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Produkt-Übersicht
The installed capacity of renewables energies has been increasing exponentially in the last decades. In the next years the development of news projects will be accelerated driven by global warming and independence of fossil energies.
Wind power and photovoltaic systems are based on powerful AC-DC and DC-AC converters. They require reliable power capacitors for AC filtering and voltage stabilization in the DC link circuits. TDK offers a complete portfolio of power capacitors customized for these issues with a wide range of voltages and capacitances.

Overview

Renewable energy systems consist of multiple components, mechanical and electrical connections. They regulate and modify the electrical output. The generated electricity can be stored, used directly or fed into a large grid powered by central generating plants connected or tied to the grid.

The wind and solar inverters transforms DC to AC current. Power electronic designers are under increasing pressure to achieve higher power requirements with very high efficiencies, overvoltage and overcurrent protection due to switching failures, lightning, ground faults and safety regulations. Long-term stability and reliability is a furthermore issue.

TDK offers special products for many circuit functions, depending on the application requirements. Thus, its film based capacitor technology is particularly suitable for power electronics designers looking for proven performance.

  • Higher rated voltages compared to other capacitor technologies
  • High overvoltage capability due to their self-healing properties
  • Low equivalent serial resistance (ESR) and inductance (ESL)
  • High power operation (IRMS vs. frequency)
  • Stability of electrical parameters over time and temperature

Schematic circuit

A typical renewable energy inverter needs DC link capacitors for the reduction of ripple current in the transformation from AC to DC voltage. Depending on the power electronic topology DC link capacitor can be used according to the electrical parameters needed.

Figure 1

Feature comparison

Table 1
Type /
Series
MKP DC Standard MKP DC Resin top MKP DC Metal top ModCap™ MF ModCap™ HF
B2562* Series B2569* Series B2568* Series B25645* Series B25647* Series
Rated capacitance (µF) 40 - 4000 40 - 5500 60 - 4000 335 - 3900 660 - 1900
Voltage (V DC) 700 - 2000 700 - 3000 900 - 3000 900 - 2300 900 - 1600
Temperature up to 85 °C 85 °C 85 °C 90 °C 90 °C
ESL < 20 nH
possible (depending on H and D)
< 20 nH
possible (depending on H and D)
< 10 nH
(for 4 terminal capacitors)
< 14 nH 8 nH
Dimensions 75, 85, 116 mm (D)
70...345 mm (H)
75, 85, 100, 116, 136 mm (D)
95...370 mm (H)
85, 116, 136 mm (D)
99...368 mm (H)
205, 220 mm (L)
90, 115 mm (W)
170, 215 mm (H)
205, 220 mm (L)
90, 115 mm (W)
170, 215 mm (H)
Standards IEC 61071
UL recognized
IEC 61071
UL recognized
IEC 61071 IEC 61071, IEC 61881-1
UL recognized
IEC 61071, IEC 61881-1
UL recognized
EN 45545 HL3 R23 (fire/smoke) HL3 R23 (fire/smoke) HL3 R23 (fire/smoke)
Case Aluminum Aluminum Aluminum
Hermetically sealed for harsh environment
Plastic Plastic

Higher energy density and compactness

There is a clear market trend to have lighter and more compact inverters in order to optimize volume-weight ratio of the whole system.
This market trend is directly influencing the design of DC link capacitors, so compactness is a must.

Compactness of DC link capacitors may be achieved by optimizing the internal volume of the case by using the right winding technology and
increasing the field strength (V/µm), which is directly linked with the use of thinner films for the same nominal voltage.

Figure 2

Better efficiency for solar and wind inverters

  • Solar
    Since PV is strongly influenced by cost pressure then new inverters are forced to offer very high efficiency of up to 98 percent with longer maintenance periods.
    This application is demanding cost optimized standard products with reduced ESR and ESL. The capacitors should be optimized to work at higher frequencies.

  • Wind
    It is as well strongly influenced by cost pressure with a trend to increase nominal voltage (high power specially in off-shore application) and reduce weight, low ESR and ESL are important parameters .

    Both applications are demanding higher current densities.