RO117657B1 - Digital system for controlling, adjusting and measuring the poly-phase electric generators for callibrating the electric power meters - Google Patents

Abstract

The invention relates to a digital system for controlling, adjusting and measuring the poly-phase electric generators applicable to the installations for callibrating and/or checking the electric power meters, thereby simplifying the installations and reducing the number of current and voltage ranges, there maintaining the accuracy of adjustment. According to the invention, the system comprises a control block (BC) which receives controls from a functional key block (BT) of the installation or from a (PC) computer equipped with an operating display (M), the generated controls being applied to a power source (I) or a voltage source (U) of the installation, in order to select certain values of these quantities, said values being measured by a measuring block (BM) and then transmitted to a (PC) computer, where the prescribed and measured values are compared and decisions are taken in the process of adjusting the same, up to reaching the prescribed value, the measured values of the characteristic quantities of the installation for callibrating/checking meters being diplayed on an auxiliary (MA) display.

Description

RO 117657 Β

The invention relates to a numerical control, regulation and measurement system for polyphase electricity generators, used in installations for calibrating and/or verifying electricity meters.

In order to perform the control, regulation and measurement operations of polyphase generators of electricity, integrated in the installations for calibrating/verifying electricity meters, there are known installations that have the generator control block made of relays and relay interlocking logic, as elements for measuring electrical quantities, being equipped with panel instruments, and the adjustment operations are performed manually, the result of the adjustment being monitored on the measuring instruments. These installations have two major disadvantages.

The first disadvantage is that, in order to increase the regulation accuracy, it was necessary to divide it into many current and voltage ranges, which leads to a high number of components (relays), therefore to a high price and low reliability.

The second disadvantage is that the adjustment of electrical quantities is done manually, being influenced by the operator's subjectivity when reading the measuring instruments.

A device for regulating a three-phase voltage source with thyristors is also known, comprising an analog-digital converter, which digitizes a signal proportional to the source voltage, and a microprocessor associated with a memory in which the signal provided by the converter is compared with a preset value, the microprocessor providing control signals 20 to the gates of the thyristors of the source.

The disadvantage of this device is the difficulty of adapting it for electricity meter calibration installations.

The numerical control, regulation and measurement system of polyphase electric energy generators for calibrating electric energy meters, intended for an installation 25 for calibrating and/or verifying energy meters, provided with adjustable voltage and current sources, according to the invention, eliminates the above disadvantages, in that it consists of a control block that receives commands from a block of functional keys of the installation or from a computer equipped with a work monitor and transmits commands to the sources, for regulating them to prescribed voltage and current values, the values 30 from the sources' outputs being measured by a measurement block and then transmitted to the computer, which compares the prescribed values with the measured ones and continues the process of regulating them until the prescribed values are reached, the measured values of the installation's characteristic quantities being displayed on an auxiliary monitor, connected to the computer.

The system according to the invention has the following advantages:

- it allows reducing the number of current and voltage ranges, while maintaining regulation precision, simplifying the current transformer, eliminating the contactors and elements corresponding to the respective ranges, which leads to increased reliability and a decrease in the price of the installation;

- eliminates operator subjectivity in adjusting prescribed quantities;

- it can be implemented on any calibration facility equipped with autotransformers with servomotors, for prescribing working quantities.

An embodiment of the invention is given below, in relation to Fig. 1, 2, 3 and 4, which represent:

- fig. 1, block diagram of the system, according to the invention, together with the main elements of the electrical quantity generation part of a meter calibration/verification installation;

- fig.2, schematic diagram of the control block;

- fig.3, principle diagram of the measurement block;

- fig.4, operating diagrams of the microcontrollers and the computer program.

RO 117657 B

The system according to the invention (fig. 1) consists of a control block BC, which 50 receives commands from a PC computer, processes them and controls two sources: one voltage SOURCE U and one current SOURCE I, with the role of generating the three-phase system of voltages, respectively of currents, necessary for calibrating electricity meters, the other blocks SOURCE U, SOURCE I and DEF, according to the algorithms for prescribing the voltage, current and phase shift between them. The control block BC permanently monitors 55 the energy measurement conditions, in order to disconnect the corresponding phases and the zero current condition, in order to change the current ranges.

A BM measurement block receives commands from a PC computer and performs the measurement of the requested parameters (voltage, current, the gap between them, active power, reactive power, network frequency), as well as their transmission to the PC computer. In the same way, the commands for adjusting the parameters are transmitted, depending on the selected working mode.

.¾ The PC computer is IBM-PC compatible and has a monitor M, with the role of transmitting

And the commands to the control and measurement blocks, the computer also being equipped with a monitor

H auxiliary MA, with the role of allowing the display of the prescribed electrical quantities. The software implemented on the PC computer tracks the measured and prescribed values of the installation's 65 parameters and performs their adjustment function.

The operation of the system, according to the invention, at the block diagram level, proceeds as follows.

' The possible working modes for the system are facilitated by a software package implemented on the PC, in the control block and in the measurement block. Thanks to these 70 programs and due to the system configuration, it can perform the following functions: voltage range selection, current range selection, measurement mode selection and phase sequence, autotransformer operation control and panel connection.

Functions are selected via several types of keys: 75

- there are keys for selecting the voltage range, for selecting the percentage of the voltage, of the type one key pressed once, the other keys pressed are not taken into account;

- there are panel connection keys for voltage and current; each time a voltage or current connection key is pressed on the three separate phases, the state of the corresponding relay changes, and if the keys are pressed at once, the state of the three relays changes, 80 if the three phase connection commands are in the same state, or they are disconnected otherwise;

- there are current range selection keys, of the type of a single key pressed once from all the keys associated with the current ranges; when a key is pressed, the relays corresponding to the current ranges are controlled until the zero current condition, after which the range corresponding to the pressed key is connected;

- are autotransformer actuation keys for current, voltage and the gap between current and voltage, with the observation that several keys actuated simultaneously are accepted, the command to the relays being given simultaneously. In this type of keys, there are two actuation speeds of the autotransformers. If the actuation of a key lasts more than one second, the second actuation speed is automatically connected. The actuation speed of the autotransformers becomes zero when the key actuation ends;

- there are measurement mode selection keys, of the type of a single key pressed once, with the role of automatically activating the relay corresponding to a certain mode;

- there are phase sequence selection keys, with the observation that upon connection a certain state of the corresponding relay is imposed, a state that changes with each actuation.

RO 117657 Β ; The BC control block consists of a microcontroller M1, provided with three input/output ports (PO, P1, P2) with eight lines each (P0.0..P0.7; P1.0...P1.7; P2.0...P2.7). The P1 and PO ports are connected through the buffer circuits B10...B17 and B20...B27 100 to the TIO.. TI7 and TO0...TO7 lines of the functional key matrix. A resistor R1...R8 is connected to each input of the buffer circuits B20...B27 with the second terminal connected to ground.

Through four lines of port P2 (P2.0...P2.3) microcontroller M1 is connected to inputs A, B, C, D of a decoder circuit DEC with eight outputs Q0...Q7, each output being 105 connected to a control input of a control block BC0...BC7. These blocks have the same structure each, they are made with a latch circuit L0...L7, with data inputs D0...D7 connected to the lines of port P1 of microcontroller M1. The outputs of the latch ILO.. iL7 are connected through resistors R19...R26 based on transistors T3...T10; through the collector > of these transistors, the commands are transmitted to the execution elements, i.e. the relays

110 intermediate and display devices, the emitter being connected to the assembly ground. Three other lines of port P2 (P2.2...P2.6) are connected to the outputs of buffer circuits B31...B33, through H whose inputs, connected through a resistor R10...R12 to the assembly ground, are connected to the three phases R, S and T of the CTW energy metering block.

. : Communication with the PC is done through two serial lines SI and LD. On the SI input,

115 the commands from the PC computer are received, which reach the serial input RxD of the microcontroller M1 through a buffer circuit B30 with the input connected through a resistor R9 to the positive potential of the voltage source Vcc. The transmission of information to the PC computer is done on the LD line, from the TxD output of the microcontroller M1 through the following circuit chain: the TxD output is connected through a resistor R13 to the base of a transistor T2, the base connected 120 to the positive potential of the power supply Vcc through a resistor R14. The transistor T2 has its emitter connected to the positive potential of the voltage source Vcc through a resistor R16 and its collector connected to ground through a resistor R15, a resistor that is also connected to the base of a transistor T1, The transistor TI has its emitter connected to the system ground, and the collector is connected to the LD line of communication with the PC computer. Also, a port output 125 P2.7 of the microcontroller M1 is connected to the collector of an optocoupler OP which is connected through a resistor R17 to the positive potential of the voltage source Vcc. The emitter of the optocoupler is connected to the system ground, and on the receiving side, in parallel with the optocoupler diode OP, a diode D1 is connected, with one terminal to the positive potential of the voltage source Vcc and with the second terminal through a resistor R18, to an input CZ, with the role of sensing the zero condition of the current autotransformers.

The operation of the control block, according to the invention, is as follows:

The control block, based on the M1 microcontroller, is provided with two input/output ports through which a maximum of 64 function keys can be processed, organized in an 8x8 matrix. The key pressed is determined by the pair of 135 ports P1(P1.0...P1.7) and P2(P2.0...P2.7) connected to the TI0...TI7 and TO0...TO7 lines of the function key matrix through the buffer circuits B10...B17 and B20...B27, respectively. Depending on the decoded key, on four lines of the P2 port (P2.0..P2.3), the microcontroller generates a number from 0 to 7 in binary, a number decoded by the DEC decoder which at the Q0...Q7 outputs will have only a signal with the value 0 logic, the other outputs being at the value 140 logic 1. The corresponding output with logical value 0 will activate the corresponding control circuit, in the sense that the circuit Li with I = 0...7 will activate the corresponding output IL0...IL7 depending on the pressed key, determined by the potential values at the outputs of port P1, respectively the inputs D0...D7 of the corresponding control circuits. Output activated

RO 117657Β

ILi, with i = 0...7, acts through the resistor-transistor pair on the execution elements, i.e. the intermediate relays and display devices, in the sense of executing the function of the pressed key 145.

The BM measurement block consists of a converter CI1, which contains six precision analog-to-digital converters, which has three inputs 11,12 and I3, connected to current transformers and three inputs U1, U2 and U3 connected to voltage dividers. Through a selection input CSI, the circuit is connected to a gate Шl CI2, whose inputs are connected to the outputs INI and SOUT1 of a decoder circuit CI3 and a digital signal processor circuit CI4, respectively. The digital signal processor CI4 is connected through four control inputs SC and a data input DATA, to the circuit CI1, and with the outputs SOUT0 and SOUT1 to the inputs SK and D1 of an EEPROM memory circuit, CI5. A selection input CS5 of the circuit CI5 is connected to the output INI of the circuit CI3, and a data input DO is 155

Î4 connected to the data input/output of the CI1 circuit. The CI4 circuit has a data bus (8 lines) DBUSO-7, through which it is connected to a FIFO memory circuit CI6. Writing and reading from the FIFO memory is controlled by a W input, an input connected to the output of an AND-NOT gate circuit, CI7. The inputs of the CI7 circuit are connected one by one to an ADDR1 output of the CI4 circuit and to a STROBE output of the CI4 circuit, passed through an inverter circuit 160 CI8. The same STROBE output is also connected to a CL input of the CI3 circuit. The CI3 and CI4 circuits are also connected to each other through an additional 8-line S/MBUS data bus.

To an input G of the CI3 circuit, the output of an AND-NOT gate circuit CI9 is connected, which has its inputs connected to the ADDRO and RD/WR outputs of the CI4 circuit, the RD/WR output being passed through an inverter circuit CI10. The CI3 circuit has an output connected to an INTO input 165 of a microcontroller circuit CI11. The CI11 circuit is connected through its inputs P1.0 and P1.1 to the R and RS outputs of the FIFO memory CI6. On a DO-7 bus, the CI6 and Cil 1 circuits are connected, and through the P3.0 (R*D) and P3.1 (TxD) lines of the CI11 microcontroller, the BM measurement block and the BC control block are connected, through an adaptation circuit CI12, which is connected to the SI and LD lines of the numerical control, regulation and measurement system of polyphase energy generators.

The operation of the measuring block, according to the invention, is as follows:

At the current inputs 11,12,13 and at the voltage inputs U1, U2, U3 of the CI1 circuit formed by six analog-digital converters CI1, the analog current and voltage quantities from the current transformers and voltage dividers 175 are applied. The CI1 circuit converts the analog signals into digital signals, with a precision ensured by some constants programmed in the CI5 EEPROM memory. The memory is of the serial type, the data being transmitted from the DO output of the CI5 circuit to the DATA input/output of the Cil circuit. The EEPROM memory is programmed on the SK and D1 lines with the data and clock signal from the CI4 signal processor. The memory selection is made at the CS5 input, 180 with the INI signal generated by decoding the additional bus of the signal processor by the CI3 decoder circuit. The reading of the numerical values from Cil is done when the circuit is selected on the selection input CS1. The selection signal is obtained by a logical function Шl between the general INI signal of CI3 and SOUT1, generated by the digital signal processor CI4. The establishment of the data transfer is done under certain conditions managed 185 by the command and control signals SC between the circuits CI1 and CI4. The digital signal processor CI4 transfers, in turn, the data received from the converters into a FIFO memory CI6 on the data lines DBUSO-7. The signal that commands the writing into the FIFO memory, applied to the W input of the circuit CI6, is obtained as a logical AND-NOT function between a STROBE signal complemented by the inverter circuit CI8 and the ADDR1 signal generated by the processor 190

Claims (4)

RO 117657 B signal. The data saved in the FIFO memory are taken over by the microcontroller CI11 on the DO-7 lines, at the time determined by a signal obtained by decoding the additional bus of the signal processor by the decoder CI3. The signal appears when the data of the measured parameters are already converted and read by the circuit chain CI1, CI4 and CI6. By the set of 195 programs implemented in the microcontroller CI11 are used to process the numerical values of the input quantities: current, voltage and the gap between them. Also, the network frequency, active and reactive power consumed are measured. The signals applied to the inputs P1.0 and P1.1 of the microcontroller CI11 from the outputs R and RS of the FIFO memory CI6 establish the conditions for the transfer of information between the two circuits. Upon the command transmitted 200 by the PC computer on the SI line of the CI12 circuit, acting as a voltage level adapter and galvanic separator, the processed data is transmitted to the computer on the LD line, also through the CI12 circuit. The signals for receiving the command and transmitting the requested data are applied to the P3.0 (R*D) input, respectively to the P3.1 (TxD) output of the CI11 microcontroller. The PC computer receives the data and makes a comparison between the programmed and measured values. in 205 depending on the result of the comparison, it is decided on the command that is transmitted to the control block. Also, on the auxiliary monitor display, the measured values of the current, phase shift, network frequency, active and reactive power will be displayed. Fig. 4 shows the operating diagrams of the programs implemented in the processors in the control block and the measurement and regulation block, as well as in the PC computer. 210 The microcontroller M1 in the control block has a program implemented according to the diagram (blocks 1 to 7). After the initializations that are made, block 1, a key is expected to be pressed, block 3. If a key has been pressed, block 5, the type of key pressed is determined, block 6, and then the chain of operations specific to that key is launched into execution, block 7. If no key has been pressed, it is checked whether a command has been received from 215 the PC computer, block 4. If a command has come from the PC, block 5, after executing the chain of operations specific to the pressed key, the block sends a response to the PC, in which it communicates the received value. If no command has come from the PC, block 2, it still waits for a key to be pressed. The M2 microcontroller in the measurement and control block has a program implemented 220 according to the diagram (blocks 8 to 17). After the initializations that are made, block 8, the program enters an interrupt waiting loop, block 10, a way through which it communicates with the signal processor and the PC computer. If an interrupt has come, it is executed, block 11, after which the wait for a new interrupt is resumed, block 9. If the interrupt came from the PC computer, block 12, determines and executes 225 the requested command, block 13^ after which the return to the main program is made, block 14. If the interruption was generated by the signal processor, block 15, the information coming from the signal processor which includes the last set of processor measurements is read from the FIFO memory, block 16, preparing the data for transmission to the PC, then the subroutine returns to the main program, block 17. 230 demand 1. Numerical control, regulation and measurement system for polyphase electricity generators for calibrating electricity meters, intended for an installation 235 for calibrating and/or verifying energy meters, provided with adjustable voltage sources (source U) and current sources (source I), characterized in that it consists of a control block (BC) which receives commands from a functional key block (BT) of the installation or from a computer (PC) equipped with a work monitor (M) and transmits RO 117657 Β commands to the current and voltage sources (source I, source U) for their regulation to prescribed values, the values from the sources' outputs being measured by a measurement block (BM) 240 and then transmitted to the computer (PC), which compares the prescribed values with the measured ones and continues the process of regulating them until the prescribed values are reached, the measured values of the installation's characteristic quantities being displayed on an auxiliary monitor (NIA), connected to the computer. 2. System according to claim 1, characterized in that the control block 245 (BC) is made with a microcontroller (M1), in the memory of which a set of programs is implemented that controls and manages all the functions of the keys, the microcontroller having three input/output ports (P0, PI and P2), with eight lines each (P0.0..P0.7; P1.0...P1.7; P2.0...P2.7), the lines of the first two ports (P1 and P0) being connected through buffer circuits (B10...B17 respectively B20...B27) to lines (TIO...TI7 respectively TO0...TO7) of the matrix of 250 functional keys of the installation, four lines of the third port (P2.0...P2.3) being connected to the inputs of a decoder circuit (DEC) with eight outputs (Q0...Q7), each output being connected to the control input of a control circuit (BC0...BC7) with latches, having the data inputs (D0...D7) connected to the lines of the second port (P1) of the microcontroller (Ml) and the outputs (IL0...IL7) connected, through some resistors (R19...R26) and some 255 transistors! (T3...T10), to the outputs of the control block (BC) through which the commands are transmitted to intermediate relays and display devices, three other lines (P2.4...P2.6) of the second port (P2) being connected to the outputs of other buffer circuits (B31...B33) whose inputs are connected to the three phases (R, S and T) of the energy metering block (CTW), the communication with the computer (PC) being made through two serial lines (SI and LD), one line (SI) for receiving 260 commands from the computer, and another (LD) for transmitting information to the computer from an output (TxD) of the microcontroller (M1) through two transistors (T2 and T1), another line of the third port (P2.7) of the microcontroller (M1) being connected, through an optocoupler (OP) and a resistor (R18), to an input (CZ) of detection of the zero condition of current autotransformers. 265 3. System according to claim 1, characterized in that the measuring block (BM) is made up of a converter (CI1), which contains six precision analog-digital converters, with three inputs (11,12 and I3) connected to the current transformers and three inputs (U1, U2 and U3) connected to the voltage dividers of the installation and with a digital output (DATA) through which data are supplied to a digital signal processor (CI4) with the help of control signals (SC), the processor (Cl4) also being connected, on the one hand, through a data bus (DBUSO-7), with a FIFO memory (CI6), connected to a microcontroller (CI11), on the other hand, with a decoder circuit (CI3), through an additional data bus (S-MBUS8), and, on the other hand, with an EEPROM memory (CI5), in which, and from which, the processor (CI4) prescribes and takes constants that define the signal conversion parameters, the processor 275 (CI4) taking over from the converter (CI1) the measured value of the parameters, at a time determined by the transmitted signal, through an AND gate (CI2), from an output (INI) of the decoder circuit (CI3), to a selection input (CS1) of the converter, the same output (INI) being also connected to the selection input (CS5) of the EEPROM memory (CI5), the AND gate (CI2) having a second input connected to an output (SOUT0) of the processor (CI4), which is also connected to the data input 280 of the EEPROM memory (D1), the writing and reading to/from the FIFO memory (CI6) being controlled by an addressing output (ADDR1) of the processor (CI4) through an AND-NOT gate (CI7) validated with a strobe signal (STROBE) which is also applied to an input (CL) of the decoder circuit (CI3), the decoder circuit (CI3) also having a selection input (G), controlled through an AND-NOT logic gate (CI9) by two outputs of the processor (CI4), and an output connected to a 285 RO 117657 Β input (INTO) of the microcontroller circuit (CI11), the communication of the measurement block (BM) with the computer (PC) being achieved through two lines (LD and SI) connected through a level translation and galvanic separation circuit (CI12) to the microcontroller (CI11). 4. System according to claims 1, 2 and 3, characterized in that it performs 290 control of the installation from a PC computer based on a set of implemented software programs, programs that perform the equivalence of the actuation of the station's function keys with the transmission of commands from the computer (PC) to the control block (BC). President of the examination committee: Eng. Popescu Livia Examiner: Eng. Savin Rodica