CN111146964A

CN111146964A - Multi-voltage solar inverter

Info

Publication number: CN111146964A
Application number: CN201811373487.2A
Authority: CN
Inventors: 林福泳
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-11-03
Filing date: 2018-11-03
Publication date: 2020-05-12

Abstract

A solar inverter is composed of a voltage reduction circuit and a load full-bridge circuit thereof, wherein the output of the full-bridge circuit is connected with an alternating current load. The voltage dropping circuit consists of two inductors and two switching tubes. The full-bridge circuit consists of four switching tubes. The control circuit is composed of a fast comparator, a preset current waveform generator, a field effect transistor driver and a delay circuit or is composed of a sine wave PWM circuit.

Description

Multi-voltage solar inverter

Technical Field

The invention belongs to an inverter, and particularly relates to a non-isolated inverter.

Background

The solar inverter generally comprises a booster circuit, a transformer conversion circuit and a conversion circuit or comprises the booster circuit and a chopper circuit, wherein the transformer conversion circuit comprises four open tubes and a high-frequency transformer, the transformer conversion circuit converts the output electric energy of the booster circuit into half sine wave electric energy, and the conversion circuit comprises four open tubes, the conversion circuit converts the half sine wave electric energy output by the transformer conversion circuit into alternating current sine wave electric energy. The structure has the advantages of complex circuit, large loss, high cost and mature and reliable circuit. The non-isolated solar inverter consists of a booster circuit, four switching tubes and a chopper circuit consisting of inductors. The principle is that the boosted direct-current voltage is converted into alternating-current sine-wave electricity through a chopper circuit. The switch tube with the structure has the defects that the IGBT is required to be used, the switching speed of the IGBT is low, the switching frequency is low, a control circuit is complex, and the requirement on an output filter circuit is high. The novel puff holding structure solves the defects and has the advantages of simple structure, efficiency and the like. It is composed of a multi-step-down circuit and a bridge type conversion circuit.

Disclosure of Invention

The inverter consists of a voltage reduction circuit and a bridge type conversion circuit, the input of the inverter is connected with the output direct current voltage of the voltage boosting circuit, and the direct current voltage is higher than the online alternating current peak value. The working principle is as follows, the step-down circuit compares with the output current of establishing the system through detecting output current, according to the turn-off and the switch-on of error signal control step-down switch pipe of comparison for the step-down circuit outputs suitable half-wave alternating current power. The bridge type conversion circuit converts half-wave alternating current electric energy into sine wave alternating current electric energy. The present invention is not limited to the above specific circuits, and according to the principle of the present invention, not only the output current is detected and compared with the set output current to generate the control signal for controlling the output of the step-down circuit, but also various circuits can be designed, and all the circuits are within the protection scope of the present invention.

Drawings

Fig. 1 shows an inverter according to the present invention.

Fig. 2 is another inverter of the present invention.

Fig. 3 is yet another inverter of the present invention.

Fig. 4 is an analog half-wave current waveform (sinusoidal current forming circuit output).

Fig. 5 is an analog full-wave current waveform (output of the full-bridge circuit).

Fig. 6 is a two buck circuit inverter.

Fig. 7 is a multiple two voltage input inverter.

Fig. 8 shows a switching tube in series with a diode.

Circuit Structure figure 1

The first switch tube Q10, the second switch tube Q11, the third switch tube Q12, the first inductor L10, the second inductor L11, the resistor R10 and the control circuit form a half-wave sinusoidal current forming circuit. The fourth switch tube Q13, the fifth switch tube Q14, the sixth switch tube Q15 and the seventh switch tube Q16 form a conversion circuit from direct current half-wave sinusoidal current to alternating current sinusoidal current, namely a full-bridge circuit, and the resistor R10 is connected with the switch tube Q10 to serve as a signal for detecting output current.

Working principle (half-wave sine current forming circuit)

When the preset current is higher than the detection current of the resistor R10, the comparator sends a signal to turn off the third switch tube Q12, turn on the first switch tube Q10 and the second switch tube Q11 for the FET driver through some delay, at this time, the direct current passes through the first switch tube Q10, the second switch tube Q11, the resistor R10, the first inductor L10 and the second inductor L11 to supply power to the full bridge circuit, and output alternating current through the full bridge circuit, when the currents of the first inductor L10 and the second inductor L11 increase to the preset current, the comparator sends a signal to the FET driver, so that the FET driver turns off the first switch tube Q10 and the second switch tube Q11, turns on the third switch tube Q12, at this time, the electric energy of the first inductor L10 and the second inductor L11 supplies power to the full bridge circuit through the switch tube Q13 and outputs alternating current through the circuit, at this time, the current of the first inductor L10 and the second inductor L11 starts to decrease, the current reduction is related to the alternating current instantaneous voltage, and the higher the voltage is, the larger the current reduction is; the current decrease is related to the delay time, i.e., the current decrease is larger the longer the delay time. The delay time also determines whether the inductor is in a continuous working current state or in an intermittent working current state. After the first switch tube Q10 and the second switch tube Q11 are turned on, the currents in the first inductor L10 and the second inductor L11 start to increase; the time for increasing the current to the given current is related to the ac instantaneous voltage, i.e., the higher the voltage, the longer the current of the first inductor L10 and the second inductor L11 increases to the given current; there are two main factors, the higher the voltage, the greater the current reduction; the higher the two voltages, the smaller the voltage difference across the inductor. The output power can be controlled by controlling the amplitude of the pre-given current or controlling (decreasing or increasing) the resistance of the detection resistor R10.

The control method of the first switch tube Q10 and the second switch tube Q11 can also adopt a PWM control method; that is, when the external circuit voltage is in a peak, the pulse width is maximum, the peak pulse width is reduced along with the reduction of the external circuit instantaneous voltage, that is, when the external circuit instantaneous voltage is zero, the peak pulse width is zero, and the control method of the third switching tube Q12 is opposite to the control method of the first switching tube Q10 and the second switching tube Q11, that is, when the external circuit instantaneous voltage is zero, the peak pulse width is maximum; when the external circuit voltage is in a peak, the peak pulse width is minimum.

Fig. 2 is substantially the same as fig. 1, and a diode D10 is used to replace the third switching tube Q12.

The difference between fig. 3 and fig. 2 is that a small flyback transformer is added to prevent a large current from flowing through the diode D10 in the reverse direction at the moment when the switching transistors Q10 and Q11 are turned on, because the initial current of the primary of the flyback transformer is zero, and when the switching transistors Q10 and Q11 are turned off, the flyback transformer discharges the primary power of the flyback transformer to the capacitor C10 through the secondary thereof.

Fig. 6 is composed of two sets of voltage reduction circuits and a full-bridge circuit, each set of voltage reduction circuits has a corresponding controller, and the structure can be expanded into a plurality of sets of voltage reduction circuits and a full-bridge circuit to form the inverter. The circuit structure has the advantages that the parameter requirement on the switching tube of the voltage reduction circuit can be reduced, and meanwhile, if the corresponding controller of the voltage reduction circuit uses different delay time or the corresponding inductor of the voltage reduction circuit uses different parameters of inductors, the output ripple can be reduced.

If the same sine wave and different time are used in the PWM control method, the triangular wave with the same frequency is used for controlling different groups of voltage reduction circuits in a dividing mode, and output ripples are reduced.

FIG. 7 shows a two-voltage input buck circuit, where V2 > V1, and when the AC instantaneous voltage > V1, the switches Q10, Q11 are on and Q20 is off; when the alternating current instantaneous voltage is less than the voltage V1, the switching tube Q20 and the switching tube Q11 work, and the switching tube Q10 is closed; at the instant when the switching tube Q20 is turned on, the voltage between the poles of the switching tube Q10 does not change from the off state (the voltage of the inter-pole capacitor), and the switching tube Q10 is not turned on.

Fig. 8 shows a diode and a switch tube connected in series, which can be used to replace the third switch tube Q12 in fig. 1 and the diode D10 in fig. 3 and 2.

Claims

1. The inverter consists of a voltage reduction circuit, a full-bridge circuit and a controller, wherein the input of the voltage reduction circuit is connected with the power supply, the output of the voltage reduction circuit is connected with the input of the full-bridge circuit, and the output of the full-bridge circuit is used as the output of the inverter; the controller comprises a comparator, a delayer, a driver and a preset current signal generating circuit; another type of controller is a PWM control circuit.

2. The inverter of claim 1, wherein the voltage reduction circuit comprises a first switch, a second switch, a resistor, a capacitor, a flyback transformer, a first diode, a second diode, a first inductor, and a second inductor; the first switch tube, the primary of the flyback transformer and the first inductor are connected in series, wherein the first switch tube is connected with the positive terminal of the power supply, and the first inductor is used as the output positive terminal of the voltage reduction circuit; the second inductor, the second switch tube and the resistor are connected in series, the resistor is connected with the negative pole end of the power supply, and the second inductor is used as the output negative pole end of the voltage reduction circuit; the cathode of the first diode is connected with the junction of the primary of the flyback transformer and the first inductor, the anode of the first diode is connected with the junction of the second inductor and the second switch tube, and the secondary of the flyback transformer and the second diode are connected in series and connected to the two output ends of the capacitor and the voltage reduction circuit.

3. The inverter of claim 1, wherein the voltage step-down circuit comprises a first switch tube, a second switch tube, a relay circuit, a resistor, a first inductor and a second inductor, the first switch tube is connected in series with the first inductor, wherein the first switch tube is connected to the positive power supply terminal, and the first inductor is used as the positive output terminal of the voltage step-down circuit; the second inductor, the second switch tube and the resistor are connected in series, wherein the resistor is connected with the negative pole end of the power supply, and the second inductor is used as the output negative pole end of the voltage reduction circuit; the relay circuit is provided with two terminals, one terminal of the relay circuit is connected with the first switch tube and the first inductor, and the other terminal of the relay circuit is connected with the second inductor and the second switch tube; the relay circuit has three types, one is a diode, the other is a switch tube, and the other is a switch tube connected with a diode in series.

4. The inverter of claim 1, wherein the full bridge circuit comprises a fourth switching transistor, a fifth switching transistor, a sixth switching transistor, and a seventh switching transistor, wherein the fourth switching transistor is connected in series with the fifth switching transistor, and the sixth switching transistor is connected in series with the seventh switching transistor; the fourth switching tube is connected with the sixth switching tube, and the fifth switching tube is connected with the seventh switching tube; the fourth switching tube and the sixth switching tube are used as first inductors of which the input anodes are connected with the voltage reduction circuit, and the fifth switching tube and the seventh switching tube are used as second inductors of which the input cathodes are connected with the voltage reduction circuit; and the joint of the fourth switching tube and the fifth switching tube and the joint of the sixth switching tube and the seventh switching tube are used as alternating current output ends.

5. The inverter of claim 1, wherein the control circuit comprises a fast comparator, a delay circuit, a fet driver, and a predetermined current signal generating circuit.

6. An inverter according to claim 1, 2 or 3, wherein the control circuit comprises a PWM control circuit.

7. An inverter according to claim 1, 2, 3, 5 wherein the comparator compares the predetermined current signal with the signal on the resistor and generates a control signal, and when the predetermined current signal is less than the signal on the resistor, the control signal turns off the first switch tube and the second switch tube and turns on the relay circuit; when the preset current signal is larger than the signal on the resistor, the signal turns on the first switch tube and the second switch tube through a little delay, and the relay circuit is turned off.

8. An inverter as claimed in claim 1, 2, 3 or 5 wherein the comparator compares the predetermined current signal with the resistive signal and generates the control signal, the predetermined current signal being less than the resistive signal and turning off the first switch and the second switch with a small delay to turn on the relay circuit, and the predetermined current signal being greater than the resistive signal and turning on the first switch and the second switch with a small delay to turn off the relay circuit.

9. An inverter according to claims 1 and 3, wherein the step-down circuit has two paths of different voltage inputs, a first path and a second path; the first path of input voltage is greater than the second path of input voltage; the first route is connected with the first inductor through the first switch tube, and the second route is connected with the first inductor through the tenth switch tube and the third triode in series; when the alternating current instant voltage is larger than the second path of input voltage, the first path of input voltage provides electric energy, namely the first switch tube and the second switch tube work; when the alternating current instant voltage is less than the second path of input voltage, the second path of input voltage provides electric energy, and the tenth switching tube and the second switching tube work.

10. An inverter according to claims 1, 3 and 4, characterized by comprising more than two sets of buck circuits and a full bridge circuit; the first group of voltage reduction circuits comprise a first switch tube, a second switch tube, a first diode, a first resistor, a first inductor and a second inductor; the second group of voltage reduction circuits comprises an eighth switch tube, a ninth open tube, a second diode, a second resistor, a third inductor and a fourth inductor.