CN202309554U

CN202309554U - Photovoltaic grid-connected converter

Info

Publication number: CN202309554U
Application number: CN 201120438180
Authority: CN
Inventors: 郑文英; 周家琪; 周维来; 王刚; 何建华; 胡丽刚
Original assignee: Harbin Jiuzhou Electric Co Ltd
Current assignee: Harbin Jiuzhou Electrical Technology Co.,Ltd.
Priority date: 2011-11-08
Filing date: 2011-11-08
Publication date: 2012-07-04
Anticipated expiration: 2021-11-08

Abstract

A photovoltaic grid-connected converter consists of a DC bus filter capacitor, three sets of IGBT (insulated gate bipolar translator) bridge arms, a freewheel diode and an LC filter circuit, wherein the DC voltage of a solar panel is filtered by the DC bus filter capacitor and stable bus voltage Vdc is obtained; a three-phase full-bridge converter consisting of the three sets of IGBT bridge arm converts the DC bus voltage into three-phase AC; the freewheel diode has an overvoltage protection effect on the IGBT; the three-phase AC is filtered by the LC filter circuit consisting of a three-phase inductor and an AC filter capacitor; and the filtered AC is transmitted to a power grid by a transformer. The photovoltaic grid-connected converter has the characteristics of high response speed, high control precision, safety, reliability, high interference resistance and the like.

Description

A kind of grid-connected converter

Technical field

The utility model belongs to the photovoltaic power generation technology field, is specifically related to a kind of grid-connected converter.

Background technology

The present electric power of China is main with hydroelectric power generation and thermal power generation mainly; In case it is nervous to run into drought or coal supply; Supply of electric power just receives very big influence, and meanwhile China also is faced with the potential threat of energy crisis and environmental pollution, and it is extremely urgent therefore to readjust the energy structure.The development and use new and renewable sources of energy is one of the valid approach of readjusting the energy structure.And in the development and use of regenerative resource, photovoltaic generation is the regenerative resource of tool DEVELOPMENT PROSPECT, is described as " green electric power supply ".In order to seek the alternative energy source of primary energy, the development for new forms of energy has all been accelerated in countries in the world.Wherein the solar energy regenerative resource is nexhaustible, and therefore green non-pollution enjoys national governments to pay close attention to simultaneously.Solar energy is as the energy eternal on the earth, and launch 1.8 * 10 with the light radiation form to earth surface every year ¹⁸The energy of KWh because its radiation scope is wide, can be regenerated, and is simultaneously free from environmental pollution, international community with it as desirable alternative energy source.Along with the fast development of photovoltaic generation industry, the production application of parallel network power generation equipment is generally risen in the whole world, and related accessory supporting with it and control device have also obtained development rapidly.The utility model is exactly the supporting electric equipment for the photovoltaic generation development of complete equipment, a kind of grid-connected converter.

Summary of the invention

Two pwm converters are because its good input and output performance has obtained application widely in the parallel network power generation field.The used two pwm converters of photovoltaic DC-to-AC converter are actually the voltage type PWM converter.Inverter is as the device for converting electric energy in the photovoltaic system, and its performance has directly determined the quality of photovoltaic system.For stand alone generating system; Require on the one hand the inverter can safe and reliable operation; Require it can stablize battery tension on the other hand, make the latter in charge and discharge process, keep stable, this is for the inverter demands for higher performance in the grid-connected system.At first, in order to improve entire system efficient, inverter need can be good at carrying out maximum power point tracking; Secondly, inverter need detect the existence and the generation outage of isolated island rapidly after isolated island takes place, avoid island effect possibly cause the injury and the device damage of field personnel's health; The 3rd; Because the photovoltaic parallel in system capacity is bigger; To the quality of power supply of its output etc. strict requirement will be arranged all, and, also need further consider the influence of photovoltaic parallel in system for whole network system safe and stable operation along with the grid-connected further increase of proportion in electrical network.

For achieving the above object; The technical scheme of the utility model patent is following: a kind of grid-connected converter is made up of dc bus filter capacitor, three groups of IGBT brachium pontis, fly-wheel diode, LC type filter circuits, it is characterized in that: the direct voltage of solar panel obtains stable busbar voltage V after through the filtering of dc bus filter capacitor _DcConvert DC bus-bar voltage into three-phase alternating current through the three phase full bridge converter of forming by three groups of IGBT brachium pontis then; Fly-wheel diode plays the effect of IGBT overvoltage protection; Three-phase alternating current carries out filtering through the LC type filter circuit of being made up of three pole reactor and ac filter electric capacity, and filtered alternating current is sent into electrical network through transformer.

The utility model patent also has some technical characterictics like this:

1, wide bandwidth, low-power consumption, high accurancy and precision, low temperature drift, respond signal acquisition circuit fast the outside signal of telecommunication of system measured in real time, improved the control precision and the response speed of software systems.

2, the signal adopted of signal acquisition circuit is at first sent into signal conditioning circuit, by signal conditioning circuit the interference signal in the sampled signal is handled again, has guaranteed to send into the signal quality of A/D change-over circuit, and then has guaranteed the reliability of controller.

3, adopt DSP as kernel processor chip, improved the control precision and the real time response speed of system.

4, translation circuit and control circuit independent design are isolated fully, and the class of insulation is high, handling safety.

5, adopt optical fiber to transmit signalling technique between control circuit and the IGBT drive circuit, avoided the phase mutual interference between the strong and weak electricity, effectively prevented the intervention of electromagnetic interference.

6, converter has all been set up alternating voltage overvoltage protection, dc bus overvoltage protection and the overcurrent protection function that is incorporated into the power networks on hardware and software, the harm that when effectively having prevented to take place above fault the person and equipment has been caused.

7, on software algorithm grid-connected converter using high accurancy and precision, respond current loop controller fast.

8, stronger antijamming capability.The disturbance of grid-connected converter mainly comes from electrical network.To disturbance, adopted the control strategy of current feed-forward on the software algorithm.

Description of drawings

Fig. 1 is the main circuit block diagram of grid-connected converter;

Fig. 2 is grid-connected converter control circuit block diagram;

Fig. 3 is grid-connected converter current loop control circuit block diagram;

Fig. 4 is that circuit block diagram is simplified in grid-connected converter current ring control.

Embodiment

Do more detailed explanation below in conjunction with 4 pairs of this patents of accompanying drawing 1 to accompanying drawing:

As shown in Figure 1; The utility model is made up of dc bus filter capacitor, three groups of IGBT brachium pontis, fly-wheel diode, LC type filter circuits, and this device specifically is that direct voltage with solar panel obtains stable busbar voltage V after through the filtering of dc bus filter capacitor _Dc, convert DC bus-bar voltage into three-phase alternating current through the three phase full bridge converter of forming by three groups of IGBT brachium pontis then, wherein fly-wheel diode plays the effect of IGBT overvoltage protection, three pole reactor L and ac filter capacitor C _fForm LC type filter circuit, will carry out filtering to the three-phase alternating current that the three phase full bridge converter obtains, at last filtered interchange is incorporated into the power networks through transformer through this filter circuit.

Grid-connected converter described in the utility model patent is that core component constitutes by full-control type power device IGBT; On hardware control circuit, comprise signals collecting and modulate circuit, A/D change-over circuit and DSP main circuit; Through the voltage hall sensor collection through filtered three-phase alternating current line voltage; On software algorithm, adopt advanced line voltage directional vector control; As shown in Figure 2, two closed loop tandem type control structures are adopted in the control of line voltage directional vector: outer voltage, current inner loop.The main effect of Voltage loop is the control DC bus-bar voltage; Electric current loop is then controlled the AC side input current according to the current-order that Voltage loop provides, and realizes the unity power factor operation.Be specially: line voltage directional vector control algolithm earlier with the line voltage vector through coordinate transform by three phase static (a, b, c) the mutually static vertically (α of coordinate system transformation to two; β) coordinate system; Again by two mutually static vertical (α, β) coordinate system transformation rotates (d, q) coordinate system to two synchronised; With (d, q) the d axle of synchronous rotating frame is pressed line voltage vector E orientation.And the d axle component of grid side converter ac-side current vector I is active current, and q axle component is a reactive current.The reference value of this reactive current component is made as 0 can realizes netting the operation of side unity power factor.

In addition, can find out from system mathematic model that the dq component of grid side converter ac-side current exists and intercouple that be difficult to realize that the dq axle component of current on line side vector controls separately, for this reason, this patent has adopted the feedforward decoupling control policy.As shown in Figure 3, we can find out that current on line side dq component has symmetry, and controller can use identical parameter, so design of Controller can only be considered one of them.Be not difficult to find out: the output of pi regulator has compensated the voltage drop on the AC side inductance; Controller adopts the decoupling zero item of electric current dq component to offset the cross-couplings item of two components in the real system, and the feedforward component of line voltage has been offset the influence of line voltage in the real system.

Control structure block diagram after the decoupling zero is as shown in Figure 4, can find out, the controlled device of this moment is reduced to the AC side inductance, and controlled quentity controlled variable is the electric current that flows through inductance.The output of PI controller is the voltage that is added on the inductance from the actual physics meaning, K _pValue determined that directly moment appears in current deviation, will be added in the voltage swing on the inductance, and when getting into stable state PI controller output by the integral part decision of controller.

The reference signal of electric current loop is made up of output and feed-forward signal two parts of the Voltage loop PI controller of process MPPT controller for solar algorithm.Initial period, busbar voltage is less, and voltage PI controller input deviation is bigger, and its output accounts for the overwhelming majority of electric current loop reference; After the output of voltage PI controller reached amplitude limit value, along with the rising of busbar voltage, electric current loop continued to increase with reference to the increase because of feed-forward signal, reaches the amplitude limit value of electric current loop reference; When system's entering stable state, the output of PI controller is almost nil, and the feed-forward signal component is as the reference of electric current loop, and system has had good antijamming capability to the fluctuation of disturbance and line voltage.

The utility model patent also has some technical characterictics like this:

1, wide bandwidth, low-power consumption, high accurancy and precision, low temperature drift, respond signal acquisition circuit fast the outside signal of telecommunication of system measured in real time, improved the control precision and the response speed of software systems;

2, the signal adopted of signal acquisition circuit is at first sent into signal conditioning circuit, by signal conditioning circuit the interference signal in the sampled signal is handled again, has guaranteed to send into the signal quality of A/D change-over circuit, and then has guaranteed the reliability of controller;

3, adopt DSP as kernel processor chip, improved the control precision and the real time response speed of system;

4, translation circuit and control circuit independent design are isolated fully, and the class of insulation is high, handling safety;

5, adopt optical fiber to transmit signalling technique between control circuit and the IGBT drive circuit, avoided the phase mutual interference between the strong and weak electricity, effectively prevented the intervention of electromagnetic interference;

6, converter has all been set up alternating voltage overvoltage protection, dc bus overvoltage protection and the overcurrent protection function that is incorporated into the power networks on hardware and software, the harm that when effectively having prevented to take place above fault the person and equipment has been caused;

7, on software algorithm grid-connected converter using high accurancy and precision, respond current loop controller fast;

8,,, make this converter that stronger antijamming capability arranged so, on software algorithm, adopted the control strategy of current feed-forward to disturbance because the disturbance of grid-connected converter mainly comes from electrical network.

Claims

1. grid-connected converter; Be made up of dc bus filter capacitor, three groups of IGBT brachium pontis, fly-wheel diode, LC type filter circuits, it is characterized in that: the direct voltage of solar panel obtains stable busbar voltage V after through the filtering of dc bus filter capacitor _DcConvert DC bus-bar voltage into three-phase alternating current through the three phase full bridge converter of forming by three groups of IGBT brachium pontis then; Fly-wheel diode plays the effect of IGBT overvoltage protection; Three-phase alternating current carries out filtering through the LC type filter circuit of being made up of three pole reactor and ac filter electric capacity, and filtered alternating current is sent into electrical network through transformer.