Development of a State-Space Observer for Active Noise Control Systems

Active noise control (ANC) is a method of reducing the unwanted sound. This is realized by artificially generating canceling (secondary) source(s) of sound through detecting the unwanted (primary) noise and processing it by an electronic controller, so that when the secondary wave is superimposed on the primary wave the two destructively interfere and cancellation occurs at the observation point. ANC system is an active research area for its high demand especially in the acoustic noise and vibration control systems. A lot of work in modeling an ANC system involves the transfer function approach, but unfortunately this method allows observation at a single point or mode. It is of interest to measure the level of cancellation not only at the observer but also around it. Therefore, a state space approach would allow observation at multi modes simultaneously and became the subject of this research. This thesis is concerned with the study and development of a state-space model (SSM) for ANC system in on dimensional free-field medium instead of Finite Impulse Response (FIR) Models. In this work, the derivation of the SSM of each propagation path of ANC system is presented and hence the system is termed Feedforward state space control system with feedback inclusion single input single output (SISO) architecture. The criterions of success considered the evaluation process are the length of the propagation path, level of cancellation, convergence rate, number of modes of each path, and destructive interferences occur at the cancellation path. The secondary path of the ANC system is modeled by using the LMS algorithm to complete the design of the Filtered-X Least Mean Square (FXLMS) controller. Then the adaptive FXLMS controller is presented and incorporated with the proposed model for both Feedforward with / without the acoustic Feedback cases. As a result, the comparisons between the two cases are presented by mean of level of cancellation and convergence rate. The simulation results of the proposed model show that the level of the disturbance signal at ten modes along the primary path is decreasing as much as the modes go away from the source indicating that this model is suitable to build the mechanism of the ANC system which satisfies the relation between the wave dissipation against the number of modes which are distributed along the length of path. The derivation of the SSM gives the opportunity to extend the work furthermore to involve the derivation of a state-space optimal observer which is named State Space Least Mean Square (SSLMS) observer. This observer is employed to observe and monitor the pressure modes along the propagation path through simulating it in an offline structure i.e. without controller, or to observe the modes at the cancellation path through simulating the SSLMS in an on-line structure i.e. while the controller is converging. The comparison results between the real and observed modes of the secondary propagation show an accurate observing. Finally, the comparisons of the observed pressures of three modes along the cancellation path while the controller is converging (on-line structure) are shown with the mode which is located at the observer achieving the best cancellation

A model reference-based adaptive PSS4B stabilizer for the multi-machines power system

Two-inputs adaptive IEEE multi-bands power system stabilizer (PSS4B) was developed for oscillations damping control in power systems. Two supplementary loops based on model reference (MR) adaptive control were added to the typical PSS4B design. The MR has the same loops’ parameters of the typical PSS4B, and hence, avoiding a complex tuning process. The proposed PSS has a self-tuning gain reduction block to avoid any negative impact due to the high gains value during the disturbance time. The proposed PSS was applied on the four-machine benchmark power system. To evaluate the robustness of the proposed PSS, it was tested in comparison with the Delta W PSS, one-input multi-bands PSS4B (1iMB) and two-inputs multi-bands PSS4B (2iMB) stabilizers. The integration of the proposed PSS was demonstrating using different study cases. These cases consider the small-signal stability (SSS), large-signal stability (LSS) and the coordination test for the local and inter-area excited power modes. The proposed PSS demonstrated robust and superior responses in all cases

Dynamic frequency response from controlled domestic heat pumps

The capability of domestic heat pumps to provide dynamic frequency response to an electric power system was investigated. A thermal model was developed to represent a population of domestic heat pumps. A decentralized dynamic control algorithm was developed, enabling the heat pumps to alter their power consumption in response to a system frequency. The control algorithm ensures a dynamic relationship between the temperature of building and grid frequency. The availability of heat pumps to provide low-frequency response was obtained based on data supplied by Element Energy. Case studies were carried out by connecting a representative model of the aggregated heat pumps to the regional Great Britain (GB) transmission system model, which was developed by National Grid. It was shown that the dynamically controlled heat pumps distributed over GB zones have a significant impact on the GB system frequency and reduce the dependency on frequency services that are currently supplied by expensive frequency-sensitive generators. The rate of change of frequency was also reduced when there is a reduction in system inertia

Local dynamic frequency response using domestic electric vehicles

There is an increasing interest to penetrate low carbon vehicles into the transport system. Take the Great Britain (GB) as an example, the number of electric and plug-in hybrid vehicles will make up to at least half of new vehicle sales. Electric vehicles (EVs) are expected to contribute to the ancillary services of the frequency response because EVs can provide immediate frequency response and sustain its response for considerable period of time. This paper addresses the design of a Dynamic Vehicle Grid Support (DVGS) control algorithm for the provision of local frequency response. The DVGS considers a dynamic relationship between the state of charge of EVs and frequency set-points. Thus, it can be installed locally avoiding the cost and the time delay associated with the communication system between EVs and the control centre. The DVGS control algorithm was demonstrated using the reduced GB transmission power system model with a reduced system inertia. The simulation results showed that the EVs are promising assets for the provision of frequency response and reducing the rate of change of frequency (RoCoF). Moreover, EVs can be controlled geographically to provide the zonal frequency response, reducing the dependency on the power from the spinning reserve, especially with a reduced system inertia. The financial benefits of using the aggregated DVGS for firm frequency response (FFR) service in the GB is calculated

Control of a population of battery energy storage systems for frequency response

The control of multiple battery energy storage systems (BESSs) to provide frequency response will be a challenge in future smart grids. This paper proposes a hierarchical control of BESSs with two decision layers: the aggregator layer and the BESS control layer. The aggregator layer receives the states of charge (SoC) of BESSs and sends a command signal to enable/disable the BESS control layer. The BESS controller was developed to enable the BESSs to respond from the highest to lowest SoC when the frequency drops, and from lowest to highest when it rises. Hence, the BESS’s response is prioritised to reduce the impact on the power system and end-users during the service. The BESS controller works independently when a failure occurs in the communication with the aggregator. The dynamic behaviour of the population of the controllable BESSs was modelled based on a Markov chain. The model demonstrates the value of aggregation of BESSs for providing frequency response and evaluates the effective capacity of the service. The model was demonstrated on the 14-machine South-East Australian power system with a 14.5 GW load. 254 MW of responsive capacity of aggregated batteries was effective in reducing the system frequency deviation below 0.2 Hz following a sequence of disturbances

Potential of demand side response aggregation for the stabilization of the grids frequency

The role of ancillary services related to the frequency control have become increasingly important in the smart grids. Demand Side Response is a competitive resource that can be used to regulate the grid frequency. This paper describes the use of heat pumps and fridges to provide ancillary services of frequency response so that to continuously balance the supply with demand. The power consumption of domestic units is usually small and, therefore, the aggregation of large numbers of small units should be able to provide sufficient capacity for frequency response. In this research, dynamic frequency control was developed to evaluate the capacity that can be gathered from the aggregation of domestic heat pumps and fridges for frequency response. The potential of frequency response was estimated at a particular time during winter and summer days. We also investigated the relationship between both loads (domestic heat pumps and fridges) to provide Firm Frequency Response service. A case study on the simplified Great Britain power system model was developed. Based on this case study, three scenarios of load combination were simulated according to the availability of the load and considering cost savings. It was demonstrated that the aggregation of heat pumps and fridges offered large power capacity and, therefore, an instantaneous frequency response service was achievable. Finally, the economic benefit of using an aggregated load for Firm Frequency Response service was estimated

Development of the propagation paths and deriving observer of feedforward active noise control system by using state-space formulation

This paper presents the derivation and simulation of the propagation paths of a feedforward active noise control (ANC) system in one dimensional free-field medium using state-space model (SSM) instead of Finite Impulse Response (FIR) model. Furthermore, a new observer namely State Space Least Mean Square (SSLMS) observer will be derived. This observer will be used to estimate the states along the propagation path which can not be estimated using LMS algorithm because LMS based on the FIR models. The system is simulated in MATLAB and the results of the pressure modes along the noise path are depicted and have shown that the level of the acoustic signal decreases gradually against the modes. The results of the novel observer to show the comparison of the tracking the pressures of three modes along the interfering region between the primary and secondary path are shown with the mode which is located at the observer achieving accurate estimation

Design of a hybrid Fuzzy/Markov chain-based hierarchal demand-side frequency control

A developed model of the Thermostatically-based controllable loads (TCLs) is proposed for a hierarchal Demand Side Frequency Response (DSR). The model involves three layers based on Markov chain, Fuzzy Logic, and Particle Swarm Optimization (PSO) method. Layer 1 is the local Markov population of the TCLs, Layer 2 is the Fuzzy/Markov-based Frequency controller, and Layer 3 is the PSO-based Supervisory control. Layer 1 can detect a non-zero frequency deviation to start-up the process of Layer 2. Layer 2 is dynamically updating the switching probabilities of the Markov model of Layer 1 to control the power consumption of the controllable load. Layer 3 is dealing with a global optimization issue to obtain the start/end values of the switching settings as well as the amount of the droop value. The proposed design was tested in the Great Britain (GB) single bus machine as well as a multi-machines dynamic benchmark system

Power system oscillations and control: Classifications and PSSs' design methods: A review

In this paper, a review of the classifications of power system oscillation modes, as well as power system stabilizer (PSS) design structures, is proposed. Four major oscillation modes and their effects on power system stability have been investigated and analyzed, and the critical elements affecting each mode, frequency range, and PSS application have been summarized using important published work. Next, the PSS's structure has been classified according to the number of inputs and compensation filters, and a combination of the PSS with the intelligent systems, optimal evolutionary-based, and non-intelligent adaptive-based PSS has been highlighted. The effect of the oscillation modes in Great Britain's (GB) power system has been identified, as well as the possible solutions to damp this oscillation. It was found that the inter-area and the local machine modes have a greater impact on wide area power system stability and sustainability. Integrating new Renewable Energy Resources (RESs) can lead to more transient and dynamic instability. Therefore, more research is required to design solutions to tackle this grave problem. Four PSSs presented in the literature have been applied and tested in two different multi-machine Benchmark systems

Small Microgrid stability and performance analysis in isolated island

A generalized model of a Microgrid in an island mode is proposed for assessing the system power and frequency performances. This Microgrid (MG) includes a diesel backup generator along with a number of Distributed Energy Resources (DES): Wind Turbine Generator (WTG), Photovoltaic System (PV), Fly- Wheel Energy Storage system (FESS), and Battery Energy Storage System (BESS). Controlling the frequency deviation is posing a great challenge in stand-alone mode due to the mismatch between load demand and generation. Five different study cases were modelled in Matlab to investigate the performance and stability of the power system. Furthermore, two PD Fuzzy logic control plus Integral (PDFLC+I) act as supplementary controller were incorporated locally with diesel and storage elements in order to improve the robustness and safety of the system. Fuzzy rule and integral parameters were chosen to achieve fast response and small power and frequency deviation throughout step change in load profile. Classical PID controller was introduced for comparison purposes. The potential of using responsive charging electric vehicles (EVs) under three scenarios as a form of primary response was investigated. Simulation results showed that the decentralized controller eliminates the fluctuation effect of the wind turbine and stabilizes the system frequency. EVs can play important role in system primary frequency respons