CN211377902U - Multi-level boost circuit, inverter, photovoltaic power generation device and photovoltaic power generation system - Google Patents

Abstract

The utility model discloses a multi-level boost circuit, an inverter, a photovoltaic power generation device and a photovoltaic power generation system, wherein TVS tubes are arranged between an output node and a first capacitor, a second diode and other auxiliary devices, thereby not only solving the problem that a lower arm switch tube is easy to be punctured when the power is on, but also solving the problem that the second diode is punctured under the condition of low input voltage, so that the selection of related devices is easier and the cost is lower; in addition, after the circuit is added with corresponding devices, the normal boosting process is not influenced, the voltage of the output end is easy to control, and meanwhile, the probability of electric shock accidents when the input end is operated is also reduced.

Description

Multi-level boost circuit, inverter, photovoltaic power generation device and photovoltaic power generation system

Technical Field

The utility model relates to a circuit technical field that steps up, more specifically say, relate to a many level step up circuit, inverter, photovoltaic power generation device and photovoltaic power generation system.

Background

The input voltage of a photovoltaic power generation system is gradually increased to 1500V at present, and a preceding stage booster circuit of a photovoltaic inverter is usually changed from a two-level circuit to a three-level circuit in consideration of cost and other factors. When the flying capacitor type three-level boost circuit shown in fig. 1 is initially powered up, the voltage across the flying capacitor C1 is zero, which may cause the lower arm switch Q2 to bear the full input voltage, and may easily cause the switch Q2 to be damaged.

In addition, the above-mentioned boost circuit has another drawback that, when it is applied to the field of photovoltaic power generation and forms a distributed photovoltaic power generation system, there may be a case where a bus voltage is established because other parallel boost circuits have been powered up. In this case, when the photovoltaic module PV shown in fig. 1 is not connected to the input terminal of the booster circuit or the voltage of the photovoltaic module PV is low, i.e., a low input voltage condition, the input voltage is lower than the starting voltage of the booster circuit, and the bus voltage will act against the booster circuit, resulting in the second diode D2 bearing substantially the entire bus voltage, which is easily damaged.

Therefore, the conventional boost circuit in fig. 1 has the problems that the switching transistor Q2 and the second diode D2 are difficult to select or have high cost due to the above-mentioned defects. Some solutions have been proposed in the prior art to solve the above-mentioned problems to some extent.

For example, in order to solve the problem of the switching transistor Q2, the patent document CN110299837A adopts a charging circuit including an inductor, a capacitor and a controllable switch to pre-charge the flying capacitor C1 before power-on, so as to reach a safe threshold, thereby reducing the voltage stress of the switching transistor Q2 during power-on. In order to solve the problem of the switching tube Q2 with low cost, another prior art is based on fig. 1, and a diode is arranged between the flying capacitor C1 and the midpoint NE of the output bus to ensure that the switching tube Q2 is not broken down by overvoltage during startup. However, when the booster circuit works normally, the input voltage will be transmitted to the output bus midpoint NE through the diode, so that the voltage is difficult to control, and the risk of bias exists.

In order to solve the problem of the second diode D2, in a prior art, on the basis of fig. 1, a diode is disposed between the midpoint NE of the output bus and the anode of the second diode, so that the half bus voltage is applied to the anode of the second diode, and the diode is only required to bear the half bus voltage under the condition of the low input voltage, and is not easily broken down when the withstand voltage value is not high. However, when the boost circuit is operating normally, when the lower arm switching tube Q2 is turned on and the flying capacitor is in the charging cycle, the half bus voltage charges the flying capacitor through the diode, which also causes the output capacitor to be unbalanced in voltage and causes a bias risk, and the diode is easily damaged by the transient sudden charging current.

Therefore, although the scheme can solve the corresponding problems in the corresponding special cases, the newly added devices still have influence on the normal operation of the main devices, so that the output of the booster circuit is difficult to control.

In addition, the second solution has the problem that in case of low input voltage, half bus voltage is transmitted to the input end through the diode, flying capacitor C1 and the body diode of switching tube Q1, and since the half bus voltage may be as high as 750V, an electric shock accident may occur when the operator operates the input end.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to solve above-mentioned technical problem, provide a many level boost circuit, inverter, photovoltaic power generation device and photovoltaic power generation system, its problem that the lower arm switch tube is easily punctured on can solving at least, and does not influence the normal work of circuit, and bus voltage is easily controlled.

In order to achieve the above object, a first aspect of the present invention provides a multi-level boost circuit, which has a first input terminal, a second input terminal, a first output terminal, and a second output terminal, and includes an inductor, a first controllable switch, a second controllable switch, a first capacitor, a first diode, a second diode, a first TVS transistor, and an output capacitor set;

the first controllable switch and the second controllable switch are connected in series to form a first branch circuit, wherein a first end of the first controllable switch and a second end of the second controllable switch respectively form a first end and a second end of the first branch circuit;

the first diode and the second diode are connected in series to form a second branch circuit, wherein the anode of the first diode and the cathode of the second diode respectively form a first end and a second end of the second branch circuit;

the first capacitor forms a third branch, and two ends of the third branch respectively form a first end and a second end of the third branch;

the first TVS tube forms a fourth branch, and the negative electrode and the positive electrode of the first TVS tube respectively form a first end and a second end of the fourth branch;

the output capacitor group is connected with the first output end and the second output end and comprises at least two output capacitors connected in series to form at least one output node configured as a common point between the output capacitors;

the first ends of the first branch circuit and the second branch circuit are connected with a first input end through the inductor, and the second ends of the first branch circuit and the second branch circuit are respectively connected with a second input end and a first output end; the second input end is also connected with a second output end;

the first end of the third branch circuit is connected with the common point of the first diode and the second diode in the second branch circuit, and the second end of the third branch circuit is connected with the common point of the first controllable switch and the second controllable switch in the first branch circuit; and the first end of the fourth branch is connected with the second end of the third branch, and the second end of the fourth branch is connected with an output node.

In one embodiment: the first TVS tube is a unidirectional TVS tube; the fourth branch is also provided with a third diode, the cathode of the third diode is connected with the cathode of the first TVS tube, and the anode of the third diode forms the first end of the fourth branch.

In one embodiment: the fourth branch is also provided with a second TVS tube, the anode of the second TVS tube is connected with the anode of the first TVS tube, and the cathode of the second TVS tube forms a second end of the fourth branch; the first TVS tube and the second TVS tube are both unidirectional TVS tubes.

In one embodiment: the first TVS tube is a bidirectional TVS tube, and two ends of the first TVS tube respectively form a first end and a second end of the fourth branch.

In one embodiment: the voltage booster circuit further comprises a fifth branch circuit, wherein a fourth diode is arranged on the fifth branch circuit and used for clamping the common point of the first diode and the second diode when the input voltage between the first input end and the second input end is lower than the starting voltage of the voltage booster circuit; the cathode of the fourth diode is connected with the common point of the first diode and the second diode, and the anode of the fourth diode is connected with the second end of the fourth branch or the common point of the first TVS tube and the third diode.

In one embodiment: the fifth branch is also provided with one of a second TVS tube or a third controllable switch; when the fifth branch is provided with a second TVS tube, the anode of the fifth branch is connected with the anode of the fourth diode, and the cathode of the fifth branch is connected with the second end of the fourth branch or the common point of the first TVS tube and the third diode; when the fifth branch is provided with a third controllable switch, the third controllable switch is a normally closed relay, and the circuit further comprises a controller which is used for controlling the third controllable switch to be switched off when the circuit works normally.

In one embodiment: the fourth branch is also provided with a third diode, the cathode of the third diode is connected with the cathode of the first TVS tube, and the anode of the third diode forms the first end of the fourth branch; the circuit also comprises a fifth branch circuit, wherein a fourth diode is arranged on the fifth branch circuit and is used for clamping the common point of the first diode and the second diode when the input voltage between the first input end and the second input end is lower than the starting voltage of the booster circuit; the cathode of the fourth diode is connected with the common point of the first diode and the second diode, and the anode of the fourth diode is connected with the common point of the first TVS tube and the second TVS tube.

In one embodiment: the fourth branch is also provided with a third diode, the cathode of the third diode is connected with one end of the first TVS tube, and the anode of the third diode forms the first end of the fourth branch; the circuit also comprises a fifth branch circuit, wherein a fourth diode is arranged on the fifth branch circuit and is used for clamping the common point of the first diode and the second diode when the input voltage between the first input end and the second input end is lower than the starting voltage of the booster circuit; the cathode of the fourth diode is connected with the common point of the first diode and the second diode, and the anode of the fourth diode is connected with the common point of the first TVS tube and the third diode.

In one embodiment: and the fifth branch circuit is also provided with a current-limiting resistor which is connected in series with the fourth diode.

In one embodiment: the output capacitor bank comprises two output capacitors with the same capacitance value.

In order to achieve the above object, a second aspect of the present invention provides an inverter device, which includes a rear inverter circuit and a front stage circuit; the front-stage circuit adopts a multi-level boost circuit provided by any one of the above technical schemes;

the multi-level booster circuit is used for boosting the voltage input by the input end of the multi-level booster circuit and then outputting the boosted voltage from the output end;

the input end of the inverter circuit is coupled with the output end of the multi-level booster circuit and used for inverting the direct current output by the inverter circuit into alternating current.

In order to achieve the above object, a third aspect of the present invention provides a photovoltaic power generation apparatus, which includes a photovoltaic module, a preceding stage circuit, and a subsequent stage circuit; the front-stage circuit adopts a multi-level boost circuit provided by any one of the above technical schemes;

the photovoltaic components correspond to the multilevel booster circuits one by one and are coupled with the input ends of the multilevel booster circuits; the multi-level boosting circuit is used for boosting the output voltage of the photovoltaic module and then outputting the boosted output voltage to the post-stage circuit through the output end of the multi-level boosting circuit.

In order to achieve the above object, the fourth aspect of the present invention provides a photovoltaic power generation system, characterized in that: the photovoltaic power generation device comprises at least two photovoltaic power generation devices provided by the technical scheme; the output ends of the front-stage circuits of the photovoltaic power generation devices are connected in parallel and then connected to the rear-stage circuit.

Compared with the prior art, the beneficial effects of the utility model reside in that:

(1) the multi-level boost circuit provided by the embodiment of the utility model has the advantages that the fourth branch with the first TVS tube is arranged between the output node and the second end of the third branch, and the voltage at the two ends of the second controllable switch is controlled to be lower than the input voltage during power-on, so that the second controllable switch is not easy to break down after model selection under the conventional cost; during normal operation, the voltage of the second end of the third branch circuit is generally not higher than the voltage of the output node connected with the first TVS tube, so that the voltage of the second end of the third branch circuit is not transmitted to the output node, and the voltage-sharing of each output capacitor is not influenced during normal operation of the fourth branch circuit;

(2) in the multi-level boost circuit of the embodiment of the present invention, the fourth branch is further provided with a third diode or a second TVS tube or the first TVS tube is configured as a bidirectional TVS tube, so that the voltage of the output node can be prevented from being transmitted to the output end through the first controllable switch under the condition of low input voltage, thereby causing an electric shock accident;

(3) the embodiment of the utility model provides a when the clamp voltage of the second TVS pipe that sets up in the fourth branch road or the first TVS pipe that is configured as two-way TVS pipe can not be selected to be higher than the voltage of output node, through adding current limiting resistor or third diode on the fourth branch road, with the transmission to the output through first controllable switch of limiting current level or assurance output node's voltage, and then reduce the probability that the electric shock accident takes place;

(4) the utility model discloses many level boost circuit through being equipped with the fifth branch road, can be under the low-voltage condition with second diode anode voltage clamp at output node's voltage, protects the second diode not punctured, makes things convenient for its low-cost lectotype.

(5) The embodiment of the utility model provides a multi-level boost circuit, the fifth branch road still has the second TVS pipe, under the low input voltage condition, through making it can reverse the switch-on in suitable value with the clamp voltage parameter selection of second TVS pipe for the fifth branch road can be switched on to the second diode positive pole by output node and is located a certain suitable voltage value with its positive pole voltage clamp, and then makes the voltage that the second diode both ends bore be less than selected withstand voltage value, therefore still can guarantee under conventional cost that the second diode is not punctured, make things convenient for its low-cost lectotype; when the second TVS tube works normally, the output node can be prevented from charging the first capacitor, and the problem of non-voltage-sharing of the output capacitor caused by the introduction of the fifth branch circuit is solved;

(6) the multi-level boost circuit provided by the embodiment of the utility model has the advantages that under the condition that the fourth branch is provided with the second TVS tube, the fifth branch only needs to be provided with the fourth diode to ensure that the output capacitor does not have the problem of non-uniform voltage caused by the introduction of the fifth branch;

the second TVS tube of the fourth branch circuit can cut off or divide the voltage of the output node for the second end of the third branch circuit and the anode of the second diode, so that a corresponding isolation or voltage protection effect is achieved, and a key effect is achieved on the improvement and solution of the breakdown problem of the second controllable switch during power-on, the breakdown problem of the second diode under the condition of low input voltage and the voltage-sharing problem of the output capacitor during normal operation;

(7) the multi-level boost circuit provided by the embodiment of the utility model has the advantages that under the condition that the first TVS tube of the fourth branch is configured as a bidirectional TVS tube, the fifth branch only needs to be provided with the fourth diode to ensure that the output capacitor does not generate the problem of non-voltage-sharing due to the introduction of the fifth branch;

a bidirectional TVS (transient voltage suppressor) is directly configured on the fourth branch, and under the condition that the bidirectional clamping voltage parameter can meet the specific application requirement, the second end of the third branch and the anode of the second diode can both have the function of cutting off or dividing the voltage of an output node, so that the corresponding isolation or voltage protection function is realized; therefore, the breakdown problem of the second controllable switch during power-on and the breakdown problem of the second diode under the condition of low input voltage are solved simultaneously, the model selection meets the cost requirement, and the voltage-sharing of the output capacitor cannot be influenced by newly introduced devices of the fourth branch circuit and the fifth branch circuit during normal work;

(8) the multi-level boost circuit provided by the embodiment of the utility model can prevent the breakdown of the multi-level boost circuit under the condition and reduce the anode voltage of the second diode through the second TVS tube or the first TVS tube configured as the bidirectional TVS tube under the condition of low input voltage; the current limiting resistor is additionally arranged on the fifth branch, so that the current is limited in a safety range, and the probability of electric shock accidents at the input end is reduced.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is a structural diagram of a conventional flying capacitor type three-level booster circuit;

fig. 2 is a structure diagram of a three-level booster circuit according to embodiment 1 of the present invention;

fig. 3 is a structure diagram of a three-level booster circuit according to embodiment 2 of the present invention;

fig. 4 is a structure diagram of a three-level booster circuit according to embodiment 3 of the present invention;

fig. 5 is a structure diagram of a three-level booster circuit according to embodiment 4 of the present invention;

fig. 6 is a structure diagram of a three-level booster circuit according to embodiment 5 of the present invention;

fig. 7 is a structure diagram of a three-level booster circuit according to embodiment 6 of the present invention;

fig. 8 is a structure diagram of a three-level booster circuit according to embodiment 7 of the present invention;

fig. 9 is a structure diagram of a three-level booster circuit according to embodiment 8 of the present invention;

fig. 10 is a structure diagram of a three-level booster circuit according to embodiment 9 of the present invention;

fig. 11 is a structure diagram of a three-level booster circuit according to embodiment 10 of the present invention;

fig. 12 is a structure diagram of a three-level booster circuit according to embodiment 11 of the present invention;

fig. 13 is a structure diagram of a three-level booster circuit according to embodiment 12 of the present invention;

fig. 14 is a structure diagram of a three-level booster circuit according to embodiment 13 of the present invention;

fig. 15 is a structure diagram of a three-level booster circuit according to embodiment 14 of the present invention;

fig. 16 is a structure diagram of a three-level booster circuit according to embodiment 15 of the present invention;

fig. 17 is a schematic structural view of an inverter according to embodiment 16 of the present invention;

fig. 18 is a schematic structural view of a photovoltaic power generation apparatus according to embodiment 17 of the present invention;

fig. 19 is a schematic structural diagram of a photovoltaic power generation system according to embodiment 18 of the present invention.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are preferred embodiments of the invention and should not be considered as excluding other embodiments. Based on the embodiment of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative work belong to the protection scope of the present invention.

In the claims, the specification and the drawings, unless otherwise expressly limited, the terms "first," "second," or "third," etc. are used for distinguishing between different elements and not for describing a particular sequence. In the claims, the specification and the drawings, the terms "including", "comprising" and variations thereof, if used, are intended to be inclusive and not limiting.

Example 1

Referring to fig. 2, embodiment 1 of the present invention provides a three-level boost circuit having an input terminal and an output terminal. The input end comprises a first input end and a second input end, and the output end comprises a first output end and a second output end.

Generally, the boost circuit of the present embodiment can be used in various applications, and thus, the input terminal thereof can be coupled to various power input devices to receive power input therefrom. The utility model discloses an in each embodiment, all use the application scene in photovoltaic power generation field to introduce as the example, therefore boost circuit's input coupling photovoltaic module PV1, it inputs boost circuit behind the conversion of light energy into direct current electric energy, through stepping up it in order to carry out effective utilization to light energy. The positive pole of photovoltaic module PV1 is connected to the first input terminal, and the negative pole is connected to the second input terminal. In other embodiments, it is also feasible to change the input relationship between the positive electrode and the negative electrode of the photovoltaic module and the boost circuit.

Furthermore, the utility model discloses a be equipped with output capacitance group between first output and the second output, it contains two at least output electric capacity (C2 and C3) that concatenate to constitute at least one output node between first output and second output, it is configured as the common point between each output capacitance. The utility model discloses an in each embodiment and corresponding attached drawing, all use three level boost circuit to introduce as the example, its output capacitance group contains two output capacitance that the appearance value is the same, makes output node's voltage is the median of first output and second output terminal voltage. In other embodiments, the output capacitor bank may also contain more output capacitors to form a multi-level boost circuit, in order to correspondingly achieve the object of the present invention, only the parameters of the corresponding devices of the present invention need to be adaptively adjusted. It should be noted that, when the three-level boost circuit according to the embodiment of the present invention is applied to the field of photovoltaic power generation, the output end is generally referred to as a bus, each output capacitor is referred to as a bus capacitor, and the output node is also referred to as a bus midpoint accordingly.

It should be understood that the present invention is not limited to the application scenario in the field of photovoltaic power generation, and therefore, the coupling form of the input end and the output end is not limited to the form of each specific embodiment herein.

In a specific structure of embodiment 1, the booster circuit further includes the following devices: the circuit comprises an inductor L1, a first controllable switch Q1, a second controllable switch Q2, a first capacitor C1, a first diode D1, a second diode D2 and a first TVS tube TVS 1.

The inductor L1 is used for cycling between electric energy storage and electric energy discharge during a working period, so as to boost the voltage at the input end and output the boosted voltage to the output end. In embodiment 1 of the present invention, the first branch, the second branch, the third branch, and the fourth branch are connected to correspond to other devices except the inductor L1.

The first controllable switch Q1 and the second controllable switch Q2 are connected in series to form a first branch, wherein a first end of the first controllable switch Q1 and a second end of the second controllable switch Q2 form a first end and a second end of the first branch, respectively. In this embodiment, the first controllable switch Q1 and the second controllable switch Q2 may be transistors, field effect transistors, or IGBTs. When a triode is adopted, the first ends of the first controllable switch Q1 and the second controllable switch Q2 are collectors, and the second ends are emitters; when a field effect transistor is adopted, the first ends of the first controllable switch Q1 and the second controllable switch Q2 are drains, and the second ends are sources; when IGBTs are used, the first ends of the first controllable switch Q1 and the second controllable switch Q2 are collectors, and the second ends are emitters.

The first diode D1 and the second diode D2 are connected in series to form a second branch circuit, wherein an anode of the first diode D1 and a cathode of the second diode D2 respectively form a first end and a second end of the second branch circuit.

The first capacitor C1 forms a third branch, and two ends of the third branch form a first end and a second end of the third branch, respectively.

The first TVS transistor TVS1 is configured as a unidirectional TVS transistor, which constitutes a fourth branch, and the negative and positive electrodes of which constitute the first and second ends of the fourth branch, respectively.

The following describes a specific connection relationship of each branch in the booster circuit of embodiment 1:

the first ends of the first branch and the second branch are connected with the first input end through the inductor L1, and the second ends of the first branch and the second branch are respectively connected with the second input end and the first output end. The second input end is also connected with the second output end.

The third branch has a first terminal connected to the common point of the first diode D1 and the second diode D2 in the second branch and a second terminal connected to the common point of the first controllable switch Q1 and the second controllable switch Q2 in the first branch. And the first end of the fourth branch is connected with the second end of the third branch, and the second end of the fourth branch is connected with the middle point NE of the bus.

After the above connection is performed to form the boost circuit of the present embodiment, each branch mainly achieves the following functions.

The first branch circuit comprising a controllable switch is used for controlling the on-off of each loop in the boosting circuit during normal operation, so that the inductor L1 is correspondingly in the state of storing electric energy and releasing electric energy, and the boosting process is completed. In this embodiment, the first controllable switch Q1 and the second controllable switch Q2 are various transistors, so as to control the on/off of the transistors rapidly and conveniently by electronic signals.

The first end and the second end of the second branch circuit point to the input end and the output end respectively, and the common point of two diodes in the second branch circuit is connected with the third branch circuit with a capacitance device, so that the one-way conduction characteristic of current is formed between the corresponding devices, and the electric energy is prevented from reversely flowing back to the input end to cause electric energy loss.

The first capacitor C1 in the third branch is used as a flying capacitor for storing and releasing electric energy during normal operation, and also plays a role in boosting the input voltage. In normal operation, the voltage of the first capacitor C1 is substantially kept near half the bus voltage due to its selection of capacitance, but still fluctuates due to the charging and discharging processes.

The fourth branch is used for establishing a charging loop of the first capacitor C1 when the boost circuit is powered on, so as to protect the second controllable switch Q2 from breakdown. Meanwhile, the TVS tube adopted by the circuit can also ensure that the fourth branch does not participate in the power consumption when the circuit normally works, and the working principle of the circuit will be detailed below.

Because the utility model discloses a boost circuit is at normal during operation, and its specific working process and the principle that steps up to input voltage have been for technical staff's in the field of common general knowledge, the utility model discloses just no longer describe repeatedly. The following describes how to prevent the second controllable switch Q2 from breaking down when the boost circuit is powered up, and to allow the bus capacitor to equalize voltage when the boost circuit is in normal operation.

Specifically, at power up, the first controllable switch Q1 and the second controllable switch Q2 are both in an off state, the voltage of the first capacitor C1 is zero, and since the input voltage is up to 1500V, two loops may be formed in the boost circuit when the clamping voltage of the first TVS transistor TVS1 is selected at a suitable value. The first loop is a charging loop formed by an input end through an inductor L1, a first diode D1 and a second diode D2 so as to charge a two-bus capacitor, and the second loop is a charging loop formed by an input end through an inductor L1, a first diode D1, a first capacitor C1, a first TVS tube TVS1 and a bus capacitor C3 so as to charge a first capacitor C1 and a bus capacitor C3. Since the capacities of the two bus capacitors are equal, after a certain time both the first capacitor C1 and the two bus capacitors will be charged to half the input voltage. At this time, the voltage at the point a (the second end of the third branch, the first end of the fourth branch) in the figure is stabilized at substantially half of the input voltage, that is, the voltages at the two ends of the first controllable switch Q1 and the second controllable switch Q2 are both half of the input voltage, so that when the first controllable switch Q1 and the second controllable switch Q2 are subjected to model selection, only a device with a voltage withstanding value slightly higher than half of the input voltage is basically needed, and when the input voltage of this embodiment reaches 1500V, the voltage withstanding value is about 800-900V, which meets the cost requirement of device model selection.

During normal operation, because the voltage across the first capacitor C1 is substantially maintained near the half-bus voltage, the maximum value of the voltage at the point a is only slightly higher than the half-bus voltage, when the clamping voltage of the first TVS tube TVS1 is selected to be a proper value, it can be ensured that the point a is not conducted to the bus midpoint NE, and the voltage at the point a is not transmitted to the bus midpoint NE through the first TVS tube TVS1, so that the voltage sharing of the bus capacitors is not affected. In this embodiment 1, the clamping voltage range of the TVS1 of the first TVS transistor may be about 100V, and the fourth branch is conducted from the first end to the second end during power-up, and cannot be conducted from the first end to the second end during normal operation.

Therefore, the embodiment of the utility model provides a 1 sets up first TVS pipe TVS1 on the fourth branch road, not only can prevent when the electricity that second controllable switch Q2 is punctured, can also guarantee simultaneously that this fourth branch road does not influence boost circuit's normal work for the voltage-sharing of each bus-bar electric capacity is controlled easily.

Examples 2 to 6

Referring to fig. 3-7, it corresponds to embodiments 2-6 of the present invention respectively, and it is improved on the basis of embodiment 1, and after embodiment 1 introduces the first TVS tube TVS1 configured as an unidirectional TVS tube, because it is equivalent to a common diode when working in the forward direction, under the condition of low input voltage, the bus midpoint voltage can be transmitted to the input end through the body diodes of the first TVS tube TVS1 and the first controllable switch Q1, which easily causes the problem of the electric shock accident.

In the embodiment 2 shown in fig. 3, the fourth branch is further provided with a third diode D3, the cathode of which is connected to the cathode of the first TVS tube TVS1, and the anode of which forms the first end of the fourth branch. In the case of the low input voltage, the bus midpoint voltage cannot be transmitted to the point a by the reverse cut-off of the third diode D3, and further cannot be transmitted to the input end by the body diode of the first controllable switch Q1, so as to solve the above problem. In addition, when the input voltage is 1500V, since the bus midpoint voltage is 750V, the withstand voltage value of the third diode D3 is only required to be greater than 750V, and the type selection is also easy and the cost is low.

In the embodiment 3 shown in fig. 4, the fourth branch is further provided with a second TVS tube TVS2 also configured as a unidirectional TVS tube, whose positive electrode is connected to the positive electrode of the first TVS tube TVS1, and whose negative electrode constitutes the second end of the fourth branch; the first TVS tube TVS1 and the second TVS tube TVS2 are both unidirectional TVS tubes. In the low input voltage condition, the fourth branch can be conducted because the bus midpoint voltage needs to be higher than the clamping voltage of the second TVS transistor TVS 2. Therefore, when the clamping voltage of the second TVS transistor TVS2 is selected to be higher than the bus midpoint voltage, the bus midpoint voltage cannot be transmitted to the input terminal, thereby solving the above problem; however, when the clamping voltage of the second TVS tube TVS2 cannot be selected to be higher than the bus midpoint voltage for some reason, in order to better solve the above problem, a current limiting resistor or, preferably, a third diode D3 in the same form as that of embodiment 2 may be provided on the fourth branch to constitute embodiment 4 shown in fig. 5.

Fig. 6 shows an embodiment 5, which directly configures the first TVS transistor TVS1 of the fourth branch as a bidirectional TVS transistor, the two ends of which respectively constitute the first end and the second end of the fourth branch. Embodiment 5 has the same principle as embodiment 3, but has the disadvantage that the bidirectional clamping voltage parameters of the bidirectional TVS transistor are the same, which is inconvenient for the design circuit to select the clamping voltage parameters. Thus, when its bi-directional clamping voltage cannot be selected to be higher than the bus midpoint voltage for some reason, a current-limiting resistor, or preferably a third diode D3 of the same form as in embodiment 2, may also be provided in the fourth branch to constitute embodiment 6 shown in fig. 7.

It should be noted that, in embodiments 2 to 6, since the fourth branch still has the characteristics of the first TVS transistor TVS1 in embodiment 1, the voltage-sharing of the bus capacitor is not affected when the boost circuit operates normally.

Examples 7 to 8

Referring to fig. 8 to 9, which correspond to embodiments 7 to 8 of the present invention, respectively, and which are improved on the basis of embodiment 2 shown in fig. 3, it is intended to solve the problem that the second diode D2 is easily broken down in the case of a low input voltage.

It can be seen that the circuit further comprises a fifth branch, in which a fourth diode D4 is arranged for clamping the common point of the first diode D1 and the second diode D2, when the input voltage between the first input terminal and the second input terminal is lower than the start-up voltage of the voltage booster circuit, i.e. at said low input voltage.

One end of the fifth branch is connected to a common point of the first diode D1 and the second diode D2, and the other end of the fifth branch may be connected to the second end of the fourth branch, or may be connected to a common point of the first TVS tube TVS1 and the third diode D3.

In embodiment 7 and embodiment 8 shown in fig. 8 and 9, respectively, in the case of the low input voltage, the bus midpoint voltage is loaded to the point C (the anode of the second diode D2) in the figure through the fourth diode D4, so that the voltage across the second diode D2 is clamped at half the bus voltage, and the second diode D2 is protected from breakdown, thereby facilitating the low-cost model selection thereof.

However, the above embodiment still has the problem that when the circuit normally works, the lower arm switching tube Q2 is turned on, and the flying capacitor is in the charging cycle, half bus voltage can charge the flying capacitor through the fifth branch, which also causes the problem of non-voltage-sharing of the bus capacitor; in addition, the fourth diode D4 is easily broken by the sudden change of the charging current, and the voltage of the flying capacitor C1 is deviated from the set value due to the presence of the abnormal charging circuit, which makes it difficult to control the voltage.

Examples 9 to 10

Referring to fig. 10-11, which correspond to embodiments 9-10 of the present invention, respectively, and are improved based on embodiment 7 shown in fig. 8 and embodiment 8 shown in fig. 9, respectively, to solve the problem of non-voltage-sharing of bus capacitors during normal operation due to the fourth diode D4 having the fifth branch.

The fifth branch is further provided with a third controllable switch K1, which is connected in series with the fourth diode D4. The third controllable switch K1 can be a relay, a contactor, a triode and other devices, and is preferably a normally closed relay. Correspondingly, the circuit further comprises a controller for controlling the third controllable switch K1 to be turned off when the circuit is operating normally, i.e. when the input voltage between the first input terminal and the second input terminal is higher than the start-up voltage of the voltage boosting circuit.

When the circuit normally works, the third controllable switch K1 is turned off, that is, the fifth branch is not turned on, so that the normal work of the circuit is not affected, and the problem of non-voltage-sharing of the bus capacitor does not exist. When the circuit is in the low input voltage condition, the third controllable switch K1 is closed, and the bus midpoint voltage is loaded to the point C in the figure (the anode of the second diode D2) through the third controllable switch K1 and the fourth diode D4, so that the voltage across the second diode D2 is clamped at the half bus voltage, the second diode D2 is protected from breakdown, and the low-cost model selection is facilitated.

It should be noted that, since the voltage at the point C may be higher than the bus midpoint voltage during normal operation, in the case of using the relay as the third controllable switch K1, since the withstand voltage value of the conventional relay is not high, the fourth diode D4 in embodiments 9 and 10 also plays a role of blocking the voltage at the point C from being transmitted to the bus midpoint NE during the normal operation of the boost circuit, thereby further ensuring the voltage equalization of the bus capacitor during the normal operation of the boost circuit and protecting the safety of the relay.

Examples 11 to 12

Referring to fig. 12-13, which correspond to embodiments 11-12 of the present invention, respectively, and which are improved on the basis of embodiment 7 shown in fig. 8 and embodiment 8 shown in fig. 9, respectively, in order to solve the problem of non-uniform voltage of the bus capacitors during normal operation due to the fourth diode D4 having the fifth branch.

In the embodiment 11 shown in fig. 12, the fifth branch is further provided with a second TVS transistor TVS2, the anode of which is connected to the anode of the fourth diode D4, and the cathode of which is connected to the second end of the fourth branch, i.e. the bus midpoint NE. In the embodiment 12 shown in fig. 13, the fifth branch is further provided with a second TVS transistor TVS2, the anode thereof is connected to the anode of the fourth diode D4, and the cathode thereof is connected to the common point of the first TVS transistor TVS1 and the third diode D3.

In the embodiments 11 and 12, in the case of the low input voltage, the clamping voltage of the second TVS transistor TVS2 is selected to be a proper value so that it can conduct reversely, so that the fifth branch can conduct from the bus midpoint NE to the C point, and the C point voltage clamp is set to a proper voltage value, so that the voltage borne across the second diode D2 is lower than the selected withstand voltage value, and therefore, the second diode D2 can still be ensured not to break down at normal cost, and the low-cost model selection thereof is facilitated.

Since the withstand voltage of the second diode D2 is generally 1200V when the input voltage reaches 1500V, the clamping voltage of the second TVS tube TVS2 is generally about 300V in embodiments 11 and 12. When the bus voltage is 1500V and the bus midpoint voltage is 750V, the voltage at point C is about 450V, and the voltage difference across the second diode D2 is around 1050V, so that it can still ensure that the second diode D2 is not broken down at the conventional cost. Obviously, in this case, the clamping voltage of the second TVS transistor TVS2 cannot be higher than 450V, otherwise, the protection effect of the second diode D2 at the low input voltage cannot be realized when the withstand voltage is selected to be 1200V.

In addition, since the second TVS2 can divide voltage when operating in reverse, the bus midpoint voltage will generate a voltage drop corresponding to the clamping voltage after passing through the second TVS2, so that the C-point voltage can be controlled to a level lower than the bus midpoint voltage, which provides a low voltage environment for solving the electric shock accident at the input end.

During normal operation, due to the existence of the second TVS transistor TVS2, the bus midpoint voltage needs to be higher than the C-point voltage by the clamping voltage of the second TVS transistor TVS2, so that the fifth branch is conducted from the bus midpoint NE to the C-point. However, during normal operation, the first capacitor C1 is in a periodic charging and discharging process, so that the voltage at the point C generally fluctuates from half-bus voltage to bus voltage, and the value of the voltage discharged by the first capacitor C1 is slightly lower than half-bus voltage. Therefore, in normal operation, as long as the clamping voltage of the second TVS transistor TVS2 is selected to be a proper value, the bus midpoint voltage cannot be transmitted to the point C, and the first capacitor C1 is not charged through the point C when the voltage at the point C is slightly lower than the voltage at the point C, so that the bus capacitor does not have the problem of uneven voltage due to the introduction of the fifth branch. In the embodiments 11 and 12, the clamping voltage of the TVS2 is generally selected to be about 300V, which meets the requirement of the TVS2 to cut off the transmission of the midpoint voltage of the bus to the point C during normal operation.

It should be noted that, since the voltage at the point C may be higher than the bus midpoint voltage during normal operation, the fourth diode D4 in embodiments 11 and 12 also plays a role of blocking the voltage at the point C from being transmitted to the bus midpoint NE during this condition, so as to further ensure that the bus capacitors can equalize voltage during normal operation of the voltage boost circuit.

Examples 13 to 14

Reference is made to fig. 14 to 15, which correspond to embodiments 13 to 14 of the present invention, respectively, and which are improved on the basis of embodiment 4 shown in fig. 5 and embodiment 6 shown in fig. 7, respectively. Because it has second TVS2 and is configured as the first TVS of two-way TVS pipe TVS1 respectively, therefore can directly form comparatively perfect solution on its basis, it not only can solve the easy problem of puncturing down of second diode D2 under the low input voltage condition, can also solve simultaneously because the former problem further causes the not voltage-sharing problem of bus capacitance when normal work.

In the embodiment 13 shown in fig. 14, the circuit further includes a fifth branch having a fourth diode D4 arranged thereon for clamping the common point of the first diode D1 and the second diode D2 when the input voltage between the first input terminal and the second input terminal is lower than the start-up voltage of the booster circuit. One end of the fifth branch is connected to a common point of the first diode D1 and the second diode D2, and the other end of the fifth branch is connected to a common point of the first TVS tube TVS1 and the second TVS tube TVS2 in the fourth branch.

In the embodiment 14 shown in fig. 15, the circuit further includes a fifth branch having a fourth diode D4 arranged thereon for clamping the common point of the first diode D1 and the second diode D2 when the input voltage between the first input terminal and the second input terminal is lower than the start-up voltage of the booster circuit. One end of the fifth branch is connected to a common point of the first diode D1 and the second diode D2, and the other end of the fifth branch is connected to a common point of the first TVS tube TVS1 and the third diode D3.

Since the fourth branch of the embodiment 13 is already provided with the second TVS2, and the first TVS1 of the fourth branch of the embodiment 14 is a bidirectional TVS, the principle of simultaneously solving the problem of the breakdown of the second diode D2 and the problem of the non-uniform voltage of the bus capacitor during normal operation caused by the introduction of the fourth diode D4 of the fifth branch is the same as that of the embodiments 11 and 12, and will not be described herein again.

It should be noted that the clamping voltage of the second TVS transistor TVS2 is also selected to be around 300V in embodiment 13, while the bidirectional clamping voltage of the second TVS transistor TVS2 configured as a bidirectional TVS transistor is also selected to be around 300V in embodiment 14. Also because of this, in embodiment 3 and embodiment 5, in order to enable them to simultaneously solve the problems mainly solved by embodiments 13 to 14, the corresponding clamp voltage cannot be selected to be higher than the bus midpoint voltage, which would otherwise result in the fifth branch not functioning to protect the second diode D2 in the case of a low input voltage.

It can be seen that in embodiment 13, the second TVS pipe TVS2 of fourth branch road can play the effect of ending or dividing the busbar midpoint voltage to a point and C point homoenergetic to play corresponding isolation or voltage protection effect, it does the utility model discloses a perfect solution of the voltage-sharing problem of bus capacitor of second diode D2 under the breakdown problem of second controllable switch Q2, the low input voltage condition when booster circuit was to last electricity and normal work had played the key effect.

In the embodiment 14, the bidirectional TVS tube is directly configured, and under the condition that the bidirectional clamping voltage parameter can meet the specific application requirement, the second end of the third branch and the anode of the second diode D2 can both perform the cutoff or voltage division function on the voltage of the output node, thereby performing the corresponding isolation or voltage protection function. Therefore, the breakdown problem of the second controllable switch Q2 and the breakdown problem of the second diode D2 under the condition of low input voltage during power-on are solved, the type selection meets the cost requirement, and devices of the newly introduced fourth branch and the fifth branch cannot influence voltage-sharing of the bus capacitor during normal work.

Example 15

Reference is made to fig. 16, which corresponds to embodiment 15 of the present invention, and which is improved on the basis of embodiment 14 shown in fig. 15. Example 14 although the C-point voltage is reduced to about 450V at low input voltage, as in examples 11-12, to provide a low voltage environment at C, the C-point voltage is still transmitted to the input terminal through the first capacitor C1 and the body diode of the first controllable switch Q1, and if the resistance of the input terminal is not large enough, a shock event may still occur. In order to make the operation of the input end safer, the fifth branch is also provided with a current limiting resistor R1 which is connected in series with the fourth diode D4 to limit the current in a safe range and reduce the probability of electric shock accidents at the input end.

It should be understood that the current limiting resistor R1 of this embodiment can be added to any of the fifth branches of embodiments 7-13 to achieve the same effect, especially in the case of embodiments 11, 12, and 13 that provides a low voltage environment at point C.

Examples 16 to 18

Specific applications of the above-described multilevel voltage boosting circuit are described below through embodiments 16 to 18, but the specific application scenarios are not limited to these embodiments.

Referring to fig. 17, embodiment 16 of the present invention provides an inverter device, which includes a preceding stage circuit and a subsequent stage inverter circuit. The front-stage circuit adopts the multi-level boost circuit in the technical scheme.

The multi-level booster circuit is used for boosting the voltage input from the input end of the multi-level booster circuit and then outputting the boosted voltage from the output end, and the input end of the inverter circuit is coupled with the output end of the multi-level booster circuit and used for inverting the direct current output by the inverter circuit into alternating current.

Referring to fig. 18, embodiment 17 of the present invention provides a photovoltaic power generation apparatus, which includes a photovoltaic module PV, a front-stage circuit, and a rear-stage circuit; the preceding stage circuit adopts the multi-level boost circuit according to the technical scheme.

The photovoltaic modules PV correspond to the multilevel booster circuits one by one and are coupled with the input ends of the multilevel booster circuits; the boosting circuit is used for boosting the output voltage of the photovoltaic module PV and then outputting the boosted output voltage to the post-stage circuit through the output end of the boosting circuit.

Referring to fig. 19, embodiment 18 of the present invention provides a photovoltaic power generation system, including at least two photovoltaic power generation apparatuses as provided in embodiment 17; the output ends of the front stage circuits of the photovoltaic power generation devices are connected in parallel and then connected to the rear stage circuit, so that the distributed photovoltaic power generation system is formed.

The apparatus and system of embodiments 16-18, which employ the multi-level boost circuit of the previous embodiments, inherit all the advantages of the boost circuit.

The description of the above specification and examples is intended to illustrate the scope of the invention, but should not be construed as limiting the scope of the invention. Modifications, equivalents and other improvements which may be made to the embodiments of the invention or to some of the technical features thereof by a person of ordinary skill in the art through logical analysis, reasoning or limited experimentation in light of the above teachings of the invention or the above embodiments are intended to be included within the scope of the invention.

Claims (13)

1. A multi-level booster circuit is provided with a first input end, a second input end, a first output end and a second output end, and comprises an inductor, a first controllable switch, a second controllable switch, a first capacitor, a first diode, a second diode and an output capacitor group; the method is characterized in that: the device also comprises a first TVS tube;

the first controllable switch and the second controllable switch are connected in series to form a first branch circuit, wherein a first end of the first controllable switch and a second end of the second controllable switch respectively form a first end and a second end of the first branch circuit;

the first diode and the second diode are connected in series to form a second branch circuit, wherein the anode of the first diode and the cathode of the second diode respectively form a first end and a second end of the second branch circuit;

the first capacitor forms a third branch, and two ends of the third branch respectively form a first end and a second end of the third branch;

the first TVS tube forms a fourth branch, and the negative electrode and the positive electrode of the first TVS tube respectively form a first end and a second end of the fourth branch;

the output capacitor group is connected with the first output end and the second output end and comprises at least two output capacitors connected in series to form at least one output node configured as a common point between the output capacitors;

the first ends of the first branch circuit and the second branch circuit are connected with a first input end through the inductor, and the second ends of the first branch circuit and the second branch circuit are respectively connected with a second input end and a first output end; the second input end is also connected with a second output end;

the first end of the third branch circuit is connected with the common point of the first diode and the second diode in the second branch circuit, and the second end of the third branch circuit is connected with the common point of the first controllable switch and the second controllable switch in the first branch circuit; and the first end of the fourth branch is connected with the second end of the third branch, and the second end of the fourth branch is connected with an output node.

2. The multilevel boost circuit of claim 1, wherein: the first TVS tube is a unidirectional TVS tube;

the fourth branch is also provided with a third diode, the cathode of the third diode is connected with the cathode of the first TVS tube, and the anode of the third diode forms the first end of the fourth branch.

3. The multilevel boost circuit of claim 1, wherein: the fourth branch is also provided with a second TVS tube, the anode of the second TVS tube is connected with the anode of the first TVS tube, and the cathode of the second TVS tube forms a second end of the fourth branch;

the first TVS tube and the second TVS tube are both unidirectional TVS tubes.

4. The multilevel boost circuit of claim 1, wherein: the first TVS tube is a bidirectional TVS tube, and two ends of the first TVS tube respectively form a first end and a second end of the fourth branch.

5. The multilevel boost circuit of claim 2, wherein: the voltage booster circuit further comprises a fifth branch circuit, wherein a fourth diode is arranged on the fifth branch circuit and used for clamping the common point of the first diode and the second diode when the input voltage between the first input end and the second input end is lower than the starting voltage of the voltage booster circuit;

the cathode of the fourth diode is connected with the common point of the first diode and the second diode, and the anode of the fourth diode is connected with the second end of the fourth branch or the common point of the first TVS tube and the third diode.

6. The multilevel boost circuit of claim 5, wherein: the fifth branch is also provided with one of a second TVS tube or a third controllable switch;

when the fifth branch is provided with a second TVS tube, the anode of the fifth branch is connected with the anode of the fourth diode, and the cathode of the fifth branch is connected with the second end of the fourth branch or the common point of the first TVS tube and the third diode;

when the fifth branch is provided with a third controllable switch, the third controllable switch is a normally closed relay; the circuit further comprises a controller for controlling the third controllable switch to be switched off when the circuit is in normal operation.

7. The multilevel boost circuit of claim 3, wherein: the fourth branch is also provided with a third diode, the cathode of the third diode is connected with the cathode of the first TVS tube, and the anode of the third diode forms the first end of the fourth branch;

the circuit also comprises a fifth branch circuit, wherein a fourth diode is arranged on the fifth branch circuit and is used for clamping the common point of the first diode and the second diode when the input voltage between the first input end and the second input end is lower than the starting voltage of the booster circuit;

the cathode of the fourth diode is connected with the common point of the first diode and the second diode, and the anode of the fourth diode is connected with the common point of the first TVS tube and the second TVS tube.

8. The multilevel boost circuit of claim 4, wherein: the fourth branch is also provided with a third diode, the cathode of the third diode is connected with one end of the first TVS tube, and the anode of the third diode forms the first end of the fourth branch;

the circuit also comprises a fifth branch circuit, wherein a fourth diode is arranged on the fifth branch circuit and is used for clamping the common point of the first diode and the second diode when the input voltage between the first input end and the second input end is lower than the starting voltage of the booster circuit;

the cathode of the fourth diode is connected with the common point of the first diode and the second diode, and the anode of the fourth diode is connected with the common point of the first TVS tube and the third diode.

9. The multilevel boost circuit of any of claims 5-8, wherein: and the fifth branch circuit is also provided with a current-limiting resistor which is connected in series with the fourth diode.

10. The multilevel boost circuit of any of claims 1-8, wherein: the output capacitor bank comprises two output capacitors with the same capacitance value.

11. An inverter device, characterized in that: the inverter comprises a rear-stage inverter circuit and a front-stage circuit; the pre-stage circuit employs a multi-level boost circuit as claimed in any one of claims 1 to 10;

the multi-level booster circuit is used for boosting the voltage input by the input end of the multi-level booster circuit and then outputting the boosted voltage from the output end of the multi-level booster circuit;

the input end of the inverter circuit is coupled with the output end of the multi-level booster circuit and used for inverting the direct current output by the inverter circuit into alternating current.

12. A photovoltaic power generation device characterized in that: the photovoltaic module comprises a photovoltaic module, a front-stage circuit and a rear-stage circuit; the pre-stage circuit employs a multi-level boost circuit as claimed in any one of claims 1 to 10;

the photovoltaic components correspond to the multilevel booster circuits one by one and are coupled with the input ends of the multilevel booster circuits; the multi-level boosting circuit is used for boosting the output voltage of the photovoltaic module and then outputting the boosted output voltage to the post-stage circuit through the output end of the multi-level boosting circuit.

13. A photovoltaic power generation system, characterized in that: comprising at least two photovoltaic power generation devices according to claim 12; the output ends of the front-stage circuits of the photovoltaic power generation devices are connected in parallel and then connected to the rear-stage circuit.

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