TWI554020B - Inverter apparatus and control method thereof - Google Patents

Description

Inverter device and control method thereof

The present invention relates to an inverter device, and more particularly to an inverter device that can detect an operating state of a primary side conversion circuit to adaptively adjust a primary side control signal and an associated control method thereof.

Photovoltaic inverter is used to convert the DC power outputted by the solar panel into AC power and output to the grid. The primary side conversion circuit of the PV inverter operates in the deep intermittent mode when the solar power output is low. (deep burst mode). For example: (1) when the power output from the solar panel is too small, the primary side conversion circuit will enter the deep intermittent mode; and (2) when the light intensity is greatly reduced, the operating voltage and energy output of the solar panel will be low. The level causes the primary side switching circuit to enter the deep intermittent mode.

However, when the primary side conversion circuit operates in the deep intermittent mode, the internal circuit of the photovoltaic inverter may abnormally or suspend operation due to insufficient output power of the primary side conversion circuit, resulting in damage of circuit components. Therefore, there is a need for an innovative photovoltaic inverter state detection circuit architecture to avoid side effects caused by intermittent mode.

In view of the above, it is an object of the present invention to provide an inverter device that can detect an operation state of a primary side conversion circuit to adaptively adjust a primary side control signal and an associated control method thereof to solve the above problems.

According to an embodiment of the invention, an inverter device is disclosed. The inverter device comprises a DC-DC converter, a DC-to-AC converter and a control circuit. The DC to DC converter is configured to convert an input power source into a DC power source according to a control signal. The DC-to-DC converter is coupled to the DC-to-DC converter for receiving the DC power source and generating an AC power source according to the DC power source. The control circuit is coupled to the DC to DC converter for generating the control signal according to a reference power source and the input power source to control the operation of the DC to DC converter, and detecting the control signal to generate a detection. As a result, and controlling the reference power source according to the detection result to adjust a duty cycle of the control signal.

According to an embodiment of the invention, a method of controlling an inverter device is disclosed. The inverter device comprises a DC converter and a DC converter. The DC to DC converter converts an input power source into a DC power source. The DC-to-AC converter converts the DC power source into an AC power source. The control method includes the following steps: generating a control signal according to a reference power source and the input power source to control operation of the DC to DC converter; detecting the control signal to generate a detection result; and according to the detection result The reference power is controlled to adjust a duty cycle of the control signal.

The inverter device provided by the invention can detect the working state of the control signal by detecting the control signal of the primary side conversion circuit, and adaptively adjust the signal level/responsibility period of the control signal, so that the inverter can be stably maintained in the intermittent mode. It works and is widely used in various energy conversion architectures.

100, 300‧‧‧Inverter

102‧‧‧ solar cells

110, 310‧‧‧DC to DC converter

120‧‧‧DC to AC converter

130, 330‧‧‧ control circuit

322‧‧‧LLC resonant converter

326‧‧‧ drive circuit

332‧‧‧ Controller

336‧‧‧Processing circuit

D _L , D _R ‧‧‧ diode

R ₁ , R ₂ ‧‧‧ resistance

C‧‧‧ capacitor

V _PV ‧‧‧ input power supply

V _BUS ‧‧‧DC power supply

V _AC ‧‧‧AC power supply

V _CMD ‧‧‧reference power supply

DR‧‧‧ test results

S _C ‧‧‧Control signal

S _D ‧‧‧Drive Signal

V _C1 , V _C2 , V _CA , V _CB ‧ ‧ voltage level

t ₀ , t ₁ , t ₂ , t ₃ , T _a , T _b , T _c , T _d ‧‧‧ time

S _CL ‧‧‧left arm control signal

S _CR ‧‧‧Right arm control signal

S _DL ‧‧‧Left arm drive signal

S _DR ‧‧‧Right arm drive signal

V _C ‧‧‧ voltage

L1‧‧‧ first position

L2‧‧‧ second level

FIG. 1 is a functional block diagram of an embodiment of an inverter device according to the present invention.

Fig. 2 is a signal waveform diagram showing an example of a control signal shown in Fig. 1.

Fig. 3 is a schematic view showing an example of the implementation of the inverter device shown in Fig. 1.

Fig. 4 is a partial circuit diagram showing an example of the implementation of the controller shown in Fig. 3.

Fig. 5 is a signal waveform diagram showing an example of a control signal shown in Fig. 3.

The inverter architecture provided by the invention can detect the working state of the primary side conversion circuit by detecting the control signal of the primary side conversion circuit, and adaptively adjust the duty cycle of the control signal according to the detected result, so Improve the flexibility of inverter control and provide good circuit protection mechanism. In order to facilitate the understanding of the technical features of the present invention, a photovoltaic inverter is used as an implementation example of the inverter device provided by the present invention. However, the inverter architecture provided by the present invention is not limited to a photovoltaic inverter. Further explanation is as follows.

Please refer to FIG. 1 , which is a functional block diagram of an embodiment of an inverter device according to the present invention. The inverter device 100 is coupled to a photovoltaic cell (PV cell) 102 and may include, but is not limited to, a direct current to direct current converter (DC/DC converter) 110. A direct current to alternating current converter (DC/AC converter) 120 and a control circuit 130. The DC to DC converter 110 can receive the input power V _PV provided by the solar cell 102 and convert the input power V _PV into a DC power source V _BUS (eg, a DC bus voltage) according to a control signal S _C . The DC-to-DC converter 120 is coupled to the DC-to-DC converter 110 for receiving the DC power source V _BUS and generating an AC power source V _AC according to the DC power source V _BUS . In this embodiment (but the invention is not limited thereto), the DC-to-DC converter 110 may include an LLC resonant converter to improve conversion efficiency and reduce electromagnetic interference by utilizing the characteristics of its soft switching. The DC-to-AC converter 120 can also be referred to as a DC/AC inverter.

The control circuit 130 is coupled to the DC to DC converter 110 for generating a control signal S _C to control the operation of the DC to DC converter 110 according to a reference power source V _CMD and an input power source V _PV . For example (but the invention is not limited thereto), the control circuit 130 can compare the reference power source V _CMD with the input power source V _PV to generate the control signal S _C , thereby controlling the operating frequency and operating state of the DC-to-DC converter 110 ( For example, normal mode or intermittent mode). In another example, the control circuit 130 can also perform a numerical operation on the reference power source V _CMD and the input power source V _PV to generate the control signal S _C .

In order to monitor the working state of the inverter device 100 in real time, the control circuit 130 can further process/detect the control signal S _C to generate a detection result DR, and control the reference power source V _CMD according to the detection result DR, thereby adjusting the DC control. The control signal S _{C of the} DC to DC converter 110. For example (but the invention is not limited thereto), please refer to FIG. 2 together with FIG. Fig. 2 is a signal waveform diagram showing an example of the control signal S _C shown in Fig. 1. The control signal S _C may have a first level L1 and a second level L2 (different from the first level L1). When the DC-to-DC converter 110 continues to be at the second level L2, the control signal S _C Then the power conversion operation is suspended (ie, operating in the intermittent mode). Therefore, in a case where the level of the control signal S _C can be changed by adjusting the reference power source V _CMD , the control circuit 130 can adjust the energy level of the reference power source V _CMD according to the detection result DR to switch the control signal S _{C .} The level is adjusted to immediately adjust the operation of the DC-DC converter 110 in the intermittent mode to prevent the DC-DC converter 110 from being powered abnormally.

In a practical example, the control circuit 130 can also control the reference power V _CMD according to the detection result DR to adjust the duty cycle of the control signal S _C , thereby controlling the operation of the DC-DC converter 110 in the intermittent mode. . In this implementation example, the DC to DC converter 110 is operated in the intermittent mode according to the control signal S _C at the time point t ₁ , wherein the DC to DC converter 110 is turned on during the time point t ₀ ~ t ₁ , And it is closed during the period from time point t ₁ to t ₂ . In addition, since the DC-DC converter 110 is continuously in the off state for a long time, the power supply abnormality may occur, and the control circuit 130 may generate the detection result DR by detecting the time that the DC-DC converter 110 is continuously in the off state.

In the intermittent mode, the control circuit 130 turns on the DC to DC converter 110 at the time point t ₃ , however, since the time interval between the time point t ₁ and the time point t ₃ exceeds a certain time (this embodiment) Medium, equal to the time interval between the time point t ₁ and the time point t ₂ ), which causes the DC-to-DC converter 110 to generate a power abnormality before the time point t ₃ , and therefore, when the detection result DR indicates DC-DC When the converter 110 is turned off for more than the specific time (that is, when the control signal S _C continues to be at the second level L2 exceeds the specific time), the control circuit 130 can pass the voltage level V _{C1 of the} reference power source V _CMD . adjusted to a voltage level V _C2, so that the control signal S _C earlier than the time point t ₂ level switching signal to the first level L1, at this time, the DC-DC converter 110 will be advanced at a time point t ₂ is turned on. In other words, the control circuit 130 can change the duty cycle of the control signal S _C by adjusting the voltage level V _{C1 of the} reference power source V _CMD to achieve the purpose of controlling the turn-on and turn-off timing of the DC-DC converter 110 in the intermittent mode.

In order to further understand the technical features of the present invention, a practical example will be further used to further explain the details of the inverter device of the present invention. However, other circuit implementations based on the circuit architecture shown in FIG. 1 are also feasible. Please refer to FIG. 3 , which is a schematic diagram of an implementation example of the inverter device 100 shown in FIG. 1 . In this implementation example, the inverter device 300 includes a DC-DC converter 310, a control circuit 330, and a DC-to-AC converter 120 shown in FIG. 1, wherein the DC-to-DC converter 110 shown in FIG. The control circuit 130 can be implemented by the DC to DC converter 310 and the control circuit 330, respectively. The control circuit 330 can include, but is not limited to, a controller 332 and a processing circuit 336. The controller 332 can detect the control signal S _C to generate the detection result DR, and generate/control the reference power V according to the detection result DR. _CMD , and the processing circuit 336 can generate the control signal S _C according to the reference power source V _CMD and the input power source V _PV . The DC-to-DC converter 310 can include, but is not limited to, an LLC resonant converter 322 and a driving circuit 326. The driving circuit 326 can generate a driving signal S _D according to the control signal S _C generated by the control circuit 330. The LLC resonant converter 322 can convert the input power V _PV into a DC power source V _BUS according to the driving signal S _D .

In this implementation example, the LLC resonant converter 322 can include a left arm switch and a right arm switch (not shown in FIG. 3), wherein the left arm switch and the right arm switch can each be an upper switch. And the lower switch is composed, and the control signals of the upper and lower switches of the left arm switch are complementary, and the control signals of the upper and lower switches of the right arm switch are also complementary. The foregoing is the infrastructure of the LLC resonant converter 322. Since the infrastructure is not the technical focus of the present invention, it will not be described here. In this implementation example, the driving signal S _D received by the LLC resonant converter 322 can include a left arm driving signal S _DL and a right arm driving signal S _DR , and the control signal S _C generated by the processing circuit 336 can be A left arm control signal S _CL and a right arm control signal S _{CR are included} . See Figure 4 for an implementation of the detection control signal S _C . FIG. 4 is a partial circuit diagram showing an example of the implementation of the controller 332 shown in FIG. 3. As can be seen from FIG. 4, the controller 332 can learn the information of the control signal S _C by detecting the voltage V _{C of the} capacitor C. The controller 332 can receive the left signal via the diode D _L , the resistor R ₁ and the resistor R ₂ . The arm control signal S _CL and the right arm control signal S _CR are received via the diode D _R , the resistor R ₁ and the resistor R ₂ . However, the signal acquisition architecture shown in FIG. 4 is for illustrative purposes only and is not intended to be a limitation of the present invention.

The control circuit 330 can compare a voltage level of the input power source V _{PV with a} voltage level of the reference power source V _CMD to generate a comparison result, and generate a control signal S _C according to the comparison result (the left arm control signal S _CL With the right arm control signal S _CR ). For example, the processing circuit 336 can include a comparator (not shown in FIG. 3) for performing voltage level comparison to generate the comparison result, and the processing circuit 336 can generate a control signal according to the comparison result. S _C . The function of the comparator can also be achieved by a controller circuit composed of an operational amplifier, a resistor and a capacitor. By adjusting the frequency of the control signal S _C , the duty cycle, etc., the DC-to-DC converter 310 (LLC resonant converter 322) can operate in different modes, such as the normal mode, with different solar energy output power. Or intermittent mode. In addition, in order to prevent the DC-DC converter 310 from being in the off state for a long time, the control circuit 330 can adjust the voltage level of the reference power source V _CMD according to the detection result DR to adjust the control signal S _C (for example, , adjust the signal level and / or responsibility cycle).

For example, when the detection result DR indicates that the DC-to-DC converter 310 is continuously in the off state for more than a certain time, the control circuit 330 can reduce the voltage level of the reference power source V _CMD to adjust the responsibility of the control signal S _C . The cycle causes the DC to DC converter 310 to turn on. Please refer to Figure 5 together with Figure 3. Fig. 5 is a signal waveform diagram showing an example of the control signal S _C shown in Fig. 3. In this implementation example, the DC-to-DC converter 310 is turned on during the time points T _a to T _{b and} is turned off during the time points T _b to T _c . When the DC to DC converter 310 operates in an intermittent mode according to the control signal S _C (for example, the illumination intensity is suddenly decreased at the time point T _b ), the controller 332 can detect the off time of the DC to DC converter 310 by detecting the off time of the DC to DC converter 310. The detection result DR is generated, and the voltage level V _{CA of the} reference power source V _CMD is adjusted accordingly. When the detection result DR indicates that the off time of the DC to DC converter 310 exceeds a certain time, the control circuit 330 can adjust the control signal S _C by lowering the voltage level V _{CA of the} reference power source V _CMD , wherein the control circuit 330 can The voltage level V _{CA is} lowered until the control signal S _C causes the DC to DC converter 310 to turn on (eg, time point T _c ). As can be seen from FIG. 5, before the voltage level V _{CA of the} reference power source V _{CMD is} not reduced to the voltage level V _CB , the processing circuit 336 is scheduled to switch the left arm control signal S _CL and the right arm control at the time point T _{d .} The signal level of the signal S _CR ; when the voltage level V _{CA of the} reference power source V _CMD is adjusted to the voltage level V _CB , the processing circuit 336 can switch the left arm control signal S _CL and the right arm control ahead of the time point T _{c .} The signal level of the signal S _CR is avoided to prevent the DC-to-DC converter 310 from being turned off for a long time.

The implementation of the above adjustment control signal S _C is for illustrative purposes only and is not intended to be a limitation of the present invention. In addition, in the case where another type of power converter is used to implement the DC-to-DC converter 310 shown in FIG. 3, the type/number of control signals received by the DC-to-DC converter 310 may have corresponding values. Adjustments, and the way the control signals are adjusted may vary.

Furthermore, as long as the control circuit 330 shown in FIG. 3 can adjust the reference power V _CMD by detecting the control signal S _C and adjust the duty cycle of the control signal S _{C ,} it is feasible to implement the control circuit 330 by using other circuit architectures. of. For example, the control circuit 330 can also store a relationship table of the duty cycle of the input power V _PV , the reference power V _CMD and the control signal S _C , and the control circuit 330 can select the voltage level of the reference power V _CMD according to the detection result DR. .

It is to be noted that the control mechanism of the inverter device 300 shown in FIG. 3 described above can also be applied to the inverter device 100 shown in FIG. In summary, the inverter device provided by the present invention can detect the working state of the control signal by detecting the control signal of the primary side conversion circuit, and adaptively adjust the signal level/responsibility period of the control signal, so that it can be in the intermittent mode. Maintain stable operation and widely used in various energy conversion architectures.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

100‧‧‧Inverter

102‧‧‧ solar cells

110‧‧‧DC to DC converter

120‧‧‧DC to AC converter

130‧‧‧Control circuit

V _PV ‧‧‧ input power supply

V _BUS ‧‧‧DC power supply

V _AC ‧‧‧AC power supply

V _CMD ‧‧‧reference power supply

DR‧‧‧ test results

S _C ‧‧‧Control signal

Claims (14)

An inverter device includes: a DC-DC converter for converting an input power into a DC power according to a control signal; and a DC-to-DC converter coupled to the DC-DC converter for receiving the a DC power source, and an AC power source is generated according to the DC power source; and a control circuit coupled to the DC to DC converter, the control circuit is configured to generate the control signal according to a reference power source and the input power source to control the The operation of the DC-to-DC converter detects the control signal to generate a detection result, and controls the reference power according to the detection result to adjust a duty cycle of the control signal. The inverter device of claim 1, wherein the control signal has a first level and a second level different from the first level; and when the DC to DC converter is in accordance with the control When the signal is operated in a burst mode, the control signal continues to be at the second level, and the control circuit detects that the control signal continues to be at the second level to generate the detection result. The inverter device of claim 2, wherein the control circuit adjusts a voltage level of the reference power source when the detection result indicates that the control signal continues to be at the second level for more than a specific time. . The inverter device of claim 1, wherein the control circuit compares a voltage level of the input power source with a voltage level of the reference power source to generate a comparison result, and according to the comparison result To generate the control signal. The inverter device of claim 4, wherein the comparison result indicates the input When the voltage level of the power source is less than the voltage level of the reference power source, the DC to DC converter operates in an intermittent mode according to the control signal. The inverter device of claim 4, wherein the control circuit adjusts the voltage level of the reference power source according to the detection result to adjust the duty cycle of the control signal. The inverter device of claim 6, wherein the control signal has a first level and a second level different from the first level; when the DC to DC converter is based on the control signal When the operation mode is in an intermittent mode, the control signal continues to be at the second level, and when the detection result indicates that the control signal continues to be at the second level for more than a certain time, the control circuit lowers the reference The voltage level of the power supply. The inverter device of claim 7, wherein the control circuit reduces the voltage level of the reference power source until the control signal is converted from the second level to the first level. A control method for an inverter device, comprising: a DC-DC converter and a DC-DC converter, wherein the DC-DC converter converts an input power into a DC power source, and the DC-to-AC converter converts the DC The control method comprises: generating a control signal according to a reference power source and the input power source to control the operation of the DC to DC converter; detecting the control signal to generate a detection result; The reference power source is controlled according to the detection result to adjust one duty cycle of the control signal. The control method of claim 9, wherein the step of generating a control signal according to a reference power source and the input power source comprises: performing voltage level of one of the input power sources and one voltage level of the reference power source Compare to produce one Comparing the result; and generating the control signal according to the comparison result. The control method of claim 10, wherein when the comparison result indicates that the voltage level of the input power source is less than the voltage level of the reference power source, the DC-to-DC converter according to the control signal To operate in a pause mode. The control method of claim 9, wherein the step of controlling the reference power according to the detection result to adjust the duty cycle of the control signal comprises: adjusting the voltage level of the reference power according to the detection result To adjust the duty cycle of the control signal. The control method of claim 12, wherein the control signal has a first level and a second level different from the first level; when the DC to DC converter is based on the control signal When the operation mode is in an intermittent mode, the control signal continues to be at the second level; and when the detection result indicates that the control signal continues to be at the second level for more than a specific time, the reference is adjusted according to the detection result. The step of the voltage level of the power supply includes: reducing the voltage level of the reference power supply. The control method of claim 13, wherein the step of lowering the voltage level of the reference power source comprises: lowering the voltage level of the reference power source until the control signal is converted from the second level to the first A level is up.