CN114062743B - A full-bridge switch characteristic current generating device applied in the electric power industry - Google Patents

Abstract

The invention discloses a full-bridge switch characteristic current generating device applied to the power industry, which comprises an energy storage inductor L1, a safety capacitor C1 for filtering, an electrolytic capacitor C2 for energy storage, MOS tubes Q1 and Q2 and MOS tubes Q3 and Q4 for selecting a power supply working mode, wherein the safety capacitor C2 is used for energy storage; the first end of C1 is connected with the first end of L1 in electric wire netting live wire, and the second end of L1 is connected with Q4 source electrode, Q1 drain electrode, Q4 drain electrode and Q2 drain electrode, C2 positive pole are connected, and C1 second end is connected with Q3 source electrode, Q2 drain electrode in electric wire netting zero line, and Q1 source electrode is connected with Q2 source electrode, C2 negative pole. On the basis of ensuring the accuracy of phase identification, the invention realizes the generation of near-lossless characteristic current by alternately working the BUCK and BOOST circuits, has higher power conversion efficiency, effectively reduces the line loss, improves the safety of the line, and has strong engineering practicability.

Description

A full-bridge switch characteristic current generating device applied in the electric power industry

technical field

The invention relates to the technical field of phase identification, in particular to a full-bridge switch characteristic current generating device used in the electric power industry.

Background technique

When the three-phase lines of the low-voltage distribution network are extended to the user's end for wiring, it is often difficult to distinguish phases A, B, and C, so they can only be wired casually. In this case, the unbalanced power consumption of the three phases will easily lead to the overload of one phase or two phases, resulting in unbalanced three-phase current, increasing line loss, and even causing the transformer to burn out and cause a fire. Therefore, the need for phase identification Came into being. In order to realize phase identification, the commonly used method today is to inject a characteristic current signal of a certain frequency into the power line, and the signal receiving end judges the phase by analyzing the characteristics of the current signal.

At present, there are two common schemes for characteristic current injection: 1. Resistor switching scheme, this scheme is based on the switching resistance connected in parallel in the line to generate the characteristic current, but the problem is that the existence of the switching resistance causes the power of this part 2. The capacitor switching scheme, the power grid first charges the switching capacitors connected in parallel in the line, and converts the charged electric energy into a characteristic current and injects it into the power line for analysis. There is no power loss in the whole process, but this The amplitude of the current injected by the scheme is limited, the analyzed features are not obvious enough, and it is easily disturbed by the noise of the power grid, resulting in relatively insufficient recognition accuracy.

Contents of the invention

Aiming at the deficiencies and defects of the prior art, the present invention provides a full-bridge switch characteristic current generating device applied in the electric power industry, which ensures the accuracy of the phase identification, and realizes it by alternately working with BUCK and BOOST circuits. A nearly lossless characteristic current takes place.

The purpose of the present invention can be achieved through the following technical solutions:

A full-bridge switch characteristic current generator used in the power industry, including energy storage inductor L1, safety capacitor C1 for filtering, electrolytic capacitor C2 for energy storage, MOS tubes Q1 and Q2 working at high frequencies, Working at low frequency, MOS tubes Q3 and Q4 are used to select the power supply mode;

The connection relationship is as follows: the first end of the capacitor C1 and the first end of the inductor L1 are connected to the live wire of the grid, the second end of the inductor L1 is connected to the source of the MOS transistor Q4 and the drain of the MOS transistor Q1, and the MOS transistor Q4’s The drain is connected to the drain of the MOS transistor Q2 and the anode of the capacitor C2, the second end of the capacitor C1 is connected to the source of the MOS transistor Q3, and the drain of the MOS transistor Q2 is connected to the neutral line of the grid, and the source of the MOS transistor Q1 is connected to The source of the MOS transistor Q2 is connected to the cathode of the capacitor C2.

Further, when the power grid voltage of the device is positive and the power supply works in BOOST mode, the MOS transistor Q1 is used as the main switch, the body diode of the MOS transistor Q4 is a freewheeling diode, and the MOS transistors Q2, Q3, and Q4 are turned off;

When Q1 is turned on, it charges the energy storage inductor L1, and the current flow direction is: the body diode of the live line L-L1-Q1-Q2-the neutral line N;

When Q1 is turned off, L1 discharges, and L1 and the grid supply power to electrolytic capacitor C2 at the same time, and the current flow direction is: live wire L-L1-Q4 body diode-C2 anode-C2 cathode-Q2 body diode-neutral line N.

Further, when the power grid voltage of the device is positive and the power supply works in BUCK mode, the MOS transistor Q2 is used as the main switch, the body diode of the MOS transistor Q3 is a freewheeling diode, the MOS transistors Q1 and Q3 are turned off, and the MOS transistor Q4 is turned on. Pass;

When Q2 is turned on, it charges the energy storage inductor L1, and the current flow direction is: anode of electrolytic capacitor C2-Q4-L1-safety capacitor C1 and live wire L connection end-C1 and neutral wire N connection end-Q2-C2 cathode;

When Q2 is turned off, L1 discharges, and L1 and the power grid supply power to C2 at the same time. The current flow direction is: L1 left end-C1 and live wire L connection end-C1 and neutral wire N connection end-Q3 body diode-Q4-L1 right end.

Further, when the power grid voltage of the device is negative and the power supply works in BOOST mode, the MOS transistor Q2 is used as the main switch, the body diode of the MOS transistor Q1 is a freewheeling diode, and the MOS transistors Q1, Q3, and Q4 are turned off;

When Q2 is turned on, it charges the energy storage inductor L1, and the current flow direction is: the body diode of the neutral line N-Q2-Q1-L1-the live line L;

When Q2 is turned off, L1 discharges, and L1 and the grid supply power to electrolytic capacitor C2 at the same time. The current flow direction is: neutral line N-body diode of Q3-C2 anode-C2 cathode-body diode of Q1-L1-live line L.

Further, when the power grid voltage of the device is negative and the power supply works in BUCK mode, the MOS transistor Q1 is used as the main switch, the body diode of the MOS transistor Q2 is a freewheeling diode, the MOS transistors Q2 and Q4 are turned off, and the MOS transistor Q3 is turned on. Pass;

When Q1 is turned on, it charges the energy storage inductor L1, and the current flow direction is: anode of electrolytic capacitor C2-Q3-safety capacitor C1 and zero line N-phase terminal-C1 and live wire L-phase terminal-L1-Q1-C2 cathode;

When Q1 is turned off, L1 discharges, and L1 and the grid supply power to C2 at the same time. The current flow direction is: the right end of L1-the body diode of Q4-Q3-C1 and the N connection end of the neutral wire-C1 and the L connection end of the live wire-the left end of L1.

Further, the MOS tubes in the device can be replaced by any switch tubes.

Further, the number of frequency points of the current signal injected by the device into the grid can be arbitrary, and the frequency point value can be: (m±50n)Hz, where m is an integer not less than 300, and n is an integer.

Beneficial technical effects of the present invention: On the basis of ensuring the accuracy of phase identification, the generation of characteristic current close to lossless is realized through the alternate operation of BUCK and BOOST circuits, which has higher power conversion efficiency and effectively reduces the line voltage. damage, which improves the safety of the line and has strong engineering practicability.

Description of drawings

Fig. 1 is the overall circuit schematic diagram of the present invention.

Fig. 2 is a working principle diagram of the device when the power grid voltage is positive and the power supply works in BOOST mode in the present invention.

Fig. 3 is a working principle diagram of the device when the grid voltage is positive and the power supply works in BUCK mode in the present invention.

Fig. 4 is a working principle diagram of the device when the grid voltage is negative and the power supply works in BOOST mode in the present invention.

Fig. 5 is a working principle diagram of the device when the grid voltage is negative and the power supply works in BUCK mode in the present invention.

FIG. 6 is a time sequence diagram of the characteristic current and the working status of each MOS tube in the embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

As shown in Figure 1, a full-bridge switch characteristic current generating device used in the power industry includes an energy storage inductor L1, a safety capacitor C1 for filtering, and an electrolytic capacitor C2 for energy storage. MOS tubes Q1 and Q2, working at low frequency, are used to select the MOS tubes Q3 and Q4 of the power supply mode;

Wherein, the first end of the capacitor C1 and the first end of the inductor L1 are connected to the live wire of the grid, the second end of the inductor L1 is connected to the source of the MOS transistor Q4 and the drain of the MOS transistor Q1, and the drain of the MOS transistor Q4 is connected to the The drain of the MOS transistor Q2 is connected to the anode of the capacitor C2, the second terminal of the capacitor C1 is connected to the source of the MOS transistor Q3, and the drain of the MOS transistor Q2 is connected to the neutral line of the grid, and the source of the MOS transistor Q1 is connected to the MOS transistor Q2 The source of the capacitor C2 is connected to the cathode.

The device has 4 working modes:

1. As shown in Figure 2, when the grid voltage is positive and the power supply works in BOOST mode, the MOS transistor Q1 acts as the main switch, the body diode of the MOS transistor Q4 is a freewheeling diode, and the MOS transistors Q2, Q3, and Q4 are turned off;

When Q1 is turned on, it charges the energy storage inductor L1, and the current flow direction is: the body diode of the live line L-L1-Q1-Q2 (when the MOS tube is turned off, the current flows through the parasitic body diode in the MOS tube, the same below)-zero line N;

When Q1 is turned off, L1 discharges, and L1 and the grid supply power to electrolytic capacitor C2 at the same time, and the current flow direction is: live wire L-L1-Q4 body diode-C2 anode-C2 cathode-Q2 body diode-neutral line N.

2. As shown in Figure 3, when the grid voltage is positive and the power supply works in BUCK mode, the MOS transistor Q2 acts as the main switch, the body diode of the MOS transistor Q3 is a freewheeling diode, the MOS transistors Q1 and Q3 are turned off, and the MOS transistor Q2 Q4 is turned on;

When Q2 is turned on, it charges the energy storage inductor L1, and the current flow direction is: anode of electrolytic capacitor C2-Q4-L1-safety capacitor C1 and live wire L connection end-C1 and neutral wire N connection end-Q2-C2 cathode;

When Q2 is turned off, L1 discharges, and L1 and the power grid supply power to C2 at the same time. The current flow direction is: L1 left end-C1 and live wire L connection end-C1 and neutral wire N connection end-Q3 body diode-Q4-L1 right end.

3. As shown in Figure 4, when the grid voltage is negative and the power supply works in BOOST mode, the MOS transistor Q2 acts as the main switch, the body diode of the MOS transistor Q1 is a freewheeling diode, and the MOS transistors Q1, Q3, and Q4 are turned off;

When Q2 is turned on, it charges the energy storage inductor L1, and the current flow direction is: the body diode of the neutral line N-Q2-Q1-L1-the live line L;

When Q2 is turned off, L1 discharges, and L1 and the grid supply power to electrolytic capacitor C2 at the same time. The current flow direction is: neutral line N-body diode of Q3-C2 anode-C2 cathode-body diode of Q1-L1-live line L.

4. As shown in Figure 5, when the grid voltage is negative and the power supply works in BUCK mode, the MOS transistor Q1 acts as the main switch, the body diode of the MOS transistor Q2 is a freewheeling diode, the MOS transistors Q2 and Q4 are turned off, and the MOS transistor Q3 is turned on;

When Q1 is turned on, it charges the energy storage inductor L1, and the current flow direction is: anode of electrolytic capacitor C2-Q3-safety capacitor C1 and zero line N-phase terminal-C1 and live wire L-phase terminal-L1-Q1-C2 cathode;

When Q1 is turned off, L1 discharges, and L1 and the grid supply power to C2 at the same time. The current flow direction is: the right end of L1-the body diode of Q4-Q3-C1 and the N connection end of the neutral wire-C1 and the L connection end of the live wire-the left end of L1.

The MOS tubes in the device can be replaced by switching tubes such as triodes and IGBTs.

The number of frequency points of the current signal injected by the device into the grid can be arbitrary, and the frequency point value can be: (m±50n)Hz, where m is an integer not less than 300, and n is an integer. The setting of multiple frequency points helps to further improve the recognition accuracy.

In order to realize the solution of the present invention, the digital power supply chip needs to have at least: 3 channels of ADC sampling function, 1 channel of capture function and two complementary PWM generators. In this embodiment, dsPIC33ck32MP102 is selected as the digital power supply chip, which meets the above requirements. Among them, two complementary PWM generators are used to generate the control signals of 4 switching tubes; 3-way ADC sampling function is used to collect the voltage and current information of the circuit to realize closed-loop control; 1-way capture function is used to capture the current sending signal of the host, The device starts to work when the signal is captured, otherwise it is in standby state and does not send characteristic current information.

The simulation verification of the scheme shows that the output voltage ripple is within 10V, and the peak current is about 1.5A. Under the power frequency voltage, the device can realize the normal switching between BUCK energy release and BOOST energy storage and reach a steady state, which proves the effectiveness of the scheme. feasibility.

The embodiment selects hardware parameters as follows:

Output power: 35.8W;

Input voltage: 154～286Vac;

Input frequency: 50Hz;

Output voltage: 390V;

Output capacitance: 10μF;

Inductance: 100μH;

Switching frequency: 400 ~ 600kHz.

As shown in Figure 6, when receiving the current signal sent by the host, the device starts to work. According to the above-mentioned principle, in the full power frequency cycle, the device works alternately by controlling the on and off of the four switch tubes In BOOST and BUCK modes, a current signal with a frequency of 833 Hz and a duty cycle of 33% is injected into the 220V power grid, and the peak value of the current signal follows a sinusoidal trend, with a maximum value of 2A. Subsequently, the host continuously collects the current information of the power grid and performs Fourier decomposition on it. When the host and the device are in the same phase line, it can detect the frequency point energy of 833Hz, that is, the phase line detection is completed, otherwise it is considered that the host and the device Devices are not on the same phase.

Furthermore, the characteristic current signal sent by the present invention is decomposed by Fourier and set to detect 5 frequency points. In the embodiment, the frequency points of the field equipment are 733Hz, 783Hz, 833Hz, 883Hz, and 933Hz. The present invention can perfectly adapt to For field equipment, extra frequency points can be used for redundant design, which helps to further improve the accuracy of detection.

The characteristic current generation process of the scheme of the present invention is nearly lossless, and the frequency point energy of the generated current signal can be consistent with the resistance switching scheme. When the power density space is sufficient, the amplitude of the generated current can also be adjusted as needed.

The foregoing embodiments are descriptions of specific implementations of the present invention, rather than limitations of the present invention. Those skilled in the art may also make various transformations and changes without departing from the spirit and scope of the present invention to obtain Corresponding equivalent technical solutions, therefore all equivalent technical solutions should fall into the patent protection scope of the present invention.

Claims (3)

1. The full-bridge switch characteristic current generating device is applied to the power industry and is characterized by comprising an energy storage inductor L1, a safety capacitor C1 for filtering, an electrolytic capacitor C2 for energy storage, MOS tubes Q1 and Q2 and MOS tubes Q3 and Q4 for selecting a power supply working mode;

the connection relation is as follows: the first end of the capacitor C1 is connected with the first end of the inductor L1 to be connected with a live wire of a power grid, the second end of the inductor L1 is connected with the source electrode of the MOS tube Q4 and the drain electrode of the MOS tube Q1, the drain electrode of the MOS tube Q4 is connected with the drain electrode of the MOS tube Q2 and the anode of the capacitor C2, the second end of the capacitor C1 is connected with the source electrode of the MOS tube Q3 and the drain electrode of the MOS tube Q2 to be connected with a zero line of the power grid, and the source electrode of the MOS tube Q1 is connected with the source electrode of the MOS tube Q2 and the cathode of the capacitor C2;

when the power grid voltage is positive and the power supply works in a BOOST mode, the MOS transistor Q1 is used as a main switching transistor, the body diode of the MOS transistor Q4 is a freewheeling diode, and the MOS transistors Q2, Q3 and Q4 are turned off; when Q1 is conducted, the energy storage inductor L1 is charged, and the current flow direction is as follows: live wire L-L1-Q1-Q2-zero line N; when Q1 is turned off, L1 discharges, and the current flows to: live wire L-L1-Q4-C2 anode-C2 cathode-Q2-zero line N;

when the power grid voltage is positive and the power supply works in the BUCK mode, the MOS transistor Q2 is used as a main switch transistor, the body diode of the MOS transistor Q3 is a freewheeling diode, the MOS transistors Q1 and Q3 are turned off, and the MOS transistor Q4 is turned on; when Q2 is conducted, the energy storage inductor L1 is charged, and the current flow direction is as follows: the anode of the electrolytic capacitor C2 is-Q4-L1-the cathode of the safety capacitor C1, the connecting end-C1 of the live wire L and the connecting end-Q2-C2 of the zero wire N; when Q2 is turned off, L1 discharges, and the current flows to: the left end-C1 of the L1, the connecting end-C1 of the live wire L and the connecting end-Q3-Q4-L1 of the zero line N are connected;

when the power grid voltage is negative and the power supply works in a BOOST mode, the MOS transistor Q2 is used as a main switching transistor, the body diode of the MOS transistor Q1 is a freewheeling diode, and the MOS transistors Q1, Q3 and Q4 are turned off; when Q2 is conducted, the energy storage inductor L1 is charged, and the current flow direction is as follows: zero line N-Q2-Q1-L1-live line L; when Q2 is turned off, L1 discharges, and the current flows to: zero line N-Q3-C2 anode-C2 cathode-Q1-L1-fire line L;

when the power grid voltage is negative and the power supply works in the BUCK mode, the MOS transistor Q1 is used as a main switch transistor, the body diode of the MOS transistor Q2 is a freewheeling diode, the MOS transistors Q2 and Q4 are turned off, and the MOS transistor Q3 is turned on; when Q1 is conducted, the energy storage inductor L1 is charged, and the current flow direction is as follows: the anode of the electrolytic capacitor C2 is connected with the zero line N, the end-C1 of the safety capacitor C1 is connected with the live line L, and the cathode of the capacitor C1 is connected with the end-L1-Q1-C2; when Q1 is turned off, L1 discharges, and the current flows to: the right end of the L1, the connecting end of the Q4Q 3C 1 and the zero line N, the connecting end of the C1 and the live wire L, and the left end of the L1.

2. The full-bridge switching characteristic current generating device applied to the power industry according to claim 1, wherein all MOS tubes in the device can be replaced by any switching tube.

3. The full-bridge switching characteristic current generating device applied to the power industry according to claim 1, wherein the number of frequency points of a current signal injected into a power grid by the device can be any, and the frequency point value can be: (m + -50 n) Hz, wherein m is an integer not less than 300 and n is an integer.