Direct current side protection device of frequency conversion system

Abstract

The invention discloses a direct current side protection device of a frequency conversion system. The direct current side protection device comprises a controller, an AD sampling circuit and a switching value control circuit, the controller comprises an AD control module, a calculation and judgment module and a digital quantity output control module which are connected in sequence, the AD control module is connected with the AD sampling circuit, and the digital quantity output control module is connected with the switching value control circuit. The controller calculates a power difference value between the direct-current side and the alternating-current side according to the collected direct-current side voltage, direct-current side current, alternating-current side voltage and alternating-current side current, and sends a control signal; and the switching value control circuit controls the direct current side circuit breaker and the alternating current side circuit breaker of the frequency conversion system to be switched off according to the received control signal. According to the invention, the insulation resistance of the DC side can be obtained simply and rapidly, and the insulation resistance is taken as a judgment basis, so that safety protection is provided for a frequency conversion system timely and reliably when a fault occurs.

Description

TECHNICAL FIELD

[0001] The present application relates to a variable frequency system, in particular to a direct current side protection device of a variable frequency system. BACKGROUND

[0002] In a variable frequency system, faults are prone to occur between direct current side inputs. For example, a short circuit between direct current side inputs will generate a large instantaneous current, thus causing damage to components, fire hazards and the like. In the prior art, a direct current side protection device is generally provided to avoid the occurrence of the above-mentioned hazards.

[0003] Generally, the existing direct current side protection device adopts a bridge measurement or a leakage current sensor to detect the insulation impedance between the input positive pole and the ground and the insulation impedance between the input negative pole and the ground, respectively, to calculate the insulation impedance between the positive pole and the negative pole of the direct current input side according to the detected data, and to control the alternating current-direct current circuit breaker of the frequency converter to be disconnected based on the insulation impedance, so as to realize protection of the variable frequency system.

[0004] However, the existing direct current side protection device has the following disadvantages: first, the calculation process of the insulation impedance between the positive pole and the negative pole of the direct current input side is relatively complex; second, due to the change speed of the insulation impedance of the direct current side, for example, in a photovoltaic system, the direct current side input of the photovoltaic inverter is a photovoltaic panel, even if the panel has a short circuit and generates a large instantaneous current, the insulation impedance decreases rapidly, and the short circuit current cannot make the direct current circuit breaker to be disconnected; thus, the variable frequency system cannot be timely and reliably protected in the event of a fault in the direct current side.

[0005] Therefore, the present application is proposed. SUMMARY

[0006] The present application aims to provide a direct current side protection device of a variable frequency system to solve the above-mentioned technical problems in the prior art.

[0007] The present application is achieved by the following technical solutions:

[0008] The direct current side protection device of the variable frequency system of the present application comprises:

[0009] a controller 110, and an AD sampling circuit 120 and a switching value control circuit 130 connected to the controller 110, respectively;

[0010] The AD sampling circuit 120 is used to collect the direct current side voltage, the direct current side current, the alternating current side voltage and the alternating current side current of the variable frequency system.

[0011] The controller 110 is configured to calculate a power difference between the DC side and the AC side according to the collected DC side voltage, DC side current, AC side voltage and AC side current, and when the power difference is greater than a power threshold, calculate an insulation impedance of the DC side according to the power difference and the DC voltage, and when the insulation impedance is less than an impedance threshold, send a control signal;

[0012] The switch quantity control circuit 130 is configured to control the DC side circuit breaker and the AC side circuit breaker of the frequency conversion system to be both open according to the received control signal.

[0013] Compared with the prior art, the DC side protection device of the frequency conversion system provided by the present application can simply and quickly obtain the insulation impedance of the DC side, and uses the insulation impedance as a judgment basis, thereby providing safety protection for the frequency conversion system in a timely and reliable manner when a fault occurs. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 The DC side protection device of the frequency conversion system provided by the present application is shown in the schematic diagram.

[0015] Figure 2 The structural block diagram of the controller in the protection device in the embodiment of the present application is shown. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application; obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application, which do not constitute a limitation on the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0017] First, the terms possibly used in the present application are described as follows:

[0018] The terms “include”, “contain”, “have”, “possess” or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example: including a technical feature element (such as raw materials, components, ingredients, carriers, dosage forms, materials, sizes, parts, components, mechanisms, devices, steps, processes, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products or articles, etc.), should be interpreted as not only including the explicitly listed technical feature element, but also including other technical feature elements not explicitly listed in the art.

[0019] The contents not described in detail in the embodiments of this invention are prior art known to those skilled in the art. Where specific conditions are not specified in the embodiments of this invention, they shall be performed according to conventional conditions in the art or conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments used in the embodiments of this invention are not specified, they are all conventional products that can be purchased commercially.

[0020] The DC-side protection device of the frequency converter system of the present invention includes:

[0021] The controller 110, and the AD sampling circuit 120 and the switch control circuit 130 respectively connected to the controller 110;

[0022] The AD sampling circuit 120 is used to collect the DC side voltage, DC side current, AC side voltage, and AC side current of the frequency converter system.

[0023] The controller 110 is used to calculate the power difference between the DC side and the AC side based on the collected DC side voltage, DC side current, AC side voltage and AC side current, and when the power difference is greater than the power threshold, calculate the insulation impedance of the DC side based on the power difference and the DC voltage, and when the insulation impedance is less than the impedance threshold, send a control signal.

[0024] The switching control circuit 130 is used to control both the DC-side circuit breaker and the AC-side circuit breaker of the frequency converter system to open according to the received control signal.

[0025] The controller 110 includes:

[0026] The AD control module 210, the calculation and judgment module 220, and the digital output control module 230 are connected in sequence. The AD control module 210 is connected to the AD sampling circuit 120, and the digital output control module 230 is connected to the switch control circuit 130.

[0027] The calculation and judgment module 220 is sequentially connected to the fault alarm module 240 and the display and alarm circuit 140.

[0028] In summary, the DC-side protection device of the frequency converter system in this embodiment of the invention can easily and quickly obtain the insulation impedance of the DC side and use it as a basis for judgment, thereby providing timely and reliable safety protection for the frequency converter system when a fault occurs.

[0029] To more clearly demonstrate the technical solution and its effects provided by the present invention, the embodiments of the present invention will be described in detail below with reference to specific examples.

[0030] Example 1

[0031] like Figure 1 As shown:

[0032] The DC side protection device of the frequency conversion system in the principle diagram comprises:

[0033] The controller 110, and the AD sampling circuit 120 and the switch quantity control circuit 130 connected with the controller 110 respectively; the AD sampling circuit 120 is used for collecting the DC side voltage, the DC side current, the AC side voltage and the AC side current of the frequency conversion system;

[0034] The controller 110 is used for calculating the power difference between the DC side and the AC side according to the collected DC side voltage, DC side current, AC side voltage and AC side current, and when the power difference is greater than the power threshold value, calculating the insulation impedance of the DC side according to the power difference and the DC voltage, and when the insulation impedance is less than the impedance threshold value, sending a control signal;

[0035] The switch quantity control circuit 130 is used for controlling the DC side circuit breaker and the AC side circuit breaker of the frequency conversion system to be disconnected according to the received control signal.

[0036] As shown in the structure diagram: Figure 2

[0037] The controller 110 in the structure diagram comprises:

[0038] The AD control module 210, the calculation and judgment module 220 and the digital quantity output control module 230 connected in sequence, the AD control module 210 is connected with the AD sampling circuit 120, and the digital quantity output control module 230 is connected with the switch quantity control circuit 130.

[0039] The beneficial effects brought by the technical scheme of the application are as follows:

[0040] The DC side voltage, the DC side current, the AC side voltage and the AC side current of the inverter system are collected by the AD sampling circuit, the controller calculates the power difference between the DC side and the AC side according to the collected data, further calculates the insulation impedance of the DC side when the power difference is greater than the power threshold value, sends a control signal to the switch quantity control circuit when the insulation impedance is less than the impedance threshold value, the switch quantity control circuit controls the DC side circuit breaker and the AC side circuit breaker of the inverter system to be disconnected according to the control signal, and the insulation impedance of the DC side can be obtained simply and quickly, and the safety protection for the inverter system is provided in time and reliably when a fault occurs.

[0041] The technical key points of the application are as follows:

[0042] The DC side protection device of the frequency conversion system can simply and quickly obtain the insulation impedance of the DC side, and the safety protection for the frequency conversion system is provided in time and reliably when a fault occurs. ​

[0043] The above description is only the preferred embodiment of the present application, but the protection scope of the present application is not limited to this. Any change or replacement within the technical range disclosed by the present application can be easily thought by those skilled in the art, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims. The information disclosed in the background section of the present application is only intended to deepen the understanding of the general background of the present application, and should not be regarded as acknowledging or implying in any form that the information constitutes the prior art known by those skilled in the art.

Claims

1. A DC-side protection device for a frequency converter system, characterized in that, include: The controller (110), and the AD sampling circuit (120) and the switch control circuit (130) respectively connected to the controller (110); The AD sampling circuit (120) is used to collect the DC side voltage, DC side current, AC side voltage and AC side current of the frequency conversion system; The controller (110) is used to calculate the power difference between the DC side and the AC side based on the collected DC side voltage, DC side current, AC side voltage and AC side current, and when the power difference is greater than the power threshold, calculate the insulation impedance of the DC side based on the power difference and the DC voltage, and when the insulation impedance is less than the impedance threshold, send a control signal. The switching control circuit (130) is used to control both the DC-side circuit breaker and the AC-side circuit breaker of the frequency converter system to open according to the received control signal.

2. The DC-side protection device for the frequency converter system according to claim 1, characterized in that, The controller (110) includes: The AD control module (210), the calculation and judgment module (220) and the digital output control module (230) are connected in sequence. The AD control module (210) is connected to the AD sampling circuit (120), and the digital output control module (230) is connected to the switch control circuit (130).

3. The DC-side protection device for the frequency converter system according to claim 2, characterized in that, The calculation and judgment module (220) is connected in sequence to the fault alarm module (240) and the display and alarm circuit (140).

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