An Aggregated Energy Management Methodology for Air Conditioning System With DAB Converter

An air conditioner load has a major role in power consumption from utility grid in tropical countries. Most of the air conditioning systems are migrated to variable speed drive technology that optimizes the power utilization. Renewable energy sources like photovoltaics (PV) and energy storage system like batteries produce dc power. In this article, considering the advantages of variable speed drive technology, the power is directly injected to the dc side of the variable speed drive from PV array and the battery. The compressor at the outdoor unit consumes major portion of power from the grid and therefore the additional power is integrated to this unit to support the grid. The voltage level of the battery is boosted to match with the dc bus voltage level of the grid using a bidirectional isolated dc–dc converter. A low-power dc–ac conversion stage is present to run the indoor unit and to supply the auxiliary power. In this methodology, air conditioner is operated uninterruptedly and high-power dc to ac (50 Hz) conversion stages are eliminated, thus it reduces the blukiness of the system, cost, and conversion losses. A seamless bidirectional power is exchanged between the battery and utility grid without interrupting the main operation of the air conditioner. The bidirectional power flow is controlled at the dc side based on the time-of-use tarriff levied by the utility and the frequency of the grid. A small-scale labratory prototype of the system is set up for the validation of the concept. The effect of injecting power is investigated with different scenarios. With dc side power support, the consumer is benefitted with reduced power consumption during high tariff periods. Moreover, the harmonic components are reduced and the power quality is significantly improved. This scheme is utilized in building energy management system where air conditioner is extensively used.

I. Introduction

In Tropical countries during summer season, the power consumed by air conditioning load creates a deep impact on the utility grid. Due to the high cooling demands, high tariff rate has to be paid by the consumer. Therefore, a solution has to be devised that can reduce the power consumption from the utility grid when the tariff rate is high without interrupting the normal operation of the air conditioning load. Moreover, it should also facilitate continuous operation in absence of the grid. Thus, a power transfer architecture is proposed, which supports the air conditioning load in combination with photovoltaics (PV) power and energy storage system (ESS) like battery power as shown in Fig. 1. Fig. 1.

Block diagram of system.