The number of systems using wind power generation worldwide is increasing. In 2009, wind power installed capacity in Europe was 75 GW, an increase of 10 GW over 2008; in the United States, wind power installed capacity is 35 GW, and China is 25 GW, which is 10 GW and 14 GW higher than 2008. Wind power installed capacity increased by 38 GW in 2009 worldwide. A total of 100,000 wind turbines are installed worldwide, meeting 2% of global energy demand. By the end of 2010, the installed capacity of wind power will reach 29GW, corresponding to an increase of 12,000 wind turbines.
This article refers to the address: http://
As the demand for wind energy continues to grow, so does the demand for components that meet wind turbine requirements. Modern power electronics in wind turbines not only limits the number of components, but also requires the circuit to last for 20 years in extreme temperatures and vibrations.
In this article, we will introduce the functions of "large" resistors and capacitors used in wind turbines and power grids, as well as the requirements for devices in these applications. Capacitor applications include DC chains, IGBT buffers, and AC filter components. Resistance applications include current limiting, DC chopping, shunt triggering, and current measurement during capacitor pressurization. Small capacitors and resistors used in wind turbine control circuits are beyond the scope of this article.
The resistors in the resistance wind turbine include pre-charge, chopper, short-circuit and AC filter resistors. The pre-charge resistor limits the inrush current into the DC link capacitance when the switch is turned on. To do this, the device requires high single pulse energy and high voltage rating. The impedance of the resistor also helps to limit the inrush current. Therefore, wirewound resistors are the best choice. The single pulse energy used to precharge the resistor is typically 5J.
Figure 1 Resistance in a wind turbine
When the chopper switch is turned on, the chopping resistor limits the current. Choppers typically control the DC voltage at very high frequencies. Therefore, the resistor must be able to withstand high voltages and have high rated repeatable pulse energy (equivalent to high rated continuous power). There must be low parasitic inductance in the chopper resistor because it operates at high switching frequencies in the kilohertz range, which can be obtained by thin film technology. The need to achieve high power ratings in a small volume is met by resistors that can be mounted in the heat sink components. This resistor can be installed in the heat sink system just like the chopper switch.
The shunt resistor limits current and voltage to prevent low and high voltages from passing. Wind turbine applications require up to 4 MJ of energy pulse capacity, 10 to 100 mΩ of resistance, 1 to 20 mW of rated power, a maximum current rating of 10 to 20 kA, and a typical failure period of 200 ms.
In the RC filter, the AC filter resistor is used together with the AC filter capacitor; and the AC filter resistor is used together with the inductive reactance in the output transformer to form an RL filter. For AC filter capacitors, a high continuous power rating is required. The corrugated strip structure increases the cooling effect, and the inductive reactance of the wirewound resistor contributes to the filtering effect.
The shunt resistor is mainly used for measurement. The requirements include: rated current of 800 ~ 900A, impedance of 0.1 ~ 0.6mΩ, rated power of 500W, temperature coefficient of 100 × 10-6 / K.
The capacitance of the capacitor in the wind turbine includes a DC link, a buffer, and an AC filter capacitor. The DC link capacitor is used to stabilize the DC link voltage. Whether it is a metal film or an aluminum electrode, the inductance capacity in the wind turbine should be 3300 ~ 4700μF, and the rated voltage is 690 ~ 1000V. The film capacitor in a wind turbine has two advantages: the self-recovery function after the dielectric is electrically broken down; it does not affect the life due to the loss of the liquid electrode.
Figure 2 Capacitance in a wind turbine
Aluminum electrolytic capacitors can be used in DC link capacitors. The advantage is that it has a higher capacitance volume ratio and cost performance than a film capacitor. However, the aluminum capacitor is rated at 450V, so the device must be used as a voltage divider, which reduces C/V efficiency and increases cost. The disadvantage is the lack of a self-healing mechanism to protect against media failure, and electrolyte loss leads to limited life. However, aluminum electrolytic capacitors are the best choice for small wind power systems in the kW class.
The snubber capacitor reduces current and voltage spikes in power semiconductor switching applications, protecting the semiconductor and reducing total losses and EMI. Wind turbines require devices with capacitances less than 1μF and rated voltages ranging from 1000 to 1200V.
The AC filter capacitor reduces harmonics in the line frequency. Its application requirements are 760V ~ 24kV voltage and 50 ~ 800kVAr power.
When selecting core components for these wind turbines from DC link, buffer or AC filter capacitors, and pre-charge, chopper or shunt resistors, designers should not only look for devices with the required characteristics, but also The design is based on a solid design to ensure that the system can work reliably for 20 years.
We disign and manufacture Linear Actuators for Medical Care, such as Medical Chair
The Linear Actuator for Medical Chair with heavy load, where strong force is needed. It is very quiet, and strong. Hall sensor for position feedback is available.
We disign and manufacture Linear Actuators for Message Bed.
U2 is the linear actuators which is widely used for medical care.
TOMUU focuses on developing andmanufacturing high quality actuator system, and Offer reliable solution for non-standardand new area application.TOMUU has always been devotingherself to improve human`s life. TOMUU has unique idea in development, manufacturingand corporate culture, which has been applied toFurniture, medical care,industrial equipment and smart home.
Electric Linear Actuator For Medical Chair, Linear Actuator for Medical Chair, Actuator For Medical Chair
TOMUU (DONGGUAN) ACTUATOR TECHNOLOGY CO., LTD. , http://www.tomuu.com