Self-adaptive photovoltaic power supply system

Abstract

The invention discloses a self-adaptive photovoltaic power supply system, and relates to the field of photovoltaic power supply, the self-adaptive photovoltaic power supply system comprises a frequency converter and a photovoltaic direct current controller, the input end of the photovoltaic direct current controller is adaptively connected with a photovoltaic array, and the output end of the photovoltaic direct current controller is connected with the direct current input end of the frequency converter through a frequency converter direct current bus; the frequency converter is connected with a load; when the photovoltaic array works, a direct-current input voltage is generated and input to the photovoltaic direct-current controller, and the photovoltaic direct-current controller converts the direct-current input voltage into a direct-current output voltage matched with the direct-current bus voltage of the frequency converter so as to supply power to the frequency converter. The system can realize adaptive DC coupling of the photovoltaic DC controller and the frequency converter, and improves the efficiency of a photovoltaic power supply system.

Description

Technical Field

[0001] The invention relates to the field of photovoltaic power supply, and in particular to an adaptive photovoltaic power supply system. Background Art

[0002] As the energy situation becomes increasingly tense, solar energy, as a clean and renewable energy source, has received more and more attention from people, and the power supply system based on photovoltaic power generation has also been widely used. At present, the common structure of the power supply system based on photovoltaic power generation is: the photovoltaic array generates direct current, which is converted into alternating current by the grid-connected photovoltaic inverter to connect to the national power grid or power the energy storage and diesel engine system. Depending on the voltage of the connected system, the grid-connected photovoltaic inverter can output voltages ranging from AC220V, AC380, and AC690V, but the existing photovoltaic power supply system still has problems such as low photovoltaic energy utilization.

[0003] As an energy-saving motor speed control device, the inverter has significant technical advantages in the power supply system formed by combining it with photovoltaic energy. However, the current combination of photovoltaic energy and inverter is often rough, and fails to fully improve the utilization rate of photovoltaic energy. Most inverters have both AC input and DC input, but in the power supply systems that currently use inverters, most of them only use AC power to power the inverter, which makes it impossible for the photovoltaic power generation system to be directly coupled with the inverter, increasing the complexity of the combination of photovoltaic energy and inverter, and is not conducive to improving power supply efficiency. Summary of the invention

[0004] In view of the above problems and technical requirements, the inventors have proposed an adaptive photovoltaic power supply system. The technical solution of the present invention is as follows:

[0005] An adaptive photovoltaic power supply system includes a frequency converter and a photovoltaic DC controller, wherein the input end of the photovoltaic DC controller is adaptively connected to a photovoltaic array, the output end of the photovoltaic DC controller is connected to the DC input end of the frequency converter through the frequency converter DC bus, and the output end of the frequency converter is connected to a load;

[0006] When the photovoltaic array is working, it generates a DC input voltage which is input to the photovoltaic DC controller. The photovoltaic DC controller converts the DC input voltage into a DC output voltage matching the DC bus voltage of the inverter to power the inverter. The inverter works and supplies power to the load.

[0007] Its further technical solution is that the photovoltaic DC controller includes an adaptively connected Boost conversion circuit, a controller and a voltage measuring device;

[0008] The voltage measuring device is connected to the inverter DC bus and is used to detect the inverter DC bus voltage and transmit it to the controller before the photovoltaic DC controller supplies power to the inverter. The controller adjusts the duty cycle of the Boost conversion circuit based on the inverter DC bus voltage so that the DC output voltage output by the photovoltaic DC controller matches the inverter DC bus voltage.

[0009] A further technical solution is that when the controller adjusts the duty cycle of the Boost conversion circuit based on the DC bus voltage of the inverter, it includes determining the target DC output voltage V according to the DC bus voltage of the inverter. out , and based on the DC input voltage V of the Boost conversion circuit in and the target DC output voltage V out Obtain the duty cycle D of the Boost conversion circuit;

[0010] The DC input voltage V of the Boost converter circuit in 、Target DC output voltage V out The relationship between the duty cycle D of the Boost conversion circuit is:

[0011]

[0012] A further technical solution is that the target DC output voltage V out Not less than the detected inverter DC bus voltage.

[0013] A further technical solution is that the AC input terminal of the frequency converter is connected to the mains;

[0014] When the photovoltaic array is working, the photovoltaic DC controller is preferentially used to supply power to the inverter;

[0015] When the output power of the inverter is not less than the rated power of the load, the inverter is powered only by the photovoltaic DC controller; when the output power of the inverter is less than the rated power of the load, the inverter is powered by the mains and the photovoltaic DC controller together.

[0016] A further technical solution is that the photovoltaic array includes a plurality of photovoltaic module strings, the photovoltaic DC controller includes a plurality of DC switches and a plurality of MPPT controllers, and the DC switches, MPPT controllers and photovoltaic module strings are in one-to-one correspondence;

[0017] The photovoltaic component strings are connected to the corresponding MPPT controllers via corresponding DC switches.

[0018] A further technical solution is that the photovoltaic DC controller also includes a first DC bus and a second DC bus, each MPPT controller is connected to the input end of the Boost conversion circuit through the first DC bus, and the output end of the Boost conversion circuit is connected to the second DC bus.

[0019] A further technical solution is that the photovoltaic DC controller further includes a first DC filter unit, a second DC filter unit and a DC output switch, and each DC switch is connected to the corresponding MPPT controller through the first DC filter unit;

[0020] The output end of the Boost conversion circuit is connected to a second DC filter unit via a second DC bus, and the second DC filter unit is connected to a frequency converter via a DC output switch.

[0021] Its further technical solution is that the photovoltaic DC controller also includes a first DC lightning protection unit and a second DC lightning protection unit for preventing lightning wave intrusion, each photovoltaic component string is connected to the first DC lightning protection unit through a corresponding DC switch, and the output end of the second DC filter unit is connected to the second DC lightning protection unit.

[0022] A further technical solution is that the photovoltaic DC controller also includes a backflow prevention diode, the positive pole of the backflow prevention diode is connected to the positive output terminal of the second DC filter unit, and the negative pole of the backflow prevention diode is connected to the positive pole of the inverter DC bus through a DC output switch.

[0023] The beneficial technical effects of the present invention are:

[0024] The present invention provides an adaptive photovoltaic power supply system, which converts the DC input voltage output by the photovoltaic array into a DC output voltage matching the DC bus voltage of the inverter through a photovoltaic DC controller, and the photovoltaic array is directly coupled with the inverter through the photovoltaic DC controller and supplies power to the load, thereby realizing adaptive DC coupling, reducing the complexity of the power supply system composed of photovoltaic energy and the inverter, and improving the utilization rate of photovoltaic energy. According to the working principle of the inverter, the DC input voltage generated by the photovoltaic array is directly loaded into the DC input terminal of the inverter in the form of DC power through the photovoltaic DC controller, which can save the link of inverting the input AC power into DC power in the inverter, thereby improving the efficiency of the power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic block diagram of an embodiment of the adaptive photovoltaic power supply system provided by the present invention.

[0026] Figure 2 This is a circuit topology diagram of an embodiment of a photovoltaic DC controller provided by the present invention. DETAILED DESCRIPTION

[0027] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0028] The present invention provides an adaptive photovoltaic power supply system, comprising a frequency converter and a photovoltaic DC controller, wherein the input end of the photovoltaic DC controller is adaptively connected to a photovoltaic array, the output end of the photovoltaic DC controller is connected to the DC input end of the frequency converter via a DC bus of the frequency converter, and the output end of the frequency converter is connected to a load;

[0029] When the photovoltaic array is working, it generates a DC input voltage which is input to the photovoltaic DC controller. The photovoltaic DC controller converts the DC input voltage into a DC output voltage matching the DC bus voltage of the inverter to power the inverter. The inverter works and supplies power to the load.

[0030] Specifically, the photovoltaic array can convert solar energy into electrical energy and load it to the input end of the photovoltaic DC controller in the form of direct current. The specific form of the adaptive connection between the input end of the photovoltaic DC controller and the photovoltaic array can refer to the following description. The photovoltaic DC controller steps up or down the DC input voltage, and converts the DC input voltage into a DC output voltage that matches the DC bus voltage of the inverter to power the inverter. The inverter outputs the power supply voltage required by the load to power the load. The DC output voltage matches the DC bus voltage of the inverter, which specifically refers to making the DC output voltage greater than or equal to the DC bus voltage of the inverter. In this embodiment, the inverter adopts the ACS510 series inverter of Asea Brown Boveri, and the DC bus voltage of the inverter is 576V. In specific implementation, the model of the inverter can be selected according to actual needs, and the inverter used can have a DC input end.

[0031] The DC input voltage generated by the photovoltaic array is directly coupled to the DC input terminal of the inverter through the photovoltaic DC controller, and no longer needs to be inverted into AC power before being loaded into the inverter, which reduces the complexity of the power supply system composed of photovoltaic energy and the inverter. The DC output voltage of the photovoltaic DC controller changes adaptively with the inverter bus voltage, which improves the utilization rate of photovoltaic energy and enhances the reliability and stability of the power supply system. At the same time, according to the working principle of the inverter, the DC input voltage generated by the photovoltaic array is directly loaded into the DC input terminal of the inverter in the form of DC power through the photovoltaic DC controller, which can save the link of inverting the input AC power into DC power in the inverter, thereby improving the efficiency of the power supply system.

[0032] Furthermore, the AC input terminal of the frequency converter is connected to the mains;

[0033] When the photovoltaic array is working, the photovoltaic DC controller is preferentially used to supply power to the inverter;

[0034] When the output power of the inverter is not less than the rated power of the load, the inverter is powered only by the photovoltaic DC controller; when the output power of the inverter is less than the rated power of the load, the inverter is powered by the mains and the photovoltaic DC controller together.

[0035] Specifically, considering that the operation of the photovoltaic array depends on sunlight resources, the size of the DC input voltage generated by the photovoltaic array is determined by the sunlight resources. In order to enable the inverter to continuously meet the power supply needs of the load, the AC input end of the inverter is connected to the mains, and the mains is always in hot standby state.

[0036] When the photovoltaic array is working, the photovoltaic DC controller will preferentially power the inverter. When the sunshine resources are sufficient, the inverter can meet the power supply demand of the load only by the photovoltaic DC controller, that is, the output power of the inverter is greater than or equal to the rated power of the load. When the sunshine resources are insufficient, the inverter automatically connects to the mains, and the inverter is powered by the mains and the photovoltaic DC controller; when the photovoltaic array is under maintenance or there is no sunshine resource, that is, when the photovoltaic array is not working, the inverter is powered only by the mains. The photovoltaic power supply system provided by the present invention can adopt a diversified power supply mode, enrich the power supply type, enhance the reliability and stability of the power supply system, and improve the utilization rate of green energy.

[0037] Furthermore, the photovoltaic DC controller includes an adaptively connected Boost conversion circuit, a controller and a voltage measuring device;

[0038] The voltage measuring device is connected to the inverter DC bus and is used to detect the inverter DC bus voltage and transmit it to the controller before the photovoltaic DC controller supplies power to the inverter. The controller adjusts the duty cycle of the Boost conversion circuit based on the inverter DC bus voltage so that the DC output voltage output by the photovoltaic DC controller matches the inverter DC bus voltage.

[0039] When the controller adjusts the duty cycle of the Boost conversion circuit based on the DC bus voltage of the inverter, it includes determining the target DC output voltage V according to the DC bus voltage of the inverter. out , and based on the DC input voltage V of the Boost conversion circuit in and the target DC output voltage V out Get the duty cycle D of the Boost conversion circuit.

[0040] Specifically, the first end of the controller is connected to the Boost conversion circuit, and the second end is connected to the voltage measuring device. The Boost conversion circuit generally operates under the control of a pulse width modulation (PWM) signal. The duty cycle of the Boost conversion circuit is the duty cycle of the pulse width modulation signal that controls the Boost conversion circuit. The specific implementation form of the Boost (boost) conversion circuit can be consistent with the prior art.

[0041] In this embodiment, the DC input voltage V in 、Target DC output voltage V out The relationship between the duty cycle D of the Boost conversion circuit can be expressed as:

[0042]

[0043] In specific implementation, according to the specific form of the Boost conversion circuit, the DC input voltage V of the Boost conversion circuit is in 、Target DC output voltage V out and the duty cycle D of the Boost conversion circuit can be changed accordingly.

[0044] The voltage measuring device detects the DC bus voltage of the inverter before the photovoltaic DC controller supplies power to the inverter and transmits it to the controller. The controller determines the target DC output voltage V according to the DC bus voltage of the inverter. out , the controller can also receive the DC input voltage V of the Boost conversion circuit in The duty cycle D is calculated according to the above formula. After the duty cycle D is calculated, the controller outputs a pulse width modulation signal corresponding to the duty cycle to the Boost conversion circuit, so that the DC output voltage of the photovoltaic DC controller is equal to the target DC output voltage V out The target DC output voltage V out is greater than or equal to the detected inverter DC bus voltage. Preferably, in order to enable the photovoltaic DC controller to power the inverter as quickly as possible, the target DC output voltage V out Slightly larger than the detected inverter DC bus voltage, that is, the preset value is added to the inverter DC bus voltage to obtain the target DC output voltage V out .

[0045] Furthermore, the photovoltaic array includes a plurality of photovoltaic component strings, the photovoltaic DC controller includes a plurality of DC switches and a plurality of MPPT controllers, the DC switches, MPPT controllers and photovoltaic component strings are in one-to-one correspondence, and the photovoltaic component strings are connected to the corresponding MPPT controllers via the corresponding DC switches.

[0046] Specifically, photovoltaic component strings are set according to the sunshine resources of the environment in which the photovoltaic array is located and the DC input voltage required by the photovoltaic DC controller. In this embodiment, n photovoltaic component strings are set, and correspondingly, n DC switches and n MPPT (Maximum Power Point Tracking) controllers are set in the photovoltaic DC controller. Each photovoltaic component string is indirectly connected to an MPPT controller through a DC switch. The MPPT controller can adjust the output power of the photovoltaic array according to characteristic values ​​such as different environmental factors, so that the output power of the corresponding photovoltaic component string in the photovoltaic array is always maintained at the maximum value. The specific form and working principle of the MPPT controller can be consistent with the prior art.

[0047] Furthermore, the photovoltaic DC controller also includes a first DC bus and a second DC bus, each MPPT controller is connected to the input end of the Boost conversion circuit through the first DC bus, and the output end of the Boost conversion circuit is connected to the second DC bus.

[0048] The photovoltaic DC controller also includes a first DC filter unit, a second DC filter unit and a DC output switch, each DC switch is connected to the corresponding MPPT controller through the first DC filter unit; the output end of the Boost conversion circuit is connected to the second DC filter unit through the second DC bus, and the second DC filter unit is connected to the inverter through the DC output switch.

[0049] Specifically, the first DC filter unit can be a plurality of single-input and output DC filters, or a multi-input and output DC filter. In this embodiment, the first DC filter unit adopts a multi-input and output first DC filter. The output of each photovoltaic component string is filtered by the first DC filter to remove harmonics and then output to the corresponding MPPT controller. The outputs of n MPPT controllers are input to the Boost conversion circuit after being converged by the first DC bus. Under the control of the controller, the Boost conversion circuit converts the DC output voltage into the target DC output voltage and then inputs it to the second DC filter unit after being converged by the second DC bus. The second DC filter unit is a single-input and output second DC filter, which is used to filter out the harmonics generated by the Boost conversion circuit. In specific implementation, the voltage measuring device detects the DC bus voltage of the inverter and transmits it to the controller before the photovoltaic DC controller supplies power to the inverter, that is, the voltage measuring device detects the DC bus voltage of the inverter and transmits it to the controller before the DC output switch is closed.

[0050] Furthermore, the photovoltaic DC controller also includes a first DC lightning protection unit and a second DC lightning protection unit for preventing lightning wave intrusion. Each photovoltaic component string is connected to the first DC lightning protection unit through a corresponding DC switch, and the output end of the second DC filter unit is connected to the second DC lightning protection unit.

[0051] Specifically, the first DC lightning protection unit can be a plurality of single-channel input DC lightning protection devices, or a multi-channel input DC lightning protection device. In this embodiment, the first DC lightning protection unit is a multi-channel input first DC lightning protection device, and each photovoltaic module string is connected to the first DC lightning protection device, which is used to prevent lightning waves from intruding on the input side of the photovoltaic DC controller and protect the photovoltaic DC controller. The second DC unit is a single-channel input second DC lightning protection device, which is used to prevent lightning waves from intruding on the output side of the photovoltaic DC controller. Both the first DC lightning protection device and the second DC lightning protection device are grounded, and the forms of the first DC lightning protection device and the second DC lightning protection device can be consistent with the prior art.

[0052] Furthermore, the photovoltaic DC controller also includes a backflow prevention diode, the positive pole of the backflow prevention diode is connected to the positive output terminal of the second DC filter unit, and the negative pole of the backflow prevention diode is connected to the positive pole of the inverter DC bus through the DC output switch.

[0053] Specifically, the positive electrode of the anti-backcurrent diode is connected to the positive output end of the second DC filter, and the negative electrode of the anti-backcurrent diode is connected to the positive electrode of the DC bus of the inverter through the DC output switch, which is used to prevent the photovoltaic array from having no power output due to insufficient sunshine resources and other reasons when the load is running and the DC output switch is closed, and the AC power flows back into the photovoltaic DC controller, thereby realizing the anti-backcurrent protection function.

[0054] It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the above description refer to directions in the drawings of the present application specification, and the words "front" and "back", "inner" and "outer" refer to directions toward or away from a specific component, respectively. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features.

[0055] The above is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention.

Claims

1. An adaptive photovoltaic power supply system, characterized in that: It includes a frequency converter and a photovoltaic DC controller, wherein the input end of the photovoltaic DC controller is adaptively connected to the photovoltaic array, the output end of the photovoltaic DC controller is connected to the DC input end of the frequency converter through the DC bus of the frequency converter, and the output end of the frequency converter is connected to the load; When the photovoltaic array is working, it generates a DC input voltage which is input to the photovoltaic DC controller. The photovoltaic DC controller converts the DC input voltage into a DC output voltage matching the DC bus voltage of the inverter to power the inverter. The inverter works and supplies power to the load.

2. The adaptive photovoltaic power supply system according to claim 1, characterized in that: The photovoltaic DC controller includes an adaptively connected Boost conversion circuit, a controller and a voltage measuring device; The voltage measuring device is connected to the inverter DC bus and is used to detect the inverter DC bus voltage and transmit it to the controller before the photovoltaic DC controller supplies power to the inverter. The controller adjusts the duty cycle of the Boost conversion circuit based on the inverter DC bus voltage so that the DC output voltage output by the photovoltaic DC controller matches the inverter DC bus voltage.

3. The adaptive photovoltaic power supply system according to claim 2, characterized in that: When the controller adjusts the duty cycle of the Boost conversion circuit based on the DC bus voltage of the inverter, it includes determining the target DC output voltage V according to the DC bus voltage of the inverter. out , and based on the DC input voltage V of the Boost conversion circuit in and the target DC output voltage V out Obtain the duty cycle D of the Boost conversion circuit; The DC input voltage V of the Boost converter circuit in 、Target DC output voltage V out The relationship between the duty cycle D of the Boost conversion circuit is:

4. The adaptive photovoltaic power supply system according to claim 3, characterized in that: The target DC output voltage V out Not less than the detected inverter DC bus voltage.

5. The adaptive photovoltaic power supply system according to claim 1, characterized in that: The AC input terminal of the frequency converter is connected to the mains; When the photovoltaic array is working, the photovoltaic DC controller is preferentially used to supply power to the inverter; When the output power of the inverter is not less than the rated power of the load, the inverter is powered only by the photovoltaic DC controller; when the output power of the inverter is less than the rated power of the load, the inverter is powered by the mains and the photovoltaic DC controller together.

6. The adaptive photovoltaic power supply system according to claim 2, characterized in that: The photovoltaic array includes a plurality of photovoltaic component strings, and the photovoltaic DC controller includes a plurality of DC switches and a plurality of MPPT controllers, wherein the DC switches, the MPPT controllers and the photovoltaic component strings are in one-to-one correspondence; The photovoltaic component strings are connected to the corresponding MPPT controllers via corresponding DC switches.

7. The adaptive photovoltaic power supply system according to claim 6, characterized in that: The photovoltaic DC controller also includes a first DC bus and a second DC bus. Each MPPT controller is connected to the input end of the Boost conversion circuit via the first DC bus, and the output end of the Boost conversion circuit is connected to the second DC bus.

8. The adaptive photovoltaic power supply system according to claim 7, characterized in that: The photovoltaic DC controller also includes a first DC filter unit, a second DC filter unit and a DC output switch, and each DC switch is connected to the corresponding MPPT controller through the first DC filter unit; The output end of the Boost conversion circuit is connected to a second DC filter unit via a second DC bus, and the second DC filter unit is connected to a frequency converter via a DC output switch.

9. The adaptive photovoltaic power supply system according to claim 8, characterized in that: The photovoltaic DC controller also includes a first DC lightning protection unit and a second DC lightning protection unit for preventing lightning wave intrusion. Each photovoltaic component string is connected to the first DC lightning protection unit through a corresponding DC switch, and the output end of the second DC filter unit is connected to the second DC lightning protection unit.

10. The adaptive photovoltaic power supply system according to claim 7, characterized in that: The photovoltaic DC controller also includes a backflow prevention diode, the positive electrode of which is connected to the positive output terminal of the second DC filter unit, and the negative electrode of which is connected to the positive electrode of the inverter DC bus through a DC output switch.

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