Quasi-Z-source high-gain boost type mobile photovoltaic charging device

Abstract

The invention relates to the technical field of photovoltaic power generation, and discloses a quasi-Z-source high-gain boost type mobile photovoltaic charging device, which comprises a portable photovoltaic module, a combiner box, a boost system, a body charging pile, a charging device and mobile wheels. The invention relates to a quasi-Z-source high-gain boost type mobile photovoltaic charging device, a boost structure is a quasi-Z-source-based low-stress high-gain boost converter, and under the condition of solar illumination, the mobile charging device can obtain electric energy which is equivalent to a power supply; the generated direct current voltage can be directly supplied to the charging device after being boosted by the boosted circuit, and the charging device can realize directional movement. The boost converter is small in size, low in duty ratio and high in voltage gain, heat dissipation of the system is facilitated, the boost effect is good, and the boost system is arranged on the upper portion of the charging device, is integrally designed, becomes a movable photovoltaic power supply type charging device and can provide electric energy for other loads anytime and anywhere.

Description

Technical Field

[0001] The present invention relates to the technical fields of photovoltaic power generation technology and charging technology of charging devices, and particularly to a quasi-Z-source high-gain boost mobile photovoltaic charging device. Background Art

[0002] With the development of photovoltaic power generation technology, the application of photovoltaic power generation in various fields is becoming more and more extensive. Traditional photovoltaic module power generation is fixed power generation with low power generation efficiency. Combining photovoltaic module power generation with a charging device can reduce economic costs and obtain a clean and pollution-free power source. However, generally, the charging device and photovoltaic modules are fixedly installed, and the voltage generated by photovoltaic power generation is usually low, and it needs to be converted into a voltage suitable for charging the load through a highly efficient boost system. Therefore, a quasi-Z-source high-gain boost mobile photovoltaic charging device is proposed. Summary of the Invention

[0003] The object of the present invention is to provide a quasi-Z-source high-gain boost mobile photovoltaic charging device, which can efficiently convert the direct current of photovoltaic power generation into a high-voltage direct current suitable for charging the load, and is equipped with a mobile charging device to achieve high-efficiency and high-convenience charging. The specific implementation means are as follows:

[0004] A quasi-Z-source high-gain boost mobile photovoltaic charging device includes a portable photovoltaic module, a busbar box, a main body charging pile, a charging gun head and mobile wheels. The photovoltaic module is connected to the main body charging pile through a bracket and is connected to the busbar box through a busbar line. The bottom of the main body charging pile is connected to the mobile wheels through a fixing frame. The interior of the shell of the busbar box is provided with a DC controller, a circuit breaker, a control relay and a boost system. The interior of the boost system is a quasi-Z-source structure. The main body charging pile is electrically connected to the busbar box and the charging gun head respectively.

[0005] Preferably, the boost system includes a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a first inductor, a second inductor, a third inductor, a first diode, a second diode, a third diode, a fourth diode, a first load, a switching tube and an input voltage. The positive pole of the input voltage is connected to the first inductor, and the other end is connected to the negative pole of the first capacitor. The input side of the input voltage corresponds to the output side of the control relay. One end of the first load should be connected to the positive pole side of the sixth capacitor, and the other end should be connected to the negative pole side of the second capacitor. The output side of the first load corresponds to the input side of the main body charging pile.

[0006] Preferably, the negative electrodes of the third inductor and the fourth capacitor are connected to the positive electrode of the third diode, the negative electrodes of the second inductor and the fifth capacitor are connected to the negative electrode of the third diode. The second inductor, the third inductor, the fourth capacitor, the fifth capacitor and the third diode form an internal quasi-Z-source structure, which greatly improves the voltage gain.

[0007] Preferably, the positive electrode of the second capacitor is connected to the negative electrode of the third capacitor, the positive electrode of the third capacitor is connected to the negative electrode of the sixth capacitor, the negative electrode of the sixth capacitor is connected to one end of the load, the negative electrode of the second capacitor is connected to the other end of the load. The second capacitor, the third capacitor and the sixth capacitor are connected in series on both sides of the first load to reduce the voltage stress of each capacitor. One end of the switching tube is connected to the negative electrode of the sixth capacitor, and the other end of the switching tube is connected to the negative electrode of the first capacitor.

[0008] Preferably, the input voltage is the voltage of the photovoltaic module power generation passing through the bus bar, the DC controller, the circuit breaker and the control relay.

[0009] Preferably, the positive electrode of the first diode is connected to the first inductor, and the negative electrode of the first diode is connected to the positive electrode of the first capacitor; the positive electrode of the second diode is connected to the positive electrode of the first capacitor, and the negative electrode of the second diode is connected to the positive electrode of the sixth capacitor; the positive electrode of the fourth diode is connected to the first load, and the negative electrode of the fourth diode is connected to the negative electrode of the first capacitor.

[0010] Among them, the first diode, the second diode, the third diode and the fourth diode control the current direction, and the on and off of the first switching tube control the charging and power generation of the overall system.

[0011] When the first switching tube is turned on, the second diode is forward-biased and turned on, and the first diode, the third diode and the fourth diode are reverse-biased and turned off. The input voltage and the third capacitor charge the first inductor; the first capacitor, the fifth capacitor and the sixth capacitor release energy to the second inductor, the third inductor and the sixth capacitor; the second capacitor and the third capacitor release energy to the sixth capacitor and the first load.

[0012] When the first switching tube is turned off, the first diode, the third diode and the fourth diode are forward-biased and turned on, and the second diode is reverse-biased and turned off. The input voltage and the first inductor release energy to the first capacitor; the second inductor and the third inductor release energy to the third capacitor, the fourth capacitor and the fifth capacitor; the sixth capacitor releases energy to the second capacitor; the input voltage, the first inductor, the second inductor, the third inductor and the sixth capacitor release energy to the first load together.

[0013] Meanwhile, each of the electrical components can obtain the voltage gain of the boost system, and at the same time, the voltage relationship and current relationship between the electrical components can be obtained.

[0014] Furthermore, according to the voltage relationship and current relationship between the electrical components, the value selection ranges of the first capacitor, second capacitor, third capacitor, fourth capacitor, fifth capacitor, sixth capacitor, first inductor, second inductor, third inductor, first diode, second diode, third diode, fourth diode, and first switching tube can be obtained.

[0015] Even further, the charging strategy of the quasi-Z-source high-gain boost mobile photovoltaic charging system and integrated device can be obtained.

[0016] For a quasi-Z-source high-gain boost mobile photovoltaic charging device of the present invention, the relationship between the internal electrical components can be verified by simulation using Matlab / Simulink software, proving the correctness of the present invention.

[0017] Beneficial Effects

[0018] 1. The present invention is a quasi-Z-source high-gain boost mobile photovoltaic charging device. The boost system is a low-stress high-gain boost converter based on a quasi-Z-source. Under solar illumination, the mobile charging device can obtain electrical energy, acting as a power source. The DC voltage generated by it can be directly supplied to the charging device after being boosted by the boost circuit, and the charging device can achieve directional movement. The boost system has a small volume, a low duty cycle and high voltage gain, which is beneficial to the heat dissipation of the system, has a good boost effect, and the boost system is located above the charging device, which is an integrated design, becoming a mobile photovoltaic-powered charging device that can provide electrical energy for other loads at any time and anywhere.

[0019] 2. By adding movable pulleys and equipping with a highly efficient boost system, the present invention can adapt to different environments and scenarios. It is not restricted by conditions such as terrain and buildings, and can be flexibly deployed in various places to meet the charging needs of different users. The connected boost converter plays a major role in central connection, which can further improve the energy utilization efficiency. In some areas with harsh environments, it can also be used as a rescue-type charging device to achieve the charging task with higher efficiency. Description of the Drawings

[0020] Figure 1 It is the overall structure diagram of Embodiment 1 of the present invention;

[0021] Figure 2 It is the system structure diagram of Embodiment 1 of the present invention;

[0022] Figure 3 It is the circuit topology diagram of Embodiment 2 of the present invention;

[0023] Figure 4 It is the circuit principle structure diagram of Embodiment 2 of the present invention;

[0024] Figure 5 It is the turn-on mode circuit diagram of Embodiment 3 of the present invention;

[0025] Figure 6 It is the turn-off mode circuit diagram of Embodiment 3 of the present invention;

[0026] Figure 7 It is the current-voltage relationship diagram of Embodiment 4 of the present invention;

[0027] Figure 8 It is the charging flow chart of Embodiment 5 of the present invention;

[0028] Figure 9 It is the first simulation verification diagram of Embodiment 6 of the present invention;

[0029] Figure 10 It is the second simulation verification diagram of Embodiment 6 of the present invention;

[0030] Figure 11 It is the third simulation verification diagram of Embodiment 6 of the present invention;

[0031] Figure 12 It is the efficiency curve diagram of Embodiment 7 of the present invention.

[0032] Among them, 1. Main body charging pile; 2. Charging device; 3. Boosting system; 4. Busbar box; 5. Busbar line; 6. Photovoltaic module; 7. Movable wheel; 8. Fixed frame. Specific embodiments

[0033] Embodiment 1

[0034] A quasi-Z-source high-gain boost type mobile photovoltaic charging system of the present invention is an integrated device. As shown in the appendix Figure 1 It is composed of a photovoltaic module 1, a bracket, a busbar line 5, a busbar box 4, a boosting system 3, a main body charging pile, a charging gun head 2, a movable wheel 7 and a fixed frame. The photovoltaic module 1 efficiently collects solar energy, which is centrally transmitted to the boosting system 3 through the busbar line 5 and the busbar box 4. High-gain boosting is achieved through a Z-source converter, and then the main body charging pile 1 cooperates with the charging gun head 2 to charge the device. The movable wheel 7 facilitates flexible movement, and the fixed frame 8 is a braking structure to stabilize the device. The overall design has a high integration degree and is suitable for various scenarios.

[0035] A quasi-Z-source high-gain boost type mobile photovoltaic charging system, as shown in the appendix Figure 2As shown in the figure, it includes a busbar box 4 and a boosting device part: mainly a DC controller, a circuit breaker, a control relay, and a boosting converter part. The core key lies in the boosting part, which adopts a special topology structure and is composed of six capacitors, three inductors, four diodes, and one switching tube.

[0036] Embodiment 2

[0037] In the boosting part of the present invention, as shown in the appendix Figure 3 figure, C1 is the first capacitor, C2 is the second capacitor, C3 is the third capacitor, C4 is the fourth capacitor, C5 is the fifth capacitor, C6 is the sixth capacitor, L1 is the first inductor, L2 is the second inductor, L3 is the third inductor, S is the first switching tube, D1 is the first diode, D2 is the second diode, D3 is the third diode, D4 is the fourth diode, R is the first load, and V in is the input power supply.

[0038] In the present invention, as shown in the appendix Figure 4 figure, this topology adds a switched-inductor-capacitor structure on the basis of the quasi-Z-source topology, which can greatly improve the voltage gain; secondly, three capacitors are connected in series to divide the voltage, which can reduce the voltage stress of the capacitors, and the diodes are used to control the direction of the current.

[0039] The working principle of the circuit is based on the symmetry of the quasi-Z-source:

[0040] (1)

[0041] Embodiment 3

[0042] Turn-on mode [0 < t < DT]: As shown in the appendix Figure 5 figure, the switching tube S conducts, the diode D2 is forward-biased and conducts, and D1, D3, and D4 are reverse-biased and turn off. The DC power supply V in and the capacitor C3 release energy to the inductor L1 together through the loop "V in -L1-C3-S"; the capacitors C1, C4, and C 5， release energy to the capacitor C6, the inductor L2, and the inductor L3 respectively through the loops "C1-D2-C6-S", "C1-C5-L2-S", and "C1-L3-C4-S"; the capacitors C3 and C2 release energy to the capacitor C6 and the load R together through the loop "C3-C6-R-C2". The appendix Figure 4 shows the current path. In this mode, the voltage across the inductor can be expressed as:

[0043] (2)

[0044] In the formula:

[0045] V L1(ON) ~V L3(ON)The voltage across inductors L1 to L3 in Mode 1, with the unit of V;

[0046] V in and V R are the input and output voltages, with the unit of V;

[0047] V C1 to V C6 are the voltages across capacitors C1 to C6, with the unit of V;

[0048] Turn-off Mode [DT < t < T]: As shown in the appendix Figure 6 As shown, the switch S is turned off, and diodes D1, D3, and D4 are forward-biased and conducting, while D2 is reverse-biased and turned off. The DC power supply V in and inductor L1 release energy to capacitor C1 together through the loop "V in - L1 - D1 - C1"; inductor L3 and inductor L2 change from the energy storage state to the energy release state, charging capacitors C4 and C5 respectively, and at the same time, inductors L2 and L3 release energy to capacitor C3 through the loop "L3 - D3 - L2 - C3 - D1"; V in , inductor L1, inductor L3, inductor L2, and capacitor C6 release energy to the load R together through the loop "V in - L1 - D1 - L3 - D3 - L2 - C6 - R - D4".

[0049] The voltage across the inductor in this mode can be expressed as:

[0050] (3)

[0051] In the formula:

[0052] V L1(ON) to V L3(ON) are the voltages across inductors L1 to L3 in Mode 1, with the unit of V;

[0053] V in and V R are the input and output voltages, with the unit of V;

[0054] V C1 to V C6 are the voltages across capacitors C1 to C6, with the unit of V;

[0055] Embodiment 4

[0056] In the present invention, as shown in the appendix Figure 7 shows the voltage and current waveforms of each component within a period.

[0057] According to the inductor volt-second balance characteristic, analyzing the DC steady state of this quasi-Z-source converter can obtain

[0058] Formula 4

[0059] (4)

[0060] From formulas (1)-(4), the voltages across capacitors C1 to C6 can be obtained:

[0061] (5)

[0062] Through formula (5), the voltage gain of this converter in CCM mode can be obtained:

[0063] (6)

[0064] Voltage stress:

[0065] From Figure 3 it can be obtained that the voltage stress of switch S and the voltage stresses of each diode are respectively:

[0066] (7)

[0067] Current relationship:

[0068] According to Appendix Figure 5 it can be obtained that when the switch is in the on state, the current flowing through the capacitor can be expressed as:

[0069] (8)

[0070] In the formula: I C1(ON) —I C6(ON) is the current flowing through capacitors C1 to C6 when the switch is on, with the unit of A;

[0071] I L1 —I L3 is the average current of the inductor, with the unit of A;

[0072] I R is the load output current, with the unit of A.

[0073] According to Appendix Figure 6 it can be obtained that when the switch is in the off state, the current flowing through the capacitor can be expressed as:

[0074] (9)

[0075] Combining the capacitor ampere-second balance characteristic, formulas (8) and (9) are sorted out to obtain the average current of the inductor as:

[0076] (10)

[0077] Through formulas (8), (9), and (10), when the switch is on, the current flowing through switch S and diode V D2The current is

[0078] (11)

[0079] When the switch tube is turned off, the current flowing through the diodes V D1 、V D3 、V D4 is

[0080] (12)

[0081] Design of inductor and capacitor parameters: The differential equations of inductor voltage and capacitor current are respectively

[0082] (13)

[0083] For the design of inductor parameters, from formula (13), the peak value of inductor current of this converter in operating mode a can be obtained as:

[0084] (14)

[0085] Substituting formulas (2), (5), (6), and (10) into (14), the values of inductors L1, L2, and L3 can be obtained as:

[0086] (15)

[0087] where X L is the allowable fluctuation range of inductor current, X L =(Δi L / I L )×100%. Generally, the inductor current ripple rate is less than 10%.

[0088] For the design of capacitor parameters, from formula (13), the peak value of capacitor voltage in this converter

[0089] in operating mode a can be obtained as:

[0090] (16)

[0091] Substituting formulas (5), (8), and (10) into (16), the capacitor can be obtained as:

[0092] (17)

[0093] X C is the allowable voltage fluctuation range of the capacitor, X C =(ΔV C / V C )×100%. Generally, the output voltage filtering is less than 1%.

[0094] Device Selection: After theoretical calculation, the parameters of the proposed high-gain converter are shown in Table 1

[0095] Table 1 Device Parameters in Simulation

[0096] Device Loss: The efficiency of the proposed converter mainly depends on the switching loss and conduction loss, including the resistance losses of diodes, switches, inductors, and capacitors, as well as the switch loss. The parasitic internal resistances of these components, namely switches, diodes, inductors, and capacitors, are represented by r DS 、r VD 、r L 、r C respectively. To calculate the theoretical efficiency of the converter, it is assumed that the parasitic internal resistances of the same type of devices are the same.

[0097] The switching loss of the switch can be expressed as:

[0098] (18)

[0099] (19)

[0100] t on is the turn-on delay time of the switch;

[0101] t off is the turn-off delay time of the switch; the unit is ns for both.

[0102] The conduction loss of the switch is:

[0103] (20)

[0104] When the diode is conducting, it will generate a forward conduction loss. The sum of the forward conduction losses of the four diodes is:

[0105] (21)

[0106] Among them, V D1 、V D2 、V D3 and V D4 are the conduction voltage drops of each diode respectively.

[0107] Diode Parasitic Internal Resistance Loss:

[0108] (22)

[0109] The loss of the inductor can be expressed as:

[0110] (23)

[0111] The loss of the capacitor can be expressed as:

[0112] (24)

[0113] The total loss of the converter is:

[0114] (25)

[0115] The efficiency of the converter can be expressed as:

[0116] (26)

[0117] Embodiment 5

[0118] Charging strategy:

[0119] The object of the present invention is to provide a boost system for a small-sized movable photovoltaic-powered charging device, and a reasonable photovoltaic output charging voltage is provided by changing the duty cycle of the converter of the boost system. The specific implementation steps are as follows Figure 8 :

[0120] Step S0, the input end of the boost system of the small-sized movable photovoltaic charging device of the present invention is connected to the output voltage of the photovoltaic module;

[0121] Step S1, determine whether the output voltage of the photovoltaic module is greater than the rated voltage (100 V) of the charging device. If so, go to step S2; otherwise, go to step S3;

[0122] Step S2, determine whether the output voltage is much greater than the rated voltage (120 V) of the charging device. If so, go to step S7; otherwise, go to step S11;

[0123] Step S3, appropriately increase the duty cycle of the boost converter (increase the duty cycle by 0.01), and then enter step S4;

[0124] Step S4, the output voltage of the photovoltaic module increases appropriately, resulting in step S5, and then enter step S6;

[0125] Step S5, the output current of the photovoltaic module decreases appropriately, and end;

[0126] Step S6, determine whether the changed voltage meets the requirements of the charging voltage (80 V - 120 V). If so, go to step S11; otherwise, go to step S3 for recycling;

[0127] Step S7, appropriately decrease the duty cycle of the boost converter (decrease the duty cycle by 0.01), and then enter step S8;

[0128] Step S8, the output voltage of the photovoltaic module is appropriately reduced, resulting in step S9, and then proceed to step S10;

[0129] Step S9, the output current of the photovoltaic module is appropriately increased, and it ends;

[0130] Step S10, determine whether the changed voltage meets the requirement of the charging voltage (80 V - 120 V). If so, proceed to step S11; otherwise, go back to step S7 for recycling;

[0131] Step S11, the current photovoltaic output voltage meets the rated voltage of the charging device (80 V - 120 V), and the charging device can be used, thus proceeding to step S12;

[0132] Step S12, the charging device can supply power to other loads, thus proceeding to step S13;

[0133] Step S13, stop and end the process.

[0134] Embodiment 6

[0135] Simulation verification:

[0136] To verify the ability of the proposed converter to achieve low stress and high gain, when the input voltage is 50 V and the duty cycle is 0.10, a simulation model under ideal conditions is built in Matlab / Simulink simulation software with reference to the device parameters in Table 1. The simulation results are as shown in the appendix. Figures 9 - 11 as shown.

[0137] Appendix Figure 9 shows that when the input voltage is given as 50 V and the duty cycle D = 0.10, the output voltage is 127 V, and the simulation results are consistent with the theoretical calculations.

[0138] From the appendix Figure 10 it can be seen that when the switch is turned off, V S = 71 V, V D1 = V D3 = V D4 = 70 V; when the switch is turned on, the diode V D2 is turned off due to the reverse bias voltage, then V D2 = 70 V.

[0139] Appendix Figure 11 the voltage values across the capacitors in it are in line with the theoretical calculated values, V C1 = V C2 = V C6 = 57 V, V C3 = 14 V, V C4 = V C5 = 7 V, further proving the correctness of the theoretical analysis.

[0140] Example 7

[0141] Experimental analysis: To further verify the correctness and feasibility of the theoretical analysis of the boost system of the present invention, an experimental prototype of a boost system converter was built.

[0142] The parameters of the experimental prototype and the simulation values. The model of the switching transistor S is CSD19505KCS, and the diode V D1 ~V D4 has the model of RHRP3060.

[0143] With the input voltage V in = 50 V remaining unchanged, the actual efficiency curve of the converter was measured by changing the load size as shown in the appendix Figure 12 shown. Compared with the theoretical efficiency curve, when the output power is 60 W, the efficiency is 92.2%, slightly lower than the theoretical efficiency curve.

[0144] Among the above embodiments, the proposed quasi-Z-source boost converter has been verified by theoretical calculation, simulation waveform and actual measurement, and has the advantages of high gain and high efficiency, and is applicable to the boost converter part of the mobile photovoltaic charging system in Embodiment 1 above.

[0145] The above preferred embodiments should be regarded as illustrative examples of the embodiments of the present application. Any technical deductions, substitutions and improvements that are identical, similar or based on this application should be regarded as within the protection scope of this patent.

Claims

1. A quasi-Z source high-gain boost mobile photovoltaic charging device, characterized in that: The invention comprises a portable photovoltaic module (6), a junction box (4), a main charging pile (1), a charging gun head (2) and a moving wheel (7); the photovoltaic module (6) is connected to the main charging pile (1) via a bracket and is connected to the junction box (4) via a junction line (5); the bottom of the main charging pile (1) is connected to the moving wheel (7) via a fixing frame (8); a DC controller, a trip switch, a control relay and a boost system (3) are arranged in a shell of the junction box (4); the boost system (3) has a quasi-Z source structure inside; the main charging pile (1) is electrically connected to the junction box (4) and the charging gun head (2) respectively.

2. According to claim 1, a quasi-Z source high-gain boost type mobile photovoltaic charging device is characterized in that: The boost system (3) comprises a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a first inductor, a second inductor, a third inductor, a first diode, a second diode, a third diode, a fourth diode, a first load, a first switch tube and an input voltage, wherein the positive electrode of the input voltage is connected to the first inductor, and the other end is connected to the negative electrode of the first capacitor, the input side of the input voltage corresponds to the output side of the control relay, one end of the first load should be connected to the positive electrode side of the sixth capacitor, and the other end should be connected to the negative electrode side of the second capacitor, and the output side of the first load corresponds to the input side of the main charging pile (1).

3. According to claim 2, a quasi-Z source high-gain boost type mobile photovoltaic charging device is characterized in that: The cathodes of the third inductor and the fourth capacitor are connected to the anode of the third diode, the cathodes of the second inductor and the fifth capacitor are connected to the cathode of the third diode, and the second inductor, the third inductor, the fourth capacitor, the fifth capacitor and the third diode constitute an internal quasi-Z source structure.

4. According to claim 2, a quasi-Z source high-gain boost type mobile photovoltaic charging device is characterized in that: The positive electrode of the second capacitor is connected to the negative electrode of the third capacitor, the positive electrode of the third capacitor is connected to the negative electrode of the sixth capacitor, the negative electrode of the sixth capacitor is connected to one end of the load, the negative electrode of the second capacitor is connected to the other end of the load, the second capacitor, the third capacitor and the sixth capacitor are connected in series on both sides of the first load, one end of the first switch tube is connected to the negative electrode of the sixth capacitor, and the other end of the first switch tube is connected to the negative electrode of the first capacitor.

5. According to claim 2, a quasi-Z source high-gain boost type mobile photovoltaic charging device is characterized in that: The input voltage is the voltage generated by the photovoltaic assembly (6) through the busbar (5), the DC controller, the trip switch and the control relay.

6. A quasi-Z source high-gain boost mobile photovoltaic charging device according to claim 2, characterized in that: The positive electrode of the first diode is connected to the first inductor, and the negative electrode of the first diode is connected to the positive electrode of the first capacitor; the positive electrode of the second diode is connected to the positive electrode of the first capacitor, and the negative electrode of the second diode is connected to the positive electrode of the sixth capacitor; the positive electrode of the fourth diode is connected to the first load, and the negative electrode of the fourth diode is connected to the negative electrode of the first capacitor.

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