CN206671441U - A kind of anti-isolated island test device of photovoltaic combining inverter electronics - Google Patents

Abstract

An electronic anti-islanding test device for photovoltaic grid-connected inverters, including a DC side (4), an input side (3), an output side (5) and a control system. The electronic anti-islanding device is connected in series between the photovoltaic grid-connected inverter (2) and the large power grid (6), the electronic anti-islanding device absorbs energy from the grid side to stabilize the DC side voltage, and the input side is inverted to form a voltage source; After the grid-connected inverter detects a voltage source with a stable frequency, it tracks the voltage output in real time. The power flow of the grid-connected inverter flows to the electronic anti-islanding input side, and the output side feeds energy back to the grid through a four-quadrant control strategy. The utility model adopts the real-time control technology, which can detect the active power and reactive power output by the photovoltaic inverter in real time and calculate the load resistance, inductance and capacitance to be simulated in real time. During the islanding test, anti-islanding protection test experiments can be carried out in various working conditions such as load matching required by the national standard, so that the anti-islanding protection test experiment can not be constrained by site conditions.

Description

A photovoltaic grid-connected inverter electronic anti-islanding test device

technical field

The utility model relates to an electronic anti-islanding test device for a photovoltaic grid-connected inverter, which belongs to the technical field of photovoltaic power generation.

Background technique

In recent years, distributed new energy generation has maintained a continuous growth trend due to its economy and effectiveness, and its access to the distribution network has also brought a series of problems to the power grid, among which "island" is currently the most widely studied one of the subjects. Once islanding occurs, it may cause problems such as personal safety, economic benefits, and power quality. According to the standard, the inverter should be integrated into the 10KV and below voltage level distribution network and should have the protection function of anti-islanding effect. If the power supply of the grid into which the inverter is integrated is interrupted, the inverter shall stop supplying power to the grid within 2s and send out a warning signal at the same time.

At present, with the maturity of photovoltaic grid-connected inverter technology, many islanding detection algorithms have emerged. Anti-islanding detection methods for photovoltaic grid-connected inverters can be divided into two categories: passive and active. Among them, the passive island detection method judges the island based on detecting whether the parameters such as voltage, frequency, and harmonic content exceed the limit. Phase angle jump detection method, harmonic detection method, etc. The main advantage of the passive detection method is that it will not affect the power quality, but there is a large detection blind area; the active detection method is the amplitude and frequency of the inverter current. Inject disturbances such as , phase, etc. When islanding occurs, the voltage parameters of the common point will change to determine the islanding state. Its main advantage is to reduce or even eliminate blind spots, but it will deteriorate the power quality of the power grid and even affect the stability of the power grid. characteristics; small disturbances are generated for the photovoltaic inverter, and a certain parameter of the power grid changes, including frequency drift method, reactive power change method, and harmonic injection method.

At present, the anti-islanding protection of photovoltaic grid-connected inverters mainly uses adjustable RLC parallel simulation load laboratory tests. This test method is not only complicated in the test process, but also under harsh test conditions. With the development of power electronics technology, PWM control technology is becoming more and more mature. , not only accurately control the rectification and inverter to realize the voltage source and current source, but also realize the two-way transmission of energy.

At present, the anti-islanding protection of photovoltaic grid-connected inverters mainly uses adjustable RLC parallel simulation load laboratory tests. This test method is not only complicated in the test process, but also under harsh test conditions.

The traditional RLC load anti-islanding protection test platform is mainly composed of a DC source, a photovoltaic grid-connected inverter, an RLC test unit, a digital oscilloscope, and a large power grid. The traditional experimental method can adjust the RLC parallel load to simulate the island load, and adjust the RLC load through the switch K2 , adjust the value of resistance, inductance, and capacitance, and monitor the input power of manually adjusted RLC load through a digital oscilloscope, which is close to the grid-connected power of the photovoltaic grid-connected inverter. Difficult to achieve accurate power matching.

Contents of the invention

The purpose of the utility model is to improve the anti-islanding test level of photovoltaic grid-connected inverters, effectively solve the limitations of traditional RLC load test conditions, and aim at the shortcomings of the traditional RLC load anti-islanding protection test platform, the utility model discloses a Photovoltaic grid-connected inverter electronic anti-islanding test device.

The technical solution for realizing the utility model is an electronic anti-islanding test device for photovoltaic grid-connected inverters, including a DC side, an input side, an output side and a control system; the input side is connected to the output side through the DC side; the control system controls the DC side , the working parameters of input side and output side.

The electronic anti-islanding device is connected in series between the photovoltaic grid-connected inverter and the large power grid, the electronic anti-islanding device absorbs energy from the grid side to stabilize the DC side voltage, and the input side is inverted to form a voltage source; the grid-connected inverter detects After reaching a voltage source with a stable frequency, the voltage output is tracked in real time, the power flow of the grid-connected inverter flows to the input side of the electronic anti-islanding, and the output side feeds energy back to the grid through a four-quadrant control strategy.

The device adopts a three-phase four-wire back-to-back structure power electronic anti-islanding protection strategy for real-time power matching, realizes real-time matching with the power of photovoltaic grid-connected inverters, automatically generates R, L, and C parameters, and intelligently calculates active power, reactive power The deviation percentage between the power and the rated value realizes the automatic test of the anti-islanding function of the photovoltaic grid-connected inverter, and at the same time feeds the energy of the whole process of the test back to the grid to realize the recycling of energy.

The input side of the device simulates an AC voltage source to achieve high-precision matching of active power and reactive power between the photovoltaic grid-connected inverter and the test device; the output side feeds back the active power absorbed from the input side to the grid efficiently, and the control system uses Adaptive fuzzy PI control.

The self-adaptive fuzzy PI control is based on the premise of conventional PI control, adopts fuzzy inference thought, takes error e and error rate of change e _c as two input quantities of fuzzy controller, and uses fuzzy rule Real-time tuning of PID parameters to optimize PID parameters;

Fuzzy control is to adjust the two parameters in real time to meet different input error e and error change rate e _c , to ensure that the controlled object has good dynamic and static performance; , and then obtain the corrected values △k _p and △k _i through fuzzy reasoning, and get the optimal k _p and k _i from the empirical value and the corrected value;

In the above formula is the classic PI parameter of the system, and △k _p and △k _i are the adjusted values obtained by fuzzy reasoning;

According to the adaptive fuzzy PID control structure, the optimization of PI parameters is realized, and according to the control formula of PI:

△e(t)＝e ^* (t)-e(t)

In the formula, k _p is the proportional coefficient; _ki is the integral coefficient.

Both the input side and the output side are composed of a four-arm IGBT and a filter reactor; the filter reactor of each phase is connected to one arm of the four-arm IGBT; the other end of the filter reactor is connected to the grid-connected inverter Each phase of each phase; the output end of the four-H bridge arm IGBT is connected to both ends of the DC side capacitor.

Similarly, the structure of the output side is the same as that of the input side. Each bridge arm of the four-arm IGBT on the output side is connected to one end of the filter reactor on the output side; the other end of the filter reactor on the output side is connected to each phase of the large power grid; the four-arm IGBT on the output side The output terminal is connected to both ends of the capacitor on the DC side.

The control system includes a calculation module, a voltage phase-locked loop, a PI controller, a control module and a four-quadrant control module; each phase voltage on the input side is connected to the voltage input port of the calculation module and the input end of the voltage phase-locked loop; the input side The output terminals of the reactors in each phase are connected to the current input port of the calculation module, and the current of each phase is input to the calculation module; the voltage and frequency signals output by the voltage phase-locked loop are calculated in real time to calculate the active power command P ^* and reactive power command and Q ^* , The required output voltage and frequency are calculated through adaptive fuzzy PI adjustment, and the pulse generation module generates 16 pulses to control the operation of the four-arm IGBT on the input side; the output voltage on the output side is connected to the voltage input port of the four-quadrant control module; The output current of each phase of the bridge arm IGBT is connected to the current input port of the four-quadrant control module; the output end of the four-quadrant control module is connected to the input end of the control module to control the operation of the four-arm IGBT on the output side.

The control system can be integrated by a controller to realize the control of the electronic anti-islanding test device.

The electronic anti-islanding test device has two working conditions. After the voltage source start mode, it turns into the electronic anti-islanding mode. In the voltage source mode, after the output side detects the grid voltage and frequency parameters, it absorbs the energy from the grid side to stabilize the DC side voltage. The input side inverts the three-phase voltage. After the photovoltaic grid-connected inverter transmits energy on the input side, in order to maintain the stability of the DC side voltage, the output side inverts the energy back to the grid.

The test method of the electronic anti-islanding test device is as follows:

(1) Before the photovoltaic converter performs island detection, the device operates as an AC source first, and outputs a stable voltage amplitude and frequency. After the photovoltaic grid-connected inverter detects a stable voltage, it runs normally in grid connection;

(2) The electronic anti-islanding device detects the active power, reactive power, voltage, frequency, harmonics, and phase parameters input by the equipment in real time, and calculates the load resistance and load inductance that need to be simulated in real time based on the detected amount and the required quality factor Q _f L, load capacitance C;

Through the above formula, calculate the simulated load resistance, load inductance L, and load capacitance C;

(3) After receiving the island mode instruction command, the control system uses the analog R, L, and C parameters to adjust and calculate the instruction through adaptive fuzzy PI, and close-loop control the output voltage amplitude, frequency, phase and harmonic;

(4) Photovoltaic grid-connected inverter electronic anti-islanding test device has both active detection method and passive detection method, passive detection method - the input side of the electronic anti-islanding test device periodically adjusts the voltage frequency, voltage amplitude, and phase angle jump Functions such as variable and superimposed voltage harmonics simulate the sudden changes in voltage, frequency, and phase angle caused by changes in grid parameters during grid islanding, so as to detect the passive anti-islanding function of photovoltaic grid-connected inverters; active anti-islanding - pass the electronic anti-islanding test The device enters the electronic anti-islanding mode and detects the output voltage, active power, reactive power, current, frequency, harmonic and phase parameters of the photovoltaic grid-connected inverter in real time. Calculate the voltage amplitude, frequency, phase, and harmonic modification commands on the input side of the electronic anti-islanding test device, and superimpose the modified commands on the original commands through closed-loop control, so as to realize the changes in voltage amplitude, frequency, phase and harmonics. This is used to test the active anti-islanding function of photovoltaic grid-connected inverters.

The beneficial effect of the utility model is that the utility model adopts the real-time control technology, which can detect the active power and reactive power output by the photovoltaic inverter in real time and calculate the load resistance, inductance and capacitance to be simulated in real time. During the islanding test, anti-islanding protection test experiments can be carried out in various working conditions such as load matching required by the national standard, so that the anti-islanding protection test experiment can not be constrained by site conditions.

The utility model relies on the power electronics technology to develop the power electronics anti-islanding device, and adopts the self-adaptive fuzzy PI controller in the control strategy, which not only overcomes the problem that the traditional PI controller cannot guarantee the steady-state accuracy and dynamic performance of the active or reactive commands. problems, and has a good ability to suppress factors such as changes in parameters due to the environment; the innovative topology of the device adopts a back-to-back three-phase four-wire topology to achieve real-time matching with the power of the photovoltaic grid-connected inverter and automatically generate R , L, and C parameters, intelligently calculate the deviation percentage between active power, reactive power and rated value, and realize the automatic test of the anti-islanding function of photovoltaic grid-connected inverters. At the same time, the whole process of testing energy is fed back to the grid to realize energy recycling. , Overcoming various limitations and drawbacks of traditional testing, improving testing accuracy, and standardizing testing procedures.

Description of drawings

Fig. 1 is the schematic diagram of the electronic anti-islanding protection test platform of the utility model;

In the figure, 1 is the photovoltaic panel/DC source; 2 is the grid-connected inverter; 3 is the input side; 4 is the DC side; 5 is the output side; 6 is the large power grid;

Fig. 2 is the control system of the anti-islanding protection test device of the utility model;

Fig. 3 is the self-adaptive fuzzy PID control structure of the anti-islanding protection test device of the present invention;

Figure 4 is a comparison chart of the anti-islanding response trend under the condition of 100% power of 20kW photovoltaic grid-connected inverter;

Figure 5 is a comparison chart of the anti-islanding response trend under the condition of 60% power of 20kW photovoltaic grid-connected inverter;

Figure 6 is a comparison chart of the anti-islanding response trend under the condition of 33% power of 20kW photovoltaic grid-connected inverter;

Figure 7 is a comparison chart of the anti-islanding response trend under the condition of 100% power of 10kW photovoltaic grid-connected inverter;

Figure 8 is a comparison chart of the anti-islanding response trend under the condition of 60% power of 10kW photovoltaic grid-connected inverter;

Figure 9 is a comparison chart of the anti-islanding response trend under the condition of 33% power of a 10kW photovoltaic grid-connected inverter.

detailed description

The specific embodiment of the utility model is shown in Fig. 1 and Fig. 2 .

In this embodiment, a photovoltaic grid-connected inverter electronic anti-islanding test device includes a DC side 4, an input side 3, an output side 5 and a control system; the input side is connected to the output side 5 through the DC side 4; the control system controls the DC side 4 , the working parameters of input side 3 and output side 5.

In this embodiment, the electronic anti-islanding device is connected in series between the photovoltaic grid-connected inverter 2 and the large power grid 6. The electronic anti-islanding device absorbs energy from the large power grid 6 to stabilize the DC side voltage, and the input side 3 is inverted to form a voltage source; The grid-connected inverter 2 detects a voltage source with a stable frequency and tracks the voltage output in real time. The power flow of the grid-connected inverter 2 flows to the electronic anti-islanding input side 3, and the output side 5 feeds energy back to the grid through a four-quadrant control strategy.

The control system of the electronic anti-islanding device in this embodiment includes a calculation module, a voltage phase-locked loop, a PI controller, a control module and a four-quadrant control module; each phase voltage on the input side is respectively connected to the voltage input port of the calculation module and the voltage phase-locked loop The input terminal of each phase reactor on the input side is connected to the current input port of the calculation module, and the current of each phase is input to the calculation module; the voltage and frequency signals output by the voltage phase-locked loop are calculated in real time ^. The output voltage and frequency are calculated through adaptive fuzzy ^PI adjustment, and the pulse generation module generates 16 pulses to control the operation of the four-arm IGBT on the input side; the output voltage on the output side is connected to the voltage of the four-quadrant control module The input port; the output current of each phase of the four-arm IGBT on the output side is connected to the current input port of the four-quadrant control module; the output end of the four-quadrant control module is connected to the input end of the control module to control the operation of the four-arm IGBT on the output side.

The self-adaptive fuzzy PI system adopted by the electronic anti-islanding device in this embodiment is based on the premise of conventional PI control, adopts the idea of fuzzy reasoning, and uses the error e and the error change rate e _c as the two input quantities of the fuzzy controller, through the fuzzy controller The output variables of the fuzzy rules are used to adjust the PID parameters in real time, so that the PID parameters are optimized. The adaptive fuzzy PID control structure is shown in Figure 3.

The adaptive PI regulator of this embodiment is designed as follows:

Collect the three-phase voltage U _a , U _b , U _c on the AC bus on the input side of the electronic anti-islanding system, calculate the amplitude and frequency of the voltage, and calculate the active and reactive commands P ^* and Q in real time according to the RLC load parameters to be simulated ^* , through the adaptive fuzzy PI adjustment, the output voltage and frequency are calculated and the pulse generation module generates 16 pulses to control the operation of the four-arm IGBT. The output power of the inverter changes with the change of the AC voltage and RLC parameters, and the response at the fundamental frequency is consistent with the real RLC load. As shown in Figure 2, the process includes an active power comparison unit and a reactive power comparison unit.

Assuming that the work command P ^* = U ² /R,

Reactive power instruction Q*＝U ² ·2πf·CU ² /2πf·L,

Feedback active power calculation: P=u _α ·i _α +u _β ·i _β ,

Feedback reactive power calculation: Q＝u _α ·i _α +u _β ·i _β .

The difference between P ^* , Q ^* and P, Q is used as the input of the adaptive modulus PI regulator,

The basic idea of fuzzy control in this embodiment is to adjust the two parameters in real time to meet different input error e and error change rate e _c , so as to ensure good dynamic and static performance of the controlled object. First set according to the experience value , and then the corrected values △k _p and △ki are obtained through fuzzy reasoning, and the optimal _{k p} and _ki are obtained from the empirical values and corrected values.

In the above formula is the classic PI parameter of the system, and △k _p and △k _i are the adjusted values obtained by fuzzy reasoning. According to Figure 3, the optimization of PI parameters is realized, and according to the control formula of PI, it can be obtained:

△e(t)＝e ^* (t)-e(t)

In the formula, k _p is the proportional coefficient; _ki is the integral coefficient.

The test method of the electronic anti-islanding test device of this embodiment is as follows:

(1) Before the photovoltaic converter performs island detection, the device operates as an AC source first, and outputs a stable voltage amplitude and frequency. After the photovoltaic grid-connected inverter detects a stable voltage, it runs normally in grid connection;

(2) The electronic anti-islanding device detects the active power, reactive power, voltage, frequency, harmonics, and phase parameters input by the equipment in real time, and calculates the load resistance and load inductance that need to be simulated in real time based on the detected amount and the required quality factor Q _f L, load capacitance C;

Through the above formula, calculate the simulated load resistance, load inductance L, and load capacitance C;

(4) After receiving the island mode instruction command, the control system uses the analog R, L, and C parameters to adjust and calculate the instruction through adaptive fuzzy PI, and close-loop control the output voltage amplitude, frequency, phase and harmonic;

(4) Photovoltaic grid-connected inverter electronic anti-islanding test device has both active detection method and passive detection method, passive detection method - the input side of the electronic anti-islanding test device periodically adjusts the voltage frequency, voltage amplitude, and phase angle jump Functions such as variable and superimposed voltage harmonics simulate the sudden changes in voltage, frequency, and phase angle caused by changes in grid parameters during grid islanding, so as to detect the passive anti-islanding function of photovoltaic grid-connected inverters; active anti-islanding - pass the electronic anti-islanding test The device enters the electronic anti-islanding mode and detects the output voltage, active power, reactive power, current, frequency, harmonic and phase parameters of the photovoltaic grid-connected inverter in real time. Calculate the voltage amplitude, frequency, phase, and harmonic modification commands on the input side of the electronic anti-islanding test device, and superimpose the modified commands on the original commands through closed-loop control, so as to realize the changes in voltage amplitude, frequency, phase and harmonics. This is used to test the active anti-islanding function of photovoltaic grid-connected inverters.

In this embodiment, for inverters with different capacities, the comparative experiments of using electronic anti-islanding and traditional RLC anti-islanding tests under different powers were carried out respectively under 100% power and 60% power of 20kW photovoltaic grid-connected inverters. 33% power experiment; 10kW photovoltaic grid-connected inverter 100% power experiment, 60% power experiment, 33% power experiment.

In this embodiment, the comparison test between electronic anti-islanding and traditional RLC islanding test was carried out for photovoltaic grid-connected inverters with different capacities of 10kW and 20kW, under the three power conditions of 100% power experiment, 60% power experiment and 33% power experiment, respectively. Nine working conditions of active power and reactive power deviation were tested. Through various working conditions, it can be found that the results of the traditional RLC test method and the electronic anti-islanding test are consistent and meet the requirements of the national standard.

Claims (5)

1. a kind of anti-isolated island test device of photovoltaic combining inverter electronics, it is characterised in that described device includes DC side, input Side, outlet side and control system；Input side connects outlet side by DC side；Control system control DC side, input side and defeated Go out the running parameter of side；

The anti-isolated island device of electronics is connected between photovoltaic combining inverter and bulk power grid, and the anti-isolated island device of electronics is from electricity Net side absorbs energy stabilization DC voltage, and input side inversion forms voltage source；Combining inverter detects the electricity of stable frequency Real-time tracking voltage output after potential source, combining inverter power flow flow to the anti-isolated island input side of electronics, and outlet side passes through four-quadrant Control strategy is limited by energy back power network.

2. the anti-isolated island test device of a kind of photovoltaic combining inverter electronics according to claim 1, it is characterised in that described Device input side analog AC voltage source realize photovoltaic combining inverter and test device active power, reactive power it is high-precision Degree matching；The active power high-efficiency inversion absorbed from input side is fed back power network by outlet side.

3. the anti-isolated island test device of a kind of photovoltaic combining inverter electronics according to claim 1, it is characterised in that described Input side and outlet side form by four bridge legs IGBT and filter reactor；The filter reactor connection four bridge legs IGBT of each phase In a bridge arm；The other end of filter reactor is connected to a phase of combining inverter；Four bridge legs IGBT output end connection DC bus capacitor device both ends.

4. the anti-isolated island test device of a kind of photovoltaic combining inverter electronics according to claim 1, it is characterised in that described Control system includes computing module, voltage phaselocked loop, adaptive PI controller, control module and four-quadrant control module；Input Each phase voltage of side connects the control source port of computing module and the input of voltage phaselocked loop respectively；Each mutually electricity of input side The current input terminal mouth of the output end connection computing module of anti-device, each phase current is inputted to computing module；Voltage phaselocked loop exports Voltage and frequency signal through calculating active command P in real time^*With reactive command and Q^*, adjusted and counted by adaptive PI controller Calculating needs output voltage size and frequency, and 16 road Pulse Width Control input side four bridge legs IGBT works are produced through extra pulse generation module Make；The control source port of the output voltage connection four-quadrant control module of outlet side；Outlet side four bridge legs IGBT's is each mutually defeated Go out the current input terminal mouth of electric current connection four-quadrant control module；The output end link control module of four-quadrant control module it is defeated Enter end to control outlet side four bridge legs IGBT work.

5. the anti-isolated island test device of a kind of photovoltaic combining inverter electronics according to claim 4, it is characterised in that described Control system is integrated by a controller.