CN103812114A - Front feed type voltage series compensation device based on wind electricity - Google Patents

Abstract

A feedforward voltage series compensation device based on wind power, comprising: a controller, a rectification unit, an H-bridge inverter unit, a series transformer, a DC voltage sensor, a DC current sensor, an AC voltage transformer, and a grid-connected inverter. The invention controls the output of wind power. When the power grid is running normally, the wind power feeds electric energy to the power grid through the grid-connected inverter, and the output voltage of the series compensator is zero; Control the series compensator to quickly output the corresponding compensation voltage, so that the voltage at the load end remains unchanged, so as to protect the load from the influence of the grid fault, and at the same time use the grid-connected inverter to maintain the stability of the DC bus voltage; use wind energy to solve the problem The energy storage problem of the traditional series compensator, the grid-connected inverter adopts the feed-forward method, so the extra capacity of the series transformer and the series-compensated inverter unit is not increased, so it has the characteristics of wind power feed-forward and fast compensation for grid voltage changes.

Description

A Feedforward Voltage Series Compensation Device Based on Wind Power

technical field

The invention relates to the technical field of power quality, in particular to a feedforward voltage series compensation device based on wind power.

Background technique

Developed countries have very high requirements on power quality. Power quality problems will not only bring great economic losses to the industry, such as shutdown and restart, which will increase production costs, damage responsive equipment, scrap semi-finished products, and reduce product quality. Marketing difficulties will damage the company's image and good business relations with users, etc., and will also bring harm to equipment in important power-consuming departments such as medical care, causing serious production and operation accidents. Research by the American Electric Power Research Institute (EPRI) shows that electric energy Quality problems cause US industry to lose $30 billion in data, materials and productivity every year (Electric Power Research Institute, 1999); developed countries such as Japan also have high requirements for power quality. With the rapid development of my country's high-tech industry, the requirements for power quality are getting higher and higher, and voltage sags (sags, dips) are the main problems. Voltage sags will not only cause voltage quality problems in power systems, but also endanger The safe work of electrical equipment, power system failure, large-scale motor startup, branch circuit short circuit, etc. will cause voltage sag. Although the voltage sag time is short, it will cause interruption or shutdown of the industrial process, and the shutdown period of the industrial process caused It is far longer than the time of the voltage sag accident itself, so the loss caused is very large.

Traditional methods, such as voltage regulators, cannot solve these problems. Although uninterruptible power supply UPS devices can solve these problems, their cost and operating costs are extremely expensive. In order to solve the above problems, dynamic voltage compensators have been developed at home and abroad. Research. Compared with UPS, dynamic voltage compensator can effectively solve the problem of voltage sag. However, the problem of energy storage has always plagued the problem of dynamic voltage compensators. Although advanced methods such as the minimum energy injection method have been proposed, the additional energy storage has always affected its further promotion and development.

Contents of the invention

In view of the above problems, the purpose of the present invention is to provide a feed-forward voltage series compensation device based on wind power, which makes full use of wind energy. When the power grid is normal, it uses green wind energy to convert wind energy into electrical energy and supply it to the power grid; When the voltage fails, it outputs the corresponding voltage, compensates the difference of the grid voltage, and ensures that the load voltage does not change, thus protecting the load.

Technical solution of the present invention is as follows:

A feed-forward voltage series compensation device based on wind power, characterized in that it consists of: a controller, a rectifier unit, an H-bridge inverter unit, a series transformer, a DC voltage sensor, a DC current sensor, an AC voltage transformer, and a grid-connected inverter device;

The connection relationship of the above components is as follows:

The rectification control terminal of the controller is connected to the corresponding control terminal of the rectification unit, and the H-bridge inverter control terminal of the controller is connected to the corresponding control terminal of the H-bridge inverter unit; The DC voltage input terminal of the controller is connected with the output terminal of the DC voltage sensor, the DC current input terminal of the controller is connected with the output terminal of the DC current sensor, and the AC current input terminal of the controller It is connected with the output terminal of the AC voltage transformer, the input terminal of the rotor speed and rotor angle input signal of the controller is connected with the output terminal of the speed measuring code disc of the synchronous generator, and the grid-connected inverter of the controller The control terminal is connected to the corresponding control terminal of the grid-connected inverter;

The AC input end of the rectification unit is connected to the output end of the synchronous generator, and the DC output end of the rectification unit is connected to the H-bridge inverter unit and the DC bus end of the grid-connected inverter;

The AC output terminal of the H-bridge inverter unit is connected to both ends of the primary coil of the series transformer;

The secondary coil of the series transformer is connected in series in the transmission line of the power grid, and is respectively connected with the power supply end and the load end of the power grid;

The input end of the DC voltage sensor is connected to the DC output end of the rectification unit;

The input end of the DC current sensor is connected in series with the DC output end of the rectification unit;

The input end of the AC voltage transformer is connected to the grid common point voltage;

The DC bus terminal of the grid-connected inverter is connected to the DC bus terminal of the H-bridge inverter unit and the DC output terminal of the rectifier unit, and the AC output terminal of the grid-connected inverter is connected to the grid common point voltage connected.

The controller is realized by a central processing unit, the core of which is a digital signal processor, a single-chip microcomputer or a computer.

The method for performing series compensation using the wind power-based feedforward voltage series compensation device includes the following specific steps:

1) The controller measures the AC supply voltage U _S , the DC voltage U _w and DC current I _w output by the rectifier unit, the speed and rotor angle of the synchronous generator;

2) Calculate the output power P _w of the rectifier unit: P _w = U _w × I _w ;

3) Control the rectifier unit for maximum power tracking of wind power:

Wind energy maximum power tracking: judge whether the output active power P _w of the rectifier unit is greater than the previous output value, if so, continue to increase the synchronous generator speed; otherwise, maintain the synchronous generator speed unchanged;

4) Let U _S0 be the AC power supply voltage value when the power grid is normal:

If the power grid is normal, that is, when the AC power supply voltage U _S is equal to or higher than 90% of the normal voltage U _S0 , the output voltage of the H-bridge inverter unit is controlled to be zero, so that the voltage of the AC line injected into the power supply by the series transformer is zero, and the control and The grid inverter injects wind power into the grid and feeds it back to the grid;

If the power grid fails, that is, when the AC power supply voltage U _S is lower than 90% of the normal voltage U _S0 , the H-bridge inverter unit is controlled so that the voltage output by the series transformer satisfies: U _j = (U _S0 -U _S ), excess wind power can still be injected into the grid by controlling the grid-connected inverter, and if the wind power is not enough, power can be injected into the DC bus through the grid-connected inverter to maintain the stability of the DC bus voltage.

Compared with prior art, characteristics of the present invention are as follows:

1. When the grid voltage drops, the output voltage is connected in series to protect important loads;

2. The series transformer method is adopted to make the applicable voltage range wider;

3. Use wind energy to solve the problem of energy storage for compensation of grid voltage sags (sudden dips, dips).

4. The grid-connected inverter adopts a feed-forward method, so that the capacity of the series transformer and the series-compensated inverter unit are not additionally increased.

Description of drawings

Fig. 1 is a schematic structural diagram of a wind power-based feed-forward voltage series compensation device according to the present invention.

Fig. 2 is a topological diagram of the single-phase H-bridge inverter unit of the present invention.

Fig. 3 is a topological diagram of the grid-connected inverter of the present invention.

Fig. 4 is a block diagram of series compensation control in the present invention.

Detailed ways

The present invention will be further described below in conjunction with the embodiments and accompanying drawings, but the protection scope of the present invention should not be limited thereby.

Please refer to FIG. 1 first. FIG. 1 is a schematic structural diagram of a wind power-based feed-forward voltage series compensation device according to the present invention. It can be seen from the figure that a feedforward voltage series compensation device based on wind power includes: a controller 1, a rectifier unit 2, an H-bridge inverter unit 3, a series transformer 4, a DC voltage sensor 5, a DC current sensor 6, and an AC voltage sensor. Transformer 7, grid-connected inverter 8.

The connection relationship of the above components is as follows:

The rectification control terminal of the controller 1 is connected to the corresponding control terminal of the rectification unit 2, and the H-bridge inverter control terminal of the controller 1 is connected to the corresponding control terminal of the H-bridge inverter unit 3 connected; the DC voltage input terminal of the controller 1 is connected with the output terminal of the DC voltage sensor 5, the DC current input terminal of the controller 1 is connected with the output terminal of the DC current sensor 6, and the The AC current input terminal of the controller 1 is connected to the output terminal of the AC voltage transformer 7, and the input terminal of the rotor speed and rotor angle input signal of the controller 1 is connected to the output terminal of the speed measuring code disc of the synchronous generator , the grid-connected inverter control terminal of the controller is connected to the corresponding control terminal of the grid-connected inverter 8;

The AC input terminal of the rectification unit 2 is connected to the output terminal of the synchronous generator, and the DC output terminal of the rectification unit 2 is connected to the DC bus terminal of the H-bridge inverter unit 3 and the grid-connected inverter 8 connected;

The AC output end of the H-bridge inverter unit 3 is connected to both ends of the primary coil of the series transformer 4;

The secondary coils of the series transformer 4 are connected in series in the transmission line of the power grid, and are respectively connected to the power supply end and the load end of the power grid;

The input end of the DC voltage sensor 5 is connected to the DC output end of the rectification unit 2;

The input end of the DC current sensor 6 is connected in series with the DC output end of the rectification unit 2;

The input terminal of the AC voltage transformer 7 is connected to the grid common point voltage;

The DC bus terminal of the grid-connected inverter 8 is connected to the DC bus terminal of the H-bridge inverter unit 3 and the DC output terminal of the rectifier unit 2, and the AC output terminal of the grid-connected inverter 8 is connected to the The grid common point voltage is connected.

The specific implementation is as follows:

The controller 1 controls the rectification unit 2 to track the maximum power of wind energy, and converts the alternating current output by the synchronous generator into direct current. The DC bus bar of the device 8 is connected; the AC output terminal of the H-bridge inverter unit 3 is connected with the two ends of the primary coil of the series transformer 4, and the secondary coil of the series transformer 4 is connected in series in the transmission line of the power grid , respectively connected to the grid power supply terminal and the load terminal, the AC output terminal of the grid-connected inverter 8 is connected to the grid; the DC voltage input terminal of the controller 1 is connected to the output terminal of the DC voltage sensor 5, and the control The DC current input terminal of the controller 1 is connected with the output terminal of the DC current sensor 6, and the DC voltage and the DC current output by the rectifier unit 2 are respectively measured by the DC voltage sensor 5 and the DC current sensor 6; the AC voltage input of the controller 1 The end is connected with the output end of the AC voltage transformer 7, and the AC power supply voltage of the power grid is measured through the AC voltage transformer 7.

When the power grid is normal, the controller 1 controls the H-bridge inverter unit 3 so that the output AC voltage is zero, and by controlling the grid-connected inverter 8, the wind power is injected into the grid through the grid-connected inverter 8; the grid voltage is lower than normal When the voltage is 90%, the H-bridge inverter is controlled to perform series voltage compensation, and the excess wind power is injected into the grid through the grid-connected inverter 8. When the wind power is insufficient, the power is fed back to the DC bus through the grid to maintain the DC bus voltage. constant.

Figure 2 is a topological structure diagram of a single-phase H-bridge, and the three-phase structure is the same.

Figure 3 is a two-level topology diagram of a three-phase grid-connected inverter.

Figure 4 is a block diagram of the series compensation control method, through the measured DC voltage and DC current, calculate the output power P _w of wind power, and carry out the maximum power tracking control of wind power; by detecting the AC voltage of the power grid, it is judged whether the AC voltage of the power grid is normal. When the grid fails, the controller 1 controls the inverter unit 3 to output a corresponding AC voltage variation, and controls the grid-connected inverter 8 to inject wind power into the grid.

Specific steps are as follows:

1) The controller 1 measures the AC supply voltage U _S , the DC voltage U _w and the DC current I _w output by the rectifier unit 2, the speed and rotor angle of the synchronous generator;

2) Calculate the active power P _w output by the rectification unit 2: P _w = U _w × I _w ;

3) Control the rectifier unit 2 to track the maximum power of wind power:

Wind energy maximum power tracking: judge whether the active power _Pw output by the rectifier unit 2 is greater than the previous output value, if so, continue to increase the synchronous generator speed; otherwise, keep the synchronous generator speed unchanged;

4) Let U _S0 be the AC power supply voltage value when the power grid is normal:

If the power grid is normal, that is, when the AC power supply voltage U _S is equal to or higher than 90% of the normal voltage U _S0 , the output voltage of the H-bridge inverter unit 3 is controlled to be zero, so that the series transformer 4 injects the power supply AC line voltage to be zero, and Control the grid-connected inverter 11 to inject wind power into the grid and feed it back to the grid;

If the power grid fails, that is, when the AC supply voltage U _S is lower than 90% of the normal voltage U _S0 , the H-bridge inverter unit 3 is controlled so that the voltage output by the series transformer 4 satisfies: U _j =( U _S0 -U _S ), excess wind power can still inject power into the grid by controlling the grid-connected inverter 8, if the wind power is not enough, inject power into its DC bus through the grid-connected inverter 8, so as to maintain the stability of the DC bus voltage .

Claims (3)

1. the feed-forward type Voltage Series compensation arrangement based on wind-powered electricity generation, is characterised in that to form to comprise: controller (1), rectification unit (2), H bridge inversion unit (3), series transformer (4), direct current voltage sensor (5), DC current sensor (6), AC voltage transformer (7), combining inverter (8);

The annexation of above-mentioned parts is as follows:

The rectification control end of described controller (1) is connected with the corresponding control end of described rectification unit (2), and the H bridge inversion control end of described controller (1) is connected with the corresponding control end of described H bridge inversion unit (3), the DC voltage input end of described controller (1) is connected with the output of described direct current voltage sensor (5), the direct current input of described controller (1) is connected with the output of described DC current sensor (6), the alternating current input of described controller (1) is connected with the output of described AC voltage transformer (7), the rotor speed of described controller (1), the input of rotor angle input signal is connected with the code-disc output that tests the speed of synchronous generator, the parallel network reverse control end of described controller is connected with the described corresponding control end of combining inverter (8),

The ac input end of described rectification unit (2) is connected with the output of synchronous generator, and the DC output end of described rectification unit (2) is connected with the DC bus end of combining inverter (8) with described H bridge inversion unit (3);

The ac output end of described H bridge inversion unit (3) is connected with the two ends of the primary coil of described series transformer (4);

The secondary coil of described series transformer (4) is serially connected in the power transmission line of electrical network, is connected respectively with the feeder ear of electrical network with load end;

The input of described direct current voltage sensor (5) is connected with the DC output end of described rectification unit (2);

The input of described DC current sensor (6) is serially connected with the DC output end of described rectification unit (2);

The input of described AC voltage transformer (7) is connected with electrical network common point voltage;

The DC bus end of described combining inverter (8) is connected with the DC output end of the DC bus end of described H bridge inversion unit (3) and rectification unit (2), and the ac output end of described combining inverter (8) is connected with electrical network common point voltage.

2. the feed-forward type Voltage Series compensation arrangement based on wind-powered electricity generation according to claim 1, is characterized in that, described controller (1) is realized by CPU, and its core is digital signal processor, single-chip microcomputer or computer.

3. utilize the feed-forward type Voltage Series compensation arrangement based on wind-powered electricity generation described in claim 1 to carry out the method for series compensation, it is characterized in that, the method comprises following concrete steps:

1) controller (1) is measured alternating supply voltage U _s, rectification unit (2) output direct voltage U _wwith direct current I _w, synchronous generator rotating speed and rotor angle;

2) calculate rectification unit (2) active power of output P _w: P _w=U _w× I _w;

3) control rectification unit (2) carries out the maximal power tracing of wind-powered electricity generation:

Wind energy maximal power tracing: judge this rectification unit (2) active power of output P _wwhether be greater than output valve last time, if continue to increase synchronous generator rotating speed; Otherwise, maintain synchronous generator rotating speed constant;

4) establish U _s0for electrical network alternating supply voltage value when normal:

If when electrical network is normal, i.e. alternating supply voltage U _sbe equal to or higher than normal voltage U _s090% time, controlling H bridge inversion unit (3) output voltage is zero, making series transformer (4) inject supply and AC line voltage distribution is zero, and controls combining inverter (11) wind-powered electricity generation is injected to electrical network, feeds back to electrical network;

If electric network fault, i.e. alternating supply voltage U _slower than normal voltage U _s090% time, control described H bridge inversion unit (3), make to meet by the voltage of described series transformer (4) output: U _j=(U _s0-U _s), unnecessary wind-powered electricity generation still can, by controlling combining inverter (8) to electrical network injecting power, if wind-powered electricity generation is inadequate, pass through combining inverter (8) to DC bus injecting power, thereby it be stable to maintain DC bus-bar voltage.

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