Buck-boost grid-connected inversion device, control device and control method

Abstract

The invention discloses a buck-boost grid-connected inverter device, a control device and a control method. The buck-boost grid-connected inverter device comprises a first Buck-boost circuit, a second Buck-boost circuit and a filter circuit, wherein the first Buck-boost circuit, the second Buck-boost circuit and the filter circuit are connected with a control signal; a direct current power supply is connected with the first Buck-boost circuit and the second Buck-boost circuit; the first Buck-boost circuit and the second Buck-boost circuit are arranged in parallel, and the first Buck-boost circuit and the second Buck-boost circuit are arranged in parallel. And the filter circuit is connected with the first Buck-boost circuit and the second Buck-boost circuit, and the filter circuit outputs a power grid voltage. Compared with a traditional inverter which can only reduce voltage, the inverter can not only provide voltage reduction in the conversion process, but also has a voltage boosting function, and meets the requirements of various electrical devices for alternating current. And the requirement that a special boosting device or a transformer often needs to be added when a traditional inverter needs to meet the grid connection requirement of the power grid voltage is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic equipment, and in particular to a buck-boost grid-connected inverter device, a control device and a control method. Background Art

[0002] An inverter is a power electronic device that converts direct current (DC) into alternating current (AC). That is, it converts a stable DC power supply into a periodically changing AC power supply. The inverter usually contains power semiconductor devices (such as IGBT or MOSFET) and control circuits. These components work together to achieve DC to AC conversion, but this does not mean that they can automatically adjust the output voltage. Traditional inverters do not have a boost function. If the voltage needs to be increased, a special boost device or transformer is usually required. These devices achieve voltage boost through electromagnetic induction or other physical principles.

[0003] However, as the application areas of inverters continue to expand, such as solar power generation systems and electric vehicle charging stations, higher voltages are required to meet the needs of long-distance power transmission or fast charging. There are also new energy power supply occasions such as wind power generation, fuel cell power generation, and battery applications. These fields also require efficient power conversion equipment and stable voltage output.

[0004] Traditional inverters can only step down the voltage, so to meet the grid voltage requirements, it is often necessary to use a special boost device or transformer. For example, in a solar power generation system, the output DC voltage of new energy modules such as photovoltaics and fuel cells is generally 18 to 56V. In order to meet the requirements of electrical equipment or grid-connected power generation, multiple modules need to be connected in series, and then energy conversion is performed through a traditional inverter. When multiple modules are connected in series, it is easy to form a barrel effect, reducing the reliability of the system. Or it is necessary to pass through a special boost device such as a boost converter. The introduction of this link will inevitably cause a certain amount of energy loss, resulting in a reduction in the overall efficiency of the entire system. Summary of the invention

[0005] In order to overcome the above technical defects, the present invention provides a step-down and step-up grid-connected inverter device and a control device and a control method, which can provide voltage drop and boost functions.

[0006] In order to solve the above problems, the present invention is implemented according to the following technical solutions:

[0007] A buck-boost grid-connected inverter device, comprising: a first Buck-boost circuit connected to a control signal, a second Buck-boost circuit and a filter circuit;

[0008] A DC power supply is connected to the first Buck-boost circuit and the second Buck-boost circuit;

[0009] The first Buck-boost circuit and the second Buck-boost circuit are arranged in parallel;

[0010] The filter circuit is connected to the first Buck-boost circuit and the second Buck-boost circuit, and the filter circuit outputs a grid voltage.

[0011] As a further improvement of the present invention, the first Buck-boost circuit includes: a first inductor, a first switch tube, a second switch tube, a third switch tube and a first diode; and also includes: a second inductor;

[0012] The positive electrode of the DC power supply is connected to the second Buck-boost circuit, the source electrode of the first switch tube, and the drain electrode of the third switch tube;

[0013] The negative electrode of the DC power supply is connected to the drain of the second switch tube and the second Buck-boost circuit;

[0014] The drain of the first switch tube is connected to the source of the second switch tube through the first inductor, and the source of the second switch tube is connected to the filter circuit through the first forward-conducting diode and the second inductor;

[0015] The gates of the first switch tube, the second switch tube, and the third switch tube are connected to a control signal;

[0016] The source of the third switch tube is connected to the filter circuit.

[0017] As a further improvement of the present invention, the second Buck-boost circuit includes: a third inductor, a fourth switch tube, a fifth switch tube, a sixth switch tube and a second diode;

[0018] The positive electrode of the DC power supply is connected to the source electrode of the fourth switch tube and the drain electrode of the sixth switch tube;

[0019] The negative electrode of the DC power supply is connected to the drain of the fifth switch tube, the drain of the fourth switch tube is connected to the source of the fifth switch tube through the third inductor, and the source of the fifth switch tube is connected to the filter circuit through the second diode which is forward-conducting;

[0020] The fourth switch tube, the fifth switch tube, and the sixth switch tube are connected to a control signal;

[0021] The source of the sixth switch tube is connected to the filter circuit.

[0022] As a further improvement of the present invention, the present invention further comprises: a capacitor, a fourth inductor, and the filtering circuit comprises: a seventh switch tube, a fifth inductor, a sixth inductor, and a third diode;

[0023] One end of the fifth inductor is connected to the cathode of the third diode, and the other end is connected to the cathode of the third triode, and two ends of the fifth inductor are respectively connected to the anode and cathode of the third diode;

[0024] The source of the seventh switch tube is connected to the cathode of the third switch tube through a capacitor, the two ends of the fourth inductor are respectively connected to the source and drain of the seventh switch tube, and the source of the seventh switch tube is connected to the cathode of the second diode through the second inductor;

[0025] The anode of the third diode and the drain of the seventh transistor serve as outputs;

[0026] The seventh switch tube is connected to the control signal.

[0027] The present invention also provides a control device for a buck-boost grid-connected inverter device, which is used to control the buck-boost grid-connected inverter device, comprising: a first selection switch, a subtractor, a PI controller, a triangular carrier generator, a comparator, a logical negation operator, and a second selection switch;

[0028] An input end of the first selection switch is connected to the first Buck-boost circuit, the second Buck-boost circuit, and the filter circuit;

[0029] The input end of the subtractor is connected to the first selection switch and the PI controller;

[0030] The input end of the comparator is connected to the output end of the subtractor and the triangular carrier generator;

[0031] The comparator is connected to the second selection switch, and the comparator is connected to the second selection switch via the logical NOT operator;

[0032] An output end of the second selection switch is connected to the first Buck-boost circuit and the second Buck-boost circuit.

[0033] The present invention also provides a control method for a buck-boost grid-connected inverter device, which is used to control the above control device, comprising the steps of:

[0034] The first selection switch obtains a first current value of the first Buck-boost circuit or a second current value of the second Buck-boost circuit according to the grid voltage;

[0035] Calculating a difference between a given current value and the first current value or the second current value;

[0036] The first input terminal of the PI controller obtains the difference, the second input terminal obtains the triangular carrier signal, and outputs a modulated wave signal;

[0037] The second selection switch selects the modulated wave signal and the modulated wave signal after logical negation processing to obtain the driving signals of the first Buck-boost circuit and the second Buck-boost circuit.

[0038] Compared with the prior art, the present invention has the following beneficial effects: by providing a first Buck-boost circuit and a second Buck-boost circuit connected in parallel, voltage step-down and voltage step-up functions can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings, wherein:

[0040] Figure 1 This is a schematic structural diagram of the buck-boost grid-connected inverter device described in Example 1;

[0041] Figure 2 This is a waveform diagram of the boost inversion operation in Example 1;

[0042] Figure 3 This is the operating waveform diagram of the buck inverter in Example 1;

[0043] Figure 4 This is a schematic diagram of the structure of the control device described in Example 2. DETAILED DESCRIPTION

[0044] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0045] Example 1

[0046] This embodiment provides a buck-boost grid-connected inverter device, such as Figure 1 As shown, it includes: a first Buck-boost circuit, a second Buck-boost circuit and a filter circuit with a control signal; a DC power supply is connected to the first Buck-boost circuit and the second Buck-boost circuit; the first Buck-boost circuit and the second Buck-boost circuit are arranged in parallel; the filter circuit is connected to the first Buck-boost circuit and the second Buck-boost circuit, and the filter circuit outputs a grid voltage.

[0047] The working modes of the first Buck-boost circuit and the second Buck-boost circuit are alternately operated with the grid voltage. When the grid voltage is in the positive half cycle, the first Buck-boost circuit works; when the grid voltage is in the negative half cycle, the second Buck-boost circuit works.

[0048] This embodiment also includes: a second inductor L2, and the first Buck-boost circuit includes: a first inductor L1, a first switch tube V T1 , the second switch tube V T2 , the third switch tube V T3 and the first diode D1; DC power supply u dc The positive electrode is connected to the second Buck-boost circuit and the first switch tube V T1 The source of the third switch tube V T3 Drain; DC power supply u dc The negative electrode is connected to the second switch tube V T2 The drain of the second Buck-boost circuit; the first switch tube V T1 The drain of the second switch tube V is connected to the second switch tube V through the first inductor L1. T2 The source of the second switch tube V T2 The source of the first switch tube V T1 , the second switch tube V T2 , the third switch tube V T3 The gate of the third switch tube V T3 The source of the filter circuit is connected.

[0049] Furthermore, the second Buck-boost circuit includes: a third inductor L3, a fourth switch tube V T4 , the fifth switch tube V T5 , the sixth switch tube V T6 and the second diode D2; DC power supply u dc The positive electrode is connected to the fourth switch tube V T4 The source of the sixth switch tube V T6 Drain; DC power supply u dc The negative electrode is connected to the fifth switch tube V T5 The drain of the fourth switch tube V T4 The drain of the fifth switch tube V is connected to the fifth switch tube V through the third inductor L3. T5 The source of the fifth switch tube V T5 The source of the fourth switch tube V T4 , the fifth switch tube V T5 , the sixth switch tube V T6 Connect control signal; the sixth switch tube V T6The source of the filter circuit is connected.

[0050] This embodiment further includes: a capacitor C, a fourth inductor L4, and a filter circuit including: a seventh switch tube V T7 , a fifth inductor L5, a sixth inductor L6, and a third diode D3; one end of the fifth inductor L5 is connected to the cathode of the third diode D3, and the other end is connected to the cathode of the third triode D3, and the two ends of the fifth inductor L5 are respectively connected to the anode and cathode of the third diode D3; the seventh switch tube V T7 The source of is connected to the third switch tube V through capacitor C T3 The cathode of the fourth inductor L4 is connected to the seventh switch tube V T7 The source and drain of the seventh switch tube V T7 The source of the second diode D2 is connected to the cathode of the second diode D2 through the second inductor L2; the anode of the third diode D3 and the seventh transistor V T7 The drain of the seventh switch tube V T7 Connect the control signal.

[0051] Next, this embodiment is further explained in conjunction with the specific implementation process, as follows:

[0052] In the specific working mode, when the grid voltage is in the positive half cycle, the first switch tube V T1 Always on, the second switch tube V T2 And the third switch tube V T3 Interactive conduction, at this time the first switch tube V T1 , the second switch tube V T2 and the sixth switch tube V T6 And the seventh switch tube V in the filter circuit T7 Not conducting; the operation is as shown in Mode 1 and Mode 2, where the current flow in Mode 1 is from the DC power supply udc to the first switch tube V T1 →First inductor L1→Second switch tube V T2 → DC power supply udc; the current in mode 2 flows to the first switch tube V T1 → first inductor L1 → first diode D1 → second inductor L2 → capacitor C and fourth inductor L4 and grid voltage u g →The third diode D3→The third switch tube V T3 →The first switch tube V T1 In the negative half cycle, the fourth switch tube V T4 Always on, the fifth switch tube V T5 and the sixth switch tube V T6 Interactive conduction, at the same time the seventh switch tube V in the filter circuit T7 and the sixth switch tube V T6 At the same time, the first switch tube V T1 , the second switch tube VT2 And the third switch tube V T3 The operation is as shown in Modes 3 and 4, where the current in Mode 3 flows to the DC power supply u dc →The fourth switch tube V T4 →The third inductor L3→The fourth switch tube V T4 →DC power supply dc ; The current in mode 4 flows to the fourth switch tube V T4 →The third inductor L3 →The second diode D2 →The fifth inductor L5 →The capacitor C is connected in parallel with the sixth inductor L6 and the grid voltage u g →The seventh switch tube V T7 →The sixth switch tube V T6 →The fourth switch tube V T4 .

[0053] For example, the parameters of each device in this embodiment are set as follows: DC power supply u dc =60V, grid-connected inverter switching frequency f s =20μs, the third inductor L3 = 0.2mH, the first inductor L1 = 0.2mH; the capacitor C = 200μF, the fifth inductor L5 = 0.2mH, the sixth inductor L6 = 0.2mH; when the grid-connected voltage of the buck-boost grid-connected power generation system is in boost operation, u g =80V, 50Hz; when step-down operation u g =40V, 50Hz, given grid-connected current boost operation i g =4A, 50Hz; when running at reduced voltage i g =2A, 50Hz.

[0054] Figure 2 is the result of boost operation, Figure 2 (a) is the current i passing through the first inductor L1 L1 From the waveform, we can see that the first inductor L1 only works when the voltage is in the positive half cycle. Figure 2 (d) is the current i passing through the third inductor L3 L3 From the waveform, we can see that the third inductor L3 works only when the voltage is in the negative half cycle. Figure 2 (b) is the grid voltage u g Waveform diagram, when boost operation is in progress, the output voltage is a 80V, 50Hz sinusoidal voltage wave. Figure 2 (c) is the grid-connected current waveform. When the voltage is boosted, the grid-connected current i g =4A, 50Hz. It can be seen from the waveform that the grid-connected current can track the given current. Figure 4 It is the result of system voltage reduction operation. Figure 3 (a) is the current i passing through the first inductor L1 L1 From the waveform, we can see that the first inductor L1 works only when the voltage is in the positive half cycle. Figure 3 (d) is the current i of the third inductor L3 L3 From the waveform, we can see that the third inductor L3 works only when the voltage is in the negative half cycle. Figure 3 (b) is the grid voltage waveform. During step-down operation, the output voltage is a 40V, 50Hz sinusoidal voltage wave. Figure 3 (c) is the grid-connected current waveform. When the voltage is stepped down, the grid-connected current i g =2A, 50Hz, from the waveform, we can see that the grid-connected current can track the given current. Figure 2 and Figure 3 It can be seen from the results that the buck-boost grid-connected inverter device of this embodiment can stably operate in the buck and boost states.

[0055] Example 2

[0056] This embodiment provides a control device for a buck-boost grid-connected inverter device, which is used to control the buck-boost grid-connected inverter device in Embodiment 1. Figure 4 As shown, it includes: a first selection switch, a subtractor, a PI controller, a triangular carrier generator, a comparator, a logical NOT operator, and a second selection switch; the input end of the first selection switch is connected to the first Buck-boost circuit, the second Buck-boost circuit, and the filter circuit; the input end of the subtractor is connected to the first selection switch and the PI controller; the input end of the comparator is connected to the output end of the subtractor and the triangular carrier generator; the comparator is connected to the second selection switch, and the comparator is connected to the second selection switch through the logical NOT operator; the output end of the second selection switch is connected to the first Buck-boost circuit and the second Buck-boost circuit.

[0057] Specifically, the first input terminal of the first selection switch is connected to the first Buck-boost circuit and receives the first inductor L1 current i L1 The second input terminal is connected to the second Buck-boost circuit and receives the current i of the third inductor L3. L3 , the first selection switch is for current i L1 、Current i L3 After selection, output, given current i gref , the output value of the first selection switch is input to the subtractor, and the difference is output to the PI controller. The output of the PI controller is sent to one port of the comparator. The other port of the comparator is connected to the triangular carrier generator, and the output of the comparator is connected to the selection switch. The output signal is sent to the selection switch after logical negation processing. The selection switch selects the output signal of the comparator and the logical negation operator to obtain the driving signal g (V T1 )、g(V T2 )、g(V T3 )、g(V T4)、g(V T5 )、g(V T6 )、g(V T7 ), wherein the second selection switch is connected via the grid voltage u g judge.

[0058] Example 3

[0059] This embodiment provides a control method for a buck-boost grid-connected inverter device, which is used to control the control device in Embodiment 2, and includes the following steps:

[0060] The first selection switch obtains a first current value of the first Buck-boost circuit or a second current value of the second Buck-boost circuit according to the grid voltage;

[0061] Calculating a difference between a given current value and a first current value or a second current value;

[0062] The first input terminal of the PI controller obtains the difference value, the second input terminal obtains the triangular carrier signal, and outputs a modulated wave signal;

[0063] The second selection switch selects the modulation wave signal and the modulation wave signal after logical negation processing to obtain the driving signals of the first Buck-boost circuit and the second Buck-boost circuit.

[0064] Specifically, given the current i gref and the inductor current i L The difference obtained by the subtractor is sent to the PI controller, and the inductor current value i L The output is selected by the first selection switch. The switching condition of the first selection switch is the grid voltage u g ,u g ≥0, the first Buck-boost circuit works, i L =i L1 ; When ug<0, the second Buck-boost circuit works, i L =i L3 The output of the PI controller is sent to one port of the comparator. The other port of the comparator is connected to the triangular carrier generator. The output of the comparator is connected to the selection switch. The output signal is sent to the selection switch after logical negation processing. The selection switch selects the output signal of the comparator and the logical negation operator to obtain the driving signal g (V T1 )、g(V T2 )、g(V T3 )、g(V T4 )、g(V T5 )、g(V T6 )、g(V T7), wherein the second selection switch is connected via the grid voltage u g judge.

[0065] In summary, the buck-boost grid-connected inverter device, control device, and control method of the present invention, compared with the traditional inverter that can only buck, can not only provide voltage bucking during the conversion process, but also have a boosting function to meet the AC power requirements of various electrical equipment. This avoids the need for traditional inverters to meet the grid voltage requirements, which often require the addition of special boosting equipment or transformers.

[0066] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A buck-boost grid-connected inverter device, characterized in that: include: A first Buck-boost circuit, a second Buck-boost circuit and a filter circuit connected to the control signal; A DC power supply is connected to the first Buck-boost circuit and the second Buck-boost circuit; The first Buck-boost circuit and the second Buck-boost circuit are arranged in parallel; The filter circuit is connected to the first Buck-boost circuit and the second Buck-boost circuit, and the filter circuit outputs a grid voltage.

2. The buck-boost grid-connected inverter device according to claim 1, characterized in that: The first Buck-boost circuit includes: a first inductor, a first switch tube, a second switch tube, a third switch tube and a first diode; and also includes: a second inductor; The positive electrode of the DC power supply is connected to the second Buck-boost circuit, the source electrode of the first switch tube, and the drain electrode of the third switch tube; The negative electrode of the DC power supply is connected to the drain of the second switch tube and the second Buck-boost circuit; The drain of the first switch tube is connected to the source of the second switch tube through the first inductor, and the source of the second switch tube is connected to the filter circuit through the first forward-conducting diode and the second inductor; The gates of the first switch tube, the second switch tube, and the third switch tube are connected to a control signal; The source of the third switch tube is connected to the filter circuit.

3. The buck-boost grid-connected inverter device according to claim 2, characterized in that: The second Buck-boost circuit includes: a third inductor, a fourth switch tube, a fifth switch tube, a sixth switch tube and a second diode; The positive electrode of the DC power supply is connected to the source electrode of the fourth switch tube and the drain electrode of the sixth switch tube; The negative electrode of the DC power supply is connected to the drain of the fifth switch tube, the drain of the fourth switch tube is connected to the source of the fifth switch tube through the third inductor, and the source of the fifth switch tube is connected to the filter circuit through the second diode which is forward-conducting; The fourth switch tube, the fifth switch tube, and the sixth switch tube are connected to a control signal; The source of the sixth switch tube is connected to the filter circuit.

4. The buck-boost grid-connected inverter device according to claim 3, characterized in that: Also includes: The filter circuit includes: a seventh switch tube, a fifth inductor, a sixth inductor, and a third diode; One end of the fifth inductor is connected to the cathode of the third diode, and the other end is connected to the cathode of the third triode, and two ends of the fifth inductor are respectively connected to the anode and cathode of the third diode; The source of the seventh switch tube is connected to the cathode of the third switch tube through a capacitor, the two ends of the fourth inductor are respectively connected to the source and drain of the seventh switch tube, and the source of the seventh switch tube is connected to the cathode of the second diode through the second inductor; The anode of the third diode and the drain of the seventh transistor serve as outputs; The seventh switch tube is connected to the control signal.

5. A control device for a step-up / step-down grid-connected inverter device, characterized in that: Used to control the buck-boost grid-connected inverter device according to any one of claims 1 to 4, comprising: a first selection switch, a subtractor, a PI controller, a triangular carrier generator, a comparator, a logical negation operator, and a second selection switch; An input end of the first selection switch is connected to the first Buck-boost circuit, the second Buck-boost circuit, and the filter circuit; The input end of the subtractor is connected to the first selection switch and the PI controller; The input end of the comparator is connected to the output end of the subtractor and the triangular carrier generator; The comparator is connected to the second selection switch, and the comparator is connected to the second selection switch via the logical NOT operator; An output end of the second selection switch is connected to the first Buck-boost circuit and the second Buck-boost circuit.

6. A control method for a control device, characterized in that: For controlling the control device as claimed in claim 5, comprising the steps of: The first selection switch obtains a first current value of the first Buck-boost circuit or a second current value of the second Buck-boost circuit according to the grid voltage; Calculating a difference between a given current value and the first current value or the second current value; The first input terminal of the PI controller obtains the difference, the second input terminal obtains the triangular carrier signal, and outputs a modulated wave signal; The second selection switch selects the modulated wave signal and the modulated wave signal after logical negation processing to obtain the driving signals of the first Buck-boost circuit and the second Buck-boost circuit.

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