Unified power control method and system for optical storage integrated system

Abstract

The invention discloses a unified power control method and system for an optical storage integrated system. The core of the method is to construct a fixed core power control loop, and internal logic and proportional integral (PI) parameters of all controllers are kept unchanged in different working modes. The control loop comprises a main power control loop (battery power loop) and at least one auxiliary constraint loop (grid power loop). Smooth and seamless switching from a grid-connected mode and an off-grid mode to various charging and discharging and power limiting modes can be realized by only adjusting external given values (such as battery power given PbatRef, on-grid power given Pexport and off-grid power given Pimport) and carrying out dynamic amplitude limiting on the output of a main ring by utilizing the output of an auxiliary constraint ring. The system thoroughly solves the problems that a traditional multi-mode parallel control scheme is complex in structure, easy to oscillate in mode switching, tedious in debugging and the like, and unprecedented system simplification, switching stability and operation simplicity and convenience are achieved.

Description

Technical Field

[0001] This invention relates to the field of power electronics and control technology, and in particular to a unified power control method and system for integrated photovoltaic and energy storage systems. Background Technology

[0002] With the development of new energy technologies, integrated photovoltaic and energy storage systems (including photovoltaics, battery energy storage, grid, and load) are being used more and more widely. These systems need to operate in multiple modes, such as: photovoltaics prioritizing power supply to the load and charging with surplus power; battery discharge supplementing the load; limiting grid input power; and limiting grid output power.

[0003] Traditional control schemes typically design independent control loops and parameter tuning strategies for each operating mode. For example, grid-connected mode, off-grid mode, constant voltage mode, and constant current mode each have their own dedicated control logic and PI parameters. The drawbacks of this approach are quite obvious: 1. System complexity: Multiple control loops coexist, resulting in structural redundancy and complex hardware and software implementation.

[0004] 2. Unstable mode switching: When switching between different modes, the controller's structure, logic and parameters may change abruptly, causing the system's power, voltage or current to oscillate or surge, which seriously threatens the safety of the equipment.

[0005] 3. Cumbersome debugging: The PI parameters for each mode need to be debugged separately, which is a lot of work and makes it difficult to guarantee excellent dynamic performance in all modes.

[0006] Therefore, there is an urgent need in this field for a new control scheme that can simplify system structure, achieve uninterrupted mode switching, and reduce debugging complexity. Summary of the Invention

[0007] To address the aforementioned deficiencies in existing technologies, this invention aims to provide a unified power control method and system for integrated photovoltaic and energy storage systems. The core objective of this invention is to construct a unique, unified power control loop. The control logic of its core circuit and the proportional-integral (PI) parameters of the controller remain constant across all operating modes. Switching between all operating modes is achieved solely by adjusting the external setpoint and limiting value of this unified loop. This significantly simplifies the system structurally and achieves unprecedented switching stability and ease of debugging.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention proposes a unified power control method for a photovoltaic-storage integrated system, characterized in that the method is based on a fixed set of control logic and fixed controller parameters, and achieves the switching of system operating modes by adjusting external setpoints and limiting values; The method includes the following steps: S1: A first adjustment signal is generated through a main power control loop based on the battery power setpoint PbatRef and the battery power feedback value PbatFb; S2: Generate at least one constraint signal based on the grid power setpoint Pexport or the downstream power setpoint Pimport and the grid power feedback value Pgrid_Fdb through at least one auxiliary constraint loop; S3: Using the constraint signal as a dynamic limiting value, the first adjustment signal is limited to generate the inverter's power setpoint PinvRef.

[0009] Furthermore, in step S1, the main power control loop is implemented using a first PI controller. The input of the first PI controller is the difference between the battery power setpoint PbatRef and the battery power feedback value PbatFb, and its output is inverted and used as the first adjustment signal.

[0010] Further, in step S2, the auxiliary constraint loop includes a grid power loop, which is implemented using a second PI controller. The input of the second PI controller is the difference between the grid power setpoint Pexport and the grid power feedback value Pgrid_Fdb, and its output is used as a second adjustment signal. In step S3, the second adjustment signal is used as a dynamic upper limit for limiting the amplitude of the first adjustment signal.

[0011] Further, in step S2, the auxiliary constraint loop includes a grid-connected power loop, which is implemented using a third PI controller. The input of the third PI controller is the difference between the grid-connected power setpoint Pimport and the grid power feedback value Pgrid_Fdb, and its output is used as a third adjustment signal. In step S3, the third adjustment signal is used as a dynamic lower limit for limiting the amplitude of the first adjustment signal.

[0012] Furthermore, the method further includes a photovoltaic total power control step S0: S0: The fourth PI controller generates an adjustment value based on the photovoltaic charging power setpoint Ppv_batRef and the battery power feedback value PbatFb, and then adds this adjustment value to the maximum available photovoltaic power PpvRate to generate the total power setpoint PpvRef of the photovoltaic inverter.

[0013] Furthermore, the proportional-integral parameters of the first PI controller, the second PI controller, the third PI controller, and the fourth PI controller remain unchanged in all operating modes of the system.

[0014] Furthermore, by setting the output upper limit PI_Bat_Outmax of the first PI controller to 0, the function of preventing the grid from charging the battery can be achieved.

[0015] Furthermore, by collaboratively setting the battery power setpoint PbatRef and the photovoltaic charging power setpoint Ppv_batRef, priority management of energy flow is achieved, so that photovoltaic power is preferentially supplied to local loads, the remaining power is used for battery charging, and any surplus is fed into the grid.

[0016] Secondly, this invention proposes a unified power control system for an integrated photovoltaic-storage system, used to implement the method described in any of the preceding claims, the system comprising: The first PI controller is configured to perform the functions of the main power control loop; The second PI controller and / or the third PI controller are configured to perform the function of the auxiliary constraint loop; A limiting controller is configured to dynamically limit the output of the first PI controller using the output of the second PI controller and / or the third PI controller. The fourth PI controller is configured to generate an adjustment based on the photovoltaic charging power setpoint Ppv_batRef and the battery power feedback value PbatFb, and to add it to the maximum available photovoltaic power PpvRate to generate the total power setpoint PpvRef of the photovoltaic inverter. In this system, the control logic and parameters of all controllers are fixed and cannot be changed in all operating modes.

[0017] Beneficial effects of the present invention Compared with the prior art, the present invention has the following significant advantages: 1. Simplified structure: By constructing a unified core control loop, multiple parallel control logics in the traditional solution are replaced, which greatly simplifies the system's hardware and software structure and reduces costs and design complexity.

[0018] 2. Seamless Switching and Ultra-High Stability: Since the core logic and PI parameters of the controller remain constant across all modes, mode switching is achieved solely by changing external setpoints (such as PbatRef, Pexport, Pimport) and limiting values. This fundamentally eliminates power oscillations and shocks caused by abrupt changes in controller structure or parameters, enabling smooth, seamless, and stable switching between different operating modes.

[0019] 3. Easy debugging: Engineers only need to tune and optimize the only set of PI parameters once to ensure that the system has good dynamic and static performance in all working modes. This greatly reduces the debugging workload, reduces the requirements for the experience of debugging personnel, and improves the reliability of the system.

[0020] 4. Complete functions: Despite the simplified structure, by flexibly configuring the given and limit values, this unified architecture can cover all common and complex working modes such as grid connection, off-grid, charge and discharge, power-limited grid connection, and power-limited grid disconnection, achieving the control effect of "responding to all changes with the same method". Brief Description of the Drawings

[0021] Figure 1 is a schematic diagram of the structure of a multi-mode power control system in the prior art.

[0022] Figure 2 is a schematic diagram of the structure of the unified power control system of the present invention.

[0023] Figure 3 is a topology diagram of a photovoltaic energy storage inverter.

[0024] Figure 4 is a block diagram of the structure of the unified power control system of the present invention. Detailed Embodiment

[0025] The following will combine the drawings to detail a preferred embodiment of the present invention.

[0026] Build a unique set of unified power control loops. The control logic of the core circuit and the proportional integral (PI) parameters of the controller remain unchanged in all working modes. Only by adjusting the external given value and limit value of this unified loop can all working mode switches be realized, thus greatly simplifying the system in terms of structure and achieving unprecedented switching stability and easy debugging in terms of function.

[0027] First, refer to Figure 3 , which shows a typical topology of a photovoltaic energy storage inverter that can implement the present invention. The system includes main components such as a photovoltaic array PV, a battery BAT, a bidirectional DC / AC inverter INV, and a grid connection switch. The control method of the present invention is applied to the central controller of this system to coordinate the power flow between components. The bidirectional DC / AC inverter executes the power command PinvRef by controlling the DC side bus voltage command Vinv of it. Specifically, when the inverter needs to discharge, set Vinv > Vbat (Vbat is the battery terminal voltage); when the inverter needs to charge, set Vinv < Vbat. The direction of the voltage difference determines the power flow direction.

[0028] Please refer to Figure 4The unified power control system of this invention mainly includes four PI controllers and one limiting controller, which constitutes... Figure 2 The specific implementation of the simplified structure shown.

[0029] The system involves the following parameter definitions: PinvRef is the inverter (INV) power reference (positive value for discharge direction, negative value for charging direction). PpvRef is the given total photovoltaic power (including grid connection and charging). Pexport is the given value for the mains power supply loop. Pimport is the given value for the mains power supply loop. PbatRef is the given value for the battery charging power loop. PI_Bat_Outmax is the upper limit of the battery charging power loop output. PI_Bat_Outmin is the lower limit of the battery charging power loop output. Ppv_batRef is a given value for the photovoltaic charging power loop. PbatFb is the battery power feedback (positive value indicates the discharge direction, negative value indicates the charging direction). Prate is the system's rated power.

[0030] The core control process of the system: 1. Battery power control loop (main loop): The first PI controller calculates the error between PbatRef and PbatFb and outputs an adjustment signal. This signal is inverted and sent to the limit controller Sat as the first adjustment signal.

[0031] 2. Power grid constraint loop (auxiliary loop): The second PI controller calculates the error between Pexport and Pgrid_Fdb and outputs the second adjustment signal.

[0032] The third PI controller calculates the error between Pimport and Pgrid_Fdb and outputs the third adjustment signal.

[0033] 3. Limiting Coordination: The limiting controller Sat limits the first regulating signal with the second regulating signal as the upper limit and the third regulating signal as the lower limit. Its output is PinvRef, which is sent to the inverter for execution.

[0034] At the same time, check the positive and negative values ​​of PinvRef. If it is positive, it indicates discharge, Vinv = Vbat - 15V; if it is negative, it indicates charging, Vinv = Vbat + 15V. 4. Photovoltaic power control loop: The fourth PI controller calculates the error between Ppv_batRef and PbatFb, and its output is superimposed on PpvRate to generate PpvRef, which is sent to the photovoltaic inverter.

[0035] To illustrate more specifically how this invention achieves multiple operating modes by adjusting externally given values, the parameter configuration and control processes in several typical application scenarios are listed below. In all modes, the internal logic and parameters of each PI controller remain unchanged.

[0036] Example 1: Self-generation and self-consumption with backup power mode In this mode, the system prioritizes the use of photovoltaics and batteries, minimizes the use of electricity from the grid, and limits grid feedback.

[0037] Parameter settings: PbatRef = PbatchgMax - 200W (Set a charging target slightly lower than the maximum charging power) Ppv_batRef = PbatchgMax (The photovoltaic system aims to charge the battery to its maximum capacity). PI_Bat_Outmax = 0 (The upper limit of the battery ring output is 0. Combined with the inversion operation, this is equivalent to disabling the inverter from drawing power from the grid to charge the battery.) PI_Bat_Outmin = -Prate (The lower limit of the battery ring output is the negative of the system's rated power) Working principle and effects: When photovoltaic (PV) power is sufficient, PbatFb (actual charging power) will exceed PbatRef. The first PI controller output accumulates in the negative direction. After inversion, PinvRef becomes positive, controlling the inverter to operate in the discharge direction, feeding excess PV power into the grid. However, because the second PI controller (Pexport loop) limits the grid-connected power, the final result is: PV prioritizes supplying local loads, surplus energy charges batteries, and the remainder is fed into the grid. If the grid-connected power reaches the limit, the fourth PI controller will reduce PpvRef, causing PV curtailment.

[0038] When photovoltaic power is insufficient, both photovoltaic power and batteries supply power to the load. Due to the limitation of PI_Bat_Outmax=0, the mains power will not charge the battery, but will only supplement the load deficit when it is most insufficient.

[0039] Example 2: Backup power mode (allows mains charging) This mode is similar to Example 1, but allows the battery to be charged with mains power.

[0040] Parameter settings: Basically the same as in Example 1, but the key difference is PI_Bat_Outmax = Prate (remove the positive limit of the battery ring output upper limit).

[0041] Working principle and effects: When photovoltaic power is sufficient, the behavior is consistent with Example 1. When photovoltaic power is insufficient, PbatFb is less than PbatRef, the output of the first PI controller is positive, and after inversion, PinvRef is negative, and the inverter operates in the charging direction. At this time, under the constraint of the grid-connected power loop Pimport, the grid power and photovoltaic power will jointly supply power to the load and charge the battery at the same time.

[0042] Example 3: Full Grid Connection Mode of Photovoltaic Power In this mode, all photovoltaic power generation is fed into the grid, and the batteries remain idle.

[0043] Parameter settings: PbatRef = 0 (Battery power target is 0, i.e., no charging and no discharging) Ppv_batRef = PbatchgMax PI_Bat_Outmax = Prate PI_Bat_Outmin = -Prate Working principle and effects: When solar power is available, PbatFb ≈ 0, slightly greater than PbatRef (=0). The first PI controller outputs a negative value, which, after inversion, makes PinvRef positive, driving the inverter to feed all the solar power into the grid. When grid-connected power is limited, excess energy will be diverted to charge the battery (because PbatRef=0, the system will attempt to consume excess power through charging). When solar power is insufficient or absent, the mains power supplies the load, and the battery does not operate.

[0044] Example 4: Photovoltaic + Battery Full Grid Connection Mode In this mode, both photovoltaics and batteries deliver power to the grid at maximum capacity.

[0045] Parameter settings: PbatRef = -PbatdischgMax (Set to the negative of the battery's maximum discharge power, i.e., the opposite of the maximum charging direction, which essentially requires the battery to discharge at its maximum power) Ppv_batRef = PbatchgMax PI_Bat_Outmax = Prate PI_Bat_Outmin = -Prate Working principle and effects: The first PI controller will strive to discharge the battery at maximum power (PbatFb is a very large positive value). Under the drive of the battery loop and the constraints of the grid loop, PinvRef controls the inverter to combine the battery discharge power with the photovoltaic power before feeding it into the grid. When the total grid-connected power is limited, the system will prioritize ensuring the photovoltaic power is fed into the grid, and then the battery will supplement the difference; if the photovoltaic power already meets the grid-connected limit, the excess photovoltaic power will charge the battery.

[0046] Throughout all the aforementioned mode switching processes, the internal control logic (such as error calculation, integral accumulation, output limiting, etc.) and parameters such as proportional gain (Kp) and integral time (Ti) of the first, second, third, and fourth PI controllers remain completely unchanged. Mode switching and function implementation are achieved entirely through the upper-level management system changing externally assigned values ​​such as PbatRef, Pexport, Pimport, and Ppv_batRef. This perfectly achieves the invention's objectives of "simplified structure, stable switching, and easy debugging."

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Those skilled in the art can make various modifications and variations to the above embodiments without departing from the spirit and scope of the present invention, and these modifications and variations should also be considered within the protection scope of the present invention.

Claims

1. A unified power control method for a photovoltaic-storage integrated system, characterized in that, The method is based on a fixed set of control logic and fixed controller parameters, and switches the system operating mode by adjusting the external setpoint and limit value; The method includes the following steps: S1: A first adjustment signal is generated through a main power control loop based on the battery power setpoint PbatRef and the battery power feedback value PbatFb; S2: Generate at least one constraint signal based on the grid power setpoint Pexport or the downstream power setpoint Pimport and the grid power feedback value Pgrid_Fdb through at least one auxiliary constraint loop; S3: Using the constraint signal as a dynamic limiting value, the first adjustment signal is limited to generate the inverter's power setpoint PinvRef.

2. The method according to claim 1, characterized in that, In step S1, the main power control loop adopts a first PI controller. The input of the first PI controller is the difference between the battery power setpoint PbatRef and the battery power feedback value PbatFb. Its output is inverted and used as the first adjustment signal.

3. The method according to claim 2, characterized in that, In step S2, the auxiliary constraint loop includes a grid power loop, which is implemented using a second PI controller. The input of the second PI controller is the difference between the grid power setpoint Pexport and the grid power feedback value Pgrid_Fdb, and its output is used as a second adjustment signal. In step S3, the second adjustment signal is used as a dynamic upper limit for limiting the amplitude of the first adjustment signal.

4. The method according to claim 2, characterized in that, In step S2, the auxiliary constraint loop includes a grid-connected power loop, which is implemented using a third PI controller. The input of the third PI controller is the difference between the grid-connected power setpoint Pimport and the grid power feedback value Pgrid_Fdb, and its output is used as a third adjustment signal. In step S3, the third adjustment signal is used as a dynamic lower limit for limiting the amplitude of the first adjustment signal.

5. The method according to claim 2, characterized in that, The method further includes a photovoltaic total power control step S0: S0: The fourth PI controller generates an adjustment value based on the photovoltaic charging power setpoint Ppv_batRef and the battery power feedback value PbatFb, and then adds this adjustment value to the maximum available photovoltaic power PpvRate to generate the total power setpoint PpvRef of the photovoltaic inverter.

6. The method according to any one of claims 3, 4, and 5, characterized in that, The proportional-integral parameters of the first PI controller, the second PI controller, the third PI controller, and the fourth PI controller remain unchanged in all operating modes of the system.

7. The method according to claim 2, characterized in that, By setting the output limit PI_Bat_Outmax of the first PI controller to 0, the function of preventing the grid from charging the battery can be achieved.

8. The method according to claim 5, characterized in that, By collaboratively setting the battery power setpoint PbatRef and the photovoltaic charging power setpoint Ppv_batRef, priority management of energy flow is achieved, so that photovoltaic power is given priority to local loads, the remaining power is used for battery charging, and any surplus is fed into the grid.

9. A unified power control system for a photovoltaic-storage integrated system, characterized in that, The system for implementing the method of any one of claims 1-8 comprises: The first PI controller is configured to perform the functions of the main power control loop; The second PI controller and / or the third PI controller are configured to perform the function of the auxiliary constraint loop; A limiting controller is configured to dynamically limit the output of the first PI controller using the output of the second PI controller and / or the third PI controller. The fourth PI controller is configured to generate an adjustment based on the photovoltaic charging power setpoint Ppv_batRef and the battery power feedback value PbatFb, and to add it to the maximum available photovoltaic power PpvRate to generate the total power setpoint PpvRef of the photovoltaic inverter. In this system, the control logic and parameters of all controllers are fixed and cannot be changed in all operating modes.

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