TWI460979B - Control method of a dc-dc converter and a voltage coverting system - Google Patents

Description

DC/DC converter control method and voltage conversion system

The invention relates to a driving control method for a DC/DC converter, and in particular to a driving control method and a voltage conversion system suitable for managing a DC/DC converter for controlling a solar power supply system.

In recent years, with the continuous development of science and technology, energy (such as oil, coal and natural gas) has been continuously exploited and consumed, resulting in energy crisis and global warming effects. Therefore, the development and research of various types of green alternative renewable energy sources such as solar energy, wind power, and water power have become one of the major research projects in the world. Among the above-mentioned various types of green alternative energy sources, solar power supply is the most important, because solar energy sources are inaccessible, inexhaustible and have no environmental pollution. At the same time, the safety and utilization of solar energy sources are much higher than others. Various types of green alternative renewable energy. Accordingly, research and development using solar power systems and improving solar power efficiency have become the most important research topics at present.

Generally, a solar cell is composed of a plurality of solar photovoltaic cells (PV) in series or in parallel, and converts light energy into electric energy by using a photovoltaic effect to establish a photovoltaic system. At present, solar power supply systems can be integrated or operated independently with municipal power and have been widely used in homes, industries, buildings and other facilities.

Please refer to FIG. 1 , which illustrates a schematic diagram of a typical solar power supply system 1 . A typical solar power system 1 includes a solar module 11 and a boost DC/DC converter 13. The solar power system 1 can be used to drive the load 15. The solar module 11 is coupled to the input of the boost DC/DC converter 13. The output of the boost DC/DC converter 13 is coupled to the load 15.

The solar module 11 can be composed of a plurality of solar photovoltaic panels in series or in parallel, and the received light energy is converted into a DC power output by a photovoltaic effect. In other words, the solar module 11 can generate an output current I _PV and an output voltage V _PV .

The boost DC/DC converter 13 is a conventional conventional boost DC/DC converter circuit including an input capacitor C1, an inductor L1, a power transistor Q1, a diode D1, and an output capacitor C2. The output end of the solar module 11 is coupled to the input capacitor C1 to charge the input capacitor C1 by injecting an output current IPv1. In addition, the first end of the input capacitor C1 is coupled to the first end of the inductor L1, and the second end of the inductor L1 is coupled to the drain of the power transistor Q1. The source of the power transistor Q1 is coupled to the second end of the input capacitor C1. The diode D1 is coupled between the drain of the power transistor Q1 and the first end of the output capacitor C2. The second end of the output capacitor C2 is coupled to the source of the power transistor Q1. The gate of the power transistor Q1 is used to receive the pulse wave control signal PWM1 to correspondingly control the on and off times of the power transistor Q1. In other words, by controlling the operation of the power transistor Q1, the boost mode of the boost DC/DC converter 13 can be adjusted, thereby obtaining the desired output voltage Vo to drive the load 15.

The actual operating condition of the boost DC/DC converter 13 can be as shown in FIG. 2, which shows a schematic diagram of the circuit operation waveform of the boost DC/DC converter 13. Curve C11 is the inductor current waveform when the boost DC/DC converter 13 is operating. The curve C13 is a 跨-source voltage-crossing waveform curve when the power transistor Q1 is turned off when the boost DC/DC converter 13 operates. The curve C15 is a waveform of the pulse wave control signal PWM1 input to the gate of the power transistor Q1 when the boost DC/DC converter 13 operates. Curve C17 is the output voltage Vo waveform when the boost DC/DC converter 13 is operating. .

It is generally known that the boost DC/DC converter 13 operates with different input voltages corresponding to the duty cycle of the different pulse control signals PWM1 (ie, on-time, T ₂ - T ₁ / T ₃ - T ₁ ). That is to say, when the output voltage V _{PV of the} solar module 11 forms a voltage across the input capacitor C1, the duty cycle of the pulse wave control signal PWM1 can be adjusted according to the voltage level of the different output voltage V _{PV to} enable the boost DC/ The DC converter 13 stabilizes the output voltage Vo for use by the load 15. However, as shown in FIG. 2, in order to stabilize the voltage level of the output voltage Vo, the power transistor Q1 must continuously switch on and off. However, frequent switching may make the system more unstable, so that the solar power supply system 1 cannot fully utilize the energy output by the solar module 11 while reducing the power supply efficiency of the solar power supply system 1. In addition, the solar photovoltaic panels in the solar module 11 continue to operate continuously, accelerating the aging of the photovoltaic panels, the damage rate, and the high cost of the solar photovoltaic panels, thereby increasing the maintenance cost of the solar power supply system 1.

In view of this, the embodiment of the present invention provides a DC/DC converter control method, which can be applied to a solar power supply system. The DC/DC converter control method can control the DC/DC converter in stages according to the power supply requirements of the solar power supply system, so as to avoid switching the DC/DC converter too frequently, thereby improving energy conversion efficiency and system stability, and being effective at the same time. Improve the energy utilization rate of solar photovoltaic panels and establish a smart solar power supply system.

The embodiment of the invention provides a DC/DC converter control method, which is used for converting a first DC voltage generated by a solar module to a voltage through a DC/DC converter, and outputting a second DC. Voltage to DC bus. First, the second DC voltage is detected. When it is determined that the second DC voltage is higher than the preset operating voltage range, the injection energy is stopped to the DC busbar by stopping the operation of the DC/DC converter. When it is determined that the second DC voltage is within a preset operating voltage range, the DC/DC converter is driven into a fixed on-time mode, that is, a fixed switching DC/DC converter is maintained to maintain the second DC voltage. In addition, when it is determined that the second DC voltage is lower than the preset working voltage range, the DC/DC converter is driven to enter the maximum power tracking mode, and the maximum power tracking calculation is performed to obtain the maximum operating power point of the solar module, thereby providing maximum power. To the DC bus.

The embodiment of the invention further provides a DC/DC converter control method, wherein the DC/DC converter control method is used to convert the first DC voltage generated by the solar module to a voltage through a DC/DC converter, and output the second The DC voltage is supplied to the load to drive the load. First, the current and voltage of the driving load are detected. Then, the power of the driving load is obtained through calculation. Determine whether the power of the driving load is greater than a preset power value. When the power of the driving load is less than the preset power value (ie, the light load state), the DC/DC converter is driven into a fixed on-time mode to maintain the voltage required to drive the load. When the power of the driving load is greater than the preset power value (ie, the heavy load state), the DC/DC converter is driven into the maximum power tracking mode and the maximum power tracking calculation is performed to obtain the maximum operating power point of the solar module. To make full use of the energy provided by solar modules, to improve power efficiency.

In one embodiment of the present invention, the method for establishing the maximum power tracking mode includes first detecting a first direct current output by the solar module. Secondly, a maximum power calculation is performed on the first DC voltage and the first DC current to obtain a maximum power operating point of the solar module. Then, based on the maximum power operating point, a maximum power control signal is generated to drive the control DC/DC converter to provide maximum power to the load. The maximum power operating point is the first DC voltage and the first DC current output when the solar module operates at the maximum power.

In one embodiment of the present invention, the method for establishing the fixed on-time mode includes first detecting a first DC voltage. Secondly, a fixed on-time control signal is generated according to the detected first DC voltage and the second DC voltage. Then, the DC/DC converter is driven and controlled by the fixed on-time control signal to maintain the second DC voltage.

The embodiment of the invention provides a voltage conversion system, which is suitable for converting a first DC voltage outputted by a solar module by a voltage, and outputting a second DC voltage to provide a DC bus. The voltage conversion system includes a DC/DC converter, a first voltage sensing module, a first current sensing module, a second voltage sensing module, and a control device. The DC/DC converter is coupled to the output end of the solar module for converting the first DC voltage into a voltage and outputting the second DC voltage to the DC bus. The first voltage sensing module is coupled to the output end of the solar module for detecting the first DC voltage. The first current sensing module is coupled between the output end of the solar module and the input end of the DC/DC converter to detect the first DC current output by the solar module. The second voltage sensing module is coupled to the output of the DC/DC converter for detecting the second DC voltage. In addition, the control device is coupled to the first voltage sensing module, the first current sensing module, the second voltage sensing module, and the DC/DC converter. The control device is configured to compare the second DC voltage with a predetermined operating voltage range, and when the second DC voltage is within the preset operating voltage range, the control device outputs a fixed on-time control signal to drive the DC/DC converter to maintain the fixed The second DC voltage. When the second DC voltage is lower than the preset operating voltage range, the control device outputs a maximum power control signal to drive the DC/DC converter for maximum power tracking calculation to provide maximum power to the DC bus.

The embodiment of the invention further provides a voltage conversion system, which is adapted to output a second DC voltage to drive the load after the first DC voltage outputted by the solar module is converted by voltage. The voltage conversion system includes a DC/DC converter, a first voltage sensing module, a first current sensing module, a second voltage sensing module, a second current sensing module, and a control device. The DC/DC converter is coupled to the output end of the solar module for converting the first DC voltage to a voltage and outputting the second DC voltage to the load. The first voltage sensing module is coupled to the output end of the solar module for detecting the first DC voltage. The first current sensing module is coupled between the output end of the solar module and the input end of the DC/DC converter to detect the first DC current output by the solar module. The second voltage sensing module is coupled to the output of the DC/DC converter. The second voltage sensing module is configured to detect the second DC voltage. The second current sensing module is coupled between the output of the DC/DC converter and the load, wherein the second current sensing module is configured to detect the second DC current of the DC/DC converter. The control device is coupled to the first voltage sensing module, the first current sensing module, the second voltage sensing module, the second current sensing module, and the DC/DC converter. The control device is configured to calculate the second DC voltage and the second DC current, and obtain output power. The control device further compares the output power with a predetermined output power value. When the output power is less than the preset output power value, the control device outputs a fixed on-time control signal to drive the DC/DC converter to maintain the fixed second DC voltage. When the output power is greater than the preset output power value, the control device outputs a maximum power control signal to drive the DC/DC converter for maximum power tracking calculation to provide maximum power to the load.

In one embodiment of the invention, the solar module is comprised of a plurality of solar photovoltaic panels in series or in parallel.

In summary, the DC/DC converter control method and voltage conversion system provided by the embodiments of the present invention are suitable for managing and controlling a solar power supply system. The DC/DC converter control method can effectively control the driving DC according to the demand state of the rear end circuit detected by the voltage and current sensing components (such as the voltage of the bus bar or the state of the load) and the power supply of the solar photovoltaic panel. A DC converter is used to enable the solar powered system to operate the maximum operating power point of the solar photovoltaic panel. At the same time, the method can make the DC/DC converter output a fixed voltage under the preset condition, thereby avoiding the DC/DC converter switching frequency being too frequent, thereby improving system stability and power supply efficiency, and extending the solar photovoltaic panel. Operation time, thereby improving the utilization and economic benefits of solar photovoltaic panels.

The detailed description of the present invention and the accompanying drawings are to be understood by the claims The scope is subject to any restrictions.

[Example of parallel operation type solar power supply system architecture]

Please refer to FIG. 3 , which illustrates a functional block diagram of the parallel operation solar power supply system 2 . The parallel operation solar power supply system 2 connected in parallel with the DC bus bar 20 includes a solar module 21, a boost DC/DC conversion module 23, a control device 25, a current sensing module 27, and a first voltage sensing module. 29a and a second voltage sensing module 29b. The output end of the solar module 21 is coupled to the input end of the boost DC/DC converter module 23. In addition, the output end of the boost DC/DC converter module 23 is coupled to the DC bus bar 20. The current sensing module 27 is coupled between the output end of the solar module 21 and the input end of the boost DC/DC converter module 23 . The first voltage sensing module 29a is coupled to the output end of the solar module 21 . The second voltage sensing module 29b is coupled to the DC bus bar 20.

The parallel operation solar power supply system 2 can convert the energy outputted by the solar module 21 through the boost DC/DC conversion module 23 for voltage boost conversion and then into the DC bus bar 20 to maintain the voltage of the DC bus bar 20 _Bus (ie the second DC voltage). Further, the control device 25 included in the parallel operation solar power supply system 2 can control the operation of the boost DC/DC conversion module 23 according to the voltage level of the DC bus 20 and the power supply state of the solar module 21. The multi-stage mode controls the power supply state of the parallel operation solar power supply system, thereby making full use of the energy generated by the solar module 21.

For example, the control device 25 can switch the cut-off boost DC/DC conversion module 23 when the voltage V _{bus of the} DC bus 20 is greater than the maximum voltage of the preset DC bus 20 (for example, 400 V DC). In operation, the parallel operation solar power supply system 2 is turned off to stop the transmission of power to the DC bus bar 20. The control device 25 can further DC bus voltage level of the voltage V _bus 20 is interposed within the normal operating voltage range (e.g., between 390V ~ 395V DC), the switching control means 25 may be driven by a fixed on-time boost DC The mode of operation of the /DC converter module 23 maintains the voltage _{Vbus of the} stabilized DC busbar 20. In other words, the boost mode is controlled by adjusting the switching period of the boost DC/DC converter module 23 to maintain the voltage _Vbus delivered to the DC bus 20. The control device 25 can also be that the voltage level of the voltage V _bus of the DC bus 20 is lower than the normal operating voltage range (for example, less than 390 V), and the control device 25 according to the power supply state of the solar module 21, that is, the solar module. The output current I _PV (ie, the first direct current) of 21 and the output voltage V _{PV of the} solar module 21 (ie, the first direct current voltage) are calculated by searching for the maximum operating power point of the solar module 21, and then the solar mode is The output voltage V _{PV of} the group 21 corresponding to the maximum operating power point is boosted by the boost DC/DC converter module 23, and then converted into the voltage V _bus of the DC bus 20 to boost the power of the DC bus 20 . It should be noted that the specific control method of the parallel operation solar power supply system 2 will be described by other embodiments, and therefore will not be described herein.

Then, in the physical architecture of the parallel-operated solar power supply system 2, the solar module 21 is composed of a plurality of solar photovoltaic panels in series or in parallel as described above, and the light energy can be converted into electrical energy by the photovoltaic effect to generate Output voltage V _PV and output current I _PV .

The boost DC/DC converter module 23 can be a conventional boost DC/DC converter for boosting the output voltage V _PV generated by the solar module 21 while being regulated by the output capacitor C4. The bus bar 20 maintains or raises the voltage level of the DC bus 20.

The operation mode of the boost DC/DC converter module 23 is simply assumed, that is, the input capacitor C3 and the output capacitor C4 are charged. When the power transistor Q2 is turned on, the energy output by the solar module 21 is stored in the inductor. L2, at this time, the inductor current rises, causing the diode D2 to be reverse biased, whereby the output capacitor C4 outputs energy to the DC busbar 20. When the power transistor Q2 is turned off, the inductor L2 changes the magnetic field, and the polarity of the voltage of the inductor L2 is reversed, so that the diode D2 is biased in the forward direction. At this time, the energy stored in the inductor L2 flows into the DC bus bar 20 via the diode D2. In other words, the operation of the boost DC/DC converter module 23 can be controlled by controlling the turn-on and turn-off times of the switching power transistor Q2. Accordingly, the voltage conversion mode of the boost DC/DC conversion module 23 can be expressed by the following equation.

In the above equation, v _bus is the voltage value of the DC bus 20, v _PV is the DC voltage value output by the solar module 21, and D is the conduction time of the power transistor Q2 (that is, the duty cycle of the power transistor Q2). Those skilled in the art should be able to infer the derivation of the above equations and the control mode of the boost DC/DC conversion module 23, and therefore will not be described herein.

In addition, the current sensing module 27 can be used to capture the output current I _{PV of the} solar module 21 for sampling to the control device 25. The first voltage sensing module 29a and the second voltage sensing module 29b are respectively configured to capture the output voltage V _{PV of the} solar module 21 and the voltage V _{bus of the} DC bus 20 for sampling to the control device 25. The control device 25 can use the second voltage sensing module 29b to feedback the voltage V _{bus of} the captured DC busbar 20 to determine the operation mode of the parallel-operated solar power supply system 2.

In detail, the control device 25 includes a maximum power tracking module 251, a switch control device 253, and a micro processing module 255. The maximum power tracking module 251 and the switch control device 253 are respectively coupled to the micro processing module 255. The maximum power tracking module 251 can be used to receive the current sensing module 27 and the first voltage sensing module 29a to detect the output voltage V _PV and the output current I _{PV of the} solar module 21 . The maximum power tracking module 251 can perform maximum power calculation on the output voltage V _PV and the output current I _PV of the captured solar module 21 to obtain the solar module 21 under different conditions (eg, sunshine, temperature, etc.). The maximum operating power point (ie, the maximum output voltage V _PV and the maximum output current I _PV ). Accordingly, the microprocessor module 255 can control the boost DC/DC converter module 23 to operate the solar module 21 at the maximum power point even if the solar module 21 maintains maximum power output. The micro-processing module 255 can respectively capture and feedback the output voltage V _{PV of the} solar module 21 and the voltage V _{bus of the} DC bus 20 according to the first voltage sensing module 29a and the second voltage sensing module 29b. And the switch control device 253 outputs a pulse wave control signal PWM2 with a corresponding duty cycle to the power transistor Q2 to control the turn-on and turn-off time of the power transistor Q2.

During the actual operation of the circuit, the solar module 21 generates and outputs an output voltage V _PV to the boost DC/DC conversion module 23 via a photovoltaic effect. In general, the solar module 21 can provide 150V-300V DC, and the voltage of the DC bus 20 V _bus is 380V +/- 20V DC. Therefore, the control device 25 can drive the switch control device 253 to generate the pulse wave control signal PWM2 with the corresponding duty cycle according to the voltage V _{bus of the} DC bus bar 20 detected by the second voltage sensing module 29b, and input the power to the power. The gate of crystal Q2 controls the operation of power transistor Q2. Thereby, the boost DC/DC converter module 23 can be controlled to output the required power to the DC busbar 20, thereby boosting or maintaining the voltage _{Vbus of the} DC busbar 20. In addition, the control device 25 can also adjust the operation of the boost DC/DC conversion module 23 (that is, the operating power point of the solar module 21) after the calculation according to the power supply condition of the solar module 21 to reach the solar module 21. The maximum power output is to improve the power supply efficiency of the parallel operation solar power supply system 2. The specific implementation management control mode will be described by other embodiments, and will not be further described herein.

Incidentally, the definition of the maximum operating power point of the solar module 21 can be referred to FIG. 4. FIG. 4 shows the output current-output voltage (IV) and the output power-output voltage of a typical solar photovoltaic panel under a specific sunlight and temperature conditions. Schematic diagram of the (PV) characteristic curve. Curve C21 shows the output current (Ipv) and output voltage (Vpv) characteristics of a typical solar photovoltaic panel. Curve C23 shows the output power-output voltage (P-V) characteristic curve of a typical solar photovoltaic panel. Curve C25 shows a typical solar photovoltaic panel having a fixed slope of closed circuit current (Isc) and open circuit voltage (Voc). It is worth mentioning that no matter how the solar photovoltaic panel operates, its operating power point will be located to the right of the open circuit voltage Voc and the short circuit current Isc curve. In addition, the highest vertex P1 of C23 is the maximum power that the solar photovoltaic panel can output. P2 is above the curve C21 and is the operating power point corresponding to P1. That is to say, when the solar photovoltaic panel is operated at P2 (that is, when the output current is I* and the output voltage is V*), the solar photovoltaic panel can output the maximum power P1.

In addition, as shown in Fig. 4, the output power changes nonlinearly. Therefore, the voltage converter and the maximum power point tracking (MPPT) algorithm are required to operate the solar photovoltaic panel output power at the maximum power point to improve the solar photovoltaic panel. Power efficiency.

In actual implementation, the solar module 21 is composed of a solar photovoltaic panel, and the solar module 21 can be implemented by multiple modules in series, multiple modules in parallel, or a combination thereof as described above. The multi-module series can increase the voltage level of the output of the solar module 21, and the multi-module parallel connection can upgrade the solar module 21 The amount of current output. In other words, the design of the solar module 21 can be set according to the requirements of the overall power supply system. The current sensing module 27 can be implemented by using a Hall Effect Sensor and an analog digital conversion circuit. Similarly, the first voltage sensing module 29a and the second voltage sensing module 29b can be implemented by a voltage dividing circuit and an analog digital circuit. The control device 25 can be implemented by a digital signal processor (DSP), that is, the maximum power tracking module 251, the switch control device 253, and the micro processing module 255 can be programmed to be integrated into the digital signal processor. The parallel operation solar power supply system 2 is controlled by the control.

It should be noted that the present invention does not limit the solar module 21, the boost DC/DC conversion module 23, the control device 25, the current sensing module 27, the first voltage sensing module 29a, and the second voltage sense. The type, physical architecture and/or implementation of the test module 29b.

[Example of DC/DC Converter Control Method]

Next, please refer to FIG. 5 and simultaneously refer to FIG. 3. FIG. 5 is a flow chart of a DC/DC converter control method according to an embodiment of the present invention. In this implementation, the DC/DC converter control method can be used to manage the parallel-operated solar power system 2 connected to the DC busbar 20.

First, the parameters of the parallel operation solar power supply system are initialized, for example, the duty cycle of the boost DC/DC conversion module 23, the initial input voltage value of the power supply system, the initial input current value of the power supply system, and the initial output voltage value of the power supply system. And an initial output current value of the power supply system, a first preset voltage value, a second preset voltage value, and a third preset voltage value, etc. (step S101). Then, in step S103, the voltage value V _bus [n] of the current DC bus bar 20 (ie, the voltage level of the second DC voltage) is detected and captured by the second voltage sensing module 29b. Next, in step S105, comparing the current voltage value V _bus [n] of the DC bus bar 20 with the first preset voltage value, determining whether the current voltage value V _bus [n] of the DC bus bar 20 is greater than the first preset voltage value. . If the current voltage value V _bus [n] of the DC bus 20 is greater than the first predetermined voltage value, the control device 25 turns off the parallel operation solar power supply system 2, that is, stops inputting energy to the DC bus 20 (step S107). On the other hand, if the current voltage value V _bus [n] of the DC bus 20 is less than the first preset voltage value, compare whether the current voltage value V _bus [n] of the DC bus 20 is between the second preset voltage value and the first Between three preset voltage values (step S109). In other words, it is judged whether the current voltage value V _bus [n] of the DC bus 20 is smaller than the second preset voltage value and greater than the third preset voltage value. If the current voltage value V _bus [n] of the DC bus 20 is between the second preset voltage value and the third preset voltage value, the control device 25 then uses the first voltage sensing module 29a in step S111. Detecting and capturing the voltage value input to the boost DC/DC conversion module 23 (that is, the output voltage V _{PV of the} solar module 21 or the voltage level of the first DC voltage) to the current DC bus 20 The current voltage value V _bus [n] is calculated with the output voltage value V _PV [n] of the solar module 21 to obtain a duty cycle of the corresponding pulse wave control signal PWM2 (step S113). Thereby, the control device 25 drives the switch control device 253 to output the pulse transistor control signal PWM2 (ie, the fixed on-time control signal) corresponding to the duty cycle to the power transistor Q2 in the boost DC/DC converter module 23, Further, the current voltage value V _bus [n] of the current DC bus 20 is maintained, so that the DC/DC conversion module 23 enters a constant on time mode. On the other hand, if the current voltage value V _bus [n] of the DC bus 20 is less than the third preset voltage value, the control device 25 performs the maximum power calculation using the maximum power tracking module 251 to drive the DC/DC conversion in step S115. The module 23 enters a maximum power tracking mode to obtain a maximum operating power point of the corresponding solar module 21, that is, a maximum output voltage V _PV and a maximum output current I _{PV of the} solar module 21. Subsequently, the control device 25 performs calculation according to the current output voltage value V _PV [n] of the solar module 21 and the current output current value I _PV [n] (ie, the first DC current value), and obtains the duty cycle of the pulse wave control signal PWM2. (Step S117). Thereby, the control device 25 drives the switch control device 253 to output the pulse wave control signal PWM2 (ie, the maximum power control signal) corresponding to the duty cycle to the power transistor Q2 in the boost DC/DC conversion module 23, Increase the power of the current DC bus 20 . Thereafter, when the control of the DC/DC conversion module 23 is completed, step S103 is re-executed until the parallel-operated solar power supply system 2 is turned off or stopped.

Incidentally, the first preset voltage value is greater than the second preset voltage value, and the second preset voltage value is greater than the third preset voltage value. In other words, the first predetermined voltage value can be the maximum voltage that the DC bus 20 can withstand. The third preset voltage value may be the lowest voltage value of the DC bus 20 . Thereby, the second preset voltage value and the third preset voltage value can form an operating voltage range. It should be noted that the first preset voltage value, the second preset voltage value, and the third preset voltage value may be set according to actual requirements, so the present invention is not limited to the first preset voltage value, and the second The preset voltage value and the third preset voltage value are actually set.

For example, the parallel-operated solar power supply system 2 can be operated in parallel with the mains power supply system, and the voltage of the required DC bus 20 is required. Generally it is 380V DC. Accordingly, as previously described, the first predetermined voltage value can be set to 400V DC, that is, the maximum voltage value of the DC bus 20 . Next, the second preset voltage value is set to 395V DC, and the third preset voltage value is 390V DC.

When the detected voltage value V _bus [n] of the current DC bus 20 rises and is greater than 400V DC, the control device 25 then switches the cut-off boost DC/DC conversion because the current DC bus 20 is greater than the maximum voltage value. The module 23 is configured to turn off the parallel operation solar power supply system 2. When the current voltage value V _bus [n] of the DC bus 20 drops but is lower than 395V DC and greater than 390V DC (that is, the DC/DC conversion module 23 enters the fixed on-time mode), the control device 25 is the current DC bus. The voltage value of 20 is calculated by the input voltage value of the boost DC/DC converter module 23 (ie, the current output voltage of the solar module 21 V _PV [n]), and the duty cycle of the pulse wave control signal PWM2 is obtained (ie, fixed) The duty cycle of the on-time control signal). When the current voltage value V _bus [n] of the DC bus 20 drops below 390V DC (that is, the DC/DC conversion module 23 enters the maximum power tracking mode), the control device 25 can utilize the maximum power tracking. The module 251 performs maximum power tracking calculation, obtains the operating voltage and operating current of the corresponding solar module 21, and performs calculation to obtain a duty cycle of the pulse wave control signal PWM2 (ie, a duty cycle of the maximum power control signal). After the control of the DC/DC conversion module 23 is completed, the voltage value V _bus [n] of the DC bus 20 is re-detected, and the state of the voltage value of the current DC bus 20 is determined to convert the DC/DC. The module 23 is controlled accordingly until the parallel-operated solar power supply system 2 is turned off or stopped.

The maximum power tracking algorithm in this DC/DC converter control method further includes a masking algorithm. When the solar photovoltaic panel in the solar module 21 is shielded (for example, cloud layer, building shadow or dust cover), the solar module 21 will have multiple regions of maximum power and one global maximum power. Accordingly, if the masking function is not added, the maximum power tracking algorithm usually only catches up to the maximum power value of the region, and the maximum performance of the solar module 21 cannot be fully utilized. Because when the solar module 21 solar panels generating portion or all of the shielding, solar module 21 that the output current I _PV will be substantially reduced, it can be based on the output of the solar module 21 the current I _PV, it determines whether masking occurred The phenomenon can be re-tracked to the global maximum operating power point by changing the duty cycle of the pulse control signal PWM2 to deviate from the regional maximum.

Furthermore, the maximum power tracking algorithm used in this embodiment is a perturbation observation method.

Specifically, please refer to FIG. 6. FIG. 6 illustrates a maximum power tracking calculation method provided by an embodiment of the present invention. First, in step S201, the current sensing module 27 and the first voltage sensing module 29a are used to respectively detect the current output current value I _PV [n] (ie, the first DC current value) of the solar module 21 and the solar mode. Group 21 current output voltage value V _PV [n] (ie, the first DC voltage value). Next, in step S203, the current output current value I _PV [n] of the captured solar module 21 is compared with the previous output current value I. The current difference between _PV [n-1] and the preset current value (first preset current value) to determine whether there is a shadow condition (ie, some or all of the solar photovoltaic panels in the solar module 21 have a shadowing condition). If the current difference between the current output current value I _PV [n] of the solar module 21 and the last output current value I _PV [n-1] is less than the preset current value, that is, shielding occurs, and the captured solar mode is obtained. Group 21 currently performs an output current value I _PV [n] to obtain a global maximum operating power point (step S205). Then, using the maximum operating power point obtained by the calculation result (ie, the maximum output voltage of the solar module 21 and the maximum output current), the duty cycle of the corresponding pulse wave control signal PWM2 is obtained, that is, the duty cycle of the shielding control signal (step S207). The control device 25 then drives the switch control device 253 to output the pulse transistor control signal PWM2 (ie, the masking control signal) corresponding to the duty cycle to the power transistor Q2 in the boost DC/DC converter module 23 to improve the current DC. The power of bus 20 .

Incidentally, the algorithm described in step S205 may be to obtain a fixed slope (ie, an open circuit voltage Voc/short current Isc) by using the open circuit voltage Voc and the short circuit current Isc fixed in the solar module 21. In the foregoing, regardless of how the solar photovoltaic panel operates, the operating power point is located to the right of the open circuit voltage Voc and the short circuit current Isc curve, so that when the shielding occurs, the solar module 21 detected by the current sensing module 27 can be detected. The current output current I _PV [n] is multiplied by this fixed slope to deviate from the regional maximum and re-track to the global maximum operating power point.

On the other hand, if the current difference between the current output current I _PV [n] of the solar module 21 and the previous output current value I _PV [n-1] is greater than the preset current value, that is, no masking occurs, that is, the captured The current output current value I _PV [n] of the solar module 21 and the current output voltage value V _PV [n] of the solar module 21 are calculated to obtain the current output power value P _PV [n] of the solar module 21 (step S209). Subsequently, in step S211, the current output power value P _PV [n] of the solar module 21 is compared with the last output power value P _PV [n-1]. If the current output power value P _PV [n] of the solar module 21 is greater than the previous output power value P _PV [n-1] (that is, the power shows an upward trend), the current output voltage value V of the solar module 21 is compared and judged. Whether _PV [n] is greater than the last output voltage value V _PV [n-1] (step S213). If the current output voltage value V _PV [n] of the solar module 21 is greater than the previous output voltage value V _PV [n-1], the control device 25 reduces the duty cycle of the pulse wave control signal PWM2 (step S215). On the other hand, if the current output voltage value V _PV [n] of the solar module 21 is smaller than the previous output voltage value V _PV [n-1], the control device 25 increases the duty cycle of the pulse wave control signal PWM2 (step S217).

If the current output power value P _PV [n] of the solar module 21 is smaller than the previous output power value P _PV [n-1] (that is, the power exhibits a downward trend), the current output voltage value of the solar module 21 is compared and judged. Whether V _PV [n] is greater than the previous output voltage value V _PV [n-1] (step S219). If the current output voltage value V _PV [n] of the solar module 21 is greater than the previous output voltage value V _PV [n-1], the control device 25 increases the duty cycle of the pulse wave control signal PWM2 (step S221). On the other hand, if the current output voltage value V _PV [n] of the solar module 21 is smaller than the previous output voltage value V _PV [n-1], the control device 25 reduces the duty cycle of the pulse wave control signal PWM2 (step S223).

In step S215, S217, S221 or S223, after the duty cycle of calculating the pulse wave control signal PWM2 is completed, the current output voltage value V _PV [n] of the currently acquired solar module 21, the solar module 21 The current output current value I _PV [n] and the current output power value P _PV [n] of the solar module 21 replace the last output voltage value V _PV [n-1], the output current value I _PV [n-1] and The output power value P _PV [n-1] is output (step S225).

It should be noted that the embodiment of the present invention uses the disturbance observation method as the maximum power tracking algorithm, but other maximum power tracking algorithms, such as voltage feedback method, incremental conductance method, linear approximation method, etc., can be applied to the present invention. However, those skilled in the art should be familiar with the above various types of maximum power tracking calculation methods, and therefore will not be described herein. In addition, the present invention does not limit the actual implementation method of the maximum power tracking algorithm as long as the solar photovoltaic can be calculated. The maximum power operation point of the board is sufficient. In addition, FIG. 6 is merely an exemplary embodiment of a maximum power tracking algorithm and is not intended to limit the present invention.

It is worth mentioning that the DC/DC converter control method described in FIG. 5 and the maximum power tracking calculation method described in FIG. 6 can be programmed in the control device 25 as described above to supply power to the parallel operation solar power. System 2 performs control. However, the present invention does not limit the actual setting mode and operation mode of the DC/DC converter control method and the maximum power tracking calculation method.

[Embodiment of Independent Operational Solar Power System Architecture]

The stand alone solar power system, as the name suggests, uses solar panels directly through a DC/DC converter to convert energy into the power required by the load to drive the load. Therefore, the independent power supply system can be protected from the power outage of the city's power grid, so it is suitable for areas such as mountains or isolated islands that are remote and difficult to set up.

Please refer to FIG. 7. FIG. 7 is a functional block diagram of the independently operated solar power supply system 3. The independent operation solar power supply system 3 includes a solar module 21, a boost DC/DC conversion module 23, a control device 25, a battery unit 33, a first current sensing module 31a, and a second voltage sensing module 31b. The first voltage sensing module 29a and the second voltage sensing module 29b. The stand-alone solar power system 3 can be used to provide the energy generated by the solar module 21 to the DC load 30. The battery unit 33 can include a charging and discharging module (not shown in FIG. 7) and a battery (not shown in FIG. 7). The control device 25 includes a maximum power tracking module 251, a switch control device 253, and a micro processing module 255. The output end of the solar module 21 is coupled to the input end of the boost DC/DC converter module 23. The output end of the boost DC/DC converter module 23 is coupled to the DC load 30. The battery unit 33 is coupled between the output end of the solar module 21 and the input end of the boost DC/DC conversion module 23 . The first current sensing module 31a is coupled between the output end of the solar module 21 and the input end of the boost DC/DC converter module 23 . The second current sensing module 31b is coupled between the DC load 30 and the output of the boost DC/DC converter module 23. The first voltage sensing module 29a is coupled to the output end of the solar module 21 . The second voltage sensing module 29b is connected in parallel with the DC load 30.

In a simple operation, the control unit 25 can provide the power required for the DC load 30 after the voltage is boosted and converted by the boosting DC/DC converter module 23 through the solar module 21. At the same time, the solar module 21 can be charged when the battery in the battery unit 33 does not reach the upper limit. The battery in battery unit 33 can provide the power required for DC load 30 when the energy in solar module 21 is exhausted (eg, at night or when there is insufficient sunshine). The basic structure and operation mode of the independent operation solar power supply system 3 are similar to those of the parallel operation type solar power supply system 2 described above. Therefore, those skilled in the art should be able to infer that the independent operation type solar power supply system 3 is actually controlled, so that it is no longer Narration.

The control device 25 in the independent-operated solar power supply system 3 can utilize the DC/DC converter control method described in the above embodiments to segmentally control the independently-operated solar power supply system 3 according to the condition of the DC load 30. Make full use of the energy generated by the solar module 21 after being converted by the photovoltaic effect.

The control device 25 can detect the output current I _{L of the} boost DC/DC conversion module 23 (ie, the second DC current) and the output of the boost DC/DC conversion module 23 by using the second current sensing module 31b. The voltage V _L (ie, the second DC voltage) determines the condition of the DC load 30, and further controls the operation of the independently operated solar power supply system 3 according to the preset mode.

Specifically, the control device 25 can detect the output current I _{L of the} boost DC/DC conversion module 23 by using the second current sensing module 31b, and the second voltage sensing module 29b detects the boost DC/ The output voltage V _{L of the} DC conversion module 23 is calculated to obtain the power P _L required to drive the DC load 30. When the power P _L required for the DC load 30 is less than the preset output power value, it means that the DC load 30 is in a light load state. The control device 25 drives the boost DC/DC conversion module 23 to perform a fixed on-time mode, and the first voltage sensing module 29a and the second voltage sensing module 29b respectively capture the output voltage and DC of the solar module 21. The voltage across the load 30 is calculated to obtain a duty cycle (ie, a duty cycle of the fixed on-time control signal) required to control the pulse wave control signal PWM2 required by the boost DC/DC converter module 23. Thereby, the control device 25 will drive the switch control device 253 to output the pulse wave control signal PWM2 (ie, the fixed on-time control signal) corresponding to the duty cycle to the power transistor Q2 in the boost DC/DC conversion module 23. To maintain a fixed output voltage V _L . It should be noted that this mode control method is similar to steps S105 to S113 of FIG.

When the control device 25 calculates the output current I _L detected by the second current sensing module 31b and the output voltage V _L detected by the second voltage sensing module 29b, the power required to drive the DC load 30 is obtained. _{L is} greater than the preset output power value, that is, the DC load 30 is in a heavy load state. At this time, the control device 25 can drive the boost DC/DC conversion module 23 to perform the maximum power tracking mode as described in the previous embodiment, using the first voltage sensing module 29a and the first current sensing module 31a, respectively. Obtaining the output voltage V _{PV of the} solar module 21 (ie, the first DC voltage) and the output current I _{PV of the} solar module 21 (ie, the first DC current) to obtain the maximum operating power point of the solar module 21 and the corresponding pulse The duty cycle of the wave control signal PWM2 (ie, the duty cycle of the maximum power control signal) is controlled correspondingly to the boost DC/DC converter module 23. Thereby, the control device 25 will drive the switch control device 253 to output the pulse wave control signal PWM2 (ie, the maximum power control signal) corresponding to the duty cycle to the power transistor Q2 in the boost DC/DC converter module 23, To increase the output power. In other words, this mode management method is similar to steps S201 to S225 of FIG.

It is worth mentioning that the control mode of the independent operation solar power supply system 3 can be programmed in the micro processing module 255 in the control device 25 as described above. The preset output power value can also be set in the microprocessor module 255 in the control device 25 according to system design requirements. The control device 25 can also be implemented by a digital signal processor, that is, the maximum power tracking module 251, the switch control device 253, and the micro processing module 255 can be programmed in a digital signal processor to control and manage the independent operation solar power supply system. 3. It should be noted that the present invention does not limit the physical architecture and or the actual design of the control device 25 and the preset output power value. In addition, FIG. 7 is only a schematic diagram of an independent operation solar power system architecture, and is not intended to limit the present invention.

[Possible efficacy of the embodiment]

Please refer to FIG. 8. FIG. 8 is a schematic diagram showing the circuit operation waveforms of the parallel operation solar power supply system 2 according to an embodiment of the present invention. Curve C31 is a schematic diagram of the current waveform flowing through the inductor L2. Curve C33 is a schematic diagram of the voltage across the voltage when the power transistor Q2 is turned off. The curve C35 is a waveform diagram of the pulse wave control signal input to the gate of the power transistor Q2 in the step-up DC/DC conversion module 23. Curve C37 shows a schematic diagram of the voltage waveform of the DC bus 20 .

As shown in FIG. 8, the control device 25 manages and controls the parallel operation solar power supply system 2 in a multi-stage manner by controlling the boost DC/DC conversion module 23.

For example, taking the maximum voltage of the DC bus 20 as 400V DC as an example, when the detected current DC bus 20 voltage is greater than 400V DC (ie, time point T _B ), the control device 25 stops the boosting mode. The operation of the DC/DC conversion module 23 is to stop the solar module 21 from supplying power to the DC bus bar 20. When the detected current DC bus 20 voltage is between 390V and 395V DC (ie, time points T _A and T _C ), the control device 25 drives the boost DC/DC conversion module 23 to maintain the DC bus. The voltage V _bus 20 is such that the parallel-operated solar power supply system 2 operates in a fixed on-time mode. Similarly, when the detected current DC bus 20 voltage is lower than 390V DC (ie, time point T _D ), the control device 25 performs a maximum power tracking mode to search for the maximum operating power point of the solar module 21 until The voltage of the DC bus 20 is higher than 390V DC. Accordingly, the boost DC/DC converter module 23 according to the embodiment of the present invention utilizes the DC described above in comparison with the operation mode of the boost DC/DC converter module generally used in the circuit of the solar power supply system (FIG. 2). The DC/DC converter control method can fixedly switch the boost DC/DC conversion module 23 within the output voltage working range of the power supply system, thereby preventing the boost DC/DC conversion module 23 from switching too frequently and improving The stability of the system can also make full use of the energy generated by the solar module 21.

In summary, the DC/DC converter control method and voltage conversion system provided by the embodiments of the present invention are suitable for managing and controlling a solar power supply system. The DC/DC converter control method can effectively control the driving DC according to the demand state of the rear end circuit detected by the voltage and current sensing components (such as the voltage of the bus bar or the state of the load) and the power supply of the solar photovoltaic panel. A DC converter is used to enable the solar powered system to operate the maximum operating power point of the solar photovoltaic panel. At the same time, this method can make the DC/DC converter output a fixed voltage under preset conditions, thereby avoiding the DC/DC converter switching frequency being too frequent, thereby improving system stability, power supply efficiency, and extending solar photovoltaic The operation time of the board will enhance the utilization and economic benefits of solar photovoltaic panels.

The above description is only an embodiment of the present invention, and is not intended to limit the scope of the invention.

1. . . Traditional typical solar power supply system

11, 21. . . Solar module

13,23. . . Boost DC/DC converter module

15. . . load

2. . . Parallel operation solar power supply system

20. . . DC bus

25. . . Control device

251. . . Maximum power tracking module

253. . . Switch control device

255. . . Micro processing module

27. . . Current sensing module

3. . . Independently operating solar power system

30. . . DC load

31a. . . First current sensing module

31b. . . Second current sensing module

29a. . . First voltage sensing module

29b. . . Second voltage sensing module

L1, L2. . . inductance

C1~C4. . . capacitance

Q1, Q2. . . Power transistor

D1, D2. . . Dipole

Vo. . . The output voltage

V _PV . . . Solar module output voltage

I _PV . . . Solar module output current

V _BUS . . . DC bus voltage

V _L . . . Load voltage

I _L . . . Load current

V*. . . Maximum operating voltage of the solar module

I*. . . Maximum operating current of the solar module

Voc. . . Open circuit voltage of solar module

Isc. . . Closed circuit current of solar module

T ₁ , T ₂ , T ₃ , T _A , T _B , T _C , T _D . . . Circuit operation time point

PWM1, PWM2. . . Pulse wave control signal

P1, P2. . . point

C11~C17. . . curve

C21~25. . . curve

S101~S117. . . step

S201~S225. . . step

1 is a schematic diagram of a system architecture of a conventional typical solar power supply system.

FIG. 2 is a schematic diagram showing the circuit operation waveform of a typical boost DC/DC converter.

3 is a functional block diagram of a parallel operation solar power supply system according to an embodiment of the present invention.

Figure 4 is a schematic diagram showing the characteristic curve of a typical solar photovoltaic panel.

FIG. 5 is a flow chart of a DC/DC converter control method according to an embodiment of the present invention.

FIG. 6 is a schematic diagram of a maximum power tracking calculation method provided by an embodiment of the present invention.

FIG. 7 is a functional block diagram of an independently operated solar power supply system according to an embodiment of the present invention.

FIG. 8 is a schematic diagram of circuit operation waveforms of a solar power supply system according to an embodiment of the present invention.

S101~S117. . . step

Claims (10)

A DC/DC converter control method for converting a first DC voltage of a solar module output and outputting a second DC voltage to a DC bus, the control method comprising: detecting the second a DC voltage; determining whether the second DC voltage is within a predetermined operating voltage range; and driving the DC/DC converter to enter a fixed ON time mode when the second DC voltage is within the preset operating voltage range, To maintain the second DC voltage; and if the second DC voltage is lower than the preset operating voltage range, drive the DC/DC converter to enter a maximum power tracking mode, and perform maximum power tracking to increase DC output power. . The control method of the DC/DC converter of claim 1, wherein the control method further comprises: when the second DC voltage is higher than the preset operating voltage range, turning off the DC/DC converter to operate Stop outputting the second DC voltage to the DC bus. The method for controlling a DC/DC converter according to claim 1, wherein the method for establishing the fixed on-time mode comprises: detecting the first DC voltage; and detecting the first DC voltage and the second DC a voltage that produces a fixed on-time control signal; and driving the DC/DC converter with the fixed on-time control signal to maintain the second DC voltage. The method for controlling a DC/DC converter according to claim 1, wherein the method for establishing the maximum power tracking mode comprises: detecting a first direct current of the solar module output; and the first DC voltage and the The first DC current is subjected to maximum power calculation to obtain a maximum power operation point of the solar module; according to the maximum power operation point, a maximum power control signal is generated; and the maximum power control signal is driven to control the DC/DC And a converter for boosting DC output power; wherein the maximum power operating point is the first DC voltage and the first DC current output when the solar module operates at maximum power. The method for controlling a DC/DC converter according to claim 4, wherein the method for establishing the maximum power tracking mode further comprises: after detecting the first DC current, performing calculation and acquiring the first DC current. a current difference; comparing the current difference with a preset current value and determining whether the current difference is less than the preset current value; when the current difference is less than the preset current value, performing the first direct current Calculating to obtain a global maximum power operating point of the solar module; generating a shielding control signal according to the global maximum power operating point; and outputting the shielding control signal to correspondingly drive the DC/DC converter, thereby improving DC Output Power. A voltage conversion system is suitable for converting a first DC voltage outputted by a solar module by a voltage, and outputting a second DC voltage and supplying the current to the bus bar, including: a DC/DC converter, coupled The output voltage of the solar module is used to convert the first DC voltage into a voltage, and output the second DC voltage to the DC bus. A first voltage sensing module is coupled to the solar module. The output terminal is configured to detect the first DC voltage; a first current sensing module is coupled between the output end of the solar module and the input end of the DC/DC converter to detect the current a first DC current is outputted by the solar module; a second voltage sensing module is coupled to the output of the DC/DC converter for detecting the second DC voltage; and a control device coupled The first voltage sensing module, the first current sensing module, the second voltage sensing module, and the DC/DC converter, the control device is configured to compare the second DC voltage with a preset operation Voltage range and when the second When the DC voltage is within the preset operating voltage range, outputting a fixed on-time control signal to drive the DC/DC converter to maintain the second DC voltage; when the second DC voltage is lower than the preset operating voltage range A maximum power control signal is output to drive the DC/DC converter for maximum power tracking calculation to increase DC output power. A control method for a DC/DC converter, which converts a first DC voltage of a solar module output into a voltage and converts a second DC voltage to drive a load, the control method comprising: detecting the second DC voltage And outputting, by the DC/DC converter, a second DC current; calculating the second DC voltage and the second DC current to obtain an output power; comparing the output power with a preset output power value; When the output power is less than the preset output power value, driving the DC/DC converter to enter a fixed on-time mode to maintain the fixed second DC voltage; and if the output power is greater than the preset output power value, driving The DC/DC converter enters a maximum power tracking mode and performs maximum power tracking to boost DC bus power. The method for controlling a DC/DC converter according to claim 7 , wherein the method of establishing the fixed on-time mode comprises: detecting the first DC voltage; and detecting the first DC voltage and the second DC a voltage, a fixed on-time control signal is generated; and the fixed on-time control signal is driven to control the DC/DC converter to maintain the second DC voltage. The method for controlling a DC/DC converter according to claim 7 , wherein the method for establishing the maximum power tracking mode comprises: detecting a first direct current of the solar module output; and the first DC voltage and the The first DC current is subjected to maximum power calculation to obtain a maximum power operation point of the solar module; according to the maximum power operation point, a maximum power control signal is generated; and the maximum power control signal is driven to control the DC/DC And a converter for boosting DC output power; wherein the maximum power operating point is the first DC voltage and the first DC current output when the solar module operates at maximum power. A voltage conversion system is adapted to convert a first DC voltage outputted by a solar module to a load, and output a second DC voltage to drive a load, comprising: a DC/DC converter coupled to the solar energy The output end of the module is configured to output the second DC voltage to the load after the first DC voltage is converted into a voltage; a first voltage sensing module is coupled to the output end of the solar module, The first current sensing module is coupled between the output end of the solar module and the input end of the DC/DC converter for detecting the output of the solar module. a first DC current sensing module coupled to the output of the DC/DC converter for detecting the second DC voltage; and a second current sensing module coupled Between the output end of the DC/DC converter and the load, for detecting a second DC current of the DC/DC converter; and a control device coupled to the first voltage sensing module, the a first current sensing module, the second a voltage sensing module, the second current sensing module, and the DC/DC converter, wherein the control device is configured to calculate the second DC voltage and the second DC current, and obtain an output power; the control The device compares the output power with a preset output power value; when the output power is less than the preset output power value, outputting a fixed on-time control signal to drive the DC/DC converter to maintain the second DC voltage; If the output power is greater than the preset output power value, outputting a maximum power control signal to drive the DC/DC converter for maximum power tracking calculation to increase the DC output power.