Showing papers on "Maximum power point tracking published in 2001"

Development of a microcontroller-based, photovoltaic maximum power point tracking control system

Abstract: Maximum power point tracking (MPPT) is used in photovoltaic (PV) systems to maximize the photovoltaic array output power, irrespective of the temperature and irradiation conditions and of the load electrical characteristics. A new MPPT system has been developed, consisting of a buck-type DC/DC converter, which is controlled by a microcontroller-based unit. The main difference between the method used in the proposed MPPT system and other techniques used in the past is that the PV array output power is used to directly control the DC/DC converter, thus reducing the complexity of the system. The resulting system has high-efficiency, lower-cost and can be easily modified to handle more energy sources (e.g., wind-generators). The experimental results show that the use of the proposed MPPT control increases the PV output power by as much as 15% compared to the case where the DC/DC converter duty cycle is set such that the PV array produces the maximum power at 1 kW/m/sup 2/ and 25/spl deg/C.

Evaluating MPPT Converter Topologies Using a Matlab PV Model

Abstract: An accurate PV module electrical model is presented based on the Shockley diode equation. The simple model has a photo-current current source, a single diode junction and a series resistance, and includes temperature dependences. The method of parameter extraction and model evaluation in Matlab is demonstrated for a typical 60W solar panel. This model is used to investigate the variation of maximum power point with temperature and isolation levels. A comparison of buck versus boost maximum power point tracker (MPPT) topologies is made, and compared with a direct connection to a constant voltage (battery) load. The boost converter is shown to have a slight advantage over the buck, since it can always track the maximum power point.

Novel maximum-power-point-tracking controller for photovoltaic energy conversion system

Abstract: A novel maximum-power-point-tracking (MPPT) controller for a photovoltaic (PV) energy conversion system is presented. Using the slope of power versus voltage of a PV array, the proposed MPPT controller allows the conversion system to track the maximum power point very rapidly. As opposed to conventional two-stage designs, a single-stage configuration is implemented, resulting in size and weight reduction and increased efficiency. The proposed system acts as a solar generator on sunny days, in addition to working as an active power line conditioner on rainy days. Finally, computer simulations and experimental results demonstrate the superior performance of the proposed technique.

Generation control circuit for photovoltaic modules

Abstract: Photovoltaic modules must generally be connected in series in order to produce the voltage required to efficiently drive an inverter. However, if even a very small part of photovoltaic module (PV module) is prevented from receiving light, the generation power of the PV module is decreased disproportionately. This greater than expected decrease occurs because PV modules which do not receive adequate light cannot operate on the normal operating point, but rather operate as loads. As a result, the total power from the PV modules is decreased if even only a small part of the PV modules are shaded. In the present paper, a novel circuit, referred to as the generation control circuit (GCC), which enables maximum power to be obtained from all of the PV modules even if some of the modules are prevented from receiving light. The proposed circuit enables the individual PV modules to operate effectively at the maximum power point tracking, irrespective of the series connected PV module system. In addition, the total generated power is shown experimentally to increase for the experimental set-up used in the present study.

A fast dynamic DC-link power-balancing scheme for a PWM converter-inverter system

Abstract: The authors propose a new power converter control scheme for a converter-inverter system. The strategy is to fully utilize the inverter dynamics in controlling the converter dynamics. The authors obtain the power dynamics for both converter and inverter systems, and control the converter power so that it matches the required inverter power exactly. Then, in the ideal case, no power flows through the DC-link capacitors and, thus, the DC-link voltage does not fluctuate even though a very small amount of the DC-link capacitance is used. In forcing the converter power to match the inverter power, the authors utilize the master-slave control concept. They control the DC-link voltage level indirectly through the stored capacitor energy in order to exploit the advantage of the linear dynamic behavior of the capacitor energy. This helps them to circumvent a complex control method in regulating the DC-link voltage. Through simulation and experimental results, the superiority of the proposed converter control scheme is demonstrated.

Maximum power tracking solar power system

Abstract: A maximum power tracker maximizes the power deliverable from a power source, such as a solar array using increasing, decreasing and maintaining states controlled by a set point signal modulated by a dither signal for stabilized regular power tracking during under demand conditions and maximum power tracking during periods with over demand conditions of a load. Multiple converters and respectively maximum power trackers can be coupled in parallel using shared bus control signal for fault tolerant equalized power conversion through the converters.

A novel maximum power point tracking control for photovoltaic power system under rapidly changing solar radiation

Abstract: This paper proposes a novel MPPT control algorithm for a digitally implemented photovoltaic power system under rapidly changing solar radiation. The method of the MPPT control algorithm can be classified into two categories: perturb and observe (P&O) and incremental conductance (IncCond). In comparing the P&O and IncCond algorithms, the dynamic and tracking characteristic of the IncCond algorithm is better than P&O algorithm under rapidly changing solar radiation. But in the case of digital implementation, the InCond algorithm has an error on the decision of maximum power operation point (MPOP). To solve this problem, this paper proposes a improved IncCond algorithm, which can determine the MPOP under rapidly changing solar radiation by inserting a test signal in the control input. By simulation and experimentation, the validity of the proposed control algorithm is proved.

Turbogenerator power control system

Abstract: A power control system for a turbogenerator which provides electrical power to one or more pump-jack oil wells. When the induction motor of a pump-jack oil well is powered by three-phase utility power, the speed of the pump-jack shaft varies only slightly over the pumping cycle but the utility power requirements can vary by four times the average pumping power. This power variation makes it impractical to power a pump-jack oil well with a stand-alone turbogenerator controlled by a conventional power control system. This power control system comprises a turbogenerator inverter, a load inverter, and a central processing unit which controls the frequency and voltage/current of each inverter. Throughout the oil well's pumping cycle, the central processing unit increases or decreases the frequency of the load inverter in order to axially accelerate and decelerate the masses of the down hole steel pump rods and oil, and to rotationally accelerate and decelerate the masses of the motor rotors and counter balance weights. This allows kinetic energy to be alternately stored in and extracted from the moving masses of the oil well and allows the oil pumping power to be precisely controlled. Historical data on the load inverter's frequency versus time profile throughout previous pumping cycles, which resulted in nearly constant turbogenerator power requirements, is utilized to further reduce variations in power.

Maximum power point tracking control of IDB converter supplied PV system

Abstract: The photovoltaic generator exhibits nonlinear V-I characteristics and its maximum-power point varies with solar insolation. An interleaved dual boost (IDB) converter is used to match the PV system to the load and to operate the solar cell array at maximum power point. A maximum power point tracking algorithm is developed using only load voltage information, eliminating array current detection. Analytical expressions for the PV array current and duty ratio of the converter corresponding to maximum power point operation of the solar cell array (SCA) are derived. SCA power output expressions with boost and interleaved dual boost converters are deduced. Load voltage based tracking effectiveness is demonstrated through simulation results. Experimental results validate the proposed method. Observations are also presented for partial shading conditions. The results obtained with this converter are compared with the boost converter PV system. It is demonstrated that the interleaved dual boost converter is more efficient and capable of reducing the ripple content in both source and load sides. As a result the interleaved dual boost converter photovoltaic systems require lower values of array input capacitance. SCA performance improves because of lower array ripple magnitudes.

Fault tolerant maximum power tracking solar power system

Abstract: A maximum power tracker maximizes the power deliverable from a power source, such as a solar array using increasing, decreasing and maintaining states controlled by a set point signal modulated by a dither signal for stabilized regular power tracking during under demand conditions and maximum power tracking during periods with over demand conditions of a load. For multiple power sources, respective multiple sets of parallel-connected converters and respectively maximum power trackers can be coupled in parallel using shared bus and control signals for fault tolerant equalized power conversion among the parallel-connected converters. Among multiple solar array sources that can have quite different characteristics, some maximum power trackers may actively regulate maximum power flows from respective array sources that have deficient power while the remaining maximum power trackers are inactive because respective remaining solar array sources provide sufficient power to allow respective DC-DC converters to regulate the load voltage to a regulated level.

Local area grid for distributed power

Abstract: The invention in the simplest form is a system for managing distributed power sources connected to a power grid. The present invention manages power flow to/from the power grid whether for a stand-alone power sourece or for local area utility grid or microgrid. When two or more power sources are interconnected by the local grid, each source has a power conditioning unit and a circuit breaker manager for controlling and regulating the electric flow to/from the grid. The individual power sources are able to independently draw power from the grid when required without extensive master control schemes. In a preferred embodiment the power sources are reformer equipped fuel cells and the heat from the fuel cell is used as a heat source for efficiency.

Single-stage photovoltaic energy conversion system

Abstract: For a photovoltaic (PV) array, the nonlinear output power relation of dP/dV against V and the near linear relation of dP/dV against I are discussed Thus, using dP/dV as an index for current control is easier than for voltage control, allowing a simpler design The current controller is employed in the PV energy conversion system to perform a rapid maximum power point tracking and to provide power to utilities with a unity power factor As opposed to conventional two-stage designs, a single-stage PV energy conversion system is implemented, resulting in size and weight reduction, and increased efficiency The proposed system performs a dual function; acting as a solar generator on sunny days and as an active power filter on rainy days Computer simulations and experimental results demonstrate the superior performance of the proposed technique

Power converting apparatus, control method therefor, and solar power generation apparatus

Abstract: The object is to reliably detect a ground fault of a solar battery. To detect a ground fault position to take an efficient measure against the ground fault, DC power input from a solar battery is converted into AC power and supplied to a system. In a system interconnection inverter (utility connected inverter) having non-insulated input and output, the input voltage of a converter circuit and/or the intermediate voltage between the converter circuit and an inverter circuit are varied to control the potential to ground at each portion of the solar battery to a value other than a value close to zero.

Power sensor-less MPPT control scheme utilizing power balance at DC link-system design to ensure stability and response

Abstract: The authors previously proposed a new MPPT (maximum power point tracking) control scheme for PV (photovoltaic) power systems connected in parallel with the AC system line. It is characterised by utilizing power balance at the DC link under steady state conditions, hence eliminating the array output power detection and achieving power sensorless operation. However, the system response and stability greatly depend on its main circuit and control system parameters. This paper shows a system design to ensure stability and response based on system transfer functions. Response of the experimental system has been proved fast enough for practical use. Full-daytime testing data show the successful tracking results of the system.

Control of multiple fuel cell power plants at a site to provide a distributed resource in a utility grid

Abstract: A site management system (11) is provided for a power system (8) at site in a utility distribution grid (10). The power system (8) includes multiple fuel cell power plants (18) and one or more loads (14), for selective connection/disconnection with the grid (10). The site management system (11) operates to control the power plants (18) in an integrated manner, alternatively in a grid connected mode and in a grid independent mode. The utility is able to view and treat the multiple power plants (18) at the site as a single, unified distributed resource on the grid (10). The site management system (11) provides signals representative of the present power capability (Kw Capacity—88) of each of the power plants (18), and a signal (Total Kw Capacity—95) representative of the total present power capability at the site. These power representations are used to appropriately assign power dispatch loadings to the respective fuel cells (18) in the grid connected mode and in the grid independent mode. The site management system (11) also functions in the grid independent mode to monitor present demand of the loads (14) and, if necessary, to shed loads (14) in accordance with a predetermined schedule.

Voltage source inverters for high-power, variable-voltage DC power sources

Abstract: The paper discusses the applications of voltage source inverter (VSI) based power electronic systems for interfacing variable-voltage DC sources to the grid. A variable-speed wind power conversion system is used for illustration, where the VSI-based interface needs to convert a variable DC voltage to a nearly constant AC voltage with high-quality power. The power control principles of VSI are described. Various system configurations and switching strategies are examined by analysis, simulation and experimental methods. It is shown that better utilisation of semiconductors and more flexible control may be achieved by using a separately controlled DC link, rather than a directly connected VSI that has to operate at a lower modulation ratio at higher power. In some cases, multipulse inverter structures may be preferred, despite higher component count, because of reduced switching losses, fault tolerance and the absence of filters. The solutions developed in the study could be applied at a different scale to other renewable energy sources, such as wave or solar photovoltaic devices.

Power control of a photovoltaic array in a hybrid electric generation system using sliding mode techniques

Abstract: A variable structure controller to regulate the output power of a standalone hybrid generation system is presented. The system comprises photovoltaic and wind generation, a storage battery bank and a variable monophasic load. The control law admits two modes of operation. The first takes place when the insolation regime is sufficient to satisfy the power demand. The second mode of operation takes place under insufficient insolation regimes. The latter leads the system operation at the maximum power operation point to save as much stored energy as possible. A new method based on the IncCond algorithm is developed. Sliding mode control techniques are used to design the control law. These techniques provide a simple control law design framework and contribute with their well known robustness properties. Finally, guidelines based on chattering considerations are given for the design of the practical system.

Power converting apparatus, control method therefor, and power generation system

Abstract: In a solar power generation system having an inverter, if a smoothing capacitor in the inverter degrades, the operation of the inverter is interrupted, and a loss in the amount of power generation occurs inevitably. To prevent this loss, a degradation determination section (211) and output suppressing section (212) are provided in an inverter (2). If the degradation determination section (211) determines a degradation in capacitor (24), the operation of the inverter (2) is continued while suppressing the output current of the inverter (2) by the output suppressing section (212). In addition, a warning section (213) warns the user about the degradation in capacitor (24). With this arrangement, a solar power generation system capable of detecting a degradation in smoothing capacitor in the inverter (2) and appropriately operating the inverter (2) can be provided.

A predictive control scheme for DC voltage and AC current in grid-connected photovoltaic inverters with minimum DC link capacitance

Abstract: This paper describes a discrete time control algorithm for regulation of both DC voltage and AC currents in three-phase inverters. It is suitable for application in grid-connected photovoltaic (PV) generation plants due to the intrinsic ability to perform maximum power point tracking (MPPT) of the PV array. Furthermore, the transient response time is of the order of a few PWM sampling periods, therefore the energy storage requirements of the DC capacitor are significantly reduced, and a small nonelectrolytic type can be employed. Considering that the DC buffer capacitor of an inverter is often the limiting factor in terms of reliability, the proposed approach can lead to a substantial improvement in the way the entire system is perceived. The technique has similar harmonic performance to regularly sampled PWM, with a fixed switching frequency and low current distortion, and operates at unity power factor. This predictive method avoids problems of stability and loop interactions present in controllers employing cascaded DC voltage and AC current feedback loops. The theory of the algorithm is presented in this paper, together with simulation results.

Solar power management system

Abstract: A solar power management system includes a plurality of photovoltaic cell panels, and a solar power cell manager coupled to the photovoltaic cell panels. The solar power cell manager includes an input stage for combining current draws from the photovoltaic cells, and a load manager in communication with the input stage for managing the combined current draw.

Maximum power tracking technique for solar panels

Abstract: The present invention provides an apparatus and method for tracking the maximum power point of a solar panel. A pulsewidth-modulated converter, for example a SEPIC or Cuk converter, is provided between the output of the panel and the load, and a perturbation is introduced into a switching parameter of the converter.

Power conditioner for solar energy generation

Abstract: PROBLEM TO BE SOLVED: To provide a power conditioner for a solar energy generation, which can produce the maximum power from the solar cells even in an independent operation. SOLUTION: The power conditioner is composed in order to provide the output of a storage battery 21 to the input side of an inverter 13 via a bidirectional chopper 14. Accordingly, it is possible to produce the maximum power Pmax from a solar cell 20 in the same way as in a grid-connected operation. Further, the DC power from the storage battery 21 is supplied to the inverter 13 side via the bidirectional chopper 14, it is enough to control the output voltage of the bidirectional chopper 14 to a constant value of the peak value of the output voltage of the inverter 13 or higher. COPYRIGHT: (C)2003,JPO

Novel inverter topologies for single-phase stand-alone or grid-connected photovoltaic systems

Abstract: Photovoltaic and battery systems often operate in small stand-alone or grid-connected applications, where the generator voltage is lower than the grid voltage. To boost the voltage up to the grid level a further element, either a DC/DC converter or 50 Hz transformer, is connected in series with a PWM inverter. To reduce the high cost of such low power systems, the costs of the power electronics should be minimized. In this paper, several new low-cost inverters with and without HF-transformers are presented. Simulation and experimental results of their operation and control for stand-alone as well for grid-connected applications are discussed.

Method and apparatus for a solar power conditioner

Abstract: A method and apparatus for supplementing electrical power production during peak demand power consumption is presented. A solar power conditioner converts DC electrical power provided by solar panels (or otherwise) to AC power and uses this to supplement main AC electrical power generated by a power utility (or otherwise) when needed. Both the DC power and the main AC power are digitalized by analog to digital (A/D) converters and continuously monitored by a central processor (CPU). The CPU aims to match the generated AC power of the inverter to that of the main AC power and, after tripping a breaker, supplements the main AC power with that of the converted power provided by the solar panels. In such a supplementary role, the solar power conditioner can be inserted into a utility's distributed power grid.

Three-phase grid-connected inverters interface for alternative energy sources with unified constant-frequency integration control

Abstract: A new control approach for three-phase grid-connected inverters is presented. The inverter stage is a standard three-phase half bridge. During each 60/spl deg/ of line cycle, the three-phase half bridge can be de-coupled into parallel-connected dual-buck inverter. Based on one-cycle control, a unified constant-frequency integration controller (UCI) is proposed for the dual-buck inverter. The controller is comprised of an integrator with reset, along with some linear and logic components. No multipliers are required. Low current distortion and unity-power-factor are achieved in the control loop. The input to the inverter can be fuel cells, photovoltaic power, wind power, etc. The three-phase currents injected to the grid are sinusoidal. The simplicity and performance of the proposed inverter make it a good candidate for grid-connected alternative energy generation.

Power conversion with stop conversion during low integrated power conditions

Abstract: In a solar power generation apparatus, when power necessary for a control circuit and the like is supplied from the load side of an inverter, a period from when the input voltage becomes lower than a threshold voltage at which the inverter should be stopped to when the inverter is stopped after the elapse of a predetermined time includes a period when power consumed by the inverter become larger than power output from the inverter, i.e., power is wasted. To solve this problem, input power is integrated for a predetermined time to calculate integrated electric energy. The calculated integrated electric energy W 1 is compared with a threshold value Y 1. If W 1

Controller of elevator

Abstract: This invention provides a controller of an elevator in which a space for mounting a power accumulating device can be saved and the controller can be applied to the elevator having no machine room. Therefore, the controller has power accumulating means arranged between DC buses between a converter and an inverter, and accumulating DC power from the DC buses at a regenerative operation time of the elevator and supplying the DC power accumulated on the DC buses at a power running operation time; and charging-discharging control means for controlling charging and discharging operations of the power accumulating means with respect to the DC buses. The power accumulating means is constructed by a secondary battery and a DC-DC converter for controlling charging and discharging operations of the secondary battery, and the secondary battery is constructed by connecting plural cells in series to each other. The secondary battery is arranged at any one of four corners within an ascending/descending path, a portion near a rail, or a portion near a cable within the ascending/descending path.

Power outputting device and vehicle mounting it, control method, storing medium and program for the power outputting device, drive device and vehicle mounting it, and, control method, storing medium and program for the drive device

Abstract: A power outputting device for outputting a motive power by driving a motor (22) rotationally using an electric power from a DC power source (32) This DC power source (32) is enabled, when cold, to exhibit its performance sufficiently by heating it quickly In the power outputting device in which a capacitor (30) is mounted to connect an anode bus (26) and a cathode bus (28) of an inverter circuit (24) and in which the DC power source (32) is mounted to connect the cathode bus (28) of the inverter circuit (24) and a neutral point of the motor (22), an electronic control unit (40) switches transistors (T1 to T6) by setting the inter-terminal voltage of the capacitor (30) higher than at a normal time and the frequency of a carrier wave lower than at a normal time when the power temperature (Tb) of the DC power source (32) detected by a temperature sensor (50) is not higher than a threshold value (Tblow) at which a necessary electric power can be supplied to the motor (22) As a result, the ripple of the neutral-point current flowing through the DC power source (32) can be increased to promote the heat generation of the DC power source (32)