Mixed H2/H∞ Optimal Voltage Control Design for Smart Transformer Low-Voltage Inverter

The smart transformer has been widely applied for the integration of renewables and loads. For the smart transformer application, the voltage control of low-voltage inverter is important for feeding the load. In this paper, a multi-objective optimization control design approach which comprehensively considers all aspects of indexes, such as linear quadratic (LQ) index, H∞ norm, and closed-loop poles placement, is proposed based on the linear matrix inequality (LMI) solution. The proposed approach is able to alleviate the weight of the designer from the tedious design process of the multiple resonant controllers and the selection of the weighting matrix for the LQ control. Besides that, some excellent performances such as fast recovering time, low total harmonic distortion (THD) and high robustness are achieved by the proposed approach. The THD are 0.5% and 1.7% for linear and non-linear loads, respectively. The voltage drop for linear load step is reduced to 10 V. The proposed approach is applied to a 5 kVA three-phase inverter to yield an optimal control law. Results from the simulation and experiment presented herein will illustrate and validate the proposed approach.

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A Novel VSG-Based Accurate Voltage Control and Reactive Power Sharing Method for Islanded Microgrids

Sustainability ◽

10.3390/su11236666 ◽

2019 ◽

Vol 11 (23) ◽

pp. 6666 ◽

Cited By ~ 1

Author(s):

Bowen Zhou ◽

Lei Meng ◽

Dongsheng Yang ◽

Zhanchao Ma ◽

Guoyi Xu

Keyword(s):

Reactive Power ◽

Control Method ◽

Low Voltage ◽

Voltage Drop ◽

Reference Value ◽

Voltage Control ◽

Synchronous Generator ◽

Stability Control ◽

Control Area ◽

Power Sharing

Islanded microgrids (IMGs) are more likely to be perturbed by renewable generation and load demand fluctuation, thus leading to system instability. The virtual synchronous generator (VSG) control has become a promising method in the microgrids stability control area for its inertia-support capability. However, the improper power sharing and inaccurate voltage control problems of the distributed generations (DGs) in microgrids still has not been solved with a unified method. This paper proposes a novel VSG equivalent control method named Imitation Excitation Control (IEC). In this method, a multi-objective control strategy for voltage and reactive power in a low voltage grid that considers a non-negligible resistance to reactance ratio (R/X) is proposed. With the IEC method, the voltage drop across feeders is compensated, thus the terminal voltage of each inverter will be regulated, which will effectively stabilize the PCC (point of common coupling) voltage and inhibit the circular current. Meanwhile, this method can realize accurate reactive power tracking the reference value, making it accessible for reactive power scheduling. What is more, the reasonability of the IEC model, namely the equivalent mechanical characteristic and transient process inertia support between VSGs and conventional synchronous generators (SG), is illustrated in this paper. Moreover, steady-state stability is proved by the small-signal modeling method, and the energy required by inertia support is given. Finally, the simulation result validates the effectiveness of the proposed method, and it is also demonstrated that the proposed method outperforms the conventional droop control method.

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Two-degree-of-freedom multi-input multi-output proportional–integral–derivative control design: Application to quadruple-tank system

Proceedings of the Institution of Mechanical Engineers Part I Journal of Systems and Control Engineering ◽

10.1177/0959651818791687 ◽

2018 ◽

Vol 233 (3) ◽

pp. 303-319

Author(s):

Jatin Kumar Pradhan ◽

Arun Ghosh ◽

Chandrashekhar Narayan Bhende

Keyword(s):

State Feedback ◽

Control Design ◽

Linear Quadratic Regulator ◽

Linear Matrix ◽

Feedback Gain ◽

Matrix Inequality ◽

Proportional Integral Derivative ◽

Linear Quadratic ◽

Proportional Integral Derivative Controller ◽

Proportional Integral

This article is concerned with designing a 2-degree-of-freedom multi-input multi-output proportional–integral–derivative controller to ensure linear quadratic regulator performance and H∞ performance using a non-iterative linear matrix inequality–based method. To design the controller, first, a relation between the state feedback gain and proportional–integral–derivative gain is obtained. As the gains of proportional–integral–derivative controller cannot, in general, be found out from this relation for arbitrary stabilizing state feedback gain, a suitable form of the matrices involved in linear matrix inequality–based state feedback design is then chosen to obtain the proportional–integral–derivative gains directly. The special structure of the above matrices allows one to design proportional–integral–derivative controller in non-iterative manner. As a result, multi-objective performances, such as linear quadratic regulator and H∞, can be achieved simultaneously without increasing the computational burden much. To enhance the reference-input-to-output characteristics, a feedforward gain is also introduced and designed to minimize certain closed-loop H∞ performance. The proposed control design method is applied for multi-input multi-output proportional–integral compensation of a laboratory-based quadruple-tank process. The performance of the compensation is studied through extensive simulations and experiments.

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Reduction of the Low Voltage Substation Constraints by Inserting Photovoltaic Systems in Underserved Areas

Recent Advances in Electrical & Electronic Engineering (Formerly Recent Patents on Electrical & Electronic Engineering) ◽

10.2174/2352096511666180523095219 ◽

2019 ◽

Vol 12 (2) ◽

pp. 105-112

Author(s):

Benbouza Naima ◽

Benfarhi Louiza ◽

Azoui Boubekeur

Keyword(s):

Low Voltage ◽

Voltage Drop ◽

Electrical Energy ◽

Utilization Rate ◽

Photovoltaic Systems ◽

Voltage Distribution ◽

Medium Voltage ◽

Pv Systems ◽

Transformer Substation ◽

Load Pattern

Background: The improvement of the voltage in power lines and the respect of the low voltage distribution transformer substations constraints (Transformer utilization rate and Voltage drop) are possible by several means: reinforcement of conductor sections, installation of new MV / LV substations (Medium Voltage (MV), Low Voltage (LV)), etc. Methods: Connection of mini-photovoltaic systems (PV) to the network, or to consumers in underserved areas, is a well-adopted solution to solve the problem of voltage drop and lighten the substation transformer, and at the same time provide clean electrical energy. PV systems can therefore contribute to this solution since they produce energy at the deficit site. Results: This paper presents the improvement of transformer substation constraints, supplying an end of low voltage electrical line, by inserting photovoltaic systems at underserved subscribers. Conclusion: This study is applied to a typical load pattern, specified to the consumers region.

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Dynamic Low Voltage Ride through Detection and Mitigation in Brushless Doubly Fed Induction Generators

Energies ◽

10.3390/en14154461 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4461

Author(s):

Ahsanullah Memon ◽

Mohd Wazir Mustafa ◽

Muhammad Naveed Aman ◽

Mukhtar Ullah ◽

Tariq Kamal ◽

...

Keyword(s):

Fuzzy Logic ◽

Fuzzy Logic Controller ◽

Low Voltage ◽

Voltage Drop ◽

Low Voltage Ride Through ◽

Induction Generators ◽

Doubly Fed Induction Generators ◽

Reactive Current ◽

Doubly Fed ◽

Rotor Side Converter

Brushless doubly-fed induction generators have higher reliability, making them an attractive choice for not only offshore applications but also for remote locations. These machines are composed of two back-to-back voltage source converters: the grid side converter and the rotor side converter. The rotor side converter is typically used for reactive current control of the power winding using the control winding current. A low voltage ride through (LVRT) fault is detected using a hysterisis comparison of the power winding voltage. This approach leads to two problems, firstly, the use of only voltage to detect faults results in erroneous or slow response, and secondly, sub-optimal control of voltage drop because of static reference values for reactive current compensation. This paper solves these problems by using an analytical model of the voltage drop caused by a short circuit. Moreover, using a fuzzy logic controller, the proposed technique employs the voltage frequency in addition to the power winding voltage magnitude to detect LVRT conditions. The analytical model helps in reducing the power winding voltage drop while the fuzzy logic controller leads to better and faster detection of faults, leading to an overall faster response of the system. Simulations in Matlab/Simulink show that the proposed technique can reduce the voltage drop by up to 0.12 p.u. and result in significantly lower transients in the power winding voltage as compared to existing techniques.

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Review of Voltage Control in Low Voltage Distribution Networks with High Penetration of Photovoltaics

Proceedings of the 2nd International Conference on Information Technologies and Electrical Engineering ◽

10.1145/3386415.3387036 ◽

2019 ◽

Author(s):

Zheng Lan ◽

Yang Long ◽

Yao Rao

Keyword(s):

Low Voltage ◽

Voltage Control ◽

Distribution Networks ◽

Voltage Distribution ◽

High Penetration

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Linear Quadratic Nash Game of Stochastic Singular Time-Delay Systems with Multiple Decision Makers

Journal of Systems Science and Information ◽

10.1515/jssi-2015-0472 ◽

2015 ◽

Vol 3 (5) ◽

pp. 472-480

Author(s):

Huainian Zhu ◽

Guangyu Zhang ◽

Chengke Zhang ◽

Ying Zhu ◽

Haiying Zhou

Keyword(s):

Time Delay ◽

Decision Makers ◽

Delay Systems ◽

Linear Matrix ◽

Time Delay Systems ◽

Linear Quadratic ◽

Nash Game ◽

Multiple Decision Makers ◽

Nash Strategies ◽

Singular Time

AbstractThis paper discusses linear quadratic Nash game of stochastic singular time-delay systems governed by Itô’s differential equation. Sufficient condition for the existence of Nash strategies is given by means of linear matrix inequality for the first time. Moreover, in order to demonstrate the usefulness of the proposed theory, stochastic H2∕H∞control with multiple decision makers is discussed as an immediate application.

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Robust Tracking Control for Takagi–Sugeno Fuzzy Systems With Unmeasurable Premise Variables: Application to Tank System

Journal of Dynamic Systems Measurement and Control ◽

10.1115/1.4026467 ◽

2014 ◽

Vol 136 (4) ◽

Cited By ~ 13

Author(s):

H. Ghorbel ◽

A. El Hajjaji ◽

M. Souissi ◽

M. Chaabane

Keyword(s):

Tracking Control ◽

Fuzzy Systems ◽

Design Procedure ◽

Control Design ◽

Linear Matrix ◽

Robust Tracking Control ◽

Fuzzy Observer ◽

Tank System ◽

System States ◽

Takagi Sugeno

In this paper, a robust fuzzy observer-based tracking controller for continuous-time nonlinear systems presented by Takagi–Sugeno (TS) models with unmeasurable premise variables, is synthesized. Using the H∞ norm and Lyapunov approach, the control design for TS fuzzy systems with both unmeasurable premises and system states is developed to guarantee tracking performance of closed loop systems. Sufficient relaxed conditions for synthesis of the fuzzy observer and the fuzzy control are driven in terms of linear matrix inequalities (LMIs) constraints. The proposed method allows simplifying the design procedure and gives the observer and controller gains in only one step. Numerical simulation on a two tank system is provided to illustrate the tracking control design procedure and to confirm the efficiency of the proposed method.

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