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December 4, 2020
Operation of Micro Hydro Power System
Hydraulic power generation can be explained on the schematic of overall system structure depicted. Water requirement for hydraulic power generation is supplied from an artesian well via a pump to the water reservoir. Centrifuge type five water pumps with total power output of 180kw fill a water storage tower. To reject water disturbances on the turbine input, water input is passed through a pipe line which is fitted vertically within the tower. This pipe line is 12m in height. There are two valves one at entrance of the tower and one at exit point. In the system, a newly designed cross flow type hydraulic turbine powered by 20kVA is used. Water flow to generator and level of the water in tower are controlled by a host PC in accordance with sensor feedback signals. An acoustic flow meter Mag 5000 (400mm diameter) is used to measure water flow into the turbine. A pressure sensor (Keller PA21Y) with upper limit pressure of 4 bars is fixed within the tower to measure atmospheric pressures. The signals generated by these devices and others obtained from temperature and speed sensors are collected by data acquisition card NI USB 6009 which is connected to a PC. Water input to hydro turbine is regulated by a revolver clamp
fixed internally to the turbine, Governor control: Block diagram of turbine speed regulation governor for hydro power system.
The actuator is controlled by a hydraulic power unit (HPU) by regulating oil pressure. Operation is planned automatically but, automatic control unit is under development.
TESTING MICRO HYDRO POWER GENERATION
A. Tests carried out at Lab.
As pioneer work, before installing both generators into the micro hydro system, an electrical power flow test from both generators to utility grid were performed under lab.conditions. In the test another induction motor powered with 22kW, 1GL4-M186 4AA was used as a prime mover instead of a hydro turbine. The mover machine is delta connected and controlled in a closed loop speed mode by a vector controlled AC driver MICMASTER 440 with 47kW (Siemens). Each test setup is shown in. Synchronization of the asynchronous generator to grid was performed as follows: generator shaft is rotated by an AC driver at synchronous speed and then generator stator windings are connected to utility lines by a contactor. After grid connection increasing rotor shaft speed generator stars to feed grid. In the experiment a long term loaded grid connected operation is achieved at driver frequency of 50.8Hz. In case, grid connected operation of synchronous generators, some additional requirements are necessary.
These requirements are voltage and frequency matching between grid and the generator which will be connected to grid and the phase angle between generator terminal voltage and the grid supply must be same at least within specified range. Then, interconnection can be done automatically by synchronizing check relay SELCO T4000 providing the phase shift remains within specified limit for 10 seconds. Power factor correction and voltage regulation can be provided by the generator excitation system via adjustment of automatic voltage regulator (AVR). The normal operating status of low voltage (400V) distribution network is achieved separately by each generator in the lab. During each test, measured data which is associated to variables such as voltage, current, power, power factor and so on were recoded via the monitoring device UMG507 and only one value for each variable is provided at full load condition see The recorded data in Table.1 shows that the power factor of each generator is different. This value should be 0.8 for proper operation of the generators with unity power Fig.6. Laboratory test setups, for both genrators syncronous (up) and asynchronous (down) requirements. Therefore, power factor correction is needed for both generators; this can be achieved in different ways:
Paralleling capacitors for the asynchronous generator and regulating excitation voltage for synchronous generator via AVR device that provides capacitive load to offset the demand for lagging reactive powerfor synchronous generator
B. Tests carried out at the micro hydro plant Micro hydro power system is newly installed. Fig.4 shows turbine-gear box- generator group installed into power house of micro hydro system. Stand alone operation with RL load currently under testing. Test results to be added to the revised manuscript. Grid connected operation is a logical next step however at present still in development phase. C. Further studies and tests This micro hydro test system is taking advantage of having real objects. Thus it can also be used for aims at serving research studies of current problems related to connection of a single source using renewable energy to low voltage network under loads; impact of source and loads operation on the network; influence of the network on the source. Moreover, monitoring and control of different type generators including control of network and stand-alone operation. Further more, power flow studies will be performed to check the nominal operating status at low voltage network; interconnection with inverter interfacing or direct connection with/without reverse power flow; the requirement necessary for safety operation studies Fig.7. Turbine-gearbox-generator group may help to determine additional requirements such as individual cases being able to exceed present standards.
Structure of a micro hydro hardware setup is presented. A new designed cross flow type micro hydro turbine with 20kW is under testing. The objectives such as protection from reverse power flow, metering and management of grid connected operation and islanding are considerable concern on their impact, hence in further studies, power quality, stability and safety in distributed system connected to the grid at low voltage possibly will be focused. Thus, the hardware structure will be provide capability of testing different managing operation of distributed generators, extending the system with other types of generation system like solar and wind power. In essence a fully efficient and reliable Hydro electric generation test system for country wide usage is an achievable goal.