Grid-connected inverter and control method and device thereof, and phase-locked power supply system

Abstract

The present disclosure relates to a grid-connected inverter and a control method and device thereof, and a phase-coherent power supply system. The grid-connected inverter comprises a power supply circuit and an inductive auxiliary voltage dividing circuit, wherein the power supply circuit and the inductive auxiliary voltage dividing circuit are connected; the grid-connected inverter is configured to boost the output voltage of an alternating current power supply; the power supply circuit comprises at least one single-phase power supply circuit, wherein each single-phase power supply circuit is connected with the inductive auxiliary voltage dividing circuit. The present disclosure provides a common-ground inverter with reduced switch quantity, the inverter of the present disclosure has a boosting characteristic, and can be extended to a three-phase system while maintaining the common-ground characteristic of the inverter.

Description

Technical Field

[0001] This disclosure relates to the field of power supply technology, and in particular to a grid-connected inverter and its control method and device, and a phase-connected power supply system. Background Technology

[0002] Since transformerless (TL) grid-connected inverters can reduce the risk of ground leakage current and improve the overall efficiency and power density of grid-connected systems, this patent has paved the way for the application of renewable energy as long as its inherent boost characteristics can be realized in a single power processing stage. Therefore, transformerless (TL) grid-connected inverters with common grounding (CG) characteristics are particularly popular in the field of renewable energy. Summary of the Invention

[0003] The inventors discovered through research that although the switching boost (SB) and switched capacitor (SC) technologies integrated into the traditional virtual DC link in CG-based three-level (3L) inverters currently used in related technologies can increase the overall boost gain of the converter, and the more components there are, the higher the output voltage can be generated, such TL inverters can only generate levels suitable for single-phase circuit configurations. For three-phase expansion, the number of components will increase threefold. Therefore, related technologies require more passive and active components.

[0004] In view of at least one of the above technical problems, this disclosure provides a grid-connected inverter and its control method and apparatus, and a co-phase power supply system, which is a new type of common-grounded inverter that reduces the number of switches.

[0005] According to one aspect of this disclosure, a grid-connected inverter is provided, comprising a power supply circuit and an inductive auxiliary voltage divider circuit, wherein:

[0006] The power supply circuit and the inductive auxiliary voltage divider circuit are connected;

[0007] Grid-connected inverters are configured to boost the output voltage of AC power supplies;

[0008] The power supply circuit includes at least one single-phase power supply circuit, wherein each single-phase power supply circuit is connected to an inductive auxiliary voltage divider circuit.

[0009] In some embodiments of this disclosure, the power supply circuit is a single-phase power supply circuit or a three-phase power supply circuit, wherein:

[0010] In the case of a three-phase power supply circuit, the power supply circuit includes three single-phase power supply circuits, wherein each single-phase power supply circuit is connected to an inductive auxiliary voltage divider circuit.

[0011] When the power supply circuit is a single-phase power supply circuit, the single-phase power supply circuit is connected to the inductive auxiliary voltage divider circuit.

[0012] In some embodiments of this disclosure, the inductive auxiliary voltage divider circuit includes a DC input power supply, a first switching transistor, a second switching transistor, a first capacitor, and a first inductor, wherein:

[0013] The first and second switching transistors are connected in series to form a switching transistor circuit; the DC input power supply and the first capacitor are connected in series to form a voltage divider circuit; the voltage divider circuit and the switching transistor circuit are connected in parallel.

[0014] The connection point between the first and second switching transistors is the first connection point, the connection point between the DC input power supply and the first capacitor is the second connection point, and the first inductor is located between the first and second connection points; the first switching transistor and the DC input power supply are connected through a grounding point, and the second switching transistor and the first capacitor are connected through a third connection point.

[0015] In some embodiments of this disclosure, each single-phase power supply circuit is connected to an inductive auxiliary voltage divider circuit via a second connection point, a third connection point, and a ground point.

[0016] In some embodiments of this disclosure, each single-phase power supply circuit includes a first power switch, a second power switch, a third power switch, a fourth power switch, a fifth power switch, an inductive filter, a resonant inductor, a second capacitor, and a diode, wherein:

[0017] The first power switch, the third power switch, the inductive filter, and the AC power supply are connected in series between the third connection point and the ground point;

[0018] The fifth power switch is located between the second connection point and the fourth connection point, wherein the fourth connection point is the connection point between the first power switch and the third power switch;

[0019] The second power switch is located between the third connection point and the grounding point;

[0020] The second capacitor and the fourth power switch are connected in series, and then connected in parallel with the third power switch.

[0021] The diode and resonant inductor are connected in series between the fifth connection point and the ground point, where the fifth connection point is the connection point of the second capacitor and the fourth power switch.

[0022] In some embodiments of this disclosure, when the first switch is turned on and the second switch is turned off, the DC input power supply, the first switch, and the first inductor form a conduction circuit to charge the first inductor.

[0023] In some embodiments of this disclosure, when the first switch is off and the second switch is on, the second switch, the first inductor, and the first capacitor form a conduction circuit, and the first inductor discharges to charge the first capacitor.

[0024] In some embodiments of this disclosure, the first switch and the second switch are turned on alternately at a predetermined time interval, and when one of the first switch and the second switch is turned on, the other switch is turned off.

[0025] In some embodiments of this disclosure, the voltage across the first capacitor is equal to the DC voltage of the DC input power supply.

[0026] In some embodiments of this disclosure, when the power supply circuit includes N single-phase power supply circuits, the number of different voltage levels output by the power supply circuit is 4N+1, where N is a natural number greater than 0.

[0027] In some embodiments of this disclosure, the number of different voltage levels output by a single-phase power supply circuit is 5; the number of different voltage levels output by a three-phase power supply circuit is 13.

[0028] In some embodiments of this disclosure, when the second switch, the second power switch, and the third power switch are turned on, and the first switch, the first power switch, the fourth power switch, and the fifth power switch are turned off, the AC power supply, the inductive filter, the second power switch, and the third power switch form a conducting loop, the single-phase power supply circuit is in the first operating state, and the output voltage of the AC power supply is 0.

[0029] In some embodiments of this disclosure, when the first switch, the fifth power switch, and the third power switch are turned on, and the second switch, the first power switch, the fourth power switch, and the second power switch are turned off, the AC power supply, the inductive filter, the third power switch, the fifth power switch, the input DC power supply, the first inductor, and the first switch form a conduction loop, the single-phase power supply circuit is in the second operating state, and the output voltage of the AC power supply is the DC voltage of the DC input power supply.

[0030] In some embodiments of this disclosure, when the first power switch and the third power switch are turned on, and the fifth power switch, the fourth power switch and the second power switch are turned off, the AC power supply, the inductive filter, the third power switch, the first power switch, the input DC power supply, the first capacitor, the second capacitor, the diode and the resonant inductor form a conducting loop, the single-phase power supply circuit is in the third operating state, and the output voltage of the AC power supply is twice the DC voltage of the DC input power supply.

[0031] In some embodiments of this disclosure, when the fourth and fifth power switches are on and the first, second, and third power switches are off, the AC power supply, the inductive filter, the fourth power switch, the diode, and the resonant inductor form a conducting loop, the single-phase power supply circuit is in the fourth operating state, and the output voltage of the AC power supply is 0.

[0032] In some embodiments of this disclosure, when the fifth power switch is turned on and the first power switch, the third power switch, and the second power switch are turned off, the AC power supply, the inductive filter, the fourth power switch, the second capacitor, the fifth power switch, and the input DC power supply form a conducting loop, the single-phase power supply circuit is in the fifth operating state, and the output voltage of the AC power supply is the opposite of the DC voltage of the DC input power supply.

[0033] In some embodiments of this disclosure, when the second power switch and the fourth power switch are turned on and the first power switch, the third power switch and the fifth power switch are turned off, the AC power supply, the inductive filter, the fourth power switch, the second capacitor and the second power switch form a conducting loop, the single-phase power supply circuit is in the sixth operating state, and the output voltage of the AC power supply is the opposite of twice the DC voltage of the DC input power supply.

[0034] In some embodiments of this disclosure, a single-phase power supply circuit is configured to switch from a first operating state to a second operating state by controlling the on and off states of a switching transistor after a predetermined time interval from being in a first operating state; switch from a second operating state to a third operating state by controlling the on and off states of a switching transistor after a predetermined time interval from being in the second operating state; switch from a third operating state to a fourth operating state by controlling the on and off states of a switching transistor after a predetermined time interval from being in the third operating state; switch from a fourth operating state to a fifth operating state by controlling the on and off states of a switching transistor after a predetermined time interval from being in the fourth operating state; switch from a fifth operating state to a sixth operating state by controlling the on and off states of a switching transistor after a predetermined time interval from being in the sixth operating state; and switch from a sixth operating state to a first operating state by controlling the on and off states of a switching transistor after a predetermined time interval from being in the sixth operating state. The switching transistors include a first and a second switching transistor in an inductive auxiliary voltage divider circuit, and a first, second, third, fourth, and fifth power switch in the single-phase power supply circuit.

[0035] According to another aspect of this disclosure, a non-phase power supply system is provided, including a grid-connected inverter as described in any of the above embodiments.

[0036] According to another aspect of this disclosure, a grid-connected inverter control method is provided, comprising:

[0037] The grid-connected inverter is controlled to boost the output voltage of the AC power supply, wherein the grid-connected inverter is the grid-connected inverter as described in any of the above embodiments.

[0038] In some embodiments of this disclosure, controlling the grid-connected inverter to boost the output voltage of the AC power supply includes:

[0039] The first and second switching transistors in the inductive auxiliary voltage divider circuit that controls the grid-connected inverter are turned on alternately at a predetermined time interval.

[0040] In some embodiments of this disclosure, the step of controlling the grid-connected inverter to boost the output voltage of the AC power supply further includes:

[0041] After a predetermined time interval in the first working state, the first working state is switched to the second working state by controlling the switching transistor to turn on and off.

[0042] In some embodiments of this disclosure, the step of controlling the grid-connected inverter to boost the output voltage of the AC power supply further includes:

[0043] After a predetermined time interval in the second operating state, the second operating state is switched to the third operating state by controlling the switching transistor to turn on and off.

[0044] In some embodiments of this disclosure, the step of controlling the grid-connected inverter to boost the output voltage of the AC power supply further includes:

[0045] After a predetermined time interval in the third operating state, the third operating state is switched to the fourth operating state by controlling the switching transistor to turn on and off.

[0046] In some embodiments of this disclosure, the step of controlling the grid-connected inverter to boost the output voltage of the AC power supply further includes:

[0047] After a predetermined time interval in the fourth operating state, the fourth operating state is switched to the fifth operating state by controlling the switching transistor to turn on and off.

[0048] In some embodiments of this disclosure, the step of controlling the grid-connected inverter to boost the output voltage of the AC power supply further includes:

[0049] After a predetermined time interval in the fifth operating state, the fifth operating state is switched to the sixth operating state by controlling the switching transistor to turn on and off.

[0050] In some embodiments of this disclosure, the step of controlling the grid-connected inverter to boost the output voltage of the AC power supply further includes:

[0051] After a predetermined time interval in the sixth operating state, the sixth operating state is switched to the first operating state by controlling the conduction and turn-off of the switching transistors. The switching transistors include the first and second switching transistors in the inductive auxiliary voltage divider circuit, and the first, second, third, fourth, and fifth power switches in the single-phase power supply circuit.

[0052] According to another aspect of this disclosure, a grid-connected inverter control device is provided, comprising:

[0053] Memory, used to store instructions;

[0054] A processor is configured to execute the instructions, causing the grid-connected inverter control device to perform operations implementing the grid-connected inverter control method as described in any of the above embodiments.

[0055] According to another aspect of this disclosure, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores computer instructions that, when executed by a processor, implement the grid-connected inverter control method as described in any of the above embodiments.

[0056] This disclosure provides a common-ground inverter with reduced number of switches. The inverter has boost characteristics and can be extended to a three-phase system while maintaining the common-ground characteristics of the inverter. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 This is a schematic diagram of some embodiments of the grid-connected inverter disclosed herein.

[0059] Figure 2 This is a schematic diagram of some other embodiments of the grid-connected inverter disclosed herein.

[0060] Figure 3 This is a schematic diagram of an inductive auxiliary voltage divider circuit in some embodiments of this disclosure.

[0061] Figure 4 This is a schematic diagram of an inductive auxiliary voltage divider circuit in some other embodiments of this disclosure.

[0062] Figure 5 The following are timing diagrams for switch control in some embodiments of this disclosure.

[0063] Figure 6This is a schematic diagram of a grid-connected inverter in its first operating state in some embodiments of this disclosure.

[0064] Figure 7 This is a schematic diagram of a grid-connected inverter in a second operating state in some embodiments of this disclosure.

[0065] Figure 8 This is a schematic diagram of a grid-connected inverter in a third operating state in some embodiments of this disclosure.

[0066] Figure 9 This is a schematic diagram of a grid-connected inverter in a fourth operating state in some embodiments of this disclosure.

[0067] Figure 10 This is a schematic diagram of a grid-connected inverter in its fifth operating state in some embodiments of this disclosure.

[0068] Figure 11 This is a schematic diagram of the grid-connected inverter in the sixth operating state in some embodiments of this disclosure.

[0069] Figure 12 This is a schematic diagram of some embodiments of the grid-connected inverter control method disclosed herein.

[0070] Figure 13 This is a schematic diagram of the structure of some embodiments of the grid-connected inverter control device disclosed herein. Detailed Implementation

[0071] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this disclosure or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0072] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of this disclosure.

[0073] At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn according to actual scale.

[0074] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0075] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0076] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0077] The inventors discovered through research that the TL inverters of the related technology can only generate levels that are only applicable to single-phase circuit configurations. However, for three-phase expansion, the number of overall components increases threefold. Therefore, more passive and active components are required, and the inverter may lose its applicability in terms of reliability and power density. In addition, SC-based TL inverters have large pulsating input current waveforms, which leads to a decrease in the performance of the entire system at high power ratios.

[0078] In view of at least one of the above technical problems, this disclosure provides a grid-connected inverter and its control method and apparatus, as well as a non-phase power supply system. The disclosure will be described below through specific embodiments.

[0079] Figure 1 This is a schematic diagram of some embodiments of the grid-connected inverter disclosed herein. Figure 2 These are schematic diagrams illustrating other embodiments of the grid-connected inverter disclosed herein. For example... Figure 1 and Figure 2 As shown, the grid-connected inverter of this disclosure may include a power supply circuit and an inductive auxiliary voltage divider circuit 20, wherein:

[0080] The power supply circuit and the inductive auxiliary voltage divider circuit 20 are connected.

[0081] A grid-connected inverter is configured to boost the output voltage of an AC power supply.

[0082] like Figure 1 and Figure 2 As shown, the power supply circuit includes at least one single-phase power supply circuit 10, wherein each single-phase power supply circuit 10 is connected to an inductive auxiliary voltage divider circuit.

[0083] In some embodiments of this disclosure, the power supply circuit is a single-phase power supply circuit, a three-phase power supply circuit, a two-phase power supply circuit, a four-phase power supply circuit, a five-phase power supply circuit, or other multi-phase power supply circuits.

[0084] In some embodiments of this disclosure, the power supply circuit may include two, three, four, or more single-phase power supply circuits.

[0085] In some embodiments of this disclosure, such as Figure 1As shown, when the power supply circuit is a single-phase power supply circuit, the single-phase power supply circuit is connected to the inductive auxiliary voltage divider circuit.

[0086] In some embodiments of this disclosure, such as Figure 2 As shown, in the case of a three-phase power supply circuit, the power supply circuit includes three single-phase power supply circuits, each of which is connected to an inductive auxiliary voltage divider circuit. Figure 2 Each single-phase power supply circuit in the embodiment is associated with Figure 1 The single-phase power supply circuits in the embodiments are the same or similar.

[0087] The embodiments of this disclosure can directly expand a single DC power supply into a three-phase system, thereby solving the technical problem that related technologies cannot directly expand a single DC power supply into a three-phase system. The inverter of this disclosure has boost characteristics and can be expanded into a three-phase system while maintaining the inverter's common grounding characteristic.

[0088] The embodiments described above use the same SB unit (inductive auxiliary voltage divider circuit) to generate the required output voltage boost DC link. By integrating the SB unit and cascading (parallel connecting) the remaining parts of the proposed circuit (single-phase power supply circuit), the embodiments described above can achieve a three-phase extension of the proposed TL inverter, which is also easily identifiable.

[0089] Figure 3 This is a schematic diagram of an inductive auxiliary voltage divider circuit in some embodiments of this disclosure. Figure 4 This is a schematic diagram of an inductive auxiliary voltage divider circuit in some other embodiments of this disclosure. For example... Figures 1-4 As shown in any embodiment, the inductive auxiliary voltage divider circuit of this disclosure includes a DC input power supply V. in First switching transistor S SB Second switching transistor D SB A first capacitor C1 and a first inductor Lm, wherein:

[0090] First switching transistor S SB Second switching transistor D SB Connected in series to form a switching transistor circuit; DC input power supply V in It is connected in series with the first capacitor C1 to form a voltage divider circuit; the voltage divider circuit and the switching transistor circuit are connected in parallel.

[0091] First switching transistor S SB Second switch D SB The connection point is the first connection point 1, and the DC input power supply V in The connection point of the first capacitor C1 is the second connection point 2, and the first inductor Lm is located between the first connection point 1 and the second connection point 2; the first switching transistor and the DC input power supply V inThe second switch and the first capacitor C1 are connected through the grounding point GND, and the second switch and the first capacitor C1 are connected through the third connection point 3.

[0092] Since the inductor-assisted voltage divider circuit of the above embodiments of this disclosure includes an inductor, the grid-connected inverter of the above embodiments of this disclosure has the advantage that the input current waveform will not have large pulsating discontinuous waveforms.

[0093] In some embodiments of this disclosure, such as Figures 1-4 As shown in any embodiment, each single-phase power supply circuit is connected to the inductive auxiliary voltage divider circuit 20 through the second connection point 2, the third connection point 3 and the ground point GND.

[0094] Therefore, the above embodiments of this disclosure can be extended to three-phase systems while maintaining the common grounding characteristic of the inverter.

[0095] In some embodiments of this disclosure, the operation of the inductive auxiliary voltage divider circuit can be achieved through... Figure 3 and Figure 4 This is achieved through inductive auxiliary voltage divider, which is also based on the basic unit, such as... Figures 1-4 As shown, it mainly includes two series-connected switching transistors with anti-parallel diodes (i.e., the first switching transistor S). SB Second switch D SB and the first switching transistor S SB Second switch D SB The voltage divider circuit is connected in parallel, and includes a first capacitor C1 connected in series and a DC input power supply V. in The first inductor Lm is a temporary energy storage inductor Lm, which is connected between the voltage divider circuit and the switching transistor circuit, thereby preventing any capacitor from short-circuiting through the switching transistor or the anti-parallel diode. The control of each basic unit is the same and there is no mutual influence between them.

[0096] In some embodiments of this disclosure, such as Figures 1-4 As shown in any embodiment, in the inductive auxiliary voltage equalization circuit, the DC input power supply V in The energy is stored in the first inductor Lm, and then the first inductor Lm discharges to charge the first capacitor C1, so that the first capacitor C1 receives the same voltage.

[0097] In some embodiments of this disclosure, in order to achieve the goal of voltage division, the switching rules of the auxiliary voltage divider circuit should meet the following requirements:

[0098] First, the two series-connected switches in a basic voltage divider unit cannot be turned on simultaneously. The two switches must be complementary; when one is on, the other must be off.

[0099] In some embodiments of this disclosure, such as Figures 1-4As shown in any embodiment, the first switching transistor S SB Second switch D SB The switches are alternately turned on at predetermined time intervals, and when one of the first and second switches is turned on, the other switch is turned off.

[0100] Secondly, in one switching cycle, for the basic voltage divider unit, the DC input power supply V... in The first switch S connected in parallel SB First, turn on the circuit to better ensure the flow of charging and discharging current between the inductor and capacitor in the auxiliary voltage divider circuit.

[0101] To simplify the analysis, the following assumptions are made within one equilibrium cycle: 1. The switching frequency is high enough that the increase and decrease of current are almost linear. 2. The capacitor voltage is not affected by the main circuit and is only related to the auxiliary voltage equalization circuit. 3. Within one switching cycle, the switch's on-time is shorter than its off-time, thus ensuring complete discharge of the inductor current. Based on these assumptions, the inductor voltage divider circuit can be divided into three stages within one switching cycle:

[0102] The first stage involves the DC input power supply V. in The first switching transistor S SB First, turn on the DC input power supply V. in Discharge into the first inductor Lm for storage.

[0103] In the second stage, the first switching transistor S SB Turn off, second switch D SB When the circuit is turned on, the first capacitor C1, which has a low voltage, is charged, and the current of the voltage divider inductor decreases to zero.

[0104] In the third stage, after the inductor current reaches zero, the voltage divider circuit enters a stable state.

[0105] In some embodiments of this disclosure, such as Figure 3 As shown, in the first switching transistor S SB On, second switch D SB When the circuit is off, the DC input power supply and the first switching transistor S SB Together with the first inductor Lm, they form a conducting circuit, charging the first inductor Lm. The current i flowing through the inductor... Lm It will continue to increase. Therefore, the fixed DC voltage value V at the input DC source... dc and the instantaneous voltage V across the inductor Lm The relationship between them can be represented as shown in formula (1).

[0106]

[0107] In some embodiments of this disclosure, such as Figure 4 As shown, in the first switching transistor S SB Turn off, second switch D SB When the circuit is on, the second switch D SB The first inductor Lm and the first capacitor C1 form a conducting circuit. When the first inductor Lm discharges, it charges the first capacitor C1. In this case, i Lm It has a negative slope and the first capacitor C1 is charged according to formula (2):

[0108]

[0109] In formula (2), V C1 This is the steady-state voltage of C1. Therefore, considering... Figure 3 and Figure 4 In the embodiment, the first switching transistor S SB Second switch D SB With the same ON and OFF switching time interval, for the first inductor Lm, the voltage across the first capacitor C1 is equal to the DC voltage V of the DC input power supply. dc V C1 =V dc .

[0110] Similar to the series-parallel SC circuits of related technologies, the inductive auxiliary voltage divider circuit in the above embodiments of this disclosure also has boost characteristics, and can provide two different voltage levels at the output of the inductive auxiliary voltage divider circuit, one of which is directly related to the input DC source (V). dc One is the input DC power supply V, and the other is the input DC power supply V. dc Series connection with C1 voltage (V) dc +V C1 The output voltage of the inductive auxiliary voltage divider circuit is the voltage between the third connection point 3 and the ground point GND in the inductive auxiliary voltage divider circuit.

[0111] Therefore, the inductive auxiliary voltage divider circuit of the above embodiments of this disclosure can output V. dc and 2V dc .

[0112] In some embodiments of this disclosure, such as Figure 1 and Figure 2 As shown, each single-phase power supply circuit includes a first power switch S1, a second power switch S2, a third power switch S3, a fourth power switch S4, a fifth power switch Sb, an inductive filter Lg, a resonant inductor Lr, a second capacitor C2, and a diode D, wherein:

[0113] The first power switch S1, the third power switch S3, the inductive filter Lg, and the AC power supply are connected in series between the third connection point 3 and the ground point GND.

[0114] The fifth power switch Sb is located between the second connection point 2 and the fourth connection point, wherein the fourth connection point is the connection point of the first power switch S1 and the third power switch S3.

[0115] The second power switch S2 is located between the third connection point 3 and the grounding point GND.

[0116] The second capacitor C2 and the fourth power switch S4 are connected in series, and then connected in parallel with the third power switch S3.

[0117] Diode D and resonant inductor Lr are connected in series between the fifth connection point and ground point GND. The fifth connection point is the connection point of the second capacitor C2 and the fourth power switch S4.

[0118] The SBCG-TL (Switching Boost Common Ground Transformerless) inverter topology and its overall circuit configuration for related power switches disclosed herein are as follows: Figure 1 and Figure 2 As shown, this topology has CG characteristics, and the L-type filter, LG, is an inductive filter. Figure 1 and Figure 2 The circuit acts as a connection between the SBCG-TL inverter and the power grid. At this point, all switches except the fifth power switch Sb are unidirectional. The fifth power switch Sb is a bidirectional switch, and the current in the branch containing the fifth power switch needs to be controlled in both directions. Lm and Lr represent the inductor and resonant inductor of the inductive auxiliary voltage divider circuit unit, respectively. Similar to other existing CG-based 5L-TL inverters, the topology of the above embodiment of this disclosure uses two capacitors C1 and C2 as a virtual DC link. C2 provides a quasi-soft charge operation (QSC) to the converter, while simultaneously charging through the first capacitor C1 and the DC input power supply Vin, making it easily identifiable.

[0119] The embodiments of this disclosure propose a new CG inverter with a reduced number of switches, requiring seven power switches, two capacitors, two power diodes and one inductor. This significantly reduces the number of components compared to the three-phase TL inverters of the related art, thus maintaining the applicability of the embodiments of this disclosure in terms of reliability and power density.

[0120] Figure 5 This is a timing diagram of switch control in some embodiments of this disclosure. The first switch transistor S... SB Second switch D SB The first switch S is alternately turned on at predetermined time intervals. SB Second switch D SB When one switch is on, the other switch is off. For example... Figure 5As shown, the second switch D is given. SB The diagram shows the switching states of the second switch transistor D, where 0 represents the second switch transistor D. SB Off, 1 indicates the second switch D SB Conduction.

[0121] In some embodiments of this disclosure, a single-phase power supply circuit is configured to, after a predetermined time interval in a first operating state, switch to a second operating state by controlling the on and off states of a switching transistor; after a predetermined time interval in the second operating state, switch to a third operating state by controlling the on and off states of a switching transistor; after a predetermined time interval in the third operating state, switch to a fourth operating state by controlling the on and off states of a switching transistor; after a predetermined time interval in the fourth operating state, switch to a fifth operating state by controlling the on and off states of a switching transistor; after a predetermined time interval in the fifth operating state, switch to a sixth operating state by controlling the on and off states of a switching transistor; and after a predetermined time interval in the sixth operating state, switch to the first operating state by controlling the on and off states of a switching transistor. The switching transistors include a first and second switching transistor in an inductive auxiliary voltage divider circuit, and a first power switch S1, a second power switch S2, a third power switch S3, a fourth power switch S4, and a fifth power switch Sb in the single-phase power supply circuit.

[0122] The switch (first switching transistor S) of the inductive auxiliary voltage divider circuit unit in the above embodiments of this disclosure. SB Second switch D SB At each switching frequency, the switching continues its on / off commutation, while the remaining switches (first power switch S1, second power switch S2, third power switch S3, fourth power switch S4 and fifth power switch Sb) can be modulated during sinusoidal PWM (SPWM) commutation.

[0123] In some embodiments of this disclosure, such as Figure 5 As shown, t0 is the initial time, which is the start time of the first working state. t1 is the time when the first working state switches to the second working state, and t1-t0 is a predetermined time interval.

[0124] In some embodiments of this disclosure, such as Figure 5 As shown, the single-phase power supply circuit outputs 5 different voltage levels. Therefore, the single-phase TL inverter of this disclosure can generate 5 corresponding output voltage levels per phase (0, V...). dc 2V dc -V dc -2V dcThe output voltages for the first, second, third, fourth, fifth, and sixth operating states are 0, V, and V, respectively. dc 2V dc , 0, -V dc and -2V dc The first, second, and third operating states correspond to the positive half-cycle of the grid voltage; the fourth, fifth, and sixth operating states correspond to the negative half-cycle of the grid voltage.

[0125] Figures 6-11 These are schematic diagrams illustrating different current flow paths during different operating states when the grid-connected inverter generates different output voltages in some embodiments of this disclosure.

[0126] Figure 6 This is a schematic diagram of a grid-connected inverter in its first operating state according to some embodiments of this disclosure. For example... Figure 6 As shown, when the second switch, the second power switch S2, and the third power switch S3 are turned on, and the first switch, the first power switch S1, the fourth power switch S4, and the fifth power switch Sb are turned off, the AC power supply, the inductive filter Lg, the second power switch S2, and the third power switch S3 form a conducting loop, and the single-phase power supply circuit is in the first operating state. The voltages across the inductive filter Lg, the second power switch S2, and the third power switch S3 are all 0, so the output voltage of the AC power supply is 0.

[0127] Figure 7 This is a schematic diagram of a grid-connected inverter in a second operating state according to some embodiments of this disclosure. For example... Figure 7 As shown, with the first switch, the fifth power switch Sb, and the third power switch S3 on, and the second switch, the first power switch S1, the fourth power switch S4, and the second power switch S2 off, the AC power supply, the inductive filter Lg, the third power switch S3, the fifth power switch Sb, the input DC power supply, the first inductor Lm, and the first switch form a conducting loop. The single-phase power supply circuit is in its second operating state. The voltages across the inductive filter Lg, the third power switch S3, and the fifth power switch Sb are all 0. Therefore, the output voltage of the AC power supply is the DC voltage V of the DC input power supply. dc Similar to the first operating state, due to the upcoming steady-state voltage of C2, diode D will be reverse-biased, at which point C2 will again disconnect the DC power supply from the grid. Here, regardless of the direction of the grid current, V dc Both can be used to recharge C1 through the aforementioned working principle of the inductive auxiliary voltage divider circuit unit. The inductive voltage divider circuit unit obtains the same voltage in both the upper and lower parts (C1 receives V). dc ).

[0128] Figure 8 This is a schematic diagram of a grid-connected inverter in a third operating state in some embodiments of this disclosure. For example... Figure 8 As shown, with the first power switch S1 and the third power switch S3 on, and the fifth power switch Sb, the fourth power switch S4, and the second power switch S2 off, the AC power supply, the inductive filter Lg, the third power switch S3, the first power switch S1, the input DC power supply, the first capacitor C1, the second capacitor C2, the diode D, and the resonant inductor Lr form a conducting loop. The single-phase power supply circuit is in the third operating state. The voltages across the inductive filter Lg, the third power switch S3, the diode D, and the resonant inductor Lr are all 0. Therefore, the output voltage of the AC power supply is the voltage across the second capacitor C2, that is, the output voltage of the AC power supply is twice the DC voltage of the DC input power supply, 2V. dc In the third operating state, the output voltage of the TL inverter disclosed herein is the maximum positive level of 2V. dc .

[0129] Figure 9 This is a schematic diagram of a grid-connected inverter in a fourth operating state in some embodiments of this disclosure. For example... Figure 9 As shown, when the fourth power switch S4 and the fifth power switch Sb are on, and the first power switch S1, the second power switch S2 and the third power switch S3 are off, the AC power supply, the inductive filter Lg, the fourth power switch S4, the diode D and the resonant inductor Lr form a conducting loop, and the single-phase power supply circuit is in the fourth operating state. The voltages across the inductive filter Lg, the fourth power switch S4, the diode D and the resonant inductor Lr are all 0, so the output voltage of the AC power supply is 0.

[0130] Figure 10 This is a schematic diagram of a grid-connected inverter in a fifth operating state in some embodiments of this disclosure. For example... Figure 10 As shown, with the fifth power switch Sb and the third power switch S3 and the second power switch S2 turned off, the AC power supply, inductive filter Lg, fourth power switch S4, second capacitor C2, fifth power switch Sb, and input DC power supply form a conducting loop. The single-phase power supply circuit is in the fifth operating state, and the voltages across the inductive filter Lg, fourth power switch S4, and fifth power switch Sb are all 0. Therefore, the output voltage of the AC power supply is determined by the sum of the voltage across the second capacitor C2 and the input DC power supply voltage. Specifically, the output voltage of the AC power supply is the negative of the DC voltage of the DC input power supply -V. dc .exist Figure 10 In the middle, the first negative level of the output voltage -V dc The charging voltage of C2 is -2Vdc and input DC power supply V dc produce.

[0131] Figure 11 This is a schematic diagram of a grid-connected inverter in a sixth operating state in some embodiments of this disclosure. For example... Figure 11 As shown, with the second power switch S2 and the fourth power switch S4 on, and the first power switch S1, the third power switch S3, and the fifth power switch Sb off, the AC power supply, the inductive filter Lg, the fourth power switch S4, the second capacitor C2, and the second power switch S2 form a conducting loop. The single-phase power supply circuit is in the sixth operating state, and the voltages across the inductive filter Lg, the fourth power switch S4, and the second power switch S2 are all 0. Therefore, the output voltage of the AC power supply is the opposite of twice the DC voltage of the DC input power supply, which is -2V. dc The highest negative level of the output voltage is -2V. dc It is generated by capacitor C2 when Sb and S4 are in the on / off state.

[0132] Single-phase circuit configuration as follows Figure 1 , Figures 6-11 As shown, it includes seven power switches (one of which is in the inductive auxiliary voltage divider circuit, namely the first switching transistor S). SB The single-phase power supply circuit has six switches: the first power switch S1, the second power switch S2, the third power switch S3, the fourth power switch S4, and the fifth power switch Sb. The fifth power switch Sb includes two switching power supplies, two capacitors (the first capacitor C1 and the second capacitor C2), and two diodes (diode D and the second switching transistor D). SB ) and inductors (first inductor Lm, inductive filter Lg, resonant inductor Lr). Figure 1 The single-phase TL inverter in this embodiment can generate five output voltage levels per phase (0, Vdc, 2Vdc, -Vdc, -2Vdc). In contrast, the same five-level inverter in related technologies requires 24 switching transistors. Therefore, the number of components in the three-phase TL inverter of related technologies is greatly reduced, and its applicability is better maintained in terms of reliability and power density.

[0133] In some embodiments of this disclosure, such as Figure 2 As shown, with Figure 1 Compared to the previous embodiment, by retaining the original inductive auxiliary voltage divider circuit unit and expanding the parallel connection of three identical CG-based TL inverters, a novel single-source single-stage three-phase boost inverter with inherent CG characteristics for each phase can be derived.

[0134] In some embodiments of this disclosure, such as Figure 2As shown, each single-phase power supply circuit is connected to phase a, phase b, and phase c of the AC power supply Grid, respectively. The power supply circuit for phase a includes a first power switch S1,a, a second power switch S2,a, a third power switch S3,a, a fourth power switch S4,a, a fifth power switch Sb,a, an inductive filter Lg,a, a resonant inductor Lr,a, a second capacitor C2,a, and a diode D,a; the power supply circuit for phase b includes a first power switch S1,b, a second power switch S2,b, a third power switch S3,b, a fourth power switch S4,b, a fifth power switch Sb,b, an inductive filter Lg,b, a resonant inductor Lr,b, a second capacitor C2,b, and a diode D,b; the power supply circuit for phase c includes a first power switch S1,c, a second power switch S2,c, a third power switch S3,c, a fourth power switch S4,c, a fifth power switch Sb,c, an inductive filter Lg,c, a resonant inductor Lr,c, a second capacitor C2,c, and a diode D,c.

[0135] In some embodiments of this disclosure, when the power supply circuit includes N single-phase power supply circuits, the number of different voltage levels output by the power supply circuit is 4N+1, where N is a natural number greater than 0.

[0136] In some embodiments of this disclosure, the number of different voltage levels output by a single-phase power supply circuit is 5; the number of different voltage levels output by a two-phase power supply circuit is 9; and the number of different voltage levels output by a three-phase power supply circuit is 13.

[0137] In some embodiments of this disclosure, the two-phase TL inverter can still generate five output voltage levels per phase (0, Vdc, 2Vdc, -Vdc, -2Vdc), while the number of phase-to-phase output voltage levels of the two-phase TL inverter can be extended to nine (-Vdc, -2Vdc, -3Vdc, -4Vdc, 0, Vdc, 2Vdc, 3Vdc, 4Vdc).

[0138] Figure 2 The three-phase TL inverter in this embodiment can still generate five output voltage levels per phase (0, Vdc, 2Vdc, -Vdc, -2Vdc), and the number of phase-to-phase output voltage levels of the three-phase TL inverter can be extended to 13 (-Vdc, -2Vdc, -3Vdc, -4Vdc, -5Vdc, -6Vdc, 0, Vdc, 2Vdc, 3Vdc, 4Vdc, 5Vdc, 6Vdc).

[0139] from Figure 2 It can be seen that the total number of power switches in this three-phase system is 19 (one of which is in the inductive auxiliary voltage divider circuit, namely the first switching transistor S). SBThere are 6 in each single-phase power supply circuit, for a total of 18; one boost inductor Lm; and four power diodes (second switching transistor D). SB Each phase has one diode (D) and four DC bus capacitors (first capacitor C1, and one second capacitor C2 for each single-phase power circuit). In related technologies, the same five-level inverter requires 24 switching transistors alone. Compared to this, the number of components in the three-phase TL inverter of related technologies is greatly reduced, maintaining its applicability in terms of reliability and power density.

[0140] In the above embodiments of the present disclosure, the switches of the inductive auxiliary voltage divider circuit unit continue their on / off commutation at each switching frequency, while the remaining switches can be modulated during sinusoidal PWM (SPWM) commutation.

[0141] The CG-based TL inverters of related technologies cannot be directly extended to three phases from a single DC power supply, while the inverter disclosed herein overcomes this shortcoming; and because the inductor-assisted voltage divider circuit contains an inductor, the present disclosure has the advantage that the input current waveform will not exhibit large pulsating discontinuous waveforms.

[0142] In the topology of the above embodiments of this disclosure, two capacitors C1 and C2 are used as a virtual DC link, wherein C2 serves to provide the converter with a quasi-soft charge operation (QSC), while simultaneously providing a quasi-soft charge operation through C1 and V. in Charging is relatively easy to identify. Furthermore, the single-phase circuit configuration in the above embodiments of this disclosure requires seven power switches, two capacitors, two power diodes, and one inductor, using the same SB unit (inductive auxiliary voltage divider circuit) to generate the required output voltage boost DC link. The above embodiments of this disclosure, by integrating the SB unit and cascading (parallel connecting) the remaining parts of the proposed circuit, can realize the three-phase expansion of the proposed TL inverter, which is also relatively easy to identify.

[0143] The above embodiments of this disclosure propose a novel CG inverter with reduced number of switches, which has boost characteristics and can be scaled up to three-phase systems while maintaining its CG characteristics.

[0144] The embodiments described above present a novel topology for a CG-based TL inverter, which has the capability to generate five output voltage levels per phase and can be extended to a three-phase configuration in a modular design and single-power processing stage.

[0145] According to another aspect of this disclosure, a non-phase power supply system is provided, including any of the embodiments described above (e.g., Figures 1-4 , Figures 6-11 The grid-connected inverter described in any embodiment.

[0146] The through-phase power supply system of the three-phase to single-phase converter disclosed in the above embodiments is a novel traction power supply system. It realizes three-phase / single-phase conversion through controllable power electronic devices, realizes the full-line continuity of the traction network, and can completely solve the problem of excessive phase separation.

[0147] Figure 12 This is a schematic diagram of some embodiments of the grid-connected inverter control method of this disclosure. Preferably, this embodiment can be executed by the grid-connected inverter control device of this disclosure, the grid-connected inverter of this disclosure, or the in-phase power supply system of this disclosure. The method includes step 200, wherein:

[0148] Step 200: Control the grid-connected inverter to boost the output voltage of the AC power supply, wherein the grid-connected inverter is as described in any of the above embodiments (e.g., Figures 1-4 , Figures 6-11 The grid-connected inverter described in any embodiment.

[0149] In some embodiments of this disclosure, step 200 may include: controlling the first and second switching transistors in the inductive auxiliary voltage divider circuit of the grid-connected inverter to be turned on alternately at a predetermined time interval.

[0150] In some embodiments of this disclosure, step 200 may include only one of steps 210-260, wherein:

[0151] Step 210: After a predetermined time interval in the first working state, the first working state is switched to the second working state by controlling the switching transistor to turn on and off.

[0152] Step 220: After a predetermined time interval in the second working state, the second working state is switched to the third working state by controlling the switching transistor to turn on and off.

[0153] Step 230: After a predetermined time interval in the third working state, switch the third working state to the fourth working state by controlling the switching transistor to turn on and off.

[0154] Step 240: After a predetermined time interval in the fourth working state, switch the fourth working state to the fifth working state by controlling the switching transistor to turn on and off.

[0155] Step 250: After a predetermined time interval in the fifth working state, switch the fifth working state to the sixth working state by controlling the switching transistor to turn on and off.

[0156] Step 260: After a predetermined time interval in the sixth working state, the sixth working state is switched to the first working state by controlling the conduction and turn-off of the switching transistors. The switching transistors include the first and second switching transistors in the inductive auxiliary voltage divider circuit, and the first power switch S1, the second power switch S2, the third power switch S3, the fourth power switch S4, and the fifth power switch Sb in the single-phase power supply circuit.

[0157] The above embodiments of this disclosure propose a control method for a CG-based TL inverter that can generate five output voltage levels per phase and can be extended to a three-phase configuration in a modular design and single-power processing stage.

[0158] The switch (first switching transistor S) of the inductive auxiliary voltage divider circuit unit in the above embodiments of this disclosure. SB Second switch D SB At each switching frequency, the switching continues its on / off commutation, while the remaining switches (first power switch S1, second power switch S2, third power switch S3, fourth power switch S4 and fifth power switch Sb) can be modulated during sinusoidal PWM (SPWM) commutation.

[0159] Figure 13 This is a schematic diagram of the structure of some embodiments of the grid-connected inverter control device disclosed herein. For example... Figure 13 As shown, the grid-connected inverter control device disclosed herein may include a memory 131 and a processor 132.

[0160] Memory 131 is used to store instructions, and processor 132 is coupled to memory 131. Processor 132 is configured to execute instructions stored in memory as described in any of the above embodiments (e.g., Figures 1-4 , Figures 6-11 The method described in any embodiment.

[0161] like Figure 7 As shown, the controller 13 also includes a communication interface 133 for exchanging information with other devices. Additionally, the controller 13 includes a bus 134, through which the processor 132, communication interface 133, and memory 131 communicate with each other.

[0162] The memory 131 may include high-speed RAM, and may also include non-volatile memory, such as at least one disk storage device. The memory 131 may also be a memory array. The memory 131 may also be divided into blocks, and the blocks may be combined into virtual volumes according to certain rules.

[0163] Furthermore, processor 132 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present disclosure.

[0164] According to another aspect of this disclosure, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores computer instructions that, when executed by a processor, implement any of the embodiments described above. Figures 1-4 , Figures 6-11 The grid-connected inverter control method described in any embodiment.

[0165] In some embodiments of this disclosure, the computer-readable storage medium may be a non-transitory computer-readable storage medium.

[0166] Those skilled in the art will understand that embodiments of this disclosure can be provided as methods, apparatus, or computer program products. Therefore, this disclosure can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this disclosure can take the form of a computer program product embodied on one or more computer-usable non-transitory storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0167] This disclosure is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this disclosure. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0168] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0169] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0170] The grid-connected inverter control device described above can be implemented as a general-purpose processor, programmable logic controller (PLC), digital signal processor (DSP), application-specific integrated circuit (ASIC), field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic device, discrete hardware component or any suitable combination thereof for performing the functions described in this application.

[0171] This concludes the detailed description of the present disclosure. To avoid obscuring the concept of the disclosure, some details known in the art have not been described. Those skilled in the art will fully understand how to implement the technical solutions disclosed herein based on the above description.

[0172] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware, or by a program instructing the relevant hardware to implement them. The program can be stored in a non-transitory computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0173] The description in this disclosure is provided for illustrative and descriptive purposes only and is not intended to be exhaustive or to limit the disclosure to its forms. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of this disclosure and to enable those skilled in the art to understand this disclosure and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A grid-connected inverter comprising a power circuit and an inductive auxiliary voltage dividing circuit, wherein: the power circuit and the inductive auxiliary voltage dividing circuit are connected; the grid-connected inverter is configured to boost an output voltage of an alternating current power supply; the power circuit comprises at least one single-phase power circuit, wherein each single-phase power circuit is connected with the inductive auxiliary voltage dividing circuit, and each single-phase power circuit comprises a first power switch, a third power switch, a fifth power switch and an inductive filter, the first power switch, the third power switch, the inductive filter and the alternating current power supply are connected in series between a third connection point and a ground point; the fifth power switch is arranged between a second connection point and a fourth connection point, and the fourth connection point is a connection point of the first power switch and the third power switch; wherein the inductive auxiliary voltage dividing circuit comprises a direct current input power supply, a first switch tube, a second switch tube, a first capacitor and a first inductor; the first switch tube and the second switch tube are connected in series to form a switch tube circuit; the direct current input power supply and the first capacitor are connected in series to form a voltage dividing circuit; the voltage dividing circuit and the switch tube circuit are connected in parallel; a connection point of the first switch tube and the second switch tube is a first connection point, a connection point of the direct current input power supply and the first capacitor is a second connection point, and the first inductor is arranged between the first connection point and the second connection point; the first switch tube and the direct current input power supply are connected through the ground point, and the second switch tube and the first capacitor are connected through the third connection point; each single-phase power circuit is connected with the inductive auxiliary voltage dividing circuit through the second connection point, the third connection point and the ground point; an output voltage of the inductive auxiliary voltage dividing circuit comprises a voltage between the second connection point and the ground point and a voltage between the third connection point and the ground point, the voltage between the second connection point and the ground point is equal to a voltage of the direct current input power supply, and the voltage between the third connection point and the ground point is equal to twice the voltage of the direct current input power supply.

2. The grid-tied inverter of claim 1, wherein, the power circuit is a single-phase power circuit or a three-phase power circuit, wherein: in the case that the power circuit is a three-phase power circuit, the power circuit comprises three single-phase power circuits; in the case that the power circuit is a single-phase power circuit, the single-phase power circuit is connected with the inductive auxiliary voltage dividing circuit.

3. The grid-tied inverter of claim 1, wherein, each single-phase power circuit further comprises a second power switch, a fourth power switch, a resonant inductor, a second capacitor and a diode, wherein: the second power switch is arranged between the third connection point and the ground point; the second capacitor and the fourth power switch are connected in series and then connected in parallel with the third power switch; the diode and the resonant inductor are connected in series between a fifth connection point and the ground point, and the fifth connection point is a connection point of the second capacitor and the fourth power switch. 4.The grid-connected inverter according to any one of claims 1-3, wherein: in the case that the first switch tube is turned on and the second switch tube is turned off, the direct current input power supply, the first switch tube and the first inductor form a conduction loop to charge the first inductor; in the case that the first switch tube is turned off and the second switch tube is turned on, the second switch tube, the first inductor and the first capacitor form a conduction loop, the first inductor discharges and charges the first capacitor. 5.The grid-connected inverter according to claim 4, wherein: The first switch tube and the second switch tube are alternately turned on at a predetermined time interval, and one of the first switch tube and the second switch tube is turned on while the other is turned off; The voltage across the first capacitor is equal to the DC voltage of the DC input power supply.

6. The grid-connected inverter of any one of claims 1-3, wherein: In the case where the power supply circuit includes N single-phase power supply circuits, the number of different level voltages output by the power supply circuit is 4N+1, where N is a natural number greater than 0.

7. The grid-connected inverter of claim 6, wherein: The number of different level voltages output by the single-phase power supply circuit is 5; The number of different level voltages output by the three-phase power supply circuit is 13.

8. The grid-connected inverter of claim 3, wherein: In the case where the second switch tube, the second power supply switch, and the third power supply switch are turned on, and the first switch tube, the first power supply switch, the fourth power supply switch, and the fifth power supply switch are turned off, the AC power supply, the inductive filter, the second power supply switch, and the third power supply switch form a conduction loop, the single-phase power supply circuit is in the first working state, and the output voltage of the AC power supply is 0.

9. The grid-connected inverter of claim 8, wherein: In the case where the first switch tube, the fifth power supply switch, and the third power supply switch are turned on, and the second switch tube, the first power supply switch, the fourth power supply switch, and the second power supply switch are turned off, the AC power supply, the inductive filter, the third power supply switch, the fifth power supply switch, the input DC power supply, the first inductor, and the first switch tube form a conduction loop, the single-phase power supply circuit is in the second working state, and the output voltage of the AC power supply is the DC voltage of the DC input power supply.

10. The grid-connected inverter of claim 9, wherein: In the case where the first power supply switch and the third power supply switch are turned on, and the fifth power supply switch, the fourth power supply switch, and the second power supply switch are turned off, the AC power supply, the inductive filter, the third power supply switch, the first power supply switch, the input DC power supply, the first capacitor, the second capacitor, the diode, and the resonant inductor form a conduction loop, the single-phase power supply circuit is in the third working state, and the output voltage of the AC power supply is twice the DC voltage of the DC input power supply.

11. The grid-connected inverter of claim 10, wherein: In the case where the fourth power supply switch and the fifth power supply switch are turned on, and the first power supply switch, the second power supply switch, and the third power supply switch are turned off, the AC power supply, the inductive filter, the fourth power supply switch, the diode, and the resonant inductor form a conduction loop, the single-phase power supply circuit is in the fourth working state, and the output voltage of the AC power supply is 0.

12. The grid-connected inverter of claim 11, wherein: In the case where the fifth power supply switch and the fifth power supply switch are turned on, and the first power supply switch, the third power supply switch, and the second power supply switch are turned off, the AC power supply, the inductive filter, the fourth power supply switch, the second capacitor, the fifth power supply switch, and the input DC power supply form a conduction loop, the single-phase power supply circuit is in the fifth working state, and the output voltage of the AC power supply is the opposite of the DC voltage of the DC input power supply.

13. The grid-connected inverter of claim 12, wherein: In the case that the second power switch and the fourth power switch are turned on, and the first power switch, the third power switch and the fifth power switch are turned off, the AC power supply, the inductive filter, the fourth power switch, the second capacitor and the second power switch form a conduction loop, the single-phase power supply circuit is in the sixth working state, and the output voltage of the AC power supply is the opposite number of twice the DC voltage of the DC input power supply.

14. The grid-connected inverter of claim 13, wherein: The single-phase power supply circuit is configured to switch the first working state to the second working state by controlling the turn-on and turn-off of the switching tubes after being in the first working state for a predetermined time interval; switch the second working state to the third working state by controlling the turn-on and turn-off of the switching tubes after being in the second working state for a predetermined time interval; switch the third working state to the fourth working state by controlling the turn-on and turn-off of the switching tubes after being in the third working state for a predetermined time interval; switch the fourth working state to the fifth working state by controlling the turn-on and turn-off of the switching tubes after being in the fourth working state for a predetermined time interval; switch the fifth working state to the sixth working state by controlling the turn-on and turn-off of the switching tubes after being in the fifth working state for a predetermined time interval; and switch the sixth working state to the first working state by controlling the turn-on and turn-off of the switching tubes after being in the sixth working state for a predetermined time interval, wherein the switching tubes include the first switching tube and the second switching tube in the inductive auxiliary voltage dividing circuit, and the first power switch, the second power switch, the third power switch, the fourth power switch and the fifth power switch in the single-phase power supply circuit.

15. A phase-locked power supply system, comprising the grid-connected inverter of any one of claims 1-14.

16. A grid-connected inverter control method, comprising: controlling the grid-connected inverter to step up the output voltage of the AC power supply, wherein the grid-connected inverter is the grid-connected inverter of any one of claims 1-14.

17. The grid-tied inverter control method of claim 16, wherein, The controlling the grid-connected inverter to step up the output voltage of the AC power supply comprises: controlling the first switching tube and the second switching tube in the inductive auxiliary voltage dividing circuit of the grid-connected inverter to alternately turn on at a predetermined time interval.

18. The grid-tied inverter control method of claim 17, wherein, The controlling the grid-connected inverter to step up the output voltage of the AC power supply further comprises: switching the first working state to the second working state by controlling the turn-on and turn-off of the switching tubes after being in the first working state for a predetermined time interval; and / or, switching the second working state to the third working state by controlling the turn-on and turn-off of the switching tubes after being in the second working state for a predetermined time interval; and / or, switching the third working state to the fourth working state by controlling the turn-on and turn-off of the switching tubes after being in the third working state for a predetermined time interval; and / or, switching the fourth working state to the fifth working state by controlling the turn-on and turn-off of the switching tubes after being in the fourth working state for a predetermined time interval; and / or, switching the fifth working state to the sixth working state by controlling the turn-on and turn-off of the switching tubes after being in the fifth working state for a predetermined time interval; and / or, After being in the sixth working state for a predetermined time interval, the sixth working state is switched to the first working state by controlling the turn-on and turn-off of the switch tubes, The switch tubes include a first switch tube and a second switch tube in an inductive auxiliary voltage division circuit, and a first power switch, a second power switch, a third power switch, a fourth power switch and a fifth power switch in a single-phase power supply circuit. 19.A grid-connected inverter control device, comprising: a memory configured to store instructions; a processor configured to execute the instructions to cause the grid-connected inverter control device to implement the grid-connected inverter control method of any one of claims 16-18.

20. A computer readable storage medium, wherein, The computer readable storage medium stores computer instructions, and the instructions are executed by the processor to implement the grid-connected inverter control method of any one of claims 16-18.

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