Dynamic Reactive Power Compensation In Power Distribution System

1. Dynamic reactive power compensation device in power distribution system

Reactive power compensation, referred to as reactive compensation, is mainly used in our entire system to increase the power of the power grid and reduce losses, so as to improve our work efficiency and actively improve our power environment. Through the above, we found that it is very important to do a good job of reactive work. At work, we must carefully select the equipment for compensation, so that we can well reduce network losses and improve the quality of power supply. On the contrary, if we cannot effectively select the equipment, it will bring many unfavorable factors to our system and affect the work of the system. There are two ways of so-called reactive power, one is dynamic and the other is dynamic. Static reactive power compensation is to install a fixed capacity compensation capacitor or compensation inductor according to the load situation, and dynamic compensation is to switch the compensation capacitor capacity or inductance at any time according to the inductive or capacitive changes of the load for compensation. The compensation used at ordinary times is graded. In other words, commonly used compensation devices such as capacitors are switched in groups. In simple terms, the amount generated by the system and the amount you compensate will not be the same. Although it is not perfect, this method has greatly improved the power, so it is worth using. However, there are some loads whose reactive power changes greatly during operation, and the speed is very fast, sometimes as fast as milliseconds. The most common one is the welding machine, which has a working time of only 0.2 seconds, and there are tens of seconds of half load and tens of seconds of pause in between. There is no regular pattern to follow when the reactive power changes during operation. At this time, if we still use the previous method, it will be ineffective. We should use the above dynamic mode.

Dynamic means fast speed and good timeliness. The first point is that the speed must be guaranteed, and the second point is that the load should not be used indiscriminately. The compensation equipment should compensate for the reactive power used by the load. The above two points are the basic characteristics of dynamic. Although there are two points, not both are required. In many cases, individual loads have very fast speeds, but the reactive power will not change. In other words, dynamic emphasizes speed.

The dynamic reactive power compensation device is composed of high-voltage switchgear, parallel capacitors, series reactors, discharge coils, zinc oxide arresters, support insulators, frames, etc. The dynamic reactive power compensation device is based on improving and increasing the power factor, reducing line losses, and giving full play to the efficiency of power generation and power supply equipment. It has powerful functions, LCD field display, reliable and stable performance, and strong anti-interference ability. This method will meet the standard in a specific environment, that is, when the compensation amount is just right.

There are three types of reactive power compensation equipment: factor type, power type, and current type. The most common type is the factor type, which is more convenient in terms of sampling and control. The current type can well solve the defects of the first type, has good adaptability, can solve the problem of line instability, and can do a good job of inspection and compensation. The controller used for dynamic compensation has higher requirements. It is generally considered together with the trigger pulse forming circuit. It has great requirements on the anti-interference performance of the equipment, and also requires speed. The most important requirement is high work efficiency.

2. Optimal utilization method and principle function of dynamic reactive power compensation device

Reactive power compensation for distribution lines is achieved by installing capacitors on line towers. At this time, the number of compensation points on the line should be as small as possible, and the group control method should be used as little as possible. At the same time, the compensation capacity should be reasonably controlled to reduce the occurrence of over-compensation as much as possible. In addition, the protection method should be as simple as possible, generally using fuses and lightning protection equipment. This method is characterized by low investment and fast results, convenient management, simple maintenance, and is more practical for low-power and heavy-load lines.

In my country's cities and rural areas, low-voltage three-phase four-wire mode is mostly used: in many cases, users are single-phase loads or single-phase and three-phase mixed use, and the key is that the loads are different and the time is different. Therefore, unbalanced current will exist, and this situation is irregular and unpredictable. This has led to a long-term imbalance to a large extent. For this imbalance, we have no good countermeasures except to distribute the load as effectively as possible.

This imbalance will not only increase the copper loss of the line, but also cause serious iron loss, reduce the output of the transformer, and in severe cases affect the operation, which will eventually lead to voltage imbalance.

The reactive power compensation device for adjusting unbalanced current effectively solves this problem. It can not only compensate reactive power, but also adjust active power. Theoretically, it can effectively compensate the factor to 1, and ultimately ensure current balance. In actual work, we found that the actual effect can reach a standard higher than 0.95, and can effectively adjust the current.

The device tracks and measures the voltage, current, reactive power, etc. of the load in real time, and obtains the reactive power through computer analysis, which is then compared with the set value to finally obtain the best compensation. At present, there are still some problems between domestic equipment and similar foreign equipment, which are manifested in ineffective compensation, too large impact current, poor characteristics, and high maintenance costs. In addition, it cannot respond dynamically quickly. In addition, there is no perfect standard system, etc. This makes the development slow. However, its advantages cannot be ignored, such as fast calculation, good resistance to interference, and the most effective is good work efficiency.

Practical method: Connect a device with a capacitive power load and an inductive power load in parallel in the same circuit. At this time, energy can be well exchanged between these two different loads.

The main functions of the dynamic power-off compensation device are: first, it improves the working stability, second, it maintains the voltage well and further promotes the stability, third, it can compensate for the reactive power well and increase the power, which can effectively reduce the line loss and achieve energy saving, fourth, it can effectively resist the fluctuation phenomenon, and the last point is that it can ensure the three-phase balance.

The problems faced by dynamic reactive power are: first, the equipment is prone to damage, second, the components are prone to fuse, and third, the efficiency is low.

3. Differences between dynamic and static

(I) The former means that the reactive power controller automatically switches on and off the compensation amount according to the line power factor to ensure that the power factor is basically constant near a certain set value, the latter means that a fixed value compensation amount is manually switched on and off, and the compensation amount does not change with the line power factor. Unless very good compensation can be achieved, the power can be guaranteed to be qualified. If the compensation is too large or too small, it will lead to low power.

(II) The so-called dynamic means ensuring fast time, which is generally achieved through thyristor switching capacitor group TSC, controllable reactor to adjust reactive power TCR type SVC or static reactive power generating device SVG adjusted by IGBT device.