There is concern that the levels of inertia in power systems may decrease in future, due to increased levels of energy being provided from renewable sources, which typically have little or no inertia. Voltage Source Converters (VSC) used in high voltage direct current (HVDC) transmission applications are often deliberately controlled in order to de-couple transients to prevent propagation of instability between interconnected systems. However, this can deny much needed support during transients that would otherwise be available from system inertia provided by rotating plant. This paper proposes a novel VSC-HVDC control system termed "INEC" (INertia Emulation Control) which enables a VSC HVDC system to provide support that emulates the inertia of a synchronous generator (SG). The energy to do so comes from the capacitance of the HVDC connection, which may be augmented by the installation of additional capacitance. This paper indicates that the proposed INEC system allows a VSC-HVDC system with a fixed capacitance to emulate a wide range of inertia constants (H) by specifying the amount of permissible DC voltage variation. The proposed INEC scheme has been demonstrated through simulations, and its performance is evaluated for transients that include faults and also changes in load.

ARDS is associated with poor clinical outcomes, with a pooled mortality rate of approximately 40% despite best standards of care. Current therapeutic strategies are based on improving oxygenation and pulmonary compliance while minimizing ventilator-induced lung injury. It has been demonstrated that relative hypoxemia can be well tolerated, and improvements in oxygenation do not necessarily translate into survival benefit. Cardiac failure, in particular right ventricular dysfunction (RVD), is commonly encountered in moderate to severe ARDS and is reported to be one of the major determinants of mortality. The prevalence rate of echocardiographically evident RVD in ARDS varies across studies, ranging from 22% to 50%. Although there is no definitive causal relationship between RVD and mortality, severe RVD is associated with increased mortality. Factors that can adversely affect RV function include hypoxic pulmonary vasoconstriction, hypercapnia, and invasive ventilation with high driving pressure. It might be expected that early diagnosis of RVD would be of benefit; however, echocardiographic markers (qualitative and quantitative) used to prospectively evaluate the right ventricle in ARDS have not been tested in adequately powered studies. In this review, we examine the prognostic implications and pathophysiology of RVD in ARDS and discuss available diagnostic modalities and treatment options. We aim to identify gaps in knowledge and directions for future research that could potentially improve clinical outcomes in this patient population.

The rollout of smart meters raises the prospect that domestic customer electrical demand can be responsive to changes in supply capacity. Such responsive demand will become increasingly relevant in electrical power systems, as the proportion of weather-dependent renewable generation increases, due to the difficulty and expense of storing electrical energy. One method of providing response is to allow direct control of customer devices by network operators, as in the UK 'Economy 7' and 'White Meter' schemes used to control domestic electrical heating. However, such direct control is much less acceptable for loads such as washing machines, lighting and televisions. This study instead examines the use of real-time pricing of electricity in the domestic sector. This allows customers to be flexible but, importantly, to retain overall control. A simulation methodology for highlighting the potential effects of, and possible problems with, a national implementation of real-time pricing in the UK domestic electricity market is presented. This is done by disaggregating domestic load profiles and then simulating price-based elastic and load-shifting responses. Analysis of a future UK scenario with 15 GW wind penetration shows that during low-wind events, UK peak demand could be reduced by 8-11 GW. This could remove the requirement for 8-11 GW of standby generation with a capital cost of £2.6 to £3.6 billion. Recommended further work is the investigation of improved demand-forecasting and the price-setting strategies. This is a fine balance between giving customers access to plentiful, cheap energy when it is available, but increasing prices just enough to reduce demand to meet the supply capacity when this capacity is limited

Venoarterial (VA) and venovenous (VV) extracorporeal membrane oxygenation (ECMO) support is increasingly being used in recent years in the adult population. Owing to the underlying disease precipitating severe respiratory or cardiac failure, echocardiography plays an important role in the management of these patients. Nevertheless, there are currently no guidelines on the use of echocardiography in the setting of ECMO support. This review describes the current state of application of echocardiography for patients supported with both VA and VV ECMO.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-015-1042-2) contains supplementary material, which is available to authorized users.

The new standard C37.118.1 lays down strict performance limits for phasor measurement units (PMUs) under steady-state and dynamic conditions. Reference algorithms are also presented for the P (performance) and M (measurement) class PMUs. In this paper, the performance of these algorithms is analysed during some key signal scenarios, particularly those of off-nominal frequency, frequency ramps, and harmonic contamination. While it is found that total vector error (TVE) accuracy is relatively easy to achieve, the reference algorithm is not able to achieve a useful ROCOF (rate of change of frequency) accuracy. Instead, this paper presents alternative algorithms for P and M class PMUs which use adaptive filtering techniques in real time at up to 10 kHz sample rates, allowing consistent accuracy to be maintained across a ±33% frequency range. ROCOF errors can be reduced by factors of >40 for P class and >100 for M class devices.