TWI664800B - Boost-type dc power converter and method for voltage ripple inhibition of pv module - Google Patents

Abstract

The invention discloses a step-up DC power conversion device. A boost control unit of a step-up DC power conversion device receives a voltage signal output from the solar module and generates a boost signal. A feedback unit generates a feedback signal based on the boost signal. A feedforward unit generates a feedforward signal according to the voltage signal. A signal processing unit outputs a command signal according to the feedforward signal and a reference signal. A compensation amplifier unit outputs a control signal according to the feedback signal and the command signal; when the ripple value of the command signal is greater than the ripple value of the feedback signal, a pulse width modulation unit adds a responsibility of conducting a switching element based on the control signal. Period to suppress the voltage ripple of the voltage signal. The invention also discloses a method for suppressing the ripple of the solar module.

Description

Step-up DC power conversion device and method for suppressing voltage ripple of solar module

The invention relates to a step-up DC power conversion device and a method for suppressing voltage ripple of a solar module.

In recent years, due to the rising awareness of environmental protection and the gradual depletion of petrochemical energy (such as oil and coal), countries around the world have realized the importance of new energy development. Because sunlight is an inexhaustible and inexhaustible natural energy source, in addition to no doubt of energy exhaustion, the problem of monopolized energy sources can also be avoided. Therefore, countries around the world are also actively developing the application of solar energy technology, and it is expected that by increasing the use of solar energy sources, we will reduce our dependence on petrochemical energy. Among them, the most important use of solar energy is solar cells (also called photovoltaics, photovoltaics), which directly convert light energy into electrical energy, and the output power can be supplied to load equipment after conversion.

FIG. 1 is a schematic diagram of a system in which a conventional solar module is converted by a frequency converter. As shown in Figure 1, after the DC voltage output by the solar module is converted into an AC voltage by a DC / AC inverter, it can be provided to the load grid. Due to the conversion effect of the DC / AC inverter, the AC voltage ripple is fed back to the solar module end, so that the output end of the solar module has a ripple. In addition to this ripple, the solar module is equivalent to the DC capacitor C _BUS equivalent series In addition to the power consumption of the resistor, the life of the solar module and the capacitor C _BUS will also be shortened.

In order to suppress the ripple voltage feedback from the inverter, the traditional general method is to use a large capacitance electrolytic capacitor for the capacitor C _BUS (the larger the capacitance value, the better the suppression effect). However, this method has the effect of increasing the circuit size and cost. In addition, the residual ripple current easily reduces the life of the electrolytic capacitor. Another method is to use the LC series resonance network to bypass the AC components of the ripple current, or use a half-bridge or full-bridge voltage ripple cancellation circuit to reduce the ripple at the solar module end. However, these methods have a large number of circuit components, and the control circuit is also complicated, making the circuit cost relatively high.

The purpose of the present invention is to provide a step-up DC power conversion device and a method for suppressing the voltage ripple of a solar module. In addition to suppressing the DC voltage ripple of the solar module end caused by a post-stage frequency conversion circuit, it also has a DC boost The voltage function can improve the Modulation Index (Modulation Index) of the post-stage frequency conversion circuit.

To achieve the above object, the present invention provides a step-up DC power conversion device, which is used in conjunction with a solar module and includes a step-up control unit, a feedback unit, a feed-forward unit, a signal processing unit, a Compensation amplifier unit and a pulse width modulation unit. The boost control unit receives a voltage signal output from the solar module and generates a boost signal. The boost control unit includes a switching element. The feedback unit generates a feedback signal according to the boost signal. The feedforward unit generates a feedforward signal according to the voltage signal. The signal processing unit outputs a command signal according to the feedforward signal and a reference signal. The compensation amplifier unit outputs a control signal according to the feedback signal and the command signal. The pulse width modulation unit controls the switching element according to the control signal; wherein, when the ripple value of the command signal is greater than the ripple value of the feedback signal, the pulse width modulation unit increases a duty cycle of the switching element according to the control signal to suppress Voltage ripple of the voltage signal.

In an embodiment, the step-up DC power conversion device further includes a frequency conversion unit, and the step-up control unit further includes an inductor, a capacitor, and a diode. The first end of the inductor is electrically connected to the first end of the capacitor and A voltage output terminal of the solar module, a second terminal of the inductor are electrically connected to one end of the switching element and the first terminal of the diode, and a second terminal of the capacitor is electrically connected to the second terminal of the diode and the frequency conversion unit.

In an embodiment, when the ripple value of the command signal is greater than the ripple value of the feedback signal, the control signal increases the duty cycle of a pulse width modulation signal output by the pulse width modulation unit, thereby increasing the flow-through inductance. Of current.

In one embodiment, the DC boost ratio of the boost control unit is equal to 1 / (1-D), where D is the duty cycle of the switching element.

In one embodiment, the signal processing unit includes a filter. The DC component in the compression signal causes a filtered signal generated by the filter to include a ripple of 120 Hz.

In one embodiment, the signal processing unit further includes an adder circuit. The adder circuit adds the filtered signal to the reference signal and outputs a command signal.

In one embodiment, the compensation amplifier unit includes an operational amplifier, a command signal is input to a positive terminal of the operational amplifier, a feedback signal is input to a negative terminal of the operational amplifier, and an output terminal of the operational amplifier outputs a control signal.

In one embodiment, the boost signal includes an AC signal at 120 Hz.

In one embodiment, the step-up DC power conversion device further includes a frequency conversion unit that converts the step-up signal and filters out high-frequency noise to output an AC load signal at 60 Hz.

To achieve the above object, the present invention provides a method for suppressing voltage ripple of a solar module, which is performed by a step-up DC power conversion device. The step-up DC power conversion device includes a boost control unit, A boosting unit, a feedforward unit, a signal processing unit, a compensation amplifier unit, and a pulse width modulation unit. The method includes: a boost control unit receives a voltage signal output from the solar module and generates a boost signal; The feedback unit generates a feedback signal based on the boost signal; the feedforward unit generates a feedforward signal based on the voltage signal; the signal processing unit outputs a command signal based on the feedforward signal and a reference signal; and the compensation amplifier unit responds to the feedback The signal and the command signal output a control signal; and the switching element is controlled by the pulse width modulation unit based on the control signal; wherein, when the ripple value of the command signal is greater than the ripple value of the feedback signal, the pulse width modulation unit is based on the control signal A duty cycle of one of the switching elements of the boost control unit is increased to suppress the voltage ripple of the voltage signal.

As mentioned above, in the step-up DC power conversion device and the method for suppressing the voltage ripple of the solar module of the present invention, when the signal processing unit outputs a ripple value of the command signal according to the feedforward signal and the reference signal, the ripple value is greater than When the feedback unit is based on the ripple value of the feedback signal generated by the boost signal, the pulse width modulation unit can increase the duty cycle of the switching element of the boost control unit according to the control signal output from the compensation amplifier unit, thereby suppressing solar energy. Voltage ripple of the voltage signal output by the module. Therefore, the present invention suppresses the DC voltage ripple of the solar module end caused by the feedback ripple current of the post-stage frequency conversion circuit through the feedforward and feedback mechanism. In addition, the DC step-up conversion ratio of the step-up DC power conversion device of the present invention can boost the DC voltage at the solar module end, thereby increasing the modulation coefficient of the post-stage frequency conversion circuit, so as to use relatively low-voltage solar energy. Module, making the equipment cost relatively low.

1‧‧‧ Boost DC Power Conversion Device

11‧‧‧Boost control unit

111‧‧‧switching element

12‧‧‧ feedback unit

13‧‧‧ Feedforward Unit

14‧‧‧Signal Processing Unit

141, 172‧‧‧ Filter

142‧‧‧adder circuit

1421, 151‧‧‧ Operational Amplifiers

15‧‧‧Compensation amplification unit

16‧‧‧ Pulse Width Modulation Unit

161‧‧‧ Comparator

17‧‧‧Frequency conversion unit

171‧‧‧Switch circuit

AC‧‧‧AC

C ₁ , C _BUS , C _b , C _c1 , C _c2 , C _c3 , C _f , C _h ‧‧‧ capacitor

D ₁ , D ₂ ‧‧‧ Diode

DC‧‧‧DC

i _inv , i _L , i _PV , I _{PV, avg} , Δi _inv , I _{INV, avg} , Δi _pv ‧‧‧ current

I _SC ‧‧‧ Current source

L ₁ , L _f ‧‧‧ Inductance

PV‧‧‧Solar Module

R _a , R _ac , R _b , R _c , R _c1 , R _c2 , R _c3 , R _d , R _DC , R _FB1 , R _FB2 , R _FF1 , R _FF2 , R _h , R _S , R _SH ‧‧‧ resistance

S01 ~ S06‧‧‧step

S ₁ , S ₂ , S ₃ , S ₄ , S ₅ ‧‧‧ Switch

t‧‧‧time

v _a ‧‧‧ filtered signal

v _B ‧‧‧ Order signal

v _C ‧‧‧Control signal

v _FB ‧‧‧ feedback signal

v _FF ‧‧‧ feedforward signal

v _g ‧‧‧Pulse width modulation signal

v _INV ‧‧‧Boost signal

V _INV , V _PV ‧‧‧ DC voltage

V _L ‧‧‧Inductive voltage across

v _PV ‧‧‧ Voltage signal

V _REF ‧‧‧Reference signal

△ v _inv , V _{INV, avg} , △ v _pv , V _{PV, avg} ‧‧‧Voltage difference

FIG. 1 is a schematic diagram of a system in which a conventional solar module is converted by a frequency converter.

FIG. 2 is a functional block diagram of a step-up DC power conversion device according to an embodiment of the present invention.

3A is a schematic circuit diagram of a step-up DC power conversion device according to an embodiment of the present invention.

FIG. 3B is a schematic diagram illustrating a step-up ratio analysis of the circuit of the step-up control unit of FIG. 3A.

4A and 4B are schematic diagrams of voltage waveforms of a boost signal and a voltage signal of a boost DC power conversion device according to an embodiment.

4C and 4D are schematic diagrams of current waveforms of a boost signal and a voltage signal of a boost DC power conversion device according to an embodiment.

FIG. 5 is a schematic diagram of a curve of average output power vs. voltage ripple rate of a solar module terminal under different control modes in a step-up DC power conversion device according to an embodiment.

FIG. 6 is a graph showing a relationship between a peak value of a load current and a terminal voltage ripple value of a DC capacitor under different DC capacitor values of a solar module.

FIG. 7 is a schematic flow chart of a method for suppressing voltage ripple of a solar module according to an embodiment of the present invention.

In the following, a step-up DC power conversion device and a method for suppressing voltage ripple of a solar module according to a preferred embodiment of the present invention will be described with reference to related drawings. The same components will be described with the same reference symbols. It is explained first that if the lower-case + upper-case subscripts (for example, v _PV ) appear in the following signals, it means that it is a DC voltage signal with AC ripple, or an AC signal with DC voltage; if it is uppercase + uppercase A subscript (for example, V _REF ) indicates that it is a DC voltage signal; if it is a lowercase + lowercase index (for example, v _inv ), it indicates that it is an AC voltage signal.

FIG. 2 is a functional block diagram of a step-up DC power conversion device 1 according to an embodiment of the present invention. As shown in FIG. 2, the step-up DC power conversion device 1 of this embodiment is applied in cooperation with a solar module PV. Among them, the solar module PV can output a voltage signal v _PV . Theoretically, the voltage signal v _PV is a DC voltage signal, but the voltage signal v _PV output by the solar module PV will be a DC voltage signal including AC ripple due to the feedback current of the post-stage frequency conversion circuit.

The step-up DC power conversion device 1 is a DC / AC step-up power converter, which may include a boost control unit 11, a feedback unit 12, a feedforward unit 13, and a signal processing unit. 14. A compensation amplifier unit 15 and a pulse width modulation unit 16. In addition, the step-up DC power conversion device 1 may further include a frequency conversion unit 17.

The boost control unit 11 is electrically connected to the solar module PV, and can receive a voltage signal v _PV output from the solar module _PV . The boost control unit 11 can convert and boost the voltage signal v _PV to generate a boost signal v _INV . The boosting control unit 11 may include a switching element 111 which can control the switching element 111 to convert and boost the voltage signal v _PV to generate a boosted signal v _INV .

The frequency conversion unit 17 is a digital-to-analog converter (DAC), and is electrically connected to the boost control unit 11 to receive the boosted signal v _INV generated by the boost control unit 11 and convert it And after filtering the high frequency noise, an AC load signal of 60 Hz is output and provided to a load. Here, the frequency conversion unit 17 is a single-phase DAC. Therefore, the boosted signal v _INV will include an AC ripple of 120 Hz, and this AC ripple will be fed back to the PV end of the solar module.

The feedback unit 12 is electrically connected to the boost control unit 11 and the frequency conversion unit 17, respectively. The feedback unit 12 can generate a feedback signal v _FB according to the boost signal v _{INV at} the output end of the boost control unit 11.

The feedforward unit 13 is electrically connected to the solar module PV and the boost control unit 11 respectively. The feedforward unit 13 can generate a feedforward signal v _FF according to the voltage signal v _PV output from the solar module PV.

Signal processing unit 14 is electrically connected to the feed forward unit 13, and based on the feedforward signal v feedforward _FF unit 13 with a reference signal V _REF outputs a command signal v _B. The signal processing unit 14 may include a filter and an adder. The filter may filter the low-frequency signal of the feed-forward signal v _FF , and the adder may output the low-frequency feed-forward signal v _FF and the reference signal V _REF . Command signal v _B.

The compensation amplifying unit 15 is electrically connected to the feedback unit 12 and the signal processing unit 14 respectively, and can output a control signal v _C according to the feedback signal v _{FB of the} feedback unit 12 and the command signal v _{B of the} signal processing unit 14. The compensation amplifier unit 15 is an error signal compensation amplifier, which can amplify signals of a desired frequency and output the signals.

The pulse width modulation unit 16 is electrically connected to the compensation amplifier unit 15 and the boost control unit 11. The pulse width modulation unit 16 is a Pulse Width Modulation (PWM) generation circuit, which can be based on the control signal v _C outputs a pulse width modulation signal v _g to control the on or off of the switching element 111 of the boost control unit 11. Wherein, when the ripple value of the command signal v _B of the signal processing unit 14 is greater than the ripple value of the feedback signal v _FB of the feedback unit 12, the pulse width modulation unit 16 may increase the switching element 111 according to the control signal v _C One duty cycle is to suppress the voltage ripple of the voltage signal v _PV at the PV end of the solar module, thereby reducing the DC voltage ripple at the PV end of the solar module. In addition, the step-up DC power conversion device 1 also has a DC step-up function, which can step up the DC voltage at the PV end of the solar module to increase the modulation coefficient of the post-stage frequency conversion unit 17. Hereinafter, the technical content of each unit in FIG. 2 will be described in detail with the implementation circuits of FIGS. 3A and 3B.

Please refer to FIG. 3A, which is a schematic circuit diagram of a step-up DC power conversion device 1 according to an embodiment of the present invention. It is first explained that those skilled in the art can see from the circuit diagram in FIG. 3A that the components of each unit and their relative connection relationships are indisputable. Therefore, the connection relationship of the following components will only explain the more important parts, and the rest please refer to the connection relationship of the components in FIG. 3A.

The solar module PV can output a voltage signal v _PV after being illuminated. The equivalent circuit of the solar module PV may include a current source I _SC , a diode D _2, and two resistors R _SH and R _S. The specific connection relationship of these elements can be referred to the diagram, and will not be described further.

Boost control means 11: control means boosting switching element 11 of the present embodiment is a 111 of active switch S _5, and is MOSFET (MOSFET) as an example. In addition, the boost control unit 11 in this embodiment may further include an inductor L ₁ , a capacitor C _1, and a diode D ₁ . Inductor L ₁ is an energy storage element. The first end of the inductor L ₁ is electrically connected to the first end of the capacitor C ₁ and the voltage output terminal of the solar module PV, and the second end of the inductor L ₁ is electrically connected to the switching element 111 (switch S ₅ ). one end of the diode D ₁ is a first end, a second end of the capacitor C are electrically connected _a diode D ₁ and the second end of the inverter unit 17. Further, the PWM signal can be input switch S v _g a second end ₅ (control terminal) to control the switch S ₅ is turned on or off, and a third terminal of the switch S ₅ is grounded. In addition, one end of the (DC) capacitor C _BUS is electrically connected to the boost control unit 11 and the frequency conversion unit 17 respectively, and the other end thereof is grounded. Wherein the capacitor C ₁ may provide a reverse voltage ripple voltage of the capacitor C _{BUS, BUS} voltage of the capacitor C and the voltage of the capacitor C ₁ after the addition of nearly DC voltage, thereby to suppress (or eliminate) the solar Voltage ripple of the PV terminal voltage of the module.

In addition, please refer to FIG. 3B, which is a schematic diagram of a step-up ratio analysis of the circuit of the boost control unit 11 in FIG. 3A.

The analysis of the DC boost ratio performed by the boost control unit 11 is as follows: 0 <D‧T _S <T _S (S ₅ on, D ₁ off)

V _L = V _PV

0 <(1-D) ‧T _S <T _S (S ₅ off, D ₁ on)

V _L = V _PV -V _INV

V _PV ‧D‧T _S + (V _INV -V _PV ) ‧ (1-D) ‧T _S = 0

According to the calculation of the inductance volt-second balance theorem, the DC voltage conversion ratio in the continuous conduction mode (CCM) can be derived: V _INV / V _PV = 1 / (1-D); where D is the responsible conduction of switch S ₅ Period (generally less than 1). Therefore, the boost control unit 11 can increase the DC average voltage (ie, boost) of the solar module PV terminal to the inverter unit 17 (one end of the capacitor C _BUS ), thereby increasing the modulation coefficient of the subsequent inverter unit 17.

Frequency conversion unit 17: Please refer to FIG. 3A again. The frequency conversion unit 17 of this embodiment is a single-phase DAC, which may include a switching circuit 171 and a filter 172. The switching circuit 17 ¹ may The output terminal voltage (v _INV ) is converted into a 60Hz square wave noise with high frequency switching noise, and the filter 172 is a low-pass filter, which can filter high frequency noise and make the output The AC load signal is an AC signal of 60Hz to provide to the load (represented by resistor R _ac ). The switching circuit 171 is electrically connected to the boost control unit 11. The switch circuit 171 of this embodiment has four switches S ₁ , S ₂ , S ₃ , and S ₄ . The switches S ₁ , S ₂ , S ₃ , and S ₄ may be power transistors, such as but not limited to MOSFETs. Here, the switches S ₁ , S ₂ , S ₃ , S ₄ can control the switches S ₁ , S ₂ , S ₃ , S of the switching circuit 171 by a sinusoidal pulse width modulation (SPWM) technology. ₄ is on or off. In addition, the filter 172 is electrically connected to the switching circuit 171. The filter 172 can filter the high-frequency components generated when the switches S ₁ , S ₂ , S ₃ , and S _{4 of the} switching circuit 171 are switched to generate a single-phase 60 Hz sine wave signal to the resistor R _ac . Here, the filter 172 includes a low-pass filter having an inductor L _f and a capacitor C _f .

Feedback unit 12: The feedback unit 12 of this embodiment is a feedback voltage-dividing resistor circuit, and can detect the boosted signal v _INV at the end of the frequency conversion unit 17 to generate a feedback signal v _FB after voltage division. The feedback unit 12 in this embodiment includes two resistors R _FB1 and R _FB2 . Therefore, the feedback signal v _FB = v _INV × R _FB2 / (R _FB1 + R _FB2 ).

Feed-forward unit 13: The feed-forward unit 13 of this embodiment is a feed-forward voltage-dividing resistor circuit, and can detect the terminal voltage of the solar module PV (that is, v _PV ) and generate the voltage according to the voltage signal v _PV. The feedforward signal v _FF , therefore, the feedforward signal v _FF = v _PV × R _FF2 / (R _FF1 + R _FF2 ).

Signal processing unit 14: The signal processing unit 14 in this embodiment includes a filter 141 and an adder circuit 142. The filter 141 is a high-pass filter, which has a capacitor C _h and a resistor R _h , and can filter the DC component in the feedforward signal v _FF , so that the filter signal generated by the filter 141 is a filtering signal. v _a (a voltage signal at one end of the resistor _Rh ) includes a ripple of 120 Hz, that is, the filter 141 can filter the ripple of the 120 Hz component of the voltage signal v _PV for subsequent processing by the adder circuit 142. In addition, the adder circuit 142 can output the command signal v _B according to the feedforward signal v _FF and the reference signal V _REF . Among them, the adder circuit 142 can filter the 120 Hz ripple component (ie, the filtered signal v _a ) Is added to the DC reference signal V _REF to output a command signal v _B (that is, v _B = v _a + V _REF ). This, adder circuit 142 may include an operational amplifier 1421, four resistors _{R a, R b, R c} , R d and a capacitor C _b. The two ends of the resistor R _b are respectively connected to the reference signal V _REF and the positive end of the operational amplifier 1421, the two ends of the resistor R _a are respectively connected to the filtered signal v _a and the positive end of the operational amplifier 1421, and the capacitor C _b and the resistance R _{d is} connected in parallel across the negative terminal and the output terminal of the operational amplifier 1421, two ends of the resistor R _c are connected across the negative terminal and the ground terminal of the operational amplifier 1421, and the voltage at the output terminal of the operational amplifier 1421 is the command signal v _B. In addition, for the relative connection relationship of other components of the adder circuit 142, refer to the figure.

Compensation amplifier unit 15: The compensation amplifier unit 15 of this embodiment includes an operational amplifier 151, three resistors (R _c1 , R _c2 , R _c3 ), and three capacitors (C _c1 , C _c2 , C _c3 ). The operational amplifier 151 can compare signals at two input terminals (ie, v _FB and v _B ) and output a control signal v _C. The command signal v _{B is} input to the positive terminal of the operational amplifier 151, and the feedback signal v _FB is input to the negative terminal of the operational amplifier 151 through the series connection of the capacitor C _c1 and the resistor R _c1 and then in parallel with the resistor Rc ₂ , and the capacitor C _c2 and the resistor R after a further series _{c3 c3} parallel capacitance C is connected across the negative terminal and an output terminal of the operational amplifier 151, and the output terminal of the operational amplifier 151 outputs the control signal v _C. The relative connection relationship of the components of the compensation amplifying unit 15 can be referred to the figure. Here, the design of the parameter values of the resistors R _c1 to R _c3 and the capacitors C _c1 to C _c3 filters out unwanted frequencies. When the ripple value of the command signal v _B rises and is greater than the ripple value of the feedback signal v _FB , the compensation amplifying unit 15 can amplify the desired frequency signal and output the control signal v _C (v _C will rise).

Pulse width modulation unit 16: The pulse width modulation unit 16 of this embodiment may include a comparator 161, which compares the analog control signal v _C with a sawtooth wave signal and outputs a pulse width modulation signal v _g , and inputs Control terminal of the switch S ₅ of the boost control unit 11. Here, the gain of the comparator 161 is the inverse of the peak value of the sawtooth wave. In addition, in this embodiment, when the ripple value of the command signal v _B of the signal processing unit 14 is greater than the ripple value of the feedback signal v _FB of the feedback unit 12, the pulse width modulation unit 16 may amplify the signal according to the compensation. The control signal v _C output by the unit 15 increases the duty cycle of the output pulse width modulation signal v _g (ie, increases the on-time of the switch S ₅ and decreases the off-time). When the on-time of the switch S ₅ increases, the The current i _L flowing through the inductor L ₁ becomes larger, thereby reducing the voltage signal v _PV and reducing the DC voltage ripple at the PV end of the solar module.

Specifically, when the ripple value of the voltage signal v _PV at the PV end of the solar module rises, the ripple value of the feedforward signal v _FF also rises, so the ripple value of the filtered signal v _a also rises, making the signal processing The ripple value of the command signal v _B output by the unit 14 also rises. After comparing the command signal v _B with the feedback signal v _FB through the compensation amplifying unit 15, the output control signal v _C also rises, making the pulse width modulation signal The duty cycle of v _g is increased, so that the current i _L flowing through the inductor L ₁ becomes larger, and the ripple of the voltage signal v _PV can be pulled down to reduce the DC voltage ripple of the PV end of the solar module.

In conclusion, in the step-up DC power conversion device 1 of this embodiment, after processing by the feedforward and feedback mechanism, the DC voltage ripple at the PV end of the solar module caused by the feedback ripple current of the frequency conversion unit 17 can be suppressed. wave. In addition, the DC step-up conversion ratio of the step-up DC power conversion device 1 of this embodiment can step up the DC voltage at the PV end of the solar module, thereby increasing the modulation coefficient of the post-stage frequency conversion unit 17 in order to use a relatively low-voltage Solar modules.

In one embodiment, the specifications of each resistor, capacitor, and inductor in the step-up DC power conversion device 1 may be as follows: L ₁ = 40 μH, C ₁ = 33 μF, C _BUS = 47 μF, L _f = 10 mH, and C _f = 1μF, R _FB1 = 36kΩ, R _FB2 = 1.5kΩ, R _FF1 = R _FF2 = 1kΩ, C _h = 160nF, R _h = 150kΩ, C _b = 160nF, R _a = R _b = R _c = R _d = 1MΩ, V _REF = 4V, C _c1 = 560pF, C _c2 = 10nF, C _c3 = 680pF, R _c1 = 3kΩ, R _c2 = 50kΩ, R _c3 = 2.7kΩ.

In addition, please refer to FIG. 4A to FIG. 4D, wherein FIG. 4A and FIG. 4B are schematic diagrams of voltage waveforms of the boost signal v _INV and the voltage signal v _PV of the boost DC power conversion device 1 according to an embodiment, and 4C and FIG. 4D are schematic diagrams of current waveforms of the boosted signal v _INV and the voltage signal v _PV of the boosted DC power conversion device 1 according to an embodiment.

Figure 4A to Figure 4D can be obtained after analyzing the voltage ripple suppression effect by time-domain simulation. It can be seen from FIG. 4A that Δv _inv / V _{INV, avg} = 31%, the voltage ripple of the voltage at the 17 end of the frequency conversion unit (that is, the boosted signal v _INV ) is quite large; however, the boosted DC power of this embodiment After processing and suppression of the feedforward and feedback mechanism of the conversion device 1, as shown in FIG. 4B, Δv _pv / V _{PV, avg} = 4.5%, it can be seen that the ripple voltage suppression effect is quite significant. In addition, it can be seen from FIG. 4C that Δi _inv / I _{INV, avg} = 431%, and the current ripple of the voltage (boost signal v _INV ) at the end of the frequency conversion unit 17 is also quite large; however, the boost type of this embodiment After processing and suppression of the feedforward and feedback mechanism of the DC power conversion device 1, as shown in FIG. 4D, Δi _pv / I _{PV, avg} = 7%, it can be seen that the ripple current suppression effect is also quite significant.

In addition, FIG. 5 is a schematic diagram of the curve of the average output power versus the voltage ripple rate of the solar module terminal under different control modes in the step-up DC power conversion device 1 of an embodiment. Here, under open loop mode and voltage feedback control, if the output load is greater than 68W, the solar module cannot output power. In addition, in the step-up DC power conversion device 1 using the feedforward and feedback control of the solar module terminal voltage ripple suppression force can be significantly improved, under full load can reduce the solar module terminal voltage ripple rate to 4.5% Right and left, and the lighter the load, the better the effect of eliminating ripples.

In addition, FIG. 6 is a graph showing the relationship between the peak value of the load current and the terminal voltage ripple value of the DC capacitor under different DC capacitor values (C _BUS ) of the solar module. It can be seen from FIG. 6 that when the voltage ripple is suppressed by the capacitance C _BUS with different capacitance values, the larger the capacitance value, the better the suppression effect of the voltage ripple value at the DC capacitor end. However, even the capacitance of the capacitor C _BUS When the value is increased to 220μF, the voltage ripple value will also exceed 5V (when the current peak is equal to 2.5A). However, as described above, when using the step-up DC power conversion device 1 of this embodiment, the capacitor C _BUS only needs to be 47 μF. Even when 33 μF of the capacitor C ₁ of the boost control unit 11 is added, the total capacitance is only 80 μF, and It does not require the use of a large capacitance electrolytic capacitor to have a good ripple suppression effect.

In addition, FIG. 7 is a schematic flow chart of a method for suppressing a voltage ripple of a solar module according to an embodiment of the present invention. The method for suppressing the voltage ripple of the PV of the solar module of this embodiment can be executed by a step-up DC power conversion device 1. The technical features of the step-up DC power conversion device 1 have been described in detail above, and will not be repeated here.

As shown in FIG. 7, the method for suppressing the voltage ripple of the solar module may include: receiving a voltage signal output by the solar module and generating a boost signal by the boost control unit (step S01); The feedback signal generates a feedback signal (step S02); the feedforward unit generates a feedforward signal according to the voltage signal (step S03); the signal processing unit outputs a command signal according to the feedforward signal and a reference signal (step S04); The compensation amplifier unit outputs a control signal according to the feedback signal and the command signal (step S05); and the pulse width modulation unit controls the switching element according to the control signal; wherein when the ripple value of the command signal is greater than the ripple of the feedback signal When the value is equal to one, the pulse width modulation unit increases a duty cycle of one of the switching elements of the boost control unit according to the control signal to suppress the voltage ripple of the voltage signal (step S06).

In addition, other technical features of the method for suppressing the voltage ripple of the solar module have been described in detail above, and will not be described further here.

In summary, in the step-up DC power conversion device and the method for suppressing the voltage ripple of the solar module of the present invention, when the signal processing unit outputs the ripple value of the command signal according to the feedforward signal and the reference signal, the ripple value is greater than When the feedback unit is based on the ripple value of the feedback signal generated by the boost signal, the pulse width modulation unit can increase the duty cycle of the switching element of the boost control unit according to the control signal output from the compensation amplifier unit, thereby suppressing solar energy. Voltage ripple of the voltage signal output by the module. Therefore, the present invention suppresses the DC voltage ripple of the solar module end caused by the feedback ripple current of the post-stage frequency conversion circuit through the feedforward and feedback mechanism. In addition, the DC step-up conversion ratio of the step-up DC power conversion device of the present invention can boost the DC voltage at the solar module end, thereby increasing the modulation coefficient of the post-stage frequency conversion circuit, so that a relatively low-voltage solar module is used. Group, so that equipment costs can be relatively low.

The above description is exemplary only, and not restrictive. Any equivalent modification or change made without departing from the spirit and scope of the present invention shall be included in the scope of the attached patent application.

Claims (10)

A step-up DC power conversion device is used in conjunction with a solar module and includes: a step-up control unit that receives a voltage signal output by the solar module and generates a step-up signal. The step-up control unit includes a Switching element; a feedback unit, which generates a feedback signal based on the boost signal; a feedforward unit, which generates a feedforward signal based on the voltage signal; a signal processing unit, which outputs one based on the feedforward signal and a reference signal A command signal; a compensation amplifier unit that outputs a control signal based on the feedback signal and the command signal; and a pulse width modulation unit that controls the switching element according to the control signal; wherein when the ripple value of the command signal is greater than When the feedback signal has a ripple value, the pulse width modulation unit increases a duty cycle of the switching element according to the control signal to suppress the voltage ripple of the voltage signal. The step-up DC power conversion device according to item 1 of the scope of patent application, wherein the step-up DC power conversion device further includes a frequency conversion unit, and the step-up control unit further includes an inductor, a capacitor, and a diode. The first end of the inductor is electrically connected to the first end of the capacitor and a voltage output terminal of the solar module, and the second end of the inductor is electrically connected to one end of the switching element and the first end of the diode, respectively. The second end of the capacitor is electrically connected to the second end of the diode and the frequency conversion unit, respectively. The boost DC power conversion device according to item 2 of the scope of patent application, wherein when the ripple value of the command signal is greater than the ripple value of the feedback signal, the control signal causes the pulse width modulation unit to output The duty cycle of a pulse width modulation signal increases, thereby increasing the current flowing through the inductor. The step-up DC power conversion device according to item 1 of the scope of patent application, wherein the DC step-up ratio of the step-up control unit is equal to 1 / (1-D), where D is the duty-on period of the switching element. . The step-up DC power conversion device according to item 1 of the scope of patent application, wherein the signal processing unit includes a filter, which filters out a DC component in the voltage signal, so that the filter generates a filtered signal Including 120Hz ripple. The step-up DC power conversion device according to item 5 of the patent application scope, wherein the signal processing unit further includes an adder circuit that adds the filtered signal to the reference signal to output the command signal. The step-up DC power conversion device according to item 1 of the patent application scope, wherein the compensation amplifier unit includes an operational amplifier, the command signal is input to the positive terminal of the operational amplifier, and the feedback signal is input to the negative terminal of the operational amplifier. And the output end of the operational amplifier outputs the control signal. The step-up DC power conversion device according to item 1 of the scope of patent application, wherein the step-up signal includes an AC signal of 120 Hz. The step-up DC power conversion device according to item 8 of the patent application scope further includes a frequency conversion unit that converts the step-up signal and filters out high-frequency noise to output an AC load signal of 60 Hz. A method for suppressing voltage ripple of a solar module is performed by a step-up DC power conversion device. The step-up DC power conversion device includes a boost control unit, a feedback unit, a feedforward unit, A signal processing unit, a compensation amplifier unit, and a pulse width modulation unit. The method includes: receiving, by the boost control unit, a voltage signal output by the solar module and generating a boost signal; the feedback unit is based on The boost signal generates a feedback signal; the feedforward unit generates a feedforward signal based on the voltage signal; the signal processing unit outputs a command signal based on the feedforward signal and a reference signal; The feedback signal and the command signal output a control signal; and the pulse width modulation unit controls the switching element according to the control signal; wherein when the ripple value of the command signal is greater than the ripple value of the feedback signal The pulse width modulation unit increases a duty cycle of one of the switching elements of the boost control unit according to the control signal to suppress the voltage signal. Ripple.