Experimental validation of the general power theory using power hardware-in-the-loop : opportunities for new converter controls

Jankee, Pitambar and Gaunt, C. Trevor and Feng, Zhiwang and Burt, Graeme (2024) Experimental validation of the general power theory using power hardware-in-the-loop : opportunities for new converter controls. In: CIGRE Paris Session 2024, 2024-08-25 - 2024-08-30, Palais des Congrès.

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Abstract

Concept models, theories, and definitions of electric power quantities feed into the control of powerelectronic converters and compensators. A definition of power quantities based on a measurement model respecting the laws of physics of circuits is therefore important for the optimal control of the energy injected into the grid from power-electronic converters. Most power definitions use reactive power (Q) as a parameter defined in the average domain. However, Q is always zero if calculated as an average value within a fundamental frequency cycle. The physical interpretation of Q, especially during conditions of unbalance and harmonic distortion, is unclear. The General Power Theory (GPT) for electrical circuits provides a rigorous approach to identifying the reference currents to be drawn from or injected into the system by a compensator or inverter to minimise power delivery loss and improve relative power delivery efficiency. It can be applied even in conditions of unbalance and harmonic distortion. Electromagnetic Transient (EMT) simulations have shown that minimum loss can be achieved using GPT-control of power-electronic converters instead of conventional approaches. This paper focuses on the application of the novel theory to power electronic converter control. It demonstrates through experimental validation the feasibility of a fundamentally new approach to converter control that may prove invaluable as the challenges of inverter-dominated grids and grid forming converter coordination emerge. The effect of applying pq-compensation and GPT-compensation in a 3-phase 4-wire test network with a source, delivery system and load was studied using Simulink-simulations. The EMT simulation results were validated with Controller Hardware-in-the-Loop (CHIL) tests using a Digital Real-Time Simulator (DRTS) from Typhoon HIL. In a collaboration between the Universities of Cape Town and Strathclyde under the ERIGrid 2.0 transnational access programme, the approach was tested practically using the Power Hardware-in-the-Loop (PHIL) approach on a DRTS test bed interfaced with a 10 kW converter retrofitted with GPT control. The paper describes how the GPT’s abc reference frame approach to compensator and inverter control can completely replace the use of power components defined in a fictitious rotating reference frame. Implications for the design of converters with harmonic and unbalance capabilities, and some relevant aspects of PHIL testing are also described. Results from this study showed that compensation for a resistive and inductive load was achieved without the need for the concept of Q. The efficiency of power transfer to the load was improved, and the delivery losses decreased. It was also shown that a GPT-compensated system was more efficient than a pq-compensated system. The experience with testing and analysing electrical circuits using the GPT approach has shown that power systems’ electromagnetic phenomena can be explained – and the system performance can be controlled and improved – simply using voltages and currents. The consistency between the simulated and physical demonstration of the technology in a power system confirms the validity and usefulness of the GPT in measurement and control. It brings a novel concept to the field of power electronics and has implications for the standardisation of measurement devices and the control of power electronic hardware.

ORCID iDs

Jankee, Pitambar, Gaunt, C. Trevor, Feng, Zhiwang ORCID logoORCID: https://orcid.org/0000-0001-5612-0050 and Burt, Graeme ORCID logoORCID: https://orcid.org/0000-0002-0315-5919;
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