A power conversion system, insulation impedance detection method and related devices

Abstract

The disclosure discloses a power conversion system, an insulation impedance detection method and related devices, comprising: a controller and N DC / DC circuits, N is an integer greater than or equal to 2; the first end of the DC / DC circuit is used for connecting the corresponding DC source, and the second end of the DC / DC circuit is used for connecting the DC bus; N DC / DC circuits are connected in common anode or common cathode; the controller is used for positioning the target DC / DC circuit of the power conversion system on the side of the non-common anode insulation fault; according to the voltage of the DC source, the common anode-to-ground voltage and the DC bus voltage of the target DC / DC circuit at the first time, and the voltage of the DC source, the common anode-to-ground voltage and the DC bus voltage of the target DC / DC circuit at the second time, the insulation impedance of the power conversion system is obtained. The technical scheme can accurately detect the insulation impedance when the voltage of the DC source fluctuates.

Description

Technical Field

[0001] This disclosure relates to the field of power electronics technology, specifically to a power conversion system, an insulation impedance detection method, and related devices. Background Technology

[0002] The DC side of the power converter is connected to at least one of photovoltaic cells or batteries. In order to ensure the safety of the power converter and the DC source, it is generally necessary to test the ground insulation impedance of the DC side of the power converter.

[0003] However, in related technologies, when the voltage of the DC source fluctuates, especially when the photovoltaic panel is connected to the DC side, different light levels will cause voltage fluctuations in the DC source, resulting in inaccurate detection of the DC side's insulation resistance to ground. Summary of the Invention

[0004] In view of this, the present disclosure provides a power conversion system, an insulation resistance detection method and related device, which can accurately detect insulation resistance when the voltage of a DC source fluctuates.

[0005] This disclosure provides a power conversion system, including: a controller and N DC / DC / DC circuits, where N is an integer greater than or equal to 2; a first terminal of each DC / DC circuit is used to connect to a corresponding DC source, and a second terminal of each DC / DC circuit is used to connect to a DC bus; the N DC / DC circuits are connected in a common-pole configuration, which includes a common negative connection or a common positive connection; the controller is used to locate a target DC / DC circuit on the non-common-pole side of the power conversion system that has a ground insulation fault; and to obtain the insulation impedance of the power conversion system based on the DC source voltage, common-pole-to-ground voltage, and DC bus voltage of the target DC / DC circuit at a first time, and at a second time.

[0006] One possible implementation also includes: an impedance disturbance circuit connected to the DC bus;

[0007] The controller is used to obtain the insulation impedance of the power conversion system based on the voltage of the DC source of the target DC / DC circuit, the common-to-ground voltage, the DC bus voltage and the ground impedance before the impedance disturbance circuit is disturbed at a first time, and the voltage of the DC source of the target DC / DC circuit, the common-to-ground voltage, the DC bus voltage and the ground impedance after the impedance disturbance circuit is disturbed at a second time.

[0008] One possible implementation is that the controller is used to locate a target DC / DC circuit in the power conversion system that has a non-common-to-ground insulation fault in the following manner:

[0009] Control at least one of the DC / DC circuits to operate to reduce the voltage of the DC source to which it is connected; if the voltage change of the i-th DC / DC circuit before and after operation exceeds a preset voltage range, then the i-th DC / DC circuit has a non-common-pole insulation fault to ground; the i-th DC / DC circuit is one or more of the N DC / DC circuits.

[0010] One possible implementation is that the controller is configured to locate a target DC / DC circuit in the power conversion system that has a ground insulation fault by:

[0011] The i-th DC / DC circuit is controlled to operate to reduce the voltage of the DC source to which it is connected; if the first voltage of the i-th DC / DC circuit is less than the first voltage of the other DC / DC circuits, then the i-th DC / DC circuit has a non-common-pole insulation fault to ground; when N DC / DC circuits are connected with a common negative terminal, the first voltage is the positive terminal voltage to ground; when N DC / DC circuits are connected with a common positive terminal, the first voltage is the negative terminal voltage to ground.

[0012] One possible implementation is that the controller is configured to locate a target DC / DC circuit in the power conversion system that has a ground insulation fault by:

[0013] The i-th DC / DC circuit is controlled to operate to reduce the voltage of the DC source connected to the DC / DC circuit; if the difference between the second voltage of the i-th DC / DC circuit before and after energy consumption exceeds the first voltage threshold, then the i-th DC / DC circuit has a non-common-polarity ground insulation fault; when N DC / DC circuits are connected with a common negative terminal, the second voltage is the negative terminal to ground voltage; when N DC / DC circuits are connected with a common positive terminal, the second voltage is the positive terminal to ground voltage.

[0014] In one possible implementation, the controller is further configured to, when a ground insulation fault occurs on the common side of the power conversion system or the DC / DC circuit is normally insulated from ground, obtain the insulation impedance of the power conversion system based on the common-to-ground voltage, DC bus voltage, and ground impedance before the impedance disturbance circuit disturbance at a first moment, and the common-to-ground voltage, DC bus voltage, and ground impedance after the impedance disturbance circuit disturbance at a second moment.

[0015] In one possible implementation, the controller is configured to control at least one of the DC / DC circuits to boost the DC bus voltage to reduce the voltage of the DC source connected to the DC / DC circuit, thereby consuming energy on the DC bus and making the DC bus voltage less than a bus voltage threshold.

[0016] In one possible implementation, the DC bus is connected to a load; the controller is configured to consume energy on the DC bus by controlling the operation of the load.

[0017] Alternatively, at least one of the DC / DC circuits is connected to a battery as a DC source, and the controller is used to control the DC / DC circuit connected to the battery to charge the battery in order to consume energy on the DC bus.

[0018] One possible implementation further includes: a DC / AC circuit, wherein the DC side of the DC / AC circuit is connected to the DC bus, and the AC side of the DC / AC circuit is connected to a filter, wherein the filter includes at least an inductor;

[0019] The controller is used to control the DC / AC circuit to power the inductor, thereby consuming the energy on the DC bus.

[0020] In one possible implementation, the controller is further configured to determine that a ground insulation fault has occurred on the common side by the following method: if the difference between the voltage to ground on the common side and the voltage to ground on the non-common side exceeds a difference threshold, it is determined that a ground insulation fault has occurred on the common side.

[0021] The controller is further configured to determine that a ground insulation fault has occurred on both the common side and the non-common side in the following manner: when the difference between the voltage to ground on the common side and the voltage to ground on the non-common side is within the difference threshold, the controller controls the i-th DC / DC circuit to operate to reduce the voltage of the DC source connected to the DC / DC circuit; when the voltage to ground on the common side is less than a second voltage threshold, the controller identifies that a ground insulation fault has occurred on both the common side and the non-common side of the i-th DC / DC circuit.

[0022] This disclosure also provides a method for detecting insulation resistance, including:

[0023] The target DC / DC circuit with a ground insulation fault on the non-common side of the power conversion system is located; the power conversion system includes N DC / DC circuits, where N is an integer greater than or equal to 2; the first terminal of each DC / DC circuit is used to connect to the corresponding DC source, and the second terminal of each DC / DC circuit is used to connect to the DC bus; the N DC / DC circuits are connected in a common-pole configuration, which includes a common negative connection or a common positive connection.

[0024] The insulation impedance of the power conversion system is obtained based on the DC source voltage, common-to-ground voltage, and DC bus voltage of the target DC / DC circuit at the first moment, and the DC source voltage, common-to-ground voltage, and DC bus voltage of the target DC / DC circuit at the second moment.

[0025] One possible implementation involves obtaining the insulation impedance of the power conversion system based on the DC source voltage, common-to-ground voltage, and DC bus voltage of the target DC / DC circuit at a first moment, and at a second moment, the same voltage levels.

[0026] Based on the DC source voltage, common-to-ground voltage, DC bus voltage, and ground impedance of the target DC / DC circuit before the disturbance of the impedance disturbance circuit connected to the DC bus at the first moment, and the DC source voltage, common-to-ground voltage, DC bus voltage, and ground impedance of the target DC / DC circuit after the disturbance of the impedance disturbance circuit at the second moment, the insulation impedance of the power conversion system is obtained.

[0027] One possible implementation, wherein locating the target DC / DC circuit in the power conversion system that has a ground insulation fault, includes:

[0028] Control the operation of the i-th DC / DC circuit to reduce the voltage of the DC source to which it is connected;

[0029] If the voltage change of the i-th DC / DC circuit before and after operation exceeds the preset voltage range, then the i-th DC / DC circuit has a non-common-pole ground insulation fault.

[0030] One possible implementation, wherein locating the target DC / DC circuit in the power conversion system that has a ground insulation fault, includes:

[0031] Control the operation of the i-th DC / DC circuit to reduce the voltage of the DC source to which it is connected;

[0032] If the first voltage of the i-th DC / DC circuit is less than the first voltage of the other DC / DC circuits, then the i-th DC / DC circuit has a non-common-pole insulation fault to ground; the insulation impedance of the power conversion system is obtained based on the non-common-pole impedance to ground of the i-th DC / DC circuit; when N DC / DC circuits are connected with a common negative terminal, the first voltage is the positive terminal voltage to ground; when N DC / DC circuits are connected with a common positive terminal, the first voltage is the negative terminal voltage to ground.

[0033] One possible implementation, wherein locating the target DC / DC circuit in the power conversion system that has a ground insulation fault, includes:

[0034] Control the i-th DC / DC circuit to reduce the voltage of the DC source connected to the DC / DC circuit;

[0035] If the difference between the second voltage of the i-th DC / DC circuit before and after energy consumption exceeds the first voltage threshold, then the i-th DC / DC circuit has a non-common-polarity ground insulation fault; when N DC / DC circuits are connected with a common negative terminal, the second voltage is the negative terminal to ground voltage; when N DC / DC circuits are connected with a common positive terminal, the second voltage is the positive terminal to ground voltage.

[0036] One possible implementation of the insulation impedance detection method further includes: when a ground insulation fault occurs on the common side of the power conversion system or when the ground insulation of the DC / DC circuit is normal, obtaining the insulation impedance of the power conversion system based on the common-to-ground voltage, DC bus voltage, and ground impedance before the disturbance of the impedance disturbance circuit at a first moment, and the common-to-ground voltage, DC bus voltage, and ground impedance after the disturbance of the impedance disturbance circuit at a second moment.

[0037] One possible implementation involves controlling at least one of the DC / DC circuits to operate in order to reduce the voltage of the DC source to which it is connected, including:

[0038] Control at least one of the DC / DC circuits to boost the DC bus voltage to reduce the voltage of the DC source connected to the DC / DC circuit, consume energy on the DC bus, and make the DC bus voltage less than the bus voltage threshold.

[0039] One possible implementation method for insulation impedance detection further includes: if the difference between the voltage to ground on the common pole side and the voltage to ground on the non-common pole side exceeds a threshold, it is determined that an insulation fault to ground has occurred on the common pole side.

[0040] One possible implementation of the insulation impedance detection method further includes: when the difference between the voltage to ground on the common side and the voltage to ground on the non-common side is within the difference threshold, controlling the i-th DC / DC circuit to operate to reduce the voltage of the DC source connected to the DC / DC circuit; when the voltage to ground on the common side is less than a second voltage threshold, locating a ground insulation fault on both the common side and the non-common side of the i-th DC / DC circuit.

[0041] This disclosure also provides a control device including 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 perform the methods described above.

[0042] This disclosure also provides a computer-readable storage medium storing a computer program that is loaded by a processor to execute the methods described above.

[0043] The power conversion system provided in this disclosure, when including multiple DC / DC circuits, first identifies the faulty DC / DC circuit. Based on the faulty DC / DC circuit, the system's insulation impedance to ground is obtained, reducing unknowns and simplifying calculations. Furthermore, the impact of DC source voltage fluctuations on the accuracy of the insulation impedance to ground is considered. Obtaining the insulation impedance to ground based on the DC source voltage at two different times improves the accuracy of the insulation impedance to ground. Attached Figure Description

[0044] Figure 1 A schematic diagram of a power conversion system provided in an embodiment of this disclosure;

[0045] Figure 2 A schematic diagram of yet another power conversion system provided in this disclosure embodiment;

[0046] Figure 3 A schematic diagram of another power conversion system provided in this disclosure embodiment;

[0047] Figure 4A A schematic diagram of a DC source for a power conversion system, including a battery, provided for an embodiment of this disclosure;

[0048] Figure 4B A schematic diagram of a DC source for a power conversion system provided in an embodiment of this disclosure, including a battery;

[0049] Figure 5 A schematic diagram of another power conversion system provided in an embodiment of this disclosure;

[0050] Figure 6 A flowchart of an insulation impedance detection method provided in this disclosure embodiment;

[0051] Figure 7 A flowchart illustrating yet another insulation impedance detection method provided in this disclosure embodiment;

[0052] Figure 8 A flowchart of another insulation impedance detection method provided in this disclosure embodiment;

[0053] Figure 9 A flowchart illustrating another insulation resistance detection method provided in this disclosure embodiment;

[0054] Figure 10 This is a schematic diagram of a control device provided in an embodiment of the present disclosure. Detailed Implementation

[0055] To make the above-mentioned objectives, features and advantages of this disclosure more apparent and understandable, the embodiments of this disclosure will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0056] See Figure 1 The figure is a schematic diagram of a power conversion system provided in an embodiment of this disclosure.

[0057] The power conversion system provided in this embodiment includes: a controller (not shown) and N DC / DC / DC circuits, where N is an integer greater than or equal to 2. The first terminal of each DC / DC circuit is used to connect to a corresponding DC source. This embodiment does not specifically limit the type of DC source; it can be at least one of photovoltaic or battery technology. Figure 1 Taking photovoltaic (PV) as an example, the DC / DC power source is configured such that the first terminal of the first DC / DC circuit is connected to the first PV string PV1+, the first terminal of the second DC / DC circuit is connected to the second PV string PV2+, and so on, until the first terminal of the Nth DC / DC circuit is connected to the Nth PV string PVN+. The second terminal of the DC / DC circuit is used to connect to the DC bus, such as... Figure 1 As shown, the second terminal of the first DC / DC circuit is connected to the DC positive bus BUS+, the second terminal of the second DC / DC circuit is connected to the DC positive bus BUS+, and so on until the second terminal of the Nth DC / DC circuit is connected to the DC positive bus BUS+, that is, the second terminals of all DC / DC circuits are connected together.

[0058] N DC / DC circuits are connected in a common-pole configuration, which includes either a common negative connection or a common positive connection. Figure 1 Taking the example of N DC / DC circuits connected together at their negative terminals (common negative terminal connection), it can be seen that the first terminal of the input capacitor of the N DC / DC circuits is connected to the positive input terminal, and the second terminal of the input capacitor is connected to the negative terminal PV-. PV- is connected to the DC negative bus BUS-.

[0059] The first resistor R1 is the impedance of the positive terminal of the first DC / DC circuit to ground, the second resistor R2 is the impedance of the positive terminal of the first DC / DC circuit to ground, and the Nth resistor RN is the impedance of the positive terminal of the Nth DC / DC circuit to ground. Here, R- represents the impedance of the negative terminal PV- to ground.

[0060] Since a power conversion system includes multiple DC / DC circuits, directly obtaining the DC-side insulation impedance to ground involves many unknowns and is computationally complex. To reduce computational difficulty and the number of unknowns, the power conversion system provided in this disclosure first locates the target DC / DC circuit experiencing a ground insulation fault. The insulation impedance of the power conversion system can then be obtained based on the ground insulation impedance of the target DC / DC circuit. When only one DC / DC circuit in the power conversion system is faulty, the insulation impedance of the power conversion system is equal to the ground insulation impedance of the target DC / DC circuit. When the power conversion system includes multiple DC / DC circuits with ground insulation faults, the range of the power conversion system's ground insulation impedance can be obtained based on the ground insulation impedances of multiple target DC / DC circuits.

[0061] The controller is used to locate the target DC / DC circuit that has a ground insulation fault on the non-common side of the power conversion system; based on the DC source voltage, common-to-ground voltage and DC bus voltage of the target DC / DC circuit at the first moment, and the DC source voltage, common-to-ground voltage and DC bus voltage of the target DC / DC circuit at the second moment, the insulation impedance of the power conversion system is obtained.

[0062] The non-common pole side refers to the side that is not connected in a common pole configuration. For example, when connected in a common negative pole configuration, it is determined whether there is a grounding insulation fault in the positive pole. When connected in a common positive pole configuration, it is determined whether there is a grounding insulation fault in the negative pole.

[0063] Furthermore, since voltage fluctuations occur, this embodiment samples the DC source voltage at two different times before and after the target DC / DC circuit. For example, if the i-th DC / DC circuit malfunctions, the DC source voltage of the i-th DC / DC circuit at the first time is denoted by Vi, and the DC source voltage of the target DC / DC circuit at the second time is denoted by Vi′. Additionally, the DC bus voltage needs to be sampled; the DC bus voltage refers to the voltage between the positive DC bus BUS+ and the negative DC bus BUS-.

[0064] For a system with a common negative terminal connection, the common-to-ground voltage refers to the negative-to-ground voltage. For a system with a common positive terminal connection, the common-to-ground voltage refers to the positive-to-ground voltage.

[0065] The power conversion system provided in this disclosure, when including multiple DC / DC circuits, first identifies the target DC / DC circuit with a ground insulation fault. The ground insulation impedance of the system is then obtained based on the target DC / DC circuit, reducing unknowns and simplifying calculations. Furthermore, the impact of DC source voltage fluctuations on the accuracy of the ground insulation impedance is considered. Obtaining the ground insulation impedance based on the DC source voltage at two different times improves the accuracy of the ground insulation impedance.

[0066] In actual products, most power conversion systems adopt a common negative terminal connection. Therefore, the power conversion systems shown in the accompanying drawings of the embodiments of this disclosure are all described with a common negative terminal connection as an example. The technical solutions provided in the embodiments of this disclosure are also applicable to common positive terminal systems, and the working principle is similar.

[0067] For power conversion systems with a common negative terminal connection, when R- has a problem, since all DC / DC circuits are connected with a common negative terminal, the fault is directly located to the negative terminal's insulation to ground without distinguishing between DC / DC circuits with insulation to ground faults.

[0068] To improve the accuracy of insulation impedance, the power conversion system provided in this disclosure embodiment also includes an impedance disturbance circuit connected to the DC bus. The equivalent impedance disturbance circuit can be considered to have three terminals: the first terminal is connected to the DC positive bus, the second terminal is connected to the DC negative bus, and the third terminal is grounded. However, this disclosure embodiment does not specifically limit the specific topology of the impedance disturbance circuit. When calculating the insulation impedance, the equivalent impedance of the impedance disturbance circuit before and after disturbance is used. The impedance disturbance circuit generally includes a resistor and a switch. By changing the impedance connected to the power conversion system through the switch action, impedance disturbance is achieved. The equivalent impedance of the impedance disturbance circuit includes the positive bus-to-ground impedance and the negative bus-to-ground impedance.

[0069] The embodiments disclosed herein do not specifically limit the type of DC / DC circuit. It can be a boost circuit, a buck circuit, or a buck-boost circuit. For ease of understanding, the following description uses a Boost circuit as an example of DC / DC circuit.

[0070] See Figure 2 This figure is a schematic diagram of another power conversion system provided in an embodiment of this disclosure.

[0071] The power conversion system provided in this embodiment is a common negative terminal connection system. Figure 2 The following example uses three Boost circuits. The negative terminals of the first terminals of each Boost circuit are connected together, all connected to PV-. The negative terminals of the second terminals of each Boost circuit are connected together, all connected to BUS-.

[0072] Figure 2 The diagram only illustrates the equivalent impedance of the impedance disturbance circuit. Ra is the equivalent impedance of the positive bus to ground before the first time disturbance, Rb is the equivalent impedance of the negative bus to ground before the first time disturbance, Rc is the equivalent impedance of the positive bus to ground after the second time disturbance, and Rd is the equivalent impedance of the negative bus to ground after the second time disturbance.

[0073] The controller is used to obtain the insulation impedance of the power conversion system based on the voltage of the DC source of the target DC / DC circuit (e.g., photovoltaic PV voltage), the common-to-ground voltage, the DC bus voltage, and the impedance to ground (Ra / Rb) before the impedance disturbance circuit disturbance at a first moment, and the voltage of the DC source of the target DC / DC circuit, the common-to-ground voltage, the DC bus voltage, and the impedance to ground (Rc / Rd) after the impedance disturbance circuit disturbance at a second moment.

[0074] The following is combined Figure 2 This disclosure introduces the principle and formula derivation process for obtaining insulation impedance according to the embodiments provided.

[0075] Let the voltage between PV1+ and PV- of the first photovoltaic string at the first moment be V1, the voltage between PV2+ and PV- be V2, and the voltage between PV3+ and PV- be V3. Taking the common negative terminal connection as an example, the voltage between the common terminal and the ground is the voltage between the negative terminal and the ground, which is V-, that is, the voltage between PV- and PE. The DC bus voltage is Vbus.

[0076] Let the voltage between PV1+ and PV- at the second moment be V1′, the voltage between PV2+ and PV- be V2′, and the voltage between PV3+ and PV- be V3′. Taking a common-negative connection as an example, the voltage between the common terminal and ground is the same as the voltage between the negative terminal and ground, which is V. - The DC bus voltage is Vbus.

[0077] According to Kirchhoff's current law, the following equation can be derived regarding the fact that the current flowing into the ground from the positive terminal is equal to the current flowing into the ground from the negative terminal:

[0078]

[0079] Subtract formula (2) from formula (1), and combine the system's insulation resistance R iso The conductance of the circuit is equal to the sum of the conductances of all the circuits, that is... Formula (3) can be obtained.

[0080]

[0081] As can be seen from the expression in the brackets of the denominator of formula (3), there are unknowns in formula (3).

[0082] Therefore, in calculating R iso These unknown quantities need to be calculated first.

[0083] As can be seen from formula (3), this disclosure considers the voltage fluctuation of the DC source, that is, it includes the voltage of each photovoltaic string. In the conventional technology, the voltage fluctuation of the DC source is not considered when obtaining the insulation impedance. Therefore, the voltage of the DC source is not included in the calculation of the insulation impedance. However, in the embodiment of this disclosure, the voltage of the DC source is included in the calculation of the insulation impedance, and the voltage fluctuation of the DC source is considered. The final insulation impedance has higher accuracy and can more accurately reflect the insulation status of the system.

[0084] When the insulation to ground is normal, the impedance to ground of both the positive and negative terminals on the DC side of the power conversion system is relatively large (typically reaching megaohms). i is a positive integer greater than or equal to 1, according to the formula It can be approximated that for a system with a common negative terminal connection, when there is a problem with the positive terminal impedance to ground of a certain DC / DC circuit, the insulation impedance of the power conversion system is approximately equal to the positive terminal impedance to ground of the target DC / DC circuit.

[0085] Assuming the first DC / DC circuit has a ground insulation fault, i.e., the positive terminal of the first DC / DC circuit has a low ground insulation fault, then Substituting back into formula (3), we get formula (4):

[0086]

[0087] As can be seen from formula (4), R can be calculated using the collected voltages and the equivalent resistance of the impedance disturbance circuit. iso .

[0088] It is clear that formula (4) assumes that the first DC / DC circuit is faulty to ground. By analogy, it can be extended to the case that any DC / DC branch is insulated from ground, that is, the positive terminal of the i-th DC / DC circuit is insulated from ground, and then formula (5) can be obtained.

[0089]

[0090] Formula (5) describes the situation when one DC / DC circuit in the power conversion system experiences an insulation failure to ground. When the power conversion system includes multiple DC / DC circuits that all experience insulation failures to ground, the insulation impedance value cannot be accurately calculated. Instead, a range of insulation impedance values ​​is obtained. This will be explained in detail below.

[0091] Extending to N DC / DC circuits, according to When both the positive and negative terminals of a DC / DC circuit experience simultaneous insulation faults to ground, assuming Ri and R- are abnormal, we can obtain:

[0092]

[0093] The controller is also used to determine whether a ground insulation fault has occurred on both the common-pole side and the non-common-pole side in the following manner: that is, regardless of whether it is a common positive-pole system or a common negative-pole system, a ground insulation fault has occurred on both the positive and negative poles. Specifically, when the difference between the voltage to ground on the common-pole side and the voltage to ground on the non-common-pole side is within the difference threshold, the controller controls the i-th DC / DC circuit to operate to reduce the voltage of the DC source connected to the DC / DC circuit. When the voltage to ground on the common-pole side is less than a second voltage threshold, the controller locates that a ground insulation fault has occurred on both the common-pole side and the non-common-pole side of the i-th DC / DC circuit.

[0094] In addition, according to When there are two or more DC / DC circuits with positive-to-ground insulation faults, assuming Ri and R(i+1) are abnormal, it can be qualitatively determined that... therefore as well as

[0095] Then we can get:

[0096]

[0097] Furthermore, for example, taking two DC / DC circuit malfunctions as an example, when the i-th and i+1-th DC / DC circuits are malfunctioning, and the voltage fluctuation difference between the DC sources of the two DC / DC circuits is equal, i.e., Vi′-Vi=V(i+1)′-V(i+1)=V, the insulation impedance of the system can be obtained. This insulation impedance can be obtained as a definite value, rather than a range of insulation impedance, by simplifying the following formula (7). That is, formula (7) is simplified to the following formula:

[0098]

[0099] When there are three or more DC / DC circuits with abnormal ground insulation impedance in the power conversion system, the principle and formulas introduced above can be used to deduce the solution, which will not be repeated here.

[0100] The above describes the calculation method for a ground insulation fault occurring on the non-common side. The following describes the calculation method for a power conversion system where all DC / DC circuits have normal ground insulation, or where a ground insulation fault occurs on the common side of the power conversion system. This latter case is simpler than the calculation method for a ground insulation fault occurring on the non-common side.

[0101] Specifically, the controller is also used to obtain the insulation impedance of the power conversion system when a ground insulation fault occurs on the common side of the power conversion system or when the ground insulation of the DC / DC circuit is normal, based on the common-to-ground voltage, DC bus voltage and ground impedance before the impedance disturbance circuit disturbance at the first moment, and the common-to-ground voltage, DC bus voltage and ground impedance after the impedance disturbance circuit disturbance at the second moment.

[0102] The controller is also used to determine if a ground insulation fault has occurred on the common side by the following method: if the difference between the voltage to ground on the common side and the voltage to ground on the non-common side exceeds a difference threshold, it is determined that a ground insulation fault has occurred on the common side.

[0103] For example, in a power conversion system with a common negative terminal connection, a low negative terminal-to-ground insulation fault indicates a ground insulation fault on the common negative terminal side. Therefore... Substituting back into equation (3), we obtain equation (8):

[0104]

[0105] As can be seen from formula (8), when a ground fault occurs on the common pole side, the terms in the denominator of formula (3) containing the voltage of the DC source are all approximately 0, thus simplifying the formula.

[0106] For a common positive electrode system, the negative electrode voltage to ground in formula (8) can be replaced with the positive electrode voltage to ground.

[0107] The following describes the method for locating ground insulation faults. The controller primarily pulls down the DC source voltage of the DC / DC circuit sequentially to determine if the voltage to ground on the non-common side of the DC / DC circuit fluctuates significantly. If a large voltage change occurs, it indicates that a ground insulation fault has occurred in that DC / DC circuit. This embodiment does not specifically limit whether the sequential pull-down involves pulling down the DC source voltage of one DC / DC circuit at a time or pulling down multiple DC / DC circuits simultaneously. However, during the pull-down process, some DC / DC circuits need to be pulled down first, while the voltage of the DC source of the remaining DC / DC circuits is not initially pulled down.

[0108] Since each DC / DC circuit is connected to its corresponding DC source, whether the voltage of the DC source of one DC / DC circuit is pulled down at a time or the voltage of the DC sources of multiple DC / DC circuits is pulled down at a time, the judgment is independent for each DC / DC circuit, and the judgment principle is the same. Therefore, the technical solution is described from the perspective of any one DC / DC circuit below. The similarities of multiple DC / DC circuits are all within the protection scope of the technical solution provided in the embodiments of this disclosure.

[0109] The controller is used to locate the target DC / DC circuit in the power conversion system that has a ground insulation fault in the following ways:

[0110] The i-th DC / DC circuit is controlled to reduce the voltage of its connected DC source. If the voltage change on the non-common side of the i-th DC / DC circuit before and after operation exceeds a preset voltage range, then the non-common side of the i-th DC / DC circuit has a ground insulation fault. The i-th DC / DC circuit can be any one of N DC / DC circuits, i.e., it refers to one of the DC / DC circuits in general. Since the DC sources of each DC / DC circuit are independent and connected to their respective corresponding DC sources, when judging whether a ground insulation fault occurs on the non-common side, each DC / DC circuit does not affect the others and can be judged independently.

[0111] This disclosure does not specifically limit the voltage on the non-common side of the i-th DC / DC circuit. The comparison object for voltage changes before and after operation can be different. For example, the voltage on the non-common side of the i-th DC / DC circuit after operation can be compared with the voltage on the non-common side before operation. Alternatively, the voltage of the i-th DC / DC circuit can be compared with the voltages of other DC / DC circuits. This comparison aims to determine whether the voltage of the i-th DC / DC circuit has undergone a significant change before and after operation. If the voltage change is significant, it indicates a non-common insulation fault to ground in the i-th DC / DC circuit.

[0112] When a DC / DC circuit is working, the energy of the DC source is transferred to the DC bus, causing the voltage of the DC source to decrease. For example, when the DC / DC circuit is a Boost circuit, the DC / DC circuit can be controlled to work to lower the voltage of the DC source.

[0113] The following section compares the non-common voltage of a DC / DC circuit that has been pulled low with the non-common voltage of other DC / DC circuits.

[0114] The controller is used to locate the target DC / DC circuit in the power conversion system that has a ground insulation fault in the following ways:

[0115] The i-th DC / DC circuit is controlled to reduce the voltage of its connected DC source. If the first voltage of the i-th DC / DC circuit is less than the first voltage of the other DC / DC circuits, then the i-th DC / DC circuit has a non-common-pole insulation fault to ground. The insulation impedance of the power conversion system is obtained based on the non-common-pole impedance of the i-th DC / DC circuit to ground. When N DC / DC circuits share a common negative pole, the first voltage is the positive-to-ground voltage; when N DC / DC circuits share a common positive pole, the first voltage is the negative-to-ground voltage. The i-th DC / DC circuit can be any one of the N DC / DC circuits, i.e., it refers to one of the DC / DC circuits in general. Since the DC sources of each DC / DC circuit are independent and connected to their respective corresponding DC sources, when judging whether a ground insulation fault occurs on the non-common-pole side, the individual DC / DC circuits do not affect each other and can be judged independently.

[0116] For a system with a common negative terminal connection, if the positive terminal voltage to ground of the i-th DC / DC circuit is less than the positive terminal voltage to ground of the other DC / DC circuits, then the positive terminal of the i-th DC / DC circuit has an insulation fault to ground. For example, when N is 10, the i-th DC / DC circuit is the first DC / DC circuit. Therefore, if the positive terminal voltage to ground of the first DC / DC circuit is less than the positive terminal voltages to ground of the other nine DC / DC circuits, it indicates that the positive terminal of the first DC / DC circuit has an insulation fault to ground.

[0117] The following describes a comparison of the common-to-ground voltage before and after the i-th DC / DC circuit is pulled down. The purpose of this disclosure in comparing the common-to-ground voltage is to determine whether the non-common-to-ground voltage has changed significantly, thereby determining whether the i-th DC / DC circuit has experienced a ground insulation fault.

[0118] Specifically, the controller is used to locate the target DC / DC circuit in the power conversion system that has a ground insulation fault in the following manner:

[0119] The operation of the i-th DC / DC circuit is controlled to reduce the voltage of the DC source connected to it. If the difference between the second voltage of the i-th DC / DC circuit before and after energy consumption exceeds the first voltage threshold, then the i-th DC / DC circuit has a non-common-polarity insulation fault to ground. When N DC / DC circuits share a common negative terminal, the second voltage is the negative terminal to ground voltage; when N DC / DC circuits share a common positive terminal, the first voltage is the positive terminal to ground voltage. The i-th DC / DC circuit can be any one of the N DC / DC circuits, i.e., it refers to one of the DC / DC circuits in general. Since the DC sources of each DC / DC circuit are independent and connected to their respective corresponding DC sources, when judging whether a ground insulation fault occurs on the non-common-polarity side, each DC / DC circuit does not affect the others and can be judged independently.

[0120] For example, in a system with a common negative terminal connection, if the negative terminal voltage to ground of the i-th DC / DC circuit before energy consumption is less than the negative terminal voltage to ground of the i-th DC / DC circuit after energy consumption, then the positive terminal of the i-th DC / DC circuit has an insulation fault to ground.

[0121] To prevent excessive DC bus voltage during DC / DC circuit operation, especially during DC / DC boost, it is necessary to dissipate the DC bus's energy. Several methods for dissipating DC bus energy are described below.

[0122] For example, a controller is used to control at least one DC / DC circuit to boost the DC bus voltage, thereby reducing the voltage of the DC source connected to the DC / DC circuit. To protect the electrical components in the power conversion system, it is necessary to limit the DC bus voltage from rising too high. Therefore, it is also necessary to dissipate energy on the DC bus to keep the DC bus voltage below a bus voltage threshold.

[0123] See Figure 3 The figure is a schematic diagram of another power conversion system provided in an embodiment of this disclosure.

[0124] The power conversion system provided in this embodiment of the disclosure further includes a load 10, which is connected to a DC bus. Figure 3 The following is an example using two DC / DC circuits. The first terminal of the first DC / DC circuit is connected to PV1+, and the first terminal of the second DC / DC circuit is connected to PV2+.

[0125] The first energy consumption method: The controller is used to consume energy on the DC bus by controlling the operation of load 10.

[0126] This disclosure does not specifically limit the type of load 10. For example, load 10 can be a fan, and the controller controls the fan to work to dissipate heat and consume the energy of the DC bus.

[0127] See Figure 4A and Figure 4B The figure is a schematic diagram of another power conversion system provided in an embodiment of this disclosure.

[0128] Figure 4A Continuing with the example of two DC / DC circuits, at least one DC / DC circuit is connected to a battery as its DC source. For example, the first terminal of the first DC / DC circuit is connected to a photovoltaic string PV+, and the first terminal of the second DC / DC circuit is connected to a battery BAT+.

[0129] The second energy consumption method involves the controller controlling the second DC / DC circuit connected to battery BAT+ to charge battery BAT+, thereby consuming energy on the DC bus and making the DC bus voltage lower than the bus voltage threshold.

[0130] Figure 4B Continuing with the example of two DC / DC circuits, for instance, the first terminal of the first DC / DC circuit is connected to the first battery BAT1+, and the first terminal of the second DC / DC circuit is connected to the second battery BAT2+.

[0131] The second energy consumption method involves the controller controlling the first DC / DC circuit to charge the first battery BAT1+, or controlling the second DC / DC circuit to charge the second battery BAT2+, in order to consume energy on the DC bus and make the DC bus voltage less than the bus voltage threshold.

[0132] See Figure 5 The figure is a schematic diagram of another power conversion system provided in an embodiment of this disclosure.

[0133] The third energy consumption method, the power conversion system provided in this embodiment, further includes a DC / AC circuit 20, the DC side of the DC / AC circuit 20 is connected to a DC bus, and the AC side of the DC / AC circuit 20 is connected to a filter, the filter including at least an inductor L.

[0134] Figure 5 The DC / AC circuit 20 described here is only an example of a passive clamped three-level inverter circuit. The DC / AC circuit 20 can also be other topologies. The specific topology of the DC / AC circuit 20 is not limited. The AC side of the DC / AC circuit 20 is generally connected to a filter, and the filter contains an inductor.

[0135] The controller is used to control the operation of the DC / AC circuit 20 to supply power to the inductor L, thereby consuming energy on the DC bus and keeping the DC bus voltage below the voltage threshold. The operation of the DC / AC circuit 20 mainly refers to the controller controlling the switching transistors within the DC / AC circuit 20 to convert the DC power on the DC bus into AC power to charge and discharge the inductor L. For example, the path from the DC positive bus BUS+ to the switching transistor, then to the inductor L and filter capacitor C, and finally back to the bus capacitor Cbus utilizes the inductor L's own impedance to consume energy from the DC bus.

[0136] Based on the power conversion system provided in the above embodiments, this disclosure also provides an insulation impedance detection method, which will be described in detail below with reference to the accompanying drawings.

[0137] See Figure 6 The figure is a flowchart of an insulation impedance detection method provided in an embodiment of this disclosure.

[0138] The insulation resistance detection method provided in this disclosure includes the following steps:

[0139] S601: Target DC / DC circuit with a ground insulation fault on the non-common side of the power conversion system.

[0140] The power conversion system includes N DC / DC circuits; N is an integer greater than or equal to 2. The first terminal of the DC / DC circuit is used to connect to the corresponding DC source, and the second terminal of the DC / DC circuit is used to connect to the DC bus. The N DC / DC circuits are connected in a common polarity, which includes a common negative polarity connection or a common positive polarity connection.

[0141] S602: Based on the DC source voltage, common-to-ground voltage, and DC bus voltage of the target DC / DC circuit at the first moment; and the DC source voltage, common-to-ground voltage, and DC bus voltage of the target DC / DC circuit at the second moment, obtain the insulation impedance of the power conversion system.

[0142] Furthermore, since voltage fluctuations occur, this embodiment samples the DC source voltage at two different times before and after the target DC / DC circuit. For example, if the i-th DC / DC circuit malfunctions, the DC source voltage of the i-th DC / DC circuit at the first time is denoted by Vi, and the DC source voltage of the target DC / DC circuit at the second time is denoted by Vi′. Additionally, the DC bus voltage needs to be sampled; the DC bus voltage refers to the voltage between the positive DC bus BUS+ and the negative DC bus BUS-.

[0143] For a system with a common negative terminal connection, the common-to-ground voltage refers to the negative-to-ground voltage. For a system with a common positive terminal connection, the common-to-ground voltage refers to the positive-to-ground voltage.

[0144] The insulation impedance detection method provided in this disclosure, when including multiple DC / DC circuits, first locates the faulty DC / DC circuit, and obtains the system's insulation impedance to ground based on the faulty DC / DC circuit, which can reduce unknowns and lower the calculation difficulty. Furthermore, it considers the impact of DC source voltage fluctuations on the accuracy of the insulation impedance to ground, and obtains the insulation impedance to ground based on the DC source voltage at two different times, which can improve the accuracy of the insulation impedance to ground.

[0145] One possible implementation involves obtaining the insulation impedance of the power conversion system based on the DC source voltage, common-to-ground voltage, and DC bus voltage of the target DC / DC circuit at a first moment; and the DC source voltage, common-to-ground voltage, and DC bus voltage of the target DC / DC circuit at a second moment. This includes: obtaining the insulation impedance of the power conversion system based on the DC source voltage, common-to-ground voltage, DC bus voltage, and ground impedance before the impedance disturbance circuit disturbance at the first moment; the impedance disturbance circuit being connected to the DC bus; and the DC source voltage, common-to-ground voltage, DC bus voltage, and ground impedance after the impedance disturbance circuit disturbance at the second moment.

[0146] One possible implementation involves locating the target DC / DC circuit in the power conversion system that has a ground insulation fault. This includes controlling the i-th DC / DC circuit to operate and reduce the voltage of its connected DC source. If the voltage change of the i-th DC / DC circuit before and after operation exceeds a preset voltage range, then the i-th DC / DC circuit has a non-common-pole ground insulation fault. The i-th DC / DC circuit can be any one of N DC / DC circuits, i.e., it refers to any one of the DC / DC circuits. Since the DC sources of each DC / DC circuit are independent and connected to their respective corresponding DC sources, when determining if a ground insulation fault has occurred on the non-common-pole side, the individual DC / DC circuits do not affect each other and can be determined independently. One possible implementation involves locating the target DC / DC circuit in the power conversion system that has a ground insulation fault. This includes: controlling the i-th DC / DC circuit to reduce the voltage of its connected DC source; if the first voltage of the i-th DC / DC circuit is less than the first voltage of the other DC / DC circuits, then the i-th DC / DC circuit has a non-common-polarity ground insulation fault; obtaining the insulation impedance of the power conversion system based on the non-common-polarity ground impedance of the i-th DC / DC circuit; when N DC / DC circuits share a common negative terminal, the first voltage is the positive terminal-to-ground voltage; when N DC / DC circuits share a common positive terminal, the first voltage is the negative terminal-to-ground voltage. The i-th DC / DC circuit can be any one of the N DC / DC circuits, i.e., it refers to one of the DC / DC circuits in general. Since the DC sources of each DC / DC circuit are independent and connected to their respective corresponding DC sources, when determining if a ground insulation fault has occurred on the non-common-polarity side, the individual DC / DC circuits do not affect each other and can be determined independently.

[0147] One possible implementation involves locating the target DC / DC circuit in the power conversion system that has a ground insulation fault. This includes: controlling the i-th DC / DC circuit to reduce the voltage of the DC source connected to the DC / DC circuit; if the difference between the second voltage of the i-th DC / DC circuit before and after energy consumption exceeds a first voltage threshold, then the i-th DC / DC circuit has a non-common-polarity ground insulation fault; when N DC / DC circuits share a common negative terminal, the second voltage is the negative terminal-to-ground voltage; when N DC / DC circuits share a common positive terminal, the first voltage is the positive terminal-to-ground voltage. The i-th DC / DC circuit can be any one of the N DC / DC circuits, i.e., it refers to one of the DC / DC circuits in general. Since the DC sources of each DC / DC circuit are independent and connected to their respective corresponding DC sources, when determining if a ground insulation fault has occurred on the non-common-polarity side, each DC / DC circuit does not affect the others and can be determined independently.

[0148] One possible implementation, the method provided in this disclosure, further includes: when a ground insulation fault occurs on the common side of the power conversion system or the ground insulation of the DC / DC circuit is normal, obtaining the insulation impedance of the power conversion system based on the common-to-ground voltage, DC bus voltage and ground impedance before the impedance disturbance circuit disturbance at a first moment; and the common-to-ground voltage, DC bus voltage and ground impedance after the impedance disturbance circuit disturbance at a second moment.

[0149] One possible implementation, when the DC / DC circuit is a boost circuit, involves controlling at least one DC / DC circuit to operate to reduce the voltage of the DC source to which it is connected, including: controlling at least one DC / DC circuit to boost the voltage, raising the DC bus voltage to reduce the voltage of the DC source to which the DC / DC circuit is connected, consuming energy on the DC bus, and making the DC bus voltage less than a voltage threshold.

[0150] The following flowchart illustrates the method for detecting the insulation impedance of a power conversion system with a common negative terminal connection.

[0151] See Figure 7 The figure is a flowchart of another insulation impedance detection method provided in the embodiments of this disclosure.

[0152] S702: Determine whether the difference between the negative terminal voltage to ground and the positive terminal voltage to ground exceeds the threshold. If yes, execute S705; otherwise, execute S703.

[0153] For a common negative electrode system, if the difference between the negative electrode voltage to ground and the positive electrode voltage to ground exceeds a threshold, it indicates that there is a ground insulation fault on the common negative electrode side.

[0154] S703: Determine whether the value of the negative terminal voltage to ground being greater than the positive terminal voltage to ground exceeds the threshold. If yes, execute S704; otherwise, execute S706.

[0155] It should be understood that when the voltage between the negative terminal and the voltage between the positive terminal and the ground are similar and the difference between them is small, it is considered that the ground insulation impedance of the power conversion system is normal and no DC / DC circuit has a ground insulation fault.

[0156] S704: Operate the DC / DC circuits sequentially to locate the target DC / DC circuit with a ground insulation fault on the positive side, and calculate the insulation impedance of the abnormal DC / DC circuit according to formula (5).

[0157] The location of the target DC / DC circuit can be described in the above power conversion system embodiment for the common negative system, and will not be repeated here.

[0158] S705: A ground insulation fault occurs on the common negative side. The insulation impedance is calculated using formula (8).

[0159] S706: The power conversion system is normal. Calculate the insulation impedance using formula (8).

[0160] The following flowchart illustrates the method for detecting the insulation impedance of a power conversion system with a common positive terminal connection.

[0161] See Figure 8 The figure is a flowchart of another insulation impedance detection method provided in an embodiment of this disclosure.

[0162] S802: Determine whether the difference between the positive terminal voltage to ground and the negative terminal voltage to ground exceeds the threshold. If yes, execute S805; otherwise, execute S803.

[0163] For a common positive electrode system, if the difference between the positive electrode voltage to ground and the negative electrode voltage to ground exceeds a threshold, it indicates that there is a ground insulation fault on the common positive electrode side.

[0164] S803: Determine whether the value of the positive terminal voltage to ground being greater than the negative terminal voltage to ground exceeds the threshold. If yes, execute S804; otherwise, execute S806.

[0165] It should be understood that when the voltage between the positive terminal and the voltage between the negative terminal and the ground are similar and the difference between them is small, it is considered that the ground insulation impedance of the power conversion system is normal and no DC / DC circuit has a ground insulation fault.

[0166] S804: Operate the DC / DC circuits sequentially to locate the target DC / DC circuit with a ground insulation fault on the negative side, and calculate the insulation impedance of the abnormal DC / DC circuit according to formula (9).

[0167]

[0168] V +V is the voltage between the positive terminal and ground at the first moment. + ′ represents the voltage of the positive terminal to ground at the second moment.

[0169] The location of the target DC / DC circuit can be described in the above power conversion system embodiment, and will not be repeated here.

[0170] S805: A ground insulation fault occurs on the common positive side. The insulation impedance is calculated using formula (10).

[0171]

[0172] S806: The power conversion system is normal. Calculate the insulation impedance using formula (10).

[0173] The method provided in this disclosure further includes: determining that a ground insulation fault has occurred on the common electrode side when the difference between the voltage to ground on the common electrode side and the voltage to ground on the non-common electrode side exceeds a difference threshold. For example, in a common negative electrode system, when the voltage to ground on the negative electrode is less than the voltage to ground on the positive electrode, it indicates that a negative electrode ground insulation fault has occurred in the system. Similarly, the same applies to a common positive electrode system, which will not be elaborated further here.

[0174] The following describes a method for determining whether both the positive and negative electrodes have ground insulation faults, provided by embodiments of this disclosure.

[0175] The method provided in this disclosure further includes: when the difference between the voltage to ground on the common side and the voltage to ground on the non-common side is within a difference threshold, controlling the i-th DC / DC circuit to operate to reduce the voltage of the DC source connected to the DC / DC circuit; and when the voltage to ground on the common side is less than a second voltage threshold, locating that both the common side and the non-common side of the i-th DC / DC circuit have ground insulation faults.

[0176] The following describes, with reference to the accompanying drawings, an embodiment of the present disclosure providing a method for determining whether an insulation fault has occurred in both the positive terminal to ground and the negative terminal to ground.

[0177] See Figure 9 The figure is a flowchart of another insulation impedance detection method provided in the embodiments of this disclosure.

[0178] S901: Determine whether the difference between the voltage to ground on the common pole side and the voltage to ground on the non-common pole side exceeds the difference threshold. If yes, proceed to S902; otherwise, it indicates that there is only one side of the insulation fault to ground, and calculate the insulation impedance according to the method described above.

[0179] S902: Control the i-th DC / DC circuit to reduce the voltage of the DC source connected to the DC / DC circuit, and determine whether the voltage to ground on the common side is less than the second voltage threshold; if yes, execute S903, otherwise execute S904.

[0180] S903: The common-pole side and the non-common-pole side of the i-th DC / DC circuit have both experienced ground insulation faults.

[0181] S904: It is determined that both the common electrode side and the non-common electrode side are normal when connected to ground.

[0182] In one possible implementation, see Figure 10 The figure is a schematic diagram of a control device provided in an embodiment of this disclosure.

[0183] The control device may include a memory 1011 and a processor 1012. The processor 1012 may be connected to the power converter and can drive the switches in the various power conversion circuits of the power converter. For example... Figure 10 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.

[0184] 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 method. The memory 1011 can also store data, such as information like the first voltage threshold, the second voltage threshold, and the bus voltage threshold involved in the above embodiments.

[0185] 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 disclosure 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)).

[0186] This disclosure 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.

[0187] 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. The same or similar parts between the various embodiments can be referred to each other.

[0188] The above description of the disclosed embodiments enables those skilled in the art to make or use this disclosure. 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 disclosure. Therefore, this disclosure 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 system, characterized in that, include: The controller and N DC / DC / DC circuits, where N is an integer greater than or equal to 2; the first terminal of each DC / DC circuit is used to connect to a corresponding DC source, and the second terminal of each DC / DC circuit is used to connect to a DC bus; the N DC / DC circuits are connected in a common-pole configuration, which may include a common negative connection or a common positive connection. The controller is used to locate the target DC / DC circuit that has a ground insulation fault on the non-common side of the power conversion system. The insulation impedance of the power conversion system is obtained based on the DC source voltage, common-to-ground voltage, and DC bus voltage of the target DC / DC circuit at the first moment, and the DC source voltage, common-to-ground voltage, and DC bus voltage of the target DC / DC circuit at the second moment.

2. The system according to claim 1, characterized in that, Also includes: An impedance disturbance circuit connected to the DC bus; The controller is used to obtain the insulation impedance of the power conversion system based on the voltage of the DC source of the target DC / DC circuit, the common-to-ground voltage, the DC bus voltage and the ground impedance before the impedance disturbance circuit is disturbed at a first time, and the voltage of the DC source of the target DC / DC circuit, the common-to-ground voltage, the DC bus voltage and the ground impedance after the impedance disturbance circuit is disturbed at a second time.

3. The system according to claim 1 or 2, characterized in that, The controller is used to locate the target DC / DC circuit in the power conversion system that has a non-common-to-ground insulation fault in the following manner: Control at least one of the DC / DC circuits to operate to reduce the voltage of the DC source to which it is connected; if the voltage change of the i-th DC / DC circuit before and after operation exceeds a preset voltage range, then the i-th DC / DC circuit has a non-common-pole insulation fault to ground; the i-th DC / DC circuit is one or more of the N DC / DC circuits.

4. The system according to claim 3, characterized in that, The controller is configured to locate the target DC / DC circuit in the power conversion system that has a ground insulation fault in the following manner: The i-th DC / DC circuit is controlled to operate to reduce the voltage of the DC source to which it is connected; if the first voltage of the i-th DC / DC circuit is less than the first voltage of the other DC / DC circuits, then the i-th DC / DC circuit has a non-common-pole insulation fault to ground; when N DC / DC circuits are connected with a common negative terminal, the first voltage is the positive terminal voltage to ground; when N DC / DC circuits are connected with a common positive terminal, the first voltage is the negative terminal voltage to ground.

5. The system according to claim 3, characterized in that, The controller is configured to locate the target DC / DC circuit in the power conversion system that has a ground insulation fault in the following manner: Control the i-th DC / DC circuit to reduce the voltage of the DC source connected to the DC / DC circuit; If the difference between the second voltage of the i-th DC / DC circuit before and after energy consumption exceeds the first voltage threshold, then the i-th DC / DC circuit has a non-common-polarity ground insulation fault; when N DC / DC circuits are connected with a common negative terminal, the second voltage is the negative terminal to ground voltage; when N DC / DC circuits are connected with a common positive terminal, the second voltage is the positive terminal to ground voltage.

6. The system according to claim 2, characterized in that, The controller is further configured to, when a ground insulation fault occurs on the common side of the power conversion system or when the ground insulation of the DC / DC circuit is normal, obtain the insulation impedance of the power conversion system based on the common-to-ground voltage, DC bus voltage and ground impedance before the disturbance of the impedance disturbance circuit at a first moment, and the common-to-ground voltage, DC bus voltage and ground impedance after the disturbance of the impedance disturbance circuit at a second moment.

7. The system according to any one of claims 3-5, characterized in that, The controller is used to control at least one of the DC / DC circuits to boost the DC bus voltage to reduce the voltage of the DC source connected to the DC / DC circuit, consume energy on the DC bus, and make the DC bus voltage less than the bus voltage threshold.

8. The system according to claim 7, characterized in that, The DC bus is connected to the load; the controller is used to consume energy on the DC bus by controlling the operation of the load. Alternatively, at least one of the DC / DC circuits is connected to a battery as a DC source, and the controller is used to control the DC / DC circuit connected to the battery to charge the battery in order to consume energy on the DC bus.

9. The system according to claim 7, characterized in that, Also includes: A DC / AC circuit, wherein the DC side of the DC / AC circuit is connected to the DC bus, and the AC side of the DC / AC circuit is connected to a filter, wherein the filter includes at least an inductor; The controller is used to control the DC / AC circuit to power the inductor, thereby consuming the energy on the DC bus.

10. The system according to claim 6, characterized in that, The controller is also used to determine that a ground insulation fault has occurred on the common pole side in the following manner: the difference between the voltage to ground on the common pole side and the voltage to ground on the non-common pole side exceeds the difference threshold, and it is determined that a ground insulation fault has occurred on the common pole side. The controller is further configured to determine that a ground insulation fault has occurred on both the common side and the non-common side in the following manner: when the difference between the voltage to ground on the common side and the voltage to ground on the non-common side is within the difference threshold, the controller controls the i-th DC / DC circuit to operate to reduce the voltage of the DC source connected to the DC / DC circuit; when the voltage to ground on the common side is less than a second voltage threshold, the controller identifies that a ground insulation fault has occurred on both the common side and the non-common side of the i-th DC / DC circuit.

11. A method for detecting insulation resistance, characterized in that, include: The target DC / DC circuit with a ground insulation fault on the non-common side of the power conversion system is located. The power conversion system includes N DC / DC circuits, where N is an integer greater than or equal to 2; the first terminal of each DC / DC circuit is used to connect to a corresponding DC source, and the second terminal of each DC / DC circuit is used to connect to a DC bus; the N DC / DC circuits are connected in a common-pole configuration, which may include a common-negative connection or a common-positive connection. The insulation impedance of the power conversion system is obtained based on the DC source voltage, common-to-ground voltage, and DC bus voltage of the target DC / DC circuit at the first moment, and the DC source voltage, common-to-ground voltage, and DC bus voltage of the target DC / DC circuit at the second moment.

12. The method according to claim 11, characterized in that, The step of obtaining the insulation impedance of the power conversion system based on the DC source voltage, common-to-ground voltage, and DC bus voltage of the target DC / DC circuit at a first moment, and at a second moment, includes: Based on the DC source voltage, common-to-ground voltage, DC bus voltage, and ground impedance of the target DC / DC circuit before the disturbance of the impedance disturbance circuit connected to the DC bus at the first moment, and the DC source voltage, common-to-ground voltage, DC bus voltage, and ground impedance of the target DC / DC circuit after the disturbance of the impedance disturbance circuit at the second moment, the insulation impedance of the power conversion system is obtained.

13. The method according to claim 11 or 12, characterized in that, The target DC / DC circuit for locating the ground insulation fault in the power conversion system includes: Control the operation of the i-th DC / DC circuit to reduce the voltage of the DC source to which it is connected; If the voltage change of the i-th DC / DC circuit before and after operation exceeds the preset voltage range, then the i-th DC / DC circuit has a non-common-pole ground insulation fault.

14. The method according to claim 13, characterized in that, The target DC / DC circuit for locating the ground insulation fault in the power conversion system includes: Control the operation of the i-th DC / DC circuit to reduce the voltage of the DC source to which it is connected; If the first voltage of the i-th DC / DC circuit is less than the first voltage of the other DC / DC circuits, then the i-th DC / DC circuit has a non-common-pole insulation fault to ground; the insulation impedance of the power conversion system is obtained based on the non-common-pole impedance to ground of the i-th DC / DC circuit; when N DC / DC circuits are connected with a common negative terminal, the first voltage is the positive terminal voltage to ground; when N DC / DC circuits are connected with a common positive terminal, the first voltage is the negative terminal voltage to ground.

15. The method according to claim 13, characterized in that, The target DC / DC circuit for locating the ground insulation fault in the power conversion system includes: Control the i-th DC / DC circuit to reduce the voltage of the DC source connected to the DC / DC circuit; If the difference between the second voltage of the i-th DC / DC circuit before and after energy consumption exceeds the first voltage threshold, then the i-th DC / DC circuit has a non-common-polarity ground insulation fault; when N DC / DC circuits are connected with a common negative terminal, the second voltage is the negative terminal to ground voltage; when N DC / DC circuits are connected with a common positive terminal, the second voltage is the positive terminal to ground voltage.

16. The method according to claim 12, characterized in that, Also includes: When a ground insulation fault occurs on the common side of the power conversion system or the ground insulation of the DC / DC circuit is normal, the insulation impedance of the power conversion system is obtained based on the common-to-ground voltage, DC bus voltage and ground impedance before the impedance disturbance circuit disturbance at the first moment, and the common-to-ground voltage, DC bus voltage and ground impedance after the impedance disturbance circuit disturbance at the second moment.

17. The method according to claim 13, characterized in that, Controlling at least one of the DC / DC circuits to reduce the voltage of its connected DC source includes: Control at least one of the DC / DC circuits to boost the DC bus voltage to reduce the voltage of the DC source connected to the DC / DC circuit, consume energy on the DC bus, and make the DC bus voltage less than the bus voltage threshold.

18. The method according to claim 16, characterized in that, Also includes: If the difference between the voltage to ground on the common pole side and the voltage to ground on the non-common pole side exceeds the difference threshold, it is determined that there is a ground insulation fault on the common pole side.

19. The method according to claim 16, characterized in that, Also includes: When the difference between the voltage to ground on the common side and the voltage to ground on the non-common side is within the difference threshold, the i-th DC / DC circuit is controlled to operate to reduce the voltage of the DC source connected to the DC / DC circuit. When the voltage to ground on the common side is less than the second voltage threshold, a ground insulation fault is located on both the common side and the non-common side of the i-th DC / DC circuit.

20. 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 perform the method as described in any one of claims 11-19.

21. A computer-readable storage medium, characterized in that, The system contains a computer program that is loaded by a processor to perform the method as described in any one of claims 11-19.

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