CN110729913A - Single-stage high-gain five-switch Boost type inverter - Google Patents

Abstract

The invention relates to a single-stage high-gain five-switch Boost inverter. Aiming at the problem of large loss of the low-voltage side commutation diode of the single-stage Boost inverter with a coupled inductor, a switch tube is introduced to remove the problem. There are two commutation diodes on the low-voltage side, thereby reducing the conduction loss caused by the low-voltage side diodes and improving the overall efficiency. Calculate and simulate the loss of the topology and the topology with low-voltage side commutation diode with the same switch tube parameters. Taking 200W output power as an example, the conduction loss is reduced by nearly 10W, accounting for nearly 5% of the overall efficiency. It can be seen that all The conduction loss reduction effect of the above topology is obvious. When the output power is further increased and the input voltage is further decreased, the conduction loss of the original topology with a low-voltage side commutation diode will be further increased, and the advantages of the topology will be more obvious.

Description

A single-stage high-gain five-switch boost inverter

technical field

The invention belongs to the field of power electronics, and relates to a single-stage high-gain five-switch Boost inverter.

Background technique

In photovoltaic micro-inverter applications, the inverter is usually required to have a high voltage gain due to the low output voltage of a single photovoltaic panel and a high output grid side voltage. In general, due to easy control and implementation, a two-stage inverter is used, the first stage is a high-gain DC-DC converter, and the second stage is an ordinary bridge inverter. However, due to lower cost and higher efficiency, single-stage inverters are increasingly of interest to researchers. Looking at the solutions proposed so far, it mainly involves several types of flyback, Boost, and Buck-Boost.

In the solution adopted by the single-stage inverter, the flyback topology can have a high voltage gain due to the use of a transformer. However, due to its single-stage structure, a decoupling circuit has to be added to reduce the decoupling capacitance. This will weaken the simple structure of the flyback topology, which will increase the number of devices and reduce the efficiency; most of the Buck-Boost topology is still limited by a limited voltage conversion ratio. Individual topologies can achieve high conversion ratios, but the number of devices is limited. Greatly increased; Boost-type topology makes power decoupling simple due to its high-voltage bus, but most of the current topologies suffer from the disadvantage of limited gain.

Some literatures have proposed a new Boost inverter topology to greatly improve the voltage gain by introducing a coupled inductor. However, due to the single-stage topology, two commutation diodes are introduced on the low-voltage side, and these two diodes suffer from high current. It causes a larger conduction loss, and when the input voltage is lower, the diode loss accounts for a larger proportion of the overall loss.

SUMMARY OF THE INVENTION

technical problem to be solved

In order to avoid the shortcomings of the prior art, the present invention proposes a single-stage high-gain five-switch Boost inverter, which solves the problem of large loss of the low-voltage side commutation diode of the single-stage Boost inverter with a coupled inductor. question. By introducing a switch tube to remove the two commutation diodes on the low-voltage side, the loss caused by the low-voltage side diodes is reduced and the overall efficiency is improved.

Technical solutions

A single-stage high-gain five-switch Boost inverter is characterized in that it includes M ₁ to M ₅ switch tubes, L _cp coupled inductors, D boost diodes, and output filter networks L _o -C _o and C _dc decoupling Capacitor _; the source _of M1 switch tube and M3 switch tube are connected to the negative pole of the power supply and grounded; the positive pole of the power supply is connected to the same name terminal of the winding W1 _of the _Lcp coupling inductor _; the drain of the M1 switch tube, the _M5 switch The source of the tube is connected to the same-named end of the winding W2 and the non _- same _- named end of W1; the C _o output filter capacitor is connected in series with the L _o inductance, and its one end is connected to the source _of the _M4 switch tube and the drain of the M3 switch tube , the other end is connected to the source of the _M2 switch tube and the drain of the _M5 switch tube _; the drains of the _M2 switch tube and the M4 switch tube are connected to the DC bus capacitor _Cdc , and are connected to the cathode of the diode D; The anode of the diode D is connected with the non-identical end of the coupled inductor winding W ₂ ; when working, the _RL load is connected in parallel with the C _o output filter capacitor.

The number of turns of the primary winding of the L _cp coupled inductor is N ₁ , the number of turns of the secondary winding is N ₂ , and the transformation ratio is n=N ₂ /N ₁ .

The transformation ratio n is selected according to the required voltage gain.

beneficial effect

A single-stage high-gain five-switch Boost inverter proposed by the present invention aims at the problem of large loss of the low-voltage side commutation diode of the single-stage Boost inverter with a coupled inductor. In addition to the two commutation diodes on the low-voltage side, the conduction loss caused by the low-voltage side diodes is reduced and the overall efficiency is improved. Calculate and simulate the loss of the topology and the topology with low-voltage side commutation diode with the same switch tube parameters. Taking 200W output power as an example, the conduction loss is reduced by nearly 10W, accounting for nearly 5% of the overall efficiency. It can be seen that all The conduction loss reduction effect of the above topology is obvious. When the output power is further increased and the input voltage is further reduced, the conduction loss of the original topology with a low-voltage side commutation diode will be further increased, and the advantages of the topology will be more obvious.

At the same time, the topology maintains a single-stage compact topology, with a small number of devices, and the high-voltage DC bus can use a small decoupling capacitor, so as to avoid introducing a decoupling circuit or placing a large capacitance value on the low-voltage side. capacitor, can improve the reliability and life of the inverter.

Description of drawings

Figure 1 shows the proposed single-stage high-gain five-switch Boost inverter topology

Fig. 2 is the working modal diagram of the present invention

Figure 2(a) Mode A

Figure 2(b) Mode B

Figure 2(c) Mode C

Figure 2(d) Mode A'

Figure 2(e) Mode B'

Figure 2(f) Mode C'

Fig. 3 is the main working waveform of the present invention

Detailed ways

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

According to the technical solution provided by the present invention, the single-stage high-gain five-switch Boost inverter includes: a bridge circuit composed of five switch tubes M ₁ to M ₅ , a coupled inductor L _cp , a boost diode D, DC bus capacitance C _dc , output filter network L _o -C _o and equivalent load R _L . The number of turns of the primary winding of the coupled inductance is N ₁ , the number of turns of the secondary winding is N ₂ , and the transformation ratio is n=N ₂ /N ₁ . The required voltage gain can be achieved by rationally designing the transformation ratio of the coupled inductance. The two commutation diodes on the low-voltage side in the original circuit are removed by introducing an intermediate _- stage switch tube M5 into the full-bridge circuit, and the normal operation of the inverter circuit can be realized through the designed logic control.

The circuit connection relationship of the topology is as follows: the sources of the switch tubes M ₁ and M ₃ are connected to the negative pole of the input power supply and grounded; the positive pole of the input power supply is connected to the same-named end of the winding W ₁ of the coupled inductor L _cp ; the drain of the switch tube M ₁ is connected to the ground; pole, the source of M5 is connected with the same name terminal of winding W2 and the non _- identical terminal of W1 _; the load R _L is connected in parallel with the output filter capacitor C _o and in series with the inductor L _o , and one end of it is _connected with the source of the switching tube M ₄ The other end is connected to the source of the switch _M2 and the drain _of the switch _{M5 ;} the drains of the switches _M2 and M4 are connected to the DC bus capacitor _Cdc , and Connect to the cathode of diode D; the anode of diode D is connected to the non _- identical end of the coupled inductor winding W2.

As shown in Figure 1, the inverter is composed of switch tubes M ₁ to M ₅ , coupling inductor L _cp , boost diode D, output filter network L _o -C _o , load R _L , decoupling capacitor C _dc and so on. The required voltage gain can be achieved by adjusting the transformation ratio of the coupling inductance, and the on-off of M ₁ to M ₅ can be reasonably controlled to make the circuit work correctly so as to obtain the required output AC voltage or current.

When the output voltage is positive, the switch M4 is always _on , and the switch M3 is always off. _The output voltage is controlled by controlling the on and off _of the switches M1, _M2 and _M5 .

The working mode of the topology is: there are three working modes in each switching cycle. When the output voltage is positive, the topology works in modes A, B and C, and when the output voltage is negative, the topology works in modes A', B ' and C'.

When the output voltage is positive, the switch M3 is always off, and the switch M4 is always _on , and the output voltage is controlled by controlling the _on and off _of the switches M1, _M2 and _M5 .

Mode _A : _The switches M1 and M5 are turned on, the switch _M2 is turned off, the input voltage source starts to charge the primary winding W1 _of the coupled inductor, and at the same time, the switches M4 and M1 are _{turned on} to make the DC bus to the load terminal. powered by. The circuit of this mode is shown in Figure 2(a)

Mode B: At the moment of D _bk T _s , the switch _M5 is turned off and the switch _M2 is turned _on , the current continues to flow through the switches M4 and _M2 , and the output capacitor supplies power to the load. The input voltage source continues to charge the primary winding W1 _of the coupled inductor. The circuit of this mode is shown in 2(b)

Mode C: At the time _of D _bst T _s , the switch M1 is turned off, the input voltage source and the coupled inductor charge the DC bus capacitor through the two windings and the diode D, and the rest of the switches remain unchanged. The circuit of this mode is shown in Figure 2(c)

When the output voltage is negative, the switch _M2 is always turned _on and M5 is always turned off. _The output voltage is controlled by controlling the switches _of M1, M3 and M4, thereby obtaining the working modes _A ', B' and C'.

Mode _A ': _The switches M1 and M3 are turned _on , the switch M4 is turned off, the input voltage source charges the primary winding N1 _of the coupled inductor, and the switches _M2 and M3 are turned _on to make the DC bus to the load terminal. Reverse power supply. The circuit of this mode is shown in Figure 2(d)

Mode B': at the moment of D _bk T _s , the switch M3 is turned off and the switch _M4 is turned _on , the current continues to flow through the switches _M2 and _M4 , and the output capacitor supplies power to the load. The input voltage source continues to charge the primary winding N1 _of the coupled inductor. The circuit of this mode is shown in Figure 2(e)

Mode C': At the time _of D _bst T _s , the switch M1 is turned off, the input voltage source and the coupled inductor charge the DC bus capacitor through the two windings and the diode D, and the rest of the switches remain unchanged. The circuit of this mode is shown in Figure 2(f)

Among them, D _bst is the boost duty cycle, which can be calculated according to the relationship between the input and output voltage or obtained by the maximum power tracking algorithm; D _bk is the SPWM wave with sinusoidal variation, and the sinusoidal wave can be obtained at the output end according to the modulation of D _bk AC voltage or current. In this topology, the maximum value of D _bk is smaller than D _bst .

The switching mode of the switch tube of the topology is shown in Table 1.

Topological switch modes described in Table 1

When the output voltage is negative, the switch _M2 is always turned _on and M5 is always turned off. _The output voltage is controlled by controlling the switches _of M1, M3 and M4, thereby obtaining the working modes _A ', B' and C', as shown in Fig. 2(d), Fig. 2(e) and Fig. 2(f).

The main working waveforms of the topology are shown in Fig. 3 , wherein S _M1 ˜ S _M5 are switching signals of the switching tubes M ₁ ˜ M ₅ respectively. By adjusting the duty ratio D _bst , the required DC bus voltage can be obtained; by adjusting the duty ratio D _bk , the required sinusoidal output waveform can be obtained.

Claims (3)

1. A single-stage high-gain five-switch Boost inverter, characterized in that it comprises M ₁ to M ₅ switch tubes, L _cp coupled inductors, D boost diodes, output filter networks L _o -C _o and C _dc Decoupling capacitor; the source of M ₁ switch tube and M ₃ switch tube is connected to the negative pole of the power supply and grounded; the positive pole of the power supply is connected to the same name terminal of the winding W ₁ of the L _cp coupling inductor; the drain of the M ₁ switch tube, M _5. The source of the switch tube is connected to the same-named end of the winding W2 and the non _- same _- named end of W1; the C _o output filter capacitor is connected in series with the L _o inductance, and one end of the switch is connected to the source _of the M4 switch tube and the drain of the M3 switch tube _. The other end is connected to the source of the _M2 switch tube and the drain of the _M5 switch tube _; the drains of the _M2 switch tube and the M4 switch tube are connected to the DC bus capacitor C _dc , and to the cathode of the diode D Connected; the anode of the diode D is connected to the non-same-named end of the coupled inductor winding W ₂ ; when working, the _RL load is connected in parallel with the C _o output filter capacitor. 2. The single-stage high-gain five-switch Boost inverter according to claim 1, characterized in that: the primary winding turns of the L _cp coupled inductor are N ₁ , the secondary winding turns N ₂ , and the transformation ratio is n=N ₂ /N ₁ . 3 . The single-stage high-gain five-switch Boost inverter according to claim 2 , wherein the transformation ratio is n selected according to the required voltage gain. 4 .

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