Photovoltaic equipment and method for improving photovoltaic utilization rate of photovoltaic equipment

Abstract

The present invention discloses a photovoltaic device and a method for improving the photovoltaic utilization rate of the photovoltaic device. The method for improving the photovoltaic utilization rate of the photovoltaic device includes: when the photovoltaic device is disconnected from the power grid and the photovoltaic device of the photovoltaic device is directly connected to the DC bus, monitoring the DC bus of the photovoltaic device and the electrical parameters of the photovoltaic device, the energy storage device and the load mounted on the DC bus; according to the electrical parameter characteristic curve of the photovoltaic device, controlling the photovoltaic device to operate in power tracking mode or maximum power output mode; when the photovoltaic device operates in maximum power output mode, according to the supply and demand relationship between the photovoltaic device, the energy storage device and the load, adjusting or limiting the charge and discharge state of the energy storage device and the electrical parameters of the load, so that the photovoltaic device, the energy storage device and the load are balanced at the maximum power output point of the photovoltaic device. The present invention can make the photovoltaic device of the photovoltaic device operate in the maximum power output mode as much as possible.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic equipment, and in particular to a method for improving photovoltaic utilization rate of photovoltaic equipment. Background Art

[0002] With the shortage of energy and the increase of public environmental awareness, many photovoltaic devices have appeared. Photovoltaic devices usually have a DC bus, which can be connected to the city grid through a DC / DC converter, so that when photovoltaic power generation is insufficient, the city power can be used to maintain the normal operation of the load of the photovoltaic device. However, when photovoltaic power generation is sufficient or in some special circumstances, photovoltaic devices are usually disconnected from the city power, so the DC / DC converter between the DC bus and the AC bus stops working. At this time, the photovoltaic device (such as the photovoltaic array) of the photovoltaic device does not have a dedicated DC / DC converter. The photovoltaic device is directly connected to the DC bus, and the energy storage device is connected to the DC bus through a DC / DC converter. The DC / DC converter controls the DC bus, resulting in the photovoltaic solar cell not operating at maximum power, resulting in a certain loss of power generation.

[0003] Taking photovoltaic air conditioning as an example, with the increase in the application scenarios of photovoltaic DC air conditioning systems, various operating conditions can occur. In certain specific areas, such as islands, remote highlands and mountainous areas, which are long-term off-grid (grid) environments, energy storage photovoltaics and other supply and demand are unbalanced, and energy utilization is low.

[0004] Therefore, how to provide a method to enable the photovoltaic solar cells to operate at maximum power when the photovoltaic device is directly connected to the DC bus in an off-grid state and improve the photovoltaic utilization rate of the photovoltaic device is a technical problem to be solved. Summary of the invention

[0005] In order to solve the technical problem of low photovoltaic utilization rate of photovoltaic equipment in the prior art, the present invention proposes a photovoltaic equipment and a method for improving the photovoltaic utilization rate of the photovoltaic equipment.

[0006] The method for improving the photovoltaic utilization rate of photovoltaic equipment proposed by the present invention comprises:

[0007] When the photovoltaic equipment is disconnected from the power grid and the photovoltaic device of the photovoltaic equipment is directly connected to the DC bus, monitoring the electrical parameters of the DC bus of the photovoltaic equipment and the photovoltaic device, energy storage device and load mounted on the DC bus;

[0008] According to the electrical parameter characteristic curve of the photovoltaic device, controlling the photovoltaic device to operate in a power tracking mode or a maximum power output mode;

[0009] When the photovoltaic device operates in the maximum power output mode, the charge and discharge state of the energy storage device and the electrical parameters of the load are adjusted or limited according to the supply and demand relationship between the photovoltaic device, the energy storage device and the load, so that the photovoltaic device, the energy storage device and the load are balanced at the maximum power output point of the photovoltaic device.

[0010] Furthermore, the electrical parameter characteristic curve of the photovoltaic device is specifically a relationship curve between the output power of the photovoltaic device and the voltage of the DC bus.

[0011] Furthermore, when the power state of the energy storage device is fully charged, if the power of the load is less than the maximum power of the photovoltaic device, the photovoltaic device runs a power tracking mode and continues to monitor the DC bus of the photovoltaic device and the electrical parameters of the photovoltaic device, the energy storage device and the load mounted on the DC bus.

[0012] Furthermore, when the power state of the energy storage device is fully charged, if the power of the load is equal to the maximum power of the photovoltaic device, the photovoltaic device operates in a maximum power output mode.

[0013] Furthermore, when the energy storage device is fully charged, if the power of the load is greater than the maximum power of the photovoltaic device, the photovoltaic device operates in a maximum power output mode and limits the power of the load based on the maximum discharge power of the energy storage device.

[0014] Furthermore, when the power state of the energy storage device is not fully charged, if the power of the load is less than the maximum power of the photovoltaic device minus the maximum charging power of the energy storage device, the photovoltaic device runs a power tracking mode and continues to monitor the DC bus of the photovoltaic device and the electrical parameters of the photovoltaic device, the energy storage device and the load mounted on the DC bus.

[0015] Furthermore, when the power state of the energy storage device is not fully charged, if the power of the load is equal to the maximum power of the photovoltaic device minus the maximum charging power of the energy storage device, the photovoltaic device operates in a maximum power output mode.

[0016] Furthermore, when the power state of the energy storage device is not fully charged, if the power of the load is greater than the maximum power of the photovoltaic device minus the maximum charging power of the energy storage device, the photovoltaic device operates in a maximum power output mode and, based on the maximum discharge power of the energy storage device, limits the power of the load.

[0017] The photovoltaic device proposed in the present invention comprises: a photovoltaic device, an energy storage device, and a load, and is characterized in that it also comprises a detection module and a control module for mutually cooperating to execute the method for improving the photovoltaic utilization rate of the photovoltaic device described in the above technical solution;

[0018] The detection module is used to monitor the electrical parameters of the DC bus of the photovoltaic equipment and the photovoltaic device, energy storage device and load mounted on the DC bus;

[0019] The control module controls the photovoltaic device to operate in power tracking mode or maximum power output mode according to the electrical parameter characteristic curve of the photovoltaic device; when the photovoltaic device operates in maximum power output mode, the charge and discharge state of the energy storage device and the electrical parameters of the load are adjusted or limited according to the supply and demand relationship between the photovoltaic device, the energy storage device and the load, so that the photovoltaic device, the energy storage device and the load are balanced at the maximum power output point of the photovoltaic device.

[0020] Furthermore, the photovoltaic equipment includes a photovoltaic air conditioner.

[0021] The present invention utilizes the PU characteristic curve of the photovoltaic device to maintain the power balance among the photovoltaic device, the energy storage device and the load. It can automatically adjust the output power of the photovoltaic device to achieve a power tracking control strategy for power balance, and combined with the DC bus voltage control strategy of the energy storage unit, it can realize rapid switching between power tracking and maximum power output. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is described in detail below with reference to the embodiments and accompanying drawings, wherein:

[0023] Figure 1 is a flow chart of an embodiment of the present invention.

[0024] Figure 2 It is a schematic diagram of the effect of load power changes on the operating point of the photovoltaic device when the energy storage is fully charged according to the present invention.

[0025] Figure 3 It is a schematic diagram of the effect of load power changes on the operating point of the photovoltaic device when the energy storage is not fully charged in the present invention.

[0026] Figure 4 It is a block diagram of the composition of a photovoltaic DC storage air conditioning system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] Thus, a feature indicated in this specification will be used to illustrate one of the features of an embodiment of the present invention, rather than implying that each embodiment of the present invention must have the described feature. In addition, it should be noted that this specification describes many features. Although some features can be combined together to illustrate possible system designs, these features can also be used in other combinations that are not explicitly described. Thus, unless otherwise stated, the described combinations are not intended to be limiting.

[0029] like Figure 1 As shown, the photovoltaic device of the present invention includes a DC bus, a photovoltaic device, an energy storage device and a load, and the photovoltaic device, the energy storage device and the load are all mounted on the DC bus. The energy storage device can be connected to the DC bus through a DC / DC converter, for example, through a bidirectional DC / DC converter. However, the photovoltaic device lacks a dedicated DC / DC converter to connect the DC bus.

[0030] Based on the photovoltaic device described above, the method for improving the photovoltaic utilization rate of the photovoltaic device of the present invention mainly includes the following steps.

[0031] When the photovoltaic device of the photovoltaic equipment lacks a dedicated DC / DC converter to connect the DC bus, for example, it is disconnected from the power grid, resulting in the original DC / DC converter between the DC bus and the AC bus being unable to control the photovoltaic device of the photovoltaic device. At this time, the photovoltaic device is directly connected to the DC bus, and the DC / DC converter of the energy storage device controls the DC bus. At this time, the electrical parameters of the DC bus of the photovoltaic device and the photovoltaic device, energy storage device and load mounted on the DC bus are monitored. In view of the fact that electrical parameters can be converted to each other, the present invention does not limit the electrical parameters of the photovoltaic device, the energy storage device and the load. For example, the output voltage and output current of the photovoltaic device can be monitored, the charging and discharging state of the energy storage device, as well as the corresponding voltage, current, etc., can be monitored, and the power of the load or the corresponding voltage, current, etc. can be monitored.

[0032] Then, the present invention controls the photovoltaic device to operate in power tracking mode or maximum power output mode according to the electrical parameter characteristic curve of the photovoltaic device. And when the photovoltaic device operates in maximum power output mode, the photovoltaic device adjusts or limits the charge and discharge state of the energy storage device and the electrical parameters of the load according to the supply and demand relationship between the photovoltaic device, the energy storage device and the load, so that the photovoltaic device, the energy storage device and the load are balanced at the maximum power output point of the photovoltaic device.

[0033] Regarding the electrical parameter characteristic curves of photovoltaic devices, common ones include the relationship curve between the output power of the photovoltaic device and the voltage of the DC bus, and the relationship curve between the voltage and current of the photovoltaic device. In one embodiment, the electrical parameter characteristic curve of the photovoltaic device of the present invention is specifically the relationship curve between the output power of the photovoltaic device and the voltage of the DC bus. When the photovoltaic device is a photovoltaic array, the relationship curve between the output power of the photovoltaic device and the voltage of the DC bus is also called the PU characteristic curve of the photovoltaic array.

[0034] The principles of the inventive concept of the present invention are mainly based on the following principles.

[0035] Under strong light conditions, if the photovoltaic device of the photovoltaic equipment is still at the maximum power output point, the output power of the photovoltaic device is greater than the load power consumption, which will cause the voltage of the DC bus to rise. If the SOC of the energy storage device is not 1 at this time, SOC stands for state-of-charge, which refers to the charging state of the battery, also known as the remaining capacity, indicating the ability of the battery to continue working. SOC of 1 means that the battery of the energy storage device is fully charged, and the difference power between the photovoltaic device and the load demand is used to charge the battery of the energy storage device, so that the DC bus voltage remains at the maximum power output point.

[0036] When the battery of the energy storage device reaches the maximum charging power or is fully charged, if the power generation power of the photovoltaic device is still in surplus, that is, the output power of the photovoltaic device is greater than the power of the load, the voltage of the DC bus will also increase.

[0037] According to the PU characteristic curve of the photovoltaic array, when the DC bus voltage is greater than the MPPT voltage, the photovoltaic output power will drop sharply after the DC bus voltage increases. When the photovoltaic output power and the system power consumption reach a balance, the DC bus voltage will stabilize again and will stabilize to the right of the MPPT point on the PU characteristic curve. The full name of MPPT here is Maximum Power Point Tracking. The MPPT voltage represents the voltage of the maximum power point of the photovoltaic device, and the MPPT point represents the maximum power point of the photovoltaic device.

[0038] When the surplus power of the photovoltaic equipment decreases, the DC bus voltage will drop. The drop in DC bus voltage increases the photovoltaic output power, thus achieving supply and demand balance again.

[0039] When the DC bus voltage drops to the left of the MPPT point, the power regulation of the energy storage unit will stabilize the DC bus voltage at the MPPT point, thereby achieving smooth switching from power tracking to maximum power output.

[0040] Therefore, based on the above principles, the present invention describes below a specific technical solution in which the photovoltaic device is controlled to operate in power tracking mode or maximum power output mode according to the electrical parameter characteristic curve of the photovoltaic device, and when the photovoltaic device operates in maximum power output mode, the photovoltaic device adjusts or limits the charge and discharge state of the energy storage device and the electrical parameters of the load according to the supply and demand relationship between the photovoltaic device, the energy storage device and the load, so that the photovoltaic device, the energy storage device and the load are balanced at the maximum power output point of the photovoltaic device.

[0041] When the energy storage device is fully charged, if the power of the load is less than the maximum power of the photovoltaic device, the photovoltaic device runs a power tracking mode and continues to monitor the DC bus of the photovoltaic device and the electrical parameters of the photovoltaic device, energy storage device and load mounted on the DC bus.

[0042] When the energy storage device is in a fully charged state, if the power of the load is equal to the maximum power of the photovoltaic device, the photovoltaic equipment operates in a maximum power output mode, and the photovoltaic utilization rate of the photovoltaic device is the highest.

[0043] When the energy storage device is fully charged, if the power of the load is greater than the maximum power of the photovoltaic device, the photovoltaic device operates in the maximum power output mode, the photovoltaic utilization rate of the photovoltaic device is the highest, and the power of the load is limited based on the maximum discharge power of the energy storage device.

[0044] When the power state of the energy storage device is not fully charged, if the power of the load is less than the maximum power of the photovoltaic device minus the maximum charging power of the energy storage device, the photovoltaic device runs the power tracking mode and continues to monitor the DC bus of the photovoltaic device and the electrical parameters of the photovoltaic device, energy storage device and load mounted on the DC bus.

[0045] When the power state of the energy storage device is not fully charged, if the power of the load is equal to the maximum power of the photovoltaic device minus the maximum charging power of the energy storage device, the photovoltaic equipment operates in the maximum power output mode, and the photovoltaic utilization rate of the photovoltaic device is the highest.

[0046] When the power state of the energy storage device is not fully charged, if the power of the load is greater than the maximum power of the photovoltaic device minus the maximum charging power of the energy storage device, the photovoltaic device operates in the maximum power output mode, the photovoltaic utilization rate of the photovoltaic device is the highest, and the power of the load is limited based on the maximum discharge power of the energy storage device.

[0047] Combine the following Figure 2 , Figure 3 The relationship curve between the output power of the photovoltaic device and the voltage of the DC bus is shown in the figure, and the influence of the load power, the state of the energy storage device, and the operating mode of the photovoltaic device on the DC bus voltage is analyzed in detail.

[0048] Assuming that the light intensity and temperature remain unchanged and the energy storage device is fully charged, the voltage of the DC bus changes with the load power when it is fully charged. Figure 2 shown.

[0049] Assume that initially, the load power is P m1 , which is equal to the maximum output power of the photovoltaic device. The system power of the entire photovoltaic equipment is balanced, and the voltage of the DC bus is U1. At this time, the photovoltaic device is in maximum power output mode.

[0050] When the load power decreases to P m2 When the power output of the photovoltaic device is greater than the power consumed by the load, since the SOC of the energy storage device is 1, that is, the battery of the energy storage device is fully charged, it cannot absorb the surplus power of the photovoltaic device, thus causing the DC bus voltage to increase.

[0051] When the DC bus voltage increases to U 2 When the output power of the photovoltaic device and the power of the load are balanced again, the voltage of the DC bus is stabilized at U 2 .

[0052] When the load power increases to P m3 When the output power of the photovoltaic device is less than the power of the load, the voltage of the DC bus decreases. When the voltage of the DC bus decreases to less than the MPPT voltage, the energy storage device will discharge for the load to make up for the insufficient power of the photovoltaic device in order to maintain the MPPT operation of the photovoltaic device, that is, to maintain the maximum power output mode of the photovoltaic device, so that the DC bus voltage is stabilized at the maximum power output point. At the same time, since the maximum discharge power of the energy storage device is limited, the power of the load needs to be limited at this time.

[0053] Let P dechmax is the maximum discharge power of the energy storage device, P dechmax =P m3 -P m1 , when the load power is P m1 With P m3 When the power consumption of a photovoltaic device changes between 100 and 200 W, the energy storage device can adjust its discharge power so that the photovoltaic array of the photovoltaic device operates in the MPPT mode, that is, the photovoltaic device operates in the maximum power output mode.

[0054] In summary, when the energy storage device is fully charged, when the load power is less than P m1 When the photovoltaic device operates in power tracking mode, the load power is at P m1 With P m3 When the photovoltaic device is in the MPPT mode, the photovoltaic device is in the maximum power output mode, and the power of the photovoltaic device to control the load cannot exceed P m3, otherwise part of the load needs to be cut off.

[0055] When the energy storage device is not fully charged, if the photovoltaic device has sufficient power generation, the energy storage device can absorb part of the surplus power of the photovoltaic device. At this time, the impact of load changes on the DC bus voltage is as follows: Figure 3 shown.

[0056] Figure 3 In, P chmax is the maximum charging power of the energy storage device, P chmax =P m1 -P m4 , when the load power is at P m1 With P m4 During this time, the energy storage device can adjust the charging power so that the voltage of the DC bus is stabilized at the maximum power output point, that is, the photovoltaic device operates in the maximum power output mode.

[0057] When the load power decreases to P m2 When the output power of the photovoltaic device is greater than the sum of the maximum charging power of the load and the energy storage device, the voltage of the DC bus increases and finally stabilizes at U 3 At this time, the output power of the photovoltaic device is equal to the sum of the charging power of the energy storage battery and the power consumed by the load.

[0058] In summary, when the energy storage device is not fully charged, when the load power is less than P m4 When the photovoltaic device operates in power tracking mode, the load power is at P m4 With P m3 When the photovoltaic device is in the MPPT mode, the photovoltaic device is in the maximum power output mode, and the power of the photovoltaic device to control the load cannot exceed P m3 .

[0059] By comparing various controls of the fully charged state and the non-fully charged state of the above energy storage device, it can be found that compared with the fully charged state, when the energy storage device is in the non-fully charged state, the load power range that can be operated in the MPPT mode is wider.

[0060] The present invention also protects photovoltaic equipment, which includes: a photovoltaic device, an energy storage device, and a load. On this basis, the photovoltaic equipment also includes a detection module and a control module, and the detection module and the control module cooperate with each other to perform the above method for improving the photovoltaic utilization rate of the photovoltaic equipment.

[0061] The detection module is used to monitor the DC bus of the photovoltaic equipment and the electrical parameters of the photovoltaic device, energy storage device and load mounted on the DC bus.

[0062] The control module controls the photovoltaic device to operate in a power tracking mode or a maximum power output mode according to the electrical parameter characteristic curve of the photovoltaic device.

[0063] When the photovoltaic device operates in the maximum power output mode, the control module adjusts or limits the charge and discharge state of the energy storage device and the electrical parameters of the load according to the supply and demand relationship between the photovoltaic device, the energy storage device and the load, so that the photovoltaic device, the energy storage device and the load are balanced at the maximum power output point of the photovoltaic device.

[0064] In one embodiment, the photovoltaic device of the present invention comprises a photovoltaic air conditioner.

[0065] Figure 4 A block diagram of the composition of the photovoltaic air conditioner of the present invention is shown. The photovoltaic air conditioner includes a DC bus, a photovoltaic array (i.e., a photovoltaic device), an energy storage battery (i.e., an energy storage device), and an air conditioning load. The photovoltaic array, the energy storage battery, and the air conditioning load are all mounted on the DC bus. The energy storage battery can be connected to the DC bus through a DC / DC converter, for example, through a bidirectional DC / DC converter. The DC bus is connected to the AC bus through a bidirectional AC / DC converter. The AC load is mounted on the AC bus, and the power grid provides power to the AC bus. The bidirectional AC / DC converter is responsible for power interaction with the power grid. When the photovoltaic array of the photovoltaic air conditioner generates insufficient power, the city power is controlled to provide power to the air conditioning load and the energy storage battery. When the photovoltaic array of the photovoltaic air conditioner generates sufficient power, the photovoltaic air conditioner is off-grid, and the bidirectional AC / DC converter between the DC bus and the AC bus does not play a role. The photovoltaic device automatically adjusts the output power of the photovoltaic array according to the PU characteristic curve of its photovoltaic array to achieve a power tracking control strategy of power balance, and combines the DC bus voltage control strategy of the energy storage battery to achieve fast switching between power tracking and maximum power output.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for improving photovoltaic utilization of photovoltaic equipment, characterized in that: include: When the photovoltaic equipment is disconnected from the power grid and the photovoltaic device of the photovoltaic equipment is directly connected to the DC bus, monitoring the electrical parameters of the DC bus of the photovoltaic equipment and the photovoltaic device, energy storage device and load mounted on the DC bus; According to the electrical parameter characteristic curve of the photovoltaic device, controlling the photovoltaic device to operate in a power tracking mode or a maximum power output mode; When the energy storage device is in a fully charged state, if the power of the load is less than the maximum power of the photovoltaic device, or when the energy storage device is in a non-fully charged state, if the power of the load is less than the maximum power of the photovoltaic device minus the maximum charging power of the energy storage device, the photovoltaic device operates in a power tracking mode; When the photovoltaic device operates in the maximum power output mode, the charge and discharge state of the energy storage device and the electrical parameters of the load are adjusted or limited according to the supply and demand relationship between the photovoltaic device, the energy storage device and the load, so that the photovoltaic device, the energy storage device and the load are balanced at the maximum power output point of the photovoltaic device; When the energy storage device is in a fully charged state, if the power of the load is greater than the maximum power of the photovoltaic device, or, when the energy storage device is not in a fully charged state, if the power of the load is greater than the maximum power of the photovoltaic device minus the maximum charging power of the energy storage device, the photovoltaic device operates in a maximum power output mode and, at the same time, limits the power of the load based on the maximum discharge power of the energy storage device.

2. The method for improving photovoltaic utilization rate of photovoltaic equipment according to claim 1, characterized in that: The electrical parameter characteristic curve of the photovoltaic device is specifically a relationship curve between the output power of the photovoltaic device and the voltage of the DC bus.

3. The method for improving photovoltaic utilization rate of photovoltaic equipment according to claim 2, characterized in that: When the photovoltaic device operates in a power tracking mode, the electrical parameters of the DC bus of the photovoltaic device and the photovoltaic device, energy storage device and load mounted on the DC bus are continuously monitored.

4. The method for improving photovoltaic utilization rate of photovoltaic equipment according to claim 2, characterized in that: When the power state of the energy storage device is in a fully charged state, if the power of the load is equal to the maximum power of the photovoltaic device, the photovoltaic device operates in a maximum power output mode.

5. The method for improving photovoltaic utilization rate of photovoltaic equipment according to claim 2, characterized in that: When the power state of the energy storage device is not fully charged, if the power of the load is equal to the maximum power of the photovoltaic device minus the maximum charging power of the energy storage device, the photovoltaic device operates in a maximum power output mode.

6. A photovoltaic device comprising: A photovoltaic device, an energy storage device, and a load, characterized in that they also include a detection module and a control module for mutually cooperating to perform the method for improving the photovoltaic utilization rate of a photovoltaic device as described in any one of claims 1 to 5; The detection module is used to monitor the electrical parameters of the DC bus of the photovoltaic equipment and the photovoltaic device, energy storage device and load mounted on the DC bus; The control module controls the photovoltaic device to operate in power tracking mode or maximum power output mode according to the electrical parameter characteristic curve of the photovoltaic device; when the photovoltaic device operates in maximum power output mode, the charge and discharge state of the energy storage device and the electrical parameters of the load are adjusted or limited according to the supply and demand relationship between the photovoltaic device, the energy storage device and the load, so that the photovoltaic device, the energy storage device and the load are balanced at the maximum power output point of the photovoltaic device.

7. The photovoltaic device according to claim 6, characterized in that The photovoltaic device includes a photovoltaic air conditioner.

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