Photovoltaic device, photovoltaic inverter, system and power limiting control method

Abstract

The present application discloses a photovoltaic device, a photovoltaic inverter, a system and a power limiting control method, wherein the device comprises: a DCDC conversion circuit, an inverter circuit and a controller; the input end of the DCDC conversion circuit is connected to a photovoltaic array, and the output end of the DCDC conversion circuit is connected to the input end of the inverter circuit; the controller is used to receive a power dispatch instruction, and the power dispatch instruction carries a power reference value; when the power reference value is less than the power at the maximum power point, the input current of the DCDC conversion circuit is reduced to increase the input voltage of the DCDC conversion circuit; when the input voltage of the DCDC conversion circuit is greater than or equal to a preset voltage, the input current of the DCDC conversion circuit is increased to reduce the input voltage of the DCDC conversion circuit until the output power of the inverter is consistent with the power reference value. This scheme avoids overvoltage of the DC bus voltage, and can protect the DC bus capacitor and each switch device in the photovoltaic device at the same time. If the voltage is too high, it will exceed the voltage stress of the switch device and damage the switch device.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic power generation technology, and in particular to a photovoltaic device, a photovoltaic inverter, a system and a power limiting control method. Background Art

[0002] At present, in order to improve the efficiency of photovoltaic power generation, the photovoltaic system is usually controlled to operate at the maximum power point. However, due to the influence of many factors, the photovoltaic system does not always operate at the maximum power point during actual operation, such as DC over-loading, grid scheduling, power factor limitation, power limitation and voltage over-limit.

[0003] See also Figure 1 , this figure is the PV curve of the photovoltaic module.

[0004] As can be seen from the figure, the PV curve of the photovoltaic module has similar characteristics to the parabola. When the photovoltaic module works at a certain power, the photovoltaic module can output two different voltages. Figure 1 As shown, for power P1, the photovoltaic module can output the first voltage U1 or the second voltage U2. Obviously, the second voltage U2 located on the right side of the voltage U0 corresponding to the maximum power point Pmax is greater than the first voltage U1 located on the left side of U0. U1 corresponds to the working point B, and U2 corresponds to the working point A.

[0005] At present, when the photovoltaic system needs to limit the power operation, that is, limit the output power, referred to as power limiting, the output voltage of the photovoltaic module is generally controlled to be U2. Specifically, the output current of the photovoltaic module can be reduced, the output voltage of the photovoltaic module can be increased, and the output power of the inverter can be reduced, even if the photovoltaic module works in a state of high voltage and low current.

[0006] However, the above control method will increase the input voltage of the inverter front-stage circuit. When there is a Boost circuit in the front-stage of the inverter, it will cause the DC bus voltage of the inverter to be overvoltage, which may exceed the voltage stress that the switching device can withstand. When there is a Buck circuit in the front-stage of the inverter, it will cause the loss of the Buck circuit to increase and reduce the power conversion efficiency. Summary of the invention

[0007] The present application provides a photovoltaic device, a photovoltaic inverter, a system and a power limiting control method, which can prevent the DC bus voltage from being over-voltage when the power is limited, reduce the voltage stress of the switching device, and improve the power conversion efficiency.

[0008] The photovoltaic device provided in the embodiment of the present application does not specifically limit the specific category, nor does it limit the size of the photovoltaic power station to which the photovoltaic device is applied. For example, the photovoltaic device can be a two-stage inverter, that is, the two-stage inverter includes a DCDC conversion circuit and an inverter circuit. In this case, the inverter completes the power limit control. In addition, the photovoltaic device can also be a junction box, the junction box and the inverter are separately provided, and the output end of the junction box is connected to the input end of the inverter. In this case, the junction box completes the power limit control.

[0009] The photovoltaic device includes: a DCDC conversion circuit, an inverter circuit and a controller; the input end of the DCDC conversion circuit is connected to the photovoltaic array, and the output end of the DCDC conversion circuit is connected to the input end of the inverter circuit; the controller receives a power scheduling instruction, for example, the power scheduling instruction received from the host computer carries a power reference value; for example, when the power reference value is the power of the maximum power point, the inverter is controlled to perform MPPT so that the inverter outputs the power of the maximum power point. When the power reference value is less than the power of the maximum power point, when limiting the power, the input current of the DCDC conversion circuit is reduced, and the input voltage of the DCDC conversion circuit will naturally increase. As the input current of the DCDC conversion circuit continues to decrease, the input voltage of the DCDC conversion circuit will gradually increase. When it increases to exceed the preset voltage, the control strategy is changed, and the input current of the DCDC conversion circuit is no longer reduced, but the input current of the DCDC conversion circuit is increased instead, until the output power of the inverter is consistent with the power reference value.

[0010] From the IV curve, it can be seen that as I increases, the input voltage of the DCDC conversion circuit is forced to decrease, and then the input voltage of the DCDC conversion circuit is lower than the preset voltage, avoiding DC bus voltage overvoltage. Since the DC bus capacitor is connected between the DC positive bus and the DC negative bus, it can protect the DC bus capacitor and the various switching devices in the photovoltaic device. If the voltage is too high, it will exceed the voltage stress of the switching device and damage the switching device. In addition, for the Buck circuit, it can reduce power loss and improve power generation efficiency.

[0011] Preferably, the general controller reduces the output power by reducing the input current, that is, by performing closed-loop control on the input current, the controller is used to reduce the input current reference value of the DCDC conversion circuit, and controls the input current of the DCDC conversion circuit to decrease according to the input current reference value, and the input voltage of the DCDC conversion circuit increases as the input current decreases.

[0012] Preferably, in order to prevent the input voltage from exceeding the limit and causing overvoltage, when the input voltage of the DCDC conversion circuit is greater than or equal to the preset voltage, the controller needs to force an increase in the input current, that is, increase the input current reference value of the DCDC conversion circuit, and control the increase in the input current of the DCDC conversion circuit according to the input current reference value. According to the IV curve, when the input current of the DCDC conversion circuit is increased, the input voltage of the DCDC conversion circuit will be forced to be lowered, thereby avoiding overvoltage of the DC bus caused by overvoltage, or exceeding the voltage stress of the switching device.

[0013] Preferably, when the power reference value is greater than or equal to the power at the maximum power point, the controller controls the output power of the inverter to be the power at the maximum power point, that is, MPPT control is performed.

[0014] Preferably, in order to protect the switching device from being damaged by overvoltage, the preset voltage may be selected based on a principle that the voltage stress of the switching device in the DCDC conversion circuit is smaller than that of the switching device in the inverter circuit.

[0015] Preferably, the DCDC conversion circuit and the inverter circuit are integrated in the inverter; the controller is the controller of the inverter. In addition, the controller can also be the controller of the photovoltaic power station, as long as the controller can communicate with the DCDC conversion circuit, the power limit control can be completed.

[0016] Preferably, when the output capacity of a photovoltaic power station needs to be increased, a combiner box is generally required to combine the outputs of multiple photovoltaic arrays. For example, the combiner box includes multiple DCDC conversion circuits, which are integrated in the combiner box. The output end of the combiner box is connected to the input end of the inverter circuit. The controller is the controller of the combiner box. The controller can also be the controller of the photovoltaic power station. As long as the controller can communicate with the DCDC conversion circuit, power limiting control can be completed.

[0017] The embodiment of the present application also provides a photovoltaic inverter. The photovoltaic device provided in the above embodiments includes a DCDC conversion circuit, but the photovoltaic inverter provided in this embodiment does not include a DCDC conversion circuit, and includes an inverter circuit and a controller, that is, a single-stage inverter; the input end of the inverter circuit is connected to a photovoltaic array; the inverter circuit is used to convert the direct current output by the photovoltaic array into alternating current output; the controller is used to receive a power scheduling instruction, and the power scheduling instruction carries a power reference value; when the power reference value is less than the power at the maximum power point, the output current of the photovoltaic array is reduced to increase the output voltage of the photovoltaic array; when the output voltage of the photovoltaic array is greater than or equal to a preset voltage, the output current of the photovoltaic array is increased to reduce the output voltage of the photovoltaic array until the output power of the inverter is consistent with the power reference value.

[0018] The inverter provided in this embodiment can protect the switching devices in the inverter circuit from being impacted by high voltage during power limiting control, which is lower than its voltage stress, so that it can work safely and stably. In addition, the DC bus capacitor will not be impacted by high voltage, protecting its safety. The DC bus of the inverter provided in this embodiment refers to the DC bus at the input end of the inverter, that is, the DC bus voltage refers to the voltage at the input end of the inverter, and the switching device refers to the switching device of the inverter itself.

[0019] Preferably, since the inverter provided in this embodiment does not include a DCDC conversion circuit, the input current of the inverter circuit is the output current of the photovoltaic array, and what is controlled is the output current of the photovoltaic array to adjust the output power of the inverter. The controller reduces the output current reference value of the photovoltaic array, controls the output current of the photovoltaic array to decrease according to the output current reference value, and the output voltage of the photovoltaic array increases as the output current decreases.

[0020] Preferably, when the output voltage of the photovoltaic array is greater than or equal to a preset voltage, the controller increases the output current reference value of the photovoltaic array, and controls the output current of the photovoltaic array to increase according to the output current reference value. According to the IV curve, when the output current of the photovoltaic array increases, the output voltage of the photovoltaic array will be forced to decrease, thereby preventing the output voltage of the photovoltaic array from exceeding the preset voltage, that is, the input voltage of the inverter will not exceed the preset voltage, thereby protecting the switching devices and DC bus capacitors of the inverter.

[0021] Preferably, when the power reference value is greater than or equal to the power of the maximum power point, the controller controls the output power of the inverter to be the power of the maximum power point, that is, maximum power point tracking (MPPT) is performed.

[0022] An embodiment of the present application also provides a photovoltaic system, including the photovoltaic device introduced above or the photovoltaic inverter introduced above, and also including: a photovoltaic array; when the photovoltaic device is included, the photovoltaic array is connected to the input end of the photovoltaic device; when the photovoltaic inverter is included, the photovoltaic array is connected to the input end of the photovoltaic inverter.

[0023] The photovoltaic system includes the photovoltaic inverter described in the above embodiment, and the photovoltaic inverter includes an inverter circuit and a controller. Since the inverter can control the input voltage to be less than the preset voltage when performing power limiting control, the switch device and the DC bus capacitor can be better protected, and the DC bus voltage can be prevented from overvoltage.

[0024] An embodiment of the present application also provides a power control method for photovoltaic power generation, including: receiving a power scheduling instruction, the power scheduling instruction carrying a power reference value; when the power reference value is less than the power at the maximum power point, reducing the output current of the photovoltaic array to increase the output voltage of the photovoltaic array; when the output voltage of the photovoltaic array is greater than or equal to a preset voltage, increasing the output current of the photovoltaic array to reduce the output voltage of the photovoltaic array until the output power of the inverter is consistent with the power reference value.

[0025] From the IV curve, it can be seen that as I increases, the input voltage of the DCDC conversion circuit is forced to decrease, and then the input voltage of the DCDC conversion circuit is lower than the preset voltage, avoiding DC bus voltage overvoltage. Since the DC bus capacitor is connected between the DC positive bus and the DC negative bus, it can protect the DC bus capacitor and the various switching devices in the photovoltaic device. If the voltage is too high, it will exceed the voltage stress of the switching device and damage the switching device. In addition, for the Buck circuit, it can reduce power loss and improve power generation efficiency.

[0026] Preferably, the output current of the photovoltaic array is reduced, specifically including: reducing the output current reference value of the photovoltaic array, and controlling the output current of the photovoltaic array to decrease according to the output current reference value. According to the IV curve, when the output current of the photovoltaic array decreases, the output voltage of the photovoltaic array increases as the output current decreases, that is, the output voltage of the photovoltaic array is forced to increase.

[0027] Preferably, the output power of the inverter can be adjusted by adjusting the current reference value, that is, adjusting the current to achieve power regulation. When the output voltage of the photovoltaic array is greater than or equal to a preset voltage, the output current of the photovoltaic array is increased, specifically including: when the output voltage of the photovoltaic array is greater than or equal to a preset voltage, the output current reference value of the photovoltaic array is increased, and the output current of the photovoltaic array is controlled to increase according to the output current reference value.

[0028] Preferably, the method further comprises: when the power reference value is greater than or equal to the power of the maximum power point, controlling the output power of the inverter to be the power of the maximum power point, that is, performing maximum power point tracking (MPPT).

[0029] The present application also provides a photovoltaic power generation power control device, including:

[0030] A receiving unit, configured to receive a power dispatching instruction of an inverter, wherein the power dispatching instruction carries a power reference value;

[0031] A current reducing unit, used for reducing the output current of the photovoltaic array to increase the output voltage of the photovoltaic array when the power reference value is less than the power at the maximum power point;

[0032] The current increasing unit is used to increase the output current of the photovoltaic array when the output voltage of the photovoltaic array is greater than or equal to a preset voltage, so as to reduce the output voltage of the photovoltaic array until the output power of the inverter is consistent with the power reference value.

[0033] The current reduction unit specifically includes a current reduction module, which is used to reduce the output current reference value of the photovoltaic array, control the output current of the photovoltaic array to decrease according to the output current reference value, and the output voltage of the photovoltaic array increases as the output current decreases.

[0034] The current increasing unit specifically includes a current increasing module, which is used to increase the output current reference value of the photovoltaic array when the output voltage of the photovoltaic array is greater than or equal to a preset voltage, and control the output current increase of the photovoltaic array according to the output current reference value.

[0035] It also includes a control unit, which is used to control the output power of the inverter to be the power of the maximum power point when the power reference value is greater than or equal to the power of the maximum power point.

[0036] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0037] The photovoltaic device includes: a DCDC conversion circuit, an inverter circuit and a controller; when limiting the output power of the inverter, the input current of the DCDC conversion circuit is reduced. According to the current-voltage IV curve of the photovoltaic module, the input voltage of the DCDC conversion circuit will naturally increase. As the input current of the DCDC conversion circuit continues to decrease, the input voltage of the DCDC conversion circuit will gradually increase. When it increases to exceed the preset voltage, the control strategy is changed, and the input current of the DCDC conversion circuit is no longer reduced, but the input current of the DCDC conversion circuit is increased instead. According to the IV curve, as I increases, the input voltage of the DCDC conversion circuit is forced to decrease, and then the input voltage of the DCDC conversion circuit is lower than the preset voltage, avoiding DC bus voltage overvoltage. Since a DC bus capacitor is connected between the DC positive bus and the DC negative bus, the DC bus capacitor can be protected at the same time, as well as the various switch devices in the photovoltaic device. If the voltage is too high, it will exceed the voltage stress of the switch device and damage the switch device. In addition, for the Buck circuit, it can reduce power loss and improve power generation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a curve diagram of the power and voltage PV of the photovoltaic module;

[0039] Figure 2 A schematic diagram of a photovoltaic device provided in an embodiment of the present application;

[0040] Figure 3 A schematic diagram of another photovoltaic system provided in an embodiment of the present application;

[0041] Figure 4 An IV curve diagram of a photovoltaic module provided in an embodiment of the present application;

[0042] Figure 5 A schematic diagram of power limiting control provided in an embodiment of the present application;

[0043] Figure 6 A schematic diagram of another photovoltaic device provided in an embodiment of the present application;

[0044] Figure 7 A power control flow chart provided in an embodiment of the present application;

[0045] Figure 8 Two combiner boxes corresponding to the embodiment of the present application;

[0046] Fig. 9 An application scenario diagram of a photovoltaic inverter provided in an embodiment of the present application;

[0047] Fig.10 A schematic diagram of a photovoltaic system including a photovoltaic device provided in an embodiment of the present application;

[0048] Fig.11 A schematic diagram of a photovoltaic system including an inverter provided in an embodiment of the present application;

[0049] Fig.12 A flow chart of a photovoltaic power generation power control method provided in an embodiment of the present application;

[0050] Fig.13 A flow chart of another photovoltaic power control method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0051] In order to enable those skilled in the art to better understand the technical solutions provided in the embodiments of the present application, Figure 1 Let me introduce the PV curve of photovoltaic modules. Figure 1 It can be seen that, except for the power Pmax at the maximum power point, all other power points have one power corresponding to two voltages. Generally, in order to maximize the output power and the highest power generation efficiency, the inverter is controlled to perform maximum power point tracking (MPPT), that is, to control the inverter to operate at the maximum power point.

[0052] At present, for the sake of working stability, when performing power limit control, the inverter is generally controlled to operate at a point on the right side of the maximum power point. For example, point A in the figure is the point on the right side of the maximum power point. For the convenience of description, the point on the right side corresponding to the same power is called the first working point, and the point on the left side is called the second working point ( Figure 1 point B in the figure).

[0053] If the power limit for all situations controls the inverter to operate at the first working point on the right, when the voltage is high, if there is a DCDC conversion circuit in the front stage of the inverter circuit, if the DCDC conversion circuit is a boost circuit, such as a Boost circuit, if the output voltage of the photovoltaic array is large, the Boost circuit will boost the larger input voltage, and the output voltage will be higher, which may easily cause the input side of the inverter circuit, that is, the DC bus voltage to be overvoltage, causing damage to the circuit, such as damage to the DC bus capacitor. For the DCDC conversion circuit in the front stage of the inverter circuit, which is a step-down voltage, such as a Buck circuit, if the output voltage of the photovoltaic array is large, the Buck circuit needs to step down the larger output voltage of the photovoltaic array, which will cause greater damage and affect the photovoltaic power generation efficiency. When there is a DCDC conversion circuit, the input voltage of the DCDC conversion circuit is the output voltage of the photovoltaic array.

[0054] In addition to being a Boost or Buck circuit, the DCDC conversion circuit can also be a BuckBoost circuit. The embodiment of the present application does not specifically limit the specific implementation form of the DCDC conversion circuit, and the DCDC conversion circuit can be an isolated type or a non-isolated type.

[0055] Therefore, in order to solve this technical problem, the technical solution provided in the embodiment of the present application, when limiting the output power of the inverter, is treated differently according to the output voltage of the photovoltaic array, that is, according to the size of the input voltage of the DCDC conversion circuit, and dynamically performs power limiting control, rather than always and exclusively controlling the inverter to work at the first working point. Specifically, it can be judged according to the size of the input voltage of the DCDC conversion circuit. When the input voltage of the DCDC conversion circuit is large, that is, greater than the preset voltage, the inverter is controlled to work at the second working point. Since the voltage of the second working point is lower than the first working point, the DC bus voltage can be prevented from overvoltage, and if the DCDC conversion circuit is a step-down circuit, the power consumption can be reduced and the power generation efficiency can be improved.

[0056] The embodiments of the present application do not specifically limit the type of photovoltaic equipment to which the technical solution is specifically applied, and the size of the photovoltaic power station. For example, the photovoltaic equipment can be a two-stage inverter, that is, the two-stage inverter includes a DCDC conversion circuit and an inverter circuit. In this case, the inverter completes the power limit control. In addition, the photovoltaic equipment can also be a junction box, the junction box and the inverter are separately provided, and the output end of the junction box is connected to the input end of the inverter. In this case, the junction box completes the power limit control.

[0057] Photovoltaic device embodiment 1:

[0058] See also Figure 2 , which is a schematic diagram of a photovoltaic device provided in an embodiment of the present application.

[0059] The photovoltaic device 200 provided in this embodiment includes: a DCDC conversion circuit 201, an inverter DCAC circuit 202 and a controller 203;

[0060] The input end of the DCDC conversion circuit 201 is connected to the photovoltaic array 100, and the output end of the DCDC conversion circuit 201 is connected to the input end of the inverter circuit 202;

[0061] The controller 203 is used to receive a power scheduling instruction of the inverter, and the power scheduling instruction carries a power reference value; when the power reference value is less than the power of the maximum power point, the input current of the DCDC conversion circuit is reduced to increase the input voltage of the DCDC conversion circuit; when the input voltage of the DCDC conversion circuit is greater than or equal to a preset voltage, the input current of the DCDC conversion circuit is increased to reduce the input voltage of the DCDC conversion circuit until the output power of the inverter is consistent with the power reference value.

[0062] The power dispatching instruction received by the controller 203 may be received from a host computer or from a control center of the photovoltaic power station. Figure 2 It is just a simple schematic diagram. For example, a photovoltaic power station includes multiple photovoltaic devices, and the host computer is used to control the power output of multiple photovoltaic devices. The photovoltaic power station is responsible for the power control of the photovoltaic devices and will issue power dispatching instructions to the photovoltaic devices. The power dispatching instructions carry a power reference value. The photovoltaic devices control the inverter to output power consistent with the power reference value according to the power reference value. For example, when the power reference value is the power of the maximum power point, the inverter is controlled to perform MPPT so that the inverter outputs the power of the maximum power point. If the power reference value is lower than the power of the maximum power point, power limit control is required, that is, limiting the output power of the inverter to be lower than the power of the maximum power point.

[0063] like Figure 3 As shown in the figure, this figure is a specific implementation method of the photovoltaic system. Figure 3Photovoltaic equipment can be found in Figure 2 , Figure 3 In the description, a photovoltaic array including two photovoltaic strings is taken as an example.

[0064] The first photovoltaic string 101 and the second photovoltaic string 102 are connected in parallel at the input end of the photovoltaic device 200;

[0065] The first photovoltaic string 101 includes a plurality of photovoltaic modules connected in series. Similarly, the second photovoltaic string 102 includes a plurality of photovoltaic modules connected in series.

[0066] The photovoltaic device provided in this embodiment controls its output power by controlling the input current of the DCDC conversion circuit. In order to more clearly introduce the technical solution provided in the embodiment of the present application, the following first introduces Figure 4 The IV curve diagram of the photovoltaic module shown is used to introduce the relationship between the output voltage and output current of the photovoltaic module.

[0067] from Figure 4 It can be seen that for photovoltaic modules, the voltage U and current I are inversely proportional to each other, that is, as the current I decreases, the voltage U will naturally increase.

[0068] When limiting power, the input current of the DCDC conversion circuit is reduced, and the input voltage of the DCDC conversion circuit will naturally increase. As the input current of the DCDC conversion circuit continues to decrease, the input voltage of the DCDC conversion circuit will gradually increase. When it increases to exceed the preset voltage, the control strategy is changed, and the input current of the DCDC conversion circuit is no longer reduced, but the input current of the DCDC conversion circuit is increased instead. From the IV curve, it can be seen that as I increases, the input voltage of the DCDC conversion circuit is forced to decrease, and then the input voltage of the DCDC conversion circuit is lower than the preset voltage, avoiding DC bus voltage overvoltage. Since the DC bus capacitor is connected between the DC positive bus and the DC negative bus, the DC bus capacitor can be protected at the same time, as well as the various switching devices in the photovoltaic device. If the voltage is too high, it will exceed the voltage stress of the switching device and damage the switching device. In addition, for the Buck circuit, it can reduce power loss and improve power generation efficiency.

[0069] The preset voltage is less than the voltage stress of the switching device in the DCDC conversion circuit, and less than the voltage stress of the switching device in the inverter circuit. For example, when the voltage stress of the switching device in the DCDC conversion circuit and the inverter circuit is 650V, considering the margin and deviation voltage, the preset voltage can be selected to be set to about 500V. The above is only an example, and the specific setting can be selected according to the actual application scenario. The purpose of the preset voltage is to protect the switching device and the DC bus capacitor.

[0070] Combine the following Figure 5 The implementation process of power limiting control provided in the embodiments of the present application is introduced in detail.

[0071] See also Figure 5 , which is a schematic diagram of power limiting control provided in an embodiment of the present application.

[0072] by Figure 3 Taking the first photovoltaic string 101 as an example, in order to simplify the calculation, it is assumed that the first photovoltaic string 101 includes 15 photovoltaic modules connected in series, and the parameters of each photovoltaic module are consistent, as shown in the following Table 1. Ignoring the loss, the conversion efficiency of the photovoltaic device is 100%.

[0073] Table 1

[0074] parameter value unit Open circuit voltage Voc 38.25 V Short circuit current Isc 9.95 A MPPT voltage Vmp 30.6 V MPPT current Imp 8.5 A MPPT power Pmp 260.1 W

[0075] If the output power of the photovoltaic equipment is not limited, that is, when the photovoltaic equipment is normally connected to the grid for power generation, it operates at the maximum power point A, such as Figure 5 As shown, the power corresponding to the maximum power point A, since a photovoltaic string includes 15 photovoltaic modules, the Pmp of a photovoltaic module is 260.1W, and since the photovoltaic array includes two photovoltaic strings in parallel, the Pmpp of the entire photovoltaic array is 260.1*15*2=7803W.

[0076] Since one photovoltaic string includes 15 photovoltaic modules and two photovoltaic strings are connected in parallel, the output voltage is the same. The Vmp of one photovoltaic module is 30.6V, so the Vmpp corresponding to the entire photovoltaic string is 306*15=459V, and the input voltage corresponding to the maximum power point is 459V.

[0077] Combine the following Figure 5 There are two cases for introduction, namely, when the input voltage is less than the preset voltage during power limiting, and when the input voltage is greater than or equal to the preset voltage during power limiting control.

[0078] Assume that the preset voltage is set to Ulmt of 500V and the corresponding power of the PV string is 6000W;

[0079] The first type: when the power is limited, the input voltage is less than the preset voltage;

[0080] In this case, since the input voltage of the DCDC conversion circuit is less than the preset voltage, the input voltage will not cause the DC bus voltage to be overvoltage. Therefore, in order to work more stably, the photovoltaic device can be controlled to work at the first working point to the right of the maximum power point.

[0081] If the controller receives a power scheduling instruction, the power reference value P carried by the power scheduling instruction ref1 =7000W, due to Pref1 =7000W<P mpp =7803W; therefore, the controller reduces the input current of the DCDC conversion circuit to increase the input voltage of the DCDC conversion circuit.

[0082] In a specific implementation, the controller reduces the input current reference value Iref of the DCDC conversion circuit, and controls the input current of the DCDC conversion circuit to decrease according to the input current reference value Iref. According to the IV curve, the input voltage of the DCDC conversion circuit increases as the input current decreases.

[0083] As the input voltage of the DCDC conversion circuit increases, when it runs to the first operating point B on the right side of the maximum power point A, that is, P ref1 =U in ×I in When the input current reference I ref The inverter remains unchanged and operates stably at the first operating point B to the right of the maximum power point.

[0084] The second type: when the power is limited, the input voltage is greater than or equal to the preset voltage;

[0085] If the power reference value P carried in the power dispatch instruction received by the photovoltaic device ref2 =3000W, then similar to the above process, it is also necessary to first reduce the input current reference value Iref of the DCDC conversion circuit, and control the input current of the DCDC conversion circuit to decrease according to the input current reference value Iref. According to the IV curve, it can be seen that the input voltage of the DCDC conversion circuit increases as the input current decreases.

[0086] When it reaches point C, U in =U lmt =500V, at this time U in ×I in =6000W>P ref2 When 6000W>P ref2 =3000W, so the photovoltaic equipment has not reached the stable working point, and the output power needs to be further reduced. However, continuing to increase the input voltage may cause the DC bus voltage to be over-voltage, causing damage to the DC bus capacitor and switching devices. Therefore, in order to achieve the protection effect, it is necessary to reduce the input voltage, specifically:

[0087] The controller increases the input current reference value of the DCDC conversion circuit, and controls the input current of the DCDC conversion circuit to increase according to the input current reference value. As the input current increases, according to the IV curve, the input voltage naturally decreases until it reaches the second operating point D on the left side of the maximum power point A, that is, the corresponding power is P ref2When , the input current reference value remains unchanged, and the inverter works stably at the second working point D on the left side of the maximum power point. The dynamic adjustment process is A->B->C->D.

[0088] It should be noted that, in the process of controlling from point C to point D, in order to meet the requirements, the adjustment speed can be controlled so that it can be adjusted to point D as quickly as possible.

[0089] It can be seen that the photovoltaic device with power limit adjustment provided in this embodiment, when performing power limit control, first adjusts to the right side of the maximum power point A, and when the input voltage is greater than or equal to the preset voltage, it is adjusted back until it is adjusted to the left side of the maximum power point A, and stably works at the working point corresponding to the power reference value. Because the voltage corresponding to the power cannot be predicted during the adjustment process, the output voltage of the photovoltaic array varies with the different illumination, and it can only be adjusted to the right first, and gradually determine whether the voltage exceeds the preset voltage. When it exceeds, the adjustment direction is changed to adjust to the left. The traditional adjustment method is that in the power limit adjustment process, the input voltage is not considered, and it is only adjusted to the required power limit value. Even if the inverter circuit outputs the power corresponding to the power reference value, regardless of the corresponding input voltage, for example, when the power reference value is, the traditional adjustment method is A->B->C->E. The voltage corresponding to point E is greater than the preset voltage, which will cause the DC bus voltage to be overvoltage, damage the DC bus capacitor and switch components, and reduce their service life.

[0090] Figure 2 In the photovoltaic device 200 shown, the DCDC conversion circuit 201 and the inverter circuit 202 are integrated in the inverter; the controller 203 is the controller of the inverter. That is, the photovoltaic device 200 can be a two-stage inverter. The controller of the inverter controls the input current of the inverter to adjust the output power. Since the input voltage will change during the process of adjusting the input current, it is necessary to judge the size of the input voltage and the preset voltage to adjust the input voltage reference value.

[0091] Photovoltaic device embodiment 2:

[0092] Another photovoltaic device is introduced below, for the case where the photovoltaic system includes a combiner box, and the combiner box includes a DCDC conversion circuit, and the inverter only includes an inverter circuit.

[0093] See also Figure 6 , which is a schematic diagram of another photovoltaic device provided in an embodiment of the present application.

[0094] The photovoltaic device provided in this embodiment includes a combiner box 204 and an inverter circuit DCAC202 , wherein the inverter circuit DCAC202 is independently provided from the combiner box 204 , that is, a separately provided single-stage inverter, and the DCDC conversion function is implemented by the combiner box 204 .

[0095] The DCDC conversion circuit 201 is integrated in a combiner box, and the output end of the combiner box 201 is connected to the input end of the inverter circuit 202;

[0096] The controller 203 is a controller of the combiner box 204 .

[0097] The input end of the combiner box 204 is connected to the first photovoltaic array 101 and the second photovoltaic array 102, and the output ends of the first photovoltaic array 101 and the second photovoltaic array 102 are connected in parallel to the input end of the combiner box 205. The figure is only for reference. The first photovoltaic array 101 and the second photovoltaic array 102 can be connected in parallel outside the combiner box 205, or they can be connected in parallel inside the combiner box 205. The embodiments of the present application are not specifically limited.

[0098] The working process of power control is described in detail below with reference to the method flow chart.

[0099] See also Figure 7 , which is a power control flow chart provided in an embodiment of the present application.

[0100] S701: receiving a power scheduling instruction, the power scheduling instruction carrying a power reference value Pref;

[0101] S702: Determine whether the power reference value Pref is less than the power of the maximum power point Pmpp, if yes, execute S704, otherwise execute S703;

[0102] S703: Control to operate stably at the maximum power point, that is, when Pref>Pmpp, control to output the power at the maximum power point, that is, perform MPPT control.

[0103] S704: reducing the input current, that is, reducing the input current by reducing the input current reference value. As the input current decreases, the input voltage increases accordingly. Therefore, it is necessary to determine whether the input voltage Uin is greater than the preset voltage Ulmt. If so, execute S705, otherwise execute S706;

[0104] S705: Since Uin>Ulmt, Uin needs to be reduced. In order to reduce Uin, the input current reference value needs to be reduced, that is, the input current needs to be reduced to force Uin to be reduced, so as to stably operate at the second working point, that is, the left side of point A.

[0105] S706: When the power is reduced, if the situation of Uin>Ulmt does not occur, the system can stably operate at the first working point, that is, the right side of point A.

[0106] The following briefly explains why the operating stability is higher on the right side of the maximum power point. Figure 4From the typical IV curve, we can see that the equivalent internal resistance of the photovoltaic module changes dramatically with the change of voltage V, that is, R = dv / di. Near the open circuit voltage, the equivalent internal resistance is small, which is approximately a constant voltage source characteristic; near the short circuit voltage, the equivalent internal resistance is large, which is approximately a constant current source characteristic. When the equivalent internal resistance tends to infinity, the working stability condition is the most stringent, that is, the equivalent internal resistance on the right side of the maximum power point is small, and the corresponding working stability is better. Therefore, it is generally hoped to work in the right area, that is, for a power, it is hoped to work at the first working point corresponding to the power.

[0107] In the above control process, it is necessary to obtain the output power Pout of the inverter and determine whether Pout is equal to Pref. If not, control needs to be continued. If equal, it means that the power limit adjustment is in place and control can be stopped to stabilize the movement in the power limit state. The output power of the inverter can be obtained by detecting the output voltage and output current of the inverter.

[0108] The input current reference value of the inverter is the result of the outer loop closed-loop control. To control the input current of the inverter to be equal to the input current reference value, it is necessary to perform closed-loop control of the inner loop of the inverter, that is, to control the input current of the inverter according to the input current reference value of the inverter. Specifically, the input current of the inverter can be periodically detected, and the detected input current can be compared with the input current reference value. The duty cycle of the driving pulse signal of the switching device in the inverter can be controlled according to the current comparison result, thereby realizing the control of the size of the input current of the inverter. For example, the specific current closed-loop control can be achieved using a proportional-integral regulator.

[0109] Figure 6 In the example, only two photovoltaic arrays are used for illustration. In the specific implementation, the number of photovoltaic arrays connected to the input end of a single combiner box is not limited. Similarly, in order to increase the power output, multiple combiner boxes can correspond to the same inverter circuit, that is, the same inverter. The output ends of multiple combiner boxes are connected in parallel. They can be connected in parallel outside the inverter or inside the inverter. This embodiment does not make specific limitations.

[0110] For multiple combiner boxes connected in parallel, please refer to Figure 8 As shown, two combiner boxes are used as an example for description, namely a first combiner box 205a and a second combiner box 205b. The input end of the second combiner box 205b is connected to the third photovoltaic array 103 and the fourth photovoltaic array 104 connected in parallel.

[0111] The output ends of the first combiner box 205a and the second combiner box 205b are both connected to the inverter, and can be connected in parallel inside the inverter 202 , or can be connected in parallel outside the inverter 202 and then connected to the input end of the inverter 202 .

[0112] In addition, for Figure 2 The photovoltaic device shown may also include a combiner box having only a current combining function at the front stage of the DCDC conversion circuit, that is, it only combines current but does not have the function of voltage conversion.

[0113] In the above embodiments, regardless of whether the DCDC conversion circuit is inside the junction box or inside the inverter, the controlled input current refers to the input current of the DCDC conversion circuit, and the input current of the DCDC conversion circuit is the output current of the corresponding photovoltaic array. For scenarios including a DCDC conversion circuit, the DC bus refers to the bus between the output end of the DCDC conversion circuit and the input end of the inverter circuit, and the DC bus voltage refers to the voltage between the DC positive bus and the DC negative bus. Generally, a pair of DC bus capacitors are connected between the DC positive bus and the DC negative bus.

[0114] The photovoltaic devices provided above all include a DCDC conversion circuit. The following describes the working principle of a single-stage inverter when power is limited. The single-stage inverter only has an inverter function and does not perform DCDC conversion.

[0115] Photovoltaic inverter implementation

[0116] See also Fig. 9 , this figure is an application scenario diagram of a photovoltaic inverter provided in an embodiment of the present application.

[0117] The photovoltaic inverter 300 provided in this embodiment includes an inverter circuit 301 and a controller 302;

[0118] The input end of the inverter circuit 301 is connected to the photovoltaic array 100;

[0119] The inverter circuit 301 is used to convert the direct current output by the photovoltaic array 100 into alternating current output;

[0120] The controller 302 is used to receive a power scheduling instruction of the inverter, and the power scheduling instruction carries a power reference value; when the power reference value is less than the power at the maximum power point, the output current of the photovoltaic array is reduced to increase the output voltage of the photovoltaic array; when the output voltage of the photovoltaic array 100 is greater than or equal to a preset voltage, the output current of the photovoltaic array 100 is increased to reduce the output voltage of the photovoltaic array 100 until the output power of the inverter is consistent with the power reference value.

[0121] Since the inverter provided in this embodiment does not include a DCDC conversion circuit, the input current of the inverter circuit is the output current of the photovoltaic array, and what is controlled is the output current of the photovoltaic array to adjust the output power of the inverter.

[0122] The DC bus of the inverter provided in this embodiment refers to the DC bus of the inverter input terminal, that is, the DC bus voltage refers to the voltage of the inverter input terminal. The switch device refers to the switch device of the inverter itself.

[0123] The inverter provided in this embodiment can protect the switch components in the inverter circuit from being impacted by high voltage during power limiting control, and the voltage stress is lower than that of the inverter circuit, so that the inverter circuit can work safely and stably. In addition, the DC bus capacitor will not be impacted by high voltage, so that its safety is protected.

[0124] The preset voltage needs to be smaller than the voltage stress of the switching device of the inverter and smaller than the withstand voltage of the DC bus capacitor, so that the switching device and the DC bus capacitor can be protected at the same time.

[0125] The specific implementation form of the photovoltaic array 100 can be found in Figure 3 , does not specifically limit the number of photovoltaic strings, nor does it specifically limit the number of photovoltaic panels included in the photovoltaic strings.

[0126] In this embodiment, the controller 302 reduces the output current of the photovoltaic array, specifically:

[0127] The controller reduces the output current reference value of the photovoltaic array, controls the output current of the photovoltaic array to decrease according to the output current reference value, and the output voltage of the photovoltaic array increases as the output current decreases.

[0128] Since the output voltage and output current of the photovoltaic module have a relationship as shown in the IV curve, if the output current of the photovoltaic module is controlled to decrease, the output voltage of the photovoltaic module will naturally increase.

[0129] The controller increases the output current of the photovoltaic array as follows:

[0130] When the output voltage of the photovoltaic array is greater than or equal to the preset voltage, the controller is used to increase the output current reference value of the photovoltaic array, and control the output current of the photovoltaic array to increase according to the output current reference value. Similarly, according to the IV curve, when the output current of the photovoltaic array increases, the output voltage of the photovoltaic array will be forced to decrease, thereby preventing the output voltage of the photovoltaic array from exceeding the preset voltage, that is, the input voltage of the inverter will not exceed the preset voltage, thereby protecting the switching devices and DC bus capacitors of the inverter.

[0131] In addition, if the power reference value is greater than or equal to the power at the maximum power point, the controller controls the output power of the inverter to be the power at the maximum power point.

[0132] The specific control method of the controller in this embodiment is the same as that described above and will not be described in detail here. Please refer to the introduction of the photovoltaic device embodiment.

[0133] It should be noted that the inverter circuit in the above embodiment can work bidirectionally, that is, when working in the forward direction, it realizes the inversion function, and when working in the reverse direction, it realizes the rectification function. When the photovoltaic system includes an energy storage device, for example, when the photovoltaic array does not output electrical energy, the inverter circuit can rectify the AC power of the AC power grid into DC power to charge the energy storage device.

[0134] Based on the photovoltaic device and inverter provided in the above embodiment, the embodiment of the present application further provides a photovoltaic system, which may include the photovoltaic device introduced in the above embodiment, or include the inverter introduced in the above embodiment.

[0135] Photovoltaic system example

[0136] See also Fig.10 , which is a schematic diagram of a photovoltaic system including photovoltaic equipment provided in an embodiment of the present application.

[0137] The photovoltaic system provided in this embodiment is described by taking the photovoltaic device 1001 described in the above embodiment as an example, and further includes: a photovoltaic array 100;

[0138] When the photovoltaic system includes the photovoltaic device 1001, the input end of the photovoltaic device 1001 is connected to the photovoltaic array 100.

[0139] The photovoltaic system includes the photovoltaic device described in the above embodiment, and the photovoltaic device 1001 may include a DCDC conversion circuit, an inverter circuit and a controller. Since the photovoltaic device can control the input voltage to be less than the preset voltage when performing power limiting control, the switching device and the DC bus capacitor can be better protected. When the DCDC conversion circuit is a boost circuit, the DC bus voltage can be prevented from being over-voltage. Moreover, when the DCDC conversion circuit is a buck circuit, the power consumption of the buck circuit during power conversion can be reduced, thereby improving the power generation efficiency of the photovoltaic system.

[0140] The specific implementation form of the photovoltaic array is not limited in this embodiment, for example, multiple photovoltaic groups may be connected in series and in parallel.

[0141] The following describes a photovoltaic system that includes only a single-stage inverter.

[0142] See also Fig.11 , which is a schematic diagram of a photovoltaic system including an inverter provided in an embodiment of the present application.

[0143] When the photovoltaic system includes a single-stage inverter 300, the input end of the single-stage inverter 300 is connected to the photovoltaic array 100. The specific implementation of the single-stage inverter 300 can be found in Fig. 9 .

[0144] The present embodiment does not specifically limit the specific implementation form of the photovoltaic array, which can be set according to actual application scenarios. For example, it can include multiple photovoltaic strings connected in parallel, or it can include one photovoltaic string.

[0145] The photovoltaic system includes the photovoltaic inverter described in the above embodiment, and the photovoltaic inverter includes an inverter circuit and a controller. Since the inverter can control the input voltage to be less than the preset voltage when performing power limiting control, the switch device and the DC bus capacitor can be better protected, and the DC bus voltage can be prevented from overvoltage.

[0146] Based on a photovoltaic device, an inverter and a photovoltaic system provided in the above embodiments, an embodiment of the present application further provides a power limiting control method, which can be applied to the photovoltaic device or inverter introduced in the above embodiments and is described in detail below in conjunction with the accompanying drawings.

[0147] Method Example 1

[0148] See also Fig.12 , which is a flow chart of a photovoltaic power generation power control method provided in an embodiment of the present application.

[0149] The photovoltaic power generation power control method provided in this embodiment includes the following steps:

[0150] S1201: Receive a power dispatch instruction of an inverter, where the power dispatch instruction carries a power reference value;

[0151] Photovoltaic power stations often perform power dispatching, and control the operation of photovoltaic equipment according to the power reference value, so that the photovoltaic equipment outputs power consistent with the power reference value. Strictly speaking, the output power is the same as the power reference value. Generally, it operates at the maximum power point.

[0152] S1202: When the power reference value is less than the power at the maximum power point, reducing the output current of the photovoltaic array to increase the output voltage of the photovoltaic array;

[0153] Reducing the output current of the photovoltaic array specifically includes: reducing the output current reference value of the photovoltaic array, controlling the output current of the photovoltaic array to decrease according to the output current reference value, and the output voltage of the photovoltaic array increases as the output current decreases.

[0154] When the power reference value is less than the power at the maximum power point, it means that power limiting control is required, so the output power of the inverter circuit needs to be reduced. Specifically, the power can be reduced by reducing the output current of the photovoltaic array. Reducing the output current specifically means reducing the output current reference value. It should be noted that the output current for the photovoltaic array is the input current for the photovoltaic device. Due to the IV characteristics of the photovoltaic module, as I decreases, U will naturally increase. Therefore, in order to avoid the voltage being too high, damaging the switching devices and DC bus capacitors, and causing the DC bus voltage to be overvoltage, voltage control is performed during the power limiting process, which is also achieved through current control.

[0155] S1203: When the output voltage of the photovoltaic array is greater than or equal to a preset voltage, increasing the output current of the photovoltaic array to reduce the output voltage of the photovoltaic array until the output power of the inverter is consistent with the power reference value.

[0156] Increasing the output current of the photovoltaic array specifically includes: when the output voltage of the photovoltaic array is greater than or equal to a preset voltage, increasing the output current reference value of the photovoltaic array, and controlling the output current of the photovoltaic array to increase according to the output current reference value.

[0157] When the power reference value is greater than or equal to the power at the maximum power point, the output power of the inverter is controlled to be the power at the maximum power point.

[0158] The method provided in this embodiment is applicable to the photovoltaic devices and inverters provided in all the above embodiments. When applicable to photovoltaic devices, the output current of the photovoltaic array is the input current of the DCDC conversion circuit. When applicable to a single-stage inverter, the output current of the photovoltaic array is the input current of the inverter.

[0159] When limiting the output power of the inverter, the output current of the photovoltaic array is reduced, and the output voltage of the photovoltaic array will naturally increase. As the output current of the photovoltaic array continues to decrease, the output voltage of the photovoltaic array will gradually increase. When it increases to exceed the preset voltage, the control strategy is changed. The output current of the photovoltaic array is no longer reduced, but increased instead. From the voltage-current IV curve of the photovoltaic module, it can be seen that as I increases, the output voltage is forced to decrease, and then the output voltage is lower than the preset voltage to avoid DC bus voltage overvoltage. Since a DC bus capacitor is connected between the DC positive bus and the DC negative bus, it can protect the DC bus capacitor and the various switching devices in the photovoltaic equipment or single-stage inverter. If the voltage is too high, it will exceed the voltage stress of the switching device and damage the switching device.

[0160] Method Example 2

[0161] The complete process of power limiting control is described in detail below with reference to the flow chart.

[0162] See also Fig.13 , which is a flow chart of another photovoltaic power control method provided in an embodiment of the present application.

[0163] S1301: receiving a power scheduling instruction, and obtaining a power reference value Pref from the power scheduling instruction.

[0164] S1302: Determine whether the power reference value is less than the power of the maximum power point Pmpp, that is, Pref<Pmpp; if yes, execute S1304; otherwise, execute S1303;

[0165] S1303: The inverter operates stably at the maximum power point, that is, the output power Pout of the inverter is controlled to be Pmpp.

[0166] The output power of the inverter can be obtained by detecting the output voltage and output current of the inverter.

[0167] S1304: Determine whether the power reference value is less than the output power, that is, Pref<Pout; if yes, execute S1305; otherwise, execute S1307;

[0168] S1305: Reduce the input current reference value Iref of the inverter. Here, the input current of the inverter is the output current of the photovoltaic array for a single-stage inverter, and is the output current of the photovoltaic array for a two-stage inverter, and is also the input current of the DCDC conversion circuit.

[0169] The control of the input current reference value of the inverter is the result of the outer loop closed-loop control, while the control of the inverter input current belongs to the closed-loop control of the current inner loop. The input current of the inverter is controlled according to the input current reference value of the inverter. Specifically, the input current of the inverter can be detected, and the detected input current is compared with the input current reference value. According to the comparison result, the duty cycle of the driving pulse signal of the switching device in the inverter is controlled, thereby realizing the control of the size of the input current of the inverter. For example, the specific current closed-loop control can be achieved by using a proportional-integral regulator.

[0170] S1306: Determine whether the input voltage of the inverter is less than the preset voltage, that is, Uin>Ulmt. If yes, execute S1307, otherwise execute S1308;

[0171] S1307: Increase the input current reference value Iref of the inverter;

[0172] S1308: Determine whether the output power of the inverter reaches the power reference value, that is, determine whether Pout and Pref are equal in theory. In actual implementation, there is generally a certain error in control. The two can be considered equal within the allowable error range.

[0173] S1309: The inverter performs stable operation with limited power.

[0174] The method provided in this embodiment adds a judgment on the input voltage of the inverter after S1305. When the input voltage is greater than the preset voltage, it means that the voltage is high, so the voltage needs to be limited to avoid overvoltage on the DC bus. It also includes switching devices and DC bus capacitors. Since the voltage is reduced, the input current reference value needs to be increased, so S1307 needs to be executed.

[0175] The above embodiments of the present application do not limit the implementation form of the switching device, and it can be, for example, a controllable semiconductor switching device such as IGBT, MOS, etc.

[0176] Based on the photovoltaic devices, inverters, photovoltaic systems and methods provided in the above embodiments, the present application also provides a photovoltaic power control device, including:

[0177] A receiving unit, configured to receive a power dispatching instruction of an inverter, wherein the power dispatching instruction carries a power reference value;

[0178] A current reducing unit, used for reducing the output current of the photovoltaic array to increase the output voltage of the photovoltaic array when the power reference value is less than the power at the maximum power point;

[0179] The current increasing unit is used to increase the output current of the photovoltaic array when the output voltage of the photovoltaic array is greater than or equal to a preset voltage, so as to reduce the output voltage of the photovoltaic array until the output power of the inverter is consistent with the power reference value.

[0180] The current reduction unit specifically includes a current reduction module, which is used to reduce the output current reference value of the photovoltaic array, control the output current of the photovoltaic array to decrease according to the output current reference value, and the output voltage of the photovoltaic array increases as the output current decreases.

[0181] The current increasing unit specifically includes a current increasing module, which is used to increase the output current reference value of the photovoltaic array when the output voltage of the photovoltaic array is greater than or equal to a preset voltage, and control the output current increase of the photovoltaic array according to the output current reference value.

[0182] It also includes a control unit, which is used to control the output power of the inverter to be the power of the maximum power point when the power reference value is greater than or equal to the power of the maximum power point.

[0183] It should be noted that the device can be applied to the above photovoltaic equipment, especially to a controller.

[0184] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0185] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A photovoltaic device, characterized in that: include: DCDC conversion circuit, inverter circuit and controller; The input end of the DCDC conversion circuit is connected to the photovoltaic array, and the output end of the DCDC conversion circuit is connected to the input end of the inverter circuit; The controller reduces the input current of the DCDC conversion circuit to increase the input voltage of the DCDC conversion circuit when the power reference value is less than the power at the maximum power point; and increases the input current of the DCDC conversion circuit to reduce the input voltage of the DCDC conversion circuit when the input voltage of the DCDC conversion circuit is greater than or equal to a preset voltage, until the output power of the photovoltaic device is consistent with the power reference value; The reference power value is carried in the power scheduling instruction; The controller is further configured to control the output power of the photovoltaic device to be the power at the maximum power point when the power reference value is greater than or equal to the power at the maximum power point.

2. The photovoltaic device according to claim 1, characterized in that The controller is specifically used to reduce the input current reference value of the DCDC conversion circuit, and control the input current of the DCDC conversion circuit to decrease according to the input current reference value, and the input voltage of the DCDC conversion circuit increases as the input current decreases.

3. The photovoltaic device according to claim 1, characterized in that: The controller is specifically used to increase the input current reference value of the DCDC conversion circuit when the input voltage of the DCDC conversion circuit is greater than or equal to a preset voltage, and control the input current of the DCDC conversion circuit to increase according to the input current reference value.

4. The photovoltaic device according to any one of claims 1 to 3, characterized in that: The preset voltage is smaller than the voltage stress of the switch device in the DCDC conversion circuit, and smaller than the voltage stress of the switch device in the inverter circuit.

5. The photovoltaic device according to any one of claims 1 to 3, characterized in that: The DCDC conversion circuit and the inverter circuit are integrated in the inverter; The controller is a controller of the inverter.

6. The photovoltaic device according to any one of claims 1 to 3, characterized in that: The DCDC conversion circuit is integrated in a combiner box, and the output end of the combiner box is connected to the input end of the inverter circuit; The controller is a controller of the combiner box.

7. A photovoltaic inverter, characterized in that: Including inverter circuit and controller; The input end of the inverter circuit is connected to a photovoltaic array; The inverter circuit is used to convert the direct current output by the photovoltaic array into alternating current output; The controller is used to reduce the output current of the photovoltaic array to increase the output voltage of the photovoltaic array when the power reference value is less than the power at the maximum power point; and to increase the output current of the photovoltaic array to reduce the output voltage of the photovoltaic array when the output voltage of the photovoltaic array is greater than or equal to a preset voltage until the output power of the inverter is consistent with the power reference value; The reference power value is carried in the power scheduling instruction; The controller is further configured to control the output power of the photovoltaic inverter to be the power at the maximum power point when the power reference value is greater than or equal to the power at the maximum power point.

8. The inverter according to claim 7, characterized in that: The controller is specifically used to reduce the output current reference value of the photovoltaic array, and control the output current of the photovoltaic array to decrease according to the output current reference value, and the output voltage of the photovoltaic array increases as the output current decreases.

9. The inverter according to claim 7, characterized in that: The controller is specifically used to increase the output current reference value of the photovoltaic array when the output voltage of the photovoltaic array is greater than or equal to a preset voltage, and control the output current of the photovoltaic array to increase according to the output current reference value.

10. A photovoltaic system, characterized in that: include: The photovoltaic device according to any one of claims 1 to 6 or the photovoltaic inverter according to any one of claims 7 to 9, further comprising: a photovoltaic array; When the photovoltaic device is included, the input end of the photovoltaic device is connected to the photovoltaic array; When the photovoltaic inverter is included, the input terminal of the photovoltaic inverter is connected to the photovoltaic array.

11. A photovoltaic power generation power control method, characterized in that: include: When the power reference value is less than the power at the maximum power point, reducing the output current of the photovoltaic array to increase the output voltage of the photovoltaic array; When the output voltage of the photovoltaic array is greater than or equal to a preset voltage, increasing the output current of the photovoltaic array to reduce the output voltage of the photovoltaic array until the output power of the photovoltaic power generation is consistent with the power reference value; The reference power value is carried in the power scheduling instruction; When the power reference value is greater than or equal to the power at the maximum power point, the output power of the photovoltaic power generation is controlled to be the power at the maximum power point.

12. The control method according to claim 11, characterized in that: The step of reducing the output current of the photovoltaic array specifically includes: The output current reference value of the photovoltaic array is reduced, and the output current of the photovoltaic array is controlled to decrease according to the output current reference value, and the output voltage of the photovoltaic array increases as the output current decreases.

13. The control method according to claim 11, characterized in that: When the output voltage of the photovoltaic array is greater than or equal to a preset voltage, increasing the output current of the photovoltaic array specifically includes: When the output voltage of the photovoltaic array is greater than or equal to a preset voltage, an output current reference value of the photovoltaic array is increased, and the output current of the photovoltaic array is controlled to increase according to the output current reference value.

Images