JP2017112816A - Inverter circuit having self-boosting function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct a circuit capable of rising a DC pressure of an inverter only by changing a DC input point without increasing the number of switching elements in the inverter that converts a DC into an AC.SOLUTION: In the conventional inverter INV, there is two stage of a BC and INV, a circuit combined with a control circuit becomes complication and is increased in cost. Although an input DC voltage is normally applied to between lines of an A point 51 and a C point 53, the voltage is changed to a line between a B point 52 and the C point 53. A signal for driving an AC load of Lo19 and Ro20 is inputted to a switch S14, and the signal is also used as the signal for the BC. In a triangular wave to sine wave comparison system of the most general as an INV signal, a mean conductive rate (On rate of one period) is equal to 0.5. Therefore, on the basis of a theory of the BC relating to pressure rising, a line DC voltage of the INV is increased about two times, and the INV of which the voltage is increased can be realized without the BC to be conventionally desired to be provided.SELECTED DRAWING: Figure 1

Description

The inverter (INV) has many uses for boosting a DC voltage. In that case, a boost converter (BC) is used in the first stage. This includes power sources for driving AC motors such as photovoltaic power generation and electric vehicles that perform grid interconnection. A normal circuit is boosted and used as a two-stage configuration of BC and INV. In FIG. 1, the input DC voltage of INV is generally applied between the line between the point A 51 and the point C 53, but in the invention, it is connected between the line between the point B 52 and the point C 53. The switch S ₂ 14 is supplied with a signal for driving the AC load of Lo 19 and Ro 20, and for example, in the most general triangular wave-sine wave comparison method in control, an average energization rate (ON ratio of one cycle) Therefore, according to the theory of BC, the voltage of INV between lines is boosted by about twice, and an additional BC is unnecessary. For this reason, it is possible to obtain AC power of a target boosted voltage with one INV.

Conventional problems

  The reason for boosting the DC voltage in INV is that in solar power generation, boosting voltage beyond boosted system voltage waveform is required in addition to boosting power transmission efficiency by boosting. In addition, the use of a high voltage motor allows a significant improvement in efficiency. This necessitates the installation of a boosting BC, resulting in a two-stage configuration combined with INV. Along with this, the control circuit must be doubled, and it is necessary not only to increase the number of elements constituting the circuit, but also to provide a detector for the other party's output for mutual control, and it is inevitable that the circuit is complicated and expensive. .

Industrial application fields

  In order to operate a conventional system efficiently in a driving power source of a photovoltaic power generation system or an electric vehicle, it is composed of two circuits that boost a first-stage DC voltage such as a solar battery or a battery and transmit it to the second-stage INV. Has been. In solar power generation systems such as grid interconnections, higher peak system voltages are required, and electric vehicles are used to increase the voltage so that they can be used efficiently with respect to motor miniaturization. It was a two-stage configuration. The invention is designed to have a boosting function with a single INV circuit, and while these technological fields requiring recent energy saving and high efficiency have attracted a great deal of public attention, they can provide advanced innovations. This technology can be expected to be widely used in the industrial field.

Response to conventional technology

  Conventionally, solar power generation and electric vehicles have been required to boost the DC voltage in order to use the inverter (INV) effectively. Since the boost converter (BC) and INV are intended to be used in different applications, there is no concept of combining BC and INV. “The DC voltage is boosted by BC and then AC is obtained by INV.” There was no development from the idea. Initially, boosting with a transformer was also proposed. In addition, a method of boosting voltage by connecting cascaded solar cells or storage batteries was used, but it has not been widely adopted because of troubles caused by routing of high-voltage lines and the necessity of voltage adjustment. Various methods have been sought in this way, but recently, boosting with BC has become common. This means that the circuit is composed of two stages of BC and INV, and the control circuit and the combined control of both have brought complexity and cost.

Problems to be solved by the invention

  If BC is not used in the conventional system with a two-stage configuration of BC and INV, a low input DC voltage is used directly as an INV DC voltage, so the low input DC voltage is insufficient for the system voltage and motor voltage. This will cause severe distortion in the output and a significant reduction in efficiency. For this reason, it is inevitable to boost the voltage using BC in the first stage. Therefore, the circuit has a two-stage configuration of BC and INV, and the circuit together with the control circuit is complicated and expensive. By realizing this boosting function only with INV, an extra BC, its control circuit, and a function for controlling BC and INV in cooperation with each other become unnecessary, and the configuration and control thereof become extremely simple.

Means for solving the problem

A method for solving the above problem will be described with reference to the detailed drawing of the basic principle configuration diagram of INV in FIG. In the conventional INV, the input DC voltage is applied between the line between the point A 51 and the point C 53, but in the invention, it is changed between the line between the point B 52 and the point C 53. The conventional method has a two-stage configuration, and the boosting of INV is performed by the BC provided in the first stage. In the present invention, this BC is omitted. Therefore, there is no switch for BC, and this is also used by the switch S ₂ 14 for INV. Conventionally, in BC, monotonous switching is generally performed, and pulse width modulation switching is performed in order to obtain a target output frequency at the next stage INV. In this way, the switch S ₂ 14 receives a signal for driving the AC load of Lo 19 and Ro 20, and this is utilized in the BC of the invention. In the most common triangular wave-sine wave comparison method, the average current-carrying ratio (on ratio of one cycle) is 0.5. Therefore, the line voltage of INV is boosted by about twice from the theory of BC, and the function of BC is increased. Can also be used as S ₂ 14.

FIG. 2 shows a practical embodiment for carrying out the invention. It is the circuit configuration of the invention developed into a single-phase full-bridge type. In the conventional INV, the input DC voltage is applied between the line between the D point 61 and the F point 63, but in the invention, it is changed between the line between the G point 62 and the F point 63. In the invention, BC is omitted, so the BC switch and circuit are eliminated, and the INV switch S ₂ 24 is also used. The switch S ₂ 24 receives a signal for driving the AC load of Lo 31 and Ro 32 together with S ₃ 25, and in the most general triangular wave-sine wave comparison method, the average energization rate (one cycle ON-state) Since the ratio) is 0.5, the direct current line voltage of INV is boosted by about twice from the theory of BC, and the function of BC can be shared by this S ₂ 24. In the case of this full bridge, the input power source input terminal is connected to the left end side A point 33, but the input power source E21 can also be connected to the right end side A point 34 via the inductor L ₂ 35, and the switch S ₄ 26 Together with this, a boost converter (BC) of this part is constituted. Also in this case, the signal waveform given to the conventional S ₄ 26 can be used as it is as a BC signal without any change. Furthermore, by distributing the input terminals to the two points G point 62 and H point 64, it is possible to share power and smooth the inflow current ripple.

It is a half bridge circuit which becomes the basic composition of the present invention. It is a practical single phase full bridge circuit diagram of the present invention.

[Figure 1]
11 DC power supply 12 Current limiting inductor 13 Inverter switch 14 Inverter switch 15 Freewheeling diode 16 Freewheeling diode 17 Power supply capacitor 18 Power supply capacitor 19 Load inductor 20 Load resistance 51 Inverter direct current positive voltage terminal 52 Inverter direct current neutral point voltage terminal 53 Inverter direct current Negative voltage terminal (Fig. 2)
21 DC power supply 22 Current limiting inductor 23 Inverter switch 24 Inverter switch 25 Inverter switch 26 Inverter switch 27 Freewheeling diode 28 Freewheeling diode 29 Freewheeling diode 30 Freewheeling diode 31 Load inductor 32 Load resistance 33 Left end inductor terminal 34 Right end inductor terminal 35 Current limiting inductor 41 Inverter DC negative voltage terminal 42 Power supply capacitor 61 Inverter DC positive voltage terminal 62 Inverter DC neutral point voltage terminal 63 Inverter DC negative voltage terminal 64 Inverter DC neutral point voltage terminal

Claims (4)

  In the half-bridge type inverter (INV) circuit, without using a boost converter (BC) in the previous stage, the input point for the DC of the DC power supply is connected to the INV cascade instead of being input to the terminal of the DC link voltage of the conventional INV. An inverter circuit configuration in which the DC link voltage can be boosted as in the case of using BC by connecting through an inductor to the midpoint of the branches constituting two switches.   In a single-phase full-bridge inverter (INV) circuit, without using a boost converter (BC) in the previous stage, instead of inputting the input point for the INV of the DC power supply to the terminal of the DC link voltage of the conventional INV, the INV is connected in cascade. An inverter circuit configuration in which the DC link voltage of INV can be boosted as in the case of using BC by connecting through inductors to the midpoints of the branches constituting two switches.   In a single-phase full-bridge inverter (INV) circuit, without using a boost converter (BC) in the previous stage, instead of inputting the input point for the INV of the DC power supply to the terminal of the DC link voltage of the conventional INV, the INV is connected in cascade. By connecting the inductor to the midpoint of the two switches and connecting the midpoint of the other switch through the inductor in the same manner, the DC link voltage of the INV is the same as when using BC. Inverter circuit configuration that can boost the voltage.   Two switches connected in cascade instead of inputting the input point for the INV of the DC power supply to the terminal of the DC link voltage of the conventional INV without using the boost converter (BC) in the previous stage in the three-phase inverter (INV) circuit An inverter circuit configuration in which the DC link voltage can be boosted as in the case of using BC by connecting through the respective inductors to the midpoint of the branch that constitutes and the midpoint of each of the other two sets of branches.

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