KR102592228B1 - Device and method for controlling non-isolated buck-boost inverter - Google Patents

Abstract

The non-isolated buck-boost inverter control device of the present invention determines the sign of the output voltage of the non-isolated buck-boost inverter, and turns on/off a plurality of switches included in the non-isolated buck-boost inverter according to the determination result. and a control unit that controls (on/off) based on a duty ratio related to the duty cycle of the control signal, wherein the non-isolated buck-boost inverter includes: a first switch and a second switch connected in series with each other; a third switch and a fourth switch connected in parallel with the first switch and the second switch and connected in series with each other; A first two-way switch and a second two-way switch connected to a node between the first switch and the second switch and a node between the third switch and the fourth switch, and the first two-way switch and the second two-way switch. The switch may operate at a higher frequency than the first to fourth switches.

Description

Non-isolated buck-boost inverter control device and control method {DEVICE AND METHOD FOR CONTROLLING NON-ISOLATED BUCK-BOOST INVERTER}

The present invention relates to a non-isolated buck-boost inverter control device and control method, and more specifically, to a control device and method that can solve leakage current, which is a problem of non-isolated inverters, and simultaneously boost and step down the output voltage of the inverter. It's about.

Inverters are used to convert DC input to AC output and can be classified as voltage power inverters or current power inverters. Voltage power inverters are widely used in various industrial applications, especially renewable energy systems (e.g. solar power systems). However, just as the output voltage of a solar power panel is affected by shading and temperature changes, the output voltage of a renewable energy source can fluctuate significantly depending on the surrounding environment. Therefore, to regulate the fluctuating output voltage, the inverter system must have a buck-boost power conversion function.

A two-stage buck-boost inverter with a boost DC-DC converter and an H-bridge inverter can regulate the output voltage by stepping up and down. However, two-stage buck-boost inverters have problems such as complex control, two-stage power processing, and low efficiency. Therefore, a single-stage non-isolated buck-boost inverter that can solve the above problems is needed.

One object of the present invention relates to an inverter control device and method for solving leakage current by reducing the number of switches operating at high frequencies.

One object of the present invention relates to an inverter control device and method that can adjust the output voltage by boosting and lowering it.

A non-isolated buck-boost inverter control device according to an embodiment is a non-isolated buck-boost inverter control device that determines the sign of the output voltage of the non-isolated buck-boost inverter and controls the non-isolated buck boost inverter according to the determination result. - A control unit that controls on/off of a plurality of switches included in the boost inverter based on a duty ratio related to the duty cycle of the control signal, the non-isolated buck-boost inverter comprising: a first switch and a second switch connected in series with each other; a third switch and a fourth switch connected in parallel with the first switch and the second switch and connected in series with each other; A first two-way switch and a second two-way switch connected to a node between the first switch and the second switch and a node between the third switch and the fourth switch, and the first two-way switch and the second two-way switch. The switch may operate at a higher frequency than the first to fourth switches.

Here, the first two-way switch may include a first switch element and a second switch element, and the second two-way switch may include a third switch element and a fourth switch element.

Here, when the sign of the output voltage is positive, the control unit operates the first switch, the fourth switch, the second switch element, and the fourth switch element in an on state, and the second switch and the fourth switch element are turned on. 3 The switch may be operated in an off state, the first switch element may be controlled based on a first control signal, and the second switch element may be controlled based on a second control signal.

Here, the control unit generates the first control signal and the second control signal based on a first duty ratio and a second duty ratio, respectively, and the first duty ratio and the second duty ratio are the non-isolated buck- It is determined by the modulation index and line frequency, which are the ratio of the input voltage and output voltage of the boost inverter, and the sum of the first duty ratio and the second duty ratio may be 1.

Here, when the sign of the output voltage is positive, the control unit sets the first mode to the first mode when the first switch element is in an on state and the third switch element is in an off state, and the first switch element and the third switch element are set to the first mode. The case in which the switch element is in the off state is set to the second mode, and the case in which the first switch element is in the off state and the third switch element is in the on state is set to the third mode, and the first mode and the second mode are set to the third mode. The first control signal and the second control signal may be generated so that the mode, the third mode, and the second mode are sequentially repeated.

Here, when the sign of the output voltage is negative, the control unit operates the second switch, the third switch, the first switch element, and the third switch element in an on state, and the first switch and the third switch element are turned on. 4 The switch may be operated in an off state, the second switch element may be controlled based on a third control signal, and the fourth switch element may be controlled based on a fourth control signal.

Here, the control unit generates the third control signal and the fourth control signal based on the third duty ratio and the fourth duty ratio, respectively, and the third duty ratio and the fourth duty ratio are the non-isolated buck- It is determined by the modulation index and line frequency, which are the ratio of the input voltage and output voltage of the boost inverter, and the sum of the third duty ratio and the fourth duty ratio may be 1.

Here, when the sign of the output voltage is negative, the control unit sets the fourth mode when the second switch element is in an on state and the fourth switch element is in an off state, and the second switch element and the fourth switch element are set to the fourth mode. The case in which the switch element is in the off state is set to the fifth mode, and the case in which the second switch element is in the off state and the fourth switch element is in the on state is set to the sixth mode, and the fourth mode and the fifth mode are set to the sixth mode. The third control signal and the fourth control signal may be generated so that the mode, the sixth mode, and the fifth mode are sequentially repeated.

A method of controlling a non-isolated buck-boost inverter according to an embodiment is a method of controlling a non-isolated buck-boost inverter including first to fourth switches and first to second bidirectional switches, wherein the non-isolated buck-boost determining the sign of the output voltage of the inverter; controlling on/off of the first to fourth switches according to the sign of the output voltage; It may include generating first and second control signals that control the first to second bidirectional switches to operate at a higher frequency than the first to fourth switches depending on the sign of the output voltage.

Here, the step of controlling the on/off of the first to fourth switches includes operating the first switch and the fourth switch connected in parallel with the first switch in the on state when the sign of the output voltage is positive. and operating the second switch in series with the first switch and the third switch in series with the fourth switch in an off state.

Here, the step of generating the first and second control signals bases the first control signal and the second control signal on a first duty ratio and a second duty ratio, respectively, related to the duty cycle of the control signal. and generating, wherein the first duty ratio and the second duty ratio are determined by a modulation index and a line frequency that are the ratio of the input voltage and the output voltage of the non-isolated buck-boost inverter, and the first duty ratio And the sum of the second duty ratios may be 1.

Here, setting the mode according to the on/off operation of the first and second switch elements included in the first two-way switch and the third and fourth switch elements included in the second two-way switch. Further comprising: generating the first and second control signals, when the sign of the output voltage is positive, a first mode in which the first switch element is in an on state and the third switch element is in an off state, A second mode in which the first switch element and the third switch element are in an off state, a third mode in which the first switch element is in an off state and the third switch element is in an on state, and the second mode are sequentially repeated. This may be a step of generating the first control signal and the second control signal.

Here, setting the mode according to the on/off operation of the first and second switch elements included in the first two-way switch and the third and fourth switch elements included in the second two-way switch. Further comprising: generating the first and second control signals, when the sign of the output voltage is negative, a fourth mode in which the second switch element is in an on state and the fourth switch element is in an off state, A fifth mode in which the second switch element and the fourth switch element are in an off state, a sixth mode in which the second switch element is in an off state and the fourth switch element is in an on state, and the fifth mode are sequentially repeated. This may be a step of generating the first control signal and the second control signal.

Here, a computer program stored in a computer-readable recording medium may be provided to execute the non-isolated buck-boost inverter control method.

According to an embodiment of the present invention, an inverter control device and method that solves leakage current by reducing the number of switches operating at high frequencies can be provided.

According to an embodiment of the present invention, an inverter control device and method that can adjust the output voltage by boosting and lowering it can be provided.

1 is a diagram showing a transformerless single-stage grid-connected solar power inverter.
Figure 2 is a diagram showing an inverter circuit according to an embodiment of the present invention.
Figure 3 is a timing diagram showing an inverter switching method of an inverter control device according to an embodiment of the present invention.
Figure 4 is a diagram showing a simplified circuit of an inverter according to an embodiment of the present invention.
Figure 5 is a block diagram for inputting control signals to the inverter of the present invention.
Figure 6 is a diagram showing a circuit according to the mode of the inverter when the sign of the output voltage is positive.
Figure 7 is a diagram showing a circuit according to the mode of the inverter when the sign of the output voltage is negative.
Figure 8 is a graph showing simulation results in the boost operation of the inverter.
Figure 9 is a graph showing simulation results in the buck operation of the inverter.

The embodiments described in this specification are intended to clearly explain the idea of the present invention to those skilled in the art to which the present invention pertains, and the present invention is not limited to the embodiments described in this specification, and the present invention is not limited to the embodiments described in this specification. The scope should be construed to include modifications or variations that do not depart from the spirit of the present invention.

The terms used in this specification are general terms that are currently widely used as much as possible in consideration of their function in the present invention, but this may vary depending on the intention of those skilled in the art, precedents, or the emergence of new technology in the technical field to which the present invention belongs. You can. However, if a specific term is defined and used with an arbitrary meaning, the meaning of the term will be described separately. Therefore, the terms used in this specification should be interpreted based on the actual meaning of the term and the overall content of this specification, not just the name of the term.

The drawings attached to this specification are intended to easily explain the present invention, and the shapes shown in the drawings may be exaggerated as necessary to aid understanding of the present invention, so the present invention is not limited by the drawings.

In this specification, if it is determined that a detailed description of a known configuration or function related to the present invention may obscure the gist of the present invention, the detailed description thereof will be omitted as necessary.

1 is a diagram showing a transformerless single-stage grid-connected solar power inverter.

Referring to Figure 1, a grid-connected inverter that converts DC input to AC output can be connected to solar panels and the grid. Grid-connected inverters can generally be applied to direct transmission, distribution and consumption.

Inverters can be classified into isolated inverters and non-isolated inverters. Isolated inverters are advantageous in terms of reducing leakage current, but they have the problem of requiring a low-frequency or high-frequency transformer.

Low-frequency transformers are very bulky, which reduces the power density of the inverter, while high-frequency transformers are relatively compact and low-cost, but have lower efficiency due to the various converter stages. Therefore, a non-isolated inverter that does not require a transformer may be advantageous for solar power generation facilities.

However, non-isolated inverters without a transformer have problems related to leakage current. As shown in Figure 1, leakage current (I_leakage) circulates between the solar array and the grid through the parasitic capacitor (Cp). Due to the leakage current, system reliability and efficiency may be reduced, and problems related to electromagnetic interference (EMI) and electrical safety may occur.

Regarding the above problem, various topologies have been conventionally proposed to deal with leakage current. However, the corresponding topologies only perform a step-down operation on the output voltage of the inverter, and it is difficult to perform both step-up and step-down operations.

Therefore, the present invention is a non-isolated buck-boost inverter that can solve the leakage current problem of a non-insulated inverter and has a buck-boost power conversion function that flexibly boosts and lowers the output voltage of the inverter depending on the environment of the solar power generation panel. (hereinafter referred to as inverter) is proposed.

Figure 2 is a diagram showing an inverter circuit according to an embodiment of the present invention.

Referring to FIG. 2, an inverter circuit according to an embodiment of the present invention may include a plurality of switches. The inverter circuit may include four switches (S1, S2, S3, and S4) operating at line frequency and two bidirectional switches (Sa and Sb) operating at high frequency. At this time, the line frequency may be the frequency of the system linked to the inverter.

Since the inverter of the present invention has a relatively small number of switches operating at high frequencies (two), power loss can be greatly reduced compared to the conventional inverter topology. That is, since the number of switches operating at high frequencies is smaller than in the conventional topology in which all switches operate at high frequencies, electromagnetic interference (EMI) due to interaction between switches is reduced, thereby reducing power loss.

In the inverter circuit, the first switch (S1) and the second switch (S2) are connected in series with each other. Additionally, the third switch (S3) and the fourth switch (S4) are connected to each other in series. The first switch (S1), the second switch (S2), the third switch (S3), and the fourth switch (S4) are connected to each other in parallel.

In the inverter circuit, a first two-way switch Sa and a second two-way switch are provided at the node between the first switch S1 and the second switch S2 and the node between the third switch S3 and the fourth switch S4. A circuit stage including (Sb) may be connected. Accordingly, the topology of the present invention may be a type of full bridge topology or H-bridge topology.

The first to fourth switches S1 to S4 may each include one switch element and one diode connected in anti-parallel with the switch element.

Although the two-way switches Sa and Sb are simply shown in FIG. 1, the first two-way switch Sa and the second two-way switch Sb may include two switch elements and two diodes, respectively. The diodes included in the two-way switches (Sa, Sb) may each be connected in anti-parallel with the switch element.

At this time, the direction of the first diode connected to the first switch element included in the first two-way switch (Sa) may be opposite to the direction of the second diode connected to the second switch element included in the first two-way switch (Sa). . The direction of the diode included in the second two-way switch is also the same.

Detailed circuits for the two-way switches Sa and Sb can be seen in FIGS. 4, 6, and 7 below.

The inverter circuit may include two inductors (L0, L1), a decoupling capacitor (C1), and an output filter capacitor (C0). At this time, the two inductors L0 and L1 have the same voltage at both ends, so they can be magnetically coupled.

In addition, the inverter of the present invention includes an output inductor (L0), and can continuously maintain the output voltage and current even without the output filter capacitor (C0). The voltage (V0) of the output filter capacitor (C0) is the output voltage of the inverter, and the AC output voltage of the inverter may be the voltage of the grid or AC load.

Therefore, the inductor of the present invention can continuously output current, and current in the circuit can flow in both directions. In addition, the existing inverter dissipates reactive power, but the inverter of the present invention can also flow reactive power due to its structure.

Figure 3 is a timing diagram showing an inverter switching method of an inverter control device according to an embodiment of the present invention. Processing of the inverter control device may be performed by an internal control unit (processor). At this time, the control unit may be the micro control unit (MCU) of the inverter. Specifically, the control unit may be a logic circuit that applies a control signal to the inverter.

Referring to FIG. 3, the inverter control device of the present invention can control a plurality of switches of the inverter circuit according to the sign of the output voltage.

The inverter control method of the control unit included in the inverter control device is as follows. The inverter control method includes determining the sign of the output voltage, controlling on/off of the first switch (S1) to the fourth switch (S4) according to the sign of the output voltage, and controlling the on/off of the first switch (S1) to the fourth switch (S4) according to the sign of the output voltage. It may include generating a control signal to control the switch (Sa) and the second two-way switch (Sb).

First, the control unit can determine the sign of the output voltage. Regarding timing, the control unit can be divided into cases where the sign of the output voltage is positive (positive half-cycle) and cases where the sign of the output voltage is negative (negative half-cycle).

In a positive half-cycle where the sign of the output voltage is positive, the controller may control the first switch S1 and the fourth switch S4 to be operated in the on state. Also, at this time, the controller may control the second switch S2 and the third switch S3 to operate in an off state.

Also, in the positive half cycle, the control unit operates the first switch element (S5a) and the second switch element (S5b) included in the first two-way switch (Sa) and the third switch element (S6a) included in the second two-way switch (Sb). ) and the fourth switch element (S6b) can be controlled.

Specifically, the control unit may control the first switch element S5a to operate by a first control signal and control the second switch element S5b to operate in an on state. Additionally, the controller may control the third switch element S6a to operate in accordance with the second control signal and control the fourth switch element S6b to operate in the on state.

That is, in the positive half cycle, the control unit controls the first switch (S1), the fourth switch (S4), the second switch element (S5b), and the fourth switch element (S6b) to operate in the on state, and the second switch ( S2) and the third switch (S3) can be controlled to operate in an off state. Additionally, the controller may control the first switch element S5a and the third switch element S6a to operate by their respective control signals.

At this time, the control unit may distinguish modes according to the on/off states of the first switch element (S5a) and the third switch element (S6a).

For example, the controller may set the first mode to the first mode when the first switch element (S5a) is in an on state and the third switch element (S6a) is in an off state. Specifically, the control unit switches to the first mode within a certain period from the moment the first switch element S5a is switched from the off state to the on state until the moment the first switch element S5a is switched back to the off state. You can set it.

Additionally, the controller may set the second mode when both the first switch element S5a and the third switch element S6a are in an off state. Specifically, the control unit controls the control unit from the moment when the first switch element (S5a) is switched from the on state to the off state to the moment when the third switch element (S6a) is switched from the off state to the on state within a certain period. Can be set to 2 modes.

Additionally, the control unit may set the third mode to the case where the first switch element (S5a) is in an off state and the third switch element (S6a) is in an on state. Specifically, the control unit switches to the third mode within a certain period from the moment the third switch element S6a is switched from the off state to the on state until the moment the third switch element S6a is switched back to the off state. You can set it.

Additionally, the control unit may set the fourth mode when both the first switch element S5a and the third switch element S6a are in an off state. Specifically, the control unit controls the control unit from the moment the third switch element (S6a) is switched from the on state to the off state to the moment the first switch element (S5a) is switched from the off state to the on state within a certain period. Can be set to 4 modes. At this time, the fourth mode may be substantially the same as the second mode.

The control unit may control the inverter so that the pattern of the first mode - the second mode - the third mode - the fourth mode (second mode) is repeated. That is, the controller may generate control signals for the first switch element S5a and the third switch element S6a so that the patterns of the first mode, second mode, third mode, and second mode are repeated.

For a specific example, in order for the above pattern to be repeated, the length of the section in which the first switch element (S5a) is turned off may be longer than the length of the section in which the third switch element (S6a) is turned on.

Also, for example, in order for the above pattern to be repeated, the length of the section in which the first switch element (S5a) is turned on may have to be shorter than the length of the section in which the third switch element (S6a) is turned off.

That is, the control unit controls the first control signal for the first switch element (S5a) and the second switch element (S6a) so that the length of the section in which one switch element is turned on is shorter than the length of the section in which the other switch element is turned off. ) can generate a second control signal for.

The first mode, second mode, third mode, and fourth mode may be repeated in the positive half cycle by the control unit until the output voltage is 0.

In the positive half cycle, the control unit can generate a control signal according to the following equation. Equations 1 and 2 below represent the duty ratio related to the duty cycle of the control signal.

[Equation 1]

[Equation 2]

, f : 라인주파수, 변조 지수

)(

, f: line frequency, modulation index

)

Specifically, the control unit may generate a first control signal to control the first switch element (S5a) based on Equation 1, and generate a second control signal to control the third switch element (S6a) based on Equation 2. can be created. At this time, the modulation index can be set differently depending on the desired V0.

The control signal generation of the control unit is shown in detail in FIG. 5.

In the negative half-cycle where the sign of the output voltage is negative, the control unit may control the second switch S2 and the third switch S3 to be operated in the on state. Also, at this time, the first switch (S1) and the fourth switch (S4) can be controlled to operate in an off state.

In addition, in the negative half cycle, the control unit operates the first switch element (S5a) and the second switch element (S5b) included in the first two-way switch (Sa) and the third switch element (S6a) included in the second two-way switch (Sb). ) and the fourth switch element (S6b) can be controlled.

Specifically, the control unit may control the first switch element S5a to operate in the on state and control the second switch element S5b to operate by a third control signal. Additionally, the control unit may control the third switch element S6a to operate in the on state and control the fourth switch element S6b to operate by the fourth control signal.

That is, in the negative half cycle, the control unit controls the second switch (S2), the third switch (S3), the first switch element (S5a), and the third switch element (S6a) to operate in the on state, and the first switch ( S1) and the fourth switch S4 can be controlled to operate in an off state. Additionally, the controller may control the second switch element S5b and the fourth switch element S6b to operate by their respective control signals.

At this time, the control unit may distinguish modes according to the on/off states of the second switch element (S5b) and the fourth switch element (S6b).

For example, the controller may set the fifth mode when the second switch element (S5b) is in an on state and the fourth switch element (S6b) is in an off state. Specifically, the control unit switches to the fifth mode within a certain period from the moment the second switch element S5b is switched from the off state to the on state until the moment the second switch element S5b is switched back to the off state. You can set it.

Additionally, the controller may set the sixth mode when both the second switch element S5b and the fourth switch element S6b are in an off state. Specifically, the control unit controls the control unit from the moment the second switch element (S5b) is switched from the on state to the off state to the moment the fourth switch element (S6b) is switched from the off state to the on state within a certain period. Can be set to 6 modes.

Additionally, the controller may set the seventh mode when the second switch element S5b is in an off state and the fourth switch element S6b is in an on state. Specifically, the control unit switches to the seventh mode within a certain period from the moment the fourth switch element S6b is switched from the off state to the on state until the moment the fourth switch element S6b is switched back to the off state. You can set it.

Additionally, the control unit may set the case where both the second switch element S5b and the fourth switch element S6b are in the off state to the eighth mode. Specifically, the control unit controls the control unit from the moment the fourth switch element (S6b) is switched from the on state to the off state to the moment the second switch element (S5b) is switched from the off state to the on state within a certain period. Can be set to 8 modes. At this time, the eighth mode may be substantially the same mode as the sixth mode.

The control unit may control the inverter so that the pattern of the 5th mode - 6th mode - 7th mode - 8th mode (6th mode) is repeated. That is, the control unit may generate control signals for the second switch element S5b and the fourth switch element S6b so that the patterns of the fifth mode, sixth mode, seventh mode, and sixth mode are repeated.

For a specific example, in order for the above pattern to be repeated, the length of the section in which the second switch element (S5b) is turned off may be longer than the length of the section in which the fourth switch element (S6b) is turned on.

Also, for example, in order for the above pattern to be repeated, the length of the section in which the second switch element (S5b) is turned on may have to be shorter than the length of the section in which the fourth switch element (S6b) is turned off.

That is, the control unit controls the third control signal for the second switch element (S5b) and the fourth switch element (S6b) so that the length of the section in which one switch element is turned on is shorter than the length of the section in which the other switch element is turned off. ) can generate a fourth control signal for.

The fifth mode, sixth mode, seventh mode, and eighth mode may be repeated in the negative half cycle by the control unit until the output voltage is 0.

In the negative half-cycle, the control unit can generate a control signal according to the following equation. Equations 3 and 4 below represent the duty ratio related to the duty cycle of the control signal.

[Equation 3]

[Equation 4]

, f : 라인주파수, 변조 지수

)(

, f: line frequency, modulation index

)

Specifically, the control unit may generate a third control signal for controlling the second switch element (S5b) based on Equation 3, and a fourth control signal for controlling the fourth switch element (S6b) based on Equation 4. can be created. At this time, the modulation index can be set differently depending on the desired V0.

The control signal generation of the control unit is shown in detail in FIG. 5.

Figure 4 is a diagram showing a simplified circuit of an inverter according to an embodiment of the present invention.

Figure 4(a) shows the circuit in the positive half-cycle where the sign of the output voltage is positive, and Figure 4(b) shows the circuit in the negative half-cycle where the sign of the output voltage is negative.

Referring to FIG. 4(a), the circuit diagram can be simplified if one considers a switch that is always in an on or off state in the positive half cycle. Specifically, the switches that always maintain the same state in the positive half cycle are the first switch (S1) to the fourth switch (S4), the second switch element (S5b), and the fourth switch element (S6b). Therefore, if the above switches are simplified, the circuit in the positive half cycle can be shown as shown in FIG. 4(a) centering on the first switch element (S5a) and the third switch element (S6a).

Likewise, referring to FIG. 4(b), the circuit diagram can be simplified if one considers a switch that is always in an on or off state in the negative half cycle. Specifically, the switches that always maintain the same state in the negative half cycle are the first switch (S1) to the fourth switch (S4), the first switch element (S5a), and the third switch element (S6a). Therefore, if the above switches are simplified, the circuit in the negative half cycle can be represented as shown in 4(b) centered on the second switch element (S5b) and the fourth switch element (S6b).

Figure 5 is a block diagram for inputting control signals to the inverter of the present invention.

Referring to FIG. 5, the control signal generation step of the control unit can be understood through a block diagram. The control signal can be generated using the duty ratio obtained by Equations 1 to 4 above.

For example, when generating the control signal of the third switch element S6a, the reference signal Msin(wt) is multiplied by a line frequency square wave (V_rec) with a duty ratio of 0.5, an amplitude of 1, and a line frequency f. And the generated half-wave sinusoidal signal is added to the constant 1. Afterwards, the inverted DC bias half-wave sinusoidal signal and the inverted V_rec pass through an OR gate to generate a control signal.

Likewise, when generating the control signal of the fourth switch element S6b, the inverted reference signal is multiplied by the square wave signal with inverted V_rec. The resulting half-sine wave signal is added to the constant 1. Then, the inverted DC bias half-sine wave signal and the carrier signal pass through a comparator to generate a control signal.

At this time, the control signal of the second switch element (S5b) may be generated by passing the inverted control signal of the fourth switch element (S6b) and V_rec through an OR gate. Additionally, the control signal of the first switch element S5a may be generated by passing the inverted control signal of the third switch element S6a and the inverted V_rec through an OR gate.

Figure 6 is a diagram showing a circuit according to the mode of the inverter when the sign of the output voltage is positive. That is, Figure 6 is a diagram showing the circuit in the positive half cycle.

Figure 6(a) is a circuit diagram showing current flow in the first mode, Figure 6(b) is a circuit diagram showing current flow in the second mode or fourth mode, and Figure 6(c) is a circuit diagram showing current flow in the third mode. This is a circuit diagram showing the current flow.

Referring to FIG. 6(a), in the first mode, according to the timing diagram of FIG. 3, the current passes through the first switch S1 and the first bidirectional switch Sa at V_in. At this time, since both the first switch element (S5a) and the second switch element (S5b) included in the first two-way switch operate in the on state, current may pass through the first two-way switch (Sa).

Subsequently, the current may pass through the inductor (L1) and the fourth switch (S4). Additionally, the current may pass through the capacitor C1 and the inductor L0 and then through the capacitor C0 and the resistor.

At this time, the inductor current i_L1 increases linearly with the slope of V_in/L1, and the inductor current i_L0 increases linearly with the slope of V_in/L0. Capacitor C1 is discharged.

Referring to FIG. 6(b), in the second or fourth mode, according to the timing diagram of FIG. 3, current can only flow in the closed circuit shown in FIG. 6(b). In the second or fourth mode, both the first switch element (S5a) and the third switch element (S6a) are in an off state, so current flows only in the closed circuit.

At this time, since the third switch element (S6a) of the second two-way switch (Sb) is in the off state and the fourth switch element (S6b) is in the on state, the current passes through the fourth switch element (S6b) and then to the third switch. It does not pass through the element S6a and flows to the diode connected to the third switch element S6a.

At this time, the inductor current i_L1 decreases linearly with a slope of -V0/L1, and the inductor current i_L0 decreases linearly with a slope of -V0/L0. Capacitor C1 is charged.

Referring to FIG. 6(c), in the third mode, according to the timing diagram of FIG. 3, current can only flow in the closed circuit shown in FIG. 6(c). Unlike FIG. 6(b), in the third mode, since the third switch element (S6a) is on, the current may pass through the fourth switch element (S6b) and then through the third switch element (S6a).

At this time, the inductor current i_L1 decreases linearly with a slope of -V0/L1, and the inductor current i_L0 decreases linearly with a slope of -V0/L0. Capacitor C1 is charged.

Figure 7 is a diagram showing a circuit according to the mode of the inverter when the sign of the output voltage is negative. That is, Figure 7 is a diagram showing the circuit in the negative half cycle.

Figure 7(a) is a circuit diagram showing current flow in the fifth mode, Figure 7(b) is a circuit diagram showing current flow in the sixth mode and eighth mode, and Figure 7(c) is a circuit diagram showing current flow in the seventh mode. This is a circuit diagram showing the current flow.

Referring to FIG. 7(a), in the fifth mode, the current passes through the third switch S3 at V_in according to the timing diagram of FIG. 3. The current may then pass through capacitor C0 and resistor to capacitor C1 and inductor L0. Additionally, current may pass through inductor (L1).

Subsequently, the current may pass through the first two-way switch (Sa) and through the second switch (S2). At this time, since both the first switch element (S5a) and the second switch element (S5b) included in the first two-way switch (Sa) operate in the on state, current can pass through the first two-way switch (Sa).

However, since the third switch element (S6a) included in the second two-way switch (Sb) is in the off state and the diode direction of the fourth switch element (S6b) is reverse, the current does not pass through the second two-way switch (Sb). .

At this time, the inductor current i_L1 increases linearly with a slope of -V_in/L1, and the inductor current i_L0 increases linearly with a slope of -V_in/L0. Capacitor C1 is discharged.

Referring to FIG. 7(b), in the sixth mode or the eighth mode, according to the timing diagram of FIG. 3, current can only flow in the closed circuit shown in FIG. 7(b). In the sixth or eighth mode, both the second switch element (S5b) and the fourth switch element (S6b) are in an off state, so current flows only in the closed circuit.

At this time, since the third switch element (S6a) of the second two-way switch (Sb) is in the on state and the fourth switch element (S6b) is in the off state, the current passes through the third switch element (S6a) and then to the fourth switch. It does not pass through the element S6b and flows to the diode connected to the fourth switch element S6b.

At this time, the inductor current i_L1 decreases linearly with the slope of V0/L1, and the inductor current i_L0 decreases linearly with the slope of V0/L0. Capacitor C1 is charged.

Referring to FIG. 7(c), in the seventh mode, according to the timing diagram of FIG. 3, current can only flow in the closed circuit shown in FIG. 7(c). Unlike FIG. 7(b), in the seventh mode, since the fourth switch element (S6b) is in the on state, the current can pass through the third switch element (S6a) and then through the fourth switch element (S6b).

Figure 8 is a graph showing simulation results in the boost operation of the inverter. Referring to FIG. 8, the results of the boost operation of the inverter that boosts the voltage can be seen.

Figure 8(a) is a graph showing the input voltage, output voltage, and output current of the inverter, Figure 8(b) is a graph showing the input voltage, output voltage, and inductor current of the inverter, and Figure 8(c) is a graph showing the drain- This is a graph of source voltage. Referring to FIG. 8, it can be seen that the output voltage is boosted by the proposed circuit of the present invention, and the output voltage (V0) becomes higher than the input voltage (Vin).

Figure 9 is a graph showing simulation results in the buck operation of the inverter. Referring to FIG. 9, the results of the buck operation of the inverter that steps down the voltage can be seen.

Figure 9(a) is a graph showing the input voltage, output voltage, and output current of the inverter, Figure 9(b) is a graph showing the input voltage, output voltage, and inductor current of the inverter, and Figure 9(c) is a graph showing the drain- This is a graph of source voltage. Referring to FIG. 9, it can be seen that the output voltage is stepped down by the proposed circuit of the present invention, and the output voltage (V0) becomes lower than the input voltage (Vin).

The non-isolated buck-boost inverter of the present invention can solve the problem of leakage current and has a relatively simple circuit topology, making it possible to implement a low-cost, high-efficiency and high-power inverter. Therefore, the non-isolated buck-boost inverter of the present invention may be more suitable for solar power generation applications than conventional inverters. However, it is not limited to this and can be applied to other applications that require solving the problem of leakage current and need to step up and step down the output voltage.

The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc., singly or in combination. Program instructions recorded on the medium may be specially designed and configured for the embodiment or may be known and available to those skilled in the art of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic media such as floptical disks. -Includes optical media (magneto-optical media) and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. Examples of program instructions include machine language code, such as that produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

As described above, although the embodiments have been described with limited examples and drawings, various modifications and variations can be made by those skilled in the art from the above description. For example, the described techniques are performed in a different order than the described method, and/or components of the described system, structure, device, circuit, etc. are combined or combined in a different form than the described method, or other components are used. Alternatively, appropriate results may be achieved even if substituted or substituted by an equivalent.

Therefore, other implementations, other embodiments, and equivalents of the claims also fall within the scope of the claims described below.

Claims (14)

In the non-isolated buck-boost inverter control device,
Determining the sign of the output voltage of the non-isolated buck-boost inverter, and controlling the on/off of a plurality of switches included in the non-isolated buck-boost inverter according to the output voltage as the duty of the signal It includes a control unit that controls based on a duty ratio related to the cycle,
The non-isolated buck-boost inverter,
a first switch and a second switch connected in series with each other;
a third switch and a fourth switch connected in parallel with the first switch and the second switch and connected in series with each other;
It includes a first two-way switch connected to a node between the first switch and the second switch, and a second two-way switch connected to a node between the third switch and the fourth switch,
The first two-way switch includes a first switch element and a second switch element connected in series with the first switch element,
The second two-way switch includes a third switch element and a fourth switch element connected in series with the third switch element,
The first two-way switch and the second two-way switch operate at a higher frequency than the first to fourth switches,
When the sign of the output voltage is positive, the controller
Operate the first switch, the fourth switch, the second switch element, and the fourth switch element in an on state, and operate the second switch and the third switch in an off state,
Controlling the first switch element based on a first control signal generated according to the input voltage and output voltage of the non-isolated buck-boost inverter, and based on a second control signal generated according to the input voltage and the output voltage to control the third switch element
Non-isolated buck-boost inverter control unit.
delete delete According to paragraph 1,
The control unit generates the first control signal and the second control signal based on a first duty ratio and a second duty ratio, respectively,
The first duty ratio and the second duty ratio are determined by a modulation index and a line frequency, which is the ratio of the input voltage and the output voltage of the non-isolated buck-boost inverter,
The sum of the first duty ratio and the second duty ratio is 1.
Non-isolated buck-boost inverter control unit.
According to paragraph 1,
When the sign of the output voltage is positive, the controller
Setting the case where the first switch element is in an on state and the third switch element is in an off state as the first mode,
Setting the case where the first switch element and the third switch element are in an off state to a second mode,
Setting the case where the first switch element is in an off state and the third switch element is in an on state as the third mode,
Generating the first control signal and the second control signal so that the first mode, the second mode, the third mode, and the second mode are sequentially repeated.
Non-isolated buck-boost inverter control unit.
In the non-isolated buck-boost inverter control device,
Determining the sign of the output voltage of the non-isolated buck-boost inverter, and controlling the on/off of a plurality of switches included in the non-isolated buck-boost inverter according to the output voltage as the duty of the signal It includes a control unit that controls based on a duty ratio related to the cycle,
The non-isolated buck-boost inverter,
a first switch and a second switch connected in series with each other;
a third switch and a fourth switch connected in parallel with the first switch and the second switch and connected in series with each other;
It includes a first two-way switch connected to a node between the first switch and the second switch, and a second two-way switch connected to a node between the third switch and the fourth switch,
The first two-way switch includes a first switch element and a second switch element connected in series with the first switch element,
The second two-way switch includes a third switch element and a fourth switch element connected in series with the third switch element,
The first two-way switch and the second two-way switch operate at a higher frequency than the first to fourth switches,
When the sign of the output voltage is negative, the controller
Operate the second switch, the third switch, the first switch element, and the third switch element in an on state, and operate the first switch and the fourth switch in an off state,
Controlling the second switch element based on a third control signal generated according to the input voltage and output voltage of the non-isolated buck-boost inverter, and based on a fourth control signal generated according to the input voltage and the output voltage to control the fourth switch element
Non-isolated buck-boost inverter control unit.
According to clause 6,
The control unit generates the third control signal and the fourth control signal based on a third duty ratio and a fourth duty ratio, respectively,
The third duty ratio and the fourth duty ratio are determined by a modulation index and line frequency, which is the ratio of the input voltage and the output voltage of the non-isolated buck-boost inverter,
The sum of the third duty ratio and the fourth duty ratio is 1.
Non-isolated buck-boost inverter control unit.
According to clause 6,
When the sign of the output voltage is negative, the controller
Setting the case where the second switch element is in an on state and the fourth switch element is in an off state as the fourth mode,
Setting the case where the second switch element and the fourth switch element are in an off state to a fifth mode,
Setting the case where the second switch element is in the off state and the fourth switch element is in the on state as the sixth mode,
Generating the third control signal and the fourth control signal so that the fourth mode, the fifth mode, the sixth mode, and the fifth mode are sequentially repeated.
Non-isolated buck-boost inverter control unit.
In the control method of a non-isolated buck-boost inverter for controlling the non-isolated buck-boost inverter by the non-isolated buck-boost inverter control device of claim 1,
determining the sign of the output voltage of the non-isolated buck-boost inverter;
controlling on/off of the first to fourth switches according to the sign of the output voltage;
Generating first and second control signals for controlling the first and second switch elements so that the first and second bidirectional switches operate at a higher frequency than the first to fourth switches according to the sign of the output voltage. containing the steps of
Non-isolated buck-boost inverter control method.
According to clause 9,
The step of controlling on/off of the first to fourth switches,
When the sign of the output voltage is positive, the first switch and the fourth switch connected in parallel with the first switch are operated in the on state, and the second switch and the fourth switch connected in series with the first switch are operated in an on state. Comprising the step of operating the third switch connected in series in an off state.
Non-isolated buck-boost inverter control method.
According to clause 9,
Generating the first and second control signals includes:
generating the first control signal and the second control signal based on a first duty ratio and a second duty ratio, respectively, associated with a duty cycle of the control signal;
The first duty ratio and the second duty ratio are determined by a modulation index and line frequency, which is the ratio of the input voltage and output voltage of the non-isolated buck-boost inverter,
The sum of the first duty ratio and the second duty ratio is 1.
Non-isolated buck-boost inverter control method.
According to clause 9,
It further includes setting a mode according to the on/off operation of the first and second switch elements included in the first two-way switch and the third and fourth switch elements included in the second two-way switch. do,
Generating the first and second control signals includes, when the sign of the output voltage is positive,
A first mode in which the first switch element is in an on state and the third switch element is in an off state, a second mode in which the first switch element and the third switch element are in an off state, and the first switch element is in an off state, A step of generating the first control signal and the second control signal so that the third mode in which the third switch element is in the on state and the second mode are sequentially repeated.
Non-isolated buck-boost inverter control method.
According to clause 9,
It further includes setting a mode according to the on/off operation of the first and second switch elements included in the first two-way switch and the third and fourth switch elements included in the second two-way switch. do,
Generating the first and second control signals includes, when the sign of the output voltage is negative,
a fourth mode in which the second switch element is in an on state and the fourth switch element is in an off state, a fifth mode in which the second switch element and the fourth switch element are in an off state, and the second switch element is in an off state, A step of generating the first control signal and the second control signal so that the sixth mode in which the fourth switch element is in the on state and the fifth mode are sequentially repeated.
Non-isolated buck-boost inverter control method.
A computer program stored in a computer-readable recording medium to execute the non-isolated buck-boost inverter control method according to any one of claims 9 to 13.