Srinivas Ponnaluri

A modified direct power control strategy allowing the connection of three-phase inverter to the grid through LCL filters

This paper proposes a novel approach to adapt a conventional direct power control (DPC) for high-power applications, where a third-order LCL filter is frequently required. The LCL filter can cause a strong resonance and requires additional effort for system control. The application of a DPC for the control of a three-phase voltage source inverter that is connected to the grid through an filter has not yet been considered. The addition of an active damping strategy, together with a harmonic rejection control loop, to the conventional DPC is proposed and analyzed in this paper. The steady-state, as well as the dynamic performance of the proposed system, is verified with simulation results and experimental measurements.

Optimized Pulse Patterns for the 5-Level ANPC Converter for High Speed High Power Applications

This paper presents the analysis of the active neutral-point-clamped 5-level converter (ANPC5L) with regards to the total harmonic distortion (THD) for high speed, high power applications. A 5 MW machine with fundamental frequency of 500 Hz is considered. The converter can be switched up to 2 kHz, thereby making the switching frequency to fundamental frequency ratio in the range of 3-4. Different optimized pulse patterns (OPP) are studied for this case. It is shown that no extra filter is necessary to limit the THD in the considered application, when applying the proposed pulse patterns. Topology specific issues, such as the floating capacitor voltage balancing and the switching frequency of the devices, are investigated in detail for the proposed pulse patterns. The results are compared with a traditional pulse width modulation (PWM) approach

Comparison of single and two stage topologies for interface of BESS or fuel cell system using the ABB standard power electronics building blocks

The two most popular topologies used to interface the DC voltage sources such as battery energy storage systems (BESS), fuel cells with the AC network are the single and two stage topologies. In case of the single stage topology the BESS or the fuel cell system is directly connected to the dc link of a voltage source converter and the voltage source converter is interfaced to the low voltage grid with a transformer. A two-stage solution is realized using a DC-DC conversion stage followed by a DC-AC conversion stage. The DC-DC stage boosts the DC voltage so that the DC-AC stage can be directly interfaced to the low voltage grid. Detailed comparison of these topologies is carried out using battery voltage and the installed power as variables. The commercially available ABB standard Lopak PEBBs are used for comparison of the topologies. Both solutions are offered by ABB mainly depending on the dc voltage level of the BESS

Design comparison and control of medium voltage STATCOM with novel twin converter topology

A comparison of parallel and the proposed series or twin connected standard converters is presented for a 500 KVAr STATCOM. It is shown that the proposed topology is superior with respect to the filter size and maximum power output. Control issues specific to the twin topology are covered. A new way of controlling the converter under unbalance grid voltage conditions is proposed.