Optical storage and charging integrated power station topology based on hybrid energy storage and control method

Abstract

The invention discloses an optical storage and charging integrated power station topology based on hybrid energy storage and a control method, the topology comprises a direct current bus, a charging pile, a photovoltaic power generation unit, an energy storage capacitor and a three-phase grid-connected system, two ends of the charging pile are respectively connected with a positive electrode and a negative electrode of the direct current bus, and the charging pile is used for providing electric energy to the outside; two ends of the photovoltaic power generation unit are respectively connected with the positive electrode and the negative electrode of the direct-current bus; two ends of the energy storage capacitor are respectively connected with the positive electrode and the negative electrode of the direct current bus; and the three-phase grid-connected system is connected with the positive electrode and the negative electrode of the direct-current bus after passing through the inverter. By the adoption of the technical scheme, the capacitor is introduced to serve as a core component of the energy storage unit, the energy storage characteristic of the capacitor is utilized, the capacitor can release a large amount of energy in a short time, the cycle life is very long and can reach tens of thousands of times, and high stability and reliability are achieved.

Description

Technical Field

[0001] The present invention relates to the field of power electronic devices and new energy storage technology, and in particular to a photovoltaic storage and charging integrated power station topology and control method based on hybrid energy storage. Background Art

[0002] In the context of reducing carbon emissions, the energy system will be transformed into a diversified energy system with new energy as the main body and various forms of energy. Photovoltaic power generation itself has strong volatility and intermittency. After the photovoltaic unit is connected to the DC bus, the DC bus faces the risk of breakdown. Therefore, the existing technology overcomes the strong volatility and intermittency of photovoltaic power generation by integrating energy storage units in the power station topology. Energy storage units will be an indispensable component of the new generation of energy systems.

[0003] In the prior art, batteries are usually used as the core components of energy storage units. Battery energy storage systems have high energy density and are suitable for long-term, high-energy demand scenarios. The technology is relatively reliable and mature, and the safety is high. However, batteries also have corresponding problems. The charging and discharging speed of batteries is relatively slow, and it takes a long time to complete energy conversion. The cycle life is relatively short, and usually only a few thousand charging and discharging cycles can be performed. It is not suitable for long-term, high-intensity use, and does not conform to the application scenarios of all-weather, high-power and frequent use of power grid power stations. Summary of the invention

[0004] Purpose of the invention: The present invention provides a photovoltaic storage and charging integrated power station topology and control method based on hybrid energy storage, aiming to solve the technical problems of slow charging and discharging speed and short cycle life of batteries in power stations existing in the prior art.

[0005] Technical solution: The present invention provides a hybrid energy storage-based integrated power station topology, including: a DC bus, a charging pile, a photovoltaic power generation unit, an energy storage capacitor and a three-phase grid-connected system, wherein: the charging pile, both ends of which are respectively connected to the positive and negative poles of the DC bus, is used to provide external electrical energy; the photovoltaic power generation unit, both ends of which are respectively connected to the positive and negative poles of the DC bus; the energy storage capacitor, both ends of which are respectively connected to the positive and negative poles of the DC bus; the three-phase grid-connected system, is connected to the positive and negative poles of the DC bus after passing through an inverter.

[0006] Specifically, the three-phase grid-connected system is also connected to an energy storage capacitor after passing through an inverter.

[0007] Specifically, the charging pile is connected to the DC bus after passing through a bidirectional DC converter; the energy storage capacitor is connected to the DC bus and the three-phase grid-connected system respectively after passing through a bidirectional DC converter.

[0008] Specifically, the photovoltaic power generation unit is connected to the DC bus after passing through a boost converter.

[0009] Specifically, a voltage stabilizing capacitor is arranged between the positive electrode and the negative electrode of the DC bus.

[0010] Specifically, the three-phase grid-connected system is connected to the inverter after passing through the resonant filter.

[0011] The present invention also provides a control method for a photovoltaic, storage and charging integrated power station topology based on hybrid energy storage, which applies the photovoltaic, storage and charging integrated power station topology based on hybrid energy storage provided by the present invention, including: in the working process of the power station topology, based on the charging pile target power and the energy storage capacitor target power, respectively obtaining the charging pile target current and the energy storage capacitor target current; obtaining the charging pile actual current and the energy storage capacitor actual current; inputting the charging pile target current and the actual current into a first PI controller, and the first PI controller controls the charging pile actual current by controlling the modulation gain; inputting the energy storage capacitor target current and the actual current into a second PI controller, and the second PI controller controls the energy storage capacitor actual current by controlling the modulation gain.

[0012] Specifically, the low-frequency power obtained by low-pass filtering the total target power is used as the charging pile target power, and the energy storage capacitor target power is obtained by subtracting the charging pile target power from the total target power.

[0013] Specifically, in each time period, a disturbance is added to the output voltage of the photovoltaic power generation unit; after the disturbance is added, the instantaneous power of the current time period is calculated based on the collected output voltage and output current of the photovoltaic power generation unit, and the instantaneous power of the current time period is compared with the instantaneous power of the previous time period; if the instantaneous power of the current time period is greater, the disturbance amount is increased in the next time period; if the instantaneous power of the current time period is smaller, the added disturbance amount is reduced in the next time period.

[0014] Specifically, in a three-phase grid-connected system, the inner loop adopts current inner loop decoupling control, and the outer loop adopts active and reactive power control.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: by introducing capacitors as the core components of the energy storage unit and utilizing the energy storage characteristics of capacitors, the capacitors can release a large amount of energy in a short period of time, and the cycle life is very long, which can reach tens of thousands of times, and has high stability and reliability. Furthermore, charging piles are introduced into the power station topology to realize a power station with integrated energy storage and charging. Furthermore, the charging piles and capacitors are controlled separately to achieve the ideal power point and realize the maximum localization of power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the topology of a photovoltaic storage and charging integrated power station based on hybrid energy storage provided by the present invention;

[0017] Figure 2 A control block diagram of charging piles and capacitors in the photovoltaic storage and charging integrated power station topology provided by the present invention;

[0018] Figure 3 This is a block diagram of active and reactive power control for the photovoltaic storage and charging integrated power station topology provided by the present invention. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0020] See also Figure 1 , which is a structural schematic diagram of the topology of the integrated photovoltaic storage and charging power station based on hybrid energy storage provided by the present invention.

[0021] In specific implementations, in traditional localized power station topologies, battery energy storage units are used to overcome the strong volatility and intermittency of photovoltaic power generation. In contrast, the present invention uses high-capacity supercapacitors instead of batteries as the main components of the energy storage unit, utilizing the energy storage characteristics of capacitors, which has significant advantages. Supercapacitors can release a large amount of energy in a short period of time, and their cycle life is very long, reaching tens of thousands of times, with high stability and reliability. At the same time, the pollution generated during production and use is relatively small, and it is a relatively environmentally friendly energy storage technology. In a photovoltaic energy storage system, supercapacitors can absorb energy during the day when the sun is sufficient or the wind is strong, and discharge at night or when the wind is weak to maintain the balance of the system, making capacitors an effective means to deal with the volatility and indirectness of photovoltaic power generation.

[0022] In the embodiment of the present invention, the photovoltaic storage and charging integrated power station topology based on hybrid energy storage includes: a DC bus, a charging pile, a photovoltaic power generation unit, an energy storage capacitor (such as Figure 1 As shown, super capacitor) and three-phase grid-connected system, wherein: the charging pile, two ends of which are respectively connected to the positive and negative poles of the DC bus, is used to provide external power; the photovoltaic power generation unit, two ends of which are respectively connected to the positive and negative poles of the DC bus; the energy storage capacitor, two ends of which are respectively connected to the positive and negative poles of the DC bus; the three-phase grid-connected system, through an inverter (such as Figure 1 As shown, the switching device g 1 tog 6 The inverter consists of a transistor and a diode connected in anti-parallel (connected in parallel) and connected to the positive and negative poles of the DC bus.

[0023] In the embodiment of the present invention, the three-phase grid-connected system is also connected to an energy storage capacitor after passing through the inverter.

[0024] In the specific implementation, there is a connection relationship between the charging pile, photovoltaic power generation unit, energy storage capacitor and three-phase grid-connected system. During the operation of the power station, the photovoltaic power generation unit and the three-phase grid-connected system can charge the capacitor, and the photovoltaic power generation unit, energy storage capacitor and the three-phase grid-connected system can provide power for the charging pile.

[0025] In specific implementations, in order to meet the needs of energy storage and external energy charging in the power station, the capacitance value of the energy storage capacitor in the power station topology is usually set to 3000 to 5000F.

[0026] In the embodiment of the present invention, the charging pile is connected to the DC bus after passing through a bidirectional DC converter (Buck-Boost bidirectional DC / DC converter); the energy storage capacitor is connected to the DC bus and the three-phase grid-connected system respectively after passing through a bidirectional DC converter (Buck-Boost bidirectional DC / DC converter).

[0027] like Figure 1 As shown, the Buck-Boost bidirectional DC / DC converter includes an inductor and two switching devices (the switching devices are anti-parallel transistors and diodes). It is a DC power conversion device that can achieve voltage step-up and step-down. It can not only work when the input voltage is higher or lower than the output voltage, but also transfer energy in two directions.

[0028] In the embodiment of the present invention, the photovoltaic power generation unit is connected to the DC bus after passing through a boost converter (Boost converter).

[0029] like Figure 1 As shown, the Boost converter includes a capacitor, a switching device (the switching device is a transistor and a diode connected in anti-parallel), a diode and a resistor connected in parallel with the diode. Its main function is to increase a lower DC input voltage to a higher DC output voltage, thereby increasing the output of the photovoltaic power generation unit to a level that can be connected to the power station topology.

[0030] In the embodiment of the present invention, a voltage stabilizing capacitor is arranged between the positive electrode and the negative electrode of the DC bus to stabilize the voltage of the DC bus.

[0031] In the embodiment of the present invention, the three-phase grid-connected system is connected to the inverter after passing through a resonant filter (on the three-phase line, each phase is provided with an inductor and a capacitor).

[0032] See also Figure 2 , which is a control block diagram of the charging piles and capacitors of the integrated photovoltaic storage and charging power station topology provided by the present invention.

[0033] The present invention also provides a control method for a photovoltaic, storage and charging integrated power station topology based on hybrid energy storage, which applies the photovoltaic, storage and charging integrated power station topology based on hybrid energy storage provided by the present invention, including: in the working process of the power station topology, based on the charging pile target power (which can be determined according to the actual application scenario) and the energy storage capacitor target power (which can be determined according to the actual application scenario), respectively obtaining the charging pile target current and the energy storage capacitor target current; obtaining the charging pile actual current and the energy storage capacitor actual current; inputting the charging pile target current and the actual current into a first PI controller, and the first PI controller controls the charging pile actual current by controlling the modulation gain; inputting the energy storage capacitor target current and the actual current into a second PI controller, and the second PI controller controls the energy storage capacitor actual current by controlling the modulation gain.

[0034] In the embodiment of the present invention, the low-frequency power obtained by low-pass filtering the total target power is used as the charging pile target power, and the energy storage capacitor target power is obtained by subtracting the charging pile target power from the total target power.

[0035] In a specific implementation, since the voltage of the load connected to the charging pile, such as an electric vehicle battery, changes slowly, the transmission power can be controlled by its discharge current; in addition, since the change curve of the energy storage capacitor is almost similar to a constant voltage compared to the switching cycle (bidirectional DC converter), its charging and discharging power can also be controlled by controlling the current.

[0036] In the specific implementation, based on the charging pile target power P b_ref and the target power P of the energy storage capacitor sc_ref , combined with the DC bus voltage U b , the corresponding charging pile target current i can be calculated b_ref and the target current i of the energy storage capacitor sc_ref .

[0037] The charging pile target current i b_ref and the actual current i of the charging pile b As the input of the PI controller, the PI controller outputs the corresponding PWM modulation gain G PWM To control the actual current i of the charging pile b , so that it tends to the charging pile target current i b_ref .

[0038] Accordingly, the target current i of the energy storage capacitor is sc_ref and the actual current i of the energy storage capacitor sc As the input of the PI controller, the PI controller outputs the corresponding PWM modulation gain G PWM Control the actual current i of the energy storage capacitor sc , so that it tends to the target current i of the energy storage capacitor sc_ref .

[0039] In a specific implementation, the energy storage capacitor is in a charging state, or in a state of providing electric energy to the outside, depending on the actual current i sc The target current of the energy storage capacitor reflects the optimal current flow direction and current value of the energy storage capacitor. By controlling the actual current of the energy storage capacitor and the actual current of the charging pile respectively, the power station topology itself can reach the ideal power point, and the characteristic of the capacitor itself to release a large amount of energy in a short period of time can be effectively utilized to increase the power amount discharged by the energy storage capacitor, improve the efficiency of the charging pile in external power supply, reduce the power support of the three-phase grid connection to the local power station topology, and improve the degree of localization. When the energy storage capacitor absorbs electric energy, it can also ensure that the charging rate of the energy storage capacitor is increased under the premise that the charging pile outputs enough electric energy to the outside.

[0040] In a specific implementation, the low-frequency power obtained by low-pass filtering of the total target power (which can be determined according to the actual application scenario) is used as the target power of the charging pile, and the low-frequency power is provided to the charging pile, while the high-frequency power is used as the transmission power of the capacitor. The role is that the low-frequency power is more stable, and the stability of the external power supply of the charging pile is utilized, while the capacitor itself has strong stability and can withstand the high-frequency power.

[0041] In an embodiment of the present invention, a disturbance is added to the output voltage of the photovoltaic power generation unit in each time period; after the disturbance is added, the instantaneous power of the current time period is calculated based on the collected output voltage and output current of the photovoltaic power generation unit, and the instantaneous power of the current time period is compared with the instantaneous power of the previous time period; if the instantaneous power of the current time period is greater, the disturbance amount is increased in the next time period; if the instantaneous power of the current time period is smaller, the added disturbance amount is reduced in the next time period.

[0042] In a specific implementation, the maximum power tracking method is used to approach the maximum operating point of the photovoltaic power generation unit, and this cycle is repeated until the ideal voltage of the maximum power transmission point is reached.

[0043] See also Figure 3 , which is a block diagram of active and reactive power control of the photovoltaic storage and charging integrated power station topology provided by the present invention.

[0044] In the embodiment of the present invention, in the three-phase grid-connected system, the inner loop adopts current inner loop decoupling control, and the outer loop adopts active and reactive power control.

Claims

1. A photovoltaic storage and charging integrated power station topology based on hybrid energy storage, characterized in that: include: DC bus, charging pile, photovoltaic power generation unit, energy storage capacitor and three-phase grid-connected system, including: The charging pile has two ends connected to the positive and negative electrodes of the DC bus, respectively, for providing electrical energy to the outside; The photovoltaic power generation unit has two ends connected to the positive electrode and the negative electrode of the DC bus respectively; The energy storage capacitor has two ends connected to the positive electrode and the negative electrode of the DC bus respectively; The three-phase grid-connected system is connected to the positive and negative poles of the DC bus after passing through the inverter.

2. The photovoltaic storage and charging integrated power station topology based on hybrid energy storage according to claim 1 is characterized in that: The three-phase grid-connected system is also connected to an energy storage capacitor after passing through an inverter.

3. The photovoltaic storage and charging integrated power station topology based on hybrid energy storage according to claim 2 is characterized in that: The charging pile is connected to the DC bus after passing through a bidirectional DC converter; the energy storage capacitor is connected to the DC bus and the three-phase grid-connected system respectively after passing through a bidirectional DC converter.

4. The photovoltaic storage and charging integrated power station topology based on hybrid energy storage according to claim 1 is characterized in that: The photovoltaic power generation unit is connected to the DC bus after passing through a boost converter.

5. The photovoltaic storage and charging integrated power station topology based on hybrid energy storage according to claim 1 is characterized in that: A voltage stabilizing capacitor is arranged between the positive electrode and the negative electrode of the DC bus.

6. The photovoltaic storage and charging integrated power station topology based on hybrid energy storage according to claim 2 is characterized in that: The three-phase grid-connected system is connected to the inverter after passing through the resonant filter.

7. A control method for a photovoltaic storage and charging integrated power station topology based on hybrid energy storage, characterized in that: The photovoltaic storage and charging integrated power station topology based on hybrid energy storage according to any one of claims 1 to 6 comprises: During the operation of the power station topology, based on the target power of the charging pile and the target power of the energy storage capacitor, the target current of the charging pile and the target current of the energy storage capacitor are obtained respectively; the actual current of the charging pile and the actual current of the energy storage capacitor are obtained; The target current and actual current of the charging pile are input into the first PI controller, and the first PI controller controls the actual current of the charging pile by controlling the modulation gain; the target current and actual current of the energy storage capacitor are input into the second PI controller, and the second PI controller controls the actual current of the energy storage capacitor by controlling the modulation gain.

8. The control method of the photovoltaic storage and charging integrated power station topology based on hybrid energy storage according to claim 7 is characterized in that: The low-frequency power obtained by low-pass filtering the total target power is used as the charging pile target power, and the target power of the energy storage capacitor is obtained by subtracting the charging pile target power from the total target power.

9. The control method of the photovoltaic storage and charging integrated power station topology based on hybrid energy storage according to claim 8 is characterized in that: include: In each time period, a disturbance is added to the output voltage of the photovoltaic power generation unit; After adding the disturbance, the instantaneous power of the current time period is calculated based on the collected output voltage and output current of the photovoltaic power generation unit, and the instantaneous power of the current time period is compared with the instantaneous power of the previous time period; If the instantaneous power of the current time period is greater, the disturbance amount is increased in the next time period; if the instantaneous power of the current time period is smaller, the added disturbance amount is reduced in the next time period.

10. The control method of the photovoltaic storage and charging integrated power station topology based on hybrid energy storage according to claim 8 is characterized in that: include: For the three-phase grid-connected system, the inner loop adopts current inner loop decoupling control, and the outer loop adopts active and reactive power control.

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