Inverter system and control method and device of inverter system

Abstract

The invention discloses an inverter system and a control method and device of the inverter system, and belongs to the field of inverter systems. The inverter system comprises a DC-to-AC circuit, wherein a phase relay is arranged on a phase line connected with the DC-to-AC circuit; the first capacitor and the second capacitor are connected in series between the positive bus and the negative bus of the inverter system; the first switch module comprises a first end and a second end, and the first end is connected to the inverter side ground through a current-limiting resistor in the inverter night repair circuit; the second end is connected with a neutral point between the first capacitor and the second capacitor; the first switch module is set to be switched to a first working mode before grid connection of the inverter system, so that the first end and the second end are conducted, and common-mode rejection is carried out on the inverter system. According to the inverter system, the night repair circuit and the current-limiting resistor thereof can be reused to realize common-mode rejection of the inverter system, so that the common-mode rejection cost is saved, and the safety of common-mode rejection of the inverter system is improved.

Description

Technical Field

[0001] The present application belongs to the field of inverter systems, and in particular, relates to an inverter system and a control method and device for the inverter system. Background Art

[0002] A photovoltaic grid-connected inverter is a power electronic device that can convert the energy in photovoltaic modules and transmit it to the power grid. The inverter has a DC / AC converter (DC / AC) inside, and an AC filter is connected to its AC output terminal. After filtering, it is connected to the power grid through switches such as relays, and energy conversion is achieved after the relay is energized. Before the AC relay is energized, the output waveform will be synchronized with the grid voltage to avoid differential mode current between the output and grid voltage, but this measure can only reduce differential mode impact current. There is a common mode voltage difference between the inverter system and the ground and the grid, resulting in a common mode impact current when the relay is energized. This common mode impact may interfere with the sampling control and other links of the inverter, making the system unable to operate normally. Summary of the invention

[0003] The present application aims to solve at least one of the technical problems existing in the related art. To this end, the present application proposes an inverter system and a control method and device for the inverter system, which can realize the reuse of the night repair circuit and the current limiting resistor of the night repair circuit, save the common mode suppression cost on the basis of realizing the common mode suppression of the inverter system, improve the safety of the common mode suppression of the inverter system, and thus improve the safety and stability of the inverter system.

[0004] In a first aspect, the present application provides an inverter system, comprising:

[0005] A DC-to-AC circuit, wherein a phase relay is provided on a phase line connected to the DC-to-AC circuit;

[0006] A first capacitor and a second capacitor connected in series between the positive and negative busbars of the inverter system;

[0007] A first switch module, the first switch module comprising a first end and a second end, the first end being connected to the inverter side ground via a current limiting resistor in the inverter nighttime repair circuit; the second end being connected to a neutral point between the first capacitor and the second capacitor;

[0008] The first switch module is configured to switch to a first working mode before the inverter system is connected to the grid, so that the first end and the second end are connected to each other, so as to perform common-mode suppression on the inverter system.

[0009] According to the inverter system of the present application, the inverter system includes a DC-to-AC circuit, a first capacitor and a second capacitor connected in series between the positive and negative busbars of the inverter system, and a first switch module whose first end is connected to the inverter side ground via a current limiting resistor in the inverter night repair circuit and whose second end is connected to the neutral point between the first capacitor and the second capacitor. The night repair circuit and the current limiting resistor of the night repair circuit can be reused. On the basis of realizing common-mode suppression of the inverter system, there is no need to introduce additional components, optimize the circuit structure, reduce the space occupied by the circuit, save the cost of common-mode suppression, and improve the safety of common-mode suppression of the inverter system, thereby improving the safety and stability of the inverter system.

[0010] According to an embodiment of the present application, when the first switch module is switched to the first working mode and the actual voltage across the current limiting resistor is less than a target threshold, the inverter system is switched to grid-connected operation.

[0011] According to one embodiment of the present application, the inverter nighttime repair circuit includes a diode connected in series with the current limiting resistor, and the current limiting resistor is close to the anode side of the diode, and the first end is connected between the anode of the diode and the current limiting resistor.

[0012] According to one embodiment of the present application, the inverter night repair circuit includes a diode connected in series with the current limiting resistor, and the current limiting resistor is close to the anode side of the diode, and when the common-mode voltage difference between the neutral point and the inverter side ground is negative, the first end is connected to the cathode of the diode.

[0013] According to one embodiment of the present application, the first switch module includes a single-pole double-throw switch, and the third end included in the single-pole double-throw switch is connected to the other side of the DC-to-AC circuit; when the first end is conductive with the second end, the first end is disconnected from the third end.

[0014] According to one embodiment of the present application, the first switch module includes a single-pole single-throw switch, and when the single-pole single-throw switch is closed, the single-pole single-throw switch enters the first working mode.

[0015] According to one embodiment of the present application, it further includes a neutral line, one end of which is connected to the neutral point, and a neutral line relay is arranged on the neutral line.

[0016] In a second aspect, the present application provides a grid-connected control method of an inverter system, which is applied to the inverter system as described in the first aspect, and the method includes:

[0017] Before controlling the inverter system to be connected to the grid, controlling the first switch module to enter the first working mode so that the first end is connected to the second end;

[0018] When the actual voltage across the current limiting resistor is less than the target threshold, the inverter system is controlled to be connected to the grid.

[0019] According to the control method of the inverter system of the present application, before controlling the inverter system to be connected to the grid, the first switch module is controlled to enter the first working mode to make the first end and the second end conductive, and when the actual voltage across the current limiting resistor is less than the target threshold, the inverter system is controlled to be connected to the grid. This can be achieved based on the reuse of the nighttime repair circuit and the current limiting resistor of the nighttime repair circuit, thereby suppressing the common-mode voltage difference of the neutral point before the inverter system is connected to the grid without introducing additional components, optimizing the circuit structure, reducing the space occupied by the circuit, saving the common-mode suppression cost, and improving the safety of common-mode suppression of the inverter system, thereby improving the safety and stability of the inverter system.

[0020] According to an embodiment of the present application, the target threshold is determined based on a leakage current of the inverter system.

[0021] According to an embodiment of the present application, before controlling the first switch module to enter the first working mode, the method further includes:

[0022] The output voltage of the inverter system is controlled to be phase-locked and synchronized with the grid voltage.

[0023] In a third aspect, the present application provides a grid-connected control device for an inverter system, which is applied to the inverter system as described in the first aspect, and the device includes:

[0024] A first processing module, used for controlling the first switch module to enter the first working mode before controlling the inverter system to be connected to the grid, so that the first end is connected to the second end;

[0025] The second processing module is used to control the inverter system to be connected to the grid when the actual voltage across the current limiting resistor is less than a target threshold.

[0026] According to the grid-connected control device of the inverter system of the present application, before controlling the inverter system to be connected to the grid, the first switch module is controlled to enter the first working mode to make the first end and the second end conductive, and when the actual voltage across the current limiting resistor is less than the target threshold, the inverter system is controlled to be connected to the grid. This can be achieved based on the reuse of the nighttime repair circuit and the current limiting resistor of the nighttime repair circuit, thereby suppressing the common-mode voltage difference of the neutral point before the inverter system is connected to the grid without introducing additional components, optimizing the circuit structure, reducing the space occupied by the circuit, saving the common-mode suppression cost, and improving the safety of common-mode suppression of the inverter system, thereby improving the safety and stability of the inverter system.

[0027] In a fourth aspect, the present application provides a non-transitory computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the grid-connected control method of the inverter system as described in the first aspect above is implemented.

[0028] In a fifth aspect, the present application provides a computer program product, including a computer program, which, when executed by a processor, implements the grid-connected control method of the inverter system as described in the first aspect above.

[0029] The above one or more technical solutions in the embodiments of the present application have at least one of the following technical effects:

[0030] By providing an inverter system including a DC-to-AC circuit, a first capacitor and a second capacitor connected in series between the positive and negative busbars of the inverter system, and a first switch module whose first end is connected to the inverter side ground via a current limiting resistor in the inverter night repair circuit and whose second end is connected to the neutral point between the first capacitor and the second capacitor, it is possible to reuse the night repair circuit and the current limiting resistor of the night repair circuit. On the basis of achieving common-mode suppression of the inverter system, there is no need to introduce additional components, optimize the circuit structure, reduce the space occupied by the circuit, save the cost of common-mode suppression, and improve the safety of common-mode suppression of the inverter system, thereby improving the safety and stability of the inverter system.

[0031] Furthermore, when the inverter system also includes a neutral line (N line), one end of the neutral line is connected to the neutral point, and a neutral line relay is provided on the neutral line, the first switch module is set to switch to the first operating mode before the inverter system is connected to the grid, so that the first end and the second end are connected to perform common-mode suppression on the inverter system. This can achieve common-mode suppression of inverter systems of various different structures based on the first switch module, thereby improving the flexibility of common-mode suppression of the inverter system based on the first switch module and the adaptability of the inverter system structure.

[0032] Furthermore, by switching the first switch module to the first operating mode and the actual voltage across the current limiting resistor is less than the target threshold, the inverter system switches to grid-connected operation. When it is judged that the common-mode suppression of the inverter system based on the first switch module is completed based on the actual voltage across the current limiting resistor is less than the target threshold, the inverter system switches to grid-connected operation again, thereby improving the safety and reliability of the common-mode suppression of the inverter system based on the first switch module.

[0033] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0035] Figure 1 It is one of the structural schematic diagrams of the inverter system provided in the embodiment of the present application;

[0036] Figure 2 This is the second structural schematic diagram of the inverter system provided in the embodiment of the present application;

[0037] Figure 3 This is the third structural schematic diagram of the inverter system provided in the embodiment of the present application;

[0038] Figure 4 This is the fourth structural diagram of the inverter system provided in the embodiment of the present application;

[0039] Figure 5 This is the fifth structural diagram of the inverter system provided in the embodiment of the present application;

[0040] Figure 6 This is the sixth structural diagram of the inverter system provided in the embodiment of the present application;

[0041] Figure 7 This is the seventh structural diagram of the inverter system provided in the embodiment of the present application;

[0042] Figure 8 This is the eighth structural diagram of the inverter system provided in the embodiment of the present application;

[0043] Fig. 9 It is one of the flow charts of the control method of the inverter system provided in the embodiment of the present application;

[0044] Fig.10 This is a second flow chart of a control method for an inverter system provided in an embodiment of the present application;

[0045] Fig.11is a structural schematic diagram of a control device of an inverter system provided in an embodiment of the present application;

[0046] Fig.12 It is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present application to clearly describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0048] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0049] An embodiment of the present application provides an inverter system.

[0050] Combine the following Figures 1 to 8 The inverter system provided in the embodiment of the present application is described.

[0051] like Figure 1 As shown, the inverter system includes: a DC to AC circuit DC / AC, a first capacitor C1 and a second capacitor C2 connected in series between the positive and negative busbars of the inverter system, and a first switch module.

[0052] Among them, a phase relay is arranged on the phase line connected to the DC / AC circuit, such as Figure 1 Among them, the first phase relay Sa, the second phase relay Sb and the third phase relay Sc.

[0053] The first switch module includes a first end 110 and a second end 120 .

[0054] The first end 110 is connected to the inverter side ground via a current limiting resistor in the inverter nighttime repair circuit; the second end 120 is connected to the neutral point Vn between the first capacitor C1 and the second capacitor C2.

[0055] The inverter night repair circuit is used to repair the potential induced attenuation (PID effect) of photovoltaic modules. In the actual implementation process, the inverter night repair circuit can repair the PID phenomenon that occurs during the day by applying a reverse voltage during the period when the inverter stops working at night.

[0056] In the actual implementation process, the neutral point Vn can be formed by two capacitors, namely a first capacitor C1 and a second capacitor C2 connected in series on the DC bus. The first capacitor C1 and the second capacitor C2 divide the DC voltage into two halves, and the neutral point Vn is the voltage dividing point between the first capacitor C1 and the second capacitor C2.

[0057] The first switch module is configured to switch to a first working mode before the inverter system is connected to the grid, so that the first end 110 and the second end 120 are connected to each other, so as to perform common-mode suppression on the inverter system.

[0058] The first working mode is to conduct the first terminal 110 and the second terminal 120, that is, the first switch module is closed, so as to perform common-mode suppression on the inverter system.

[0059] Common-mode suppression is the suppression of common-mode impact current generated by the common-mode voltage difference at the neutral point Vn in the inverter system.

[0060] The common mode voltage difference of the neutral point Vn is the voltage difference between the neutral point Vn and the earth.

[0061] The common-mode voltage difference can be positive or negative. If the common-mode voltage difference is positive, the voltage of the neutral point Vn to the ground is positive; if the common-mode voltage difference is negative, the voltage of the neutral point Vn to the ground is negative.

[0062] like Figure 3 As shown, in the actual implementation process, Figure 3 In the figure, V+ and V- are respectively the positive and negative voltages of the DC side bus; the first capacitor C1 and the second capacitor C2 are half-bus capacitors, the first capacitor C1 and the second capacitor C2 are connected to the DC / AC link of the DC / AC converter, and the AC filter on the output side of the DC / AC converter includes: a first inductor L1, a second inductor L2, a third inductor L3, a fifth capacitor C5, a sixth capacitor C6 and a seventh capacitor C7, which are used to filter the output; the first phase relay Sa, the second phase relay Sb and the third phase relay Sc are phase relays, and the relays are connected to the power grid through a leakage current detection circuit (RCD detection). After the first phase relay Sa, the second phase relay Sb and the third phase relay Sc are energized, the inverter can transmit energy.

[0063] Among them, the inverter V+ and V- have a common-mode voltage to the ground, the third capacitor C3 is the equivalent capacitance of V+ to the ground, the fourth capacitor C4 is the equivalent capacitance of V- to the ground, and the eighth capacitor C8 is the equivalent capacitance of the power grid to the ground. These equivalent capacitors are composed of safety capacitors and parasitic capacitors. In actual work, due to the uneven equivalent impedance, there will be a common-mode voltage difference between the neutral point Vn potential and the ground. When any of the above-mentioned AC relays is attracted, there will be a common-mode impact current path.

[0064] For example, at the moment when the first-phase relay Sa is first attracted, the common-mode impact current path will be generated due to the common-mode voltage difference of the neutral point Vn: grid side ground—A phase grid—first phase relay Sa—fifth capacitor C5—neutral point Vn—second capacitor C2—fourth capacitor C4—inverter side ground and grid side ground—A phase grid—first phase relay Sa—fifth capacitor C5—neutral point Vn—first capacitor C1—third capacitor C3—inverter side ground; for another example, at the moment when the second-phase relay Sb is first attracted, the common-mode impact current path is: grid side ground—B phase grid—second phase relay Sb—sixth capacitor C6—neutral point Vn—second capacitor C2—fourth capacitor C4—inverter side ground and grid side ground. Ground—B-phase grid—second-phase relay Sb—sixth capacitor C6—neutral point Vn—first capacitor C1—third capacitor C3—ground on the inverter side; for another example, at the moment when the third-phase relay Sc is first attracted, the common-mode impulse current path is: grid-side ground—C-phase grid—third-phase relay Sc—seventh capacitor C7—neutral point Vn—second capacitor C2—fourth capacitor C4—inverter-side ground and grid-side ground—C-phase grid—third-phase relay Sc—seventh capacitor C7—neutral point Vn—first capacitor C1—third capacitor C3—inverter-side ground; due to the lack of damping in these paths, the instantaneous charging and discharging current of the capacitor is extremely large, resulting in common-mode impulse current, which will affect the normal operation of the inverter.

[0065] like Figure 1 As shown, in the actual implementation process, based on the setting of the first switch module (S1), the first end 110 of the first switch module is connected to the inverter side ground via the current limiting resistor R0 in the inverter night repair circuit (PID power supply), and the second end 120 is connected to the neutral point Vn between the first capacitor C1 and the second capacitor C2. Before the inverter is connected to the grid, that is, before closing the relays (the first phase relay Sa, the second phase relay Sb and the third phase relay Sc), the first end 110 and the second end 120 of the first switch module are turned on. Even if the first switch module is closed, a common-mode impact current path is generated due to the common-mode voltage difference of the neutral point Vn.

[0066] For example, Figure 1As shown, the common-mode impulse current path is: inverter side ground—current limiting resistor R0—neutral point Vn—first capacitor C1—third capacitor C3—inverter side ground and inverter side ground—current limiting resistor R0—neutral point Vn—second capacitor C2—fourth capacitor C4—inverter side ground.

[0067] Among them, due to the existence of a current limiting resistor in the common-mode impact current path, the common-mode impact current is converted into a smaller transient common-mode suppression current.

[0068] In some embodiments, the transient common-mode suppression current may be calculated based on the following formula:

[0069] I0=Vn′ / R0

[0070] Wherein, Vn′ is the common-mode voltage difference between the neutral point and the ground, I0 is the transient common-mode suppression current, and R0 is the current limiting resistor of the inverter nighttime repair circuit.

[0071] In the actual implementation process, the transient common-mode suppression current will decrease exponentially at the moment of generation. When the transient common-mode suppression current drops to the first threshold value, the common-mode voltage difference of the neutral point Vn can be considered to be eliminated or very small, so that the common-mode suppression of the inverter system can be considered to be completed. After that, if any relay is closed, there will be no common-mode impact current or a very small common-mode impact current (which will not affect the normal operation of the inverter system).

[0072] The first threshold value may be 0. When the transient common-mode suppression current drops to the first threshold value, the common-mode voltage difference at the neutral point Vn is considered to be eliminated, that is, the common-mode voltage difference is 0.

[0073] In some embodiments, the attenuation process of the transient common-mode suppression current can be expressed as the following formula:

[0074]

[0075] Where, I(t) is the transient common-mode suppression current, Vn′ is the common-mode voltage difference between the neutral point and the ground, R0 is the current limiting resistor of the inverter night repair circuit, t is time, e is a mathematical constant, and C3 and C4 are the parasitic capacitances of the inverter to the ground.

[0076] like Figure 2 As shown, in some embodiments, the inverter system further includes a neutral line (N line), one end of the neutral line is connected to the neutral point Vn, and a neutral line relay is provided on the neutral line.

[0077] In this embodiment, Figure 2 In the figure, Sn is the neutral line relay.

[0078] During the actual implementation process, at the moment when the neutral line relay Sn is first energized, a common-mode impulse current path will be generated due to the common-mode voltage difference of the neutral point Vn: grid side ground—neutral line relay Sn—neutral point Vn—second capacitor C2—fourth capacitor C4—inverter side ground and grid side ground—neutral line relay Sn—neutral point Vn—first capacitor C1—third capacitor C3—inverter side ground; the remaining common-mode impulse current paths generated at the moment of energizing the first phase relay Sa, the second phase relay Sb and the third phase relay Sc are similar to the case where there is no neutral line in the above-mentioned inverter system, and will not be repeated in this application.

[0079] like Figure 4 As shown, in the case where there is a neutral line (N line) in the inverter system, the first switch module can be set to switch to the first working mode before the inverter system is connected to the grid, and the first end 110 and the second end 120 are turned on to perform common-mode suppression on the inverter system, which is consistent with the case where there is no neutral line in the inverter system.

[0080] According to the inverter system provided in the embodiment of the present application, when the inverter system also includes a neutral line (N line), one end of the neutral line is connected to the neutral point Vn, and a neutral line relay Sn is provided on the neutral line, the first switch module is set to switch to the first working mode before the inverter system is connected to the grid, so that the first end 110 and the second end 120 are connected to perform common-mode suppression on the inverter system, and common-mode suppression of inverter systems of various different structures can be achieved based on the first switch module, thereby improving the flexibility of common-mode suppression of the inverter system based on the first switch module and the adaptability of the inverter system structure.

[0081] It should be noted that, when the common-mode suppression of the inverter system is achieved based on the first switch module, the power supply in the inverter nighttime repair circuit does not work.

[0082] During the research and development process, the inventor discovered that in the related art, when the inverter system includes a neutral line (N line), the common-mode suppression of the inverter system is achieved by adding an N-line inductance or an additional common-mode impact resistance hardware circuit (an anti-common-mode impact relay and an anti-common-mode impact impedance are connected in series and in parallel with the neutral line relay). This method increases additional circuits and costs, and is not suitable for the case where the inverter system does not include a neutral line (N line), so the usage scenarios are limited; or the inverter system voltage to the ground is sampled based on a software method, and the common-mode voltage difference is controlled before being connected to the grid, thereby reducing the common-mode current impact. However, this control method may cause certain devices (such as bus capacitors) to exceed voltage stress, thereby posing a threat to the safety of the inverter system.

[0083] In the present application, an inverter system includes a DC / AC circuit, a phase relay is arranged on the phase line connected to the DC / AC circuit, a first capacitor C1 and a second capacitor C2 are connected in series between the positive and negative busbars of the inverter system, and a first end 110 is connected to the inverter side ground through a current limiting resistor in the inverter night repair circuit, and a second end 120 is connected to the neutral point Vn between the first capacitor C1 and the second capacitor C2. The first switch module is configured to switch to a first working mode before the inverter system is connected to the grid, so that the first end 110 and the second end 120 are turned on to perform common-mode suppression on the inverter system. The inverter system can realize the reuse of the night repair circuit and the current limiting resistor of the night repair circuit. On the basis of realizing common-mode suppression of the inverter system, there is no need to introduce additional components, optimize the circuit structure, reduce the space occupied by the circuit, save the common-mode suppression cost, and improve the safety of common-mode suppression of the inverter system, thereby improving the safety and stability of the inverter system.

[0084] According to the inverter system provided in the embodiment of the present application, the inverter system includes a DC-to-AC circuit DC / AC, a first capacitor C1 and a second capacitor C2 connected in series between the positive and negative busbars of the inverter system, and a first end 110 connected to the inverter side ground via a current limiting resistor in the inverter night repair circuit, and a first switch module connected to the neutral point Vn between the first capacitor C1 and the second capacitor C2 at the second end 120. The night repair circuit and the current limiting resistor R0 of the night repair circuit can be reused. On the basis of realizing common-mode suppression of the inverter system, there is no need to introduce additional components, optimize the circuit structure, reduce the space occupied by the circuit, save the common-mode suppression cost, and improve the safety of common-mode suppression of the inverter system, thereby improving the safety and stability of the inverter system.

[0085] In some embodiments, when the first switch module is switched to the first operating mode and the actual voltage across the current limiting resistor R0 is less than the target threshold, the inverter system is switched to grid-connected operation.

[0086] In this embodiment, the target threshold may be a preset voltage threshold across the current limiting resistor R0.

[0087] The target threshold may be a voltage value across the current limiting resistor R0 when the transient common mode suppression current is at a first threshold.

[0088] During the actual execution, in the first working mode, the above-mentioned transient common-mode suppression current cannot be obtained in real time, and the voltage value across the current limiting resistor R0 also decreases exponentially with the exponential decay of the transient common-mode suppression current. Then, the actual voltage across the current limiting resistor R0 can be obtained in real time to determine whether the actual voltage across the current limiting resistor R0 has dropped to the target threshold, thereby deducing whether the transient common-mode suppression current has dropped to the first threshold. When the actual voltage across the current limiting resistor R0 drops to the target threshold, it is considered that the transient common-mode suppression current has dropped to the first threshold, and then it is considered that the common-mode suppression is completed, and the inverter can be switched to grid-connected operation.

[0089] In some embodiments, the attenuation process of the voltage across the current limiting resistor R0 can be expressed as the following formula:

[0090] V0=Vn'×e^(-t / (R0×(C3+C4)))

[0091] Among them, V0 is the voltage across the current limiting resistor, Vn′ is the common mode voltage difference between the neutral point and the ground, R0 is the current limiting resistor of the inverter night repair circuit, t is time, e is a mathematical constant, and C3 and C4 are the parasitic capacitances of the inverter to the ground.

[0092] According to the inverter system provided in the embodiment of the present application, when the first switch module is switched to the first working mode and the actual voltage across the current limiting resistor R0 is less than the target threshold, the inverter system switches to grid-connected operation. When it is judged that the common-mode suppression of the inverter system based on the first switch module is completed based on the actual voltage across the current limiting resistor R0 is less than the target threshold, the inverter system switches to grid-connected operation again, which can improve the safety and reliability of the common-mode suppression of the inverter system based on the first switch module.

[0093] In some embodiments, the inverter nighttime repair circuit includes a diode connected in series with a current limiting resistor R0 , and the current limiting resistor R0 is close to the anode side of the diode D1 , and the first end 110 is connected between the anode of the diode D1 and the current limiting resistor R0 .

[0094] In this embodiment, if Figure 5 As shown, the inverter night repair circuit (PID) includes a diode D1, a current limiting resistor R0 is connected to the anode side of the diode D1, and a first end 110 of the first switch module (S1) is connected to any node between the current limiting resistor R0 and the anode of the diode D1, so that complete common-mode suppression of the inverter system can be achieved based on the first switch module.

[0095] The complete common-mode suppression of the inverter system can be understood as that, regardless of whether the common-mode voltage difference of the neutral point Vn is positive or negative, the common-mode suppression of the inverter system can be achieved based on the first switch module.

[0096] According to the inverter system provided in the embodiment of the present application, by connecting the first end 110 between the anode of the diode D1 included in the inverter night repair circuit and connected in series with the current limiting resistor R0 and the current limiting resistor R0 on the anode side close to the diode D1, the night repair circuit and the current limiting resistor R0 of the night repair circuit can be reused, thereby achieving common mode suppression of the inverter system.

[0097] In some embodiments, the inverter night repair circuit includes a diode D1 connected in series with a current limiting resistor R0, and the current limiting resistor R0 is close to the anode side of the diode D1. When the common mode voltage difference between the neutral point Vn and the inverter side ground is negative, the first end 110 is connected to the cathode of the diode D1.

[0098] In this embodiment, if Figure 6 As shown, the inverter night repair circuit (PID) includes a diode D1, a current limiting resistor R0 is connected to the anode side of the diode D1, and a first end 110 of the first switch module (S1) is connected to the cathode of the diode D1, so that based on the first switch module, common-mode suppression of the inverter system can be achieved when the common-mode voltage difference of the neutral point Vn is negative.

[0099] According to the inverter system provided in the embodiment of the present application, by connecting the first end 110 to the cathode of the diode D1 included in the inverter night repair circuit and connected in series with the current limiting resistor R0, the night repair circuit and the current limiting resistor R0 of the night repair circuit can be reused, thereby achieving common-mode suppression of the inverter system when the common-mode voltage difference of the neutral point Vn is negative, providing a variety of connection methods between the first switch module and the inverter night repair circuit, and improving the flexibility and applicability of common-mode suppression of the inverter system based on the first switch module.

[0100] In some embodiments, the first switch module includes a single-pole double-throw switch, and the third end included in the single-pole double-throw switch is connected to the other side of the DC-to-AC circuit DC / AC; when the first end 110 and the second end 120 are conductive, the first end 110 is disconnected from the third end.

[0101] like Figure 7 As shown, in this embodiment, when the first switch module includes a single-pole double-throw switch, the connection relationship between the first end 110 of the first switch module and the inverter night repair circuit is: the inverter night repair circuit includes a diode D1 connected in series with a current limiting resistor R0, and the current limiting resistor R0 is close to the anode side of the diode D1, and when the common-mode voltage difference between the neutral point Vn and the inverter side ground is negative, the first end 110 is connected to the cathode of the diode D1.

[0102] In the actual implementation process, Figure 7In the embodiment, the first switch module includes a single-pole double-throw switch (S0), the third end of the single-pole double-throw switch (S0) is connected to the other side of the DC-to-AC circuit DC / AC (DC bus cathode V-), the first end 110 of the single-pole double-throw switch (S0) can be connected to the second end 120 or the third end, when the first end 110 of the single-pole double-throw switch (S0) is connected to the second end 120, the first end 110 and the third end are in a disconnected state, and the inverter system realizes common-mode suppression of the inverter system based on the first switch module when the common-mode voltage difference of the neutral point Vn is negative; when the first end 110 of the single-pole double-throw switch (S0) is connected to the third end, the first end 110 and the second end 120 are in a disconnected state, and nighttime repair of the inverter system can be realized based on the first switch module.

[0103] It should be noted that, when the first switch module includes a single-pole double-throw switch and the nighttime repair of the inverter system is implemented based on the first switch module, the power supply in the inverter nighttime repair circuit works.

[0104] According to the inverter system provided in the embodiment of the present application, through the single-pole double-throw switch included in the first switch module, the third end included in the single-pole double-throw switch is connected to the other side of the DC-to-AC circuit DC / AC, and when the first end 110 and the second end 120 are turned on, the first end 110 is disconnected from the third end, which can realize the reuse of the night repair circuit and the current limiting resistor R0 of the night repair circuit while saving the cost of the first switch module, and can switch between two different connection modes, thereby improving the flexibility of the first switch module, and the single-pole double-throw switch is a working mode of disconnecting one end and connecting the other end, which can reduce the risk of circuit short circuit and improve the safety of the inverter system.

[0105] In some embodiments, the first switch module includes a single-pole single-throw switch, and when the single-pole single-throw switch is closed, the single-pole single-throw switch enters the first working mode.

[0106] like Figure 5 , Figure 6 and Figure 8 As shown, in this embodiment, the first switch module (S1) is a single-pole single-throw switch, and the connection relationship between the first end 110 of the first switch module and the inverter night repair circuit can be: the inverter night repair circuit includes a diode D1, and the current limiting resistor R0 is connected to the anode side of the diode D1, and the first end 110 of the first switch module is connected to any node between the current limiting resistor R0 and the anode of the diode D1; or, the inverter night repair circuit includes a diode D1 connected in series with the current limiting resistor R0, and the current limiting resistor R0 is close to the anode side of the diode D1, and when the common-mode voltage difference between the neutral point Vn and the inverter side ground is negative, the first end 110 is connected to the cathode of the diode D1.

[0107] When the SPST switch is closed, that is, the first end 110 and the second end 120 of the first switch module are conductive, the first switch module, that is, the SPST switch, enters the first working mode to achieve common mode suppression of the inverter system.

[0108] According to the inverter system provided in the embodiment of the present application, through the single-pole single-throw switch included in the first switch module, when the single-pole single-throw switch is closed, the single-pole single-throw switch enters the first working mode, and common-mode suppression of the inverter system can be achieved based on the single-pole single-throw switch regardless of the positive or negative common-mode voltage difference of the neutral point Vn, thereby improving the applicability of the first switch module to various application scenarios.

[0109] In the following, in combination with the accompanying drawings, the grid-connected control method of the inverter system, the grid-connected control device of the inverter system and the readable storage medium provided in the embodiments of the present application are described in detail through specific embodiments and their application scenarios.

[0110] The grid-connected control method of the inverter system may be applied to the inverter system described in any of the above embodiments.

[0111] The grid-connected control method of the inverter system provided in the embodiment of the present application, the execution subject of the grid-connected control method of the inverter system may be the inverter system or a functional module or functional entity in the inverter system that can implement the grid-connected control method of the inverter system. The grid-connected control method of the inverter system provided in the embodiment of the present application is described below by taking the inverter system as an execution subject as an example.

[0112] like Fig. 9 As shown, the grid-connected control method of the inverter system includes: step 910 and step 920.

[0113] Step 910: Before controlling the inverter system to be connected to the grid, control the first switch module to enter the first working mode so that the first terminal 110 and the second terminal 120 are connected;

[0114] In this step, the first switch module includes a first end 110 and a second end 120, which is used to connect to the inverter side ground through the current limiting resistor R0 in the inverter night repair circuit based on the first end 110, and to connect to the neutral point Vn between the first capacitor C1 and the second capacitor C2 based on the second end 120, thereby realizing the reuse of the inverter night repair circuit and the current limiting resistor R0 of the night repair circuit, and realizing common mode suppression of the inverter system.

[0115] The first working mode is to conduct the first terminal 110 and the second terminal 120, ie, the first switch module is closed, so as to perform common-mode suppression on the inverter system.

[0116] like Figure 1As shown, in the actual implementation process, before controlling the inverter system to be connected to the grid, the first switch module is controlled to enter the first working mode to make the first end 110 and the second end 120 conductive, so that the common-mode impact current generated by the common-mode voltage difference at the neutral point Vn of the inverter system can be converted into a transient common-mode suppression current based on the existence of the current limiting resistor R0. The transient common-mode suppression current will decay and decrease in an exponential form until it drops to the first threshold value. When the transient common-mode suppression current drops to the first threshold value, the common-mode voltage difference at the neutral point Vn can be considered to be eliminated or very small, so that the common-mode suppression of the inverter system can be considered to be completed. After that, when any relay is closed, there will be no common-mode impact current or a very small common-mode impact current (which will not affect the normal operation of the inverter system).

[0117] Among them, the first threshold can be confirmed to be 0. When the transient common-mode suppression current drops to 0, the common-mode voltage difference of the neutral point Vn is considered to be eliminated, that is, the common-mode voltage difference is 0, and common-mode suppression of the inverter system can be achieved.

[0118] Step 920: When the actual voltage across the current limiting resistor R0 is less than the target threshold, the inverter system is controlled to be connected to the grid.

[0119] In this step, the target threshold may be a preset voltage threshold across the current limiting resistor R0.

[0120] The target threshold may be a voltage value across the current limiting resistor R0 when the transient common mode suppression current is at a first threshold.

[0121] During the actual execution, in the first working mode, the above-mentioned transient common-mode suppression current cannot be obtained in real time, and the voltage value across the current limiting resistor R0 also decreases exponentially with the exponential decay of the transient common-mode suppression current. Then, the actual voltage across the current limiting resistor R0 can be obtained in real time to determine whether the actual voltage across the current limiting resistor R0 has dropped to the target threshold, thereby deducing whether the transient common-mode suppression current has dropped to the first threshold. When the actual voltage across the current limiting resistor R0 drops to the target threshold, it is considered that the transient common-mode suppression current has dropped to the first threshold, and then it is considered that the common-mode suppression is completed, and the inverter can be switched to grid-connected operation.

[0122] like Fig.10 As shown, in some embodiments, the target threshold can be determined to be 0, that is, when the actual voltage across the current limiting resistor R0 drops to 0, it is considered that the transient common-mode suppression current drops to 0, then it is considered that the common-mode suppression is completed, and when the inverter is switched to grid-connected operation, no common-mode impact current will be generated.

[0123] According to the control method of the inverter system provided in the embodiment of the present application, before controlling the inverter system to be connected to the grid, the first switch module is controlled to enter the first working mode so that the first end 110 and the second end 120 are turned on. When the actual voltage across the current limiting resistor R0 is less than the target threshold, the inverter system is controlled to be connected to the grid. This can be achieved based on the reuse of the night repair circuit and the current limiting resistor R0 of the night repair circuit, thereby suppressing the common-mode voltage difference of the neutral point Vn before the inverter system is connected to the grid without introducing additional components, optimizing the circuit structure, reducing the space occupied by the circuit, saving the common-mode suppression cost, and improving the safety of common-mode suppression of the inverter system, thereby improving the safety and stability of the inverter system.

[0124] In some embodiments, the target threshold is determined based on a leakage current of the inverter system.

[0125] In this embodiment, the leakage current of the inverter system is a common mode current generated on the parasitic capacitance when a loop is formed between the parasitic capacitance, the photovoltaic system and the power grid due to the parasitic capacitance between the inverter and the ground.

[0126] In the actual implementation process, due to the circuit leakage current and non-ideal characteristics, when the voltage across the current limiting resistor R0 decreases exponentially with the transient common-mode suppression current, the voltage across the current limiting resistor R0 will not completely drop to 0. In this case, a target threshold can be set. When the current limiting resistor R0 drops to the target threshold, it is considered that the transient common-mode suppression current has dropped to the first threshold, that is, the common-mode voltage difference of the neutral point Vn has been eliminated to a very small value. When the common-mode voltage difference of the neutral point Vn is eliminated to a very small value, when the inverter system is switched to grid-connected operation, the common-mode impact current generated does not affect the normal operation of the inverter system.

[0127] It can be understood that the target threshold can be based on the voltage value across the current limiting resistor R0 so that the common-mode voltage difference of the neutral point Vn does not affect the normal operation of the inverter system when the inverter system switches to grid-connected operation and the common-mode impact current generated does not affect the normal operation of the inverter system.

[0128] According to the grid-connected control method of the inverter system provided in the embodiment of the present application, by determining the target threshold based on the leakage current of the inverter system, it is possible to reasonably determine the target threshold based on actual conditions, thereby improving the reliability of the target threshold, thereby facilitating the implementation of common-mode suppression of the inverter system based on the first switch module.

[0129] like Fig.10 As shown, in some embodiments, before controlling the first switch module to enter the first working mode, the method may further include:

[0130] Control the output voltage of the inverter system to be phase-locked with the grid voltage.

[0131] In this embodiment, the phase-locked synchronization may be to achieve phase synchronization between the output voltage of the inverter system and the grid voltage through a control system.

[0132] In the actual implementation process, controlling the output voltage of the inverter system to be phase-locked with the grid voltage can reduce the differential-mode impact current on the grid when the inverter is switched to grid-connected operation.

[0133] Among them, the differential mode impact current is the current impact caused by the sudden change of voltage when the inverter is connected to the grid. In the actual implementation process, the differential mode impact current may have adverse effects on the grid and the inverter itself, including: equipment damage, reduced grid stability and electromagnetic interference.

[0134] According to the grid-connected control method of the inverter system provided in the embodiment of the present application, by controlling the output voltage of the inverter system to be phase-locked with the grid voltage before controlling the first switch module to enter the first working mode, the differential-mode impact current on the grid can be reduced when the inverter is switched to grid-connected operation, thereby improving the safety and stability of the inverter system.

[0135] The grid-connected control method of the inverter system provided in the embodiment of the present application can be executed by a grid-connected control device of the inverter system. In the embodiment of the present application, the grid-connected control device of the inverter system executing the grid-connected control method of the inverter system is taken as an example to illustrate the grid-connected control device of the inverter system provided in the embodiment of the present application.

[0136] An embodiment of the present application also provides a grid-connected control device for an inverter system.

[0137] like Fig.11 As shown, the grid-connected control device of the inverter system includes: a first processing module 1111 and a second processing module 1120 .

[0138] The first processing module 1111 is used to control the first switch module to enter the first working mode before controlling the inverter system to be connected to the grid, so as to conduct the first terminal 110 and the second terminal 120;

[0139] The second processing module 1120 is used to control the inverter system to be connected to the grid when the actual voltage across the current limiting resistor R0 is less than the target threshold.

[0140] According to the grid-connected control device of the inverter system provided in the embodiment of the present application, before controlling the inverter system to be connected to the grid, the first switch module is controlled to enter the first working mode to make the first end 110 and the second end 120 conductive, and when the actual voltage across the current limiting resistor R0 is less than the target threshold, the inverter system is controlled to be connected to the grid. This can be achieved based on the reuse of the nighttime repair circuit and the current limiting resistor R0 of the nighttime repair circuit, thereby suppressing the common-mode voltage difference of the neutral point Vn before the inverter system is connected to the grid without introducing additional components, optimizing the circuit structure, reducing the space occupied by the circuit, saving the common-mode suppression cost, and improving the safety of common-mode suppression of the inverter system, thereby improving the safety and stability of the inverter system.

[0141] In some embodiments, the first processing module 1110 may also be used to:

[0142] Before controlling the first switch module to enter the first working mode, the output voltage of the inverter system is controlled to be phase-locked and synchronized with the grid voltage.

[0143] The grid-connected control device of the inverter system in the embodiment of the present application may be a device having an operating system. The operating system may be an Android operating system, an IOS operating system, or other possible operating systems, which are not specifically limited in the embodiment of the present application.

[0144] The grid-connected control device of the inverter system provided in the embodiment of the present application can achieve Fig. 9 and Fig.10 To avoid repetition, the various processes implemented in the method embodiment will not be described again here.

[0145] In some embodiments, Fig.12 As shown, an embodiment of the present application also provides an electronic device 1200, including a processor 1201, a memory 1202, and a computer program stored in the memory 1202 and executable on the processor 1201. When the program is executed by the processor 1201, each process of the grid-connected control method embodiment of the above-mentioned inverter system is implemented, and the same technical effect can be achieved. To avoid repetition, it will not be repeated here.

[0146] It should be noted that the electronic devices in the embodiments of the present application include the mobile electronic devices and non-mobile electronic devices mentioned above.

[0147] An embodiment of the present application also provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the various processes of the above-mentioned inverter system grid-connected control method embodiment are implemented, and the same technical effect can be achieved. To avoid repetition, it will not be repeated here.

[0148] The processor is the processor in the electronic device described in the above embodiment. The readable storage medium includes a computer readable storage medium, such as a computer read-only memory ROM, a random access memory RAM, a magnetic disk or an optical disk.

[0149] An embodiment of the present application also provides a computer program product, including a computer program, which implements the grid-connected control method of the above-mentioned inverter system when executed by a processor.

[0150] The processor is the processor in the electronic device described in the above embodiment. The readable storage medium includes a computer readable storage medium, such as a computer read-only memory ROM, a random access memory RAM, a magnetic disk or an optical disk.

[0151] An embodiment of the present application further provides a chip, which includes a processor and a communication interface, wherein the communication interface is coupled to the processor, and the processor is used to run programs or instructions to implement the various processes of the above-mentioned inverter system grid-connected control method embodiment, and can achieve the same technical effect. To avoid repetition, it will not be repeated here.

[0152] It should be understood that the chip mentioned in the embodiments of the present application can also be called a system-level chip, a system chip, a chip system or a system-on-chip chip, etc.

[0153] It should be noted that, in this article, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0154] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, or the part that contributes to the relevant technology, can be embodied in the form of a computer software product, which is stored in a storage medium (such as ROM / RAM, a disk, or an optical disk), and includes a number of instructions for a terminal (which can be a mobile phone, a computer, a server, or a network device, etc.) to execute the methods described in each embodiment of the present application.

[0155] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

[0156] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0157] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. An inverter system, characterized in that: include: A DC-to-AC circuit, wherein a phase relay is provided on a phase line connected to the DC-to-AC circuit; A first capacitor and a second capacitor connected in series between the positive and negative busbars of the inverter system; A first switch module, the first switch module comprising a first end and a second end, the first end being connected to the inverter side ground via a current limiting resistor in the inverter nighttime repair circuit; the second end being connected to a neutral point between the first capacitor and the second capacitor; The first switch module is configured to switch to a first working mode before the inverter system is connected to the grid, so that the first end and the second end are connected to each other, so as to perform common-mode suppression on the inverter system.

2. The inverter system according to claim 1, characterized in that: When the first switch module is switched to the first working mode and the actual voltage across the current limiting resistor is less than the target threshold, the inverter system is switched to grid-connected operation.

3. The inverter system according to claim 1, characterized in that: The inverter nighttime repair circuit includes a diode connected in series with the current limiting resistor, and the current limiting resistor is close to the anode side of the diode, and the first end is connected between the anode of the diode and the current limiting resistor.

4. The inverter system according to claim 1, characterized in that: The inverter nighttime repair circuit includes a diode connected in series with the current limiting resistor, and the current limiting resistor is close to the anode side of the diode. When the common-mode voltage difference between the neutral point and the inverter side ground is negative, the first end is connected to the cathode of the diode.

5. The inverter system according to claim 4, characterized in that: The first switch module includes a single-pole double-throw switch, and the third end included in the single-pole double-throw switch is connected to the other side of the DC-to-AC circuit; when the first end is connected to the second end, the first end is disconnected from the third end.

6. The inverter system according to any one of claims 1 to 4, characterized in that: The first switch module includes a single-pole single-throw switch. When the single-pole single-throw switch is closed, the single-pole single-throw switch enters the first working mode.

7. The inverter system according to any one of claims 1 to 4, characterized in that: It also includes a neutral line, one end of which is connected to the neutral point, and a neutral line relay is arranged on the neutral line.

8. A grid-connected control method for an inverter system, characterized in that: Applied to the inverter system according to any one of claims 1 to 7, the method comprises: Before controlling the inverter system to be connected to the grid, controlling the first switch module to enter the first working mode so that the first end is connected to the second end; When the actual voltage across the current limiting resistor is less than the target threshold, the inverter system is controlled to be connected to the grid.

9. The grid-connected control method of the inverter system according to claim 8, characterized in that: The target threshold is determined based on a leakage current of the inverter system.

10. The grid-connected control method of the inverter system according to claim 8 or 9, characterized in that: Before controlling the first switch module to enter the first working mode, the method further includes: The output voltage of the inverter system is controlled to be phase-locked and synchronized with the grid voltage.

11. A grid-connected control device for an inverter system, characterized in that: Applied to the inverter system according to any one of claims 1 to 7, the device comprises: A first processing module, used for controlling the first switch module to enter the first working mode before controlling the inverter system to be connected to the grid, so that the first end is connected to the second end; The second processing module is used to control the inverter system to be connected to the grid when the actual voltage across the current limiting resistor is less than a target threshold.

12. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the grid-connected control method of the inverter system as described in any one of claims 8 to 10 is implemented.

13. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, a grid-connected control method for an inverter system as claimed in any one of claims 8 to 10 is implemented.

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