CN2514538Y - Automatic power servo unit for solar battery - Google Patents

Abstract

The utility model relates to a solar cell automatic power servo device. A power conversion circuit transforms the direct current output by the solar cell into a finite voltage to supply power to loads under the control of a pulse-wide modulation PWM circuit. The current of a loading return circuit is sampled, the fall of the loading current identifies that the current finely adjusts the duty cycle of a power transformer through a voltage adjustment circuit and the PWM circuit when the loading current falls, thereby ensuring that the power transformer always works at the maximum power output point of the solar cell. The utility model is characterized in that the circuit control has no quantity operation, the processing procedures are less, the circuit errors have no influences to the control results, and the control is accurate and fine, additionally the circuit structure is simple and the cost is low.

Description

A kind of solar cell automated power servomechanism installation

Technical field

The utility model relates to solar cell, and the solar cell automatic control equipment of electric energy particularly can automatically be provided to load with maximum power under various illumination, temperature conditions.

Technical background

At present, the mankind utilize the research of aspect very active to solar energy, and especially technology reaches its maturity aspect solar cell, and application also more and more widely.Be in the electric power system of the energy with the solar cell, conventional power circuit is because of being with fixed voltage, current work, and the actual power utilance is not high.Some solar cell power tracking circuit are also arranged in the prior art, and they are operated in fixing magnitude of voltage and are aided with temperature or illuminance compensation.Yet under different illumination and temperature conditions, solar cell optimal discharge voltage is indefinite, and above Circuits System can't be carried out fine compensation, tracking.

The disclosed a kind of power-supply device of known Chinese patent publication number CN1171650A, its operation principle is to detect the output voltage and the electric current of solar cell, and this voltage and current value multiplied each other in described multiplier obtain output power value, and output switch circuit is carried out a series of adjustment by described maximum power point detection device, in order to follow the tracks of maximum power point (mpp).But processing of circuit links such as described electric current, voltage detecting circuit, multiplier and maximum power checkout gear are too much, and the trueness error of each link circuit will have influence on final result to a great extent, cause the skew of real work point and maximum power point (mpp).Because described power-supply device circuit structure is too complicated, application cost is higher in addition.

Summary of the invention

Technical problem to be solved in the utility model is: provide that a kind of data processing link is few, circuit structure is simple, cost is low, under different light, temperature conditions, always can accurately work in maximum power point, thereby improve the solar cell automated power servomechanism installation of the utilance of solar cell.

The utility model solves the problems of the technologies described above the technical scheme that is adopted: its input is connected with solar cell, and it comprises the power inverter that the direct current of solar cell output is transformed into the voltage that is fit to the load use; Be connected on the load of power inverter output; Power inverter is carried out the pwm circuit of pulse width control; The voltage sampling regulating circuit that solar cell output services voltage is taken a sample and operating voltage range is tentatively regulated; The voltage-regulating circuit that solar cell output services voltage is accurately adjusted; The load current sample circuit that the loop current of load is taken a sample; Described load current is carried out the time difference relatively to produce the load current decline judging circuit of load current falling pulse signal.

The utility model solar cell automated power servomechanism installation, allow solar cell earlier with certain fixed voltage work, then according to the operating voltage of output loop electric current micromatic setting, when the output loop electric current is maximum, the power maximum that device obtains from solar cell, this moment, corresponding operating voltage was the optimum operating voltage under precondition, and consequently under various illumination, temperature conditions, solar cell is always operating at maximum power point (mpp).

The variation tendency that the utility model just rises or descends output load current in described electric current time difference comparator is differentiated, thereby the height to operating voltage carries out fine adjustment, all the time there is not the computing of physical quantity numerical value aspect, therefore the precision of each circuit part can reach very high control precision to the not influence of final result of control.In addition, the utility model circuit structure is simple, cost is low.

Description of drawings

Fig. 1 is the circuit structure diagram of the utility model embodiment

Fig. 2 is the structure chart of the described load current decline of Fig. 1judging circuit 6 and voltage-regulatingcircuit 5

Fig. 3 is the utility model embodiment workflow diagram

Fig. 4 is the working timing figure of load current decline judging circuit among the embodiment

Fig. 5 is the output characteristic curve of solar cell

Fig. 6 is the output I/V curve of solar cell under the different condition

Specific embodiments

The circuit structure diagram of the utility model embodiment as shown in Figure 1, its input is connected withsolar cell 1, and output is connected with accumulator load 7, and it comprises the direct voltage V withsolar cell 1 output_InChange into and be fit to the output voltage V that load is used_OutPower inverter 2; Power inverter 2 is carried out the pwm circuit 3 of pulse width modulation controlled; By the resistance R that is serially connected in accumulator load 7 output loops_oThe load current sample circuit 8 that constitutes; The sampling current that load current sample circuit 8 is produced amplifies, handles, and produces the load currentdecline judging circuit 6 of a load current falling pulse signal when load current descends; Can by load current descendjudging circuit 6 output load current falling pulse signal triggering and can be to adjusting capacitor C₃Discharge and recharge operation accurately, be used for accurately controlling the voltage-regulatingcircuit 5 of the output pulse width of pulse width modulator PWM3; Voltage control signal is provided for pwm circuit 3, and definitesolar cell 1 output services voltage range by potentiometer W and resistance R₁The voltage sampling regulating circuit of forming 4.Power inverter 2 outputs are connected with load 7.

Power inverter 2 is by being serially connected in the switch element T, the outputting inductance L that are subjected to pwm circuit 3 outputs control betweensolar cell 1 and the outputting inductance L, being connected on output voltage V_OutThe output capacitance C of end₂, switching diode D constitutes.Power inverter 2 under the control of pwm circuit 3, the direct voltage V thatsolar cell 1 is produced_InConvert the direct voltage V that is fit to accumulator load 7 to_Out, accumulators load 7 chargings.Capacitor C₁, C₂Be respectively input, output filter capacitor.

As shown in Figure 2 load currentdecline judging circuit 6 and voltage-regulatingcircuit 5, load currentdecline judging circuit 6 comprises: the load current signal I that load current sample circuit 8 is provided_iAmplify by amplifier U₁The sampling current amplifier of forming 9; Will be through analog switch SW₁Be kept at C₄On previous time current signal and instant current signal constantly compare by amplifier U₂The electric current time difference comparator of forming 10; Through analog switch SW₂Constantly the load current dropping signal of electric current time difference comparator 10 outputs is carried out shaping when in sight and export a load current falling pulse signal by amplifier U₃The electric current falling pulse of forming forms circuit 11; Clocking S₁, S₂Control analog switch SW₁, SW₂, form the circuit 11clock road 12 of sequential working on request to cooperate electric current time difference comparator 10 and electric current falling pulse.

Voltage-regulatingcircuit 5 comprises: can be by the descend flip-flop circuit 13 of the load current falling pulse signal triggering thatjudging circuit 6 exported of load current; Positive output end Q by flip-flop circuit 13 controls, gives at the high level state of Q and adjust capacitor C₃The charging constant-current source 14 of charging; By the reversed-phase output Q control of flip-flop circuit 13, give the adjustment capacitor C at the high level state of Q₃The discharge constant-current source 15 of discharge.

The utility model embodiment is with the output voltage V ofsolar cell 1_InThrough a power inverter 2 of forming by the switching power circuit of routine, convert the output voltage V that is suitable for accumulator load 7 chargings to_OutAccumulators load 7 chargings, so the output voltage V ofsolar cell 1_InOutput voltage V with power inverter 2_OutBetween, there is following numerical relation:

V_out＝V_in*D

D represents the duty ratio of power inverter 2 work, the i.e. ratio of the pulsewidth TON of the output control signal of pwm circuit 3 and work period T in the formula.

Because the terminal voltage at accumulator load 7 two ends is the output voltage V of power inverter 2_OutSo relative fixed is the output voltage V ofsolar cell 1_InTo change with the variation of duty ratio D.Therefore, we can pass through to adjust the output voltage V of the duty ratio D of power inverter withsolar cell 1_InBe transferred to and optimum operating voltage U_mUnanimity, in Fig. 5, this moment, the output current ofsolar cell 1 just in time was maximum output point P_mPairing output current I_m, at this momentsolar cell 1 is operated in maximum power point P_m

As shown in Figure 6, arrow institute how is V among the figure_InFollowing range is because the output voltage V ofsolar cell 1_InUnder different illumination temperature conditions, change, so best output services voltage U_mAlso change.Therefore in an embodiment, be that duty ratio is accurately adjusted by pulsewidth to pwm circuit, make the output voltage V ofsolar cell 1_InAlways work in the optimum operating voltage point, as the u among Fig. 6₁Or u₂Or u₃, make the power output maximum ofsolar cell 1.

In Fig. 1, if do not consider circuit loss, the power output P ofsolar cell 1_In, power inverter 2 power output P_Out, output voltage V_OutAnd output loop electric current I_OutBetween following relational expression arranged:

P_in＝P_out＝V_out*I_out

Because V_OutSubstantially constant, sosolar cell 1 power output P_InVariation will be directly reflected into the variation of output loop electric current, that is to say P_InIncrease I_OutAlso increase; P_InReduce I_OutAlso reduce.Therefore can pass through the output loop electric current I_OutDetection, and learn P_InVariation tendency.

In the load currentdecline judging circuit 6 in Fig. 2, by amplifier U₁, R₄, R₃9 pairs of load circuit current sampling signals of sampling current amplifier of forming amplify, and current signal is input to comparator U₂Be kept at capacitor C with previous time₄On the previous time current signal compare, when constantly current signal is less than the previous time current signal in the time of at once, at comparator U₂Output obtain the load current dropping signal of a high level, the clock signal S that utilizesclock circuit 12 to produce₂High level connect analog switch SW when in sight constantly₂Thereby, by amplifier U₃The output that the electric current falling pulse of forming forms circuit 11 obtains a load current falling pulse signal.

As shown in Figure 4, at 0-t₁During this time, S₁The output high level, analog switch SW₁Conducting, the current signal that this moment sampling current amplifier 9 is exported is kept at capacitor C₄In; At t₁-t₂During this time, S₁Output low level, analog switch SW₁Disconnect current signal and the 0-t of this moment₁Be kept at capacitor C during this time₄In current signal together be added in amplifier U₂Two inputs compare, work as t₁-t₂Load current compares 0-t during this time₁Load current hour during this time, amplifier U₂Be output as high level; Otherwise amplifier U2 is output as low level.At t₁-t₂During this time, S₂Be output as high level, analog switch SW₂Conducting is by amplifier U₃The output level that the electric current falling pulse of forming forms circuit 11 depends on amplifier U₂Output level.As amplifier U₂When being output as high level, through amplifier U₃The load current falling pulse signal of a high level of shaping output.Therefore, only when load current descended, load currentdecline judging circuit 6 just can be exported a load current falling pulse signal.

In the voltage-regulatingcircuit 5 in Fig. 2, through the triggering of described load current falling pulse signal, the output state of flip-flop circuit 13 overturns, and that is to say, if previous time is adjusted capacitor C₃In discharge, the so instant charged state that constantly changes into; If previous time is adjusted capacitor C₃In charging, the so instant discharge condition that constantly changes into.Because can only there be a kind of stable state in 13 each moment of flip-flop circuit, so adjust capacitor C₃Each constantly can only be in a kind of operating state, or is charging, or is discharge.By to adjusting capacitor C₃The voltage at two ends carries out precision control, and passes through R₂The accurate output pulse width of adjusting pwm circuit 3 is realized the precision control to the power output ofsolar cell 1.

In Fig. 1, by potentiometer W and resistance R₁The voltage sampling of forming is adjusted circuit 4 and is provided a fixing duty ratio by pwm circuit 3, at this moment the output services voltage V ofsolar cell 1_InBe a corresponding fixed value, such as the u among Fig. 5₂, this moment, accumulator load began charging.Owing to be engraved in during voltage-regulatingcircuit 5 and exchange whole capacitor C₃Discharge and recharge operation, thereby adjust capacitor C₃Terminal voltage u_C3Constantly be in the process of rising or falling, corresponding with it, the output voltage V of the pulsewidth of pwm circuit 3,solar cell 1_In, the load circuit electric current I_OutAlso in process of rising or falling, the entire circuit device will carry out processing procedure such as Fig. 3, constantly carry out above-mentioned detection, triggering, adjustment, and the power output ofsolar cell 1 is always worked on the maximum power point.

In sum, according to the utility model solar cell automated power servomechanism installation, by the relatively-stationary load current density of voltage is taken a sample, previous electric current during certain and instant electric current are compared, can detect the variation tendency ofsolar cell 1 power output,, makesolar cell 1 accurately be operated in maximum power point by adjusting to power inverter 2 duty ratios, be not subjected to illuminance and Temperature Influence, and circuit structure is simple, cost is low.

Claims (3)

1, a kind of solar cell automated power servomechanism installation, its input is connected with solar cell (1), output is connected with load (7), it is characterized in that: it comprises the power inverter (2) that the direct current of solar cell (1) output is transformed into the voltage that is fit to the load use, power inverter (2) is carried out the pwm circuit (3) of pulse width control, the voltage sampling regulating circuit (4) that solar cell (1) output services voltage is taken a sample and operating voltage range is tentatively regulated, the voltage-regulating circuit (5) that solar cell (1) output services voltage is accurately adjusted, the load current sample circuit (8) that the loop current of load (7) is taken a sample, described load current is carried out the time difference relatively to produce the load current decline judging circuit (6) of load current falling pulse signal; Power inverter (2) output is connected with load (7).

2, solar cell automated power servomechanism installation as claimed in claim 1, it is characterized in that: load current decline judging circuit (6) comprising: the load current sampled signal is amplified and export sampling current amplifier (9) corresponding to the current signal of output current; Previous time current signal and instant current signal are constantly compared, when the pairing voltage of current signal is low constantly in the time of at once, produce the electric current time difference comparator (10) of a load current dropping signal; The electric current falling pulse of a load current falling pulse signal of the output of shaping constantly forms circuit (11) when in sight with the load current dropping signal; And clock signal is used to control described electric current time difference comparator (10) and the electric current falling pulse forms the clock circuit (12) that circuit (11) is worked.

3, solar cell automated power servomechanism installation as claimed in claim 2, it is characterized in that: voltage-regulating circuit (5) comprising: under load falling pulse signal triggering, make the output level state that the flip-flop circuit (13) of upset take place: by the control of flip-flop circuit (13) output, can be to adjusting the charging constant-current source (14) of electric capacity charging when flip-flop circuit (13) first stable states; And by the control of flip-flop circuit (13) output, can be to adjusting the discharge constant-current source (15) of capacitor discharge when flip-flop circuit (13) second stable states.

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