CN217469787U

CN217469787U - Single-phase ANPC nine-level inverter capacitor pre-charging circuit

Info

Publication number: CN217469787U
Application number: CN202220392706.7U
Authority: CN
Inventors: 李美芳; 郭力源
Original assignee: Shanxi University
Current assignee: Shanxi University
Priority date: 2022-02-25
Filing date: 2022-02-25
Publication date: 2022-09-20
Anticipated expiration: 2032-02-25

Abstract

The utility model discloses a nine level inverter electric capacity precharge circuit of single-phase ANPC, including turning right adjustable DC power supply, the pre-charge resistance return circuit that sets gradually from a left side, novel circuit topology also is the nine level inverter topology of SC-ANPC, novel circuit topology includes the two-stage elementary cell: switched capacitor unit and flying capacitor unit, switched capacitor unit contains 3 switch tubes S ₉ 、S ₁₀ 、S ₁₁ 2 switched capacitors C ₁₁ And C ₁₂ (ii) a The flying capacitor unit comprises 2 switching tubes S ₁₂ And S ₁₃ 1 flying capacitor C ₂ New, newCapacitor C on direct current side in circuit topology _d1 、C _d2 Voltage of (2), switch capacitance C ₁₁ 、C ₁₂ Voltage and flying capacitor C ₂ The voltage ratio of (a) to (b) is 4:2: 1. The utility model provides a problem of charging in electric capacity among this nine level inverter topology in advance, this many level topology utilizes self circuit structure just can charge in advance, and the circuit is retrencied, and the hardware realizes simply, and it is convenient that the control of charging in advance simultaneously, and is efficient, has guaranteed the effective operation of this kind of many level converter.

Description

Single-phase ANPC nine-level inverter capacitor pre-charging circuit

Technical Field

The utility model relates to a converter technical field especially relates to the technical design who contains switched capacitor and flying capacitor unit's single-phase SC-ANPC multilevel inverter capacitor in charging method in advance.

Background

In the fields of new energy power generation, aerospace, flywheel energy storage and the like with high requirements on power density and electric energy quality, the two-level inverter is limited by a series of technical parameters such as the response speed limit of a power device, the switching loss of the device and the like, and the requirements are difficult to meet. The multi-level inverter can output three levels or even more levels on the alternating current side by introducing more switching devices into the bridge arms, and has better voltage harmonic characteristics and lower voltage change rate. This provides a new idea for the development of high performance converters and draws the attention of students, and has been widely applied to the field of large capacity current transformation.

The novel multilevel converter comprises a multi-unit stacked type, an active clamping type (ANPC), a switched capacitor type, a modular multilevel converter and the like, wherein the ANPC inversion topology only needs one direct-current power supply, a transformer with large volume is omitted, and the ANPC inversion topology becomes a hotspot of current research, but along with the expansion of the number of levels, the number of clamping capacitors in the ANPC topology and the complexity of voltage control are obviously increased. The document "active clamping multilevel inverter with switched capacitor" proposes a principle of forming an active clamping (switched capacitor-active neutral potential clamped) multilevel topology with switched capacitor, i.e. a switched capacitor unit is used to replace a flying capacitor unit in a common ANPC multilevel topology, thereby reducing the number of capacitors and the difficulty of controlling the voltage of the capacitors, and facilitating the expansion of the output level of the inverter.

In order to enable an active clamping (SC-ANPC) nine-level inverter containing a switched capacitor to work normally, a direct-current side bus capacitor in a system, a capacitor of a flying capacitor part in a novel circuit topology and a capacitor of the switched capacitor part are set to be proper voltage before the inverter starts to work, and how to complete the presetting and charging of all capacitor voltages becomes a technical problem to be solved urgently.

Most of the multi-level converter capacitor pre-charging circuits disclosed in the prior art are directed to modular multi-level converters (MMC), and for example, a modular multi-level matrix converter capacitor pre-charging system disclosed in patent publication CN202997660U is proposed ³ C capacitor pre-charging circuit and solves M ³ C, starting a system; a full-bridge MMC-HVDC starting method disclosed in the patent with the publication number of CN102739030A provides a full-bridge MMC-HVDC staged starting strategy. The unique structure of the new SC-ANPC nine-level inverter topology makes the pre-charge circuit proposed for the MMC topology not applicable to this topology.

The seven-level ANPC converter pre-charge circuit and the seven-level ANPC converter disclosed in the patent with publication number CN207968345U are designed separately, and include a first resistor, a multi-tap transformer, a switch circuit with three parallel switch branches and a rectifier circuit.

SUMMERY OF THE UTILITY MODEL

In order to solve the defects and shortcomings of the prior art, the single-phase ANPC nine-level inverter circuit is provided based on the requirements of improving switching loss, inverter response speed and electric energy quality, the scheme of presetting and pre-charging the voltage value of the capacitor of the circuit is designed, and the problem of pre-charging of the capacitor in the nine-level inverter topology is solved.

For realizing the utility model discloses the purpose provides a nine level inverter circuit of single-phase ANPC, including the adjustable DC power supply who turns right from a left side and set gradually, pre-charge resistance return circuit, novel circuit topology also is the nine level inverter topology of SC-ANPC, including the two-stage elementary cell: switched capacitor unit and flying capacitor unit, switched capacitor unit contains 3 switch tubes S ₉ 、S ₁₀ 、S ₁₁ 2 switched capacitors C ₁₁ And C ₁₂ (ii) a The flying capacitor unit comprises 2 switching tubes S ₁₂ And S ₁₃ 1 flying capacitor C ₂ A capacitor C on the DC side in the novel circuit topology _d1 、C _d2 Voltage, switched capacitor C ₁₁ 、C ₁₂ Voltage and flying capacitor C ₂ The voltage ratio of (a) to (b) is 4:2: 1. Through switching on and switching off corresponding switch tube in this novel topology, can accomplish the precharge process to each electric capacity step by step. The method comprises the steps of firstly completing the pre-charging of the last flying capacitor, then completing the pre-charging of the switch capacitor, and finally completing the pre-charging of the direct-current side capacitor.

As a further improvement of the above scheme, the pre-charging resistance loop comprises a pre-charging resistance R _c Precharge relay K ₁ Main relay K ₂ The pre-charge resistor R _c Precharge relay K ₁ Connected in parallel to a main relay K after being connected in series ₂ Two ends of (K), main relay ₂ Two ends of the capacitor C are respectively connected with the adjustable direct current power supply and the capacitor C at the direct current side _d1 Capacitor C connected to DC side _d1 And the other end of the capacitor C and the DC side _d2 Capacitor C connected to DC side _d2 The other end of the switch tube is connected with an adjustable direct current power supply, and a switch tube S ₁ 、S ₂ 、S ₃ 、S ₄ Sequentially connected end to end and provided with a switch tube S ₁ 、S ₄ And the other end of the capacitor C and the DC side _d1 、C _d2 Is connected with the other end of the four series-connected switching tubes, the middle point of the four series-connected switching tubes and a capacitor C at the direct current side _d1 、C _d2 Is connected at one end.

As a further improvement of the above solution, the switch tube S of the switched capacitor unit ₉ One end of the switch tube S ₁₀ And a switch capacitor C ₁₂ Connection, switching tube S ₁₀ The other end of the switch tube S ₁₁ And a switch capacitor C ₁₁ Connection, switching tube S ₁₁ And a switch capacitor C ₁₁ The other end of the switch tube S ₉ And a switch capacitor C ₁₂ After being connected, are respectively connected with a switch tube S ₅ Switch tube S ₆ Connection, switching tube S ₅ Switch tube S ₆ The other ends of the two are respectively connected with a switch tubeS ₁ 、S ₂ Switching tube S ₃ 、S ₄ In the meantime.

As a further improvement of the above scheme, the switch tube S of the flying capacitor unit ₁₂ And S ₁₃ One end of each of the first and second capacitors is connected to a switch capacitor C ₁₁ And a switch capacitor C ₁₂ Connection, switching tube S ₁₂ And S ₁₃ The other end of (C) and a flying capacitor (C) ₂ Are connected across, flying capacitor C ₂ Are respectively connected with the switch tube S ₇ 、S ₈ Is connected with one end of a switching tube S ₇ 、S ₈ Are commonly connected to the output phase.

The utility model has the advantages that:

compared with the prior art, the novel single-phase SC-ANPC nine-level inverter capacitor pre-charging circuit adopts a step pre-charging method, the capacitor pre-charging completion of a flying capacitor unit is used as a first stage, the capacitor pre-charging completion of a switched capacitor unit is used as a second stage, and the capacitor pre-charging completion of a direct current side is used as a third stage. The capacitor pre-charging of the flying capacitor unit is completed firstly, then the pre-charging of the switch capacitor unit is completed, and finally the pre-charging of the capacitor on the direct current side is completed.

The scheme is ingenious in design, the technical design of two capacitor pre-charging schemes of the single-phase SC-ANPC nine-level inverter is provided, the topology reduces the number of capacitors and the difficulty of capacitor voltage control, and the expansion of the output level of the inverter is facilitated. The problem of precharging the capacitor voltage of the novel ANPC multi-level inverter in the design is solved, and the effective operation of the multi-level converter is guaranteed.

Meanwhile, the circuit topology does not need to design a pre-charging loop independently, and voltage pre-charging work of a direct-current bus capacitor, a rear switch capacitor and a flying capacitor in the single-phase SC-ANPC nine-level inverter circuit can be effectively completed. The circuit is simplified and easy to realize, the number of required components is small, direct connection caused by multiple components is avoided, the staged pre-charging control is convenient, the efficiency is high, and the application is more flexible in the distributed power generation and microgrid scenes.

Drawings

The following detailed description of embodiments of the invention is provided in conjunction with the accompanying drawings, in which:

fig. 1 is a topological diagram of a capacitor pre-charging circuit of a single-phase SC-ANPC nine-level inverter including a switched capacitor unit and a flying capacitor unit according to the present invention;

FIG. 2 is a schematic circuit diagram of the switch capacitor unit of FIG. 1;

FIG. 3 shows two switched capacitors C of the switched capacitor unit ₁₁ 、C ₁₂ A circuit diagram of parallel pre-charging;

FIG. 4 shows two switched capacitors C of the switched capacitor unit ₁₁ 、C ₁₂ Circuit diagram of series precharge.

Detailed Description

As shown in fig. 1, the main circuit topology is, from left to right: the leftmost side is an adjustable direct current power supply and a pre-charging resistor loop 1, and then a novel circuit topology 2, namely an SC-ANPC nine-level inverter topology is arranged. The novel circuit topology 2, which comprises two levels of basic cells: compared with SC-ANPC seven-level topology, the switched capacitor unit 21 and the flying capacitor unit 22 have one more flying capacitor unit 22, the novel circuit topology 2 can output 11 levels at most, and the switched capacitor unit 21 comprises 3 switching tubes S ₉ 、S ₁₀ 、S ₁₁ 2 switched capacitors C ₁₁ And C ₁₂ (ii) a The flying capacitor unit 22 includes 2 switching tubes S ₁₂ And S ₁₃ 1 flying capacitor C ₂ . Single capacitor (C) at direct current side in nine-level topology _d1 、C _d2 ) Voltage, switch capacitance (C) ₁₁ 、C ₁₂ ) Voltage and flying capacitor C ₂ The voltage ratio was 4:2: 1.

Six pairs of switching tubes (S) with mutually opposite states exist in the circuit ₁ ，S ₂ )、(S ₃ ，S ₄ )、(S ₅ ，S ₆ )、(S ₇ ，S ₈ )、(S ₉ ，S ₁₀ )、(S ₁₂ ，S ₁₃ ) And three pairs of switching tubes (S) with respective identical states ₁ ，S ₃ )、(S ₂ ，S ₄ )、(S ₉ ，S ₁₁ ) Then the switch tube in the free state in the circuit isS ₁ 、S ₅ 、S ₇ 、S ₉ 、(S ₁₀ )、S ₁₂ . The switch tube pairs with the opposite states can not be conducted at the same time (S) ₉ 、S ₁₀ There is a simultaneous turn-off condition) or else short-circuit faults of the dc-side capacitance or the switched capacitance may occur. The switch states corresponding to different output levels are shown in table 1, in which: u. u _ao Representing bridge arm output voltage; "1" indicates that the switch tube is turned on, and "0" indicates that the switch tube is turned off; "C" indicates that the capacitor is charged, "D" indicates that the capacitor is discharged, and "-" indicates that the capacitor is neither charged nor discharged.

TABLE 1 nine-level Circuit switch State

As shown in FIG. 2, a schematic diagram of a switched capacitor unit 21 according to the present invention is shown, which includes two switched capacitors C ₁₁ 、C ₁₂ And three switching tubes S ₉ 、S ₁₁ 、S ₁₀ In which S is ₉ And S ₁₁ The drive signals of (a) are the same. When the pulse signal in the loop triggers the corresponding switch tube to be conducted, different pre-charging loops are formed.

The specific process during charging is as follows:

when S is ₉ And S ₁₁ Conduction, S ₁₀ When disconnected, can be paired with C ₁₁ And C ₁₂ Parallel charging is performed, and an equivalent circuit is shown in fig. 3. When S is ₉ And S ₁₁ Breaking, S ₁₀ When conducting, can be connected to C ₁₁ And C ₁₂ Series charging is performed and the equivalent circuit is shown in fig. 4. In either case, or when S9, S11, and S10 are all off, flying capacitor C of switched capacitor cell 21 and flying capacitor cell 22 ₂ All constitute the relation of parallel connection charging, charge simultaneously together.

The capacitor pre-charging specific process implementation schemes of the single-phase SC-ANPC nine-level inverter are as follows:

the first scheme is as follows:

the method comprises the following steps: blocking trigger pulses of all power switch tubes of the inverter and disconnecting a pre-charging relay K in the circuit ₁ And a main relay K ₂ 。

Step two: closed precharge relay K ₁ A pre-charge resistor R _c In the access circuit, a pre-charge resistor R _c The loop begins to operate. In the process of pre-charging, the adjustable direct current power supply on the direct current side is slowly increased all the time, and the voltage of the adjustable direct current power supply is slowly increased. For switching tube S ₁ 、S ₄ 、S ₅ 、S ₆ 、S ₁₂ 、S ₁₃ A pulse signal is generated to trigger them to conduct, and the flying capacitor C of the flying capacitor unit 22 is connected ₂ And a switched capacitor C ₁₁ 、C ₁₂ And a capacitor C on the DC side _d1 、C _d2 Charging is performed simultaneously. Capacitance C of flying capacitor unit 22 ₂ When the voltage reaches the preset voltage level E, the switch tube S is supplied ₁₂ And S ₁₃ Generating a turn-off pulse to turn off the two switching tubes, and flying capacitor C ₂ Quitting the charging process, at the moment, switching the capacitor C ₁₁ 、C ₁₂ The charged voltage is E/2 respectively, and does not reach the preset voltage 2E, and the charged voltage and the capacitor C on the direct current side _d1 、C _d2 The preset voltage level is not reached, and the charging is required to be continued.

Step three: at this time, the switch tube S is supplied ₁ 、S ₄ 、S ₅ 、S ₆ Continuing to send conducting pulse signals to trigger them to conduct and continue to supply to the switched capacitor C ₁₁ 、C ₁₂ Charging is carried out, they do not end the switched capacitor C from the voltage E/2 until the pre-charge reaches the preset voltage level 2E ₁₁ 、C ₁₂ Pre-charging, at this time to the switching tube S ₅ 、S ₆ The pulse signal is turned off, and partial precharging of the switched capacitor unit 21 is completed. Capacitor C at the direct current side _d1 、C _d2 The preset voltage level 4E has not been reached yet and the next step still requires continuing the charging.

Step four: continue to the capacitor C of the DC side _d1 、C _d2 Charging is carried out until a preset voltage level 4E is reached, and when a set value is reached, the pre-charging resistance loop 1 is disconnected and the pre-charging relay K is disconnected ₁ Closing the main relay K ₂ . At this point the precharge operation is complete.

Scheme II:

Step two: closed precharge relay K ₁ A pre-charge resistor R _c In the access circuit, a pre-charge resistor R _c The loop begins to operate. In the process of pre-charging, the adjustable direct current power supply on the direct current side is slowly increased all the time, and the voltage of the adjustable direct current power supply is slowly increased. The process can also be set to the switch tube S ₁ 、S ₄ 、S ₅ 、S ₆ 、S ₁₂ 、S ₁₃ 、S ₉ 、S ₁₁ A pulse signal to trigger them to conduct when the flying capacitor C of the flying capacitor unit 22 ₂ When the charging reaches the preset voltage E, the switch tube S is supplied ₁₂ And S ₁₃ Sending off the cut-off pulse to cut off the two switching tubes and make the flying capacitor C ₂ Quitting the charging process, at the moment, switching the capacitor C ₁₁ 、C ₁₂ The charging voltage is also respectively E, the preset voltage is not reached to 2E, the charging is required to be continued in the next step, and meanwhile, the capacitor C on the direct current side _d1 、C _d2 The preset voltage level 4E is not reached, and the charging is continued.

Step three: at this time, the switch tube S is supplied ₁ 、S ₄ 、S ₅ 、S ₆ Continuing to send conducting pulse signals to trigger them to conduct and continue to supply to the switched capacitor C ₁₁ 、C ₁₂ Charging is carried out, they do not end the switched capacitor C from the voltage E/2 until the pre-charge reaches the preset voltage level 2E ₁₁ 、C ₁₂ Pre-charging, at this time to the switching tube S ₅ 、S ₆ The pulse signal is turned off, and partial precharging of the switched capacitor unit 21 is completed. At the time of the direct current sideCapacitor C of _d1 、C _d2 The preset voltage level 4E has not been reached yet and the next step still requires continuing the charging.

To sum up, scheme two charging time is shorter, and the efficiency of precharging is higher, can realize precharging fast to each part electric capacity.

The above embodiments are not limited to the technical solutions of the embodiments themselves, and the embodiments may be combined with each other into a new embodiment. The above embodiments are only used for illustrating the technical solutions of the present invention and are not limited thereto, and any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of the technical solutions of the present invention.

Claims

1. The utility model provides a nine level inverter of single-phase ANPC electric capacity is charging circuit which characterized in that: the novel circuit topology is also an SC-ANPC nine-level inverter topology and comprises two stages of basic units: switched capacitor unit and flying capacitor unit, switched capacitor unit contains 3 switch tubes S ₉ 、S ₁₀ 、S ₁₁ 2 switched capacitors C ₁₁ And C ₁₂ (ii) a The flying capacitor unit comprises 2 switching tubes S ₁₂ And S ₁₃ 1 flying capacitor C ₂ A capacitor C on the DC side in the novel circuit topology _d1 、C _d2 Voltage, switched capacitor C ₁₁ 、C ₁₂ Voltage and flying capacitor C ₂ The voltage ratio of (1) is 4:2:1, the pre-charge resistance loop comprises a pre-charge resistance R _c Precharge relay K ₁ Main relay K ₂ (ii) a The pre-charging resistor R _c Precharge relay K ₁ Connected in parallel with the mainRelay K ₂ Both ends of (a); main relay K ₂ With the positive electrode of the adjustable DC power supply and the capacitor C at the DC side respectively _d1 Connecting, DC side capacitance C _d1 The other end of the capacitor (C) and a DC side capacitor (C) _d2 Connecting, DC side capacitance C _d2 The other end of the anode is connected with the cathode of an adjustable direct current power supply; switch tube S ₁ 、S ₂ 、S ₃ 、S ₄ Sequentially connected end to end and provided with a switch tube S ₁ 、S ₄ One end of and a DC side capacitor C _d1 、C _d2 Is connected with the other end of the four series-connected switching tubes, the middle point of the four series-connected switching tubes and a capacitor C at the direct current side _d1 、C _d2 Is connected to the first end of the switch tube S of the switched capacitor unit ₉ One end of the switch tube S ₁₀ And a switch capacitor C ₁₂ Connecting; switch tube S ₁₀ The other end of the switch tube S ₁₁ And a switch capacitor C ₁₁ Connecting; switch tube S ₁₁ And a switched capacitor C ₁₂ Connected with a switching tube S ₆ Connection, switching tube S ₆ Is connected with the other end of the switch tube S ₃ 、S ₄ To (c) to (d); switched capacitor C ₁₁ The other end of the switch tube S ₉ After connection, it is connected with the switch tube S ₅ Connection, switching tube S ₅ Is connected to the switching tube S at the other end ₁ 、S ₂ A switching tube S of the flying capacitor unit ₁₂ And S ₁₃ One end of each of the first and second capacitors is connected to a switch capacitor C ₁₁ And a switch capacitor C ₁₂ Connection, switching tube S ₁₂ And S ₁₃ The other end of (C) and a flying capacitor (C) ₂ Are connected at both ends; flying capacitor C ₂ Are respectively connected with the switch tube S ₇ 、S ₈ Is connected with a switch tube S ₇ 、S ₈ Are commonly connected to the output phase.