CN207200598U - A kind of single-phase tri-level half-bridge inverter that can realize capacitor voltage equalizing - Google Patents

Abstract

The utility model discloses a single-phase three-level half-bridge inverter capable of realizing capacitor voltage equalization, which comprises a boost circuit and a three-level half-bridge inverter circuit, and the boost circuit includes a flyback bus voltage balance circuit . The utility model has the advantages of: through the compensation of the flyback bus voltage balance circuit, the voltage balance of the two capacitors on the DC side is balanced, and the utilization rate of the DC voltage is greatly improved; the electromagnetic compatibility is improved; through the balance of the bus capacitor voltage, It enhances the characteristics of small harmonic content in the output voltage of the traditional three-level inverter, prolongs the service life of the capacitor; it is beneficial to realize the maximum power point tracking, and fully exert the maximum efficiency of the solar photovoltaic array; thus improving the reliability of the system.

Description

A single-phase three-level half-bridge inverter that can realize capacitor voltage equalization

technical field

The utility model relates to a three-level inverter, in particular to a single-phase three-level half-bridge inverter capable of balancing DC side capacitor voltage.

Background technique

Today, with the increasing demand for energy, the development of new energy and the improvement of energy utilization are becoming more and more important. In the development of various new energy, photovoltaic solar energy is a clean and environmentally friendly energy source, so it is of great significance to the development of photovoltaic solar energy. However, the single-phase three-level half-bridge inverter is the core of photovoltaic solar energy conversion, which can convert solar direct current into alternating current required by our load, and realize maximum power tracking.

Multilevel inverters have long been a research hotspot in high-voltage and high-power applications. The three-level half-bridge inverter is a kind of multi-level inverter. The output characteristic of the three-level half-bridge inverter is that its bridge arm has three output voltages: +Vin/2, -Vin/2, and 0. Therefore, under the condition of the same output voltage harmonic standard, its equivalent switching frequency can be reduced, thereby reducing switching loss, improving efficiency and electromagnetic compatibility. On the other hand, due to the existence of the midpoint of the DC voltage dividing capacitor, the voltage stress on the switching device is only half of that of the two-level, which makes it possible to apply low voltage switching devices in high-voltage applications, greatly reducing the inverter voltage. Economical cost of device design and increased system reliability.

However, when the single-phase three-level half-bridge inverter is loaded or connected to the grid, the voltage on the two capacitors in the DC side bus will oscillate greatly, resulting in output waveform distortion. The service life of the capacitor is shortened, and the unstable voltage will affect the accuracy of the MPPT. Therefore, solving the problem of voltage imbalance on the capacitors on the DC side of the single-phase three-level half-bridge inverter is of great significance to the increase of system reliability, the reduction of harmonics, and the prolongation of the life of capacitors and related devices.

Contents of the invention

The purpose of the utility model is to solve the problem of unbalanced voltage on the capacitor of the three-level DC side of the half bridge.

In order to solve the above problems, the utility model adopts a flyback busbar voltage balance circuit to realize the half-bridge three-level DC side capacitor voltage balance.

A single-phase three-level half-bridge inverter that can realize capacitor voltage equalization, including flyback transformer T, switch tubes S1~S10, diodes D1~D10, D01 and D11~D15, capacitors C1~C3, inductors L1 and L2; characterized in that:

The right end of the inductor L1, the upper end of the switch tube S1, the cathode of the diode D1 and the anode of the diode D01 are connected to each other,

The lower end of the switch tube S1, the anode of the diode D1, the upper end of the switch tube S2, the cathode of the diode D2 and the upper end of the primary side of the flyback transformer T are connected to each other,

The lower end of the primary side of the flyback transformer T, the lower end of the switch tube S2, the anode of the diode D2, the anode of the diode D11, the lower end of the capacitor C2, the lower end of the switch tube S6, and the anode of the diode D6 are connected to each other,

The upper end of the negative side of the flyback transformer T is connected to the anode of the diode D13,

The cathode of the diode D13, the left end of the switch tube S7, the left end of the switch tube S8, the cathode of the diode D7 and the cathode of the diode D8 are connected to each other,

The right end of the switch tube S7, the anode of the diode D7 and the anode of the diode D12 are connected to each other,

The right end of the switch tube S8, the anode of the diode D8, the lower end of the capacitor C1, the upper end of the capacitor C2, the right end of the switch tube S9, the cathode of the diode D9, the anode of the diode D14 and the cathode of the diode D15 are connected to each other and grounded,

The lower end of the negative side of the flyback transformer T, the left end of the switch tube S9, the left end of the switch tube S10, the anode of the diode D9 and the anode of the diode D10 are connected to each other,

The right end of the switch tube S10, the cathode of the diode D10 and the cathode of the diode D11 are connected to each other,

The upper end of the capacitor C1, the cathode of the diode D12, the cathode of the diode D01, the upper end of the switching tube S3 and the cathode of the diode D3 are connected to each other,

The lower end of the switch tube S3, the anode of the diode D3, the cathode of the diode D14, the upper end of the switch tube S4 and the cathode of the diode D4 are connected to each other,

The lower end of the switch tube S4, the anode of the diode D4, the left end of the inductor L2, the upper end of the switch tube S5, and the cathode of the diode D5 are connected to each other,

The lower end of the switch tube S5, the anode of the diode D5, the anode of the diode D15, the upper end of the switch tube S6 and the cathode of the diode D6 are connected to each other,

The right end of the inductor L2 is connected to the upper end of the capacitor C3,

The lower end of the capacitor C3 is grounded.

The connections described are wire connections.

Connected as above, switch tubes S3~S6, diodes D3~D6, diodes D14 and D15, inductor L2, and capacitor C3 together form a half-bridge inverter circuit; switch tubes S1 and S2, S7~S10, diodes D1, D2, and D7 ～D10, diodes D01 and D11～D13, inductor L1, and flyback transformer T together form a boost circuit. In the boost circuit, switch tubes S2 and S7～S10, diodes D2 and D7～D10, diodes D01 and D11～D13, The flyback transformer T forms a flyback bus voltage balance circuit.

When in use, the left end of the inductor L1 and the lower end of the primary side of the flyback transformer T are respectively connected to the positive and negative poles of the photovoltaic panel, and the right end of the inductor L2 and the lower end of the capacitor C3 are respectively connected to the positive and negative poles of the load.

The single-phase three-level half-bridge inverter adopted in the utility model includes a flyback bus voltage balance circuit and a half-bridge inverter circuit, the input side of which is connected to a photovoltaic solar battery array, and the output side is connected to a load. The four switch tubes S7~S10 in the flyback bus voltage balance circuit are switched by the zero-crossing trigger of the power frequency grid voltage, and alternately balance the capacitor voltage on the DC side at Vin/2, prolonging the life of the capacitor and the switch tube, and improving the System reliability.

The beneficial effects of the utility model: (1) The four switch tubes in the flyback bus voltage balance circuit work in a low-frequency environment, so the electromagnetic interference is small and the switching loss is small; The capacitor voltage on the DC side can greatly improve the utilization rate of DC voltage and the service life of capacitors and switch tubes; (3) The stable voltage on the bus capacitor helps to realize the maximum power point tracking (MPPT) and maximize the power generation efficiency of solar energy ; (4) The circuit structure is simple and easy to implement.

Description of drawings

Fig. 1 is a circuit topology diagram of a single-phase three-level half-bridge inverter of the present invention.

FIG. 2 is a schematic diagram showing the compensation circuit in the flyback bus voltage balance circuit when the voltage of the capacitor C1 is pulled down.

FIG. 3 is a schematic diagram showing the compensation circuit in the flyback bus voltage balance circuit when the voltages of the capacitors C1 and C2 are not pulled down.

FIG. 4 is a schematic diagram showing the compensation circuit in the flyback bus voltage balance circuit when the voltage of the capacitor C2 is pulled down.

In the figure, 1 is a photovoltaic panel, 2 is a boost circuit, 3 is a half-bridge inverter circuit, and 4 is a load; among them, S1~S10 are switching tubes, D01, D11~D15 are diodes, L1, L2 are inductors, C1~C3 are capacitors, D1~D10 are diodes, Rload is a load, and T is a flyback transformer.

Detailed ways

Connect the circuit as shown in Figure 1. The inverter in this scheme includes a flyback bus voltage balance circuit and a half-bridge inverter circuit. In the flyback bus voltage balance circuit, the two ends of the switch tube S2 are connected to the flyback transformer T primary One end of the switch tube S8 is connected to the midpoint of the bridge arm formed by the first capacitor C1 and the second capacitor C2, and one end of the switch tube S9 is connected to the midpoint of the bridge arm formed by the first capacitor C1 and the second capacitor C2 The upper end of the negative side of the flyback transformer T is connected to the anode of the diode D13, the cathode of the diode D13 is connected to the switch tube S7 and the switch tube S8, the switch tube S7 is connected to the anode of the diode D12, the cathode of the diode D12 is connected to the upper end of the capacitor C1, and the negative side of the flyback transformer T The lower end of the side is connected with the switching tube S9 and the switching tube S10.

Analysis of working principle:

(1) As shown in Figure 2, it shows a schematic diagram of the compensation circuit in the flyback bus voltage balance circuit when the voltage of capacitor C1 is pulled down, that is, at this time V _c1 <E/2-Δ, and at the same time the switch in the flyback bus voltage balance circuit The tube S1 works normally according to the boost principle, and also serves as the main switch tube on the primary side of the flyback; the switch tube S2 is disconnected, the switch tube S7 and the switch tube S9 are turned on, the switch tube S8 and the switch tube S10 are disconnected, and the capacitor C1 Charge.

(2) As shown in Figure 3, it is a schematic diagram of the compensation circuit in the flyback bus voltage balance circuit when the voltage of capacitor C1 and capacitor C2 is not pulled down, that is, V _c1 >E/2-Δ, and the flyback bus voltage is balanced at this time The switch tube S2 in the circuit is turned on, and the switch tube S1 only works normally according to the boost principle; the switch tubes S7, S8, S9, and S10 are all cut off.

(3) As shown in Figure 4, it is a schematic diagram of the compensation circuit in the flyback bus voltage balance circuit when the voltage of the capacitor C2 is pulled down, that is, at this time V _c2 <E/2-Δ, and at the same time the switch in the flyback bus voltage balance circuit The tube S2 is disconnected, the switch tube S1 works normally according to the boost principle, and also serves as the main switch tube of the primary side of the flyback; the switch tube S8 and the switch tube S10 are turned on, the switch tube S7 and the switch tube S9 are disconnected, and the capacitor C2 Charge.

(4) As shown in Figure 3, it shows a schematic diagram of the compensation circuit of the flyback bus voltage balance circuit when the voltage across the capacitor C2 is greater than E/2-Δ, that is, V _c2 >E/2-Δ, at this time the flyback bus voltage The switch tube S2 in the balanced circuit is turned on, the switch tubes S7, S8, S9, and S10 are all turned off, and the switch tube S1 only works normally according to the boost principle.

(5) Diode D11 and diode D12 in Figure 1 play a role in preventing short circuit. First, when diode D11 charges capacitor C1 to increase its voltage when switch tube S7 and switch tube S9 are turned on, avoid the upper end of capacitor C2. The closed circuit formed by the switch S9, diode D10, and the lower end of the capacitor C2 is short-circuited, so the diode D11 should be designed to avoid the short circuit of the circuit; secondly, the function of the diode D12 is also to prevent the short circuit. First, the diode D12 is connected between the switch S8 and the switch tube. When S10 is turned on to charge the capacitor C2 to increase its voltage, it is necessary to avoid the closed circuit formed by the lower end of the capacitor C1, the switch tube S8, the diode D7, and the upper end of the capacitor C1 to be short-circuited, so the diode D11 should be designed to avoid short-circuiting the circuit.

Claims (2)

1. A single-phase three-level half-bridge inverter that can realize capacitor voltage equalization, including a flyback transformer T, a switch tube S1, a switch tube S2, a switch tube S3, a switch tube S4, a switch tube S5, and a switch tube S6 , switch tube S7, switch tube S8, switch tube S9, switch tube S10, diode D1, diode D2, diode D3, diode D4, diode D5, diode D6, diode D7, diode D8, diode D9, diode D10, diode D01, Diode D11, diode D12, diode D13, diode D14, diode D15, capacitor C1, capacitor C2, capacitor C3, inductance L1 and inductance L2; characterized in that: The right end of the inductor L1, the upper end of the switch tube S1, the cathode of the diode D1 and the anode of the diode D01 are connected to each other, The lower end of the switch tube S1, the anode of the diode D1, the upper end of the switch tube S2, the cathode of the diode D2 and the upper end of the primary side of the flyback transformer T are connected to each other, The lower end of the primary side of the flyback transformer T, the lower end of the switch tube S2, the anode of the diode D2, the anode of the diode D11, the lower end of the capacitor C2, the lower end of the switch tube S6, and the anode of the diode D6 are connected to each other, The upper end of the negative side of the flyback transformer T is connected to the anode of the diode D13, The cathode of the diode D13, the left end of the switch tube S7, the left end of the switch tube S8, the cathode of the diode D7 and the cathode of the diode D8 are connected to each other, The right end of the switch tube S7, the anode of the diode D7 and the anode of the diode D12 are connected to each other, The right end of the switch tube S8, the anode of the diode D8, the lower end of the capacitor C1, the upper end of the capacitor C2, the right end of the switch tube S9, the cathode of the diode D9, the anode of the diode D14 and the cathode of the diode D15 are connected to each other and grounded, The lower end of the negative side of the flyback transformer T, the left end of the switch tube S9, the left end of the switch tube S10, the anode of the diode D9 and the anode of the diode D10 are connected to each other, The right end of the switch tube S10, the cathode of the diode D10 and the cathode of the diode D11 are connected to each other, The upper end of the capacitor C1, the cathode of the diode D12, the cathode of the diode D01, the upper end of the switching tube S3 and the cathode of the diode D3 are connected to each other, The lower end of the switch tube S3, the anode of the diode D3, the cathode of the diode D14, the upper end of the switch tube S4 and the cathode of the diode D4 are connected to each other, The lower end of the switching tube S4, the anode of the diode D4, the left end of the inductor L2, the upper end of the switching tube S5, and the cathode of the diode D5 are connected to each other, The lower end of the switch tube S5, the anode of the diode D5, the anode of the diode D15, the upper end of the switch tube S6 and the cathode of the diode D6 are connected to each other, The right end of the inductor L2 is connected to the upper end of the capacitor C3, The lower end of the capacitor C3 is grounded. 2. The single-phase three-level half-bridge inverter capable of realizing capacitor voltage equalization according to claim 1, characterized in that: said connections are wire connections.