Optical storage inverter bus balancing device and control method thereof

Abstract

The invention relates to an optical storage inverter bus balancing device and a control method thereof. The optical storage inverter bus balancing device comprises a first switch module, a second switch module and a first energy buffer module. The first switch end of the first switch module is connected with one side of the DC bus, and the first switch end of the second switch module is connected with the other side of the DC bus. One end of the first energy buffer module is connected with the second switch end of the first switch module and the second switch end of the second switch module, and the other end is connected with the midpoint of the DC bus. Acquiring positive voltage and negative voltage of the bus; and according to the positive voltage and the negative voltage, the first switch module and the second switch module are switched on or switched off, so that the half bus with more energy is transmitted to the half bus with less energy through the path, and the energy and voltage balance of the buses is realized. And on the premise of outputting to a high-power half-wave load, excessive or overlarge electrolytic capacitors are not needed, so that the product is small in size, low in cost and high in power density.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage inverters, and in particular to a bus balancing device for a photovoltaic energy storage inverter and a control method thereof. Background Art

[0002] Photovoltaic energy storage inverter, also known as photovoltaic energy storage inverter, is a device that converts the direct current generated by photovoltaic panels into alternating current, so that it can be connected to the power grid or directly drive electrical appliances. Therefore, the system that configures the energy storage system based on the photovoltaic energy storage inverter and connects the corresponding photovoltaic equipment to the grid is the photovoltaic energy storage inverter system. The photovoltaic energy storage inverter system can realize the power supply function with external loads.

[0003] The current load capacity of photovoltaic storage inverters has the following situations: either it cannot carry half-wave loads, or it can only carry low-power half-wave loads. The method of carrying low-power half-wave loads is to use large-capacity electrolytic capacitors to increase the energy storage capacity of the bus. When outputting to a low-power half-wave load, the bus can withstand the large amount of energy that can be stored, although the small-power half-wave load only absorbs half of the bus energy. However, the use of large-capacity electrolytic capacitors will lead to an increase in product size, increased costs, and reduced power density. Summary of the invention

[0004] In view of the fact that large-capacity electrolytic capacitors are used in existing photovoltaic storage inverters to solve the problems of increased product volume, increased cost, reduced power density, etc. when carrying high-power half-wave loads, an embodiment of the present invention provides a photovoltaic storage inverter bus balancing device and a control method thereof.

[0005] An embodiment of the present invention provides a bus balancing device for a photovoltaic power storage inverter, comprising:

[0006] A first switch module, wherein a first switch end thereof is connected to one side of a DC bus;

[0007] A second switch module, a first switch end of which is connected to the other side of the DC bus;

[0008] The first energy buffer module has one end connected to the second switch end of the first switch module and the second switch end of the second switch module, and the other end connected to the midpoint of the DC bus.

[0009] The photovoltaic inverter bus balancing device of the embodiment of the present invention includes a first switch module, a second switch module and a first energy buffer module. The first switch end of the first switch module is connected to one side of the DC bus, and the first switch end of the second switch module is connected to the other side of the DC bus. One end of the first energy buffer module is connected to the second switch end of the first switch module and the second switch end of the second switch module, and the other end is connected to the midpoint of the DC bus. According to the conduction or shutdown of the first switch module and the second switch module, an energy balancing path is provided on one side and the other side of the bus, and energy buffering is designed for the path to avoid direct impact on the bus.

[0010] As one of the optional embodiments, it also includes:

[0011] A second energy buffer module has one end connected to one side of the DC bus and the other end connected to a midpoint of the DC bus.

[0012] As one of the optional embodiments, it also includes:

[0013] A third energy buffer module has one end connected to the other side of the DC bus and the other end connected to the midpoint of the DC bus.

[0014] As an optional embodiment, the first switch module includes a switch tube.

[0015] As an optional embodiment, the second switch module includes a switch tube.

[0016] As an optional embodiment, the first energy buffer module includes an inductor.

[0017] As an optional embodiment, the second energy buffer module includes two or more capacitors connected in parallel.

[0018] As an optional embodiment, the third energy buffer module includes two or more capacitors connected in parallel.

[0019] The embodiment of the present invention further provides a control method for a bus balancing device of a photovoltaic storage inverter, which is applied to the above-mentioned bus balancing device of a photovoltaic storage inverter, and comprises the following steps:

[0020] Collect the positive voltage and negative voltage of the bus; wherein the positive voltage is the voltage from one side of the DC bus to the midpoint; the negative voltage is the voltage from the other side of the DC bus to the midpoint;

[0021] The first switch module and the second switch module are turned on or off according to the positive voltage and the negative voltage.

[0022] The control method of the photovoltaic storage inverter bus balancing device of the embodiment of the present invention is applied to the photovoltaic storage inverter bus balancing device to collect the positive voltage and negative voltage of the bus; wherein the positive voltage is the voltage from one side of the DC bus to the midpoint; the negative voltage is the voltage from the other side of the DC bus to the midpoint; according to the positive voltage and the negative voltage, the first switch module and the second switch module are turned on or off to transmit the half-bus with more energy to the half-bus with less energy through a path, so as to achieve energy and voltage balance of the bus. Under the premise of being able to output to high-power half-wave loads, there is no need for too many or too large electrolytic capacitors, so that the product is small in size, low in cost, and high in power density.

[0023] As one of the optional embodiments, the process of turning on or off the first switch module and the second switch module according to the positive voltage and the negative voltage comprises the steps of:

[0024] According to the difference between the positive voltage and the negative voltage, the first switch module and the second switch module are turned on or off simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A module structure diagram of a bus balancing device for a photovoltaic power storage inverter according to a disclosed embodiment;

[0026] Figure 2 A module structure diagram of a bus balancing device for a photovoltaic storage inverter according to a preferred embodiment;

[0027] Figure 3 It is a flow chart of a control method of a bus balancing device of a photovoltaic energy storage inverter according to a disclosed embodiment. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0029] Unless otherwise defined, the technical terms or scientific terms used in the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0030] In order to keep the following description of the embodiments of the present disclosure clear and concise, the present disclosure omits detailed descriptions of some known functions and known components.

[0031] An embodiment of the present disclosure provides a bus balancing device for a photovoltaic energy storage inverter.

[0032] Figure 1 FIG. 1 is a block diagram of a busbar balancing device for a photovoltaic storage inverter according to a disclosed embodiment. Figure 1 As shown, a bus balancing device for a photovoltaic storage inverter according to a disclosed embodiment includes:

[0033] A first switch module 100, wherein a first switch end thereof is connected to one side of a DC bus;

[0034] A second switch module 101, a first switch end of which is connected to the other side of the DC bus;

[0035] The first energy buffer module 102 has one end connected to the second switch end of the first switch module 100 and the second switch end of the second switch module 101 , and the other end connected to the midpoint of the DC bus.

[0036] like Figure 1 As shown, the photovoltaic energy storage inverter needs to supply power to different types of loads, such as single-phase load, three-phase load, single-phase half-wave load, three-phase half-wave load, etc. The energy conversion hub in the photovoltaic energy storage inverter is the DC bus, and the DC bus forms a positive DC bus, a negative DC bus, and a DC bus midpoint respectively. The DC bus midpoint divides the DC bus voltage equally: the voltage from the positive DC bus to the DC bus midpoint is half the DC bus voltage, and similarly, the voltage from the negative DC bus to the DC bus midpoint is half the DC bus voltage. In the embodiments of the present disclosure, one side of the DC bus is the positive DC bus, and the other side of the DC bus is the negative DC bus for explanation.

[0037] Therefore, the system can only work normally when the voltage from the positive bus to the bus midpoint is equal to the voltage from the negative bus to the bus midpoint. This is bus balance. The DC bus energy is output to the load through the inverter circuit. Different load characteristics will affect the DC bus. Both single-phase and three-phase loads can extract energy from the positive and negative buses, so the bus is in a dynamic balance. When the load is a single-phase half-wave load or a three-phase half-wave load, the load only extracts the positive or negative energy of the bus. In the long run, the positive and negative energy and voltage of the bus will be in an unbalanced state, affecting the normal operation of the machine or even damaging the machine.

[0038] like Figure 1 As shown, the first switch module 100 establishes a path from one side of the DC bus to the midpoint when it is turned on, and the second switch module 101 establishes a path from the other side of the DC bus to the midpoint when it is turned on. The first energy buffer module 102 is used to store and buffer the energy on the path. Therefore, the first switch module 100 and the second switch module 101 are controllable switches, which are turned on or off according to the switch signal. When turned on, when carrying a single-phase half-wave load or a three-phase half-wave load, the half bus with more energy is transmitted to the half bus with less energy through the path.

[0039] As an optional embodiment, the first switch module 100 and the second switch module 101 may be semiconductor switches, relays or electronic switches.

[0040] Preferably, Figure 2 FIG. 1 is a module structure diagram of a busbar balancing device for a photovoltaic storage inverter according to a preferred embodiment of the present invention. Figure 2 As shown, the first switch module 100 and the second switch module 101 use switch tubes. When the switch tubes are turned on, an energy balance transmission path is established. At the same time, the electrical characteristics of the switch tubes themselves can also buffer part of the energy.

[0041] The first energy buffer module 102 is used for balancing the energy transmission path, and may be a resistor, an RC circuit, an LC circuit, an RLC circuit or an electrical discharge device.

[0042] Preferably, if Figure 2 As shown, the first energy buffer module 102 uses inductance as an energy storage and buffering carrier.

[0043] Preferably, if Figure 1 As shown, a bus balancing device for a photovoltaic storage inverter in a disclosed embodiment further includes:

[0044] The second energy buffer module 103 has one end connected to one side of the DC bus and the other end connected to the midpoint of the DC bus.

[0045] The second energy buffer module 103 is used to supplement the energy discharge from one side of the DC bus to the midpoint, and a resistor, an RC circuit, an LC circuit, an RLC circuit or an electrical discharge device can be selected. Figure 2 As shown, the second energy buffer module 103 includes two or more capacitors connected in parallel. Compared with traditional high-power capacitors, the second energy buffer module 103 can use capacitors with small capacity.

[0046] Similarly, if Figure 1 As shown, a bus balancing device for a photovoltaic storage inverter in a disclosed embodiment further includes:

[0047] The third energy buffer module 104 has one end connected to the other side of the DC bus and the other end connected to the midpoint of the DC bus.

[0048] The third energy buffer module 104 is used to supplement the energy discharge from the other side of the DC bus to the midpoint, and can be a resistor, an RC circuit, an LC circuit, an RLC circuit or an electrical discharge device. Figure 2 As shown, the third energy buffer module 104 includes two or more capacitors connected in parallel. Compared with traditional high-power capacitors, the third energy buffer module 104 can use capacitors with small capacity.

[0049] The bus balancing device of the photovoltaic storage inverter of any embodiment of the present disclosure includes a first switch module 100, a second switch module 101 and a first energy buffer module 102. The first switch end of the first switch module 100 is connected to one side of the DC bus, and the first switch end of the second switch module 101 is connected to the other side of the DC bus. One end of the first energy buffer module 102 is connected to the second switch end of the first switch module 100 and the second switch end of the second switch module 101, and the other end is connected to the midpoint of the DC bus. According to the conduction or shutdown of the first switch module 100 and the second switch module 101, an energy balancing path is provided on one side and the other side of the bus, and energy buffering is designed for the path to avoid direct impact on the bus.

[0050] Based on the bus balancing device of the photovoltaic power storage inverter of any of the above embodiments, the embodiment of the present disclosure also provides a control method of the bus balancing device of the photovoltaic power storage inverter.

[0051] Figure 3 FIG. 1 is a flow chart of a control method of a bus balancing device of a photovoltaic storage inverter according to a disclosed embodiment. Figure 3 As shown, a control method of a bus balancing device of a photovoltaic storage inverter according to a disclosed embodiment includes steps S100 and S101:

[0052] S100, collecting the positive voltage and negative voltage of the bus; wherein the positive voltage is the voltage from one side of the DC bus to the midpoint; and the negative voltage is the voltage from the other side of the DC bus to the midpoint;

[0053] S101 , turning on or off a first switch module and a second switch module according to the positive voltage and the negative voltage.

[0054] According to the magnitude of the positive voltage and the negative voltage, it is determined which side of the half-wave load has excessive energy, and the corresponding first switch module and the second switch module are controlled to conduct and release the pressure.

[0055] Preferably, the process of turning on or off the first switch module and the second switch module according to the positive voltage and the negative voltage comprises the steps of:

[0056] According to the difference between the positive voltage and the negative voltage, the first switch module and the second switch module are turned on or off simultaneously.

[0057] Among them, there is a voltage sampling circuit in the bus, which collects the voltage from the positive bus to the bus midpoint and the voltage from the negative bus to the bus midpoint. The sampled voltage is input to the control chip for voltage judgment. When it is judged that the two voltages are the same or the positive and negative difference is not greater than X volts, the machine does not turn on the balancing bridge. When it is judged that the positive and negative difference between the two voltages is greater than X volts, the machine turns on the balancing bridge, and transmits the half bus with more energy to the half bus with less energy through the path, so as to achieve energy and voltage balance of the bus.

[0058] Among them, X is an empirical value, which is selected according to the photovoltaic storage inverter system of different power sizes.

[0059] Preferably, the first switch module and the second switch module can also be turned on or off in different time periods, and the on-off control is performed independently according to the positive voltage and the negative voltage.

[0060] The control method of the bus balancing device of the photovoltaic storage inverter of the embodiment of the present disclosure is applied to the bus balancing device of the photovoltaic storage inverter, and collects the positive voltage and negative voltage of the bus; wherein the positive voltage is the voltage from one side of the DC bus to the midpoint; the negative voltage is the voltage from the other side of the DC bus to the midpoint; according to the positive voltage and the negative voltage, the first switch module and the second switch module are turned on or off to transmit the half-side bus with more energy to the half-side bus with less energy through a path, so as to achieve the energy and voltage balance of the bus. Under the premise of being able to output to a high-power half-wave load, there is no need for too many or too large electrolytic capacitors, so that the product is small in size, low in cost, and high in power density.

[0061] There are a few points to note about this disclosure:

[0062] (1) The drawings of the embodiments of the present disclosure only relate to the structures related to the embodiments of the present disclosure, and other structures may refer to the general design.

[0063] (2) For the sake of clarity, the thickness and size of layers or structures are exaggerated in the drawings used to describe the embodiments of the present invention. It is understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "under" another element, the element may be "directly" "on" or "under" the other element, or there may be intervening elements.

[0064] (3) In the absence of conflict, the embodiments of the present disclosure and the features in the embodiments may be combined with each other to obtain new embodiments. The above are only specific implementation methods of the present disclosure, but the protection scope of the present disclosure is not limited thereto. The protection scope of the present disclosure shall be based on the protection scope of the claims.

[0065] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0066] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A busbar balancing device for a photovoltaic storage inverter, characterized in that: include: A first switch module, wherein a first switch end thereof is connected to one side of a DC bus; A second switch module, a first switch end of which is connected to the other side of the DC bus; The first energy buffer module has one end connected to the second switch end of the first switch module and the second switch end of the second switch module, and the other end connected to the midpoint of the DC bus.

2. The bus balancing device for a photovoltaic power storage inverter according to claim 1, characterized in that: Also includes: A second energy buffer module has one end connected to one side of the DC bus and the other end connected to a midpoint of the DC bus.

3. The bus balancing device for a photovoltaic power storage inverter according to claim 1, characterized in that: Also includes: A third energy buffer module has one end connected to the other side of the DC bus and the other end connected to the midpoint of the DC bus.

4. The bus balancing device for a photovoltaic power storage inverter according to claim 1, characterized in that: The first switch module includes a switch tube.

5. The bus balancing device for a photovoltaic power storage inverter according to claim 1, characterized in that: The second switch module includes a switch tube.

6. The bus balancing device for a photovoltaic power storage inverter according to claim 1, characterized in that: The first energy buffer module includes an inductor.

7. The bus balancing device for a photovoltaic power storage inverter according to claim 2, characterized in that: The second energy buffer module includes two or more capacitors connected in parallel.

8. The bus balancing device for a photovoltaic power storage inverter according to claim 3, characterized in that: The third energy buffer module includes two or more capacitors connected in parallel.

9. A control method for a bus balancing device of a photovoltaic storage inverter, applied to the bus balancing device of a photovoltaic storage inverter as claimed in any one of claims 1 to 8, characterized in that: Includes steps: Collect the positive voltage and negative voltage of the bus; wherein the positive voltage is the voltage from one side of the DC bus to the midpoint; the negative voltage is the voltage from the other side of the DC bus to the midpoint; The first switch module and the second switch module are turned on or off according to the positive voltage and the negative voltage.

10. The control method of the bus balancing device of the photovoltaic energy storage inverter according to claim 9, characterized in that: The process of turning on or off the first switch module and the second switch module according to the positive voltage and the negative voltage comprises the steps of: According to the difference between the positive voltage and the negative voltage, the first switch module and the second switch module are turned on or off simultaneously.

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