Cocoa and chocolate HS code insights

List of the contents of this article:

• 1,The difference between small interference stability and low-frequency oscillation
• 2、 What is low-frequency oscillation? What is the main reason?
• 3, What are the main measures to suppress low-frequency oscillation
• 4, There are several analysis methods of low-frequency oscillation in the power system
• 5, What is the stability of low-frequency oscillation of the power system

The difference between small interference stability and low-frequency oscillation< /H2>

1. The dynamic stability of the power system refers to the fact that the power system does not have an increasing amplitude after interference. There are mainly: low-frequency oscillation of the power system, sub-synchronous oscillation of electromechanical coupling, self-excitation of synchronous motor, etc.

2. The rotor angle, rotation speed, and related electrical quantities of the generator, such as line power, busbar voltage, etc., occur approximately equal or increased amplitude. Because the oscillation frequency is low, generally 0.1-5Hz, it is called low-frequency oscillation.

3. Simple and stable RC oscillation circuit structure is simple, and only a feedback network and an amplifier are needed to realize sine wave output. Moreover, because the RC oscillation circuit adopts a feedback loop, it can achieve the effect of self-excited oscillation, and the output signal generated is stable.

What is low-frequency oscillation? What is the main reason?

The rotor angle, rotation speed, and related electrical quantities of the generator, such as line power, busbar voltage, etc., occur approximately the same or increase in oscillation. Due to the low frequency of the oscillation, it is generally 0.1-5Hz, so it is called low-frequency oscillation.

The reason for the low-frequency oscillation of the power system is the change in the load of the power system. When the load increases or decreases, it will lead to an imbalance between the generator and the load, that is, low-frequency oscillation.

Low-frequency oscillation is the phenomenon of continuous oscillation in the range of 0.2-5Hz between generators running in parallel under small disturbances.

What are the main measures to suppress low-frequency oscillation

1. Gasket capacitor: an auxiliary capacitor connected in series with the main capacitor of the resonant circuit. Adjusting it can make the frequency range of the oscillation signal smaller and can show Increase the oscillation frequency of the low-frequency end on the ground. Compensation capacitance: an auxiliary capacitor connected in parallel with the main capacitor of the resonant circuit. Adjusting the capacitance can expand the frequency range of the oscillation signal.

2. Regardless of whether the frequency increases or decreases, power plants should maximize the excitation current in accordance with the regulations of generator accident overload. Power plants should quickly take measures to return to normal frequency. The high-frequency power plant at the end of the delivery terminal quickly reduces the power generation capacity until the oscillation is eliminated or returned to the normal frequency.

3. The measures of the system include the pulsation number of the current conversion device, the AC filter, the active power filter, the harmonic management and the installation of the static reactive compensation device. Increasing the pulsation of the current conversion device can reduce the harmonic component of the alternating current. AC filters can absorb harmonic current and reduce the harm of harmonics to the power system.

4. The ceiling plate is composed of 80-100cm thick; through this measure, some low-frequency noise in the pump room is isolated and eliminated, and the noise reverberation in the pump room is eliminated. Separate the domestic water pump in the pump room from the fire pump with a brick-mixed wall, and install a soundproof door to carry out targeted noise reduction treatment and reduce investment.

5. The main treatment method of transformer low-frequency noise is vibration damping and transformer oscillation treatment. The vibration damping table is used for the transformer to carry out low-frequency vibration isolation management, which can control the transmission of oscillation at 0.Less than 2%, and then reduce the noise of the building structure transmitted by the transformer oscillation.

6. Reducing vibration from the source of vibration is the most direct control method. According to the mechanism and influencing factors generated by subway vibration, the following specific measures can be taken [3~6, 9]. ( 1) Vehicle lightweighting. ( 2) Smoothing the wheels.

There are several methods for analyzing low-frequency oscillation in the power system

1. Replacement method: The replacement method is a commonly used circuit fault analysis method, which may fail by replacing with intact components or circuit boards. Part, and then observe whether the circuit returns to normal. If it returns to normal, it can be determined that there is a problem with the component or circuit board and needs to be replaced or repaired.

2. The reason for the low-frequency oscillation of the power system is the change in the load of the power system. When the load increases or decreases, it will lead to the imbalance between the generator and the load, that is, it causes low-frequency oscillation.

3. It can be roughly divided into two types: local mode oscillation and interregional mode oscillation. Generally speaking, the more units involved and the wider the area, the lower the oscillation frequency. Main phenomenon: the system frequency oscillates within a certain range, and has a phenomenon similar to synchronous oscillation.

Between 4 and hz, it is usually called low-frequency oscillation (also known as power oscillation, electromechanical oscillation). Generally speaking, the oscillation mode of the power system can be divided into two types: regional oscillation mode and regional oscillation mode. If the low frequency of the system is very low (0.1~0.5 hz), it is generally considered to be the interregional oscillation mode of the interconnected system.

What is the stability of the low-frequency oscillation of the power system

1. The static stability of the power system means that the power system does not have non-periodic abray after small interference, and it automatically returns to the initial operating state.

2. The stability of the power system can be divided into static stability, transient stability and dynamic stability. ( 1) Static stability of the power system refers to the ability of the power system to automatically restore to the initial operating state without non-periodic abrogation after small interference.

3. After the system is subjected to small interference, the ability to automatically recover to the initial operating state without spontaneous oscillation or non-periodic abrasion is called the ability of small interference and stability of the power system. Small disturbance stability analysis, through the modeling of the system and the setting of small interference, to study whether the system will be unstable under small interference.

4. The circuit is simple and economical, but the stability is not high, and the adjustment is inconvenient. The C-oscillation circuit is a common electronic oscillation circuit, which has the following characteristics: simple and stable. The RC oscillation circuit has a simple structure, and only needs a feedback network and an amplifier to achieve sine wave output. .