Method for controlling output power of optical storage system and optical storage system

Abstract

The invention provides an optical storage system output power control method and an optical storage system. The method comprises the following steps: calculating the output power of a photovoltaic system according to the measured inverter output current and inverter output voltage; based on a maximum power point tracking (MPPT) algorithm and a first proportion-integration-differentiation (PID) control algorithm, controlling the output power of the photovoltaic system at the maximum power point; controlling the working mode of the energy storage system according to the output power of the photovoltaic system and a preset grid-connected power target value; and controlling the output power of the energy storage system based on a second PID control algorithm, so as to control the output power of the optical storage system at a grid-connected power target value. According to the technical scheme provided by the embodiment of the invention, the fluctuation of the output power of the photovoltaic system can be quickly responded, the output power of the photovoltaic system is relatively stable by adjusting the working mode and the output power of the energy storage system, the operation efficiency of the photovoltaic system is ensured, and the stability of a power grid is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic storage systems, and in particular to a method for controlling the output power of a photovoltaic storage system and a photovoltaic storage system. Background Art

[0002] The photovoltaic storage system consists of a photovoltaic system and an energy storage system. When the photovoltaic power generation is less than the grid-connected power, the photovoltaic system and the energy storage system jointly supply power. When the photovoltaic power generation is greater than the grid-connected power, part of the photovoltaic system's power is used to supply the grid, and part is stored in the energy storage system.

[0003] Solar-to-storage systems, as a combination of multiple renewable energy sources, offer higher prediction accuracy for photovoltaic power generation and are clean, zero-carbon, and pollution-free. However, connecting to the grid can lead to random fluctuations, and cannot guarantee grid stability during power control. To ensure system safety and reliability, operations personnel often need to increase the system's power output to stabilize grid operation. However, this approach is not feasible. Summary of the Invention

[0004] In view of the above problems, an embodiment of the present invention provides a method for controlling the output power of a photovoltaic storage system and a photovoltaic storage system, so as to solve the problem in the prior art that the connection between the photovoltaic storage system and the power grid will cause random fluctuations in the power grid and cannot ensure the stability of the power grid during the power control process.

[0005] In a first aspect, an embodiment of the present invention provides a method for controlling the output power of a photovoltaic storage system, the method comprising:

[0006] Calculate the output power of the photovoltaic system based on the measured inverter output current and inverter output voltage;

[0007] Based on the maximum power point tracking (MPPT) algorithm and the first proportional-integral-derivative (PID) control algorithm, the output power of the photovoltaic system is controlled at the maximum power point;

[0008] Controlling the operating mode of the energy storage system according to the output power of the photovoltaic system and a preset grid-connected power target value;

[0009] The output power of the energy storage system is controlled based on the second PID control algorithm to control the output power of the photovoltaic storage system to the grid-connected power target value.

[0010] In one possible implementation, controlling the output power of the photovoltaic system at a maximum power point based on the MPPT algorithm and the first PID control algorithm includes:

[0011] Using the measured photovoltaic cell output current and photovoltaic cell output voltage as inputs to the MPPT algorithm, and controlling a DC-DC converter DC-DC boost circuit using the MPPT algorithm;

[0012] Subtracting the measured photovoltaic cell boost voltage from the photovoltaic cell reference voltage to obtain a photovoltaic cell boosted voltage deviation; the photovoltaic cell boost voltage refers to the DC voltage after the photovoltaic cell output voltage is boosted by the DC-DC boost circuit;

[0013] Performing coordinate transformation on the inverter output current through a coordinate transformation matrix to obtain a DC current;

[0014] Using the boosted voltage deviation of the photovoltaic cell and the DC current as inputs of a first pulse width modulation (PWM) signal to obtain a modulated first PWM signal;

[0015] Based on the first PID control algorithm, the output power of the photovoltaic system is controlled according to the modulated first PWM signal, so as to control the output power of the photovoltaic system at a maximum power point.

[0016] In one possible implementation, the MPPT algorithm includes a conductance increment method, a constant voltage method, or a perturbation and observation method.

[0017] In one possible implementation, the second PID control algorithm includes a voltage outer loop and current inner loop control algorithm. Controlling the output power of the energy storage system based on the second PID control algorithm includes:

[0018] Based on the voltage outer loop and current inner loop control algorithm, the measured boost voltage of the energy storage battery and the output current of the energy storage battery are used as inputs of a second PWM signal to generate a modulated second PWM signal, and the bidirectional DC-DC circuit is controlled according to the modulated second PWM signal; the boost voltage of the energy storage battery refers to the voltage obtained by boosting the output voltage of the energy storage battery by the bidirectional DC-DC circuit;

[0019] Subtracting the grid-connected power target value from the acquired active output power of the photovoltaic storage system to obtain an output power deviation;

[0020] Using the output power deviation, the measured AC output current of the energy storage system, and the AC output voltage of the energy storage system as inputs of a space vector pulse width modulation (SVPWM) signal to obtain a modulated SVPWM signal;

[0021] The energy storage converter is controlled by the modulated SVPWM signal to control the output power of the energy storage system.

[0022] In one possible implementation, the voltage outer loop and current inner loop control algorithm is based on the voltage outer loop and current inner loop, uses the measured energy storage battery boost voltage and energy storage battery output current as inputs of a second PWM signal, generates a modulated second PWM signal, and controls the bidirectional DC-DC circuit according to the modulated second PWM signal, including:

[0023] Subtracting the boosted voltage of the energy storage battery from the reference voltage of the energy storage battery to obtain a boosted voltage deviation of the energy storage battery;

[0024] The boost voltage of the energy storage battery is controlled by the output current of the energy storage battery so that the voltage deviation of the boosted energy storage battery is less than a preset threshold, a modulated second PWM signal is generated, and the bidirectional DC-DC circuit is controlled according to the modulated second PWM signal.

[0025] In a possible implementation, the operating mode includes a charging mode and a discharging mode;

[0026] The controlling of the working mode of the energy storage system by the output power of the photovoltaic system and the preset grid-connected power target value includes:

[0027] If the output power of the photovoltaic system is less than the grid-connected power target value, setting the working mode of the energy storage system to a discharge mode through the DC-DC bidirectional circuit;

[0028] If the output power of the photovoltaic system is greater than the grid-connected power target value, the operating mode of the energy storage system is set to a charging mode through the DC-DC bidirectional circuit.

[0029] In a second aspect, an embodiment of the present invention provides a photovoltaic storage system, which includes a photovoltaic cell, an inverter, a box-type substation, an integrated converter, and an energy storage device;

[0030] The DC side of the inverter is electrically connected to the photovoltaic cell, and the AC side is electrically connected to the box-type substation;

[0031] The box-type substation is electrically connected to the integrated converter;

[0032] The converter is electrically connected to the energy storage device;

[0033] The box-type substation and the integrated converter are both connected to the power grid.

[0034] In one possible implementation, the integrated converter includes a transformer and an energy storage converter, and the inverter energy storage converter includes a DC-DC bidirectional circuit, which is used to achieve smooth switching of the energy storage system device between charging mode and discharging mode.

[0035] The technical solution provided in the embodiment of the present invention can quickly respond to fluctuations in the output power of the photovoltaic system. By adjusting the working mode and output power of the energy storage system, the output power of the photovoltaic storage system is made relatively stable, thereby ensuring the operating efficiency of the photovoltaic storage system and improving the stability of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a flow chart of a method for controlling the output power of a photovoltaic storage system provided by an embodiment of the present invention.

[0037] Figure 2 A schematic diagram of an MPPT algorithm provided by an embodiment of the present invention.

[0038] Figure 3 A schematic diagram of a voltage outer loop and current inner loop control algorithm provided by an embodiment of the present invention.

[0039] Figure 4 A schematic structural diagram of a photovoltaic storage system provided in an embodiment of the present invention.

[0040] Figure 5 A schematic diagram of output power provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the present invention more clear and understandable, the present invention is further described below with reference to the accompanying drawings and specific embodiments. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0042] Figure 1 A flow chart of a method for controlling the output power of a photovoltaic storage system provided by an embodiment of the present invention is shown in FIG. Figure 1 As shown, the method includes:

[0043] Step 101: Calculate the output power of the photovoltaic system according to the measured inverter output current and inverter output voltage.

[0044] Each step in the embodiment of the present invention is applied to a photovoltaic storage system, which includes a photovoltaic system and an energy storage system. The output power of the photovoltaic storage system is the sum of the output power of the photovoltaic system and the output power of the energy storage system.

[0045] Step 102: Based on the MPPT algorithm and the first PID control algorithm, the output power of the photovoltaic system is controlled at the maximum power point.

[0046] In this step, the measured photovoltaic cell output current and photovoltaic cell output voltage are used as inputs of a maximum power point tracking (MPPT) algorithm, and a DC-to-DC converter (DC-DC) boost circuit is controlled using the MPPT algorithm. The measured photovoltaic cell boost voltage is subtracted from the photovoltaic cell reference voltage to obtain a boosted photovoltaic cell voltage deviation. The photovoltaic cell boost voltage refers to the DC voltage obtained by boosting the photovoltaic cell output voltage by the DC-DC boost circuit. The inverter output current is transformed using a coordinate transformation matrix to obtain a DC current. The boosted photovoltaic cell voltage deviation and the DC current are used as inputs of a first pulse width modulation (PWM) signal to obtain a modulated first PWM signal. Based on a first PID control algorithm, the output power of the photovoltaic system is controlled according to the modulated first PWM signal to control the output power of the photovoltaic system at the maximum power point.

[0047] In this embodiment of the present invention, the MPPT algorithm includes a conductance increment method, a constant voltage method, or a perturbation-observation method. Computer equipment was simulated using Simulink. Compared with the constant voltage method and the perturbation-observation method, the conductance increment method provides more stable control of the photovoltaic system's output power.

[0048] Figure 2 A schematic diagram of an MPPT algorithm provided by an embodiment of the present invention is shown in FIG. Figure 2 As shown, the PV cell output voltage V_PV and PV cell output current I_PV are used as inputs to the MPPT algorithm. The MPPT control module and the first PID controller work together to achieve maximum power point tracking and stable control of the PV system. The MPPT control module ensures that the PV array operates at its maximum power point, while the first PID controller ensures stable system operation through closed-loop control.

[0049] In this step, the inverter output current is a three-phase AC current, which is converted into a DC current using a coordinate conversion formula.

[0050] When the unbalanced component is not considered, the coordinate transformation formula is:

[0051]

[0052] When considering the unbalanced component, the coordinate transformation formula is:

[0053]

[0054] Step 103: Control the working mode of the energy storage system according to the output power of the photovoltaic system and the preset grid-connected power target value.

[0055] In this step, the energy storage system operates in two modes: charging mode and discharging mode. If the PV system's output power is less than the grid-connected power target, the energy storage system's operating mode is set to discharging mode. If the PV system's output power is greater than the grid-connected power target, the energy storage system's operating mode is set to charging mode.

[0056] Step 104 : Control the output power of the energy storage system based on the second PID control algorithm to control the output power of the solar energy storage system to a grid-connected power target value.

[0057] In an embodiment of the present invention, both the first and second PID control algorithms are voltage outer-loop and current inner-loop control algorithms, and the first and second PID control algorithms have different numerical values. Based on the voltage outer-loop and current inner-loop control algorithms, the measured boost voltage and output current of the energy storage battery are used as inputs for a second PWM signal to generate a modulated second PWM signal, and the bidirectional DC-DC circuit is controlled based on the modulated second PWM signal. The boost voltage of the energy storage battery refers to the voltage obtained by boosting the output voltage of the energy storage battery via the bidirectional DC-DC circuit. The grid-connected power target value is subtracted from the acquired active output power of the photovoltaic storage system to obtain an output power deviation. The output power deviation, the measured AC output current of the energy storage system, and the AC output voltage of the energy storage system are used as inputs for a space vector pulse width modulation (SVPWM) signal to obtain a modulated SVPWM signal. The energy storage converter is controlled using the modulated SVPWM signal to control the output power of the energy storage system. In this embodiment of the present invention, the modulated SVPWM signal can optimize the switching pattern, improve voltage utilization, reduce harmonic distortion, improve dynamic response, simplify the control strategy, and reduce switching power consumption, thereby improving the overall performance and operating efficiency of the system.

[0058] Specifically, the boosted voltage V_dc of the energy storage battery is subtracted from the reference voltage V_dc* of the energy storage battery to obtain the boosted voltage deviation of the energy storage battery; the boosted voltage V_dc of the energy storage battery is controlled by the output current I_bat of the energy storage battery so that the boosted voltage deviation of the energy storage battery is less than a preset threshold, a modulated second PWM signal is generated, and the bidirectional DC-DC circuit is controlled according to the modulated second PWM signal.

[0059] Figure 3 A schematic diagram of a voltage outer loop and current inner loop control algorithm provided by an embodiment of the present invention is shown in FIG. Figure 3As shown, the boosted voltage V_dc of the energy storage battery and the reference voltage V_dc* of the energy storage battery are used as inputs to the PI controller. The PI controller outputs the reference current I_bat* of the energy storage battery based on the voltage deviation after the boost. A first integrator is provided after the PI controller, which is used to integrate the output signal of the PI controller to generate a corresponding control signal. A second integrator is provided after the second PID controller, which is used to integrate the output signal of the second PID controller to generate a modulated second PWM signal. In this embodiment of the present invention, dual closed-loop control of the voltage outer loop and the current inner loop is implemented using the PI controller and the second PID controller, ensuring system stability and improving system response speed.

[0060] The technical solution provided in the embodiment of the present invention can quickly respond to fluctuations in the output power of the photovoltaic system. By adjusting the working mode and output power of the energy storage system, the output power of the photovoltaic storage system is made relatively stable, thereby ensuring the operating efficiency of the photovoltaic storage system and improving the stability of the power grid.

[0061] Figure 4 A schematic diagram of the structure of a solar storage system provided by an embodiment of the present invention is shown in FIG. Figure 4 As shown, the photovoltaic storage system includes photovoltaic cells, an inverter, a modular substation, an integrated converter, and an energy storage device. The inverter's DC side is electrically connected to the photovoltaic cells, and its AC side is electrically connected to the modular substation. The modular substation is electrically connected to the integrated converter, which is then electrically connected to the energy storage device. Both the modular substation and the integrated converter are connected to the grid.

[0062] In an embodiment of the present invention, the integrated converter includes a transformer and an energy storage converter. The energy storage converter includes a DC-DC bidirectional circuit (not shown in the figure). The DC-DC bidirectional circuit is used to achieve smooth switching of the energy storage system between charging mode and discharging mode.

[0063] The technical solution provided in the embodiment of the present invention can quickly respond to fluctuations in the output power of the photovoltaic system. By adjusting the working mode and output power of the energy storage system, the output power of the photovoltaic storage system is made relatively stable, thereby ensuring the operating efficiency of the photovoltaic storage system and improving the stability of the power grid.

[0064] In the embodiment of the present invention, the initial photovoltaic irradiation intensity is set to 1000W / m 2 , the grid-connected power target value is set to 14000W. At t=1s, the irradiation intensity is 1000W / m 2 Down to 700W / m 2 At t = 2s, the irradiation intensity is 700W / m 2 Increased to 1200W / m 2To verify the output power of the photovoltaic storage system. Adjustments to the irradiation intensity will cause fluctuations in the output power of the photovoltaic system. If the output power of the energy storage system is not adjusted or intervened in time, the output power of the photovoltaic storage system will become unstable.

[0065] Figure 5 A schematic diagram of output power provided by an embodiment of the present invention is shown in FIG. Figure 5 As shown in the figure, due to the influence of radiation intensity, the output power of the PV system suddenly changes at t = 1s and t = 2s. To balance the fluctuations in the output power of the PV system, the output power of the energy storage system also changes suddenly at t = 1s and t = 2s. The energy storage system is in discharge mode from t = 0 to 2s, outputting power to the grid. From t = 2 to 3s, it is in charging mode, generating power from the PV system and feeding it into the grid while simultaneously charging the energy storage system.

[0066] like Figure 5 As shown, the output power of the photovoltaic storage system is stable at around 14000W, that is, the output power of the photovoltaic storage system is stable at around the grid-connected power target value, indicating that the control method of the photovoltaic storage system output power provided by the embodiment of the present invention can quickly respond to fluctuations in the output power of the photovoltaic system, and by adjusting the output power of the energy storage system, the output power of the photovoltaic storage system is stabilized at around the grid-connected power target value, thereby improving the stability of the power grid.

[0067] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for controlling the output power of a photovoltaic storage system, characterized in that: The method comprises: Calculate the output power of the photovoltaic system based on the measured inverter output current and inverter output voltage; Based on the maximum power point tracking (MPPT) algorithm and the first proportional-integral-derivative (PID) control algorithm, the output power of the photovoltaic system is controlled at the maximum power point; Controlling the operating mode of the energy storage system according to the output power of the photovoltaic system and a preset grid-connected power target value; The output power of the energy storage system is controlled based on the second PID control algorithm to control the output power of the photovoltaic storage system to the grid-connected power target value.

2. The method according to claim 1, characterized in that The method of controlling the output power of the photovoltaic system at a maximum power point based on the MPPT algorithm and the first PID control algorithm includes: Using the measured photovoltaic cell output current and photovoltaic cell output voltage as inputs to the MPPT algorithm, and controlling a DC-DC converter DC-DC boost circuit using the MPPT algorithm; Subtracting the measured photovoltaic cell boost voltage from the photovoltaic cell reference voltage to obtain a photovoltaic cell boosted voltage deviation; the photovoltaic cell boost voltage refers to the DC voltage after the photovoltaic cell output voltage is boosted by the DC-DC boost circuit; Performing coordinate transformation on the inverter output current through a coordinate transformation matrix to obtain a DC current; Using the boosted voltage deviation of the photovoltaic cell and the DC current as inputs of a first pulse width modulation (PWM) signal to obtain a modulated first PWM signal; Based on the first PID control algorithm, the output power of the photovoltaic system is controlled according to the modulated first PWM signal, so as to control the output power of the photovoltaic system at a maximum power point.

3. The method according to claim 2, characterized in that The MPPT algorithm includes a conductance increment method, a constant voltage method or a perturbation and observation method.

4. The method according to claim 1, wherein The second PID control algorithm includes a voltage outer loop and current inner loop control algorithm. Controlling the output power of the energy storage system based on the second PID control algorithm includes: Based on the voltage outer loop and current inner loop control algorithm, the measured boost voltage of the energy storage battery and the output current of the energy storage battery are used as inputs of a second PWM signal to generate a modulated second PWM signal, and the bidirectional DC-DC circuit is controlled according to the modulated second PWM signal; the boost voltage of the energy storage battery refers to the voltage obtained by boosting the output voltage of the energy storage battery by the bidirectional DC-DC circuit; Subtracting the grid-connected power target value from the acquired active output power of the photovoltaic storage system to obtain an output power deviation; Using the output power deviation, the measured AC output current of the energy storage system, and the AC output voltage of the energy storage system as inputs of a space vector pulse width modulation (SVPWM) signal to obtain a modulated SVPWM signal; The energy storage converter is controlled by the modulated SVPWM signal to control the output power of the energy storage system.

5. The method according to claim 4, characterized in that The method comprises: using the measured boost voltage and output current of the energy storage battery as inputs of a second PWM signal based on the voltage outer loop and current inner loop control algorithm, generating a modulated second PWM signal, and controlling the bidirectional DC-DC circuit according to the modulated second PWM signal, including: Subtracting the boosted voltage of the energy storage battery from the reference voltage of the energy storage battery to obtain a boosted voltage deviation of the energy storage battery; The boost voltage of the energy storage battery is controlled by the output current of the energy storage battery so that the voltage deviation of the boosted energy storage battery is less than a preset threshold, a modulated second PWM signal is generated, and the bidirectional DC-DC circuit is controlled according to the modulated second PWM signal.

6. The method according to claim 1, characterized in that The working mode includes a charging mode and a discharging mode; The controlling of the working mode of the energy storage system by the output power of the photovoltaic system and the preset grid-connected power target value includes: If the output power of the photovoltaic system is less than the grid-connected power target value, setting the operating mode of the energy storage system to a discharge mode; If the output power of the photovoltaic system is greater than the grid-connected power target value, the operating mode of the energy storage system is set to a charging mode.

7. A solar storage system, characterized in that: The photovoltaic storage system includes photovoltaic cells, inverters, box-type substations, integrated converters and energy storage devices; The DC side of the inverter is electrically connected to the photovoltaic cell, and the AC side is electrically connected to the box-type substation; The box-type substation is electrically connected to the integrated converter; The converter is electrically connected to the energy storage device; The box-type substation and the integrated converter are both connected to the power grid.

8. The solar storage system according to claim 7, characterized in that: The integrated converter includes a transformer and an energy storage converter. The energy storage converter includes a DC-DC bidirectional circuit. The DC-DC bidirectional circuit is used to achieve smooth switching of the energy storage system between a charging mode and a discharging mode.

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