TWI574143B - Solar power converter - Google Patents

Description

Solar power converter

The invention relates to the related technical field of power electronic technology, in particular to a solar power converter with an isolated two-stage full-bridge resonant circuit.

With the evolution and development of solar panels, different solar radiation and sunshine angles will affect the power generation of solar panels; therefore, circuit designers are actively trying to develop various solar power converters with isolated two-stage full-bridge resonant circuits to correspond It is applied to solar panels of various powers.

In view of the wide range of applications of solar power converters with isolated two-stage full-bridge resonant circuits, circuit designers are actively trying to adjust the floating voltage generated by the solar panels and can be used in the case of low voltage inputs. A more common approach is for circuit designers to use a non-isolated or isolated architecture to reduce the floating voltage generated by the solar panels.

FIG. 1 is a circuit diagram of a conventional non-isolated buck solar power converter and a buck-boost solar power converter. As shown in FIG. 1(a), a conventional buck solar power converter includes a solar cell module (PV), a buck power conversion unit, and a battery bank. The input end of the buck power conversion unit is coupled to the solar power The output of the buck power conversion unit is coupled to the energy storage unit. The technology mainly uses a low-pass filter composed of one of the buck power conversion unit and a low-pass filter to filter the high-voltage harmonic components to meet the specifications. A conventional buck-boost solar power converter is shown in FIG. 1(b): a solar battery module, a buck power conversion unit, a boost power conversion unit, and an energy storage unit, wherein the drop The input end of the step-up power conversion unit is coupled to the input end of the step-up power conversion unit, and the boost power supply is coupled to the input end of the step-up power conversion unit. The output end of the conversion unit is coupled to the energy storage unit. The technology mainly utilizes the characteristics of the boost power conversion unit and the buck power conversion unit, so that the input voltage can meet the output specification, but the disadvantage is that more switches are needed, and the control is more complicated, and the circuit cost is higher. At the same time, both the buck circuit and the buck-boost circuit require a higher leakage current in the design of the high voltage loop to ensure its safety.

Generally, the isolated power converter circuit has more selectivity, and the circuit can be implemented by single-stage or two-stage. The single-stage circuit has lower cost, but the circuit is low. Performance at high and low voltage inputs may vary widely, switching component selection is more difficult, and components may need to withstand higher voltages. The two-stage circuit is more flexible and can cope with a wider range of input voltages. The disadvantage is that the control is more complicated and the circuit cost is higher.

Figure 2 is a conventional type of single-stage isolated power converter frame FIG. 2(a) is a conventional single-stage active clamp forward solar power converter, and FIG. 2(b) is a conventional single-stage half-bridge solar power converter. Figure 2(c) is a conventional single stage full bridge solar power converter. The conventional single-stage active clamp forward solar power converter is shown in FIG. 2(a) and includes a solar battery module (PV), a buck power conversion unit, and a battery bank. Clamp circuit, and isolation transformer. The input end of the clamp circuit is coupled to the solar cell module, the output end of the clamp circuit is coupled to the input end of the isolation transformer, and the output end of the isolation transformer is coupled to the The input of the buck power conversion unit. Further, an output end of the buck power conversion unit is coupled to the energy storage unit. The conventional single-stage half-bridge solar power converter is shown in FIG. 2(b) and includes: a solar cell module (PV), a battery bank, an isolation transformer, a half bridge circuit, and a rectifier. The input end of the half-bridge circuit is coupled to the solar cell module, the output end of the half-bridge circuit is coupled to the input end of the isolation transformer, and the output end of the isolation transformer is coupled Connected to the input of the rectifier. Further, an output end of the rectifier is coupled to the energy storage unit. A conventional single-stage full-bridge solar power converter, as shown in FIG. 2(c), includes: a solar cell module (PV), a battery bank, an isolation transformer, a full-bridge circuit, and a rectifier. The input end of the full-bridge circuit is coupled to the solar cell module, the output end of the full-bridge circuit is coupled to the input end of the isolation transformer, and the output end of the isolation transformer is coupled Connected to the input of the rectifier. Further, the The output of the rectifier is coupled to the energy storage unit.

In summary, the single-stage solar power converter circuit architecture mainly uses the floating range of the input voltage, and the transformer turns ratio design needs to use the lowest voltage, and at the high input voltage, the adjustment responsibility cycle is used. Therefore, the cycle of high and low pressure responsibility varies greatly.

The two-stage circuit architecture is designed by adding a boost power conversion unit to the input side of the single-stage circuit. Please continue to refer to FIG. 3. FIG. 3(a) is a circuit diagram of a conventional isolated two-stage step-up SRC (series resonance) solar power converter, and FIG. 3(b) is a conventional isolation two-stage liter. Circuit diagram of a pressure-type LLC solar power converter. Conventional isolated two-stage SRC (series resonance) solar power converters include: solar cell module (PV), energy storage unit (Battery bank), boost power conversion unit, isolation transformer, SRC (series resonance) a half bridge circuit and a rectifier, wherein an input end of the SRC (series resonance) half bridge circuit is coupled to the solar cell module through the boost power conversion unit, and an output of the SRC (series resonance) half bridge circuit The end is coupled to the input of the isolation transformer, and the output of the isolation transformer is coupled to the input of the rectifier. Further, an output end of the rectifier is coupled to the energy storage unit. In addition, as shown in FIG. 3(b), the conventional isolated two-stage LLC solar power converter includes: a solar cell module (PV), a battery bank, a boost power conversion unit, and isolation. a transformer, an LLC half-bridge circuit, and a rectifier, wherein an input end of the LLC half-bridge circuit is coupled to the solar cell module through the boost power conversion unit, the LLC half-bridge power The output end of the circuit is coupled to the input end of the isolation transformer, and the output end of the isolation transformer is coupled to the input end of the rectifier. Further, an output end of the rectifier is coupled to the energy storage unit. In summary, the isolated two-stage solar power converter circuit architecture is mainly adjusted by the boost converter, so that the voltage of the output and input of the second-stage isolated circuit is small to improve efficiency.

Therefore, the non-isolated circuit architecture and isolated circuit architecture described in Figures 1, 2, and 3 are widely used in existing solar power converters; however, conventional non-isolated solar power converters and isolation The solar power converter still has the following main disadvantages: (1) In the non-isolated solar power converter, in order to improve the electrical safety of the non-isolated solar power converter circuit, it is generally changed to the isolated two-stage solar power. Converters to increase electrical safety; however, if the conventional isolated two-stage solar power converter is used, the duty cycle of the high and low voltage required control changes greatly, resulting in poor system performance, efficiency and stability. . (2) In the conventional isolated two-stage solar power converter, if the second-stage circuit adopts a resonant circuit, frequency conversion control is required. However, although the second-stage circuit can adopt a full-bridge circuit and use a fixed-frequency phase-shift PWM control circuit to improve, the full-bridge circuit is less likely to enter zero-voltage switching at light loads, resulting in poor conversion efficiency.

To improve the shortcomings of the prior art, the present invention provides a solar power converter. The present invention proposes a two-stage and isolated full bridge resonant type The solar power converter architecture, the first stage circuit can be a boost, buck or buck-boost converter, and has the ability to perform Maximum Power Point Tracking (MPPT) control, the second stage circuit A full-bridge resonant converter architecture is used to stabilize the output voltage and improve overall efficiency.

To achieve the above and other objects, the present invention provides a solar power converter for converting electrical energy generated by a solar module into a stable direct current, the solar power converter comprising: a multiphase The interleaved power conversion module is coupled to the solar module, and the multi-phase interleaved power conversion module receives the electric energy output by the solar module and generates a voltage, and performs a maximum power tracking action on the solar module. a filtering unit is coupled to the multi-phase interleaved power conversion module, wherein the filtering unit is configured to filter out noise outputted by the multi-phase interleaved power conversion module; and a full bridge resonant conversion module, The full-bridge resonant conversion module includes a capacitor and a four-power switch, the capacitor is coupled to the filter unit and the multi-phase interleaved power conversion module, and the four power-on relationship is a full-bridge arrangement and coupled to the Capacitor; a transformer unit is a transformer, the transformer unit is coupled to the full bridge type resonant converter module; a rectifying unit is coupled to the transformer unit; wherein the full bridge The resonant converter module of the system using the capacitance of the primary side of the transforming unit for converting the resonance frequency, in order to enhance the overall efficiency, and then outputs a stabilized direct current rectified through the rectification unit after.

In one embodiment of the present invention, the multiphase interleaved power conversion The module includes an energy storage unit coupled to the solar module, and the energy storage unit receives and stores the current generated by the solar module.

In an embodiment of the present invention, an output filtering unit is coupled to the output end of the multi-phase interleaved power conversion module.

In one embodiment of the present invention, the multi-phase interleaved power conversion module is a boost power converter, a buck power converter, or a buck-boost power converter.

In one embodiment of the invention, the power-on relationship has a bypass diode.

SUMMARY OF THE INVENTION A primary object of the present invention is to provide a solar power converter having an isolated two-stage full-bridge resonant circuit. Different from the traditional isolated two-stage solar power converter, the solar power converter of the present invention controls the full-bridge resonant converter module by a fixed uncontrolled phase shift mode. By designing, all the power switches of the full-bridge resonant converter module can achieve zero voltage switching under any load, which can not only improve the light load efficiency, but also improve and benefit the efficiency under the full load variation range.

The above summary, the following detailed description and the accompanying drawings are intended to further illustrate the manner, the Other objects and advantages of the present invention will be described in the following description and drawings.

10‧‧‧Solar modules

11‧‧‧Multiphase Interleaved Power Conversion Module

111‧‧‧ Energy storage unit

12‧‧‧Filter unit

13‧‧‧Full-bridge resonant converter module

131‧‧‧ Capacitance

132a~132d‧‧‧Power switch

14‧‧‧Transformer unit

15‧‧‧Rectifier unit

16‧‧‧Stabilizer

FIG. 1 is a circuit diagram of a conventional non-isolated buck solar power converter and a buck-boost solar power converter.

FIG. 2 is a structural diagram of a conventional single-stage isolated power converter of different types.

Figure 3 (a) is a circuit architecture diagram of a conventional isolated two-stage boost SRC (series resonant) solar power converter.

Figure 3 (b) is a circuit architecture diagram of a conventional isolated two-stage boosting LLC solar power converter.

4 is a circuit diagram of an embodiment of a solar power converter of the present invention.

5A is a theoretical equivalent circuit diagram of a solar power converter of the present invention.

FIG. 5B is an analog waveform diagram of the solar power converter of the present invention.

FIG. 6 is an analog waveform diagram of a solar module (PV) under startup and load conditions according to an embodiment of the present invention.

FIG. 7 is an analog waveform diagram of components of each part in a fully loaded state according to an embodiment of the present invention.

The embodiments of the present invention are described below by way of specific examples, and those skilled in the art can readily appreciate other advantages and functions of the present invention from the disclosure herein.

As we all know, solar power converters are divided into isolated and non-isolated types, among which non-isolated solar power converters include boost power converters, buck power converters, and boost/buck power converters; , The isolated solar power converter includes a push-pull solar power converter and a flyback solar power converter.

4 is a circuit diagram of an embodiment of a solar power converter of the present invention for explaining the operation principle of the present invention. In the solar power converter of the embodiment of the present invention, the solar power converter is used to convert the electrical energy generated by a solar module 10 into a stable direct current. The embodiment includes: a multi-phase interleaved power conversion mode The group 11 is coupled to the solar module 10, and the multi-phase interleaved power conversion module 11 receives the electrical energy output by the solar module 10 and generates a voltage, and performs a maximum power tracking operation on the solar module 10. a filtering unit 12 coupled to the multi-phase interleaved power conversion module 11 for filtering noise outputted by the multi-phase interleaved power conversion module 11; a full bridge resonant conversion The module 13 includes a capacitor 131 and a four-power switch (132a-132d). The capacitor 131 is coupled to the filter unit 12 and the multi-phase interleaved power conversion module 11. The four-power switch (132a-132d) is a full-bridge type and coupled to the capacitor 131; a transformer unit 14 is a transformer, and the transformer unit is coupled to the full-bridge resonant converter module; a rectifying unit 15 coupled to the transformer ; Wherein the full-bridge resonant converter module 13 using the capacitor line 131 and the resonant frequency conversion of the primary side of the transforming unit 14, in order to enhance the overall efficiency, and then outputs a stabilized direct current through the rectifier unit 15.

In the embodiment of the solar power converter of the present invention, the solar module 10 is a solar power device with one or multiple array solar panels. Set.

In the embodiment of the solar power converter of the present invention, the multi-phase interleaved power conversion module 11 further includes an energy storage unit 111. The energy storage unit is coupled to the solar module 10 to receive and store the solar module. 10 generated current. The multi-phase interleaved power conversion module 11 can be a boost, buck or buck-boost power converter; the energy storage unit 111 can be one or a plurality of inductors. In an embodiment of the present invention, according to the number of solar panels of the solar module 10, a set of solar panels is combined with the inductance of a group of energy storage units. When the current and voltage output of the solar module 10 changes, the amount of change is filtered by the multi-phase interleaved power conversion module 11, and the multi-phase interleaved power conversion module 11 outputs an electric energy to The full bridge type resonant conversion module 13 is provided.

In one embodiment of the present invention, the filter unit 12 is an inductor; one end of the filter unit 12 is coupled to the multi-phase interleaved power conversion module 11, the other end of which is coupled to the capacitor 131; The capacitor 131 of the full-bridge resonant converter module 13 is also coupled to the multi-phase interleaved power conversion module 11; thus, the multi-phase interleaved power conversion module 11 is stored by the inductance of the filtering unit 12 The output current is such that the input end of the full-bridge resonant converter module 13 is equally coupled to an output current source of the multi-phase interleaved power conversion module 11 , and the output voltage of the multi-phase interleaved power conversion module 11 It is also stored by the capacitor 131.

In an embodiment of the invention, the full bridge resonant conversion unit 132 further includes four power switches (132a-132d) having bypass diodes.

In an embodiment of the present invention, the power switches (132a-132d) of the full-bridge resonant conversion module 13 adopt a full-bridge architecture, and drive the power switches (132a-132d) by using a phase shift method without control. That is, the phase shift angle is constant, and the maximum phase shift amount (nearly 180 degrees) is set to obtain the best efficiency, so the control method is the same as the single-stage circuit, and the required control mechanism is quite simple. Since the resonance mode of the full-bridge resonant converter module 13 is a fixed frequency, the circuit design is easy; and the capacitor 131 directly uses the primary side inductance of the transformer unit 14 (ie, the leakage inductance of the transformer) to resonate, so Additional resonant inductors simplify circuit configuration and reduce manufacturing costs.

In an embodiment of the invention, the stabilized DC power output via the rectifying unit 15 can be stored in an energy storage battery or directly supplied to a power grid or device requiring DC power. In an embodiment of the present invention, an output terminal of the rectifying unit 15 may be additionally provided with a voltage stabilizing unit 16 to provide better DC output quality, and the voltage stabilizing unit may be a capacitor.

The solar power converter of the invention has a full bridge resonant conversion architecture, and no additional control action is required in the actual operation process, but the user needs to further accurately control the output conversion efficiency of the solar module, which can be in the invention. Add a control unit to improve control quality. An embodiment of the present invention may include a control unit (not shown) coupled to the multi-phase interleaved power conversion module 11 and the full-bridge resonant conversion module. 13. The control unit is based on the multi-phase interleaved power conversion module 11 and the output condition of the full-bridge resonant conversion module 13, the multi-phase interleaved power conversion module and the full-bridge resonant conversion module. Feedback control is performed such that the solar power converter of the present invention meets the rated output specifications.

Please refer to FIG. 5A and FIG. 5B. FIG. 5A is a theoretical equivalent circuit diagram of a solar power converter embodiment of the present invention, and FIG. 5B is an analog waveform diagram of the solar power converter of the present invention. The theoretical basis of the solar power converter embodiment of the present invention is as follows: the solar module inputs a current source I _bf , and the average voltage V _{r of} the current source is the output voltage V of the multi-phase interleaved power conversion module 11 _b : The resonance of the circuit is formed by the leakage inductance L _{r of the} primary side coil of the transformer unit 15 and the input resonant capacitor C _r (ie, the capacitance 131 of the full bridge resonant conversion module 13), and the resonant frequency ω _o is: The resonant impedance Z _o is: The boost ratio is boosted by the turns ratio of the transformer unit. The turns ratio is designed as: When the angle of the phase shift of the switch is maximum, the efficiency is high, so voltage control is not required. When using the power switch S1 (corresponding to 132a of FIG. 4) and S4 (corresponding to 132d of FIG. 4) to conduct the previous half-cycle section for analysis, the result can also be used for the power switch S2 (corresponding to 132b of FIG. 4) and S3 (corresponding diagram 4 of 132c) half a week after the conduction. When 132a and 132d are turned on, the following equation of state is obtained:

Where I _r is the inductor current, and the current rise rate of the self-inductive current I _{m is} half a week: Using (4) and (6), we can obtain: V _r ( t ) = A sin ω _o t + B cos ω _o t + V _b (8) where A and B are parameters to be determined. (8) Substituting (6): I _r ( t ) = I _bf + ω _o C _r B sin ω _o t - ω _o C _r A cos ω _o t (9) If the power switch reaches zero voltage switching and To bypass the diode to achieve zero current conduction, it is necessary to make I _r (0) = 0, and the first I _r in (9) must resonate to a negative value, that is, B <0, therefore: I _r ( 0)= I _bf - ω _o C _r A =0 (10) is available from (10): It is known that the charge and discharge of C _{r are} balanced, and the average value of V _r ( t ) half cycle in (8) is equal to V _b : Substituting (8) and (11) into (12) is available: The conditions for B <0 from (12) and (14) are: f _s < f _o (14), that is, the switching frequency of the switch needs to be lower than the resonant frequency.

In an embodiment of the present invention, the design of the turns ratio of the transforming unit 15 can be used to boost the voltage. Thus, when the angle of the phase shift of the four switches (132a-132d) of the full-bridge resonant converter module 13 is maximum (nearly 180 degrees), the efficiency is high, so that no additional voltage control action is required.

Please refer to FIG. 6 , which is an analog waveform diagram of a solar module (PV) under startup and load conditions according to an embodiment of the invention. As shown in the figure, in one embodiment of the present invention, a PV (solar module 10) having a maximum power point of 19V and 100W is used, and the output of the multi-phase interleaved power conversion module 11 is set to 25V, a storage. The required operating voltage of the DC energy storage battery converted by the present invention (ie, the DC voltage required to receive the target of the solar power converter output DC power) is set to 24V, and the transformer turns ratio of the transformer unit 14 is about 1 The switching frequency of the multi-phase interleaved power conversion module 11 and the full-bridge resonant conversion module 13 is set to 100 kHz. The full-bridge resonant converter module 13 adopts a fixed uncontrolled phase shift mode, and uses its turns ratio to maintain an output voltage of 25V, and the resonant frequency is set at 160 kHz, Cr is 20 μF, and the leakage inductance Lr is 0.05 μH. The self-inductance of the press is 8μH, and its self-inductance is low, which helps to reduce the volume of the transformer and reduce the overall construction cost of the circuit. In an embodiment of the present invention, a CL filter may be additionally coupled between the input end of the multi-phase interleaved power conversion module 11 and the solar module 10 to reduce the solar module (PV). Current chopping. In the practical application, when a control unit is used to control the working state of the multi-phase interleaved power conversion module 11, a low-pass filter with a 1 kHz cutoff frequency may be added to the current command input of the control unit. The low-pass filter is coupled between the multi-phase interleaved power conversion module 11 and the control unit, so that the startup of the multi-phase interleaved power conversion module 11 can be smooth.

Please refer to FIG. 7 again, which is an analog waveform diagram of components of each part in a full load state according to an embodiment of the present invention. As shown in the figure, in the embodiment of the present invention, the output current of the multi-phase interleaved power conversion module 11 is indeed four-phase interleaved, and the four power switches of the full-bridge resonant conversion module 13 (132a~132d) can also achieve zero voltage switching, and the bypass diode of the power switch is also turned on and off by zero current.

The invention provides a solar power converter, and the invention is characterized in that: (1) different from the conventional isolated two-stage solar power converter, the frequency of the half bridge resonant circuit is additionally controlled to achieve maximum conversion efficiency, and the invention A full bridge resonant converter module is disposed in the solar power converter, and the full bridge resonant converter module is controlled by a fixed uncontrolled phase shifting mode, and all power switches of the full bridge resonant converter module are at any load Zero voltage switching can be achieved underneath, which not only improves efficiency at light loads, but also for full load variation. The efficiency of the surrounding is also improved and helpful, and the control mechanism is simple and reliable. (2) The self-inductance of the transformer of the full-bridge resonant conversion module of the present invention is relatively low, compared to the isolated two-stage solar energy of the prior art. The architecture of the power converter, the invention can use a smaller transformer, helping to reduce costs and reduce the size of the device.

The above-described embodiments are merely illustrative of the features and functions of the present invention, and are not intended to limit the scope of the technical scope of the present invention. Modifications and variations of the above-described embodiments can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be as set forth in the scope of the claims described below.

10‧‧‧Solar modules

11‧‧‧Multiphase Interleaved Power Conversion Module

111‧‧‧ Energy storage unit

12‧‧‧Filter unit

13‧‧‧Full-bridge resonant converter module

131‧‧‧ Capacitance

132a~132d‧‧‧Power switch

14‧‧‧Transformer unit

15‧‧‧Rectifier unit

16‧‧‧Stabilizer

Claims (9)

A solar power converter for converting electrical energy generated by a solar module into a stable direct current, the solar power converter comprising: a multi-phase interleaved power conversion module coupled to the solar module, the plurality The interleaved power conversion module receives the power output by the solar module and generates a voltage, and performs a maximum power tracking operation on the solar module; a filtering unit is coupled to the multi-phase interleaved power conversion module The filtering unit is configured to filter out the noise outputted by the multi-phase interleaved power conversion module; a full-bridge resonant conversion module, the full-bridge resonant conversion module includes a capacitor and a four-power switch, The capacitor is coupled to the filter unit and the multi-phase interleaved power conversion module, wherein the four power-on relationship is a full-bridge arrangement and coupled to the capacitor; and a transformer unit is a transformer, the transformer unit Coupling the full-bridge resonant conversion module; a rectifying unit coupled to the transforming unit; wherein the full-bridge resonant switching module uses the capacitor to resonate with the primary side of the transforming unit Rate conversion, and then outputs a stabilized direct current rectified through the rectification unit after. The solar power converter of claim 1, wherein the multi-phase interleaved power conversion module comprises: an energy storage unit coupled to the The solar module, the energy storage unit receives and stores the current generated by the solar module. The solar power converter of claim 1, further comprising a control unit coupled to the multi-phase interleaved power conversion module and the full-bridge resonant conversion module, the control unit The feedback control is performed according to the output status of the multi-phase interleaved power conversion module and the full-bridge resonant conversion module. The solar power converter of claim 1, wherein the multiphase interleaved power conversion module is a boost, buck or buck-boost power converter. The solar power converter of claim 1, wherein the four power-on relationship has a bypass diode. The solar power converter of claim 1, further comprising a voltage stabilizing unit coupled to the output end of the rectifying unit. The solar power converter of claim 6, wherein the voltage stabilizing unit is a capacitor. The solar power converter of claim 1, wherein the filtering unit is an inductor. The solar power converter of claim 2, wherein the energy storage unit is one or a plurality of inductors.