CN201134680Y - Intelligent Low Voltage Reactive Power Automatic Compensation Controller - Google Patents

Abstract

The utility model discloses an intelligent low-voltage reactive power automatic compensation controller, which is characterized in that a high-speed digital signal processor is used as the core, and the high-speed calculation ability of the digital signal processor is used to realize multi-parameters of voltage, current, power and power factor Comprehensive control, using digital calibration, digital filtering, and program logic judgment to simplify peripheral hardware circuit design, reduce costs, and improve the accuracy, reliability, and anti-interference ability of the controller.

Description

Intelligent Low Voltage Reactive Power Automatic Compensation Controller

technical field

The utility model relates to an intelligent low-voltage reactive power automatic compensation control device, which belongs to the technical field of low-voltage electric appliance manufacturing.

Background technique

The low-voltage reactive power automatic compensation controller adjusts the reactive current in the distribution network by controlling the compensation capacitor. It has the functions of reducing line loss, saving energy, stabilizing the grid voltage, and increasing transformer capacity. It is widely used in power distribution systems. However, the existing controllers are basically controlled by single-chip microcomputers. Due to their low operation speed, complex control algorithms cannot be realized, and some can only be realized by using peripheral hardware circuits. There are complex circuit structures, poor precision, high cost, and poor anti-interference ability. and other shortcomings. For example, the commonly used phase discrimination method uses a comparator to identify the zero-crossing points of the voltage and current to obtain the time difference between their zero-crossing points (that is, the phase difference), so that the power factor can be calculated. However, the existence of these hardware circuits not only greatly increases the cost of the controller, but also is easily affected by factors such as harmonics and zero drift, which greatly reduces the performance and reliability of the controller.

Contents of the invention

In view of the problems existing in the above technologies, the purpose of this utility model is to provide an intelligent low-voltage reactive power automatic compensation controller with simple circuit structure, high precision, low cost and good anti-interference ability.

The technical scheme that the utility model takes is:

With a low-cost high-speed digital signal processor as the core, the peripheral hardware circuit is simplified, digital calibration precision and digital filtering are used to improve precision and anti-interference, high-speed acquisition and calculation are used to realize the calculation of power factor, and complex control such as multi-parameter comprehensive control is adopted. Algorithm to design an intelligent low-voltage reactive power automatic compensation controller.

Its specific structure: with high-speed digital signal processor as the core, including sampling circuit, frequency tracking circuit, LCD/LED display circuit, compensation capacitor control output drive circuit, EEPROM, keyboard, digital calibration switch, communication interface circuit, switching power supply, etc. part. The sampling circuit converts the grid voltage and current into small signals and connects them to the A/D port of the digital signal processor after raising the level, low-pass filtering, and limiting. The small voltage signals are captured by the frequency tracking circuit and the digital signal processor at high speed The raised level in the sampling circuit is formed by dividing the resistance, and the raised level is connected to the A/D port of the digital signal processor at the same time; LCD/LED display circuit, compensation capacitor control output drive circuit and keyboard and digital The signal processor I/O port is connected; the digital calibration switch is connected to the digital signal processor I/O port. When the switch is closed, the digital calibration program is started, and the calibration parameters are stored in EEPROM; the EEPROM is connected to the I ² C port of the digital signal processor. connected; the communication interface circuit is connected with the UART port of the digital signal processor; the switching power supply provides power for the entire controller.

The digital signal processor has a processing speed of 60MIPS, with 16 channels of 12-bit ADC, 32kB program space, 12kB RAM space, internal watchdog circuit, internal reference circuit, internal timer, high-speed capture port, I ² C\SPI\UART interface wait.

Compared with the prior art, the utility model technology after the above design has the following advantages:

1. Utilize the high-speed calculation ability and logical judgment ability of the digital signal processor, and realize the automatic identification of the same terminal of the current through the software, which saves the phase judgment of the hardware circuit, saves the cost and improves the reliability.

2. Utilizing the high-speed computing capability of the digital signal processor, through digital filtering and digital calibration, the sampling circuit only needs simple low-pass filtering and limiting processing to achieve high precision, eliminating the need for hardware circuit adjustment and filtering, improving reliability and Anti-interference ability.

3. The digital signal processor divides the frequency by 32 or 64 according to the frequency detected by the frequency tracker, and then collects the cycle data of the A/D. It can automatically track the frequency change of the power grid, and is applicable to 50Hz or 60Hz power grid.

4. Utilize the high-speed calculation capability of the digital signal processor to calculate the true effective value of the grid voltage, current, power and other parameters, and can comprehensively control the switching circuit for switching with parameters such as voltage, current, power, and power factors, avoiding single parameter control Various defects exist.

Description of drawings

Accompanying drawing 1 is a schematic block diagram of the utility model circuit.

Accompanying drawing 2 is the schematic block diagram of the circuit of an embodiment of the utility intelligent low-voltage reactive power automatic compensation controller of the present invention.

in:

1---indicates the sampling circuit; 2---indicates the frequency tracking circuit;

3---Indicates digital signal processor; 4---Indicates LCD/LED display module;

5---Indicates that the compensation capacitor controls the output drive circuit;

6---Indicates EEPROM memory; 7---Indicates keyboard input module

8---indicates the digital calibration switch; 9---indicates the communication interface circuit

10---Indicates the switching power supply module.

Detailed ways:

Below in conjunction with accompanying drawing, the specific embodiment of the present utility model is described in further detail:

The intelligent low-voltage reactive power automatic compensation controller described in the utility model is composed as shown in Figure 1, with a high-speed digital signal processor 3 as the core, including a sampling circuit 1, a frequency tracking circuit 2, and an LCD/LED display Circuit 4, compensation capacitor control output drive circuit 5, EEPROM 6, keyboard 7, digital calibration switch 8, communication interface circuit 9, switching power supply 10 and other parts. The sampling circuit 1 converts the grid voltage and current into a small signal and connects it to the A/D port of the digital signal processor 3 after raising the level, low-pass filtering and limiting, and connects to the frequency tracking circuit 2 at the same time, and the frequency tracking circuit 2 It is connected with the capture port of the digital signal processor 3; the LCD/LED display circuit (4), the compensation capacitance control output drive circuit (5) and the keyboard (7) are connected with the I/O port of the digital signal processor 3; the EEPROM6 is connected with the digital signal The I ² C port of the processor 3 is connected; the switching power supply 10 provides power for the entire controller. Wherein the memory of the digital signal processor 3 stores working programs such as digital filtering, digital calibration, and control algorithms.

As shown in Figure 2: the core of the intelligent low-voltage reactive power automatic compensation controller of this embodiment adopts the latest low-cost high-performance digital signal processor (DSP) TMS320F28015 of TI Company, which has 100 pins and 16 channels 12-bit A/D port (AN0～AN7, BN0～BN7), two high-speed capture ports (ECAP1, ECAP2), I2C interface SDA and SCL, communication interface SCIRXDA and SCIRXDA, 34 general-purpose I/O interfaces (GPIO00-GPIO34 , including display I/O interface and output driver I/O interface).

The sampling circuit (1) is composed of a voltage signal conversion circuit, a current signal conversion circuit and a level-raising circuit. The level-raising circuit is formed by dividing the power supply voltage VCC by resistors R5 and R6. The A/D port of the device 3 is connected; its voltage value is close to 1/2 of the internal reference voltage of the digital signal processor 3, and the capacitor C3 performs simple filtering with the A/D port AN7 of the digital signal processor 3, the voltage signal conversion circuit, The current signal conversion circuit and the frequency tracking circuit are connected. Since the voltage and current signals are bipolar, they are converted into unipolar by raising half of the full scale on the hardware to meet the A/ D port electrical characteristics (its specific function is described in the algorithm). The voltage signal conversion circuit converts the high voltage into a low-voltage signal that the digital signal processor (3) A/D port can withstand through the resistance R0, the transformer PT1, the resistance R1 and the level-up circuit, and passes through the resistance R2 and the capacitor C1. filter, and connected to the A/D port AN0 of the digital signal processor 3 after limiting by diodes D1 and D2. The current signal conversion circuit converts the large current into a low-voltage signal that the A/D port of the digital signal processor 3 can withstand through the transformer CT1, the resistor R3 and the level-raising circuit, and filters it through the low-pass filter of the resistor R4 and the capacitor C2, and After limited by diodes D3 and D4, it is connected to the A/D port BN0 of the digital signal processor 3 . In this example, the voltage and current signal conversion circuit is only an example of the A phase, and the other two phases are in the same way.

The frequency tracking circuit 2 is composed of resistors R7, R8, capacitors C4, C5 and integrated circuit IC1 (LM239). The AC voltage signal is converted into a square wave signal by the frequency tracking circuit and then input to the high-speed capture port of the digital signal processor 3 for digital signal processing. The device 3 calculates the frequency and period of the grid voltage and current according to the captured square wave signal, divides it by 64 and uses it for the A/D conversion startup interval time, so as to automatically track the grid frequency change, and is applicable to 50Hz or 60Hz grid .

The resistor R9 of the digital calibration switch 8 and the jumper switch K1 are composed, and the digital calibration switch 8 is connected with the general I/O port GPIO30 of the digital signal processor 3. When the jumper switch is opened, the digital signal processor 3 follows the normal control procedure Run, when the jumper switch is closed, the digital signal processor 3 starts the embedded digital calibration program, and the calibration menu is displayed. At this time, the standard signal is input to the controller, and the calibration parameters (such as voltage, current, etc.) are selected by pressing the keys, and the digital calibration program Automatically calculate the proportional coefficient k and offset b between the sampling result and the standard value and store it in EEPROM (6). After the parameter calibration is completed, turn on the jumper switch. After the system is powered on again, it will run according to the normal control program (the calibration parameters are used in the following control algorithm described).

The keyboard 7 is composed of keys (S1-S7), resistors (R11-R14), and capacitors (C11-C14), and is connected to the general-purpose I/O port of the digital signal processor 3 . EEPROM chip IC2 adopts 24LC04B, and communication interface circuit 9 adopts RS-485 communication chip ADM2483BRW with isolation function. The LCD/LED display circuit 4 , the compensation capacitance control output drive circuit 5 and the keyboard 7 are connected to the general I/O port of the digital signal processor 3 . This part of the circuit is designed using techniques known in the art, and will not be described in detail in this embodiment.

Some algorithms and control descriptions involved in this embodiment:

Wherein: k is the proportionality factor that calibration procedure is stored in EEPROM (6);

b is the offset stored in the EEPROM (6) for the calibration program;

u(n), i(n) are the digital signal processor 3 collecting the voltage and current value of the nth point;

ref is the raised level value collected by the digital signal processor 3. Since the voltage and current data collected after the raised is a unipolar value, it is necessary to subtract the collected data from the raised level value to restore it to a bipolar value;

N is the total number of points collected in one cycle, which is 64 points in this example;

n is the first point collected in one cycle.

Phase discrimination processing, because the low-voltage reactive power compensation equipment is used for end users, the active power must be positive. Based on this principle, if the active power P is negative, the user wiring phase must be wrong, and the controller needs to automatically Adjust the phase for proper control. The specific discrimination is that when the active power is positive, if the reactive power is positive, it is inductive; otherwise, it is capacitive; when the active power is negative, if the reactive power is negative, it is inductive; otherwise, it is capacitive. The hardware circuit is saved by the software discrimination method, the production cost is reduced and the product reliability is improved.

In this example, the above-mentioned voltage, current, and power are only single-cycle calculation values. In order to prevent accidental interference, the system uses 10 average values for display and control.

The keyboard 7 is available for the user to input parameters such as overvoltage, undervoltage, overcurrent, number of control channels, switching delay, communication settings, etc., and the digital signal processor 3 Comprehensive parameters such as time and time, through the digital signal processor 3 output drive I/O port interface circuit to control the switching of the compensation capacitor 5, so that the power factor of the grid can reach the best state.

Claims (3)

1, a kind of intelligent type low-voltage reactive power self-compensating controlling device, it is characterized in that this intelligent type low-voltage reactive power self-compensating controlling device is a core with high speed digital signal processor (3), include sample circuit (1), frequency tracking circuit (2), LCD/LED display circuit (4), building-out capacitor control output driving circuit (5), EEPROM (6), keyboard input (7), digital calibration switch (8), communication interface circuit (9), Switching Power Supply (10), sample circuit (1) is with line voltage and electric current is converted into small-signal and through raising level, low-pass filtering, A/D port with digital signal processor (3) behind the amplitude limit links to each other, link to each other with frequency tracking circuit (2) simultaneously, frequency tracking circuit (2) links to each other with the seizure mouth of digital signal processor (3); LCD/LED display circuit (4), building-out capacitor control output driving circuit (5) link to each other with the I/O mouth of keyboard (7) with digital signal processor (3), the I of EEPROM (6) and digital signal processor (3) ²The C mouth links to each other, and Switching Power Supply (10) provides power supply for entire controller.

2, intelligent type low-voltage reactive power self-compensating controlling device according to claim 1 is characterized in that the level of raising in the described sample circuit (1) is formed by electric resistance partial pressure, raises level and links to each other with digital signal processor (3) A/D port simultaneously.

3, intelligent type low-voltage reactive power self-compensating controlling device according to claim 1, it is characterized in that described digital calibration switch (8) resistance R 9 and jumper switch K1 form, digital calibration switch (8) also links to each other with digital signal processor (3) universaling I/O port GPIO30.

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