Voltage regulation method, power converter and inverter system

Abstract

The invention provides a voltage regulation method, a power converter and an inverter system, and the method comprises the steps: obtaining the working condition parameters of each DC conversion circuit under the condition that each DC conversion circuit of the power converter is in a bypass working mode; the input end of each direct current conversion circuit is used for connecting a direct current source, the output end of each direct current conversion circuit is connected to the direct current side of the inverter circuit through the direct current bus, and the alternating current output end of the inverter circuit is used for connecting an alternating current power supply network; and when it is detected that at least one DC conversion circuit meets an output abnormal condition according to the working condition parameters, reducing the voltage of the DC bus, so that the DC conversion circuit meeting the output abnormal condition outputs power to the DC bus. According to the invention, the overall energy transmission capability of the power converter can be improved, and the energy loss is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circuit control, and more particularly, to a voltage regulation method, a power converter and an inverter system. BACKGROUND

[0002] With the development of photovoltaic power generation technology, power converters based on the parallel architecture of multi-path direct current conversion circuits have been increasingly widely applied. Such power converters connect different photovoltaic strings through multiple direct current conversion circuits respectively, and realize centralized conversion and transmission of electric energy after the current is converged through a direct current bus.

[0003] In actual deployment, due to the difference in the number of components or the light conditions of each photovoltaic string, the input voltages of each direct current conversion circuit of the same power converter may not match. In this case, if each direct current conversion circuit is in a bypass working mode, the switch tube of each direct current conversion circuit will be in an off state, and the direct current conversion circuit cannot perform voltage boosting. At this time, the direct current bus voltage is clamped in the reverse direction by the direct current conversion circuit with the highest input voltage. This phenomenon may cause the direct current conversion circuit with an input voltage lower than the bus voltage to bear a negative voltage difference, so that the output diode of the direct current conversion circuit is reverse-biased and cannot inject electric energy into the direct current bus, resulting in output abnormalities. This leads to the idle of the photovoltaic string connected to the low-voltage direct current conversion circuit, causing energy loss. SUMMARY

[0004] Therefore, the present application provides a voltage regulation method, a power converter and an inverter system, which can reduce energy loss. The specific solutions are as follows:

[0005] In a first aspect, the present application provides a voltage regulation method, comprising:

[0006] In the case that each direct current conversion circuit of the power converter is in a bypass working mode, obtaining the working condition parameters of each direct current conversion circuit; wherein the input end of each direct current conversion circuit is used to connect a direct current source, the power converter further comprises an inverter circuit and a direct current bus, the output end of each direct current conversion circuit is connected to the direct current side of the inverter circuit through the direct current bus, and the alternating current output end of the inverter circuit is used to connect an alternating current power network; the working condition parameters include at least one of output current, input voltage and output power;

[0007] In the case that at least one direct current conversion circuit satisfies the output abnormality condition according to the working condition parameters, the voltage of the direct current bus is reduced, so that the direct current conversion circuit satisfying the output abnormality condition outputs power to the direct current bus;

[0008] The output abnormality condition includes at least one of the following:

[0009] The output current of the direct current conversion circuit is less than a first current threshold, the input voltage of the direct current conversion circuit is less than the voltage of the direct current bus, and the output power of the direct current conversion circuit is less than an output power threshold.

[0010] In a possible implementation, before the working condition parameters of each direct current conversion circuit of the power converter are acquired, the method further includes:

[0011] detecting whether each direct current conversion circuit of the power converter is in the bypass working mode, wherein the output current of each direct current conversion circuit at at least one historical time is greater than a second current threshold.

[0012] In a possible implementation, the process of detecting whether each direct current conversion circuit of the power converter is in the bypass working mode includes:

[0013] In a case where the voltage of the direct current bus is greater than a clamping voltage threshold, it is determined that each direct current conversion circuit of the power converter is in the bypass working mode.

[0014] In a possible implementation, the method further includes:

[0015] setting an upper limit value of the control voltage of the direct current bus, so that the voltage given value in the control loop corresponding to the direct current bus is not greater than the upper limit value of the control voltage; wherein the upper limit value of the control voltage is less than the clamping voltage threshold.

[0016] determining a difference between the voltage given value and the current voltage of the direct current bus;

[0017] inputting the difference into the control loop to obtain an output of the control loop;

[0018] reducing the voltage of the direct current bus according to the output of the control loop.

[0019] In a possible implementation, the method further includes:

[0020] subtracting a preset adjustment value from the clamping voltage threshold to obtain a first calculation result; and setting the first calculation result as the upper limit value of the control voltage of the direct current bus.

[0021] or,

[0022] multiplying the clamping voltage by a preset proportion value to obtain a second calculation result; and setting the second calculation result as the upper limit value of the control voltage of the direct current bus, wherein the preset proportion value is less than 1.

[0023] One possible implementation also includes:

[0024] If the duration of reducing the voltage of the DC bus is greater than the duration threshold, the upper limit of the control voltage is updated to the upper limit of the power search voltage, which is not less than the sealing voltage threshold.

[0025] In one possible implementation, the process of detecting that each DC-DC converter circuit of the power converter is in bypass operating mode includes:

[0026] When the controller of each DC-DC converter stops sending control signals to the switching transistors of each DC-DC converter, it is determined that each DC-DC converter of the power converter is in bypass operation mode.

[0027] In one possible implementation, reducing the voltage of the DC bus includes:

[0028] Reduce the input voltage of the DC-DC converter circuits other than the target DC-DC converter circuit in the power converter to reduce the voltage of the DC bus.

[0029] Secondly, this application provides a power converter, comprising:

[0030] The system includes an inverter circuit, a DC bus, multiple DC-DC converter circuits, and a controller. The input terminal of each DC-DC converter circuit is used to connect to a DC source, the output terminal of each DC-DC converter circuit is connected to the DC side of the inverter circuit through the DC bus, and the AC output terminal of the inverter circuit is used to connect to an AC power network.

[0031] The controller is used to execute the method described in the first aspect.

[0032] Thirdly, this application provides an inverter system, including:

[0033] A power converter and control system; the power converter includes an inverter circuit, a DC bus, and multiple DC-DC converter circuits; the input terminal of each DC-DC converter circuit is used to connect to a DC source, the output terminals of the multiple DC-DC converter circuits are connected to the DC side of the inverter circuit through the DC bus, and the output terminal of the inverter circuit is used to connect to an AC power network;

[0034] The control system is used to perform the method described in the first aspect.

[0035] This application has the following beneficial effects:

[0036] This application provides a voltage regulation method, a power converter, and an inverter system. The method includes: First, with each DC-DC converter circuit of the power converter in bypass mode, acquiring the operating parameters of each DC-DC converter circuit; wherein, the input terminal of each DC-DC converter circuit is used to connect to a DC source, the power converter also includes an inverter circuit and a DC bus, the output terminal of each DC-DC converter circuit is connected to the DC side of the inverter circuit through the DC bus, and the AC output terminal of the inverter circuit is used to connect to an AC power network; the operating parameters include at least one of output current, input voltage, and output power; then, if at least one DC-DC converter circuit is detected to meet an output abnormality condition based on the operating parameters, the voltage of the DC bus is reduced, so that the DC-DC converter circuit meeting the output abnormality condition outputs power to the DC bus; wherein, the output abnormality condition includes at least one of the following: the output current of the DC-DC converter circuit is less than a first current threshold, the input voltage of the DC-DC converter circuit is less than the voltage of the DC bus, and the output power of the DC-DC converter circuit is less than an output power threshold. In other words, this application enables the DC bus voltage to be reduced when the DC-DC converter circuit is detected to meet the abnormal output conditions, so that the voltage of the DC-DC converter circuit is not lower than the voltage of the DC bus. This allows the DC-DC converter circuit with abnormal output to resume output, reduces the idle capacity of the photovoltaic string power generation, effectively improves the overall energy delivery capacity of the power converter, and reduces energy loss. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0038] Figure 1 A flowchart illustrating a voltage regulation method provided in this application embodiment;

[0039] Figure 2 This is a schematic diagram of the structure of a DC-DC converter circuit in a power converter provided in an embodiment of this application;

[0040] Figure 3 A schematic diagram of the DC-DC converter circuit in another power converter provided in this application embodiment;

[0041] Figure 4 A flowchart of a bus voltage regulation process is provided for an embodiment of this application;

[0042] Figure 5 This is a schematic diagram of the structure of a power converter provided in an embodiment of this application;

[0043] Figure 6 This is a schematic diagram of the structure of an inverter system provided in an embodiment of this application. Detailed Implementation

[0044] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0045] This application provides a voltage regulation method that can be applied to controllers or control systems in power converters, etc. The flowchart of this voltage regulation method is shown below. Figure 1 As shown, it specifically includes:

[0046] S101: When each DC-DC converter circuit of the power converter is in bypass mode, obtain the operating parameters of each DC-DC converter circuit; wherein, the operating parameters include at least one of output current, input voltage and output power, the input terminal of each DC-DC converter circuit is used to connect to a DC source, the power converter also includes an inverter circuit and a DC bus, the output terminal of each DC-DC converter circuit is connected to the DC side of the inverter circuit through the DC bus, and the AC output terminal of the inverter circuit is used to connect to the AC power network.

[0047] In this embodiment, the DC-DC converter circuit can be a boost circuit, and the DC source connected to the input terminal of the DC-DC converter circuit can include at least one of a photovoltaic string and a photovoltaic analog source DC power supply system, wherein the photovoltaic string includes at least one photovoltaic module.

[0048] Optionally, the operating parameters include at least one of output current, input voltage, and output power, and the operating parameters of the DC-DC converter circuit can be acquired by sensors installed at the input and output terminals of each DC-DC converter circuit.

[0049] In this embodiment, each DC-DC converter is in bypass mode, meaning that the boost ratio of each DC-DC converter is 1. In this case, the voltage of the DC bus is the maximum value among the input voltages of each DC-DC converter.

[0050] See Figure 2An exemplary schematic diagram of a power converter is provided. Each DC-DC converter circuit in the power converter includes an inductor L, a switch T, and a diode D. The DC source is a photovoltaic string PV. Each DC-DC converter circuit is connected in parallel to a DC bus BUS, which is also used to connect to the DC side of the inverter circuit. When each DC-DC converter circuit is in bypass operation mode, the loop between inductor L1 and DC source PV1 is broken, such as... Figure 3 The diagram shows the equivalent circuit diagram of each DC-DC converter circuit in bypass mode. Since the number of photovoltaic strings connected to the input terminals of each DC-DC converter circuit may differ, the input voltage of each DC-DC converter circuit may also differ. If at least two DC-DC converter circuits have different input voltages, the voltage of the DC bus is equal to the maximum value among the input voltages of each DC-DC converter circuit. For the other DC-DC converter circuits besides the one with the maximum input voltage, their input voltage is less than the voltage of the DC bus, causing the diodes to be reverse-biased and cut off, thus preventing them from outputting current to the DC bus, resulting in an output abnormality. If the output voltages of all DC-DC converter circuits are the same, it means that the input voltage of each DC-DC converter circuit is not less than the voltage of the DC bus, and each DC-DC converter circuit can output power to the DC bus.

[0051] S102: If at least one DC-DC converter circuit is detected to meet the output abnormality condition based on the operating parameters, the voltage of the DC bus is reduced so that the DC-DC converter circuit that meets the output abnormality condition outputs power to the DC bus.

[0052] The abnormal output conditions include at least one of the following:

[0053] The output current of the DC-DC converter is less than the first current threshold, the input voltage of the DC-DC converter is less than the voltage of the DC bus, and the output power of the DC-DC converter is less than the output power threshold.

[0054] In this embodiment, an output anomaly can refer to a situation where the input voltage of the DC-DC converter circuit is lower than the voltage of the DC bus, causing the DC-DC converter circuit to fail to output current and power to the DC bus. The presence of an output anomaly in each DC-DC converter circuit can be determined by analyzing its operating parameters, such as input voltage, output current, and output power.

[0055] Optionally, if there is a DC-DC converter circuit in the power converter that meets the output abnormality condition, the DC-DC converter circuit that meets the output abnormality condition can be used as the target DC-DC converter circuit. The voltage of the DC bus is controlled to decrease so that the voltage of the DC bus is not greater than the input voltage of the target DC-DC converter circuit, thereby enabling each target DC-DC converter circuit to output power to the DC bus.

[0056] Optionally, the first current threshold can be set to zero. In some embodiments, since the current sensor has an error, the first current threshold can be set according to the maximum error of the current sensor to reduce the identification of a DC-DC converter circuit with abnormal output as a normal DC-DC converter short circuit due to sensor error; similarly, the output power threshold can also be set according to the error of the current sensor.

[0057] In this embodiment, the DC-DC converter circuit can be used to determine whether it is outputting abnormally based on one of the operating parameters, namely the output current, input voltage, and output power, which can improve the speed of identifying output abnormalities. Alternatively, multiple operating parameters can be used together to determine whether the DC-DC converter circuit is outputting abnormally, which can improve the accuracy of identifying output abnormalities.

[0058] In some embodiments, the DC-DC converter is determined to meet the output abnormality condition when the output current of the DC-DC converter is less than a first current threshold, the input voltage of the DC-DC converter is less than the voltage of the DC bus, or the output power of the DC-DC converter is less than the output power threshold.

[0059] In some embodiments, the DC-DC converter is determined to meet the output abnormality condition when the output current of the DC-DC converter is less than a first current threshold and / or the input voltage of the DC-DC converter is less than the voltage of the DC bus.

[0060] In some embodiments, if the output current of the DC-DC converter is less than a first current threshold and / or the output power of the DC-DC converter is less than an output power threshold, it is determined that the DC-DC converter meets the output abnormality condition.

[0061] In some embodiments, the DC-DC converter is determined to meet the output abnormality condition when the input voltage of the DC-DC converter is less than the voltage of the DC bus and / or the output power of the DC-DC converter is less than the output power threshold.

[0062] In some embodiments, when the output current of the DC-DC converter is less than a first current threshold, the input voltage of the DC-DC converter is less than the voltage of the DC bus, and the output power of the DC-DC converter is less than the output power threshold, it is determined that the DC-DC converter meets the output abnormality condition.

[0063] By applying the method provided in the embodiments of this application, when each DC-DC converter circuit of the power converter is in bypass operation mode, if the DC-DC converter circuit is detected to meet the output abnormality condition according to the operating parameters of the DC-DC converter circuit, the DC bus voltage can be reduced so that the voltage of the DC-DC converter circuit is not lower than the voltage of the DC bus. This allows the DC-DC converter circuit with abnormal output to resume output, reduces the idle time of photovoltaic string power generation capacity, effectively improves the overall energy transmission capacity of the power converter, and reduces energy loss.

[0064] In some embodiments, when the DC-DC converter circuits of the power converter are in bypass mode due to the DC bus voltage exceeding the saturation voltage threshold, the DC bus voltage can be reduced to ensure it does not exceed the saturation voltage threshold. This allows each DC-DC converter circuit to resume its boost function and perform maximum power point search. Specifically, the controller of each DC-DC converter circuit can send corresponding control signals to each circuit, causing the switching transistors of each circuit to switch between on and off states to adjust the output voltage of the circuit. This ensures that the voltage of each DC-DC converter circuit is not less than the DC bus voltage, ultimately enabling the DC-DC converter circuits that meet the abnormal output conditions to resume output power to the DC bus.

[0065] In some embodiments, when the switching transistors in each DC-DC converter circuit remain in the off state due to a fault, the input voltage of the DC-DC converter circuits other than the target DC-DC converter circuit in the power converter is reduced, and the voltage of the DC bus will also decrease accordingly until the voltage of the target DC-DC converter circuit is not less than that of the DC bus. In this way, the target DC-DC converter circuit can output power to the DC bus.

[0066] Optionally, the voltage of the DC bus can be reduced through a control loop corresponding to the DC bus. This control loop may include at least one of a voltage loop and a current loop. In some embodiments, the voltage of the DC bus can also be reduced by lowering the input voltage of other DC-DC converter circuits besides the target DC-DC converter circuit. In other embodiments, the voltage of the DC bus can also be reduced by increasing the output power of the DC bus, such as by turning on the voltage relief circuit connected to the DC bus or increasing the active power output of the inverter circuit.

[0067] In some embodiments provided in this application, optionally, before obtaining the operating parameters of each DC-DC converter circuit when each DC-DC converter circuit of the power converter is in bypass operating mode, the method further includes:

[0068] The system detects whether each DC-DC converter circuit of the power converter is in bypass mode, wherein the output current of each DC-DC converter circuit is greater than a second current threshold at at least one historical moment.

[0069] Optionally, the second current threshold is greater than the first current threshold.

[0070] In this embodiment, the historical time can be a time before the current time. If the output current of the DC-DC converter is greater than the second current threshold at at least one historical time, it indicates that no fault has occurred between the DC-DC converter and the DC source connected to it. In this case, it is possible to monitor whether the DC-DC converter is in bypass operation mode, so that when the switching transistors of each fault-free DC-DC converter are in the off state, it is possible to detect whether each fault-free DC-DC converter outputs abnormally.

[0071] Optionally, if the output current of the DC-DC converter circuit remains below the second current threshold, it indicates that the DC-DC converter circuit is not connected to a DC source, or that there is a fault between the DC-DC converter circuit and the DC source it is connected to. In this case, it is not necessary to detect whether the DC-DC converter circuit is in the off state, thereby reducing the risk of a DC-DC converter circuit without input affecting the voltage regulation of the DC bus.

[0072] In some embodiments, when the power converter is started, it can be detected whether the output current of each DC-DC converter circuit is greater than a second current threshold. If the output current of a DC-DC converter circuit is greater than the second current threshold, the DC-DC converter circuit can be marked as a DC-DC converter circuit to be tested. Specifically, a current flag can be set for the DC-DC converter circuit, which indicates that the DC-DC converter circuit is connected to a DC source and that no fault has occurred between the DC-DC converter circuit and the DC source. When each DC-DC converter circuit with the set current flag is in bypass operation mode, the operating parameters of each DC-DC converter circuit with the set current flag are obtained.

[0073] In some embodiments provided in this application, optionally, the process of detecting that each DC-DC converter circuit of the power converter is in bypass operating mode includes:

[0074] If the voltage of the DC bus is detected to be greater than the saturation voltage threshold, it is determined that each DC-DC converter circuit of the power converter is in bypass mode.

[0075] In this embodiment, when the DC bus voltage exceeds the saturation voltage threshold, the switching transistors in the DC-DC converter circuit will experience excessive stress. To protect the switching transistors from damage, the controller of the DC-DC converter circuit will control the switching transistors of each DC-DC converter circuit to be in the off state. That is, when the DC bus voltage is detected to be greater than the saturation voltage threshold, it can be assumed that each DC-DC converter circuit of the power converter is in bypass operation mode, thus accurately detecting whether each DC-DC converter circuit is in bypass operation mode.

[0076] In some embodiments provided in this application, optionally, reducing the voltage of the DC bus includes:

[0077] Set the upper limit of the control voltage for the DC bus so that the voltage setpoint in the control loop corresponding to the DC bus is not greater than the upper limit of the control voltage; wherein, the upper limit of the control voltage is less than the ripple voltage threshold.

[0078] Determine the difference between the voltage setpoint and the current voltage of the DC bus;

[0079] Input the difference into the control loop to obtain the output of the control loop;

[0080] The voltage of the DC bus is reduced based on the output of the control loop.

[0081] In this embodiment, the control loop may include a voltage loop. After obtaining the output of the control loop, at least one of the following can be controlled based on the output: increasing the output current of the inverter circuit, increasing the output active power, and controlling the conduction of the switching transistors between the DC-DC converter circuit and the voltage relief circuit.

[0082] Optionally, by reducing the DC bus voltage based on the output of the control loop, the reduced DC bus voltage can be made to be no greater than the blocking voltage threshold. This allows each DC-DC converter circuit to exit bypass mode. In this case, the controller of each DC-DC converter circuit can send control signals to each DC-DC converter circuit. The control signals are used to instruct the switching transistors in the DC-DC converter circuit to switch between on and off states. That is, each DC-DC converter circuit can restore its voltage regulation function, ensuring that the output voltage of the target DC-DC converter circuit is no less than the DC bus voltage. This enables the target DC-DC converter circuit to output power to the DC bus, thereby increasing the system's power generation.

[0083] In some embodiments provided in this application, optionally, setting an upper limit value for the control voltage of the DC bus includes:

[0084] Subtract the preset adjustment value from the wave blocking voltage threshold to obtain the first calculation result; set the first calculation result as the upper limit value of the control voltage of the DC bus;

[0085] or,

[0086] Multiply the wave blocking voltage by a preset ratio to obtain a second calculation result; set the second calculation result as the upper limit of the control voltage of the DC bus, wherein the preset ratio is less than 1.

[0087] In this embodiment, the upper limit of the control voltage is set by the first calculation result or the second calculation result, which makes the upper limit of the control voltage less than the sealing voltage threshold, thereby ensuring that the voltage of the DC bus is not greater than the sealing voltage threshold and effectively protecting the switching transistor.

[0088] In some embodiments provided in this application, optionally, the following additional features may be included:

[0089] If the duration of reducing the DC bus voltage exceeds the duration threshold, the upper limit of the control voltage will be updated to the upper limit of the power search voltage, and the upper limit of the power search voltage will not be less than the blocking voltage threshold.

[0090] In this embodiment, after reducing the voltage of the DC bus, each DC-DC converter circuit can perform a maximum power point search. The maximum power point voltage may be between the upper limit of the control voltage and the threshold voltage. Therefore, by increasing the upper limit of the control voltage, that is, updating the upper limit of the control voltage to the upper limit of the power search voltage, the voltage search range of each DC-DC converter circuit can be expanded, which can effectively optimize the output power of each DC-DC converter circuit and improve the output efficiency.

[0091] In some embodiments provided in this application, optionally, the process of detecting that each DC-DC converter circuit of the power converter is in bypass operating mode includes:

[0092] When the controllers of each DC-DC converter circuit stop sending control signals to the switching transistors of each DC-DC converter circuit, it is determined that each DC-DC converter circuit of the power converter is in bypass operation mode.

[0093] In this embodiment, the switching transistor can be a MOSFET or an IGBT, etc. When the control signal to the switching transistor is stopped, the driving voltage between the gate and source of the switching transistor is zero, so that the switching transistor is in the off state.

[0094] Optionally, the controller that performs the voltage regulation method in the embodiments of this application and the controller of each DC-DC converter circuit can be the same controller or different controllers.

[0095] Optionally, if the controller executing the voltage regulation method is different from the controller of each DC-DC converter, a notification message sent by the controller of each DC-DC converter can be received. The notification message indicates that the controller of the DC-DC converter stops sending control signals to the switching transistor of the DC-DC converter. In this case, the switching transistor of the DC-DC converter is in the off state.

[0096] In some embodiments provided in this application, optionally, reducing the voltage of the DC bus includes:

[0097] Reduce the input voltage of the DC-DC converter circuits other than the target DC-DC converter circuit in the power converter to reduce the voltage of the DC bus.

[0098] In this embodiment, a step-down command can be sent to the optimizer in the DC source connected to the DC-DC converter circuit. The step-down command instructs the optimizer to reduce the output voltage. Upon receiving the step-down command, the optimizer reduces the output voltage, thereby reducing the input voltage of the DC-DC converter circuit. Since the voltage of the DC bus is determined based on the input voltage of the DC-DC converter circuits other than the target DC-DC converter circuit, reducing the input voltage of each DC-DC converter circuit can reduce the voltage of the DC bus.

[0099] See Figure 4 This application provides a flowchart of a bus voltage regulation process, in which the controller of the power converter can perform the following operations:

[0100] Step 1: Detect the current Imppt of each parallel Boost circuit in the power converter. If the current of the Boost circuit is greater than the threshold I1 (the second current threshold), a current presence flag F_BoostCurExist can be set for the BoostID corresponding to that Boost circuit. This current presence flag is set once when the current first exceeds I1, and subsequent checks on whether the current of the Boost circuit exceeds the threshold I1 are unnecessary. In this embodiment, if the current of the Boost circuit is greater than the threshold I1, it indicates that the Boost circuit is connected to the photovoltaic string and there are no wiring faults, etc. In this case, a current presence flag can be set for the Boost circuit.

[0101] Step 2: Monitor the following three conditions in real time: whether the DC bus voltage Ubus is greater than the Boost capping voltage U_BoostStop (capping voltage threshold), whether the current presence flag F_BoostCurExist of at least one BoostID is set, and whether there is a Boost circuit with at least one current presence flag set whose current is less than the threshold I2 (first current threshold).

[0102] Step 3: When all conditions in Step 2 are met simultaneously, the DC bus voltage control limit flag F_UbusLimit is set. In this embodiment, to reduce the risk of excessive stress on the Boost switching transistors, the DC-DC converter circuits are placed in bypass mode when the DC bus voltage Ubus is greater than the Boost blocking voltage U_BoostStop. In this case, if the current of at least one Boost circuit with the current presence flag set is less than the threshold I2, it indicates that the Boost circuit has an output abnormality. Therefore, the DC bus voltage control limit flag F_UbusLimit can be set, which can be used to indicate a reduction in the DC bus voltage.

[0103] Step 4: If the F_UbusLimit flag is set, the upper limit of the DC bus voltage control value is set to the Boost stop voltage minus the threshold ΔV, that is, the upper limit of the control voltage is U_BoostStop-ΔV.

[0104] Step 5: After the F_UbusLimit flag is set, start the time limit timer F_UbusLimitCnt and check whether the time value is greater than the time threshold T.

[0105] Step 6: If the timing value F_UbusLimitCnt is greater than the duration threshold T, and the DC bus voltage is lower than the bypass boost voltage U_BoostWork, then the upper limit restriction of the DC bus voltage control value is removed (i.e., it is restored to the MPPT voltage upper limit value). If the timing value F_UbusLimitCnt is less than or equal to T, then the upper limit of the DC bus voltage control value is maintained at U_BoostWork, where U_BoostWork = U_BoostStop - ΔV. In this embodiment, if the timing value F_UbusLimitCnt is greater than the duration threshold T, and the DC bus voltage is lower than the bypass boost voltage U_BoostWork, it indicates that each Boost circuit can perform maximum power point search. The maximum power point voltage may be between the upper limit control voltage value and the buckling voltage threshold. In this case, by removing the upper limit restriction of the DC bus voltage control value, i.e., restoring the upper limit control voltage value, the voltage search range of each DC-DC converter circuit can be expanded, effectively optimizing the output power of each DC-DC converter circuit and improving output efficiency.

[0106] This application also provides a power converter, the structural schematic diagram of which is shown below. Figure 5 As shown, it includes:

[0107] The system includes an inverter circuit 501, a DC bus 502, multiple DC-DC converter circuits 503, and a controller 504. The input terminal of each DC-DC converter circuit 503 is used to connect to a DC source, and the output terminal of each DC-DC converter circuit 503 is connected to the DC side of the inverter circuit 501 through the DC bus 502. The AC output terminal of the inverter circuit 501 is used to connect to an AC power network.

[0108] The controller 504 is used to perform the voltage regulation method described above.

[0109] This application also provides an inverter system, the structural schematic diagram of which is shown below. Figure 6 As shown, it specifically includes:

[0110] The power converter 601 and the control system 602 are included. The power converter 601 includes an inverter circuit, a DC bus and multiple DC conversion circuits. The input terminal of each DC conversion circuit is used to connect to a DC source. The output terminals of the multiple DC conversion circuits are connected to the DC side of the inverter circuit through the DC bus. The output terminal of the inverter circuit is used to connect to an AC power network.

[0111] The control system 602 is used to execute the voltage regulation method described above.

[0112] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For apparatus embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0113] Finally, it should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0114] For ease of description, the above devices are described separately by function as various units. Of course, in implementing this application, the functions of each unit can be implemented in one or more software and / or hardware.

[0115] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of this application.

[0116] The voltage regulation method provided in this application has been described in detail above. Specific examples have been used to illustrate the principle and implementation of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this application. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A voltage regulation method, characterized in that, include: With each DC-DC converter circuit of the power converter in bypass mode, the operating parameters of each DC-DC converter circuit are obtained. The input terminal of each DC-DC converter circuit is connected to a DC source. The power converter also includes an inverter circuit and a DC bus. The output terminal of each DC-DC converter circuit is connected to the DC side of the inverter circuit via the DC bus. The AC output terminal of the inverter circuit is connected to an AC power network. The operating parameters include at least one of output current, input voltage, and output power. If at least one of the DC-DC converter circuits is detected to meet the output abnormality condition based on the operating parameters, the voltage of the DC bus is reduced, so that the DC-DC converter circuit that meets the output abnormality condition outputs power to the DC bus. The abnormal output conditions include at least one of the following: The output current of the DC-DC converter is less than a first current threshold, the input voltage of the DC-DC converter is less than the voltage of the DC bus, and the output power of the DC-DC converter is less than an output power threshold.

2. The method according to claim 1, characterized in that, Before acquiring the operating parameters of each DC-DC converter circuit when each DC-DC converter circuit of the power converter is in bypass operation mode, the method further includes: The power converter is detected to determine whether each DC-DC converter circuit is in bypass mode, wherein the output current of each DC-DC converter circuit is greater than a second current threshold at at least one historical moment.

3. The method according to claim 2, characterized in that, The process of detecting that each DC-DC converter circuit of the power converter is in bypass operation mode includes: If the voltage of the DC bus is detected to be greater than the saturation voltage threshold, it is determined that each DC-DC converter circuit of the power converter is in bypass operation mode.

4. The method according to claim 3, characterized in that, The reduction of the DC bus voltage includes: Set an upper limit value for the control voltage of the DC bus such that the voltage setpoint in the control loop corresponding to the DC bus is not greater than the upper limit value for the control voltage; wherein, the upper limit value for the control voltage is less than the wave blocking voltage threshold. Determine the difference between the voltage setpoint and the current voltage of the DC bus; The difference is input into the control loop to obtain the output of the control loop; The voltage of the DC bus is reduced according to the output of the control loop.

5. The method according to claim 4, characterized in that, Setting the upper limit value of the control voltage of the DC bus includes: Subtract the preset adjustment value from the wave blocking voltage threshold to obtain the first calculation result; set the first calculation result as the upper limit value of the control voltage of the DC bus; or, The sealing voltage is multiplied by a preset ratio to obtain a second calculation result; the second calculation result is set as the upper limit of the control voltage of the DC bus, wherein the preset ratio is less than 1.

6. The method according to claim 4, characterized in that, Also includes: If the duration of reducing the voltage of the DC bus is greater than the duration threshold, the upper limit of the control voltage is updated to the upper limit of the power search voltage, which is not less than the sealing voltage threshold.

7. The method according to claim 2, characterized in that, The process of detecting that each DC-DC converter circuit of the power converter is in bypass operation mode includes: When the controller of each DC-DC converter stops sending control signals to the switching transistors of each DC-DC converter, it is determined that each DC-DC converter of the power converter is in bypass operation mode.

8. The method according to any one of claims 1-3, characterized in that, The reduction of the DC bus voltage includes: Reduce the input voltage of the DC-DC converter circuits other than the target DC-DC converter circuit in the power converter to reduce the voltage of the DC bus. The target DC-DC converter circuit is the DC-DC converter circuit that satisfies the output abnormality condition.

9. A power converter, characterized in that, include: The system includes an inverter circuit, a DC bus, multiple DC-DC converter circuits, and a controller. The input terminal of each DC-DC converter circuit is used to connect to a DC source, the output terminal of each DC-DC converter circuit is connected to the DC side of the inverter circuit through the DC bus, and the AC output terminal of the inverter circuit is used to connect to an AC power network. The controller is used to perform the method according to any one of claims 1-8.

10. An inverter system, characterized in that, include: A power converter and control system; the power converter includes an inverter circuit, a DC bus, and multiple DC-DC converter circuits; the input terminal of each DC-DC converter circuit is used to connect to a DC source, the output terminals of the multiple DC-DC converter circuits are connected to the DC side of the inverter circuit through the DC bus, and the output terminal of the inverter circuit is used to connect to an AC power network; The control system is used to perform the method according to any one of claims 1-8.

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