CN214750547U

CN214750547U - Direct current-to-ground insulation impedance detection circuit for variable bus voltage

Info

Publication number: CN214750547U
Application number: CN202022769701.5U
Authority: CN
Inventors: 廖细文; 王祥; 顾月明; 张杜; 吴煜; 钱敏华
Original assignee: Jiangsu Weiheng Intelligent Technology Co ltd
Current assignee: Jiangsu Weiheng Intelligent Technology Co ltd
Priority date: 2020-11-25
Filing date: 2020-11-25
Publication date: 2021-11-16
Anticipated expiration: 2030-11-25

Abstract

The utility model relates to the technical field of power supply, in particular to a DC ground insulation impedance detection circuit for variable bus voltage, which is characterized by comprising a topology with variable DC bus voltage; the DC-to-ground insulation resistance detection circuit assembly comprises: insulation resistance on the direct current side, a relay S0, a resistor R0, a direct current BUS negative electrode BUS-a measurement voltage Viso to the casing PE; one end of the ground/casing PE is connected with a direct current side insulation resistance, and the other end of the ground/casing PE is connected with one of the direct current BUS voltage variable topologies of the existing power topologies of the DC/AC converter to a direct current BUS negative electrode BUS-through a series circuit of a relay S0 and a resistor R0. The utility model relates to a low-cost DC insulation impedance detection scheme, which is suitable for multi-path DC input, detects the equivalent impedance of all DC input, and has simple circuit and lower cost; the utility model discloses an utilize the variable characteristics of direct current bus voltage, only need a relay, the circuit is simple, has practiced thrift the use of relay, the cost is reduced.

Description

Direct current-to-ground insulation impedance detection circuit for variable bus voltage

Technical Field

The utility model relates to a power supply technical field is a direct current insulation impedance detection circuitry to ground that is used for busbar voltage to be changeable particularly.

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). The voltage of BUS +/BUS-to-PE is changed by switching on and off the relays S1 and S2, two equations about Rp and Rn are obtained, and Rp and Rn are solved. This technique requires two relays and other auxiliary circuits, is costly, and is not suitable for use with multiple dc simultaneous inputs.

Disclosure of Invention

The utility model provides a direct current of high accuracy is to ground insulation resistance detection circuitry to solve current direct current insulation resistance and detect the problem that cost is too high and efficiency remains to improve

In order to achieve the above object, a first aspect of the present invention provides a DC-to-ground insulation resistance detection circuit for bus voltage variation, comprising a controller, a DC/AC converter, a DC-to-ground insulation resistance detection assembly,

the power topology of the DC/AC converter is provided with a topology with variable direct-current bus voltage;

the DC-to-ground insulation resistance detection circuit assembly comprises: insulation resistance on the direct current side, a relay S0, a resistor R0, a direct current BUS negative electrode BUS-a measurement voltage Viso to the casing PE;

one end of the earth/casing PE is connected with the direct current side insulation impedance, the other end of the earth/casing PE is connected with one of the existing power topologies of the DC/AC converter through a series circuit of a relay S0 and a resistor R0 to the direct current BUS negative electrode BUS-, and the controller detects the voltage of the direct current BUS negative electrode BUS-to-casing PE by controlling the voltage change of the direct current BUS.

Preferably, relay S0 and resistor R0 may be switched in position.

Preferably, the topology with the variable direct-current bus voltage is a BOOST circuit topology.

Preferably, the direct current side insulation impedance of the single direct current input comprises a direct current side power supply, a direct current BUS positive electrode BUS +, a direct current BUS negative electrode BUS-, a direct current BUS positive electrode (BUS +) impedance Rp to the earth/casing (PE), and a direct current BUS negative electrode (BUS-) impedance Rn to the earth/casing (PE).

Preferably, according to thevenin's theorem, all the dc-side power supplies and the insulation impedances to ground are equivalent to a two-terminal network, and the dc-side insulation impedances of the multiple dc inputs include all the dc inputs equivalent total impedances to ground Riso and two-terminal network open-circuit voltage Ux.

Preferably, all the direct current input equivalent total impedances to the ground Riso are equivalent total impedances of a plurality of direct current BUS positive electrodes BUS + to the ground/machine shell PE impedance and a plurality of direct current BUS negative electrodes BUS-to the ground/machine shell PE impedance.

The utility model discloses following beneficial effect has:

the utility model relates to a low-cost DC insulation impedance detection scheme, which is suitable for multi-path DC input, detects the equivalent impedance of all DC input, and has simple circuit and lower cost; the utility model discloses an utilize the variable characteristics of direct current bus voltage, only need a relay, the circuit is simple, has practiced thrift the use of relay, the cost is reduced.

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 schematic structural diagram of a dc-to-ground insulation resistance detection circuit suitable for multiple dc inputs according to an embodiment of the present application.

Fig. 3 is a schematic flowchart of a dc-to-ground insulation resistance detection method suitable for multiple dc inputs according to an embodiment of the present disclosure.

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 drawings described above, 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 the method are used for detecting whether the direct current input end of the inverter is short-circuited to ground or low 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 DC-to-ground insulation resistance detection circuit for bus voltage variation comprises a controller, a DC/AC converter, and a DC-to-ground insulation resistance detection assembly,

the power topology of the DC/AC converter is provided with a topology with variable direct-current bus voltage; in this embodiment, the topology with the variable dc bus voltage is a BOOST circuit topology.

In this embodiment, the dc side isolation impedances of the single dc input are exemplified by a dc side power supply, a dc BUS positive electrode BUS +, a dc BUS negative electrode BUS-, a dc BUS positive electrode (BUS +) impedance Rp to the earth/casing (PE), and a dc BUS negative electrode (BUS-) impedance Rn to the earth/casing (PE).

Preferably, relay S0 and resistor R0 may be switched in position.

Example two

In this embodiment, taking the dc side insulation impedance of multiple dc inputs as an example, according to thevenin's theorem, all dc side power sources and the insulation impedances to ground are equivalent to a two-terminal network, including all dc inputs equivalent total impedance Riso to ground and two-terminal network open-circuit voltage Ux. All the direct current input equivalent total impedances to the ground Riso are equivalent total impedances of a plurality of direct current BUS positive electrodes BUS + to the ground/machine shell PE and a plurality of direct current BUS negative electrodes BUS-to the ground/machine shell PE.

As shown in fig. 3, a method for detecting dc-to-ground insulation resistance with variable bus voltage is applied to the insulation resistance detection circuit, and the specific implementation manner is as follows:

and S1, the controller controls the relay S0 to be closed, the voltage of the direct current BUS is Vbus1, and the voltage of the negative electrode BUS of the direct current BUS to the shell PE is measured and recorded as Viso 1. The equation (i) is obtained

Viso1＝Vx*R0/(Riso+R0)+Vbus1*Riso/(Riso+R0) ①

Wherein Viso1 is the voltage of the negative electrode BUS-of the S1 direct current BUS to the casing PE, Vx is the open circuit voltage of the two-terminal network, Vbus1 is the voltage of the S1 direct current BUS, Riso is the equivalent total impedance of the direct current input to the ground, and R0 is a resistor;

and S2, the controller controls the relay S0 to be closed, the voltage of the direct current BUS is changed to Vbus2, and the voltage of a negative electrode BUS-opposite casing PE of the direct current BUS is measured and recorded as Viso 2. Obtain equation 2

Viso2＝Vx*R0/(Riso+R0)+Vbus2*Riso/(Riso+R0) ②

Wherein Viso2 is the voltage of S2 DC BUS negative BUS-to-casing PE, Vx is the open circuit voltage of the two-terminal network, Vbus2 is the change DC BUS voltage, Riso is the equivalent total impedance of the DC input to ground, and R0 is a resistor;

s3, simultaneous equation (r), calculates the insulation resistance as:

Riso＝R0/[(Vbus1-Vbus2)/(Viso1-Viso2)-1] ③

where Riso is the dc input to ground equivalent total impedance, Vbus1 is the S1 dc BUS voltage, Vbus2 is the changing dc BUS voltage, Viso1 is the S1 dc BUS negative BUS-to-casing PE voltage, Viso2 is the S2 dc BUS negative BUS-to-casing PE voltage.

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

1. A DC-to-ground insulation resistance detection circuit for bus voltage variable comprises a controller, a DC/AC converter and a DC-to-ground insulation resistance detection component,

2. The DC-to-ground insulation resistance detection circuit for the variable bus voltage as claimed in claim 1, wherein the relay S0 and the resistor R0 can exchange positions.

3. The dc-to-ground isolation impedance detection circuit for bus voltage variability of claim 1, wherein the topology with dc bus voltage variability is BOOST circuit topology.

4. The circuit for detecting the insulation resistance to the ground of the direct current with the variable BUS voltage as claimed in claim 1, wherein the insulation resistance on the direct current side of the single direct current input comprises a power supply on the direct current side, a positive BUS + of the direct current BUS, a negative BUS-, a positive BUS + of the direct current BUS, an impedance Rp of the direct current BUS to the ground/casing (PE), and an impedance Rn of the negative BUS-dc to the ground/casing (PE).

5. The detection circuit for the insulation resistance of the direct current to the ground with the variable bus voltage as claimed in claim 1, wherein all the direct current side power sources and the insulation resistance to the ground are equivalent to a two-terminal network according to thevenin's theorem, and the insulation resistance of the direct current side of the multi-path direct current input comprises all the direct current input equivalent total resistance to the ground Riso and the two-terminal network open-circuit voltage Ux.

6. The DC insulation resistance detection circuit for BUS voltage variation as claimed in claim 1 or 5, wherein the equivalent total resistance Riso of all DC inputs to ground is the equivalent total resistance of several DC BUS positive BUS + to earth/chassis PE resistance, several DC BUS negative BUS-to earth/chassis PE resistance.