DE3831142A1 - Solar pump system - Google Patents

Abstract

Solar pump system having a solar cell panel, a DC/AC inverter and a submersible motor with submersible pump. Starting the motor after shutdown requires a particular torque. In addition, solar radiation is very low in the morning, because of which the solar energy for starting the pump is also very low. This is solved, according to the invention, by parallel-coupling of a comparatively large capacitor on the DC side of the inverter, there being in addition devices for protecting an inverter against short-circuit. <IMAGE>

Description

The invention relates to a solar pump system with a Solar cell panel, a DC / AC inverter and a dive motor with a submersible pump.

Starting the engine after it has stopped requires a be right torque. Furthermore, the sun's rays are in the morning very low for what reason the solar energy for that Starting the pump is also very low.

This is done according to the invention by coupling one in parallel relatively large capacitor on the DC side of the Inverters solved, the stored energy in the Moment when the pump is started.

There may also be devices which monitor whether the torque of the electric motor is outside the usual Operating range, since the inverter is switched off, if the torque is outside the usual range.

The invention is explained below with reference to the drawing. It shows

Fig. 1 is a Sonnenpaneelsystem for driving an AC motor with a pump,

Fig. 2 shows the normal operating range of the engine,

Fig. 3 shows a protection circuit for the inverter,

Fig. 4 shows the respective signals in the inverter,

Fig. 5 is a diagram of the operation of the control system,

Fig. 6 shows a circuit for extending the resolution of the A / D converter,

Fig. 8, the three-phase transistor bridge,

FIGS. 7 and 9 and control circuits control stages, and

Fig. 10 is a block diagram of the control circuit.

The sun pump system shown in FIG. 1 is suitable for driving an AC motor by means of an inverter. Starting the engine 3 after it has stopped requires a certain torque. According to the invention, a relatively large capacitor 1 is arranged on the DC side of the inverter 2 . This capacitor 1 stores a suitable amount of energy so that sufficient energy is available to start the engine 3 . The capacitor 1 preferably has 8000 μF.

If you short-circuit two of the phases, however, a relatively moderately strong current flows out due to the relatively large capacitor 1 . A circuit is therefore provided which protects the inverter 2 against short circuits. The inverter 2 is a three-phase transistor bridge. Each phase has two MOS transistors, that is, one that opens at plus voltage and one that opens at minus voltage. The three phases are alternately connected with plus voltage and minus voltage. As mentioned above, if two phases are short-circuited, a fairly strong current flows off. A relatively strong current therefore flows through the transistors, which are destroyed in the process. Conventional effect amplifiers can also not be short-circuited at the output without being destroyed. Here we measure the voltage drop across the transistor, and when the transistor is turned on, it can in principle be equated with a resistor. The voltage drop across the transistor is therefore proportional to the current. A voltage drop above a certain level is the result of an excessive current. You can set this level yourself. The voltage drop is measured in a feedback with a comparator. In this case a NAND gate is used as a comparator. When the level is exceeded, the NAND gate changes at the output, the transistor being switched off and thereby blocking. This happens within 1-2 µsec.

Fig. 3 shows a control stage for turning on a Tran sistor Q 3 in a three-phase transistor bridge. The bridge has a total of six transistors and we can consider the circuit shown in Fig. 3 as a control stage for one of the transistors. The control levels all work in the same way. In terms of time, however, they are shifted in relation to each other. We imagine that Q 3 is switched off at the beginning. Q 3 is then turned on by the signal IN going high, with one input of the NAND gate IC 1.1 going high. The second input of IC 1.1 is high in advance, which corresponds to V _cc . The output of IC 1.1 is switched (SIG 1 ) and goes low. Due to the filter C 1 , R ₁ , SIG 2 also goes low, a short pulse being generated because a voltage change on capacitor C 1 cannot happen at the moment. SIG 2 thus follows when SIG 1 goes low, after which capacitor C 1 is slowly charged by R ₁ , so that SIG 2 finally has the value V _cc , which corresponds to a high signal. In principle, we have a short, negative pulse on one leg of the NAND gate IC 1.2 . The second leg of CI 1.2 is connected to the + terminal through a resistor R ₃ and a resistor LOAD . Since the transistor Q 3 is not yet switched on, there is no voltage drop at the LOAD . This means that the full voltage drop occurs at Q 3 . This voltage is divided by means of R 2 , R 3 in such a way that a positive voltage is supplied to one leg of IC 1.2 . The second leg of IC 1.2 is therefore high. When the weak pulse of SIG 2 occurs , the output of IC 1.2 goes high for a short moment. If nothing else happens, it will go low again. The transistor Q 3 is switched on by means of the subsequent NAND gates IC 1.3 and IC 1.4 and the transistor coupling Q 1 , Q 2 . IC 1.3 has a positive signal directly from IN and the short positive pulse from SIG 4 . This causes the switching input of IC 1.3 (SIG 5 ) to briefly become negative. This signal is then passed through IC 1.4 and inverted such that a short positive pulse occurs. This short positive pulse turns on transistor Q 1 , with Q 3 coupled together with V _cc and thus turned on. If a positive pulse is supplied to the base of transistor Q 1 , the transistor is switched on since the base has almost the same potential as the collector. The moment the transistor is turned on, the resistance across the transistor is almost zero. SIG 7 gets high and almost reaches V _cc . A weak current surge passes directly from V _cc through Q 1 and Q 3 is a switched. The moment Q 3 is switched on, the resistance at Q 3 drops, so that the voltage from the plus terminal to the minus terminal is above LOAD , whereas it was previously at transistor Q 3 . This means that the top leg of IC 1.2 is pulled low by the feedback R 2 , R 3 and D 3 . This maintains a high output signal so that it does not remain the initially weak short pulse. One can say that this impulse blocks itself. Q 3 has been turned on, and will remain so due to the feedback until something happens at IN , such as IN going low because you want to turn it off.

IN thus went high, causing a short pulse at SIG 2 , which switches on transistor Q 3 with IC 1.2 , IC 1.3 , IC 1.4 and Q 1 with this short pulse. When feedback with this voltage closes this short pulse IC 1.2 in such a way that it remains low at the output and Q 3 remains switched on. When IN goes low, IN switches off the transistor Q 3 by means of the same circuit. The transistor is switched on and off by the IN signal. It can happen that the current through Q 3 becomes too high, for example if LOAD is accidentally short-circuited. In this case, the resistance from the plus to the minus terminal is almost zero. Then a much too high current flows and Q 3 starts to work linearly. In principle, one can also imagine that there is a given ON resistance in Q 3 . The higher the current, the greater the voltage at Q 3 . At some point, the voltage becomes so great that it acts as a positive signal on the top leg of IC 1.2 due to the subsequent feedback. The diode D 3 plays a role when the legs go from IC 1.2 to low. But if they are high, the potential follows from the top leg of the IC 1.2 upwards. It simply becomes V _DS , ie the voltage drops at the beginning because LOAD is loaded more and more. When the transistor is turned on, the voltage across it is very low. When the current gets too high, the voltage begins to rise.

There is also a circuit for troubleshooting based on the relationship between the DC current and the AC frequency. A light emitting diode indicates if this ratio lies outside a desired interval. We know the first harmonic frequency that is emitted to the electric gate 3 . This first harmonic frequency is controlled by a computer. An appropriate relationship must exist between the two parameter values, cf. Fig. 2, ie the higher the DC current, the faster the motor rotates. If the frequency is very high and a relatively weak DC current is flowing, something is wrong. It is typically a badge that the pump has run dry and is therefore rotating at maximum speed. If, however, the speed is very low, or if the frequency imposed is very low, the load is too high or the pump is blocked. In this case too, the system is switched off.

Fig. 5 shows the control system of the solar inverter, ie the alternation, the regulation of the DC voltage, which must be kept constant, and the monitoring function. The control system also monitors other parameters such as temperature and voltage during starting. When a voltage is applied, the computer takes up its basic position. A positive pulse is applied to a leg called a reset, and the program starts again. A check of the external conditions is carried out before the computer activates the high-voltage technical part, ie the effect part of the inverter. Some parameter values, such as an external switch, are also checked. Under no circumstances should the engine be started unless this switch is turned on. Temperature fuse is an automatic fuse, whereby the temperature is measured by means of an NTC termister. If it is too high, for example above 85 ° C, the engine will not start because the components are specified at 85 ° C. When the engine is started, the effect is stopped in the box, and the temperature continues to rise. This means that the temperature should be high in the morning. However, the temperature fuse is also activated during operation if the temperature is to be too high. The computer is constantly examining whether it has fallen to an acceptable level, which is approximately 65 ° C in practice, after which it starts again. Every waiting position has the consequence that you start from the basic position. You can therefore have a waiting position due to a too high temperature. Therefore, you naturally check the initial temperature rise. If it is still too high, there is no need to start the engine. The third parameter to be checked before starting is the DC voltage. It must lie within a few given tolerances. If it is too low, this can be a result of the radiation on the sun panels 4 being too low. If it is too low, there is insufficient energy. It is also checked whether it is too high. If it is too high, the sun panels 4 have been incorrectly connected, or simply too many connected in series, which can destroy the inverter 2 . In such a situation, the system waits. This is where it starts, provided that the three parameters are OK. Then we come down to the box called 7 Hz Boost, which is connected to the actuating capacitor 1 . One begins with the inverter at a frequency of 7 Hz with a relative overvoltage on the motor 3 . With an Asyn chron motor, the voltage is usually varied proportionally with the frequency. Here, a relatively high 7 Hz boost voltage is applied to achieve a strong surge in the starting torque to overcome the torque. The 7 Hz boost signal will hold for a second, after which you will go to the start position. This position comprises a series of eight frequency jumps down to 25 Hz. 7, 9, 11 and 13 Hz is sampled, and at every stage, which takes _^1/2 seconds to check the conditions on the upper right. The jumps are due to the fact that the engine has to be accelerated to 25 Hz. The pump does not release water until you have reached 25-30 Hz, and you need an entire data set for each frequency. These jumps are made because you reduce the number of data. If it exceeds 25 Hz, the 63 Hz control is continuous, that is, in principle, occur very small cracks of approximately ^{_1/3 of} Hz from 25 Hz and continues up to a highest frequency. Thereafter, regulation is ongoing. However, each frequency requires a series of data in the computer. To reduce the amount of data, the interval is run from 7 to 25 Hz in steps.

At 25 Hz you can choose between battery operation or solar operation using a microswitch. Usually one selects sun operation, that means that the motor accelerates up to a frequency, which coincides with the radiation on the panel 4 . This happens fairly quickly. The control parameter is the DC voltage. The DC voltage is set, for example, to 120 V, which in principle - if you are not driving a little faster - means that the voltage on the panel 4 increases because energy is available. This raises the frequency a little, which increases the power on the panel 4 , whereby the voltage drops again. This rule can be illustrated in the following way. An increased irradiation on the panel 4 increases the DC voltage, with the result that the solar inverter 2 increases the motor frequency. This consumes a little more power and the DC voltage drops. The voltage is selected according to the optimal working point of the panels 4 . If the voltage is increased, the panel characteristics will collapse and then not as much current will flow away. The tension is therefore on the optimal working point of the characteristic. It can be continuously adjusted down to 18 Hz. There is a certain hysteresis in relation to 25 Hz. When it rises, it goes all the way up to 25 Hz, and once you are above 25 Hz, you can go all the way down to 18 Hz in continuous operation. If it is regulated below, it immediately goes on hold. And if it exceeds 63 Hz, you can choose to close at 50 or 56 Hz.

Furthermore, a circuit for expanding the analog loading range of the A / D converter 7 by means of an operational amplifier coupling with controllable subtraction, cf. Fig. 6, available. According to the invention one works with a resolution of 10 bits. According to the invention, however, only an 8-bit A / D converter 7 is used, which is much cheaper than a 10-bit converter. Since we only need a resolution capability on one of the gates, this is created by an operational amplifier 8 with controllable deflection, so that in principle one can work with 0-20 V, since four different deflection voltages are coupled in, and since the A / D Converter 7 always works in the range 0-5 V. In principle, the entire measuring range from 0 to 20 V is reached. Thus, 2 bits are added by the computer control of the bending voltage. Two gates are used for the addition. The A / D converter works with the computer that creates the additional data. This means that there is a special coupling between a conventional 8-bit A / D converter and the computer. The special feature is a front-mounted operational amplifier 8 with controllable turning.

Fig. 7, 8 and 9 show the whole rectifier bridge with associated control and protection circuits. The control part is first the computer IC 1 . The software above is in this control section. The second diagram with empty blocks is to be used in the diagram in FIG. 7, where a dash-dotted square (control stages with short-circuit protection) can be seen at the bottom right. An internal power supply is arranged at the bottom of FIG. 9, which supplies voltages of 12, 8 and 5 V. A series regulator on the power circuit board supplies the printed circuit with 12 V at the power point, after which the circuit itself transforms down to 8 and 5 V. A side connector S 1-2 can be seen on the right. This connector connection is the connection to the power circuit, cf. Fig. 8. Here we start with an edge connector on the left. The connections then correspond to one another and the two printed circuits are coupled together there. We start with the computer IC 1 . This has a monitoring and LED indication. The light-emitting diodes D 4 are located at the top right of the computer IC 1 , which is able to switch all diodes on and off and thus to indicate what has been measured. In this case, possible errors are indicated. We then go into the A / D converter IC 2 , which is located to the left of the computer IC 1 . Current and voltage are measured on the DC side of the converter. The two upper channels CH 0 and CH 1 measure the voltage. A connection to V _DC can be seen on the left. This voltage passes through some Zener diodes to transform the voltage down. With J 5 you can choose whether you want to down-transform in one way or the other. One works with 105 V and 120 V nominal voltage. You then go through a voltage divider and a lowpass filter and then directly into the A / D converter, which then reads the inputs CH 0 and CH 1 and converts the read values into a binary representation, which then goes on to the computer IC 1 to be led. This was measuring the tension. The upper channel is labeled CH 0 and is used to control V _DC . The lower channel has a resolution that is half the size, which corresponds to covering a larger area. This channel is used for monitoring. We then go down to CH 2 and CH 3 . These channels are used to measure the current. On the far left are some inputs V _{H 1} and V _{H 2} . They come from the printed power circuit, cf. Fig. 8. They are outputs of a Hall generator in the form of a toroid S 1 . An integrated circuit in the form of a Hall element is arranged in the air gap of this toroid S 1 . It measures the magnetic field in the core, and in this way you can measure the current in the windings of the core. The signal is a small voltage that is proportional to the current. This signal is performed in an Operationsver IC 1 stronger. A bending voltage is removed from the amplified signal, which corresponds to the output V _H. This is also a voltage that is proportional to the DC current and is scaled down with minor deviations. The current measurement is, as I said, carried out by means of the above Hall generator with a small ring core and a small Hall element arranged in the air gap. This generates a signal voltage that is proportional to the current running in the coil. The operational amplifiers on the power panel amplify the signal. A total of two operational amplifier couplings are provided, which serve to remove a small turn from the Hall element and scale down to another amplifier, so that we have the signal V _H on the power panel. This signal is a voltage that is proportional to the DC current drawn. The signal is then connected to the control panel by means of the edge connectors S 1-2 mentioned. On the far left we see the V _{H 1} and V _{H 2} inputs. Only one input is used. The second input connects to an inverter to the power panel so that the V _H output of the control panel goes to V _{H 1} and the second to V _{H 2} . Only V _{H 1 is} relevant here, since the second one is set up accordingly. The second input V _{H 2} is calculated for a future inverter for double DC current. In such a case, at least two power panels with their respective V _H input are necessary. The signal then comes in at V _{H 1} in the form of a voltage signal that is proportional to the current, and the signal passes through the operational amplifiers mentioned. The first operational amplifier IC 1 only adds V _{H 1} and V _{H 2} , while the next operational amplifier represents a lowpass filter with a small gain. After the two operational amplifiers there is still a voltage that is proportional to the DC current, and this voltage is applied directly to CH 2 of the A / D converter IC 2 . This signal monitors that the current is neither too strong nor too weak in relation to the current frequency. The signal is then fed to the last operational amplifier IC 8 . It is precisely this part that allows deduction to be made and thus higher resolution. The signal goes in on channel 3 and has a resolution several times better than the signal on channel 2 , and this signal is therefore a so-called power maximization, max. powerpoint tracker, and this maximization is part of the current-voltage characteristic of the solar panel. One tries to reach the optimal point of the panel characteristics, so that the greatest possible performance of the sun panel 4 is drawn. Since you are already close to the optimum point, very small changes in current are important, and it is therefore necessary to have the highest resolution when measuring, for which reason the last link is coupled. This was measuring the current. Then we go up to IC 6 , which is a timer circuit with two independent timers. Two legs are referred to as the basic adjuster, two legs as the discharge, two legs as the threshold values, and two legs as the TRIG etc., ie a circuit with two independent systems, where the output signal of one leg 9 arrives at the computer's IRQ interrupter, and the output signal of the second timer is inserted into the computer at the basic setting. This circuit has two functions. First, at the interrupt input of the computer, which generates a square wave signal with a frequency of approximately 200 Hz and generates interruptions all the time, the 200 Hz signal being used by the computer. Each time it receives an interrupt signal, it knows something special needs to be done and it goes through a control routine to adjust the DC voltage according to an internal reference in the software so that the frequency at which the motor is adjusted is adjusted all the time 3 is driven by power output from the panel 4 , since the DC voltage is the controlling parameter, ie if the power is somewhat higher, the DC voltage on the panel rises a little. This is adjusted by increasing the frequency of the motor a little. The voltage on the panel 4 thus drops. The voltage control - controlled by the breaker signal - is carried out 200 times per second. This is done by part of IC 6 . The second part, the output signal of which is applied to the basic setting of the computer, partly serves to generate a so-called "power up reset". If the computer is supplied with voltage, this is 5 V on, and then the computer requires a basic setting signal, which consists only in the basic setting being low and suddenly going high, ie a rising positive edge is formed. This is called a "power up reset", after which the computer starts at the beginning of the program, which also operates the timer circuit. Two operational amplifiers IC 7 and IC 8 can be seen in the upper left corner. They represent two comparator couplings that monitor the 8 V and 5 V power supply. One monitors 8 V and the second 5 V, which means that if either the 5 V voltage or the 8 V voltage is too low, it goes low at the output and pulls down the basic setting at IC 6 , which also means that the output of IC 6 goes low, the computer also being returned to its home position. In the upper right corner there is an S 8 connector with eight legs. A series of signals are emitted from this plug-in connection, which enables external monitoring and remote control. You can also switch off using a remote control, such as a level switch. Now we come to the output signals to the transistor bridge. We start with legs 25, 26 and 27 of the IC 1 computer. The three signals are control signals to the inverter bridge, and only three signals are necessary. They work in pairs. When one pair turns on, the other turns off. Therefore, three signals contain sufficient data. Then we come into the IC 3 , which is a so-called "level converter" or level converter, which converts the output signal from level 5 V to the output signal at 8 V. It is still a digital circle. It works from 0 to 5 V at the input and from 0 to 8 V at the output. At the same time, the complementary signals are generated. We now take the input I ₀ , which has a corresponding output O ₀ and a corresponding complementary signal 0 ₀. Correspondingly with 0 ₁ and 0 ₂. Then we converted the three signals into the six signals to be used. We then come to the three signals in IC 5 , which changes the signal. Then comes a lowpass filter with a diode in the feedback. This filter acts as a time delay on the signals. When one of the lower transistors the transistor bridge is turned off, the upper transistor is turned on. It must be ensured that the lower transistor is completely switched off before the upper transistor is switched on. You don't react instantly. A weak charge must be released before they are completely switched off, and therefore the switch-on signal is delayed somewhat in relation to the switch-off signal. We then proceed to the signals G 1 , G 3 , G 4 , G 6 and G 2 , and then to the drive part in the second diagram. The drive part basically has three similar stages, where we have shown only one stage in the diagram. One has the six signals G 1 - G 6 . They are used in pairs in the drive stage and are arranged as follows: G 1 , G 4 ; G 3 , G 6 ; G 5 , G 2 . This has to do with how you quantify the transistors. G 1 and G 4 are complementary, as are G 3 and G 6 , which can be seen if the signals are fed back. You are guided through the two drive stages. G 3 is routed through the drive stage and comes out on the other side. S 3 serves as a reference for G 3 , which is to switch on one of the upper transistors. The reference for G 6 is still the framework. We are now looking at the power panel. The most important parts are the six MOS-FET transistors T 1 , T 2 , T 1 ª , T 1 b , T 2 ª , T 2 b in the other two phases. The electrical components initially serve to protect and limit the current. T 3 can be seen below, which performs voltage regulation and step-down transformation of the DC voltage to 12 V. A block diagram of the control circuit is shown in FIG. 10.

Claims (6)

1. Solar pump system with a solar cell panel, a DC / AC inverter ( 2 ), and an AC motor ( 3 ), preferably for driving a pump, and a relatively large capacitor ( 1 ) on the DC side of the inverter. 2. Sun pump system according to claim 1, characterized in that the capacitor ( 1 ) is installed in a unit which can be coupled separately. 3. Solar pump system according to claim 1 or 2, characterized in that the capacitor ( 1 ) has approximately 2000-10 000 µF. 4. Solar pump system according to the preceding claims 1 to 3, characterized in that devices for securing the inverter ( 2 ) against short circuit are also present. 5. Solar pump system according to the preceding claims 1 to 4 using a three-phase transistor bridge with MOSFET transistors, characterized in that each MOSFET transistor (Q 3 ) is protected by measuring the voltage drop across the output transistor V _DS and the mains voltage V _cc so low that the MOSFET transistor begins to work linearly with overcurrent before the maximum peak value of the current is reached, and that one then turns off the MOSFET transistor. 6. Solar pump system according to the preceding claims 1 to 5, characterized in that there are also devices before, which monitor whether the torque of the electric motor is outside the normal operating range, since the inverter is switched off if the torque is outside the usual Area is ( Fig. 2).