High-boost photovoltaic optimizer circuit structure and control method thereof

Abstract

The invention discloses a high-boost photovoltaic optimizer circuit structure and a control method thereof. The circuit is constructed by combining an interleaved Boost circuit, a switched capacitor circuit and a resonant circuit. Compared with a traditional Boost converter, the boost capability of the circuit is greatly improved; secondly, through introduction of the resonant element, zero-voltage switching-on of part of the switching tubes and zero-current switching-off of part of the diodes are realized, and the efficiency of the circuit is improved; and thirdly, the filter inductor and the resonant inductor are integrated in the transformer, so that the integration level of the circuit is improved.

Description

High-voltage photovoltaic optimizer circuit structure and control method Technical Field Background Technology

[0001] Background Art This invention relates to a high-voltage photovoltaic converter circuit structure and its control method, belonging to the field of power electronic conversion and power supply systems, and particularly to the field of DC-DC power conversion technology.

[0002] In recent years, the rapid development of photovoltaic power generation systems has placed higher demands on the boost capability, efficiency, and reliability of front-end DC / DC boost converters. Traditional boost converters have limited application scope due to their large input current ripple and limited boost ratio. To address this, researchers have proposed interleaved parallel boost converters. While the interleaved parallel boost converter structure can achieve lower input current ripple, it still suffers from limited boost capability and conversion efficiency, making it difficult to meet the requirements of photovoltaic systems for high boost ratio and high efficiency. To solve these technical problems, this invention proposes a high-boost photovoltaic booster circuit structure and its control method. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention proposes a high-boost photovoltaic (PV) converter circuit structure and its control method. While retaining the low input current ripple of the interleaved parallel Boost circuit, this invention achieves zero-voltage turn-on for half of the switching transistors and zero-current turn-off for most diodes, while significantly improving the circuit's boost capability. The technical solution adopted in this invention is as follows: the high-boost PV converter circuit consists of a DC input voltage source (V... IN ), First switch (S1), Second switch (S2), Third switch (S3), Fourth switch (S4), First diode (D1), Second diode (D2), Third diode (D3), Transformer (T1), Transformer (T2), First inductor (L) m1 ), second inductor (L m2 ), capacitor (C) o ), first capacitor (C1), second capacitor (C2), resonant capacitor (C) r ), resonant inductor (L) r It consists of a DC input voltage source (V) and a load (Z). IN The positive terminal of the first inductor (L) is connected to the same-name terminal of the primary winding of transformer (T1), the same-name terminal of the primary winding of transformer (T2), and the first inductor (L). m1 One end of the second inductor (L) and the second inductor (L) m2 One end of the transformer (T1); the non-identical terminal of the primary side of the transformer (T1) is connected to the first inductor (L). m1The other end of the transformer (T2), the source of the first switching transistor (S1), the drain of the second switching transistor (S2), and one end of the second capacitor (C2); the non-same-name terminals of the primary side of the transformer (T2) are connected to the second inductor (L). m2 The other end of the circuit, the source of the third switch (S3) and the drain of the fourth switch (S4) and the resonant capacitor (C) r One end of the first switch (S1) and the third switch (S3) are connected together to the anode of the first diode (D1) and one end of the first capacitor (C1); the sources of the second switch (S2) and the fourth switch (S4) are connected together to the DC input voltage source (V). IN The negative terminal, the other end of the first capacitor (C1), and the capacitor (C) o One end of the first diode (D1) is connected to the other end of the second capacitor (C2) and the anode of the second diode (D2); the cathode of the second diode (D2) is connected to the anode of the third diode (D3) and the non-same-name terminal of the secondary side of the transformer (T2); the cathode of the third diode (D3) is connected to the capacitor (C2). o The other end of the transformer (T1) and the other end of the load (Z); the same-name terminal of the secondary side of transformer (T2) is connected to the same-name terminal of the secondary side of transformer (T1); the non-same-name terminal of the secondary side of transformer (T1) is connected to the resonant inductor (L). r One end of the resonant inductor (L) r The other end of the capacitor is connected to the resonant capacitor (C). r The other end of the circuit; based on the control method of the above-mentioned high-voltage photovoltaic inverter circuit, the characteristic is that: the control circuit adopts a fixed-frequency duty cycle adjustment method, the control loop is a single voltage loop control, and the output voltage sampling value v o With output voltage reference v o_ref The voltage error value is obtained by comparison, and the voltage error value is processed by a PI regulator to obtain the modulation signal v. ea Modulation signal v ea respectively with triangular carrier v T1 v T2 When comparing, when v ea >v T1 The second switch (S2) is turned on; when v ea <=v T1 The first switch (S1) is turned on; when v ea >v T2 The fourth switch (S4) is turned on; when v ea <=v T2 The third switch (S3) is turned on; to reduce the total input current ripple of the circuit, the triangular carrier wave v T1 and v T2A triangular carrier wave with a 180° phase difference is used; to achieve zero-current turn-off of the second diode (D2) and the third diode (D3), the resonant inductor (L... r ) and resonant capacitor (C r The resonant period T r It must be less than the duty cycle D and the switching period T s The product DT s .

[0004] This invention provides a high-voltage photovoltaic booster circuit structure and its control method, which has the following advantages compared with the prior art: (1) This invention significantly improves the boost capability of the circuit; (2) By controlling the resonant period, this invention achieves zero-voltage turn-on of the first switch (S1) and the third switch (S3), and zero-current turn-off of the second diode (D2) and the third diode (D3), thereby improving the efficiency and reliability of the circuit; (3) Inductor L m1 L m2 It can be partially or entirely achieved by the magnetizing inductance of transformers T1 and T2, and the resonant inductance L r It can be partially or entirely achieved by the leakage inductance of transformers T1 and T2, reducing the size and number of circuit components. Attached Figure Description

[0005] Figure 1 is a schematic diagram of a high-voltage photovoltaic power amplifier circuit proposed in this invention; Figure 2 is a closed-loop control method for a high-voltage photovoltaic power amplifier circuit proposed in this invention; Figure 3 is a key waveform of a high-voltage photovoltaic power amplifier circuit proposed in this invention when the duty cycle D < 0.5; Figure 4 is a key waveform of a high-voltage photovoltaic power amplifier circuit proposed in this invention when the duty cycle D > 0.5; Figure 5 is the equivalent circuit of the circuit shown in Figure 1 in mode one; Figure 6 is the equivalent circuit of the circuit shown in Figure 1 in mode two; Figure 7 is the equivalent circuit of the circuit shown in Figure 1 in mode three; Figure 8 is the equivalent circuit of the circuit shown in Figure 1 in mode four; in the above figures, v GS1 v GS2 v GS3 v GS4 These represent the driving voltage waveforms of switching transistors S1, S2, S3, and S4, respectively; i Lm1 i Lm2 The current flows through inductor L respectively m1 and inductor L m2 The current waveform; i Lr For resonant inductance L r Current waveform on; i T1 For the current flowing through inductor L m1 The sum of the currents on the primary side of transformer T1; i T2 For the current flowing through inductor L m2 The sum of the currents on the primary side of transformer T2; Detailed Implementation

[0006] The present invention will now be described in detail with reference to the accompanying drawings.

[0007] As shown in Figure 1, the high-voltage photovoltaic power generation circuit consists of a DC input voltage source (V... IN ), First switch (S1), Second switch (S2), Third switch (S3), Fourth switch (S4), First diode (D1), Second diode (D2), Third diode (D3), Transformer (T1), Transformer (T2), Magnetizing inductor (L m1 ), magnetizing inductance (L) m2 ), capacitor (C) o ), capacitor (C1), capacitor (C2), resonant capacitor (C) r ), resonant inductor (L) r It consists of a DC input voltage source (V) and a load (Z). IN The positive terminal of the first switch (S1) is connected to the same-name terminal of the primary side of transformer (T1) and the same-name terminal of the primary side of transformer (T2); the non-same-name terminal of the primary side of transformer (T1) is connected to the source of the first switch (S1), the drain of the second switch (S2), and one end of capacitor (C2); the non-same-name terminal of the primary side of transformer (T2) is connected to the source of the third switch (S3), the drain of the fourth switch (S4), and the resonant capacitor (C). r One end of the first switch (S1) and the third switch (S3) are connected together to the anode of the first diode (D1) and one end of the capacitor (C1); the drains of the second switch (S2) and the fourth switch (S4) are connected together to the DC input voltage source (V IN The negative terminal, the other end of the capacitor (C1), and the capacitor (C) o One end of the capacitor (C1) and one end of the load (Z); the cathode of the first diode (D1) is connected to the other end of the capacitor (C2) and the anode of the second diode (D2); the cathode of the second diode (D2) is connected to the anode of the third diode (D3) and the non-same-name terminal of the secondary side of the transformer (T2); the cathode of the third diode (D3) is connected to the capacitor (C2). o The other end of the transformer (T2) and the other end of the load (Z); the same-name terminal of the secondary side of the transformer (T1) is connected to the same-name terminal of the secondary side of the transformer (T1); the non-same-name terminal of the secondary side of the transformer (T1) is connected to the resonant inductor (L). r One end of the resonant inductor (L) r The other end of the capacitor is connected to the resonant capacitor (C). r The other end of ).

[0008] The control method based on the circuit shown in Figure 1 is shown in Figure 2. Its characteristic is that the control circuit adopts a single-voltage loop control method, and the output voltage sampling value v... oWith output voltage reference v o_ref The voltage error value is obtained by comparison, and the voltage error value is processed by a PI regulator to obtain the modulation signal v. ea Modulation signal v ea respectively with triangular carrier v T1 v T2 When comparing, when v ea >v T1 The second switch (S2) is turned on; when v ea <=v T1 The first switch (S1) is turned on; when v ea >v T2 The fourth switch (S4) is turned on; when v ea <=v T2 The third switch (S3) is turned on; to reduce the total input current ripple of the circuit, the triangular carrier wave v T1 and v T2 A triangular carrier wave with a 180° phase difference is used; to achieve zero-current turn-off of the second diode (D2) and the third diode (D3), the resonant inductor (L... r ) and resonant capacitor (C r The resonant period T r It must be less than the duty cycle D and the switching period T s The product DT s .

[0009] Figure 3 shows the key waveforms of the circuit shown in Figure 1 when the duty cycle D < 0.5; Figure 4 shows the key waveforms of the circuit shown in Figure 1 when the duty cycle D > 0.5; when the duty cycle D < 0.5 and the circuit shown in Figure 1 operates at (0-t1), the equivalent circuit is shown in Mode 1 of Figure 5. At t=0, the first switch S1 is turned on at zero voltage as a synchronous rectifier, the fourth switch S4 is turned on, the second switch S2 and the third switch S3 are turned off, the transformer T1 is subjected to a negative voltage for demagnetization, and the current i Lm1 The voltage drops, transformer T2 is magnetized by a positive voltage, and the current i Lm2 Rise; capacitor C1 charges, capacitor C2 discharges, resonant inductor L r and resonant capacitor C r The voltage v of the resonant cavity r 2V c1 +V c2 Due to the resonance period T r It must be less than the product of the duty cycle and the switching period, DT. s Before t=t1, the resonant current i LrWhen the resonance drops to 0, the second diode D2 turns off with zero current. When the duty cycle D of the circuit shown in Figure 1 is less than 0.5 and operates at (t1-t2), the equivalent circuit is shown in Mode 2 of Figure 6. At time t1, the first switch S1 is turned off, the second switch S2 is turned on, and both transformers T1 and T2 are subjected to positive voltage magnetization, with current i Lm1 and i Lm2 The circuit rises; capacitor C1 discharges, capacitor C2 charges; when the duty cycle D of the circuit shown in Figure 1 is less than 0.5 and it operates at (t2-t3), the equivalent circuit is shown in Mode 3 of Figure 7. At time t2, the fourth switch S4 is turned off, the third switch S3 is turned on at zero voltage as a synchronous rectifier, the transformer T1 is magnetized by a positive voltage, and the current i Lm1 As the voltage rises, transformer T2 is subjected to a negative voltage for demagnetization, and the current i Lm2 The voltage drops; capacitor C1 charges, capacitor C2 charges, and the resonant inductor L... r and resonant capacitor C r The voltage v of the resonant cavity r For V o- 2V c1 Due to the resonance period T r It must be less than the product of the duty cycle and the switching period, DT. s Before t=t3, the resonant current i Lr When the resonance drops to 0, the third diode D3 turns off with zero current. When the duty cycle D of the circuit shown in Figure 1 is less than 0.5 and operates between (t3 and t4), the equivalent circuit is shown in Mode 2 of Figure 6. At time t3, the third switch S3 is turned off, the fourth switch S4 is turned on, and both transformers T1 and T2 are subjected to positive voltage magnetization, with current i Lm1 and i Lm2 The capacitor C1 discharges while the capacitor C2 charges.

[0010] When the duty cycle D of the circuit shown in Figure 1 is greater than 0.5 and operates at (0-t1), the equivalent circuit is shown in Mode 3 of Figure 7; when the duty cycle D is greater than 0.5 and the circuit shown in Figure 1 operates at (t2-t3), the equivalent circuit is shown in Mode 1 of Figure 5; the working principle of these two cases is exactly the same as above, and will not be repeated; when the duty cycle D of the circuit shown in Figure 1 is greater than 0.5 and operates at (t1-t2), the equivalent circuit is shown in Mode 4 of Figure 8. At time t1, the second switch S2 is turned off, and the first switch S1 is turned on at zero voltage as a synchronous rectifier. Transformers T1 and T2 are both subjected to positive voltage magnetization, and the current i Lm1 and i Lm2 Rise; capacitor C1 charges, resonant inductor L r and resonant capacitor C r The voltage v of the constructed resonant cavity r For V o- 2V c1When the duty cycle D of the circuit shown in Figure 1 is greater than 0.5 and it operates between (t3 and t4), the equivalent circuit is shown in Mode 3 of Figure 7. At time t3, the fourth switch S4 is turned off, the third switch S3 is turned on, and both transformers T1 and T2 are subjected to positive voltage magnetization, and the current i Lm1 and i Lm2 The capacitor C1 discharges while the capacitor C2 charges.

[0011] The above inductor L m1 L m2 It can be partially or entirely achieved by the magnetizing inductance of transformers T1 and T2, and the resonant inductance L r It can be partially or entirely achieved by the magnetizing inductance of transformers T1 and T2, which can effectively reduce the size and number of circuit components; the above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. The high-voltage photovoltaic converter circuit consists of a DC input voltage source (V... IN ), First switch (S1), Second switch (S2), Third switch (S3), Fourth switch (S4), First diode (D1), Second diode (D2), Third diode (D3), Transformer (T1), Transformer (T2), First inductor (L) m1 ), second inductor (L m2 ), capacitor (C) o ), first capacitor (C1), second capacitor (C2), resonant capacitor (C) r ), resonant inductor (L) r It consists of ) and load (Z). Among them, DC input voltage source (V IN The positive terminal of the first inductor (L) is connected to the same-name terminal of the primary winding of transformer (T1), the same-name terminal of the primary winding of transformer (T2), and the first inductor (L). m1 One end of the second inductor (L) and the second inductor (L) m2 One end of the transformer (T1); the non-identical terminal of the primary side of the transformer (T1) is connected to the first inductor (L). m1 The other end of the transformer (T2), the source of the first switching transistor (S1), the drain of the second switching transistor (S2), and one end of the second capacitor (C2); the non-same-name terminals of the primary side of the transformer (T2) are connected to the second inductor (L). m2 The other end of the circuit, the source of the third switch (S3) and the drain of the fourth switch (S4) and the resonant capacitor (C) r One end of the first switch (S1) and the third switch (S3) are connected together to the anode of the first diode (D1) and one end of the first capacitor (C1); the sources of the second switch (S2) and the fourth switch (S4) are connected together to the DC input voltage source (V). IN The negative terminal, the other end of the first capacitor (C1), and the capacitor (C) o One end of the first diode (D1) is connected to the other end of the second capacitor (C2) and the anode of the second diode (D2); the cathode of the second diode (D2) is connected to the anode of the third diode (D3) and the non-same-name terminal of the secondary side of the transformer (T2); the cathode of the third diode (D3) is connected to the capacitor (C2). o The other end of the transformer (T1) and the other end of the load (Z); the same-name terminal of the secondary side of transformer (T2) is connected to the same-name terminal of the secondary side of transformer (T1); the non-same-name terminal of the secondary side of transformer (T1) is connected to the resonant inductor (L). r One end of the resonant inductor (L) r The other end of the capacitor is connected to the resonant capacitor (C). r The other end of ).

2. The control method based on the above-mentioned high-voltage photovoltaic inverter circuit is characterized in that: The control circuit adopts a single voltage loop control method, and the output voltage sampling value v o With output voltage reference v o_ref The voltage error value is obtained by comparison, and the voltage error value is processed by a PI regulator to obtain the modulation signal v. ea Modulation signal v ea respectively with triangular carrier v T1 v T2 When comparing, when v ea >v T1 The second switch (S2) is turned on; when v ea <=v T1 The first switch (S1) is turned on; when v ea >v T2 The fourth switch (S4) is turned on; when v ea <=v T2 The third switch (S3) is turned on; to reduce the total input current ripple of the circuit, the triangular carrier wave v T1 and v T2 A triangular carrier wave with a 180° phase difference is used; to achieve zero-current turn-off of the second diode (D2) and the third diode (D3), the resonant inductor (L... r ) and resonant capacitor (C r The resonant period T r It must be less than the duty cycle D and the switching period T s The product DT s .

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