Research On The Photovoltaic Grid-connected Power Conditioner System And It's Control Strategies

According to the characteristics of inverter main circuits normally used in photovoltaic grid-connected systems, a novel control strategy is proposed for a photovoltaic grid-connected power conditioner (PVPC) system, in which a photovoltaic grid-connected generation is integrated with reactive power compensation and active filter. In this way, PVPC can provide not only active power but also reactive power, which simplifies system configuration, improves the power quality of mains with saving the investment of the equipment. The system has broad prospect.The main contents of this paper are as follows:1. A three-phased PVPC topology with reactive power compensation is proposed. And its operation principle and math model are further analyzed. The effect of main circuit parameters on performances of the system is discussed in details.2. According to the instantaneous p-q power theory, the algorithm is presented based on digital signal processor (DSP) instantaneous reactive power and harmonic current detection so that instantaneous reactive power and harmonic current damping are realized effectively.3. A novel algorithm - twice incremental conductance is proposed, which can find the maximum power point (MPP) when solar radiation is changing rapidly. This method ensures the small swing of solar array voltage in the process of searching the MPP.4. The PVPC prototype can also be applied in large -scale photovoltaic grid-connected system, so the topology and the control strategy of grid-connected group-control system are analyzed here, which can be called fixed master/slaver (FMS) and rotating master/slaver (RMS) basing on CAN bus.5. The generalized integral PI control method is put forward in the paper. It can not only realize zero error tracking of the alternating current, but also enhance power factor in all power range and improve the effect of reactive power compensation.6. The paper describes a novel anti-islanding method of frequency error displacement. Experimental results indicate that it significantly shrinks the response time near resonant load and has strong competence of anti noise.7. The prototype of 30KVA photovoltaic grid-connected power conditioner has been put into use in solar generation demonstration. It has been working in good condition since the prototype was put into use one year before.