Boost circuit of photovoltaic inverter

Abstract

The boost circuit of the photovoltaic inverter comprises a first boost branch circuit, the first boost branch circuit comprises a switch Q1 and an inductor L1, the boost circuit further comprises a second boost branch circuit, the second boost branch circuit comprises a switch Q2 and an inductor L2, the inductor L2 is connected with the inductor L1 in parallel, the switch Q2 is connected with the switch Q1 in a homopolar parallel mode, the power of the switch Q2 is the same as that of the switch Q1, and the inductor L2 is connected with the switch Q2. And the control end of the switch Q1 and the switch Q2 are also connected with a driving unit for controlling the switch Q1 and the switch Q2 to be switched on alternately. The alternating conduction of the power switch tubes S1 and S2 not only increases the voltage gain, but also reduces the current ripples on the input inductor, but the voltage stress of the output diode D is higher, and the voltage stress of the power diode D can be reduced by arranging the diode D'in parallel.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of power electronics, specifically relates to a boost circuit suitable for high gain photovoltaic photovoltaic inverter. BACKGROUND

[0002] The non-isolated photovoltaic inverter includes a DC-DC boost circuit, and the voltage gain of the existing boost circuit is small and the current ripple on the input inductor L is large. The diode D also has a reverse recovery problem, which not only increases the loss of the diode, but also causes a large electromagnetic interference. When the frequency increases, the switching and conduction are frequent, the loss is more serious, the contradiction is more prominent, the diode is seriously heated and cannot be used, and the current ripple on the inductor is too large, which causes a large loss to the switching tube. SUMMARY

[0003] To solve the above technical problems, the utility model provides the following:

[0004] A boost circuit of a photovoltaic inverter, comprising a first boost branch, the first boost branch comprising a switch Q1 and an inductor L1, further comprising: a second boost branch, the second boost branch comprising a switch Q2 and an inductor L2, the switch Q2 being parallelly connected with the switch Q1 with the same polarity and the same power as the switch Q1, the control end of the switch Q1 and the switch Q2 further connecting a driving unit for controlling the switches Q1 and Q2 to alternately conduct.

[0005] Further, a diode D' is parallelly connected with the diode D in the boost circuit, the diode D' having the same power and conduction direction as the diode D. The diode D' is used to reduce the voltage stress of the diode D.

[0006] Further, the switching period of the controllable switch is much larger than the discharge time of the capacitor.

[0007] Further, the switch is a high-power switching tube, the switching tube is a MOS tube, and the MOS tube comprises a drain pin, a source pin and a gate pin.

[0008] Further, the driving unit comprises a switching tube S1, a diode D2, resistors R1, R2 and R3.

[0009] The first end of the R2 is connected with the switching tube S1 and the cathode of the diode D2, and the second end is connected with the control end of the switch Q1, the first end of the resistor R1 and the first end of the resistor R3.

[0010] The second end of the R3 is grounded.

[0011] The diode D2 is connected with the resistor R1 in series to form a current interruption branch.

[0012] The current interception branch is connected in parallel with the resistor R2.

[0013] Further, the switch tube S1 is a high-power switch tube, and the switch tube is a MOS tube, including a drain pin, a source pin and a gate pin.

[0014] Further, the switch Q1 is an insulated gate bipolar transistor, including a gate, a collector and an emitter.

[0015] The utility model discloses the beneficial effect lies in: through adopting double boost branch design, namely first boost branch and second boost branch, respectively by switch Q1 and inductance L1, and switch Q2 and inductance L2 are formed, and switch Q1 and Q2 alternate conduction, realize the remarkable promotion of voltage gain.This design not only effectively reduces the current ripple on input inductance L, but also optimizes the performance of the whole boost circuit.Meanwhile, through parallel diode D', further reduce the voltage stress of original diode D, thereby reduce the loss and electromagnetic interference of diode. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Prior boost circuit diagram;

[0017] Figure 2 The utility model discloses the circuit of embodiment Figure 1 ;

[0018] Figure 3 The utility model discloses the circuit of embodiment Figure 2 ;

[0019] Figure 4 The utility model discloses the partial circuit diagram of embodiment;

[0020] Figure 5 The utility model discloses the circuit of embodiment Figure 3 ;

[0021] Figure 6 The utility model discloses the circuit of embodiment Figure 4 . DETAILED DESCRIPTION

[0022] The following embodiments further illustrate the content of the utility model, but should not be understood as limiting the utility model. The modification or replacement of the method, step or condition of the utility model without departing from the spirit and essence of the utility model belongs to the range of the utility model.

[0023] In some embodiments, as shown in Figure 1 、 Figure 2 and Figure 3 :

[0024] A boost circuit of a photovoltaic inverter, comprising a first boost branch, the first boost branch comprising a switch Q1 and an inductor L1, further comprising: a second boost branch, the second boost branch comprising a switch Q2 and an inductor L2, the switch Q2 being in parallel with the switch Q1 and having the same polarity and power as the switch Q1, and the control end of the switch Q1 and the switch Q2 being connected to a driving unit for controlling the switch Q1 and the switch Q2 to alternately conduct.

[0025] In these embodiments:

[0026] A switching DC boost circuit, which can make the output voltage higher than the input voltage. Mainly used in DC motor drive, single-phase power factor correction (PFC) circuit and other AC / DC power supply.

[0027] The boost process is an energy transfer process of an inductor. When charging, the inductor absorbs energy, and when discharging, the inductor releases energy. If the capacitance is large enough, a continuous current can be maintained at the output end during discharging. If this on-off process is repeated continuously, a voltage higher than the input voltage can be obtained across the capacitor.

[0028] As shown in Figure 3 , the driving unit controls the switch Q1 and the switch Q2 to alternately conduct and turn off. When the switch Q1 is on and the switch Q2 is off, the first boost branch is on, the inductor L1 is charged, and the electrical energy is stored in the inductor L1. At this time, the inductor L2 is in a discharging state, and the previously stored electrical energy is released to the load through the second boost branch. When the switch Q1 is off and the switch Q2 is on, the situation is reversed, the inductor L2 is charged, and the inductor L1 is discharged. This alternating on-off mode realizes continuous energy transfer and gradual voltage increase. During charging, the switch is closed, at this time, the input voltage flows through the inductor. The diode prevents the capacitor from discharging to ground. Since the input is DC, the current flowing through the inductor increases linearly at a certain ratio, which is related to the size of the inductor. As the inductor current increases, some energy is stored in the inductor.

[0029] Due to the current holding characteristic of the inductor, when the switch on the corresponding branch is turned off, the current flowing through the inductor will not immediately become 0, but will slowly change from the value at the end of charging to 0. The original circuit has been disconnected, so the inductor can only discharge through the new circuit, i.e. the inductor starts to charge the capacitor, and the voltage across the capacitor rises. At this time, the voltage has already risen above the input voltage. At this time, the boost is complete.

[0030] The alternating conduction of the power switches S1 and S2 not only increases the voltage gain, but also reduces the current ripple on the input inductor, but the voltage stress of the output diode D is relatively high.

[0031] In some embodiments, as shown in Figures 4-6 , the boost circuit of the photovoltaic inverter further comprises:

[0032] Diode D', which is the same power as diode D in boost circuit, the same direction, and parallel to diode D.

[0033] In these embodiments:

[0034] The voltage stress of single output diode D is relatively high, and the parallel diode D' can reduce the voltage stress of power diode D. Diode D' can be the same model as diode D2.

[0035] In some embodiments, as shown in Figure 5 and Figure 6 :

[0036] The boost circuit of the photovoltaic inverter, the driving unit comprises: switch tube S1, diode D2, resistor R1, resistor R2, resistor R3;

[0037] The first end of R2 is connected with the switch tube S1 and the cathode of diode D2, and the second end is connected with the control end of switch Q1, the first end of resistor R1, and the first end of resistor R3;

[0038] The second end of R3 is grounded;

[0039] Diode D2 is connected in series with resistor R1 to form a switch Q1 current interruption branch;

[0040] The current interruption branch is connected in parallel with the resistor R2.

[0041] In these embodiments: the control switch tube S1 controls the switch Q1 to be off for a time greater than the inductance response time T, and controls the switch Q1 and the switch Q2 to be turned on alternately.

[0042] In order to realize the boost control of photovoltaic array and the constant voltage control of load, the voltage of photovoltaic array and the voltage of load terminal are closed-loop controlled at the same time, which requires adjusting the duty cycle and the switching frequency at the same time, so as to control the voltage after the boost of photovoltaic array.

[0043] In some embodiments, as shown in Figures 1-6 :

[0044] The boost circuit of the photovoltaic inverter, the switching period of switch Q1 is much greater than the discharge time of capacitor C in boost circuit

[0045] In some embodiments, the switch is a high-power switch tube, and the switch tube is a MOS tube, which includes a drain pin, a source pin, and a gate pin.

[0046] In some embodiments, the boost circuit of the photovoltaic inverter, the switch Q1 is an insulated gate bipolar transistor, comprising a gate, a collector and an emitter.

[0047] In some embodiments, the boost circuit of the photovoltaic inverter, the driving unit further comprises:

[0048] The switch tube S2, the diode D3, the resistor R4, the resistor R5, and the resistor R6;

[0049] The first end of the R5 is connected with the switch tube S2 and the cathode of the diode D3, and the second end is connected with the control end of the switch Q2, the first end of the resistor R4, and the first end of the resistor R6;

[0050] The second end of the R6 is grounded;

[0051] The diode D3 and the resistor R4 are connected in series to form a current interruption branch of the switch Q2;

[0052] The current interruption branch of the Q2 is connected in parallel with the resistor R5.

[0053] In these embodiments:

[0054] The alternating conduction of the power switch tubes S1 and S2 increases the voltage gain and reduces the current ripple on the input inductor, but the voltage stress of the output diode D is relatively high.

[0055] The selection of the components is not limited, and the optimization is as follows: an IGBT (such as Infineon IKW50N65EH5) with 650V and 50A is adopted, and a fast recovery diode (such as VS-EPH6007L-N3) with 650V and 60A is adopted.

[0056] Although the utility model has been described in detail above by general description, specific embodiments and tests, some modifications or improvements can be made on the basis of the utility model, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not deviating from the spirit of the utility model all belong to the scope of protection required by the utility model.

Claims

1. A boost circuit of a photovoltaic inverter, comprising a first boost branch, the first boost branch comprising a switch Q1 and an inductance L1, characterized in that, Also include: Second boost branch, the second boost branch includes switch Q2 and inductance L2, the inductance L2 is parallelly connected with the inductance L1, the switch Q2 is parallelly connected with the switch Q1 same polarity, and the switch Q1 control end and the switch Q2 are still connected drive unit, for controlling switch Q1 and Q2 alternate conduction.

2. The boost circuit of a photovoltaic inverter according to claim 1, characterized in that, The second boost branch further includes: Diode D', the diode D' is same power with diode D in first boost branch, and the conduction direction is same, and is parallelly connected with diode D.

3. The boost circuit of a photovoltaic inverter according to claim 1, characterized in that, The drive unit includes: switch tube S1, diode D2, resistance R1, resistance R2, resistance R3; The R2 first end is connected with the switch tube S1 and diode D2 cathode, and the second end is connected with the switch Q1 control end, resistance R1 first end, resistance R3 first end; The R3 second end is grounded; The diode D2 is connected with resistance R1 in series, and constitutes the switch Q1 cut-off branch; The cut-off branch is connected with the resistance R2 in parallel.

4. The boost circuit of a photovoltaic inverter according to claim 1, characterized in that, The switch cycle of the switch Q1 is far greater than the discharge time of the capacitor C in boost circuit.

5. The boost circuit of a photovoltaic inverter according to claim 3, characterized in that, The switch tube S1 is a high-power switch tube, and the switch tube is MOS tube, including: drain pin, source pin, gate pin.

6. The boost circuit of a photovoltaic inverter according to claim 1, characterized in that, The switch Q1 is an insulated gate bipolar transistor, including gate, collector and emitter.

7. The boost circuit of a photovoltaic inverter according to claim 1, characterized in that, The drive unit further includes: Switch tube S2, diode D3, resistance R4, resistance R5, resistance R6; The R5 first end is connected with the switch tube S2 and diode D3 cathode, and the second end is connected with the switch Q2 control end, resistance R4 first end, resistance R6 first end; The R6 second end is grounded; The diode D3 is connected with resistance R4 in series, and constitutes the switch Q2 cut-off branch; The Q2 cut-off branch is connected with the resistance R5 in parallel.

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