WO2012027962A1

WO2012027962A1 - High-frequency isolation grid-connected inverter circuit

Info

Publication number: WO2012027962A1
Application number: PCT/CN2011/001472
Authority: WO
Inventors: 李晓峰
Original assignee: 江苏艾索新能源股份有限公司
Priority date: 2010-08-31
Filing date: 2011-08-31
Publication date: 2012-03-08
Also published as: CN101917134A

Abstract

A high-frequency isolation grid-connected inverter circuit includes a high-frequency modulation unit (1) with isolation, a cycle inverter unit (2) which is in charge of cutting the positive and negative semi-cycle of alternating current, and an LC (inductor & capacitoor) filtering unit (3). The high-frequency modulation unit (1) with isolation is connected with the cycle inverter unit (2) and the LC filtering unit (3) in sequence. The high-frequency modulation unit (1) with isolation includes a high-frequency SPWM modulation unit which performs sine modulation on the input direct current so as to generate pulse based on sine, a high-frequency transformer and a diode rectification unit which are connected in sequence. The high-frequency isolation grid-connected inverter is featured by a simple structure, stable performance and high integration conversion efficiency. The using ratio of the high-frequency isolation transformer is high, and the switching consumption is reduced. The circuit is of small volume and light weight.

Description

High frequency isolated grid-connected inverter circuit

The invention relates to a high frequency isolated grid-connected inverter circuit. Background technique

The grid-connected inverter with transformer isolation can electrically isolate the input and output, and can better solve electromagnetic interference problems and electrical safety problems.

In some cases, an isolated inverter unit is required, such as a home user power unit with a Back-contact panel and a thin-film solar panel. Considering the surface polarization of the Back-contact panel, a panel is required. The ground is negative, blocking leakage current and improving power generation efficiency. For thin-film batteries, in order not to affect the performance of the panel itself (such as corrosion), the panel needs to be positive to the ground. At this time, the positive or negative terminal of the panel needs to be grounded, compared to the inverter without the isolation transformer. Inverter with isolation transformer can easily do this.

In addition, in some countries, based on safety considerations, solar power inverters sold in the country need to increase electrical isolation to ensure electrical isolation of the front and rear stages of solar power generation, further reducing accidents involving accidental electric shocks.

There are two types of isolated inverters: low frequency isolation and high frequency isolation. Low-frequency isolated inverters require a large volume of low-frequency transformer isolation, large size, heavy weight, high cost, and extremely inconvenient to install. The other is a high-frequency isolated inverter. Generally, high-frequency isolation is first performed by DC high-frequency isolation, and then rectified and then high-frequency inverter. Such a circuit has a large switching loss, and some of the switching tube stresses have high defects. Summary of the invention The object of the present invention is to provide a high-frequency isolated grid-connected inverter circuit which has simple structure, stable performance, high overall conversion efficiency, high utilization rate of high-frequency isolation transformer, low switching loss, small volume and light weight.

The technical solution of the circuit of the invention is: a high-frequency isolated grid-connected inverter circuit, comprising a high-frequency modulation unit with isolation, a cycle inverter unit responsible for slitting the positive and negative half cycles of the alternating current, the high isolation The frequency modulation unit is connected to the frequency inverter unit.

The above technical solutions are further explained below:

Further, the isolated high frequency modulation unit includes a high frequency SPWM modulation unit that sinusoidally modulates the input direct current to generate a high frequency pulse based on a sinusoidal high frequency transformer, a high frequency transformer TX1, and a diode rectifier unit.

Further, the high frequency isolation grid-connected inverter circuit further includes an inductor-capacitor filter unit, and the cycle inverter unit is connected to the inductor-capacitor filter unit.

Further, the high frequency SPWM modulation unit may be selected from a half bridge circuit, a full bridge circuit, or a push pull circuit.

Further, the inductor-capacitor filter unit is located at an output end of the cycle inverter unit, and the cycle inverter unit is connected to the inductor-capacitor filter unit.

The inductor-capacitor filter unit includes at least one inductor, which may be one inductor or two inductors or multiple inductors. The inductor can be connected in series to any of the electrodes at the output of the cycloid inverter unit, or two inductors (or multiple inductors) can be connected in series to different electrodes.

A filter capacitor is connected in parallel between the two electrodes after the filter inductor. That is: the capacitor is located at the output of the inductor and is connected in parallel between the two poles of the grid.

Since the power generation inverter is usually a grid-connected inverter, there may be a relatively high surge on the mains Vac side. The inductor-capacitor filter unit is located at the output of the cycle inverter unit because the latter stage With inductance and capacitance as a barrier, it can greatly reduce the chance of damage from instantaneous high voltage or large current. At the same time, since the path of the inductor freewheeling of the present invention is relatively short, the number of components passing through is relatively small, so the loss is also small, and the space for improvement is improved. A more preferred technical solution of the present invention: the high frequency SPWM modulation unit includes a full bridge circuit composed of a switch tube S1, a switch tube S2, a switch tube S3, and a switch tube S4; the diode rectification unit includes a diode D1 and a diode D2. a full-wave rectifier bridge diode unit composed of a diode D3 and a diode D4; the periodic inverter unit includes a full-bridge circuit composed of a switch tube S5, a switch tube S6, a switch tube S7, and a switch tube S8; an inductor-capacitor filter unit For the inductor L1, the capacitor C1; when the high-frequency SPWM modulation unit is working, the primary side voltage pair of the transformer TX1 is divided into a pulse one and a pulse two; the current loop when the pulse is applied, the primary current passes through the switch tube S1, the transformer TX1 The switch tube S4 flows back to the negative end, and the energy is transmitted to the secondary side through the transformer TX1, and the secondary side flows back to the negative end of the transformer through the diode D1, the switch tube S5, the AC output terminal Vac, the inductor L1, the switch tube S8, and the diode D4. At this time, the energy is supplied from the DC of the previous stage to the rear pole; when the pulse is over, the voltage of the TX1 terminal of the primary transformer is zero, and the secondary side passes through the switch S5, and the AC The electric output terminal Vac, the inductor L1, the switch tube S7 are connected in parallel with the diode, and the other freewheeling circuit is the switch tube S8, the switch tube S6 is connected in parallel with the diode, the AC output terminal Vac, the inductor L1 is freewheeling; the current loop when the pulse 2 appears The primary current flows back to the negative terminal through the switch S3, the transformer TX1, and the switch S2, and the energy is transmitted to the secondary side through the transformer TX1, and the secondary side passes through the diode D3, the switch tube S5, the AC output terminal Vac, the inductor L1, the switch The tube S8 and the diode D2 flow back to the negative end of the transformer. At this time, the energy is supplied from the DC of the front stage to the rear pole. When the pulse 2 ends, the voltage of the TX1 terminal of the primary transformer is zero, and the secondary side passes through the switch S5 and the AC output. Vac, inductor Ll, switch S7 parallel diode freewheeling, another freewheeling circuit is switch S8, switch S6 parallel diode, AC output terminal Vac, inductor L1 freewheeling.

The traditional high-frequency isolation mainly completes the DC-to-DC isolation. The present invention completes the SPWM modulation of the inverter at the high-frequency isolation end, so that the output voltage can be directly sinusoidally filtered by the inductor.

The core of the preferred embodiment of the present invention is: First, the input DC is sinusoidally modulated (the modulation mode is a sinusoidal modulation mode, and the implementation is shown in FIG. 2), so that it generates a high frequency pulse, and the high frequency pulse is pulsed. The circuit is symmetrically applied to both ends of the primary side of the transformer (implementation diagram, for example Figure 4). Thus, the energy of the DC terminal is transmitted from the primary side of the transformer to the secondary side by high frequency modulation. The secondary side is then diode rectified, cycle inverter and inductively filtered to produce a sinusoidal current output.

The advantages of the invention are:

1. The high-frequency isolated grid-connected inverter circuit of the invention has high overall conversion efficiency, and has the advantages of light weight, small volume, stable performance and the like. The four switching transistors of the primary side SPWM modulation can adopt soft switching technology to reduce switching losses. Through the control circuit, the transformer will work in the first and third quadrants, greatly improving the utilization of the transformer. For the secondary side, the rectifier bridge diode is turned off at zero voltage, which greatly reduces the switching loss of the diode. The switching frequency of the secondary inverter on the secondary side is the mains frequency, so the switching loss is also very small, the freewheeling circuit It is generated at the peripheral inverter and has two paths to reduce conduction loss and diode switching loss.

2. The high-frequency isolated grid-connected inverter circuit of the present invention adopts the design of the inductor-capacitor filter unit at the rear of the cycle inverter unit, because the latter stage has inductance and the capacitor acts as a block, which can greatly reduce the instantaneous high voltage in the power grid or The probability of damage from high currents. At the same time, since the path of the inductor freewheeling of the present invention is relatively short, the number of components passing through is relatively small, so the loss is also small, and the efficiency is improved. DRAWINGS

The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

Figure 1 is a schematic structural view of the present invention;

Figure 2 is a schematic diagram of the function of the high frequency modulation part with isolation;

Figure 3 is a schematic structural view of an embodiment of the present invention;

4 is a waveform diagram of a pulse voltage at the primary side of the transformer TX1 under SPWM modulation in the embodiment shown in FIG. 3;

Figure 5 is a schematic diagram of the current loop of the pulse of Figure 4;

6 is a schematic diagram of a freewheeling circuit of a post-polarum inverter after the end of the pulse of FIG. 4; Figure 7 is a schematic diagram of the current loop of the pulse two action of Figure 4;

Figure 8 is a circuit diagram of the freewheeling circuit of the circuit after the end of the pulse 2 of Figure 4;

Figure 9 is a voltage waveform of the diode rectifier bridge in one voltage cycle in the embodiment shown in Figure 3;

Figure 10 is a schematic diagram of the low frequency drive signal of the cycle inverter (switch S5, switch S8); Figure 11 is a schematic diagram of the low frequency drive signal of the cycle inverter (switch S6, switch S7); Figure 12 is the latter stage The output current and voltage waveform of the circuit after the inductor is filtered.

Among them: 1 with high frequency modulation unit; 2 cycle inverter unit; 3 inductor and capacitor filter unit; 11 pulse one; 12 pulse two; 15 sinusoidal voltage; 16 sinusoidal current; 21 control unit; 22 low frequency IGBT drive unit; 23 switch tube drive control unit; 24 SPWM modulation.

detailed description

Embodiment: As shown in FIG. 1 and FIG. 3, a high-frequency isolated grid-connected inverter circuit includes a high-frequency modulation unit with isolation, a frequency-wave inverter unit, and an inductor-capacitor filter unit 3. The high-frequency modulation unit with isolation 1 is connected to the frequency inverter unit 2 and the inductor-capacitor filter unit 3 in sequence.

The isolated high frequency modulation unit 1 includes a high frequency SPWM modulation unit that sinusoidally modulates the input direct current to produce a high frequency pulse based on a sinusoidal high frequency pulse, a high frequency transformer TX1, and a diode rectification unit. The cycle inverter unit is responsible for cutting the positive and negative half cycles of the alternating current. The inductor-capacitor filter unit 3 can be connected to one pole or two poles of the mains by using one inductor or two or more inductors.

The high frequency SPWM modulation unit may be selected from a half bridge circuit, a full bridge circuit, or a push pull circuit. In this embodiment, a full bridge circuit is taken as an example.

The high frequency SPWM modulation unit includes a full bridge circuit composed of a switch tube S1, a switch tube S2, a bypass tube S3, and a switch tube S4. The control of the switch tube S1, the switch tube S2, the switch tube S3, and the switch tube S4 can be controlled by phase shifting, or by ordinary full bridge to pulse control. The diode rectifying unit comprises a full-wave rectifying bridge diode unit composed of a diode D1, a diode D2, a diode D3, and a diode D4.

The cycle inverter unit includes a full bridge circuit composed of a switch tube S5, a switch tube S6, a switch tube S7, and a switch tube S8.

The inductor-capacitor filter unit includes at least one inductor, which may be one inductor or two inductors or multiple inductors. The inductor can be connected in series to any of the electrodes at the output of the cycloid inverter unit, or two inductors (or multiple inductors) can be connected in series to different electrodes. In this embodiment, only one inductor L1 is used as an example.

The inductor-capacitor filter unit 3 further includes a capacitor Cl, which is located at the output of the inductor L1. In the high-frequency isolated grid-connected inverter circuit of the embodiment, the inductor-capacitor filter unit is located at the output end of the frequency-wave inverter unit, because the inductor L1 is used as the block in the latter stage, and the high-voltage or high-current is greatly reduced. The probability of damage.

The situation of this embodiment at work is as follows:

As shown in Figure 4, for the SPWM modulation, the pulse voltage waveform at the primary side of the transformer TX1. As shown in Fig. 5, the current loop of the positive half-cycle pulse of the mains supply, the primary current flows back to the negative terminal through the switch S3, the transformer TX1, and the switch S2, and the energy is transmitted to the secondary side through the transformer TX1, the secondary side Then, the diode D1, the switch S5, the AC output terminal Vac, the inductor L1, the switch tube S8, and the diode D4 flow back to the negative end of the transformer. At this time, energy is supplied from the DC of the preceding stage to the rear pole.

As shown in Fig. 6, when the positive half cycle pulse of the mains is over, the voltage of the primary side transformer TX1 is zero, and the secondary side is freewheeled through the switch S5, the AC output terminal Vac, the inductor L1, and the switch S7. A freewheeling circuit is a diode connected to the switch S8 and the switch S6, and the AC output terminal Vac and the inductor L1 continue to flow.

As shown in Fig. 7, the current loop of the positive half cycle of the mains pulse occurs, the primary current flows back to the negative terminal through the switch S1, the transformer TX1, and the switch S4, and the energy passes through the transformer TX1. Passed to the secondary side, the secondary side flows back to the negative terminal of the transformer through diode D3, switch S5, AC output terminal Vac, inductor L1, switch S8, and diode D2. At this time, energy is supplied from the DC of the preceding stage to the rear pole.

As shown in Figure 8, when the positive half cycle pulse of the mains is over, the voltage of the primary transformer TX1 is zero, and the secondary side is continuously flowed through the switch S5, the AC output terminal Vac, the inductor L1, and the switch S7. A freewheeling circuit is a diode connected to the switch S8 and the switch S6, and the AC output terminal Vac and the inductor L1 continue to flow.

When the mains negative half cycle, the transformer primary pulse one and the pulse two work in the same way, the negative half cycle frequency inverter opens the switch S7 and the switch S6. (The positive half cycle is to open the switch S5 and the switch S8) ₀

Figure 9 is a diagram showing the voltage waveforms behind the diode rectifier bridge during a voltage cycle in the embodiment of Figure 3. Figure 10 is a schematic diagram of the low-frequency drive signal of the cycle inverter (switch S5, switch S8), Figure 11 is a schematic diagram of the low-frequency drive signal of the cycle inverter (switch S6, switch S7). Figure 12 shows the output current and voltage waveforms of the circuit after the inductor is filtered by the latter stage.

By the above pulse one (or pulse two) ending the subsequent flow path diagram, the path of the inductor freewheeling in this embodiment is relatively short, and the number of components passing through is relatively small, so the loss is also small, and there is a higher efficiency improvement space.

It should be noted that various modifications and adaptations of the present invention are possible without departing from the specific embodiments of the embodiments described above. The above embodiments are merely illustrative and not limiting. In conclusion, the scope of the invention should be construed to include any alterations or substitutions and modifications which are obvious to those skilled in the art.

Claims

Claim

A high frequency isolated grid-connected inverter circuit, characterized in that: it comprises an isolated high frequency modulation unit (1), a periodic inverter unit (2) responsible for slitting alternating current positive and negative half cycles, The isolated high frequency modulation unit (1) is connected to the cyclonic inverter unit (2).

2. The high frequency isolated grid-connected inverter circuit according to claim 1, wherein: the isolated high frequency modulation unit (1) comprises sinusoidal modulation of the input direct current connected in sequence to generate a sine based High frequency pulsed high frequency SPWM modulation unit, high frequency transformer, diode rectification unit.

3. The high frequency isolated grid-connected inverter circuit according to claim 2, wherein: the high frequency isolated grid-connected inverter circuit further comprises an inductor-capacitor filter unit (3), the inductor-capacitor filter unit ( 3) Located at the output end of the cycle inverter unit (2), the cycle inverter unit (2) is connected to the inductor-capacitor filter unit (3).

4. The high frequency isolated grid-connected inverter circuit according to claim 3, wherein: the inductor-capacitor filter unit (3) comprises at least one inductor, and the inductor can be connected in series to the frequency inverter unit.

(2) Any one of the electrodes on the output; the inductor-capacitor filter unit (3) further includes a capacitor located at the output of the inductor and connected in parallel between the two poles of the grid.

The high frequency isolated grid-connected inverter circuit according to claim 2, wherein the high frequency SPWM modulation unit is selected from a half bridge circuit, a full bridge circuit, or a push pull circuit.

The high-frequency isolated grid-connected inverter circuit according to claim 2, wherein: the high-frequency SPWM modulation unit comprises a full bridge composed of a switch tube S1, a switch tube S2, a switch tube S3, and a switch tube S4. Circuit.

The high frequency isolated grid-connected inverter circuit according to claim 6, wherein: the driving portion of the switch tube S1, the switch tube S2, the switch tube S3, and the switch tube S4 can adopt a finite bipolar modulation double Pulse halving, or direct double pulse halving to drive the diagonal bridge arm switch.

8. The high frequency isolated grid-connected inverter circuit according to claim 2, wherein: The diode rectifying unit comprises a full-wave rectifying bridge diode unit composed of a diode D1, a diode D2, a diode D3, and a diode D4.

9. The high frequency isolated grid-connected inverter circuit according to claim 1, wherein: the periodic inverter unit (2) comprises a switch tube S5, a switch tube S6, a switch tube S7, and a switch tube S8. Full bridge circuit.

10. The high frequency isolated grid-connected inverter circuit according to claim 3, wherein: the high frequency SPWM modulation unit comprises a full bridge composed of a switch tube S1, a switch tube S2, a switch tube S3, and a switch tube S4. The diode rectifying unit includes a full-wave rectifying bridge diode unit composed of a diode D1, a diode D2, a diode D3, and a diode D4; the periodic inverter unit (2) includes a switch tube S5, a switch tube S6, The full-bridge circuit composed of the switch tube S7 and the switch tube S8; the inductor-capacitor filter unit (3) is the inductor L1; when the high-frequency SPWM modulation unit is operated, the primary side voltage of the transformer TX1 is divided into a pulse one and a pulse two; In the current loop of the action, the primary current flows back to the negative terminal through the switch S1, the transformer TX1, and the switch S4, while the energy is transmitted to the secondary side through the transformer TX1, and the secondary side passes through the diode D1, the switch tube S5, and the AC output terminal. Vac, inductor Ll, switch S8, diode D4 flow back to the negative end of the transformer, at this time the energy is supplied from the DC of the front stage to the rear pole; After that, the voltage of the primary side transformer TX1 is zero, the secondary side is continuously flowed through the switching tube S5, the alternating current output terminal Vac, the inductor L1, and the switch tube S7, and the other freewheeling circuit is a parallel circuit of the switch tube S8 and the switch tube S6. The AC output terminal Vac and the inductor L1 are freewheeling; when the pulse 2 appears, the primary current flows back to the negative terminal through the switch S3 and the transformer TX switch S2, and the energy is transmitted to the secondary side through the transformer TX1, and the secondary side is Through the diode D3, the switch tube S5, the AC output terminal Vac, the inductor L1, the switch tube S8, the diode D2 flow back to the negative end of the transformer, at this time the energy is supplied from the DC of the front stage to the rear pole; when the pulse two ends, the primary side The voltage at the TX1 terminal of the transformer is zero, and the secondary side is freewheeled through the switching transistor S5, the AC output terminal Vac, the inductor L1, and the switching transistor S7 in parallel. The other freewheeling circuit is the switching transistor S8, the switching transistor S6 is connected in parallel with the diode, and the AC output terminal Vac , inductor L1 freewheeling.