Power Control Of Photovoltaic System Research Articles

Voltage Rise Mitigation in PV Rich LV Distribution Networks Using DC/DC Converter Level Active Power Curtailment Method

In low voltage (LV) distribution systems, the problem of overvoltage is common during the lower load intervals. This problem arises because of the high value of R/X ration of these systems. Many techniques are available in literature to cope up with this problem at the converter level; mostly these methods control the reactive or active power of the photovoltaic (PV) systems. However, there are certain restrictions and complications with the reactive power control of PV systems. Most of the active power control methods have been implemented at the inverter stage of the PV system, resulting in implementation complexities and excessive oversizing of the converter. Therefore, in this paper, a simple, de-rating based voltage control algorithm is proposed to overcome the problem of overvoltage. So far de-rating technique has been used to enable frequency support functions in PVs; in a first of its kind, de-rating technique is used here to control the voltages in PV rich LV distribution systems. The entire control is implemented on the dc/dc converter stage of the PV system and the inverter stage is kept untouched. The effectiveness of the control is verified by simulating a sample PV-rich three bus LV distribution system on the MATLAB software. The proposed control avoids the overvoltage by approx. 700 V for the best-case scenario.

Examination of the effect of the reactive power control of photovoltaic systems on electric power grids and the development of a voltage-regulation method that considers feeder impedance sensitivity

When relatively high-capacity renewable photovoltaic (PV) systems are connected to a grid, they can increase or decrease the voltage along feeders because of reverse power flow, even exceeding ± five percent of the rated voltage. Nowadays, grid-connected inverter-based PV systems that can control reactive power can alleviate such an increase or decrease in voltage by adjusting the reactive power, which is referred to as Volt/Var control and management. Therefore, the objective of this paper is to (a) perform case studies to analyze the steady-state response of a large distribution network (i.e., with more than 1000 buses) with high-capacity PV systems that can control Volt/Var (i.e., either producing or consuming reactive power) and (b) present a Volt/Var-control method for three-phase voltage regulation that uses the positive-sequence sensitivity impedance matrix with power-factor constraints. This method is verified in the IEEE 34-bus test feeder. Thus, the proposed methods can be used to regulate the voltage of a bus to which a PV system is connected if the system controls reactive power. These proposed methods can also be used for various impact studies for the operation or planning of distribution systems with such PV systems.

Reducing Cost and Size in Photovoltaic Systems Using Three-Level Boost Converter Based on Fuzzy Logic Controller

Photovoltaic (PV) systems are dependent on two main factors of temperature and solar radiation, changing the PV system into a nonlinear system. Therefore, it is necessary to propose an intelligent control system for power control of PV systems to tackle this issue. So, a three-level boost converter (TLBC) based on the maximum power point tracking (MPPT) with fuzzy intelligent control is suggested to solve the problems. In this paper, instead of using the conventional boost converter, TLBC is used. However, the conventional boost converter is typically used in PV systems as the interface between the PV panel and the consumer. TLBC has a lower weight and cost than the conventional boost converter. In addition, the main scope of this paper is reducing the system weight and employing TLBC with MPPT for controlling the output power without any fluctuations. In addition, the MPPT controller for TLBC is developed based on fuzzy logic and is compared with perturb and observe (P&O) algorithm, proportional–integral (PI) controller, particle swarm optimization (PSO) algorithm, and hybrid simplified accelerated particle swarm optimization (HSAPSO) algorithm. Using fuzzy logic controller (FLC), the value of MPP is tracked suitably under different climatic conditions as well as different temperatures and radiation, where TLBC passes the energy from a PV panel to the output in a high-speed and free-oscillation manner. Furthermore, balancing the voltage of TLBC capacitors with the proportional controller (P) is done due to their non-equivalent series resistance. The simulation results in MATLAB suggest the accuracy and performance of the system.

Rapid Active Power Control of Photovoltaic Systems for Grid Frequency Support

As deployment of power electronic coupled generation such as photovoltaic (PV) systems increases, grid operators have shown increasing interest in calling on inverter-coupled generation to help mitigate frequency contingency events by rapidly surging active power into the grid. When responding to contingency events, the faster the active power is provided, the more effective it may be for arresting the frequency event. This paper proposes a predictive PV inverter control method for very fast and accurate control of active power. This rapid active power control (RAPC) method will increase the effectiveness of various higher-level controls designed to mitigate grid frequency contingency events, including fast power-frequency droop, inertia emulation, and fast frequency response, without the need for energy storage. The RAPC method, coupled with a maximum power point estimation method, is implemented in a prototype PV inverter connected to a PV array. The prototype inverter’s response to various frequency events is experimentally confirmed to be fast (beginning within 2 line cycles and completing within 4.5 line cycles of a severe test event) and accurate (below 2% steady-state error).