CN112379171A - Direct-current ground insulation impedance detection circuit and method for bridge arm topology converter - Google Patents
Direct-current ground insulation impedance detection circuit and method for bridge arm topology converter Download PDFInfo
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- CN112379171A CN112379171A CN202011339760.7A CN202011339760A CN112379171A CN 112379171 A CN112379171 A CN 112379171A CN 202011339760 A CN202011339760 A CN 202011339760A CN 112379171 A CN112379171 A CN 112379171A
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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Abstract
The invention relates to the technical field of power supplies, in particular to a direct current to ground insulation impedance detection circuit and a direct current to ground insulation impedance detection method for a bridge arm topology converter, and the direct current to ground insulation impedance detection circuit comprises a controller and a direct current to ground insulation impedance detection assembly, wherein the direct current to ground insulation impedance detection circuit assembly comprises: the direct current side insulation resistance consists of a direct current side power supply, a direct current BUS positive electrode BUS + resistance Rp to the earth/machine shell PE, a direct current BUS negative electrode BUS-resistance Rn to the earth/machine shell PE, a relay S0 and a resistor R0; one end of the ground/casing PE is connected with a direct-current side insulation impedance, the other end of the ground/casing PE is connected with the middle point of one bridge arm of the existing power topology of the DC/AC converter through a series circuit of a relay S0 and a resistor R0, and the controller changes the voltage on the resistor R0 and detects the voltage on the resistor R0 by controlling the on and off of a power switch tube on the upper part of the bridge arm and a power switch tube on the lower part of the bridge arm. The invention utilizes one of the existing power topology bridge arms of the DC/AC converter, only needs one relay, and has simple circuit and lower cost.
Description
Technical Field
The invention relates to the technical field of power supplies, in particular to a direct current to ground insulation impedance detection circuit and a direct current to ground insulation impedance detection method for a current transformer with a bridge arm topology.
Background
The converter is used as a common electrical appliance, can change the voltage, frequency, phase number and other electric quantities or characteristics of a power supply system, and is widely applied. According to the practical application occasions, an alternating current power supply needs to be changed into a direct current power supply in some occasions, and the direct current power supply is defined as a rectifying circuit; in other cases, the dc power needs to be changed into ac power, and the inverter circuit is defined corresponding to the reverse process of rectification. Under certain conditions, a set of thyristor circuit can be used as both a rectifying circuit and an inverter circuit, and the device is called a converter.
Converter classes include rectifiers (AC to DC < AC/DC >), inverters (DC to AC < DC/AC >), AC converters (AC frequency converter < AC/AC >) and DC converters (DC Chopper < DC Chopper >). For a non-isolated grid-connected DC/AC converter, such as a photovoltaic grid-connected inverter, if the DC-to-ground insulation impedance is too low, it may cause personnel injury or equipment damage, so it is necessary to detect the DC-to-ground insulation impedance before grid-connected operation.
A scheme for detecting dc insulation resistance generally used in the prior art, as shown in fig. 1, a schematic diagram of dc side insulation resistance in a dashed line frame includes a dc side power supply, a dc BUS positive electrode (BUS +) resistance Rp to the ground/casing (PE), and a dc BUS negative electrode (BUS-) resistance Rn to the ground/casing (PE). And solving Rp and Rn through relaying. This technique requires two relays and other auxiliary circuits, and is costly.
Disclosure of Invention
The invention provides a direct current to ground insulation impedance detection circuit and a direct current to ground insulation impedance detection method suitable for a current transformer with a bridge arm topology, and aims to solve the problem that the existing direct current insulation impedance detection cost is too high.
In order to achieve the above object, a first aspect of the present invention provides a DC-to-ground insulation resistance detection circuit suitable for a converter with a bridge arm topology, comprising a controller, a DC/AC converter, a DC-to-ground insulation resistance detection assembly,
the power topology of the DC/AC converter has a bridge arm characteristic topology and is provided with a bridge arm upper power switch tube group and a bridge arm lower power switch tube group;
the DC-to-ground insulation resistance detection circuit assembly comprises: the direct current side insulation resistance consists of a direct current side power supply, a direct current BUS positive electrode BUS + resistance Rp to the earth/machine shell PE, a direct current BUS negative electrode BUS-resistance Rn to the earth/machine shell PE, a relay S0 and a resistor R0;
one end of the ground/casing PE is connected with a direct-current side insulation impedance, the other end of the ground/casing PE is connected with the middle point of one bridge arm of the existing power topology of the DC/AC converter through a series circuit of a relay S0 and a resistor R0, and the controller changes the voltage on the resistor R0 and detects the voltage on the resistor R0 by controlling the on and off of a power switch tube on the upper part of the bridge arm and a power switch tube on the lower part of the bridge arm.
Preferably, relay S0 and resistor R0 may be switched in position.
Preferably, the topology with the bridge arm feature is suitable for DC/AC topology, including but not limited to single-phase H4 full bridge, H5 topology, H6 topology, Heric topology, three-phase NPC topology, multi-level topology, and the like.
Preferably, the bridge arm upper power switch tube group comprises a first switch tube Q1; the bridge arm lower power switch tube group comprises a second switch tube Q2.
Preferably, the bridge arm upper power switch tube group comprises a first switch tube Q1 and a second switch tube Qn which are connected in series; the power switch tube group at the lower part of the bridge arm comprises a third switch tube Qk and a fourth switch tube Qt which are connected in series.
Preferably, for three-level or multi-level topologies, relay S0 and one end of resistor R0 may be connected at any point in the middle of the bridge arm.
In order to achieve the above object, another aspect of the present invention provides a dc-to-ground insulation resistance detection method suitable for a converter with a bridge arm topology, which is applied to the insulation resistance detection circuit according to any one of claims 1 to 6, and the embodiments are as follows:
s1, controlling a closing relay S0 by a controller, closing a switching tube Q1 at the upper part of a bridge arm, and measuring the voltage on a resistor R0, wherein the voltage is recorded as Viso 1; the equation (i) is obtained
Viso1＝Vbus*(Rp//R0)/[(Rp//R0)+Rn] ①
S2, controlling a closing relay S0 by a controller, closing a switching tube Q2 at the lower part of a bridge arm, and measuring the voltage on a resistor R0, wherein the voltage is recorded as Viso 2; obtain equation 2
Viso2＝Vbus*(Rn//R0)/[(Rn//R0)+Rp] ②
S3, simultaneous equation (r), calculates the insulation resistance as:
Rp＝R0(Vbus-Viso1-Viso2)/Viso2 ③
Rn＝R0(Vbus-Viso1-Viso2)/Viso1 ④
the invention has the following beneficial effects:
the invention relates to a low-cost direct-current insulation impedance detection scheme which is suitable for all topologies with bridge arm characteristics in DC/AC topologies, including but not limited to single-phase H4 full-bridge, H5 topology, H6 topology, Heric topology, three-phase NPC topology, multi-level topology and the like. The invention utilizes one of the existing power topology bridge arms of the DC/AC converter, only needs one relay, and has simple circuit and lower cost. The key point of the invention is to utilize the power switch tube originally existing in the DC/AC converter, save the use of the relay, simplify the circuit structure and effectively reduce the manufacturing cost.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
Fig. 1 is a schematic diagram of an insulation resistance detection circuit provided in the prior art;
fig. 2 is a first structural schematic diagram of a dc-to-ground insulation resistance detection circuit suitable for a converter with a bridge arm topology provided in an embodiment of the present application.
Fig. 3 is a schematic structural diagram of a dc-to-ground insulation resistance detection circuit suitable for a converter with a bridge arm topology according to an embodiment of the present application.
Fig. 4 is a schematic flowchart of a dc-to-ground insulation resistance detection process applicable to a converter with a bridge arm topology according to an embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The terms "first," "second," "third," "fourth," and the like in the description and in the claims of the present application and in the above-described drawings (if any) are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions.
The technical solution of the present application will be described in detail below with specific examples. The following several specific embodiments may be combined with each other, and details of the same or similar concepts or processes may not be repeated in some embodiments.
The direct current to ground insulation impedance detection circuit and method suitable for the converter with the bridge arm topology are used for detecting whether the direct current input end of the inverter is short-circuited to ground or low in impedance. The insulation resistance detection circuit can prevent the direct current input end of the inverter from being short-circuited to the ground or low-resistance before the inverter is connected to the grid and when the shell is not connected to the ground, so that grid connection insulation failure is prevented. The insulation impedance detection circuit can be applied to a solar cell panel grid-connected system and can also be applied to other systems for converting direct current into alternating current and converting alternating current into direct current.
In the embodiment of the application, a relay switch of a relay in an inverter circuit is connected in parallel with an impedor, the change of a measured value between a direct current input end of an inverter and a grounding point is detected by switching the switching state of the relay switch of the relay, and if the direct current input end of the inverter and the grounding point are short-circuited to the ground or have low impedance, the change of the measured value is small or has no change, so that whether the direct current input end of the inverter is short-circuited to the ground or has low impedance is determined.
Example one
As shown in fig. 2, a first structural schematic diagram of a DC-to-ground insulation impedance detection circuit suitable for a converter with a bridge arm topology provided in this embodiment includes a controller, a DC/AC converter, and a DC-to-ground insulation impedance detection assembly, where the power topology of the DC/AC converter has a bridge arm characteristic topology, and is provided with a bridge arm upper power switch Q1 and a bridge arm lower power switch Q2; the DC-to-ground insulation resistance detection circuit assembly comprises: the direct current side insulation resistance consists of a direct current side power supply, a direct current BUS positive electrode BUS + resistance Rp to the earth/machine shell PE, a direct current BUS negative electrode BUS-resistance Rn to the earth/machine shell PE, a relay S0 and a resistor R0; one end of the ground/casing PE is connected with a direct-current side insulation impedance, the other end of the ground/casing PE is connected with the middle point of one bridge arm of the existing power topology of the DC/AC converter through a series circuit of a relay S0 and a resistor R0, and the controller changes the voltage on the resistor R0 and detects the voltage on the resistor R0 by controlling the on and off of a power switch tube on the upper part of the bridge arm and a power switch tube on the lower part of the bridge arm.
Specifically, one end of an impedance Rp is electrically connected with a positive electrode BUS + of a direct current BUS, one end of a tap is connected to one end of a power switch tube Q1 at the upper part of a bridge arm, the other end of the impedance Rp is electrically connected with a ground/casing PE, the ground/casing PE is connected with the other end of a power switch tube Q1 at the upper part of the bridge arm through a series circuit of a relay S0 and a resistor R0, one end of an impedance Rn is electrically connected with a negative electrode BUS-of the direct current BUS, one end of the tap is connected to one end of a power switch tube Q2 at the lower part of the bridge arm, the other end of the tap is electrically connected with the ground/casing PE, and the.
Of course, in the above connection, the relay S0 and the resistor R0 may be switched.
As shown in fig. 4, a method for detecting dc-to-ground insulation impedance of a converter with a bridge arm topology includes the following specific embodiments:
s1, controlling a closing relay S0 by a controller, closing a switching tube Q1 at the upper part of a bridge arm, and measuring the voltage on a resistor R0, wherein the voltage is recorded as Viso 1; the equation (i) is obtained
Viso1＝Vbus*(Rp//R0)/[(Rp//R0)+Rn] ①
Wherein, Viso1 is resistance R0 voltage, Vbus is direct current power voltage, Rp is direct current BUS positive electrode BUS + to earth/casing PE impedance, R0 is resistance, Rn is direct current BUS negative electrode BUS-to earth/casing PE impedance
S2, the controller controls the closed relay S0, the closed switch tube Q2 at the lower part of the bridge arm, the voltage on the resistor R0 is measured and recorded as Viso2, and an equation is obtained
Viso2＝Vbus*(Rn//R0)/[(Rn//R0)+Rp] ②
Wherein Viso2 is resistance R0 voltage, Vbus is direct current power supply voltage, Rp is direct current BUS positive electrode BUS + earth/casing PE impedance, R0 is resistance, and Rn is direct current BUS negative electrode BUS-earth/casing PE impedance;
s3, simultaneous equation (r), calculates the insulation resistance as:
Rp＝R0(Vbus-Viso1-Viso2)/Viso2 ③
wherein Viso1 is resistance R0 voltage, Vbus is direct current power supply voltage, Rp is direct current BUS positive electrode BUS + earth/casing PE impedance, R0 is resistance, and Rn is direct current BUS negative electrode BUS-earth/casing PE impedance;
Rn＝R0(Vbus-Viso1-Viso2)/Viso1 ④
wherein, Viso1, Viso2 are resistance R0 voltage, Vbus is direct current power voltage, Rp is direct current BUS positive electrode BUS + earth/machine shell PE impedance, R0 is resistance, Rn is direct current BUS negative electrode BUS-earth/machine shell PE impedance.
Example two
As shown in fig. 3, relay S0 and one end of resistor R0 may be connected at any point in the middle of the bridge arm, preferably for three-level or multi-level topologies. The power switch tube group on the upper part of the bridge arm comprises a first switch tube Q1 and a second switch tube Qn which are connected in series; the power switch tube group at the lower part of the bridge arm comprises a third switch tube Qk and a fourth switch tube Qt which are connected in series.
Regardless of the first embodiment or the second embodiment, the topology with the bridge arm feature is applicable to the DC/AC topology, including but not limited to a single-phase H4 full bridge, H5 topology, H6 topology, Heric topology, three-phase NPC topology, multi-level topology, and the like of a photovoltaic inverter.
Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present application.
Claims (8)
1. A direct current to ground insulation impedance detection circuit for a bridge arm topology converter comprises a controller, a DC/AC converter and a direct current to ground insulation impedance detection assembly, and is characterized in that the power topology of the DC/AC converter has a bridge arm characteristic topology and is provided with a bridge arm upper power switch tube group and a bridge arm lower power switch tube group;
the DC-to-ground insulation resistance detection circuit assembly comprises: the direct current side insulation resistance consists of a direct current side power supply, a direct current BUS positive electrode BUS + resistance Rp to the earth/machine shell PE, a direct current BUS negative electrode BUS-resistance Rn to the earth/machine shell PE, a relay S0 and a resistor R0;
one end of the ground/casing PE is connected with a direct-current side insulation impedance, the other end of the ground/casing PE is connected with the middle point of one bridge arm of the existing power topology of the DC/AC converter through a series circuit of a relay S0 and a resistor R0, and the controller changes the voltage on the resistor R0 and detects the voltage on the resistor R0 by controlling the on and off of the power switch tube group at the upper part of the bridge arm and the power switch tube group at the lower part of the bridge arm.
2. The direct current-to-ground insulation resistance detection circuit for the bridge arm topology converter is characterized in that a relay S0 and a resistor R0 can exchange positions.
3. The direct current-to-ground insulation resistance detection circuit for the bridge arm topology converter is characterized in that the direct current-to-ground insulation resistance detection circuit is suitable for the DC/AC topology with the bridge arm characteristics, and the direct current-to-ground insulation resistance detection circuit is suitable for the DC/AC topology and comprises but not limited to a single-phase H4 full bridge, an H5 topology, an H6 topology, a Heric topology, a three-phase NPC topology, a multi-level topology and the like.
4. The direct-current-to-ground insulation impedance detection circuit for the bridge arm topology converter is characterized in that the bridge arm upper power switch tube group comprises a first switch tube Q1; the bridge arm lower power switch tube group comprises a second switch tube Q2.
5. The direct-current to ground insulation impedance detection circuit for the bridge arm topology converter is characterized in that the bridge arm upper power switch tube group comprises a first switch tube Q1 and a second switch tube Qn which are connected in series; the power switch tube group at the lower part of the bridge arm comprises a third switch tube Qk and a fourth switch tube Qt which are connected in series.
6. The direct current-to-ground insulation resistance detection circuit for the bridge arm topology converter is characterized in that one end of a relay S0 and one end of a resistor R0 can be connected to any point in the middle of a bridge arm when the direct current-to-ground insulation resistance detection circuit is used for a three-level topology or a multi-level topology.
7. The direct current-to-ground insulation resistance detection circuit for the bridge arm topology converter is characterized in that the direct current side insulation resistance comprises a direct current side power supply, a direct current BUS positive electrode BUS + earth/casing PE resistance Rp, a direct current BUS negative electrode BUS-earth/casing PE resistance Rn, one end of the resistance Rp is electrically connected with the direct current BUS positive electrode BUS +, the other end of the resistance Rp is electrically connected with the earth/casing PE, one end of the resistance Rn is electrically connected with the direct current BUS negative electrode BUS, and the other end of the resistance Rn is electrically connected with the earth/casing PE.
8. A direct current-to-ground insulation resistance detection method for a bridge arm topology converter is applied to an insulation resistance detection circuit as claimed in any one of claims 1 to 7, and the specific implementation mode is as follows:
s1, controlling a closing relay S0 by a controller, closing a switching tube Q1 at the upper part of a bridge arm, and measuring the voltage on a resistor R0, wherein the voltage is recorded as Viso 1; the equation (i) is obtained
Viso1＝Vbus*(Rp//R0)/[(Rp//R0)+Rn] ①
Wherein, Viso1 is resistance R0 voltage, Vbus is direct current power voltage, Rp is direct current BUS positive electrode BUS + to earth/casing PE impedance, R0 is resistance, Rn is direct current BUS negative electrode BUS-to earth/casing PE impedance
S2, the controller controls the closed relay S0, the closed switch tube Q2 at the lower part of the bridge arm, the voltage on the resistor R0 is measured and recorded as Viso2, and an equation is obtained
Viso2＝Vbus*(Rn//R0)/[(Rn//R0)+Rp] ②
Wherein Viso2 is resistance R0 voltage, Vbus is direct current power supply voltage, Rp is direct current BUS positive electrode BUS + earth/casing PE impedance, R0 is resistance, and Rn is direct current BUS negative electrode BUS-earth/casing PE impedance;
s3, simultaneous equation (r), calculates the insulation resistance as:
Rp＝R0(Vbus-Viso1-Viso2)/Viso2 ③
wherein Viso1 is resistance R0 voltage, Vbus is direct current power supply voltage, Rp is direct current BUS positive electrode BUS + earth/casing PE impedance, R0 is resistance, and Rn is direct current BUS negative electrode BUS-earth/casing PE impedance;
Rn＝R0(Vbus-Viso1-Viso2)/Viso1 ④
wherein, Viso1, Viso2 are resistance R0 voltage, Vbus is direct current power voltage, Rp is direct current BUS positive electrode BUS + earth/machine shell PE impedance, R0 is resistance, Rn is direct current BUS negative electrode BUS-earth/machine shell PE impedance.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011339760.7A CN112379171A (en) | 2020-11-25 | 2020-11-25 | Direct-current ground insulation impedance detection circuit and method for bridge arm topology converter |
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| CN202011339760.7A CN112379171A (en) | 2020-11-25 | 2020-11-25 | Direct-current ground insulation impedance detection circuit and method for bridge arm topology converter |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113777514A (en) * | 2021-09-24 | 2021-12-10 | 重庆电哥科技(集团)有限公司 | Insulation detection circuit, system and method for backup energy storage system |
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- 2020-11-25 CN CN202011339760.7A patent/CN112379171A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113777514A (en) * | 2021-09-24 | 2021-12-10 | 重庆电哥科技(集团)有限公司 | Insulation detection circuit, system and method for backup energy storage system |
| CN113777514B (en) * | 2021-09-24 | 2023-06-16 | 重庆电哥科技(集团)有限公司 | Insulation detection circuit, system and method of back-up energy storage system |
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