CN103915854A - Stochastic integral gain current controller for photovoltaic grid-connected system - Google Patents

Abstract

The invention discloses a stochastic integral gain current controller for a photovoltaic grid-connected system. The stochastic integral gain current controller for the photovoltaic grid-connected system comprises a proportional controller, an integral controller and a random signal generator. The proportional controller controls deviation of an actual output current and a reference current of the photovoltaic system, and when the deviation occurs in the system, the adjusting action of a proportional adjustor takes effect immediately to reduce the deviation; the integral controller enables the photovoltaic system to eliminate steady-state errors, error free degree is enhanced due to the fact that if the errors exist, the integral controller starts work and stops work until all the errors are eliminated, and a stochastic integral gain is generated by the combination of the random signal generator and the integral controller. A stochastic integral gain controller is applied to photovoltaic power generation systems, and low-order harmonic components generated in the grid-connected system can be reduced greatly.

Description

For the random integral gain current controller of photovoltaic parallel in system

Technical field

The present invention relates to a kind of controller, particularly relate to a kind of random integral gain current controller for photovoltaic parallel in system.

Background technology

In recent years, along with updating of photovoltaic power generation technology, and people are to the improving constantly of regenerative resource consciousness, and distributed photovoltaic power generation is favored by people more and more.Distributed photovoltaic power generation system generally includes: parts such as solar module, inverter, support, distribution box, and photovoltaic combining inverter is the heart component of system, have vital impact to energy output and the quality of power supply of generating electricity.Current, photovoltaic DC-to-AC converter is to adopt power electronics HF switch to realize power converter substantially, this can produce a large amount of switch harmonic, low-frequency harmonics, a harmonic wave and DC component etc. undoubtedly, after being connected to the grid, can produce " harmonic pollution ", after large-scale application, can produce hardly imaginable serious consequence to whole electric power networks.But, current most research focus is to concentrate in the generating efficiency of inverter, adopt high frequency technique to come to pursue efficiency simply and ignored power quality problem, the output current harmonics of most of inverter producer has all exceeded domestic, international quality of power supply standard-required.In order to improve the harmonic inhibition capability of combining inverter, being optimized by the hardware topology structure to inverter or pulse-width modulation (PWM) technology is also to realize, but can increase undoubtedly the cost of system.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of random integral gain current controller for photovoltaic parallel in system, and it proposes randomness storage gain, can greatly reduce the low-order harmonic component producing in grid-connected inverting system.

The present invention solves above-mentioned technical problem by following technical proposals: a kind of random integral gain current controller for photovoltaic parallel in system, it is characterized in that, it comprises proportional controller, integral controller and random signal generator, the actual output current of proportional controller control photovoltaic system and the deviation of reference current, once deviation has appearred in system, proportional controller produces regulating action immediately in order to reduce deviation; Integral controller makes photovoltaic system eliminate steady-state error, improves without margin, because there is error, integral controller just carries out, until indifference, integral controller stops; Random signal generator combines to produce a random integral gain with integral controller.

Preferably, the discrete transfer function of the described current controller based on random integral gain become as shown in the formula:

$G_{\mathrm{PI}}\left(s\right)=K_P+\frac{K_{\mathrm{IR}}}{1-z^{-1}}$

Wherein, K _pfixed proportion gain, K _istorage gain, K _iRbe random integral gain, G represents transfer function symbol, and Z represents discrete domain.

Positive progressive effect of the present invention is: the present invention is directed to grid-connected photovoltaic system, on the constant basis of original hardware topology, PWM modulation technique, propose the PI current controller based on random integral gain, can greatly reduce the low-order harmonic component producing in grid-connected inverting system.

Accompanying drawing explanation

Fig. 1 is the theory diagram for the photovoltaic parallel in system of the random integral gain current controller of photovoltaic parallel in system based on the present invention.

Fig. 2 is the theory diagram of random integral gain current controller of the present invention.

Embodiment

Provide preferred embodiment of the present invention below in conjunction with accompanying drawing 1, to describe technical scheme of the present invention in detail.

As shown in Figure 1, comprise photovoltaic array 1 based on the present invention for the photovoltaic parallel in system of the random integral gain current controller of photovoltaic parallel in system, DC (direct current)/AC (interchange) converter 2, pulse-width modulation (PWM) device 3, phase-locked loop (PLL) 4, maximal power tracing (MPPT) controller 5 and the current controller 6 based on random integral gain, photovoltaic array 1, pulse width modulator 3 is all connected with DC/AC converter 2, for the random integral gain current controller 6 of photovoltaic parallel in system, phase-locked loop (PLL) 4 is all connected with maximal power tracing (MPPT) controller 5, random integral gain current controller 6 for photovoltaic parallel in system is also connected with pulse width modulator 3.

As shown in Figure 2, the present invention comprises proportional controller, integral controller and random signal generator for the random integral gain current controller of photovoltaic parallel in system, proportional controller effect is to control the actual output current of photovoltaic system and the deviation of reference current, once deviation has appearred in system, proportional controller produces regulating action immediately in order to reduce deviation; The effect of integral controller is to make photovoltaic system eliminate steady-state error, improves without margin.Because there is error, integral controller just carries out, until indifference, integral controller stops; Random signal generator effect is to combine to produce a random integral gain K with integral controller _iR.Wherein, the I in Fig. 2 _refreference current value, I _measureactual measurement current value, Y _outit is controller output valve.

Due to the intrinsic randomness of system itself, for the moment finds best storage gain to mate, increase a random signal generator, form random integral gain K _iR, replace original fixing storage gain K _i, then with original proportional gain K _psynthetic joining in system controller, finally becomes new random integral gain PI control system, by digital random generator to the storage gain K in conventional PI control device _icarry out random adjustment automatically, and proportional gain K _premain unchanged, finally become random integral gain PI controller of the present invention.That is to say, the storage gain of controller is random adjustment, and produces an output harmonic wave frequency spectrum changing along with the time, thereby realizes more excellent control effect.Current controller based on random integral gain is applied in can suppress electric harmonic distortion (THD) problem of being produced by high frequency electronic switch after single-phase photovoltaic grid-connected inversion system better, compare and adopt traditional preset parameter current controller, THD value can reduce 15%.This invention main thought is: by digital random generator to the storage gain K in traditional controller _icarry out random adjustment automatically, and fixed proportion gain K _premain unchanged.Therefore, in the situation that photovoltaic combining inverter total cost remains unchanged, obtain the better quality of power supply by applying the current controller based on random integral gain proposed by the invention, realize better grid-connected effect.

The discrete transfer function that is used for the random integral gain current controller of photovoltaic parallel in system becomes as shown in the formula (1):

$G_{\mathrm{PI}}\left(s\right)=K_P+\frac{K_{\mathrm{IR}}}{1-z^{-1}}...\left(1\right)$

Wherein, K _pfixed proportion gain, K _iRbe random integral gain, G represents transfer function symbol, and Z represents discrete domain.

In practical operation, need to modulate in advance a fixed proportion gain K who optimized _pwith storage gain K _i, then at storage gain K _ion add a random number.In order to suppress the unsteadiness of output current, within random signal need to being limited in to a scope, this scope is defined as: modulation makes output current start to become unsettled critical minimum and maximum value by experiment.In addition, need to connect a low pass RC filter and carry out level and smooth variable signal after the sampled signal of random signal generator, filter cutoff frequency is approximately elected 560Hz as.

Current controller is to follow the tracks of fast and exactly electrical network reference current for control inverter actual output current, is an extremely important factor that determines the inverter output quality of power supply.Current controller of the present invention is the current controller based on random integral gain, proposes randomness storage gain, can greatly reduce the low-order harmonic component producing in grid-connected inverting system, and improves the power quality problem of inverter output.

Those skilled in the art can carry out various remodeling and change to the present invention.Therefore, the present invention has covered various remodeling and the change in the scope that falls into appending claims and equivalent thereof.

Claims (2)

1. the random integral gain current controller for photovoltaic parallel in system, it is characterized in that, it comprises proportional controller, integral controller and random signal generator, the actual output current of proportional controller control photovoltaic system and the deviation of reference current, once deviation has appearred in system, proportional controller produces regulating action immediately in order to reduce deviation; Integral controller makes photovoltaic system eliminate steady-state error, improves without margin, because there is error, integral controller just carries out, until indifference, integral controller stops; Random signal generator combines to produce a random integral gain with integral controller.

2. the random integral gain current controller for photovoltaic parallel in system as claimed in claim 1, is characterized in that, the discrete transfer function of the described current controller based on random integral gain become as shown in the formula:

$G_{\mathrm{PI}}\left(s\right)=K_P+\frac{K_{\mathrm{IR}}}{1-z^{-1}}$

Wherein, K _pfixed proportion gain, K _istorage gain, K _iRbe random integral gain, G represents transfer function symbol, and Z represents discrete domain.