CN102624027A - A multi-process islanding effect detection device and method - Google Patents

Abstract

A multiprocess island effect detection device and a multiprocess island effect detection method belong to the field of distributed power generation system fault detection. Compared with the traditional island detection device, the multi-process island effect detection device provided by the invention has the characteristics of small detection blind area, high detection accuracy, strong applicability and the like; the system is subjected to island detection by adopting a passive detection mode with various independent detection variables, so that the system is subjected to island detection more comprehensively. Compared with the traditional island detection device adopting single passive detection and active detection, the device has the advantages of rapidity of passive detection and small pollution to harmonic waves of the power grid, realizes that the detection device firstly performs rapid judgment on the system, and quickly cuts the system from the power grid if the distributed power generation system is in an island state. And secondly, the active detection is called to recheck the passive detection result, so that the advantage of high accuracy of the active detection is fully exerted, and the defects of long detection time and large pollution degree to the harmonic wave of the power grid are overcome.

Description

A multi-process islanding effect detection device and method

technical field

The invention belongs to the field of fault detection of distributed power generation systems, and in particular relates to a multi-process islanding effect detection device and method.

Background technique

Since the 20th century, with the rapid development of economy and society, energy consumption has been increasing day by day, and the rapid growth of power demand has made people pay more and more attention to the development of renewable energy. more attention. As the number of distributed power generation systems connected to the grid increases year by year, the island effect has become the main factor restricting distributed power generation technology. Due to the characteristics of small power generation capacity and scattered layout, the traditional dispatching method cannot be effectively controlled. In this way, when the power grid fails, the grid-connected distributed power generation system will fall into an island state. In order to improve the reliability and controllability of the grid-connected distributed power generation system and give full play to the advantages of the distributed power generation system, all countries require the island effect detection function for the grid-connected distributed power generation system. For example, in Japan, at least There is a passive detection method and an active detection method; in North America, manufacturers are required to adopt an active islanding detection method based on frequency, phase or voltage offset; in China, GB/T19939-2005 grid-connected technical requirements for photovoltaic systems require At least one each of active and passive islanding detection means. Therefore, the research on the islanding effect detection technology and related devices has become a research hotspot for domestic and foreign electric power researchers.

Nowadays, there are many detection methods for the islanding effect of distributed generation systems, which are mainly divided into two categories: active detection and passive detection. For now, passive detection has the advantages of simple technology, easy implementation, no need to inject disturbance into the system, and reduced harmonic influence. However, passive detection can only detect the power generation system after the islanding effect, and make corresponding processing, it can not detect the islanding phenomenon in advance, and the detection blind area of passive detection is large. Although the active detection method has the advantages of high detection accuracy and small detection blind area, the control of this method is more complicated, and because the detection process needs to inject disturbance signals, the quality of the inverter output power is reduced. Because both the passive detection method and the active detection method have their own advantages and disadvantages, the combination of active detection and passive detection has become a new research direction of island detection technology. There are many types of island detection technologies that combine active detection and passive detection, such as the combination of over-undervoltage/over-underfrequency detection method and frequency offset detection method, the combination of voltage harmonic detection method and sliding mode frequency drift detection method... .. But these methods all have technical defects, such as high technical difficulty in implementation, large detection blind spots, complex control devices, and long detection time.

Contents of the invention

Aiming at the shortcomings of the existing methods, the present invention proposes a multi-process islanding detection device and method, so as to achieve the purpose of more comprehensive islanding detection of the system.

The technical solution of the present invention is achieved in that a multi-process islanding effect detection method comprises the following steps:

Step 1: Perform filtering, noise reduction, voltage transformation processing and analog-to-digital conversion on the collected three-phase voltage, current and frequency, and normalize the converted digital signal, and send it to the data memory unit for storage;

Step 2: Initialize system parameters, the system parameters include system resistance value R, inductance value L and capacitance value C;

Step 3: Using the data stored in step 1, calculate the active power P and reactive power Q of the system, and store the active power value and reactive power value in the data memory unit for preservation;

Step 4: Send the data in the data storage to the CPU of the DSP, and perform passive islanding detection to determine whether the islanding occurs. Unbalance degree; (2) Utilize phase mutation detection method to calculate voltage and current phase difference angle; (3) Utilize power/frequency change rate detection method to calculate active power conversion rate, reactive power conversion rate and frequency conversion rate; use the above ( 1) From the results of (2) and (3), calculate the comprehensive evaluation index value of passive detection. If the value is not greater than 10, it indicates that the distributed power generation system is in the normal grid-connected operation state. Use the active island detection process to carry out the results of passive island detection Check and execute step 5; if the value is greater than 10, it means that the distributed generation system is in an island state. At this time, the system DSP sends out a PWM wave to drive the circuit breaker controller to cut off the distributed generation system from the grid;

Step 5: Active island detection, the method is: use the active frequency shift method to calculate the maximum value ω _max and the minimum value ω _min of the frequency shift, and calculate the angular frequency ω _P at the node between the distributed generation system and the power grid. If ω _min < ω _P < ω _max , indicating that the result of passive detection is incorrect, at this time DSP sends out PWM waves to drive the circuit breaker controller to cut off the distributed generation system from the grid; otherwise, it means that the result of passive detection is correct, go to step 6;

Step 6: The distributed power generation system is in an island operation state, and the communication unit is used to communicate with the upper computer remotely, and the operator is prompted that the system has been disconnected from the grid;

Step 7: The data stored in the data storage unit is used to display the status of the distributed power generation system through the display unit, and provide maintenance basis for system maintenance personnel;

Step 8: For the distributed generation system that has been disconnected from the grid, the island detection device will actively detect the distributed generation system through active island detection, and judge whether the distributed generation system meets the requirements for reconnecting to the grid. If so, DSP A PWM wave is sent out to drive the circuit breaker controller so that the distributed generation system can be connected to the grid again.

A device for implementing a multi-process islanding effect detection method, comprising:

Signal collection unit: used to collect the three-phase voltage, current and frequency at the nodes of the distributed power generation system and the power grid, and perform filtering, noise reduction and voltage transformation processing on the collected signals;

Main control unit: used to further process the signal collected by the signal acquisition unit, perform passive island detection and active island detection, and control the connection and shutdown of the distributed power generation system and the power grid according to the detection results;

Data memory unit: used to store the unbalance degree of active power and reactive power, voltage and current phase difference angle, active power conversion rate, reactive power conversion rate and frequency conversion rate;

Communication unit: used to realize the network communication between the island effect detection device and the host computer.

Advantages of the present invention: Compared with traditional islanding detection devices, the multi-process islanding detection device proposed by the present invention has the characteristics of small detection blind area, high detection accuracy and strong applicability. The islanding detection device detects the islanding of the system by adopting a passive detection method in which multiple detection variables are independent of each other, and performs the islanding detection of the system more comprehensively. Compared with the traditional island detection device that adopts a single passive detection and active detection, it fully utilizes the advantages of rapid passive detection and less harmonic pollution to the power grid, and realizes that the detection device first quickly judges the system. If distributed If the power generation system is in an island state, the system is quickly cut off from the grid. Secondly, active detection is used to review the results of passive detection, which fully utilizes the advantages of high detection accuracy of active detection and overcomes the shortcomings of long detection time and large degree of harmonic pollution to the power grid. Generally speaking, compared with the traditional islanding detection device, the multi-process islanding effect detection device proposed by the present invention reduces the detection blind area by 25%, shortens the detection time by 40%, improves the detection accuracy by 90%, and reduces the harmonic pollution of the power grid. reduced by 92%.

Description of drawings

Fig. 1 is a structural block diagram of a multi-process islanding effect detection device according to an embodiment of the present invention;

Fig. 2 is a circuit schematic diagram of a bandpass filter circuit according to an embodiment of the present invention;

Fig. 3 is a schematic circuit diagram of a three-phase voltage sampling signal modulation circuit according to an embodiment of the present invention;

Fig. 4 is a schematic circuit diagram of a three-phase current sampling signal modulation circuit according to an embodiment of the present invention;

5 is a schematic circuit diagram of a frequency sampling signal modulation circuit according to an embodiment of the present invention;

Fig. 6 is the circuit schematic diagram of a kind of embodiment DSP of the present invention and power supply module thereof;

FIG. 7 is a schematic circuit diagram of a data storage unit according to an embodiment of the present invention;

FIG. 8 is a schematic circuit diagram of a communication module in an embodiment of the present invention;

FIG. 9 is a schematic circuit diagram of a liquid crystal display module according to an embodiment of the present invention;

Fig. 10 is a flow chart of islanding effect detection of multi-process in an embodiment of the present invention;

FIG. 11 is a flow chart of passive island detection in an embodiment of the present invention;

FIG. 12 is a flow chart of an over-undervoltage/over-underfrequency detection method according to an embodiment of the present invention;

FIG. 13 is a flowchart of a phase mutation detection method according to an embodiment of the present invention;

Fig. 14 is a flow chart of a power frequency change rate detection method according to an embodiment of the present invention;

Fig. 15 is a flow chart of active island detection in an embodiment of the present invention.

Detailed ways

Embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

FIG. 1 is a structural block diagram of a multi-process islanding effect detection device. The multi-process islanding effect detection device mainly includes: a signal acquisition unit, a main control unit, a data storage unit, a communication unit, a liquid crystal display unit, a circuit breaker controller and a power supply module of the main control unit. Among them, the signal acquisition unit includes: a voltage sensor (VT), a current sensor (CT), a frequency tester, a band-pass filter circuit, a three-phase voltage sampling signal modulation circuit, a three-phase current sampling signal modulation circuit and a frequency sampling signal modulation circuit.

In this embodiment, 3 voltage sensors (VT) and 3 current sensors (CT) are used to collect the three-phase voltage and current at the node (PCC node) between the distributed power generation system and the grid, where the model of the voltage sensor It is HNV500T, and the model of the current sensor is ACS712ELCTR-05A5ASOP-8. A frequency tester is used to collect the frequency at the distributed generation system and the grid node (PCC node), and the model of the frequency tester is BT3C.

The signals collected by the voltage sensor (VT), the current sensor (CT) and the frequency tester are transmitted to the band-pass filter circuit, and the band-pass filter circuit is shown in FIG. 2 . The voltage signal output terminal of the voltage sensor (VT) (including 3 voltage signals), the current signal output terminal of the current sensor (CT) (including 3 current signals) and the frequency signal (including 1 frequency signal) output of the frequency tester terminal, and at the same time connect the input terminal u _i of the band-pass filter circuit to filter the collected signal. After the filtered signal is processed by the signal modulation circuit (including three-phase voltage sampling signal modulation circuit, three-phase current sampling signal modulation circuit and frequency sampling signal modulation circuit) for noise reduction and voltage transformation, the output voltage signal with an amplitude of 3.3V , passed to the main control unit (such as the central processing unit DSP).

The output pin u _o of the band-pass filter circuit outputs 7 signals, among which 3 voltage signals are connected to u _a , u _b , u _c interfaces of the three-phase voltage sampling signal modulation circuit, as shown in figure 3, the three-phase voltage The output terminals OUT _a , OUT _b and OUT _c of the sampling signal modulation circuit are respectively connected to the signal input terminals of the main control unit (such as the ADCINA0 ADCINA2 terminal of the DSP); the three current signals are connected to the i _a of the three-phase current sampling signal modulation circuit , i _b , i _c interfaces, as shown in Figure 4, the output terminals OUT _a1 , OUT _b1 and OUT _c1 of the three-phase current sampling signal modulation circuit are respectively connected to the signal input terminals of the main control unit (such as the ADCINA3 ADCINA5 terminal of the DSP) ; No. 1 frequency signal is connected to the input terminal f _g of the frequency sampling signal modulation circuit, as shown in Figure 5, the output terminal OUT _f end of the frequency sampling signal modulation circuit is connected to the signal input terminal of the main control unit (such as the ADCINA6 end of DSP) .

This embodiment adopts DSP as the main control unit, which is used to perform A/D conversion on the collected three-phase voltage, current and voltage frequency of the PCC point, and perform islanding detection on the converted signal, and trigger the corresponding Trigger the control signal to drive the actuator at the PCC point to perform corresponding actions.

Its model is TMS320F2812, see Fig. 6, Fig. 6 also includes the power supply module of DSP, DSP power supply module provides the 3.3V voltage that meets working requirement to DSP.

The output signal of the DSP is sent to the data storage unit, the communication unit, the liquid crystal display unit and the circuit breaker controller, and the described data storage unit and the liquid crystal display unit mainly realize the storage and display of the key data of the operating state of the distributed power generation system respectively, so that Operators understand the operating status of the system and make correct processing operations based on the recorded key data.

In this embodiment, the model of the data storage unit is CY7C1041BV, and its data input terminal D0-D15 pins are connected with XD0-XD15 pins of DSP, and A0-A17 pins are connected with XA0-XA17 pins of DSP chip. As shown in Figure 7.

The communication unit is used to realize the network communication between the island detection device and the upper computer, which is convenient for dispatchers to make reasonable arrangements for the distributed power generation system and realize the maximum benefit operation of the distributed power generation system. In this implementation mode, the RS485 communication protocol is adopted, and the MAX232 driver chip is used for realization, and its circuit schematic diagram is shown in FIG. 8 . Its R2OUT, T2IN, R1OUT, T1IN pins are respectively connected with the SCIRXDA, SCITXDA, SCIRXDB, SCITXDB pins of the DSP chip.

Described liquid crystal display unit adopts liquid crystal display to realize, and the model of described liquid crystal display is LCM12864ZK, as shown in Figure 9, the RS pin of liquid crystal display is connected with the IOPF4 pin of TMS320LF2812 chip, the R/W pin of liquid crystal display Connect with the IOPF5 pin of the DSP, connect the E pin of the LCD with the IOPF6 pin of the DSP, connect the D0~D7 pins with the IOPB1~IOPB7 pins of the DSP, and connect the /RST pin of the LCD with the IOPC1 pin of the DSP connect.

The multi-process island detection device generates a PWM control wave signal through the I/O port of the DSP. After the control signal is amplified by the signal amplification circuit, it is connected to the grid-connected control relay at the PCC point (the model used in this embodiment is DW15 circuit breaker control relay) switch) to control the on-off state, and realize the cut-off operation of the distributed generation system in the island operation state and the reclosing operation of the distributed generation system in the island state.

An embodiment of the present invention provides a flow of a multi-process islanding effect detection method, as shown in FIG. 10 . The process starts at step 1001. In step 1002, carry out analog-to-digital conversion (for example, utilize the A/D converter of DSP to realize analog-to-digital conversion) to the collected three-phase voltage, current and frequency, call the voltage signal that amplitude is 3.3V, and convert The final digital signal is normalized and sent to the data memory unit for storage;

In step 1003, system parameters are initialized, and the system parameters include system resistance value R, inductance value L and capacitance value C;

In step 1004, use the data stored in step 1 to calculate the active power P and reactive power Q of the system, and store the active power value and the reactive power value into the data memory unit for preservation;

Among them, the present embodiment adopts the three-phase instantaneous power method to calculate active power, reactive power and power factor angle, and the process is as follows:

The three-phase phase voltage and three-phase line current sampled in step 1002 are respectively u _a , _ub , u _c , _ia , i _b , and i _c , and are converted from three phases a, b, and c to two phases α-β After that, u _α , u _β and i _α , i _β are obtained.

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;\&beta;</span>}}\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\end{array}\right]<span\; class="notranslate">\; ,</span>$ $\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;\&beta;</span>}}\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula $C_{\mathrm{\&alpha;\&beta;}}=\sqrt{\frac{2}{3}}\left[\begin{array}{ccc}1& -\frac{1}{2}& -\frac{1}{2}\\ 0& \frac{\sqrt{3}}{3}& -\frac{\sqrt{3}}{2}\end{array}\right]$

和

分别合成为(旋转)电压矢量

和电流矢量 Put the vector on the α-β plane

and

respectively synthesized into (rotated) voltage vectors

and current vector

的模，分别为矢量的相角。where u and i are vectors respectively

the mold, are vectors the phase angle.

Calculate the instantaneous active current and instantaneous reactive current of a three-phase circuit:

where the power factor angle

The product of u and i _p is the instantaneous active power of the three-phase circuit, and the product of u and i _q is the instantaneous reactive power of the three-phase circuit. Right now

p=ui _p q=ui _q (3)

Substitute formula (2) into formula (3):

$\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; p</span>}\\ \mathrm{<span\; class="notranslate">\; q</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{cc}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}& {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}& <span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; pq</span>}}\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}\\ {\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

In the formula $C_{\mathrm{pq}}=\left[\begin{array}{cc}{u}_{\mathrm{\&alpha;}}& u_{\mathrm{\&beta;}}\\ u_{\mathrm{\&beta;}}& -u_{\mathrm{\&alpha;}}\end{array}\right]$

Substitute formula (1) into formula (4):

P＝u _a i _a +u _b i _b +u _c i _c $Q=\frac{1}{\sqrt{3}}[(u_b-u_c)i_a+(u_c-u_a)i_b+(u_a-u_b)i_c]$

与无功功率的不平衡度，流程如图12所示。该流程开始于步骤1201。在步骤1202，计算有功功率不平衡度与无功功率

的不平衡度，公式如下：In step 1005, the data in the data storage is sent to the CPU of the DSP, and a passive island detection is performed to determine whether an island occurs, as shown in FIG. 11 . The process starts at 1101. In step 1102, (1) use the over-undervoltage/over-underfrequency detection method to calculate the unbalance degree of active power between the distributed generation system and the grid node (PCC node)

and reactive power The unbalance degree, the process is shown in Figure 12. The process starts at step 1201 . In step 1202, the active power unbalance degree is calculated and reactive power

The imbalance degree, the formula is as follows:

$\frac{\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; ,</span>$ $\frac{\mathrm{<span\; class="notranslate">\; \&Delta;Q</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}}\frac{\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; Z</span>}}}{\mathrm{<span\; class="notranslate">\; Q</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

In the formula: ω _g is the angular frequency of the grid, and ω _g = 2πf _g , f _g is the grid frequency; ω _p is the angular frequency at the PCC, and ω _p = 2πf _p , f _p is the frequency at the PCC node; u _g is the grid voltage; u _p is the voltage at the PCC node; Q _Z is the reactive power on the resonant capacitor, and there is $Q_Z={\mathrm{\&omega;}}_g{\mathrm{Cu}}_g^2.$

和无功功率不平衡度

储存至数据存储器单元。In step 1203, the calculated active power imbalance

and reactive power unbalance

Stored to the data memory unit.

的两个电压瞬时值u_n，u_n-1，电流传感器测出相隔

的两个电流瞬时值i_n，i_n-1。计算出电压相位角和电流相位角，公式如下：(2) Using the phase mutation detection method to calculate the voltage phase angle and current phase angle, the flow chart is shown in Figure 13. The process starts at step 1301 . In step 1302, the voltage sensor measures the separation

Two voltage instantaneous values u _n , u _n-1 , measured by the current sensor are separated by

Two current instantaneous values _in , in _{-1 of} . Calculate the voltage phase angle and current phase angle, the formula is as follows:

为电压相位角；

为电流相位角。In the formula,

is the voltage phase angle;

is the current phase angle.

得到电压与电流上位相位差角θ。In step 1303, the calculated in step 1302 Into the formula

Obtain the upper phase difference angle θ of voltage and current.

In step 1304, the voltage-current phase difference angle θ calculated in step 1103 is stored in the data storage unit.

(3) The rate of change of active power, rate of change of reactive power and rate of change of frequency at the PCC node is calculated by using the power/frequency rate of change detection method. The process is shown in Figure 14. The process starts at step 1401 . In step 1402, the rate of change of active power, the rate of change of reactive power and the rate of change of frequency at the PCC node are calculated, the formula is as follows:

$\frac{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; P</span>}}{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}<span\; class="notranslate">\; ,</span>$ $\frac{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; Q</span>}}{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}<span\; class="notranslate">\; ,</span>$ $\frac{{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}}{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; Pn</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; Pn</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}$

为第n次采集到的PCC节点处的频率，

为第n-1次采集到的PCC节点处的频率。In the formula, n and n-1 represent the system data obtained from the nth and n-1th sampling respectively; Δt represents the time interval between the nth and n-1th sampling;

is the frequency at the PCC node collected for the nth time,

is the frequency at the PCC node collected for the n-1th time.

无功功率的变化率

和频率的变化率

存入数据存储单元。In step 1403: the calculated rate of change of active power

Rate of change of reactive power

and the rate of change of frequency

into the data storage unit.

无功功率的变化率

和频率的变换率

代入到被动孤岛检测综合指标评价公式，计算综合指标评价β，公式如下：In step 1103, the unbalance degree of active power and reactive power calculated in (1) step 1102 (2) the voltage and current phase difference angle θ calculated in step 1106; (3) the rate of change of active power calculated in step 1108

Rate of change of reactive power

and the conversion rate of the frequency

Substituting it into the comprehensive index evaluation formula of passive island detection to calculate the comprehensive index evaluation β, the formula is as follows:

$\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}\sqrt{\frac{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;Q</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span><span\; class="notranslate">\; \&PartialD;</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}$

In step 1104, it is judged whether the passive detection comprehensive evaluation index value β is less than 10, and if so, go to step 1105, otherwise go to step 1106.

In step 1105, it indicates that the detection result of the distributed power generation system by the passive island detection is normal grid-connected operation, and at this time, the active island detection process is started to review the result of the passive island detection, and step 1006 is executed;

In step 1106, because β>10, it means that the distributed generation system is in an island state. At this time, the system DSP sends out a PWM wave to drive the circuit breaker controller to disconnect the distributed generation system from the grid.

In step 1107, end.

In step 1006, active islanding detection is performed by using the active frequency shift method, as shown in FIG. 15 . The process starts at step 1501 . In step 1502, the angular frequency ω of the inverter output current i _inv is changed,

和扰动后的PCC节点处的角频率值ω_P，其中，ω_p＝2πf_p。In step 1503, collect the three-phase voltage and current values at the PCC node, and calculate the phase angle of the voltage and current after the disturbance

and the perturbed angular frequency value ω _P at the PCC node, where ω _p =2πf _p .

In step 1504: Calculate the impedance angle of the distributed generation system, the formula is as follows:

的差等于负载阻抗角

即有：

If the distributed generation system is in an island state, the phase angle of the voltage and current at the PCC node

The difference is equal to the load impedance angle

That is:

In step 1505, calculate the frequency shift range ω _max and ω _min of the active frequency shift method, the formula is as follows:

In step 1506, compare the angular frequency ω _P at the PCC node, if ω _P does not satisfy the relation constant ω _min <ω _P <ω _max , it means that the result of passive detection is incorrect, go to step 1508, otherwise go to step 1507.

In step 1507, it is determined that the result of the passive detection is correct, and step 1509 is executed.

In step 1508, at this time, the DSP sends a PWM wave to drive the circuit breaker controller to disconnect the distributed generation system from the grid, and execute step 1509;

End in step 1509.

In step 1007, the distributed generation system is in an island operation state, and the communication unit is used to communicate remotely with the upper computer, prompting the operator that the system has been disconnected from the power grid.

In step 1008, the data stored in the data storage unit is used to display the status of the distributed power generation system through the display unit, providing maintenance basis for system maintenance personnel.

In step 1009, for the distributed generation system that has been disconnected from the grid, the islanding detection device will actively detect the distributed generation system through active island detection, and judge whether the distributed generation system meets the requirements for reconnecting to the grid. If so, then The DSP sends out PWM waves to drive the circuit breaker controller to make the distributed generation system reconnect to the grid.

On the basis of one or more flowcharts described in Fig. 10 to Fig. 15, one or more software can be developed for a person skilled in the art without creative work. The software developed in this way will execute the passive islanding detection process described in FIGS. 10 to 14 and the active islanding detection process shown in FIG. 15 . The software is stored in the main control unit (DSP).

Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that these are only examples, and various changes or modifications can be made to these embodiments without departing from the principles and principles of the present invention. substance. The scope of the invention is limited only by the appended claims.

Claims (4)

1. A multi-process islanding detection method, the process is as follows: Step 1: Perform filtering, noise reduction, voltage transformation processing and analog-to-digital conversion on the collected three-phase voltage, current and frequency, and normalize the converted digital signal, and send it to the data memory unit for storage; Step 2: Initialize system parameters, the system parameters include system resistance value R, inductance value L and capacitance value C; Step 3: Using the data stored in step 1, calculate the active power P and reactive power Q of the system, and store the active power value and reactive power value in the data memory unit for preservation; It is characterized in that: it also includes the following steps: Step 4: Send the data in the data storage to the CPU of the DSP, and perform passive islanding detection to determine whether the islanding occurs. Unbalance degree; (2) Utilize phase mutation detection method to calculate voltage and current phase difference angle; (3) Utilize power/frequency change rate detection method to calculate active power conversion rate, reactive power conversion rate and frequency conversion rate; use the above ( 1) From the results of (2) and (3), calculate the comprehensive evaluation index value of passive detection. If the value is less than or equal to 10, it means that the distributed power generation system is in the normal grid-connected operation state. Use the active island detection process to detect the results of passive island Check and execute step 5; if the value is greater than 10, it means that the distributed generation system is in an island state. At this time, the system DSP sends out a PWM wave to drive the circuit breaker controller to cut off the distributed generation system from the grid; Step 5: Active island detection, the method is: use the active frequency shift method to calculate the maximum value ω _max and the minimum value ω _min of the frequency shift, the formula is as follows:

In the formula,

is the voltage phase angle;

is the current phase angle; Calculate the angular frequency ω _P at the node between the distributed generation system and the power grid, and there is ω _p = 2πf _p , if ω _min <ω _P <ω _max is not satisfied, it means that the result of passive detection is incorrect. At this time, the DSP sends out a PWM wave to drive The circuit breaker controller disconnects the distributed generation system from the grid; otherwise, it means that the result of the passive detection is correct, and proceed to step 6; Step 6: The distributed power generation system is in an island operation state, and the communication unit is used to communicate with the upper computer remotely, and the operator is prompted that the system has been disconnected from the grid; Step 7: The data stored in the data storage unit is used to display the status of the distributed power generation system through the display unit, and provide maintenance basis for system maintenance personnel; Step 8: For the distributed generation system that has been disconnected from the grid, the island detection device will actively detect the distributed generation system through active island detection, and judge whether the distributed generation system meets the requirements for reconnecting to the grid. If so, DSP A PWM wave is sent out to drive the circuit breaker controller so that the distributed generation system can be connected to the grid again. 2. The multi-process islanding detection method according to claim 1, characterized in that: the passive islanding detection in step 4 comprises the following steps: Step 4-1: Calculate the active power imbalance between the distributed generation system and the grid node (PCC node) by using the over-undervoltage/over-underfrequency detection method

and reactive power

The imbalance degree, the formula is as follows: $\frac{\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; ,</span>$ $\frac{\mathrm{<span\; class="notranslate">\; \&Delta;Q</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}}\frac{\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; Z</span>}}}{\mathrm{<span\; class="notranslate">\; Q</span>}}<span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; g</span>}}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}$ In the formula: ω _g is the angular frequency of the grid, and ω _g = 2πf _g , f _g is the grid frequency; ω _p is the angular frequency at the PCC, and ω _p = 2πf _p , f _p is the frequency at the PCC node; u _g is the grid voltage; u _p is the voltage at the PCC node; Q _Z is the reactive power on the resonant capacitor, and there is $Q_Z={\mathrm{\&omega;}}_g{\mathrm{Cu}}_g^2;$ Step 4-2: The calculated active power unbalance

and reactive power unbalance

storing to the data memory unit; Step 4-3: Using the phase mutation detection method, calculate the voltage phase angle and current phase angle: The separation is measured by the voltage sensor

Two voltage instantaneous values u _n , u _n-1 , measured by the current sensor are separated by

The two current instantaneous values i _n , i _n-1 , calculate the voltage phase angle and current phase angle, the formula is as follows:

Step 4-4: Calculated in Step 4-3

Into the formula

Get the voltage and current upper phase difference angle θ; Step 4-5: storing the voltage and current phase difference angle θ calculated in step: 4-4 into the data storage unit; Step 4-6: Using the power/frequency rate of change detection method, calculate the rate of change of active power, the rate of change of reactive power and the rate of change of frequency at the PCC node, the formula is as follows: $\frac{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; P</span>}}{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}<span\; class="notranslate">\; ,</span>$ $\frac{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; Q</span>}}{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}<span\; class="notranslate">\; ,</span>$ $\frac{{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}}{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; Pn</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; Pn</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}}$ In the formula, n and n-1 respectively represent the system data obtained from the nth and n-1th sampling; Δt represents the time interval between the nth and n-1th sampling;

is the frequency at the PCC node collected for the nth time,

is the frequency at the PCC node collected for the n-1th time; Step 4-7: Calculate the rate of change of active power

Rate of change of reactive power

and the rate of change of frequency into the data storage unit. 3. the islanding effect detection method of multi-process according to claim 1, is characterized in that: the calculation formula of the passive detection comprehensive evaluation index value described in step 4 is as follows: $\mathrm{<span\; class="notranslate">\; \&beta;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}\sqrt{\frac{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;P</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\frac{{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&Delta;Q</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&theta;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span><span\; class="notranslate">\; \&PartialD;</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; P</span>}}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; /</span><span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>}$ 4. realize the device of the islanding effect detection method of multi-process described in claim 1, it is characterized in that: comprise: Signal collection unit: used to collect the three-phase voltage, current and frequency at the nodes of the distributed power generation system and the power grid, and perform filtering, noise reduction and voltage transformation processing on the collected signals; Main control unit: used to further process the signal collected by the signal acquisition unit, perform passive island detection and active island detection, and control the connection and shutdown of the distributed power generation system and the power grid according to the detection results; Data memory unit: used to store the unbalance degree of active power and reactive power, voltage and current phase difference angle, active power conversion rate, reactive power conversion rate and frequency conversion rate; Communication unit: used to realize the network communication between the island effect detection device and the host computer.

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