Power conversion equipment, insulation detection method and device and medium

Abstract

The invention discloses power conversion equipment, an insulation detection method and device and a medium. The power conversion equipment comprises a controller, an energy discharge path and an inverter circuit, the input end of the inverter circuit is connected with a direct-current bus, and at least part of energy of the direct-current bus comes from a photovoltaic panel; the energy discharge access is connected to the direct current side or the alternating current side of the inverter circuit; and the controller is used for controlling the energy discharge path to work before the inverter circuit performs insulation resistance detection so as to consume the energy of the direct current bus to stabilize the voltage of the direct current bus. According to the technical scheme, the insulation resistance of the DC side of the photovoltaic system power conversion equipment can be accurately detected, and the safety requirements are met.

Description

Technical Field

[0001] This application relates to the field of insulation testing technology, specifically to a power conversion device, insulation testing method, apparatus, and medium. Background Technology

[0002] In related technologies, when testing insulation impedance, it is assumed that the open-circuit voltage and DC bus voltage of the photovoltaic panel are stable and constant. However, the output voltage of the photovoltaic panel will change with the changes in light and temperature. That is, the output voltage of the photovoltaic panel will fluctuate in real time. The real-time change in output voltage will lead to a decrease in the accuracy of insulation impedance, which does not meet the requirements of safety regulations and other standards. Summary of the Invention

[0003] In view of this, this application provides a power conversion device, insulation testing method, apparatus and medium that can accurately detect the insulation impedance of the DC side of the power conversion device and meet safety requirements.

[0004] This application provides a power conversion device, including: a controller, an energy discharge path, and an inverter circuit; the input terminal of the inverter circuit is connected to a DC bus, and the energy of the DC bus is at least partially derived from a photovoltaic panel; the energy discharge path is connected to the DC side or AC side of the inverter circuit; the controller is used to control the energy discharge path to operate before the inverter circuit performs insulation impedance detection, so as to consume the energy of the DC bus to stabilize the DC bus voltage.

[0005] One possible implementation includes an energy discharge path comprising: a bidirectional converter and a rechargeable DC source; a first end of the bidirectional converter is connected to the rechargeable DC source, and a second end of the bidirectional converter is connected to the DC bus; the bidirectional converter is used to bidirectionally transfer energy between the rechargeable DC source and the DC bus; the rechargeable DC source is a battery or a supercapacitor; the controller is used to control the output voltage of the second end of the bidirectional converter according to a first reference voltage, so that the output voltage of the second end of the bidirectional converter is consistent with the first reference voltage, thereby stabilizing the DC bus voltage.

[0006] One possible implementation further includes: a DC-DC converter; a first terminal of the DC-DC converter is used to connect to the photovoltaic panel, and a second terminal of the DC-DC converter is connected to the DC bus; the controller is used to first control the DC-DC converter to stabilize the input voltage of the first terminal of the DC-DC converter to a first reference voltage, and then control the output voltage of the second terminal of the bidirectional converter according to a second reference voltage.

[0007] In one possible implementation, when the power conversion device includes multiple DC-DC converters, the input terminal of each DC-DC converter is connected to a corresponding photovoltaic panel; the controller is further configured to determine the second reference voltage based on the maximum voltage among the input voltages of the first terminals of the multiple DC-DC converters; and to determine the first reference voltage based on the open-circuit voltage of the photovoltaic panel.

[0008] One possible implementation includes a plurality of DC-DC converters comprising: a first DC-DC converter and a second DC-DC converter; a first terminal of the first DC-DC converter is used to connect to a first photovoltaic panel, and a first terminal of the second DC-DC converter is used to connect to a second photovoltaic panel; the controller is specifically configured to control the input voltage of the first terminal of the first DC-DC converter according to the open-circuit voltage of the first photovoltaic panel, and to control the input voltage of the first terminal of the second DC-DC converter according to the open-circuit voltage of the second photovoltaic panel.

[0009] In one possible implementation, the controller is specifically configured to control the input voltage of the first terminal of the first DC converter based on the difference between the open-circuit voltage of the first photovoltaic panel and a first voltage, and to control the input voltage of the first terminal of the second DC converter based on the difference between the open-circuit voltage of the second photovoltaic panel and a second voltage.

[0010] In one possible implementation, the controller is specifically configured to use the sum of the maximum voltage and the third voltage among the input voltages of the first terminals of the plurality of DC converters as the second reference voltage; and to use the difference between the open-circuit voltage of the photovoltaic panel and the first voltage as the first reference voltage.

[0011] One possible implementation is that the bidirectional converter is a bidirectional buck-boost converter or a bidirectional full-bridge converter.

[0012] In one possible implementation, the controller is specifically configured to generate a modulation wave based on the comparison result between the DC bus voltage and the second reference voltage, control the operation of the switching transistors in the bidirectional converter based on the modulation wave, and adjust the output voltage at the second terminal of the bidirectional converter.

[0013] In one possible implementation, the controller is specifically configured to generate a modulation wave based on the comparison result between the DC bus voltage and the first reference voltage, control the operation of the switching transistors in the bidirectional converter based on the modulation wave, and adjust the output voltage at the second terminal of the bidirectional converter.

[0014] One possible implementation includes an energy discharge path comprising: a load and a DC-side switch; the load being connected to the DC bus via the DC-side switch; and a controller configured to: control the DC-side switch to close before the inverter circuit performs insulation impedance detection, thereby consuming the energy of the DC bus to stabilize the DC bus voltage; and control the DC-side switch to open when the inverter circuit completes the insulation impedance detection.

[0015] One possible implementation includes an AC-side switch; the AC side of the inverter circuit is connected to the AC-side switch; and a controller is configured to control the AC-side switch to open before the inverter circuit performs insulation impedance detection, thereby controlling the inverter circuit to operate off-grid and consuming the energy of the DC bus to stabilize the DC bus voltage.

[0016] In one possible implementation, the controller is used to control the carrier frequency of the drive signal of the switching device of the inverter circuit, the amplitude of the output voltage of the inverter circuit, or the frequency of the output voltage of the inverter circuit when the inverter circuit is running off-grid, so as to consume the energy of the DC bus to stabilize the DC bus voltage.

[0017] This application also provides an insulation detection method for a power conversion device, the power conversion device comprising: an energy discharge path and an inverter circuit; the input terminal of the inverter circuit is connected to a DC bus, the energy of the DC bus being at least partially derived from a photovoltaic panel; the energy discharge path is connected to the DC side or AC side of the inverter circuit; the method comprises: before performing insulation impedance detection on the inverter circuit, controlling the energy discharge path to operate to consume the energy of the DC bus to stabilize the DC bus voltage; after the DC bus voltage stabilizes, detecting the insulation impedance on the DC side of the inverter circuit.

[0018] One possible implementation is that the energy discharge path includes: a bidirectional converter and a rechargeable DC source; a first end of the bidirectional converter is connected to the rechargeable DC source, and a second end of the bidirectional converter is connected to the DC bus; controlling the operation of the energy discharge path specifically includes: controlling the output voltage of the second end of the bidirectional converter according to a first reference voltage, so that the output voltage of the second end of the bidirectional converter is consistent with the first reference voltage, so as to stabilize the DC bus voltage.

[0019] In one possible implementation, the power conversion device further includes: a DC-DC converter; a first terminal of the DC-DC converter is used to connect to the photovoltaic panel, and a second terminal of the DC-DC converter is connected to the DC bus; the control of the energy discharge path specifically includes: first controlling the DC-DC converter to stabilize the voltage at the first terminal of the DC-DC converter at a first reference voltage, and then controlling the output voltage at the second terminal of the bidirectional converter according to a second reference voltage.

[0020] One possible implementation is that there are multiple DC-DC converters; it further includes: obtaining the output voltages of the multiple DC-DC converters connected to the DC bus, determining a second reference voltage based on the maximum voltage among the input voltages at the first terminals of the multiple DC-DC converters, and determining the first reference voltage based on the open-circuit voltage of the photovoltaic panel.

[0021] In one possible implementation, the sum of the maximum voltage and the third voltage among the input voltages of the first terminals of the plurality of DC converters is used as the second reference voltage; the difference between the open-circuit voltage of the photovoltaic panel and the first voltage is used as the first reference voltage.

[0022] One possible implementation, wherein controlling the output voltage of the second terminal of the bidirectional converter according to the second reference voltage, specifically includes: generating a modulation wave based on the comparison result of the DC bus voltage and the second reference voltage, and controlling the operation of the switching transistor in the bidirectional converter according to the modulation wave to adjust the output voltage of the second terminal of the bidirectional converter. Another possible implementation, wherein the energy discharge path includes: a load and a DC-side switch; the load is connected to the DC bus through the DC-side switch; controlling the operation of the energy discharge path specifically includes: before the inverter circuit performs insulation impedance detection, controlling the DC-side switch to close to consume the energy of the DC bus and stabilize the DC bus voltage.

[0023] One possible implementation is that the energy discharge path includes: an AC side switch; the AC side of the inverter circuit is connected to the AC side switch; controlling the operation of the energy discharge path specifically includes: before the inverter circuit performs insulation impedance detection, controlling the AC side switch to open, controlling the inverter circuit to operate off-grid, and consuming the energy of the DC bus to stabilize the DC bus voltage.

[0024] One possible implementation involves controlling the inverter circuit to operate off-grid, specifically including: controlling the carrier frequency of the drive signal of the switching device of the inverter circuit, the amplitude of the output voltage of the inverter circuit, or the frequency of the output voltage of the inverter circuit when the inverter circuit is operating off-grid.

[0025] One possible implementation, wherein controlling the output voltage of the second terminal of the bidirectional converter according to the first reference voltage, specifically includes: generating a modulation wave based on the comparison result between the DC bus voltage and the first reference voltage, controlling the operation of the switching transistor in the bidirectional converter according to the modulation wave, and adjusting the output voltage of the second terminal of the bidirectional converter.

[0026] One possible implementation also includes: triggering an alarm when the insulation impedance is less than or equal to a preset impedance; and controlling the inverter circuit to start when the insulation impedance is greater than the preset impedance.

[0027] This application also provides a control device, including a processor and a memory, wherein the memory is used to store programs, instructions or code, and the processor is used to execute the programs, instructions or code in the memory to complete the insulation detection method for the power conversion device described above.

[0028] This application also provides a computer-readable storage medium storing a computer program, which is loaded by a processor to execute the insulation detection method for the power conversion device described above.

[0029] The power conversion device provided in this application embodiment has an energy discharge path set on the DC or AC side of the inverter circuit. Before performing insulation impedance detection, the energy discharge path is controlled to be turned on, thereby consuming the energy of the DC bus. This is beneficial to the discharge of DC bus energy, will not cause energy accumulation, is beneficial to the stability of DC bus voltage, and thus helps to improve the accuracy of insulation impedance detection. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a power conversion device provided in an embodiment of this application;

[0031] Figure 2 A schematic diagram of another power conversion device provided in an embodiment of this application;

[0032] Figure 3A A schematic diagram of another power conversion device provided in the embodiments of this application;

[0033] Figure 3B A schematic diagram of yet another power conversion device provided in an embodiment of this application;

[0034] Figure 4A A schematic diagram of another power conversion device provided in the embodiments of this application;

[0035] Figure 4B A schematic diagram of another power conversion device provided in an embodiment of this application;

[0036] Figure 5AA schematic diagram of another power conversion device provided in an embodiment of this application;

[0037] Figure 5B A schematic diagram of another power conversion device provided in the embodiments of this application;

[0038] Figure 6 A control schematic diagram of a BuckBoost circuit provided in an embodiment of this application;

[0039] Figure 7 A control schematic diagram of a Boost circuit provided in an embodiment of this application;

[0040] Figure 8 A schematic diagram of yet another power conversion device provided in an embodiment of this application;

[0041] Figure 9 A schematic diagram of another power conversion device provided in the embodiments of this application;

[0042] Figure 10 A flowchart illustrating an insulation detection method for a power conversion device provided in this application embodiment;

[0043] Figure 11 This is a schematic diagram of a control device provided in an embodiment of this application. Detailed Implementation

[0044] To enable those skilled in the art to better understand and implement the technical solutions provided in the embodiments of this application, the power conversion device will be described below in conjunction with the accompanying drawings.

[0045] See Figure 1 The figure is a schematic diagram of a power conversion device provided in an embodiment of this application.

[0046] The embodiments of this application do not specifically limit the number of DC converters connected to the DC bus; there can be one or more. For ease of introduction and understanding, Figure 1 The following description uses two DC-DC converters as an example: a first DC-DC converter 101 and a second DC-DC converter 102. The input terminal of the first DC-DC converter 101 is connected to a first photovoltaic panel PV1, and the input terminal of the second DC-DC converter 102 is connected to a second photovoltaic panel PV2.

[0047] In addition, the power conversion device also includes an inverter circuit 200 and an insulation resistance detection device 300. This application does not specifically limit the implementation of the insulation resistance detection device 300. For example, the insulation resistance detection device 300 may include an insulation detection circuit, such as an insulation detection bridge and a switch, as well as a voltage sampling circuit. By operating the switch, the impedance to ground of the DC positive bus and the DC negative bus, as well as the impedance between the DC positive bus and the DC negative bus, are changed, thereby detecting various voltages. The insulation resistance can be obtained by setting up equations.

[0048] Generally, the insulation resistance of the DC side of an inverter circuit 200 is tested before startup. However, in power conversion equipment scenarios, the output voltage of the photovoltaic panel changes with sunlight or temperature. Currently, insulation resistance testing is assumed to assume that the photovoltaic panel voltage is stable and does not fluctuate. However, in reality, voltage fluctuations can cause inaccurate insulation resistance calculations based on the sampled voltage.

[0049] To address the above problems, this application embodiment adds a bidirectional converter and a rechargeable DC source to the power conversion device. The rechargeable DC source can be a battery or a supercapacitor. The bidirectional converter enables the exchange of energy between the rechargeable DC source and the DC bus. When it is necessary to increase the DC bus voltage, energy from the rechargeable DC source is transferred to the DC bus. When it is necessary to decrease the DC bus voltage, energy from the DC bus is transferred to the rechargeable DC source. The power conversion device provided in this application embodiment can also be a photovoltaic-storage system.

[0050] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0051] See Figure 2 This figure is a schematic diagram of another power conversion device provided in an embodiment of this application.

[0052] The power conversion device provided in this application includes: a controller 400, an energy discharge path 500, and an inverter circuit 200.

[0053] The input terminal of the inverter circuit 200 is connected to the DC bus, and the energy of the DC bus comes at least partially from the photovoltaic panel;

[0054] The energy discharge path 500 is connected to either the DC or AC side of the inverter circuit 200; the energy discharge path 500 can be connected to either the DC or AC side. Figure 2 The diagram is for illustrative purposes only. Alternatively, both the DC and AC sides may include energy discharge paths 500.

[0055] The controller 400 is used to control the energy discharge path 500 to operate before the inverter circuit 200 performs insulation resistance detection, so as to consume the energy of the DC bus to stabilize the DC bus voltage.

[0056] Since the inverter circuit 200 is generally not started when the power conversion equipment is performing insulation impedance testing, i.e., it is not connected to the grid, the DC bus voltage changes with the changes in external light and temperature. This is not conducive to the stability of the DC bus voltage, thus affecting the accuracy of insulation impedance testing.

[0057] The power conversion device provided in this application embodiment has an energy discharge path set on the DC or AC side of the inverter circuit. Before performing insulation impedance detection, the energy discharge path is controlled to be turned on, thereby consuming the energy of the DC bus. This is beneficial to the discharge of DC bus energy, will not cause energy accumulation, is beneficial to the stability of DC bus voltage, and thus helps to improve the accuracy of insulation impedance detection.

[0058] This application does not specifically limit the implementation method of the energy discharge path. For example, it can be implemented through a battery, charging and discharging the battery; it can also be implemented through a load, consuming energy through the load; or it can consume energy by operating the inverter circuit off-grid. The following descriptions are in conjunction with the accompanying drawings. See also... Figure 3A This figure is a schematic diagram of another power conversion device provided in an embodiment of this application.

[0059] The energy discharge path includes: bidirectional converter 501 and rechargeable DC source.

[0060] The first and second terminals of the bidirectional converter 501 are used to connect the rechargeable DC source and the DC bus, respectively. The bidirectional converter 501 is used to transfer the energy of the rechargeable DC source and the energy of the DC bus in both directions. The input terminal of the inverter circuit 200 is connected to the DC bus. The rechargeable DC source is a battery or a supercapacitor. Figure 3A Taking a rechargeable DC power source, specifically a battery (Bat), as an example, the key is to ensure bidirectional energy flow as long as charging and discharging can be achieved.

[0061] This application does not specifically limit the specific topology of the bidirectional converter. It can be a buck-boost circuit or a bidirectional full-bridge circuit. For example, the buck-boost circuit is a BuckBoost circuit, which can charge the battery Bat and discharge the battery Bat.

[0062] A capacitor C is also connected between the positive and negative input terminals of the inverter circuit 200. Figure 1 This example uses only one capacitor, but it can also contain multiple capacitors.

[0063] The controller 400 is used to control the output voltage of the second terminal of the bidirectional converter 501 according to the first reference voltage, so that the output voltage of the second terminal of the bidirectional converter 501 is consistent with the first reference voltage, thereby stabilizing the DC bus voltage. It should be noted that in this embodiment, consistency can mean that the two compared are equal, or it can include the comparison having a certain error, which, if within an acceptable range, is considered equal, and the adjustment is complete. For example, when the output voltage of the second terminal of the bidirectional converter 501 is adjusted to be consistent with the first reference voltage, it is considered that the adjustment is complete, and it is unnecessary to continue adjusting the output voltage of the second terminal of the bidirectional converter 501.

[0064] The power conversion device provided in this application embodiment can control the DC bus voltage via a bidirectional converter 501. Since the inverter circuit 200 has not yet started operating during insulation impedance detection, the DC bus voltage is controlled by the DC side.

[0065] The power conversion device provided in this application embodiment has a bidirectional converter connected to the DC bus, and the other end of the bidirectional converter is connected to a rechargeable DC source. The bidirectional converter can realize bidirectional energy flow and control the DC bus voltage to stabilize the DC bus voltage and avoid the DC bus voltage being affected by the voltage fluctuation of the photovoltaic panel. Then, when the DC bus voltage is stable, the insulation impedance on the DC side is detected to ensure the accuracy of the detected insulation impedance.

[0066] The embodiments of this application do not specifically limit the number of DC-DC converters; there may be one or more. The following description uses a power conversion device comprising two DC-DC converters as an example. Furthermore, this application does not specifically limit the specific topology of the DC-DC converters; they may be boost circuits, such as Boost converters.

[0067] See Figure 3B This figure is a schematic diagram of another power conversion device provided in an embodiment of this application.

[0068] The power conversion device provided in this application embodiment includes multiple DC-DC converters, with the input terminal of each DC-DC converter connected to a corresponding photovoltaic panel. The controller 400 is further configured to use the maximum voltage among the input voltages of the first terminals of the multiple DC-DC converters as a second reference voltage.

[0069] like Figure 3B As shown, the multiple DC converters include: a first DC converter 101 and a second DC converter 102; the first end of the first DC converter 101 is used to connect to the first photovoltaic panel PV1, and the first end of the second DC converter 102 is used to connect to the second photovoltaic panel PV2.

[0070] The second end of the first DC converter 101 and the second end of the second DC converter 102 are both connected to the DC bus. It should be understood that the insulation resistance detection device 300 is also connected to the DC bus.

[0071] The controller 400 is specifically used to control the input voltage of the first terminal of the first DC converter 101 according to the open-circuit voltage of the first photovoltaic panel PV1, and to control the input voltage of the first terminal of the second DC converter 102 according to the open-circuit voltage of the second photovoltaic panel PV2. The second terminal of the bidirectional converter 501 is also connected to the DC bus.

[0072] The following section uses DC-DC converters including Boost circuits and bidirectional converters including BuckBoost circuits as examples.

[0073] See Figure 4A This figure is a schematic diagram of another power conversion device provided in an embodiment of this application.

[0074] The power conversion device provided in this application includes a first Boost circuit 101, a second Boost circuit 102, and a BuckBoost circuit 501.

[0075] The controller 400 is specifically used to control the input voltage of the first terminal of the first Boost circuit 101 based on the difference between the open-circuit voltage Voc1 of the first photovoltaic panel PV1 and the first voltage V1, and to control the input voltage of the first terminal of the second Boost circuit 102 based on the difference between the open-circuit voltage Voc2 of the second photovoltaic panel PV2 and the second voltage V2. The controller uses the difference between the open-circuit voltage and the set voltage to control the output voltage of the DC-DC converter, so that the output voltage of the DC-DC converter is maintained at the difference between the open-circuit voltage and the set voltage.

[0076] The first reference voltage can be the difference between the open-circuit voltage of the photovoltaic panel and the first voltage.

[0077] This application does not specifically limit the values ​​of V1 and V2; generally, a smaller voltage is chosen. A smaller value reduces the voltage stress on the hardware. V1 and V2 may be equal or unequal. This application also does not limit the magnitude of the DC bus voltage of the power conversion device.

[0078] The controller is specifically used to take the sum of the maximum input voltage among the first-terminal input voltages of multiple DC-DC converters and the third voltage V3 as the second reference voltage Vref. For example, if Voc2 > Voc1, then Voc2 + V2 is used as the second reference voltage Vref. The embodiments of this application do not specifically limit the value of V3; generally, a smaller voltage is chosen. V3, V1, and V2 can be equal or unequal.

[0079] Once the input voltage and bus voltage of the DC-DC converter are stable, the insulation resistance detection is activated. If the insulation resistance is less than or equal to the preset impedance, an alarm is triggered; if the insulation resistance is greater than the preset impedance, the inverter circuit is started.

[0080] The embodiments of this application do not specifically limit the number of DC-DC converters, and can have N, where N is an integer greater than or equal to 2. For ease of explanation, the figures in the embodiments of this application use two DC-DC converters as an example. The case of N converters will be described below.

[0081] See Figure 4B This figure is a schematic diagram of another power conversion device provided in an embodiment of this application.

[0082] As shown in the figure, all N DC-DC converters are Boost circuits, from the first Boost circuit 101, the second Boost circuit 102, to the Nth Boost circuit 10N. The input terminal of the Nth Boost circuit 10N is connected to the corresponding photovoltaic panel PVN. The remaining working principles are similar to those of the two DC-DC converters described above, and will not be repeated here.

[0083] above Figure 3B and Figure 4A The power conversion equipment introduced is based on examples including DC-DC converters, but it may also exclude DC-DC converters; see [link to relevant documentation]. Figure 5A As shown in the figure, this figure is a schematic diagram of another power conversion device provided in an embodiment of this application.

[0084] As can be seen, the power conversion equipment includes multiple photovoltaic panels. Figure 5A Taking two photovoltaic panels as an example, PV1 and PV2 are both connected to the DC bus, and the rest is similar to Figure 4, so it will not be described again here.

[0085] See Figure 5B This figure is a schematic diagram of another power conversion device provided in an embodiment of this application.

[0086] Figure 5B The circuit diagram corresponding to Figure 4 shows a specific circuit where the first Boost circuit 101 includes a first inductor L1, a first switching transistor S1, and a first diode D1. The voltage of PV1 is represented by Vpv1.

[0087] The second Boost circuit 102 includes a first inductor L2, a first switching transistor S2, and a first diode D2. The voltage of PV2 is represented by Vpv2.

[0088] The DC bus voltage is represented by Vbus.

[0089] The BuckBoost circuit 501 includes a third switch S3, a fourth switch S4, and an inductor L.

[0090] The following is in conjunction with the appendix Figure 6 The control method of the BuckBoost circuit 501 in Figure 5 is introduced.

[0091] See Figure 6 The figure is a control principle diagram of a BuckBoost circuit provided in an embodiment of this application.

[0092] The power conversion device provided in this application embodiment can control the BuckBoost circuit using dual-loop control (inner current loop and outer voltage loop) or single-loop control (only voltage loop).

[0093] The single-loop control is as follows: the controller generates a modulation wave based on the comparison result of the DC bus voltage and the second reference voltage, and controls the operation of the switching transistors in the bidirectional converter according to the modulation wave to adjust the output voltage of the second terminal of the bidirectional converter.

[0094] Figure 6 The diagram shows a dual-loop control system. Specifically, the controller generates a current reference value through the control loop Gv_bus based on the comparison result between the DC bus voltage Vbus and the second reference voltage Vref. This current reference value is then compared with the current iL at the first terminal of the bidirectional converter. The control loop Gi_bus then generates modulation waves S3 and S4. Based on these modulation waves, the controller controls the operation of switches S3 and S4 in the bidirectional converter, thereby stabilizing the DC bus voltage and ensuring that the DC bus voltage Vbus and the second reference voltage Vref are consistent. In this embodiment, consistency includes a preset tolerance range; the voltages can be completely equal or within the allowable error range, which is considered sufficient for the DC bus voltage adjustment.

[0095] See Figure 7 The figure is a control principle diagram of a Boost circuit provided in an embodiment of this application.

[0096] In this embodiment, the controller controls the two Boost circuits in a similar manner; the following description focuses on the control of the first Boost circuit.

[0097] The controller generates a current reference value through the control loop Gv_pv based on the comparison result between the input voltage Vpv1 and the first reference voltage Vpv1ref. The current reference value is compared with the current iL1 of the first inductor through the control loop Gi_pv to generate the modulation wave of S1. The controller controls the operation of the switching transistor S1 of the first Boost circuit based on the modulation wave of S1, thereby stabilizing the input voltage of the first Boost circuit and making the input voltage Vpv1 of the first Boost circuit consistent with the first reference voltage Vpv1ref.

[0098] The power conversion equipment provided in this application can achieve stable control of the DC bus voltage before insulation impedance detection, as well as stable control of the input voltage of each DC converter. Therefore, when the voltage is stable, the insulation impedance detection result is more accurate, ensuring that the insulation impedance accuracy meets the requirements of various standards. Furthermore, accurate insulation impedance detection is beneficial for subsequent grid-connected power generation, preventing grid connection delays caused by large insulation impedance deviations, which would affect power generation. Especially in scenarios involving photovoltaic string grounding short circuits, insulation impedance detection errors are large and prone to misjudgment.

[0099] The power conversion device provided in the above embodiments is implemented through a bidirectional converter with an energy discharge path. Two other implementation methods are introduced below.

[0100] See Figure 8 This figure is a schematic diagram of another power conversion device provided in an embodiment of this application.

[0101] The power conversion device provided in this application embodiment includes an energy discharge path including a load and a DC-side switch 801; this application embodiment does not specifically limit the implementation form of the load, for example, it can be a resistor.

[0102] The load is connected to the DC bus via DC-side switch 801.

[0103] The controller 400 is used to control the DC side switch 801 to close before the inverter circuit performs insulation impedance detection, so as to consume the energy of the DC bus to stabilize the DC bus voltage.

[0104] This application embodiment achieves energy consumption of the DC bus by connecting the load to the DC bus, thereby suppressing energy accumulation on the DC bus, which is beneficial to the stability of the DC bus voltage and thus improves the accuracy of insulation resistance detection.

[0105] See Figure 9 This figure is a schematic diagram of another power conversion device provided in an embodiment of this application.

[0106] The power conversion device provided in this application embodiment includes an energy discharge path including: an AC side switch 901;

[0107] The AC side of the inverter circuit 200 is connected to the AC side switch 901; generally, the AC side of the inverter circuit 200 is connected to the power grid through the AC side switch 901.

[0108] The controller 400 is used to control the AC side switch 901 to open before the inverter circuit 200 performs insulation impedance detection, thereby controlling the inverter circuit 200 to operate off-grid and consuming the energy of the DC bus to stabilize the DC bus voltage.

[0109] This application embodiment consumes the energy of the DC bus by operating the inverter circuit off-grid, thereby suppressing the energy accumulation of the DC bus, which is beneficial to the stability of the DC bus voltage and thus improves the accuracy of insulation impedance detection.

[0110] The embodiments of this application do not specifically limit the way in which the inverter circuit consumes energy. For example, a controller is used to control the carrier frequency of the drive signal of the switching device of the inverter circuit, the amplitude of the output voltage of the inverter circuit, or the frequency of the output voltage of the inverter circuit when the inverter circuit is running off-grid, so as to consume the energy of the DC bus to stabilize the DC bus voltage.

[0111] Based on the power conversion device provided in the above embodiments, this application also provides an insulation detection method for the power conversion device, which will be described in detail below with reference to the accompanying drawings.

[0112] See Figure 10 The figure is a flowchart of an insulation detection method for a power conversion device provided in an embodiment of this application.

[0113] This application provides an insulation detection method for a power conversion device. The power conversion device includes an energy discharge path and an inverter circuit. The input terminal of the inverter circuit is connected to a DC bus, and the energy of the DC bus is at least partially derived from a photovoltaic panel. The energy discharge path is connected to the DC side or AC side of the inverter circuit.

[0114] The method includes:

[0115] S1001: Before the inverter circuit performs insulation impedance detection, control the energy discharge path to consume the energy of the DC bus to stabilize the DC bus voltage.

[0116] S1002: After the DC bus voltage stabilizes, detect the insulation resistance on the DC side of the inverter circuit.

[0117] Since the inverter circuit 200 is generally not started when the power conversion equipment performs insulation impedance testing, i.e., it is not connected to the grid, when the energy of the photovoltaic panel reaches the DC bus, if there is no energy discharge path, the energy accumulated on the DC bus will increase as the output power of the photovoltaic panel increases. This is not conducive to the stability of the DC bus voltage, thus affecting the accuracy of insulation impedance testing.

[0118] The insulation impedance detection method for power conversion equipment provided in this application embodiment sets up an energy discharge path on the DC or AC side of the inverter circuit. Before performing insulation impedance detection, the energy discharge path is first controlled to conduct, thereby consuming the energy of the DC bus. This is beneficial for the discharge of DC bus energy, preventing energy accumulation, stabilizing the DC bus voltage, and thus improving the accuracy of insulation impedance detection.

[0119] The embodiments of this application do not specifically limit the implementation method of the energy discharge path. For example, it can be implemented through a battery, charging and discharging the battery; it can also be implemented through a load, consuming energy through the load; or it can consume energy by operating the inverter circuit off-grid. These will be described in detail below.

[0120] The energy discharge path includes: a bidirectional converter and a rechargeable DC source; the first end of the bidirectional converter is connected to the rechargeable DC source, and the second end of the bidirectional converter is connected to the DC bus;

[0121] Controlling the energy discharge path specifically includes: controlling the output voltage of the second terminal of the bidirectional converter according to a first reference voltage, so that the output voltage of the second terminal of the bidirectional converter is consistent with the first reference voltage, thereby stabilizing the DC bus voltage. The power conversion device also includes: a DC converter; the first terminal of the DC converter is used to connect to the photovoltaic panel, and the second terminal of the DC converter is connected to the DC bus; controlling the energy discharge path specifically includes: first controlling the DC converter to stabilize the input voltage of the first terminal of the DC converter at the first reference voltage, and then controlling the output voltage of the second terminal of the bidirectional converter according to a second reference voltage.

[0122] A bidirectional converter and a rechargeable DC source are added to the power conversion device. The rechargeable DC source can be a battery or a supercapacitor. The bidirectional converter enables the exchange of energy between the rechargeable DC source and the DC bus. When it is necessary to increase the DC bus voltage, energy from the rechargeable DC source is transferred to the DC bus. When it is necessary to decrease the DC bus voltage, energy from the DC bus is transferred to the rechargeable DC source. The power conversion device provided in this application embodiment can also be a photovoltaic-storage system.

[0123] The insulation detection method for power conversion equipment provided in this application embodiment involves connecting a bidirectional converter to the DC bus, with the other end of the bidirectional converter connected to a rechargeable DC source. The bidirectional converter enables bidirectional energy flow and controls the DC bus voltage to stabilize it, preventing the DC bus voltage from being affected by voltage fluctuations of the photovoltaic panel. Furthermore, when the DC bus voltage is stable, the insulation impedance on the DC side is detected to ensure the accuracy of the detected insulation impedance.

[0124] The insulation detection method provided in this application further includes: obtaining the output voltage of multiple DC-DC converters connected to a DC bus, and using the maximum voltage among the input voltages at the first terminals of the multiple DC-DC converters as a second reference voltage. Using the maximum voltage as the second reference voltage facilitates the control of voltage stability at the first terminals of each DC-DC converter.

[0125] One possible implementation is to use the maximum voltage among the input voltages of the first terminals of multiple DC-DC converters as the second reference voltage, specifically by using the sum of the maximum voltage among the input voltages of the first terminals of multiple DC-DC converters and a third voltage as the second reference voltage.

[0126] One possible implementation involves controlling the output voltage at the second terminal of the bidirectional converter based on a second reference voltage, specifically including:

[0127] A modulation wave is generated based on the comparison between the DC bus voltage and the second reference voltage. The operation of the switching transistors in the bidirectional converter is controlled based on the modulation wave to adjust the output voltage at the second terminal of the bidirectional converter.

[0128] One possible implementation involves controlling the output voltage at the second terminal of the bidirectional converter based on a second reference voltage, specifically including:

[0129] A current reference value is generated based on the comparison between the DC bus voltage and the second reference voltage. A modulation wave is generated based on the comparison between the current reference value and the current at the first terminal of the bidirectional converter. The operation of the switching transistors in the bidirectional converter is controlled based on the modulation wave.

[0130] The power conversion device provided in the above embodiments is implemented through a bidirectional converter with an energy discharge path. Two other implementation methods are introduced below.

[0131] One possible implementation is that the energy discharge path includes: a load and a DC-side switch; the load is connected to the DC bus through the DC-side switch; controlling the operation of the energy discharge path specifically includes: before the inverter circuit performs insulation impedance detection, controlling the DC-side switch to close, so as to consume the energy of the DC bus to stabilize the DC bus voltage.

[0132] Another possible implementation includes an AC-side switch; the AC side of the inverter circuit is connected to the AC-side switch; controlling the operation of the energy discharge path specifically includes: before the inverter circuit performs insulation impedance detection, controlling the AC-side switch to open, controlling the inverter circuit to operate off-grid, and consuming the energy of the DC bus to stabilize the DC bus voltage.

[0133] The embodiments of this application do not specifically limit the way in which the inverter circuit consumes energy. For example, controlling the inverter circuit to operate off-grid specifically includes: controlling the carrier frequency of the drive signal of the switching device of the inverter circuit, the amplitude of the output voltage of the inverter circuit, or the frequency of the output voltage of the inverter circuit when the inverter circuit is operating off-grid.

[0134] One possible implementation of the insulation detection method provided in this application embodiment further includes: triggering an alarm when the insulation impedance is less than or equal to a preset impedance; and controlling the inverter circuit to start when the insulation impedance is greater than the preset impedance.

[0135] In one possible implementation, see Figure 11 The figure is a schematic diagram of a control device provided in an embodiment of this application.

[0136] The control device may include a memory 1011 and a processor 1012. The processor 1012 may be connected to a power conversion device and may drive the switches in the power conversion device. Figure 11 As shown, the memory can be random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (Electronic Programmable ROM), registers, hard disks, removable disks, etc.

[0137] The memory 1011 can store computer instructions. When the computer instructions stored in the memory 1011 are executed by the processor 1012, the processor 1012 can be used to execute the insulation detection method of the power conversion device. The memory 1011 can also store data, such as information like the first reference voltage and the second reference voltage involved in the above embodiments.

[0138] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape) or a semiconductor medium (e.g., solid-state disk (SSD)).

[0139] This application also provides a readable storage medium for storing the methods provided in the above embodiments. Examples include random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (EPROM), registers, hard disks, removable disks, or any other form of storage medium in the art.

[0140] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the methods disclosed in the embodiments, since they correspond to the product embodiments disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the description of the product embodiments.

[0141] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power conversion device, characterized in that, include: Controller, energy discharge path and inverter circuit; The input terminal of the inverter circuit is connected to a DC bus, and the energy of the DC bus is at least partially derived from the photovoltaic panel; The energy discharge path is connected to the DC side or AC side of the inverter circuit; The controller is used to control the energy discharge path to operate before the inverter circuit performs insulation impedance detection, so as to consume the energy of the DC bus to stabilize the DC bus voltage.

2. The power conversion device according to claim 1, characterized in that, The energy discharge path includes: a bidirectional converter and a rechargeable DC source; The first end of the bidirectional converter is connected to the rechargeable DC source, and the second end of the bidirectional converter is connected to the DC bus; the bidirectional converter is used to transfer the energy of the rechargeable DC source and the energy of the DC bus in both directions; the rechargeable DC source is a battery or a supercapacitor. The controller is used to control the output voltage of the second terminal of the bidirectional converter according to the first reference voltage, so that the output voltage of the second terminal of the bidirectional converter is consistent with the first reference voltage, so as to stabilize the DC bus voltage.

3. The power conversion device according to claim 2, characterized in that, Also includes: DC-DC converter; The first end of the DC converter is used to connect to the photovoltaic panel, and the second end of the DC converter is connected to the DC bus. The controller is used to first control the DC converter to stabilize the input voltage at the first terminal of the DC converter at a first reference voltage, and then control the output voltage at the second terminal of the bidirectional converter according to the second reference voltage.

4. The power conversion device according to claim 3, characterized in that, In the case where the power conversion device includes multiple DC-DC converters, the input terminal of each DC-DC converter is connected to a corresponding photovoltaic panel; The controller is further configured to determine the second reference voltage based on the maximum voltage among the input voltages at the first terminals of the plurality of DC converters; and to determine the first reference voltage based on the open-circuit voltage of the photovoltaic panel.

5. The power conversion device according to claim 4, characterized in that, The plurality of DC-DC converters include: a first DC-DC converter and a second DC-DC converter; The first end of the first DC converter is used to connect to the first photovoltaic panel, and the first end of the second DC converter is used to connect to the second photovoltaic panel; The controller is specifically configured to control the input voltage of the first terminal of the first DC converter based on the open-circuit voltage of the first photovoltaic panel, and to control the input voltage of the first terminal of the second DC converter based on the open-circuit voltage of the second photovoltaic panel.

6. The power conversion device according to claim 5, characterized in that, The controller is specifically configured to control the input voltage of the first terminal of the first DC converter based on the difference between the open-circuit voltage of the first photovoltaic panel and the first voltage, and to control the input voltage of the first terminal of the second DC converter based on the difference between the open-circuit voltage of the second photovoltaic panel and the second voltage.

7. The power conversion device according to claim 4, characterized in that, The controller is specifically configured to use the sum of the maximum voltage and the third voltage among the input voltages of the first terminals of the plurality of DC converters as the second reference voltage; and to use the difference between the open-circuit voltage of the photovoltaic panel and the first voltage as the first reference voltage.

8. The power conversion device according to claim 2, characterized in that, The controller is specifically used to generate a modulation wave based on the comparison result between the DC bus voltage and the first reference voltage, control the operation of the switching transistor in the bidirectional converter based on the modulation wave, and adjust the output voltage of the second terminal of the bidirectional converter.

9. The power conversion device according to any one of claims 3-7, characterized in that, The controller is specifically used to generate a modulation wave based on the comparison result between the DC bus voltage and the second reference voltage, control the operation of the switching transistor in the bidirectional converter based on the modulation wave, and adjust the output voltage of the second terminal of the bidirectional converter.

10. The power conversion device according to claim 1, characterized in that, The energy discharge path includes: a load and a DC-side switch; The load is connected to the DC bus via the DC-side switch; The controller is used to control the DC-side switch to close before the inverter circuit performs insulation impedance detection, so as to consume the energy of the DC bus to stabilize the DC bus voltage; and to control the DC-side switch to open when the inverter circuit completes the insulation impedance detection.

11. The power conversion device according to claim 1, characterized in that, The energy discharge path includes: an AC side switch; The AC side of the inverter circuit is connected to the AC side switch; The controller is used to control the AC side switch to open before the inverter circuit performs insulation impedance detection, control the inverter circuit to operate off-grid, and consume the energy of the DC bus to stabilize the DC bus voltage.

12. The power conversion device according to claim 11, characterized in that, The controller is used to control the carrier frequency of the drive signal of the switching device of the inverter circuit, the amplitude of the output voltage of the inverter circuit, or the frequency of the output voltage of the inverter circuit when the inverter circuit is off-grid, so as to consume the energy of the DC bus to stabilize the DC bus voltage.

13. An insulation testing method for a power conversion device, characterized in that, The power conversion device includes: an energy discharge path and an inverter circuit; the input terminal of the inverter circuit is connected to a DC bus, and the energy of the DC bus is at least partially derived from the photovoltaic panel; the energy discharge path is connected to the DC side or AC side of the inverter circuit. The method includes: Before the inverter circuit performs insulation impedance detection, the energy discharge path is controlled to operate in order to consume the energy of the DC bus to stabilize the DC bus voltage. After the DC bus voltage stabilizes, the insulation resistance on the DC side of the inverter circuit is detected.

14. The method according to claim 13, characterized in that, The energy discharge path includes: a bidirectional converter and a rechargeable DC source; the first end of the bidirectional converter is connected to the rechargeable DC source, and the second end of the bidirectional converter is connected to the DC bus; The control of the energy discharge path specifically includes: The output voltage of the second terminal of the bidirectional converter is controlled according to the first reference voltage, so that the output voltage of the second terminal of the bidirectional converter is consistent with the first reference voltage, thereby stabilizing the DC bus voltage.

15. The method according to claim 14, characterized in that, The power conversion device further includes: a DC converter; a first end of the DC converter is used to connect to the photovoltaic panel, and a second end of the DC converter is connected to the DC bus; The control of the energy discharge path specifically includes: First, the DC-DC converter is controlled to stabilize the voltage at its first terminal at a first reference voltage. Then, the output voltage at the second terminal of the bidirectional converter is controlled according to the second reference voltage.

16. The method according to claim 15, characterized in that, There are multiple DC-DC converters; It also includes: obtaining the output voltage of a plurality of DC-DC converters connected to the DC bus; determining the second reference voltage based on the maximum voltage among the input voltages at the first terminals of the plurality of DC-DC converters; and determining the first reference voltage based on the open-circuit voltage of the photovoltaic panel.

17. The method according to claim 16, characterized in that, The sum of the maximum voltage and the third voltage among the input voltages of the first terminals of the plurality of DC converters is used as the second reference voltage; the difference between the open-circuit voltage of the photovoltaic panel and the first voltage is used as the first reference voltage.

18. The method according to claim 17, characterized in that, The step of controlling the output voltage of the second terminal of the bidirectional converter according to the second reference voltage specifically includes: A modulation wave is generated based on the comparison result between the DC bus voltage and the second reference voltage. The operation of the switching transistor in the bidirectional converter is controlled based on the modulation wave to adjust the output voltage of the second terminal of the bidirectional converter.

19. The method according to claim 13, characterized in that, The energy discharge path includes: a load and a DC-side switch; the load is connected to the DC bus through the DC-side switch; The control of the energy discharge path specifically includes: Before the inverter circuit performs insulation impedance detection, the DC side switch is closed to consume the energy of the DC bus and stabilize the DC bus voltage.

20. The method according to claim 13, characterized in that, The energy discharge path includes: an AC side switch; the AC side of the inverter circuit is connected to the AC side switch; The control of the energy discharge path specifically includes: Before the inverter circuit performs insulation impedance detection, the AC side switch is controlled to open, and the inverter circuit is controlled to operate off-grid, consuming the energy of the DC bus to stabilize the DC bus voltage.

21. The method according to claim 20, characterized in that, Controlling the inverter circuit to operate off-grid specifically includes: When controlling the inverter circuit to operate off-grid, the carrier frequency of the drive signal of the switching device of the inverter circuit, the amplitude of the output voltage of the inverter circuit, or the frequency of the output voltage of the inverter circuit are controlled.

22. The method according to claim 14, characterized in that, The step of controlling the output voltage of the second terminal of the bidirectional converter according to the first reference voltage specifically includes: A modulation wave is generated based on the comparison result between the DC bus voltage and the first reference voltage. The switching transistors in the bidirectional converter are controlled according to the modulation wave to adjust the output voltage of the second terminal of the bidirectional converter.

23. The method according to any one of claims 13-22, characterized in that, Also includes: An alarm is triggered when the insulation resistance is less than or equal to a preset impedance; the inverter circuit is started when the insulation resistance is greater than the preset impedance.

24. A control device, characterized in that, It includes a processor and a memory, the memory being used to store programs, instructions, or code, and the processor being used to execute the programs, instructions, or code in the memory to complete the insulation detection method for the power conversion device as described in any one of claims 13-23.

25. A computer-readable storage medium, characterized in that, The device contains a computer program that is loaded by a processor to execute the insulation detection method for the power conversion device as described in any one of claims 13-23.

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