Patent ID: 12249905

DETAILED DESCRIPTION OF THE EMBODIMENTS

The embodiments may provide a serial-parallel converter protection system, a controller, and a converter. The converter is bypassed when a voltage is excessively large, thereby preventing the voltage and a current from impacting a component inside the converter.

In the embodiments and the accompanying drawings, the terms “first”, “second”, “third”, “fourth”, and the like (if existent) are intended to distinguish between similar objects but do not necessarily indicate an order or sequence. It should be understood that the data termed in such a way is interchangeable in proper circumstances, so that the embodiments described herein can be implemented in other orders than the order illustrated or described herein. Moreover, terms “include”, “correspond to”, and any other variants thereof mean to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a list of steps or units is not necessarily limited to those steps or units, but may include other steps or units not expressly listed or inherent to such a process, method, product, or device.

In addition, in the embodiments, the word “example” or “for example” is used to represent giving an example, an illustration, or a description. Any embodiment described with the word “example” or “for example” o should not be explained as being more preferred or having more advantages than another embodiment. Use of the word “example” or “for example” or the like may be intended to present a relative concept.

FIG.1is a schematic diagram of serial-parallel converters connected to an inverter. After being connected in parallel, a first optimizer101and a second optimizer102are connected to an inverter103. The first optimizer101includes a plurality of converters1012, and an input terminal of each converter1012may be connected to a photovoltaic panel1011. Two output terminals are formed after output terminals of the converters1012are connected in parallel in a manner shown inFIG.1, and the two output terminals are used as output terminals of the first optimizer101.

An internal structure of the second optimizer102may be similar to that of the first optimizer101and is not drawn in detail inFIG.1, and details are not described herein again. In some other cases, the second optimizer102may alternatively have another internal structure. This is not limited in this embodiment.

In the first optimizer101, the photovoltaic panel1011may be an apparatus for converting solar energy into electric power. A model, a mounting manner, an area, and the like of the photovoltaic panel are not limited in this embodiment. In another new energy power generating system or an energy storage system, the photovoltaic panel1011may be replaced with a corresponding apparatus. For example, in a wind energy power generating system, the photovoltaic panel1011may be replaced with a wind-driven generator. For another example, in an energy storage system, the photovoltaic panel1011may be replaced with an energy storage battery. In actual application, the photovoltaic panel1011may be replaced with a different apparatus according to an actual requirement, and is connected to a converter1012. Details are not described in this embodiment.

In the first optimizer101, the converter1012may be a direct current-direct current converter. In actual application, the converter1012may alternatively be another type of converter. This is not limited in this embodiment.

FIG.2is a schematic diagram of an internal structure of the converter1012. The internal structure of the converter1012may include a switching transistor Q1, a switching transistor Q2, a capacitor C1, a capacitor C2, and an inductor L. The capacitor C1is connected in parallel between an input terminal201and an input terminal202of the converter, and the capacitor C2is connected in parallel between an output terminal203and an output terminal204of the converter. The switching transistor Q1and the inductor L are connected in series between the input terminal201and the output terminal203. The switching transistor Q2is connected in parallel between the output terminal204and a connection terminal of the switching transistor Q1and the inductor L.

The switching transistor Q1or the switching transistor Q2may be a triode, a MOS transistor, or a transistor of another type in actual application, for example, an insulated gate bipolar transistor (IGBT). This is not limited in this embodiment. In some embodiments, the switching transistor Q1and the switching transistor Q2each may be anti-parallel with a diode.

With reference toFIG.1, when a first photovoltaic panel1011of the first optimizer101needs maintenance or replacement, a worker disconnects an input terminal of a corresponding converter1012. In this case, an output voltage of the second optimizer102impacts the converter1012, thereby damaging a component (for example, a capacitor or a switching transistor) inside the converter. InFIG.1, a line104is a current path before the worker disconnects the input terminal of the corresponding converter1012, and a line105is a current path after the worker disconnects the input terminal of the corresponding converter1012. It can be understood that after the worker disconnects the input terminal of the corresponding converter1012, a current and a voltage are applied to an input capacitor, and the capacitor is damaged. In some cases, the current and the voltage may further impact the switching transistor Q2, and the switching transistor Q2is damaged.

To resolve the foregoing problem, the embodiments may provide a serial-parallel converter protection system, as shown inFIG.3.FIG.3is a schematic diagram of a serial-parallel converter protection system. The serial-parallel converter protection system includes: a controller301, a drive303, a switching transistor Q1, and a switching transistor Q2. A connection relationship of the switching transistor Q1, the switching transistor Q2, an input capacitor, an output capacitor, an inductor, and the like is similar to that of the corresponding converter in FIG.2, and details are not described herein again. The input terminal of the converter may be connected to the output terminal of the converter through the switching transistor Q1, and the controller301may be connected to the switching transistor Q1through the drive303and may be configured to control on and off of the switching transistor Q1. The output terminal of the converter is connected in parallel with the switching transistor Q2, and the controller301is connected to the switching transistor Q2through the drive303and is configured to control on and off of the switching transistor Q2.

In this embodiment, when an output voltage Vo of the converter is greater than a first threshold, the controller controls the switching transistor Q1to be turned off and controls the switching transistor Q2to be turned on. That the output voltage Vo of the converter is greater than the first threshold shows that a voltage of the output terminal of the converter is high and damages a component inside the converter. Therefore, in this case, the controller301may control the switching transistor Q1to be turned off and control the switching transistor Q2to be turned on, so that a current path is short-circuited through the switching transistor Q2instead of the switching transistor Q1and is output to another output terminal. Actually, the converter1012is bypassed, thereby avoiding damage to the converter, and resolving a problem that the converter is damaged when the output voltage is excessively high.

FIG.4is a schematic diagram of a current path in a protection process according to an embodiment. As shown inFIG.4, after the controller301controls the switching transistor Q1to be turned off and controls the switching transistor Q2to be turned on, the current path flows through the switching transistor Q2in the converter1012(as shown by a line106inFIG.4), and the converter1012is bypassed.

In actual application, the controller301may detect the output voltage Vo through a voltage detection unit304. The voltage detection unit304may be a circuit or component that can detect a voltage, for example, a voltage sensor. This is not limited in this embodiment.

In actual application, the controller301may control the switching transistor Q1and the switching transistor Q2through the drive303. The drive303may be a drive circuit that is configured to receive a control signal of the controller301, convert the control signal into a corresponding high/low level, and output the level to the switching transistor Q1and the switching transistor Q2, thereby controlling on and off of both the switching transistor Q1and the switching transistor Q2. In this embodiment, a circuit or a structure of the drive303is not limited.

In some cases, an auxiliary power supply302provides electric energy for the controller301and the drive303. An input terminal of the auxiliary power supply302is connected in parallel with the input terminal of the converter, and is configured to obtain electric energy. The auxiliary power supply302is further connected to the controller301and the drive303, and is configured to output the obtained electric energy to the controller301and the drive303.

After the controller controls the switching transistor Q1to be turned off and controls the switching transistor Q2to be turned on, an input voltage Vin and the output voltage Vo of the converter decrease. When the input voltage Vin of the converter decreases to a second threshold, the auxiliary power supply302may not obtain enough electric energy. Therefore, when the input voltage Vin of the converter decreases to the second threshold, the controller301may control both the switching transistor Q1and the switching transistor Q2to be turned off. As a result, a current of the second optimizer102continues to flow to the input terminal of the converter through a diode anti-parallel with the switching transistor Q1. In this way, the input voltage Vin of the converter increases, to maintain the power supply of the auxiliary power supply.

In this embodiment, through control logic of the controller301, when the output voltage of the converter is excessively high, the switching transistor Q2can be controlled to bypass the converter, to prevent an excessively high voltage from damaging a component inside the converter. On the other hand, when the input voltage of the converter is excessively low, the switching transistor Q2can be controlled to be turned off, so that electric energy can continue to flow to the input terminal of the converter, thereby maintaining normal operation of the controller301and the drive303, and implementing continuous protection of the converter.

After a worker maintains or replaces a photovoltaic panel1011, a corresponding converter1012may be reconnected by the worker. In this case, the worker may input instructions to enable the controller301to control the switching transistor Q1to be turned on and the switching transistor Q2to be turned off, so that the converter1012resumes normal operation. When the worker does not input the instructions, the controller301may perform timing after detecting for the first time that the output voltage Vo of the converter is greater than the first threshold. When the timing reaches a preset time threshold, the controller301re-detects the output voltage Vo of the converter. If the output voltage Vo of the converter is less than the first threshold, the controller301may control the switching transistor Q1to be turned on and the switching transistor Q2to be turned off, so that the converter1012resumes normal operation. In this case, after the photovoltaic panel1011is reconnected to the converter by the worker, the controller301can automatically control the converter to resume normal operation, which is more automatic without operation of the worker.

Based on the foregoing control logic, the controller301may perform steps shown inFIG.5.FIG.5is a flowchart of a protection policy method of a controller301according to an embodiment. The process includes the following steps.

501: Detect an output voltage of a converter.

In this embodiment, the controller301may detect the output voltage Vo of the converter through a voltage detection unit304. This is similar to the description of the foregoing embodiment, and details are not described herein again.

502: If the output voltage of the converter is greater than a first threshold, perform overvoltage protection, and start timing.

In this embodiment, the overvoltage protection may include following control logic:

when the output voltage Vo of the converter is greater than the first threshold, controlling a switching transistor Q1to be turned off and a switching transistor Q2to be turned on; and

when an input voltage Vin of the converter is less than a second threshold, controlling both the switching transistor Q1and the second switching transistor Q2to be turned off.

In actual application, the foregoing control logic may be directly performed in the controller, or a related procedure (an overvoltage protection procedure) may be set to implement the foregoing logic. This is not limited in this embodiment.

For example, the overvoltage protection may perform steps as shown inFIG.6, and for details, refer to a subsequent embodiment.

The overvoltage protection may control the output voltage Vo of the converter in a reasonable range, and maintain the input voltage Vin of the converter, to prevent power shortage of an auxiliary power supply302. Therefore, when a worker replaces or maintains a photovoltaic panel1011, the overvoltage protection may prevent damage to a component inside the converter due to an excessively high voltage.

503: If counted time reaches a preset time threshold, exit the overvoltage protection procedure, and return to perform step501.

In this embodiment, the controller301may count time by using a timer. When the time counted by the timer reaches the preset time threshold, the controller301may exit the overvoltage protection procedure (or may control the switching transistor Q2to be turned off, so that the converter is not bypassed), and then re-detect the output voltage of the converter. In some embodiments, after the controller301exits the overvoltage protection procedure, both the switching transistor Q1and the switching transistor Q2may be turned off, and step401is performed again (that is, re-detect the output voltage of the converter). It may be understood that, after a period of time, the worker may have completed the maintenance or replacement of the photovoltaic panel1011and reconnected the photovoltaic panel to the converter. Therefore, the converter is re-detected at regular intervals, so that restoration of normal operation can be implemented after the photovoltaic panel1011is reconnected to the converter.

504: If the output voltage of the converter is not greater than the first threshold, operate the converter normally.

In this embodiment, if the photovoltaic panel1011is not removed and the worker does not disconnect an input interface of the converter, the output voltage Vo of the converter may be in a normal operating state, and does not exceed the first threshold, so the converter operates normally. In may be understood that the controller301may control both the switching transistor Q1and the switching transistor Q2to return to work normally, so that the converter returns to operate normally. In some embodiments, the controller may control the switching transistor Q1to be turned on and control the switching transistor Q2to be turned off, so that the converter returns to operate normally.

The foregoing steps of the overvoltage protection may be directly performed by the controller301, or may be performed by an overvoltage protection unit305inside the controller301. The overvoltage protection unit305is a logic module inside the controller301and may include a microprocessor and a memory. The memory stores instructions, and the microprocessor reads the instructions to perform the steps of the overvoltage protection. The steps of the overvoltage protection may be as shown inFIG.6.FIG.6is a flowchart of the steps of the overvoltage protection according to an embodiment. The process includes the following steps.

601: Detect the input voltage Vin and the output voltage Vo of the converter.

In this embodiment, the controller301may separately detect the input voltage Vin and the output voltage Vo of the converter through the voltage detection unit304. This is similar to the description of the voltage detection unit304in the foregoing embodiment, and details are not described herein again.

602: Detect whether the output voltage Vo of the converter is greater than the first threshold Vth1and perform step603if the output voltage Vo of the converter is greater than the first threshold Vth1, or perform step605, if the output voltage Vo of the converter is not greater than the first threshold Vth1.

In this embodiment, when the controller detects that the output voltage Vo of the converter is greater than the first threshold Vth1, step603is performed (the switching transistor Q2is turned on), so that the converter is bypassed. When the controller detects that the output voltage Vo of the converter is not greater than the first threshold Vth1, step605is performed (the switching transistor Q2is turned off).

603: Turn on the switching transistor Q2.

In this embodiment, when the controller301controls the switching transistor Q2to be turned on through the drive303, a current received by the converter flows through the switching transistor Q2. In this case, the converter is bypassed, and a component inside the converter is not damaged.

In some cases, the controller may turn on the switching transistor Q2and turn off the switching transistor Q1at the same time, to prevent the current from impacting the input terminal of the converter. If the switching transistor Q1is turned off, only the switching transistor Q2may be turned on.

604: Detect whether the input voltage Vin of the converter is greater than the second threshold Vth2and perform step605if the input voltage Vin of the converter is greater than the second threshold Vth2, or return to step603if the input voltage Vin of the converter is not greater than the second threshold Vth2.

In this embodiment, that the input voltage Vin of the converter is less than the second threshold Vth2indicates that the input voltage will not continue to provide electric energy for the auxiliary power supply302. Therefore, the controller may perform step605to turn off the switching transistor Q2, so that the current may flow through the input terminal of the converter, and the input voltage Vin increases again.

605: Turn off the switching transistor Q2.

In this embodiment, after the controller301turns off the switching transistor Q2, the current may be transmitted to the input terminal of the converter through a diode anti-parallel with the switching transistor Q1, so that the input voltage Vin increases again.

FIG.7is a voltage sequence diagram corresponding to the steps inFIG.6. At the beginning of t1 duration, the controller301detects that the output voltage Vo of the converter exceeds the first threshold Vth1. In this case, the switching transistor Q2is turned on (and the switching transistor Q1is turned off). Therefore, the converter is bypassed, and the input voltage and the output voltage of the converter decrease.

After the t1 duration, the input voltage Vin of the converter is less than the second threshold Vth2. In this case, the controller301may turn off the switching transistor Q2, so that the converter is not bypassed, the current may flow into the converter again, and the input voltage and the output voltage of the converter may increase.

After t2 duration, the output voltage of the converter is greater than the first threshold Vth1. In this case, the controller301may turn on the switching transistor Q2, so that the converter is bypassed, and the input voltage and the output voltage of the converter decrease.

In this embodiment, the controller301turns on or off the switching transistor Q2based on a condition of the input voltage and the output voltage of the converter, so that the input voltage and the output voltage of the converter circularly decrease and increase and are always kept in a reasonable range. Therefore, no damage is caused to the component inside the converter, and a problem that the converter is damaged when the output voltage of the converter is excessive high is resolved.

In some other embodiments, the controller301may control the switching transistor Q2to be turned on through pulse width modulation (PWM) chopping, as shown inFIG.8.

FIG.8is a corresponding sequence diagram when the controller301turns on the switching transistor Q2through PWM chopping according to an embodiment.

In the embodiment corresponding toFIG.8, the controller301turns on the switching transistor Q2through PWM chopping. As shown inFIG.8, the switching transistor Q2performs PWM based on a duty ratio. The duty ratio may be set based on an actual condition. This is not limited in this embodiment.

In the embodiment corresponding toFIG.8, the controller301turns on the switching transistor Q2through PWM chopping, to slow down the decrease of the output voltage Vo and the input voltage Vin of the converter, so that the controller301does not need to frequently switch a control state, to improve system stability. Another case of this embodiment is similar to that of the foregoing embodiments, and details are not described herein again.

The first threshold Vth1, the second threshold Vth2, the preset time threshold, and the like in each foregoing embodiment may be set based on an actual condition. In this embodiment, values of the foregoing thresholds are not limited.

An embodiment further provides a converter, including a converter circuit. The converter circuit is similar to the circuit corresponding toFIG.2. An input terminal of the converter circuit is connected to at least one photovoltaic panel, and an output terminal of the converter circuit is connected to a power grid.

The converter may include the serial-parallel converter protection system shown inFIG.3. The serial-parallel protection system is connected to the converter circuit through a switching transistor Q1and a switching transistor Q2and is similar to that inFIG.3. Details are not described herein again.

Alternatively, the converter may include a controller. The controller is similar to the controller301in the embodiment corresponding toFIG.3, and details are not described herein again. The controller may be connected to the switching transistor Q1and the switching transistor Q2through a drive. In some embodiments, the converter further includes an auxiliary power supply which is similar to the auxiliary power supply302in the embodiment corresponding toFIG.3.

It can be clearly understood by a person skilled in the art that, for a purpose of convenient and brief description, for detailed working processes of the foregoing system, apparatus, and unit, refer to corresponding processes in the foregoing method embodiments. Details are not described herein.

In the several embodiments, it should be understood that the system, apparatus, and method may be implemented in other manners. For example, the described apparatus embodiments are merely examples. For example, division into units is merely logical function division and may be other division during actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented through some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electrical, mechanical, or another form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. Some or all of the units may be selected based on actual requirements to achieve the objectives of the solutions of the embodiments.

In addition, functional units in embodiments may be integrated into one processing unit, or each of the units may exist alone physically, or two or more units may be integrated into one unit. The integrated unit may be implemented in a form of hardware or may be implemented in a form of a software functional unit.

When the integrated unit is implemented in the form of a software functional unit and is sold or used as an independent product, the integrated unit may be stored in a computer-readable storage medium. Based on such an understanding, the embodiments may be implemented in the form of a software product. The computer software product is stored in a non-transitory storage medium and includes several instructions for instructing a computer device (which may be a personal computer, a server, or a network device) to perform all or some of the steps of the methods described in the embodiments. The foregoing non-transitory storage medium includes any medium that can store program code, such as a USB flash drive, a removable hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disc.