Dc link converter topologies

PWM (Pulse Width Modulation) frequency converter controlled AC motors are being used in a big numbers throughout a wide range of industrial applications. The rectifier takes the three phase, fixed voltage, fixed frequency power source from the AC power lines and converts it to DC voltage. The DC-link takes the DC voltage from the rectifier and filters it to provide a smoother fixed DC voltage to the inverter.
The switching frequency for PWM voltage creating commonly referred to as the "carrier frequency" can be of a fixed value or in newer technologies a variable value. Today's PWM frequency converters employ a several types of semiconductor devices in the inverter. Induction motor powered by frequency converter may require additional testing following a fault identified as a stator related anomaly.
The input circuitry of most static frequency converters is essentially a three-phase diode rectifier bridge with capacitor filter. Frankly we are stuck to our system frequency, say 50Hz in India and Europe vs 60Hz in USA and Canada, We have no choice.
Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. The operating range of a wind turbine can be separated into four regions as it is hinted out in Figure 1.
A windmill is an aerodynamic machine with a torque-to-speed characteristic that, to certain extend, is defined by the blade’s geometry. From mechanical aspects it is mandatory to keep the tip speed at subsonic levels, thus a limitation of the rotor’s speed is mandatory at high wind speeds. To adapt the rotor’s characteristic to continuously suit the changing conditions, the blades have to be turned along their longitudinal axes. The Pitch-Controller suffers from several influences coming from the location it is mounted in. Atmospheric conditions can include dry heat and dust in deserts as well as high humidity and salty mists in offshore plants.
Electrically, pitch controllers resemble the structure of an uninterruptable power supply (UPS) as they have to operate safely in case of grid failure. From the diagram and the mode of operation, several special demands not usually seen in a drive application can be derived. As the pitch controller has to operate in case of short-term grid failures in the range of several hundred milliseconds, there is a high probability that the motor is active the moment the grid voltage returns.
In pitch controllers, this is a reoccurring scenario whenever the grid voltage is restored while the motor is driven from the battery. To prevent both from happening, a half controlled thyristor-bridge as an input rectifier poses a viable solution. The power modules are based on the EconoPACK™ 4 which is especially designed to support applications with demands resulting from extended mechanical stress.
Besides the mechanical robustness, pitch control is a highly demanding application regarding thermally induced stress. At the speed demanded by the grid codes, changing the blade’s alignment only takes a few seconds which makes pitch control an application delivering short burst of high torque.
Finally, proper torque-to-speed characteristics have to be maintained during the start of the rotation to minimize the excitation of the springsystem in the beginning.
Windmills as power plants are connected to the grid and are required to cope with the according transient changes without shutting down. The approach is valid for synchronous generators; asynchronous machines like the double fed induction generator (DFIG) would require an additional crow bar to operate properly. This particular brake chopper is designed to operate without the grid being available and therefore needs a power source that is independent from the grid. In case the brake chopper is designed as a part of the grid-side inverter, it depends on the power level demanded, what kind of power module could be used.
Starting from several hundred amps, a PrimePACK™ in either highside or low-side chopper configuration is an excellent option to create a customized design. A dedicated solution offered by Infineon is based on the fact that the low-voltage-ride-through chopper only needs to be operational for less than two seconds and most likely only a few times a day. The internal half bridge can be configured to either be a high-side or a low-side chopper depending on customer’s preferences. Infineon - who has written 143 posts on PowerGuru – Power Electronics Information Portal. Your use of this website constitutes acknowledgement and acceptance of our Terms & Conditions. Please note that due to the vast array of products that we can source from our suppliers, it is impossible for us to keep stock of eveything on our premises.
To provide our clients with a wider variety of products, we have listed numerous items that are in stock with our suppliers but, due to ever changing stock levels, the quantities available are not always guarenteed.
If you are interested in purchasing more than the quantity listed, please ask us to check for additional stock and depending on quantity, we may pass on bulk discounts. If you don't see an item that you are looking for, please ask through any of our other listings and we will try and source the product for you. Please take note of the classification of items ie: Small, Medium Large etc and the related charges and ensure you select the correct shipping method on checkout. In this paper a systematic fuzzy sliding mode controller is presented for permanent magnet synchronous motor (PMSM) sensorless drives.
ReferencesAchour AY, Mendil B, Bacha S, Munteanu I (2009) Passivity-based current controller design for a permanent-magnet synchronous motor. JavaScript is currently disabled, this site works much better if you enable JavaScript in your browser.

The benefits are huge, such as enhanced process control, energy savings, and small inrush currents and torque pulsations during the starting period which gives a longer life for water pumps and applications with motors, better reliability and performance.
This characteristic of carrier frequency will determine the audible motor noise, as well as how closely the PWM frequency converter to a closed pure sine wave power. For higher performance frequency converters the last mentioned may apply field-oriented control. It has the MOSFET's desired features on the input and the BJT's best features on the output. It often remains unnoticed, that controlling the mechanical parameters of the power plant also involves power electronic. This function, known as Pitch Control, is achieved by geared motors at the base of each blade; each motor is equipped with a converter that is referred to as Pitch Controller. Rotating with the hub of the mill, the inverter is subject to low frequency centrifugal forces and has to withstand the vibrations inside the hub.
Therefore, batteries are part of the design, and in case of grid failure the DC-link voltage given by the battery in use differs from the one in case the grid is available. In this instant, a difference between input voltage and DClink voltage will lead to an inrush current that could damage the input rectifier. Charging the DC-link using a resistor may take too long as some of the input current will go to the motor. In combination with a sixpack to drive the motor, the resulting schematic is depicted in Figure 4 also including power modules suitable for this application. These can be chosen to provide current levels high enough to ensure fast charging of the DC-link even if the motor is operated at full power. So-called power cycling, a rapid heating and cooling of the power electronic component’s internal construction, is the consequence. One phenomenon that has to be handled is a voltage drop for a period of several hundred milliseconds. To achieve this so-called Low-Voltage-Ride-Through capability, it is mandatory to control the energy generated during this time. Several design possibilities can be covered using Infineon building blocks or power modules. From these conditions it is obvious, that a cost-efficient thermal capacitance can be installed to replace the more expensive heat sink or even cold plates.
The thermal capacitance is dimensioned to allow an operation of the device for 10 seconds at full power and therefore is well suitable for the task. As a power plant, it can only operate properly if all interacting subsystems are considered. Thereafter, the item may be relisted.Should payment not be made within 7 days, a SNC (Sale Not Complete) will be filed to recover fees and the item will be relisted. These items will be marked as "PLEASE CONFIRM STOCK" and we ask that you please check with us before placing an order for these items. The fuzzy sliding mode controller is designed based on input–output feedback linearization control technique. PWM frequency converter controlled AC motors are usually more reliable than those supplied directly on grid. However, the induction motor's mechanical design, in terms of bearings and balancing, limits the maximum frequency on which it can be operated in good condition.
In general, the higher the carrier frequency the closer the output waveform is to pure sine wave. To properly control the mechanical components of the plant, adapt its aerodynamic properties to the wind speed, allow for safe shut down during grid failure and enable the demanded low-voltage–ride-through capability, highly reliable power electronic components are mandatory. Maximum power point tracking can be done in this region by choosing a proper output current rather than adapting the mechanical characteristic of the rotor.
The diagram is based on the assumption that the blades are kept at constant angle to the wind. A closer look to this particular application of power electronics reveals the high demands that need to be fulfilled. Thus, extensive heat would be generated inside the charging resistor leading to accelerated ageing or even destruction. Given that a single blade of a 6MW windmill has a mass of up to 20 tons it becomes obvious that moving these masses comes with large inertias and high breakaway torques that need to be overcome in addition to the aerodynamic forces applied to the blade. During this low-voltage period, the countertorque to the generator is reduced leading to a sudden increase in the rotor speed, possibly leading to overspeed conditions. As the grid is not available, converting the energy to heat is the most widely spread option.
Due to their enlarged creepage and clearance distances along with outstanding mechanical robustness, these modules are predestined to be used in wind-mill applications. Infineon therefore has designed a chopper based on the well-established PrimeSTACKÔ components, making use of eight paralleled 62mm modules in half-bridge configuration. Special care has to be taken regarding the design of auxiliary drives that are mandatory for the safe operation of the whole system. J Electr Eng 58(5):285–290Andreescu GD, Popa A, Spilca A (2002) Two sliding mode based observers for sensorless control of PMSM drives.
For instance, the problem of broken rotor bars, mainly due to excessive starting torque, is practically avoided by means of soft starting with a frequency converter.
The power supplied to the induction motor by a PWM frequency converter has some disadvantages too (increased heating, high peak voltages, and increased operation noise).
The main advantages are the power range, the good conductive features, the high switching frequency and the simple control.
Being connected to a DC-link with voltage levels higher than the battery voltage, decoupling diodes are installed to protect the battery from DC-link voltages exceeding its specification.

Using a resistor and a relay contact is the most widely used method in low-power drives applications. Keeping the resistor bridged using the relay contact will lead to high inrush currents threatening the rectifier diodes. Their thermo-mechanically induced movements lead to deterioration and bond lift-off in the final state. As in the instance the voltage sag takes place the duration of the effect is not predictable, the mill’s control can protect the rotor from overspeeding by realigning the blades to produce a braking torque.
A brake chopper is added to the power electronics of the grid inverter, consisting of a choppertype module and a brake resistor.
As can be seen in Figure 6, an aluminum plate is used to mount the electronic units, serving as a carrier and as a thermal capacitance at the same time. Making use of the thermal capacity only, fans or even more advanced cooling systems are omitted, making this a cost-efficient and reliable solution as no external, especially mechanical, components can fail.
Infineon, with extensive knowledge in both, the application and the semiconductors needed, can contribute to this application providing highly reliable solutions for a power range spanning from kilowatt to megawatt. Most industrial applications in the power range from less than 1 kilowatt up to some hundred kilowatts make use of Voltage Source Inverter (VSI) type converters. The resistor limits the current; the relay contact is activated to bridge the resistor as soon as the DC-link voltage reaches a certain limit. To compensate this effect, proper dimensioning of the semiconductor and appropriate thermal management has to be done; characteristically, oversizing of the power electronic components is a consequence of this mode of operation. In IEEE international conference on industrial technology ICIT, vol 2, pp 683–687Bosg BK (1985) Sliding mode control of inuctioii motor. The procedure is well established and works properly in industrial drives as during the time needed to charge the DC-link capacitors no current is delivered to the application. Larger semiconductors inherently feature larger thermal capacitances, thus the thermal swing to the internal construction is reduced. Though this protects the mill from mechanical point of view, the plant goes off-line and its contribution to power generation is lost in case the voltage levels are restored within a certain time. This control technique allows the minimization of harmonics introduced by the line converter, including the control of power factor and DC-link voltage. In: IEEE international conferenceCapolino GA, Golea A, Henao H (1992) Modelisation et simulation d’un asservissement a vitesse variable avec mode glissant, Journees d’etudes Avertissement Electromecaniques Rapides. Special care in dimensioning has to be taken, also taking the batterypowered operation into account.
Lately, this effect has lead to a shut-down of complete wind parks in Asia with turbines not able to handle this situation. Thereafter, the item may be relisted.Should payment not be made within 7 days, a SNC (Sale Not Complete) will be filed to recover fees and the item will be relisted. The robustness of the overall system is studied using simulation for different operating modes and varied parameters. Modelisation et Regulation Avancees, MetzCernat M, Comnac V, Cotorogea M, Korondi P, Ryvkin S, Cernat RM (2000) Sliding mode control o4f interior permanent magnet synchronous motors. In: VII IEEE international power electronics congress, Acapulco, MEXICO, pp 48–53Chi S, Xu L (2006) Sliding mode sensorless control of PM synchronous motor for direct-driven washing machines. If constant output power is driven to the application, the currents to the motor have to be increased to compensate for the lower voltage. In: IEEE international conference on industry applications, pp 873–879Chung S-K, Bae J-D, Youn M-J (1999) Integral variable structure controller for current control of PWM inverter-fed AC drives.
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Due to the construction of the blade it acts as a torsion spring element, excited by starting the rotation.
In: Proceedings of the IEEE international conference on automation and logistics, pp 2349–2354Janiszewski D (2006) Extended Kalman filter based speed sensorless PMSM control with load reconstruction.
Oscillations like this have to be kept at tolerable limits and damage to the mechanical components has to be prevented. In: The 23nd annual conference of the IEEE industrial electronics society, pp 1465–1468Jezemik K (1999) VSS control of unity power factor. To do so, regulation strategies include the regenerative operation of the pitch controller to smoothly dampen these oscillations. This in turn leads to the necessity of integrating a brake chopper to control the DC-link voltage in case it reaches critical limits. In: IEEE international conference on control and automation, Guangzhou, pp 630–635Sayeef S, Rahman MF (2007) Comparison of proportional + integral control and variable structure control of interior permanent magnet synchronous motor drives.
In: 38th IEEE power electronics specialists conference, Orlando, USA, pp 1645–1650Senthil Kumar N, Sadasivam V, Asan Sukriya HM (2008) A comparative study of PI, fuzzy, and ANN controllers for chopper-fed DC drive with embedded systems approach.
Nauka, MoskvaYu-Sheng L, Wang X-W (2009) Sliding-mode repetitive learning control with integral sliding-mode perturbation compensation.
In: The international conference on “computer as a tool”, EUROCON, Warsaw, pp 1851–1855Zhuang X, Rahman MF (2003) Sensorless sliding mode control of an interior permanent magnet synchronous motor based on extended Kalman filter.

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