CN107681699A - A kind of grid-connected detection means of distributed power source and method - Google Patents

Abstract

The invention discloses a distributed power grid-connected detection device, including an electrical parameter signal acquisition module, a disturbance frequency generation module, a general control and analysis module, and a human-computer interaction module: the electrical parameter signal acquisition module receives instructions from the general control and analysis module Corresponding electrical parameters; the disturbance frequency generation module generates a disturbance current of a specified size according to the instructions of the general control and analysis module; the general control and analysis module receives instructions from the processing personnel and controls the corresponding modules to complete the work; the human-computer interaction module is used for personnel operations and results show. The invention also discloses a detection method based on the detection device, which divides distributed grid-connected detection items into power quality detection items and isolated island detection items, and completes the detection work by operating on the detection device. The device and method disclosed in the present invention are developed for small-scale household use, and fill the gap in this respect in the field of grid-connected detection of distributed power sources.

Description

A distributed power grid-connected detection device and method

technical field

The invention belongs to the technical field of grid-connected detection of distributed power sources in electric power systems, and in particular relates to a small household distributed power source grid-connected device and method.

Background technique

In recent years, the emergence of the global energy crisis has promoted the development of new energy power generation. As a small-capacity power supply at the end of the grid and located near the load, distributed power has a positive effect on improving energy utilization and solving power problems in remote areas. significance. At present, the distributed power industry represented by photovoltaics is developing rapidly in my country's power industry. However, from the perspective of the safe operation of the power system distribution network, the access of distributed power to the distribution network will affect many aspects of the distribution network. Common influences include power quality, grid reliability, power distribution loss, relay protection, grid planning, etc. Therefore, it is very necessary to detect the grid-connected characteristics of distributed power generation. In the field of distributed power grid-connected detection, relevant research and practice have been carried out at home and abroad. Due to the late development of distributed power in our country, it is still in its infancy. At present, most of the research on distributed power in China focuses on the power itself, and there is less research on its grid-connected detection. In response to this situation, the State Grid Corporation of China has issued a number of standards including the "Distributed Power Supply Access Distribution Network Test Specification", but domestic research is still focused on the theoretical field, and there is insufficient research on the implementation of distributed power generation. At present, a mobile grid-connected detection system for MW-level large-scale photovoltaic power generation has been developed in China. However, the test platform contains a lot of equipment and requires too much space for the test site, so it is not suitable for kW-level household photovoltaic power generation devices. Therefore, it is very necessary to research on small-scale test equipment and technical solutions for kW-level household distributed power grid-connected test technology.

Contents of the invention

In view of the above-mentioned deficiencies in the prior art, the present invention proposes a distributed power grid-connected detection device and method, and its technical solution is:

A distributed power grid-connected detection device is characterized in that it includes an electrical parameter signal acquisition module, a disturbance frequency generation module, a general control and analysis module, and a human-computer interaction module:

The electrical parameter signal acquisition module is connected with the master control and analysis module, and is provided with a voltage transformer for collecting the voltage signal of the network point to be measured and a current transformer for collecting the current signal of the network point to be measured;

The disturbance frequency generation module is connected with the master control and analysis module to generate a disturbance signal for active island detection;

The general control and analysis module is used to: receive the electrical signal output by the electrical parameter signal acquisition module, and perform processing and analysis; send the measured value of the received electrical signal and the processing and analysis result to the human-computer interaction module; receive the signal transmitted by the human-computer interaction module Control instructions; coordinate or control the operation of the electrical parameter signal acquisition module and the disturbance frequency generation module according to the instructions or preset instructions transmitted by the human-computer interaction module;

The human-computer interaction module is connected with the general control and analysis module, and is used to display the information required for grid connection detection to the control personnel, and transmit the control personnel's operation instructions to the general control and analysis module.

On the basis of the above scheme, further improved or preferred schemes also include:

The overall control and analysis module performs analog-to-digital conversion on the electrical signal output by the electrical parameter signal acquisition module, extracts frequency information and amplitude information from the voltage signal, and uses FFT (fast Fourier transform algorithm, fast fouriertransform) for the current signal algorithm) or DFT (Discrete Fourier Transform, Discrete Fourier Transform) to extract harmonic information, and compare the measured value of the collected electrical signal with the standard value to calculate its deviation value.

The disturbance frequency generation module includes a frequency generator and a current amplifier for generating a disturbance current with adjustable frequency and amplitude.

The distributed power grid-connected detection device is provided with a movable platform, and the parameter signal acquisition module, disturbance frequency generation module, general control and analysis module and human-computer interaction module are installed on the movable platform.

A detection method based on the above-mentioned distributed power grid-connected detection device, including power quality detection and island detection, characterized in that:

The power quality detection includes voltage detection and harmonic detection:

The step of voltage detection is: collecting the voltage amplitude of the network point to be tested, comparing the collected value with the voltage amplitude of the rated grid voltage, and calculating the difference, and judging whether the voltage quality of the network point to be tested meets the requirements according to the difference;

The step of described harmonic detection is: collect the electric current value of network point to be tested, process electric current by means such as FFT, DFT, calculate its THD, judge whether harmonic meets requirement according to THD;

The island detection includes passive island detection and active island detection:

The steps of the passive island detection are: set a reference network point on the large power grid system, collect the voltage amplitude and frequency of the reference network point and the network point to be tested in the distributed power system, obtain a difference by comparison, and judge whether the difference is within the specified Within the allowable range, it can be judged whether the distributed power system is operating in an island;

The steps of the active island detection are: collect and calculate the voltage frequency f of the network point to be tested in the distributed power supply system, inject a current disturbance signal with a frequency of f+Δf into the point, Δf≠0, and monitor the voltage frequency of the network point to be measured Whether to start shifting cycle by cycle, and based on this to determine whether it is an island operation.

Beneficial effect:

The invention provides a distributed power grid-connected detection device and a detection method based on the device. By extracting and simplifying necessary detection items and detection steps, the purposes of lightness, portability, and economical flexibility can be achieved. The safety and stability issues, power quality issues, power control issues, abnormal response and anti-islanding protection issues after entering the distribution network provide useful ideas. The economy and operating efficiency of the back-grid system solve the problem of lack of detection devices and detection methods in the field of distributed power grid-connected detection in the field of small-scale household-scale distributed power grid-connected detection.

Description of drawings

Figure 1 is a schematic structural diagram of a distributed power grid-connected detection device;

Fig. 2 is a functional block diagram of the master control and analysis module;

Fig. 3 is a detection flow chart of a distributed power grid-connected detection method.

detailed description

In order to further clarify the technical scheme and working principle of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, a distributed power grid-connected detection device includes an electrical parameter signal acquisition module, a disturbance frequency generation module, a general control and analysis module, and a human-computer interaction module.

The electrical parameter signal acquisition module is connected with the master control and analysis module, collects the voltage signal of the network point to be tested through the voltage transformer, and collects the current signal of the network point to be tested through the current transformer.

The disturbance frequency generation module is connected with the master control and analysis module, and is provided with a frequency generator and a current amplifier for generating disturbance currents with adjustable frequency and amplitude, mainly for generating disturbance signals used in active island detection .

The general control and analysis module is mainly used to: receive the electrical signal output by the electrical parameter signal acquisition module, and perform processing and analysis; send the measured value and processing and analysis result of the received electrical signal to the human-computer interaction module; receive the human-computer interaction module The transmitted instructions; coordinate or control the operation of the electrical parameter signal acquisition module and the disturbance frequency generation module according to the instructions transmitted by the human-computer interaction module or the preset instructions.

In this embodiment, the general control and analysis module is integrated on an MCU, which is the control center and data processing center of the whole device. As shown in Figure 2, the general control and analysis module is divided into four functional areas: interface function Area, Power Quality Detection Functional Area, Passive Islanding Detection Functional Area and Active Islanding Detection Functional Area.

The interface functional area is responsible for the information transmission with the human-computer interaction interface, and its functions include receiving the control personnel's instructions transmitted from the human-computer interaction module, and calling the corresponding functional areas in the other three functional areas to complete the test by identifying the control personnel's instructions work; and receive the processing results of each functional module, and process it into a specified format and transmit it to the human-machine interaction module for display.

The power quality testing functional area is responsible for testing the power quality of the network to be tested, including voltage quality testing and harmonic quality testing. The voltage quality inspection collects the voltage signal by using the electrical parameter signal acquisition module, extracts the voltage amplitude information and frequency information, calculates the difference between it and the specified value, and finally transmits the calculated difference to the interface function area. The harmonic quality detection functional area collects the current signal by using the electrical parameter signal acquisition module, processes the current signal with DFT or FFT to extract its harmonic information, calculates THD, and finally transmits the calculated THD to the interface functional area.

The passive island detection function area judges whether the system under test is operating in an island by detecting the voltage amplitude, phase and frequency. It first collects the voltage signal through the electrical parameter signal acquisition module, extracts the voltage amplitude and frequency information of the measured outlet, then calculates the difference between it and the specified value, and finally judges whether the system is running in an island by judging the difference, and calculates the difference And the judgment result is sent to the interface functional area. Active function detection collects the voltage signal of the measured outlet through the electrical parameter signal acquisition module, extracts its current frequency f and transmits it to the interface function area for display, and then receives the Δf set by the personnel and the disturbance current amplitude A to start the disturbance frequency generation The module generates an interference current with a frequency of f+Δf (Δf≠0) and an amplitude of A, and monitors the change of the frequency f of the network point under test at the same time. By judging whether the frequency is shifted cycle by cycle, it can be judged whether the system is running in an island, and the measured The point frequency and discrimination results are transmitted to the interface functional area in real time for display

The human-computer interaction module is connected with the master control and analysis module, and is equipped with a touch screen and corresponding control switches, which are used to display the information required for grid connection detection to the controller, such as the measured value of the electrical signal of the grid point to be tested and the master control and The analysis module processes the analysis results, etc., and transmits the control personnel's operation instructions to the master control and analysis module. Fig. 3 is a detection flow chart of the distributed power grid-connected detection method, the controller selects power quality detection, passive island detection or active detection items through the display interface of the human-computer interaction module of the distributed power grid-connected detection device, and can Check the detection results in real time; in the active island detection project, the controller needs to set the frequency and amplitude of the interference current according to the current frequency of the measured network.

In this embodiment, the detection device is further provided with a portable movable platform, and the parameter signal acquisition module, disturbance frequency generation module, general control and analysis module, and human-computer interaction module are installed on the movable platform.

The detection method based on the above-mentioned distributed power grid-connected detection device includes items such as power quality detection and islanding detection.

The power quality detection includes voltage detection and harmonic quality detection.

The steps of the voltage detection are:

1) Collect the voltage amplitude of the network points to be tested in the distributed power system;

2) Compare the voltage amplitude of the collected value in step 1) with the rated grid voltage, and calculate the difference;

3) According to the difference obtained in step 2), judge whether the voltage quality of the outlet to be tested meets the requirements.

The steps of the harmonic quality detection are:

1) Collect the current parameters of the outlets to be tested;

2) Process the current through FFT, DFT, etc., calculate its THD (Total Harmonic Distortion), and judge whether the harmonics meet the requirements according to the THD.

The island detection includes passive island detection and active island detection.

The steps of the passive island detection are:

1) Set a reference network point on the large power grid system, and collect the voltage amplitude and frequency of the reference network point and the network point to be tested in the distributed power system;

2) By comparing the collected values in step 1), the difference in voltage amplitude and frequency between the distributed power system and the large power grid system is obtained;

3) Determine whether the difference obtained in step 2) is within the allowable range of relevant regulations, so as to determine whether the distributed power system is operating in an isolated manner.

The steps of the active island detection are:

1) Collect and calculate the voltage frequency f of the network points to be tested in the distributed power system;

2) Inject a current disturbance signal with frequency f+Δf into the network point to be tested, Δf≠0;

3) Monitor whether the voltage frequency of the network point to be tested begins to shift cycle by cycle, and judge whether it is an island operation or not.

The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have For various changes and improvements, the protection scope of the present invention is defined by the appended claims, description and their equivalents.

Claims (5)

1. a kind of grid-connected detection means of distributed power source, it is characterised in that given birth to including electric parameter signal acquisition module, forcing frequency Into module, master control and analysis module and human-computer interaction module：

The electric parameter signal acquisition module is connected with master control and analysis module, provided with the voltage for gathering site voltage signal to be measured Transformer and the current transformer for gathering site current signal to be measured；

The forcing frequency generation module is connected with master control and analysis module, generates the interference letter for active alone island detection Number；

The master control and analysis module are used for：The electric signal of electric parameter signal acquisition module output is received, and carries out Treatment Analysis； The measured value and Treatment Analysis result for receiving electric signal are sent to human-computer interaction module；Receive the control of human-computer interaction module transmission Instruction；The instruction transmitted according to human-computer interaction module or preset instructions coordinate or control electric parameter signal acquisition module, disturbance frequency The work operation of rate generation module；

The human-computer interaction module is connected with master control and analysis module, for showing the letter needed for grid-connected detection to controllers Cease, and the operational order of controllers is transmitted to master control and analysis module.

A kind of 2. grid-connected detection means of distributed power source according to claim 1, it is characterised in that：

After the electric signal that the master control and analysis module export to electric parameter signal acquisition module carries out analog-to-digital conversion, believe from voltage Frequency information and amplitude information are extracted in number, harmonic information is extracted using FFT or DFT modes to current signal, by the electricity of collection Signal measurements calculate its deviation compared with standard value.

A kind of 3. grid-connected detection means of distributed power source according to claim 1, it is characterised in that：

The forcing frequency generation module includes frequency generator and current amplifier, adjustable dry for producing frequency and amplitude Disturb electric current.

4. the grid-connected detection means of a kind of distributed power source according to claim 1, it is characterised in that removable flat provided with one Platform, the parameter signals acquisition module, forcing frequency generation module, master control and analysis module and human-computer interaction module are arranged on institute State on moveable platform.

5. a kind of detection method based on the grid-connected detection means of distributed power source any one of claim 1-4, including electricity Energy quality testing and isolated island detection, it is characterised in that：

The Power Quality Detection detects including voltage detecting harmonic：

The step of voltage detecting is：Site voltage magnitude to be measured is gathered, compares the voltage of collection value and specified line voltage Amplitude, and difference is calculated, judge whether site quality of voltage to be measured meets to require according to the difference；

The step of harmonic detecting is：Gather the current value of site to be measured, by the modes such as FFT, DFT to electric current at Reason, calculates its THD, judges whether harmonic wave meets to require according to THD；

The isolated island detection includes the detection of passive type isolated island and active alone island detection：

The step of passive type isolated island detection is：Set on bulk power system with reference to site, gather the reference site with dividing The voltage magnitude and frequency of cloth power-supply system site to be measured, difference is drawn by comparing, and judges whether difference allows in regulation In the range of, judge whether the distributed power supply system is islet operation with this；

The step of active alone island detection is：Collection calculates the electric voltage frequency f of distributed power supply system site to be measured, to The injected frequency is f+ Δs f current disturbing signal, and Δ f ≠ 0 monitors whether the site electric voltage frequency to be measured starts Cycle by Cycle Skew, and islet operation is determined whether accordingly.