Inverter circuit and photovoltaic inverter

Abstract

The utility model relates to an inverter circuit and a photovoltaic inverter. According to the inverter circuit, a seventh transistor and a first diode are connected to a fifth transistor in parallel, and an eighth transistor and a second diode are connected to a sixth transistor in parallel. Through the transistors and the diode which are connected in parallel, when the first transistor or the second transistor is connected, the transistors connected in parallel are firstly connected, and the diode becomes a main current path due to relatively low forward voltage drop, so that the problem caused by reverse recovery of the body diode of the fifth transistor or the sixth transistor is avoided; when the first transistor or the second transistor is turned off, the transistors connected in parallel can be quickly turned off, and the diode can efficiently process the reverse recovery process, so that the technical problems that an existing inverter circuit consumes energy in the reverse recovery process and the switching loss is increased when the inverter circuit is turned on again are solved; the technical effect of reducing energy loss and switching loss is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of inverters, and in particular to an inverter circuit and a photovoltaic inverter. Background Art

[0002] Heric inverter circuits are widely used in renewable energy conversion systems such as photovoltaic and wind power. Figure 1 As shown, the existing Heric inverter circuit is composed of a first transistor Q1, a second transistor Q2, a third transistor Q3, a fourth transistor Q4, a fifth transistor Q5 and a sixth transistor Q6. When the Heric inverter circuit is inverting, Q1 and Q2 are used as main switching devices. When Q1 and Q2 are turned on, there will be a relatively large current. This current is Q6. Q5 works in synchronous rectification mode. After Q1 and Q2 are turned off, the current continues to flow through the body diodes of Q6 and Q5. When Q1 is turned on, the body diode of Q6 will be reversely cut off. Since the characteristics of the body diode of Q6 are relatively poor, a relatively large reverse recovery current will be generated when reversely cut off. This current will cause the turn-on loss of Q1 to increase. Similarly, when Q2 is turned on, the body diode of Q5 will be reversely cut off. Since the characteristics of the body diode of Q5 are relatively poor, a relatively large reverse recovery current will be generated when reversely cut off. This current will cause the turn-on loss of Q2 to increase.

[0003] To address the above-mentioned problems, no effective solution has been proposed yet. Utility Model Content

[0004] The embodiments of the present application provide an inverter circuit and a photovoltaic inverter to at least solve the technical problem that the existing inverter circuit consumes energy during the reverse recovery process and increases the switching loss when it is turned on again.

[0005] According to one aspect of an embodiment of the present application, an inverter circuit is provided, comprising: a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor, a first diode and a second diode; wherein: the collector of the first transistor is connected to the collector of the second transistor as a first input terminal of the inverter circuit, and the first input terminal of the inverter circuit is used to access the positive electrode of a DC power supply; the emitter of the third transistor is connected to the emitter of the fourth transistor as a second input terminal of the inverter circuit, and the second input terminal of the inverter circuit is used to access the negative electrode of a DC power supply; the emitter of the first transistor, the negative electrode of the first diode and the emitter of the fifth transistor are connected as a first output terminal of the inverter circuit, The first output end of the inverter circuit is used to access the positive electrode of the power grid; the collector of the fourth transistor, the emitter of the fifth transistor and the cathode of the second diode are connected to serve as the second output end of the inverter circuit, and the second output end of the inverter circuit is used to access the negative electrode of the power grid; the emitter of the first transistor is connected to the collector of the third transistor, and the emitter of the second transistor is connected to the collector of the fourth transistor; the collector of the fifth transistor is connected to the collector of the sixth transistor, and the collectors of the seventh transistor and the eighth transistor are respectively connected to the line between the fifth transistor and the sixth transistor, the anode of the first diode is connected to the emitter of the seventh transistor, and the anode of the second diode is connected to the emitter of the eighth transistor.

[0006] Optionally, both the first diode and the second diode are silicon carbide diodes.

[0007] According to another aspect of the embodiments of the present application, a photovoltaic inverter is provided, wherein the photovoltaic inverter includes the inverter circuit as described above.

[0008] Optionally, it also includes: a filter circuit, which is arranged on the line between the inverter circuit and the power grid; the filter circuit includes a first inductor, a second inductor and a capacitor; wherein: the first end of the first inductor serves as the first input end of the filter circuit, and the first input end of the filter circuit is connected to the first output end of the inverter circuit; the first end of the second inductor serves as the second input end of the filter circuit, and the second input end of the filter circuit is connected to the second output end of the inverter circuit; the second end of the first inductor is connected to the first end of the capacitor and serves as the first output end of the filter circuit, and the first output end of the filter circuit is connected to the positive pole of the power grid; the second end of the second inductor is connected to the second end of the capacitor and serves as the second output end of the filter circuit, and the second output end of the filter circuit is connected to the negative pole of the power grid.

[0009] In the embodiment of the present application, the inverter circuit connects the seventh transistor and the first diode in parallel to the fifth transistor, and connects the eighth transistor and the second diode in parallel to the sixth transistor. Through the parallel transistors and diodes, when the first transistor or the second transistor is turned on, the parallel transistor is turned on first, and the diode becomes the main current path due to its lower forward voltage drop, thereby avoiding the problem caused by the reverse recovery of the body diode of the fifth transistor or the sixth transistor; when the first transistor or the second transistor is turned off, the parallel transistor will also be turned off quickly, and the diode can efficiently handle the reverse recovery process, thereby solving the technical problem that the existing inverter circuit consumes energy during the reverse recovery process and increases the switching loss when it is turned on again, and achieving the technical effect of reducing energy loss and switching loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other embodiments can be obtained based on these drawings without creative work.

[0011] Figure 1 A schematic diagram of an inverter circuit provided by the prior art;

[0012] Figure 2 A schematic diagram of an inverter circuit provided in an embodiment of the present application;

[0013] Figure 3 A schematic diagram of a filter circuit provided in an embodiment of the present application;

[0014] Figure 4 A schematic diagram of drive waveforms corresponding to S1, S4, S5, S6 and S7 of the inverter provided in an embodiment of the present application under working condition 1;

[0015] Figure 5 A schematic diagram of driving waveforms corresponding to S2, S3, S5, S6 and S8 of the inverter provided in an embodiment of the present application under working condition 2.

[0016] The above drawings include the following reference numerals:

[0017] Q1, a first transistor; Q2, a second transistor; Q3, a third transistor; Q4, a fourth transistor; Q5, a fifth transistor; Q6, a sixth transistor; Q7, a seventh transistor; Q8, an eighth transistor; D1, a first diode; D2, a second diode; L1, a first inductor; L2, a second inductor; C1, a capacitor. DETAILED DESCRIPTION

[0018] The embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present application are shown in the accompanying drawings, it should be understood that the embodiments of the present application can be implemented in various forms and should not be interpreted as being limited to the embodiments described herein. Instead, these embodiments are provided to provide a more thorough and complete understanding of the embodiments of the present application. It should be understood that the drawings and embodiments of the present application are only for exemplary purposes and are not intended to limit the scope of protection of the present application.

[0019] According to one aspect of an embodiment of the present application, an inverter circuit is provided. Figure 2 A schematic diagram of an inverter circuit provided in an embodiment of the present application is shown as follows: Figure 2 As shown, the inverter circuit includes: a first transistor Q1, a second transistor Q2, a third transistor Q3, a fourth transistor Q4, a fifth transistor Q5, a sixth transistor Q6, a seventh transistor Q7, an eighth transistor Q8, a first diode D1 and a second diode D2; wherein:

[0020] The collector of the first transistor Q1 is connected to the collector of the second transistor Q2 and serves as a first input terminal of the inverter circuit. The first input terminal of the inverter circuit is used to access the positive electrode of the DC power supply.

[0021] The emitter of the third transistor Q3 is connected to the emitter of the fourth transistor Q4 and serves as the second input terminal of the inverter circuit. The second input terminal of the inverter circuit is used to access the negative electrode of the DC power supply.

[0022] The emitter of the first transistor Q1, the cathode of the first diode D1 and the emitter of the fifth transistor Q5 are connected to serve as the first output end of the inverter circuit, and the first output end of the inverter circuit is used to access the positive electrode of the power grid;

[0023] The collector of the fourth transistor Q4, the emitter of the fifth transistor Q5 and the cathode of the second diode D2 are connected to serve as the second output end of the inverter circuit, and the second output end of the inverter circuit is used to access the negative electrode of the power grid;

[0024] The emitter of the first transistor Q1 is connected to the collector of the third transistor Q3, the emitter of the second transistor Q2 is connected to the collector of the fourth transistor Q4; the collector of the fifth transistor Q5 is connected to the collector of the sixth transistor Q6, the collector of the seventh transistor Q7 and the collector of the eighth transistor Q8 are respectively connected to the line between the fifth transistor Q5 and the sixth transistor Q6, the anode of the first diode D1 is connected to the emitter of the seventh transistor Q7, and the anode of the second diode D2 is connected to the emitter of the eighth transistor Q8.

[0025] In the embodiment of the present application, the inverter circuit connects the seventh transistor Q7 and the first diode D1 in parallel to the fifth transistor Q5, and connects the eighth transistor Q8 and the second diode D2 in parallel to the sixth transistor Q6. Through the parallel transistor (Q7 or Q8) and the diode (D1 or D2), when the first transistor Q1 or the second transistor Q2 is turned on, the parallel transistor (Q7 or Q8) is turned on first, and the diode (D1 or D2) becomes the main current path due to its lower forward voltage drop, thereby avoiding the problem caused by the reverse recovery of the body diode of the fifth transistor Q5 or the sixth transistor Q6; when the first transistor Q1 or the second transistor Q2 is turned off, the parallel transistor (Q7 or Q8) will also be quickly turned off, and the diode (D1 or D2) can efficiently handle the reverse recovery process, thereby solving the technical problem that the existing inverter circuit consumes energy during the reverse recovery process and increases the switching loss when it is turned on again, and achieving the technical effect of reducing energy loss and switching loss.

[0026] It should be noted that the base corresponding to each transistor is represented by S. For example, the base of Q1 is S1, the base of Q2 is S2, the base of Q3 is S3, the base of Q4 is S4, the base of Q5 is S5, the base of Q6 is S6, the base of Q7 is S7, and the base of Q8 is S8.

[0027] As an optional embodiment, the first diode D1 and the second diode D2 are both silicon carbide diodes.

[0028] Silicon carbide diodes have extremely short reverse recovery time and low reverse recovery charge, which can significantly reduce switching losses. Silicon carbide diodes have lower voltage drop during forward conduction than traditional silicon diodes, which helps reduce conduction losses.

[0029] According to another aspect of an embodiment of the present application, a photovoltaic inverter is provided, and the photovoltaic inverter includes the inverter circuit as described above.

[0030] Figure 3 A schematic diagram of a filter circuit provided in an embodiment of the present application is shown in FIG. Figure 3 As shown, a filter circuit is added on the basis of the inverter circuit, that is, the filter circuit is arranged on the line between the inverter circuit and the power grid. The filter circuit includes a first inductor L1, a second inductor L2 and a capacitor C1; wherein:

[0031] The first end of the first inductor L1 serves as the first input end of the filter circuit, and the first input end of the filter circuit is connected to the first output end of the inverter circuit;

[0032] The first end of the second inductor L2 serves as the second input end of the filter circuit, and the second input end of the filter circuit is connected to the second output end of the inverter circuit;

[0033] The second end of the first inductor L1 is connected to the first end of the capacitor C1 to serve as the first output end of the filter circuit, and the first output end of the filter circuit is connected to the positive electrode of the power grid;

[0034] The second end of the second inductor L2 is connected to the second end of the capacitor C1 to serve as the second output end of the filter circuit. The second output end of the filter circuit is connected to the negative pole of the power grid.

[0035] When the current output by the inverter passes through L1 and L2, the inductor C1 will hinder the rapid change of the current, especially the change of high-frequency components, thereby filtering out harmonics. The capacitor C1 plays the role of blocking DC and allowing AC components to pass through, and at the same time forms an LC filtering network with L1 and L2 to further eliminate harmonics of specific frequencies, making the output current closer to a sine waveform and reducing the impact on the power grid.

[0036] Working condition 1: When the inverter is working and the output is inverted, Q1 and Q4 work to output the positive half-wave of AC. After Q1 and Q4 are turned on, they store energy in the inverter inductors L1 and L2, and then Q6 and Q5 realize the continuous flow of L1 and L2. After Q6 is turned off, the body diode of Q6 continues to release energy. When the next cycle starts working, Q1 needs to provide reverse recovery energy to the body diode of Q6, resulting in a large pulse current of Q1 at the moment of turning on, and the S1 drive waveform will also become very poor. Figure 4 Schematic diagram of the drive waveforms corresponding to S1, S4, S5, S6 and S7 of the inverter provided in the embodiment of the present application under working condition 1, as shown in FIG. Figure 4 As shown, Q7 of the embodiment of the present application is turned on before Q5 is turned off, so that the body diode of Q6 does not reverse, and the recovery loss reduces the turn-on loss of Q1, but it will bring reverse recovery loss of D1. The reverse recovery characteristics of D1 are better and the loss is relatively small.

[0037] Working condition 2: When the inverter is working and the output is inverted, Q3 and Q2 work to output the negative half-wave of AC. After Q2 and Q3 are turned on, the inverter inductors L1 and L2 store energy, and then the inductors L1 and L2 are freewheeling through Q6 and Q5. After Q5 is turned off, the body diode of Q5 freewheels and releases energy. When the next cycle starts working, Q2 needs to provide reverse recovery energy to the body diode of Q6, resulting in a large pulse current at the moment of Q2 turning on, and the S2 drive waveform will also become very poor. Figure 5 Schematic diagram of the drive waveforms corresponding to S2, S3, S5, S6 and S8 of the inverter provided in the embodiment of the present application under working condition 2, as shown in FIG. Figure 5 As shown, Q8 of the embodiment of the present application is turned on before Q6 is turned off, so that the body diode of Q5 has no reverse recovery loss, reducing the turn-on loss of Q2, but it will bring reverse recovery loss of D2. The reverse recovery characteristics of D2 are better and the loss is relatively small.

[0038] In summary, with respect to the two working conditions, the embodiments of the present application not only reduce the working losses of Q1, Q2, Q5, and Q6, but also improve the inverter efficiency of the inverter and reduce the heat generation of the device.

[0039] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0040] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0041] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An inverter circuit, characterized in that: include: a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor, a first diode, and a second diode; wherein: The collector of the first transistor and the collector of the second transistor are connected to serve as the first input end of the inverter circuit, and the first input end of the inverter circuit is used to connect to the positive electrode of the DC power supply; The emitter of the third transistor is connected to the emitter of the fourth transistor and serves as the second input end of the inverter circuit, and the second input end of the inverter circuit is used to access the negative electrode of the DC power supply; The emitter of the first transistor, the cathode of the first diode and the emitter of the fifth transistor are connected to serve as the first output end of the inverter circuit, and the first output end of the inverter circuit is used to access the positive electrode of the power grid; The collector of the fourth transistor, the emitter of the fifth transistor and the cathode of the second diode are connected to serve as the second output end of the inverter circuit, and the second output end of the inverter circuit is used to access the negative electrode of the power grid; The emitter of the first transistor is connected to the collector of the third transistor, the emitter of the second transistor is connected to the collector of the fourth transistor; the collector of the fifth transistor is connected to the collector of the sixth transistor, the collector of the seventh transistor and the collector of the eighth transistor are respectively connected to the line between the fifth transistor and the sixth transistor, the anode of the first diode is connected to the emitter of the seventh transistor, and the anode of the second diode is connected to the emitter of the eighth transistor.

2. The inverter circuit according to claim 1, characterized in that: The first diode and the second diode are both silicon carbide diodes.

3. A photovoltaic inverter, characterized in that: The photovoltaic inverter comprises the inverter circuit according to any one of claims 1 to 2.

4. The photovoltaic inverter according to claim 3, characterized in that: Also includes: A filter circuit is provided on a line between the inverter circuit and the power grid; the filter circuit comprises a first inductor, a second inductor and a capacitor; wherein: The first end of the first inductor serves as the first input end of the filter circuit, and the first input end of the filter circuit is connected to the first output end of the inverter circuit; The first end of the second inductor serves as the second input end of the filter circuit, and the second input end of the filter circuit is connected to the second output end of the inverter circuit; The second end of the first inductor is connected to the first end of the capacitor to serve as the first output end of the filter circuit, and the first output end of the filter circuit is connected to the positive electrode of the power grid; The second end of the second inductor is connected to the second end of the capacitor to serve as the second output end of the filter circuit, and the second output end of the filter circuit is connected to the negative pole of the power grid.

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