Interconnected power grid high-gain inverter for distributed energy access

Abstract

The present utility model relates to the technical field of electrical energy conversion and new energy power generation, and in particular relates to an interconnected power grid high-gain inverter for distributed energy access. The interconnected power grid high-gain inverter consists of a switched capacitor unit and an L-shaped extension unit. At a left end and a right end, two half bridges are used to convert polarities of output levels, two capacitors can be simultaneously connected in parallel with a direct-current power supply for charging, and three times of voltage gain and seven voltage levels can be generated by means of switching series-parallel connection states between the capacitors and the power supply. The switched capacitor unit comprises the direct-current power supply Vdc, an electrolytic capacitor C1, an electrolytic capacitor C2, a diode D1, a power switch S5, a power switch S6, a power switch S7, a power switch S8, and a power switch S9. The interconnected power grid high-gain inverter for distributed energy access enables the series-parallel connections between the capacitors and the direct-current power supply to be switched to carry out periodic charging and discharging, the voltages of the capacitors can be self-balanced without the need for additional control, and relatively high voltage gain can be generated.

Description

A high-gain inverter for interconnected power grids for distributed energy access Technical Field

[0001] The utility model relates to the technical field of electric energy conversion and new energy power generation, and in particular to a high-gain inverter for an interconnected power grid for accessing distributed energy. Background Art

[0002] Energy consumption is accelerating worldwide. The development and utilization of new energy sources can, to a certain extent, transform my country's energy structure, meet the energy needs of economic development, and promote sustainable social development. Multilevel inverters, with their advantages of low electromagnetic interference, low device withstand voltage, and high output waveform quality, have attracted widespread attention in fields such as photovoltaic power generation and motor drives.

[0003] Traditional multilevel inverters mainly include diode-clamped, flying capacitor, and cascaded multilevel inverters. The diode-clamped multilevel inverter was the first to be proposed. It uses diodes to clamp the switches to output a step wave with the corresponding number of levels. It has the characteristics of simple structure and easy control, but the reverse voltage of the clamping diode is difficult to recover. The subsequently proposed flying capacitor clamped multilevel inverter uses flying capacitors instead of diodes to balance the reverse voltage of the power switches, but it still uses algorithms to solve the DC side capacitor voltage balancing problem. As the number of output levels increases, the number of power devices used also increases significantly.

[0004] Compared to clamped inverters, cascaded multilevel inverters connect basic units consisting of independent DC power supplies and H-bridges in series. There's no capacitor voltage divider on the DC side, eliminating the need for voltage balance. Furthermore, the voltage stress of each switch is limited to the DC power supply voltage of the basic unit, facilitating further inverter expansion. However, cascaded inverters use multiple, costly DC power supplies and lack voltage gain at the output.

[0005] Utility Model Content

[0006] The purpose of the present utility model is to provide a high-gain inverter for interconnected power grids for distributed energy access, so as to solve the problem raised in the above background technology of how to convert capacitors and DC power supplies into series-parallel connections for periodic charging and discharging, so as to achieve self-balancing of the capacitor voltage without additional control and generate a higher voltage gain.

[0007] To achieve the above objectives, the present invention provides a high-gain inverter for distributed energy access in an interconnected power grid. The inverter is composed of a switched capacitor unit and an L-shaped expansion unit. Two half-bridges are used on the left and right ends to convert the polarity of the output level. The two capacitors can be charged in parallel with the DC power supply at the same time. By switching the series and parallel states of the capacitors and the power supply, a three-fold voltage gain and seven voltage levels can be generated.

[0008] The switched capacitor unit includes a DC power supply Vdc, electrolytic capacitors C1 and C2, a diode D1, a power switch S5, a power switch S6, a power switch S7, a power switch S8, and a power switch S9;

[0009] The L-shaped expansion unit includes an L-shaped structure consisting of a power switch S10, a power switch S11, a power switch S12, an electrolytic capacitor C3, and a diode D2;

[0010] The two half-bridge structures include a power switch S1 , a power switch S2 , a power switch S3 and a power switch S4 .

[0011] Preferably, the positive electrode of the DC power supply Vdc is connected to the input end of the power switch S5 and the positive electrode of the diode D1, and the negative electrode of the DC power supply Vdc is connected to the output end of the power switch S6; the negative electrode of the diode D1 is connected to the input end of the power switch S8 and the positive electrode of the electrolytic capacitor C1; the input end of the power switch S9 is connected to the output end of the power switch S8 and the positive electrode of the electrolytic capacitor C2, and the output end of S9 is connected to the input end of the power switch S7 and the negative electrode of the electrolytic capacitor C1; the input end of the power switch S6 is connected to the output ends of the power switch S5 and the power switch S7 and the negative electrode of the electrolytic capacitor C2.

[0012] Preferably, the input end of the power switch S10 is connected to the positive electrode of the electrolytic capacitor C3, and the output end of the power switch S10 is connected to the input end of the power switch S11; the input end of the power switch S12 is connected to the output end of the power switch S11 and the negative electrode of the electrolytic capacitor C3, and the output end of the power switch S12 is connected to the positive electrode of the diode D2.

[0013] Preferably, the input end of the power switch S1 is connected to the input end of the power switch S10, the output end of the power switch S1 is connected to the input end of the power switch S2, and the output end of the power switch S2 is connected to the negative electrode of the DC power supply Vdc; the input end of the power switch S3 is connected to the positive electrode of the electrolytic capacitor C3, the output end of the power switch S3 is connected to the input end of the power switch S4, and the output end of the power switch S4 is connected to the negative electrode of the diode D2.

[0014] Preferably, the power switch S1 and the power switch S2 operate in a complementary state, the power switch S3 and the power switch S4 operate in a complementary state, the power switch S5 and the power switch S6 operate in a complementary state, the power switch S7 and the power switch S8 operate in the same state and are both complementary to the power switch S9, and the power switch S10 and the power switch S11 operate in a complementary state.

[0015] Preferably, the electrolytic capacitors C1 and C2 have the same working state and are charged in parallel with the DC power supply Vdc. The electrolytic capacitors C1, C2 and the DC power supply Vdc are connected in series and then connected in parallel with the electrolytic capacitor C3.

[0016] Preferably, the switched capacitor unit and the L-shaped expansion unit are connected via a power switch S11.

[0017] Preferably, all power switches are MOSFETs or IGBTs with anti-parallel diodes.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. In the high-gain inverter for interconnected power grids used for distributed energy access, the inverter can achieve a six-fold voltage gain and output thirteen voltage levels.

[0020] 2. This high-gain inverter for distributed energy access in an interconnected grid consists of a topology consisting of twelve power switches, two diodes, and three electrolytic capacitors. The presence of five complementary switch pairs and the self-balancing capacitor voltage simplify the control strategy.

[0021] 3. In the high-gain inverter for interconnected power grids used for distributed energy access, the switched capacitor boost unit can be connected in series with the DC power supply to generate a three-fold voltage gain at the output end. Then, combined with the L-shaped expansion structure, it can further achieve thirteen-level output and six-fold voltage gain.

[0022] 4. In this high-gain inverter for interconnected power grids used for distributed energy access, by cascading multiple L-shaped expansion units, the inverter output level and voltage gain can be greatly improved. All power switches are equipped with anti-parallel diodes, which can provide a reverse current channel for inductive loads, enabling the inverter to carry inductive loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is an expanded structure of the inverter described in an embodiment of the present utility model.

[0024] FIG2 is a schematic diagram of the carrier in-phase stacking principle of the inverter according to an embodiment of the present invention.

[0025] FIG3 is a working state diagram of the inverter according to the embodiment of the present invention when outputting a non-negative polarity voltage level.

[0026] FIG4 is a waveform diagram of output voltage and output current of the inverter with resistive inductive load according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] The utility model provides an interconnected power grid high-gain inverter for distributed energy access, as shown in Figures 1 to 4. It is composed of a switching capacitor unit and an L-shaped expansion unit. Two half-bridges are used at the left and right ends to convert the polarity of the output level. The two capacitors can be charged in parallel with a DC power supply at the same time. By switching the capacitors and the power supply in series and parallel, a three-fold voltage gain and seven voltage levels can be generated; the switching capacitor unit includes a DC power supply Vdc, an electrolytic capacitor C1 and an electrolytic capacitor C2, a diode D1, a power switch S5, a power switch S6, a power switch S7, a power switch S8 and a power switch S9; the L-shaped expansion unit includes an L-shaped structure consisting of power switches S10, S11 and S12, an electrolytic capacitor C3 and a diode D2; the two half-bridge structures include power switches S1, S2, S3 and S4.

[0029] In this embodiment, the positive electrode of the DC power supply Vdc is connected to the input terminal of the power switch S5 and the positive electrode of the diode D1, and the negative electrode of the DC power supply Vdc is connected to the output terminal of the power switch S6; the negative electrode of the diode D1 is connected to the input terminal of the power switch S8 and the positive electrode of the electrolytic capacitor C1; the input terminal of the power switch S9 is connected to the output terminal of the power switch S8 and the positive electrode of the electrolytic capacitor C2, and the output terminal of S9 is connected to the input terminal of the power switch S7 and the negative electrode of the electrolytic capacitor C1; the input terminal of the power switch S6 is connected to the output terminals of the power switches S5 and S7 and the negative electrode of the electrolytic capacitor C2.

[0030] Specifically, the input end of the power switch S10 is connected to the positive electrode of the electrolytic capacitor C3, and the output end of the power switch S10 is connected to the input end of the power switch S11; the input end of the power switch S12 is connected to the output end of the power switch S11 and the negative electrode of the electrolytic capacitor C3, and the output end of the power switch S12 is connected to the positive electrode of the diode D2.

[0031] Furthermore, the input end of the power switch S1 is connected to the input end of the power switch S10, the output end of the power switch S1 is connected to the input end of the power switch S2, and the output end of the power switch S2 is connected to the negative electrode of the DC power supply Vdc; the input end of the power switch S3 is connected to the positive electrode of the electrolytic capacitor C3, the output end of the power switch S3 is connected to the input end of the power switch S4, and the output end of the power switch S4 is connected to the negative electrode of the diode D2.

[0032] Furthermore, the power switches S1 and S2 work in a complementary state, the power switches S3 and S4 work in a complementary state, the power switches S5 and S6 work in a complementary state, the power switches S7 and S8 work in the same state and are all complementary to the power switch S9. 10 and power switch S 11 Working in a complementary state can reduce the number of drive signals and effectively reduce the complexity of inverter control.

[0033] Furthermore, the electrolytic capacitors C1 and C2 have the same working state and are charged in parallel with the DC power supply Vdc at the same time. The electrolytic capacitors C1, C2 and the DC power supply Vdc are connected in series and then connected in parallel with the electrolytic capacitor C3, so that the voltage of the electrolytic capacitor C3 reaches three times the DC power supply voltage.

[0034] Furthermore, the switched capacitor unit is connected to the L-shaped expansion unit via the power switch S11. Formulating a corresponding switch conduction sequence enables the inverter to achieve thirteen voltage level outputs and six times voltage gain.

[0035] Furthermore, all power switches are MOSFETs or IGBTs with anti-parallel diodes, which can provide a reverse current channel for the inductive load, so that the inverter has the ability to carry inductive loads.

[0036] Furthermore, the second aspect of the present invention provides a modulation strategy applied to the inverter, which adopts carrier in-phase stacked pulse width modulation technology, uses 12 triangular carriers with the same amplitude and the same frequency to be stacked from top to bottom, and compared with 1 sinusoidal modulated wave, and then logically combines the obtained 12 original pulse waveforms to generate drive signals for each power switch.

[0037] Furthermore, by cascading multiple L-type expansion units, the number of output levels and voltage gain are increased. The nth L-type expansion unit includes power switch Sn0, power switch Sn1, and power switch Sn2, electrolytic capacitor Cn+2, and diode Dn+1. In the first L-type expansion unit, the input end of power switch S10 is connected to the positive electrode of electrolytic capacitor C3, and the output end of S10 is connected to the input end of power switch S11; the input end of power switch S12 is connected to the output end of power switch S11 and the negative electrode of electrolytic capacitor C3, and the output end of S12 is connected to the positive electrode of diode D2. With each additional L-type expansion unit, the number of power switches, diodes, and capacitors also increases accordingly. When n L-type expansion units are used, the number of output voltage levels is 1+3·2. n+1 , the voltage gain is 3·2 n , the number of output levels and voltage gain both show exponential growth, while the number of required components increases linearly, indicating that the proposed inverter can achieve more voltage level outputs and higher voltage gain using fewer components.

[0038] Furthermore, the input terminal of the power switch S1 is connected to the power switch S n0 The output end of the power switch S1 is connected to the input end of the power switch S2, and the output end of the power switch S2 is connected to the DC power supply V dc The input of power switch S3 is connected to the negative electrode of electrolytic capacitor C n+2 The output end of the power switch S3 is connected to the input end of the power switch S4, and the output end of the power switch S4 is connected to the positive electrode of the diode D n+1 The negative pole is connected.

[0039] Figure 3 shows the operating principle of the proposed inverter when the output voltage is non-negative. The symbols "+" and "-" represent the positive and negative poles of the connected load. The green highlighted line indicates the charging path of the capacitor, and the red highlighted line indicates the output voltage level path. The specific operating principle is described as follows:

[0040] Working states (a) and (b): Power switches S5, S9, S10, and S12 are turned on, and electrolytic capacitors C1, C2, and DC power supply Vdc are connected in series to discharge, allowing capacitor C3 to be charged to 3 Vdc through diode D2. At this time, the output voltage can be 0 through power switches S2 and S4, and the output voltage can also be 0 through power switches S1 and S3.

[0041] Operating State (c): Power switches S6, S7, S8, and S10 are on. Electrolytic capacitors C1 and C2 are charged in parallel via diode D1 and DC power supply Vdc, while electrolytic capacitor C3 is idle. At this point, power switches S2 and S3 can output a voltage of +Vdc. Conversely, power switches S1 and S4 can output a voltage of -Vdc.

[0042] Operating state (d): Power switches S5, S7, S8, and S10 are on. Electrolytic capacitors C1 and C2 are connected in series with the DC power supply to discharge, and electrolytic capacitor C3 is idle. At this point, power switches S2 and S3 can output a voltage of +2Vdc. Conversely, power switches S1 and S4 can output a voltage of -2Vdc.

[0043] Operating state (e): Power switches S5, S9, S10, and S12 are on. Electrolytic capacitors C1, C2, and the DC power supply are connected in series, discharging. Electrolytic capacitor C3 is charged to its rated voltage of 3Vdc. At this point, power switches S2 and S3 can output a voltage of +3Vdc. Conversely, power switches S1 and S4 can output a voltage of -3Vdc.

[0044] Operating state (f): Power switches S6, S7, S8, and S11 are on. Electrolytic capacitors C1 and C2 are charged in parallel via diode D1 and the DC power supply, while electrolytic capacitor C3 is discharged in series with the DC power supply. At this point, power switches S2 and S3 output a +4Vdc voltage, while power switches S1 and S4 output a -4Vdc voltage.

[0045] Operating state (g): Power switches S5, S7, S8, and S11 are on. Electrolytic capacitors C1 and C2 are connected in parallel, then in series with the DC power supply. Then, they are connected in series with electrolytic capacitor C3 to discharge the power supply. At this point, power switches S2 and S3 can output a +5Vdc voltage, while power switches S1 and S4 can output a -5Vdc voltage.

[0046] Operating state (h): Power switches S5, S9, and S11 are on. Electrolytic capacitors C1, C2, and C3 are connected in series and then discharged in series with the DC power supply. At this point, power switches S2 and S3 can output a +6Vdc voltage, while power switches S1 and S4 can output a -6Vdc voltage.

[0047] To verify the effectiveness of the proposed multilevel inverter with enhanced gain, a prototype thirteen-level switching electrolytic capacitor inverter was constructed. The DC source voltage was set to 25V, as shown in Figure 4. Experiments were conducted under a resistive and inductive load (80Ω + 15mH). The experimental results show that the proposed inverter can stably output thirteen voltage levels, with a peak output voltage of 150V, a sixfold voltage gain, and a current waveform that is approximately sinusoidal with low harmonic content.

[0048] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-gain inverter for interconnected power grids for distributed energy access, characterized in that: It is composed of a switched capacitor unit and an L-shaped expansion unit. Two half-bridges are used at the left and right ends to convert the polarity of the output level. The two capacitors can be charged in parallel with the DC power supply at the same time. By switching the series-parallel state of the capacitor and the power supply, a three-fold voltage gain and seven voltage levels can be generated. The switch capacitor unit includes a DC power supply Vdc, an electrolytic capacitor C1 and an electrolytic capacitor C2, a diode D1, a power switch S5, a power switch S6, a power switch S7, a power switch S8 and a power switch S9; The L-shaped expansion unit includes an L-shaped structure consisting of a power switch S10, a power switch S11, a power switch S12, an electrolytic capacitor C3, and a diode D2; The two half-bridge structures include a power switch S1 , a power switch S2 , a power switch S3 and a power switch S4 .

2. The high-gain inverter for interconnected power grid for distributed energy access according to claim 1, characterized in that: The positive electrode of the DC power supply Vdc is connected to the input end of the power switch S5 and the positive electrode of the diode D1, and the negative electrode of the DC power supply Vdc is connected to the output end of the power switch S6; the negative electrode of the diode D1 is connected to the input end of the power switch S8 and the positive electrode of the electrolytic capacitor C1; the input end of the power switch S9 is connected to the output end of the power switch S8 and the positive electrode of the electrolytic capacitor C2, and the output end of S9 is connected to the input end of the power switch S7 and the negative electrode of the electrolytic capacitor C1; the input end of the power switch S6 is connected to the output ends of the power switch S5 and the power switch S7 and the negative electrode of the electrolytic capacitor C2.

3. The high-gain inverter for interconnected power grid for distributed energy access according to claim 1, characterized in that: The input end of the power switch S10 is connected to the positive electrode of the electrolytic capacitor C3, and the output end of the power switch S10 is connected to the input end of the power switch S11; the input end of the power switch S12 is connected to the output end of the power switch S11 and the negative electrode of the electrolytic capacitor C3, and the output end of the power switch S12 is connected to the positive electrode of the diode D2.

4. The high-gain inverter for interconnected power grid for distributed energy access according to claim 1, characterized in that: The input end of the power switch S1 is connected to the input end of the power switch S10, the output end of the power switch S1 is connected to the input end of the power switch S2, and the output end of the power switch S2 is connected to the negative electrode of the DC power supply Vdc; the input end of the power switch S3 is connected to the positive electrode of the electrolytic capacitor C3, the output end of the power switch S3 is connected to the input end of the power switch S4, and the output end of the power switch S4 is connected to the negative electrode of the diode D2.

5. The high-gain inverter for interconnected power grid for distributed energy access according to claim 1, characterized in that: The power switches S1 and S2 work in a complementary state, the power switches S3 and S4 work in a complementary state, the power switches S5 and S6 work in a complementary state, the power switches S7 and S8 work in the same state and are both complementary to the power switch S9. 10 and power switch S 11 Working in a complementary state.

6. The high-gain inverter for interconnected power grid for distributed energy access according to claim 1, characterized in that: The electrolytic capacitors C1 and C2 have the same working state and are charged in parallel with the DC power supply Vdc. The electrolytic capacitors C1, C2 and the DC power supply Vdc are connected in series and then connected in parallel with the electrolytic capacitor C3.

7. The high-gain inverter for interconnected power grid for distributed energy access according to claim 1, characterized in that: The switched capacitor unit is connected to the L-shaped expansion unit via a power switch S11.

8. The high-gain inverter for interconnected power grid for distributed energy access according to claim 1, characterized in that: All power switches are MOSFETs or IGBTs with anti-parallel diodes.

Images