CN105896564A - Series compensation device and safety protection method of same - Google Patents

Abstract

The invention provides a series compensation device and a safety protection method of the series compensation device. The device comprises: a compensation capacitor, a zinc oxide component, a discharge current limiting circuit, an eddy current fast switch, a current transformer and a processor. The method includes the following steps: collecting current data in the grid; judging whether there is a short circuit in the grid according to the current data, and if so, controlling the eddy current fast switch to be closed by a processor. The invention designs a series compensation device, and proposes a static current balance function and a current safety warning function, so as to ensure the operation safety of the series compensation device and ensure the normal operation of the power grid.

Description

Series compensation device and safety protection method for series compensation device

technical field

The invention relates to the technical field of computer control, in particular to a series compensation device for compensating grid voltage and a safety protection method for the series compensation device.

Background technique

Power grid loss refers to the loss and loss of power in various links such as power transmission, power transformation, and distribution box marketing during the process of power transmission from power plants to customers. The loss rate is the main economic and technical index that comprehensively reflects the planning and design, production operation and management level of the power network. The line loss of the power network mainly includes variable loss, fixed loss and management loss. Variable loss refers to the amount of electricity consumed on the resistance of power lines and power transformers, and this part of the loss is proportional to the square of the transmitted power (or current). Fixed loss refers to the loss generated on the equivalent parallel conductance of power lines and transformers. For distribution networks, it mainly includes the iron loss of power transformers, the dielectric loss of power cables and capacitors, and the leakage loss of insulators. Fixed loss and variable loss can be calculated theoretically, so they are often called theoretical line loss. Management loss refers to the part of the line loss after deducting the theoretical line loss. Power grid loss wastes a huge amount of electricity every year, and affects the quality of power supply, resulting in damage to electrical appliances.

Some power grid compensation schemes have also been proposed in the prior art, mainly using parallel capacitors for compensation, which has high cost, slow response speed, and easily burns out the compensation capacitors.

Contents of the invention

The present invention proposes the following technical solutions aiming at the above-mentioned defects in the prior art.

A series compensation device, comprising: a compensation capacitor, a zinc oxide component, a discharge current limiting circuit, an eddy current fast switch, a current transformer and a processor, wherein,

The compensation capacitor is connected in series in the power supply line of the power grid, and is used to compensate the voltage drop of the power grid;

The zinc oxide component is connected in parallel with the compensation capacitor to limit the voltage across the compensation capacitor;

The discharge current limiting circuit is connected in series with the eddy current fast switch to form a series circuit, and the series circuit is connected in parallel with the compensation capacitor to limit the discharge current of the compensation capacitor;

The processor is respectively connected with the current transformer and the eddy current fast switch;

The current transformer is used to collect the current in the power supply line, and send the collected current data to the processor;

The processor controls the opening and closing of the eddy current fast switch according to the current data.

Preferably, the series compensation device further includes: a first switch, a second switch and a hot standby switch,

the first switch is connected in series with the second switch;

The compensation capacitor is connected in series between the first switch and the second switch;

The zinc oxide component is connected in parallel with the compensation capacitor to form a parallel circuit, and the parallel circuit is located between the first switch and the second switch;

The discharge current limiting circuit and the eddy current fast switch are located between the first switch and the second switch;

The hot standby switch is connected in parallel with the first switch and the second switch.

A safety protection method for the above-mentioned series compensation device, comprising the following steps:

S1: Collect current data in the power grid;

S2: judge whether there is a short circuit in the grid according to the current data;

S3: Start a response operation according to the judgment result in S2.

Preferably, the S1 step is specifically:

Use the current transformer to set a sampling point every 0.1ms, collect 10 current data, and store the collected current data in an array current[10].

Preferably, the S2 step is specifically:

Process the current data in the array current[10] to obtain the rate of change of the current at each sampling point, and store it in the array diff_current[10], where:

if i>1

In the formula, i represents the label of the array, 1≤i≤10;

Construct the static current balance function:

I is the magnitude of the passing current, and I0 is the maximum current passing through the series compensation device when the power grid is working normally, which is obtained from the log data of the power grid operation;

Obtain the maximum value diff_current[j] in the array diff_current[10], indicating that the current rate of change at this moment is the largest, 1≤j≤10, and obtain the current value current[j] from the array current[10] at this time, construct Current safety warning function:

G(j)=α*F(current[j])+β*diff_current[j], α and β are weight values respectively, and G0 is the short-circuit threshold, which can be obtained through simulation calculation or power grid log data analysis,

When the current safety warning function value G(j)>G 0, it is determined that a short circuit occurs in the power grid.

Preferably, the S3 step is specifically:

According to the judgment result of the step S2, when a short circuit occurs in the grid, the processor controls the eddy current fast switch to close, thereby protecting the series compensation device.

The beneficial effects of the present invention are: a series compensation device is designed, and a static current balance function and a current safety warning function are proposed to ensure the operation safety of the series compensation device and ensure the normal operation of the power grid.

Description of drawings

Fig. 1 is a schematic structure diagram of the series compensation device of the present invention.

Fig. 2 is a flowchart of a safety protection method of a series compensation device according to the present invention.

detailed description

The series compensation device and its safety protection method of the present invention will be specifically described below in conjunction with the accompanying drawings.

As shown in Figure 1, a series compensation device for compensating the voltage drop of the power grid includes: a first switch 1, a second switch 2, a compensation capacitor 3, a zinc oxide component 4, a discharge current limiting circuit 5, and an eddy current fast switch 6. Hot standby switch 7, current transformer 8 and processor 9.

The first switch 1 and the second switch 2 are connected in series, and the compensation capacitor 3 is connected in series between the first switch 1 and the second switch 2, and the compensation capacitor 3 is used for compensating the line voltage drop. The zinc oxide component 4 is connected in parallel with the compensation capacitor 3, and the parallel circuit is connected in series between the first switch 1 and the second switch 2. The zinc oxide component 4 is used to protect the compensation capacitor and limit the voltage across the compensation capacitor. The discharge current limiting circuit 5 is connected in series with the fast eddy current switch 6 and then connected in parallel with the compensation capacitor 3 , and the parallel circuit is then connected in series between the first switch 1 and the second switch 2 . The hot standby switch 7 is connected in parallel with the power supply lines where the first switch 1 and the second switch 2 are located, and the hot standby switch is in an open state during normal operation. The current transformer 8 is preferably arranged at the front end of the second switch 2, and of course it can also be arranged at other positions of the power supply line, as long as it is convenient to collect the current in the power supply line. The processor 9 is set in series with the current transformer 8, the processor 9 is connected to the eddy current fast switch 6, the processor 9 receives the current data collected by the current transformer 8, and controls the opening and closing of the eddy current fast switch 6 according to the processing result of the current data.

The working principle of the current transformer 8 is the principle of electromagnetic induction. The current transformer 8 is composed of a closed iron core and a winding. Its primary winding has very few turns, and it is connected in series in the line that needs to measure the current, so it often has all the current of the line flowing. The number of turns of the secondary winding is relatively large, and it is connected in series in the measuring instrument and the protection circuit. When the current transformer 8 is working, its secondary circuit is always closed, so the impedance of the series coil of the measuring instrument and the protection circuit is very small, and the current The working state of transformer 8 is close to short circuit. Due to the problems of easy saturation, nonlinearity and narrow frequency band of electromagnetic current transformers, electronic current transformers 8 are gradually emerging. Electronic current transformers generally have the advantages of anti-magnetic saturation, low power consumption, and broadband. They are digital sensors, and secondary instruments will not introduce errors. Sensor errors are system errors. Therefore, the current transformer 8 is preferably an electronic current transformer, which can simplify circuit design, avoid analog-to-digital conversion, and reduce errors.

The present invention adopts the zinc oxide component 4 developed by the dynamic equalization technology to effectively limit the voltage at both ends of the compensation capacitor 3 and guarantee the safety of the operation of the compensation capacitor 3 . The present invention uses the processor 9 to quickly determine the safe state of the series compensation device and the eddy current fast switch 6 developed based on the fast eddy current drive technology to control the switching on and off of the compensation capacitor 3 to minimize the duration of the overcurrent and greatly reduce the The energy capacity required by the zinc oxide component 4 is determined. Zinc oxide component 4 can adopt the technology of dynamic equal energy distribution, which is composed of multiple zinc oxide valve plates connected in series and parallel, which not only greatly reduces the residual voltage ratio (the ratio of the highest residual voltage UC to the 1mA reference voltage U1mA), but also has the same energy capacity The volume under the index is significantly reduced.

The discharge current limiting circuit 5 is composed of a resistor and an inductance to prevent the excessive discharge current from damaging the 6 contacts of the eddy current fast switch. The closing time of the eddy current fast switch 6 can be about 10ms or even faster.

Fig. 2 shows the safety protection method of the series compensation device of the present invention, comprising the following steps:

S1: Collect current data in the power grid: use current transformer 8 to set a sampling point every 0.1ms, collect 10 current data, and store the collected current data in an array current[10];

S2: According to the current data, it is judged whether there is a short circuit in the grid. If so, the processor 9 controls the eddy current fast switch 6 to close. The specific steps can be:

Process the current data in the array current[10] to obtain the rate of change of the current at each sampling point, and store it in the array diff_current[10], where:

if i>1

In the formula, i represents the label of the array, 1≤i≤10;

Construct the static current balance function:

I is the magnitude of the passing current, and I0 is the maximum current passing through the series compensation device when the power grid is working normally, which can be obtained from the log data of the power grid operation, and the calculation speed is greatly improved through the static current balance function;

Obtain the maximum value diff_current[j] in the array diff_current[10], indicating that the current rate of change at this moment is the largest, 1≤j≤10, and obtain the current value current[j] from the array current[10] at this time, construct Current safety warning function:

G(j)=α*F(current[j])+β*diff_current[j], α and β are weight values respectively, when the function value G(j)>G0 indicates that the power grid is in danger, and the eddy current is controlled by the processor 9 The fast switch 6 is closed to protect the series compensation device. G0 is the short-circuit threshold, which can be obtained through simulation calculation or grid log data analysis. The values of α and β are determined according to the grid parameters. For example, in a 35KV grid, α is generally 2, and β is generally 3.5, G0 is generally 8.

The safety protection can accurately identify the danger according to the magnitude of the current and the rate of change of the current, and the speed is fast. Basically, the danger can be identified within 2ms, and then the eddy current fast switch 6 is controlled to close, ensuring the safety of the series compensation device.

Finally, it should be noted that: the above embodiments are only to illustrate and not limit the technical solutions of the present invention, although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be modified or Any modification or partial replacement without departing from the spirit and scope of the present invention shall fall within the scope of the claims of the present invention.

Claims (6)

1. A series compensation apparatus, comprising: the device comprises a compensation capacitor, a zinc oxide component, a discharge current limiting circuit, an eddy current fast switch, a current transformer and a processor; wherein,

the compensation capacitor is connected in series in a power supply line of the power grid and is used for compensating the voltage drop of the power grid;

the zinc oxide component is connected with the compensation capacitor in parallel and used for limiting the voltage at two ends of the compensation capacitor;

the discharge current limiting circuit is connected with the eddy current quick switch in series to form a series circuit, and the series circuit is connected with the compensation capacitor in parallel and used for limiting the discharge current of the compensation capacitor;

the processor is respectively connected with the current transformer and the eddy current quick switch;

the current transformer is used for collecting current in a power supply line and sending collected current data to the processor;

and the processor controls the on-off of the eddy current quick switch according to the current data.

2. The series compensation apparatus of claim 1, further comprising: a first switch, a second switch and a hot standby switch,

the first switch and the second switch are connected in series;

the compensation capacitor is connected in series between the first switch and the second switch;

the zinc oxide component and the compensation capacitor are connected in parallel to form a parallel circuit, and the parallel circuit is positioned between the first switch and the second switch;

the discharge current limiting circuit and the eddy current fast switch are positioned between the first switch and the second switch;

the hot standby switch is connected in parallel with the first switch and the second switch.

3. A method of securing a series compensation arrangement as claimed in claim 1, comprising the steps of:

s1: collecting current data in a power grid;

s2: judging whether a short circuit exists in the power grid or not according to the current data;

s3: a response operation is started according to the determination result in S2.

4. The security protection method according to claim 2, wherein the step S1 specifically comprises:

a current transformer is used for setting a sampling point every 0.1ms, 10 current data are collected, and the collected current data are stored in an array current [10 ].

5. The safety protection method according to claim 3, wherein the step S2 specifically comprises:

processing the current data in the logarithm group current [10] to obtain the change rate of the current of each sampling point, and storing the change rate in the logarithm group diff _ current [10], wherein:

wherein i represents the number of the array, i is more than or equal to 1 and less than or equal to 10;

constructing a static current balance function:

i is the passing current, I0 is the maximum current passing through the series compensation device when the power grid normally works, and is obtained through log data of the power grid operation;

obtaining a maximum value diff _ current [ j ] in the array diff _ current [10], wherein the maximum value diff _ current [ j ] represents that the current change rate at the moment is maximum, j is more than or equal to 1 and less than or equal to 10, obtaining a current value current [ j ] at the moment from the array current [10], and constructing a current safety early warning function:

g (j) ═ α × F (current [ j ]) + β diff _ current [ j ], α and β are weighted values respectively, G0 is a short-circuit threshold value, and can be obtained by simulation calculation or grid log data analysis,

and when the current safety early warning function value G (j) > G0, judging that the power grid is short-circuited.

6. The security protection method of claim 4, wherein: the step of S3 is specifically:

and according to the judgment result of the step S2, when the power grid is short-circuited, the processor controls the eddy current quick switch to be closed, so that the series compensation device is protected.