High-efficiency microgrid inverter and control method thereof

Abstract

The application discloses a high-efficiency micro-grid inverter and a control method thereof, and belongs to the technical field of micro-grid. The specific structure and driving generation mode of horizontal pipe switch tubes Ta2 and Ta3 and vertical pipe switch tubes Ta1 and Ta4 are used to optimize the circuit structure and the control method from the aspects of the micro-grid inverter circuit structure and the control method, reduce the heat loss of devices, improve the waveform quality of alternating current side current and voltage, and thus improve the efficiency and power quality of the micro-grid inverter.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro-grid, in particular to a high-efficiency micro-grid inverter and a control method thereof. BACKGROUND

[0002] Micro-Grid, also known as micro-grid, is a small power distribution system composed of distributed power supply, energy storage device, energy conversion device, load, monitoring and protection device, etc. The micro-grid inverter is the energy conversion device.

[0003] The micro-grid itself has three characteristics: first, the distribution is relatively dispersed; second, the capacity is generally not large, and the scale is relatively small; third, the investment and operation and maintenance cost is high. Based on the above characteristics, the micro-grid inverter is required to have the advantages of simple circuit structure, low cost, high efficiency and high power quality.

[0004] At present, most of the micro-grid inverter technologies have two-stage structure circuit and complex control, low efficiency and low power quality. For example, the public technologies CN115411964A and CN117498459A construct a relatively complex system and control method to improve the efficiency and power quality of the micro-grid inverter, but it is the key point of the micro-grid inverter technology to make the system not complex and not increase the cost. SUMMARY

[0005] The present application aims to provide a high-efficiency micro-grid inverter and a control method thereof. The horizontal pipe adopts low-frequency control, the vertical pipe adopts high-frequency control, the horizontal pipe switching loss is eliminated, and three-level is realized only through the high-frequency switching of the vertical pipe. The output voltage waveform is three-level, and the power quality is improved.

[0006] To achieve the above-mentioned purpose, the following technical solutions are adopted:

[0007] A high-efficiency micro-grid inverter, comprising: a horizontal pipe switching tube Ta2 and its body diode Da2, a horizontal pipe switching tube Ta3 and its body diode Da3, a vertical pipe switching tube Ta1 and its body diode Da1, and a vertical pipe switching tube Ta4 and its body diode Da4, the horizontal pipe switching tubes Ta2 and Ta3 are connected in series between point O and point OUT, the point OUT is the connection point of the vertical pipe switching tubes Ta1 and Ta4, and the point O is the connection point of the upper bus capacitor C1 and the lower bus capacitor C2.

[0008] Further, it further comprises an input filter inductance L and an input capacitor C, one end of the input filter inductance L is connected with the point OUT, the other end is connected with one end of the input capacitor C, the other end of the input capacitor C is connected with the point O, one end of the upper bus capacitor is connected with the positive electrode PV+ of the photovoltaic panel, the other end is connected with the lower bus capacitor at the point O, and the other end of the lower bus capacitor is connected with the negative electrode PV of the photovoltaic panel.

[0009] Further, the horizontal pipe switch tube Ta2, Ta3 is IGBT, the vertical pipe switch tube Ta1, Ta4 is mosfet or SiCmosfet.

[0010] A high-efficiency microgrid inverter control method is used to control the above-mentioned high-efficiency microgrid inverter, the drive of the horizontal pipe switch tube Ta2, Ta3 is controlled by the modulation wave Us, and the drive of the vertical pipe switch tube Ta1, Ta4 is controlled by the comparison result of the modulation wave Us and the upper carrier wave Ucp and the lower carrier wave Ucn.

[0011] Further, the drive generation mode of the horizontal pipe switch tube Ta2, Ta3 is that when Us is in the positive half axis, Ta2 is turned on and Ta3 is turned off; when Us is in the negative half axis, Ta3 is turned on and Ta2 is turned off.

[0012] The drive generation mode of the vertical pipe switch tube Ta1, Ta4 is that when Us is in the positive half axis, Us is compared with Ucp, when Us>Ucp, Ta1 is turned on and Ta4 is turned off, otherwise Ta1 is turned off and Ta4 is turned on; when Us is in the negative half axis, Us is compared with Ucn, when Us>Ucn, Ta1 is turned on and Ta4 is turned off, otherwise Ta1 is turned off and Ta4 is turned on.

[0013] Further, when Us is in the positive half axis, Us>0, and Us>Ucp, Ta2 is turned on, Ta3 is turned off, Ta1 is turned on, and Ta4 is turned off, which is three-level P state.

[0014] When Us>0 and Us

[0015] When Us is in the negative half axis, Us<0, and Us>Ucn, Ta2 is turned off, Ta3 is turned on, Ta1 is turned on, and Ta4 is turned off, which is three-level O state.

[0016] When Us<0 and Us

[0017] Further, the voltage between the point OUT and the point O is defined as U OUTO , and the voltage between the positive electrode PV+ of the photovoltaic panel and the negative electrode PV- of the photovoltaic panel is PV.

[0018] When the positive half axis is in three-level P state, U OUTO =0.5PV, the microgrid inverter works in the positive half axis, the current flows out of the microgrid inverter, the vertical pipe switch tube Ta1 is turned on, and the horizontal pipe switch tube Ta2 is turned on, the current flows through the vertical pipe switch tube Ta1, and then flows back to the connection point O of the upper bus capacitor C1 and the lower bus capacitor C2 through the input filter inductance L and the input filter capacitance C.

[0019] When the positive half axis is in three-level O state, UOUTO =0, the micro-grid inverter works in the positive half-axis, the current flows out of the micro-grid inverter, the horizontal pipe switch tube Ta2 and the vertical pipe switch tube Ta4 are turned on, the current flows through the IGBT switch tube Ta2 and the diode Da3, and then returns to the connection point O of the upper bus capacitor C1 and the lower bus capacitor C2 through the filter inductor L and the filter capacitor C.

[0020] Further, the voltage between the point OUT and the point O is defined as U OUTO , and the voltage between the positive electrode PV+ of the photovoltaic panel and the negative electrode PV- of the photovoltaic panel is PV.

[0021] When the three-level N state of the negative half-axis is U OUTO =-0.5PV, the micro-grid inverter works in the negative half-axis, the current flows into the micro-grid inverter, the horizontal pipe switch tube Ta3 and the vertical pipe switch tube Ta4 are turned on, the current flows from the point OUT, passes through the switch tube Ta4 and the lower bus capacitor C2, passes through the point O, flows through the filter capacitor C and the filter inductor L, and returns to the point OUT.

[0022] When the negative half-axis O state of Us is U OUTO =0, the micro-grid inverter works in the negative half-axis, the current flows into the micro-grid inverter, the horizontal pipe switch tube Ta3 and the vertical pipe switch tube Ta4 are turned on, the current flows from the point OUT, passes through the switch tube Ta3 and the diode Da2, passes through the point O, flows through the filter capacitor C and the filter inductor L, and returns to the point OUT.

[0023] The present application has the advantages of:

[0024] The present application eliminates the high-frequency switching loss of the horizontal pipe and improves the efficiency of the micro-grid inverter through low-frequency control of the horizontal pipe and high-frequency control of the vertical pipe.

[0025] The present application realizes three-level output voltage of the micro-grid inverter and improves the power quality of the micro-grid inverter through low-frequency control of the horizontal pipe and high-frequency control of the vertical pipe.

[0026] The control method of the present application improves the overall switching frequency of the micro-grid inverter using IGBT low-frequency switch tubes to the level of the high-frequency switching frequency of mosfet.

[0027] The present application has simple hardware circuit and low cost, and the control method is simple, stable and reliable. DETAILED DESCRIPTION

[0028] Figure 1 The present application has simple hardware circuit and low cost, and the control method is simple, stable and reliable.

[0029] Figure 2 The present application has simple hardware circuit and low cost, and the control method is simple, stable and reliable.

[0030] Figure 3This is a diagram showing the three-level P-state operation of the high-efficiency microgrid inverter on the positive half-axis in Embodiment 2 of the present invention.

[0031] Figure 4 This is a diagram showing the three-level O-state operation of the high-efficiency microgrid inverter on the positive half-axis in Embodiment 2 of the present invention.

[0032] Figure 5 This is a diagram showing the three-level N-state operation of the high-efficiency microgrid inverter on the negative half-axis in Embodiment 2 of the present invention.

[0033] Figure 6 This is a diagram showing the three-level O-state operation of the high-efficiency microgrid inverter on the negative half-axis in Embodiment 2 of the present invention. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0035] Example 1

[0036] This embodiment discloses a high-efficiency microgrid inverter. Please refer to [link / reference]. Figure 1 The system includes: an upper bus capacitor C1, a lower bus capacitor C2, a horizontal switch transistor Ta2 and its body diode Da2, a horizontal switch transistor Ta3 and its body diode Da3, a vertical switch transistor Ta1 and its body diode Da1, a vertical switch transistor Ta4 and its body diode Da4, an input filter inductor L, and an input capacitor C. The horizontal switches Ta2 and Ta3 are connected in series between points O and OUT. Point OUT is the connection point between the vertical switches Ta1 and Ta4. Point O is the connection point between the upper bus capacitor C1 and the lower bus capacitor C2. One end of the input filter inductor L is connected to point OUT, and the other end is connected to one end of the input capacitor C. The other end of the input capacitor C is connected to point O. One end of the upper bus capacitor is connected to the positive terminal PV+ of the photovoltaic panel, and the other end is connected to the lower bus capacitor at point O. The other end of the lower bus capacitor is connected to the negative terminal -PV of the photovoltaic panel.

[0037] In this embodiment, the horizontal tube switches Ta2 and Ta3 are IGBTs, and the vertical tube switches Ta1 and Ta4 are MOSFETs or SiC MOSFETs.

[0038] Example 2

[0039] For the high-efficiency microgrid inverter described in Example 1, this example proposes a modulation method, please refer to... Figure 2 As shown, the horizontal tube switches Ta2 and Ta3 are driven by the modulation wave Us, while the vertical tube switches Ta1 and Ta4 are driven by the comparison result of the modulation wave Us with the upper carrier wave Ucp and the lower carrier wave Ucn.

[0040] The driving method of the horizontal tube switching transistors Ta2 and Ta3 is as follows: when Us is on the positive half axis, Ta2 is turned on and Ta3 is turned off; when Us is on the negative half axis, Ta3 is turned on and Ta2 is turned off.

[0041] The driving method of the vertical tube switch tubes Ta1 and Ta4 is as follows: When Us is on the positive half axis, Us is compared with Ucp. If Us>Ucp, Ta1 is turned on and Ta4 is turned off. Otherwise, Ta1 is turned off and Ta4 is turned on. When Us is on the negative half axis, Us is compared with Ucn. If Us>Ucn, Ta1 is turned on and Ta4 is turned off. Otherwise, Ta1 is turned off and Ta4 is turned on.

[0042] That is, when Us is located on the positive half axis, Us>0, Us>Ucp, Ta2 is turned on, Ta3 is turned off, Ta1 is turned on, and Ta4 is turned off, which is a three-level P state;

[0043] When Us > 0 and Us < Ucp, Ta2 is on, Ta3 is off, Ta4 is on, and Ta1 is off, which is a three-level 0 state;

[0044] When Us is located on the negative half axis, Us < 0, Us > Ucn, Ta2 is off, Ta3 is on, Ta1 is on, and Ta4 is off, which is a three-level 0 state;

[0045] When Us < 0 and Us < Ucn, Ta2 is off, Ta3 is on, Ta4 is on, and Ta1 is off, forming a three-level N-state.

[0046] Define the voltage between point OUT and point O as U. OUTO The voltage between the positive electrode PV+ and the negative electrode PV- of the photovoltaic panel is PV, and the current flowing through the input filter inductor L is IL. IL is defined as flowing from the input filter inductor L to the input capacitor C in the positive direction.

[0047] When the positive half-axis is in the three-level P state, U OUTO =0.5PV, IL>0, the microgrid inverter is working on the positive half axis, the current flows out of the microgrid inverter, the vertical switch Ta1 is turned on, the horizontal switch Ta2 is turned on, the current flows through the vertical switch Ta1, through the input filter inductor L and the input filter capacitor C, and returns to the connection point O of the upper bus capacitor C1 and the lower bus capacitor C2.

[0048] When the positive half-axis three-level is in state O, U OUTO =0, IL>0, the microgrid inverter is working on the positive half axis, the current flows out of the microgrid inverter, the horizontal switch Ta2 and the vertical switch Ta4 are turned on, the current flows through the IGBT switch Ta2 and the diode Da3, and after passing through the filter inductor L and the filter capacitor C, it returns to the connection point O of the upper bus capacitor C1 and the lower bus capacitor C2.

[0049] When the negative half-axis is in the three-level N-state, U OUTO=-0.5PV, IL<0, the microgrid inverter is working in the negative half-axis, the current flows into the microgrid inverter, the horizontal switch Ta3 and the vertical switch Ta4 are turned on, the current flows from point OUT through switch Ta4 and lower bus capacitor C2, passes through point O, flows through filter capacitor C and filter inductor L and returns to point OUT.

[0050] When Us is in state O on the negative half-axis, U OUTO =0, IL<0, the microgrid inverter is working in the negative half axis, the current flows into the microgrid inverter, the horizontal switch Ta3 and the vertical switch Ta4 are turned on, the current flows from point OUT through switch Ta3 and diode Da2, through point O, through filter capacitor C and filter inductor L and back to point OUT.

[0051] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high efficiency microgrid inverter control method for controlling a high efficiency microgrid inverter, characterized by, The driving of the horizontal pipe switch tubes Ta2 and Ta3 is controlled by the modulation wave Us, and the driving of the vertical pipe switch tubes Ta1 and Ta4 is controlled by the comparison result of the modulation wave Us and the upper carrier wave Ucp and the lower carrier wave Ucn. The driving of the horizontal pipe switch tubes Ta2 and Ta3 is generated in the following manner: when Us is in the positive half axis, Ta2 is turned on and Ta3 is turned off; When Us is in the negative half axis, Ta3 is turned on and Ta2 is turned off. The driving of the vertical pipe switch tubes Ta1 and Ta4 is generated in the following manner: when Us is in the positive half axis, Us is compared with Ucp, and when Us>Ucp, Ta1 is turned on and Ta4 is turned off, otherwise, Ta1 is turned off and Ta4 is turned on; when Us is in the negative half axis, Us is compared with Ucn, and when Us>Ucn, Ta1 is turned on and Ta4 is turned off, otherwise, Ta1 is turned off and Ta4 is turned on. The high-efficiency micro-grid inverter comprises: The horizontal pipe switch tube Ta2 and its body diode Da2, the horizontal pipe switch tube Ta3 and its body diode Da3, the vertical pipe switch tube Ta1 and its body diode Da1, and the vertical pipe switch tube Ta4 and its body diode Da4, wherein the horizontal pipe switch tubes Ta2 and Ta3 are connected in series between a point O and a point OUT, the point OUT is a connection point of the vertical pipe switch tubes Ta1 and Ta4, and the point O is a connection point of the upper bus capacitor C1 and the lower bus capacitor C2. The horizontal pipe switch tubes Ta2 and Ta3 are IGBTs, and the vertical pipe switch tubes Ta1 and Ta4 are mosfets or SiC mosfets.

2. The control method of the high efficiency microgrid inverter according to claim 1, wherein, The high-efficiency micro-grid inverter further comprises an input filter inductor L and an input capacitor C, wherein one end of the input filter inductor L is connected to the point OUT, the other end of the input filter inductor L is connected to one end of the input capacitor C, the other end of the input capacitor C is connected to the point O, one end of the upper bus capacitor is connected to the positive electrode PV+ of the photovoltaic panel, the other end of the upper bus capacitor is connected to the point O, and the other end of the lower bus capacitor is connected to the negative electrode PV of the photovoltaic panel.

3. The high-efficiency micro-grid inverter control method according to claim 1, wherein: when Us is in the positive half axis and Us>0 and Us>Ucp, Ta2 is turned on, Ta3 is turned off, Ta1 is turned on, and Ta4 is turned off, which is a three-level P state; when Us>0 and Us when Us is in the negative half axis and Us<0 and Us>Ucn, Ta2 is turned off, Ta3 is turned on, Ta1 is turned on, and Ta4 is turned off, which is a three-level O state; when Us<0 and Us when Us<0 and Us 4. The control method of claim 3, wherein, The voltage between the point OUT and the point O is defined as U OUTO The voltage between the positive pole of the photovoltaic panel PV+ and the negative pole of the photovoltaic panel PV- is defined as PV. Positive half-axis three-level P state, U OUTO = 0.5PV, the microgrid inverter works in the positive half-axis, the current flows out of the microgrid inverter, the vertical pipe switch tube Ta1 is turned on, the horizontal pipe switch tube Ta2 is turned on, the current flows through the vertical pipe switch tube Ta1, and then returns to the upper bus capacitor C1 and the lower bus capacitor C2 connection point O through the input filter inductor L and the input filter capacitor C. Positive half-axis three-level O state, U OUTO = 0, the micro-grid inverter works in the positive half-axis, the current flows out of the micro-grid inverter, the horizontal pipe switch tube Ta2 and the vertical pipe switch tube Ta4 are turned on, the current flows through the IGBT switch tube Ta2 and the diode Da3, and then returns to the connection point O of the upper bus capacitor C1 and the lower bus capacitor C2 through the filter inductor L and the filter capacitor C.

5. The control method of claim 3, wherein, The voltage between the point OUT and the point O is defined as U OUTO The voltage between the positive pole of the photovoltaic panel PV+ and the negative pole of the photovoltaic panel PV- is defined as PV. U OUTO = -0.5 PV, the microgrid inverter works in the negative half axis, the current flows into the microgrid inverter, the horizontal pipe switch tube Ta3 and the vertical pipe switch tube Ta4 are turned on, the current flows from the point OUT through the switch tube Ta4 and the lower bus capacitor C2, passes through the point O, flows through the filter capacitor C and the filter inductor L back to the point OUT; Us in the negative half-axis O state, U OUTO =0, the micro-grid inverter works in the negative half-axis, the current flows into the micro-grid inverter, the horizontal pipe switch tube Ta3 and the vertical pipe switch tube Ta4 are turned on, the current flows from the point OUT through the switch tube Ta3 and the diode Da2, passes through the point O, flows through the filter capacitor C and the filter inductor L back to the point OUT.

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