Double-separation-source multi-level converter and power supply system

Abstract

The invention relates to the technical field of new energy and energy conservation, in particular to a double-separation-source multi-level converter and a power supply system, and the converter mainly comprises a double-separation-source converter unit and a switched capacitor unit which are arranged in parallel. The switched capacitor unit is used for controlling the charging process or the discharging process of the direct-current capacitors corresponding to the capacitor switches at different positions according to the state of the accessed direct-current power supply and load requirements, and outputting different levels of voltages; the double-separation-source converter unit is used for accessing two direct-current power supplies; comprising two inverter loops, and the inverter loops are arranged corresponding to a direct-current power supply and used for rectifying and boosting different levels of voltage to generate alternating-current voltage meeting the load requirement. The converter can adapt to various different working scenes and load requirements, and the flexibility and adaptability of the system are improved.

Description

Technical Field

[0001] The invention relates to the technical field of new energy and energy-saving, and in particular to a dual-separation-source multi-level converter and a power supply system. Background Art

[0002] With the rapid development of the world's industry, the extensive use of traditional energy and the corresponding carbon emissions are gradually causing a significant impact on the world's environmental sustainability. In response to these challenges, people are paying more and more attention to renewable energy technologies, such as energy storage batteries, photovoltaic (PV) systems and hydrogen fuel cells, which have promoted decarbonization in industry and received widespread attention.

[0003] However, most renewable energy power generation units still face some technical challenges. For example, in the power grid system, due to the diversity and complexity of power generation units and loads, the bus output voltage is usually low and fluctuating, which requires the deployment of high-performance boost inverters to ensure a stable voltage level that meets the diverse load / grid requirements. The DC side voltage requirement of the traditional unipolar DC-AC inverter is greater than the AC side voltage. Such a circuit topology is not applicable to low-voltage renewable energy power generation units, so a boost DC-DC converter is integrated between the low-voltage renewable energy power generation unit and the DC end of the DC-AC inverter. Despite its advantages, the actual voltage gain capability of this combination is limited. In addition, the two-stage power conversion process also increases losses and system complexity. In response to the above problems, some people have designed a new topology combining a DC-DC converter and a DC-AC converter: a Z-source converter and a single separated source converter (DSSI).

[0004] The Z-source converter uses an impedance network, which includes four passive components and a diode, as a buck-boost inverter. However, the inductor and capacitor parameters of the converter are different in different application scenarios, which increases the complexity of actual deployment. At the same time, when the converter is in a stable working state, the output current of the DC source is intermittent, which will have a great impact on the life of the DC source.

[0005] The topology of the single separated source converter (DSSI) can achieve continuous and stable output current of the DC source, which completely solves the fatal problem of the Z source converter. However, this topology still has many challenges, such as excessive voltage stress on the switch tube, the circuit topology requires a larger volume and value of DC capacitors to reduce the double frequency ripple, and requires a larger volume and value of filter devices to eliminate PWM harmonics. In addition, in the actual deployment scenario of new energy systems, external environmental factors need to be considered. For example, in the case of partial shading during the operation of photovoltaic panels, the energy conversion efficiency of the single separated source converter (DSSI) will be reduced, which will reduce the overall reliability of the power generation unit. Therefore, it is necessary to consider the combination of multiple new energy power generation units and converters to improve the reliability and efficiency of the overall system. At the same time, the connection between the new energy power generation unit and the power electronic converter is mostly one-to-one, and the ability to cope with sudden environmental changes is insufficient. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a dual-separation-source multi-level converter and a power supply system for solving the technical problems of insufficient adaptability and small application range of current converters in view of the deficiencies in the above-mentioned prior art.

[0007] The objective of the present invention is achieved by the following technical solutions: In a first aspect, the present invention provides a dual-split-source multi-level converter, comprising a dual-split-source converter unit and a switch capacitor unit arranged in parallel; The switch capacitor unit is used to control the charging process or discharging process of the DC capacitors corresponding to the capacitor switches at different positions according to the state of the connected DC power supply and the load requirements, and output voltages of different levels; The dual-separation source converter unit is used to access two DC power supplies; it includes two inverter circuits, and the inverter circuits are set corresponding to the DC power supplies to rectify and boost voltages of different levels to generate AC voltages that meet load requirements. As a further improvement of the present invention, the switched capacitor unit includes a plurality of switched capacitor submodules arranged in parallel, the switched capacitor network submodule includes a capacitor, at least one capacitor switch connected in series at both ends of the capacitor, and a capacitor switch arranged in parallel at both ends of the capacitor; the control capacitor switches act on the DC power supplies in the dual separation source converter units respectively; the capacitors of the switched capacitor submodules are arranged on another switched capacitor submodule and connected in series with the capacitor switches arranged in parallel.

[0008] As a further improvement of the present invention, the switch capacitor submodule includes a capacitor and a first capacitor switch, a second capacitor switch and a third capacitor switch; the first capacitor switch is arranged in series with the capacitor as a first circuit; the second capacitor switch and the third capacitor switch are arranged in series as a second circuit, and the second circuit is arranged in parallel at both ends of the capacitor.

[0009] As a further improvement of the present invention, the dual-separation source converter unit comprises a first inverter circuit and a second inverter circuit arranged in parallel; The first inverter circuit includes a first inductor, a first diode, a second diode, a first switch and a second switch; the anode of the first diode is connected to the switch capacitor unit through the first switch, the cathode of the first diode is connected in parallel with the cathode of the second diode in the same direction, and connected to a DC power supply through the first inductor after being connected in parallel, and the anode of the second diode is connected to the switch capacitor unit through the second switch; The second inverter circuit includes a second inductor, a third diode, a fourth diode, a third switch and a fourth switch; the cathode of the third diode is connected to the switch capacitor unit through the third switch, and the anode is arranged in parallel with the anode of the fourth diode in the same direction, and is connected to the DC power supply through the second inductor after parallel connection; the cathode of the fourth diode is connected to the switch capacitor unit through the fourth switch.

[0010] As a further improvement of the present invention, a fifth switch is further provided in the first inverter circuit and the second inverter circuit. The fifth switch is provided in parallel between the anode of the first diode and the cathode of the third diode.

[0011] As a further improvement of the present invention, the first capacitor switch, the second capacitor switch and the third capacitor switch are all field effect transistors, MOS transistors or IGBT transistors; The first switch, the second switch, the third switch, the fourth switch and the fifth switch all adopt field effect tubes, MOS tubes or IGBT tubes.

[0012] As a further improvement of the present invention, the switching capacitor unit of the converter includes two parallel switching capacitor sub-modules; the converter is configured to generate a first effective voltage level, a second effective voltage level, a third effective voltage level and a fourth effective voltage level in a positive half-cycle and a negative half-cycle of a cycle; the voltage value of the first effective voltage level is equal to the AC side voltage value; the value of the second effective voltage level is twice the AC side voltage value; the third effective voltage level is three times the AC side voltage value; and the fourth effective voltage level is a zero voltage value.

[0013] As a further improvement of the present invention, when the output voltage is in the first effective voltage level state, the second capacitor switch in each switch capacitor submodule is in an open state, the first capacitor switch and the third capacitor switch are in a closed state, the voltage of the capacitor in each switch capacitor submodule is balanced and distributed, and any switch in the first inverter circuit and the second inverter circuit is in an open state; When the output voltage is in the second effective voltage level state, the first capacitor switch and the third capacitor switch in the first switch capacitor submodule are in the open state, and the second capacitor switch is in the closed state; and the second capacitor switch in the other switch capacitor submodule is in the open state, the first capacitor switch and the third capacitor switch are in the closed state, and any switch in the first inverter circuit and the second inverter circuit is in the open state; When the output voltage is in the third effective voltage level state, the first capacitor switch and the third capacitor switch in each switch capacitor submodule are in the open state, the second capacitor switch is in the closed state, and any switch in the first inverter loop and the second inverter loop is in the open state; When the output voltage is in the fourth effective voltage level state, the second capacitor switch in each switch capacitor submodule is in the disconnected state, the first capacitor switch and the third capacitor switch are in the closed state, and the dual separation source converter unit satisfies any of the following conditions: the first switch and the second switch in the first inverter circuit are in the disconnected state, and the third switch and the fourth switch in the second inverter circuit are in the closed state; the first switch and the second switch in the first inverter circuit are in the closed state, and the third switch and the fourth switch in the second inverter circuit are in the disconnected state; the first switch and the second switch in the first inverter circuit are in the closed state; the fourth switch and the fifth switch in the second inverter circuit are in the disconnected state.

[0014] As a further improvement of the present invention, the converter adopts a level-shift PWM method to control the switching capacitor unit and the dual-separation source converter unit, and the level-shift PWM method adopts a positive reference voltage signal, a negative reference voltage signal and a zero reference voltage signal; the positive reference voltage signal and the negative reference voltage signal are placed between the peak values ​​of the sinusoidal reference wave and the triangular carrier.

[0015] In a second aspect, the present invention provides a power supply system, comprising a dual-split-source multilevel converter and two DC power sources, wherein one end of the converter is used to connect to the two DC power sources, and the other end is used to connect to a load, and the converter adopts the above-mentioned dual-split-source multilevel converter.

[0016] The beneficial effects of the present invention are as follows: the dual-separation source multi-level converter of the present invention, wherein the switch capacitor unit can accurately control the charging and discharging process of the DC capacitor corresponding to the capacitor switch at different positions according to the DC power supply state and load requirements, thereby outputting voltages of different levels. This enables the converter of the present invention to adapt to a variety of different working scenarios and load requirements, and improves the flexibility and adaptability of the system. The two inverter circuits in the dual-separation source converter unit can rectify and boost voltages of different levels to generate an AC voltage that meets the load requirements, wherein the two inverter circuits of the dual-separation source converter unit are independent of each other, which can improve the reliability and fault tolerance of the system. If one inverter circuit fails, the other inverter circuit can still continue to work to ensure the normal power supply of the load. This multi-level conversion method can provide a smoother output voltage waveform, reduce the voltage harmonic content, and improve the power quality. The design of the converter of the present invention in which two DC power supplies are connected enables the converter to make full use of energy from different sources and improve the comprehensive utilization efficiency of energy. The design of the switch capacitor unit can reduce the influence of the voltage fluctuation of the DC power supply on the output voltage, and improve the stability and reliability of the system. At the same time, the capacitor in the switched capacitor unit can play a filtering role, reduce the ripple in the output voltage, and improve the power quality.

[0017] Furthermore, multiple switched capacitor submodules arranged in parallel provide the system with a rich means of voltage regulation. By controlling the capacitor switches in different submodules, the charge and discharge state of the capacitor can be accurately adjusted, thereby outputting different levels of voltage to meet the needs of various loads.

[0018] Furthermore, by controlling the states of the three capacitor switches, different circuit combinations can be realized. Different connection modes of the first circuit and the second circuit can realize fine control of the charging and discharging process of the capacitor. According to actual needs, fast charging, slow discharging or other specific charging and discharging modes can be selected, which improves the flexibility and adaptability of the system. By using the switched capacitor structure, the system output voltage can be significantly improved, the harmonic content and the voltage stress on the switch tube can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] FIG. 1( a ) is a generalized N-level configuration diagram of a dual-input isolated multi-level inverter current diagram in an embodiment of the present invention; FIG1( b ) is a proposed 7-level configuration diagram of a dual-input isolated multi-level inverter current diagram in an embodiment of the present invention; FIG2( a ) is a circuit diagram of a converter topology provided by an embodiment of the present invention when the output is a first effective voltage level in a positive half cycle; FIG2( b ) is a circuit diagram of a converter topology provided by an embodiment of the present invention when the output is a first effective voltage level during a negative half cycle; FIG2( c ) is a circuit diagram of a converter topology provided by an embodiment of the present invention when the output is a second effective voltage level in a positive half cycle; FIG2( d ) is a circuit diagram of a converter topology provided by an embodiment of the present invention when the output is a second effective voltage level during a negative half cycle; FIG2( e ) is a circuit diagram of a converter topology provided by an embodiment of the present invention when the output is a third effective voltage level in a positive half cycle; FIG2( f ) is a circuit diagram of a converter topology provided by an embodiment of the present invention when the output is a third effective voltage level during a negative half cycle; FIG2( g ) is a circuit diagram of a converter topology provided by an embodiment of the present invention when the output is a fourth effective voltage level during a positive half cycle; FIG2( h ) is a circuit diagram of a converter topology provided by an embodiment of the present invention when the output is a fourth effective voltage level during a negative half cycle; FIG2(i) is a circuit diagram of a converter topology provided by an embodiment of the present invention when the output is a standard zero voltage level; Figure 3 It is a curve schematic diagram of an improved level-shifted PWM method of the topology provided by an embodiment of the present invention; Figure 4 It is a steady-state waveform diagram of the upper and lower source voltages and the inductor current when the dual input source provided by the embodiment of the present invention is working; Figure 5 It is a steady-state waveform diagram of the load voltage Vo, the AC side voltage, the load current io and the output inverter voltage Vab when the dual input source is working according to the embodiment of the present invention; Figure 6 It is a steady-state waveform diagram of the upper and lower source voltages and the inductor current when the upper input source provided by the embodiment of the present invention is working; Figure 7 is a steady-state waveform diagram of upper and lower source voltages and inductor current during lower input operation provided by an embodiment of the present invention; Figure 8 It is the steady-state waveform of the load voltage Vo, the AC side voltage, the load current io and the output inverter voltage Vab when only a single input source is working provided by the embodiment of the present invention; Fig. 9 Schematic diagram of voltage curves on the switch capacitors C1, C2 and C3 provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose and technical solution of the present invention clearer and easier to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] Explanation of relevant terms: Switching Capacitor Multilevel: Switching capacitor multilevel technology mainly achieves different levels of output by controlling a series of switches and capacitors. Its basic principle is to use the charging and discharging of capacitors to build multiple different voltage levels; Dual Input Split Source Inverter: Dual Input Split Source Inverter; PWM (Pulse Width Modulation): Pulse width modulation.

[0023] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, wherein the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0024] Example 1 As shown in Figure 1- Fig. 9 As shown, this embodiment provides a dual-split-source multi-level converter, which mainly includes a dual-split-source converter unit and a switch capacitor unit connected in series; The switching capacitor unit (Switching Capacitor Multilevel) is used to control the charging or discharging process of the DC capacitors corresponding to the capacitor switches at different positions according to the state of the connected DC power supply and the load requirements, and output voltages of different levels; The dual input split source inverter unit is used to connect two DC power supplies; it includes two inverter circuits, which are set corresponding to the DC power supply to rectify and boost voltages of different levels to generate AC voltages that meet load requirements. Each input DC source is defined by a set voltage or current standard.

[0025] Among them, the switched capacitor unit includes N (N≥2) switched capacitor submodules arranged in parallel, and the switched capacitor network submodule includes a capacitor C, at least one capacitor switch S connected in series at both ends of the capacitor, and a capacitor switch arranged in parallel at both ends of the capacitor; the control capacitor switches act on the DC power supply in the dual separation source converter unit respectively. The capacitor of the switched capacitor submodule is arranged on another switched capacitor submodule and connected in series with the capacitor switch arranged in parallel. The switched capacitor submodule is in the form of a switched capacitor network, and the scalability of the structure can be enhanced by gradually increasing the number of SC stages. Depending on the switch position, the DC capacitor can be configured in series or in parallel to achieve various output voltage levels. These output voltage levels, as well as the number of switches and capacitors required, are described in detail in the subsequent steps. Among them, the subsequent circuit adopts a 3-level configuration.

[0026] The switch capacitor submodule includes a capacitor C1 and a first capacitor switch S 11 , the second capacitor switch S 12 and a third capacitor switch S 13 ; The first capacitor switch S 11 With capacitor C T The second capacitor switch S 12 , the third capacitor switch S 13 The second circuit is connected in series with a capacitor C T The capacitor C2 in another switch capacitor submodule is also arranged in parallel in the switch capacitor submodule, and one end is connected through the first capacitor switch S 11 Connected to capacitor C1, the other end is set in series with the second capacitor switch S 12 , the third capacitor switch S 13 The other switch capacitor submodules in this embodiment are arranged in this way, until the last capacitor CN is arranged between the second capacitor switch and the third capacitor switch in the adjacent switch capacitor submodule, and is connected to the capacitor in the adjacent switch capacitor submodule through the first capacitor switch.

[0027] Specifically, in this embodiment, there are three switch capacitor submodules. Then, the capacitor C2 in the second switch capacitor submodule and the capacitor switch S 21 Set in series, capacitor switch S 22 , Capacitor switch S 23 After the series connection, the two ends of capacitor C2 are connected in parallel, and one end of the third capacitor C3 is set on the capacitor switch S 22 , Capacitor switch S 23 The other end is connected through the capacitor switch S 21 Connected to capacitor C2.

[0028] The dual-split source converter unit includes a first inverter circuit and a second inverter circuit arranged in parallel; The first inverter circuit includes a first inductor L1, a first diode D 11 , the second diode D 12 , a first switch S3 and a second switch S4; a first diode D 11 The anode of the first diode D is connected to the switched capacitor unit through the first switch S3. 11 The cathode of the second diode D 12 The cathodes of the two electrodes are connected in parallel in the same direction and connected to the DC power supply V through the first inductor L1. in1 , the second diode D 12 The anode is connected to the switched capacitor unit through the second switch S4; wherein the first DC power supply V in1 is also connected to the switch capacitor unit. in1 , first switch S3, first diode D 11 and the first inductor L1 form a first boost circuit; the first DC power supply V in1 , second switch S4, second diode D 12 The first inductor L1 forms a second boost circuit. The first DC power supply V in1 Through the first switch S3 (or the second switch S4), the inductor L1 and the diode D 11 and D 12 Form a boost circuit.

[0029] The second inverter circuit includes a second inductor L2, a third diode D 21 , the fourth diode D 22 , a third switch S1 and a fourth switch S2; a third diode D 21 The cathode of is connected to the switched capacitor unit through the third switch S1, and the anode is connected to the fourth diode D 22 The anodes of the two electrodes are connected in parallel in the same direction and then connected to a DC power supply V through a second inductor. in2 ; The fourth diode D 22 The cathode of is connected to the switch capacitor unit through the fourth switch S2. Similarly, the second DC power supply V in1 Through the third switch S3 (or the second switch S4), the inductor L1 and the diode D 11 and D 12 Form a boost circuit.

[0030] The second DC power supply V in2 , the third switch S1, the third diode D 21 and the second inductor L2 form a third boost loop; the second DC power supply V in2 , the fourth switch S2, the fourth diode D 22The second inductor L2 forms a fourth boost loop.

[0031] The first inverter circuit and the second inverter circuit are further provided with a fifth switch S5, which is connected in parallel with the first diode D 11 The anode of the third diode D 21 between the cathodes.

[0032] The load resistor is arranged at the output end of the dual split source converter unit.

[0033] In this embodiment, the generalized N-stage configuration of the SC-DSSMLI topology is shown in Figure 1(a). The structure is carefully designed and consists of two basic parts: an improved dual-input split-source inverter (DSSI) and a generalized switched capacitor (GSC) network. The primary branch of the DSSI adopts a unique three-switch layout, and the secondary branch adopts a two-switch structure. The power is taken from two different input sources V in1 and V in2 transmission, each input is defined by a specific voltage and current standard. In addition, the number of these input sources is independent of the number of required output levels, which provides flexibility in system configuration without being limited by the number of output levels. The GSC network consists of multiple switched capacitor (SC) cells, and n SC cells can be connected in the proposed topology to increase the output voltage level. Each SC cell consists of a series / parallel combination of capacitors and switches, specifically including a capacitor (CT) and three switches (S T1 , S T2 and S T3 ). The modular nature of the architecture allows the voltage level of the inverter to be systematically expanded by gradually increasing the number of stacked SC units. This inherent scalability and configuration flexibility is a key feature of the proposed topology as it enables the inverter to be tailored to specific application requirements, whether it is to increase the voltage level or enhance the output accuracy. Figure 1(b) shows the specific implementation of the 7-level configuration in the proposed SC-DSSMLI topology in detail. This configuration, by including two SC units (n=2), demonstrates the modularity and adaptability of the system and highlights the ease of topology expansion.

[0034] All the capacitor switches and switches in this embodiment are field effect transistors, MOS transistors or IGBT transistors.

[0035] According to the structure of the converter in this embodiment, the working state of the converter is configured in the positive half cycle and the negative half cycle of a cycle to generate working states of the first effective voltage level, the second effective voltage level, the third effective voltage level and the fourth effective voltage level; the voltage value of the first effective voltage level is equal to the AC side voltage value; the value of the second effective voltage level is twice the AC side voltage value; the third effective voltage level is three times the AC side voltage value; and the fourth effective voltage level is zero voltage value.

[0036] As shown in FIG2 (a) and FIG2 (b), when the output voltage is in the first effective voltage level state, the second capacitor switch in each switch capacitor submodule is in the disconnected state, the first capacitor switch and the third capacitor switch are in the closed state, the voltage of the capacitor in each switch capacitor submodule is balanced, and any switch in the first inverter circuit and the second inverter circuit is in the disconnected state; at this time, the capacitors C1, C2, and C3 in each switch capacitor submodule are arranged in parallel, so the voltages at both ends of each capacitor are equal, that is, the voltage distribution on the capacitor is balanced. Therefore, the balanced capacitor voltage makes the output voltage on the AC side exactly equal to the voltage of the output inverter circuit, that is, V ab = ±V cn , thereby achieving the desired voltage state.

[0037] As shown in FIG. 2 (c) and FIG. 2 (d), when the output voltage is in the second effective voltage level state, the first capacitor switch and the third capacitor switch in the first switch capacitor submodule are in the open state, and the second capacitor switch is in the closed state; and the second capacitor switch in the other switch capacitor submodule is in the open state, the first capacitor switch and the third capacitor switch are in the closed state, and any switch in the first inverter circuit and the second inverter circuit is in the open state; at this time, the capacitor C2 in the second switch capacitor submodule and the capacitor C3 in the third switch capacitor submodule are connected in parallel, and then connected in series with the capacitor C1 in the first switch capacitor submodule, so the total voltage is {V C1 +(V C2 / / V C3 )} (Here / / means parallel connection, and V C1 +V C2 or V C1 +V C3 ), the final output inverter circuit voltage satisfies V ab = ±2 V cn .

[0038] As shown in Figure 2 (e) and Figure 2 (f), when the output voltage is in the third effective voltage level state, the first capacitor switch and the third capacitor switch in each switch capacitor submodule are in the open state, the second capacitor switch is in the closed state, and any switch in the first inverter circuit and the second inverter circuit is in the open state. At this time, the capacitors C1, C2, and C3 in each switch capacitor submodule are connected in series. Therefore, the total equivalent voltage becomes {V C1 +V C2 +V C3}, thereby achieving the required output voltage V ab = ±3 V cn .

[0039] As shown in Figure 2 (g), Figure 2 (h) and Figure 2 (i), when the output voltage is in the fourth effective voltage level state, the second capacitor switch in each switch capacitor submodule is in the open state, the first capacitor switch and the third capacitor switch are in the closed state, and the dual separation source converter unit satisfies any of the following conditions: the first switch and the second switch in the first inverter circuit are in the open state, and the third switch and the fourth switch in the second inverter circuit are in the closed state; the first switch and the second switch in the first inverter circuit are in the closed state, and the third switch and the fourth switch in the second inverter circuit are in the open state; the first switch and the second switch in the first inverter circuit are in the closed state; the fourth switch and the fifth switch in the second inverter circuit are in the open state. In the zero voltage state, as shown in Figure 2 (g), the DC capacitor is charged using a lower input voltage. As shown in Figure 2 (h), the first DC power supply V in1 To promote the charging of the capacitors to achieve voltage balance between the capacitors. Therefore, capacitors C1, C2, and C3 must be connected in parallel to ensure that each capacitor reaches an equal voltage level. Figure 2 (i) shows the standard zero voltage state. To further clarify the switching state, capacitor connection, and its corresponding impact on the inverter output voltage, Table 1 provides a detailed and comprehensive overview of the operation of this topology.

[0040] Table 1

[0041] Table 1 shows the switch status, capacitor connection and inverter output voltage of the 7-level SC-DSSMLI, where (↑) indicates charging, (↓) indicates discharging, and (-) indicates no effect.

[0042] like Figure 3As shown, the converter of this embodiment uses a level shift PWM method to control the switch capacitor unit and the dual split source converter unit, wherein the level shift PWM method includes three reference signals and six triangular carriers. The level shift PWM method uses a positive reference voltage signal, a negative reference voltage signal and a zero reference voltage signal; the positive reference voltage signal and the negative reference voltage signal are placed between the peak values ​​of the sinusoidal reference wave and the triangular carrier. The design includes a voltage boost strategy, wherein a constant positive reference voltage signal +V const and negative reference voltage signal -V const In the sinusoidal reference wave V sine and the triangular carrier V tri This configuration is achieved by placing a fixed reference voltage +V const and -V const With the triangular carrier V tri The comparison is made to control the charging duty cycle D of the upper and lower inductors.

[0043] After simulation based on the above converter topology, corresponding simulation results are obtained. Figure 4 , Figure 5 The input voltage and current of the converter (SC-DSSMLI) in this embodiment are clearly shown, proving its efficient and reliable design. The continuous curve of input current highlights the inherent advantages of the efficient design and configuration of SC-DSSMLI. Figure 4-Figure 7 The steady-state waveform is shown, illustrating the AC side voltage generated by a well-designed switched capacitor circuit. It is worth noting that the AC side voltage waveform V inv The three-stage ladder configuration is presented, and each stage corresponds to a different operation stage of the circuit. The calculated input voltage is 30V, while the AC side voltage amplitude is 450V, with a boost factor of 15. This ladder configuration on the AC side results in a voltage V ab The reappearance of these steps in the output voltage curve indicates that the inverter uses a well-controlled switching strategy. When evaluating the inverter performance, special emphasis is placed on the output voltage V at unity power factor. o , which is a key parameter for evaluating the efficiency of power conversion systems. During the voltage analysis, the output current i under steady-state conditions is also strictly checked. o Simultaneous analysis of voltage and current profiles is critical to fully understand the operation of the inverter and its impact on the overall power converter performance.

[0044] Additionally, the SC-DSSMLI configuration offers significant advantages due to its ability to operate with single or dual input sources, utilizing inputs from above, below or simultaneously, as required. Figure 6 , Figure 7 and Figure 8The main concepts of the SC-DSSMLI are clearly demonstrated, showing its operational capabilities and performance in three different scenarios. This flexibility highlights the effectiveness of the configuration in a variety of operating environments. In single-input operation, the AC side voltage varies slightly while the DC source current remains within the 8A limit, resulting in lower output power than in the dual-input source scenario.

[0045] Fig. 9 shows continuous monitoring of the switched capacitor voltage. The results show that the voltage remains stable and balanced with only slight fluctuations or voltage ripples. This stability is critical to producing a stable and predictable output waveform. The system includes two different boost circuits that play a key role in maintaining voltage balance. These configurations are designed to ensure equal voltage charging of the switched capacitors. This balanced charging is critical to the efficient operation of the system, preventing any individual capacitor from being overcharged or undercharged relative to the others. By maintaining equal voltage across all capacitors, overall efficiency and reliability are improved, ensuring that the output waveform remains regular and stable.

[0046] Example 2 This embodiment provides a power supply system, including a dual-separation-source multi-level converter and two DC power sources, one end of the converter is used to connect to the two DC power sources, and the other end is used to connect to the load, and the converter adopts the dual-separation-source multi-level converter in the above embodiment 1. The DC power source is a new energy power generation unit, such as a photovoltaic power generation unit, a wind power generation unit, etc.

Claims

1. A dual split-source multilevel converter, characterized in that: It includes a dual split source converter unit and a switch capacitor unit arranged in parallel; The switch capacitor unit is used to control the charging process or discharging process of the DC capacitors corresponding to the capacitor switches at different positions according to the state of the connected DC power supply and the load requirements, and output voltages of different levels; The dual-separation source converter unit is used to access two DC power supplies; it includes two inverter circuits, and the inverter circuits are set corresponding to the DC power supplies to rectify and boost voltages of different levels to generate AC voltages that meet load requirements.

2. The dual split-source multi-level converter according to claim 1, characterized in that: The switch capacitor unit includes a plurality of switch capacitor submodules arranged in parallel, the switch capacitor network submodule includes a capacitor, at least one capacitor switch connected in series at both ends of the capacitor, and a capacitor switch arranged in parallel at both ends of the capacitor; the control capacitor switches act on the DC power supply in the dual separation source converter unit respectively; the capacitor of the switch capacitor submodule is arranged on another switch capacitor submodule and connected in series with the capacitor switch arranged in parallel.

3. The dual split-source multi-level converter according to claim 2, characterized in that: The switch capacitor submodule includes a capacitor and a first capacitor switch, a second capacitor switch and a third capacitor switch; the first capacitor switch is arranged in series with the capacitor as a first circuit; The second capacitor switch and the third capacitor switch are arranged in series to serve as a second circuit, and the second circuit is connected in parallel to two ends of a capacitor.

4. The dual split-source multi-level converter according to claim 1, characterized in that: The dual-separation source converter unit comprises a first inverter circuit and a second inverter circuit arranged in parallel; The first inverter circuit includes a first inductor, a first diode, a second diode, a first switch and a second switch; the anode of the first diode is connected to the switch capacitor unit through the first switch, the cathode of the first diode is connected in parallel with the cathode of the second diode in the same direction, and connected to a DC power supply through the first inductor after being connected in parallel, and the anode of the second diode is connected to the switch capacitor unit through the second switch; The second inverter circuit includes a second inductor, a third diode, a fourth diode, a third switch and a fourth switch; the cathode of the third diode is connected to the switch capacitor unit through the third switch, and the anode is arranged in parallel with the anode of the fourth diode in the same direction, and is connected to the DC power supply through the second inductor after parallel connection; the cathode of the fourth diode is connected to the switch capacitor unit through the fourth switch.

5. The dual split-source multi-level converter according to claim 4, characterized in that: A fifth switch is further provided in the first inverter circuit and the second inverter circuit. The fifth switch is provided in parallel between the anode of the first diode and the cathode of the third diode.

6. The dual split-source multi-level converter according to claim 1, characterized in that: The first capacitor switch, the second capacitor switch and the third capacitor switch all use field effect transistors, MOS transistors or IGBT transistors; The first switch, the second switch, the third switch, the fourth switch and the fifth switch all adopt field effect tubes, MOS tubes or IGBT tubes.

7. The dual-separation-source multi-level converter according to any one of claims 1 to 5, characterized in that: The switch capacitor unit of the converter includes three switch capacitor submodules connected in parallel; the converter is configured to generate a first effective voltage level, a second effective voltage level, a third effective voltage level and a fourth effective voltage level in a positive half cycle and a negative half cycle of a cycle; The voltage value of the first effective voltage level is equal to the voltage value of the AC side; The value of the second effective voltage level is twice the AC side voltage value; The third effective voltage level is 3 times the AC side voltage value; The fourth effective voltage level is a zero voltage value.

8. The dual split-source multi-level converter according to any one of claims 7, characterized in that: When the output voltage is in the first effective voltage level state, the second capacitor switch in each switch capacitor submodule is in an open state, the first capacitor switch and the third capacitor switch are in a closed state, the voltage of the capacitor in each switch capacitor submodule is balanced, and any switch in the first inverter circuit and the second inverter circuit is in an open state; When the output voltage is in the second effective voltage level state, the first capacitor switch and the third capacitor switch in the first switch capacitor submodule are in the open state, and the second capacitor switch is in the closed state; and the second capacitor switch in the other switch capacitor submodule is in the open state, the first capacitor switch and the third capacitor switch are in the closed state, and any switch in the first inverter circuit and the second inverter circuit is in the open state; When the output voltage is in the third effective voltage level state, the first capacitor switch and the third capacitor switch in each switch capacitor submodule are in the open state, the second capacitor switch is in the closed state, and any switch in the first inverter loop and the second inverter loop is in the open state; When the output voltage is in the fourth effective voltage level state, the second capacitor switch in each switch capacitor submodule is in the disconnected state, the first capacitor switch and the third capacitor switch are in the closed state, and the dual separation source converter unit satisfies any of the following conditions: the first switch and the second switch in the first inverter circuit are in the disconnected state, and the third switch and the fourth switch in the second inverter circuit are in the closed state; the first switch and the second switch in the first inverter circuit are in the closed state, and the third switch and the fourth switch in the second inverter circuit are in the disconnected state; the first switch and the second switch in the first inverter circuit are in the closed state; the fourth switch and the fifth switch in the second inverter circuit are in the disconnected state.

9. The dual split-source multi-level converter according to any one of claims 7, characterized in that: The converter uses a level shift PWM method to control the switch capacitor unit and the dual split source converter unit, and the level shift PWM method uses a positive reference voltage signal, a negative reference voltage signal and a zero reference voltage signal; The positive reference voltage signal and the negative reference voltage signal are placed between the peaks of the sine reference wave and the triangle carrier wave.

10. A power supply system, characterized in that: It comprises a dual-separation-source multilevel converter and two DC power sources, wherein one end of the converter is used to connect to the two DC power sources, and the other end is used to connect to a load, and the converter adopts the dual-separation-source multilevel converter according to any one of claims 1 to 9.

Images