CN115980448A - Power converter and insulation impedance detection method thereof - Google Patents
Power converter and insulation impedance detection method thereof Download PDFInfo
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- CN115980448A CN115980448A CN202211648478.6A CN202211648478A CN115980448A CN 115980448 A CN115980448 A CN 115980448A CN 202211648478 A CN202211648478 A CN 202211648478A CN 115980448 A CN115980448 A CN 115980448A
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Abstract
The application provides a power converter and an insulation impedance detection method thereof, and the insulation impedance detection method comprises the steps of firstly controlling the action of an inverter circuit of a grounding relay and a power converter by means of a disturbance resistor between an alternating current side grounding relay of the power converter and the ground, realizing the connection switching of the disturbance resistor on a direct current bus in the power converter, and changing the ground impedance of at least one pole of the direct current bus; when the disturbance resistors are under different switching conditions, namely when at least one pole of the direct current bus has different ground impedance, respectively acquiring the voltage of the direct current bus in the power converter and the voltage of any pole of the direct current bus to ground; then according to the detection values, calculating to obtain an insulation resistance value to ground of the direct current side of the power converter; an extra relay in the prior art is not needed, and the problems of high requirement on relay type selection and high circuit cost are further avoided.
Description
Technical Field
The present disclosure relates to the field of power electronics technologies, and in particular, to a power converter and an insulation impedance detection method thereof.
Background
Power converters such as photovoltaic inverters and energy storage converters generally require detection of ground insulation impedance for power supplies such as photovoltaic modules and storage batteries connected to the input terminals of the power converters. In a traditional detection mode, a Y-shaped resistance bridge as shown in fig. 1 is arranged, and a switch S is connected in parallel between a midpoint NET of the Y-shaped resistance bridge and a positive electrode BUS + of a direct current BUS; and voltage detection under different conditions is carried out by controlling the on-off of the switch S, and then the insulation resistance to ground detection value of the direct current side of the corresponding power converter is obtained through calculation.
In practical application, the switch S needs to meet the safety requirements of basic insulation, and needs to consider certain voltage stress and current stress, which results in high selection requirements of the relay and high circuit cost.
Disclosure of Invention
In view of this, the present application provides a power converter and an insulation resistance detection method thereof, so as to solve the problems of high requirement for relay type selection and high circuit cost in the conventional resistance bridge detection.
In order to achieve the above purpose, the present application provides the following technical solutions:
the first aspect of the application provides an insulation impedance detection method of a power converter, wherein a grounding relay on an alternating current side of the power converter is grounded through a disturbance resistor; the insulation resistance detection method comprises the following steps:
controlling the grounding relay and an inverter circuit of the power converter to act, and realizing the connection switching of the disturbance resistor to a direct current bus in the power converter;
respectively acquiring detection values of voltage to ground of any one pole of a direct-current bus voltage and a direct-current bus in the power converter under different switching conditions of the disturbance resistor;
and calculating to obtain the insulation resistance value to the ground of the direct current side of the power converter according to each detection value.
Optionally, controlling the grounding relay and the inverter circuit of the power converter to operate includes:
controlling the grounding relay to be closed; and (c) a second step of,
and controlling a switch tube connected between the AC connection point of the bridge arm and the positive electrode of the DC bus and a switch tube connected between the AC connection point of the bridge arm and the negative electrode of the DC bus in the bridge arm corresponding to the grounding relay in the inverter circuit to be respectively and independently conducted.
Optionally, controlling the grounding relay and the inverter circuit of the power converter to operate includes:
controlling the grounding relay to be closed; and the number of the first and second groups,
and controlling the conduction of a switching tube connected between an alternating-current connection point of the bridge arm and the positive pole or the negative pole of the direct-current bus in the bridge arm corresponding to the grounding relay in the inverter circuit.
Optionally, for different switching conditions of the disturbance resistor, respectively obtaining detected values of voltage to ground of any one of a dc bus voltage and a dc bus in the power converter, including:
when the disturbance resistor is connected with the positive electrode of the direct current bus, respectively acquiring the voltage of the direct current bus and the detection value of the voltage to ground of any one electrode of the direct current bus; and (c) a second step of,
and when the disturbance resistor is connected to the negative electrode of the direct current bus, respectively acquiring the voltage of the direct current bus and the voltage to ground of any one electrode of the direct current bus.
Optionally, for different switching conditions of the disturbance resistor, respectively obtaining detected values of voltage to ground of any one of a dc bus voltage and a dc bus in the power converter, including:
under the condition that the disturbance resistor is cut out, respectively acquiring the voltage of the direct current bus and the voltage to ground of any pole of the direct current bus; and the number of the first and second groups,
and when the disturbance resistor is connected with the positive pole or the negative pole of the direct current bus, respectively acquiring the voltage of the direct current bus and the voltage to ground of any pole of the direct current bus.
Optionally, any pole of the dc bus is grounded, and the voltage is: and the voltage to ground of the positive electrode of the direct current bus is high.
A second aspect of the present application provides a power converter comprising: the device comprises a controller, an inverter circuit, a Y-shaped resistance bridge, a grounding relay, a disturbance resistor and a voltage detection module; wherein the content of the first and second substances,
the direct current side of the inverter circuit is used for connecting a direct current power supply, and a bus capacitor is connected between the positive electrode and the negative electrode of the inverter circuit;
the alternating current side of the inverter circuit is connected with a grid connection point through a filtering unit;
one end of the grounding relay is connected to a zero line on one side, close to the grid connection point, of the filtering unit, and the other end of the grounding relay is grounded through the disturbance resistor;
the voltage detection module is used for collecting the direct current side voltage of the inverter circuit and outputting the direct current side voltage as the direct current bus voltage to the controller; collecting the voltage to ground of any pole of the direct current bus and outputting the voltage to the controller;
the inverter circuit and the grounding relay are controlled by the controller, and the controller is configured to execute the insulation impedance detection method of the power converter according to any one of the first aspect.
Optionally, the positive electrode and the negative electrode of the dc side of the inverter circuit are grounded through a Y-type resistor bridge.
Optionally, the method further includes: set up in proper order in between filtering unit and the grid-connected point: the alternating current side relay, the alternating current EMI filtering unit and the alternating current lightning protection unit;
the alternating current side relay is controlled by the controller and is in an off state when the controller executes the insulation resistance detection method.
Optionally, the filtering unit further sequentially passes through the ac-side relay and the off-grid EMI filtering unit, and is connected to the off-grid port.
Optionally, the ac side relay includes: the inversion relay and the grid-connected relay are connected in sequence;
the connection point between the inversion relay and the grid-connected relay is connected with an off-grid port through the off-grid EMI filtering unit;
and the grid-connected relay is used for connecting a grid-connected point.
Optionally, the grounding relay includes: two relays connected in series; the series connection point is grounded through the disturbance resistor, one end of the series connection is connected to a zero line on one side, close to the grid connection point, of the filtering unit, and the other end of the series connection is connected to a protection ground wire of the off-grid EMI filtering unit.
Optionally, the inverter circuit is: an H-bridge topology, a three-level topology, a Heric topology, or an H6 topology.
Optionally, the method further includes: and one side of the DC/DC conversion circuit is connected with a direct-current power supply, and the other side of the DC/DC conversion circuit is connected with the direct-current side of the inverter circuit through a direct-current bus.
Optionally, the dc power supply is a photovoltaic string or an energy storage battery.
According to the insulation impedance detection method of the power converter, by means of a disturbance resistor between an alternating current side grounding relay of the power converter and the ground, firstly, the grounding relay and an inverter circuit of the power converter are controlled to act, connection switching of the disturbance resistor to a direct current bus in the power converter is achieved, and the impedance of at least one pole of the direct current bus to the ground is changed; when the disturbance resistors are under different switching conditions, namely when at least one pole of the direct current bus has different ground impedance, respectively acquiring the voltage of the direct current bus in the power converter and the voltage of any pole of the direct current bus to ground; then according to the detection values, calculating to obtain an insulation resistance value to ground of the direct current side of the power converter; additional relays in the prior art are not needed, and the problems of high requirement on relay type selection and high circuit cost are further avoided.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings to be used in the description of the embodiments or the prior art will be briefly introduced below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a Y-type resistive bridge provided in the prior art;
fig. 2a is a schematic structural diagram of a single-stage power converter provided in an embodiment of the present application;
FIG. 2b is a schematic diagram of another single-stage power converter provided in the embodiments of the present application;
FIG. 2c is a schematic diagram of another single-stage power converter according to an embodiment of the present disclosure;
fig. 3 is a flowchart of an insulation resistance detection method of a power converter according to an embodiment of the present application;
fig. 4a is an equivalent structure diagram of a single-stage power converter provided in an embodiment of the present application;
FIG. 4b is a schematic diagram of another equivalent structure of a single-stage power converter provided in an embodiment of the present application;
fig. 5 is a Δ equivalent circuit diagram of a single-stage power converter provided in an embodiment of the present application;
fig. 6 is a schematic structural diagram of a Y-type resistive bridge according to an embodiment of the present disclosure.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
In this application, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising a … …" does not exclude the presence of another identical element in a process, method, article, or apparatus that comprises the element.
The application provides an insulation impedance detection method of a power converter, which aims to solve the problems of high requirement on relay type selection and high circuit cost in traditional resistance bridge detection.
Referring to fig. 2a, the power converter comprises: a controller (not shown), an inverter circuit 101, a grounding relay 202, and a disturbance resistor R E And a voltage detection module (not shown); the direct current side of the inverter circuit 101 is used for connecting a direct current power supply such as a photovoltaic string or an energy storage battery, a bus capacitor is connected between the positive electrode and the negative electrode, and the positive electrode and the negative electrode of the inverter circuit can be grounded to an EARTH via a Y-shaped resistance bridge 201; the alternating current side of the inverter circuit 101 is connected with a grid connection point through a filter unit 301; one end of the grounding relay 202 is connected to the zero line of the filtering unit 301 close to the side of the grid-connected point, and the other end passes through the disturbance resistor R E Grounding; the Y-type resistive bridge 201 includes a resistor R 1 To R 3 Resistance R 1 Connected between the midpoint NET of the bridge and the positive electrode BUS + of the DC BUS, and a resistor R 2 Connected between the midpoint NET of the bridge and the negative electrode BUS of the DC BUS, and a resistor R 3 Is connected between the midpoint NET of the electric bridge and the ground; the voltage detection module is used for acquiring the direct current side voltage of the inverter circuit 101 and outputting the direct current side voltage as the direct current bus voltage to the controller; collecting the voltage to ground of any pole of the direct current bus and outputting the voltage to the controller; the inverter circuit 101 and the grounding relay 202 are controlled by a controller.
It should be noted that fig. 2a is only shown by way of example of a single-stage inverter topology, and the inverter circuit 101 may be a Heric topology (including the switch Q) shown in fig. 2b and 2c 1 To Q 6 ) In practical applications, the inverter circuit 101 may also be usedTo adopt other topologies, such as H-bridge topology, three-level topology, H6 topology, etc., but all having the most basic switching tube Q 1 、Q 2 、Q 5 And Q 6 。
Referring to fig. 3, the method for detecting insulation resistance of a power converter includes:
s101, controlling the grounding relay and an inverter circuit of the power converter to act, and achieving connection switching of the disturbance resistor to a direct current bus in the power converter.
The control of the grounding relay specifically means controlling the attraction or non-attraction of the grounding relay; the control of the inverter circuit specifically refers to controlling the on/off of each switch tube therein, for example, controlling the conduction of at least one switch tube.
Referring to fig. 2b and 2c, when the grounding relay 202 is controlled to pull in and switch the tube Q 2 When conducting, the disturbance resistor R E Is thrown into a connection direct current BUS positive electrode BUS +; when the grounding relay 202 is controlled to pull in and switch the tube Q 6 When conducting, the disturbance resistor R E Is thrown into a negative electrode BUS-connected with a direct current BUS; when the grounding relay 202 is controlled to be turned off, the disturbance resistor R E Is cut out to connect any pole of the DC bus.
Due to the disturbance resistance R E The other end of the direct current bus is grounded, so when the direct current bus is cut out and is put into any pole of the connected direct current bus, the impedance of the direct current bus corresponding pole to the ground can be changed. If the grounding relay is in the initial state of no attraction and each switching tube is in the initial state of off before the insulation impedance detection is carried out, the grounding impedance of at least one pole of the direct current bus can be changed through the control.
S102, respectively obtaining the voltage of a direct current bus in the power converter and the voltage of any pole of the direct current bus to ground for different switching conditions of the disturbance resistor.
The different switching conditions can be disturbance resistance R E The condition of being thrown into a connection with different poles of the DC bus may also refer to disturbance resistance R E The condition of being thrown into any pole of the connected DC bus and the condition of being cut out of any pole phase of the connected DC busThe case of a connection; the present invention is not limited thereto, and any method that can change the impedance of at least one pole of the dc bus to ground is within the scope of the present invention.
The direct current BUS voltage specifically refers to the voltage between a direct current BUS positive electrode BUS + and a direct current BUS negative electrode BUS-; any pole of the direct current BUS can be earthed specifically to the earth voltage of the positive pole BUS + of the direct current BUS, and can also be earthed to the earth voltage of the negative pole BUS-of the direct current BUS.
And S103, calculating the insulation resistance value to the ground on the direct current side of the power converter according to the detection values.
In step S101, the additional relay S in the prior art shown in fig. 1 is replaced by a grounding relay on the ac side of the power converter, and the disturbance resistor R in fig. 2a to 2c is used E Disturbance of any pole of the direct-current bus to the ground impedance is achieved, different detection values of corresponding voltage are obtained, and then calculation of the ground insulation impedance value is carried out through the detection values, so that an extra relay S in the prior art can be omitted.
According to the insulation resistance detection method provided by the embodiment, the insulation resistance value to the ground on the direct current side of the power converter can be calculated through the principle; an additional relay in the prior art is not needed any more, and the problems of high requirement on relay type selection and high circuit cost are further avoided.
On the basis of the above embodiment, this embodiment provides an optional implementation form of the insulation resistance detection method, and in step S101, the controlling the actions of the grounding relay and the inverter circuit of the power converter may specifically include: controlling the grounding relay (202 shown in fig. 2 a) to pull in; and controlling a switching tube (Q shown in figures 2b and 2 c) connected between an AC connection point (NET shown in figure 2 a) of the bridge arm and the positive electrode of the DC bus in the bridge arm corresponding to the grounding relay in the inverter circuit 2 ) And, a switching tube (Q shown in FIG. 2b and FIG. 2 c) connected between the AC connection point of the bridge arm and the negative pole of the DC bus 6 ) And are respectively and independently conducted.
And step S102, for different switching conditions of the disturbance resistor, respectively obtaining detection values of the voltage to ground of any one pole of the dc bus voltage and the dc bus voltage in the power converter, specifically including: under the condition that the disturbance resistor is put into the positive pole of the connecting direct current bus, respectively acquiring the voltage of the direct current bus and the voltage to ground of any pole of the direct current bus; and acquiring the voltage to ground detection values of the direct current bus voltage and any one pole of the direct current bus under the condition that the disturbance resistor is put into the negative pole of the direct current bus.
An exemplary description of the specific process of the insulation resistance detection method is provided in conjunction with fig. 2c as follows:
firstly, the grounding relay 202 is not attracted, and the voltage V to ground of any pole of the direct current BUS, such as the positive electrode BUS +, is detected 0 And DC bus voltage V bus 。
Then controlling the grounding relay 202 to suck and simultaneously controlling the switch tube Q 2 Conducting to make the disturbance resistor R E The voltage to earth voltage V of the DC BUS positive electrode BUS + is detected 1 And DC bus voltage V bus1 。
The earth relay 202 is controlled again to maintain the pull-in state and simultaneously control the switch tube Q 2 Turn-off and switch tube Q 6 Conducting to make the disturbance resistor R E The voltage V to earth of the positive pole BUS + of the direct current BUS is detected by connecting the negative pole BUS-of the direct current BUS and the earth 2 And DC bus voltage V bus2 。
Taking a direct current power supply as an example of a photovoltaic group string PV, the ground insulation resistance of a direct current side positive electrode PV + of the power converter is R +, the ground insulation resistance of a direct current side negative electrode PV-is R-, and a disturbance resistor R is recorded E The part of the equivalent structure that is put into connection with the positive BUS BUS + of the DC BUS perturbs the resistance R, as shown in FIG. 4a, in the state when the switch is closed E The partial equivalent structure that is thrown into the time of connection to the dc BUS negative BUS-is the state when the switch is closed as shown in fig. 4 b; in fig. 4a and 4b, rm is the equivalent impedance to ground of the dc-side positive electrode PV + of the power converter, rn is the equivalent impedance to ground of the dc-side negative electrode PV-, and both are mainly caused by the sampling resistor in the corresponding sampling circuit in the power converter; k1 is a disturbance resistor R arranged in the grounding relay 202 E And the filter unit 301, vpv is the dc side voltage of the power converter.
FIG. 5 shows the corresponding Δ equivalent circuit, where R 4 Is the direct current BUS positive BUS + equivalent resistance to ground, R when the grounding relay 202 is disconnected 5 Is the direct current BUS negative electrode BUS-earth equivalent resistance when the grounding relay 202 is disconnected; when the grounding relay 202 is closed and the switch tube Q2 is conducted, i.e. the disturbance resistor R E When the DC BUS is thrown into the DC BUS positive electrode BUS +, the DC BUS positive electrode BUS + equivalent resistance to ground is changed into R 7 And the DC BUS negative electrode BUS-to-ground equivalent resistance is still R 5 (ii) a When the grounding relay 202 is closed and the switch tube Q6 is conducted, i.e. the disturbance resistor R E When the direct current BUS is thrown into the negative electrode BUS-connected, the direct current BUS positive electrode BUS + equivalent resistance to the ground is still R 4 And the DC BUS negative electrode BUS-to-ground equivalent resistance is changed into R 8 。
In three cases before the grounding relay 202 is closed, after the grounding relay 202 is closed and the switch tube Q2 is turned on, and after the grounding relay 202 is closed and the switch tube Q6 is turned on, equations of the equations (1), (2) and (3) can be obtained according to the KCL law:
equations (3) - (2), simplified theoretical value R of insulation resistance detection to ground calculated by single-switch Y-type bridge detection circuit iso The calculation formula is as follows:
wherein, the first and the second end of the pipe are connected with each other,
it can be seen from the equations (2) and (3) that the change of the ratio of the upper impedance to the lower impedance can be increased by switching the upper and lower impedance channels, so that the voltage difference value is increased twice to improve the detection accuracy.
Therefore, the embodiment does not need an extra insulation resistance relay in the prior art, and the resistance access path can be switched by switching on and off the switch tube in the inverter circuit, so that the detection precision is improved.
In practice, the insulation resistance detection method may be used to detect the voltage and calculate the insulation resistance to ground detection value by using both the case where the disturbance resistor is cut out and the case where the disturbance resistor is put into any one of the poles of the connection dc bus.
In this case, in step S101, the controlling of the operation of the grounding relay and the inverter circuit of the power converter specifically includes: controlling the grounding relay to be closed; and controlling the conduction of a switching tube connected between an alternating current connecting point of the bridge arm and the positive pole or the negative pole of the direct current bus in the bridge arm corresponding to the grounding relay in the inverter circuit.
And step S102, for different switching conditions of the disturbance resistor, respectively obtaining detection values of the voltage to ground of any one pole of the dc bus voltage and the dc bus voltage in the power converter, specifically including: under the condition that the disturbance resistor is cut out, respectively acquiring the voltage of the direct current bus and the voltage to ground of any pole of the direct current bus; and when the disturbance resistor is put into the positive electrode or the negative electrode of the direct current bus, respectively acquiring the voltage of the direct current bus and the detection value of the voltage to ground of any one electrode of the direct current bus.
At this time, the theoretical value R of the insulation resistance to ground detection is calculated iso The expressions (3) - (2) in the previous embodiment are no longer adopted, but the expressions (3) - (1) or the expressions (2) - (1) are adopted, depending on which pole the disturbance resistor is put into the connection dc bus, and the invention is not limited herein, and all of the expressions are adopted in the present applicationAnd (4) within the protection range.
Another embodiment of the present application provides a power converter, as shown in fig. 2a, including: a controller (not shown), an inverter circuit 101, a grounding relay 202 and a disturbance resistor R E And a voltage detection module (not shown); wherein:
the dc side of the inverter circuit 101 is used to connect a dc power supply such as a photovoltaic string or an energy storage battery, and a bus capacitor is connected between the positive and negative electrodes, and the positive and negative electrodes may be grounded to the EARTH ground through the Y-type resistance bridge 201.
The ac side of the inverter circuit 101 is connected to a grid connection point via a filter unit 301.
It should be noted that fig. 2a only shows a single-stage inverter topology, and the inverter circuit 101 may be a Heric topology (including the switching tubes Q1 to Q6) shown in fig. 2b and 2c, in practical applications, the inverter circuit 101 may also adopt other topologies, such as an H-bridge topology, a three-level topology, an H6 topology, and the like, but all have the most basic switching tubes Q1, Q2, Q5, and Q6.
One end of the grounding relay 202 is connected to the zero line of the filtering unit 301 close to the side of the grid-connected point, and the other end passes through the disturbance resistor R E And (4) grounding.
The Y-type resistive bridge 201 includes a resistor R 1 To R 3 Resistance R 1 Connected between the midpoint NET of the electric bridge and the positive electrode BUS + of the DC BUS, and a resistor R 2 Connected between the midpoint NET of the bridge and the negative electrode BUS of the DC BUS, and a resistor R 3 Is connected between the bridge midpoint NET and the ground. And each resistor R 1 To R 3 Can be respectively realized by a plurality of resistors in series-parallel connection (as shown in fig. 6), and in practical application, the resistor R 1 And R 2 Can be 3M omega, R 3 The resistance of (c) may be 1.5M Ω, but is not limited thereto, depending on the specific application environment.
In practical applications, as shown in fig. 2b, the power converter may further include: set up in proper order between filtering unit 301 and the grid-connected point: an ac-side relay 302, an ac EMI (Electromagnetic Interference) filtering unit 304, and an ac lightning protection unit 305. At this time, the power converter may function as a photovoltaic inverter.
Alternatively, the filtering unit 301 may also be connected to the off-grid port (e.g. EPS shown in fig. 2 c) via an ac-side relay and an off-grid EMI filtering unit (e.g. EPSEMIs filtering unit shown in fig. 2 c) 306 in sequence. At this time, as shown in fig. 2c, the grounding relay 202 may specifically include: two relays connected in series; the series connection point of the two is connected with the ground through a disturbance resistor R E And one end of the filtering unit 301, which is connected in series, is connected to the zero line on the side close to the grid-connected point, and the other end of the filtering unit, which is connected in series, is connected to the protective ground wire of the off-grid EMI filtering unit 306. In this case, the power converter may act as an energy storage converter. Moreover, in order to realize grid-connected and off-grid connection at the same time, the ac-side relay at this time may include an inverter relay 302 and a grid-connected relay 303 shown in fig. 2 c; the two are connected in sequence, and the connection point between the two is connected with an off-grid port through an off-grid EMI filtering unit 306; the other side of the grid-connected relay 303 is used for connecting a grid-connected point.
In practical applications, the power converter is not limited to the single-stage topology shown in fig. 2a to 2c, but may also be a two-stage topology, that is, at least one DC/DC conversion circuit is further disposed at a front stage of the inverter circuit 101, one side of the DC/DC conversion circuit is connected to a corresponding DC power source, the other side of the DC/DC conversion circuit is connected to a DC side of the inverter circuit 101, and the DC/DC conversion circuit is also controlled by the controller.
The voltage detection module is used for collecting the direct current side voltage of the inverter circuit 101 and outputting the direct current side voltage as the direct current bus voltage to the controller; collecting the voltage to ground of any pole (shown by taking a positive pole as an example in fig. 2a to 2 c) of the direct current bus and outputting the voltage to the controller; the inverter circuit 101 and the relays are controlled by a controller.
The inverter circuit and each relay are controlled by the controller; the controller, which may be an internal DSP (digital signal processor), is configured to execute the insulation impedance detection method of the power converter according to any of the embodiments; the specific process and principle of the insulation resistance detection method may be referred to the above embodiments, and are not described in detail herein.
It should be noted that the ac-side relay 302 in fig. 2b, and the inverter relay 302 and the grid-connected relay 303 in fig. 2c are controlled by the controller, and are in an off state when the controller executes the insulation resistance detection method; that is, the controller only needs to control the inverter circuit 101 and the grounding relay 202 to operate, and the insulation impedance detection method can be realized.
In practical application, the power converter can be a photovoltaic inverter, an energy storage converter or a light storage converter, and the power converter can be determined according to specific application environment; the grounding relay is used for realizing the switching of the resistance bridge to the ground impedance, so that an additional relay can be omitted, and the circuit cost is reduced. Moreover, different access modes of impedance can be realized through switching of the switching tube in the inverter circuit, so that the detection precision can be improved. In addition, because the disturbance resistor is connected with the grounding relay, when the insulation impedance detection is not needed, the disturbance resistor is separated by the grounding relay, no current leakage exists, and no safety regulation problem exists, so that a resistor with a small resistance value can be selected, and the detection precision is further improved.
The same and similar parts among the various embodiments in the present specification are referred to each other, and each embodiment focuses on differences from other embodiments. In particular, the system or system embodiments are substantially similar to the method embodiments and therefore are described in a relatively simple manner, and reference may be made to some of the descriptions of the method embodiments for related points. The above-described system and system embodiments are only illustrative, wherein the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the technical solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
In the above description of the disclosed embodiments, the features described in the embodiments in this specification may be replaced or combined with each other to enable those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended 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 (15)
1. The insulation impedance detection method of the power converter is characterized in that a grounding relay on the alternating current side of the power converter is grounded through a disturbance resistor; the insulation resistance detection method comprises the following steps:
controlling the grounding relay and an inverter circuit of the power converter to act, and realizing the connection switching of the disturbance resistor to a direct current bus in the power converter;
for different switching conditions of the disturbance resistor, respectively acquiring detection values of voltage of a direct current bus in the power converter and voltage to ground of any pole of the direct current bus;
and calculating the insulation resistance value to the ground of the direct current side of the power converter according to the detection values.
2. The method of claim 1, wherein controlling the grounding relay and the inverter circuit of the power converter to operate comprises:
controlling the grounding relay to be closed; and the number of the first and second groups,
and controlling a switch tube connected between the AC connection point of the bridge arm and the positive electrode of the DC bus and a switch tube connected between the AC connection point of the bridge arm and the negative electrode of the DC bus in the bridge arm corresponding to the grounding relay in the inverter circuit to be respectively and independently conducted.
3. The method of claim 1, wherein controlling the grounding relay and the inverter circuit of the power converter to operate comprises:
controlling the grounding relay to be closed; and (c) a second step of,
and controlling the conduction of a switching tube connected between an alternating-current connection point of the bridge arm and the positive pole or the negative pole of the direct-current bus in the bridge arm corresponding to the grounding relay in the inverter circuit.
4. The method for detecting the insulation impedance of the power converter according to claim 1, wherein the step of respectively obtaining the detected values of the voltage of any one pole of the direct-current bus and the voltage of any pole of the direct-current bus in the power converter to the ground for different switching conditions of the disturbance resistor comprises:
when the disturbance resistor is connected with the positive electrode of the direct current bus, respectively acquiring the voltage of the direct current bus and the detection value of the voltage to ground of any one electrode of the direct current bus; and the number of the first and second groups,
and when the disturbance resistor is connected to the negative electrode of the direct current bus, respectively acquiring the voltage of the direct current bus and the voltage to ground of any one electrode of the direct current bus.
5. The method for detecting the insulation impedance of the power converter according to claim 1, wherein the step of respectively obtaining the detected values of the voltage of any one pole of the direct-current bus and the voltage of any pole of the direct-current bus in the power converter to the ground for different switching conditions of the disturbance resistor comprises:
under the condition that the disturbance resistor is cut out, respectively acquiring the voltage of the direct current bus and the voltage to ground of any pole of the direct current bus; and the number of the first and second groups,
and when the disturbance resistor is connected with the positive pole or the negative pole of the direct current bus, respectively acquiring the voltage of the direct current bus and the voltage to ground of any pole of the direct current bus.
6. The insulation resistance detection method of the power converter according to any one of claims 1 to 5, wherein any one pole of the DC bus is connected to the ground voltage: and the voltage to ground of the positive electrode of the direct current bus.
7. A power converter, comprising: the device comprises a controller, an inverter circuit, a grounding relay, a disturbance resistor and a voltage detection module; wherein the content of the first and second substances,
the direct current side of the inverter circuit is used for connecting a direct current power supply, and a bus capacitor is connected between the positive electrode and the negative electrode of the inverter circuit;
the alternating current side of the inverter circuit is connected with a grid connection point through a filtering unit;
one end of the grounding relay is connected to a zero line on one side, close to the grid connection point, of the filtering unit, and the other end of the grounding relay is grounded through the disturbance resistor;
the voltage detection module is used for collecting the direct current side voltage of the inverter circuit and outputting the direct current side voltage as the direct current bus voltage to the controller; collecting the voltage to ground of any pole of the direct current bus and outputting the voltage to the controller;
the inverter circuit and the grounding relay are controlled by the controller, and the controller is used for executing the insulation impedance detection method of the power converter according to any one of claims 1 to 6.
8. The power converter according to claim 7, wherein the positive and negative poles of the inverter circuit on the dc side are electrically bridged by a Y-resistor.
9. The power converter of claim 7, further comprising: set up in proper order between filtering unit and the grid-connected point: the alternating current side relay, the alternating current EMI filtering unit and the alternating current lightning protection unit;
the alternating current side relay is controlled by the controller and is in an off state when the controller executes the insulation resistance detection method.
10. The power converter of claim 7, wherein the filter unit is further connected to an off-grid port via an ac-side relay and an off-grid EMI filter unit in sequence.
11. The power converter of claim 10, wherein the ac-side relay comprises: the inverter relay and the grid-connected relay are connected in sequence;
the connection point between the inversion relay and the grid-connected relay is connected with an off-grid port through the off-grid EMI filtering unit;
and the grid-connected relay is used for connecting a grid-connected point.
12. The power converter of claim 10, wherein the grounding relay comprises: two relays connected in series; the series connection point is grounded through the disturbance resistor, one end of the series connection is connected to the zero line of one side, close to the grid connection point, of the filtering unit, and the other end of the series connection is connected to the protection ground wire of the off-grid EMI filtering unit.
13. The power converter of claim 7, wherein the inverter circuit is: an H-bridge topology, a three-level topology, a Heric topology, or an H6 topology.
14. A power converter according to any of claims 7 to 13, further comprising: and one side of the DC/DC conversion circuit is connected with a direct-current power supply, and the other side of the DC/DC conversion circuit is connected with the direct-current side of the inverter circuit through a direct-current bus.
15. A power converter as claimed in any one of claims 7 to 13, wherein the dc power source is a photovoltaic string or an energy storage cell.
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| CN202211648478.6A CN115980448A (en) | 2022-12-21 | 2022-12-21 | Power converter and insulation impedance detection method thereof |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117538713A (en) * | 2024-01-10 | 2024-02-09 | 京清数电(北京)技术有限公司 | Energy storage converter, insulation detection circuit, detection method, detection device and medium thereof |
| CN117872194A (en) * | 2024-03-11 | 2024-04-12 | 西安奇点能源股份有限公司 | Detection method for insulation resistance, fault battery pack and short-circuit battery pack in energy storage system based on H bridge |
| CN117872194B (en) * | 2024-03-11 | 2024-05-14 | 西安奇点能源股份有限公司 | Detection method for insulation resistance, fault battery pack and short-circuit battery pack in energy storage system based on H bridge |
-
2022
- 2022-12-21 CN CN202211648478.6A patent/CN115980448A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117538713A (en) * | 2024-01-10 | 2024-02-09 | 京清数电(北京)技术有限公司 | Energy storage converter, insulation detection circuit, detection method, detection device and medium thereof |
| CN117872194A (en) * | 2024-03-11 | 2024-04-12 | 西安奇点能源股份有限公司 | Detection method for insulation resistance, fault battery pack and short-circuit battery pack in energy storage system based on H bridge |
| CN117872194B (en) * | 2024-03-11 | 2024-05-14 | 西安奇点能源股份有限公司 | Detection method for insulation resistance, fault battery pack and short-circuit battery pack in energy storage system based on H bridge |
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