Light-storage combined power supply design and operation coordination control method

Abstract

The invention discloses a light-storage combined power supply design and operation coordination control method, which belongs to the technical field of energy optimization control, and proposes that an error rate in a scheduling period is introduced into an energy storage system optimization control strategy due to the participation of photovoltaic equipment, storage battery equipment and the like, and an error feedback link is added before current closed-loop control by utilizing the error rate; and performing optimization control on a DC / DC bidirectional controller of the energy storage battery. The minimum root-mean-square error of the active power output and the planned active power output of the photovoltaic-energy storage combined power generation system is taken as a target, and the limiting conditions of the charge state of an energy storage battery and the allowable deviation of the combined power generation system are considered in the model. The working state of the energy storage system is determined by detecting and comparing the photovoltaic output power and the load demand power, that is, the energy storage system is used as a slack node of a power grid. In addition, a light-storage combined system hierarchical control system is adopted, and a light-storage coordination control strategy is designed for the direct-current bus voltage and the storage battery current, so that stable operation of a power grid system is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy optimization control, and in particular is a method for designing a photovoltaic and energy-storage combined power supply and coordinating operation control. Background Art

[0002] In recent years, new clean energy has begun to develop rapidly. According to data released by the National Bureau of Statistics, in the first quarter of 2024, the national photovoltaic grid-connected capacity increased by 45.74 million kilowatts, a year-on-year increase of 36%, of which distributed photovoltaics accounted for 23.8 million kilowatts. By the end of March 2024, the national photovoltaic power generation installed capacity reached 659 million kilowatts, a year-on-year increase of 55.0%, of which distributed photovoltaics accounted for 280 million kilowatts. However, the efficiency of photovoltaic power generation is affected by factors such as temperature and light, and its output presents a certain degree of uncertainty. With the popularization of photovoltaic power generation, the uncertainty of photovoltaic power generation output has posed a great challenge to the dispatch of regional power grids. In order to reduce the impact of photovoltaic output uncertainty on the power grid, domestic and foreign scholars have proposed a method of combining photovoltaics and energy storage batteries into a photovoltaic storage combined system, and using energy storage batteries to smooth the active output of photovoltaics. The basic ideas include: using the battery state of charge characteristics to smooth photovoltaic power fluctuations, other power supply equipment and energy storage battery inertia complementation control, using DC bus voltage and photovoltaic reactive power to control the photovoltaic storage combined power generation system, and coordinating and optimizing the photovoltaic storage combined system based on source-grid-load. However, the above methods all have their shortcomings. Therefore, the current research on the photovoltaic and storage combined system still has a lot of abandoned light, the internal control is not perfect, and how to ensure that the output of the photovoltaic and storage combined power generation system meets the dispatching requirements of the regional power grid without abandoning light has become one of the problems that need to be solved urgently. Summary of the invention

[0003] In view of the serious problem of abandoned light and inaccurate control in the photovoltaic and storage combined system, the present invention improves the control strategy of the energy storage part and proposes a photovoltaic and storage combined operation coordinated optimization control strategy to ensure that, under the premise of not abandoning light, the photovoltaic and storage combined power generation system can better track the planned active power output curve of the regional power grid through the optimized control strategy, so that the output of the photovoltaic and storage combined power generation system meets the dispatching requirements of the regional power grid, reduces the number of times the energy storage system operates, and improves the dispatchability of the photovoltaic and storage combined system and the stability of the control system.

[0004] The technical solution of the present invention is as follows: a method for designing a photovoltaic and energy storage combined power supply and coordinating operation control, comprising the following steps: S1 uses the charging and discharging of energy storage batteries to adjust the output power of the photovoltaic and energy storage combined power generation system, so that the planned output power of the photovoltaic and energy storage combined power generation system can track the power generation plan in real time and achieve unbiased scheduling; S2 determines the photovoltaic and battery combined working mode according to the photovoltaic working mode and the battery working mode; S3 designs a hierarchical control system for the photovoltaic and storage combined system according to the characteristics of the operating mode, and designs a photovoltaic and storage coordinated control strategy for the DC bus voltage and battery current.

[0005] Furthermore, step S1 is specifically as follows: S01 Constructing mathematical models The objective function for determining the capacity of the energy storage battery is: (1) Where: T is the scheduling period; P PV (t) is the active power output of the photovoltaic system during period t; P S (t) is the active power output of the energy storage system during period t; P L (t) is the planned output active power during period t.

[0006] The SOC of the energy storage battery needs to meet the following constraints: (2) Where: S t is the state of charge of the battery during period t; S min , S max are the minimum and maximum allowed states of charge, respectively.

[0007] The battery state of charge during period t is: (3) (4) Where: is the self-sustaining discharge rate of the battery; Δ S t is the change in charge within a time period, a positive value indicates discharge, and a negative value indicates charge; η c is the charging efficiency; η d is the discharge efficiency; Δt is the interval time of each period; The particle swarm algorithm is used to solve the mathematical model and determine the capacity of the energy storage battery; During the dispatching period, the photovoltaic energy storage system needs to achieve precise control, that is, the absolute value of the error rate λ is minimized during the dispatching period. The expression of λ is: (5) At the same time, the SOC constraints of the energy storage battery must be met, and the active output constraints of the photovoltaic and energy storage combined power generation system must also be met: (6) Where: Pt Contribute to the photovoltaic and energy storage combined power generation system; P t，min , P t，max They are the minimum and maximum allowable deviations of the photovoltaic and energy-storage combined power generation system, respectively.

[0008] Furthermore, step S2 is specifically as follows: The DC bus voltage stability and power balance need to be met, and the battery state of charge and maximum charge and discharge power need to be considered. The photovoltaic working state and the battery working state need to be combined to obtain the following system working mode: Mode 1: The power generated by the photovoltaic system is greater than the load power, and the battery's state of charge (SOC) is within the allowable operating range. At this time, the battery works in charging mode and the absorbed power does not reach the maximum limit. The DC bus voltage is maintained stable by the battery, and the photovoltaic system works in maximum power point tracking (MPPT) mode. Mode 2: The power generated by the photovoltaic power plant is less than the load power, and the SOC of the battery is within the allowable operating range. At this time, the battery works in the discharge mode and the power generated has not reached the maximum limit. The DC bus voltage is maintained stable by the battery, and the photovoltaic power plant works in the MPPT mode. Mode 3: In mode 1, if the battery SOC exceeds the allowable operating range, the battery does not work or the battery absorption power reaches the limit, and there is still surplus power from the photovoltaic power plant, the photovoltaic power plant operates in constant voltage mode to maintain the stability of the DC bus voltage. Mode 4: In mode 2, the battery SOC exceeds the allowable operating range and the battery does not work. At this time, the power generated by the photovoltaic power plant must be lower than the power consumed by the load, or the power generated by the battery reaches the limit and the power generated by the photovoltaic power plant is still insufficient. In order to maintain the stability of the DC bus voltage, a certain load needs to be removed and the photovoltaic power plant works in the constant voltage mode. Mode 5: At night or on rainy days, the photovoltaic power has no power output, and the battery is within the allowable working range. At this time, the battery works in the discharge mode and maintains the bus voltage stable; Mode 6: The battery is continuously discharged. When its SOC exceeds the allowable operating range, the battery will not work and the entire system will not work either.

[0009] Furthermore, step S3 is specifically as follows: The photovoltaic and storage combined system adopts a hierarchical control system. The upper layer determines the working mode based on the system environment, DC bus voltage, photovoltaic output power, and load power consumption, and transmits the information to the middle layer. The middle layer allocates the working status of photovoltaics and batteries based on the information from the upper layer, and then transmits the information to the lower layer for execution.

[0010] Furthermore, the DAB converter controls both the DC bus voltage and the battery current in Mode 1, Mode 2, and Mode 5. The voltage error is amplified by PI to obtain the reference value of the battery current inner loop. i bref The current error is amplified by PI to obtain the phase shift angle φ of the DAB converter, and then the driving pulse is obtained after pulse width modulation and sent to the H bridges on both sides.

[0011] Furthermore, in mode 3, when the power absorbed by the battery reaches the limit and the photovoltaic system works in the constant voltage mode, only the current of the battery is controlled.

[0012] Furthermore, the Boost converter controls the DC bus voltage in Mode 3 and Mode 4. After the voltage error is amplified by PI, the reference value of the photovoltaic cell current inner loop is obtained. i sref The current error is amplified by PI and then compared with the triangular carrier to generate the gate pulse of the switching tube.

[0013] Furthermore, in Mode 1 and Mode 2, only MPPT control is performed, a voltage reference value is generated after passing through the MPPT controller, and the voltage error is amplified by PI and then compared with the triangular carrier to generate a switch tube gate pulse.

[0014] The beneficial effects of the present invention are: The present invention adopts the participation of photovoltaic, battery and other equipment to propose the introduction of error rate within the scheduling cycle into the optimization control strategy of the energy storage system, and uses the error rate to add a feedback error link before the current closed-loop control to optimize the control of the DC / DC bidirectional controller of the energy storage battery. The goal is to minimize the root mean square error between the active output and the planned active output of the photovoltaic and storage combined power generation system. The model considers the constraints of the charge state of the energy storage battery and the allowable deviation of the combined power generation system. The working state of the energy storage system is determined by detecting and comparing the photovoltaic output power with the load demand power, that is, the energy storage system is used as the relaxation node of the power grid. In addition, a hierarchical control system of the photovoltaic and storage combined system is adopted, and a photovoltaic and storage coordination control strategy is designed for the DC bus voltage and battery current, so as to ensure the stable operation of the power grid system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural diagram of the photovoltaic storage combined system of the present invention; Figure 2 A flow chart for solving the model of the present invention; Figure 3 It is a system working mode diagram of the present invention; Figure 4 It is the bus voltage and battery control design diagram of the present invention; Figure 5 It is the control design diagram of the Boost converter of the present invention; Figure 6 It is a power difference curve diagram before and after optimization of the present invention; Figure 7 This is a stable operation curve diagram of the system under the third working mode of the present invention. DETAILED DESCRIPTION

[0016] See attached Figure 1 To Attachment Figure 7 As shown, the photovoltaic and storage joint operation coordinated optimization control strategy of the dual power supply line integrated power supply system of the photovoltaic system of the present invention takes into account the constraints of the charge state of the energy storage battery and the allowable deviation of the joint power generation system, and optimizes the DC / DC bidirectional controller of the energy storage battery with the goal of minimizing the root mean square error between the active output and the planned active output of the photovoltaic and storage combined power generation system. Design a hierarchical control system for the photovoltaic and storage combined system, and design a photovoltaic and storage coordinated control strategy for the DC bus voltage and battery current, while reducing the number of energy storage system actions, and improving the dispatchability of the photovoltaic and storage combined system and the stability of the control system. .

[0017] (1) Constructing a mathematical model 1) Objective function. The objective function for determining the capacity of the energy storage battery is: (1) Where: T is the scheduling period; PPV(t) is the active power output of the photovoltaic system in period t; PS(t) is the active power output of the energy storage system in period t; PL(t) is the planned active power output in period t.

[0018] 2) Energy storage battery constraints. SOC is an important parameter for measuring batteries, that is, the ratio of the remaining power of the battery under a certain discharge rate to the rated capacity under the same conditions. The SOC of the energy storage battery needs to meet the following constraints: (2) Where: St is the state of charge of the battery during period t; Smin and Smax are the minimum and maximum allowable states of charge, respectively.

[0019] The battery state of charge during period t is: (3) (4) Where: is the self-sustaining discharge rate of the battery; ΔSt is the change in charge within a time period, a positive value indicates discharge, and a negative value indicates charge; ηc is the charging efficiency; ηd is the discharge efficiency; Δt is the interval time of each time period.

[0020] 2) Model solution This paper uses particle swarm algorithm to solve the mathematical model and determine the capacity of the energy storage battery. The specific process is as follows Figure 2 3) Unbiased Optimized Scheduling In order to achieve non-biased scheduling optimization, the photovoltaic energy storage system needs to achieve precise control within the scheduling period, that is, the absolute value of the error rate λ is minimized within the scheduling period. The expression of λ is: (5) At the same time, the SOC constraints of the energy storage battery must be met, and the active output constraints of the photovoltaic and energy storage combined power generation system must also be met: (6) Where: Pt is the output of the photovoltaic and energy-storage combined power generation system; Pt,min and Pt,max are the minimum and maximum allowable deviations of the photovoltaic and energy-storage combined power generation system, respectively.

[0021] 3. The coordinated optimization control strategy for photovoltaic and battery combined operation according to claim 1 is characterized in that: the step (2) of determining the photovoltaic and battery combined operation mode according to the photovoltaic operation mode and the battery operation mode specifically includes: Photovoltaic can work in maximum power point tracking (MPPT) mode, constant voltage mode, and non-operating mode, while batteries can work in charging mode, discharging mode, and non-operating mode. In order to ensure the normal operation of the photovoltaic storage DC microgrid, it is necessary to meet the stability of the DC bus voltage and power balance, and consider the battery's state of charge (SOC) and maximum charge and discharge power. The photovoltaic working state and the battery working state are combined to obtain the following system working mode: Working mode 1: The power generated by the photovoltaic power plant is greater than the load power, and the SOC of the battery is within the allowable working range. At this time, the battery works in the charging mode and the absorbed power does not reach the maximum limit. The DC bus voltage is maintained stable by the battery, and the photovoltaic power plant works in the MPPT mode. Figure 3 (a) shown.

[0022] Working mode 2: The power generated by the photovoltaic power plant is less than the load power, and the SOC of the battery is within the allowable working range. At this time, the battery works in the discharge mode and the power generated has not reached the maximum limit. The DC bus voltage is maintained stable by the battery, and the photovoltaic power plant works in the MPPT mode. Figure 3 (b) as shown.

[0023] Working mode 3: In working mode 1, if the battery SOC exceeds the allowable working range, the battery does not work or the battery absorption power reaches the limit, and there is still surplus power from the photovoltaic power generation, in order to maintain the stability of the DC bus voltage, the photovoltaic power generation operates in the constant voltage mode, such as Figure 3 (c) as shown.

[0024] Working mode 4: In working mode 2, the battery SOC exceeds the allowable working range and the battery does not work. At this time, the power generated by the photovoltaic power plant is lower than the power consumed by the load, or when the power generated by the battery reaches the limit and the power generated by the photovoltaic power plant is still insufficient, in order to maintain the stability of the DC bus voltage, a certain load needs to be removed and the photovoltaic power plant works in the constant voltage mode, such as Figure 3 (d) as shown.

[0025] Working mode 5: If there is no photovoltaic power output at night or on rainy days, and the battery is within the allowable working range, At this time, the battery works in the discharge mode and maintains the bus voltage stable. Figure 3 (e) as shown.

[0026] Working mode 6: The battery is continuously discharged. When its SOC exceeds the allowable working range, the battery will not work and the entire system will not work. Figure 3 (f) as shown.

[0027] 4. The coordinated optimization control strategy for photovoltaic and storage combined operation according to claim 1 is characterized in that: the photovoltaic and storage coordinated control strategy is designed for the DC bus voltage and battery current according to different operation modes in step (3), specifically including: The photovoltaic and storage combined system adopts a hierarchical control system. The upper layer determines the working mode according to the system environment, DC bus voltage, photovoltaic output power, and load power consumption, and transmits information to the middle layer. The middle layer allocates the working status of photovoltaics and batteries based on the information from the upper layer, and then transmits the information to the lower layer for execution.

[0028] The DAB converter controls both the DC bus voltage and the battery current in operating modes 1, 2, and 5. Its control strategy is as follows: Figure 4 As shown. After the voltage error is amplified by PI, the reference value ibref of the inner loop of the battery current is obtained. After the current error is amplified by PI, the phase shift angle φ of the DAB converter is obtained, and then the driving pulse is obtained after pulse width modulation and sent to the H bridges on both sides. In working mode three, the battery absorption power reaches the limit. When the photovoltaic works in constant voltage mode, only the battery current is controlled. Udcref is the bus voltage reference value; ibref is the reference value of the inner loop of the battery current; φ is the phase shift angle of the DAB converter; ib is the actual value of the battery current; PI is a proportional integral controller.

[0029] The Boost converter controls the DC bus voltage in operating modes 3 and 4. The control strategy is as follows: Figure 5 As shown in the figure above, after the voltage error is amplified by PI, the reference value isref of the inner loop of the photovoltaic cell current is obtained. After the current error is amplified by PI, it is compared with the triangular carrier to generate the gate pulse of the switch tube. In working modes 1 and 2, only MPPT control is performed. Its control strategy is as follows Figure 5 As shown in the figure below, a voltage reference value is generated after passing through the MPPT controller. The voltage error is amplified by the PI and then compared with the triangular carrier to generate a switching tube gate pulse.

[0030] In order to verify the effectiveness of the proposed optimization strategy and control method, a photovoltaic-storage combined power generation system model was established to detect whether the problem of large active output error was improved after the optimization strategy was enabled. On the other hand, it showed that the collaborative control strategy had a good effect on improving the dispatchability and stability of the photovoltaic-storage combined system.

[0031] Depend on Figure 6 It can be seen that at the moment when the power difference passes through zero, the optimization strategy proposed by the present invention will provide a short-term power to ensure the normal operation of each power-consuming device and avoid the impact of power reverse on each power-consuming device. At this time, the instantaneous error between the planned active output curve is less than 7%, and the power error variance is only 23.5% of that when the photovoltaic power station is operating alone. Figure 7 Take the working mode 3 of the photovoltaic and energy storage combined power generation system as an example for analysis: in this mode, the battery is out of operation, the photovoltaic output power is greater than the load power, and the photovoltaic power generation not only needs to maintain the stability of the DC bus voltage, but also needs to reduce its output power. Figure 7 It can be seen that before 2.5s, the photovoltaic power plant was working in the constant voltage mode, and the DC bus voltage was stable at 600V; at 2.5s, when the load power changed and was less than the maximum power output of the photovoltaic power plant, the bus voltage stabilized at 600V after a short transient change (much less than 0.5s, and reasonable adjustment of control parameters can continuously optimize the mode switching process). The above simulation results well verify the effectiveness of the design of the coordinated optimization control method for the joint operation of photovoltaic and energy storage.

[0032] The above is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any modification, equivalent replacement and improvement made by any person skilled in the art within the technical scope disclosed by the present invention and within the spirit and principle of the present invention shall be covered within the protection scope of the present invention. At the same time, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0033] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

Claims

1. A method for designing and coordinating the operation of a photovoltaic and energy storage combined power supply, characterized in that: The following steps are involved: S1 uses the charging and discharging of energy storage batteries to adjust the output power of the photovoltaic and energy storage combined power generation system, so that the planned output power of the photovoltaic and energy storage combined power generation system can track the power generation plan in real time and achieve unbiased scheduling; S2 determines the photovoltaic and battery combined working mode according to the photovoltaic working mode and the battery working mode; S3 designs a hierarchical control system for the photovoltaic and storage combined system according to the characteristics of the operating mode, and designs a photovoltaic and storage coordinated control strategy for the DC bus voltage and battery current.

2. The method for designing and coordinating the operation of a photovoltaic and energy storage combined power supply according to claim 1 is characterized in that: Step S1 is specifically as follows: S01 Constructing mathematical models The objective function for determining the capacity of the energy storage battery is: (1) Where: T is the scheduling period; P PV (t) is the active power output of the photovoltaic system during period t; P S (t) is the active power output of the energy storage system during period t; P L (t) is the planned output active power during period t; The SOC of the energy storage battery needs to meet the following constraints: (2) Where: S t is the state of charge of the battery during period t; S min , S max are the minimum and maximum states of charge allowed respectively; The battery state of charge during period t is: (3) (4) Where: is the self-sustaining discharge rate of the battery; Δ S i It is the change of power in a time period, positive value indicates discharge, negative value indicates charge; η c is the charging efficiency; η d is the discharge efficiency; Δt is the interval time of each period; The particle swarm algorithm is used to solve the mathematical model and determine the capacity of the energy storage battery; During the dispatching period, the photovoltaic energy storage system needs to achieve precise control, that is, the absolute value of the error rate λ is minimized during the dispatching period. The expression of λ is: (5) At the same time, the SOC constraints of the energy storage battery must be met, and the active output constraints of the photovoltaic and energy storage combined power generation system must also be met: (6) Where: P t Contribute to the photovoltaic and energy storage combined power generation system; P t，min , P t，max They are the minimum and maximum allowable deviations of the photovoltaic and energy-storage combined power generation system, respectively.

3. The method for designing and coordinating the operation of a photovoltaic and energy storage combined power supply according to claim 2 is characterized in that: Step S2 is specifically as follows: The DC bus voltage stability and power balance need to be met, and the battery state of charge and maximum charge and discharge power need to be considered. The photovoltaic working state and the battery working state need to be combined to obtain the following system working mode: Mode 1: The power generated by the photovoltaic power plant is greater than the load power, and the battery's state of charge (SOC) is within the allowable operating range. At this time, the battery works in charging mode and the absorbed power does not reach the maximum limit. The DC bus voltage is maintained stable by the battery, and the photovoltaic power plant works in the maximum power point tracking (MPPT) mode. Mode 2: The power generated by the photovoltaic power plant is less than the load power, and the SOC of the battery is within the allowable operating range. At this time, the battery works in the discharge mode and the power generated has not reached the maximum limit. The DC bus voltage is maintained stable by the battery, and the photovoltaic power plant works in the MPPT mode. Mode 3: In mode 1, if the battery SOC exceeds the allowable operating range, the battery does not work or the battery absorption power reaches the limit, and there is still surplus power from the photovoltaic power plant, the photovoltaic power plant operates in constant voltage mode to maintain the stability of the DC bus voltage. Mode 4: In mode 2, the battery SOC exceeds the allowable operating range and the battery does not work. At this time, the power generated by the photovoltaic power plant must be lower than the power consumed by the load, or the power generated by the battery reaches the limit and the power generated by the photovoltaic power plant is still insufficient. In order to maintain the stability of the DC bus voltage, a certain load needs to be removed and the photovoltaic power plant works in the constant voltage mode. Mode 5: At night or on rainy days, the photovoltaic power has no power output, and the battery is within the allowable working range. At this time, the battery works in the discharge mode and maintains the bus voltage stable; Mode 6: The battery is continuously discharged. When its SOC exceeds the allowable operating range, the battery will not work and the entire system will not work either.

4. The method for designing and coordinating the operation of a photovoltaic and energy storage combined power supply according to claim 3 is characterized in that: Step S3 is specifically as follows: The photovoltaic and storage combined system adopts a hierarchical control system. The upper layer determines the working mode based on the system environment, DC bus voltage, photovoltaic output power, and load power consumption, and transmits the information to the middle layer. The middle layer allocates the working status of photovoltaics and batteries based on the information from the upper layer, and then transmits the information to the lower layer for execution.

5. The method for designing and coordinating the operation of a photovoltaic and energy storage combined power supply according to claim 4 is characterized in that: In mode 1, mode 2 and mode 5, the DC bus voltage and battery current are controlled. The voltage error is amplified by PI to obtain the reference value of the battery current inner loop. i bref The current error is amplified by PI to obtain the phase shift angle φ of the DAB converter, and then the driving pulse is obtained after pulse width modulation and sent to the H bridges on both sides.

6. The method for designing and coordinating the operation of a photovoltaic and energy storage combined power supply according to claim 4 is characterized in that: In mode 3, when the power absorbed by the battery reaches the limit and the photovoltaic system works in constant voltage mode, only the current of the battery is controlled.

7. The method for designing and coordinating the operation of a photovoltaic and energy storage combined power supply according to claim 4 is characterized in that: In mode 3 and mode 4, the DC bus voltage is controlled, and the voltage error is amplified by PI to obtain the reference value of the photovoltaic cell current inner loop. i sref The current error is amplified by PI and then compared with the triangular carrier to generate the gate pulse of the switching tube.

8. The method for designing and coordinating the operation of a photovoltaic and energy storage combined power supply according to claim 4 is characterized in that: In Mode 1 and Mode 2, only MPPT control is performed. A voltage reference value is generated after passing through the MPPT controller. The voltage error is amplified by PI and then compared with the triangular carrier to generate a switching tube gate pulse.

Images