Control and Implementation of a Standalone Solar Photo-Voltaic Hybrid System
A control algorithm for a standalone solar photovoltaic (PV)-diesel-battery hybrid system is implemented in this paper. The proposed system deals with the intermittent nature of the energy generated by the PV array and it also provides power quality improvement. The PV array is integrated through a DC-DC boost converter and controlled using a maximum power point tracking (MPPT) algorithm to obtain the maximum power under varying operating conditions. The battery energy storage system (BESS) is integrated to the diesel engine generator (DG) set for the coordinated load management and power flow within the system. The admittance based control algorithm is used for load balancing, harmonics elimination and reactive power compensation under three phase four-wire linear and nonlinear loads. A four-leg voltage source converter (VSC) with BESS also provides neutral current compensation. The performance of proposed standalone hybrid system is studied under different loading conditions experimentally on a developed prototype of the system.
Nowadays, the rapid increase in the use of nonlinear loads such as computers, electronics appliances, medical equipment, refrigerators etc. has emphasized the concern for power quality in the electrical distribution system. These loads inject harmonics and distort the current and voltage waveforms causing poor power quality problems. The possible provision for the mitigation of the power quality problems is with inclusion of custom power devices (CPDs). Three-phase four-wire loads are also known to suffer from the problem of neutral current due to non-linearity and unbalance present in the system. This may produce large amount of neutral current which consists of triplen harmonics. The neutral current may cause over-loading of the distribution system and causes additional heat losses which may be dangerous and poses a serious threat to the connected equipment. A four-leg VSC is used for neutral current compensation in addition to mitigate the current harmonics with other reported advantages.
The standalone system consists of a PV array along with a boost converter, MPPT controller, diesel engine driven permanent magnet synchronous generator (PMSG), a four-leg VSC with BESS and three-phase four-wire AC loads. The voltage at the point of common coupling is restored by coordinating the reactive power through VSC control. Under varying conditions of generation and loads, BESS offers charging during the daytime when the insolation is large and the load is less. The battery discharges to compensate for any deficits. The DG set operates while maintaining the system frequency under varying generation and loads. The terminal capacitor provides a constant rated terminal voltage at no load. A four leg VSC is interfaced along with its DC bus. The ripple filter and interfacing inductors are used to eliminate the switching harmonics.
- Eliminate harmonics, load balancing.
- Provide neutral current compensation by incorporating four-leg VSC.
- The ripple filter and interfacing inductors are used to eliminate the switching harmonics.
- PV-diesel-battery hybrid system.
- Household appliances.
- Remote missions.
- Data communications.
- Telecommunication systems.
- Electric aircrafts.
- Solar cars.