Method and apparatus for achieving fast reduction of inverter input voltage

Abstract

The present application relates to a kind of method and device for realizing the fast reduction of inverter input voltage, the method is: control boost circuit and inverter circuit in inverter open loop output, control the fan of inverter to open, to reduce the input voltage of inverter.The device includes boost module circuit in inverter, control circuit and fan, control circuit controls boost circuit to carry out open loop output, and control fan to open, to reduce the input voltage of inverter.The present application is realized by changing control method, and the fast reduction of inverter input voltage is realized with existing circuit, without increasing additional circuit and space, reduce cost, can also improve efficiency.

Description

Technical Field

[0001] This invention belongs to the field of distributed generation technology, and specifically relates to a method and apparatus for rapidly reducing the input voltage of an inverter, namely the common-mode and differential-mode voltages on the PV side and the battery side of the inverter. Background Technology

[0002] North American PVRSS safety regulations require that the photovoltaic fast shutdown function should reduce the voltage of the PV output circuit at a distance of more than 1m from the array to below 30V within 30 seconds after the fast shutdown function is triggered. The following three voltages on the PV input side of the inverter must meet this requirement: PV+ to PV-, PV+ to GND-E, and PV- to GND-E.

[0003] Traditional solutions include: connecting a small resistor between V+ and V- to quickly reduce the voltage and meet the voltage requirements between positive and negative terminals, but this means greater losses and lower efficiency; or placing a discharge resistor at the bus terminal and controlling the signal to reduce the bus voltage to meet the voltage requirements between PV+ and GND-E, and between PV- and GND-E, as shown in the attached diagram. Figure 1 As shown, this scheme introduces additional control and increases circuitry and space, thus increasing costs. Summary of the Invention

[0004] The purpose of this invention is to provide a method for rapidly reducing the input voltage of an inverter without adding components and at a low cost.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for rapidly reducing the input voltage of an inverter is provided, comprising: controlling the boost circuit in the inverter to perform open-loop output and controlling the inverter fan to turn on, thereby reducing the input voltage of the inverter.

[0006] The method includes the following steps: Step 1: Determine whether the inverter's fast shutdown function has been triggered; if so, proceed to Step 2. Step 2: Put the inverter into standby mode, and then proceed to step 3; Step 3: Determine whether the voltage difference between the bus capacitor voltage in the inverter and the voltage across the photovoltaic module connected to the inverter reaches or exceeds the voltage difference threshold. If yes, proceed to step 4; otherwise, return to step 2. Step 4: Determine whether the bus capacitor voltage in the inverter is greater than or equal to the high voltage threshold. If yes, proceed to step 5; otherwise, proceed to step 6. Step 5: Turn on the inverter fan and control the inverter's boost circuit to output in an open loop to reduce the inverter's input voltage, then return to step 4; Step 6: Turn off the inverter fan and control the inverter's boost circuit to not perform open-loop output, then proceed to step 7; Step 7: Determine whether the bus capacitor voltage in the inverter is less than or equal to the low voltage threshold. If yes, proceed to step 8; otherwise, return to step 6. Step 8: Turn off the power to the inverter.

[0007] In step 1, the system determines whether the inverter's fast shutdown function has been triggered based on the feedback signal from the fast shutdown button configured on the inverter.

[0008] In step 2, the grid-connected and off-grid relays of the inverter are disconnected, causing the inverter to enter standby mode.

[0009] In step 5, the inverter's control circuit outputs corresponding drive signals to the fan and the boost circuit to turn on the inverter's fan and control the inverter's boost circuit to perform open-loop output.

[0010] In step 6, the inverter input voltage is reduced by discharging using the discharge resistors at the photovoltaic input terminal and / or the battery input terminal.

[0011] In step 8, the inverter's control circuit sends a corresponding drive signal to the inverter's power module to shut down the inverter's power supply.

[0012] This invention also provides a device for rapidly reducing the input voltage of an inverter without adding components and at a low cost. The solution is as follows: A device for rapidly reducing the input voltage of an inverter includes a boost module circuit, a control circuit, and a fan in the inverter. The control circuit controls the boost circuit to perform open-loop output and controls the fan to turn on, thereby reducing the input voltage of the inverter.

[0013] The device for rapidly reducing the inverter input voltage also includes a fast shutdown button for triggering the inverter's fast shutdown function.

[0014] The device for rapidly reducing the input voltage of the inverter also includes discharge resistors disposed at the photovoltaic input terminal and the battery input terminal of the inverter.

[0015] Due to the application of the above technical solutions, the present invention has the following advantages compared with the prior art: By changing the control method, the present invention achieves a rapid reduction in the inverter input voltage using existing circuits, without the need to add additional circuits and space, thus reducing costs and improving efficiency. Attached Figure Description

[0016] Appendix Figure 1 This is the discharge circuit diagram for a traditional solution.

[0017] Appendix Figure 2 An inverter system block diagram for implementing the inverter input voltage rapid reduction method of the present invention.

[0018] Appendix Figure 3 This is a flowchart of the method for rapidly reducing the input voltage of an inverter according to the present invention. Detailed Implementation

[0019] The present invention will be further described below with reference to the embodiments shown in the accompanying drawings.

[0020] Example 1: As shown in the attached document Figure 2 As shown, the inverter system includes an inverter and connected photovoltaic modules, batteries, etc. The inverter includes the following main circuit components: boost module circuit, charge / discharge module circuit, bus capacitor, inverter circuit, output LC filter, relay circuit, power supply circuit, and control circuit. R1 and R2 are the discharge resistors for the photovoltaic input terminal and battery input terminal of the inverter, respectively. C1 and C4 are the filter capacitors for the photovoltaic input terminal and battery input terminal, respectively. C2, C3, C5, and C6 are the common-mode filter capacitors for the photovoltaic input terminal and battery input terminal, respectively. Vpv is the PV+ to PV- voltage; Vbus is the bus capacitor voltage; Vdrv_pv is the PV drive signal; Vdrv_inv is the inverter drive signal; Vdrv_fan is the fan drive signal; sps_off is the inverter power supply shutdown signal; and Vtrigger is the fast shutdown trigger signal.

[0021] The method to rapidly reduce the input voltage of the existing inverter is to control the boost circuit in the inverter to output in an open loop and control the inverter fan to turn on, thereby reducing the input voltage of the inverter.

[0022] As attached Figure 3 As shown, the method for rapidly reducing the input voltage of the inverter includes the following steps: Step 1: Determine whether the inverter's fast shutdown function has been triggered. If so, proceed to Step 2.

[0023] In step 1, the fast shutdown function of the inverter is determined based on the feedback signal Vtrigger of the fast shutdown button configured in the inverter. That is, when a jump in the Vtrigger level is detected, it indicates that the fast shutdown function of the inverter has been triggered.

[0024] Step 2: Disconnect the grid-connected and off-grid relays of the inverter to put the inverter into standby mode, and then proceed to step 3.

[0025] Step 3: Sample the bus capacitor voltage Vbus in the inverter and the voltage Vpv across the photovoltaic module connected to the inverter. Determine whether the difference between the bus capacitor voltage Vbus in the inverter and the voltage Vpv across the photovoltaic module connected to the inverter reaches or exceeds the voltage difference threshold B, i.e., determine whether Vbus-Vpv≥B is true. If yes, it is considered that the inverter power supply has been turned off and proceed to step 4. If not, return to step 2.

[0026] Step 4: Determine whether the bus capacitor voltage Vbus in the inverter is greater than or equal to the high voltage threshold C, that is, determine whether Vbus≥C holds true. If yes, proceed to step 5; otherwise, proceed to step 6.

[0027] Step 5: At this point, the voltage is high. Turn on the inverter fan and control the inverter's boost circuit to output in an open loop to reduce the inverter's input voltage. Then return to step 4.

[0028] In step 5, the inverter's control circuit outputs a corresponding drive signal Vdrv_fan to the fan to turn on the inverter's fan, reducing the bus voltage Vbus. It also outputs a corresponding drive signal Vdrv_pv to the boost circuit to control the inverter's boost circuit to perform open-loop output, thereby reducing the Vpv and Vbus voltages.

[0029] Step 6: At this point, the voltage is low. Turn off the inverter fan and prevent the inverter's boost circuit from opening in a loop. Discharge using the discharge resistors at the inverter's photovoltaic input and / or battery input terminals to lower the inverter input voltage to meet the requirements. Then proceed to step 7. When Vbus < C, the inverter's own power consumption will continue to lower Vbus.

[0030] Step 7: Determine whether the bus capacitor voltage Vbus in the inverter is less than or equal to the low voltage threshold D, that is, determine whether Vbus≤D holds true. If yes, proceed to step 8; otherwise, return to step 6. Step 8: The inverter's control circuit sends the corresponding drive signal sps_off to the inverter's power module, shutting off the inverter's power. Afterwards, the Vpv voltage continues to dissipate energy through the discharge resistor R1, decreasing until it approaches 0V. In a total time of 30 seconds, the voltages of PV+ to GND-E and PV- to GND-E both decrease to below 30V.

[0031] Based on the above method for rapidly reducing the inverter input voltage, a device for rapidly reducing the inverter input voltage includes a boost module circuit, a control circuit, and a fan in the inverter. The control circuit controls the boost circuit to perform open-loop output and controls the fan to turn on, thereby reducing the inverter input voltage. The device for rapidly reducing the inverter input voltage also includes a fast-shutdown button for triggering the inverter's fast-shutdown function, and discharge resistors R1 and R2 disposed at the photovoltaic input terminal and the battery input terminal of the inverter.

[0032] The above scheme can also control the inverter circuit in the inverter to also perform open-loop output while simultaneously controlling the boost circuit in the inverter to perform open-loop output. In step 5, the inverter's control circuit outputs the corresponding drive signal Vdrv_inv to the inverter circuit, controlling both the boost circuit and the inverter circuit to perform open-loop output, thereby reducing Vpv and Vbus voltages. In this case, the circuit that enables the rapid reduction of the inverter's input voltage also includes the inverter circuit within the inverter.

[0033] The scheme that controls only the boost circuit to perform open-loop output is superior in terms of safety compared to the scheme that controls both the boost circuit and the inverter circuit to perform open-loop output.

[0034] The above solution introduces a feedback signal at the fast shutdown button. Upon detecting a fast shutdown trigger, the boost circuit operates in open-loop mode, rapidly reducing the PV+ to PV- voltage. Simultaneously, the fan activates, quickly reducing the bus voltage, thus meeting the voltage requirements of PV+ to GND-E and PV- to GND-E. This approach improves efficiency without reducing the load on PV+ and PV-, and eliminates the need for additional circuitry and space, achieving rapid reduction of input differential and common-mode voltages using existing circuitry, thereby lowering costs.

[0035] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for rapidly reducing the input voltage of an inverter, characterized in that: The method is as follows: control the boost circuit in the inverter to perform open-loop output to reduce the PV+ to PV- voltage, and control the inverter fan to turn on to reduce the bus voltage, thereby reducing the input voltage of the inverter. The method includes the following steps: Step 1: Determine whether the inverter's fast shutdown function has been triggered; if so, proceed to Step 2. Step 2: Put the inverter into standby mode, and then proceed to step 3; Step 3: Determine whether the voltage difference between the bus capacitor voltage in the inverter and the voltage across the photovoltaic module connected to the inverter reaches or exceeds the voltage difference threshold. If yes, proceed to step 4; otherwise, return to step 2. Step 4: Determine whether the bus capacitor voltage in the inverter is greater than or equal to the high voltage threshold. If yes, proceed to step 5; otherwise, proceed to step 6. Step 5: Turn on the inverter fan and control the inverter's boost circuit to output in an open loop to reduce the inverter's input voltage, then return to step 4; Step 6: Turn off the inverter fan and control the inverter's boost circuit to not perform open-loop output, then proceed to step 7; Step 7: Determine whether the bus capacitor voltage in the inverter is less than or equal to the low voltage threshold. If yes, proceed to step 8; otherwise, return to step 6. Step 8: Turn off the power to the inverter.

2. The method for rapidly reducing the input voltage of an inverter according to claim 1, characterized in that: In step 1, the system determines whether the inverter's fast shutdown function has been triggered based on the feedback signal from the fast shutdown button configured on the inverter.

3. The method for rapidly reducing the input voltage of an inverter according to claim 1, characterized in that: In step 2, the grid-connected and off-grid relays of the inverter are disconnected, causing the inverter to enter standby mode.

4. The method for rapidly reducing the input voltage of an inverter according to claim 1, characterized in that: In step 5, the inverter's control circuit outputs corresponding drive signals to the fan and the boost circuit to turn on the inverter's fan and control the inverter's boost circuit to perform open-loop output.

5. The method for rapidly reducing the input voltage of an inverter according to claim 1, characterized in that: In step 6, the inverter input voltage is reduced by discharging using the discharge resistors at the photovoltaic input terminal and / or the battery input terminal.

6. The method for rapidly reducing the input voltage of an inverter according to claim 1, characterized in that: In step 8, the inverter's control circuit sends a corresponding drive signal to the inverter's power module to shut down the inverter's power supply.

7. A device for rapidly reducing the input voltage of an inverter, characterized in that: The apparatus for rapidly reducing the input voltage of the inverter adopts the method for rapidly reducing the input voltage of the inverter as described in any one of claims 1 to 6, which includes a boost circuit, a control circuit, and a fan in the inverter. The control circuit controls the boost circuit to perform open-loop output to reduce the PV+ to PV- voltage, and controls the fan to turn on to reduce the bus voltage, thereby reducing the input voltage of the inverter.

8. The apparatus for rapidly reducing the input voltage of an inverter according to claim 7, characterized in that: The device for rapidly reducing the inverter input voltage also includes a fast shutdown button for triggering the inverter's fast shutdown function.

9. The apparatus for rapidly reducing the input voltage of an inverter according to claim 8, characterized in that: The device for rapidly reducing the input voltage of the inverter also includes discharge resistors disposed at the photovoltaic input terminal and the battery input terminal of the inverter.

Images