Photovoltaic and energy storage integrated DC-DC converter

Abstract

A photovoltaic and energy storage integrated DC-DC converter is characterized in that one end of a photovoltaic DC input source PV is connected with a drain electrode of an active switch S1, and a source electrode of the active switch S1 is connected with a source electrode of an active switch S2 and one end of an inductor L1; the other end of the inductor L1 is respectively connected with one end of a capacitor C1, a drain electrode of an active switch S4 and an anode of a diode D1; the cathode of the diode D1 is connected with the drain electrode of the active switch S3, and the source electrode of the active switch S3 is connected with the drain electrode of the active switch S2 and the anode of the energy storage battery. The other end of the capacitor C1 is respectively connected with the cathode of the diode D2 and the anode of the diode D3; the cathode of the diode D3 is respectively connected with one end of a capacitor C2 and one end of a load R; and the other end of the load R, the other end of the capacitor C2, the anode of the diode D2, the source electrode of the active switch S4 and the cathode of the energy storage battery are connected with the other end of the photovoltaic direct current input source PV. According to the converter, four power supply functions can be realized only by using one DC-DC converter, so that the control difficulty and the manufacturing cost are effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation systems, and particularly to a photovoltaic and energy storage integrated DC-DC converter. Background Art

[0002] As one of the renewable and clean energy sources, solar energy is widely favored by countries around the world. However, the output power of solar photovoltaic power generation is prone to fluctuations affected by environmental factors and is uncontrollable. These problems seriously restrict the application of photovoltaic power generation systems. Energy storage technology is a good measure to solve the energy fluctuations of photovoltaic power generation systems. However, traditional photovoltaic and energy storage systems usually require separate DC-DC converters for the photovoltaic unit and the energy storage unit to work, which increases the difficulty of system control, the complexity of the converter structure, and the manufacturing cost to a certain extent.

[0003] For example, the patent document with the application publication number CN116417985A discloses a photovoltaic energy storage system using a DC bus. The system includes several photovoltaic modules connected to a photovoltaic combiner box, the photovoltaic combiner box is connected to a photovoltaic DC-DC converter, the photovoltaic DC-DC converter is connected to an energy storage converter, the energy storage converter is connected to an energy storage battery ESS system and a DC-DC charging pile, and the energy storage converter, the energy storage battery ESS system, the photovoltaic DC-DC converter, and the DC-DC charging pile are all connected to an EMS energy management system. When the photovoltaic modules stop working and the energy storage system is out of power, the energy storage converter charges the energy storage system. When there is a power outage due to an external network fault, the AC incoming line knife is automatically disconnected, and after being inverted by a bidirectional PCS, it supplies power to the second power supply box and supplies power to the control cabinet power supply. Thus, the combination of photovoltaic and energy storage is realized, which can effectively solve the energy fluctuations of the photovoltaic power generation system and improve the stability of the power supply system. However, in this system, the photovoltaic and energy storage units are respectively equipped with independent DC-DC converters, which results in a complex system structure, a large number of converters, and a high cost. Summary of the Invention

[0004] In order to solve the problems of the existing photovoltaic and energy storage systems, such as a large number of converters, complex structure, and uncontrollable fluctuations in the output power of solar photovoltaic power generation affected by environmental factors. The present invention proposes a photovoltaic and energy storage integrated DC-DC converter, which realizes the construction of a photovoltaic power supply structure and a battery charge and discharge structure in a DC-DC converter circuit. Only one DC-DC converter can realize the functions of photovoltaic power supply alone, energy storage battery power supply alone, photovoltaic charging of the energy storage battery, and photovoltaic-energy storage combined power supply, effectively reducing the number of converters, control difficulty, and manufacturing cost in the photovoltaic and energy storage systems.

[0005] The technical solution adopted by the present invention is as follows: A photovoltaic and energy storage integrated DC-DC converter, which includes: a photovoltaic DC input source PV, an energy storage battery Battery, four active switches S1, S2, S3, S4, three diodes D1, D2, D3, two capacitors C1, C2, and an inductor L1; One end of the photovoltaic DC input source PV is connected to the drain of the active switch S1, and the source of the active switch S1 is respectively connected to the source of the active switch S2 and one end of the inductor L1; The other end of the inductor L1 is respectively connected to one end of the capacitor C1, the drain of the active switch S4, and the anode of the diode D1; The cathode of the diode D1 is connected to the drain of the active switch S3, and the source of the active switch S3 is respectively connected to the drain of the active switch S2 and the positive electrode of the energy storage battery Battery; The other end of the capacitor C1 is respectively connected to the cathode of the diode D2 and the anode of the diode D3; The cathode of the diode D3 is respectively connected to one end of the capacitor C2 and one end of the load R; The other end of the load R, the other end of the capacitor C2, the anode of the diode D2, the source of the active switch S4, and the negative electrode of the energy storage battery Battery are all connected to the other end of the photovoltaic DC input source PV.

[0006] In the mode where the photovoltaic DC input source PV powers the load, the active switch S1 is in the always-on state, the active switches S2 and S3 are in the always-off state, and the active switch S4 is in the PWM mode. At this time, when the active switch S4 is turned on, the diode D2 is turned on, and the diodes D1 and D3 are turned off. The photovoltaic DC input source PV charges the inductor L1 and the capacitor C1, and the capacitor C2 discharges to power the load R. When the active switch S4 is turned off, the diode D2 is turned off, and the diode D3 is turned on. The photovoltaic DC input source PV, the inductor L1, and the capacitor C1 discharge to charge the capacitor C2 and at the same time power the load R.

[0007] At this time, the input-output voltage relationship is: , where D 4 is the duty cycle of the active switch S4, represents the voltage at the output port of the converter, represents the photovoltaic output voltage.

[0008] In the mode where the energy storage battery Battery powers the load, the active switches S1 and S3 are in the normally-off state, the active switch S2 is in the normally-open state, and the active switch S4 is in the PWM mode. At this time, when the active switch S4 conducts, the diode D2 conducts and the diode D3 turns off. The energy storage battery charges the inductor L1 and the capacitor C1, and the capacitor C2 discharges to supply power to the load R. When the active switch S4 turns off, the diode D2 turns off and the diode D3 conducts. The energy storage battery Battery, the inductor L1, and the capacitor C1 discharge to charge the capacitor C2 and supply power to the load R at the same time.

[0009] At this time, the input-output voltage relationship is: , where, represents the output voltage of the energy storage battery Battery.

[0010] In the mode where the photovoltaic DC input source PV charges the energy storage battery Battery, the active switch S1 is in the normally-on state, the active switch S2 is in the normally-off state, and the active switches S3 and S4 are in the PWM mode. At this time, when the active switch S4 conducts, the diode D2 conducts and the diodes D1 and D3 turn off. The photovoltaic DC input source PV charges the inductor L1 and the capacitor C1, and the capacitor C2 discharges to supply power to the load R. When the active switch S4 turns off, the active switch S3 turns on, the diode D2 turns off, and the diodes D1 and D3 conduct. The photovoltaic DC input source PV, the inductor L1, and the capacitor C1 discharge to charge the energy storage battery Battery and the capacitor C2 and supply power to the load R at the same time. During the stage when the active switch S4 turns off, if the active switch S3 turns off, the energy storage battery Battery stops charging.

[0011] At this time, the input-output voltage relationship is: , where, D 3 is the duty cycle of the active switch S3, represents the output voltage of the photovoltaic DC input source PV.

[0012] In the mode where the photovoltaic DC input source PV and the energy storage battery Battery supply power to the load at the same time, the active switch S3 is in the normally-off state, the active switches S1, S2, and S4 are in the PWM mode, and the active switches S1 and S2 conduct complementarily. At this time, when the active switch S4 conducts, the diode D2 conducts and the diode D3 turns off. The photovoltaic and the energy storage battery Battery charge the inductor L1 and the capacitor C1 respectively, and the capacitor C2 discharges to supply power to the load R. When the active switch S4 turns off, the diode D2 turns off and the diode D3 conducts. The photovoltaic DC input source PV, the energy storage battery Battery, the inductor L1, and the capacitor C1 discharge to charge the capacitor C2 and supply power to the load R at the same time.

[0013] At this time, the input-output voltage relationship is: , where,D $D_2$ is the duty cycle of the active switch $S_2$.

[0014] The technical effects of a photovoltaic and energy storage integrated DC-DC converter according to the present invention are as follows: 1) The present invention proposes a photovoltaic and energy storage integrated DC-DC converter, which realizes the construction of a photovoltaic power supply structure and a battery charge and discharge structure in a DC-DC converter circuit. Only one DC-DC converter can achieve the functions of photovoltaic power supply alone, energy storage battery power supply alone, photovoltaic charging of the energy storage battery, and photovoltaic-energy storage combined power supply.

[0015] 2) The present invention realizes the combination of a photovoltaic converter and an energy storage converter, and has four power supply functions: photovoltaic power supply alone, energy storage battery power supply alone, photovoltaic charging of the energy storage battery, and photovoltaic-energy storage combined power supply, effectively reducing the number of converters, control difficulty, and manufacturing cost in the photovoltaic and energy storage system.

[0016] 3) The converter of the present invention has four power supply functions: photovoltaic power supply alone, energy storage battery power supply alone, photovoltaic charging of the energy storage battery, and photovoltaic-energy storage combined power supply, and their voltage gains are as follows: Photovoltaic power supply alone mode: ; Energy storage battery power supply alone mode: ; Photovoltaic charging of the energy storage battery mode: ; Photovoltaic and energy storage battery combined power supply mode: . Brief description of the drawings

[0017] The present invention will be further described below in conjunction with the drawings and embodiments: Figure 1 is the circuit schematic diagram of the present invention.

[0018] Figure 2 is the present invention in the photovoltaic power supply mode, u PV $V_{in}=48V$, D $D = 0.44$, u o $V_{out}=200V$ simulation waveform.

[0019] Figure 3 is the present invention in the energy storage battery power supply mode, u B $V_{in}=96V$, D $D = 0.22$, u o $V_{out}=200V$ simulation waveform.

[0020] Figure 4is the charging mode of the energy storage battery by the photovoltaic in the present invention, u PV = 48V, u B = 96V, D 3 = 0.4, D 4 = 0.552, u o = 200V simulation waveform.

[0021] Figure 5 is the co - power supply mode of the photovoltaic and the energy storage battery in the present invention, u PV = 48V, u B = 96V, D 2 = 0.6, D 4 = 0.616, u o = 200V simulation waveform. Specific embodiments

[0022] The present invention will be further described in detail below with reference to the accompanying drawings. As Figure 1 shown is the converter topology diagram of the present invention. The converter includes a photovoltaic DC input source PV, an energy storage battery Battery, four active switches S1, S2, S3, S4, three diodes D1, D2, D3, two capacitors C1, C2, and an inductor L1; their connection forms are as follows: One end of the photovoltaic DC input source PV is connected to the drain of the active switch S1, and the source of the active switch S1 is respectively connected to the source of the active switch S2 and one end of the inductor L1; The other end of the inductor L1 is respectively connected to one end of the capacitor C1, the drain of the active switch S4, and the anode of the diode D1; The cathode of the diode D1 is connected to the drain of the active switch S3, and the source of the active switch S3 is respectively connected to the drain of the active switch S2 and the positive electrode of the energy storage battery Battery; The other end of the capacitor C1 is respectively connected to the cathode of the diode D2 and the anode of the diode D3; The cathode of the diode D3 is respectively connected to one end of the capacitor C2 and one end of the load R; The other end of the load R, the other end of the capacitor C2, the anode of the diode D2, the source of the active switch S4, and the negative electrode of the energy storage battery Battery are all connected to the other end of the photovoltaic DC input source PV.

[0023] In the mode where the photovoltaic DC input source PV powers the load, the active switch S1 is in the always-on state, the active switches S2 and S3 are in the always-off state, and the active switch S4 is in the PWM mode. At this time, when the active switch S4 is turned on, the diode D2 is turned on, and the diodes D1 and D3 are turned off. The photovoltaic DC input source PV charges the inductor L1 and the capacitor C1, and the capacitor C2 discharges to supply power to the load R. When the active switch S4 is turned off, the diode D2 is turned off, and the diode D3 is turned on. The photovoltaic DC input source PV, the inductor L1, and the capacitor C1 discharge to charge the capacitor C2 and supply power to the load R at the same time. At this time, the input-output voltage relationship is: , where D 4 is the duty cycle of the active switch S4, represents the voltage at the output port of the converter, represents the photovoltaic output voltage.

[0024] In the mode where the energy storage battery Battery powers the load, the active switches S1 and S3 are in the always-off state, the active switch S2 is in the always-on state, and the active switch S4 is in the PWM mode. At this time, when the active switch S4 is turned on, the diode D2 is turned on, and the diode D3 is turned off. The energy storage battery charges the inductor L1 and the capacitor C1, and the capacitor C2 discharges to supply power to the load R. When the active switch S4 is turned off, the diode D2 is turned off, and the diode D3 is turned on. The energy storage battery Battery, the inductor L1, and the capacitor C1 discharge to charge the capacitor C2 and supply power to the load R at the same time. At this time, the input-output voltage relationship is: , where represents the output voltage of the energy storage battery Battery.

[0025] In the mode where the photovoltaic DC input source PV charges the energy storage battery Battery, the active switch S1 is in the always-on state, the active switch S2 is in the always-off state, and the active switches S3 and S4 are in the PWM mode. At this time, when the active switch S4 is turned on, the diode D2 is turned on, and the diodes D1 and D3 are turned off. The photovoltaic DC input source PV charges the inductor L1 and the capacitor C1, and the capacitor C2 discharges to supply power to the load R. When the active switch S4 is turned off, the active switch S3 is turned on, the diode D2 is turned off, and the diodes D1 and D3 are turned on. The photovoltaic DC input source PV, the inductor L1, and the capacitor C1 discharge to charge the energy storage battery Battery and the capacitor C2 and supply power to the load R at the same time. During the off stage of the active switch S4, when the active switch S3 is turned off, the energy storage battery Battery stops charging. At this time, the input-output voltage relationship is: , where D 3 is the duty cycle of the active switch S3, represents the output voltage of the photovoltaic DC input source PV.

[0026] In the mode where the photovoltaic DC input source PV and the energy storage battery Battery supply power to the load simultaneously, the active switch S3 is in the normally-off state, the active switches S1, S2, and S4 are in the PWM mode, and the active switches S1 and S2 conduct complementarily. At this time, when the active switch S4 conducts, the diode D2 conducts and the diode D3 turns off. The photovoltaic and the energy storage battery Battery charge the inductor L1 and the capacitor C1 respectively, and the capacitor C2 discharges to supply power to the load R. When the active switch S4 turns off, the diode D2 turns off and the diode D3 conducts. The photovoltaic DC input source PV, the energy storage battery Battery, the inductor L1, and the capacitor C1 discharge to charge the capacitor C2 and supply power to the load R at the same time. At this time, the input-output voltage relationship is: , where, D 2 is the duty cycle of the active switch S2.

[0027] Figure 2 This is in the photovoltaic power supply mode of the present invention, u PV = 48V, D 4 = 0.44, u o = 200V simulation waveform. It can be seen that when the output voltage 48V of the photovoltaic DC input source PV is used as the input source of the converter, by controlling the duty cycle of the switch S4 at 0.44, the requirement of the converter output voltage of 200V is achieved. Figure 2 It can be seen that when the output voltage 48V of the photovoltaic DC input source PV is used as the input source of the converter, by controlling the duty cycle of the switch S4 at 0.44, the requirement of the converter output voltage of 200V is achieved.

[0028] Figure 3 This is in the energy storage battery power supply mode of the present invention, u B = 96V, D 4 = 0.22, u o = 200V simulation waveform. It can be seen that when the output voltage 96V of the energy storage battery Battery is used as the input source of the converter, by controlling the duty cycle of the switch S4 at 0.22, the requirement of the converter output voltage of 200V is achieved. Figure 3 It can be seen that when the output voltage 96V of the energy storage battery Battery is used as the input source of the converter, by controlling the duty cycle of the switch S4 at 0.22, the requirement of the converter output voltage of 200V is achieved.

[0029] Figure 4 This is in the mode of the photovoltaic charging the energy storage battery of the present invention, u PV = 48V, u B = 96V, D 3 = 0.4, D 4 = 0.552, u o = 200V simulation waveform. It can be seen from Figure 4It can be seen that when the output voltage of the photovoltaic DC input source PV is 48V as the input source of the converter, by controlling the duty cycle of switch S3 at 0.4 and the duty cycle of switch S4 at 0.552, the requirements of the output voltage of the energy storage battery Battery being 96V and the output voltage of the converter being 200V are achieved.

[0030] Figure 5 This is the co - power supply mode of the present invention for photovoltaic and energy storage batteries. u PV = 48V, u B = 96V, D 2 = 0.6, D 4 = 0.616, u o = 200V simulation waveform. From Figure 5 It can be seen that when the output voltage of the photovoltaic DC input source PV is 48V and the output voltage of the energy storage battery Battery is 60V as the dual - input power supply of the converter, by controlling the duty cycle of switch S2 at 0.6 and the duty cycle of switch S4 at 0.616, the requirement of the output voltage of the converter being 200V is achieved.

[0031] The present invention proposes a photovoltaic - energy storage integrated DC - DC converter, which includes a photovoltaic DC input source PV, an energy storage battery Battery, four active switches S1, S2, S3, S4, three diodes D1, D2, D3, two capacitors C1, C2, and an inductor L1. The present invention realizes the combination of photovoltaic and energy storage converters, and has four power supply functions: photovoltaic single - power supply, energy storage battery single - power supply, photovoltaic charging the energy storage battery, and photovoltaic - energy storage co - power supply, effectively reducing the number, control difficulty and manufacturing cost of converters in the photovoltaic - energy storage system.

Claims

1. A photovoltaic and energy storage integrated DC-DC converter, characterized in that , The converter includes: A photovoltaic DC input source PV, a storage battery, four active switches S1, S2, S3, S4, three diodes D1, D2, D3, two capacitors C1, C2, and an inductor L1; One end of the photovoltaic DC input source PV is connected to the drain of the active switch S1, and the source of the active switch S1 is respectively connected to the source of the active switch S2 and one end of the inductor L1; The other end of the inductor L1 is respectively connected to one end of the capacitor C1, the drain of the active switch S4, and the anode of the diode D1; The cathode of the diode D1 is connected to the drain of the active switch S3, and the source of the active switch S3 is respectively connected to the drain of the active switch S2 and the positive electrode of the storage battery; The other end of the capacitor C1 is respectively connected to the cathode of the diode D2 and the anode of the diode D3; The cathode of the diode D3 is respectively connected to one end of the capacitor C2 and one end of the load R; The other end of the load R, the other end of the capacitor C2, the anode of the diode D2, the source of the active switch S4, and the negative electrode of the storage battery are all connected to the other end of the photovoltaic DC input source PV.

2. The integrated photovoltaic and energy storage DC-DC converter according to claim 1, characterized in that: In the mode where the photovoltaic DC input source PV supplies power to the load, the active switch S1 is in the always-on state, the active switches S2 and S3 are in the always-off state, and the active switch S4 is in the PWM mode; at this time, when the active switch S4 is turned on, the diode D2 is turned on, and the diodes D1 and D3 are turned off. The photovoltaic DC input source PV charges the inductor L1 and the capacitor C1, and the capacitor C2 discharges to supply power to the load R; when the active switch S4 is turned off, the diode D2 is turned off, and the diode D3 is turned on. The photovoltaic DC input source PV, the inductor L1, and the capacitor C1 discharge to charge the capacitor C2, and at the same time supply power to the load R.

3. The integrated photovoltaic and energy storage DC-DC converter according to claim 2, wherein: In the mode where the photovoltaic DC input source PV supplies power to the load, the relationship between the input and output voltages is: , where D 4 is the duty cycle of the active switch S4, represents the voltage at the output port of the converter, represents the photovoltaic output voltage.

4. The integrated photovoltaic and energy storage DC-DC converter according to claim 1, characterized in that: In the mode where the storage battery supplies power to the load, the active switches S1 and S3 are in the always-off state, the active switch S2 is in the always-on state, and the active switch S4 is in the PWM mode; At this time, when the active switch S4 is turned on, the diode D2 is turned on, and the diode D3 is turned off. The storage battery charges the inductor L1 and the capacitor C1, and the capacitor C2 discharges to supply power to the load R; when the active switch S4 is turned off, the diode D2 is turned off, and the diode D3 is turned on. The storage battery, the inductor L1, and the capacitor C1 discharge to charge the capacitor C2, and at the same time supply power to the load R.

5. The integrated photovoltaic and energy storage DC-DC converter according to claim 4, characterized in that: When the energy storage battery powers the load, the relationship between the input and output voltages is as follows: , where represents the output voltage of the energy storage battery Battery.

6. The integrated photovoltaic and energy storage DC-DC converter according to claim 1, wherein: In the mode where the photovoltaic DC input source PV charges the storage battery, the active switch S1 is in the always-on state, the active switch S2 is in the always-off state, and the active switches S3 and S4 are in the PWM mode; at this time, when the active switch S4 is turned on, the diode D2 is turned on, and the diodes D1 and D3 are turned off. The photovoltaic DC input source PV charges the inductor L1 and the capacitor C1, and the capacitor C2 discharges to supply power to the load R; when the active switch S4 is turned off, the active switch S3 is turned on, the diode D2 is turned off, and the diodes D1 and D3 are turned on. The photovoltaic DC input source PV, the inductor L1, and the capacitor C1 discharge to charge the storage battery and the capacitor C2, and at the same time supply power to the load R; in the stage when the active switch S4 is turned off and the active switch S3 is turned off, the storage battery stops charging.

7. The integrated photovoltaic and energy storage DC-DC converter according to claim 6, characterized in that: When the photovoltaic DC input source PV charges the energy storage battery, the relationship between the input and output voltages is as follows: , where D 3 is the duty cycle of the active switch S3, represents the output voltage of the photovoltaic DC input source PV.

8. The integrated photovoltaic and energy storage DC-DC converter according to claim 1, wherein: In the mode where the photovoltaic DC input source PV and the energy storage battery Battery supply power to the load simultaneously, the active switch S3 is in the normally-off state, the active switches S1, S2, and S4 are in the PWM mode, and the active switches S1 and S2 conduct complementarily; at this time, when the active switch S4 conducts, the diode D2 conducts and the diode D3 turns off, and the photovoltaic and the energy storage battery Battery charge the inductor L1 and the capacitor C1 respectively, and the capacitor C2 discharges to supply power to the load R; when the active switch S4 turns off, the diode D2 turns off and the diode D3 conducts, and the photovoltaic DC input source PV, the energy storage battery Battery, the inductor L1, and the capacitor C1 discharge to charge the capacitor C2 and supply power to the load R at the same time.

9. The integrated photovoltaic and energy storage DC-DC converter according to claim 8, characterized in that: When the photovoltaic DC input source PV and the energy storage battery Battery supply power to the load simultaneously, the relationship between the input and output voltages is as follows: , where D 2 is the duty cycle of the active switch S2.

10. The integrated photovoltaic and energy storage DC-DC converter according to claim 1, characterized in that: This DC-DC converter has four power supply functions: photovoltaic power supply alone, energy storage battery power supply alone, photovoltaic charging of the energy storage battery, and photovoltaic-storage combined power supply.

Images