC min At that time, the output power of the grid-side converter is further reduced to below the output power of the photovoltaic array, and the excess photovoltaic power is used to charge the energy storage device at a low power until the state of charge is restored to a safe range.

[0011] As a further improvement to this application, the state of charge (SOC) upper limit management strategy is specifically as follows: when the energy storage device's SOC reaches the safe upper limit... max When the energy storage device is disconnected from the system, the corresponding converter is shut down. At the same time, the control target of the photovoltaic array is switched from adjusting the photovoltaic operating point to maintaining the DC bus voltage stability. The output power of the photovoltaic array is reduced to balance the output power of the grid-side converter.

[0012] As a further improvement to this application, the active power droop factor of the grid-side converter is based on the state of charge (SOC) of the energy storage device. lim2 The difference is adjusted in a linear decreasing trend, or by adopting a non-linear adjustment method of exponential decrease or segmented step decrease.

[0013] As a further improvement to this application, the SOC lim2 Higher than SOC min The SOC lim1 Higher than SOC lim2 A control response margin is reserved between the two threshold levels.

[0014] As a further improvement of this application, the photovoltaic array control target is switched to maintain the stability of the DC bus voltage, so that the DC bus voltage does not fluctuate significantly during the system power balance process.

[0015] As a further improvement of this application, the photovoltaic array is connected to the DC bus through a boost DC / DC chopper, and the adjustment of the photovoltaic operating point is achieved by changing the duty cycle of the boost chopper; when the control target of the photovoltaic array is switched to maintaining the stability of the DC bus voltage, a dual closed-loop control strategy of the outer loop of DC bus voltage and the inner loop of photovoltaic current is adopted, and the DC bus voltage is stabilized by adjusting the duty cycle of the boost chopper.

[0016] As a further improvement of this application, the energy storage device is connected to the DC bus via a bidirectional DC / DC converter, and the DC bus voltage is adjusted by changing the duty cycle of the bidirectional DC / DC converter on the energy storage side; the bidirectional DC / DC converter adopts proportional-integral resonant control, and the resonant frequency is twice the grid frequency, so as to suppress the second harmonic ripple of the DC bus voltage.

[0017] As a further improvement of this application, the energy storage device includes any one or more combinations of supercapacitors, lithium batteries, and sodium batteries, and when there are multiple combinations, each energy storage device is connected in parallel to the DC bus through its corresponding bidirectional DC / DC converter.

[0018] As a further improvement to this application, the grid-side converter control strategy of the photovoltaic-storage system also includes grid-type control and supercapacitor voltage outer loop control. The grid-based control includes: First, by collecting the output capacitor voltage and grid-side current signal, the real-time output power of the system is obtained through the power calculation module; Second, by simulating the governor equation and rotor oscillation equation of the synchronous generator through electromechanical transients, the virtual phase angle and induced electromotive force are calculated in combination with electromagnetic transients; Subsequently, a virtual impedance link is introduced to generate the inverter modulation wave reference voltage; Finally, the inverter power switching devices are driven to transmit the power of the new energy power generation unit to the grid. The outer loop control of the supercapacitor voltage includes: considering the relationship between the state of charge of the supercapacitor and its terminal voltage, controlling the state of charge of the supercapacitor by controlling its terminal voltage, adding a supercapacitor voltage outer loop with a minute-level response speed to manage the state of charge on the basis of the basic grid-type control, and slowly adjusting the state of charge of the supercapacitor by adjusting the active power command P0vsg of the grid-type control.

[0019] As a further improvement to this application, the control strategy of the photovoltaic-storage system also includes a photovoltaic-side control strategy and a supercapacitor-side control strategy; Photovoltaic-side control strategies include: increasing photovoltaic power feedforward, and shifting photovoltaic power... Increased as a feedforward term to In the photovoltaic (PV) side, power reserve control is employed. During each power reserve control cycle, the maximum output power of the PV array is first determined using the maximum power point tracking (MPPT) method. Record this power value unchanged until the next cycle, and calculate the actual power output of the photovoltaic array for the remaining time in this cycle. The system controls the photovoltaic array to switch between maximum power point tracking (MPPT) mode and constant power generation mode. When changes in ambient irradiance or temperature affect the photovoltaic output characteristics, the system can update its operation via MPPT. and ; The supercapacitor-side control strategy includes: using a bidirectional chopper on the supercapacitor side to stabilize the DC bus voltage; the control on the supercapacitor side is based on the voltage and current dual closed-loop control, and the outer loop of the DC bus voltage is improved from proportional-integral control to proportional-integral resonant control; at the same time, a virtual rotor kinetic energy feedforward control is added.

[0020] Compared with the prior art, this application has the following advantages: This invention designs a hierarchical and collaborative management strategy to address the two core issues of overcharging and over-discharging in energy storage devices. This avoids the system instability risks caused by simply disconnecting energy storage devices, significantly improving the operational reliability and adaptability of photovoltaic-storage systems under complex grid conditions. For over-discharging scenarios, power balance is achieved by dynamically adjusting the active power droop coefficient, supplemented by low-power charging to restore the state of charge. This ensures the hardware safety of the energy storage devices while maximizing the system's active support capability. For overcharging scenarios, the coordinated action of energy storage disconnection and photovoltaic control target switching avoids overcharging of the energy storage while quickly balancing photovoltaic and grid-side power, effectively suppressing DC bus voltage runaway. The entire technical solution does not rely on complex hardware modifications. Multiple objectives are achieved through optimized software control logic, adapting to various energy storage types. It is highly practical, and the control process is smooth, avoiding sudden changes in system power or voltage, further ensuring the stable operation of the grid and the photovoltaic-storage system. Attached Figure Description

[0021] Figure 1 This is a structural diagram of a photovoltaic-storage system; Figure 2 A flowchart illustrating the state-of-charge management method for energy storage devices; Figure 3 For variable active power droop coefficient control based on state of charge; Figure 4 This is a control block diagram for the energy storage charge state limit management strategy; Figure 5 Photovoltaic PU curve; Figure 6 Control block diagram for energy storage state of charge upper limit management strategy; Figure 7 The control block diagram of an existing grid-type photovoltaic converter based on supercapacitor energy storage is shown. Figure 8 This is a block diagram of the electromechanical transient control section; Figure 9 This is a block diagram of the electromagnetic transient control section; Figure 10 The diagram shows the outer loop control block diagram for the supercapacitor voltage; (a) maximum power sampling; (b) maximum power hold; (c) photovoltaic power standby. Figure 11 Workflow for photovoltaic power backup control; Figure 12 This is a control block diagram of the supercapacitor-side converter; Figure 13 For state-of-charge recovery control; Figure 14 This is a block diagram showing the switching of control strategies on the photovoltaic side. Figure 15 Waveform diagram of the supercapacitor charge limit management strategy experiment; Figure 16 Waveform diagram of the experimental strategy for managing the upper limit of the state of charge of supercapacitors; In the picture: Photovoltaic voltage; Photovoltaic current; Photovoltaic power; Boost chopper duty cycle; Supercapacitor voltage; Reference value for supercapacitor voltage; Supercapacitor discharge current; Duty cycle of the bidirectional chopper; DC bus voltage; DC bus voltage reference value; Reference value for supercapacitor current; Three-phase output voltage; Three-phase output current; Output active power; No reactive power output; Active power reference value; Virtual rotor input power; Modulation voltage. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0023] This invention proposes a method for managing the state of charge (SOC) of energy storage devices in a photovoltaic-energy storage system. To prevent the SOC of the energy storage devices from exceeding the safe operating range during charging / discharging, this invention designs a hierarchical management mechanism for the SOC of the energy storage devices. This mechanism dynamically adjusts the active power droop coefficient and the photovoltaic operating point to maintain the SOC of the energy storage devices within the safe operating range while ensuring the safe and stable operation of the system.

[0024] This invention is applicable to photovoltaic-energy storage systems where the energy storage device is connected to a DC bus structure via a converter, such as... Figure 1 The diagram shown is a structural diagram of a photovoltaic-storage system. The strategy proposed in this invention is applicable to photovoltaic-storage systems with active support capabilities and DC bus voltage controlled by energy storage devices. There are no specific requirements regarding the form of the energy storage devices or the grid-side control strategy. This invention improves the adaptability and reliability of photovoltaic-storage systems with active support capabilities and DC bus voltage controlled by energy storage devices under complex grid operating conditions.

[0025] Specifically, this invention provides a method for managing the state of charge (SOC) of an energy storage device in a photovoltaic-energy storage system. This method is applied to a photovoltaic-energy storage system with active support capabilities and where the DC bus voltage is controlled by the energy storage device. The photovoltaic-energy storage system includes a photovoltaic array, an energy storage device, a converter, and a grid-side converter. By setting a safe operating range and tiered limit thresholds for the SOC of the energy storage device, a collaborative control mechanism is constructed between a lower limit SOC management strategy and a higher limit SOC management strategy. The tiered limit thresholds include a variable active power droop coefficient activation threshold (SOC) located above the safe lower limit SOC. lim1 and governor off threshold SOC lim2 ; The specific state-of-charge (SOC) limit management strategy is as follows: when the state of charge of the energy storage device drops to SO... Clim1 At that time, based on the state of charge and SOC lim2 The difference dynamically reduces the active power droop factor of the grid-side converter, balancing the output power of the photovoltaic array with that of the grid-side converter to suppress the decline in state of charge; when the state of charge drops to SOC... lim2 When the active power droop factor is set to 0 and the system frequency support function is turned off; when the state of charge is below the safe lower limit SOC min At the same time, the output power of the grid-side converter is further reduced to below the output power of the photovoltaic array, and the excess photovoltaic power is used to charge the energy storage device at a low power until the state of charge is restored to a safe range. The specific strategy for managing the upper limit of the state of charge (SOC) is as follows: when the energy storage device reaches the safe upper limit of SOC... maxWhen the energy storage device is disconnected from the system, the corresponding converter is shut down. At the same time, the control target of the photovoltaic array is switched from adjusting the photovoltaic operating point to maintaining the DC bus voltage stability. By raising the output voltage of the photovoltaic array to reduce its output power, the output power of the photovoltaic array is balanced with the output power of the grid-side converter, thus avoiding the DC bus voltage runaway.

[0026] When the photovoltaic-storage system enters an active support transient state and the energy storage device stops charging / discharging due to its state of charge exceeding the safe operating range, if the grid-side converter is in a situation where increased output power is required, considering that the output power of the photovoltaic array has a maximum value, it is impossible to continuously increase the photovoltaic power to meet the grid-side power demand. In this case, only a portion of the active support capability can be sacrificed to reduce the grid-side power and achieve a balance between photovoltaic power and grid-side power. If the grid-side converter is in a situation where reduced output power is required, considering that the output power of the photovoltaic array can be reduced to 0, the photovoltaic operating point can be adjusted to reduce the photovoltaic power and achieve a balance between photovoltaic power and grid-side power.

[0027] Therefore, the state of charge (SOC) management method for energy storage devices in a photovoltaic-energy storage system proposed in this invention is divided into an SOC limit management strategy to address over-discharge and an SOC upper limit management strategy to address over-charging. When the SOC of the energy storage is too high, the energy storage device is disconnected from the system, and the photovoltaic operating point is adjusted to reduce photovoltaic power and suppress the increase of SOC. When the SOC of the energy storage is too low, the active support capability on the grid side is reduced to decrease the grid-side output power and suppress the decrease of SOC. If the SOC continues to decrease, the energy storage device is charged with low power to slowly restore the SOC. The overall flowchart is as follows. Figure 2 The diagram shown is a flowchart of the state of charge management method for energy storage devices.

[0028] 1) State-of-charge limit management strategy When the grid needs to increase its active power output to support the grid frequency, the photovoltaic array has a maximum power output and cannot continuously increase its power to meet the system's output power requirements. The remaining power is supplied by the energy storage device discharging, and the energy storage's state of charge begins to decline. If the grid frequency deviation is too large or remains at a low level for a long period, the energy storage may experience over-discharge, causing its state of charge to exceed the safe lower limit.

[0029] The proposed energy storage state of charge (SOC) lower limit management strategy is as follows: When the SOC approaches the safe lower limit, the system output power is reduced by actively decreasing or shutting down the system's frequency support capability, making the photovoltaic power equal to the system output power and suppressing the downward trend of SOC. If the SOC falls below the safe lower limit, the system's frequency support function is completely shut down, and the grid-side output power is further reduced to be lower than the photovoltaic power. The excess photovoltaic power is then used for low-power charging of the energy storage to restore its SOC to a safe range.

[0030] The larger the active power droop coefficient of the system, the greater the additional power output of the frequency support transient, and the stronger the frequency support capability. Therefore, this invention reduces the grid-side power by reducing the active power droop coefficient, so that the photovoltaic power and the grid-side power can be balanced.

[0031] like Figure 3 As shown, the present invention limits the State of Charge (SOC) of energy storage. min Two levels of state of charge (SOC) limiting thresholds are set above. lim1 and SOC lim2 SOC lim1 To achieve a variable active power droop factor initiating the state of charge (SOC), lim2 To disable the charging state of the speed controller. For example... Figure 3 Point A, when the energy storage state of charge drops to SOC lim1 Then, the system initiates variable active power droop control based on the state of charge (SOC). The active power droop coefficient in the speed governor will be adjusted according to the energy storage SOC and the SOC. lim2 The difference decreases (this invention takes linear descent as an example; other reduction methods can be used), such as... Figure 3 Points A to C are shown, thus dynamically balancing photovoltaic power and system output power. When they are equal, the state of charge stops decreasing, and the active power droop coefficient reaches a stable point, as shown below. Figure 3 As shown at point B.

[0032] If the energy storage state of charge does not stabilize in time, it will further decrease to SOC. lim2 The system sets the active power droop factor to 0, disables the system's frequency support function, and prevents the energy storage from continuing to discharge. Figure 3 Point C. Under this control, when the energy storage state of charge approaches the lower limit of the safe range, the active power droop coefficient can be adaptively adjusted according to the energy storage state of charge, so that the photovoltaic power is equal to the grid-side output power, ensuring the safety of the energy storage state of charge.

[0033] Limiting the drop in the state of charge (SOC) of energy storage by changing the active power droop factor requires a certain response time, and its dynamic performance is constrained by the bandwidth of the grid configuration. When the disturbance is too large, the energy storage may experience a continuous discharge, causing its SOC to fall below the level of the system's output power before the photovoltaic power and system output power reach equilibrium. lim2 Therefore, it is necessary to ensure SOC lim2 Higher than SOC min To leave a certain margin, such as Figure 3 Points C and D. Meanwhile, during the adjustment of the active power droop factor, the variable active power droop factor control may not respond in a timely manner, resulting in the energy storage state of charge (SOC) being lower than the state of charge (SOC). minTo mitigate the risks associated with energy storage hardware, the system will initiate state-of-charge (SOC) recovery control. This involves further reducing the grid-side output power below the photovoltaic (PV) power, after completely shutting down the system's frequency support function. The excess PV power is then used to charge the energy storage device, restoring its SOC. However, excessive reduction in grid-side output power could exacerbate system power imbalances and worsen grid frequency. Therefore, the charging power for energy storage should be relatively low, and the charging process should be initiated only when the energy storage's SOC is restored. min After the above steps, the energy storage should exit the state-of-charge recovery control and stop charging. Finally, when the grid frequency recovers, the system re-enters normal operating mode, and the energy storage begins to restore its state of charge to the preset value. The control block diagram for the energy storage state-of-charge limit management strategy is as follows: Figure 4 As shown.

[0034] 2) Energy storage state of charge upper limit management strategy When the grid side needs to reduce its active power output while providing active support to the grid, energy storage may exceed the safe limit of state of charge due to overcharging.

[0035] To address this, this invention proposes a state-of-charge (SOC) upper limit management strategy for energy storage: When the SOC reaches the safe upper limit, on the energy storage side, the energy storage-side converter is shut down to disconnect it from the system, preventing further charging of the energy storage and thus avoiding exceeding the safe SOC. On the photovoltaic (PV) side, the control objective of the PV-side converter shifts from adjusting the PV operating point to maintaining DC bus voltage stability, reducing PV power to match the system output power. When the grid frequency recovers, the energy storage-side converter restarts, and the control objective of the PV-side converter returns to adjusting the PV operating point. This strategy does not change the system's output power and therefore does not affect the system's active support capability.

[0036] At the instant the energy storage's state of charge reaches its safe limit and the energy storage-side converter stops operating, because the photovoltaic power exceeds the grid-side inverter's output power, the power difference will charge the DC bus capacitor, causing the DC bus voltage to rise rapidly. The photovoltaic array's output voltage will rise along with the DC bus voltage. According to the photovoltaic array's power efficiency curve (PU), its output power will gradually decrease. Figure 5 The graph shows the photovoltaic power generation (PU) curve. As indicated by the arrows, the power difference between the photovoltaic power and the grid-side output power decreases, and the rate of increase of the DC bus voltage slows down.

[0037] Simultaneously, as the photovoltaic array switches to maintaining DC bus voltage stability, after the DC bus voltage rises due to the disconnection of energy storage, the photovoltaic-side converter further increases the photovoltaic output voltage to reduce output power. Ultimately, this achieves a balance between photovoltaic power and system output power while stabilizing the DC bus voltage. The control block diagram for the frequency-supported transient energy storage state-of-charge upper limit management strategy is shown below. Figure 6 As shown.

[0038] Optionally, the active power droop coefficient of the grid-side converter is adjusted linearly based on the difference between the state of charge of the energy storage device and SOClim2, or by adopting a nonlinear adjustment method of exponential or segmented step-down; for example, the adjustment rate of the active power droop coefficient does not exceed 0.05 kW / Hz. This is to avoid system frequency or voltage oscillations caused by sudden changes in grid-side output power.

[0039] Optionally, when charging the energy storage device at low power, the charging power shall not exceed 20% of the current output power of the photovoltaic array, and the charging current shall not exceed 30% of the rated charging current of the energy storage device; when the state of charge of the energy storage device recovers to the range of 5% to 10% above SOCmin, the state of charge recovery control shall be immediately exited and charging shall be stopped, and the active power droop coefficient of the grid-side converter shall be restored to the initial setting value.

[0040] Optionally, SOC lim2 Higher than SOC min For example, SOC lim2 With SOC min The difference is SOC min 5%~15%; the SOC lim1 Higher than SOC lim2 For example, SOC lim1 With SOC lim2 The difference is SOC min The control response margin is reserved by reasonably spacing the two thresholds between 8% and 20% to prevent the energy storage device from rapidly exceeding the safe lower limit of state of charge.

[0041] Optionally, after the photovoltaic array control target is switched to maintaining the stability of the DC bus voltage, the stability control accuracy of the DC bus voltage is ±2% of the rated DC bus voltage, ensuring that the DC bus voltage does not fluctuate significantly during the system power balance process.

[0042] Optionally, the photovoltaic array is connected to the DC bus via a boost DC / DC chopper, and the photovoltaic operating point is adjusted by changing the duty cycle of the boost chopper. When the photovoltaic array control target is switched to maintaining the DC bus voltage stability, the duty cycle of the boost chopper is reduced through dual closed-loop control of the DC bus voltage outer loop and the photovoltaic current inner loop, thereby increasing the output voltage of the photovoltaic array to precisely reduce its output power.

[0043] Optionally, the energy storage device is connected to the DC bus via a bidirectional DC / DC converter, which employs proportional-integral resonant control with a resonant frequency twice the grid frequency to suppress the second harmonic ripple of the DC bus voltage.

[0044] Optionally, the state of charge of the energy storage device can be obtained indirectly by detecting its terminal voltage, specifically: When the energy storage device is a lithium battery or sodium battery, a voltage-state-of-charge (V-SOC) mapping curve is pre-stored. The current state of charge is calculated by querying the mapping curve through the real-time detected terminal voltage.

[0045] The energy storage device includes any one or more combinations of supercapacitors, lithium batteries, and sodium batteries. When there are multiple combinations, each energy storage device is connected in parallel to the DC bus through its corresponding bidirectional DC / DC converter.

[0046] For example, after the control target of the photovoltaic array is switched, if the DC bus voltage exceeds ±5% of the rated value, the photovoltaic power emergency limiting mechanism will be activated to forcibly reduce the output power of the photovoltaic array to 95%~100% of the current output power of the grid-side converter, thereby quickly suppressing the abnormal rise in DC bus voltage.

[0047] This invention designs corresponding energy storage state of charge management methods for the overcharge and over-discharge risks of energy storage devices in photovoltaic energy storage systems with active support capabilities and DC bus voltage control via energy storage devices. This ensures that the system will not shut down due to the energy storage state of charge exceeding the safe operating range, thereby improving the operational reliability of photovoltaic energy storage systems with active support capabilities under complex power grid conditions.

[0048] The energy storage state of charge lower limit management strategy proposed in this invention suppresses the downward trend of the state of charge by reducing the active power droop coefficient when the energy storage state of charge is close to the lower limit. After the state of charge reaches the lower limit, the energy storage is restored to a safe range by charging. This can ensure the safety of the energy storage device during discharge and the stability of the DC bus voltage.

[0049] The energy storage state of charge upper limit management strategy proposed in this invention shuts down the energy storage-side converter after the energy storage state of charge reaches the upper limit, ensuring the safety of energy storage. At the same time, the photovoltaic side adjusts the operating point by maintaining the DC bus voltage, so that the photovoltaic power matches the grid-side output power, ensuring the stability of the DC bus voltage.

[0050] This invention designs corresponding state-of-charge (SOC) management methods for energy storage devices in photovoltaic-energy storage systems with active support capabilities and DC bus voltage control via energy storage devices, addressing overcharging and over-discharging. These methods offer broad protection and improve the operational reliability of such systems. In these systems, before the SOC of the energy storage device reaches its lower limit, the system reduces the active power droop factor to suppress the SOC decline trend based on the current SOC. After reaching the lower limit, the system performs a short-term charge to quickly restore the SOC. Conversely, after the SOC of the energy storage device reaches its upper limit, the energy storage-side converter is shut down while the photovoltaic side is used to maintain DC bus voltage stability.

[0051] The following are specific embodiments of the control strategy proposed in this application: A typical existing grid-connected photovoltaic system based on supercapacitor energy storage has the following overall control block diagram: Figure 7 As shown, the photovoltaic array of this system is connected to the DC bus via a boost-type DC / DC chopper, while the supercapacitor energy storage uses a bidirectional DC / DC chopper connected in parallel to the same DC bus. Finally, grid-connected operation is achieved through a grid-side inverter. Specifically: the boost chopper provides power reserve by adjusting the operating point of the photovoltaic array; the bidirectional chopper on the energy storage side is responsible for maintaining stable bus voltage, ensuring dynamic power balance between the power generation unit and the grid; and the inverter provides necessary active support capabilities for the system through grid-based control.

[0052] It should be noted that although the embodiments of this invention use supercapacitors as energy storage devices, the control method proposed in this invention can be applied to different energy storage devices. Furthermore, the structures and control methods of the photovoltaic side, energy storage side, and grid side in this embodiment are not limited to this specific embodiment; it is sufficient that the energy storage device controls the DC bus voltage through the converter, and the grid-side control strategy can provide active support. Figure 7 This is a control block diagram of an existing grid-type photovoltaic converter based on supercapacitor energy storage.

[0053] The grid-side converter control strategy for photovoltaic-storage systems also includes grid-based control and supercapacitor voltage outer-loop control. This invention employs grid-based control on the grid side. The core implementation process of grid-based control includes: first, acquiring the output capacitor voltage and grid-side current signals, and obtaining the system's real-time output power through a power calculation module; second, using electromechanical transient simulation of the synchronous generator's governor equation and rotor oscillation equation, combined with electromagnetic transient calculations, to determine the virtual phase angle and induced electromotive force; subsequently, introducing a virtual impedance link to generate the inverter modulation wave reference voltage; finally, driving the inverter's power switching devices to transmit the power from the renewable energy generation unit to the grid. The control block diagram is as follows: Figure 8 , Figure 9 As shown. Figure 8 This is a block diagram of the electromechanical transient control section; Figure 9 This is a block diagram of the electromagnetic transient control section.

[0054] Considering the linear relationship between the state of charge (SOC) and terminal voltage of a supercapacitor, its SOC can be controlled by controlling the terminal voltage. Therefore, to stabilize the SOC of the supercapacitor near its rated standby value, a specific embodiment adds a slower-responding (minute-level) supercapacitor voltage outer loop to the basic grid-type control to achieve SOC management control. The SOC of the supercapacitor is slowly adjusted by regulating the active power command P0vsg of the grid-type control. Simultaneously, to reduce the supercapacitor's involvement in absorbing photovoltaic power fluctuations during active power command regulation, photovoltaic power feedforward is added to redirect the photovoltaic power... Increased as a feedforward term to In, such as Figure 10 As shown. Figure 10 This is the block diagram of the outer loop control of the supercapacitor voltage.

[0055] The photovoltaic side of this system employs power backup control, which operates on a principle similar to sample-and-hold. Figure 11 The diagram illustrates the photovoltaic power reserve control workflow. In each power reserve control cycle, the maximum output power of the photovoltaic array is first obtained using the maximum power point tracking method. Record this power value unchanged until the next cycle, and calculate the actual power output of the photovoltaic array for the remaining time in this cycle. The photovoltaic array is controlled to switch between maximum power point tracking (MPPT) mode and constant power generation mode. When changes in ambient irradiance or temperature affect the photovoltaic output characteristics, the system can update its operation via MPPT. and Maintain a high level of power reserve accuracy.

[0056] In a specific embodiment, a bidirectional chopper on the supercapacitor side is used to stabilize the DC bus voltage. Figure 12 This is the control strategy for the supercapacitor side. Based on the traditional dual-loop voltage and current control, this strategy improves the DC bus voltage outer loop from conventional proportional-integral control to proportional-integral resonant control, while adding a virtual rotor kinetic energy feedforward control. The former can transfer the second harmonic power generated by the system when the three-phase load is unbalanced from the DC bus to the supercapacitor, thereby effectively suppressing the second harmonic ripple of the DC bus voltage. The resonant frequency is twice the grid frequency, which can be obtained using the virtual angular frequency of the grid-type control. This eliminates the need for a phase-locked loop (PLL). The latter can adjust the grid-type converter input power determined by the governor due to sudden changes in grid-side load. and output power By charging / discharging the supercapacitor in advance, grid-side disturbances are directly transferred to the supercapacitor side, reducing DC bus voltage fluctuations.

[0057] Specific implementation process 1: Charged state limit management strategy When the grid frequency is too low, causing the system to enter a frequency regulation transient, the input power determined by the speed governor in the grid-side electromechanical transient control... With converter output power The power difference will no longer be equal. Part of this difference will be provided by the photovoltaic array in the form of releasing reserve power, and the remainder will be provided by the supercapacitor discharging. During this process, the state of charge (SOC) of the supercapacitor will gradually decrease. If the SOC of the supercapacitor reaches the safe lower limit (SOCmin), the energy storage should not continue to release energy to prevent further decrease in SOC.

[0058] However, if the grid frequency has not yet recovered to within the governor's dead zone, and the photovoltaic array power cannot meet the demand... Under the influence of the DC bus voltage loop, the state of charge of the supercapacitor will be further reduced to outside the safe operating range, causing the system to shut down and disconnect from the grid.

[0059] Under this condition, since the photovoltaic array is already in maximum power point tracking mode and cannot further increase the output power, in order to prevent the state of charge of the supercapacitor from continuing to decline, it is necessary to sacrifice some of the grid-side frequency support capability and reduce... By dynamically adjusting the active power droop factor to make the photovoltaic power equal to the grid-side output power, it can be ensured that the state of charge (SOC) of the supercapacitor no longer decreases. However, due to the delay in the grid-side output power response, if the supercapacitor's SOC only reaches the lower limit, further degradation can occur. min After adjusting the active power droop factor, the supercapacitor remains in a discharged state until the photovoltaic power equals the grid-side output power, posing a risk of exceeding the state of charge limit.

[0060] The proposed supercapacitor state-of-charge limit management strategy in this invention... Figure 7 The specific implementation scheme of the system shown is divided into variable active power droop coefficient control and state of charge recovery control based on the state of charge of the supercapacitor. The control principle is as follows: Figure 3 and Figure 13 As shown. This invention limits the State of Charge (SOC) of a supercapacitor under its state of charge. min The corresponding minimum operating voltage Two levels of state-of-charge limiting voltage are set above. and ,in The starting voltage is a variable active power droop factor. Turn off the voltage for the speed controller. For example... Figure 3 Point A, when the supercapacitor voltage Descending to Then, the system initiates active power droop coefficient control based on state of charge. The active power droop coefficient will be determined according to... and The difference decreases linearly. If the grid frequency deviation is too large, Further decline to The system will forcibly shut down the speed controller, and the system will lose its frequency support function, such as... Figure 3 Point C. Under this control, when the state of charge of the supercapacitor approaches SOC... min At that time, the active power droop coefficient can be determined according to Adaptive adjustment ensures that the photovoltaic backup power equals the speed controller output power, guaranteeing the safe state of charge of the supercapacitor. Figure 3 Point B.

[0061] Controlling the droop factor of the supercapacitor to limit the decline in its state of charge requires a certain response time, which is determined by the dynamic performance of the grid-side control strategy used. When disturbances are significant, the supercapacitor may experience a voltage drop below a certain level due to continuous discharge before the photovoltaic backup power and the speed controller output power reach equilibrium. Therefore, a certain margin needs to be left, such as Figure 3 Points C and D. Meanwhile, if load disturbances intensify or photovoltaic output decreases during the adjustment of the active power droop factor, the variable active power droop factor control may not respond promptly, and the risk of exceeding the state of charge limit still exists. In this case, the system will initiate state of charge recovery control, temporarily activating the outer voltage loop of the supercapacitor to restore the supercapacitor's state of charge, such as... Figure 13 As shown, this is the state-of-charge recovery control.

[0062] Since supercapacitors need to absorb some photovoltaic power when restoring their state of charge, excessive power absorption may exacerbate the power imbalance between the power source and the grid, and worsen the grid frequency. To minimize the impact of state-of-charge recovery control on the system frequency, this invention modifies the outer loop reference voltage of the supercapacitor voltage during this period to... Once the state of charge (SCC) has returned to a safe operating range, the SCC recovery control is immediately shut off. Finally, when the grid frequency returns to within the governor's dead zone, the system re-enters steady-state operation, and the supercapacitor's SCC returns to the preset value.

[0063] Specific implementation process 2: Charge state upper limit management strategy The proposed supercapacitor state-of-charge upper limit management strategy in this invention... Figure 6 The specific implementation scheme of the system shown is as follows: when the state of charge of the supercapacitor reaches the safe upper limit, that is, the supercapacitor voltage... Equal to maximum operating voltage During this process, on the supercapacitor side, the power devices of the supercapacitor-side converter are forcibly shut down, disconnecting the supercapacitor from the system to prevent it from further absorbing energy and exceeding its state of charge limit. Simultaneously, the supercapacitor exhibits self-discharge characteristics, allowing its state of charge to gradually decrease during disconnection from the main circuit, reducing the risk of overcharging. On the photovoltaic side, the photovoltaic array undergoes power point tracking control, shifting the control objective from adjusting the photovoltaic operating point to maintaining DC bus voltage stability. Figure 14 The diagram shown is a block diagram of the photovoltaic-side control strategy switching.

[0064] exist equal The instant the supercapacitor is completely disconnected from the main circuit, the power difference between the grid-side output power and the photovoltaic power will charge the DC bus capacitor, causing the DC bus voltage to rise. Since the photovoltaic array is connected to the DC bus via a boost chopper, if the boost chopper's duty cycle is not adjusted in time, the photovoltaic array output voltage will rise along with the DC bus voltage. According to the characteristics on the right side of the photovoltaic array's PU curve, as the photovoltaic power decreases, the power difference between the input power determined by the speed controller and the photovoltaic power decreases, slowing the rate of increase of the DC bus voltage. Simultaneously, as the photovoltaic array switches to maintaining a stable DC bus voltage, after the DC bus voltage rises, under the regulation of the photovoltaic current inner loop within the outer loop of the DC bus voltage, the boost chopper's duty cycle decreases, further increasing the photovoltaic array output voltage. The photovoltaic power further decreases, allowing it to gradually track the input power determined by the speed controller, ultimately achieving power balance between the source and grid while stabilizing the DC bus voltage.

[0065] When the grid frequency and voltage return to within the allowable range, the supercapacitor reconnects to the main circuit, gradually restoring its voltage to the preset value while maintaining the DC bus voltage stability. The photovoltaic array then resumes power standby control. Through the coordinated operation of the supercapacitor and the photovoltaic array, the state of charge of the supercapacitor is maintained within a safe range.

[0066] To verify the supercapacitor's state-of-charge (SOC) management strategy, a 900W three-phase symmetrical load was connected to the system at 0s, causing the system to enter a frequency support transient state. The grid-side inverter increased its output power to provide frequency regulation support for the system. The difference between the photovoltaic input power and the grid-side inverter output power was provided by the supercapacitor, and the supercapacitor voltage began to decrease. Figure 15 The figure shows the experimental waveform of the supercapacitor state-of-charge (SOC) limit management strategy. At 16.7s, the supercapacitor voltage drops to the SOC limit of 368V. Since the existing control strategy lacks management of the supercapacitor's SOC, when the supercapacitor voltage drops below 368V, the system triggers the supercapacitor undervoltage protection. The existing control will disconnect from the grid, which leads to a sudden increase in grid-side load and seriously affects the grid-side frequency.

[0067] When the supercapacitor voltage reached 372V in 12.5s, the proposed control began to reduce the active power droop factor, and the downward trend of the supercapacitor voltage slowed down. At 14.8s, it dropped to 370V and stopped decreasing, successfully limiting the supercapacitor's state of charge from exceeding the safe lower limit.

[0068] To further verify the stability of the proposed control, the illuminance of the photovoltaic array was reduced to 300W / m2 at 17.5s. The reduced output power of the grid-side inverter caused the supercapacitor voltage to drop further and quickly reach the lower limit of 368V. After that, the outer loop of the supercapacitor voltage was opened, allowing the supercapacitor voltage to return to within the safe operating range.

[0069] To verify the supercapacitor state-of-charge (SOC) upper limit management strategy for frequency support transients, a 900W three-phase symmetrical load was disconnected from the system at time 0s, and the system entered a frequency regulation transient. The grid-side inverter reduced its output power to provide frequency support for the system. The difference between the photovoltaic input power and the grid-side inverter output power was absorbed by the supercapacitor, and the supercapacitor voltage began to rise. Figure 16 The figure shows the experimental waveforms of the supercapacitor state of charge (SOC) upper limit management strategy. At 9.6 seconds, the supercapacitor voltage rises to the SOC upper limit of 438V. Because the existing control strategy lacks SOC management, the system triggers supercapacitor overvoltage protection when the voltage exceeds 438V. To ensure system hardware safety, the existing control will disconnect from the grid, which exacerbates the power imbalance between the power source and the grid, severely affecting the grid frequency.

[0070] Once the supercapacitor voltage reaches 438V, the proposed control only requires disconnecting the system from the supercapacitor. The photovoltaic side ceases power standby control and begins tracking control to automatically adjust the photovoltaic operating point, ensuring the photovoltaic power equals the output power of the grid-side inverter. After 80 seconds, the system frequency returns to the speed controller dead zone, and the system reconnects to the supercapacitor to resume steady-state operation.

[0071] A second objective of this application is to provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the aforementioned method for managing the state of charge of a photovoltaic energy storage device. The device also includes a communication interface and a bus.

[0072] The third objective of this application is to provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method for managing the state of charge of an energy storage device in a photovoltaic energy storage system.

[0073] A fourth objective of this application is to provide a computer program product, which includes computer instructions that instruct a computer to execute the above-described method for managing the state of charge of a photovoltaic energy storage device.

[0074] 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.

[0075] These computer program instructions can 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.

[0076] This application may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application may take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, readable storage media, optical storage, etc.) containing computer-usable program code.

[0077] 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.

[0078] Obviously, the described embodiments are only some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort should fall within the scope of protection of this application.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and not to limit them. Although this application has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation methods of this application. Any modifications or equivalent substitutions that do not depart from the spirit and scope of this application should be covered within the protection scope of this application.

Claims

1. A method for managing the state of charge of a photovoltaic-energy storage system, characterized in that, include: By setting the safe operating range and graded limit thresholds for the state of charge (SOC) of energy storage devices, a collaborative control mechanism is constructed between the lower limit management strategy and the upper limit management strategy for SOC. The graded limit thresholds include the variable active power droop coefficient activation threshold (SOC) located above the safe lower limit of SOC. lim1 and governor off threshold SOC lim2 ; The specific state-of-charge (SOC) management strategy is as follows: when the energy storage device's state of charge drops to its maximum charge (SOC)... lim1 At that time, based on the state of charge and SOC lim2 The difference dynamically reduces the active power droop factor of the grid-side converter, balancing the output power of the photovoltaic array with that of the grid-side converter to suppress the decline in state of charge; when the state of charge drops to SOC... lim2 When the active power droop factor is set to 0 and the system frequency support function is turned off; when the state of charge is below the safe lower limit SOC min At that time, the output power of the grid-side converter is further reduced to below the output power of the photovoltaic array, and the excess photovoltaic power is used to charge the energy storage device at a low power until the state of charge is restored to a safe range.

2. The method for managing the state of charge of a photovoltaic-energy storage system according to claim 1, characterized in that, The specific strategy for managing the upper limit of the state of charge (SOC) is as follows: when the energy storage device reaches the safe upper limit of SOC... max When the energy storage device is disconnected from the system, the corresponding converter is shut down. At the same time, the control target of the photovoltaic array is switched from adjusting the photovoltaic operating point to maintaining the DC bus voltage stability. The output power of the photovoltaic array is reduced to balance the output power of the grid-side converter.

3. The method for managing the state of charge of a photovoltaic-energy storage system energy storage device according to claim 1, characterized in that, The active power droop factor of the grid-side converter is based on the state of charge (SOC) of the energy storage device. lim2 The difference is adjusted in a linear decreasing trend, or by adopting a non-linear adjustment method of exponential decrease or segmented step decrease.

4. The method for managing the state of charge of a photovoltaic-energy storage system energy storage device according to claim 1, characterized in that, The SOC lim2 Higher than SOC min The SOC lim1 Higher than SOC lim2 A control response margin is reserved between the two threshold levels.

5. The method for managing the state of charge of a photovoltaic-energy storage system according to claim 2, characterized in that, The photovoltaic array control objective is switched to maintain a stable DC bus voltage, so that the DC bus voltage does not fluctuate significantly during the system power balance process.

6. The method for managing the state of charge of a photovoltaic-energy storage system energy storage device according to claim 1, characterized in that, The photovoltaic array is connected to the DC bus via a boost DC / DC chopper. The photovoltaic operating point is adjusted by changing the duty cycle of the boost chopper. When the photovoltaic array control target is switched to maintaining the DC bus voltage stability, a dual closed-loop control strategy of DC bus voltage outer loop and photovoltaic current inner loop is adopted. The DC bus voltage stability is controlled by adjusting the duty cycle of the boost chopper.

7. The method for managing the state of charge of a photovoltaic-energy storage system energy storage device according to claim 1, characterized in that, The energy storage device is connected to the DC bus via a bidirectional DC / DC converter. The DC bus voltage is adjusted by changing the duty cycle of the bidirectional DC / DC converter on the energy storage side. The bidirectional DC / DC converter adopts proportional-integral resonant control with a resonant frequency twice the grid frequency to suppress the second harmonic ripple of the DC bus voltage.

8. The method for managing the state of charge of a photovoltaic-energy storage system energy storage device according to claim 1, characterized in that, The energy storage device includes any one or more combinations of supercapacitors, lithium batteries, and sodium batteries. When there are multiple combinations, each energy storage device is connected in parallel to the DC bus through its corresponding bidirectional DC / DC converter.

9. The method for managing the state of charge of a photovoltaic-energy storage system according to claim 1, characterized in that, The grid-side converter control strategy of the photovoltaic-storage system also includes grid-type control and supercapacitor voltage outer loop control. The grid-based control includes: First, by collecting the output capacitor voltage and grid-side current signal, the real-time output power of the system is obtained through the power calculation module; Second, by simulating the governor equation and rotor oscillation equation of the synchronous generator through electromechanical transients, the virtual phase angle and induced electromotive force are calculated in combination with electromagnetic transients; Subsequently, a virtual impedance link is introduced to generate the inverter modulation wave reference voltage; Finally, the inverter power switching devices are driven to transmit the power of the new energy power generation unit to the grid. The outer loop control of the supercapacitor voltage includes: considering the relationship between the state of charge of the supercapacitor and its terminal voltage, controlling the state of charge of the supercapacitor by controlling its terminal voltage, adding a supercapacitor voltage outer loop with a minute-level response speed to manage the state of charge on the basis of the basic grid-type control, and slowly adjusting the state of charge of the supercapacitor by adjusting the active power command P0vsg of the grid-type control.

10. The method for managing the state of charge of a photovoltaic-energy storage system according to claim 1, characterized in that, The control strategy for the photovoltaic-storage system also includes a photovoltaic-side control strategy and a supercapacitor-side control strategy; Photovoltaic-side control strategies include: increasing photovoltaic power feedforward, and shifting photovoltaic power... Increased as a feedforward term to In the photovoltaic (PV) side, power reserve control is employed. During each power reserve control cycle, the maximum output power of the PV array is first determined using the maximum power point tracking (MPPT) method. Record this power value unchanged until the next cycle, and calculate the actual power output of the photovoltaic array for the remaining time in this cycle. The system controls the photovoltaic array to switch between maximum power point tracking (MPPT) mode and constant power generation mode. When changes in ambient irradiance or temperature affect the photovoltaic output characteristics, the system can update its operation via MPPT. and ; The supercapacitor-side control strategy includes: using a bidirectional chopper on the supercapacitor side to stabilize the DC bus voltage; the control on the supercapacitor side is based on the voltage and current dual closed-loop control, and the outer loop of the DC bus voltage is improved from proportional-integral control to proportional-integral resonant control; at the same time, a virtual rotor kinetic energy feedforward control is added.

Images