• Title/Summary/Keyword: grid-connected PCS

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High-Efficiency Power Conditioning System for Grid-Connected Photovoltaic Modules

  • Choi, Woo-Young;Choi, Jae-Yeon
    • Journal of Power Electronics
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    • v.11 no.4
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    • pp.561-567
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    • 2011
  • This paper presents a high-efficiency power conditioning system (PCS) for grid-connected photovoltaic (PV) modules. The proposed PCS consists of a step-up DC-DC converter and a single-phase DC-AC inverter for the grid-connected PV modules. A soft-switching step-up DC-DC converter is proposed to generate a high DC-link voltage from the low PV module voltage with a high-efficiency. A DC-link voltage controller is presented for constant DC-link voltage regulation. A half-bridge inverter is used for the single-phase DC-AC inverter for grid connection. A grid current controller is suggested to supply PV electrical power to the power grid with a unity power factor. Experimental results are obtained from a 180 W grid-connected PV module system using the proposed PCS. The proposed PCS achieves a high power efficiency of 93.0 % with an unity power factor for a 60 Hz / 120 Vrms AC power grid.

Active Frequency with a Positive Feedback Anti-Islanding Method Based on a Robust PLL Algorithm for Grid-Connected PV PCS

  • Lee, Jong-Pil;Min, Byung-Duk;Kim, Tae-Jin;Yoo, Dong-Wook;Yoo, Ji-Yoon
    • Journal of Power Electronics
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    • v.11 no.3
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    • pp.360-368
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    • 2011
  • This paper proposes an active frequency with a positive feedback in the d-q frame anti-islanding method suitable for a robust phase-locked loop (PLL) algorithm using the FFT concept. In general, PLL algorithms for grid-connected PV PCS use d-q transformation and controllers to make zero an imaginary part of the transformed voltage vector. In a real grid system, the grid voltage is not ideal. It may be unbalanced, noisy and have many harmonics. For these reasons, the d-q transformed components do not have a pure DC component. The controller tuning of a PLL algorithm is difficult. The proposed PLL algorithm using the FFT concept can use the strong noise cancelation characteristics of a FFT algorithm without a PI controller. Therefore, the proposed PLL algorithm has no gain-tuning of a PI controller, and it is hardly influenced by voltage drops, phase step changes and harmonics. Islanding prediction is a necessary feature of inverter-based photovoltaic (PV) systems in order to meet the stringent standard requirements for interconnection with an electrical grid. Both passive and active anti-islanding methods exist. Typically, active methods modify a given parameter, which also affects the shape and quality of the grid injected current. In this paper, the active anti-islanding algorithm for a grid-connected PV PCS uses positive feedback control in the d-q frame. The proposed PLL and anti-islanding algorithm are implemented for a 250kW PV PCS. This system has four DC/DC converters each with a 25kW power rating. This is only one-third of the total system power. The experimental results show that the proposed PLL, anti-islanding method and topology demonstrate good performance in a 250kW PV PCS.

New MPPT Control Strategy for Two-Stage Grid-Connected Photovoltaic Power Conditioning System

  • Bae, Hyun-Su;Park, Joung-Hu;Cho, Bo-Hyung;Yu, Gwon-Jong
    • Journal of Power Electronics
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    • v.7 no.2
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    • pp.174-180
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    • 2007
  • In this paper, a simple control method for two-stage utility grid-connected photovoltaic power conditioning systems (PCS) is proposed. This approach enables maximum power point (MPP) tracking control with post-stage inverter current information instead of calculating solar array power, which significantly simplifies the controller and the sensor. Furthermore, there is no feedback loop in the pre-stage converter to control the solar array voltage or current because the MPP tracker drives the converter switch duty cycle. This simple PCS control strategy can reduce the cost and size, and can be utilized with a low cost digital processor. For verification of the proposed control strategy, a 2.5kW two-stage photovoltaic grid-connected PCS hardware which consists of a boost converter cascaded with a single-phase inverter was built and tested.

Development of Low-voltage Seamless Transfer Microgrid on Grid-connected Type Islands by Autonomous Operation (자율운전에 의한 계통연계형 도서의 저압 무순단 마이크로그리드 구축)

  • Kim, Jeong Hun;Kwon, Jung-Min;Yun, Sang-Yun
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.66 no.4
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    • pp.169-176
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    • 2017
  • This paper presents research on low-voltage microgrids to maintain a continuous power supply to critical loads on grid-connected islands in Korea. The low-voltage microgrids of this paper focused on that changes public office buildings into uninterrupted microgrids by autonomous operation. For this, a microgrid controller (MGC) and a power conditioning system (PCS) that allow a seamless transfer between grid-connected and grid-isolated operation are proposed. The proposed PCS operates with a silicon controlled rectifier (SCR) switch and employs a simple structure. It supplies power continuously without operators through a coordinated operation between MGC and PCS. In addition, proposed MG has a schedule operation for minimizing electricity charges and provides ancillary services that enable the utilization of resources according to the operation purpose of utility distribution networks. To demonstrate the uninterrupted low-voltage microgrid proposed in this study, a microgrid was implemented and tested in a public office building in Anjwa Island, Jeollanam-do in Korea. A seamless, autonomous operation history, despite system disturbances, was obtained through a long-term demonstration of operation. The results showed that the proposed microgrid technology can be used to achieve energy resilience in grid-connected island areas.

Control of 30kW Grid-Connected PCS for Wave Power Generation (파력발전용 30kW 계통연계형 PCS 제어)

  • Kim, Wan-Seok;Kim, Jae-Hyuck
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.3
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    • pp.470-475
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    • 2019
  • This paper deals with a 30kW grid-connected PCS (Power Conversion System) for an Oscillating Water Column (OWC) wave-power generation system. Wave power generation in marine energy is suitable for Korea with the characteristics of a peninsula with three sides facing the sea. In the case of coastal disasters, wave generators can act as a breakwater to reduce damage, and can be integrated with other marine power generation systems to increase efficiency. Wave power generation systems are classified into various types, such as oscillating bodies, OWC, and overtopping according to the operation principle, and they can also be classified into two types according to the installation method: a fixed structure and floating structure. This paper proposes a 30kW grid-connected PCS topology and model for OWC wave power generation that is structurally stable with a turbine and generator that are relatively easy to maintain, and then provide a control method required for grid connection, including DC link voltage control. Simulation verification was performed to verify the proposed PCS.

Grid-Connected Photovoltaic System Applying the Step Variable MPPT Control and DVR (Step 가변형 MPPT 제어기법과 DVR을 적용한 계통연계형 태양광 발전 시스템)

  • Lee, Yong-Sik;Jeong, Sung-Won;Gim, Jae-Hyeon
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.26 no.8
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    • pp.42-49
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    • 2012
  • Grid-connected photovoltaic generator system requires high performance PCS(Power Conditioning System) according to the standard of 'Distributed Generation Grid-Connected Technology Standards'. This paper presents the MPPT control method which improves output efficiency through fast tracking to the maximum power point of PV and a reduced self-excited vibration. Secondly, in this paper DVR function was applied to PCS to compensate the voltage sag frequently happening for a power system. The proposed PCS control is analyzed and compared to conventional PCS operating characteristic, the various insolation and loads, and voltage sag condition through PSIM tool. It proves the utility.

The grid-connected bidirectional PCS technology of the ESS (에너지 저장장치의 계통 연계형 양방향 PCS 기술)

  • Ko, Bong-Woon
    • Journal of IKEEE
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    • v.23 no.4
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    • pp.1280-1287
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    • 2019
  • Grid-connected bidirectional PCS(Power Conditioning System) technology is a technology for implementing distributed renewable energy smart grid. And it is always charged by using power collected from solar modules and commercial grid power among vast smart grid systems, and stored when needed.It is a hybrid energy storage device that allows power to be released into the low voltage system. To this end, a PV input power converter with MPPT function, a bidirectional power converter for battery charging and discharging, and a DC Link input are output to a 3 phase 380V AC system, and if nessary, the bidirectional DC/DC converter We designed and developed a PCS with three power converter structures composed of inverters that perform battery charging. Currently, this system is applied to the site of Jeju, which is vulnerable to power outages and fire accidents.

The study on construction of the practical testing ground of grid-connected photovoltaic system (태양광발전 계통연계 실증시험장 구축에 관한 연구)

  • Kim, Euihwan;Jang, Juyeon
    • 한국신재생에너지학회:학술대회논문집
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    • 2010.06a
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    • pp.65.2-65.2
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    • 2010
  • Currently the variety of governmental business support and research for supplying solar energy have been actively progressed. As of now, however, There are no practical testing infrastructures of grid-connected photovoltaic system which test performance of solar power facility in domestic. Therefore, in KEPRI, there is in progress construction of practical testing ground of 500 kW class grid-connected PV System for developing the evaluation of the performance technology including the Module, PCS, and etc, that is the important instrument of the PV System, in Gochang area. It analyzed the site creation work for constructing the practical testing ground and new construction of control room and the unit standards, specifications and capacity of required equipment. For the system detailed design, configuration, instrument-specific parameters established, power generation predictions of Array Type and the components of testing ground are needed to build.

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Novel control algorithm for smart PCS with harmonics and reactive power compensation (고조파와 무효전력 보상기능을 가지는 Smart PCS의 새로운 제어 알고리즘)

  • Seo, Hyo-Ryong;Jang, Seong-Jae;Park, Sang-Soo;Kim, Sang-Yong;Kim, Gyeong-Hun;Park, Min-Won;Yu, In-Keun
    • Proceedings of the KIEE Conference
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    • 2009.07a
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    • pp.1053_1054
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    • 2009
  • A significant number of renewable energy systems have been connected to the grids as supplement power source. The renewable energy systems require control algorithm to maintain the power-supply reliability and quality. This paper proposes a novel control algorithm for smart Power Conditioning System (PCS) with harmonics and reactive power compensation. The smart PCS is used to feed Photovoltaic (PV) power to utility and compensate harmonics and reactive power at the same time. The experimentation is carried out on the proposed grid-connected PV generation system, and controlled by digital signal processor. The grid-connected PV generation system injects PV energy into the grid and performs as Active Filter (AF) and Static Synchronous Compensator (STATCOM) without additional devices. The experiment results show that the proposed control algorithm is effective for smart PCS with harmonics and reactive power compensation.

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Compensation of Unbalanced Neutral Voltage for Grid-Connected 3-Phase 3-Level T-type Photovoltaic PCS Using Offset Voltage (오프셋 전압을 이용한 계통 연계형 3상 3레벨 T-type 태양광 PCS의 중성점 전압 불평형 보상)

  • Park, Kwan-Nam;Choy, Ick;Choi, Ju-Yeop;Lee, Young-Kwoun
    • Journal of the Korean Solar Energy Society
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    • v.37 no.6
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    • pp.1-12
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    • 2017
  • The DC link of Grid-Connected 3-Phase 3-Level T-type Photovoltaic PCS (PV-PCS) consists of two series connected capacitors for using their neutral voltage. The mismatch between two capacitor characteristics and transient states happened in load change cause the imbalance of neutral voltage. As a result, PV-PCS performance is degraded and the system becomes unstable. In this paper, a mathematical model for analyzing the imbalance of neutral voltage is derived and a compensation method using offset voltage is proposed, where offset voltage adjusts the applying time of P-type and N-type small vectors. The validity of the proposed methods is verified by simulation and experiment.