Ensuring dynamic stability of constant power loads in DC telecom power systems and data centers using active damping

Abstract

a) (b) Fig. 1. A typical DC DER system: (a) its architecture; and (b) V-I characteristic to explain the negative incremental impedance of CPLs.Abstract -DC distribution is becoming increasingly important in telecom and buildings' power systems. The main building blocks of DC power systems are switching power converters and rectifiers that have nonlinear characteristics. When the voltages are tightly regulated, the converters will act as constant power loads (CPLs). The CPL is known to exhibit the negative incremental impedance and may cause the dynamic instability of the system. The problem associated with CPLs is traditionally tackled using passive damping which has serious drawbacks such as increased size, decreased reliability and efficiency of the system. This paper introduces an active method to inject damping current into the power bus employing an auxiliary power circuit. The proposed approach ensures that the system operates with sufficient stability margin in a small-signal sense. Comparing with previous works, the advantage of the proposed damping circuit is that the absorbed energy for damping is transferred into a neighboring bus with minimal energy losses.

Novel Droop Control of Battery Energy Storage Systems Based on Battery Degradation Cost in Islanded DC Microgrids

“…In this case, VL can be eliminated from the relation of VL and Vi (obtained from Vi=VL+IiRi and ∑ ΔI i i =0 ). However, the composite load model is usually not a constant current because the constant impedance and/or constant current loads such as lightening and data center are common in DC systems [38], [39]. Thus, the details of that case are not described herein.…”

Analysis and Design of DC-Bus Voltage Controller of Energy Storage Systems in DC Microgrids

“…Thirdly, the active damper can be used, which may incur extra costs. In most of active damping studies, the additional circuit has been implemented by the buck or special types of DC/DC converter which is implemented as a current source to inject a desired compensating current [14]- [19]. In the DC power system, however, since an energy storage system (ESS) is usually involved for energy buffering or peak power leveling [4], of which use for active damping does not require any additional cost.…”