Active Power Transfer Capability Research Articles

Impedance Reshaping Method Based on Compensating PLL Dynamic to Improve Active Power Transfer Capability of VSC Under Weak Grid

Impedance Reshaping Method Based on Compensating PLL Dynamic to Improve Active Power Transfer Capability of VSC Under Weak Grid

An Enhancement of Power Quality With Efficient Active Power Transfer Capability in a PV–BSS-Fed UAPF for Microgrid Realization

This article investigates the enhancement of power quality with an efficient active power transfer capability in a universal active power filter (UAPF) integrated with a photovoltaic (PV) and battery storage system (BSS). The UAPF operates as a bidirectional interface between the PV–BSS and point of interconnection for microgrid realization. A new control strategy is proposed to extract fast and accurate voltage and current reference signals to operate the system in a desired manner. Here, the extraction of load voltages and calculation of load and reference powers are used to generate the reference signals, thereby comparing with actual signals with hysteresis controller to produce switching pulses of converters. As a result, the shunt and series converters form a robust system by acting as a current-controlled voltage source and voltage-controlled current source, respectively. It eliminates the need for adaptive filters and low-pass filters to extract the fundamental component of the load current. Furthermore, it increases the conversion efficiency of converters and improves the static and dynamic performance of the system. The proposed system is developed with a 1-kVA prototype laboratory setup using a field-programmable gate array controller and extensively tested with various test conditions such as grid voltage fluctuations, nonlinear and imbalanced load, and change in irradiance.

Analysis and Enhancement of Active Power Transfer Capability for DFIG-Based WTs in Very Weak Grid

Wind power generation yields significant economic and social benefits, especially for developing countries. However, large wind power plants (WPPs) are usually constructed in remote areas, leading to a weak grid. Also, serious challenges, such as power blocking, threaten the stable operation of the power system and result in a great deal of wind energy wasted. For this issue, this article presents a comprehensive study for doubly fed induction generators (DFIGs) to analyze and enhance its active power transfer capability in weak grid. First, a steady model for DFIGs is established, which emphasizes the influence of reactive power and power angle features. Based on it, the active power transfer capability under common reactive power control (RPC) modes is analyzed in detail. The analysis results indicate that both the rotor current limit and the power angle will affect the active power transfer capability, and the constant voltage RPC mode is preferred in the very weak grid. Furthermore, combined with the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axis current priority, a grid-side converter (GSC)-dominated RPC method is proposed to fully utilize the GSC capacity and substantially improve the active power transfer capability. Finally, the analysis and the proposed method are validated by experiments.

A Comparison of Inverter Control Modes for Maintaining Voltage Stability During System Contingencies

Inverter-based power sources are increasingly being connected to the power system due to the global drive towards renewable generation. This paper investigates the voltage stability of a power system where a load center is supplied by the grid through a transmission system along with an inverter-based generation located close to the load center. It is also assumed that there is no additional reactive power compensation at the load center and voltage control at Point of Common Coupling (PCC) is done by the inverter. This is challenging as the inverter has an added duty. If the inverter controllers are not designed properly, the inverter could reach its current limit following to contingencies rendering it unable to support the voltage at the PCC. This is due to the fact that once the current limit is reached, the inverter ceases to function as a voltage source. When the voltage at the PCC is not supported, the active power transfer capability of both the inverter and the grid will be reduced. An effective control method is required under such circumstances to handle the active and reactive components of the inverter current. Various strategies exist for controlling the active and reactive components of the inverter current while preserving the current magnitude at the rated value. The necessity of an adequate control strategy to sustain long-term voltage stability following a system contingency is emphasized in this research. This paper further discusses three candidate control strategies and the effectiveness of the reactive current prioritizing approach as a solution for operation upon system contingencies.

A Fault-Tolerant Operation Approach for Grid-Tied Five-Phase Current-Source Converters With One-Phase Supplying Wire Broken

In this paper, an enhanced fault-tolerant operation approach is developed to maintain continued operation of five-phase grid-tied current-source converters (CSCs) during one-phase supplying wire broken. First, the instantaneous power flow of this system is analyzed based on the sequence decomposition method. It is found that through proper arrangement of positive-, negative-, and pseudozero-sequence components of line current reference and compensation of filter CL current offset, the CSC system can achieve reduction of instantaneous active power fluctuation and minimization of line current magnitude at the same time. Accordingly, multiphase CSCs are able to operate with smaller dc rail current ripples and to obtain more active power transfer capability during fault tolerant operation. In addition, this paper also briefly discusses the control of multiphase systems in the case of complex grid faults with simultaneous wire broken and imbalanced grid voltage dips. It is found that an intentional constant reactive power injection can help to reduce the peak current of the five-phase grid-tied system. Furthermore, it should be noted that the proposed method is realized in a direct current modulation manner. Thus, a large number of line current acquisition devices for conventional multiphase grid-tied converters are removed. Finally, this paper also discusses the modulation method of five-phase CSC with one-phase wire broken. A modified “ampere-second balance” principle is applied to direct obtain the gating signals that can satisfy the constraints of CSCs.

ANALISIS TRANSFER DAYA PADA SALURAN TRANSMISI 150 KV DARI GARDU INDUK AIR ANYIR KE GARDU INDUK SUNGAILIAT PLN AREA BANGKA

Ketersediaan energi listrik yang cukup dan berkualitas merupakan tuntutan yang harus dipenuhi oleh PT. PLN (Persero). Penyaluran tenaga listrik melalui saluran transmisi 150 kV dengan jarak yang relatif panjang dan menggunakan kawat penghantar jenis aluminium selalu mengalami perubahan arus dan tegangan sehingga menimbulkan kemampuan pengiriman daya listrik menjadi tidak setabil. Pengaruh lainnya juga dapat diperoleh dari perubahan faktor daya dan sudut fasanya. Metode yang digunakan adalah metode analisis persamaan dalam bentuk hiperbolis. Pada penelitian ini menunjukkan bahwa kemampuan transfer daya dipengaruhi oleh sudut fasa. Kemampuan transfer daya aktif maksimum adalah sebesar 1962,71 kW pada VS yaitu 150∠75⁰ dan VR yaitu 150∠0⁰ dengan selisih sudut fasa adalah 75⁰. Sedangkan pada VS = 150∠75⁰ dan VR = 145∠0⁰ kemampuan transfer daya aktif adalah sebesar 1911,97 kW dengan selisih sudut fasa yang sama yaitu 75⁰. Penelitian ini memperlihatkan bahwa kemampuan transfer daya aktif dipengaruhi oleh tegangan. Kemampuan transfer daya aktif maksimum untuk nilai VR = 150∠0⁰ pada VS yang konstan yakni 150∠90⁰ adalah sebesar 2134,49 kW. Sedangkan Untuk nilai VR = 145∠0⁰ pada VS yang konstan yakni 150∠90⁰ adalah sebesar 2078,03 kW.

Parallel Operation of Bidirectional Interfacing Converters in a Hybrid AC/DC Microgrid Under Unbalanced Grid Voltage Conditions

Today, interests on hybrid ac/dc microgrids, which contain the advantages of both ac and dc microgrids, are growing rapidly. In the hybrid ac/dc microgrid, the parallel-operated ac/dc bidirectional interfacing converters (IFCs) are increasingly used for large capacity renewable energy sources or as the interlinking converters between the ac and dc subsystems. When unbalanced grid faults occur, the active power transferred by the parallel-operated IFCs must be kept constant and oscillation-free to stabilize the dc bus voltage. However, under conventional control strategies in unbalanced grid conditions, the active power transfer capability of IFCs is affected due to the converters’ current rating limitations. Moreover, unbalanced voltage adverse effects on IFCs (such as output power oscillations, dc-link ripples, and output current enhancement) could be amplified by the number of parallel converters. Therefore, this paper investigates parallel operation of IFCs in hybrid ac/dc microgrids under unbalanced ac grid conditions and proposes a novel control strategy to enhance the active power transfer capability with zero active power oscillation. The proposed control strategy employs a new current sharing method which introduces adjustable current reference coefficients for parallel IFCs. In the proposed control strategy, only one IFC, named as redundant IFC, needs to be designed and installed with higher current rating to ensure the constant and oscillation-free output active power of parallel IFCs. Simulation and experimental results verify the feasibility and effectiveness of the proposed control strategy.

Interaction of Droop Control Structures and Its Inherent Effect on the Power Transfer Limits in Multiterminal VSC-HVDC

Future multi-terminal HVDC systems are expected to utilize dc voltage droop controllers and several control structures have been proposed in literature. This paper proposes a methodology to analyse the impact of various types of droop control structures using small-signal stability analysis considering all possible combinations of droop gains. The different control structures are evaluated by the active power transfer capability as a function of the droop gains, considering various possible stability margins. This reveals the flexibility and robustness against active power flow variations, due to disturbances for all the implementations. A case study analyzing a three terminal HVDC VSC-based grid with eight different kinds of droop control schemes points out that three control structures outperform the remaining ones. Additionally, a multi-vendor case is considered where the most beneficial combinations of control structures has been combined in order to find the best performing combination.