Bidirectional dcdc photovoltaic energy storage system

Abstract

The utility model relates to the technical field of photovoltaic industry, and discloses a bidirectional dcdc photovoltaic energy storage system, which comprises a photovoltaic panel. The photovoltaic panel is connected with the DC-DC bidirectional converter, the DC-DC bidirectional converter is respectively in bidirectional connection with the 10kv inverter and the storage battery pack, and the 10kv inverter is respectively connected with a power grid, a direct-current load and an alternating-current load. According to the utility model, the power utilization efficiency is ensured, the reliable power supply, environmental protection and energy saving are ensured through the storage battery, the clean and intelligent storage type emergency power supply system is constructed, and the power supply requirements under various working conditions can be met; and the system can supply power to the power grid through the storage battery in the power utilization peak period, and feed back the power grid to relieve the power utilization pressure.

Description

Technical Field

[0001] This utility model relates to the technical field of the photovoltaic industry, specifically to a bidirectional DC-DC photovoltaic energy storage system. Background Technology

[0002] Photovoltaic power generation is a clean technology that directly converts light energy into electrical energy through the photovoltaic effect, and it is characterized by being clean, sustainable, and safe. However, the disadvantages of photovoltaic power generation are that its output power is unpredictable and fluctuates greatly, which brings a series of problems to the stability of the power grid.

[0003] The solution to the above problems is to add energy storage devices to the photovoltaic power generation system. When the output power of the photovoltaic array is high and the power demand of the grid is low, the excess electrical energy can be stored in the energy storage device. When the output power of the photovoltaic array is low and the power demand of the grid is high, the electrical energy stored in the energy storage device can be transmitted to the grid, thereby improving the stability of the grid. In a photovoltaic power generation system with added energy storage devices, the photovoltaic array is connected to the grid through a photovoltaic inverter, and the energy storage device is connected to the grid through a DC-DC converter. Furthermore, the energy storage device is connected to the photovoltaic array through this DC-DC converter to store the excess electrical energy output by the photovoltaic array.

[0004] Therefore, how to design a system that can ensure the stability of the power grid while maintaining the supply and demand relationship of electricity to cope with peak and off-peak electricity demand is a technical problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0005] In order to overcome the shortcomings of the prior art, the present invention has made the following improvements and optimizations to address the aforementioned disadvantages.

[0006] To achieve the above objectives, this utility model provides the following technical solution: a bidirectional DC-DC photovoltaic energy storage system, including a photovoltaic panel;

[0007] The photovoltaic panel is connected to a DC-DC bidirectional converter, which is bidirectionally connected to a 10kV inverter and a battery pack, and the 10kV inverter is connected to the power grid, DC load and AC load.

[0008] Preferably, the bidirectional DC-DC converter includes a transformer, bridge arms, supporting capacitors, and an inductor; each end of the transformer is connected to two bridge arms, and the two ends of the two bridge arms are connected to the supporting capacitor; one end of the inductor is electrically connected to the two bridge arms.

[0009] Preferably, the bidirectional DC-DC converter further includes a sampling circuit and a driving circuit. The sampling circuit includes a current sampling circuit and a voltage sampling circuit. The current sampling circuit uses resistor voltage division sampling. The voltage sampling circuit includes an AC5712 chip.

[0010] Preferably, the driving circuit includes four IR2110 chips.

[0011] Preferably, the bidirectional DC-DC converter is also connected to an MPPT controller, which generates a PWM signal with a preset duty cycle to complete the bidirectional flow of electrical signals.

[0012] Preferably, the battery pack is a battery pack with a rated load of 600W, an input and output voltage of 220V, and a rated current of 60Ah.

[0013] Compared with the prior art, the beneficial effects of this utility model are:

[0014] This invention can construct a clean and intelligent storage-type emergency power supply system that ensures power efficiency, reliable power supply through storage batteries, and is environmentally friendly and energy-saving, while meeting the power supply needs under various working conditions. Moreover, this system can supply power to the grid through storage batteries during peak power consumption periods, thus alleviating the power pressure on the grid. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of this utility model;

[0016] Figure 2 This is a schematic diagram of the bidirectional DC-DC topology of this utility model. Detailed Implementation

[0017] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0018] Please see Figure 1 This utility model provides a technical solution: a bidirectional DC-DC photovoltaic energy storage system, including photovoltaic panels;

[0019] The photovoltaic panel is connected to a DC-DC bidirectional converter, which is bidirectionally connected to a 10kV inverter and a battery pack, and the 10kV inverter is connected to the power grid, DC load and AC load.

[0020] Preferably, the bidirectional DC-DC converter includes a transformer, bridge arms, supporting capacitors, and an inductor; each end of the transformer is connected to two bridge arms, and the two ends of the two bridge arms are connected to the supporting capacitor; one end of the inductor is electrically connected to the two bridge arms.

[0021] Preferably, the bidirectional DC-DC converter further includes a sampling circuit and a driving circuit. The sampling circuit includes a current sampling circuit and a voltage sampling circuit. The current sampling circuit uses resistor voltage division sampling. The voltage sampling circuit includes an AC5712 chip.

[0022] The system uses Hall elements for sampling. Hall elements are widely used in current sampling in power electronic circuits because they are small, lightweight, have strong electromagnetic interference resistance, provide accurate sampling, and have relatively simple off-chip circuit layout.

[0023] Preferably, the driving circuit includes four IR2110 chips.

[0024] The IR2110's internal structure consists of three parts: logic input, level shifting, and output protection. The IR2110's logic supply voltage is 5-20V, and it has two independent high-side and low-side output channels. The floating power supply is provided by a bootstrap circuit and can withstand a 500V operating voltage. A single IR2110 chip can drive two switches on the same bridge arm using its high-side and low-side output channels. The IR2110 driver chip operates at 5V, and the MOSFET's drive voltage is +15VCC. The PWM drive signal for the upper arm MOSFET is input to the high-channel input HIN of the IR2110 driver chip, and the PWM drive signal for the lower arm MOSFET is input to the low-channel input LIN of the IR2110 driver chip. Since the MOSFET's turn-on condition requires the gate drive voltage Vgs to be greater than the threshold voltage, the upper source is not grounded and is floating. When the upper transistor is turned on, VGS is kept greater than the threshold voltage, and this is achieved by the bootstrap capacitors Cb and Cc. Dd is the bootstrap diode. The +15VCC power supply charges bootstrap capacitors Cb and Cc, bringing the voltage across them close to the +15VCC power supply. The charge on capacitors Cb and Cc powers the high-side drive output IR2110. Bootstrap capacitors Cb and Cc are switched on or off by the lower transistor. The buck circuit uses the high-side driver of the IR2110. When HIN is high, the HO output is high relative to the voltage difference +15VCC.

[0025] The bootstrap capacitors Cb and Cc are charged either through the conduction of the lower transistor or through the load to ground. The lower transistor conducts when the inductor is freewheeling, and the MOSFET current flows from bottom to top. Therefore, a charging circuit cannot be provided for the bootstrap capacitors Cb and Cc, and the bootstrap capacitors can only be charged by the load. However, in actual debugging, when the load is a resistor, the bootstrap capacitors can bootstrap, and the circuit works normally. When the load is a battery, it is found that the bootstrap capacitors do not bootstrap, i.e., charging fails. The reason is that the battery itself is a power source. When the battery voltage is greater than the charging voltage of the bootstrap capacitor +15VCC, the bootstrap capacitors lack a charging circuit, the upper transistor cannot be turned on, and the circuit cannot work normally. Therefore, an isolation power supply is connected to +15V. The positive and negative terminals are connected to the two ends of the bootstrap capacitor respectively to solve the attraction problem. When the internal switch Q2 of the IR2110 is turned on, the potential of VS is pulled down, and Vcc is charged by the bootstrap diode D, the bootstrap capacitor C, and the switch Q2 to form a closed loop to charge C. This allows the bootstrap capacitor C to form a floating power supply, ensuring that when Q2 is off and Q1 is on, the energy stored in the bootstrap capacitor C drives the gate of Q1 to achieve bootstrap drive. This circuit uses four IR2110 chips to drive the eight MOSFETs of the PWM full-bridge circuit. It can be seen that this circuit can drive a bidirectional isolated converter using only four IR2110 chips. When the LO and HO pins output a pair of complementary signals to drive the upper and lower MOSFETs, if an abnormal situation occurs, both MOSFETs will turn on simultaneously, resulting in a shoot-through. For example, when the MOSFET current increases instantaneously and is compared with a set value, assuming it is greater than the set value, a high-level signal is output directly to the SD pin of the IR2110 chip. The high-level SD signal immediately changes the output signals of the LO and HO pins to low level and immediately turns off the upper and lower power switches.

[0026] Preferably, the bidirectional DC-DC converter is also connected to an MPPT controller, which generates a PWM signal with a preset duty cycle to complete the bidirectional flow of electrical signals.

[0027] Preferably, the battery pack is a battery pack with a rated load of 600W, an input and output voltage of 220V, and a rated current of 60Ah.

[0028] Working principle: Please refer to Figure 2This is a schematic diagram of the bidirectional DC-DC topology of this utility model. In one feasible embodiment, solar energy is absorbed by an externally installed photovoltaic panel and converted into electrical energy. The electrical energy is then transmitted to the DC-DC bidirectional converter. Since there are two bridge arms in the DC-DC bidirectional converter, the electrical energy enters from the left bridge arm. A preset duty cycle is generated by the connected MPPT controller, and a PWM signal with the corresponding duty cycle is sent by the IR2110 chip to control the flow of electrical energy in the bridge arm. The energy flows into the battery pack for energy storage (when there is a low electricity demand) or into the 10kV inverter. If the electrical energy flows into the 10kV inverter, the 10kV inverter converts the electrical energy from DC to AC output suitable for AC loads (household loads) or the power grid (to feed back to the power grid to alleviate electricity demand during peak electricity demand), or directly outputs it to the suitable DC load.

[0029] Finally, it should be noted that the above content is only used to illustrate the technical solution of this utility model, and is not intended to limit the scope of protection of this utility model. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of this utility model do not depart from the essence and scope of the technical solution of this utility model.

Claims

1. A bidirectional DC-DC photovoltaic energy storage system, characterized in that, Including photovoltaic panels; The photovoltaic panel is connected to a DC-DC bidirectional converter, which is bidirectionally connected to a 10kV inverter and a battery pack, and the 10kV inverter is connected to the power grid, DC load and AC load.

2. The bidirectional DC-DC photovoltaic energy storage system according to claim 1, characterized in that: The bidirectional DC-DC converter includes a transformer, bridge arms, supporting capacitors, and an inductor; each end of the transformer is connected to two bridge arms, and the two ends of the two bridge arms are connected to the supporting capacitor; one end of the inductor is electrically connected to the two bridge arms.

3. The bidirectional DC-DC photovoltaic energy storage system according to claim 1, characterized in that: The bidirectional DC-DC converter further includes a sampling circuit and a driving circuit. The sampling circuit includes a current sampling circuit and a voltage sampling circuit. The current sampling circuit uses a resistor voltage divider for sampling. The voltage sampling circuit includes an AC5712 chip.

4. The bidirectional DC-DC photovoltaic energy storage system according to claim 3, characterized in that: The driving circuit includes four IR2110 chips.

5. The bidirectional DC-DC photovoltaic energy storage system according to claim 1, characterized in that: The bidirectional DC-DC converter is also connected to an MPPT controller, which generates a PWM signal with a preset duty cycle to complete the bidirectional flow of electrical signals.

6. The bidirectional DC-DC photovoltaic energy storage system according to claim 1, characterized in that: The battery pack has a rated load of 600W, an input and output voltage of 220V, and a rated current of 60Ah.

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