KR101623239B1 - Hybrid topology system for single-phase photovoltaic inverter - Google Patents

Abstract

The present invention relates to a hybrid topology system for a single-phase solar inverter, and more particularly, to a hybrid topology system for a single-phase photovoltaic inverter capable of not only high efficiency but also low current.
To this end, the present invention applies a scheme of switching the upper switch SW2 instead of the lower switch SW3 in Negative in the conventional hybrid topology, thereby preventing the current from flowing to the ground when the current is turned inside, thereby improving the EMI performance.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a hybrid topology system for a single-

The present invention relates to a hybrid topology system for a single-phase solar inverter, and more particularly, to a hybrid topology system for a single-phase photovoltaic inverter capable of not only high efficiency but also low current.

Single-phase photovoltaic (PV) systems can be divided into a transformer type and a non-transformer type. The transformerless type has advantages such as reduced volume and weight and low production cost. However, since it is not electrically insulated, stability and reliability are lower than that of transformer type. Therefore, many researches have been made to improve stability and reliability at present, and a hybrid topology has been proposed as a part of the research. The hybrid topology uses a full bridge circuit as shown in FIG. Switching turns on / off the fourth switch (SW4) in the positive state and turns the third switch (SW3) on / off in the negative state. Since only one switch is turned on / off in this manner, it is possible to reduce the switch loss, which is a high-efficiency topology.

The simulation of such a hybrid topology is as shown in FIG. 2, and the potential difference between the ground and the power line is measured to confirm EMI (Electro Magnetic Interference) performance. (It can be seen that the switching works according to the hybrid topology as shown in [Table 1].)

For this, as shown in FIG. 2, simulation results are shown. As a result, as shown in FIG. 3, harmonic noises are generated at the potentials of the ground and the power line as shown in FIG. 3, so that the conventional hybrid topology has poor EMI performance.

It is an object of the present invention to provide a hybrid topology system for a single-phase solar inverter capable of having high efficiency as well as low earth current.

To this end, the present invention provides a hybrid topology system for a single-phase solar inverter, comprising: a hybrid topology for a single-phase solar inverter including a top switching unit composed of first and third switches and a bottom switching unit composed of second and fourth switches; During the period of the positive period, the first switch SW1 is turned on during the current-free frequency of the topology such that the current is freewheeling to the positive portion of the topology, -on and the third switch SW3 and the fourth switch SW4 are staggered when the second switch SW2 is switched-off to perform switching-on and switching-off and the third switch SW3 is switched-on and the fourth switch SW4 is switched-off during the period of the negative section, And a switching controller for causing the first switch SW1 and the second switch SW2 to alternate between switching-on and switching-off.

In order to achieve the above object, the present invention provides a hybrid topology system for a single-phase solar inverter, comprising: a top switching unit including a first switch SW1 and a third switch SW3; a second switch SW2; a fourth switch SW4; A hybrid topology for a single-phase photovoltaic inverter including a bottom switching unit including a plurality of switching units; During current phase freeing of the topology, the first switch SW1 is switched-on during the positive switching time such that the current is freewheeling to the top switching unit of the topology When the second switch SW2 is switched off, the third switch SW3 and the fourth switch SW4 are switched to each other to perform switching-on and switching-off, And during the negative switching time, when the third switch SW3 is in the switching-on state and the fourth switch SW4 is in the switching-off state, the first switch SW1 And a switching controller for causing the first switch SW2 and the second switch SW2 to alternate between switching-on and switching-off, respectively, During the positive switching time and the negative switching time, both the first and third switches It characterized in that the re-wheeling operation is to occur.

According to the present invention, it is possible to maintain the advantages of high efficiency and improve the EMI problem by modifying the existing hybrid high-efficiency hybrid topology.

1 is a flow diagram of a conventional hybrid topology system;
2 is a circuit diagram of a conventional hybrid topology simulation.
3 is a graph of a conventional hybrid topology simulation result.
4 is a flow diagram of a hybrid topology system in accordance with the present invention.
5 is a graph of a hybrid topology simulation result according to the present invention.
FIG. 6 is an overall schematic diagram including a hybrid topology system according to the present invention; FIG.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

4 shows a hybrid topology flow diagram according to the present invention. In the conventional hybrid topology, the second switch SW2 is switched in place of the third switch SW3 in Negative, so that the current does not flow toward the ground when the current is turned inside, thereby improving the EMI performance.

To this end, the present invention provides a hybrid topology including a top switching unit composed of a first switch SW1 and a second switch SW2, and a bottom switching unit composed of a third switch SW3 and a fourth switch SW4 This structure is the simplest inverter circuit that generates a single-phase AC voltage from a DC power source. The voltage applied to the load is the same as the output voltage of the basic circuit, and the desired single-phase AC voltage is half cycle / Off, which is the method of obtaining the largest output voltage. If two switches SW1 and SW2 of the upper-stage switching unit or SW3 and SW4 of the lower-stage switching unit are turned on at the same time, the DC power supply side and the switch are short-circuited. In order to prevent such a short-circuiting accident, the two switches are alternately conducting complementary switching. In such a complementary switching, the two switches are connected in various combinations such as Unipolar, Bipolar, Hybrid There are various ways.

To this end, the present invention includes a hybrid topology including a top switching unit including a first switch SW1 and a third switch SW3, and a bottom switching unit including a second switch SW2 and a fourth switch SW4 This structure is the simplest inverter circuit that generates a single-phase AC voltage from a DC power source. The voltage applied to the load is the same as the output voltage of the basic circuit, and the desired single-phase AC voltage is half cycle / Off, which is the method of obtaining the largest output voltage. If two switches SW1 and SW2 of the upper-stage switching unit or SW3 and SW4 of the lower-stage switching unit are turned on at the same time, the DC power supply side and the switch are short-circuited. In order to prevent such a short-circuiting accident, the two switches are alternately conducting complementary switching. In such a complementary switching, the two switches are connected in various combinations such as Unipolar, Bipolar, Hybrid There are various ways.

The switching controller switches off the lower switching unit and switches on the upper switching unit so that the current is freewheeling to the upper part of the topology when the current is freewheeling in the topology. The switching controller controls the first switch SW1 and the third switch SW3 to be switched on when the current is freewheeling in the topology so that the current is freewheeling to the top of the topology. And the second switch SW2 and the fourth switch SW4 are switched off.

When the first switch SW1 and the third switch SW3 are switched off and the second switch SW2 and the fourth switch SW4 are switched on, When the second switch SW2 and the fourth switch SW4 are connected to the ground at the time of freewheeling, the conductive noise may flow, which is not good for EMI measurement, and the first switch SW1 and the second switch SW2 When the third switch SW3 is switched-on and the second switch SW2 and the fourth switch SW4 are switched off, the current is separated from the ground only at the upper end, It may be freewheeling so that it does not flow toward the ground, thereby improving the EMI performance.

In addition, the switching control unit may perform switching in the order of the first switch? The fourth switch? The second switch? The third switch, or the order of the third switch? The second switch? The first switch? The fourth switch. When the first switch SW1 is switched-on and the second switch SW2 is switched-off during a period of 1 / 120Hz of the positive period, the switching controller turns on the third switch SW3 and the fourth switch SW4 repeat switching-on and switching-off and the third switch SW3 is turned on during a period of 1 / the first switch SW1 and the second switch SW2 switch-on and switch-off when the fourth switch SW4 is switched off, switching-off). The sum of the positive and negative intervals has a frequency of 1 / 60Hz, or 60Hz. At this time, when the state changes from positive to negative in FIG. 4, when the state changes from ② to ③, the third switch SW3 is kept in the switching-on state so that the switching can be connected, and from Negative to Positive, , The first switch SW1 is in the switching-on state, and the switching is minimized in the interval where the positive and negative are repeated.

When the first switch SW1 is switched-on and the second switch SW2 is switched-off during a period of 1 / 120Hz of the positive period, The third switch SW3 and the fourth switch SW4 are repeatedly switched to switch-on and switch-off, and during the period of 1 / 120Hz of the negative section, When the switch SW3 is switched-on and the fourth switch SW4 is switched-off, the first switch SW1 and the second switch SW2 are shifted from each other, (switching-on) and switching-off (switching-off). The sum of one section of the positive (positive) and the negative (negative) has a time of 1 / 60Hz, that is, a frequency of 60Hz. At this time, the third switch SW3 is kept in the switching-on state so that switching can be connected when switching from the upper (Positive) to the lower (Negative) in FIG. The first switch SW1 is in the switching-on state and the switching is minimized in the interval where the positive and negative are repeated.

Table 2 summarizes switching of the topology according to the present invention.

When this is applied to the simulation, the result shown in FIG. 5 is obtained. As a result, almost all the harmonic noises are disappeared at the potential of the ground and the power line, and the current of the system is equal.

Claims (3)

In the hybrid topology system for a single-phase solar inverter, a top switching unit including a first switch SW1 and a third switch SW3, a bottom switching unit including a second switch SW2 and a fourth switch SW4 A hybrid topology for a single-phase photovoltaic inverter; During current phase freeing of the topology, the first switch SW1 is switched-on during the positive switching time such that the current is freewheeling to the top switching unit of the topology When the second switch SW2 is switched off, the third switch SW3 and the fourth switch SW4 are switched to each other to perform switching-on and switching-off, And during the negative switching time, when the third switch SW3 is in the switching-on state and the fourth switch SW4 is in the switching-off state, the first switch SW1 And a switching controller for causing the first switch SW2 and the second switch SW2 to alternate between switching-on and switching-off, respectively, During the positive switching time and the negative switching time, both the first and third switches Lee hybrid system topology for a single phase PV inverters characterized in that the wheeling operation to occur. 2. The hybrid topology system for a single-phase solar inverter according to claim 1, wherein the topology is a single-phase inverter circuit. delete

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