Photovoltaic hybrid inverter, control method of photovoltaic hybrid inverter and related equipment

Abstract

The invention discloses a control method for a photovoltaic hybrid inverter, and the method comprises the steps: controlling an inversion unit to apply an AC voltage test signal with a preset frequency and / or a preset voltage value to the output end of the inversion unit under a no-load condition, and maintaining a maximum power point tracking module to work, so as to provide electric energy for a DC bus; judging whether the photovoltaic hybrid inverter is in a weak light state or not based on the first voltage of the direct current bus and a preset voltage threshold value; when the photovoltaic hybrid inverter is in a weak light state, the alternating current side relay is kept disconnected; and after a preset delay time, applying the AC voltage test signal to the output end of the inversion unit again, and maintaining the maximum power point tracking module to work so as to re-judge whether the photovoltaic hybrid inverter is in the weak light state or not until the photovoltaic hybrid inverter is not in the weak light state. And issuing a pull-in instruction to the alternating current side relay to control the inverter unit to operate in a grid-connected manner. And the relay is prevented from being frequently triggered to be closed when the illumination is insufficient.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new energy, in particular to a control method and device of a photovoltaic hybrid inverter, a computer device and a storage medium. BACKGROUND

[0002] One of the core working modes of the light storage hybrid inverter is the photovoltaic grid-connected operation mode. In this mode, the direct current power on the photovoltaic side is boosted by the BOOST circuit and then rectified to the direct current bus, and then the direct current power is converted into alternating current power by the inverter unit and output to the power grid. In order to realize the safe control of grid connection and disconnection, a relay needs to be configured on the power grid side to ensure the reliable connection and disconnection of the inverter and the power grid.

[0003] However, as the most critical and vulnerable device in the inverter system, the relay has a limited number of attraction times, and once it is damaged, it will directly cause safety hazards in the system and cannot operate normally.

[0004] In normal photovoltaic grid-connected operation, when the maximum power point tracking (MPPT) module starts to work, the photovoltaic energy is processed by the inverter and sent to the power grid through the relay attraction; when the photovoltaic energy is insufficient to maintain the inverter, the relay will be disconnected and the inverter will stop running. Especially in the case of overcast, cloudy and insufficient light, the photovoltaic energy fluctuates greatly, and the inverter is prone to frequent start and stop, and the relay is prone to frequent attraction and disconnection. Such high-frequency action not only accelerates the wear of the relay, but also affects the overall life and operation stability of the inverter.

[0005] Therefore, it is necessary to propose a stable and feasible photovoltaic weak light detection and control scheme to reduce the frequent action of the relay and improve the reliability and life of the inverter system. SUMMARY

[0006] Therefore, it is necessary to propose a stable and feasible photovoltaic weak light detection and control scheme to reduce the frequent action of the relay and improve the reliability and life of the inverter system.

[0007] A control method of a photovoltaic hybrid inverter, the photovoltaic hybrid inverter comprising a direct current bus, an alternating current side relay, an inverter unit and a maximum power point tracking module, the method comprising: controlling the inverter unit to apply an alternating current voltage test signal of a preset frequency and / or a preset voltage value to the output end of the inverter unit under no-load conditions, and maintaining the maximum power point tracking module to work to provide power to the direct current bus; judging whether the photovoltaic hybrid inverter is in a weak light state based on a first voltage of the direct current bus and a preset voltage threshold value; keeping the AC side relay off when the PV hybrid inverter is in a weak light state; after a preset delay time, reapplying the AC voltage test signal to the output end of the inverter unit and maintaining the maximum power point tracking module to rejudge whether the PV hybrid inverter is in a weak light state, until the PV hybrid inverter is not in a weak light state, and then issuing a suction command to the AC side relay to control the inverter unit to operate in a grid-connected mode.

[0008] Optionally, the PV hybrid inverter further comprises a PV input side, and before the step of controlling the inverter unit to apply the AC voltage test signal of a preset frequency and / or a preset voltage value to the output end of the inverter unit under a no-load condition, the method further comprises: performing insulation monitoring when the DC voltage of the PV input side reaches a preset maximum power point tracking start voltage; when the insulation monitoring passes, controlling the maximum power point tracking module to work to raise the voltage of the DC bus to a target bus voltage, and controlling the inverter unit to apply the AC voltage test signal of a preset frequency and / or a preset voltage value to the output end of the inverter unit under a no-load condition, while maintaining the maximum power point tracking module to work; when the insulation monitoring fails, stopping the operation of the PV hybrid inverter and outputting a fault alarm.

[0009] Optionally, before the step of controlling the inverter unit to apply the AC voltage test signal of a preset frequency and / or a preset voltage value to the output end of the inverter unit under a no-load condition, the method further comprises: detecting whether the AC side relay is connected with an AC power grid; if the AC side relay is connected with the AC power grid, controlling the inverter unit to apply the AC voltage test signal of a preset frequency and / or a preset voltage value to the output end of the inverter unit under a no-load condition.

[0010] Optionally, the step of reapplying the AC voltage test signal to the output end of the inverter unit and maintaining the maximum power point tracking module to rejudge whether the PV hybrid inverter is in a weak light state after a preset delay time comprises: when the PV hybrid inverter is in a weak light state, updating a weak light frequency of being in the weak light state; according to the weak light frequency, selecting a corresponding delay time in a preset time sequence; when the delay time is reached, reapplying the AC voltage test signal to the output end of the inverter unit and maintaining the maximum power point tracking module to rejudge whether the PV hybrid inverter is in a weak light state; zeroing the weak light times until the photovoltaic hybrid inverter is not in the weak light state.

[0011] Optionally, the method further comprises: when the weak light times reaches a preset times threshold, increasing the maximum power point tracking module starting voltage, and re-applying the AC voltage test signal to the output end of the inverter unit when the re-detection time is reached, and maintaining the maximum power point tracking module working at the increased starting voltage to obtain a second voltage of the DC bus; based on the second voltage and the preset voltage threshold, re-determining whether the photovoltaic hybrid inverter is in a weak light state; zeroing the weak light times until the photovoltaic hybrid inverter is not in the weak light state.

[0012] Optionally, before the AC side relay is kept open and the weak light times in the weak light state is updated, the method further comprises: determining whether the inverter unit is connected with an energy storage battery; when the inverter unit is not connected with an energy storage battery and the photovoltaic hybrid inverter is in a weak light state, keeping the AC side relay open and updating the weak light times in the weak light state.

[0013] A photovoltaic hybrid inverter, comprising: a photovoltaic input side for receiving DC power output by a photovoltaic module; a maximum power point tracking module connected with the photovoltaic input side, for performing maximum power point tracking control on the DC power and providing output DC power to a DC bus; a DC bus connected with the maximum power point tracking module and an inverter unit, for transmitting DC power; an inverter unit connected with the DC bus, for inverting DC power into AC power; an AC side relay connected with an AC output end of the inverter unit and an AC power grid, for controlling connection and disconnection between the inverter unit and the AC power grid; a control device for performing the control method of the photovoltaic hybrid inverter.

[0014] A control device of a photovoltaic hybrid inverter, the photovoltaic hybrid inverter comprising a DC bus, an AC side relay, an inverter unit and a maximum power point tracking module, the device comprising: a first control module for controlling the inverter unit to apply an AC voltage test signal of a preset frequency and / or a preset voltage value to the output end of the inverter unit under no-load conditions, and maintaining the maximum power point tracking module to work to provide power to the DC bus; a first determining module, configured to determine whether the photovoltaic hybrid inverter is in a weak light state based on a first voltage of the DC bus and a preset voltage threshold value; a first maintaining module, configured to maintain the AC side relay to be turned off when the photovoltaic hybrid inverter is in the weak light state; a first attracting module, configured to re-apply the AC voltage test signal to the output end of the inverter unit and maintain the maximum power point tracking module to work after a preset delay time, so as to re-determine whether the photovoltaic hybrid inverter is in the weak light state, and when the photovoltaic hybrid inverter is not in the weak light state, issue an attracting instruction to the AC side relay to control the inverter unit to operate in grid-connected mode.

[0015] A computer device includes a memory, a processor, and computer readable instructions stored in the memory and executable on the processor, and the processor executes the computer readable instructions to implement the control method of the photovoltaic hybrid inverter.

[0016] A readable storage medium has computer readable instructions stored thereon, and the computer readable instructions are executed by a processor to implement the control method of the photovoltaic hybrid inverter.

[0017] The control method, device, computer device, and storage medium of the photovoltaic hybrid inverter control the inverter unit to apply an AC voltage test signal of a preset frequency and / or a preset voltage value to the output end of the inverter unit under no-load conditions, and maintain the maximum power point tracking module to work to provide power to the DC bus. The control method determines whether the photovoltaic hybrid inverter is in a weak light state based on a first voltage of the DC bus and a preset voltage threshold value. When the photovoltaic hybrid inverter is in the weak light state, the AC side relay is maintained to be turned off. After a preset delay time, the AC voltage test signal is re-applied to the output end of the inverter unit, and the maximum power point tracking module is maintained to work to re-determine whether the photovoltaic hybrid inverter is in the weak light state. When the photovoltaic hybrid inverter is not in the weak light state, an attracting instruction is issued to the AC side relay to control the inverter unit to operate in grid-connected mode. By applying the AC voltage test signal to detect the weak light state and adjusting the relay action time by the preset delay time, the relay is prevented from being frequently triggered to attract when the light is insufficient, and the mechanical wear of the relay is reduced. The device has the advantages of prolonging the service life of the equipment and improving the stability of the system. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments of the present application. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor under the premise of the drawings.

[0019] Figure 1 is a flow diagram of a control method of a photovoltaic hybrid inverter in an embodiment of the present application; Figure 2 is a structural diagram of a photovoltaic hybrid inverter in an embodiment of the present application; Figure 3 is a structural diagram of a control device of a photovoltaic hybrid inverter in an embodiment of the present application; Figure 4 is a schematic diagram of a computer device in an embodiment of the present application. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0021] In an embodiment, as shown in Figure 1 , a control method of a photovoltaic hybrid inverter is provided, the photovoltaic hybrid inverter comprising a DC bus, an AC side relay, an inverter unit and a maximum power point tracking module, comprising the following steps: 101, controlling the inverter unit to apply an AC voltage test signal of a preset frequency and / or a preset voltage value to the output end of the inverter unit under no-load condition, and maintaining the maximum power point tracking module to work to provide electric energy to the DC bus.

[0022] In the embodiments of the present application, the control method of the photovoltaic hybrid inverter described above can be realized by a control device of the photovoltaic inverter. The control device can comprise a digital signal processor (DSP), a microcontroller (MCU) or other processors capable of executing control logic to realize the control function of the inverter.

[0023] Specifically, as shown in Figure 2As shown, in an embodiment of the present application, a photovoltaic hybrid inverter is provided. The photovoltaic hybrid inverter is used to carry out the control method of the photovoltaic hybrid inverter of the embodiment of the present application, and the coordinated control of the maximum power point tracking module, the inverter unit and the alternating current side relay is realized through the internal control device to ensure the stable operation of the inverter in the weak light state and the normal light state.

[0024] Specifically, it comprises: A photovoltaic input side (i.e. PV side) for receiving direct current power output by a photovoltaic module, which can be realized by a direct current terminal or a junction box; A maximum power point tracking module (i.e. MPPT controller) connected with the photovoltaic input side, for maximum power point tracking control of the direct current power and providing the output direct current power to a direct current bus, which can be realized by combining a BOOST boost circuit with an MPPT algorithm to maximize the photovoltaic module output power by adjusting the duty cycle in real time; A direct current bus (i.e. Vbus) connected with the maximum power point tracking module and the inverter unit, for transmitting direct current power, which can be realized by a copper bar or a large cross-section wire, for carrying the boosted direct current power; An inverter unit (i.e. inverter) connected with the direct current bus, for inverting the direct current power into alternating current power, which can be realized by a full-bridge IGBT topology structure cooperating with a PWM modulation technology, for generating an alternating current voltage synchronized with the power grid; An alternating current side relay (i.e. relay circuit) connected with the alternating current output end of the inverter unit and the alternating current power grid, for controlling the connection and disconnection between the inverter unit and the alternating current power grid, which can be realized by an electromagnetic relay or a solid-state relay, for realizing physical on-off under the instruction of the control device; A control device for executing the control method of the photovoltaic hybrid inverter, which can be realized by a microcontroller or a DSP chip cooperating with a voltage sampling circuit, for judging the weak light state according to the direct current bus voltage and generating a relay control signal.

[0025] Specifically, after the photovoltaic input side receives the direct current power output by the photovoltaic module, the maximum power point tracking module adjusts the duty cycle of the boost circuit to make the photovoltaic module work at the maximum power point and transmit the boosted direct current power to the direct current bus. The inverter unit converts the direct current bus power into alternating current, and connects with the power grid through the alternating current side relay. The control device continuously monitors the direct current bus voltage, and determines the weak light state when the voltage is lower than the preset threshold. At this time, the control device keeps the alternating current side relay open. After a preset delay time, the control device reactivates the inverter unit output test signal and maintains the maximum power point tracking module working, and the direct current bus voltage is detected in a cycle until it returns to the normal range, and then the relay is attracted to realize grid-connected operation.

[0026] In addition, it may include a bidirectional charging and discharging circuit for the battery connected to the energy storage battery, an AC grid side connected to the power grid, and a load side connected to the output load.

[0027] More specifically, such as Figure 2 As shown, L represents the live wire, N represents the neutral wire, K1, K2, K3, K4, K5, K6, K7, and K8 represent normally open contact relays (i.e., AC side relays) used to form a relay circuit, Vinv represents the voltage at the AC output terminal of the inverter, Vi represents the grid voltage, Vo represents the AC output terminal voltage of the output load, Vg represents the generator voltage, PV represents the photovoltaic input, and Vbus represents the voltage of the DC bus, the corresponding line of which is the DC bus.

[0028] Specifically, the control inverter unit (i.e., the inverter itself) operates under no-load conditions, at which point the AC side relay is in the open state to ensure that the output of the inverter unit is not directly connected to the AC grid or an external load. Under this no-load condition, the control inverter unit applies an AC voltage test signal with a preset frequency and / or a preset voltage value to its output to detect whether the inverter unit meets the grid connection requirements and its subsequent grid connection stability.

[0029] Simultaneously, the control unit keeps the maximum power point tracking module (MPPT controller) operational to continuously adjust the DC output of the photovoltaic modules for maximum power point tracking and to supply the tracked DC power to the DC bus (Vbus). On the DC bus, the voltage is collected in real time and used as a basis for determining whether the photovoltaic hybrid inverter is in a low-light condition. Specifically, the preset frequency and preset voltage values ​​can be 540Hz and 230V.

[0030] Among them, the AC voltage test signal refers to the simulated grid-connected signal actively generated by the inverter unit when it is not connected to the grid. Its frequency can be set to 540 Hz. The above signal is used to simulate grid-connected conditions, so that the photovoltaic hybrid inverter can maintain operation and detection under no-load conditions.

[0031] 102. Based on the first voltage of the DC bus and the preset voltage threshold, determine whether the photovoltaic hybrid inverter is in a low light state.

[0032] In this embodiment of the invention, the control device samples the voltage of the DC bus and uses this sampled voltage as the first voltage for state determination. To avoid the influence of transient fluctuations on the determination result, preferably, the first voltage can be filtered, for example, by using a low-pass filter or a moving average algorithm to obtain a smooth bus voltage value. The aforementioned DC bus voltage acquisition can be performed after a 3-second delay.

[0033] Subsequently, the control device compares the first voltage with a preset voltage threshold value: when the first voltage continuously exceeds or equals the voltage threshold value within a preset detection duration, it is determined that the photovoltaic hybrid inverter is not in a weak light state; when the first voltage continuously falls below the voltage threshold value within the preset detection duration, it is determined that the photovoltaic hybrid inverter is in a weak light state. The voltage threshold value can be set to 400-420v. Generally, the starting voltage of the MPPT is 450v, and the bus voltage after the voltage is boosted by the MPPT is about 420v.

[0034] Further, to avoid frequent switching near the voltage threshold value, preferably, a hysteresis interval can be set on the basis of the voltage threshold value, that is, the condition that the first voltage is lower than the voltage threshold value is used when entering the weak light state, and the condition that the first voltage is higher than the voltage threshold value plus a hysteresis offset value is used when the weak light state is removed, thereby improving the stability of the judgment.

[0035] In another possible implementation, the voltage change rate and the bus power maintaining capability can also be combined for comprehensive judgment. For example, when the DC bus voltage decreases at a rate exceeding a preset rate threshold value, or the bus power is insufficient to maintain the no-load loss of the inverter unit, it can also be used as an auxiliary criterion to determine that the photovoltaic hybrid inverter enters a weak light state. Through the above-mentioned manner, the weak light running state of the photovoltaic hybrid inverter can be accurately recognized in the case of unstable light such as overcast days or cloudy days, and frequent start-stop and excessive action of the AC side relay caused by misjudgment can be avoided.

[0036] 103、When the photovoltaic hybrid inverter is in a weak light state, the AC side relay is kept open.

[0037] In the embodiment of the application, the control device sets the AC side relay to an open state and keeps the state. To avoid frequent attraction and opening caused by short-time fluctuations of light, the control device freezes the grid-connected permission signal and prohibits the attraction instruction from being issued to the relay until the subsequent criterion for removing the weak light is met. Preferably, while the relay is kept open, only the "weak light running state" is marked, instead of the fault shutdown state, so as to avoid mis-triggering of the alarm and affecting the user experience; if necessary, the state code and the time stamp can be recorded for operation and maintenance tracing.

[0038] 104、After a preset delay time, the AC voltage test signal is applied to the output end of the inverter unit again, and the maximum power point tracking module is kept working, so as to re-judge whether the photovoltaic hybrid inverter is in a weak light state, and when the photovoltaic hybrid inverter is not in a weak light state, the attraction instruction is issued to the AC side relay to control the inverter unit to run in a grid-connected mode.

[0039] In the embodiment of the present application, when the photovoltaic hybrid inverter is determined to be in the weak light state, the control device starts a delay timer while keeping the AC side relay open. After a preset delay time, the control device re-triggers the detection process: the control device applies an AC voltage test signal of a preset frequency and / or a preset voltage value to the output end of the inverter unit under no-load conditions, while maintaining the maximum power point tracking module to continue to operate, to ensure that the DC bus can be maintained at a measurable voltage level.

[0040] Subsequently, the control device re-determines whether the photovoltaic hybrid inverter is still in the weak light state based on the voltage of the DC bus at this time and the preset voltage threshold. If it is determined that it is still in the weak light state, no attraction command is issued to the AC side relay, and the weak light count is updated, and the next round of delay detection is entered, to ensure that the detection process is periodic and progressive. If it is determined that the photovoltaic hybrid inverter is no longer in the weak light state, the control device immediately issues an attraction command to the AC side relay to make the inverter unit access to the AC power grid, thereby realizing normal grid-connected operation.

[0041] Through the above control strategy, frequent grid connection and disconnection caused by short-term light fluctuation of photovoltaic under conditions such as overcast and dusk can be effectively avoided, thereby reducing the mechanical action frequency of the AC side relay, prolonging the service life of the relay, and further improving the operation stability and overall reliability of the photovoltaic hybrid inverter in weak light environment.

[0042] In the embodiment of the present application, the inverter unit is controlled to apply an AC voltage test signal of a preset frequency and / or a preset voltage value to the output end of the inverter unit under no-load conditions, and the maximum power point tracking module is maintained to work to provide power to the DC bus; whether the photovoltaic hybrid inverter is in a weak light state is determined based on a first voltage of the DC bus and a preset voltage threshold; when the photovoltaic hybrid inverter is in a weak light state, the AC side relay is kept open; after a preset delay time, the AC voltage test signal is re-applied to the output end of the inverter unit, and the maximum power point tracking module is maintained to work to re-determine whether the photovoltaic hybrid inverter is in a weak light state, and when the photovoltaic hybrid inverter is not in a weak light state, an attraction command is issued to the AC side relay to control the inverter unit to operate in grid-connected mode. By applying an AC voltage test signal to detect a weak light state and adjusting the relay action time by a preset delay time, frequent triggering of the relay attraction under insufficient light is avoided, mechanical wear of the relay is reduced, and the service life of the equipment is prolonged and the operation stability of the system is improved.

[0043] Optionally, the photovoltaic hybrid inverter further comprises a photovoltaic input side, before the step of controlling the inverter unit to apply the AC voltage test signal of the preset frequency and / or the preset voltage value to the output end of the inverter unit under the no-load condition, the insulation monitoring can also be performed when the DC voltage of the photovoltaic input side reaches the preset maximum power point tracking starting voltage; when the insulation monitoring passes, the maximum power point tracking module is controlled to work to raise the voltage of the DC bus to the target bus voltage, and the inverter unit is controlled to apply the AC voltage test signal of the preset frequency and / or the preset voltage value to the output end of the inverter unit under the no-load condition while maintaining the maximum power point tracking module working; when the insulation monitoring fails, the operation of the photovoltaic hybrid inverter is stopped and a fault alarm is output.

[0044] In the embodiment of the application, the maximum power point tracking starting voltage refers to a critical value of the DC voltage of the photovoltaic input side that can trigger the maximum power point tracking module to work, and specifically, the DC voltage of the photovoltaic input side can be detected in real time by using a voltage sensor, and when the detection value exceeds a preset threshold, the insulation monitoring process is triggered.

[0045] The insulation monitoring refers to detecting the insulation resistance between the photovoltaic input side and the ground, and specifically, the insulation monitoring can be realized by injecting a low-frequency AC signal and measuring the leakage current, and is used to determine whether there is an insulation fault. The target bus voltage can be specifically 420v.

[0046] Specifically, after the DC voltage of the photovoltaic input side reaches the maximum power point tracking starting voltage, the insulation monitoring is first performed. If the insulation monitoring passes, the maximum power point tracking module is started to raise the DC bus voltage to the target value, and then the inverter unit applies the AC voltage test signal to perform the weak light state judgment; if the insulation monitoring fails, the operation is immediately stopped and an alarm signal is output. The process ensures that the insulation fault risk is ruled out before entering the grid preparation stage.

[0047] Through the above technical solution, the application can identify insulation abnormalities in advance during the starting stage of the photovoltaic hybrid inverter, prevent the inverter unit from outputting abnormal voltage to cause the relay to repeatedly attract or open under the insulation fault condition, thereby reducing the mechanical wear of the relay and improving the operation reliability.

[0048] Optionally, before the step of controlling the inverter unit to apply the AC voltage test signal of the preset frequency and / or the preset voltage value to the output end of the inverter unit under the no-load condition, it can also be detected whether the AC side relay is connected with the AC power grid; if the AC power grid is connected, the inverter unit is controlled to apply the AC voltage test signal of the preset frequency and / or the preset voltage value to the output end of the inverter unit under the no-load condition.

[0049] In the embodiment of the present application, detecting whether the AC side relay is connected with the AC power grid refers to obtaining the power grid connection state through a voltage sensor or a communication module, and specifically, a voltage sampling circuit can be used to monitor the AC side voltage amplitude in real time, and when it is detected that the voltage amplitude is within a preset power grid voltage range, it is determined that the connection is valid. This step is used to avoid false triggering of the test signal in the state of no power grid access, and to ensure the effectiveness of the subsequent test action.

[0050] Specifically, in the starting phase of the photovoltaic hybrid inverter, first, the voltage sampling circuit is used to detect whether there is an effective grid voltage on the AC side. If it is detected that the grid voltage is within a normal range, for example, the voltage effective value is between 210V and 230V, the inverter unit is started to generate a no-load test signal. At this time, the output end of the inverter unit is in a non-grid-connected state with the grid, but the test signal is synchronized with the grid voltage to avoid generating an impact current. If no effective grid voltage is detected, the test signal is prohibited from being generated to prevent invalid test actions in the state of power grid disconnection.

[0051] Optionally, in the step of reapplying the AC voltage test signal to the output end of the inverter unit and maintaining the operation of the maximum power point tracking module after a preset delay time, when the photovoltaic hybrid inverter is in the weak light state, the number of times of weak light in the weak light state can also be updated; according to the number of times of weak light, a corresponding delay time is selected in a preset time sequence; when the delay time is reached, the AC voltage test signal is re-applied to the output end of the inverter unit, and the maximum power point tracking module is maintained to re-determine whether the photovoltaic hybrid inverter is in the weak light state; until the photovoltaic hybrid inverter is not in the weak light state, the number of times of weak light is reset to zero.

[0052] In the embodiment of the present application, the number of times of weak light refers to the cumulative number of times that the photovoltaic hybrid inverter is continuously determined to be in the weak light state, which can be realized by a counter module to quantify the duration of the weak light state.

[0053] The preset time sequence refers to a set of multiple delay time values associated with the number of times of weak light, which can be stored in the form of an array or a table, for example, the first weak light corresponds to a shorter delay time, and the subsequent weak light corresponds to gradually increasing delay times. Specifically, the multiple delay time values can be calculated according to a fixed time and the number of times of weak light, for example, the fixed time is 15, and the number of times of weak light is multiplied by the fixed time to obtain the multiple delay time values.

[0054] Resetting the number of times of weak light to zero refers to resetting the counter to zero when the weak light state is removed, which can be realized by triggering a reset signal to start the accumulation of the number of times of weak light again.

[0055] Specifically, in the weak light state, the weak light times are recorded each time the weak light is detected. The preset time sequence stores the delay time corresponding to different weak light times, for example, the delay time is 5 minutes for the first weak light, 10 minutes for the second weak light, and so on. When the selected delay time is reached, the inverter unit applies the alternating voltage test signal again, while maintaining the maximum power point tracking module to detect whether the DC bus voltage is restored. If it is still in the weak light state, the above process is repeated and the delay time is continued to be extended; if the weak light state is removed, the weak light times are reset to zero and the relay is allowed to be attracted. By dynamically adjusting the delay time, the invalid operation caused by fixed interval detection is avoided.

[0056] Through the above technical solution, the application can dynamically adjust the re-detection interval according to the duration of the weak light state, reduce unnecessary detection operations when the weak light condition lasts, thereby reducing the triggering frequency of the relay attraction instruction, prolonging the service life of the relay, and ensuring timely restoration and grid operation after the weak light state is removed.

[0057] More specifically, in the case of current weak light detection failure (i.e. the photovoltaic hybrid inverter is in a weak light state), the count = 1, and the start is performed after 15 minutes. If it fails again, the weak light detection failure count = 2, and the weak light detection is performed again after 2*15 minutes. It can be understood that increasing the detection time can avoid the inverter frequently starting and stopping, thereby avoiding the user mistakenly thinking that there is a fault. At the same time, if it is in a cloudy weather, a long enough time is reserved to re-determine whether the cloud is dissipated.

[0058] Optionally, the control method of the photovoltaic hybrid inverter can also increase the maximum power point tracking module start voltage when the weak light times reach a preset number threshold, and apply an alternating voltage test signal to the output end of the inverter unit again when the re-detection time is reached, and maintain the maximum power point tracking module working at the increased start voltage to obtain a second voltage of the DC bus. Based on the second voltage and the preset voltage threshold, the photovoltaic hybrid inverter is re-judged whether it is in a weak light state. Until the photovoltaic hybrid inverter is not in a weak light state, the weak light times are reset to zero.

[0059] In the embodiment of the application, the preset number threshold refers to the upper limit value of the weak light number preset in advance, which can be implemented by a fixed value or a dynamic adjustment logic, and is used to trigger the start voltage adjustment mechanism. The maximum power point tracking module start voltage refers to the minimum working threshold of the photovoltaic input side DC voltage, which can be implemented by adjusting the boost parameter of the BOOST circuit, and is used to control the energy input condition. The second voltage refers to the voltage value obtained by the DC bus after the start voltage is increased, which can be implemented by collecting the voltage sensor, and is used to update the weak light state judgment basis.

[0060] For example, after the failure count is greater than 4 (i.e. weak light times), the DSP (i.e. control device) increases the MPPT starting point (i.e. maximum power point tracking module starting voltage) by 10V, and then re-performs weak light detection after 30 minutes, and the subsequent MPPT starting point voltage is no longer increased.

[0061] It can be understood that when it is detected that the photovoltaic hybrid inverter is continuously in a weak light state, the starting voltage of the maximum power point tracking module can be moderately increased under certain conditions, for example, by 10V. The technical intention of this is that moderately increasing the starting voltage means that the light intensity needs to be further increased when the next starting detection is performed, that is, the cloudy weather can be improved or dissipated. Through this strategy, the probability of frequent starting and stopping of the inverter unit under insufficient light conditions can be significantly reduced, the service life of the relay is prolonged, and the stability of operation is improved.

[0062] However, the increase of the starting voltage should have a reasonable upper limit. If the increase is too large, or is continuously accumulated in multiple weak light detections, the following adverse situations can occur: when the weather gradually improves and has a certain power generation capacity, the inverter cannot enter the working state in time due to the excessively high starting voltage, so that the energy storage inverter cannot be started normally, part of the power generation capacity is wasted, and the power generation income is directly affected. Therefore, in the implementation process of the present application, the increase amplitude of the starting voltage is moderately ensured through dynamic detection and strategy control, which can reduce the risk of frequent starting and stopping, and ensure that the inverter can be started in time when the light improves, so as to balance the service life and economic benefit of the entire system of the photovoltaic hybrid inverter.

[0063] Optionally, before the step of keeping the AC side relay disconnected and updating the weak light times in the weak light state, it can also be judged whether the inverter unit is connected with an energy storage battery; when the inverter unit is not connected with an energy storage battery and the photovoltaic hybrid inverter is in a weak light state, the AC side relay is kept disconnected and the weak light times in the weak light state are updated.

[0064] In the embodiment of the present application, judging whether the inverter unit is connected with an energy storage battery means that whether the energy storage battery is connected to the DC side of the inverter unit is identified through a voltage detection circuit or a communication interface, which can be realized by voltage threshold comparison or digital communication protocol, and is used to determine whether the entire system of the photovoltaic hybrid inverter has energy storage support capability.

[0065] Specifically, the control device can detect whether the inverter unit is connected to an energy storage battery. When the detection result indicates that the inverter unit is not connected to an energy storage battery and the photovoltaic hybrid inverter is in a low-light state, the AC side relay will remain in the open state, and the number of low-light cycles will be updated. In this way, the blind engagement of the AC side relay without the support of an energy storage battery can be avoided, thereby improving the overall operational safety and stability of the photovoltaic hybrid inverter system in low-light environments.

[0066] When a storage battery is connected, the control device can choose to maintain the normal operation of the inverter unit and DC bus based on the auxiliary power provided by the storage battery, and activate the AC-side relay, thereby offsetting the impact of insufficient photovoltaic energy under low light conditions to a certain extent. Alternatively, it can choose to keep the AC-side relay open and update the number of times it is in low light condition, which can be set according to actual needs and is not limited here.

[0067] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0068] In one embodiment, a control device for a photovoltaic hybrid inverter is provided, which corresponds one-to-one with the control method for the photovoltaic hybrid inverter described in the above embodiments. For example... Figure 3 As shown, the control device for this photovoltaic hybrid inverter includes a first control module 301, a first judgment module 302, a first holding module 303, and a first engagement module 304. Detailed descriptions of each functional module are as follows: The first control module 301 is used to control the inverter unit to apply an AC voltage test signal with a preset frequency and / or preset voltage value to the output terminal of the inverter unit under no-load conditions, and to maintain the operation of the maximum power point tracking module to provide power to the DC bus. The first judgment module 302 is used to determine whether the photovoltaic hybrid inverter is in a low light state based on the first voltage of the DC bus and a preset voltage threshold. The first holding module 303 is used to keep the AC side relay disconnected when the photovoltaic hybrid inverter is in a low light state; The first engagement module 304 is used to reapply the AC voltage test signal to the output terminal of the inverter unit after a preset delay time, and maintain the operation of the maximum power point tracking module to re-determine whether the photovoltaic hybrid inverter is in a low light state. When the photovoltaic hybrid inverter is no longer in a low light state, it sends an engagement command to the AC side relay to control the inverter unit to operate in grid connection.

[0069] Optionally, the photovoltaic hybrid inverter further comprises a photovoltaic input side, and the device further comprises: an insulation detection module configured to perform insulation monitoring when a direct current voltage of the photovoltaic input side reaches a preset maximum power point tracking starting voltage; a second control module configured to control the maximum power point tracking module to work to raise the voltage of the direct current bus to a target bus voltage and control the inverter unit to apply an alternating current voltage test signal of a preset frequency and / or a preset voltage value to the output end of the inverter unit under no-load conditions while maintaining the maximum power point tracking module working when the insulation monitoring passes; stop the operation of the photovoltaic hybrid inverter and output a fault alarm when the insulation monitoring fails.

[0070] Optionally, the device further comprises: a first detection module configured to detect whether the alternating current side relay is connected with an alternating current grid; a first application module configured to control the inverter unit to apply an alternating current voltage test signal of a preset frequency and / or a preset voltage value to the output end of the inverter unit under no-load conditions if the alternating current grid is connected.

[0071] Optionally, the first attraction module 304 is further configured to: update a weak light number of the photovoltaic hybrid inverter when the photovoltaic hybrid inverter is in a weak light state; select a corresponding delay time in a preset time sequence according to the weak light number; re-apply the alternating current voltage test signal to the output end of the inverter unit and maintain the maximum power point tracking module working to re-determine whether the photovoltaic hybrid inverter is in the weak light state when the delay time is reached; zero the weak light number until the photovoltaic hybrid inverter is not in the weak light state.

[0072] Optionally, the first attraction module 304 is further configured to: increase the maximum power point tracking module starting voltage when the weak light number reaches a preset number threshold, re-apply the alternating current voltage test signal to the output end of the inverter unit and maintain the maximum power point tracking module working at the increased starting voltage to obtain a second voltage of the direct current bus when the re-detection time is reached; re-determine whether the photovoltaic hybrid inverter is in the weak light state based on the second voltage and the preset voltage threshold; zero the weak light number until the photovoltaic hybrid inverter is not in the weak light state.

[0073] Optionally, the apparatus further comprises: a second judging module, configured to judge whether the inverter unit is connected with the energy storage battery; a second keeping module, configured to keep the AC side relay disconnected and update the weak light times in the weak light state when the inverter unit is not connected with the energy storage battery and the photovoltaic hybrid inverter is in the weak light state.

[0074] The specific limitation of the control apparatus of the photovoltaic hybrid inverter can refer to the limitation of the control method of the photovoltaic hybrid inverter in the above, which will not be repeated here. Each module in the control apparatus of the photovoltaic hybrid inverter can be realized by software, hardware and combination thereof in whole or in part. Each module can be embedded in or independent of the processor in the computer device in hardware form, or can be stored in the memory in the computer device in software form, so as to be called and executed by the processor to perform the operation corresponding to each module.

[0075] In an embodiment, a computer device is provided, which can be a terminal device, and an internal structure diagram thereof can be as shown in Figure 4 The computer device includes a processor, a memory and a network interface connected through a system bus. The processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device includes a readable storage medium. The readable storage medium stores computer readable instructions. The network interface of the computer device is configured to communicate with an external terminal through a network connection. The computer readable instructions are executed by the processor to implement a control method of a photovoltaic hybrid inverter. The readable storage medium provided in the embodiment includes a non-volatile readable storage medium and a volatile readable storage medium.

[0076] In the embodiment of the present application, a computer device is provided, which includes a memory, a processor and computer readable instructions stored in the memory and executable on the processor. When the processor executes the computer readable instructions, the steps of the control method of the photovoltaic hybrid inverter are implemented.

[0077] In the embodiment of the present application, a readable storage medium is provided, which stores computer readable instructions. When the computer readable instructions are executed by the processor, the steps of the control method of the photovoltaic hybrid inverter are implemented.

[0078] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing relevant hardware through computer readable instructions, and the computer readable instructions can be stored in a non-volatile readable storage medium or a volatile readable storage medium. When the computer readable instructions are executed, the processes of the above-mentioned embodiments of the methods can be included. Any reference to memory, storage, database or other medium used in the embodiments provided in the present application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration but not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0079] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the above-mentioned division of functional units and modules is exemplified, and in actual application, the above-mentioned functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above.

[0080] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A control method of a photovoltaic hybrid inverter, characterized by, The photovoltaic hybrid inverter comprises a DC bus, an AC side relay, an inverter unit and a maximum power point tracking module, and the method comprises: controlling the inverter unit to apply an AC voltage test signal of a preset frequency and / or a preset voltage value to an output end of the inverter unit under a no-load condition and maintaining the maximum power point tracking module to work to provide electric energy to the DC bus; judging whether the photovoltaic hybrid inverter is in a weak light state based on a first voltage of the DC bus and a preset voltage threshold value; when the photovoltaic hybrid inverter is in the weak light state, keeping the AC side relay open; after a preset delay time, reapplying the AC voltage test signal to the output end of the inverter unit and maintaining the maximum power point tracking module to work to rejudge whether the photovoltaic hybrid inverter is in the weak light state, and when the photovoltaic hybrid inverter is not in the weak light state, issuing a suction command to the AC side relay to control the inverter unit to operate in a grid-connected mode.

2. The control method of a hybrid photovoltaic inverter according to claim 1, wherein, The photovoltaic hybrid inverter further comprises a photovoltaic input side, and before the controlling the inverter unit to apply the AC voltage test signal of the preset frequency and / or the preset voltage value to the output end of the inverter unit under the no-load condition, the method further comprises: when a DC voltage of the photovoltaic input side reaches a preset maximum power point tracking starting voltage, performing insulation monitoring; when the insulation monitoring passes, controlling the maximum power point tracking module to work to raise the voltage of the DC bus to a target bus voltage and controlling the inverter unit to apply the AC voltage test signal of the preset frequency and / or the preset voltage value to the output end of the inverter unit under the no-load condition while maintaining the maximum power point tracking module to work; when the insulation monitoring fails, stopping the operation of the photovoltaic hybrid inverter and outputting a fault alarm.

3. The control method of a hybrid photovoltaic inverter according to claim 2, wherein Before the controlling the inverter unit to apply the AC voltage test signal of the preset frequency and / or the preset voltage value to the output end of the inverter unit under the no-load condition, the method further comprises: detecting whether the AC side relay is connected with an AC power grid; if the AC side relay is connected with the AC power grid, controlling the inverter unit to apply the AC voltage test signal of the preset frequency and / or the preset voltage value to the output end of the inverter unit under the no-load condition.

4. The control method of a hybrid photovoltaic inverter according to any one of claims 1 to 3, characterized in that, The reapplying the AC voltage test signal to the output end of the inverter unit and maintaining the maximum power point tracking module to work to rejudge whether the photovoltaic hybrid inverter is in the weak light state after the preset delay time comprises: when the photovoltaic hybrid inverter is in the weak light state, updating a weak light number of times in the weak light state; selecting a corresponding delay time in a preset time sequence according to the weak light number of times; when the delay time is reached, reapplying the AC voltage test signal to the output end of the inverter unit and maintaining the maximum power point tracking module to work to rejudge whether the photovoltaic hybrid inverter is in the weak light state; and when the photovoltaic hybrid inverter is not in the weak light state, resetting the weak light number of times.

5. The control method of a hybrid photovoltaic inverter according to claim 4, wherein The method further comprises: When the weak light times reaches a preset times threshold, the maximum power point tracking module startup voltage is increased, and when the re-detection time is reached, the AC voltage test signal is re-applied to the output end of the inverter unit, and the maximum power point tracking module is maintained to work at the increased startup voltage to obtain a second voltage of the DC bus; Based on the second voltage and the preset voltage threshold, it is re-judged whether the photovoltaic hybrid inverter is in a weak light state; Until the photovoltaic hybrid inverter is not in the weak light state, the weak light times is reset to zero.

6. The control method of a hybrid photovoltaic inverter according to claim 4, wherein Before the AC side relay is kept off and the weak light times in the weak light state is updated, it further includes: It is judged whether the inverter unit is connected with an energy storage battery; When the inverter unit is not connected with the energy storage battery and the photovoltaic hybrid inverter is in the weak light state, the AC side relay is kept off and the weak light times in the weak light state is updated.

7. A hybrid photovoltaic inverter, characterized by It includes: A photovoltaic input side for receiving DC power output by a photovoltaic module; A maximum power point tracking module connected with the photovoltaic input side, for performing maximum power point tracking control on the DC power and providing output DC power to a DC bus; A DC bus connected with the maximum power point tracking module and an inverter unit, for transmitting DC power; An inverter unit connected with the DC bus, for inverting DC power into AC power; An AC side relay connected with an AC output end of the inverter unit and an AC power grid, for controlling connection and disconnection between the inverter unit and the AC power grid; A control device for performing the control method of the photovoltaic hybrid inverter according to any one of claims 1 to 6.

8. A control device of a photovoltaic hybrid inverter, characterized by, The photovoltaic hybrid inverter includes a DC bus, an AC side relay, an inverter unit and a maximum power point tracking module, and the device includes: A first control module for controlling the inverter unit to apply an AC voltage test signal with a preset frequency and / or a preset voltage value to the output end of the inverter unit under no-load conditions, and maintaining the maximum power point tracking module to work to provide power to the DC bus; A first judgment module for judging whether the photovoltaic hybrid inverter is in a weak light state based on a first voltage of the DC bus and a preset voltage threshold; A first keeping module for keeping the AC side relay off when the photovoltaic hybrid inverter is in the weak light state; A first attraction module for re-applying the AC voltage test signal to the output end of the inverter unit after a preset delay time, and maintaining the maximum power point tracking module to work to re-judge whether the photovoltaic hybrid inverter is in the weak light state, and when the photovoltaic hybrid inverter is not in the weak light state, issuing an attraction instruction to the AC side relay to control the inverter unit to operate in grid-connected mode. 9.A computer device, comprising a memory, a processor, and computer readable instructions stored on the memory and running on the processor, wherein, The processor executes the computer readable instructions to implement the control method of the photovoltaic hybrid inverter according to any one of claims 1 to 6.

10. A readable storage medium, having stored thereon computer readable instructions, characterized in that, The computer readable instructions are executed by the processor to implement the control method of the photovoltaic hybrid inverter according to any one of claims 1 to 6.

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