CN201893550U

CN201893550U - Anti-islanding protection system for photovoltaic inverter

Info

Publication number: CN201893550U
Application number: CN2010206581354U
Authority: CN
Inventors: 宁华宏; 姜碧光; 李赟
Original assignee: ZHEJIANG EIFESUN ENERGY TECHNOLOGY Co Ltd
Current assignee: ZHEJIANG EIFESUN ENERGY TECHNOLOGY Co Ltd
Priority date: 2010-12-14
Filing date: 2010-12-14
Publication date: 2011-07-06
Anticipated expiration: 2020-12-14

Abstract

The utility model provides an anti-islanding protection system for a photovoltaic inverter. The anti-islanding protection system is characterized by comprising a microprocessor DSP (digital signal processor) and a controller CPLD (complex programmable logic device), which are mutually connected, wherein the CPLD is connected with an ADC (analog-to-digital converter), an acquisition module, a relay and a PWM (pulse-width modulation) controller respectively, the ADC is used for detecting a voltage signal of an electric network, the acquisition module is used for detecting a frequency signal of the electric network, the relay is used for controlling the on-off states of both a contactor on the DC side of the photovoltaic inverter and a contactor on the AC side of the photovoltaic inverter, and the PWM controller is used for controlling the conducting state of an IGBT (insulated-gate bipolar transistor) on the DC side of the photovoltaic inverter; the DSP is connected with the signal output terminal of the ADC; and the signal input terminal of the ADC is connected with a pressure sensor for acquiring the voltage signal of the electric network. The anti-islanding protection system for a photovoltaic inverter, which is provided by the utility model, can quickly detect the islanding effect in a grid-connected power generation system, and achieve timely response, and effective anti-islanding protection.

Description

Photovoltaic DC-to-AC converter is prevented the isolated island protection system

Technical field

The utility model relates to the parallel network power generation technology, and particularly a kind of photovoltaic DC-to-AC converter is prevented the isolated island protection system.

Background technology

As Fig. 1 for showing, be the island effect schematic diagram, island effect is meant, when electrical network hinders etc. and when disconnecting for some reason, grid-connected system fails in time to detect outage, thereby forms the isolated island of a self-energizing of being made up of distribution grid-connected system and local load on every side.

The generation of isolated island phenomenon has serious harmfulness, such as: the safety that jeopardizes maintenance personal on the grid power transmission circuit; Influence the operation program of protection switch on the distribution system, impact electric network protection device etc.

Therefore, need effective anti-island effect checkout gear in the grid-connected system badly, and take the corresponding protection measure.

The utility model content

At the above-mentioned defective that prior art exists, the utility model provides a kind of photovoltaic DC-to-AC converter to prevent the isolated island protection system, can fast detecting go out the island effect that occurs in the grid-connected system, and can in time respond, and effectively realizes anti-isolated island defencive function.

The technical solution of the utility model is as follows:

The utility model provides a kind of photovoltaic DC-to-AC converter to prevent the isolated island protection system, comprising: microprocessor DSP and controller CPLD, and described DSP is connected with described CPLD; Described CPLD links to each other with the analog to digital converter ADC that is used to detect mains voltage signal, the trapping module that is used to detect the mains frequency signal, the relay that is used to control the on off state of photovoltaic DC-to-AC converter DC side contactor and the on off state of photovoltaic DC-to-AC converter converter contactor, the pulse-width modulation PWM controller that is used to control photovoltaic DC-to-AC converter DC side insulated gate bipolar transistor IGBT conducting state respectively; Described DSP also is connected with the signal output part of described ADC, and the signal input part of described ADC is connected with the pressure sensor that is used to gather mains voltage signal.

The beneficial effects of the utility model are as follows:

The utility model provides a kind of photovoltaic DC-to-AC converter to prevent the isolated island protection system; by DSP line voltage and mains frequency are analyzed; can in time judge whether to take place island effect; and after judging generation isolated island phenomenon; on off state by control relay and PWM controller; thereby in time stop to be connected of the power output of grid-connected system and cut-out and electrical network, effectively realized anti-isolated island defencive function.

Description of drawings

Fig. 1 is the schematic diagram of island effect in the prior art;

The circuit theory diagrams of the three-phase photovoltaic DC-to-AC converter that Fig. 2 provides for the utility model;

Fig. 3 prevents the structural representation of isolated island protection system for the photovoltaic DC-to-AC converter that the utility model provides;

The schematic flow sheet of the improved positive feedback frequency displacement technology that Fig. 4 provides for the utility model;

The interruption controls output schematic flow sheet that Fig. 5 provides for the utility model.

Embodiment

Below in conjunction with accompanying drawing a concrete execution mode of the present utility model is described.

For the principle of the anti-isolated island protection system of photovoltaic DC-to-AC converter that the utility model embodiment provides clearly is described, at first introduce the principle of three-phase photovoltaic DC-to-AC converter used in the photovoltaic generating system.As shown in Figure 2, be the circuit theory diagrams of three-phase photovoltaic DC-to-AC converter.

Concrete, for three-phase photovoltaic DC-to-AC converter shown in Figure 2, its direct current side joint PV cell panel module, AC side is exported three road alternating current Ea, Eb, Ec to electrical network; Wherein, three-phase photovoltaic DC-to-AC converter DC side contactor represents that with K1 photovoltaic DC-to-AC converter AC side contactor is represented with K2; For the mating reaction generation alternating current of the direct current of exporting from PV, after the transformer transformation, obtain the alternating current Ea of voltage conforms user's request through capacitor C, Q1 (that is: insulated gate bipolar transistor IGBT), Q2 and inductance L a., do not repeat them here with the Ea road for the production process of Eb, Ec two-way alternating current.

The photovoltaic DC-to-AC converter that present embodiment provides is prevented the isolated island protection system, comprising: microprocessor DSP and controller CPLD, and described DSP is connected with described CPLD; Described CPLD links to each other with the analog to digital converter ADC that is used to detect mains voltage signal, the trapping module that is used to detect the mains frequency signal, the relay that is used to control the on off state of photovoltaic DC-to-AC converter DC side contactor K1 and the on off state of photovoltaic DC-to-AC converter converter contactor K2, the pulse-width modulation PWM controller that is used to control photovoltaic DC-to-AC converter DC side insulated gate bipolar transistor IGBT conducting state respectively; Described DSP also is connected with the signal output part of described ADC, and the signal input part of described ADC is connected with the pressure sensor that is used to gather mains voltage signal.

Therefore, for preventing the generation of island effect, pressure sensor is gathered mains voltage signal in real time, and this voltage signal is transferred to ADC, is transferred to DSP after ADC is converted to digital signal; Simultaneously, trapping module is gathered the mains frequency signal in real time, and this signal is uploaded to DSP after CPLD handles.Therefore, DSP receives line voltage and mains frequency signal in real time, and judges whether to take place island effect according to line voltage that receives and mains frequency signal; If judge island effect takes place, then send the signal of opening K1 and K2 to relay, and send the signal that disconnects Q1-Q6 to the PWM controller by CPLD.Thereby in time stop to be connected of the power output of grid-connected system and cut-out and electrical network, effectively realized anti-isolated island defencive function.

On specific implementation, adopt following 4 kinds of technology altogether:

(1) mains frequency detecting:

The 50Hz system, 49.5Hz≤F _Req≤ 50.5Hz (F _ReqBe the current mains frequency that detects), be that frequency is lost when exceeding the lasting 100ms (5 civil power cycles) of this scope, then interrupt output.The frequency loss recovery adopts 0.1Hz to stagnate and encircles, and promptly loses a 49.5Hz/50.5Hz, and recovery point 49.6Hz/50.4Hz can guarantee like this at the critical point mechanical stability against short circuit.

Wherein, the mains frequency detecting realizes by the capturing function of the trapping module of TI DSP2812, can guarantee frequency detecting precision 0.01Hz.

(2) line voltage detecting:

323V≤V _Volt≤ 418V (V _VoltThe current line voltage that finger detects), it is that voltage is lost that arbitrary line voltage effective value exceeds the lasting 200ms (10 civil power cycles) of this scope, then interrupts output.Voltage recovers the same ring method that stagnates, the V of adopting _Back=V _Loss+ 20V (V _BackBe the line voltage after recovering, V _LossBe the line voltage of losing).

Wherein, ADC adopts 16 8364ADC, thereby guarantees the high sampling precision of line voltage.

Therefore, all higher to the sampling precision of line voltage and mains frequency in this enforcement, the high precision computation that is particularly suitable for high-power machine is controlled.

Mains frequency, line voltage loss recovery all adopt the ring protection technology that stagnates, and can guarantee machine critical point stability.Mains frequency adopts 0.10Hz to stagnate and encircles, and frequency is lost 49.50Hz/50.50Hz, recovers 49.60Hz/50.40Hz; Line voltage adopts the stagnant ring of 20V poor, and promptly 322V/419V loses, and recovers 342V/439V.

(3) improved positive feedback frequency displacement technology

In order to eliminate the blind area of the passive detection method of isolated island, generally adopt the active frequency phase shift method.The utility model adopts improved positive feedback frequency displacement technology.

For guaranteeing in time to realize anti-isolated island detecting, adopt variable phase shift frequency disturbance to handle, before disturbance, increase ratio ring K, be input as frequency error value F _Error(F _Error=F _Feedback-F _Req, wherein, F _FeedbackBe the current frequency that directly collects; F _ReqBe default standard frequency, F _Req=50Hz), be output as the disturbance set-point F of shift frequency _DisturbAs shown in Figure 4, the schematic flow sheet of the improved positive feedback frequency displacement technology that provides for the utility model embodiment.

Concrete, to the F of input _Error, at first regulate the size of ratio ring K value, make it amplify K doubly, judge then and amplify the frequency values of K after doubly whether in predeterminated frequency scope (promptly amplitude limit) up and down that if in this scope, F is promptly exported in then direct output _DisturbIf exceed this scope of amplitude limit up and down, the amplitude limit value of then output correspondence, thus avoided F _DisturbExcessive and the power network current harmonic wave variation that causes of value.

Therefore, before disturbance, increase ratio ring K, increase amplitude limited amplitude protection up and down simultaneously; by being used of these two kinds of technology, after the isolated island phenomenon occurring, frequency is under improved positive feedback frequency displacement method; can cause frequency to lose protection fast, simultaneously, can not have influence on the humorous wave mass of power network current again.

(4) interruption controls output

As shown in Figure 5, the interruption controls output schematic flow sheet for present embodiment provides may further comprise the steps:

Step 501, the default every 100us of DSP regularly interrupts once, judges whether to reach the inverter output signal collection period of 1ms, if judged result is for being that then execution in step 502; If judged result is that then execution in step 504.

Step 502 is gathered the current output signal of inverter, and judges according to default each output signal standard value whether this current output signal loses.If judged result is for being that then execution in step 503; If judged result is that then execution in step 504.Wherein, the current output signal of inverter includes but not limited to: inverter current output voltage signal, frequency signal.

Step 503 is sent the signal of opening K1 and K2 by CPLD to relay, and sends the signal that disconnects Q1-Q6 to the PWM controller.Thereby in time stop to be connected of the power output of grid-connected system and cut-out and electrical network, effectively realized anti-isolated island defencive function.

Step 504 is carried out other control tasks.Include but not limited to: control PI, control AD etc.

Step 505, process ends.

By above-mentioned interruption controls output flow process, when detecting the isolated island phenomenon,, K1/K2 relay and control, PWM are stopped control putting to 100us timing interrupt task for guaranteeing faster cut-out inverter output, every 1ms judges inverter control output 1 time.Therefore, from detecting the inverter Out-Lost to stopping mains supply maximum delay 1ms.

Therefore; prevent the isolated island protection system by the photovoltaic DC-to-AC converter that the utility model embodiment provides; by DSP line voltage and mains frequency are analyzed; can in time judge whether to take place island effect; and after judging generation isolated island phenomenon; by the on off state of control relay and PWM controller, thereby in time stop to be connected of the power output of grid-connected system and cut-out and electrical network, effectively realized anti-isolated island defencive function.

Claims

1. the anti-isolated island protection system of photovoltaic DC-to-AC converter is characterized in that, comprising: microprocessor DSP and controller CPLD, and described DSP is connected with described CPLD; Described CPLD links to each other with the analog to digital converter ADC that is used to detect mains voltage signal, the trapping module that is used to detect the mains frequency signal, the relay that is used to control the on off state of photovoltaic DC-to-AC converter DC side contactor and the on off state of photovoltaic DC-to-AC converter converter contactor, the pulse-width modulation PWM controller that is used to control photovoltaic DC-to-AC converter DC side insulated gate bipolar transistor IGBT conducting state respectively; Described DSP also is connected with the signal output part of described ADC, and the signal input part of described ADC is connected with the pressure sensor that is used to gather mains voltage signal.