Photovoltaic-energy storage hybrid power spring system and control strategy thereof

Abstract

The invention relates to the field of power electronics, and discloses a photovoltaic-energy storage hybrid power spring system and a control strategy thereof. The hybrid power spring system is composed of a photovoltaic unit, an energy storage battery unit, a double-input single-output inverter, a Boost converter and a low-pass filter, a low-voltage direct-current port of the double-input single-output inverter is connected with the photovoltaic unit, and a high-voltage direct-current port of the double-input single-output inverter is connected with the energy storage battery unit. And the photovoltaic unit is connected with the energy storage battery unit through a Boost converter. According to the hybrid power spring system, reasonable distribution of power among photovoltaic power, energy storage power and load power is achieved, the power of the load can be stabilized, photovoltaic power generation power can be utilized to the maximum extent, and the energy storage requirement is reduced.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a photovoltaic-energy storage hybrid electric spring system and its control strategy. Background Technology

[0002] As global warming and the energy crisis gain increasing attention, various forms of new energy sources have been deployed into the power grid. However, the intermittent nature of renewable energy generation poses a significant challenge to the real-time supply and demand balance of the power grid. The traditional "on-demand generation" model of the power grid will be greatly weakened, and the power system will face unprecedented challenges. To address these issues, demand-side management methods, such as battery energy storage systems, have been widely adopted. However, battery energy storage systems typically require large storage capacities, increasing operating costs and potentially causing secondary pollution.

[0003] To address this issue, research has proposed the concept of a "power spring," which transfers power fluctuations in the power grid to devices insensitive to voltage changes (i.e., non-critical loads), thereby ensuring voltage stability for critical loads and reducing system energy storage capacity. Currently, most power springs use energy storage batteries as the input source on their DC side, a configuration that can directly compensate for active and reactive power in the system. However, the introduction of energy storage batteries contradicts the original intention of power springs to reduce energy storage. To solve this problem, research has proposed a photovoltaic power spring system, using photovoltaic cells as the input DC source. However, in the absence of battery energy storage, large power fluctuations in the photovoltaic cells can adversely affect the normal operation of the load. Therefore, further research has proposed connecting the photovoltaic cells and energy storage batteries in series as the input DC source. However, this series configuration requires both the photovoltaic cells and the energy storage batteries to operate simultaneously, making control extremely complex.

[0004] Therefore, more effective solutions are needed to address these challenges in order to ensure the stability and reliability of the power grid while maximizing the utilization of photovoltaic power generation. Summary of the Invention

[0005] In view of the aforementioned existing problems, the present invention is proposed.

[0006] Therefore, the technical problem solved by this invention is that when a photovoltaic unit experiences large power fluctuations in the absence of a battery energy storage unit, it will have an adverse effect on the normal operation of the load.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: In a first aspect, the present invention provides a photovoltaic-energy storage hybrid electric spring system, comprising: Photovoltaic unit, energy storage battery unit, dual-input single-output inverter, boost converter and low-pass filter; The dual-input single-output inverter has two DC input ports: a low-voltage DC port and a high-voltage DC port. The low-voltage DC port is connected to the photovoltaic unit, and the high-voltage DC port is connected to the energy storage battery unit. The photovoltaic unit and the energy storage battery unit are connected through a Boost converter; The inverter's AC output terminal is connected in series with the low-pass filter's inductor L and in parallel with the low-pass filter's capacitor C; the low-pass filter's capacitor C is connected to a non-critical load. Z NCL After being connected in series, it is connected to the common connection point PCC.

[0008] As a preferred embodiment of the photovoltaic-energy storage hybrid electric spring system described in this invention, wherein: The two DC input terminals of the dual-input single-output inverter are connected to the photovoltaic unit and the energy storage battery unit, respectively. The photovoltaic unit and the energy storage battery unit can supply power to the inverter independently or simultaneously.

[0009] As a preferred embodiment of the photovoltaic-energy storage hybrid electric spring system described in this invention, wherein: When the photovoltaic unit operates independently, the switching transistor is controlled. S L1 , S L2 , S 3 and S 4. Adjust the inverter output; When the energy storage battery unit operates independently, it is controlled by the switching transistor. S 1. S 2. S 3 and S 4. Adjust the inverter output; When the photovoltaic unit and the energy storage battery unit are working simultaneously, the inverter output is adjusted by controlling all the switching transistors.

[0010] Secondly, the present invention provides a control strategy for a photovoltaic-energy storage hybrid electric spring system, including: Collect voltage signal at the point of common coupling (PCC) v S Current signal flowing into the point of common coupling (PCC) i G Output voltage signal of hybrid electric spring system v ES Current signals flowing into non-critical loads i SL Voltage of photovoltaic unit v PV and currenti PV and the voltage of the energy storage battery unit v BAT and current i BAT ; The voltage signal at the common coupling point PCC v S effective value V S With a given voltage reference value V Sref The difference is calculated, and the difference is passed through a proportional-integral controller to output the x-axis component of the electric spring's output voltage. v ESx effective value V ESx ; The voltage signal at the common coupling point PCC v S Input to the phase-locked loop module to obtain the voltage signal at the point of common coupling (PCC). v S Real-time phase ; The voltage signal at the common junction point PCC v S and the current signal at the common junction PCC i G Input power calculation module, output real-time active power injected into the load by the power grid. P IN ; Photovoltaic voltage signal v PV and photovoltaic current signal i PV Input power calculation module, output photovoltaic unit output power P PV The controller will, according to P IN and P PV The value is used to calculate and output the reference power of the hybrid electric spring. P ESref and the reference power of the energy storage battery cell P BATref ; The voltage signal of the hybrid electric spring system v ES and current signals flowing into non-critical loads i SL Input power calculation module, output actual active power of electric spring P ES ; the voltage signal of the energy storage battery unit vBAT and the current signal of the energy storage battery cell i BAT Input power calculation module, output actual active power of energy storage battery P BAT ; The actual active power of the electric spring P ES Reference power of the hybrid electric spring P ESref The difference is input to a proportional-integral controller, which outputs the load voltage. Angle value; the obtained V ESx , , V Sref as well as The angle numerical input voltage reference calculation module outputs the reference voltage of the electric spring. v ESref The actual active power of the energy storage battery P BAT Reference power of energy storage battery cell P BATref The difference is input to a proportional-integral controller, which outputs the reference voltage of the Boost converter. v DCref ; The output reference voltage signal of the electric spring v ESref and the reference voltage of the Boost converter v DCref Input the corresponding PWM signal generators to obtain the drive signals for the switching transistors of the dual-input single-output inverter and the Boost converter.

[0011] As a preferred embodiment of the photovoltaic-energy storage hybrid electric spring system control strategy described in this invention, the system controls the power input from the grid based on the grid input power. P IN Power generated by photovoltaic units P PV Size, select working mode; when P PV =0, and P IN < P CL + P NCL At that time, the hybrid electric spring system will select operating mode one; when P PV + P IN <P CL + P NCL At this time, the hybrid electric spring system will select operating mode two; when P CL + P NCL ≤ P PV + P IN ,and P IN < P CL + P NCL At that time, the hybrid electric spring system will select operating mode three; when P CL + P NCL ≤ P IN At that time, the hybrid electric spring system will select operating mode four.

[0012] As a preferred embodiment of the control strategy for the photovoltaic-energy storage hybrid electric spring system described in this invention, in operating mode one, the energy storage battery unit supplies power to the inverter independently, and the active power output of the hybrid electric spring system is... P ES = P BAT = P CL + P NCL - P IN .

[0013] As a preferred embodiment of the control strategy for the photovoltaic-energy storage hybrid electric spring system described in this invention, in operating mode two, both the photovoltaic unit and the energy storage battery unit simultaneously supply power to the inverter, and the active power output by the hybrid electric spring system is... P ES = P BAT + P PV = P CL + P NCL - P IN .

[0014] As a preferred embodiment of the control strategy for the photovoltaic-energy storage hybrid electric spring system described in this invention, in operating mode three, the photovoltaic unit supplies power to the inverter independently, while simultaneously charging the energy storage battery with the remaining active power through the Boost converter; the active power output by the hybrid electric spring system is... P ES = P BAT + P PV = P CL + P NCL - P IN .

[0015] As a preferred embodiment of the control strategy for the photovoltaic-energy storage hybrid electric spring system described in this invention, in operating mode four, the inverter supplies power to the battery unit alone, and the photovoltaic unit is shut down; that is, the active power output of the hybrid electric spring system is... P ES = P BAT = P CL + P NCL - P IN .

[0016] As a preferred embodiment of the control strategy for the photovoltaic-energy storage hybrid electric spring system described in this invention, the source-load active power balance relationship is as follows: P PV + P IN = P CL + P NCL The active power output of the hybrid electric spring system is P ES = P PV + P BAT .

[0017] Compared with existing technologies, the beneficial effects of this invention are as follows: By using both photovoltaic units and battery energy storage units as input voltage sources, this invention constructs a hybrid electric spring system with the ability to adaptively adjust the overall active power. It can flexibly achieve multiple operating modes, including individual operation of the photovoltaic unit, individual operation of the energy storage battery, and synergistic operation of both. Compared with traditional systems with a single input source, this invention can maintain stable operation even under extreme conditions, such as insufficient photovoltaic power generation or low energy storage battery capacity, avoiding the risk of system paralysis due to the failure of a single input source. Simultaneously, this invention can dynamically adjust the power output of the photovoltaic unit and the energy storage battery unit based on real-time photovoltaic power generation and grid-injected power, maximizing the utilization of renewable energy, reducing dependence on the traditional grid, and lowering energy costs. In cases of insufficient sunlight, the energy storage battery unit can supplement the power gap, ensuring continuous and stable system operation; while in cases of excess photovoltaic power, the energy storage battery unit can store excess energy, avoiding energy waste, thereby achieving efficient energy utilization. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of a photovoltaic-energy storage hybrid electric spring system according to an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of signal sampling for a photovoltaic-energy storage hybrid electric spring system according to an embodiment of the present invention.

[0021] Figure 3 This is a control block diagram of a photovoltaic-energy storage hybrid electric spring system according to an embodiment of the present invention.

[0022] Figure 4 This is a logic block diagram of the reference power calculation process for a photovoltaic-energy storage hybrid electric spring system control strategy according to an embodiment of the present invention.

[0023] Figure 5 This is a structural block diagram of a reference voltage calculator for a photovoltaic-energy storage hybrid electric spring system control strategy according to an embodiment of the present invention.

[0024] Figure 6 This is a schematic diagram of the power distribution simulation waveform of a photovoltaic-energy storage hybrid electric spring system in mode one, according to an embodiment of the present invention.

[0025] Figure 7 This is a schematic diagram of the power distribution simulation waveform of a photovoltaic-energy storage hybrid electric spring system in mode two, according to an embodiment of the present invention.

[0026] Figure 8 This is a schematic diagram of the power distribution simulation waveform of a photovoltaic-energy storage hybrid electric spring system in mode three, according to an embodiment of the present invention.

[0027] Figure 9 This is a schematic diagram of the power distribution simulation waveform of a photovoltaic-energy storage hybrid electric spring system in mode four, according to an embodiment of the present invention. Detailed Implementation

[0028] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0029] Example 1, referring to Figures 1-2 As one embodiment of the present invention, a photovoltaic-energy storage hybrid electric spring system is provided, such as... Figure 1 As shown, typical application systems of electric springs include power grids. v G Line impedance Z 1. Critical load Z CL Non-critical load Z NCL Electric springs; In this embodiment of the application, the hybrid electric spring is composed of an energy storage battery unit, a photovoltaic unit, a dual-input single-output inverter, a boost converter, and a low-pass filter; The dual-input single-output inverter has two DC input ports: a low-voltage DC port and a high-voltage DC port. The low-voltage DC port is connected to the photovoltaic unit, and the high-voltage DC port is connected to the energy storage battery unit. The photovoltaic unit and the energy storage battery unit are connected through a Boost converter; The inverter's AC output terminal is connected in series with the low-pass filter's inductor L and in parallel with the low-pass filter's capacitor C; the low-pass filter's capacitor C is connected to a non-critical load. Z NCL After being connected in series, it is connected to the common junction point (PCC).

[0030] Figure 1 S1, S2, S3, S4, S L1 and S L2 It consists of six switching transistors that combine electric springs; i G This refers to the current flowing from the generator end into the PCC point. i SL The current flowing through the electric spring; v S This refers to the voltage at the PCC point, or the critical load voltage. v O The voltage for non-critical loads; v ES This is the output voltage of the electric spring.

[0031] It should be noted that, as Figure 2 As shown, with critical load voltage v s The direction is referenced to the x-axis, and the y-axis is perpendicular to the x-axis. The output voltage of the electric spring is... v ES It can be decomposed into x-axis components. v ESx and y-axis components v ESy Based on the relationships between the sides and angles of a triangle, we can write: v ESx and v ESy The expressions are as follows:

[0032] In the formula, V ESx x-axis components v ESx Valid value.

[0033] Active power of electric spring P ES The expression is:

[0034] In the formula, I SL The current flowing through the electric spring i SL The effective value, The impedance angle for non-critical loads. This is the output load voltage angle. From the above equation, it can be seen that it can be controlled... The angle is used to control the active power of the electric spring.

[0035] In this embodiment of the application, the two DC input terminals of the dual-input single-output inverter are respectively connected to a photovoltaic unit and an energy storage battery unit; The photovoltaic unit and the energy storage battery unit can supply power to the inverter independently or simultaneously.

[0036] Specifically, the energy storage battery unit and the photovoltaic unit serve as the input source for the electric spring, and the two are connected by a boost connection to provide an auxiliary power transmission path; Furthermore, the dual-input single-output inverter is a single-stage power converter; Furthermore, when the hybrid electric spring is operating, the photovoltaic unit can generate active power, and the energy storage battery unit can consume or release active power. The system will rationally allocate power based on the photovoltaic unit's power generation and the grid input power; It should be noted that this structure supports multiple modes of operation, including independent operation of photovoltaic units, independent operation of energy storage batteries, and joint operation of both. It can adapt to different scenarios, thereby enhancing the robustness of the system under extreme conditions and avoiding system paralysis caused by the failure of a single input source.

[0037] In this embodiment of the application, when the photovoltaic unit operates independently, the switching transistor is controlled. S L1 , S L2 , S 3 and S 4. Adjust the inverter output; When the energy storage battery unit operates independently, it is controlled by the switching transistor. S 1. S 2. S 3 and S 4. Adjust the inverter output; When the photovoltaic unit and the energy storage battery unit are working simultaneously, the inverter output is adjusted by controlling all the switching transistors.

[0038] It should be noted that the structure of the present invention can accurately adjust the output voltage and power of the power spring by real-time acquisition of voltage and current signals at the point of common coupling (PCC), combined with a proportional-integral controller (PI) and a phase-locked loop module (PLL), to ensure the power and voltage stability of critical loads, while transferring power fluctuations to non-critical loads and maintaining the overall stability of the system.

[0039] Example 2, refer to Figures 1-5 As an embodiment of the present invention, based on the above embodiment, a control strategy for a photovoltaic-energy storage hybrid electric spring system is provided.

[0040] Figure 2 All voltage and current signals required for the proposed hybrid electric spring system are given. Based on this, Figure 3 Furthermore, a control strategy for a hybrid electric spring system for real-time regulation of photovoltaic-energy storage batteries is proposed, the steps of which in one control cycle are as follows: A1: Acquire the voltage signal at PCC. v S Current signal flowing into PCC point i G Output voltage signal of hybrid electric spring system v ES Current signals flowing into non-critical loads i SL Voltage of photovoltaic unit v PV and current i PV and the voltage of the energy storage battery unit v BAT and current i BAT ; A2: Transmit voltage signal v S effective value ( Figure 3 (RMS) V S With a given voltage reference value V Sref The difference is calculated, and the difference is passed through a proportional-integral (PI) controller, whose output is the x-axis component of the electric spring's output voltage. v ESx effective value V ESx ; A3: Transmit voltage signal v S Input to the phase-locked loop module to obtain the voltage signal v S Real-time phase ; A4: Transmit voltage signal v S and current signal i G Input power calculation module, output real-time active power injected into the load by the power grid. P IN ; Photovoltaic voltage signal v PV and current signal i PV Input power calculation module, output photovoltaic unit output power P PV The controller will, according to P IN and P PVThe value is used to calculate and output the reference power of the hybrid electric spring. P ESref and the reference power of the energy storage battery cell P BATref ; A5: Transmit voltage signal v ES and current signal i SL Input power calculation module, output actual active power of electric spring P ES ; to voltage signal v BAT and current signal i BAT Input power calculation module, output actual active power of energy storage battery P BAT ; A6: Will P ES and P ESref After the difference is calculated, it is input to a proportional-integral (PI) controller, and the output is the load voltage angle ( (Angle) value; the obtained V ESx , , V Sref as well as Input voltage reference calculation module, output electric spring output reference voltage v ESref ;Will P BAT and P BATref The difference is input to a proportional-integral (PI) controller, which outputs the reference voltage of the Boost converter. v DCref ; A7: Transmit voltage signal v ESref and v DCref By inputting the corresponding pulse width modulation (PWM) signal generators, the drive signals for the switching transistors of the dual-input single-output inverter and the Boost converter are obtained, namely: Figure 2 and Figure 3 PWM1 and PWM2.

[0041] Furthermore, the load voltage angle ( (Angle) represents the critical load voltage, i.e., the voltage signal at the point of common coupling (PCC). v S Non-critical load voltage The angle between them; Furthermore, the voltage signal at the common connection point PCC... v S effective value V S and V Sref After subtraction, input to a proportional-integral controller to obtain... v ESx Reference effective value V ESxref ; In this embodiment of the application, the system selects the operating mode based on the power input from the power grid and the power output of the photovoltaic unit; definition P IN To inject real-time active power into the load side of the power grid. P CL The rated active power of the critical load. P NCL Rated active power for non-critical loads; P PV The active power generated by the photovoltaic unit. P BAT This refers to the active power of the energy storage battery unit; when P PV =0, and P IN < P CL + P NCL At that time, the hybrid electric spring system will select operating mode one; when P PV + P IN < P CL + P NCL At this time, the hybrid electric spring system will select operating mode two; when P CL + P NCL ≤ P PV + P IN ,and P IN < P CL + P NCL At that time, the hybrid electric spring system will select operating mode three; when P CL +P NCL ≤ P IN At that time, the hybrid electric spring system will select operating mode four.

[0042] Specifically, Figure 4 The flowchart for selecting the reference active power selector in step A4 is shown.

[0043] In this embodiment of the application, in operating mode one, the energy storage battery unit supplies power to the inverter independently, and the active power output of the hybrid electric spring system is... P ES = P BAT = P CL + P NCL - P IN .

[0044] Specifically, the active power of the electric spring P ES The calculation formula is:

[0045] in, I SL for i SL The valid value of is expressed as follows:

[0046] At this point, the power of critical loads and non-critical loads and P L This can be expressed as:

[0047] Based on the law of conservation of power, we can then conclude:

[0048] Combining the above formulas, we can obtain The expression, that is:

[0049] Then v O Substituting the expression P L From this, we can obtain P ES The expression is:

[0050] Through observation PES The expression, in When it falls within the range of (φ-π / 2, φ), then... P ES and The magnitudes are positively correlated. Therefore, by controlling... To control the magnitude of power fluctuations borne by non-critical loads.

[0051] In this embodiment of the application, in operating mode two, both the photovoltaic unit and the energy storage battery unit simultaneously supply power to the inverter, and the active power output of the hybrid electric spring system is... P ES = P BAT + P PV = P CL + P NCL - P IN .

[0052] In this embodiment, in operating mode three, the photovoltaic unit supplies power to the inverter independently, while simultaneously charging the energy storage battery with the remaining active power through the Boost converter; the active power output of the hybrid electric spring system is... P ES = P PV + P BAT = P CL + P NCL - P IN .

[0053] In this embodiment, in operating mode four, the inverter supplies power to the battery unit alone, and the photovoltaic unit shuts down; that is, the active power output of the hybrid electric spring system is... P ES = P BAT = P CL + P NCL - P IN .

[0054] It should be noted that this control strategy can dynamically select four operating modes based on the real-time changes in grid input power and photovoltaic power generation, thereby achieving a reasonable power distribution among photovoltaic units, energy storage battery units and loads, ensuring that the system can operate efficiently under different operating conditions, such as insufficient or excessive photovoltaic power generation.

[0055] In this embodiment of the application, the source-load active power balance relationship is as follows: P PV + P IN = P CL + P NCL The active power output of the hybrid electric spring system is P ES = P PV + P BAT。

[0056] Specifically, Figure 5 The voltage reference calculation module in step A6 is shown (i.e. Figure 3 The internal control block diagram of the voltage reference calculation module (VRC) is shown. The voltage reference calculation module calculates the voltage based on the input... V ESx , , V Sref , The value and the following two expressions:

[0057] First, two components of the reference output voltage of the electric spring are calculated: the x-axis reference component and the y-axis reference component. The x-axis direction is related to the voltage signal. v S The directions are the same, but the y-axis leads the x-axis by π / 2, thus we get:

[0058] The output reference voltage of the electric spring can then be calculated. v ES .

[0059] At the same time, P BATref and P BAT The difference is input to a proportional-integral controller, which outputs the reference output voltage signal of the Boost converter.

[0060] In summary, this invention, based on a dual-input single-output inverter, constructs a hybrid electric spring system by using both photovoltaic (PV) units and energy storage battery units as input sources for the electric spring. This system possesses the ability to adaptively adjust the overall active power, flexibly enabling various operating modes, including individual PV unit operation, individual energy storage battery operation, and synergistic operation of both. Furthermore, this hybrid electric spring system can dynamically adjust the power flow among the PV unit, energy storage battery unit, and non-critical loads based on real-time grid-injected power and PV power generation, thereby achieving efficient system operation and optimal utilization of PV power generation.

[0061] Example 3, referring to Figures 6-9 As an embodiment of the present invention, based on the above embodiment, in order to verify the effectiveness of the control strategy of the present invention, a simulation experiment of the control strategy of the photovoltaic-energy storage hybrid electric spring system is provided.

[0062] Simulation experiments were conducted using PLECS software, with the experimental parameters set as follows: rated voltage at point PCC. V Sref =220V, rated operating frequency f =50Hz, critical load Z CL =19.36Ω, non-critical load Z NCL =(12.39+ j 9.29 Ω, rated power of critical load P CL =2500W, rated power for non-critical loads P NCL =2500W. Furthermore, to verify the performance of DD-ES under different operating modes, the power injected from the generator end to the load end and the photovoltaic power generation will be adjusted to verify each operating mode.

[0063] like Figure 6 As shown, P IN =4000W and P PV Under the condition that =0, P IN <( P CL + P NCL The system operates in mode one. During the 0s-2s period when the electric spring is not engaged, the power of critical loads and non-critical loads is affected by the generated power. After the electric spring is engaged from 2s to 4s, P CL and P NCLIt is stabilized at a rated value of 2500W. The energy storage battery unit will output power through a dual-input single-output inverter. P ES = P BAT = 1000W.

[0064] like Figure 7 As shown, P IN =4100W and P PV Under the condition of 540W, P PV + P IN < P CL + P NCL The system operates in mode two. During the 0s-2s period when the power spring is not engaged, the power of critical loads and non-critical loads is affected by the generated power. The photovoltaic units charge the battery through the Boost converter. P BAT = P PV After the electric spring is applied for 2 to 4 seconds, P CL and P NCL It is stabilized at the rated value of 2500W. The photovoltaic unit and energy storage battery unit output power through a dual-input single-output inverter, i.e. P ES = P BAT + P PV =900W, P BAT =360W.

[0065] like Figure 8 As shown, P IN =4400W and P PV Under the condition of 800W, P CL + P NCL ≤ P PV + P IN ,and P IN < P CL + P NCLThe system operates in mode three. During the 0s-2s period, no power spring is engaged. The power of critical and non-critical loads is affected by the generated power. The photovoltaic units charge the battery through the Boost converter. P BAT = P PV After the electric spring is applied for 2 to 4 seconds, P CL and P NCL It is stabilized at the rated value of 2500W. The photovoltaic unit outputs power independently through a dual-input single-output inverter, while the remaining active power charges the energy storage battery unit through a boost converter. P ES =600W, P BAT = P ES - P PV =-200W.

[0066] like Figure 9 As shown, P IN Under the condition of 5500W, P CL + P NCL < P IN The system operates in mode four. During the 0s-2s period, the electric spring is not engaged, and the power of both critical and non-critical loads is affected by the generation power. After the electric spring is engaged between 2s and 4s, P CL and P NCL It was stabilized at the rated value of 2500W. At this time, the hybrid electric spring system charged the energy storage battery unit, i.e. P ES = P BAT =-500W.

[0067] Simulation results demonstrate that the hybrid electric spring proposed in this invention can achieve precise real-time power control at the load end through photovoltaic units without involving battery energy storage. Under different input power conditions, the system not only ensures power stability for critical loads but also strictly limits power fluctuations of non-critical loads within permissible ranges, thereby significantly improving the utilization rate of photovoltaic power generation. Furthermore, the system's power control strategy achieves a rational power allocation among the photovoltaic unit, battery energy storage unit, and load.

[0068] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A photovoltaic-energy storage hybrid electric spring system, characterized in that, include: Photovoltaic unit, energy storage battery unit, dual-input single-output inverter, boost converter and low-pass filter; The dual-input single-output inverter has two DC input ports: a low-voltage DC port and a high-voltage DC port. The low-voltage DC port is connected to the photovoltaic unit, and the high-voltage DC port is connected to the energy storage battery unit. The photovoltaic unit and the energy storage battery unit are connected through a Boost converter; The inverter's AC output terminal is connected in series with the low-pass filter's inductor L and in parallel with the low-pass filter's capacitor C; the low-pass filter's capacitor C is connected to a non-critical load. Z NCL After being connected in series, it is connected to the common connection point PCC.

2. The photovoltaic-energy storage hybrid electric spring system as described in claim 1, characterized in that, The two DC input terminals of the dual-input single-output inverter are connected to the photovoltaic unit and the energy storage battery unit, respectively. The photovoltaic unit and the energy storage battery unit can supply power to the inverter independently or simultaneously.

3. The photovoltaic-energy storage hybrid electric spring system as described in claim 2, characterized in that, When the photovoltaic unit operates independently, the switching transistor is controlled. S L1 , S L2 , S 3 and S 4. Adjust the inverter output; When the energy storage battery unit operates independently, it is controlled by the switching transistor. S 1. S 2. S 3 and S 4. Adjust the inverter output; When the photovoltaic unit and the energy storage battery unit are working simultaneously, the inverter output is adjusted by controlling all the switching transistors.

4. A control strategy for a photovoltaic-energy storage hybrid electric spring system, employing a photovoltaic-energy storage hybrid electric spring system as described in any one of claims 1-3, characterized in that: Collect voltage signal at the point of common coupling (PCC) v S Current signal flowing into the point of common coupling (PCC) i G Output voltage signal of hybrid electric spring system v ES Current signals flowing into non-critical loads i SL Voltage of photovoltaic unit v PV and current i PV and the voltage of the energy storage battery unit v BAT and current i BAT ; The voltage signal at the common coupling point PCC v S effective value V S With a given voltage reference value V Sref The difference is calculated, and the difference is passed through a proportional-integral controller to output the x-axis component of the electric spring's output voltage. v ESx effective value V ESx ; The voltage signal at the common coupling point PCC v S Input to the phase-locked loop module to obtain the voltage signal at the point of common coupling (PCC). v S Real-time phase ; The voltage signal at the common coupling point PCC v S and the current signal at the common junction PCC i G Input power calculation module, output real-time active power injected into the load by the power grid. P IN ; Photovoltaic voltage signal v PV and photovoltaic current signal i PV Input power calculation module, output photovoltaic unit output power P PV The controller will, according to P IN and P PV The value is used to calculate and output the reference power of the hybrid electric spring. P ESref and the reference power of the energy storage battery cell P BATref ; The voltage signal of the hybrid electric spring system v ES and current signals flowing into non-critical loads i SL Input power calculation module, output actual active power of electric spring P ES ; the voltage signal of the energy storage battery unit v BAT and the current signal of the energy storage battery unit i BAT Input power calculation module, output actual active power of energy storage battery P BAT ; The actual active power of the electric spring P ES Reference power of the hybrid electric spring P ESref The difference is input to a proportional-integral controller, which outputs the load voltage. Angle value; the obtained V ESx , , V Sref as well as The angle numerical input voltage reference calculation module outputs the reference voltage of the electric spring. v ESref The actual active power of the energy storage battery P BAT Reference power of energy storage battery cell P BATref The difference is input to a proportional-integral controller, which outputs the reference voltage of the Boost converter. v DCref ; The output reference voltage signal of the electric spring v ESref and the reference voltage of the Boost converter v DCref Input the corresponding PWM signal generators to obtain the drive signals for the switching transistors of the dual-input single-output inverter and the Boost converter.

5. The control strategy for a photovoltaic-energy storage hybrid electric spring system as described in claim 4, characterized in that, The system is based on the grid input power. P IN Power generated by photovoltaic units P PV Size, select working mode; when P PV =0, and P IN < P CL + P NCL At that time, the hybrid electric spring system will select operating mode one; when P PV + P IN < P CL + P NCL At that time, the hybrid electric spring system will select operating mode two; when P CL + P NCL ≤ P PV + P IN ,and P IN < P CL + P NCL At that time, the hybrid electric spring system will select operating mode three; when P CL + P NCL ≤ P IN At that time, the hybrid electric spring system will select operating mode four.

6. The control strategy for a photovoltaic-energy storage hybrid electric spring system as described in claim 5, characterized in that, In operating mode one, the energy storage battery unit supplies power to the inverter independently, and the active power output of the hybrid electric spring system is... P ES = P BAT = P CL + P NCL - P IN .

7. The control strategy for a photovoltaic-energy storage hybrid electric spring system as described in claim 5, characterized in that, In operating mode two, both the photovoltaic unit and the energy storage battery unit simultaneously supply power to the inverter, and the active power output of the hybrid electric spring system is... P ES = P BAT + P PV = P CL + P NCL - P IN .

8. The control strategy for a photovoltaic-energy storage hybrid electric spring system as described in claim 5, characterized in that, In operating mode three, the photovoltaic units supply power to the inverter independently, while simultaneously charging the energy storage battery through the Boost converter with the remaining active power; the active power output of the hybrid electric spring system is... P ES = P BAT + P PV = P CL + P NCL - P IN .

9. The control strategy for a photovoltaic-energy storage hybrid electric spring system as described in claim 5, characterized in that, In operating mode four, the inverter supplies power solely to the battery unit, and the photovoltaic unit shuts down. This means the hybrid electric spring system outputs an active power of [value missing]. P ES = P BAT = P CL + P NCL - P IN .

10. A control strategy for a photovoltaic-energy storage hybrid electric spring system as described in any one of claims 5-9, characterized in that, The active power balance relationship between source and load is P PV + P IN = P CL + P NCL The active power output of the hybrid electric spring system is P ES = P PV + P BAT .

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